Early Childhood Aetiology of Mental Health Problems: A Longitudinal Population-Based Study

ERIC Educational Resources Information Center

Bayer, Jordana K.; Hiscock, Harriet; Ukoumunne, Obioha C.; Price, Anna; Wake, Melissa

2008-01-01

Background: Mental health problems comprise an international public health issue affecting up to 20% of children and show considerable stability. We aimed to identify child, parenting, and family predictors from infancy in the development of externalising and internalising behaviour problems by age 3 years. Methods: "Design"…

Highly stable noble-metal nanoparticles in tetraalkylphosphonium ionic liquids for in situ catalysis.

PubMed

Banerjee, Abhinandan; Theron, Robin; Scott, Robert W J

2012-01-09

Gold and palladium nanoparticles were prepared by lithium borohydride reduction of the metal salt precursors in tetraalkylphosphonium halide ionic liquids in the absence of any organic solvents or external nanoparticle stabilizers. These colloidal suspensions remained stable and showed no nanoparticle agglomeration over many months. A combination of electrostatic interactions between the coordinatively unsaturated metal nanoparticle surface and the ionic-liquid anions, bolstered by steric protection offered by the bulky alkylated phosphonium cations, is likely to be the reason behind such stabilization. The halide anion strongly absorbs to the nanoparticle surface, leading to exceptional nanoparticle stability in halide ionic liquids; other tetraalkylphosphonium ionic liquids with non-coordinating anions, such as tosylate and hexafluorophosphate, show considerably lower affinities towards the stabilization of nanoparticles. Palladium nanoparticles stabilized in the tetraalkylphosphonium halide ionic liquid were stable, efficient, and recyclable catalysts for a variety of hydrogenation reactions at ambient pressures with sustained activity. Aerial oxidation of the metal nanoparticles occurred over time and was readily reversed by re-reduction of oxidized metal salts. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ti12Xe: A twelve-coordinated Xe-containing molecule

NASA Astrophysics Data System (ADS)

Miao, Junjian; Xu, Wenwu; Zhu, Beien; Gao, Yi

2017-08-01

A twelve-coordinated Xe-containing molecule Ti12Xe has been predicted by DFT calculations with quasi-icosahedral symmetry. Structural and NBO analyses show the chemical bonding exists between the central Xe atom and peripheral Ti atoms, which leads to the high stability of the molecule to a considerable degree. First principle molecular dynamics simulations further reveal the particularly high thermal stability of Ti12Xe up to 1500 K. This unique species may disclose new physics and chemistry of xenon element and stir interest in the Xe-transition metal cluster physics and chemistry.

The Mechanism of High Strength-Ductility Steel Produced by a Novel Quenching-Partitioning-Tempering Process and the Mechanical Stability of Retained Austenite at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Zhou, S.; Zhang, K.; Wang, Y.; Gu, J. F.; Rong, Y. H.

2012-03-01

The designed steel of Fe-0.25C-1.5Mn-1.2Si-1.5Ni-0.05Nb (wt pct) treated by a novel quenching-partitioning-tempering (Q-P-T) process demonstrates an excellent product of strength and elongation (PSE) at deformed temperatures from 298 K to 573 K (25 °C to 300 °C) and shows a maximum value of PSE (over 27,000 MPa pct) at 473 K (200 °C). The results fitted by the exponent decay law indicate that the retained austenite fraction with strain at a deformed temperature of 473 K (200 °C) decreases slower than that at 298 K (25 °C); namely, the transformation induced plasticity (TRIP) effect occurs in a larger strain range at 473 K (200 °C) than at 298 K (25 °C), showing better mechanical stability. The work-hardening exponent curves of Q-P-T steel further indicate that the largest plateau before necking appears at the deformed temperature of 473 K (200 °C), showing the maximum TRIP effect, which is due to the mechanical stability of considerable retained austenite. The microstructural characterization reveals that the high strength of Q-P-T steels results from dislocation-type martensite laths and dispersively distributed fcc NbC or hcp ɛ-carbides in martensite matrix, while excellent ductility is attributed to the TRIP effect produced by considerable retained austenite.

Some theoretical considerations of longitudinal stability in power-on flight with special reference to wind-tunnel testing, November 1942

NASA Technical Reports Server (NTRS)

Donlan, C. J.

1976-01-01

Some problems relating to longitudinal stability in power-on flight are considered. A derivation is included which shows that, under certain conditions, the rate of change of the pitching moment coefficient with lift coefficient as obtained in wind tunnel tests simulating constant power operation is directly proportional to one of the indices of stability commonly associated with flight analysis, (the slope of the curve relating the elevator angle for trim and lift coefficient). The necessity of analyzing power-on wind tunnel data for trim conditions is emphasized, and a method is provided for converting data obtained from constant thrust tests to simulated constant throttle flight conditions.

Prevalence, incidence, and natural course of anorexia and bulimia nervosa among adolescents and young adults.

PubMed

Nagl, Michaela; Jacobi, Corinna; Paul, Martin; Beesdo-Baum, Katja; Höfler, Michael; Lieb, Roselind; Wittchen, Hans-Ulrich

2016-08-01

We aimed to assess the prevalence, incidence, age-of-onset and diagnostic stability of threshold and subthreshold anorexia nervosa (AN) and bulimia nervosa (BN) in the community. Data come from a prospective-longitudinal community study of 3021 subjects aged 14-24 at baseline, who were followed up at three assessment waves over 10 years. Eating disorder (ED) symptomatology was assessed with the DSM-IV/M-CIDI at each wave. Diagnostic stability was defined as the proportion of individuals still affected with at least symptomatic eating disorders (EDs) at follow-ups. Baseline lifetime prevalence for any threshold ED were 2.9 % among females and 0.1 % among males. For any subthreshold ED lifetime prevalence were 2.2 % for females and 0.7 % for males. Symptomatic expressions of EDs (including core symptoms of the respective disorder) were most common with a lifetime prevalence of 11.5 % among females and 1.8 % among males. Symptomatic AN showed the earliest onset with a considerable proportion of cases emerging in childhood. 47 % of initial threshold AN cases and 42 % of initial threshold BN cases showed at least symptomatic expressions of any ED at any follow-up assessment. Stability for subthreshold EDs and symptomatic expressions was 14-36 %. While threshold EDs are rare, ED symptomatology is common particularly in female adolescents and young women. Especially threshold EDs are associated with a substantial risk for stability. A considerable degree of symptom fluctuation is characteristic especially for subthreshold EDs.

Stability-Derivative Determination from Flight Data

NASA Technical Reports Server (NTRS)

Holowicz, Chester H.; Holleman, Euclid C.

1958-01-01

A comprehensive discussion of the various factors affecting the determination of stability and control derivatives from flight data is presented based on the experience of the NASA High-Speed Flight Station. Factors relating to test techniques, determination of mass characteristics, instrumentation, and methods of analysis are discussed. For most longitudinal-stability-derivative analyses simple equations utilizing period and damping have been found to be as satisfactory as more comprehensive methods. The graphical time-vector method has been the basis of lateral-derivative analysis, although simple approximate methods can be useful If applied with caution. Control effectiveness has been generally obtained by relating the peak acceleration to the rapid control input, and consideration must be given to aerodynamic contributions if reasonable accuracy is to be realized.. Because of the many factors involved In the determination of stability derivatives, It is believed that the primary stability and control derivatives are probably accurate to within 10 to 25 percent, depending upon the specific derivative. Static-stability derivatives at low angle of attack show the greatest accuracy.

Complete replication-competent adenovirus 11p vectors with E1 or E3 insertions show improved heat stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mei, Ya-Fang, E-mail: ya-fang.mei@umu.se

2016-10-15

Conventional adenovirus vectors harboring E1 or E3 deletions followed by the insertion of an exogenous gene show considerably reduced virion stability. Here, we report strategies to generate complete replication-competent Ad11p(RCAd11p) vectors that overcome the above disadvantage. A GFP cassette was successfully introduced either upstream of E1A or in the E3A region. The resulting vectors showed high expression levels of the hexon and E1genes and also strongly induced the cytopathic effect in targeted cells. When harboring oversized genomes, the RCAd11pE1 and RCAd11pE3 vectors showed significantly improved heat stability in comparison to Ad11pwt;of the three, RCAd11pE3 was the most tolerant to heatmore » treatment. Electron microscopy showed that RCAd11pE3, RCAd11pE1, Ad11pwt, and Ad11pE1 Delmanifested dominant, moderate, minimum, or no full virus particles after heat treatment at 47 °C for 5 h. Our results demonstrated that both genome size and the insertion site in the viral genome affect virion stability. -- Highlights: •Replicating adenovirus 11p GFP vectors at the E1 or E3 region were generated. •RCAd11pE3 and RCAd11pE1 vectors manifested significantly improved heat stability. •RCAd11pE3 and RCAd11pE1 showed more full viral particles than Ad11pwt after heating. •We demonstrated that both genome size and the insertion site affect virion stability.« less

Dynamic stability and bifurcation analysis in fractional thermodynamics

NASA Astrophysics Data System (ADS)

Béda, Péter B.

2018-02-01

In mechanics, viscoelasticity was the first field of applications in studying geomaterials. Further possibilities arise in spatial non-locality. Non-local materials were already studied in the 1960s by several authors as a part of continuum mechanics and are still in focus of interest because of the rising importance of materials with internal micro- and nano-structure. When material instability gained more interest, non-local behavior appeared in a different aspect. The problem was concerned to numerical analysis, because then instability zones exhibited singular properties for local constitutive equations. In dynamic stability analysis, mathematical aspects of non-locality were studied by using the theory of dynamic systems. There the basic set of equations describing the behavior of continua was transformed to an abstract dynamic system consisting of differential operators acting on the perturbation field variables. Such functions should satisfy homogeneous boundary conditions and act as indicators of stability of a selected state of the body under consideration. Dynamic systems approach results in conditions for cases, when the differential operators have critical eigenvalues of zero real parts (dynamic stability or instability conditions). When the critical eigenvalues have non-trivial eigenspace, the way of loss of stability is classified as a typical (or generic) bifurcation. Our experiences show that material non-locality and the generic nature of bifurcation at instability are connected, and the basic functions of the non-trivial eigenspace can be used to determine internal length quantities of non-local mechanics. Fractional calculus is already successfully used in thermo-elasticity. In the paper, non-locality is introduced via fractional strain into the constitutive relations of various conventional types. Then, by defining dynamic systems, stability and bifurcation are studied for states of thermo-mechanical solids. Stability conditions and genericity conditions are presented for constitutive relations under consideration.

46 CFR 170.300 - Special consideration for free surface of spoil in hopper dredge hoppers.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 7 2014-10-01 2014-10-01 false Special consideration for free surface of spoil in hopper dredge hoppers. 170.300 Section 170.300 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) SUBDIVISION AND STABILITY STABILITY REQUIREMENTS FOR ALL INSPECTED VESSELS Free Surface § 170.300...

Biomechanical and performance implications of weapon design: comparison of bullpup and conventional configurations.

PubMed

Stone, Richard T; Moeller, Brandon F; Mayer, Robert R; Rosenquist, Bryce; Van Ryswyk, Darin; Eichorn, Drew

2014-06-01

Shooter accuracy and stability were monitored while firing two bullpup and two conventional configuration rifles of the same caliber in order to determine if one style of weapon results in superior performance. Considerable debate exists among police and military professionals regarding the differences between conventional configuration weapons, where the magazine and action are located ahead of the trigger, and bullpup configuration, where they are located behind the trigger (closer to the user). To date, no published research has attempted to evaluate this question from a physical ergonomics standpoint, and the knowledge that one style might improve stability or result in superior performance is of interest to countless military, law enforcement, and industry experts. A live-fire evaluation of both weapon styles was performed using a total of 48 participants. Shooting accuracy and fluctuations in biomechanical stability (center of pressure) were monitored while subjects used the weapons to perform standard drills. The bullpup weapon designs were found to provide a significant advantage in accuracy and shooter stability, while subjects showed considerable preference toward the conventional weapons. Although many mechanical and maintenance issues must be considered before committing to a bullpup or conventional weapon system, it is clear in terms of basic human stability that the bullpup is the more advantageous configuration. Results can be used by competitive shooter, military, law enforcement, and industry experts while outfitting personnel with a weapon system that leads to superior performance.

Desirability function combining metabolic stability and functionality of peptides.

PubMed

Van Dorpe, Sylvia; Adriaens, Antita; Vermeire, Simon; Polis, Ingeborgh; Peremans, Kathelijne; Spiegeleer, Bart De

2011-05-01

The evaluation of peptides as potential therapeutic or diagnostic agents requires the consideration of several criteria that are targeted around two axes: functionality and metabolic stability. Most often, a compromise has to be made between these mutually opposing characteristics. In this study, Derringer's desirability function, a multi-criteria decision-making method, was applied to determine the best peptide for opioid studies in a single figure-of-merit. The penetration of the blood-brain barrier (BBB) determines the biological functionality of neuropeptides in the brain target tissue, and consists of an influx and an efflux component. The metabolic stability in the two concerned tissues, i.e. plasma and brain, are taken into consideration as well. The overall selection of the peptide drug candidate having the highest BBB-drugability is difficult due to these conflicting responses as well as the different scalings of the four biological parameters under consideration. The highest desirability, representing the best BBB-drugability, was observed for dermorphin. This peptide is thus the most promising drug candidate from the set of eight opioid peptides that were investigated. The least desirable candidate, with the worst BBB influx and/or metabolic stability, was found to be CTAP. Validation of the desirability function by in vivo medical imaging showed that dermorphin and DAMGO penetrate the BBB, whereas EM-1 and TAPP did not. These results are thus consistent with those obtained with the desirability evaluation. To conclude, the multi-criteria decision method was proven to be useful in biomedical research, where a selection of the best candidate based on opposing characteristics is often required. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.

Resection of a cervical dumbbell schwannoma with stabilization through a single stage extended posterior approach.

PubMed

McCormick, Paul C

2014-09-01

Dumbbell tumors of the cervical spine can present considerable management challenges related to adequate exposure of both intraspinal and paraspinal tumor components, potential injury to the vertebral artery, and spinal stability. This video demonstrates the microsurgical removal of a large cervical dumbbell schwannoma with instrumented fusion via a single stage extended posterior approach. The video shows patient positioning, tumor exposure, and the sequence and techniques of tumor resection, vertebral artery identification and protection, and dural repair. The video can be found here: http://youtu.be/3lIVfKEcxss.

Treatment of fractures of the condylar head with resorbable pins or titanium screws: an experimental study.

PubMed

Schneider, Matthias; Loukota, Richard; Kuchta, Anne; Stadlinger, Bernd; Jung, Roland; Speckl, Katrin; Schmiedekampf, Robert; Eckelt, Uwe

2013-07-01

We aimed to compare in vivo the stability of fixation of condylar fractures in sheep using sonic bone welding and standard titanium screws. We assessed stability of the osteosynthesis and maintenance of the height of the mandibular ramus. Height decreased slightly in both groups compared with the opposite side. The volume of the condyle increased considerably in both groups mainly because callus had formed. The results showed no significant disadvantages for pin fixation compared with osteosynthesis using titanium screws. Copyright © 2012 The British Association of Oral and Maxillofacial Surgeons. All rights reserved.

Stability of the Baseline Holder in Readout Circuits For Radiation Detectors

PubMed Central

Chen, Y.; Cui, Y.; O’Connor, P.; Seo, Y.; Camarda, G. S.; Hossain, A.; Roy, U.; Yang, G.; James, R. B.

2016-01-01

Baseline holder (BLH) circuits are used widely to stabilize the analog output of application-specific integrated circuits (ASICs) for high-count-rate applications. The careful design of BLH circuits is vital to the overall stability of the analog-signal-processing chain in ASICs. Recently, we observed self-triggered fluctuations in an ASIC in which the shaping circuits have a BLH circuit in the feedback loop. In fact, further investigations showed that methods of enhancing small-signal stabilities cause an even worse situation. To resolve this problem, we used large-signal analyses to study the circuit’s stability. We found that a relatively small gain for the error amplifier and a small current in the non-linear stage of the BLH are required to enhance stability in large-signal analysis, which will compromise the properties of the BLH. These findings were verified by SPICE simulations. In this paper, we present our detailed analysis of the BLH circuits, and propose an improved version of them that have only minimal self-triggered fluctuations. We summarize the design considerations both for the stability and the properties of the BLH circuits. PMID:27182081

Wind-Tunnel Investigation of Effects of Unsymmetrical Horizontal-Tail Arrangements on Power-on Static Longitudinal Stability of a Single-Engine Airplane Model

NASA Technical Reports Server (NTRS)

Purser, Paul E.; Spear, Margaret F.

1947-01-01

A wind-tunnel investigation has been made to determine the effects of unsymmetrical horizontal-tail arrangements on the power-on static longitudinal stability of a single-engine single-rotation airplane model. Although the tests and analyses showed that extreme asymmetry in the horizontal tail indicated a reduction in power effects on longitudinal stability for single-engine single-rotation airplanes, the particular "practical" arrangement tested did not show marked improvement. Differences in average downwash between the normal tail arrangement and various other tail arrangements estimated from computed values of propeller-slipstream rotation agreed with values estimated from pitching-moment test data for the flaps-up condition (low thrust and torque) and disagreed for the flaps-down condition (high thrust and torque). This disagreement indicated the necessity for continued research to determine the characteristics of the slip-stream behind various propeller-fuselage-wing combinations. Out-of-trim lateral forces and moments of the unsymmetrical tail arrangements that were best from consideration of longitudinal stability were no greater than those of the normal tail arrangement.

Influence of Fe/Co ratio on structural and magnetic properties of (Fe100-xCox)84.5Nb5B8.5P2 alloy

NASA Astrophysics Data System (ADS)

Gehlot, K.; Kane, S. N.; Sinha, A. K.; Ghodke, N.; Varga, L. K.

2018-05-01

Structural and magnetic properties of a series of (Fe100-xCox)84.5Nb5B8.5P2 (x = 20, 40, 60) have been investigated respectively by using synchrotron x-ray diffraction and magnetic measurements. Results show that Fe/Co ratio: i) affects stability of the alloy against crystallization, ii) shows evidence for ordering, which has considerable effect on magnetic properties, iii) influences the grain diameter and volume fraction of the formed nano-grains range between 4.8 - 9.5 nm and 1.5 - 9 %, affects magnetic properties considerably. An empirical relation is obtained, which shows linear relationship between interatomic distances for 1st, 2nd co-ordination shell, suggests strong correlation between structural, magnetic properties.

Tunneled Mesoporous Carbon Nanofibers with Embedded ZnO Nanoparticles for Ultrafast Lithium Storage.

PubMed

An, Geon-Hyoung; Lee, Do-Young; Ahn, Hyo-Jin

2017-04-12

Carbon and metal oxide composites have received considerable attention as anode materials for Li-ion batteries (LIBs) owing to their excellent cycling stability and high specific capacity based on the chemical and physical stability of carbon and the high theoretical specific capacity of metal oxides. However, efforts to obtain ultrafast cycling stability in carbon and metal oxide composites at high current density for practical applications still face important challenges because of the longer Li-ion diffusion pathway, which leads to poor ultrafast performance during cycling. Here, tunneled mesoporous carbon nanofibers with embedded ZnO nanoparticles (TMCNF/ZnO) are synthesized by electrospinning, carbonization, and postcalcination. The optimized TMCNF/ZnO shows improved electrochemical performance, delivering outstanding ultrafast cycling stability, indicating a higher specific capacity than previously reported ZnO-based anode materials in LIBs. Therefore, the unique architecture of TMCNF/ZnO has potential for use as an anode material in ultrafast LIBs.

Effect of current vehicle’s interruption on traffic stability in cooperative car-following theory

NASA Astrophysics Data System (ADS)

Zhang, Geng; Liu, Hui

2017-12-01

To reveal the impact of the current vehicle’s interruption information on traffic flow, a new car-following model with consideration of the current vehicle’s interruption is proposed and the influence of the current vehicle’s interruption on traffic stability is investigated through theoretical analysis and numerical simulation. By linear analysis, the linear stability condition of the new model is obtained and the negative influence of the current vehicle’s interruption on traffic stability is shown in the headway-sensitivity space. Through nonlinear analysis, the modified Korteweg-de Vries (mKdV) equation of the new model near the critical point is derived and it can be used to describe the propagating behavior of the traffic density wave. Finally, numerical simulation confirms the analytical results, which shows that the current vehicle’s interruption information can destabilize traffic flow and should be considered in real traffic.

Stage structure alters how complexity affects stability of ecological networks

USGS Publications Warehouse

Rudolf, V.H.W.; Lafferty, Kevin D.

2011-01-01

Resolving how complexity affects stability of natural communities is of key importance for predicting the consequences of biodiversity loss. Central to previous stability analysis has been the assumption that the resources of a consumer are substitutable. However, during their development, most species change diets; for instance, adults often use different resources than larvae or juveniles. Here, we show that such ontogenetic niche shifts are common in real ecological networks and that consideration of these shifts can alter which species are predicted to be at risk of extinction. Furthermore, niche shifts reduce and can even reverse the otherwise stabilizing effect of complexity. This pattern arises because species with several specialized life stages appear to be generalists at the species level but act as sequential specialists that are hypersensitive to resource loss. These results suggest that natural communities are more vulnerable to biodiversity loss than indicated by previous analyses.

ITG modes in the presence of inhomogeneous field-aligned flow

NASA Astrophysics Data System (ADS)

Sen, S.; McCarthy, D. R.; Lontano, M.; Lazzaro, E.; Honary, F.

2010-02-01

In a recent paper, Varischetti et al. (Plasma Phys. Contr. F. 2008, 50, 105008-1-15) have found that in a slab geometry the effect of the flow shear in the field-aligned parallel flow on the linear mode stability of the ion temperature gradient (ITG)-driven modes is not very prominent. They found that the flow shear also has a negligible effect on the mode characteristics. The work in this paper shows that the inclusion of flow curvature in the field-aligned flow can have a considerable effect on the mode stability; it can also change the mode structure so as to effect the mixing length transport in the core region of a fusion device. Flow shear, on the other hand, has indeed an insignificant role in the mode stability and mode structure. Inhomogeneous field-aligned flow should therefore still be considered for a viable candidate in controlling the ITG mode stability and mode structure.

Local study of helical magnetorotational instability in viscous Keplerian disks

NASA Astrophysics Data System (ADS)

MahdaviGharavi, M.; Hajisharifi, K.; Mehidan, H.

2018-03-01

In this paper, regarding the recent detection of significant azimuthal magnetic field in some accretion disks such as protostellar (Donati et al. in Nature 438:466, 2005), the multi-fluid model has been employed to analysis the stability of Keplerian rotational viscous dusty plasma system in a current-free helical magnetic field structure. Using the fluid-Maxwell equations, the general dispersion relation of the excited modes in the system has been obtained by applying the local approximation method in the linear perturbation theory. The typical numerical analysis of the obtained dispersion relation in the high-frequency regime shows that the presence of azimuthal magnetic field component in Keplerian flow has a considerable role in the stability conditions of the system. It also shows that the magnetic field helicity has a stabilization role against the magnetorotational instability (MRI) in the system due to contraction of the unstable wavelength region and decreasing the maximum growth rate of the instability. In this sense, the stabilization role of the viscosity term is more considerable for HMRI (instability in the presence of azimuthal magnetic field component) than the corresponding MRI (instability in the absence of azimuthal magnetic field component). Moreover, considering the discovered azimuthal magnetic field in these systems, the MRI can be arisen in the over-all range of dust grains construction values in contract with traditional MRI. This investigation can greatly contribute to better understanding the physics of some astrophysical phenomena, such as the main source of turbulence and angular momentum transport in protostellar and the other sufficiently ionized astrophysical disks, where the azimuthal magnetic field component in these systems can play a significant role.

An extended continuum model considering optimal velocity change with memory and numerical tests

NASA Astrophysics Data System (ADS)

Qingtao, Zhai; Hongxia, Ge; Rongjun, Cheng

2018-01-01

In this paper, an extended continuum model of traffic flow is proposed with the consideration of optimal velocity changes with memory. The new model's stability condition and KdV-Burgers equation considering the optimal velocities change with memory are deduced through linear stability theory and nonlinear analysis, respectively. Numerical simulation is carried out to study the extended continuum model, which explores how optimal velocity changes with memory affected velocity, density and energy consumption. Numerical results show that when considering the effects of optimal velocity changes with memory, the traffic jams can be suppressed efficiently. Both the memory step and sensitivity parameters of optimal velocity changes with memory will enhance the stability of traffic flow efficiently. Furthermore, numerical results demonstrates that the effect of optimal velocity changes with memory can avoid the disadvantage of historical information, which increases the stability of traffic flow on road, and so it improve the traffic flow stability and minimize cars' energy consumptions.

Stability analysis of feedforward anticipation optimal flux difference in traffic lattice hydrodynamic theory

NASA Astrophysics Data System (ADS)

Sun, Di-Hua; Zhang, Geng; Zhao, Min; Cheng, Sen-Lin; Cao, Jian-Dong

2018-03-01

Recently, the influence of driver's individual behaviors on traffic stability is research hotspot with the fasting developing transportation cyber-physical systems. In this paper, a new traffic lattice hydrodynamic model is proposed with consideration of driver's feedforward anticipation optimal flux difference. The neutral stability condition of the new model is obtained through linear stability analysis theory. The results show that the stable region will be enlarged on the phase diagram when the feedforward anticipation optimal flux difference effect is taken into account. In order to depict traffic jamming transition properties theoretically, the mKdV equation near the critical point is derived via nonlinear reductive perturbation method. The propagation behavior of traffic density waves can be described by the kink-antikink solution of the mKdV equation. Numerical simulations are conducted to verify the analytical results and all the results confirms that traffic stability can be enhanced significantly by considering the feedforward anticipation optimal flux difference in traffic lattice hydrodynamic theory.

Optimal line drop compensation parameters under multi-operating conditions

NASA Astrophysics Data System (ADS)

Wan, Yuan; Li, Hang; Wang, Kai; He, Zhe

2017-01-01

Line Drop Compensation (LDC) is a main function of Reactive Current Compensation (RCC) which is developed to improve voltage stability. While LDC has benefit to voltage, it may deteriorate the small-disturbance rotor angle stability of power system. In present paper, an intelligent algorithm which is combined by Genetic Algorithm (GA) and Backpropagation Neural Network (BPNN) is proposed to optimize parameters of LDC. The objective function proposed in present paper takes consideration of voltage deviation and power system oscillation minimal damping ratio under multi-operating conditions. A simulation based on middle area of Jiangxi province power system is used to demonstrate the intelligent algorithm. The optimization result shows that coordinate optimized parameters can meet the multioperating conditions requirement and improve voltage stability as much as possible while guaranteeing enough damping ratio.

Effect of Cement on Properties of Over-Burnt Brick Bituminous Concrete Mixes

NASA Astrophysics Data System (ADS)

Sarkar, Dipankar; Pal, Manish

2016-06-01

The present investigation is carried out to propose the use of cement coated over burnt brick aggregate in the preparation of bituminous concrete mix. The effect of cement on various mechanical properties such as Marshall stability, flow, Marshall quotient (stability to flow ratio), indirect tensile strength, stripping, rutting and fatigue life of bituminous concrete overlay has been evaluated. In this study, different cement percentages such as 2, 3, 4 and 5 % by weight of aggregate have been mixed with Over Burnt Brick Aggregate (OBBA). The laboratory results indicate that bituminous concrete prepared by 4 % cement coated OBBA gives the highest Marshall stability. The bituminous concrete mix with 4 % cement shows considerable improvement in various mechanical properties of the mix compared to the plain OBBA concrete mix.

Optimally combining dynamical decoupling and quantum error correction.

PubMed

Paz-Silva, Gerardo A; Lidar, D A

2013-01-01

Quantum control and fault-tolerant quantum computing (FTQC) are two of the cornerstones on which the hope of realizing a large-scale quantum computer is pinned, yet only preliminary steps have been taken towards formalizing the interplay between them. Here we explore this interplay using the powerful strategy of dynamical decoupling (DD), and show how it can be seamlessly and optimally integrated with FTQC. To this end we show how to find the optimal decoupling generator set (DGS) for various subspaces relevant to FTQC, and how to simultaneously decouple them. We focus on stabilizer codes, which represent the largest contribution to the size of the DGS, showing that the intuitive choice comprising the stabilizers and logical operators of the code is in fact optimal, i.e., minimizes a natural cost function associated with the length of DD sequences. Our work brings hybrid DD-FTQC schemes, and their potentially considerable advantages, closer to realization.

Optimally combining dynamical decoupling and quantum error correction

PubMed Central

Paz-Silva, Gerardo A.; Lidar, D. A.

2013-01-01

Quantum control and fault-tolerant quantum computing (FTQC) are two of the cornerstones on which the hope of realizing a large-scale quantum computer is pinned, yet only preliminary steps have been taken towards formalizing the interplay between them. Here we explore this interplay using the powerful strategy of dynamical decoupling (DD), and show how it can be seamlessly and optimally integrated with FTQC. To this end we show how to find the optimal decoupling generator set (DGS) for various subspaces relevant to FTQC, and how to simultaneously decouple them. We focus on stabilizer codes, which represent the largest contribution to the size of the DGS, showing that the intuitive choice comprising the stabilizers and logical operators of the code is in fact optimal, i.e., minimizes a natural cost function associated with the length of DD sequences. Our work brings hybrid DD-FTQC schemes, and their potentially considerable advantages, closer to realization. PMID:23559088

Electronic circuit delivers pulse of high interval stability

NASA Technical Reports Server (NTRS)

Fisher, B.

1966-01-01

Circuit generates a pulse of high interval stability with a complexity level considerably below systems of comparable stability. This circuit is being used as a linear frequency discriminator in the signal conditioner of the Apollo command module.

Formulation and Evaluation of Guggul Lipid Nanovesicles for Transdermal Delivery of Aceclofenac

PubMed Central

Gaur, Praveen Kumar; Mishra, Shikha; Aeri, Vidhu

2014-01-01

Context. Most new drugs have low water solubility and liposome is an important formulation to administer such drugs; however, it is quite unstable and has negligible systemic absorption. Objective. Aceclofenac nanovesicles were made using guggul lipid for formulating stable transdermal formulation. Materials and Methods. Guggul lipid was formulated into vesicles along with cholesterol and dicetyl phosphate using film hydration method. The formulations were analyzed for physicochemical properties and stability. Then its skin permeation and anti-inflammatory activity were determined. Results. Both categories of vesicles (PC and GL) showed optimum physicochemical properties; however, accelerated stability study showed considerable differences. GL-1 was appreciably stable for over 6 months at 4°C. Corresponding gels (PCG-1 and GLG-1) showed C max values at 4.98 and 7.32 μg/mL along with the T max values at 4 and 8 hours, respectively. GLG-1 inhibited edema production by 90.81% in 6 hours. Discussion. PC liposomes are unstable at higher temperature and upon longer storage. The formulation with higher lipid content (GL-1) showed good drug retention after 24 hours and appreciable stability both at higher temperature and for longer duration. Guggul lipid being a planar molecule might be stacked in vesicle wall with cholesterol. Conclusion. The composition of the nanovesicle played an important role in stability and drug permeation. Guggul lipid is suitable for producing stable vesicles. PMID:24672328

Covalent character and electric field dependence of H2-AgX (X = F - I).

PubMed

Li, Xinying

2018-06-16

Mechanisms of Ag-X and Ag…H 2 interactions and stabilities of T-shaped H 2 -AgX (X = F - I) series were investigated at the CCSD(T) level. The "no-density" bond with smaller positive Laplacian and ELF values in interaction regions, as well as considerable delocalization index values, suggest weak covalent "charge-shift" character for the Ag…H 2 interaction. Structure and stability dependence on the electric field were investigated at the MP2 level. Relative total energy curves show obvious parabolic character, and the plots can be fitted by quadratic polynomials as functions of electric field strength.

Perfluorocarbon nanoemulsions with fluorescent, colloidal and magnetic properties

PubMed Central

Janjic, Jelena M.; Shao, Pin; Zhang, Shaojuan; Yang, Xun; Patel, Sravan K.; Bai, Mingfeng

2014-01-01

Bimodal imaging agents that combine magnetic resonance imaging (MRI) and nearinfrared (NIR) imaging formulated as nanoemulsions became increasingly popular for imaging inflammation in vivo. Quality of in vivo imaging using nanoemulsions is directly dependent on their integrity and stability. Here we report the design of nanoemulsions for bimodal imaging, where both photostability and colloidal stability are equally addressed. A highly chemically and photo stable quaterrylenediimide dye was introduced into perfluoro-15-crown-5 ether (PCE) nanoemulsions. The nanoemulsions were prepared with PCE and Miglyol 812N mixed at 1:1 v/v ratio as internal phase stabilized by non-ionic surfactants. Data shows exceptional colloidal stability demonstrated as unchanged droplet size (~130 nm) and polydispersity (<0.15) after 182 days follow up at both 4 and 25 °C. Nanoemulsions also sustained the exposure to mechanical and temperature stress, and prolonged exposure to light without changes in droplet size, 19F signal or fluorescence signal. No toxicity was observed in vitro in model inflammatory cells upon 24 h exposure while confocal microscopy showed that nanoemulsions droplets accumulated in the cytoplasm. Overall, our data demonstrates that design of bimodal imaging agents requires consideration of stability of each imaging component and that of the nanosystem as a whole to achieve excellent imaging performance. PMID:24674463

Perfluorocarbon nanoemulsions with fluorescent, colloidal and magnetic properties.

PubMed

Janjic, Jelena M; Shao, Pin; Zhang, Shaojuan; Yang, Xun; Patel, Sravan K; Bai, Mingfeng

2014-06-01

Bimodal imaging agents that combine magnetic resonance imaging (MRI) and nearinfrared (NIR) imaging formulated as nanoemulsions became increasingly popular for imaging inflammation in vivo. Quality of in vivo imaging using nanoemulsions is directly dependent on their integrity and stability. Here we report the design of nanoemulsions for bimodal imaging, where both photostability and colloidal stability are equally addressed. A highly chemically and photo stable quaterrylenediimide dye was introduced into perfluoro-15-crown-5 ether (PCE) nanoemulsions. The nanoemulsions were prepared with PCE and Miglyol 812N mixed at 1:1 v/v ratio as internal phase stabilized by non-ionic surfactants. Data shows exceptional colloidal stability demonstrated as unchanged droplet size (~130 nm) and polydispersity (<0.15) after 182 days follow up at both 4 and 25 °C. Nanoemulsions also sustained the exposure to mechanical and temperature stress, and prolonged exposure to light without changes in droplet size, (19)F signal or fluorescence signal. No toxicity was observed in vitro in model inflammatory cells upon 24 h exposure while confocal microscopy showed that nanoemulsions droplets accumulated in the cytoplasm. Overall, our data demonstrates that design of bimodal imaging agents requires consideration of stability of each imaging component and that of the nanosystem as a whole to achieve excellent imaging performance. Copyright © 2014 Elsevier Ltd. All rights reserved.

Phase stabilities at a glance: Stability diagrams of nickel dipnictides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bachhuber, F.; School of Chemical Sciences, The University of Auckland, Private Bag 92019, Auckland; Rothballer, J.

2013-12-07

In the course of the recent advances in chemical structure prediction, a straightforward type of diagram to evaluate phase stabilities is presented based on an expedient example. Crystal structures and energetic stabilities of dipnictides NiPn{sub 2} (Pn = N, P, As, Sb, Bi) are systematically investigated by first principles calculations within the framework of density functional theory using the generalized gradient approximation to treat exchange and correlation. These dipnictides show remarkable polymorphism that is not yet understood systematically and offers room for the discovery of new phases. Relationships between the concerned structures including the marcasite, the pyrite, the arsenopyrite/CoSb{sub 2},more » and the NiAs{sub 2} types are highlighted by means of common structural fragments. Electronic stabilities of experimentally known and related AB{sub 2} structure types are presented graphically in so-called stability diagrams. Additionally, competing binary phases are taken into consideration in the diagrams to evaluate the stabilities of the title compounds with respect to decomposition. The main purpose of the stability diagrams is the introduction of an image that enables the estimation of phase stabilities at a single glance. Beyond that, some of the energetically favored structure types can be identified as potential new phases.« less

Ince-Strutt stability charts for ship parametric roll resonance in irregular waves

NASA Astrophysics Data System (ADS)

Zhang, Xiao; Yang, He-zhen; Xiao, Fei; Xu, Pei-ji

2017-08-01

Ince-Strutt stability chart of ship parametric roll resonance in irregular waves is conducted and utilized for the exploration of the parametric roll resonance in irregular waves. Ship parametric roll resonance will lead to large amplitude roll motion and even wreck. Firstly, the equation describing the parametric roll resonance in irregular waves is derived according to Grim's effective theory and the corresponding Ince-Strutt stability charts are obtained. Secondly, the differences of stability charts for the parametric roll resonance in irregular and regular waves are compared. Thirdly, wave phases and peak periods are taken into consideration to obtain a more realistic sea condition. The influence of random wave phases should be taken into consideration when the analyzed points are located near the instability boundary. Stability charts for different wave peak periods are various. Stability charts are helpful for the parameter determination in design stage to better adapt to sailing condition. Last, ship variables are analyzed according to stability charts by a statistical approach. The increase of the metacentric height will help improve ship stability.

Are Anxiety and Depression Just as Stable as Personality During Late Adolescence? Results From a Three-Year Longitudinal Latent Variable Study

PubMed Central

Prenoveau, Jason M.; Craske, Michelle G.; Zinbarg, Richard E.; Mineka, Susan; Rose, Raphael D.; Griffith, James W.

2012-01-01

Although considerable evidence shows that affective symptoms and personality traits demonstrate moderate to high relative stabilities during adolescence and early adulthood, there has been little work done to examine differential stability among these constructs or to study the manner in which the stability of these constructs is expressed. The present study used a three-year longitudinal design in an adolescent/young adult sample to examine the stability of depression symptoms, social phobia symptoms, specific phobia symptoms, neuroticism, and extraversion. When considering one-, two-, and three-year durations, anxiety and personality stabilities were generally similar and typically greater than the stability of depression. Comparison of various representations of a latent variable trait-state-occasion (TSO) model revealed that whereas the full TSO model was the best representation for depression, a trait stability model was the most parsimonious of the best-fitting models for the anxiety and personality constructs. Over three years, the percentages of variance explained by the trait component for the anxiety and personality constructs (73– 84%) were significantly greater than that explained by the trait component for depression (46%). These findings indicate that symptoms of depression are more episodic in nature, whereas symptoms of anxiety are more similar to personality variables in their expression of stability. PMID:21604827

47 CFR 76.1002 - Specific unfair practices prohibited.

Code of Federal Regulations, 2010 CFR

2010-10-01

... reasonable requirements for creditworthiness, offering of service, and financial stability and standards... classes of service in pricing based on credit considerations or financial stability, although any such... technology. Vendors are not permitted to manifest factors such as creditworthiness or financial stability in...

RADIATION PASTEURIZATION OF FRESH FRUITS AND VEGETABLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Truelsen, T.A.

1963-03-01

Use of pasteurizing doses of Co/sup 60/ gamma radiation to increase the stability of fresh strawberries, raspberries, cauliflower, tomatoes, and asparagus was tested. Only with strawberries was it possible to obtain a considerable increase in stability. For all products there appeared to be a close connection between grading for taste and texture. Strawberry samples irradiated with 100, 200, 300, or 400 krad showed, a few days after treatment, no significant differences in scores between treated and untreated berries. However, after storage for 8 days all of the irradiated samples were judged better, and after 14 days, only the samples givenmore » high doses of radiation still appeared to be in better condition. At this time, however, berries from all types of treatment were judged unacceptable. Raspberries exposed to 250 to 500 krad showed deterioration of taste and texture, but 4 days after the berries were exposed to 100 krad they were given better marks than controls. Cauliflower examples exposed to 300 krad were considerably darker in 24 hours, and after 27 days discoloration was very pronounced. Irradiation of tomatoes appeared to impnir the formation of lycopene. Doses of 1000 krad in asparagus caused deterioration of both taste and texture, with best results at a radiation dose of 250 krad. Only in raspberries was it possible for the low doses later in the storage period to raise the taste marks above the level of those given untreated samples. However, the improvement was not sufficient for the increase in stability to be of practical importance. (TCO)« less

Diblock-copolymer-mediated self-assembly of protein-stabilized iron oxide nanoparticle clusters for magnetic resonance imaging.

PubMed

Tähkä, Sari; Laiho, Ari; Kostiainen, Mauri A

2014-03-03

Superparamagnetic iron oxide nanoparticles (SPIONs) can be used as efficient transverse relaxivity (T2 ) contrast agents in magnetic resonance imaging (MRI). Organizing small (D<10 nm) SPIONs into large assemblies can considerably enhance their relaxivity. However, this assembly process is difficult to control and can easily result in unwanted aggregation and precipitation, which might further lead to lower contrast agent performance. Herein, we present highly stable protein-polymer double-stabilized SPIONs for improving contrast in MRI. We used a cationic-neutral double hydrophilic poly(N-methyl-2-vinyl pyridinium iodide-block-poly(ethylene oxide) diblock copolymer (P2QVP-b-PEO) to mediate the self-assembly of protein-cage-encapsulated iron oxide (γ-Fe2 O3 ) nanoparticles (magnetoferritin) into stable PEO-coated clusters. This approach relies on electrostatic interactions between the cationic N-methyl-2-vinylpyridinium iodide block and magnetoferritin protein cage surface (pI≈4.5) to form a dense core, whereas the neutral ethylene oxide block provides a stabilizing biocompatible shell. Formation of the complexes was studied in aqueous solvent medium with dynamic light scattering (DLS) and cryogenic transmission electron microcopy (cryo-TEM). DLS results indicated that the hydrodynamic diameter (Dh ) of the clusters is approximately 200 nm, and cryo-TEM showed that the clusters have an anisotropic stringlike morphology. MRI studies showed that in the clusters the longitudinal relaxivity (r1 ) is decreased and the transverse relaxivity (r2 ) is increased relative to free magnetoferritin (MF), thus indicating that clusters can provide considerable contrast enhancement. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

How Stable Are Human Aesthetic Preferences Across the Lifespan?

PubMed Central

Pugach, Cameron; Leder, Helmut; Graham, Daniel J.

2017-01-01

How stable are human aesthetic preferences, and how does stability change over the lifespan? Here we investigate the stability of aesthetic taste in a cross-sectional study. We employed a simple rank-order preference task using paintings and photographs of faces and landscapes. In each of the four stimulus classes, we find that aesthetic stability generally follows an inverted U-shaped function, with the greatest degree of stability appearing in early to middle adulthood. We propose that one possible interpretation of this result is that it indicates a role for cognitive control (i.e., the ability to adapt cognition to current situations) in the construction of aesthetic taste, since cognitive control performance follows a generally similar trajectory across the lifespan. However, human aesthetic stability is on the whole rather low: even the most stable age groups show ranking changes of at least 1 rank per item over a 2-week span. We discuss possible implications for these findings in terms of existing theories of visual aesthetics and in terms of methodological considerations, though we acknowledge that other interpretations of our results are possible. PMID:28620290

Role of different sensory inputs for maintenance of body posture in sitting rat and rabbit.

PubMed

Deliagina, T; Beloozerova, I N; Popova, L B; Sirota, M G; Swadlow, H A; Grant, G; Orlovsky, G N

2000-10-01

In this paper, we describe the postural activity in sitting rats and rabbits. An animal was positioned on the platform that could be tilted in the frontal plane for up to +/-20-30 degrees, and postural corrections were video recorded. We found that in both rat and rabbit, the postural reactions led to stabilization of the dorsal-side-up trunk orientation. The result of this was that the trunk tilt constituted only approximately 50% (rat) and 25% (rabbit) of the platform tilt. In addition, in the rabbit the head orientation was also stabilized. Trunk stabilization persisted in the animals subjected to the bilateral labyrinthectomy and blindfolding, suggesting that the somatosensory input is primarily responsible for trunk stabilization. Trunk stabilization was due to extension of the limbs on the side moving down, and flexion of the opposite limbs. EMG recordings showed that the limb extension was caused by the active contraction of extensor muscles. We argue that signals from the Golgi tendon organs of the extensor muscles may considerably contribute to elicitation of postural corrective responses to the lateral tilt.

Laser-optical methods for earlier diagnostics of plant and seed diseases in various habitant media taking into consideration anthropogenic and biological pollution

NASA Astrophysics Data System (ADS)

Lisker, Joseph S.; Dmitriev, Andrey P.

1999-12-01

By the method of the computer laser-optical photometry the investigation of the cereal stability for the various diseases taken into consideration the stability of tomato seeds to their interaction with the phytopathogenes and the phytotoxicity of microscopic fungi on the wheat seedlings was carried out. Original result for the investigation of optical-physiological characteristics of plants and seeds are shown.

Effect of sampling rate and record length on the determination of stability and control derivatives

NASA Technical Reports Server (NTRS)

Brenner, M. J.; Iliff, K. W.; Whitman, R. K.

1978-01-01

Flight data from five aircraft were used to assess the effects of sampling rate and record length reductions on estimates of stability and control derivatives produced by a maximum likelihood estimation method. Derivatives could be extracted from flight data with the maximum likelihood estimation method even if there were considerable reductions in sampling rate and/or record length. Small amplitude pulse maneuvers showed greater degradation of the derivative maneuvers than large amplitude pulse maneuvers when these reductions were made. Reducing the sampling rate was found to be more desirable than reducing the record length as a method of lessening the total computation time required without greatly degrading the quantity of the estimates.

Stabilization of protein-protein interactions in drug discovery.

PubMed

Andrei, Sebastian A; Sijbesma, Eline; Hann, Michael; Davis, Jeremy; O'Mahony, Gavin; Perry, Matthew W D; Karawajczyk, Anna; Eickhoff, Jan; Brunsveld, Luc; Doveston, Richard G; Milroy, Lech-Gustav; Ottmann, Christian

2017-09-01

PPIs are involved in every disease and specific modulation of these PPIs with small molecules would significantly improve our prospects of developing therapeutic agents. Both industry and academia have engaged in the identification and use of PPI inhibitors. However in comparison, the opposite strategy of employing small-molecule stabilizers of PPIs is underrepresented in drug discovery. Areas covered: PPI stabilization has not been exploited in a systematic manner. Rather, this concept validated by a number of therapeutically used natural products like rapamycin and paclitaxel has been shown retrospectively to be the basis of the activity of synthetic molecules originating from drug discovery projects among them lenalidomide and tafamidis. Here, the authors cover the growing number of synthetic small-molecule PPI stabilizers to advocate for a stronger consideration of this as a drug discovery approach. Expert opinion: Both the natural products and the growing number of synthetic molecules show that PPI stabilization is a viable strategy for drug discovery. There is certainly a significant challenge to adapt compound libraries, screening techniques and downstream methodologies to identify, characterize and optimize PPI stabilizers, but the examples of molecules reviewed here in our opinion justify these efforts.

Enhanced thermal stability of Cu alloy films by strong interaction between Ni and Zr (or Fe)

NASA Astrophysics Data System (ADS)

Zheng, Yuehong; Li, Xiaona; Cheng, Xiaotian; Li, Zhuming; Liu, Yubo; Dong, Chuang

2018-04-01

Low resistivity, phase stability and nonreactivity with surrounding dielectrics are the key to the application of Cu to ultra-large-scale integrated circuits. Here, a stable solid solution cluster model was introduced to design the composition of barrierless Cu-Ni-Zr (or Fe) seed layers. The third elements Fe and Zr were dissolved into Cu via a second element Ni, which is soluble in both Cu and Zr (or Fe). The films were prepared by magnetron sputtering on the single-crystal p-Si (1 0 0) wafers. Since the diffusion characteristics of the alloying elements are different, the effects of the strong interaction between Ni and Zr (or Fe) on the film’s stability and resistivity were studied. The results showed that a proper addition of Zr-Ni (Zr/Ni  ⩽  0.6/12) into Cu could form a large negative lattice distortion, which inhibits Cu-Si interdiffusion and enhances the stability of Cu film. When Fe-Ni was co-added into Cu, the lattice distortion of Cu reached a lower value, 0.0029 Å  ⩽  |Δa|  ⩽  0.0046 Å, and the films showed poor stability. Therefore, when the model is applied to the composition design of the films, the strong interaction between the elements and the addition ratio should be taken into consideration.

Motion stability of high-speed maglev systems in consideration of aerodynamic effects: a study of a single magnetic suspension system

NASA Astrophysics Data System (ADS)

Wu, Han; Zeng, Xiao-Hui; Yu, Yang

2017-12-01

In this study, the intrinsic mechanism of aerodynamic effects on the motion stability of a high-speed maglev system was investigated. The concept of a critical speed for maglev vehicles considering the aerodynamic effect is proposed. The study was carried out based on a single magnetic suspension system, which is convenient for proposing relevant concepts and obtaining explicit expressions. This study shows that the motion stability of the suspension system is closely related to the vehicle speed when aerodynamic effects are considered. With increases of the vehicle speed, the stability behavior of the system changes. At a certain vehicle speed, the stability of the system reaches a critical state, followed by instability. The speed corresponding to the critical state is the critical speed. Analysis reveals that when the system reaches the critical state, it takes two forms, with two critical speeds, and thus two expressions for the critical speed are obtained. The conditions of the existence of the critical speed were determined, and the effects of the control parameters and the lift coefficient on the critical speed were analyzed by numerical analysis. The results show that the first critical speed appears when the aerodynamic force is upward, and the second critical speed appears when the aerodynamic force is downward. Moreover, both critical speeds decrease with the increase of the lift coefficient.

Study on the stability and reliability of Clinotron at Y-band

NASA Astrophysics Data System (ADS)

Li, Shuang; Wang, Jianguo; Chen, Zaigao; Wang, Guangqiang; Wang, Dongyang; Teng, Yan

2017-11-01

To improve the stability and reliability of Clinotron at the Y-band, some key issues are researched, such as the synchronous operating mode, the heat accumulation on the slow-wave structure, and the errors in micro-fabrication. By analyzing the dispersion relationship, the working mode is determined as the TM10 mode. The problem of heat dissipation on a comb is researched to make a trade-off on the choice of suitable working conditions, making sure that the safety and efficiency of the device are guaranteed simultaneously. The study on the effect of tolerance on device's performance is also conducted to determine the acceptable error during micro-fabrication. The validity of the device and the cost for fabrication are both taken into consideration. At last, the performance of Clinotron under the optimized conditions demonstrates that it can work steadily at 315.89 GHz and the output power is about 12 W, showing advanced stability and reliability.

General instability criterion of laminar velocity distributions

NASA Technical Reports Server (NTRS)

Tollmien, W

1936-01-01

The present paper describes the results of a stability investigation on symmetrical velocity profiles in a channel and of boundary-layer profiles. The effect of friction was assumed to be vanishing and did not occur in the stability consideration so far as it had been resorted to for preparatory asymptotic considerations. Proceeding on very general premises as regards the form of the velocity distribution, a proof was deduced of the elementary theorem that velocity profiles with inflection points are unstable.

High-temperature corrosion of metals in the salt and metallic melts containing rare earths

NASA Astrophysics Data System (ADS)

Karpov, V. V.; Abramov, A. V.; Zhilyakov, A. Yu.; Belikov, S. V.; Volkovich, V. A.; Polovov, I. B.; Rebrin, O. I.

2016-09-01

A complex of independent methods was employed to study the corrosion resistance of molybdenum, zirconium, tantalum and tungsten in chloride, chloride-fluoride and fluoride-oxide melts based on LiCl, CaCl2, NaCl- KCl, LiF, and containing rare earths. Tests were conducted for 30 h at 750-1050 °C. The metals showed excellent corrosion resistance in fused chlorides (the corrosion rates were below 0.0005 g/(m2 h). Despite the presence of chemically active fluoride ions in the chloride-fluoride melts, the metals studied also showed very low corrosion rates, except molybdenum, for which the rate of corrosion was 0,8 g/(m2 h). The corrosion resistance of tantalum was considerably reduced in the fluoride-oxide melts; the corrosion rate was over 1 g/(m2 h) corresponding to the 8-th grade of stability and placing tantalum to the group of "low stability" materials.

High temperature adhesives

NASA Technical Reports Server (NTRS)

St.clair, Terry L.

1991-01-01

The aerospace and electronics industries have an ever increasing need for higher performance materials. In recent years, linear aromatic polyimides have been proven to be a superior class of materials for various applications in these industries. The use of this class of polymers as adhesives is continuing to increase. Several NASA Langley developed polyimides show considerable promise as adhesives because of their high glass transition temperatures, thermal stability, resistance to solvents/water, and their potential for cost effective manufacture.

Insulin pumps and insulin quality--requirements and problems.

PubMed

Brange, J; Havelund, S

1983-01-01

In developing insulin solution suitable for delivery devices the chemical and biological stability, as well as the physical stability, must be taken into consideration. Addition of certain mono- and disaccharides increases the physical stability of neutral insulin solutions, but concurrently the chemical and biological stability decrease to an unacceptable degree. Addition of Ca-ions in low concentrations offers a physiologically acceptable method for stabilizing neutral insulin solutions against heat precipitation without affecting the quality, including the chemical and biological stability.

Modulating secretory pathway pH by proton channel co-expression can increase recombinant protein stability in plants.

PubMed

Jutras, Philippe V; D'Aoust, Marc-André; Couture, Manon M-J; Vézina, Louis-Philippe; Goulet, Marie-Claire; Michaud, Dominique; Sainsbury, Frank

2015-09-01

Eukaryotic expression systems are used for the production of complex secreted proteins. However, recombinant proteins face considerable biochemical challenges along the secretory pathway, including proteolysis and pH variation between organelles. As the use of synthetic biology matures into solutions for protein production, various host-cell engineering approaches are being developed to ameliorate host-cell factors that can limit recombinant protein quality and yield. We report the potential of the influenza M2 ion channel as a novel tool to neutralize the pH in acidic subcellular compartments. Using transient expression in the plant host, Nicotiana benthamiana, we show that ion channel expression can significantly raise pH in the Golgi apparatus and that this can have a strong stabilizing effect on a fusion protein separated by an acid-susceptible linker peptide. We exemplify the utility of this effect in recombinant protein production using influenza hemagglutinin subtypes differentially stable at low pH; the expression of hemagglutinins prone to conformational change in mildly acidic conditions is considerably enhanced by M2 co-expression. The co-expression of a heterologous ion channel to stabilize acid-labile proteins and peptides represents a novel approach to increasing the yield and quality of secreted recombinant proteins in plants and, possibly, in other eukaryotic expression hosts. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Short-Term Stability of Psychopathic Traits in Adolescent Offenders

ERIC Educational Resources Information Center

Lee, Zina; Klaver, Jessica R.; Hart, Stephen D.; Moretti, Marlene M.; Douglas, Kevin S.

2009-01-01

There is considerable debate about the assessment of psychopathic traits in adolescence due in part to questions regarding the stability of traits. We investigated the 6-month stability of psychopathic traits in a sample of 83 male adolescent offenders using an augmented protocol for the Psychopathy Checklist: Youth Version and the self-report…

Transit time affects the community stability of Lactobacillus and Bifidobacterium species in an in vitro model of human colonic microbiotia.

PubMed

Rodes, Laetitia; Paul, Arghya; Coussa-Charley, Michael; Al-Salami, Hani; Tomaro-Duchesneau, Catherine; Fakhoury, Marc; Prakash, Satya

2011-12-01

Retention time, which is analogous to transit time, is an index for bacterial stability in the intestine. Its consideration is of particular importance to optimize the delivery of probiotic bacteria in order to improve treatment efficacy. This study aims to investigate the effect of retention time on Lactobacilli and Bifidobacteria stability using an established in vitro human colon model. Three retention times were used: 72, 96, and 144 h. The effect of retention time on cell viability of different bacterial populations was analyzed with bacterial plate counts and PCR. The proportions of intestinal Bifidobacteria, Lactobacilli, Enterococci, Staphylococci and Clostridia populations, analyzed by plate counts, were found to be the same as that in human colonic microbiota. Retention time in the human colon affected the stability of Lactobacilli and Bifidobacteria communities, with maximum stability observed at 144 h. Therefore, retention time is an important parameter that influences bacterial stability in the colonic microbiota. Future clinical studies on probiotic bacteria formulations should take into consideration gastrointestinal transit parameters to improve treatment efficacy.

Discrete-time stability of continuous-time controller designs for large space structures

NASA Technical Reports Server (NTRS)

Balas, M. J.

1982-01-01

In most of the stable control designs for flexible structures, continuous time is assumed. However, in view of the implementation of the controllers by on-line digital computers, the discrete-time stability of such controllers is an important consideration. In the case of direct-velocity feedback (DVFB), involving negative feedback from collocated force actuators and velocity sensors, it is not immediately apparent how much delay due to digital implementation of DVFB can be tolerated without loss of stability. The present investigation is concerned with such questions. A study is conducted of the discrete-time stability of DVFB, taking into account an employment of Euler's method of approximation of the time derivative. The obtained result gives an indication of the acceptable time-step size for stable digital implementation of DVFB. A result derived in connection with the consideration of the discrete-time stability of stable continuous-time systems provides a general condition under which digital implementation of such a system will remain stable.

A consideration of the use of optical fibers to remotely couple photometers to telescopes

NASA Technical Reports Server (NTRS)

Heacox, William D.

1988-01-01

The possible use of optical fibers to remotely couple photometers to telescopes is considered. Such an application offers the apparent prospect of enhancing photometric stability as a consequence of the benefits of remote operation and decreased sensitivity to image details. A properly designed fiber optic coupler will probably show no significant changes in optical transmisssion due to normal variations in the fiber configuration. It may be more difficult to eliminate configuration-dependent effects on the pupil of the transmitted beam, and thus achieve photometric stability to guiding and seeing errors. In addition, there is some evidence for significant changes in the optical throughputs of fibers over the temperature range normally encountered in astronomical observatories.

Predicting safe sex: Assessment of autoregressive and cross-lagged effects within the Theory of Planned Behavior.

PubMed

Eggers, Sander M; Taylor, Myra; Sathiparsad, Reshma; Bos, Arjan Er; de Vries, Hein

2015-11-01

Despite its popularity, few studies have assessed the temporal stability and cross-lagged effects of the Theory of Planned Behavior factors: Attitude, subjective norms and self-efficacy. For this study, 298 adolescent learners from KwaZulu-Natal, South Africa, filled out a Theory of Planned Behavior questionnaire on teenage pregnancy at baseline and after 6 months. Structural equation modeling showed that there were considerable cross-lagged effects between attitude and subjective norms. Temporal stability was moderate with test-retest correlations ranging from 0.37 to 0.51 and the model was able to predict intentions to have safe sex (R2 = 0.69) Implications for practice and future research are discussed. © The Author(s) 2013.

Stability Error Budget for an Aggressive Coronagraph on a 3.8 m Telescope

NASA Technical Reports Server (NTRS)

Shaklan, Stuart B.; Marchen, Luis; Krist, John; Rud, Mayer

2011-01-01

We evaluate in detail the stability requirements for a band-limited coronagraph with an inner working angle as small as 2 lambda/D coupled to an off-axis, 3.8-m diameter telescope. We have updated our methodologies since presenting a stability error budget for the Terrestrial Planet Finder Coronagraph mission that worked at 4 lambda/D and employed an 8th-order mask to reduce aberration sensitives. In the previous work, we determined the tolerances relative to the total light leaking through the coronagraph. Now, we separate the light into a radial component, which is readily separable from a planet signal, and an azimuthal component, which is easily confused with a planet signal. In the current study, throughput considerations require a 4th-order coronagraph. This, combined with the more aggressive working angle, places extraordinarily tight requirements on wavefront stability and opto-mechanical stability. We find that the requirements are driven mainly by coma that leaks around the coronagraph mask and mimics the localized signal of a planet, and pointing errors that scatter light into the background, decreasing SNR. We also show how the requirements would be relaxed if a low-order aberration detection system could be employed.

Combining Structural Modeling with Ensemble Machine Learning to Accurately Predict Protein Fold Stability and Binding Affinity Effects upon Mutation

PubMed Central

Garcia Lopez, Sebastian; Kim, Philip M.

2014-01-01

Advances in sequencing have led to a rapid accumulation of mutations, some of which are associated with diseases. However, to draw mechanistic conclusions, a biochemical understanding of these mutations is necessary. For coding mutations, accurate prediction of significant changes in either the stability of proteins or their affinity to their binding partners is required. Traditional methods have used semi-empirical force fields, while newer methods employ machine learning of sequence and structural features. Here, we show how combining both of these approaches leads to a marked boost in accuracy. We introduce ELASPIC, a novel ensemble machine learning approach that is able to predict stability effects upon mutation in both, domain cores and domain-domain interfaces. We combine semi-empirical energy terms, sequence conservation, and a wide variety of molecular details with a Stochastic Gradient Boosting of Decision Trees (SGB-DT) algorithm. The accuracy of our predictions surpasses existing methods by a considerable margin, achieving correlation coefficients of 0.77 for stability, and 0.75 for affinity predictions. Notably, we integrated homology modeling to enable proteome-wide prediction and show that accurate prediction on modeled structures is possible. Lastly, ELASPIC showed significant differences between various types of disease-associated mutations, as well as between disease and common neutral mutations. Unlike pure sequence-based prediction methods that try to predict phenotypic effects of mutations, our predictions unravel the molecular details governing the protein instability, and help us better understand the molecular causes of diseases. PMID:25243403

Ab Initio Simulations of Temperature Dependent Phase Stability and Martensitic Transitions in NiTi

NASA Technical Reports Server (NTRS)

Haskins, Justin B.; Thompson, Alexander E.; Lawson, John W.

2016-01-01

For NiTi based alloys, the shape memory effect is governed by a transition from a low-temperature martensite phase to a high-temperature austenite phase. Despite considerable experimental and computational work, basic questions regarding the stability of the phases and the martensitic phase transition remain unclear even for the simple case of binary, equiatomic NiTi. We perform ab initio molecular dynamics simulations to describe the temperature-dependent behavior of NiTi and resolve several of these outstanding issues. Structural correlation functions and finite temperature phonon spectra are evaluated to determine phase stability. In particular, we show that finite temperature, entropic effects stabilize the experimentally observed martensite (B19') and austenite (B2) phases while destabilizing the theoretically predicted (B33) phase. Free energy computations based on ab initio thermodynamic integration confirm these results and permit estimates of the transition temperature between the phases. In addition to the martensitic phase transition, we predict a new transition between the B33 and B19' phases. The role of defects in suppressing these phase transformations is discussed.

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.

Stability region maximization by decomposition-aggregation method. [Skylab stability

NASA Technical Reports Server (NTRS)

Siljak, D. D.; Cuk, S. M.

1974-01-01

This work is to improve the estimates of the stability regions by formulating and resolving a proper maximization problem. The solution of the problem provides the best estimate of the maximal value of the structural parameter and at the same time yields the optimum comparison system, which can be used to determine the degree of stability of the Skylab. The analysis procedure is completely computerized, resulting in a flexible and powerful tool for stability considerations of large-scale linear as well as nonlinear systems.

Electrolytes for Hydrocarbon Air Fuel Cells.

DTIC Science & Technology

1981-01-01

finding an electrolyte with sufficient electrochemical activity and stability to replace phosphoric acid in direct oxidation fuel cells. Commercially...and stability to replace phosphoric acid in direct oxidation fuel cells. Commercially available materials received prime consideration. However, ECO’s...was to obtain an electrolyte with sufficient electrochemical activity and stability to replace phosphoric acid in direct oxidation fuel cells. This

Evolution of branched regulatory genetic pathways: directional selection on pleiotropic loci accelerates developmental system drift.

PubMed

Johnson, Norman A; Porter, Adam H

2007-01-01

Developmental systems are regulated by a web of interacting loci. One common and useful approach in studying the evolution of development is to focus on classes of interacting elements within these systems. Here, we use individual-based simulations to study the evolution of traits controlled by branched developmental pathways involving three loci, where one locus regulates two different traits. We examined the system under a variety of selective regimes. In the case where one branch was under stabilizing selection and the other under directional selection, we observed "developmental system drift": the trait under stabilizing selection showed little phenotypic change even though the loci underlying that trait showed considerable evolutionary divergence. This occurs because the pleiotropic locus responds to directional selection and compensatory mutants are then favored in the pathway under stabilizing selection. Though developmental system drift may be caused by other mechanisms, it seems likely that it is accelerated by the same underlying genetic mechanism as that producing the Dobzhansky-Muller incompatibilities that lead to speciation in both linear and branched pathways. We also discuss predictions of our model for developmental system drift and how different selective regimes affect probabilities of speciation in the branched pathway system.

Development of Eco-friendly Soy Protein Isolate Films with High Mechanical Properties through HNTs, PVA, and PTGE Synergism Effect

PubMed Central

Liu, Xiaorong; Song, Ruyuan; Zhang, Wei; Qi, Chusheng; Zhang, Shifeng; Li, Jianzhang

2017-01-01

This study was to develop novel soy protein isolate-based films for packaging using halloysite nanotubes (HNTs), poly-vinyl alcohol (PVA), and 1,2,3-propanetriol-diglycidyl-ether (PTGE). The structural, crystallinity, opacity, micromorphology, and thermal stability of the resultant SPI/HNTs/PVA/PTGE film were analyzed by the Attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), UV-Vis spectrophotometry, scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA). The SPI/HNTs/PVA/PTGE film illustrated that HNTs were uniformly dispersed in the SPI matrix and the thermal stability of the film was enhanced. Furthermore, the tensile strength (TS) of the SPI/HNTs/PVA/PTGE film was increased by 329.3% and the elongation at the break (EB) remained unchanged. The water absorption (WA) and the moisture content (MC) were decreased by 5.1% and 10.4%, respectively, compared to the unmodified film. The results highlighted the synergistic effects of SPI, HNTs, PVA, and PTGE on the mechanical properties, water resistance, and thermal stability of SPI films, which showed excellent strength and flexibility. In short, SPI films prepared from HNTs, PVA, and PTGE showed considerable potential as packaging materials. PMID:28281634

Ultimate linewidth reduction of a semiconductor laser frequency-stabilized to a Fabry-Pérot interferometer.

PubMed

Bahoura, Messaoud; Clairon, André

2003-11-01

We report a theoretical dynamical analysis on effect of semiconductor laser phase noise on the achievable linewidth when locked to a Fabry-Pérot cavity fringe using a modulation-demodulation frequency stabilization technique such as the commonly used Pound-Drever-Hall frequency locking scheme. We show that, in the optical domain, the modulation-demodulation operation produces, in the presence of semiconductor laser phase noise, two kinds of excess noise, which could be much above the shot noise limit, namely, conversion noise (PM-to-AM) and intermodulation noise. We show that, in typical stabilization conditions, the ultimate semiconductor laser linewidth reduction can be severely limited by the intermodulation excess noise. The modulation-demodulation operation produces the undesirable nonlinear intermodulation effect through which the phase noise spectral components of the semiconductor laser, in the vicinity of even multiples of the modulation frequency, are downconverted into the bandpass of the frequency control loop. This adds a spurious signal, at the modulation frequency, to the error signal and limits the performance of the locked semiconductor laser. This effect, reported initially in the microwave domain using the quasistatic approximation, can be considerably reduced by a convenient choice of the modulation frequency.

Development of Eco-friendly Soy Protein Isolate Films with High Mechanical Properties through HNTs, PVA, and PTGE Synergism Effect

NASA Astrophysics Data System (ADS)

Liu, Xiaorong; Song, Ruyuan; Zhang, Wei; Qi, Chusheng; Zhang, Shifeng; Li, Jianzhang

2017-03-01

This study was to develop novel soy protein isolate-based films for packaging using halloysite nanotubes (HNTs), poly-vinyl alcohol (PVA), and 1,2,3-propanetriol-diglycidyl-ether (PTGE). The structural, crystallinity, opacity, micromorphology, and thermal stability of the resultant SPI/HNTs/PVA/PTGE film were analyzed by the Attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), UV-Vis spectrophotometry, scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA). The SPI/HNTs/PVA/PTGE film illustrated that HNTs were uniformly dispersed in the SPI matrix and the thermal stability of the film was enhanced. Furthermore, the tensile strength (TS) of the SPI/HNTs/PVA/PTGE film was increased by 329.3% and the elongation at the break (EB) remained unchanged. The water absorption (WA) and the moisture content (MC) were decreased by 5.1% and 10.4%, respectively, compared to the unmodified film. The results highlighted the synergistic effects of SPI, HNTs, PVA, and PTGE on the mechanical properties, water resistance, and thermal stability of SPI films, which showed excellent strength and flexibility. In short, SPI films prepared from HNTs, PVA, and PTGE showed considerable potential as packaging materials.

Attachment of a hydrophobically modified biopolymer at the oil-water interface in the treatment of oil spills.

PubMed

Venkataraman, Pradeep; Tang, Jingjian; Frenkel, Etham; McPherson, Gary L; He, Jibao; Raghavan, Srinivasa R; Kolesnichenko, Vladimir; Bose, Arijit; John, Vijay T

2013-05-01

The stability of crude oil droplets formed by adding chemical dispersants can be considerably enhanced by the use of the biopolymer, hydrophobically modified chitosan. Turbidimetric analyses show that emulsions of crude oil in saline water prepared using a combination of the biopolymer and the well-studied chemical dispersant (Corexit 9500A) remain stable for extended periods in comparison to emulsions stabilized by the dispersant alone. We hypothesize that the hydrophobic residues from the polymer preferentially anchor in the oil droplets, thereby forming a layer of the polymer around the droplets. The enhanced stability of the droplets is due to the polymer layer providing an increase in electrostatic and steric repulsions and thereby a large barrier to droplet coalescence. Our results show that the addition of hydrophobically modified chitosan following the application of chemical dispersant to an oil spill can potentially reduce the use of chemical dispersants. Increasing the molecular weight of the biopolymer changes the rheological properties of the oil-in-water emulsion to that of a weak gel. The ability of the biopolymer to tether the oil droplets in a gel-like matrix has potential applications in the immobilization of surface oil spills for enhanced removal.

Case study comparison of functional vs. organic stability approaches for assessing threat potential at closed landfills in the USA.

PubMed

O'Donnell, Sean T; Caldwell, Michael D; Barlaz, Morton A; Morris, Jeremy W F

2018-05-01

Municipal solid waste (MSW) landfills in the USA are regulated under Subtitle D of the Resource Conservation and Recovery Act (RCRA), which includes the requirement to protect human health and the environment (HHE) during the post-closure care (PCC) period. Several approaches have been published for assessment of potential threats to HHE. These approaches can be broadly divided into organic stabilization, which establishes an inert waste mass as the ultimate objective, and functional stability, which considers long-term emissions in the context of minimizing threats to HHE in the absence of active controls. The objective of this research was to conduct a case study evaluation of a closed MSW landfill using long-term data on landfill gas (LFG) production, leachate quality, site geology, and solids decomposition. Evaluations based on both functional and organic stability criteria were compared. The results showed that longer periods of LFG and leachate management would be required using organic stability criteria relative to an approach based on functional stability. These findings highlight the somewhat arbitrary and overly stringent nature of assigning universal stability criteria without due consideration of the landfill's hydrogeologic setting and potential environmental receptors. This supports previous studies that advocated for transition to a passive or inactive control stage based on a performance-based functional stability framework as a defensible mechanism for optimizing and ending regulatory PCC. Copyright © 2018 Elsevier Ltd. All rights reserved.

Response of a hypersonic boundary layer to freestream pulse acoustic disturbance.

PubMed

Wang, Zhenqing; Tang, Xiaojun; Lv, Hongqing

2014-01-01

The response of hypersonic boundary layer over a blunt wedge to freestream pulse acoustic disturbance was investigated. The stability characteristics of boundary layer for freestream pulse wave and continuous wave were analyzed comparatively. Results show that freestream pulse disturbance changes the thermal conductivity characteristics of boundary layer. For pulse wave, the number of main disturbance clusters decreases and the frequency band narrows along streamwise. There are competition and disturbance energy transfer among different modes in boundary layer. The dominant mode of boundary layer has an inhibitory action on other modes. Under continuous wave, the disturbance modes are mainly distributed near fundamental and harmonic frequencies, while under pulse wave, the disturbance modes are widely distributed in different modes. For both pulse and continuous waves, most of disturbance modes slide into a lower-growth or decay state in downstream, which is tending towards stability. The amplitude of disturbance modes in boundary layer under continuous wave is considerably larger than pulse wave. The growth rate for the former is also considerably larger than the later the disturbance modes with higher growth are mainly distributed near fundamental and harmonic frequencies for the former, while the disturbance modes are widely distributed in different frequencies for the latter.

Response of a Hypersonic Boundary Layer to Freestream Pulse Acoustic Disturbance

PubMed Central

Wang, Zhenqing; Tang, Xiaojun; Lv, Hongqing

2014-01-01

The response of hypersonic boundary layer over a blunt wedge to freestream pulse acoustic disturbance was investigated. The stability characteristics of boundary layer for freestream pulse wave and continuous wave were analyzed comparatively. Results show that freestream pulse disturbance changes the thermal conductivity characteristics of boundary layer. For pulse wave, the number of main disturbance clusters decreases and the frequency band narrows along streamwise. There are competition and disturbance energy transfer among different modes in boundary layer. The dominant mode of boundary layer has an inhibitory action on other modes. Under continuous wave, the disturbance modes are mainly distributed near fundamental and harmonic frequencies, while under pulse wave, the disturbance modes are widely distributed in different modes. For both pulse and continuous waves, most of disturbance modes slide into a lower-growth or decay state in downstream, which is tending towards stability. The amplitude of disturbance modes in boundary layer under continuous wave is considerably larger than pulse wave. The growth rate for the former is also considerably larger than the later the disturbance modes with higher growth are mainly distributed near fundamental and harmonic frequencies for the former, while the disturbance modes are widely distributed in different frequencies for the latter. PMID:24737993

Proceedings from the ETS and ARI Emotional Intelligence Workshop held in Princeton, New Jersey on November 13-15, 2003. Volume 3. Session 5 and Appendix

DTIC Science & Technology

2003-11-01

decreases in standardized test scores Better problem solving and planning More use of higher level reasoning strategies; improved non-verbal reasoning... data were somewhat controversial in terms of interpretation, using a longitudinal data set enabled them to show considerable stability as a result of...cognitive behavioral programs that actually increase the attractiveness of staying. I mean you can do that structurally , through relationships. You can do

Effects of packaging and heat transfer kinetics on drug-product stability during storage under uncontrolled temperature conditions.

PubMed

Nakamura, Toru; Yamaji, Takayuki; Takayama, Kozo

2013-05-01

To predict the stability of pharmaceutical preparations under uncontrolled temperature conditions accurately, a method to compute the average reaction rate constant taking into account the heat transfer from the atmosphere to the product was developed. The average reaction rate constants computed with taken into consideration heat transfer (κ(re) ) were then compared with those computed without taking heat transfer into consideration (κ(in) ). The apparent thermal diffusivity (κ(a) ) exerted some influence on the average reaction rate constant ratio (R, R = κ(re) /κ(in) ). In the regions where the κ(a) was large (above 1 h(-1) ) or very small, the value of R was close to 1. On the contrary, in the middle region (0.001-1 h(-1) ), the value of R was less than 1.The κ(a) of the central part of a large-size container and that of the central part of a paper case of 10 bottles of liquid medicine (100 mL) fell within this middle region. On the basis of the above-mentioned considerations, heat transfer may need to be taken into consideration to enable a more accurate prediction of the stability of actual pharmaceutical preparations under nonisothermal atmospheres. Copyright © 2013 Wiley Periodicals, Inc.

Novel Bifunctional Cyclic Chelator for 89Zr Labeling–Radiolabeling and Targeting Properties of RGD Conjugates

PubMed Central

2015-01-01

Within the last years 89Zr has attracted considerable attention as long-lived radionuclide for positron emission tomography (PET) applications. So far desferrioxamine B (DFO) has been mainly used as bifunctional chelating system. Fusarinine C (FSC), having complexing properties comparable to DFO, was expected to be an alternative with potentially higher stability due to its cyclic structure. In this study, as proof of principle, various FSC-RGD conjugates targeting αvß3 integrins were synthesized using different conjugation strategies and labeled with 89Zr. In vitro stability, biodistribution, and microPET/CT imaging were evaluated using [89Zr]FSC-RGD conjugates or [89Zr]triacetylfusarinine C (TAFC). Quantitative 89Zr labeling was achieved within 90 min at room temperature. The distribution coefficients of the different radioligands indicate hydrophilic character. Compared to [89Zr]DFO, [89Zr]FSC derivatives showed excellent in vitro stability and resistance against transchelation in phosphate buffered saline (PBS), ethylenediaminetetraacetic acid solution (EDTA), and human serum for up to 7 days. Cell binding studies and biodistribution as well as microPET/CT imaging experiments showed efficient receptor-specific targeting of [89Zr]FSC-RGD conjugates. No bone uptake was observed analyzing PET images indicating high in vivo stability. These findings indicate that FSC is a highly promising chelator for the development of 89Zr-based PET imaging agents. PMID:25941834

A quality evaluation of stabilization of rotation frequency of gas-diesel engines when using an adaptive automatic control system

NASA Astrophysics Data System (ADS)

Zhilenkov, A. A.; Efremov, A. A.

2017-02-01

A possibility of quality improvement of stabilization of rotation frequency of the gas-diesels used as prime mover of generator set in the multigenerator units working for abruptly variable load of large power is considered. An evaluation is made on the condition of fuzzy controller use developed and described by the authors in a number of articles. An evaluation has shown that theoretically, the revolution range of a gas-diesel engine may be reduced 25-30 times in case of optimal settings of the controller in the whole power range. The results of modelling showing a considerable quality improvement of transient processes in the investigated system during a sharp change of loading are presented in this article.

Twenty kW fuel cell units of compact design. Part 4: Accompanying research and development

NASA Astrophysics Data System (ADS)

Mund, K.

1980-10-01

Models describing the electrochemical kinetics at porous H2 and O2 electrodes using Raney nickel and silver catalysts were developed and their parameters determined by means of stationary and impedance measurements. A correct description of the hydrogen electrode with a Raney nickel catalyst is shown to encompass proper consideration of both diffusion in the pore electrolyte and surface diffusion. Impedance measurements yield a surface diffusion coefficient of 10 sub-8 cm2 S sub-1. The addition of titanium to the catalyst results in decreased electrode polarization and higher stability. Highly active doped silver catalysts are shown to allow high current densities and diaphragm resistances as low as 3 ohm cm at the oxygen electrode. Service tests show adequate stability of the catalysts.

Feasibility of biochar manufactured from organic wastes on the stabilization of heavy metals in a metal smelter contaminated soil.

PubMed

Abdelhafez, Ahmed A; Li, Jianhua; Abbas, Mohamed H H

2014-12-01

The main objectives of the current study were to evaluate the potential effects of biochar derived from sugar cane bagasse (SC-BC) and orange peel (OP-BC) on improving the physicochemical properties of a metal smelter contaminated soil, and determining its potentiality for stabilizing Pb and As in soil. To achieve these goals, biochar was produced in a small-scale biochar producing plant, and an incubation experiment was conducted using a silt loam metal-contaminated soil treated with different application rates of biochar (0-10% w/w). The obtained results showed that, the addition of SC-BC and OP-BC increased significantly the soil aggregate stability, water-holding capacity, cation exchange capacity, organic matter and N-status in soil. SC-BC considerably decreased the solubility of Pb to values lower than the toxic regulatory level of the toxicity characteristics leaching procedure extraction (5 mg L(-1)). The rise in soil pH caused by biochar application, and the increase of soil organic matter transformed the labile Pb into less available fractions i.e. "Fe-Mn oxides" and "organic" bound fractions. On the other hand, As was desorbed from Fe-Mn oxides, which resulted in greater mobility of As in the treated soil. We concluded that SC-BC and OP-BC could be used successfully for remediating soils highly contaminated with Pb. However, considerable attention should be paid when using it in soil contaminated with As. Copyright © 2014 Elsevier Ltd. All rights reserved.

Behavioral and neural stability of attention bias to threat in healthy adolescents

PubMed Central

Britton, Jennifer C.; Sequeira, Stefanie; Ronkin, Emily G.; Chen, Gang; Bar-Haim, Yair; Shechner, Tomer; Ernst, Monique; Fox, Nathan A.; Leibenluft, Ellen; Pine, Daniel S.

2016-01-01

Considerable translational research on anxiety examines attention bias to threat and the efficacy of attention training in reducing symptoms. Imaging research on the stability of brain functions engaged by attention bias tasks could inform such research. Perturbed fronto-amygdala function consistently arises in attention bias research on adolescent anxiety. The current report examines the stability of the activation and functional connectivity of these regions on the dot-probe task. Functional magnetic resonance imaging (fMRI) activation and connectivity data were acquired with the dot-probe task in 39 healthy youth (f =18, Mean Age = 13.71 years, SD = 2.31) at two time points, separated by approximately nine weeks. Intraclass-correlations demonstrate good reliability in both neural activation for the ventrolateral PFC and task-specific connectivity for fronto-amygdala circuitry. Behavioral measures showed generally poor test-retest reliability. These findings suggest potential avenues for future brain imaging work by highlighting brain circuitry manifesting stable functioning on the dot-probe attention bias task. PMID:27129757

An extended car-following model considering the appearing probability of truck and driver's characteristics

NASA Astrophysics Data System (ADS)

Rong, Ying; Wen, Huiying

2018-05-01

In this paper, the appearing probability of truck is introduced and an extended car-following model is presented to analyze the traffic flow based on the consideration of driver's characteristics, under honk environment. The stability condition of this proposed model is obtained through linear stability analysis. In order to study the evolution properties of traffic wave near the critical point, the mKdV equation is derived by the reductive perturbation method. The results show that the traffic flow will become more disorder for the larger appearing probability of truck. Besides, the appearance of leading truck affects not only the stability of traffic flow, but also the effect of other aspects on traffic flow, such as: driver's reaction and honk effect. The effects of them on traffic flow are closely correlated with the appearing probability of truck. Finally, the numerical simulations under the periodic boundary condition are carried out to verify the proposed model. And they are consistent with the theoretical findings.

Root architecture and wind-firmness of mature Pinus pinaster.

PubMed

Danjon, Frédéric; Fourcaud, Thierry; Bert, Didier

2005-11-01

This study aims to link three-dimensional coarse root architecture to tree stability in mature timber trees with an average of 1-m rooting depth. Undamaged and uprooted trees were sampled in a stand damaged by a storm. Root architecture was measured by three-dimensional (3-D) digitizing. The distribution of root volume by root type and in wind-oriented sectors was analysed. Mature Pinus pinaster root systems were organized in a rigid 'cage' composed of a taproot, the zone of rapid taper of horizontal surface roots and numerous sinkers and deep roots, imprisoning a large mass of soil and guyed by long horizontal surface roots. Key compartments for stability exhibited strong selective leeward or windward reinforcement. Uprooted trees showed a lower cage volume, a larger proportion of oblique and intermediate depth horizontal roots and less wind-oriented root reinforcement. Pinus pinaster stability on moderately deep soils is optimized through a typical rooting pattern and a considerable structural adaptation to the prevailing wind and soil profile.

A Fluid Pulse on the Hikurangi Subduction Margin: Evidence From a Heat Flux Transect Across the Upper Limit of Gas Hydrate Stability

NASA Astrophysics Data System (ADS)

Pecher, I. A.; Villinger, H.; Kaul, N.; Crutchley, G. J.; Mountjoy, J. J.; Huhn, K.; Kukowski, N.; Henrys, S. A.; Rose, P. S.; Coffin, R. B.

2017-12-01

A transect of seafloor heat probe measurements on the Hikurangi Margin shows a significant increase of thermal gradients upslope of the updip limit of gas hydrate stability at the seafloor. We interpret these anomalously high thermal gradients as evidence for a fluid pulse leading to advective heat flux, while endothermic cooling from gas hydrate dissociation depresses temperatures in the hydrate stability field. Previous studies predict a seamount on the subducting Pacific Plate to cause significant overpressure beneath our study area, which may be the source of the fluid pulse. Double-bottom simulating reflections are present in our study area and likely caused by uplift based on gas hydrate phase boundary considerations, although we cannot exclude a thermogenic origin. We suggest that uplift may be associated with the leading edge of the subducting seamount. Our results provide further evidence for the transient nature of fluid expulsion in subduction zones.

Effect of sterilization on the physical stability of brimonidine-loaded solid lipid nanoparticles and nanostructured lipid carriers.

PubMed

El-Salamouni, Noha S; Farid, Ragwa M; El-Kamel, Amal H; El-Gamal, Safaa S

2015-12-30

Nanoparticulate delivery systems have recently been under consideration for topical ophthalmic drug delivery. Brimonidine base-loaded solid lipid nanoparticles and nanostructured lipid carrier formulations were prepared using glyceryl monostearate as solid lipid and were evaluated for their physical stability following sterilization by autoclaving at 121°C for 15min. The objective of this work was to evaluate the effect of autoclaving on the physical appearance, particle size, polydispersity index, zeta potential, entrapment efficiency and particle morphology of the prepared formulations, compared to non-autoclaved ones. Results showed that, autoclaving at 121°C for 15min allowed the production of physically stable formulations in nanometric range, below 500nm suitable for ophthalmic application. Moreover, the autoclaved samples appeared to be superior to non-autoclaved ones, due to their increased zeta potential values, indicating a better physical stability. As well as, increased amount of brimonidine base entrapped in the tested formulations. Copyright © 2015 Elsevier B.V. All rights reserved.

Aqueous and Ethanolic Valeriana officinalis Extracts Change the Binding of Ligands to Glutamate Receptors

PubMed Central

Del Valle-Mojica, Lisa M.; Cordero-Hernández, José M.; González-Medina, Giselle; Ramos-Vélez, Igmeris; Berríos-Cartagena, Nairimer; Torres-Hernández, Bianca A.; Ortíz, José G.

2011-01-01

The effects of two valerian extracts (aqueous and hydroalcoholic) were investigated through [3H]Glutamate ([3H]Glu) and [3H]Fluorowillardine ([3H]FW) receptor binding assays using rat synaptic membranes in presence of different receptor ligands. In addition, the extract stability was monitored spectrophotometrically. Both extracts demonstrated interaction with ionotropic glutamate receptors (iGluRs). However, the extracts displayed considerable differences in receptor selectivity. The hydroalcoholic extract selectively interacted with quisqualic acid (QA), group I metabotropic glutamate receptor (mGluR) ligand, while the aqueous extract did not alter the binding of QA. The stability of the extracts was examined during several weeks. Freshly prepared extract inhibited 38–60% of [3H]FW binding (AMPA). After 10 days, the aqueous extract inhibited 85% of [3H]FW binding while the hydroalcoholic extract markedly potentiated (200%) [3H]FW binding to AMPA receptors. Thus, our results showed that factors such as extraction solvent and extract stability determine the selectivity for glutamate receptor (GluR) interactions. PMID:21151614

Aqueous and Ethanolic Valeriana officinalis Extracts Change the Binding of Ligands to Glutamate Receptors.

PubMed

Del Valle-Mojica, Lisa M; Cordero-Hernández, José M; González-Medina, Giselle; Ramos-Vélez, Igmeris; Berríos-Cartagena, Nairimer; Torres-Hernández, Bianca A; Ortíz, José G

2011-01-01

The effects of two valerian extracts (aqueous and hydroalcoholic) were investigated through [(3)H]Glutamate ([(3)H]Glu) and [(3)H]Fluorowillardine ([(3)H]FW) receptor binding assays using rat synaptic membranes in presence of different receptor ligands. In addition, the extract stability was monitored spectrophotometrically. Both extracts demonstrated interaction with ionotropic glutamate receptors (iGluRs). However, the extracts displayed considerable differences in receptor selectivity. The hydroalcoholic extract selectively interacted with quisqualic acid (QA), group I metabotropic glutamate receptor (mGluR) ligand, while the aqueous extract did not alter the binding of QA. The stability of the extracts was examined during several weeks. Freshly prepared extract inhibited 38-60% of [(3)H]FW binding (AMPA). After 10 days, the aqueous extract inhibited 85% of [(3)H]FW binding while the hydroalcoholic extract markedly potentiated (200%) [(3)H]FW binding to AMPA receptors. Thus, our results showed that factors such as extraction solvent and extract stability determine the selectivity for glutamate receptor (GluR) interactions.

Consideration of critical axial properties of pristine and defected carbon nanotubes under compression.

PubMed

Ranjbartoreh, A R; Su, D; Wang, G

2012-06-01

Carbon nanotubes are hexagonally configured carbon atoms in cylindrical structures. Exceptionally high mechanical strength, electrical conductivity, surface area, thermal stability and optical transparency of carbon nanotubes outperformed other known materials in numerous advanced applications. However, their mechanical behaviors under practical loading conditions remain to be demonstrated. This study investigates the critical axial properties of pristine and defected single- and multi-walled carbon nanotubes under axial compression. Molecular dynamics simulation method has been employed to consider the destructive effects of Stone-Wales and atom vacancy defects on mechanical properties of armchair and zigzag carbon nanotubes under compressive loading condition. Armchair carbon nanotube shows higher axial stability than zigzag type. Increase in wall number leads to less susceptibility of multi-walled carbon nanotubes to defects and higher stability of them under axial compression. Atom vacancy defect reveals higher destructive effect than Stone-Wales defect on mechanical properties of carbon nanotubes. Critical axial strain of single-walled carbon nanotube declines by 67% and 26% due to atom vacancy and Stone-Wales defects.

Aeroelastic Tailoring for Stability Augmentation and Performance Enhancements of Tiltrotor Aircraft

NASA Technical Reports Server (NTRS)

Nixon, Mark W.; Piatak, David J.; Corso, Lawrence M.; Popelka, David A.

1999-01-01

The requirements for increased speed and productivity for tiltrotors has spawned several investigations associated with proprotor aeroelastic stability augmentation and aerodynamic performance enhancements. Included among these investigations is a focus on passive aeroelastic tailoring concepts which exploit the anisotropic capabilities of fiber composite materials. Researchers at Langley Research Center and Bell Helicopter have devoted considerable effort to assess the potential for using these materials to obtain aeroelastic responses which are beneficial to the important stability and performance considerations of tiltrotors. Both experimental and analytical studies have been completed to examine aeroelastic tailoring concepts for the tiltrotor, applied either to the wing or to the rotor blades. This paper reviews some of the results obtained in these aeroelastic tailoring investigations and discusses the relative merits associated with these approaches.

Protein stability: a crystallographer’s perspective

PubMed Central

Deller, Marc C.; Kong, Leopold; Rupp, Bernhard

2016-01-01

Protein stability is a topic of major interest for the biotechnology, pharmaceutical and food industries, in addition to being a daily consideration for academic researchers studying proteins. An understanding of protein stability is essential for optimizing the expression, purification, formulation, storage and structural studies of proteins. In this review, discussion will focus on factors affecting protein stability, on a somewhat practical level, particularly from the view of a protein crystallographer. The differences between protein conformational stability and protein compositional stability will be discussed, along with a brief introduction to key methods useful for analyzing protein stability. Finally, tactics for addressing protein-stability issues during protein expression, purification and crystallization will be discussed. PMID:26841758

Design and manufacturing considerations for high-performance gimbals used for land, sea, air, and space

NASA Astrophysics Data System (ADS)

Sweeney, Mike; Redd, Lafe; Vettese, Tom; Myatt, Ray; Uchida, David; Sellers, Del

2015-09-01

High performance stabilized EO/IR surveillance and targeting systems are in demand for a wide variety of military, law enforcement, and commercial assets for land, sea, air, and space. Operating ranges, wavelengths, and angular resolution capabilities define the requirements for EO/IR optics and sensors, and line of sight stabilization. Many materials and design configurations are available for EO/IR pointing gimbals depending on trade-offs of size, weight, power (SWaP), performance, and cost. Space and high performance military aircraft applications are often driven toward expensive but exceptionally performing beryllium and aluminum beryllium components. Commercial applications often rely on aluminum and composite materials. Gimbal design considerations include achieving minimized mass and inertia simultaneous with demanding structural, thermal, optical, and scene stabilization requirements when operating in dynamic operational environments. Manufacturing considerations include precision lapping and honing of ball bearing interfaces, brazing, welding, and casting of complex aluminum and beryllium alloy structures, and molding of composite structures. Several notional and previously developed EO/IR gimbal platforms are profiled that exemplify applicable design and manufacturing technologies.

Stability studies of amphetamine and ephedrine derivatives in urine.

PubMed

Jiménez, C; de la Torre, R; Ventura, M; Segura, J; Ventura, R

2006-10-20

Knowledge of the stability of drugs in biological specimens is a critical consideration for the interpretation of analytical results. Identification of proper storage conditions has been a matter of concern for most toxicology laboratories (both clinical and forensic), and the stability of drugs of abuse has been extensively studied. This concern should be extended to other areas of analytical chemistry like antidoping control. In this work, the stability of ephedrine derivatives (ephedrine, norephedrine, methylephedrine, pseudoephedrine, and norpseudoephedrine), and amphetamine derivatives (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), and 3,4-methylenedioxymethamphetamine (MDMA)) in urine has been studied. Spiked urine samples were prepared for stability testing. Urine samples were quantified by GC/NPD or GC/MS. The homogeneity of each batch of sample was verified before starting the stability study. The stability of analytes was evaluated in sterilized and non-sterilized urine samples at different storage conditions. For long-term stability testing, analyte concentration in urine stored at 4 degrees C and -20 degrees C was determined at different time intervals for 24 months for sterile urine samples, and for 6 months for non-sterile samples. For short-term stability testing, analyte concentration was evaluated in liquid urine stored at 37 degrees C for 7 days. The effect of repeated freezing (at -20 degrees C) and thawing (at room temperature) was also studied in sterile urine for up to three cycles. No significant loss of the analytes under study was observed at any of the investigated conditions. These results show the feasibility of preparing reference materials containing ephedrine and amphetamine derivatives to be used for quality control purposes.

Effects of gliadin addition on the rheological, microscopic and thermal characteristics of wheat gluten.

PubMed

Khatkar, B S; Barak, Sheweta; Mudgil, Deepak

2013-02-01

In the present study, micro-structural, thermal and rheological changes in the gluten network upon addition of gliadins at 5% and 10% levels were investigated using scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC) and dynamic rheometry. The addition of gliadins decreased the peak dough height inferring decrease in dough strength. The dough stability also decreased from 3.20 to 1.40 min upon addition of 10% gliadin to the base flour. The TGA profile and the glass transition behavior of the control gluten and gluten obtained from dough with gliadin added at 5% and 10% levels showed decrease in thermal stability. The SEM micrograph of the control gluten showed foam like protein matrix. As the gliadin percentage in the gluten was increased, the compactness of the gluten structure reduced considerably leading to the formation of a more open weak gluten network. Copyright © 2012 Elsevier B.V. All rights reserved.

Annular honeycomb seals: Test results for leakage and rotordynamic coefficients; comparisons to labyrinth and smooth configurations

NASA Technical Reports Server (NTRS)

Childs, Dara W.; Elrod, David; Hale, Keith

1989-01-01

Test results are presented for leakage and rotordynamic coefficients for seven honeycomb seals. All seals have the same radius, length, and clearance; however, the cell depths and diameters are varied. Rotordynamic data, which are presented, consist of the direct and cross-coupled stiffness coefficients and the direct damping coefficients. The rotordynamic-coefficient data show a considerable sensitivity to changes in cell dimensions; however, no clear trends are identifiable. Comparisons of test data for the honeycomb seals with labyrinth and smooth annular seals show the honeycomb seal had the best sealing (minimum leakage) performance, followed in order by the labyrinth and smooth seals. For prerotated fluid entering the seal, in the direction of shaft rotation, the honeycomb seal has the best rotordynamic stability followed in order by the labyrinth and smooth. For no prerotation, or fluid prerotation against shaft rotation, the labyrinth seal has the best rotordynamic stability followed in order by the smooth and honeycomb seals.

Dynamics of unforced and vertically forced rocking elliptical and semi-elliptical disks

NASA Astrophysics Data System (ADS)

Wang, Xue-She; Mazzoleni, Michael J.; Mann, Brian P.

2018-03-01

This paper presents the results of an investigation on the dynamics of unforced and vertically forced rocking elliptical and semi-elliptical disks. The full equation of motion for both rocking disks is derived from first principles. For unforced behavior, Lamb's method is used to derive the linear natural frequency of both disks, and harmonic balance is used to determine their amplitude-dependent rocking frequencies. A stability analysis then reveals that the equilibria and stability of the two disks are considerably different, as the semi-elliptical disk has a super-critical pitchfork bifurcation that enables it to exhibit bistable rocking behavior. Experimental studies were conducted to verify the trends. For vertically forced behavior, numerical investigations show the disk's responses to forward and reverse frequency sweeps. Three modes of periodicity were observed for the steady state behavior. Experiments were performed to verify the frequency responses and the presence of the three rocking modes. Comparisons between the experiments and numerical investigations show good agreement.

Reflex Responses to Ligament Loading: Implications for Knee Joint Stability

DTIC Science & Technology

2001-10-25

white noise approach", Prentice-Hall".:, 1978. [15] B. Grenfield and B. Wyke, "Reflex innervation of the temporo - mandibular joint .". Nature. 211(52...selective, depending on the magnitude of the angular perturbation. Keywords - Reflex, Periarticular tissue afferents, Joint stability I...INTRODUCTION Traditionally, joint stability has been considered to be purely mechanical in origin, with little or no consideration of neuromuscular

Crystallization in Micellar Cores: confinement effects and dynamics

NASA Astrophysics Data System (ADS)

Lund, Reidar; Zinn, Thomas; Willner, Lutz; Department of Chemistry, University of Oslo Team; Forschungszentrum Jülich Collaboration

It is well known that liquids confined to small nanoscopic pores and droplets exhibit thermal behavior very different from bulk samples. Here we demonstrate that n-alkanes forming 2-3 nm small micellar cores are considerably affected by confinement in analogue with hard confined systems. We study micelles form by self-assembly of a series of well-defined n-Alkyl-PEO polymers in aqueous solutions. By using small-angle X-ray scattering (SAXS), densiometry and differential scanning calorimetry (DSC), we show that n-alkane exhibit a first-order phase transition i.e. melting. Correlating the structural and thermodynamic data, we find that a melting depression can be accurately described by the Gibbs-Thomson equation. ∖f1 The effect of core crystallinity on the molecular exchange kinetics is investigated using time-resolved small-angle neutron scattering (TR-SANS). We show that there are considerable entropic and enthalpic contributions from the chain packing that affect the kinetic stability of micelles. ∖pard

Space-time slicing in Horndeski theories and its implications for non-singular bouncing solutions

NASA Astrophysics Data System (ADS)

Ijjas, Anna

2018-02-01

In this paper, we show how the proper choice of gauge is critical in analyzing the stability of non-singular cosmological bounce solutions based on Horndeski theories. We show that it is possible to construct non-singular cosmological bounce solutions with classically stable behavior for all modes with wavelengths above the Planck scale where: (a) the solution involves a stage of null-energy condition violation during which gravity is described by a modification of Einstein's general relativity; and (b) the solution reduces to Einstein gravity both before and after the null-energy condition violating stage. Similar considerations apply to galilean genesis scenarios.

Enhanced removal of humic acid from aqueous solution by novel stabilized nano-amorphous calcium phosphate: Behaviors and mechanisms

NASA Astrophysics Data System (ADS)

Jiang, Ling; Li, Yiming; Shao, Yi; Zhang, Yong; Han, Ruiming; Li, Shiyin; Wei, Wei

2018-01-01

Stabilized nano-amorphous calcium phosphate (nACP) was prepared using polyethylene glycol as stabilizer to obtain a nanosized amorphous adsorbent. The produced nACP was evaluated by using XRD, FTIR, SEM and X-ray photoelectron spectroscopy (XPS). The sedimentation test demonstrated that nACP exhibited better stability than crystallized hydroxyapatite. The adsorption efficiency of the nACP material for aqueous humic acid (HA) was evaluated from the point of view of medium pH, adsorption time, temperature, and ionic strength, as well as the presences of metal ions. The results of the study showed very good adsorption performance towards aqueous HA. The Sips modeling results revealed that the stabilized nACP adsorbent had a considerably high adsorption capacity (248.3 mg/g) for HA at 298 K. The adsorption data fitted well into pseudo-second order and Elovich kinetic models. XPS analyses indicated that HA retention on nACP material might be due to the surface complexation reaction between oxygen-containing group and calcium of HA and nACP, respectively. Moreover, the HA adsorption capacity of nACP could still keep more than 86% after four adsorption-desorption cycles. By taking into account all results it was concluded that the nACP adsorbent leveraged its stability in combination with its high uptake capacity to offer a great promise for HA adsorption from water.

Setting cumulative emissions targets to reduce the risk of dangerous climate change

PubMed Central

Zickfeld, Kirsten; Eby, Michael; Matthews, H. Damon; Weaver, Andrew J.

2009-01-01

Avoiding “dangerous anthropogenic interference with the climate system” requires stabilization of atmospheric greenhouse gas concentrations and substantial reductions in anthropogenic emissions. Here, we present an inverse approach to coupled climate-carbon cycle modeling, which allows us to estimate the probability that any given level of carbon dioxide (CO2) emissions will exceed specified long-term global mean temperature targets for “dangerous anthropogenic interference,” taking into consideration uncertainties in climate sensitivity and the carbon cycle response to climate change. We show that to stabilize global mean temperature increase at 2 °C above preindustrial levels with a probability of at least 0.66, cumulative CO2 emissions from 2000 to 2500 must not exceed a median estimate of 590 petagrams of carbon (PgC) (range, 200 to 950 PgC). If the 2 °C temperature stabilization target is to be met with a probability of at least 0.9, median total allowable CO2 emissions are 170 PgC (range, −220 to 700 PgC). Furthermore, these estimates of cumulative CO2 emissions, compatible with a specified temperature stabilization target, are independent of the path taken to stabilization. Our analysis therefore supports an international policy framework aimed at avoiding dangerous anthropogenic interference formulated on the basis of total allowable greenhouse gas emissions. PMID:19706489

Temporal, thermal, and light stability of continuously tunable cholesteric liquid crystal laser array.

PubMed

Jeong, Mi-Yun; Chung, Ki Soo; Wu, Jeong Weon

2014-11-01

Fine-structured polymerized cholesteric liquid crystal (PCLC) wedge laser devices have been realized, with high fine spatial tunability of the lasing wavelength. With resolution less than 0.3 nm in a broad spectral range, more than one hundred laser lines could be obtained in a PCLC cell without extra devices. For practical device application, we studied the stability of the device in detail over time, and in response to strong external light sources, and thermal perturbation. The PCLC wedge cells had good temporal stability for 1 year and showed good stability for strong perturbations, with the lasing wavelength shifting less than 1 nm, while the laser peak intensities decreased by up to 34%, and the high energy band edge of the photonic band gap (PBG) was red shifted 3 nm by temperature perturbation. However, when we consider the entire lasing spectrum for the PCLC cell, the 1-nm wavelength shift may not matter. Although the laser peak intensities were decreased by up to 34% in total for all of the perturbation cases, the remaining 34% laser peak intensity is considerable extent to make use. This good stability of the PCLC laser device is due to the polymerization of the CLC by UV curing. This study will be helpful for practical CLC laser device development.

A field-validated model for in situ transport of polymer-stabilized nZVI and implications for subsurface injection.

PubMed

Krol, Magdalena M; Oleniuk, Andrew J; Kocur, Chris M; Sleep, Brent E; Bennett, Peter; Xiong, Zhong; O'Carroll, Denis M

2013-07-02

Nanoscale zerovalent iron (nZVI) particles have significant potential to remediate contaminated source zones. However, the transport of these particles through porous media is not well understood, especially at the field scale. This paper describes the simulation of a field injection of carboxylmethyl cellulose (CMC) stabilized nZVI using a 3D compositional simulator, modified to include colloidal filtration theory (CFT). The model includes composition dependent viscosity and spatially and temporally variable velocity, appropriate for the simulation of push-pull tests (PPTs) with CMC stabilized nZVI. Using only attachment efficiency as a fitting parameter, model results were in good agreement with field observations when spatially variable viscosity effects on collision efficiency were included in the transport modeling. This implies that CFT-modified transport equations can be used to simulate stabilized nZVI field transport. Model results show that an increase in solution viscosity, resulting from injection of CMC stabilized nZVI suspension, affects nZVI mobility by decreasing attachment as well as changing the hydraulics of the system. This effect is especially noticeable with intermittent pumping during PPTs. Results from this study suggest that careful consideration of nZVI suspension formulation is important for optimal delivery of nZVI which can be facilitated with the use of a compositional simulator.

A Study of Power Systems Stability Enhancement Effects by Excitation Control of Superconducting Generator with High Response Excitation based on Detailed Excitation Circuit Model

NASA Astrophysics Data System (ADS)

Wu, Guohong; Shirato, Hideyuki

SCG (Superconducting Generator) has a superconducting field winding, which leads to many advantages such as small size, high generation efficiency, low impedance, and so on, and be considered as one of the candidates to meet the needs of high stability and high efficiency in the future power system networks. SCG with high response excitation is especially expected to be able to enhance the transient stability of power system by its SMES (Superconducting Magnetic Energy System) effect. The SMES effect of SCG is recognized that its behaviors are dominated by the structures and controls of its excitation system. For this reason, in order to verify exactly how the SMES effect of SCG influences on the power system stability, the electrical circuits of SCG high response excitation are modeled in detail for conducting digital simulation, and its influence on excitation voltage and active power output of SCG are discussed as well. The simulation results with a typical one machine - infinite bus power system model shows that the SMES effect can be certainly obtained when its exciting power is supplied from SCG terminal bus and may considerably lead to an improvement of power system transient stability.

Setting cumulative emissions targets to reduce the risk of dangerous climate change.

PubMed

Zickfeld, Kirsten; Eby, Michael; Matthews, H Damon; Weaver, Andrew J

2009-09-22

Avoiding "dangerous anthropogenic interference with the climate system" requires stabilization of atmospheric greenhouse gas concentrations and substantial reductions in anthropogenic emissions. Here, we present an inverse approach to coupled climate-carbon cycle modeling, which allows us to estimate the probability that any given level of carbon dioxide (CO2) emissions will exceed specified long-term global mean temperature targets for "dangerous anthropogenic interference," taking into consideration uncertainties in climate sensitivity and the carbon cycle response to climate change. We show that to stabilize global mean temperature increase at 2 degrees C above preindustrial levels with a probability of at least 0.66, cumulative CO2 emissions from 2000 to 2500 must not exceed a median estimate of 590 petagrams of carbon (PgC) (range, 200 to 950 PgC). If the 2 degrees C temperature stabilization target is to be met with a probability of at least 0.9, median total allowable CO2 emissions are 170 PgC (range, -220 to 700 PgC). Furthermore, these estimates of cumulative CO2 emissions, compatible with a specified temperature stabilization target, are independent of the path taken to stabilization. Our analysis therefore supports an international policy framework aimed at avoiding dangerous anthropogenic interference formulated on the basis of total allowable greenhouse gas emissions.

Shear flow behaviour and emulsion-stabilizing effect of natural polysaccharide-protein gum in aqueous system and oil/water (O/W) emulsion.

PubMed

Amid, Bahareh Tabatabaee; Mirhosseini, Hamed

2013-03-01

The main objective of the current work was to characterize the shear rheological flow behaviour and emulsifying properties of the natural biopolymer from durian seed. The present study revealed that the extraction condition significantly affected the physical and functional characteristics of the natural biopolymer from durian seed. The dynamic oscillatory test indicated that the biopolymer from durian seed showed more gel (or solid) like behaviour than the viscous (or liquid) like behaviour (G'>G″) at a relatively high concentration (20%) in the fixed frequency (0.1 Hz). This might be explained by the fact that the gum coils disentangle at low frequencies during the long period of oscillation, thus resulting in more gel like behaviour than the viscous like behaviour. The average droplet size of oil in water (O/W) emulsions stabilized by durian seed gum significantly varied from 0.42 to 7.48 μm. The results indicated that O/W emulsions showed significant different stability after 4 months storage. This might be interpreted by the considerable effect of the extraction condition on the chemical and molecular structure of the biopolymer, thus affecting its emulsifying capacity. The biopolymer extracted by using low water to seed (W/S) ratio at the low temperature under the alkaline condition showed a relatively high emulsifying activity in O/W emulsion. Copyright © 2012 Elsevier B.V. All rights reserved.

Visco-instability of shear viscoelastic collisional dusty plasma systems

NASA Astrophysics Data System (ADS)

Mahdavi-Gharavi, M.; Hajisharifi, K.; Mehidan, H.

2018-04-01

In this paper, the stability of Newtonian and non-Newtonian viscoelastic collisional shear-velocity dusty plasmas is studied, using the framework of a generalized hydrodynamic (GH) model. Motivated by Banerjee et al.'s work (Banerjee et al., New J. Phys., vol. 12 (12), 2010, p. 123031), employing linear perturbation theory as well as the local approximation method in the inhomogeneous direction, the dispersion relations of the Fourier modes are obtained for Newtonian and non-Newtonian dusty plasma systems in the presence of a dust-neutral friction term. The analysis of the obtained dispersion relation in the non-Newtonian case shows that the inhomogeneous viscosity force depending on the velocity shear profile can be the genesis of a free energy source which leads the shear system to be unstable. Study of the dust-neutral friction effect on the instability of the considered systems using numerical analysis of the dispersion relation in the Newtonian case demonstrates that the maximum growth rate decreases considerably by increasing the collision frequency in the hydrodynamic regime, while this reduction can be neglected in the kinetic regime. Results show a more significant stabilization role of the dust-neutral friction term in the non-Newtonian cases, through decreasing the maximum growth rate at any fixed wavenumber and construction of the instable wavenumber region. The results of the present investigation will greatly contribute to study of the time evolution of viscoelastic laboratory environments with externally applied shear; where in these experiments the dust-neutral friction process can play a considerable role.

Rice industrial processing worldwide and impact on macro- and micronutrient content, stability, and retention

USDA-ARS?s Scientific Manuscript database

Various processing methods are used in the food industry worldwide to produce numerous rice products with desirable sensory qualities based on cultural and cooking preferences and nutritional considerations. The processes result in variable degrees of macro- and micronutrient content, stability, and...

Computer aided modeling of soil mix designs to predict characteristics and properties of stabilized road bases.

DOT National Transportation Integrated Search

2009-07-01

"Considerable data exists for soils that were tested and documented, both for native properties and : properties with pozzolan stabilization. While the data exists there was no database for the Nebraska : Department of Roads to retrieve this data for...

Benchmarking the stability of human detergent-solubilised voltage-gated sodium channels for structural studies using eel as a reference

PubMed Central

Slowik, Daria; Henderson, Richard

2015-01-01

With the ultimate goal of detailed structural analysis of mammalian and particularly human voltage-gated sodium channels (VGSCs), we have investigated the relative stability of human and rat VGSCs and compared them with electric eel VGSC. We found that NaV1.3 from rat was the most stable after detergent solubilisation. The order of stability was rNaV1.3 > hNaV1.2 > hNaV1.1 > hNaV1.6 > hNaV1.3 > hNaV1.4. However, a comparison with the VGSC from Electrophorus electricus, which is most similar to NaV1.4, shows that the eel VGSC is considerably more stable in detergent than the human VGSCs examined. We conclude that current methods of structural analysis, such as single particle electron cryomicroscopy (cryoEM), may be most usefully targeted to eel VGSC or rNaV1.3, but that structural analysis on the full spectrum of VGSCs, by methods that require greater stability such as crystallisation and X-ray crystallography, will require further stabilisation of the channel. PMID:25838126

Cholesterol-directed nanoparticle assemblies based on single amino acid peptide mutations activate cellular uptake and decrease tumor volume† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c7sc02616a Click here for additional data file.

PubMed Central

Li, Shang; Zou, Rongfeng; Tu, Yaoquan

2017-01-01

Peptide drugs have been difficult to translate into effective therapies due to their low in vivo stability. Here, we report a strategy to develop peptide-based therapeutic nanoparticles by screening a peptide library differing by single-site amino acid mutations of lysine-modified cholesterol. Certain cholesterol-modified peptides are found to promote and stabilize peptide α-helix formation, resulting in selectively cell-permeable peptides. One cholesterol-modified peptide self-assembles into stable nanoparticles with considerable α-helix propensity stabilized by intermolecular van der Waals interactions between inter-peptide cholesterol molecules, and shows 68.3% stability after incubation with serum for 16 h. The nanoparticles in turn interact with cell membrane cholesterols that are disproportionately present in cancer cell membranes, inducing lipid raft-mediated endocytosis and cancer cell death. Our results introduce a strategy to identify peptide nanoparticles that can effectively reduce tumor volumes when administered to in in vivo mice models. Our results also provide a simple platform for developing peptide-based anticancer drugs. PMID:29163910

The effect of charge-introduction mutations on E. coli thioredoxin stability.

PubMed

Perez-Jimenez, Raul; Godoy-Ruiz, Raquel; Ibarra-Molero, Beatriz; Sanchez-Ruiz, Jose M

2005-04-01

Technological applications of proteins are often hampered by their low-stability and, consequently, the development of procedures for protein stabilization is of considerable biotechnological interest. Here, we use simple electrostatics to determine positions in E. coli thioredoxin at which mutations that introduce new charged residues are expected to lead to stability enhancement. We also obtain the corresponding mutants and characterize their stability using differential scanning calorimetry. The results are interpreted in terms of the accessibility in the native structure of the mutated residues and the potential effect of the mutations on the residual structure of the denatured state.

Manipulating semiconductor colloidal stability through doping.

PubMed

Fleharty, Mark E; van Swol, Frank; Petsev, Dimiter N

2014-10-10

The interface between a doped semiconductor material and electrolyte solution is of considerable fundamental interest, and is relevant to systems of practical importance. Both adjacent domains contain mobile charges, which respond to potential variations. This is exploited to design electronic and optoelectronic sensors, and other enabling semiconductor colloidal materials. We show that the charge mobility in both phases leads to a new type of interaction between semiconductor colloids suspended in aqueous electrolyte solutions. This interaction is due to the electrostatic response of the semiconductor interior to disturbances in the external field upon the approach of two particles. The electrostatic repulsion between two charged colloids is reduced from the one governed by the charged groups present at the particles surfaces. This type of interaction is unique to semiconductor particles and may have a substantial effect on the suspension dynamics and stability.

Acetylation and characterization of banana (Musa paradisiaca) starch.

PubMed

Bello-Pérez, L A; Contreras-Ramos, S M; Jìmenez-Aparicio, A; Paredes-López, O

2000-01-01

Banana native starch was acetylated and some of its functional properties were evaluated and compared to corn starch. In general, acetylated banana starch presented higher values in ash, protein and fat than corn acetylated starch. The modified starches had minor tendency to retrogradation assessed as % transmittance of starch pastes. At high temperature acetylated starches presented a water retention capacity similar to their native counterpart. The acetylation considerably increased the solubility of starches, and a similar behavior was found for swelling power. When freeze-thaw stability was studied, acetyl banana starch drained approximately 60% of water in the first and second cycles, but in the third and fourth cycles the percentage of separated water was low. However, acetyl corn starch showed lower freeze-thaw stability than the untreated sample. The modification increased the viscosity of banana starch pastes.

Study of thermal stability of Cu{sub 2}Se thermoelectric material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bohra, Anil, E-mail: anilbohra786@gmail.com; Bhatt, Ranu; Bhattacharya, Shovit

2016-05-23

Sustainability of thermoelectric parameter in operating temperature range is a key consideration factor for fabricating thermoelectric generator or cooler. In present work, we have studied the stability of thermoelectric parameter of Cu{sub 2}Se within the temperature range of 50-800°C. Temperature dependent Seebeck coefficients and electrical resistivity measurement are performed under three continuous thermal cycles. X-ray diffraction pattern shows the presence of mixed cubic-monoclinic Cu{sub 2}Se phase in bare pellet which transforms to pure α-Cu{sub 2}Se phase with repeating thermal cycle. Significant enhancement in Seebeck coefficient and electrical resistivity is observed which may be attributed to (i) Se loss observed inmore » EDS and (ii) the phase transformation from mixed cubic-monoclinic structure to pure monoclinic α-Cu{sub 2}Se phase.« less

Front fingering and complex dynamics driven by the interaction of buoyancy and diffusive instabilities.

PubMed

D'Hernoncourt, J; Merkin, J H; De Wit, A

2007-09-01

Traveling fronts can become transversally unstable either because of a diffusive instability arising when the key variables diffuse at sufficiently different rates or because of a buoyancy-driven Rayleigh-Taylor mechanism when the density jump across the front is statically unfavorable. The interaction between such diffusive and buoyancy instabilities of fronts is analyzed theoretically for a simple model system. Linear stability analysis and nonlinear simulations show that their interplay changes considerably the stability properties with regard to the pure Rayleigh-Taylor or diffusive instabilities of fronts. In particular, an instability scenario can arise which triggers convection around statically stable fronts as a result of differential diffusion. Moreover, spatiotemporal chaos can be observed when both buoyancy and diffusive effects cooperate to destabilize the front. Experimental conditions to test our predictions are suggested.

Thermal Stability of Distillate Hydrocarbon Fuels. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Reddy, Kishenkumar Tadisina; Cernansky, Nicholas P.

1987-01-01

Thermal stability of fuels is expected to become a severe problem in the future due to the anticipated use of broadened specification and alternative fuels. Future fuels will have higher contents of heteroatomic species which are reactive constituents and are known to influence fuel degradation. To study the degradation chemistry of selected model fuels, n-dodecane and n-dodecane plus heteroatoms were aerated by bubbling air through the fuels amd stressed on a modified Jet Fuel Thermal Oxidation Tester facility operating at heater tube temperatures between 200 to 400 C. The resulting samples were fractionated to concentrate the soluble products and then analyzed using gas chromatographic and mass spectrometric techniques to quantify and identify the stable reaction intermediate and product specifically. Heteroatom addition showed that the major soluble products were always the same, with and without heteroatoms, but their distributions varied considerably.

49 CFR Appendix A to Part 611 - Description of Measures Used for Project Evaluation.

Code of Federal Regulations, 2010 CFR

2010-10-01

...) Livable Communities initiatives and local economic activities; (5) Consideration of alternative land use... to fixed guideway systems and extensions may not be limited to a single project). (b) The stability and reliability of the proposed capital financing plan, according to: (i) The stability, reliability...

On the Stability of a Can of Soda

ERIC Educational Resources Information Center

Benesh, G. A.; Olafsen, J. S.

2014-01-01

Stability is often an important consideration in both static and dynamic systems. While introductory students soon grasp the balance of forces required for constant velocity motion, it generally takes longer for them to reliably identify the various torques involved in producing rotational equilibrium. Accelerating systems have the additional…

Influence of atmospheric stability on wind-turbine wakes: A large-eddy simulation study

NASA Astrophysics Data System (ADS)

Abkar, Mahdi; Porté-Agel, Fernando

2014-05-01

In this study, large-eddy simulation is combined with a turbine model to investigate the influence of atmospheric stability on wind-turbine wakes. In the simulations, subgrid-scale turbulent fluxes are parameterized using tuning-free Lagrangian scale-dependent dynamic models. These models optimize the local value of the model coefficients based on the dynamics of the resolved scales. The turbine-induced forces are parameterized with an actuator-disk model with rotation. In this technique, blade-element theory is used to calculate the lift and drag forces acting on the blades. Emphasis is placed on the structure and characteristics of wind-turbine wakes in the cases where the incident flows to the turbine have the same mean velocity at the hub height but different stability conditions. The simulation results show that atmospheric stability has a significant effect on the spatial distribution of the mean velocity deficit and turbulent fluxes in the wake region. In particular, the magnitude of the velocity deficit increases with increasing stability in the atmosphere. In addition, the locations of the maximum turbulence intensity and turbulent stresses are closer to the turbine in convective boundary layer compared with neutral and stable ones. Detailed analysis of the resolved turbulent kinetic energy (TKE) budget inside the wake reveals also that the thermal stratification of the incoming wind considerably affects the magnitude and spatial distribution of the turbulent production, transport term and dissipation rate (transfer of energy to the subgrid scales). It is also shown that the near-wake region can be extended to a farther distance downstream in stable condition compared with neutral and unstable counterparts. In order to isolate the effect of atmospheric stability, additional simulations of neutrally-stratified atmospheric boundary layers are performed with the same turbulence intensity at hub height as convective and stable ones. The results show that the turbulence intensity alone is not sufficient to describe the impact of atmospheric stability on the wind-turbine wakes.

Multidimensional Signal Processing

DTIC Science & Technology

1988-06-01

prove the second half let a - e.f, where e and f are respectively the scattering Schur and reactance Schur factors of a (cf. theroem 2.2.6). Notice...considerations. The fact that 85 this difference in consideration does indeed lead to diverging formulations of stability in multidimensions (m>l), but not in

Tunnel Face Stability and the Effectiveness of Advance Drainage Measures in Water-Bearing Ground of Non-uniform Permeability

NASA Astrophysics Data System (ADS)

Zingg, Sara; Anagnostou, Georg

2018-01-01

Non-uniform permeability may result in complex hydraulic head fields with potentially very high hydraulic gradients close to the tunnel face, which may be adverse for stability depending on the ground strength. Pore pressure relief by drainage measures in advance of the tunnel excavation improves stability, but the effectiveness of drainage boreholes may be low in the case of alternating aquifers and aquitards. This paper analyses the effects of hydraulic heterogeneity and advance drainage quantitatively by means of limit equilibrium computations that take account of the seepage forces acting upon the ground in the vicinity the tunnel face. The piezometric field is determined numerically by means of steady-state, three-dimensional seepage flow analyses considering the heterogeneous structure of the ground and a typical advance drainage scheme consisting of six axial boreholes drilled from the tunnel face. A suite of stability analyses was carried out covering a wide range of heterogeneity scales. The computational results show the effect of the orientation, thickness, location, number and permeability ratio of aquifers and aquitards and provide valuable indications about potentially critical situations, the effectiveness of advance drainage and the adequate arrangement of drainage boreholes. The paper shows that hydraulic heterogeneity results in highly variable face behaviour, even if the shear strength of the ground is constant along the alignment, but ground behaviour is considerably less variable in the presence of advance drainage measures.

Unfolding of chondroitinase ABC Ι is dependent on thermodynamic driving force by kinetically rate constant-amplitude compensation: A stopped-flow fluorescence study.

PubMed

Shirdel, S Akram; Khalifeh, Khosrow; Ranjbar, Bijan; Golestani, Abolfazl; Khajeh, Khosro

2016-11-01

We had previously investigated the role of a loop on the activity and conformational stability of chondroitinase ABC Ι (cABC Ι) by constructing some representative mutants in which a network interaction around Asp 689 was manipulated. Here we extended our study by measuring the proteolytic resistance, long term and thermal stability as well as unfolding kinetics of these variants. Long term stability data at 4 and 25°C for 3 weeks indicates that all mutants remain considerably active at 4°C. Thermoinactivation rates for all variants shows that the wild type (WT) enzyme retained 50% of its activity after 2min keeping at 40°C, while L701T, H700N and H700N/L701T as conformationally stabilized variants, have slower inactivation rate. It was also found that compact and thermodynamically stabilized variants are more resistant to tryptolytic digestion. Also, kinetic curves of chemical unfolding of the enzyme variants from stopped-flow fluorescence measurements were best fitted into a three-exponential function with three rate constants and corresponding amplitudes. We found that the energy barrier of the fast unfolding phase is lower in stabilized variants; while the amplitude of this phase to the whole amplitude of the unfolding reaction is lower than that of destabilized variants, indicating more population of stabilized mutants unfold via slower unfolding phase. We concluded that the rate of local conformational change alone is not the same that is expected from global thermodynamic stability; however the corresponding amplitude can compensate the rate constant toward thermodynamic stability. Copyright © 2016 Elsevier Inc. All rights reserved.

Subtraction method in the Second Random Phase Approximation

NASA Astrophysics Data System (ADS)

Gambacurta, Danilo

2018-02-01

We discuss the subtraction method applied to the Second Random Phase Approximation (SRPA). This method has been proposed to overcome double counting and stability issues appearing in beyond mean-field calculations. We show that the subtraction procedure leads to a considerable reduction of the SRPA downwards shift with respect to the random phase approximation (RPA) spectra and to results that are weakly cutoff dependent. Applications to the isoscalar monopole and quadrupole response in 16O and to the low-lying dipole response in 48Ca are shown and discussed.

Connections Underlying Translation and mRNA Stability.

PubMed

Radhakrishnan, Aditya; Green, Rachel

2016-09-11

Gene expression and regulation in organisms minimally depends on transcription by RNA polymerase and on the stability of the RNA product (for both coding and non-coding RNAs). For coding RNAs, gene expression is further influenced by the amount of translation by the ribosome and by the stability of the protein product. The stabilities of these two classes of RNA, non-coding and coding, vary considerably: tRNAs and rRNAs tend to be long lived while mRNAs tend to be more short lived. Even among mRNAs, however, there is a considerable range in stability (ranging from seconds to hours in bacteria and up to days in metazoans), suggesting a significant role for stability in the regulation of gene expression. Here, we review recent experiments from bacteria, yeast and metazoans indicating that the stability of most mRNAs is broadly impacted by the actions of ribosomes that translate them. Ribosomal recognition of defective mRNAs triggers "mRNA surveillance" pathways that target the mRNA for degradation [Shoemaker and Green (2012) ]. More generally, even the stability of perfectly functional mRNAs appears to be dictated by overall rates of translation by the ribosome [Herrick et al. (1990), Presnyak et al. (2015) ]. Given that mRNAs are synthesized for the purpose of being translated into proteins, it is reassuring that such intimate connections between mRNA and the ribosome can drive biological regulation. In closing, we consider the likelihood that these connections between protein synthesis and mRNA stability are widespread or whether other modes of regulation dominate the mRNA stability landscape in higher organisms. Copyright © 2016. Published by Elsevier Ltd.

Production of superparamagnetic nanobiocatalysts for green chemistry applications.

PubMed

Gasser, Christoph A; Ammann, Erik M; Schäffer, Andreas; Shahgaldian, Patrick; Corvini, Philippe F-X

2016-08-01

Immobilization of enzymes on solid supports is a convenient method for increasing enzymatic stability and enabling enzyme reuse. In the present work, a sorption-assisted surface conjugation method was developed and optimized to immobilize enzymes on the surface of superparamagnetic nanoparticles. An oxidative enzyme, i.e., laccase from Trametes versicolor was used as model enzyme. The immobilization method consists of the production of superparamagnetic nanoparticles by co-precipitation of FeCl2 and FeCl3. Subsequently, the particle surface is modified with an organosilane containing an amino group. Next, the enzymes are adsorbed on the particle surface before a cross-linking agent, i.e., glutaraldehyde is added which links the amino groups on the particle surface with the amino groups of the enzymes and leads to internal cross-linking of the enzymes as well. The method was optimized using response surface methodology regarding optimal enzyme and glutaraldehyde amounts, pH, and reaction times. Results allowed formulation of biocatalysts having high specific enzymatic activity and improved stability. The biocatalysts showed considerably higher stability compared with the dissolved enzymes over a pH range from 3 to 9 and in the presence of several chemical denaturants. To demonstrate the reusability of the immobilized enzymes, they were applied as catalysts for the production of a phenoxazinone dye. Virtually, 100 % of the precursor was transformed to the dye in each of the ten conducted reaction cycles while on average 84.5 % of the enzymatic activity present at the beginning of a reaction cycle was retained after each cycle highlighting the considerable potential of superparamagnetic biocatalysts for application in industrial processes.

Cloning and heterologous expression of cellulose free thermostable xylanase from Bacillus brevis.

PubMed

Goswami, Girish K; Krishnamohan, Medichtrla; Nain, Vikrant; Aggarwal, Chetana; Ramesh, Bandarupalli

2014-01-01

Xylanase gene isolated from Bacillus brevis was expressed in E. coli BL21. Sequencing of the gene (Gen Bank accession number: HQ179986) showed that it belongs to family 11 xylanases. The recombinant xylanase was predominantly secreted to culture medium and showed mesophilic nature (optimum activity at 55°C and pH 7.0). The cell free culture medium exhibited 30 IU/ml xylanse activity. The enzyme did not show any cellulose activity and was active under wide range of temperature (40°C to 80°C) and pH (4 to 9). The enzyme showed considerable thermo stability and regained over 90% of activity, when returned to 55°C after boiling for 5 min. These physiochemical properties of B. brevis xylanse show high potential of its applications in paper and pulp industry.

All-inside, anatomical lateral ankle stabilization for revision and complex primary lateral ankle stabilization: a technique guide.

PubMed

Prissel, Mark A; Roukis, Thomas S

2014-12-01

Lateral ankle instability is a common mechanical problem that often requires surgical management when conservative efforts fail. Historically, myriad open surgical approaches have been proposed. Recently, consideration for arthroscopic management of lateral ankle instability has become popular, with promising results. Unfortunately, recurrent inversion ankle injury following lateral ankle stabilization can occur and require revision surgery. To date, arthroscopic management for revision lateral ankle stabilization has not been described. We present a novel arthroscopic technique combining an arthroscopic lateral ankle stabilization kit with a suture anchor ligament augmentation system for revision as well as complex primary lateral ankle stabilization. © 2014 The Author(s).

Application of electrochemical peroxidation (ECP) process for waste-activated sludge stabilization and system optimization using response surface methodology (RSM).

PubMed

Gholikandi, Gagik Badalians; Kazemirad, Khashayar

2018-03-01

In this study, the performance of the electrochemical peroxidation (ECP) process for removing the volatile suspended solids (VSS) content of waste-activated sludge was evaluated. The Fe 2+ ions required by the process were obtained directly from iron electrodes in the system. The performance of the ECP process was investigated in various operational conditions employing a laboratory-scale pilot setup and optimized by response surface methodology (RSM). According to the results, the ECP process showed its best performance when the pH value, current density, H 2 O 2 concentration and the retention time were 3, 3.2 mA/cm 2 , 1,535 mg/L and 240 min, respectively. In these conditions, the introduced Fe 2+ concentration was approximately 500 (mg/L) and the VSS removal efficiency about 74%. Moreover, the results of the microbial characteristics of the raw and the stabilized sludge demonstrated that the ECP process is able to remove close to 99.9% of the coliforms in the raw sludge during the stabilization process. The energy consumption evaluation showed that the required energy of the ECP reactor (about 1.8-2.5 kWh (kg VSS removed) -1 ) is considerably lower than for aerobic digestion, the conventional waste-activated sludge stabilization method (about 2-3 kWh (kg VSS removed) -1 ). The RSM optimization process showed that the best operational conditions of the ECP process comply with the experimental results, and the actual and the predicted results are in good conformity with each other. This feature makes it possible to predict the introduced Fe 2+ concentrations into the system and the VSS removal efficiency of the process precisely.

Specific effects of Ca2+ ions and molecular structure of β-lactoglobulin interfacial layers that drive macroscopic foam stability† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sm00636a Click here for additional data file.

PubMed Central

Schulze-Zachau, Felix; Nagel, Eva; Engelhardt, Kathrin; Stoyanov, Stefan; Gochev, Georgi; Khristov, Khr.; Mileva, Elena; Exerowa, Dotchi; Miller, Reinhard; Peukert, Wolfgang

2016-01-01

β-Lactoglobulin (BLG) adsorption layers at air–water interfaces were studied in situ with vibrational sum-frequency generation (SFG), tensiometry, surface dilatational rheology and ellipsometry as a function of bulk Ca2+ concentration. The relation between the interfacial molecular structure of adsorbed BLG and the interactions with the supporting electrolyte is additionally addressed on higher length scales along the foam hierarchy – from the ubiquitous air–water interface through thin foam films to macroscopic foam. For concentrations <1 mM, a strong decrease in SFG intensity from O–H stretching bands and a slight increase in layer thickness and surface pressure are observed. A further increase in Ca2+ concentrations above 1 mM causes an apparent change in the polarity of aromatic C–H stretching vibrations from interfacial BLG which we associate to a charge reversal at the interface. Foam film measurements show formation of common black films at Ca2+ concentrations above 1 mM due to considerable decrease of the stabilizing electrostatic disjoining pressure. These observations also correlate with a minimum in macroscopic foam stability. For concentrations >30 mM Ca2+, micrographs of foam films show clear signatures of aggregates which tend to increase the stability of foam films. Here, the interfacial layers have a higher surface dilatational elasticity. In fact, macroscopic foams formed from BLG dilutions with high Ca2+ concentrations where aggregates and interfacial layers with higher elasticity are found, showed the highest stability with much smaller bubble sizes. PMID:27337699

Communications and control for electric power systems: Power system stability applications of artificial neural networks

NASA Technical Reports Server (NTRS)

Toomarian, N.; Kirkham, Harold

1994-01-01

This report investigates the application of artificial neural networks to the problem of power system stability. The field of artificial intelligence, expert systems, and neural networks is reviewed. Power system operation is discussed with emphasis on stability considerations. Real-time system control has only recently been considered as applicable to stability, using conventional control methods. The report considers the use of artificial neural networks to improve the stability of the power system. The networks are considered as adjuncts and as replacements for existing controllers. The optimal kind of network to use as an adjunct to a generator exciter is discussed.

Connective stability of nonlinear matrix systems

NASA Technical Reports Server (NTRS)

Siljak, D. D.

1974-01-01

Consideration of stability under structural perturbations of free dynamic systems described by the differential equation dx/dt = A(t,x)x, where the matrix A(t,x) has time-varying nonlinear elements. The concept of 'connective stability' is introduced to study the structural properties of competitive-cooperative nonlinear matrix systems. It is shown that stability reliability in such systems is high and that they remain stable despite time-varying (including 'on-off') interaction among individual agents present in the system. The results obtained can be used to study stability aspects of mathematical models arising in as diverse fields as economics, biology, arms races, and transistor circuits.

Effect of sugar additives on stability of human serum albumin during vacuum foam drying and storage.

PubMed

Hajare, A A; More, H N; Pisal, S S

2011-11-01

No literature on the protein stabilization of human serum albumin (HSA) by vacuum foam drying (VFD) has been reported. The purpose of this study was to investigate the effect of sugar-additive systems on the stability of HSA by VFD. For the assessment, HSA was formulated with sucrose and mannitol, respectively, alone or in combination with stabilizers, which were vacuum foam dried and stored at 25C. Protein content of the resulting dried formulations was analyzed by Lowry method. Fourier-transform infrared spectroscopy (FT-IR) analysis of the HSA secondary structure showed apparent protein structure-stabilizing effects of the amorphous sugar and phosphate combination during the VFD. In particular, sucrose-sodium phosphate monobasic mixture provide an interesting alternative to pure saccharide formulations due to their high glass transition temperatures and their increased ability to maintain a low melting transition temperature in the presence of small amounts of water. Inhibition of the sucrose crystallization in solutions under vacuum resulted in highly amorphous sucrose. Changes in the endothermic melting transition suggested reduced sucrose molecular mobility with increase in the sodium phosphate ratio. The addition of phosphate salts to sugar systems has several interesting features that merit its consideration in formulations to protect dehydrated labile biomaterials. In conclusion, our data suggest that sucrose and phosphate as additives seem to protect HSA during VFD better than lyophilized products and also maintain its stability in the VFD state during storage.

Effect of acid rain pH on leaching behavior of cement stabilized lead-contaminated soil.

PubMed

Du, Yan-Jun; Wei, Ming-Li; Reddy, Krishna R; Liu, Zhao-Peng; Jin, Fei

2014-04-30

Cement stabilization is a practical approach to remediate soils contaminated with high levels of lead. However, the potential for leaching of lead out of these stabilized soils under variable acid rain pH conditions is a major environmental concern. This study investigates the effects of acid rain on the leaching characteristics of cement stabilized lead contaminated soil under different pH conditions. Clean kaolin clay and the same soil spiked with 2% lead contamination are stabilized with cement contents of 12 and 18% and then cured for 28 days. The soil samples are then subjected to a series of accelerated leaching tests (or semi-dynamic leaching tests) using a simulated acid rain leachant prepared at pH 2.0, 4.0 or 7.0. The results show that the strongly acidic leachant (pH ∼2.0) significantly altered the leaching behavior of lead as well as calcium present in the soil. However, the differences in the leaching behavior of the soil when the leachant was mildly acidic (pH ∼4.0) and neutral (pH ∼7.0) prove to be minor. In addition, it is observed that the lead contamination and cement content levels can have a considerable impact on the leaching behavior of the soils. Overall, the leachability of lead and calcium is attributed to the stability of the hydration products and their consequent influence on the soil buffering capacity and structure. Copyright © 2014 Elsevier B.V. All rights reserved.

46 CFR 175.400 - Definitions of terms used in this subchapter.

Code of Federal Regulations, 2010 CFR

2010-10-01

... designated in § 1.01 of this chapter.; Consideration means an economic benefit, inducement, right, or profit... stability criteria and means: (1) Waters, except the Great Lakes, more than 20 nautical miles from a harbor... bulkhead that must be maintained watertight in order for the vessel to meet the damage stability and...

Seeking stability for research and applied uses of entomopathogenic fungi as biological control agents

USDA-ARS?s Scientific Manuscript database

Future progress in research with entomopathogenic fungi depends on a number of diverse considerations that help to stabilize the state of knowledge while supporting research about the documentation of the biodiversity and systematics of these fungi as well as those studies about their actions as pat...

Protein stability: a crystallographer’s perspective

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deller, Marc C., E-mail: mdeller@stanford.edu; Kong, Leopold; Rupp, Bernhard

An understanding of protein stability is essential for optimizing the expression, purification and crystallization of proteins. In this review, discussion will focus on factors affecting protein stability on a somewhat practical level, particularly from the view of a protein crystallographer. Protein stability is a topic of major interest for the biotechnology, pharmaceutical and food industries, in addition to being a daily consideration for academic researchers studying proteins. An understanding of protein stability is essential for optimizing the expression, purification, formulation, storage and structural studies of proteins. In this review, discussion will focus on factors affecting protein stability, on a somewhatmore » practical level, particularly from the view of a protein crystallographer. The differences between protein conformational stability and protein compositional stability will be discussed, along with a brief introduction to key methods useful for analyzing protein stability. Finally, tactics for addressing protein-stability issues during protein expression, purification and crystallization will be discussed.« less

Preserving catalytic activity and enhancing biochemical stability of the therapeutic enzyme asparaginase by biocompatible multilayered polyelectrolyte microcapsules.

PubMed

Karamitros, Christos S; Yashchenok, Alexey M; Möhwald, Helmuth; Skirtach, Andre G; Konrad, Manfred

2013-12-09

The present study focuses on the formation of microcapsules containing catalytically active L-asparaginase (L-ASNase), a protein drug of high value in antileukemic therapy. We make use of the layer-by-layer (LbL) technique to coat protein-loaded calcium carbonate (CaCO3) particles with two or three poly dextran/poly-L-arginine-based bilayers. To achieve high loading efficiency, the CaCO3 template was generated by coprecipitation with the enzyme. After assembly of the polymer shell, the CaCO3 core material was dissolved under mild conditions by dialysis against 20 mM EDTA. Biochemical stability of the encapsulated L-asparaginase was analyzed by treating the capsules with the proteases trypsin and thrombin, which are known to degrade and inactivate the enzyme during leukemia treatment, allowing us to test for resistance against proteolysis by physiologically relevant proteases through measurement of residual l-asparaginase activities. In addition, the thermal stability, the stability at the physiological temperature, and the long-term storage stability of the encapsulated enzyme were investigated. We show that encapsulation of l-asparaginase remarkably improves both proteolytic resistance and thermal inactivation at 37 °C, which could considerably prolong the enzyme's in vivo half-life during application in acute lymphoblastic leukemia (ALL). Importantly, the use of low EDTA concentrations for the dissolution of CaCO3 by dialysis could be a general approach in cases where the activity of sensitive biomacromolecules is inhibited, or even irreversibly damaged, when standard protocols for fabrication of such LbL microcapsules are used. Encapsulated and free enzyme showed similar efficacies in driving leukemic cells to apoptosis.

Strengthening transversus abdominis in pregnancy related pelvic pain: the pressure biofeedback stabilization training.

PubMed

Rajalakshmi, Dharmarajan; Senthil Kumar, N Sundaramurthy

2012-05-28

Pregnancy related pelvic pain (PRPP) refers to musculoskeletal type of persistent posterior pelvic pain during and after pregnancy with feature of reduced endurance capacity for standing, walking and sitting which leads to severe discomfort and considerable impairment of daily activities. To test the effect of pressure biofeedback stabilizer training, on the pain and dysfunction of a thirty year old subject who presented with PRPP. Single case design. Oswestry pain and disability index, TrA efficacy. An initial assessment was followed by treatment sessions which consist of 2 phases (Phase A & Phase B). The baseline phase (A) consists of conventional therapeutic exercises while the intervention phase (B) consists of pressure biofeedback training in conjunction with the conventional therapeutic exercises. The study data demonstrated that the subject showed minimal improvement in pain, disability and TrA efficacy during the baseline phase and shown a steady improvement in all these variables during the intervention phase. Core muscle performance (TrA) can be retrained with pressure biofeedback stabilization training program in subject with PRPP thereby reducing pain and disability.

Diagonal recurrent neural network based adaptive control of nonlinear dynamical systems using lyapunov stability criterion.

PubMed

Kumar, Rajesh; Srivastava, Smriti; Gupta, J R P

2017-03-01

In this paper adaptive control of nonlinear dynamical systems using diagonal recurrent neural network (DRNN) is proposed. The structure of DRNN is a modification of fully connected recurrent neural network (FCRNN). Presence of self-recurrent neurons in the hidden layer of DRNN gives it an ability to capture the dynamic behaviour of the nonlinear plant under consideration (to be controlled). To ensure stability, update rules are developed using lyapunov stability criterion. These rules are then used for adjusting the various parameters of DRNN. The responses of plants obtained with DRNN are compared with those obtained when multi-layer feed forward neural network (MLFFNN) is used as a controller. Also, in example 4, FCRNN is also investigated and compared with DRNN and MLFFNN. Robustness of the proposed control scheme is also tested against parameter variations and disturbance signals. Four simulation examples including one-link robotic manipulator and inverted pendulum are considered on which the proposed controller is applied. The results so obtained show the superiority of DRNN over MLFFNN as a controller. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

From Cell to Module: Fabrication and Long-term Stability of Dye-sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Nursam, N. M.; Hidayat, J.; Muliani, L.; Anggraeni, P. N.; Retnaningsih, L.; Idayanti, N.

2017-07-01

Dye-sensitized solar cell (DSSC), which has been firstly developed by Graetzel et al back in 1991, has attracted a considerable interest since its discovery. However, two of the main challenges that the DSSC technology will have to overcome towards commercialization involve device scale-up and long-term stability. In our group, the fabrication technology of DSSC has been developed from laboratory to module scale over the past few years, nevertheless, the long-term stability has still became a major concern. In this contribution, the long-term DSSC performance in relation to their scale-up from cell to module is investigated. The photoelectrode of the DSSCs were fabricated using nanocrystalline titanium dioxide materials that were subsequently sensitized using ruthenium-based dye. Additionally, TiCl4 pre- and post-treatment were carried out to enhance the overall device efficiency. When fabricated as cells, the DSSC prototypes showed relatively stable performance during repeated tests over three months. In order to increase the output power of the solar cells, the DSSCs were then connected in a Z-type series connection to obtain sub-module panels. The DSSC sub-modules exhibit poor stability, particularly as indicated by the significant decrease in the short circuit current (ISC ). Herein, the effect of photoelectrode and sealant materials as well as module design are investigated, highlighting their profound influence upon the DSSC efficiency and long-term stability.

Study of VLCC tanker ship damage stability during off-shore operation

NASA Astrophysics Data System (ADS)

Hanzu-Pazara, R.; Arsenie, P.; Duse, A.; Varsami, C.

2016-08-01

Today, for the carriage of crude oil on sea are used larger tanker ships, especially from VLCC class. The operation of this type of ships requires in many cases special conditions, mainly related to water depth in the terminal area and enough maneuvering space for entrance and departure. Because, many ports from all over the world don't have capacity to operate this type of ships inside, in designed oil terminal, have chosen for development of outside terminals, off-shore oil terminals. In case of this type of terminals, the problems of water depth and manoeuvring space are fixed, but other kind of situations appears, regarding the safety in operation and environment factors impact on ship during mooring at oil transfer buoy. In the present paper we intend to show a study made using simulation techniques about VLCC class tanker ship in case of a damage condition resulted after a possible collision with another ship during loading operation at an off-shore terminal. From the beginning, we take in consideration that the ship intact stability, during all loading possible situations, has to be high enough, so that in case of some damage with flooding of different compartments due to hypothetical dimension water hole, the ship stability in the final stage of flooding to correspond to the requirements for damage stability and, also, to complementary requirements for damage ship stability.

Intervention criterion and control research for active front steering with consideration of road adhesion

NASA Astrophysics Data System (ADS)

Wu, Xiaojian; Zhou, Bing; Wen, Guilin; Long, Lefei; Cui, Qingjia

2018-04-01

A multi-objective active front steering (AFS) control system considering the road adhesion constraint on vehicle stability is developed using the sliding mode control (SMC) method. First, an identification function combined with the relationship between the yaw rate and the steering angle is developed to determine whether the tyre state is linear or nonlinear. On this basis, an intervention criterion for the AFS system is proposed to improve vehicle handling and stability in emergent conditions. A sideslip angle stability domain enveloped by the upper, lower, left, and right boundaries, as well as the constraint of road adhesion coefficient, is constructed based on the ? phase-plane method. A dynamic weighting coefficient to coordinate the control of yaw rate and sideslip angle, and a control strategy that considers changing control objectives based on the desired yaw rate, the desired sideslip angle, and their proportional weights, are proposed for the SMC controller. Because road adhesion has a significant effect on vehicle stability and to meet the control algorithm's requirement of real-time access to vehicle states, a unscented Kalman filter-based state observer is proposed to estimate the adhesion coefficient and the required states. Finally, simulations are performed using high and low road adhesion conditions in a Matlab/Simulink environment, and the results show that the proposed AFS control system promptly intervenes according to the intervention criterion, effectively improving vehicle handling and stability.

Theoretical considerations of some nonlinear aspects of hypersonic panel flutter

NASA Technical Reports Server (NTRS)

Mcintosh, S. C., Jr.

1974-01-01

A research project to analyze the effects of hypersonic nonlinear aerodynamic loading on panel flutter is reported. The test equipment and procedures for conducting the tests are explained. The effects of aerodynamic linearities on stability were evaluated by determining constant-initial-energy amplitude-sensitive stability boundaries and comparing them with the corresponding linear stability boundaries. An attempt to develop an alternative method of analysis for systems where amplitude-sensitive instability is possible is presented.

Progress on plutonium stabilization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurt, D.

1996-05-01

The Defense Nuclear Facilities Safety Board has safety oversight responsibility for most of the facilities where unstable forms of plutonium are being processed and packaged for interim storage. The Board has issued recommendations on plutonium stabilization and has has a considerable influence on DOE`s stabilization schedules and priorities. The Board has not made any recommendations on long-term plutonium disposition, although it may get more involved in the future if DOE develops plans to use defense nuclear facilities for disposition activities.

Stability-Augmentation Devices for Miniature Aircraft

NASA Technical Reports Server (NTRS)

Wood, RIchard M.

2005-01-01

Non-aerodynamic mechanical devices are under consideration as means to augment the stability of miniature autonomous and remotely controlled aircraft. Such aircraft can be used for diverse purposes, including military reconnaissance, radio communications, and safety-related monitoring of wide areas. The need for stability-augmentation devices arises because adverse meteorological conditions generally affect smaller aircraft more strongly than they affect larger aircraft: Miniature aircraft often become uncontrollable under conditions that would not be considered severe enough to warrant grounding of larger aircraft. The need for the stability-augmentation devices to be non-aerodynamic arises because there is no known way to create controlled aerodynamic forces sufficient to counteract the uncontrollable meteorological forces on miniature aircraft. A stability-augmentation device of the type under consideration includes a mass pod (a counterweight) at the outer end of a telescoping shaft, plus associated equipment to support the operation of the aircraft. The telescoping shaft and mass pod are stowed in the rear of the aircraft. When deployed, they extend below the aircraft. Optionally, an antenna for radio communication can be integrated into the shaft. At the time of writing this article, the deployment of the telescoping shaft and mass pod was characterized as passive and automatic, but information about the deployment mechanism(s) was not available. The feasibility of this stability-augmentation concept was demonstrated in flights of hand-launched prototype aircraft.

The stabilized, wavelet-Mellin transform for analyzing the size and shape information of vocalized sounds

NASA Astrophysics Data System (ADS)

Irino, Toshio; Patterson, Roy

2005-04-01

We hear vowels produced by men, women, and children as approximately the same although there is considerable variability in glottal pulse rate and vocal tract length. At the same time, we can identify the speaker group. Recent experiments show that it is possible to identify vowels even when the glottal pulse rate and vocal tract length are condensed or expanded beyond the range of natural vocalization. This suggests that the auditory system has an automatic process to segregate information about shape and size of the vocal tract. Recently we proposed that the auditory system uses some form of Stabilized, Wavelet-Mellin Transform (SWMT) to analyze scale information in bio-acoustic sounds as a general framework for auditory processing from cochlea to cortex. This talk explains the theoretical background of the model and how the vocal information is normalized in the representation. [Work supported by GASR(B)(2) No. 15300061, JSPS.

Influence of the local-spin-density correlation functional on the stability of bcc ferromagnetic iron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, D.; Clougherty, D.P.; MacLaren, J.M.

1991-10-01

The influence of local-spin-dependent correlation effects on the predicted stable ground-state phase of iron is reexamined with use of general-potential linearized augmented-plane-wave calculations. Differences in the form of the Vosko-Wilk-Nusair (VWN) local-spin-density functional used in previous studies are noted, since in previous studies significant additional approximations were made with respect to those of Vosko, Wilk, and Nusan (Can. J. Phys. 58, 1200 (1980)) and of MacLaren, Clougherty, and Albers (Phys. Rev. B 42, 3205 (1990)). While the results of previous linear muffin-tin orbital calculations using the VWN functional predict a bcc ferromagnetic ground state, the present calculations show that themore » VWN spin-correlation effects fail to stabilize a bcc ground state. Considerable sensitivity to the form of the spin interpolation is found.« less

Power generation costs and ultimate thermal hydraulic power limits in hypothetical advanced designs with natural circulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duffey, R.B.; Rohatgi, U.S.

Maximum power limits for hypothetical designs of natural circulation plants can be described analytically. The thermal hydraulic design parameters are those which limit the flow, being the elevations, flow areas, and loss coefficients. WE have found some simple ``design`` equations for natural circulation flow to power ratio, and for the stability limit. The analysis of historical and available data for maximum capacity factor estimation shows 80% to be reasonable and achievable. The least cost is obtained by optimizing both hypothetical plant performance for a given output,a nd the plant layout and design. There is also scope to increase output andmore » reduce cost by considering design variations of primary and secondary pressure, and by optimizing component elevations and loss coefficients. The design limits for each are set by stability and maximum flow considerations, which deserve close and careful evaluation.« less

Early stages of transition in viscosity-stratified channel flow

NASA Astrophysics Data System (ADS)

Govindarajan, Rama; Jose, Sharath; Brandt, Luca

2013-11-01

In parallel shear flows, it is well known that transition to turbulence usually occurs through a subcritical process. In this work we consider a flow through a channel across which there is a linear temperature variation. The temperature gradient leads to a viscosity variation across the channel. A large body of work has been done in the linear regime for this problem, and it has been seen that viscosity stratification can lead to considerable changes in stability and transient growth characteristics. Moreover contradictory effects of introducing a non uniform viscosity in the system have been reported. We conduct a linear stability analysis and direct numerical simulations (DNS) for this system. We show that the optimal initial structures in the viscosity-stratified case, unlike in unstratified flow, do not span the width of the channel, but are focussed near one wall. The nonlinear consequences of the localisation of the structures will be discussed.

Nanoscale analysis of the morphology and surface stability of calcium carbonate polymorphs

PubMed Central

Sekkal, W.; Zaoui, A.

2013-01-01

Under earth surface conditions, in ocean and natural water, calcium carbonate is ubiquitous, forming anhydrous and hydrous minerals. These hydrous phases are of considerable interest for their role as precursors to stable carbonate minerals. Atomistic simulation techniques have been employed here to perform a comprehensive and quantitative study of the structural and energetic stability of dry and hydrous surfaces of calcium carbonate polymorphs using two recently developed forcefields. Results show that the dry forms are prone to ductility; while hydrous phases are found to be brittle. The (001) surface of monohydrocalcite appears to be the most stable (0.99 J/m2) whereas for the ikaite phase, the (001) surface is the most stable. The corresponding value is 0.2 J/m2, i.e. even lower than the surface energy of the Beautiful computed morphology pictures are obtained with Xiao's model and are very similar to the observed SEM images. PMID:23545842

Nanoscale analysis of the morphology and surface stability of calcium carbonate polymorphs.

PubMed

Sekkal, W; Zaoui, A

2013-01-01

Under earth surface conditions, in ocean and natural water, calcium carbonate is ubiquitous, forming anhydrous and hydrous minerals. These hydrous phases are of considerable interest for their role as precursors to stable carbonate minerals. Atomistic simulation techniques have been employed here to perform a comprehensive and quantitative study of the structural and energetic stability of dry and hydrous surfaces of calcium carbonate polymorphs using two recently developed forcefields. Results show that the dry forms are prone to ductility; while hydrous phases are found to be brittle. The (001) surface of monohydrocalcite appears to be the most stable (0.99 J/m(2)) whereas for the ikaite phase, the (001) surface is the most stable. The corresponding value is 0.2 J/m(2), i.e. even lower than the surface energy of the Beautiful computed morphology pictures are obtained with Xiao's model and are very similar to the observed SEM images.

Nanoscale analysis of the morphology and surface stability of calcium carbonate polymorphs

NASA Astrophysics Data System (ADS)

Sekkal, W.; Zaoui, A.

2013-04-01

Under earth surface conditions, in ocean and natural water, calcium carbonate is ubiquitous, forming anhydrous and hydrous minerals. These hydrous phases are of considerable interest for their role as precursors to stable carbonate minerals. Atomistic simulation techniques have been employed here to perform a comprehensive and quantitative study of the structural and energetic stability of dry and hydrous surfaces of calcium carbonate polymorphs using two recently developed forcefields. Results show that the dry forms are prone to ductility; while hydrous phases are found to be brittle. The (001) surface of monohydrocalcite appears to be the most stable (0.99 J/m2) whereas for the ikaite phase, the (001) surface is the most stable. The corresponding value is 0.2 J/m2, i.e. even lower than the surface energy of the Beautiful computed morphology pictures are obtained with Xiao's model and are very similar to the observed SEM images.

Extremely Stable Polypyrrole Achieved via Molecular Ordering for Highly Flexible Supercapacitors.

PubMed

Huang, Yan; Zhu, Minshen; Pei, Zengxia; Huang, Yang; Geng, Huiyuan; Zhi, Chunyi

2016-01-27

The cycling stability of flexible supercapacitors with conducting polymers as electrodes is limited by the structural breakdown arising from repetitive counterion flow during charging/discharging. Supercapacitors made of facilely electropolymerized polypyrrole (e-PPy) have ultrahigh capacitance retentions of more than 97, 91, and 86% after 15000, 50000, and 100000 charging/discharging cycles, respectively, and can sustain more than 230000 charging/discharging cycles with still approximately half of the initial capacitance retained. To the best of our knowledge, such excellent long-term cycling stability was never reported. The fully controllable electropolymerization shows superiority in molecular ordering, favoring uniform stress distribution and charge transfer. Being left at ambient conditions for even 8 months, e-PPy supercapacitors completely retain the good electrochemical performance. The extremely stable supercapacitors with excellent flexibility and scalability hold considerable promise for the commerical application of flexible and wearable electronics.

Experimental investigation of influence of acid rain on leaching and hydraulic characteristics of cement-based solidified/stabilized lead contaminated clay.

PubMed

Du, Yan-Jun; Jiang, Ning-Jun; Shen, Shui-Long; Jin, Fei

2012-07-30

Remediation of contaminated lands in China urban areas is of great concern. Degradation of construction facilities caused by acid rain is a serious environmental pollution issue in China. This paper presents an investigation of the effects of acid rain on leaching and hydraulic properties of cement-based solidified/stabilized lead contaminated soil. Laboratory tests including infiltration test and soaking test are conducted. It is found that the soil hydraulic conductivity decreases with increase in the pore volume of flow of permeant liquids (acid rain and distilled water). The decreasing rate in the case of the acid rain is lower than that in the case of the distilled water. The soaking test results show that pH and the presence of sulfate ions of acid rain have considerable influence on the leached concentrations and leaching rate of calcium. Copyright © 2012 Elsevier B.V. All rights reserved.

Structural and electronic phase transitions of MoTe2 induced by Li ionic gating

NASA Astrophysics Data System (ADS)

Hwang, Jeongwoon; Zhang, Chenxi; Cho, Kyeongjae

2017-12-01

Monolayer MoTe2 has semiconducting and semimetallic phases with small energy difference, and the relative stability is readily reversed by gating. By first-principles calculations, we investigate the changes in atomic structure, electronic structure, and relative stability of two phases induced by Li ionic gating. To model Li ionic gating, we employ two approaches; one is direct adsorption of Li on MoTe2 and the other is introducing non-contacting Li plate over MoTe2. We show phonon instability in H-phase of MoTe2 with increasing the amount of charge transfer from Li, which implies a large electron-phonon coupling in the system resulting in a charge density wave state. Structural distortion is also observed in highly doped T d phase. The transition energy barrier from distorted H phase to distorted T d phase is reduced considerably compared to that of pristine MoTe2.

Conceptualization of preferential flow for hillslope stability assessment

NASA Astrophysics Data System (ADS)

Kukemilks, Karlis; Wagner, Jean-Frank; Saks, Tomas; Brunner, Philip

2018-03-01

This study uses two approaches to conceptualize preferential flow with the goal to investigate their influence on hillslope stability. Synthetic three-dimensional hydrogeological models using dual-permeability and discrete-fracture conceptualization were subsequently integrated into slope stability simulations. The slope stability simulations reveal significant differences in slope stability depending on the preferential flow conceptualization applied, despite similar small-scale hydrogeological responses of the system. This can be explained by a local-scale increase of pore-water pressures observed in the scenario with discrete fractures. The study illustrates the critical importance of correctly conceptualizing preferential flow for slope stability simulations. It further demonstrates that the combination of the latest generation of physically based hydrogeological models with slope stability simulations allows for improvement to current modeling approaches through more complex consideration of preferential flow paths.

Cu doped diamond: Effect of charge state and defect aggregation on spin interactions in a 3d transition metal doped wide band-gap semiconductor

NASA Astrophysics Data System (ADS)

Benecha, E. M.; Lombardi, E. B.

2018-05-01

We present a first principles study of Cu in diamond using DFT+U electronic structure methods, by carefully considering the impact of co-doping, charge state, and Fermi level position on its stability, lattice location, spin states, and electronic properties. We show that the energetic stability and spin states of Cu are strongly dependent on the Fermi level position and the type of diamond co-doping, with Cu being energetically more favorable in n-type or p-type co-doped diamond compared to intrinsic diamond. Since Cu has been predicted to order magnetically in a number of other wide band-gap semiconductors, we have also evaluated this possibility for Cu doped diamond. We show that while Cu exhibits strong spin interactions at specific interatomic separations in diamond, a detailed consideration of the impact of Fermi level position and Cu aggregation precludes magnetic ordering, with Cu forming non-magnetic, antiferromagnetic, or paramagnetic clusters. These results have important implications in the understanding of the properties of transition metal dopants in diamond for device applications.

Preparation and evaluation of tilmicosin-loaded hydrogenated castor oil nanoparticle suspensions of different particle sizes.

PubMed

Chen, Xiaojin; Wang, Ting; Lu, Mengmeng; Zhu, Luyan; Wang, Yan; Zhou, WenZhong

2014-01-01

Three tilmicosin-loaded hydrogenated castor oil nanoparticle (TMS-HCO-NP) suspensions of different particle sizes were prepared with different polyvinyl alcohol surfactant concentrations using a hot homogenization and ultrasonic technique. The in vitro release, in vitro antibacterial activity, mammalian cytotoxicity, acute toxicity in mice, and stability study were conducted to evaluate the characteristics of the suspensions. The in vitro tilmicosin release rate, antibacterial activity, mammalian cytotoxicity, acute toxicity in mice, and stability of the suspensions were evaluated. When prepared with polyvinyl alcohol concentrations of 0.2%, 1%, and 5%, the mean diameters of the nanoparticles in the three suspensions were 920±35 nm, 452±10 nm, and 151±4 nm, respectively. The three suspensions displayed biphasic release profiles similar to that of freeze-dried TMS-HCO-NP powders, with the exception of having a faster initial release. Moreover, suspensions of smaller-sized particles showed faster initial release, and lower minimum inhibitory concentrations and minimum bactericidal concentrations. Time-kill curves showed that within 12 hours, the suspension with the 151 nm particles had the most potent bactericidal activity, but later, the suspensions with larger-sized particles showed increased antibacterial activity. None of the three suspensions were cytotoxic at clinical dosage levels. At higher drug concentrations, all three suspensions showed similar concentration-dependent cytotoxicity. The suspension with the smallest-sized particle showed significantly more acute toxicity in mice, perhaps due to faster drug release. All three suspensions exhibited good stability at 4°C and at room temperature for at least 6 months. These results demonstrate that TMS-HCO-NP suspensions can be a promising formulation for tilmicosin, and that nanoparticle size can be an important consideration for formulation development.

Preparation and evaluation of tilmicosin-loaded hydrogenated castor oil nanoparticle suspensions of different particle sizes

PubMed Central

Chen, Xiaojin; Wang, Ting; Lu, Mengmeng; Zhu, Luyan; Wang, Yan; Zhou, WenZhong

2014-01-01

Three tilmicosin-loaded hydrogenated castor oil nanoparticle (TMS-HCO-NP) suspensions of different particle sizes were prepared with different polyvinyl alcohol surfactant concentrations using a hot homogenization and ultrasonic technique. The in vitro release, in vitro antibacterial activity, mammalian cytotoxicity, acute toxicity in mice, and stability study were conducted to evaluate the characteristics of the suspensions. The in vitro tilmicosin release rate, antibacterial activity, mammalian cytotoxicity, acute toxicity in mice, and stability of the suspensions were evaluated. When prepared with polyvinyl alcohol concentrations of 0.2%, 1%, and 5%, the mean diameters of the nanoparticles in the three suspensions were 920±35 nm, 452±10 nm, and 151±4 nm, respectively. The three suspensions displayed biphasic release profiles similar to that of freeze-dried TMS-HCO-NP powders, with the exception of having a faster initial release. Moreover, suspensions of smaller-sized particles showed faster initial release, and lower minimum inhibitory concentrations and minimum bactericidal concentrations. Time-kill curves showed that within 12 hours, the suspension with the 151 nm particles had the most potent bactericidal activity, but later, the suspensions with larger-sized particles showed increased antibacterial activity. None of the three suspensions were cytotoxic at clinical dosage levels. At higher drug concentrations, all three suspensions showed similar concentration-dependent cytotoxicity. The suspension with the smallest-sized particle showed significantly more acute toxicity in mice, perhaps due to faster drug release. All three suspensions exhibited good stability at 4°C and at room temperature for at least 6 months. These results demonstrate that TMS-HCO-NP suspensions can be a promising formulation for tilmicosin, and that nanoparticle size can be an important consideration for formulation development. PMID:24920902

Approximation methods for the stability analysis of complete synchronization on duplex networks

NASA Astrophysics Data System (ADS)

Han, Wenchen; Yang, Junzhong

2018-01-01

Recently, the synchronization on multi-layer networks has drawn a lot of attention. In this work, we study the stability of the complete synchronization on duplex networks. We investigate effects of coupling function on the complete synchronization on duplex networks. We propose two approximation methods to deal with the stability of the complete synchronization on duplex networks. In the first method, we introduce a modified master stability function and, in the second method, we only take into consideration the contributions of a few most unstable transverse modes to the stability of the complete synchronization. We find that both methods work well for predicting the stability of the complete synchronization for small networks. For large networks, the second method still works pretty well.

Material selection for a constructed wetroof receiving pre-treated high strength domestic wastewater.

PubMed

Zapater-Pereyra, M; van Dien, F; van Bruggen, J J A; Lens, P N L

2013-01-01

A constructed wetroof (CWR) is defined in this study as the combination of a green roof and a constructed wetland: a shallow wastewater treatment system placed on the roof of a building. The foremost challenge of such CWRs, and the main aim of this investigation, is the selection of an appropriate matrix capable of assuring the required hydraulic retention time, the long-term stability and the roof load-bearing capacity. Six substrata were subjected to water dynamics and destructive tests in two testing-tables. Among all the materials tested, the substratum configuration composed of sand, light expanded clay aggregates, biodegradable polylactic acid beads together with stabilization plates and a turf mat is capable of retaining the water for approximately 3.8 days and of providing stability (stabilization plates) and an immediate protection (turf mat) to the system. Based on those results, a full-scale CWR was built, which did not show any physical deterioration after 1 year of operation. Preliminary wastewater treatment results on the full-scale CWR suggest that it can highly remove main wastewater pollutants (e.g. chemical oxygen demand, PO4(3-)-P and NH4(+)-N). The results of these tests and practical design considerations of the CWR are discussed in this paper.

Effect of fjord geometry on tidewater glacier stability

NASA Astrophysics Data System (ADS)

Åkesson, Henning; Nisancioglu, Kerim H.; Nick, Faezeh M.

2016-04-01

Many marine-terminating glaciers have thinned, accelerated and retreated during the last two decades, broadly consistent with warmer atmospheric and oceanic conditions. However, these patterns involve considerable spatial and temporal variability, with diverse glacier behavior within the same regions. Similarly, reconstructions of marine-terminating glaciers indicate highly asynchronous retreat histories. While it is well known that retrograde slopes can cause marine ice sheet instabilities, the effect of lateral drag and fjord width has received less attention. Here, we test the hypothesis that marine outlet glacier stability is largely controlled by fjord width, and to a less extent by regional climate forcing. We employ a dynamic flowline model on idealized glacier geometries (representative of different outlet glaciers) to investigate geometric controls on decadal and longer times scales. The model accounts for driving and resistive stresses of glacier flow as well as along-flow stress transfer. It has a physical treatment of iceberg calving and a time-adaptive grid allowing for continuous tracking of grounding-line migration. We apply changes in atmospheric and oceanic forcing and show how wide and narrow fjord sections foster glacier (in)stabilities. We also evaluate the effect of including a surface mass balance - elevation feedback in such a setting. Finally, the relevance of these results to past and future marine-terminating glacier stability is discussed.

Graphene oxide wrapped Ag{sub 3}PO{sub 4} sub-microparticles with highly enhanced photocatalytic activity and stability under visible light irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiu, Zhiliang; Shandong Provincial Key Laboratory of Processing and Testing Technology of Glass and Functional Ceramics, Key Laboratory of Amorphous and Polycrystalline Materials, Qilu University of Technology, Jinan 250353; Wu, Yongzhong, E-mail: wuyz@sdu.edu.cn

2014-11-15

Highlights: • Graphene oxide wrapped Ag{sub 3}PO{sub 4} sub-microparticles were prepared. • The photocatalytic activity of Ag{sub 3}PO{sub 4} is increased by 6 times by GO wrapping. • The hybrid photocatalysts exhibited excellent stability. - Abstract: Graphene oxide (GO) wrapped Ag{sub 3}PO{sub 4} sub-microparticles were prepared by in situ deposition–precipitation method. By hybridization of Ag{sub 3}PO{sub 4} with GO nanosheets, a 6-fold enhancement in the photodegradation rate toward orange methyl (MO) under visible light irradiation (λ ≥ 420 nm) was observed compared with the pure Ag{sub 3}PO{sub 4} sub-microsparticles. The hybrid photocatalysts also exhibited excellent stability in the successive MOmore » degradation experiments. The highly enhanced photocatalytic activity and stability were mainly attributed to the quick transfer of the photogenerated electrons from Ag{sub 3}PO{sub 4} to GO nanosheets, which could effectively suppress the electron–hole pairs recombination and thus inhibit the photocorrosion of Ag{sub 3}PO{sub 4}. These high-efficient and stable hybrid photocatalysts were expected to show considerable potential applications in wastewater treatment and water splitting.« less

Early Diagnosis of Autism Spectrum Disorder: Stability and Change in Clinical Diagnosis and Symptom Presentation

ERIC Educational Resources Information Center

Guthrie, Whitney; Swineford, Lauren B.; Nottke, Charly; Wetherby, Amy M.

2013-01-01

Background: Although a diagnosis of autism spectrum disorder (ASD) appears to be stable in children as young as age three, few studies have explored stability of a diagnosis in younger children. Predictive value of diagnostic tools for toddlers and patterns of symptom change are important considerations for clinicians making early diagnoses. Most…

Stability and oscillations in a CML model

NASA Astrophysics Data System (ADS)

Badralexi, Irina; Halanay, Andrei

2017-01-01

We capture the evolution in competition of healthy and leukemic cells in Chronic Myelogenous Leukemia (CML) taking into consideration the response of the immune system. Delay-differential equations in a Mackey-Glass approach are used. We start with the study of stability of the equilibrium points of the system. Conditions on parameters for the local stability are given. Oscillatory behaviors occur naturally in biological phenomena. Thus, we investigate the periodic behavior of solutions and we obtain conditions for periodic solutions to appear through a Hopf bifurcation.

Minimizing Postsampling Degradation of Peptides by a Thermal Benchtop Tissue Stabilization Method

PubMed Central

Segerström, Lova; Gustavsson, Jenny

2016-01-01

Enzymatic degradation is a major concern in peptide analysis. Postmortem metabolism in biological samples entails considerable risk for measurements misrepresentative of true in vivo concentrations. It is therefore vital to find reliable, reproducible, and easy-to-use procedures to inhibit enzymatic activity in fresh tissues before subjecting them to qualitative and quantitative analyses. The aim of this study was to test a benchtop thermal stabilization method to optimize measurement of endogenous opioids in brain tissue. Endogenous opioid peptides are generated from precursor proteins through multiple enzymatic steps that include conversion of one bioactive peptide to another, often with a different function. Ex vivo metabolism may, therefore, lead to erroneous functional interpretations. The efficacy of heat stabilization was systematically evaluated in a number of postmortem handling procedures. Dynorphin B (DYNB), Leu-enkephalin-Arg6 (LARG), and Met-enkephalin-Arg6-Phe7 (MEAP) were measured by radioimmunoassay in rat hypothalamus, striatum (STR), and cingulate cortex (CCX). Also, simplified extraction protocols for stabilized tissue were tested. Stabilization affected all peptide levels to varying degrees compared to those prepared by standard dissection and tissue handling procedures. Stabilization increased DYNB in hypothalamus, but not STR or CCX, whereas LARG generally decreased. MEAP increased in hypothalamus after all stabilization procedures, whereas for STR and CCX, the effect was dependent on the time point for stabilization. The efficacy of stabilization allowed samples to be left for 2 hours in room temperature (20°C) without changes in peptide levels. This study shows that conductive heat transfer is an easy-to-use and efficient procedure for the preservation of the molecular composition in biological samples. Region- and peptide-specific critical steps were identified and stabilization enabled the optimization of tissue handling and opioid peptide analysis. The result is improved diagnostic and research value of the samples with great benefits for basic research and clinical work. PMID:27007059

Coordination in Fast Repetitive Violin-Bowing Patterns

PubMed Central

Schoonderwaldt, Erwin; Altenmüller, Eckart

2014-01-01

We present a study of coordination behavior in complex violin-bowing patterns involving simultaneous bow changes (reversal of bowing direction) and string crossings (changing from one string to another). Twenty-two violinists (8 advanced amateurs, 8 students with violin as major subject, and 6 elite professionals) participated in the experiment. We investigated the influence of a variety of performance conditions (specific bowing patterns, dynamic level, tempo, and transposition) and level of expertise on coordination behavior (a.o., relative phase and amplitude) and stability. It was found that the general coordination behavior was highly consistent, characterized by a systematic phase lead of bow inclination over bow velocity of about 15° (i.e., string crossings were consistently timed earlier than bow changes). Within similar conditions, a high individual consistency was found, whereas the inter-individual agreement was considerably less. Furthermore, systematic influences of performance conditions on coordination behavior and stability were found, which could be partly explained in terms of particular performance constraints. Concerning level of expertise, only subtle differences were found, the student and professional groups (higher level of expertise) showing a slightly higher stability than the amateur group (lower level of expertise). The general coordination behavior as observed in the current study showed a high agreement with perceptual preferences reported in an earlier study to similar bowing patterns, implying that complex bowing trajectories for an important part emerge from auditory-motor interaction. PMID:25207542

Evaluation of antitumor activity and development of solid lipid nanoparticles of metronidazole analogue.

PubMed

Lages, Eduardo Burgarelli; de Freitas, Maria Betânia; Gonçalves, Isadora Marques Brum; Alves, Ricardo José; Vianna-Soares, Cristina Duarte; Ferreira, Lucas Antônio Miranda; de Oliveira, Mônica Cristina; de Oliveira, Renata Barbosa

2013-11-01

Nitroheterocyclic compounds have received considerable interest as hypoxia-selective cytotoxins (HSC) for cancer treatment. In the present study, we investigated antitumor activity of an iodide analogue of metronidazole, 1-(2-iodoethyl)-2-methyl-5-nitroimidazole (MTZ-I), using Swiss mice bearing solid Ehrlich tumor. MTZ-I showed potent anti-cancer activity at a dose of 40 mg/kg. MTZ-I loaded solid lipid nanoparticles (SLN) were developed as an alternative colloidal carrier system to enhance tumor drug uptake. SLN were characterized for particle size, polydispersity index, zeta potential and entrapment efficiency. In addition, the influence of presence of the cationic lipid stearylamine (STE) on stability of formulation was assessed. The results of DSC study showed that MTZ-I exhibited interaction with STE.

Formulation and process considerations affecting the stability of solid dosage forms formulated with methacrylate copolymers.

PubMed

Petereit, H U; Weisbrod, W

1999-01-01

General considerations concerning the stability of coated dosage forms are discussed, in order to avoid predictable interactions which may cause long-term stability problems. As polymers themselves maintain a high chemical stability and a low reactivity, instability phenomena mainly have to be explained by interactions of low molecular weight substances or physical changes. Possible interactions of functional groups can be predicted easily and insulating subcoates are proper countermeasures. Impurities, remaining in the polymeric material from the manufacturing process, may accelerate the hydrolysis of sensitive drugs. Instabilities of coated dosage forms are mainly based on physical interactions, caused by improper formulations of coating suspensions (i.e. plasticizers or pigments) or the film coating process. Residual moisture or solvents, probably enclosed in the core and migrating over time, may increase the permeability of coatings, due to plasticizing effects. The functionality of coatings from aqueous dispersions is linked to coalescence of latex particles. Thus any incomplete film formation, caused by too high or too low coating temperatures, may result in high permeable coatings. During storage, preferably under stress conditions this process will continue and thus change the release profile. Therefore bed temperatures of 10-20 degrees C above MFT must ensure the formation of homogeneous polymer layers during the coating process. Stability test procedures and packaging materials also need to be adapted to the physicochemical properties of the dosage form, in order to get meaningful results in stability tests.

On the stability treatment in WAsP

NASA Astrophysics Data System (ADS)

Giebel, G.; Gryning, S.-E.

2003-04-01

An assessment of the treatment of atmospheric stability in the standard package for wind resource estimation, WAsP (from Risø National Laboratory), is presented. Emphasis is on the vertical wind profiles in WAsP and the treatment of stability therein, under special consideration of the nightly situation. The study starts with an introduction to WAsP and the way it treats the vertical extrapolation, under special consideration of the stability. The two parameters available for changing the stability treatment in WAsP are identified as RMS heat flux and offset heat flux. Four years worth of data from the meteorological mast at Risø, plus data from Egypt and Bermuda, is used for the identification of the parameter settings for stable conditions. To this aim, the measured heat fluxes from the mast were used to extract three data sets with successively higher stability in four different heights. These data sets were then run through the Observed Wind Climate Wizard (part of the WAsP package), resulting in Weibull fits to the data. Using these observed wind climates, a prediction of the highest level wind climate using the lowest level wind climate under all different stable conditions is undertaken and compared with the measured data set. To expand on this study, a systematic variation of the two heat flux parameters in WAsP is done, finding the parameters yielding the lowest overall errors for the predictions. Parts of this study were financed by the Landesumweltamt Brandenburg.

Assessing postural stability via the correlation patterns of vertical ground reaction force components.

PubMed

Hong, Chih-Yuan; Guo, Lan-Yuen; Song, Rong; Nagurka, Mark L; Sung, Jia-Li; Yen, Chen-Wen

2016-08-02

Many methods have been proposed to assess the stability of human postural balance by using a force plate. While most of these approaches characterize postural stability by extracting features from the trajectory of the center of pressure (COP), this work develops stability measures derived from components of the ground reaction force (GRF). In comparison with previous GRF-based approaches that extract stability features from the GRF resultant force, this study proposes three feature sets derived from the correlation patterns among the vertical GRF (VGRF) components. The first and second feature sets quantitatively assess the strength and changing speed of the correlation patterns, respectively. The third feature set is used to quantify the stabilizing effect of the GRF coordination patterns on the COP. In addition to experimentally demonstrating the reliability of the proposed features, the efficacy of the proposed features has also been tested by using them to classify two age groups (18-24 and 65-73 years) in quiet standing. The experimental results show that the proposed features are considerably more sensitive to aging than one of the most effective conventional COP features and two recently proposed COM features. By extracting information from the correlation patterns of the VGRF components, this study proposes three sets of features to assess human postural stability during quiet standing. As demonstrated by the experimental results, the proposed features are not only robust to inter-trial variability but also more accurate than the tested COP and COM features in classifying the older and younger age groups. An additional advantage of the proposed approach is that it reduces the force sensing requirement from 3D to 1D, substantially reducing the cost of the force plate measurement system.

Asymptotic behavior of modulated Taylor-Couette flows with a crystalline inner cylinder

NASA Technical Reports Server (NTRS)

Braun, R. J.; Mcfadden, G. B.; Murray, B. T.; Coriell, S. R.; Glicksman, M. E.; Selleck, M. E.

1993-01-01

The linear stability of a modulated Taylor-Couette system when the inner cylindrical boundary consists of a crystalline solid-liquid interface is considered. Both experimentally and in numerical calculations it is found that the two-phase system is significantly less stable than the analogous rigid-walled system for materials with moderately large Prandtl numbers. A numerical treatment based on Floquet theory is described, which gives results that are in good agreement with preliminary experimental findings. In addition, this instability is further examined by carrying out a formal asymptotic expansion of the solution in the limit of large Prandtl number. In this limit the Floquet analysis is considerably simplified, and the linear stability of the modulated system can be determined to leading order through a conventional stability analysis, without recourse to Floquet theory. The resulting simplified problem is then studied for both the narrow gap geometry and for the case of a finite gap. It is surprising that the determination of the linear stability of the two-phase system is considerably simpler than that of the rigid-walled system, despite the complications introduced by the presence of the crystal-melt interface.

Some effects of external stores on the static stability of fighter airplanes

NASA Technical Reports Server (NTRS)

Spearman, M. L.

1972-01-01

Fighter airplanes may have a seemingly limitless number of external store arrangements. Some practical considerations and some aerodynamic considerations must be taken into account in the arrangements of the external stores. The nature of the problems concerning the type of store arrangement involved and the type of airplane on which the stores are installed are reported.

Early Universe Higgs dynamics in the presence of the Higgs-inflaton and non-minimal Higgs-gravity couplings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ema, Yohei; Karčiauskas, Mindaugas; Lebedev, Oleg

Apparent metastability of the electroweak vacuum poses a number of cosmological questions. These concern evolution of the Higgs field to the current vacuum, and its stability during and after inflation. Higgs-inflaton and non-minimal Higgs-gravity interactions can make a crucial impact on these considerations potentially solving the problems. In this work, we allow for these couplings to be present simultaneously and study their interplay. We find that different combinations of the Higgs-inflaton and non-minimal Higgs-gravity couplings induce effective Higgs mass during and after inflation. This crucially affects the Higgs stability considerations during preheating. In particular, a wide range of the couplingsmore » leading to stable solutions becomes allowed.« less

Stability of a diffuse linear pinch with axial boundaries

NASA Technical Reports Server (NTRS)

Einaudi, G.; Van Hoven, G.

1981-01-01

A formulation of the stability behavior of a finite-length pinch is presented. A general initial perturbation is expressed as a uniformly convergent sum over a complete discrete k set. A variational calculation is then performed, based on the energy principle, in which the end-boundary conditions appear as constraints. The requisite Lagrange multipliers mutually couple the elemental periodic excitations. The resulting extended form of delta-W still admits a proper second-variation treatment so that the minimization and stability considerations of Newcomb remain applicable. Comparison theorems are discussed as is the relevance of this end-effect model to the stability of solar coronal loops.

Equilibrium high entropy alloy phase stability from experiments and thermodynamic modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saal, James E.; Berglund, Ida S.; Sebastian, Jason T.

Long-term stability of high entropy alloys (HEAs) is a critical consideration for the design and practical application of HEAs. It has long been assumed that many HEAs are a kinetically-stabilized metastable structure, and recent experiments have confirmed this hypothesis by observing HEA ecomposition after long-termequilibration. In the presentwork,we demonstrate the use of the CALculation of PHAse Diagrams (CALPHAD) approach to predict HEA stability and processing parameters, comparing experimental long-term annealing observations to CALPHAD phase diagrams from a commercially-available HEA database. As a result, we find good agreement between single- and multi-phase predictions and experiments.

Equilibrium high entropy alloy phase stability from experiments and thermodynamic modeling

DOE PAGES

Saal, James E.; Berglund, Ida S.; Sebastian, Jason T.; ...

2017-10-29

Long-term stability of high entropy alloys (HEAs) is a critical consideration for the design and practical application of HEAs. It has long been assumed that many HEAs are a kinetically-stabilized metastable structure, and recent experiments have confirmed this hypothesis by observing HEA ecomposition after long-termequilibration. In the presentwork,we demonstrate the use of the CALculation of PHAse Diagrams (CALPHAD) approach to predict HEA stability and processing parameters, comparing experimental long-term annealing observations to CALPHAD phase diagrams from a commercially-available HEA database. As a result, we find good agreement between single- and multi-phase predictions and experiments.

Life raft stabilizer

NASA Technical Reports Server (NTRS)

Radnofsky, M. I.; Barnett, J. H., Jr.; Harrison, F. L.; Marak, R. J. (Inventor)

1973-01-01

An improved life raft stabilizer for reducing rocking and substantially precluding capsizing is discussed. The stabilizer may be removably attached to the raft and is defined by flexible side walls which extend a considerable depth downwardly to one another in the water. The side walls, in conjunction with the floor of the raft, form a ballast enclosure. A weight is placed in the bottom of the enclosure and water port means are provided in the walls. Placement of the stabilizer in the water allows the weighted bottom to sink, producing submerged deployment thereof and permitting water to enter the enclosure through the port means, thus forming a ballast for the raft.

Diamagnetic drift effects on the low-n magnetohydrodynamic modes at the high mode pedestal with plasma rotation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, L. J.; Kotschenreuther, M. T.; Valanju, P.

2014-06-15

The diamagnetic drift effects on the low-n magnetohydrodynamic instabilities at the high-mode (H-mode) pedestal are investigated in this paper with the inclusion of bootstrap current for equilibrium and rotation effects for stability, where n is the toroidal mode number. The AEGIS (Adaptive EiGenfunction Independent Solutions) code [L. J. Zheng and M. T. Kotschenreuther, J. Comp. Phys. 211 (2006)] is extended to include the diamagnetic drift effects. This can be viewed as the lowest order approximation of the finite Larmor radius effects in consideration of the pressure gradient steepness at the pedestal. The H-mode discharges at Jointed European Torus is reconstructedmore » numerically using the VMEC code [P. Hirshman and J. C. Whitson, Phys. Fluids 26, 3553 (1983)], with bootstrap current taken into account. Generally speaking, the diamagnetic drift effects are stabilizing. Our results show that the effectiveness of diamagnetic stabilization depends sensitively on the safe factor value (q{sub s}) at the safety-factor reversal or plateau region. The diamagnetic stabilization are weaker, when q{sub s} is larger than an integer; while stronger, when q{sub s} is smaller or less larger than an integer. We also find that the diamagnetic drift effects also depend sensitively on the rotation direction. The diamagnetic stabilization in the co-rotation case is stronger than in the counter rotation case with respect to the ion diamagnetic drift direction.« less

Housing flexibility effects on rotor stability

NASA Technical Reports Server (NTRS)

Davis, L. B.; Wolfe, E. A.; Beatty, R. F.

1985-01-01

Preliminary rotordynamic evaluations are performed with a housing stiffness assumption that is typically determined only after the hardware is built. In addressing rotor stability, a rigid housing assumption was shown to predict an instability at a lower spin speed than a comparable flexible housing analysis. This rigid housing assumption therefore provides a conservative estimate of the stability threshold speed. A flexible housing appears to act as an energy absorber and dissipated some of the destabilizing force. The fact that a flexible housing is usually asymmetric and considerably heavier than the rotor was related to this apparent increase in rotor stability. Rigid housing analysis is proposed as a valuable screening criteria and may save time and money in construction of elaborate housing finite element models for linear stability analyses.

46 CFR 151.03-17 - Compatible.

Code of Federal Regulations, 2011 CFR

2011-10-01

... prime considerations are the chemical, physical, or thermal properties of the reaction including heat, pressure, toxicity, stability, and explosive nature of the reaction and its end products. ...

46 CFR 151.03-17 - Compatible.

Code of Federal Regulations, 2010 CFR

2010-10-01

... prime considerations are the chemical, physical, or thermal properties of the reaction including heat, pressure, toxicity, stability, and explosive nature of the reaction and its end products. ...

Profile and Functional Properties of Seed Proteins from Six Pea (Pisum sativum) Genotypes

PubMed Central

Barac, Miroljub; Cabrilo, Slavica; Pesic, Mirjana; Stanojevic, Sladjana; Zilic, Sladjana; Macej, Ognjen; Ristic, Nikola

2010-01-01

Extractability, extractable protein compositions, technological-functional properties of pea (Pisum sativum) proteins from six genotypes grown in Serbia were investigated. Also, the relationship between these characteristics was presented. Investigated genotypes showed significant differences in storage protein content, composition and extractability. The ratio of vicilin:legumin concentrations, as well as the ratio of vicilin + convicilin: Legumin concentrations were positively correlated with extractability. Our data suggest that the higher level of vicilin and/or a lower level of legumin have a positive influence on protein extractability. The emulsion activity index (EAI) was strongly and positively correlated with the solubility, while no significant correlation was found between emulsion stability (ESI) and solubility, nor between foaming properties and solubility. No association was evident between ESI and EAI. A moderate positive correlation between emulsion stability and foam capacity was observed. Proteins from the investigated genotypes expressed significantly different emulsifying properties and foam capacity at different pH values, whereas low foam stability was detected. It appears that genotype has considerable influence on content, composition and technological-functional properties of pea bean proteins. This fact can be very useful for food scientists in efforts to improve the quality of peas and pea protein products. PMID:21614186

Profile and functional properties of seed proteins from six pea (Pisum sativum) genotypes.

PubMed

Barac, Miroljub; Cabrilo, Slavica; Pesic, Mirjana; Stanojevic, Sladjana; Zilic, Sladjana; Macej, Ognjen; Ristic, Nikola

2010-01-01

Extractability, extractable protein compositions, technological-functional properties of pea (Pisum sativum) proteins from six genotypes grown in Serbia were investigated. Also, the relationship between these characteristics was presented. Investigated genotypes showed significant differences in storage protein content, composition and extractability. The ratio of vicilin:legumin concentrations, as well as the ratio of vicilin + convicilin: Legumin concentrations were positively correlated with extractability. Our data suggest that the higher level of vicilin and/or a lower level of legumin have a positive influence on protein extractability. The emulsion activity index (EAI) was strongly and positively correlated with the solubility, while no significant correlation was found between emulsion stability (ESI) and solubility, nor between foaming properties and solubility. No association was evident between ESI and EAI. A moderate positive correlation between emulsion stability and foam capacity was observed. Proteins from the investigated genotypes expressed significantly different emulsifying properties and foam capacity at different pH values, whereas low foam stability was detected. It appears that genotype has considerable influence on content, composition and technological-functional properties of pea bean proteins. This fact can be very useful for food scientists in efforts to improve the quality of peas and pea protein products.

Combining Protein and Strain Engineering for the Production of Glyco-Engineered Horseradish Peroxidase C1A in Pichia pastoris

PubMed Central

Capone, Simona; Ćorajević, Lejla; Bonifert, Günther; Murth, Patrick; Maresch, Daniel; Altmann, Friedrich; Herwig, Christoph; Spadiut, Oliver

2015-01-01

Horseradish peroxidase (HRP), conjugated to antibodies and lectins, is widely used in medical diagnostics. Since recombinant production of the enzyme is difficult, HRP isolated from plant is used for these applications. Production in the yeast Pichia pastoris (P. pastoris), the most promising recombinant production platform to date, causes hyperglycosylation of HRP, which in turn complicates conjugation to antibodies and lectins. In this study we combined protein and strain engineering to obtain an active and stable HRP variant with reduced surface glycosylation. We combined four mutations, each being beneficial for either catalytic activity or thermal stability, and expressed this enzyme variant as well as the unmutated wildtype enzyme in both a P. pastoris benchmark strain and a strain where the native α-1,6-mannosyltransferase (OCH1) was knocked out. Considering productivity in the bioreactor as well as enzyme activity and thermal stability, the mutated HRP variant produced in the P. pastoris benchmark strain turned out to be interesting for medical diagnostics. This variant shows considerable catalytic activity and thermal stability and is less glycosylated, which might allow more controlled and efficient conjugation to antibodies and lectins. PMID:26404235

The physical and chemical stability of anti-tuberculosis fixed-dose combination products under accelerated climatic conditions.

PubMed

Bhutani, H; Mariappan, T T; Singh, S

2004-09-01

To determine the physical and chemical stability of anti-tuberculosis fixed-dose combinations (FDC) of rifampicin (RMP), isoniazid (INH), pyrazinamide (PZA) and ethambutol (EMB) sold on the Indian market. The products were stored for 3 months under ICH/WHO accelerated conditions (40 degrees C / 75% RH), with and without the original packaging in the presence and absence of light. The initial RMP, INH and PZA content was found to be within the range of 90-110% of the label claim. However, the products were found to have some chemical instability even initially; one of the tablets also showed physical instability. Under accelerated conditions, the unpackaged products underwent severe changes, whereas both physical and chemical changes were also observed in the packaged formulations. The physical changes were stronger under lighted conditions. A significant finding is that PZA and perhaps EMB may play a catalytic role in the interaction between INH and RMP. This study suggests that, unless they are packed in barrier packaging, anti-tuberculosis FDC formulations should be considered unstable, and due consideration should be given to their development pharmaceutics, packaging and stability testing.

Reusable launch vehicle model uncertainties impact analysis

NASA Astrophysics Data System (ADS)

Chen, Jiaye; Mu, Rongjun; Zhang, Xin; Deng, Yanpeng

2018-03-01

Reusable launch vehicle(RLV) has the typical characteristics of complex aerodynamic shape and propulsion system coupling, and the flight environment is highly complicated and intensely changeable. So its model has large uncertainty, which makes the nominal system quite different from the real system. Therefore, studying the influences caused by the uncertainties on the stability of the control system is of great significance for the controller design. In order to improve the performance of RLV, this paper proposes the approach of analyzing the influence of the model uncertainties. According to the typical RLV, the coupling dynamic and kinematics models are built. Then different factors that cause uncertainties during building the model are analyzed and summed up. After that, the model uncertainties are expressed according to the additive uncertainty model. Choosing the uncertainties matrix's maximum singular values as the boundary model, and selecting the uncertainties matrix's norm to show t how much the uncertainty factors influence is on the stability of the control system . The simulation results illustrate that the inertial factors have the largest influence on the stability of the system, and it is necessary and important to take the model uncertainties into consideration before the designing the controller of this kind of aircraft( like RLV, etc).

Stability and Change in Autism Spectrum Disorder Diagnosis from Age 3 to Middle Childhood in a High-Risk Sibling Cohort

ERIC Educational Resources Information Center

Brian, Jessica; Bryson, Susan E.; Smith, Isabel M.; Roberts, Wendy; Roncadin, Caroline; Szatmari, Peter; Zwaigenbaum, Lonnie

2016-01-01

Considerable evidence on autism spectrum disorder emergence comes from longitudinal high-risk samples (i.e. younger siblings of children with autism spectrum disorder). Diagnostic stability to age 3 is very good when diagnosed as early as 18-24 months, but sensitivity is weaker, and relatively little is known beyond toddlerhood. We examined…

The Considere Condition and Rapid Stretching of Linear and Branched Polymer Melts

NASA Technical Reports Server (NTRS)

McKinley, Gareth H.; Hassager, Ole

1999-01-01

We analyze the onset of "necking" and subsequent filament failure during the transient uniaxial elongation of viscoelastic fluid samples in extensional rheometers. In the limit of rapid elongation (such that no molecular relaxation occurs), the external work applied is all stored elastically and the Considere criterion originally developed in solid mechanics can be used to quantitatively predict the critical Hencky strain to failure. By comparing the predictions of the Doi-Edwards model for linear homopolymer melts with those of the "Pom-Pom" model for prototypical branched melts we show that the critical strain to failure in rapid elongation of a rubbery material is intimately linked to the molecular topology of the chain, especially the degree of chain branching. The onset of necking instability is monotonically shifted to larger Hencky strains as the number of branches is increased. Numerical computations at finite Deborah numbers also show that there is an optimal range of deformation rates over which homogeneous extensions can be maintained to large strain. We also consider other rapid homogeneous stretching deformations, such as biaxial and planar stretching, and show that the degree of stabilization afforded by inclusion of material with long-chain branching is a sensitive function of the imposed mode of deformation.

Theranostic Magnetic Nanostructures (MNS) for Cancer

PubMed Central

Nandwana, Vikas; De, Mrinmoy; Chu, Shihyao; Jaiswal, Manish; Rotz, Matt; Meade, Thomas J.

2015-01-01

Despite the complexities of cancer, remarkable diagnostic and therapeutic advances have been made during the past decade, which include improved genetic, molecular, and nanoscale understanding of the disease. Physical science and engineering, and nanotechnology in particular, have contributed to these developments through out-of-the-box ideas and initiatives from perspectives that are far removed from classical biological and medicinal aspects of cancer. Nanostructures, in particular, are being effectively utilized in sensing/diagnostics of cancer while nanoscale carriers are able to deliver therapeutic cargo for timed and controlled release at localized tumor sites. Magnetic nanostructures (MNS) have especially attracted considerable attention of researchers to address cancer diagnostics and therapy. A significant part of the promise of MNS lies in their potential for “theranostic” applications, wherein diagnostics makes use of the enhanced localized contrast in magnetic resonance imaging (MRI) while therapy leverages the ability of MNS to heat under external radio frequency (RF) field for thermal therapy or use of thermal activation for release of therapy cargo. In this chapter, we report some of the key developments in recent years in regard to MNS as potential theranostic carriers. We describe that the r2 relaxivity of MNS can be maximized by allowing water (proton) diffusion in the vicinity of MNS by polyethylene glycol (PEG) anchoring, which also facilitates excellent fluidic stability in various media and extended in vivo circulation while maintaining high r2 values needed for T2-weighted MRI contrast. Further, the specific absorption rate (SAR) required for thermal activation of MNS can be tailored by controlling composition and size of MNS. Together, emerging MNS show considerable promise to realize theranostic potential. We discuss that properly functionalized MNS can be designed to provide remarkable in vivo stability and accompanying pharmacokinetics exhibit organ localization that can be tailored for specific applications. In this context, even iron-based MNS show extended circulation as well as diverse organ accumulation beyond liver, which otherwise renders MNS potentially toxic to liver function. We believe that MNS, including those based on iron oxides, have entered a renaissance era where intelligent synthesis, functionalization, stabilization, and targeting provide ample evidence for applications in localized cancer theranostics. PMID:25895864

Shore Stabilization with Salt Marsh Vegetation.

DTIC Science & Technology

1983-01-01

seedlings - more expensive to grow and plant, more awkward to handle and transport, but relatively easy to produce. (3) Plugs - most expensive to...to sprigs, particularly if trans- planted late in the growing season. Pot-grown seedlings are relatively easy to produce but considerably more...transplanted late in the growing season. Pot-grown seedlings are relatively easy to produce but considerably more expensive than sprigs (Fig. 25). To prepare

Novel carboxymethyl cellulose-polyvinyl alcohol blend films stabilized by Pickering emulsion incorporation method.

PubMed

Fasihi, Hadi; Fazilati, Mohammad; Hashemi, Mahdi; Noshirvani, Nooshin

2017-07-01

The aim of this study was to investigate the possibility of increasing the antimicrobial and antioxidant properties of biodegradable active films stabilized via Pickering emulsions. The blend films were prepared from carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA), emulsified with oleic acid (OL) and incorporated with rosemary essential oil (REO). Formation of Pickering emulsion was confirmed by scanning electron microscopy (SEM), optical microscopy, mean droplet size and emulsion stability. Morphological, optical, physical, mechanical, thermal, antifungal and antioxidant properties of the films incorporated with different concentrations of REO (0.5, 1.5 and 3%) were determined. The results showed an increase in UV absorbance and elongation at break but, a decrease in tensile strength and thermal stability of the films. Interestingly, films containing REO exhibited considerable antioxidant and antimicrobial properties. In vitro microbial tests exhibited 100% fungal inhibition against Penicillium digitatum in the films containing 3% REO. In addition, no fungal growth were observed after 60days of storage at 25°C in bread slices were stored with active films incorporated with 3% REO, could attributed to the slow and regular release of REO caused by Pickering emulsions. The results of this study suggest that Pickering emulsion is a very promising method, which significantly affects antioxidant and antimicrobial activities of the films. Copyright © 2017 Elsevier Ltd. All rights reserved.

The effects of surfactant and electrolyte concentrations on the size of nanochitosan during storage

NASA Astrophysics Data System (ADS)

Primaningtyas, Annisa; Budhijanto, Wiratni; Fahrurrozi, Mohammad; Kusumastuti, Yuni

2017-05-01

The nano-sized particle of chitosan (nanochitosan) is a potential natural preservative agent for fresh fish and fish product preservation. Theoretically, nano-sized particles exert strong van der Waals force to each other so that the problem associated with nanochitosan is agglomeration that leads to size instability during storage. Size stability is of importance in the application of nanochitosan as an antimicrobial agent because it considerably affects the antimicrobial activity of chitosan. In this study, the formulation of nanochitosan was optimized with respect to the two major factors in colloid dispersion theory, which were the presence of surfactant and electrolyte. Polysorbate-80 was chosen as the representative of food grade surfactant while NaCl was used as the electrolyte. The purposes of this study were to evaluate the effect of polysorbate-80 concentration and to determine the effect of NaCl ions on the particle size of nanochitosan for at least one month storage period. Data were analyzed using Analysis of Variance (ANOVA) to identify the factors significantly affect the size stability. The dynamics of particle size distribution during storage was measured by Particle Size Analyzer (PSA). The result showed that surfactant did not significantly affect the particle size stability. On the other hand, the addition of electrolyte into the colloidal dispersion of nanochitosan consistently stabilized and also narrowed the particle size distribution during storage in the range of 175-391 nm.

Anatomic ligament consolidation of the superior acromioclavicular ligament and the coracoclavicular ligament complex after acute arthroscopically assisted double coracoclavicular bundle stabilization.

PubMed

Jobmann, S; Buckup, J; Colcuc, C; Roessler, P P; Zimmermann, E; Schüttler, K F; Hoffmann, R; Welsch, F; Stein, T

2017-09-18

The consolidation of the acromioclavicular (AC) and coracoclavicular (CC) ligament complex after arthroscopically assisted stabilization of acute acromioclavicular joint (ACJ) separation is still under consideration. Fifty-five consecutive patients after arthroscopically assisted double-CC-bundle stabilization within 14 days after acute high-grade ACJ separation were studied prospectively. All patients were clinically analysed preoperatively (FU0) and post-operatively (FU1 = 6 months; FU2 = 12 months). The structural MRI assessments were performed at FU0 (injured ACJ) and at FU2 bilateral (radiologic control group) and assessed separately the ligament thickness and length at defined regions for the conoid, trapezoid and the superior AC ligament. Thirty-seven patients were assessed after 6.5 months and after 16.0 months. The 16-month MRI analysis revealed for all patients continuous ligament healing for the CC-complex and the superior AC ligament with in the average hypertrophic consolidation compared to the control side. Separate conoid and trapezoid strands (double-strand configuration) were detected in 27 of 37 (73%) patients, and a single-strand configuration was detected in 10 of 37 (27%) patients; both configurations showed similar CCD data. The ligament healing was not influenced by the point of surgery, age at surgery and heterotopic ossification. The clinical outcome was increased (FU0-FU2): Rowe, 47.7-97.0 pts.; TAFT, 3.9-10.6 pts.; NAS pain , 8.9-1.4 pts. (all P < 0.05). The arthroscopically assisted double-CC-bundle stabilization within 14 days after acute high-grade ACJ separation showed 16 months after surgery sufficient consolidations of the AC and double-CC ligament complex in 73%. III, Case series.

Thiol antioxidant-functionalized CdSe/ZnS quantum dots: Synthesis, Characterization, Cytotoxicity

PubMed Central

Zheng, Hong; Mortensen, Luke J.; DeLouise, Lisa A.

2016-01-01

Nanotechnology is a growing industry with wide ranging applications in consumer product and technology development. In the biomedical field, nanoparticles are finding increasing use as imaging agents for biomolecular labeling and tumor targeting. The nanoparticle physiochemical properties must be tailored for the specific application but chemical and physical stability in the biological milieu (no oxidation, aggregation, agglomeration or toxicity) are often required. Nanoparticles used for biomolecular fluorescent imaging should also have high quantum yield (QY). The aim of this paper is to examine the QY, stability, and cell toxicity of a series of positive, negative and neutral surface charge quantum dot (QD) nanoparticles. Simple protocols are described to prepare water soluble QDs by modifying the surface with thiol containing antioxidant ligands and polymers keeping the QD core/shell composition constant. The ligands used to produce negatively charged QDs include glutathione (GSH), N-acetyl-L-cysteine (NAC), dihydrolipoic acid (DHLA), tiopronin (TP), bucilliamine (BUC), and mercaptosuccinic acid (MSA). Ligands used to produce positively charged QDs include cysteamine (CYS) and polyethylenimine (PEI). Dithiothreitol (DTT) was used to produce neutral charged QDs. Commercially available nonaqueous octadecylamine (ODA) capped QDs served as the starting material. Our results suggest that QD uptake and cytotoxicity are both dependent on surface ligand coating composition. The negative charged GSH coated QDs show superior performance exhibiting low cytotoxicity, high stability, high QY and therefore are best suited for bioimaging applications. PEI coated QD also show superior performance exhibiting high QY and stability. However, they are considerably more cytotoxic due to their high positive charge which is an advantageous property that can be exploited for gene transfection and/or tumor targeting applications. The synthetic procedures described are straightforward and can be easily adapted in most laboratory settings. PMID:23620993

Cytochrome P450-Mediated Phytoremediation using Transgenic Plants: A Need for Engineered Cytochrome P450 Enzymes

PubMed Central

Kumar, Santosh; Jin, Mengyao; Weemhoff, James L

2013-01-01

There is an increasing demand for versatile and ubiquitous Cytochrome P450 (CYP) biocatalysts for biotechnology, medicine, and bioremediation. In the last decade there has been an increase in realization of the power of CYP biocatalysts for detoxification of soil and water contaminants using transgenic plants. However, the major limitations of mammalian CYP enzymes are that they require CYP reductase (CPR) for their activity, and they show relatively low activity, stability, and expression. On the other hand, bacterial CYP enzymes show limited substrate diversity and usually do not metabolize herbicides and industrial contaminants. Therefore, there has been a considerable interest for biotechnological industries and the scientific community to design CYP enzymes to improve their catalytic efficiency, stability, expression, substrate diversity, and the suitability of P450-CPR fusion enzymes. Engineered CYP enzymes have potential for transgenic plants-mediated phytoremediation of herbicides and environmental contaminants. In this review we discuss: 1) the role of CYP enzymes in phytoremediation using transgenic plants, 2) problems associated with wild-type CYP enzymes in phytoremediation, and 3) examples of engineered CYP enzymes and their potential role in transgenic plant-mediated phytoremediation. PMID:25298920

Carbon-supported, selenium-modified ruthenium-molybdenum catalysts for oxygen reduction in acidic media.

PubMed

Guinel, Maxime J-F; Bonakdarpour, Arman; Wang, Biao; Babu, Panakkattu K; Ernst, Frank; Ramaswamy, Nagappan; Mukerjee, Sanjeev; Wieckowski, Andrzej

2009-07-20

The stability and oxygen reduction activity of two carbon-supported catalyst materials are reported. The catalysts, Se/Ru and Se/(Ru-Mo), were prepared by using a chemical reduction method. The catalyst nanoparticles were evenly dispersed onto globular amorphous carbon supports, and their average size was ca. 2.4 nm. Thermal treatment at 500 °C for 2 h in an inert argon atmosphere resulted in coarsening of the nanoparticles, and also in some decrease of their activity. A gradual reduction of activity was also observed for Se/Ru during potential-cycle experiments. However, the incorporation of small amounts of Mo into the Se/Ru catalysts considerably improved the stability of the catalyst against dissolution. The Mo-containing samples showed excellent oxygen reduction activities even after cycling the potential 1000 times between 0.7 and 0.9 V. Furthermore, they showed excellent fuel-cell behavior. The performance of the Se/Ru catalysts is greatly improved by the addition of small amounts of elemental Mo. Possible mechanisms responsible for the improvement of the activity are discussed. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

On the Complexity of the Metric TSP under Stability Considerations

NASA Astrophysics Data System (ADS)

Mihalák, Matúš; Schöngens, Marcel; Šrámek, Rastislav; Widmayer, Peter

We consider the metric Traveling Salesman Problem (Δ-TSP for short) and study how stability (as defined by Bilu and Linial [3]) influences the complexity of the problem. On an intuitive level, an instance of Δ-TSP is γ-stable (γ> 1), if there is a unique optimum Hamiltonian tour and any perturbation of arbitrary edge weights by at most γ does not change the edge set of the optimal solution (i.e., there is a significant gap between the optimum tour and all other tours). We show that for γ ≥ 1.8 a simple greedy algorithm (resembling Prim's algorithm for constructing a minimum spanning tree) computes the optimum Hamiltonian tour for every γ-stable instance of the Δ-TSP, whereas a simple local search algorithm can fail to find the optimum even if γ is arbitrary. We further show that there are γ-stable instances of Δ-TSP for every 1 < γ< 2. These results provide a different view on the hardness of the Δ-TSP and give rise to a new class of problem instances which are substantially easier to solve than instances of the general Δ-TSP.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pern, F.J.; Glick, S.H.; Czanderna, A.W.

Results from extensive studies of the commercial ethylene vinyl acetate (EVA) formulations show that the UV absorber and curing-generated UV-excitable, {alpha},{beta}-unsaturated carbonyl chromophores facilitate the EVA discoloration, which is further enhanced by curing-generated acetic acid and probably residual peroxide curing agent also. Formation and concentration of the UV-excitable chromophores are substantially promoted by the antioxidant, Naugard P. The discoloration rate is greater under higher UV light intensity and temperatures. Heating in the dark at elevated temperatures (e.g., 85&hthinsp;{degree}C) in the air for {approximately}200 days only results in light yellowing. The discoloration reactions compete with photobleaching reactions, which destroy curing-generated chromophoresmore » and result in non-discoloring of EVA. By using better performance stabilizers to minimize the curing-generated UV-excitable chromophores, a new fast curing agent, and no UV absorber, the NREL-developed EVA formulations show a superior photothermal stability against browning to the commercial counterparts. Alternatively, the discoloration rate of the commercial EVA pottants can be considerably reduced by using UV-filtering glass superstrates that largely inhibit the UV-induced photooxidation reactions, or completely eliminated by using air-permeable polymer superstrate films that enable photobleaching reactions. {copyright} {ital 1999 American Institute of Physics.}« less

A new approach to the stability analysis of transient natural convection in porous media

NASA Astrophysics Data System (ADS)

Tilton, Nils

2016-11-01

Onset of natural convection due to transient diffusion in porous media has attracted considerable attention for its applications to CO2 sequestration. Stability analyses typically investigate onset of convection using an initial value problem approach in which a perturbation is introduced to the concentration field at an initial time t =tp . This leads to debate concerning physically appropriate perturbations, the critical time tc for linear instability, and to the counter-intuitive notion of an optimal initial time tp that maximizes perturbation growth. We propose a new approach in which transient diffusion is continuously perturbed by small variations in the porosity. With this approach, instability occurs immediately (tc = 0) without violating any physical constraints, such that the concepts of initial time tp and critical time tc have less relevance. We argue that the onset time for nonlinear convection is a more physically relevant parameter, and show that it can be predicted using a simple asymptotic expansion. Using the expansion, we consider porosity perturbations that vary sinusoidally in the horizontal and vertical directions, and show there are optimal combinations of wavelengths that minimize the onset time of nonlinear convection.

Stabilities of lead(II) complexes formed in aqueous solution with methyl thiophosphate (MeOPS(2-)), uridine 5'- O-thiomonophosphate (UMPS(2-)) or adenosine 5'- O-thiomonophosphate (AMPS(2-)).

PubMed

Da Costa, Carla P; Krajewska, Danuta; Okruszek, Andrzej; Stec, Wojciech J; Sigel, Helmut

2002-04-01

The acidity constants of twofold protonated methyl thiophosphate (MeOPS(2-)) and of monoprotonated uridine 5'- O-thiomonophosphate (UMPS(2-)) have been determined in aqueous solution (25 degrees C; I= 0.1 M, NaNO(3)) by potentiometric pH titration. The stability constants of their 1:1 complexes formed with Pb(2+), i.e. Pb(MeOPS) and Pb(UMPS), have also been measured. The results show that replacement of a phosphate oxygen by a sulfur atom increases the acidity by about 1.4 p K units. On the basis of recently established log versus plots ( = simple phosphate or phosphonate ligands where R is a non-coordinating residue), it is shown that the stability of the Pb(thiophosphate) complexes is by log Delta= 2.43+/-0.09 larger than expected for a Pb(2+)-phosphate interaction. The identity of the stability increase (log Delta) observed for Pb(MeOPS) and Pb(UMPS) shows that the nucleobase residue in the Pb(UMPS) complex has no influence on complex formation. To be able to carry out the mentioned comparisons, we have also determined the stability constant of the complex formed between Pb(2+) and methyl phosphate; the corresponding data for Pb(UMP) were already known from our earlier studies. The present results allow an evaluation of other Pb(2+) complexes formed with thiophosphate derivatives and they are applied now to the Pb(2+) complexes of adenosine 5'- O-thiomonophosphate (AMPS(2-)). The stability constants of the Pb(H;AMPS)(+) and Pb(AMPS) complexes were measured and it is shown that, within the error limits, the stability of the Pb(AMPS) complex is determined by the basicity of the thiophosphate group of AMPS(2-); in other words, no hint for macrochelate formation involving N7 was observed. More important, with the aid of micro-stability-constant considerations it is concluded that the structure of the dominating isomer of the Pb(H;AMPS)(+) species is the one where the proton is located at the N1 site of the adenine residue and Pb(2+) is coordinated to the deprotonated thiophosphate group. The insights gained from this study with regard to thiophosphate-altered single-stranded nucleic acids and their affinity towards Pb(2+) are discussed.

Vaccine stabilization: research, commercialization, and potential impact.

PubMed

Kristensen, Debra; Chen, Dexiang; Cummings, Ray

2011-09-22

All vaccines are susceptible to damage by elevated temperatures and many are also damaged by freezing. The distribution, storage, and use of vaccines therefore present challenges that could be reduced by enhanced thermostability, with resulting improvements in vaccine effectiveness. Formulation and processing technologies exist that can improve the stability of vaccines at temperature extremes, however, customization is required for individual vaccines and results are variable. Considerations affecting decisions about stabilization approaches include development cost, manufacturing cost, and the ease of use of the final product. Public sector agencies can incentivize vaccine developers to prioritize stabilization efforts through advocacy and by implementing policies that increase demand for thermostable vaccines. Copyright © 2011 Elsevier Ltd. All rights reserved.

Measuring self-esteem in context: the importance of stability of self-esteem in psychological functioning.

PubMed

Kernis, Michael H

2005-12-01

In this article, I report on a research program that has focused on the joint roles of stability and level of self-esteem in various aspects of psychological functioning. Stability of self-esteem refers to the magnitude of short-term fluctuations that people experience in their current, contextually based feelings of self-worth. In contrast, level of self-esteem refers to representations of people's general, or typical, feelings of self-worth. A considerable amount of research reveals that self-esteem stability has predictive value beyond the predictive value of self-esteem level. Moreover, considering self-esteem stability provides one way to distinguish fragile from secure forms of high self-esteem. Results from a number of studies are presented and theoretical implications are discussed.

Meteorological Measurements from Satellite Platforms. [stability and control of flexible stochastic satellites

NASA Technical Reports Server (NTRS)

Suomi, V. E.

1975-01-01

The stability of stochastic satellites and the stability and control of flexible satellites were investigated. The effects of random environmental torques and noises in the moments of inertia of spinning and three-axes stabilized satellites were first compared analytically by four methods and by analog simulations. Among the analytical methods, it was shown that the Fokker-Planck formulation yields predictions which most coincide with the simulation results. It was then shown that the required stability criterion of a satellite is quite different from that obtained by a deterministic approach, under the assumption that the environmental and control torques experienced by the satellite are random. Finally, it was demonstrated that, by monitoring the deformations of the flexible elements of a satellite, the effectiveness of the satellite control system can be increased considerably.

The addition of body armor diminishes dynamic postural stability in military soldiers.

PubMed

Sell, Timothy C; Pederson, Jonathan J; Abt, John P; Nagai, Takashi; Deluzio, Jennifer; Wirt, Michael D; McCord, Larry J; Lephart, Scott M

2013-01-01

Poor postural stability has been identified as a risk factor for lower extremity musculoskeletal injury. The additional weight of body armor carried by Soldiers alters static postural stability and may predispose Soldiers to lower extremity musculoskeletal injuries. However, static postural stability tasks poorly replicate the dynamic military environment, which places considerable stress on the postural control system during tactical training and combat. Therefore, the purpose of this study was to examine the effects of body armor on dynamic postural stability during single-leg jump landings. Thirty-six 101st Airborne Division (Air Assault) Soldiers performed single-leg jump landings in the anterior direction with and without wearing body armor. The dynamic postural stability index and the individual stability indices (medial-lateral stability index, anterior-posterior stability index, and vertical stability index) were calculated for each condition. Paired sample t-tests were performed to determine differences between conditions. Significant differences existed for the medial-lateral stability index, anterior-posterior stability index, vertical stability index, and dynamic postural stability index (p < 0.05). The addition of body armor resulted in diminished dynamic postural stability, which may result in increased lower extremity injuries. Training programs should address the altered dynamic postural stability while wearing body armor in attempts to promote adaptations that will result in safer performance during dynamic tasks.

Stability Behavior and Thermodynamic States of Iron and Manganese in Sandy Soil Aquifer, Manukan Island, Malaysia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Chin Yik, E-mail: cy_lin_ars@hotmail.com; Abdullah, Mohd. Harun; Musta, Baba

2011-03-15

A total of 20 soil samples were collected from 10 boreholes constructed in the low lying area, which included ancillary samples taken from the high elevation area. Redox processes were investigated in the soil as well as groundwater in the shallow groundwater aquifer of Manukan Island, Sabah, Malaysia. Groundwater samples (n = 10) from each boreholes were also collected in the low lying area to understand the concentrations and behaviors of Fe and Mn in the dissolved state. This study strives to obtain a general understanding of the stability behaviors on Fe and Mn at the upper unsaturated and themore » lower-saturated soil horizons in the low lying area of Manukan Island as these elements usually play a major role in the redox chemistry of the shallow groundwater. Thermodynamic calculations using PHREEQC showed that the groundwater samples in the study area are oversaturated with respect to goethite, hematite, Fe(OH){sub 3} and undersaturated with respect to manganite and pyrochroite. Low concentrations of Fe and Mn in the groundwater might be probably due to the lack of minerals of iron and manganese oxides, which exist in the sandy aquifer. In fact, high organic matters that present in the unsaturated horizon are believed to be responsible for the high Mn content in the soil. It was observed that the soil samples collected from high elevation area (BK) comprises considerable amount of Fe in both unsaturated (6675.87 mg/kg) and saturated horizons (31440.49 mg/kg) compared to the low Fe content in the low lying area. Based on the stability diagram, the groundwater composition lies within the stability field for Mn{sup 2+} and Fe{sup 2+} under suboxic condition and very close to the FeS/Fe{sup 2+} stability boundary. This study also shows that both pH and Eh values comprise a strong negative value thus suggesting that the redox potential is inversely dependent on the changes of pH.« less

Stability and Hopf bifurcation of a delayed ratio-dependent predator-prey system

NASA Astrophysics Data System (ADS)

Wang, Wan-Yong; Pei, Li-Jun

2011-04-01

Since the ratio-dependent theory reflects the fact that predators must share and compete for food, it is suitable for describing the relationship between predators and their preys and has recently become a very important theory put forward by biologists. In order to investigate the dynamical relationship between predators and their preys, a so-called Michaelis-Menten ratio-dependent predator-prey model is studied in this paper with gestation time delays of predators and preys taken into consideration. The stability of the positive equilibrium is investigated by the Nyquist criteria, and the existence of the local Hopf bifurcation is analyzed by employing the theory of Hopf bifurcation. By means of the center manifold and the normal form theories, explicit formulae are derived to determine the stability, direction and other properties of bifurcating periodic solutions. The above theoretical results are validated by numerical simulations with the help of dynamical software WinPP. The results show that if both the gestation delays are small enough, their sizes will keep stable in the long run, but if the gestation delays of predators are big enough, their sizes will periodically fluctuate in the long term. In order to reveal the effects of time delays on the ratio-dependent predator-prey model, a ratio-dependent predator-prey model without time delays is considered. By Hurwitz criteria, the local stability of positive equilibrium of this model is investigated. The conditions under which the positive equilibrium is locally asymptotically stable are obtained. By comparing the results with those of the model with time delays, it shows that the dynamical behaviors of ratio-dependent predator-prey model with time delays are more complicated. Under the same conditions, namely, with the same parameters, the stability of positive equilibrium of ratio-dependent predator-prey model would change due to the introduction of gestation time delays for predators and preys. Moreover, with the variation of time delays, the positive equilibrium of the ratio-dependent predator-prey model subjects to Hopf bifurcation.

Exploring the hyperchargeless Higgs triplet model up to the Planck scale

NASA Astrophysics Data System (ADS)

Khan, Najimuddin

2018-04-01

We examine an extension of the SM Higgs sector by a Higgs triplet taking into consideration the discovery of a Higgs-like particle at the LHC with mass around 125 GeV. We evaluate the bounds on the scalar potential through the unitarity of the scattering matrix. Considering the cases with and without Z_2-symmetry of the extra triplet, we derive constraints on the parameter space. We identify the region of the parameter space that corresponds to the stability and metastability of the electroweak vacuum. We also show that at large field values the scalar potential of this model is suitable to explain inflation.

Polypyrrole based nanocomposites for supercapacitor applications: A review

NASA Astrophysics Data System (ADS)

Sardar, A.; Gupta, P. S.

2018-05-01

Recently conducting polymers have attracted great interest for supercapacitor applications. Among conducting polymers polypyrrole is most popular due to its unique electrical conductivity, optoelectrical properties, redox property and excellent environmental stability. In this article, we present a comprehensive review of polypyrrole and polypyrrole based nanocomposites for supercapacitor applications. We have included study of various parameters like power density, energy density, specific-capacitance by various authors for different kinds of nanocomposites where fillers are metal oxides, metal sulphides, graphene etc. Some polypyrrole nanocomposits show good electrochemical performances. The extremely stable supercapacitors with excellent flexibility and scalability hold considerable promise for the commerical application of flexible and wearable electronics.

An improved car-following model accounting for the preceding car's taillight

NASA Astrophysics Data System (ADS)

Zhang, Jian; Tang, Tie-Qiao; Yu, Shao-Wei

2018-02-01

During the deceleration process, the preceding car's taillight may have influences on its following car's driving behavior. In this paper, we propose an extended car-following model with consideration of the preceding car's taillight. Two typical situations are used to simulate each car's movement and study the effects of the preceding car's taillight on the driving behavior. Meanwhile, sensitivity analysis of the model parameter is in detail discussed. The numerical results show that the proposed model can improve the stability of traffic flow and the traffic safety can be enhanced without a decrease of efficiency especially when cars pass through a signalized intersection.

A Comparison of Two Path Planners for Planetary Rovers

NASA Technical Reports Server (NTRS)

Tarokh, M.; Shiller, Z.; Hayati, S.

1999-01-01

The paper presents two path planners suitable for planetary rovers. The first is based on fuzzy description of the terrain, and genetic algorithm to find a traversable path in a rugged terrain. The second planner uses a global optimization method with a cost function that is the path distance divided by the velocity limit obtained from the consideration of the rover static and dynamic stability. A description of both methods is provided, and the results of paths produced are given which show the effectiveness of the path planners in finding near optimal paths. The features of the methods and their suitability and application for rover path planning are compared

Computational study of elements of stability of a four-helix bundle protein biosurfactant

NASA Astrophysics Data System (ADS)

Schaller, Andrea; Connors, Natalie K.; Dwyer, Mirjana Dimitrijev; Oelmeier, Stefan A.; Hubbuch, Jürgen; Middelberg, Anton P. J.

2015-01-01

Biosurfactants are surface-active molecules produced principally by microorganisms. They are a sustainable alternative to chemically-synthesized surfactants, having the advantages of being non-toxic, highly functional, eco-friendly and biodegradable. However they are currently only used in a few industrial products due to costs associated with production and purification, which exceed those for commodity chemical surfactants. DAMP4, a member of a four-helix bundle biosurfactant protein family, can be produced in soluble form and at high yield in Escherichia coli, and can be recovered using a facile thermal phase-separation approach. As such, it encompasses an interesting synergy of biomolecular and chemical engineering with prospects for low-cost production even for industrial sectors. DAMP4 is highly functional, and due to its extraordinary thermal stability it can be purified in a simple two-step process, in which the combination of high temperature and salt leads to denaturation of all contaminants, whereas DAMP4 stays stable in solution and can be recovered by filtration. This study aimed to characterize and understand the fundamental drivers of DAMP4 stability to guide further process and surfactant design studies. The complementary use of experiments and molecular dynamics simulation revealed a broad pH and temperature tolerance for DAMP4, with a melting point of 122.4 °C, suggesting the hydrophobic core as the major contributor to thermal stability. Simulation of systematically created in silico variants of DAMP4 showed an influence of number and location of hydrophilic mutations in the hydrophobic core on stability, demonstrating a tolerance of up to three mutations before a strong loss in stability occurred. The results suggest a consideration of a balance of stability, functionality and kinetics for new designs according to their application, aiming for maximal functionality but at adequate stability to allow for cost-efficient production using thermal phase separation approaches.

Span-Load Distribution as a Factor in Stability in Roll

NASA Technical Reports Server (NTRS)

Knight, Montgomery; Noyes, Richard W

1932-01-01

This report gives the results of pressure-distribution tests made to study the effects on lateral stability of changing the span-load distribution on a rectangular monoplane wing model of fairly thick section. Three methods of changing the distribution were employed: variation in profile along the span to a thin symmetrical section at the tip, twist from +5 degrees to -15 degrees at the tip, and sweepback from +20 degrees to -20 degrees. The tests were conducted in a 5-foot closed-throat atmospheric wind tunnel. The investigation shows the following results: (1) change in profile along the span from the NACA-84 at the root to the NACA-M2 at the tip considerably reduces lateral instability, but also reduces the general effectiveness of the wing. (2) washout up to 11 degrees progressively reduces maximum lateral instability. (3) transition from sweepforward to sweepback gradually reduces the useful angle-of-attack range, but has no clearly defined effect on maximum lateral instability.

Photocatalytic activity and reusability of ZnO layer synthesised by electrolysis, hydrogen peroxide and heat treatment.

PubMed

Akhmal Saadon, Syaiful; Sathishkumar, Palanivel; Mohd Yusoff, Abdull Rahim; Hakim Wirzal, Mohd Dzul; Rahmalan, Muhammad Taufiq; Nur, Hadi

2016-08-01

In this study, the zinc oxide (ZnO) layer was synthesised on the surface of Zn plates by three different techniques, i.e. electrolysis, hydrogen peroxide and heat treatment. The synthesised ZnO layers were characterised using scanning electron microscopy, X-ray diffraction, UV-visible diffuse reflectance and photoluminescence spectroscopy. The photocatalytic activity of the ZnO layer was further assessed against methylene blue (MB) degradation under UV irradiation. The photocatalytic degradation of MB was achieved up to 84%, 79% and 65% within 1 h for ZnO layers synthesised by electrolysis, heat and hydrogen peroxide treatment, respectively. The reusability results show that electrolysis and heat-treated ZnO layers have considerable photocatalytic stability. Furthermore, the results confirmed that the photocatalytic efficiency of ZnO was directly associated with the thickness and enlarged surface area of the layer. Finally, this study proved that the ZnO layers synthesised by electrolysis and heat treatment had shown better operational stability and reusability.

Antitumor Activity of Lankacidin Group Antibiotics Is Due to Microtubule Stabilization via a Paclitaxel-like Mechanism.

PubMed

Ayoub, Ahmed Taha; Abou El-Magd, Rabab M; Xiao, Jack; Lewis, Cody Wayne; Tilli, Tatiana Martins; Arakawa, Kenji; Nindita, Yosi; Chan, Gordon; Sun, Luxin; Glover, Mark; Klobukowski, Mariusz; Tuszynski, Jack

2016-10-27

Lankacidin group antibiotics show strong antimicrobial activity against various Gram-positive bacteria. In addition, they were shown to have considerable antitumor activity against certain cell line models. For decades, the antitumor activity of lankacidin was associated with the mechanism of its antimicrobial action, which is interference with peptide bond formation during protein synthesis. This, however, was never confirmed experimentally. Due to significant similarity to paclitaxel-like hits in a previous computational virtual screening study, we suggested that the cytotoxic effect of lankacidin is due to a paclitaxel-like action. In this study, we tested this hypothesis computationally and experimentally and confirmed that lankacidin is a microtubule stabilizer that enhances tubulin assembly and displaces taxoids from their binding site. This study serves as a starting point for optimization of lankacidin derivatives for better antitumor activities. It also highlights the power of computational predictions and their aid in guiding experiments and formulating rigorous hypotheses.

3D Orbital Stability and Dynamic Environment of Asteroid 216 Kleopatra

NASA Astrophysics Data System (ADS)

Winter, Othon; Chanut, Thierry

A peculiar asteroid that might be the target of future space mission explorations is 216 Kleopatra, which has two small satellites and a peculiar dog-bone shape. Recent data processing showed the existence of a difference that can reach 25% for the dimensions of 216 Kleopatra between the radar observations and the light curves. We rebuild the shape of the asteroid 216 Kleopatra from these new data and estimate certain physical features by using the polyhedral model method. In our computations we use a code that avoids singularities from the line integrals of a homogeneous arbitrary shaped polyhedral source. This code evaluates the gravitational potential function and its first and second order derivatives. Then, we find the location of the and zero velocity curves. Finally, taking the rotation of asteroid 216 Kleopatra into consideration, the aims of this work is to analyze the stability against impact and the dynamics of numerical simulations of 3D initially equatorial and polar orbits near the body.

Storage stability of cooked sausages containing vegetable oils.

PubMed

Papavergou, E J; Ambrosiadis, J A; Psomas, J

1995-01-01

Comminuted cooked sausages were produced using standard industrial practices, by substituting corn oil, sunflower oil, cotton seed oil, soybean oil and hydrogenated vegetable fat for animal fat. When processed, products were assessed for their stability with respect to autoxidation and change in organoleptic properties during vacuum-packed storage in a domestic refrigerator at 4 degrees C. Data obtained indicated that changes in thiobarbituric acid (TBA) values and organoleptic properties of products produced using corn oil, sunflower oil and hydrogenated vegetable fat were similar to those observed for reference material produced using lard. In the case of samples produced using soybean and cotton seed oil, TBA value changes were more pronounced, but did not exceed acceptable limits. A more rapid deterioration of organoleptic characteristics was also observed for the same samples, which showed flavour problems after 3 months of storage at 4 degrees C. Substitution of plant oils for lard considerably reduced the cholesterol content and increased the ratio of unsaturated to saturated fatty acids of cooked sausages.

Use of olive oil-in-water gelled emulsions in model turkey breast emulsions

NASA Astrophysics Data System (ADS)

Serdaroğlu, M.; Öztürk, B.

2017-09-01

Today, gelled emulsion systems offer a novel possibility in lipid modification of meat products. In this study, we aimed to investigate the quality characteristics of model turkey emulsions that were prepared with olive oil-in-water gelled emulsion (GE) as partial or total beef fat replacer. The results indicated that while most of the GE treatments showed equivalent emulsion characteristics in terms of emulsion stability, water-holding capacity and cook yield, utilization of 100% GE as the lipid source could increase total expressible fluid of the model turkey emulsion and thus negatively affect the quality. Utilization of GE was effective in total fat reduction, as the model turkey emulsions formulated with more than 50% GE had significantly lower fat content compared to full-beef fat control model emulsion. However, beef fat replacement with GE produced considerable changes in colour parameters. Finally, it was concluded that utilization of GE as a partial beef fat replacer has good potential to enhance stability and reduce total fat in turkey meat emulsion products.

Achieving High Efficiency and Eliminating Degradation in Solid Oxide Electrochemical Cells Using High Oxygen-Capacity Perovskite.

PubMed

Jun, Areum; Kim, Junyoung; Shin, Jeeyoung; Kim, Guntae

2016-09-26

Recently, there have been efforts to use clean and renewable energy because of finite fossil fuels and environmental problems. Owing to the site-specific and weather-dependent characteristics of the renewable energy supply, solid oxide electrolysis cells (SOECs) have received considerable attention to store energy as hydrogen. Conventional SOECs use Ni-YSZ (yttria-stabilized zirconia) and LSM (strontium-doped lanthanum manganites)-YSZ as electrodes. These electrodes, however, suffer from redox-instability and coarsening of the Ni electrode along with delamination of the LSM electrode during steam electrolysis. In this study, we successfully design and fabricate highly efficient SOECs using layered perovskites, PrBaMn2 O5+δ (PBM) and PrBa0.5 Sr0.5 Co1.5 Fe0.5 O5+δ (PBSCF50), as both electrodes for the first time. The SOEC with layered perovskites as both-side electrodes shows outstanding performance, reversible cycling, and remarkable stability over 600 hours. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Facile fabrication of HDPE-g-MA/nanodiamond nanocomposites via one-step reactive blending.

PubMed

Song, Ping'an; Yu, Youming; Wu, Qiang; Fu, Shenyuan

2012-06-29

In this letter, nanocomposites based on maleic anhydride grafted high density polyethylene (HDPE-g-MA) and amine-functionalized nanodiamond (ND) were fabricated via one-step reactive melt-blending, generating a homogeneous dispersion of ND, as evidenced by transmission electron microscope observations. Thermal analysis results suggest that addition of ND does not affect significantly thermal stability of polymer matrix in nitrogen. However, it was interestingly found that incorporating pure ND decreases the thermal oxidation degradation stability temperature, but blending amino-functionalized ND via reactive processing significantly enhances it of HDPE in air condition. Most importantly, cone tests revealed that both ND additives and reactive blending greatly reduce the heat release rate of HDPE. The results suggest that ND has a potential application as flame retardant alternative for polymers. Tensile results show that adding ND considerably enhances Young's modulus, and reactive blending leads to further improvement in Young's modulus while hardly reducing the elongation at break of HDPE.

Facile fabrication of HDPE-g-MA/nanodiamond nanocomposites via one-step reactive blending

PubMed Central

2012-01-01

In this letter, nanocomposites based on maleic anhydride grafted high density polyethylene (HDPE-g-MA) and amine-functionalized nanodiamond (ND) were fabricated via one-step reactive melt-blending, generating a homogeneous dispersion of ND, as evidenced by transmission electron microscope observations. Thermal analysis results suggest that addition of ND does not affect significantly thermal stability of polymer matrix in nitrogen. However, it was interestingly found that incorporating pure ND decreases the thermal oxidation degradation stability temperature, but blending amino-functionalized ND via reactive processing significantly enhances it of HDPE in air condition. Most importantly, cone tests revealed that both ND additives and reactive blending greatly reduce the heat release rate of HDPE. The results suggest that ND has a potential application as flame retardant alternative for polymers. Tensile results show that adding ND considerably enhances Young’s modulus, and reactive blending leads to further improvement in Young’s modulus while hardly reducing the elongation at break of HDPE. PMID:22747773

Dynamic effects of memory in a cobweb model with competing technologies

NASA Astrophysics Data System (ADS)

Agliari, Anna; Naimzada, Ahmad; Pecora, Nicolò

2017-02-01

We analyze a simple model based on the cobweb demand-supply framework with costly innovators and free imitators and study the endogenous dynamics of price and firms' fractions in a homogeneous good market. The evolutionary selection between technologies depends on a performance measure in which a memory parameter is introduced. The resulting dynamics is then described by a two-dimensional map. In addition to the locally stabilizing effect due to the presence of memory, we show the existence of a double stability threshold which entails for different dynamic scenarios occurring when the memory parameter takes extreme values (i.e. when consideration of the last profit realization prevails or it is too much neglected). The eventuality of different coexisting attractors as well as the structure of the basins of attraction that characterizes the path dependence property of the model with memory is shown. In particular, through global analysis we also illustrate particular bifurcations sequences that may increase the complexity of the related basins of attraction.

Templated assembly of photoswitches significantly increases the energy-storage capacity of solar thermal fuels.

PubMed

Kucharski, Timothy J; Ferralis, Nicola; Kolpak, Alexie M; Zheng, Jennie O; Nocera, Daniel G; Grossman, Jeffrey C

2014-05-01

Large-scale utilization of solar-energy resources will require considerable advances in energy-storage technologies to meet ever-increasing global energy demands. Other than liquid fuels, existing energy-storage materials do not provide the requisite combination of high energy density, high stability, easy handling, transportability and low cost. New hybrid solar thermal fuels, composed of photoswitchable molecules on rigid, low-mass nanostructures, transcend the physical limitations of molecular solar thermal fuels by introducing local sterically constrained environments in which interactions between chromophores can be tuned. We demonstrate this principle of a hybrid solar thermal fuel using azobenzene-functionalized carbon nanotubes. We show that, on composite bundling, the amount of energy stored per azobenzene more than doubles from 58 to 120 kJ mol(-1), and the material also maintains robust cyclability and stability. Our results demonstrate that solar thermal fuels composed of molecule-nanostructure hybrids can exhibit significantly enhanced energy-storage capabilities through the generation of template-enforced steric strain.

Synthesis of Caffeine/Maleic Acid Co-crystal by Ultrasound-assisted Slurry Co-crystallization.

PubMed

Apshingekar, Prafulla P; Aher, Suyog; Kelly, Adrian L; Brown, Elaine C; Paradkar, Anant

2017-01-01

A green approach has been used for co-crystallization of noncongruent co-crystal pair of caffeine/maleic acid using water. Ultrasound is known to affect crystallization; hence, the effect of high power ultrasound on the ternary phase diagram has been investigated in detail using a slurry co-crystallization approach. A systematic investigation was performed to understand how the accelerated conditions during ultrasound-assisted co-crystallization will affect different regions of the ternary phase diagram. Application of ultrasound showed considerable effect on the ternary phase diagram, principally on caffeine/maleic acid 2:1 (disappeared) and 1:1 co-crystal (narrowed) regions. Also, the stability regions for pure caffeine and maleic acid in water were narrowed in the presence of ultrasound, expanding the solution region. The observed effect of ultrasound on the phase diagram was correlated with solubility of caffeine and maleic acid and stability of co-crystal forms in water. Copyright © 2016. Published by Elsevier Inc.

Thermal transport in boron nitride nanotorus—towards a nanoscopic thermal shield

NASA Astrophysics Data System (ADS)

Loh, G. C.; Baillargeat, D.

2013-11-01

Nanotori, or nanorings, are topological variants of nanotubes and are conceived to have different properties from their tubular form. In this study, the toroidal arrangement of boron nitride is introduced. Using classical molecular dynamics simulations, the thermal behaviour (thermal conductivity and thermal stability) of the boron nitride nanotorus and its relationship with the structural characteristics are investigated. Its circumferential thermal rectification strength displays a linear dependence on the bending coefficient of the nanostructure. Surface kinks are relatively inconsequential on its circumferential mode of conduction, as compared to its axial sense. The circumferential conductivity in the diffusive regime is calculated to be approximately 10 W/m K, while the axial conductivity is more than tenfold of this value. All nanotori with different toroidal characters show excellent thermal stability at extremely high temperatures approaching 3400 K. With consideration to its favourable properties, a thermal shield made up of a parallel row of nanotori is proposed as a nanoscale thermal insulation device.

Radio frequency induced hyperthermia mediated by dextran stabilized LSMO nanoparticles: in vitro evaluation of heat shock protein response

NASA Astrophysics Data System (ADS)

Bhayani, K. R.; Rajwade, J. M.; Paknikar, K. M.

2013-01-01

Dextran stabilized La0.7Sr0.3MnO3 (Dex-LSMO) is an alternative cancer hyperthermia agent holding considerable promise. Here, we have carried out a comparative study on radio frequency (˜264 kHz) induced Dex-LSMO mediated heating and extraneous heating (mimicking generalized hyperthermia) in terms of changes in the morphology, proliferation pattern and induction of heat shock proteins in a human melanoma cell line (A375). Our results clearly show that the cellular effects seen with extraneous heating (60 min at 43 °C) could be reproduced by just six minutes of radio frequency induced Dex-LSMO mediated heating. More importantly, the observed enhanced levels of HSP 70 and 90 (molecular markers of heat shock that trigger favorable immunological reactions) seen with Dex-LSMO mediated heating were comparable to extraneous heating. These results suggest the possible utility of Dex-LSMO as a cancer hyperthermia agent.

MoSbTe for high-speed and high-thermal-stability phase-change memory applications

NASA Astrophysics Data System (ADS)

Liu, Wanliang; Wu, Liangcai; Li, Tao; Song, Zhitang; Shi, Jianjun; Zhang, Jing; Feng, Songlin

2018-04-01

Mo-doped Sb1.8Te materials and electrical devices were investigated for high-thermal-stability and high-speed phase-change memory applications. The crystallization temperature (t c = 185 °C) and 10-year data retention (t 10-year = 112 °C) were greatly enhanced compared with those of Ge2Sb2Te5 (t c = 150 °C, t 10-year = 85 °C) and pure Sb1.8Te (t c = 166 °C, t 10-year = 74 °C). X-ray diffraction and transmission electron microscopy results show that the Mo dopant suppresses crystallization, reducing the crystalline grain size. Mo2.0(Sb1.8Te)98.0-based devices were fabricated to evaluate the reversible phase transition properties. SET/RESET with a large operation window can be realized using a 10 ns pulse, which is considerably better than that required for Ge2Sb2Te5 (∼50 ns). Furthermore, ∼1 × 106 switching cycles were achieved.

Comparative study of imide-based Li salts as electrolyte additives for Li-ion batteries

NASA Astrophysics Data System (ADS)

Sharova, Varvara; Moretti, Arianna; Diemant, Thomas; Varzi, Alberto; Behm, R. Jürgen; Passerini, Stefano

2018-01-01

Herein, we report the results of a detailed study on the use of different Li imide salts (LiTFSI, LiFSI, and LiFTFSI) as electrolyte additives for lithium-ion batteries. The introduction of lithium imide salts in the electrolyte is shown to considerably improve the first cycle coulombic efficiency and the long-term cycling stability of graphite/LiFePO4 cells. Using LiTFSI, a capacity fading of only ∼2% occurred over 600 cycles while the control cell with the state-of-the-art additive (VC) lost ∼20% of the initial capacity at 20 °C. The results of the XPS and impedance spectroscopy measurements of graphite electrodes show that, after the formation cycle, the SEI obtained in the presence of imide salts is thinner, contains more LiF and is less resistive than that obtained using VC. Despite the beneficial effect of the imide salts on the lithium-ion cell performance, a slightly reduced thermal stability of the SEI is observed.

MAP4 Mechanism that Stabilizes Mitochondrial Permeability Transition in Hypoxia: Microtubule Enhancement and DYNLT1 Interaction with VDAC1

PubMed Central

Zhang, Yi-ming; Zhang, Jia-ping; Hu, Jiong-yu; Zhang, Qiong; Dai, Xia; Teng, Miao; Zhang, Dong-xia; Huang, Yue-sheng

2011-01-01

Mitochondrial membrane permeability has received considerable attention recently because of its key role in apoptosis and necrosis induced by physiological events such as hypoxia. The manner in which mitochondria interact with other molecules to regulate mitochondrial permeability and cell destiny remains elusive. Previously we verified that hypoxia-induced phosphorylation of microtubule-associated protein 4 (MAP4) could lead to microtubules (MTs) disruption. In this study, we established the hypoxic (1% O2) cell models of rat cardiomyocytes, H9c2 and HeLa cells to further test MAP4 function. We demonstrated that increase in the pool of MAP4 could promote the stabilization of MT networks by increasing the synthesis and polymerization of tubulin in hypoxia. Results showed MAP4 overexpression could enhance cell viability and ATP content under hypoxic conditions. Subsequently we employed a yeast two-hybrid system to tag a protein interacting with mitochondria, dynein light chain Tctex-type 1 (DYNLT1), by hVDAC1 bait. We confirmed that DYNLT1 had protein-protein interactions with voltage-dependent anion channel 1 (VDAC1) using co-immunoprecipitation; and immunofluorescence technique showed that DYNLT1 was closely associated with MTs and VDAC1. Furthermore, DYNLT1 interactions with MAP4 were explored using a knockdown technique. We thus propose two possible mechanisms triggered by MAP4: (1) stabilization of MT networks, (2) DYNLT1 modulation, which is connected with VDAC1, and inhibition of hypoxia-induced mitochondrial permeabilization. PMID:22164227

Mononuclear cell membranes: stabilization by reproterol and cromoglycate, destabilization by fenoterol and salbutamol.

PubMed

Zimmer, Guido; Bernhörster, Markus; Pilz, Patrizius; Schuchmann-Fix, Jutta; Hüggelmeier, Rolf; Blüm, Nicole; Libertus, Herman

2006-01-01

Electron paramagnetic resonance (EPR) spectroscopy with spin labels 5- and 16-doxyl-stearic acid (DSA) was used to differentiate between actions of beta-agonists on human mononuclear cell membrane. Reproterol (CAS 13055-82-8), salbutamol (CAS 51022-70-9) and fenoterol (CAS 1944-12-3) compared to cromoglycate (CAS 15826-37-6) were used at concentrations of 10-100 nmol/l per 10(7) cells. With reproterol, order and polarity was not much changed, whereas salbutamol and fenoterol significantly destabilized the membrane to similar extent. Cromoglycate acted in a stabilizing fashion. With trypan blue exclusion, reproterol and cromoglycate showed stable values, whereas salbutamol and fenoterol augmented permeability. Thus, by conventional lipid spin labeling the discrimination between salbutamol and fenoterol could not be carried out. In contrast, previous lipid peroxidation studies in a model system had revealed a decrease by reproterol, no change by salbutamol and an increase by fenoterol. Also, using fenoterol, protein spin label 4-maleimido-TEMPO (2, 2, 6, 6-tetramethyl-1-piperidinyloxy) showed an increase of membrane rigidity of mononuclear cells. Moreover, mast cells of different origin were previously found tween beta-agonists. Reproterol in all tests behaved in a therapeutically profitable way. In conclusion, in addition to lipid spin labeling other methods and materials should be considered, to finally arrive at a more realistic differentiation between, for instance, salbutamol and fenoterol. The term "membrane (de) stabilization" should not generally be used without careful consideration of the type of cell/membrane in question.

Biomechanical analysis for primary stability of shoulder arthrodesis in different resection situations.

PubMed

Lerch, Solveig; Keller, Sebastian; Kirsch, Ludger; Berndt, Thomas; Rühmann, Oliver

2013-07-01

Only very few publications dealing with shoulder arthrodesis after bone resection procedures and no biomechanical studies are available. The presented biomechanical analysis should ascertain the type of arthrodesis with the highest primary stability in different bone loss situations. On 24 fresh cadaveric shoulder specimens three different bone loss situations were investigated under the stress of abduction, adduction, anteversion and retroversion without destruction by the use of a material testing machine. In each of the testings a 16-hole reconstruction plate was used and compared to arthrodesis with an additional dorsal 6-hole plate. The primary stability of shoulder arthrodesis with a 16-hole reconstruction plate after humeral head resection could be increased significantly if an additional dorsal plate was used. However, no significant improvement with the additional plate was detected after resection of the acromion. Of all investigated forms, arthrodesis after humeral head resection with additional plate showed the highest and arthrodesis after humeral head resection without additional plate showed the lowest force values. The mean values for forces achieved in abduction and adduction were considerably higher than those in anteversion and retroversion. There are no consistent specifications of arthrodesis techniques after resection situation available, thus the presented biomechanical testings give important information about the most stable form of arthrodesis in different types of bone loss. These findings provide an opportunity to minimize complications such as pseudarthrosis for a satisfying clinical outcome. Copyright © 2013 Elsevier Ltd. All rights reserved.

First-principles density functional calculation of electrochemical stability of fast Li ion conducting garnet-type oxides.

PubMed

Nakayama, Masanobu; Kotobuki, Masashi; Munakata, Hirokazu; Nogami, Masayuki; Kanamura, Kiyoshi

2012-07-28

The research and development of rechargeable all-ceramic lithium batteries are vital to realize their considerable advantages over existing commercial lithium ion batteries in terms of size, energy density, and safety. A key part of such effort is the development of solid-state electrolyte materials with high Li(+) conductivity and good electrochemical stability; lithium-containing oxides with a garnet-type structure are known to satisfy the requirements to achieve both features. Using first-principles density functional theory (DFT), we investigated the electrochemical stability of garnet-type Li(x)La(3)M(2)O(12) (M = Ti, Zr, Nb, Ta, Sb, Bi; x = 5 or 7) materials against Li metal. We found that the electrochemical stability of such materials depends on their composition and structure. The electrochemical stability against Li metal was improved when a cation M was chosen with a low effective nuclear charge, that is, with a high screening constant for an unoccupied orbital. In fact, both our computational and experimental results show that Li(7)La(3)Zr(2)O(12) and Li(5)La(3)Ta(2)O(12) are inert to Li metal. In addition, the linkage of MO(6) octahedra in the crystal structure affects the electrochemical stability. For example, perovskite-type La(1/3)TaO(3) was found, both experimentally and computationally, to react with Li metal owing to the corner-sharing MO(6) octahedral network of La(1/3)TaO(3), even though it has the same constituent elements as garnet-type Li(5)La(3)Ta(2)O(12) (which is inert to Li metal and features isolated TaO(6) octahedra).

Stability of the nakedness of Weyl singularities

NASA Technical Reports Server (NTRS)

Haugan, M. P.; Liang, E. P. T.

1979-01-01

The stability of the nakedness of the Weyl singularities against matter perturbations is investigated. Consideration is given to the effects of infalling test matter on the convergence of outgoing null rays. It is shown that the additional convergence induced by infalling test matter does not blow up sufficiently fast to reconverge diverging outgoing rays, at least in the equator, and that the nakedness seems to be stable in this limited sense.

Note: Improving long-term stability of hot-wire anemometer sensors by means of annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lundström, H., E-mail: hans.lundstrom@hig.se

2015-08-15

Annealing procedures for hot-wire sensors of platinum and platinum-plated tungsten have been investigated experimentally. It was discovered that the two investigated sensor metals behave quite differently during the annealing process, but for both types annealing may improve long-term stability considerably. Measured drift of sensors both without and with prior annealing is presented. Suggestions for suitable annealing temperatures and times are given.

Oxidative stability and ignition quality of algae derived methyl esters containing varying levels of methyl eicosapentaenoate and methyl docosahexaenoate

NASA Astrophysics Data System (ADS)

Bucy, Harrison

Microalgae is currently receiving strong consideration as a potential biofuel feedstock to help meet the advanced biofuels mandate of the 2007 Energy Independence and Security Act because of its theoretically high yield (gallons/acre/year) in comparison to current terrestrial feedstocks. Additionally, microalgae also do not compete with food and can be cultivated with wastewater on non-arable land. Microalgae lipids can be converted into a variety of biofuels including fatty acid methyl esters (e.g. FAME biodiesel), renewable diesel, renewable gasoline, or jet fuel. For microalgae derived FAME, the fuel properties will be directly related to the fatty acid composition of the lipids produced by the given microalgae strain. Several microalgae species under consideration for wide scale cultivation, such as Nannochloropsis, produce lipids with fatty acid compositions containing substantially higher quantities of long chainpolyunsaturated fatty acids (LC-PUFA) in comparison to terrestrial feedstocks. It is expected that increased levels of LC-PUFA will be problematic in terms of meeting all of the current ASTM specifications for biodiesel. For example, it is known that oxidative stability and cetane number decrease with increasing levels of LC-PUFA. However, these same LC-PUFA fatty acids, such as eicosapentaenoic acid (EPA: C20:5) and docosahexaenoic acid (DHA: C22:6) are known to have high nutritional value thereby making separation of these compounds economically attractive. Given the uncertainty in the future value of these LC-PUFA compounds and the economic viability of the separation process, the goal of this study was to examine the oxidative stability and ignition quality of algae-based FAME with varying levels of EPA and DHA removal. Oxidative stability tests were conducted at a temperature of 110°C and airflow of 10 L/h using a Metrohm 743 Rancimat with automatic induction period determination following the EN 14112 Method from the ASTM D6751 and EN 14214 Standards, which call for induction periods of at least three hours and six hours, respectively. Derived Cetane Number testing was conducted using a Waukesha FIT following the ASTM D7170 Method. Tests were conducted with synthetic algal oil blends manufactured from various sources to match the fatty acid compositions of several algae strains subjected to varying removal amounts of roughly 0 -- 100 percent LC-PUFA. In addition, tests were also conducted with real algal methyl esters produced from multiple sources. The bis-allylic position equivalent (BAPE) was calculated for each fuel sample to quantify the level of unsaturation. The induction period was then plotted as a function of BAPE, which showed that the oxidative stability varied exponentially with the amount of LC-PUFA. The results suggest that removal of 45 -- 65 percent of the LC-PUFA from Nannochloropsis-based algal methyl esters would be sufficient for meeting existing ASTM specifications for oxidative stability and 75 -- 85 percent removal would be needed to meet the EN specification. The oxidative stability additive tert-butylhydroquinone (THBQ) was found to increase Nannochloropsis-based algal methyl esters' oxidative stability to ASTM and EN specifications at only 0.03 percent and 0.06 percent additions by mass, respectively, when no LC-PUFA was removed. The ignition quality tests showed that the Derived Cetane Number varied linearly with BAPE and the algae formulations were found to pass the ASTM cetane specification of 47 only if all the LC-PUFA were removed.

BIOREACTOR LANDFILL DESIGN

EPA Science Inventory

Modern landfill design entails many elements including foundations, liner systems, leachate collection systems, stormwater control systems, slope stability considerations, leachate management systems, gas extraction systems, and capping and closure. The use of bioreactor technolo...

Surface-bonded ionic liquid stationary phases in high-performance liquid chromatography--a review.

PubMed

Pino, Verónica; Afonso, Ana M

2012-02-10

Ionic liquids (ILs) are a class of ionic, nonmolecular solvents which remain in liquid state at temperatures below 100°C. ILs possess a variety of properties including low to negligible vapor pressure, high thermal stability, miscibility with water or a variety of organic solvents, and variable viscosity. IL-modified silica as novel high-performance liquid chromatography (HPLC) stationary phases have attracted considerable attention for their differential behavior and low free-silanol activity. Indeed, around 21 surface-confined ionic liquids (SCIL) stationary phases have been developed in the last six years. Their chromatographic behavior has been studied, and, despite the presence of a positive charge on the stationary phase, they showed considerable promise for the separation of neutral solutes (not only basic analytes), when operated in reversed phase mode. This aspect points to the potential for truly multimodal stationary phases. This review attempts to summarize the state-of-the-art about SCIL phases including their preparation, chromatographic behavior, and analytical performance. Copyright © 2011 Elsevier B.V. All rights reserved.

Ab-initio study of structural, electronic, and transport properties of zigzag GaP nanotubes.

PubMed

Srivastava, Anurag; Jain, Sumit Kumar; Khare, Purnima Swarup

2014-03-01

Stability and electronic properties of zigzag (3 ≤ n ≤ 16) gallium phosphide nanotubes (GaP NTs) have been analyzed by employing a systematic ab-intio approach based on density functional theory using generalized gradient approximation with revised Perdew Burke Ernzerhoff type parameterization. Diameter dependence of bond length, buckling, binding energy, and band gap has been investigated and the analysis shows that the bond length and buckling decreases with increasing diameter of the tube, highest binding energy of (16, 0) confirms this as the most stable amongst all the NTs taken into consideration. The present GaP NTs shows direct band gap and it increases with diameter of the tubes. Using a two probe model for (4, 0) NT the I-V relationship shows an exponential increase in current on applying bias voltage beyond 1.73 volt.

Basic principles of stability.

PubMed

Egan, William; Schofield, Timothy

2009-11-01

An understanding of the principles of degradation, as well as the statistical tools for measuring product stability, is essential to management of product quality. Key to this is management of vaccine potency. Vaccine shelf life is best managed through determination of a minimum potency release requirement, which helps assure adequate potency throughout expiry. Use of statistical tools such a least squares regression analysis should be employed to model potency decay. The use of such tools provides incentive to properly design vaccine stability studies, while holding stability measurements to specification presents a disincentive for collecting valuable data. The laws of kinetics such as Arrhenius behavior help practitioners design effective accelerated stability programs, which can be utilized to manage stability after a process change. Design of stability studies should be carefully considered, with an eye to minimizing the variability of the stability parameter. In the case of measuring the degradation rate, testing at the beginning and the end of the study improves the precision of this estimate. Additional design considerations such as bracketing and matrixing improve the efficiency of stability evaluation of vaccines.

Three-dimensional tomographic mapping related to primary stability and structural miniscrew characteristics.

PubMed

Silvestrini Biavati, A; Tecco, S; Migliorati, M; Festa, F; Panza, G; Marzo, G; Gherlone, E; Tetè, S

2011-05-01

To evaluate the maxilla, mandible, and cortical plates on computerized tomographic (CT) scans to achieve accurate three-dimensional bone thickness measurements. We selected the CT scans of 25 subjects (among 102), aged 18-58 years (10 men, 15 women), with nearly complete dentition. We performed interradicular and bucco-lingual (including cortical plate thickness) measurements in dental areas distal to the canines in both alveolar arches, at three levels (5, 8, and 11 mm) from the alveolar ridge. The mean thicknesses of the cortical plates in the maxilla were 1.10 mm buccally and 1.27 mm on the palatal side (p < 0.05). In the mandible, cortical plates were 2.23 mm buccally and 2.02 mm lingually. Mandibular buccal and lingual cortical plates became thicker distally in the second and third molar areas. There was considerable variation in cortical thickness (from 0.25 to 5.50 mm). Based on interradicular distances, only 13% of measured sites in the maxilla were suitable for miniscrew insertion (≥3.3 mm), but 63% of sites were suitable in the mandible. This study showed considerable individual variation in bone thickness. Our data suggested that the palatal/lingual side may provide greater primary stability for miniscrews. The palatal area, between the second upper bicuspid and the first molar, appeared to be the most suitable area for tapered 7- to 9-mm miniscrews, starting at 1.5-2 mm from the alveolar crest. © 2011 John Wiley & Sons A/S.

Establishing permanent vegetation after highway construction.

DOT National Transportation Integrated Search

2013-09-01

The Nebraska Department of Roads (NDOR) has considerable challenges stabilizing soils on highway shoulders following construction activities. Exposed soils can be prone to erosion and offsite sediment flow during precipitation events. NDOR primarily ...

Formulation and optimization of doxorubicin loaded polymeric nanoparticles using Box-Behnken design: ex-vivo stability and in-vitro activity.

PubMed

Shaikh, Muhammad Vaseem; Kala, Manika; Nivsarkar, Manish

2017-03-30

Biodegradable nanoparticles (NPs) have gained tremendous interest for targeting chemotherapeutic drugs to the tumor environment. Inspite of several advances sufficient encapsulation along with the controlled release and desired size range have remained as considerable challenges. Hence, the present study examines the formulation optimization of doxorubicin loaded PLGA NPs (DOX-PLGA-NPs), prepared by single emulsion method for cancer targeting. Critical process parameters (CPP) were selected by initial screening. Later, Box-Behnken design (BBD) was used for analyzing the effect of the selected CPP on critical quality attributes (CQA) and to generate a design space. The optimized formulation was stabilized by lyophilization and was used for in-vitro drug release and in-vitro activity on A549 cell line. Moreover, colloidal stability of the NPs in the biological milieu was assessed. Amount of PLGA and PVA, oil:water ratio and sonication time were the selected independent factors for BBD. The statistical data showed that a quadratic model was fitted to the data obtained. Additionally, the lack of fit values for the models was not significant. The delivery system showed sustained release behavior over a period of 120h and was governed by Fickian diffusion. The multipoint analysis at 24, 48 and 72h showed gradual reduction in IC50 value of DOX-PLGA-NPs (p<0.05, Fig. 9). DOX-PLGA-NPs were found to be stable in the biological fluids indicating their in-vivo applicability. In conclusion, optimization of the DOX-PLGA-NPs by BBD yielded in a promising drug carrier for doxorubicin that could provide a novel treatment modality for cancer. Copyright © 2017 Elsevier B.V. All rights reserved.

Consideration of Gravity Gradient Stabilization for Orion

DTIC Science & Technology

1989-03-01

AND ERIC ANDionl STABILIZATION TION. MAY NEED SECOND CONTROL SYSTEM TO CONTROL OVERALL ANGULAR MOMENTUM I MOMENTUM DUMPING I IN RESPONSE TO...FURTHER EXPERIENCE IS GAINED RPEFERS TO ANY DEVICE THAT MAY BEl USED Ift A PRIOCESS TOE ECHANGE ANGULAR MOMENTUM WITH THME SPACIECRAFTI BODY Figure 5...rotating with angular velocity w relative to XYZ. If unit vectors along the X, Y, and Z axes are ij, and k, respectively, the vector r can be written

Analysis of seismic stability of large-sized tank VST-20000 with software package ANSYS

NASA Astrophysics Data System (ADS)

Tarasenko, A. A.; Chepur, P. V.; Gruchenkova, A. A.

2018-05-01

The work is devoted to the study of seismic stability of vertical steel tank VST-20000 with due consideration of the system response “foundation-tank-liquid”, conducted on the basis of the finite element method, modal analysis and linear spectral theory. The calculations are performed for the tank model with a high degree of detailing of metallic structures: shells, a fixed roof, a bottom, a reinforcing ring.

A linear quadratic regulator approach to the stabilization of uncertain linear systems

NASA Technical Reports Server (NTRS)

Shieh, L. S.; Sunkel, J. W.; Wang, Y. J.

1990-01-01

This paper presents a linear quadratic regulator approach to the stabilization of uncertain linear systems. The uncertain systems under consideration are described by state equations with the presence of time-varying unknown-but-bounded uncertainty matrices. The method is based on linear quadratic regulator (LQR) theory and Liapunov stability theory. The robust stabilizing control law for a given uncertain system can be easily constructed from the symmetric positive-definite solution of the associated augmented Riccati equation. The proposed approach can be applied to matched and/or mismatched systems with uncertainty matrices in which only their matrix norms are bounded by some prescribed values and/or their entries are bounded by some prescribed constraint sets. Several numerical examples are presented to illustrate the results.

Flow Distribution Control Characteristics in Marine Gas Turbine Waste- Heat Recovery Systems. Phase 2. Flow Distribution Control in Waste-Heat Steam Generators

DTIC Science & Technology

1982-07-01

waste-heat steam generators. The applicable steam generator design concepts and general design consideration were reviewed and critical problems...a once-through forced-circulation steam generator design should be selected because of stability, reliability, compact- ness and lightweight...consists of three sections and one appendix. In Section I, the applicable steam generator design conccpts and general design * considerations are reviewed

Stability Performance of Inductively Coupled Plasma Mass Spectrometry-Phenotyped Kernel Minerals Concentration and Grain Yield in Maize in Different Agro-Climatic Zones

PubMed Central

Mallikarjuna, Mallana Gowdra; Thirunavukkarasu, Nepolean; Hossain, Firoz; Bhat, Jayant S.; Jha, Shailendra K.; Rathore, Abhishek; Agrawal, Pawan Kumar; Pattanayak, Arunava; Reddy, Sokka S.; Gularia, Satish Kumar; Singh, Anju Mahendru; Manjaiah, Kanchikeri Math; Gupta, Hari Shanker

2015-01-01

Deficiency of iron and zinc causes micronutrient malnutrition or hidden hunger, which severely affects ~25% of global population. Genetic biofortification of maize has emerged as cost effective and sustainable approach in addressing malnourishment of iron and zinc deficiency. Therefore, understanding the genetic variation and stability of kernel micronutrients and grain yield of the maize inbreds is a prerequisite in breeding micronutrient-rich high yielding hybrids to alleviate micronutrient malnutrition. We report here, the genetic variability and stability of the kernel micronutrients concentration and grain yield in a set of 50 maize inbred panel selected from the national and the international centres that were raised at six different maize growing regions of India. Phenotyping of kernels using inductively coupled plasma mass spectrometry (ICP-MS) revealed considerable variability for kernel minerals concentration (iron: 18.88 to 47.65 mg kg–1; zinc: 5.41 to 30.85 mg kg–1; manganese: 3.30 to17.73 mg kg–1; copper: 0.53 to 5.48 mg kg–1) and grain yield (826.6 to 5413 kg ha–1). Significant positive correlation was observed between kernel iron and zinc within (r = 0.37 to r = 0.52, p < 0.05) and across locations (r = 0.44, p < 0.01). Variance components of the additive main effects and multiplicative interactions (AMMI) model showed significant genotype and genotype × environment interaction for kernel minerals concentration and grain yield. Most of the variation was contributed by genotype main effect for kernel iron (39.6%), manganese (41.34%) and copper (41.12%), and environment main effects for both kernel zinc (40.5%) and grain yield (37.0%). Genotype main effect plus genotype-by-environment interaction (GGE) biplot identified several mega environments for kernel minerals and grain yield. Comparison of stability parameters revealed AMMI stability value (ASV) as the better representative of the AMMI stability parameters. Dynamic stability parameter GGE distance (GGED) showed strong and positive correlation with both mean kernel concentrations and grain yield. Inbreds (CM-501, SKV-775, HUZM-185) identified from the present investigation will be useful in developing micronutrient-rich as well as stable maize hybrids without compromising grain yield. PMID:26406470

Stability Performance of Inductively Coupled Plasma Mass Spectrometry-Phenotyped Kernel Minerals Concentration and Grain Yield in Maize in Different Agro-Climatic Zones.

PubMed

Mallikarjuna, Mallana Gowdra; Thirunavukkarasu, Nepolean; Hossain, Firoz; Bhat, Jayant S; Jha, Shailendra K; Rathore, Abhishek; Agrawal, Pawan Kumar; Pattanayak, Arunava; Reddy, Sokka S; Gularia, Satish Kumar; Singh, Anju Mahendru; Manjaiah, Kanchikeri Math; Gupta, Hari Shanker

2015-01-01

Deficiency of iron and zinc causes micronutrient malnutrition or hidden hunger, which severely affects ~25% of global population. Genetic biofortification of maize has emerged as cost effective and sustainable approach in addressing malnourishment of iron and zinc deficiency. Therefore, understanding the genetic variation and stability of kernel micronutrients and grain yield of the maize inbreds is a prerequisite in breeding micronutrient-rich high yielding hybrids to alleviate micronutrient malnutrition. We report here, the genetic variability and stability of the kernel micronutrients concentration and grain yield in a set of 50 maize inbred panel selected from the national and the international centres that were raised at six different maize growing regions of India. Phenotyping of kernels using inductively coupled plasma mass spectrometry (ICP-MS) revealed considerable variability for kernel minerals concentration (iron: 18.88 to 47.65 mg kg(-1); zinc: 5.41 to 30.85 mg kg(-1); manganese: 3.30 to 17.73 mg kg(-1); copper: 0.53 to 5.48 mg kg(-1)) and grain yield (826.6 to 5413 kg ha(-1)). Significant positive correlation was observed between kernel iron and zinc within (r = 0.37 to r = 0.52, p < 0.05) and across locations (r = 0.44, p < 0.01). Variance components of the additive main effects and multiplicative interactions (AMMI) model showed significant genotype and genotype × environment interaction for kernel minerals concentration and grain yield. Most of the variation was contributed by genotype main effect for kernel iron (39.6%), manganese (41.34%) and copper (41.12%), and environment main effects for both kernel zinc (40.5%) and grain yield (37.0%). Genotype main effect plus genotype-by-environment interaction (GGE) biplot identified several mega environments for kernel minerals and grain yield. Comparison of stability parameters revealed AMMI stability value (ASV) as the better representative of the AMMI stability parameters. Dynamic stability parameter GGE distance (GGED) showed strong and positive correlation with both mean kernel concentrations and grain yield. Inbreds (CM-501, SKV-775, HUZM-185) identified from the present investigation will be useful in developing micronutrient-rich as well as stable maize hybrids without compromising grain yield.

Three-dimensional modelling of slope stability using the Local Factor of Safety concept

NASA Astrophysics Data System (ADS)

Moradi, Shirin; Huisman, Sander; Beck, Martin; Vereecken, Harry; Class, Holger

2017-04-01

Slope stability is governed by coupled hydrological and mechanical processes. The slope stability depends on the effective stress, which in turn depends on the weight of the soil and the matrix potential. Therefore, changes in water content and matrix potential associated with infiltration will affect slope stability. Most available models describing these coupled hydro-mechanical processes either rely on a one- or two-dimensional representation of hydrological and mechanical properties and processes, which obviously is a strong simplification in many applications. Therefore, the aim of this work is to develop a three-dimensional hydro-mechanical model that is able to capture the effect of spatial and temporal variability of both mechanical and hydrological parameters on slope stability. For this, we rely on DuMux, which is a free and open-source simulator for flow and transport processes in porous media that facilitates coupling of different model approaches and offers flexibility for model development. We use the Richards equation to model unsaturated water flow. The simulated water content and matrix potential distribution is used to calculate the effective stress. We only consider linear elasticity and solve for statically admissible fields of stress and displacement without invoking failure or the redistribution of post-failure stress or displacement. The Local Factor of Safety concept is used to evaluate slope stability in order to overcome some of the main limitations of commonly used methods based on limit equilibrium considerations. In a first step, we compared our model implementation with a 2D benchmark model that was implemented in COMSOL Multiphysics. In a second step, we present in-silico experiments with the newly developed 3D model to show the effect of slope morphology, spatial variability in hydraulic and mechanical material properties, and spatially variable soil depth on simulated slope stability. It is expected that this improved physically-based three-dimensional hydro-mechanical model is able to provide more reliable slope instability predictions in more complex situations.

On the stability of a superspinar

NASA Astrophysics Data System (ADS)

Nakao, Ken-ichi; Joshi, Pankaj S.; Guo, Jun-Qi; Kocherlakota, Prashant; Tagoshi, Hideyuki; Harada, Tomohiro; Patil, Mandar; Królak, Andrzej

2018-05-01

The superspinar proposed by Gimon and Hořava is a rapidly rotating compact entity whose exterior is described by the over-spinning Kerr geometry. The compact entity itself is expected to be governed by superstringy effects, and in astrophysical scenarios it can give rise to interesting observable phenomena. Earlier it was suggested that the superspinar may not be stable but we point out here that this does not necessarily follow from earlier studies. We show, by analytically treating the Teukolsky equations by Detwiler's method, that in fact there are infinitely many boundary conditions that make the superspinar stable at least against the linear perturbations of m = l modes, and that the modes will decay in time. Further consideration leads us to the conclusion that it is possible to set the inverse problem to the linear stability issue: since the radial Teukolsky equation for the superspinar has no singular point on the real axis, we obtain regular solutions to the Teukolsky equation for arbitrary discrete frequency spectrum of the quasi-normal modes (no incoming waves) and the boundary conditions at the "surface" of the superspinar are found from obtained solutions. It follows that we need to know more on the physical nature of the superspinar in order to decide on its stability in physical reality.

Proximate composition of Karkadeh (Hibiscus sabdariffa) seeds and some functional properties of seed protein isolate as influenced by pH and NaCl.

PubMed

Salah, E O Mahgoub; Hayat, Z E Elbashir

2009-05-01

Seeds of an inbred line (B-11-90) of Karkadeh (Hibiscus sabdariffa) were investigated for their proximate composition (AOAC methods), nitrogen solubility and protein isolate (Karkadeh seed protein isolates [KSPI]) functional properties (standard methods). The fat and protein contents of the seeds were 22.43% and 32.46%, respectively. Nitrogen solubility was good in both water and 1.0 M NaCl at alkaline pH rather than at acidic pH, with better solubility at higher pH levels in water than in 1.0 M NaCl. The functional properties of the KSPI were as follows: water absorption capacity, 181 ml/100 g; fat absorption capacity, 110 ml/100 g; bulk density, 0.77 g/ml; and apparent viscosity (at 20 degrees C), 13.42 cps. KSPI showed a maximum foaming capacity at pH 12 and 1.6 M NaCl, a maximum emulsification capacity at pH 11 and 1.8 M NaCl, and a weaker foam stability at neutral pH than at acidic or alkaline pH, with a better foam stability at alkaline pH. The foam stability was considerably improved by treatment with 1.6 M NaCl.

Relative contributions of plantar fascia and ligaments on the arch static stability: a finite element study.

PubMed

Tao, Kai; Ji, Wen-Ting; Wang, Dong-Mei; Wang, Cheng-Tao; Wang, Xu

2010-10-01

The plantar fascia (PF) and major ligaments play important roles in keeping the static foot arch structure. Their functions and relative contributions to the arch stability have not been well studied. A three-dimensional finite element foot model was created based on the reconstruction of magnetic resonance images. During balanced standing, four cases after individual releases of the PF, spring ligament (SL), and long and short plantar ligaments (LPL and SPL) were simulated, to compare their biomechanical consequences with the normal predictions under the intact structure. Although the predictions showed the arch did not collapse obviously after each structure sectioning, the internal mechanical behaviors changed considerably. The PF release resulted in the maximal increases of approximately 91%, 65% and 47% in the tensions of the LPF, SPL and SL, produced the largest changes in all bone rotations, and brought an obvious shift of high stress from the medial metatarsals to the lateral metatarsals. The SL release mainly enhanced bone rotation angles and weakened the joint stability of the arch structure. The LPL and the SPL performed the roles of mutual compensation as either one was released. The influence of the LPL on the load distribution among metatarsals was greater than for the SPL and the SL.

Thermozymes and their applications: a review of recent literature and patents.

PubMed

Bruins, M E; Janssen, A E; Boom, R M

2001-02-01

Enzymes from thermophilic microorganisms, thermozymes, have unique characteristics such as temperature, chemical, and pH stability. They can be used in several industrial processes, in which they replace mesophilic enzymes or chemicals. Thermozymes are often used when the enzymatic process is compatible with existing (high-temperature) process conditions. The main advantages of performing processes at higher temperatures are reduced risk of microbial contamination, lower viscosity, improved transfer rates, and improved solubility of substrates. However, cofactors, substrates, or products might be unstable or other side reactions may occur. Recent developments show that thermophiles are a good source of novel catalysts that are of great industrial interest. Thermostable polymer-degrading enzymes such as amylases, pullulanases, xylanases, proteases, and cellulases are expected to play an important role in food, chemical, pharmaceutical, paper, pulp, and waste-treatment industries. Considerable research efforts have been made to better understand the stability of thermozymes. There are no major conformational differences with mesophilic enzymes, and a small number of extra salt bridges, hydrophobic interactions, or hydrogen bounds seem to confer the extra degree of stabilization. Currently, overexpression of thermozymes in standard Escherichia coli allows the production of much larger quantities of enzymes, which are easy to purify by heat treatment. With wider availability and lower cost, thermophilic enzymes will see more application in industry.

The Proximal and Distal Femoral Canal Geometry Influences Cementless Stem Anchorage and Revision Hip and Knee Implant Stability.

PubMed

Heinecke, Markus; Rathje, Fabian; Layher, Frank; Matziolis, Georg

2018-05-01

Although cementless revision arthroplasty of the hip has become the gold standard, revision arthroplasty of the distal femur is controversial. This study evaluated the anchoring principles of different femoral revision stem designs in extended bone defect situations, taking into account the anatomical conditions of the proximal and distal femur, and the resulting primary stability. Cementless press-fit stems of 4 different designs were implanted in synthetic femurs. The specimens were analyzed by computed tomography and were tested considering axial/torsional stiffness and migration resistance. Different stem designs anchored in different femoral canal geometries achieved comparable primary stability. Despite considerably different anchorage lengths, no difference in migration behavior or stiffness was found. Both in the distal femur and in the proximal femur, the conical stems showed a combination of conical and 3-point anchorage. Regarding the cylindrical stem tested, a much shorter anchorage length was sufficient in the distal femur to achieve comparable primary stability. In the investigated osseous defect model, the stem design (conical vs cylindrical), not the geometry of the femoral canal (proximal vs distal), was decisive regarding the circumferential anchorage length. For the conical stems, it can be postulated that there are reserves available for achieving a conical-circular fixation as a result of the large contact length. For the cylindrical stems, only a small reserve for a stable anchorage can be assumed. [Orthopedics. 2018; 41(3):e369-e375.]. Copyright 2018, SLACK Incorporated.

Changes in the Balance Performance of Polish Recreational Skiers after Seven Days of Alpine Skiing

PubMed Central

Wojtyczek, Beata; Pasławska, Małgorzata; Raschner, Christian

2014-01-01

Alpine skiing is one of the most popular leisure time winter sporting activities. Skiing imposes high requirements concerning physical fitness, particularly regarding balance abilities. The main objective of this study was to evaluate the changes in balance performance of recreational skiers after a seven-day ski camp. A total of 78 students - 24 women and 54 men - participated in the study. The ski course was held in accordance with the official program of the Polish Ski Federation. The study sample was comprised of 43 beginners and 35 intermediate skiers. All students were tested with the MFT S3-Check, the day before and the day after the ski camp. The test system consisted of an unstable uniaxial platform, with an integrated sensor and corresponding software. Changes in balance performance (sensory and stability index) were evaluated using paired t-tests. Additionally, changes in sensory and stability categories, which were based on the norm data, were analyzed. Female and male participants showed significantly better sensory and stability indices after skiing. Considerable changes from weak or very weak to average or good balance categories could be seen after skiing for both sexes. Regarding skiing experience, both beginners and intermediate skiers improved their sensory and stability indices significantly after skiing. Hence, recreational alpine skiing resulted in better balance performance regardless of sex or skiing experience. Skiing as an outdoor activity offers the opportunity to improve balance performance with a positive impact on everyday life activities. PMID:25713663

Changes in the balance performance of polish recreational skiers after seven days of alpine skiing.

PubMed

Wojtyczek, Beata; Pasławska, Małgorzata; Raschner, Christian

2014-12-09

Alpine skiing is one of the most popular leisure time winter sporting activities. Skiing imposes high requirements concerning physical fitness, particularly regarding balance abilities. The main objective of this study was to evaluate the changes in balance performance of recreational skiers after a seven-day ski camp. A total of 78 students - 24 women and 54 men - participated in the study. The ski course was held in accordance with the official program of the Polish Ski Federation. The study sample was comprised of 43 beginners and 35 intermediate skiers. All students were tested with the MFT S3-Check, the day before and the day after the ski camp. The test system consisted of an unstable uniaxial platform, with an integrated sensor and corresponding software. Changes in balance performance (sensory and stability index) were evaluated using paired t-tests. Additionally, changes in sensory and stability categories, which were based on the norm data, were analyzed. Female and male participants showed significantly better sensory and stability indices after skiing. Considerable changes from weak or very weak to average or good balance categories could be seen after skiing for both sexes. Regarding skiing experience, both beginners and intermediate skiers improved their sensory and stability indices significantly after skiing. Hence, recreational alpine skiing resulted in better balance performance regardless of sex or skiing experience. Skiing as an outdoor activity offers the opportunity to improve balance performance with a positive impact on everyday life activities.

[Cement augmentation on the spine : Biomechanical considerations].

PubMed

Kolb, J P; Weiser, L; Kueny, R A; Huber, G; Rueger, J M; Lehmann, W

2015-09-01

Vertebral compression fractures are the most common osteoporotic fractures. Since the introduction of vertebroplasty and screw augmentation, the management of osteoporotic fractures has changed significantly. The biomechanical characteristics of the risk of adjacent fractures and novel treatment modalities for osteoporotic vertebral fractures, including pure cement augmentation by vertebroplasty, and cement augmentation of screws for posterior instrumentation, are explored. Eighteen human osteoporotic lumbar spines (L1-5) adjacent to vertebral bodies after vertebroplasty were tested in a servo-hydraulic machine. As augmentation compounds we used standard cement and a modified low-strength cement. Different anchoring pedicle screws were tested with and without cement augmentation in another cohort of human specimens with a simple pull-out test and a fatigue test that better reflects physiological conditions. Cement augmentation in the osteoporotic spine leads to greater biomechanical stability. However, change in vertebral stiffness resulted in alterations with the risk of adjacent fractures. By using a less firm cement compound, the risk of adjacent fractures is significantly reduced. Both screw augmentation techniques resulted in a significant increase in the withdrawal force compared with the group without cement. Augmentation using perforated screws showed the highest stability in the fatigue test. The augmentation of cement leads to a significant change in the biomechanical properties. Differences in the stability of adjacent vertebral bodies increase the risk of adjacent fractures, which could be mitigated by a modified cement compound with reduced strength. Screws that were specifically designed for cement application displayed greatest stability in the fatigue test.

The stability and change of etiological influences on depression, anxiety symptoms and their co-occurrence across adolescence and young adulthood.

PubMed

Waszczuk, M A; Zavos, H M S; Gregory, A M; Eley, T C

2016-01-01

Depression and anxiety persist within and across diagnostic boundaries. The manner in which common v. disorder-specific genetic and environmental influences operate across development to maintain internalizing disorders and their co-morbidity is unclear. This paper investigates the stability and change of etiological influences on depression, panic, generalized, separation and social anxiety symptoms, and their co-occurrence, across adolescence and young adulthood. A total of 2619 twins/siblings prospectively reported symptoms of depression and anxiety at mean ages 15, 17 and 20 years. Each symptom scale showed a similar pattern of moderate continuity across development, largely underpinned by genetic stability. New genetic influences contributing to change in the developmental course of the symptoms emerged at each time point. All symptom scales correlated moderately with one another over time. Genetic influences, both stable and time-specific, overlapped considerably between the scales. Non-shared environmental influences were largely time- and symptom-specific, but some contributed moderately to the stability of depression and anxiety symptom scales. These stable, longitudinal environmental influences were highly correlated between the symptoms. The results highlight both stable and dynamic etiology of depression and anxiety symptom scales. They provide preliminary evidence that stable as well as newly emerging genes contribute to the co-morbidity between depression and anxiety across adolescence and young adulthood. Conversely, environmental influences are largely time-specific and contribute to change in symptoms over time. The results inform molecular genetics research and transdiagnostic treatment and prevention approaches.

Alloy selection considerations and service experience of the first ''in-service'' 439 stainless steel moisture-separator-reheater tube bundles at Kewaunee nuclear power plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kratz, J.L.; Minard, P.G.; Weinberg, D.E.

1982-01-01

The need for an alternate moisture-reheater tubing alloy is explored and the reasoning behind the selection of 439 stainless steel is presented. Significant advantages that are evident by using special tubing chemistry and special tubing heat treatment are discussed in relation to fin-die wear, alloy stabilization, maintaining a fully ferritic structure, and reducing the susceptibility to stress-corrosion cracking. Comparisons made between the fatigue response of 439SS tube-to-tube sheet welded specimens ''in air'' at 525/sup 0/F (274/sup 0/C) show a distinct advantage of the use of the 439SS tubing alloy over previously used tubing alloys. An ''in-service'' record of over twomore » years at Kewaunee shows excellent tubing operating experience.« less

Enzyme Encapsulation by a Ferritin Cage.

PubMed

Tetter, Stephan; Hilvert, Donald

2017-11-20

Ferritins, conserved across all kingdoms of life, are protein nanocages that evolved to mineralize iron. The last several decades have shown that these cages have considerable technological and medical potential owing to their stability and tolerance to modification, as well as their ability to template nanoparticle synthesis and incorporate small molecules. Here we show that it is possible to encapsulate proteins in a ferritin cage by exploiting electrostatic interactions with its negatively charged interior. Positively supercharged green fluorescent protein is efficiently taken up by Archaeoglobus fulgidus ferritin in a tunable fashion. Moreover, several enzymes were readily incorporated when genetically tethered to this fluorescent protein. These fusion proteins retained high catalytic activity and showed increased tolerance to proteolysis and heat. Equipping ferritins with enzymatic activity paves the way for many new nanotechnological and pharmacological applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A note on a corrector formula for the numerical solution of ordinary differential equations

NASA Technical Reports Server (NTRS)

Chien, Y.-C.; Agrawal, K. M.

1979-01-01

A new corrector formula for predictor-corrector methods for numerical solutions of ordinary differential equations is presented. Two considerations for choosing corrector formulas are given: (1) the coefficient in the error term and (2) its stability properties. The graph of the roots of an equation plotted against its stability region, of different values, is presented along with the tables that correspond to various corrector equations, including Hamming's and Milne and Reynolds'.

Design considerations of a thermally stabilized continuous flow electrophoresis chamber 2

NASA Technical Reports Server (NTRS)

Jandebeur, T. S.

1982-01-01

The basic adjustable parameters of a Beckman Continouous Particle Electrophoresis (CPE) Apparatus are investigated to determine the optimum conditions for ground based operation for comparison with space experiments. The possible application of electrically insulated copper/aluminum chamber walls is evaluated as a means to thermally stabilize or equilibrate lateral temperature gradients which exist on the walls of conventional plastic chambers and which distort the rectilinear base flow of buffer through the chamber, significantly affecting sample resolution.

Probing the Structure, Stability and Hydrogen Adsorption of Lithium Functionalized Isoreticular MOF-5 (Fe, Cu, Co, Ni and Zn) by Density Functional Theory

PubMed Central

Venkataramanan, Natarajan Sathiyamoorthy; Sahara, Ryoji; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

2009-01-01

Li adsorption on isoreticular MOFs with metal Fe, Cu, Co, Ni and Zn was studied using density function theory. Li functionalization shows a considerable structural change associated with a volume change in isoreticular MOF-5 except for the Zn metal center. Hydrogen binding energies on Li functionalized MOFs are seen to be in the range of 0.2 eV, which is the desired value for an ideal reversible storage system. This study has clearly shown that Li doping is possible only in Zn-based MOF-5, which would be better candidate to reversibly store hydrogen. PMID:19468328

Noninteractive macroscopic reliability model for whisker-reinforced ceramic composites

NASA Technical Reports Server (NTRS)

Duffy, Stephen F.; Arnold, Steven M.

1990-01-01

Considerable research is underway in the field of material science focusing on incorporating silicon carbide whiskers into silicon nitride and alumina matrices. These composites show the requisite thermal stability and thermal shock resistance necessary for use as components in advanced gas turbines and heat exchangers. This paper presents a macroscopic noninteractive reliability model for whisker-reinforced ceramic composites. The theory is multiaxial and is applicable to composites that can be characterized as transversely isotropic. Enough processing data exists to suggest this idealization encompasses a significantly large class of fabricated components. A qualitative assessment of the model is made by presenting reliability surfaces in several different stress spaces and for different values of model parameters.

Evaluation Of Rotation Frequency Gas-Diesel Engines When Using Automatic Control System

NASA Astrophysics Data System (ADS)

Zhilenkov, A.; Efremov, A.

2017-01-01

A possibility of quality improvement of stabilization of rotation frequency of the gas-diesels used as prime mover of generator set in the multigenerator units working for abruptly variable load of large power is considered. An evaluation is made on condition of fuzzy controller use developed and described by the authors in a number of articles. An evaluation has shown that theoretically, the revolution range of gas-diesel engine may be reduced at 25-30 times at optimal settings of the controller in all the power range. The results of modeling showing a considerable quality improvement of transient processes in the investigated system at a sharp change of loading are presented in this article.

Detrimental effect of interfacial Dzyaloshinskii-Moriya interaction on perpendicular spin-transfer-torque magnetic random access memory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Peong-Hwa; Lee, Seo-Won, E-mail: swlee-sci@korea.ac.kr, E-mail: kj-lee@korea.ac.kr; Song, Kyungmi

2015-11-16

Interfacial Dzyaloshinskii-Moriya interaction in ferromagnet/heavy metal bilayers is recently of considerable interest as it offers an efficient control of domain walls and the stabilization of magnetic skyrmions. However, its effect on the performance of perpendicular spin transfer torque memory has not been explored yet. We show based on numerical studies that the interfacial Dzyaloshinskii-Moriya interaction decreases the thermal energy barrier while increases the switching current. As high thermal energy barrier as well as low switching current is required for the commercialization of spin torque memory, our results suggest that the interfacial Dzyaloshinskii-Moriya interaction should be minimized for spin torque memorymore » applications.« less

Influence of weathering effect in natural environment on thermal properties hybrid kenaf blast/glass fibre and unsaturated polyester composite

NASA Astrophysics Data System (ADS)

Mohammed, M.; Rozyanty, A. R.; Beta, B. O.; Adam, T.; Osman, A. F.; Salem, I. A. S.; Dahham, O. S.; Al-Samarrai, M. N.; Mohammed, A. M.

2017-10-01

Unprecedented growing on environmental concern has put research on completive driven effort to quest for new material in various application, the effort toward producing thermally stable polymer is ever gaining considerable interest. Thus, this study proposed the integration of glass fiber with kenaf based polymer to improve thermal properties. Based on the TGA and DSC results, the composites show slow and steady initial weight loss until major weight loss at 360°C. Thus, with incorporation of glass fiber extend region of degradation until 260-360 °Cshow no exothermic or endothermic changes, this reflected that the composites thermally stability have been improved.

Technical considerations to avoid delayed and non-union.

PubMed

McMillan, Tristan E; Johnstone, Alan J

2017-06-01

For many years intramedullary nails have been a well accepted and successful method of diaphyseal fracture fixation. However, delayed and non unions with this technique do still occur and are associated with significant patient morbidity. The reason for this can be multi-factorial. We discuss a number of technical considerations to maximise fracture reduction, fracture stability and fracture vascularity in order to achieve bony union. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Design of a fiber-optic transmitter for microwave analog transmission with high phase stability

NASA Technical Reports Server (NTRS)

Logan, R. T., Jr.; Lutes, G. F.; Primas, L. E.; Maleki, L.

1990-01-01

The principal considerations in the design of fiber-optic transmitters for highly phase-stable radio frequency and microwave analog transmission are discussed. Criteria for a fiber-optic transmitter design with improved amplitude and phase-noise performance are developed through consideration of factors affecting the phase noise, including low-frequency laser-bias supply noise, the magnitude and proximity of external reflections into the laser, and temperature excursions of the laser-transmitter package.

Stability of Chitosan—A Challenge for Pharmaceutical and Biomedical Applications

PubMed Central

Szymańska, Emilia; Winnicka, Katarzyna

2015-01-01

Chitosan—one of the natural multifunctional polymers—due to its unique and versatile biological properties is regarded as a useful compound in medical and pharmaceutical technology. Recently, considerable research effort has been made in order to develop safe and efficient chitosan products. However, the problem of poor stability of chitosan-based systems restricts its practical applicability; thus, it has become a great challenge to establish sufficient shelf-life for chitosan formulations. Improved stability can be assessed by controlling the environmental factors, manipulating processing conditions (e.g., temperature), introducing a proper stabilizing compound, developing chitosan blends with another polymer, or modifying the chitosan structure using chemical or ionic agents. This review covers the influence of internal, environmental, and processing factors on the long-term stability of chitosan products. The aim of this paper is also to highlight the latest developments which enable the physicochemical properties of chitosan-based applications to be preserved upon storage. PMID:25837983

Stabilizing human regulatory T cells for tolerance inducing immunotherapy.

PubMed

He, Xuehui; Koenen, Hans Jpm; Slaats, Jeroen Hr; Joosten, Irma

2017-08-01

Many autoimmune diseases develop as a consequence of an altered balance between autoreactive immune cells and suppressive FOXP3 + Treg. Restoring this balance through amplification of Treg represents a promising strategy to treat disease. However, FOXP3 + Treg might become unstable especially under certain inflammatory conditions, and might transform into proinflammatory cytokine-producing cells. The issue of heterogeneity and instability of Treg has caused considerable debate in the field and has important implications for Treg-based immunotherapy. In this review, we discuss how Treg stability is defined and what the molecular mechanisms underlying the maintenance of FOXP3 expression and the regulation of Treg stability are. Also, we elaborate on current strategies used to stabilize human Treg for clinical purposes. This review focuses on human Treg, but considering that cell-intrinsic mechanisms to regulate Treg stability in mice and in humans might be similar, data derived from mice studies are also discussed in this paper.

High-κ gate dielectrics: Current status and materials properties considerations

NASA Astrophysics Data System (ADS)

Wilk, G. D.; Wallace, R. M.; Anthony, J. M.

2001-05-01

Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.1 μm complementary metal-oxide-semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric are (a) permittivity, band gap, and band alignment to silicon, (b) thermodynamic stability, (c) film morphology, (d) interface quality, (e) compatibility with the current or expected materials to be used in processing for CMOS devices, (f) process compatibility, and (g) reliability. Many dielectrics appear favorable in some of these areas, but very few materials are promising with respect to all of these guidelines. A review of current work and literature in the area of alternate gate dielectrics is given. Based on reported results and fundamental considerations, the pseudobinary materials systems offer large flexibility and show the most promise toward successful integration into the expected processing conditions for future CMOS technologies, especially due to their tendency to form at interfaces with Si (e.g. silicates). These pseudobinary systems also thereby enable the use of other high-κ materials by serving as an interfacial high-κ layer. While work is ongoing, much research is still required, as it is clear that any material which is to replace SiO2 as the gate dielectric faces a formidable challenge. The requirements for process integration compatibility are remarkably demanding, and any serious candidates will emerge only through continued, intensive investigation.

New phosphate-based binder for stabilization of soils contaminated with heavy metals: leaching, strength and microstructure characterization.

PubMed

Du, Yan-Jun; Wei, Ming-Li; Reddy, Krishna R; Jin, Fei; Wu, Hao-Liang; Liu, Zhi-Bin

2014-12-15

Cement stabilization is used extensively to remediate soils contaminated with heavy metals. However, previous studies suggest that the elevated zinc (Zn) and lead (Pb) concentrations in the contaminated soils would substantially retard the cement hydration, leading to the deterioration of the performance of cement stabilized soils. This study presents a new binder, KMP, composed of oxalic acid-activated phosphate rock, monopotassium phosphate and reactive magnesia. The effectiveness of stabilization using this binder is investigated on soils spiked with Zn and Pb, individually and together. Several series of tests are conducted including toxicity characteristic leaching (TCLP), ecotoxicity in terms of luminescent bacteria test and unconfined compressive strength. The leachability of a field Zn- and Pb- contaminated soil stabilized with KMP is also evaluated by TCLP leaching test. The results show that the leached Zn concentrations are lower than the China MEP regulatory limit except when Zn and Pb coexist and for the curing time of 7 days. On the other hand, the leached Pb concentrations for stabilized soils with Pb alone or mixed Zn and Pb contamination are much lower than the China MEP or USEPA regulatory limit, irrespective of the curing time. The luminescent bacteria test results show that the toxicity of the stabilized soils has been reduced considerably and is classified as slightly toxic class. The unconfined compressive strength of the soils decrease with the increase in the Zn concentration. The stabilized soils with mixed Zn and Pb contaminants exhibit notably higher leached Zn concentration, while there is lower unconfined compressive strength relative to the soils when contaminated with Zn alone. The X-ray diffraction and scanning electron microscope analyses reveal the presence of bobierrite (Mg3(PO4)2·8H2O) and K-struvite (MgKPO4·6H2O) as the main products formed in the KMP stabilized uncontaminated soils; the formation of hopeite (Zn3(PO4)2·4H2O), scholzite (CaZn2(PO4)2·2H2O), zinc hydroxide (Zn(OH)2), and fluoropyromorphite (Pb5(PO4)3F) in the soils are the main mechanisms for immobilization of Zn and Pb with the KMP binder. The change in the relative quantities of the formed phosphate-based products, with respect to the Zn concentration and presence of mixed Zn and Pb contaminants, can well explain the measured impact of the Zn concentration levels and presence of both Zn and Pb contaminants on the unconfined compressive strength of the KMP stabilized soils. Copyright © 2014 Elsevier Ltd. All rights reserved.

Wind-Tunnel Investigation of the Low-Speed Static Stability and Control Characteristics of a Model of the Bell MX-776 (RASCAL) in Combined Angle of Attack and Sideslip

NASA Technical Reports Server (NTRS)

Letko, William

1949-01-01

An investigation has been made in the Langley stability tunnel to determine the low-speed static stability and control characteristics of a model of the Bell MX-776. The results show the model to be longitudinally unstable in the angle-of-attack range around zero angle of attack and to become stable at moderate angles of attack. The results of the present investigation agree reasonably well with results obtained in other facilities at low speed. The present pitching-moment results at low Mach numbers also agree reasonably well with unpublished results of tests of the model at supersonic Mach numbers (up to Mach number 1.86). Unpublished results at moderate and high subsonic speeds, however, indicate considerably greater instability at low angles of attack than is indicated by low-speed results. The results of the present tests also showed that the pitching-moment coefficients for angles of attack up to 12deg remained fairly constant with sideslip angle up to 12deg. The elevators tested produced relatively large pitching moments at zero angle of attack but, as the angle of attack was increased, the elevator effectiveness decreased. The rate of decrease of elevator effectiveness with angle of attack was less for 8deg than for 20deg elevator deflection. Therefore although 8deg deflection caused an appreciable change in longitudinal trim angle and trim lift coefficient a deflection of 20deg caused only a small additional increase in trim angle and trim lift coefficient.

Deciphering Molecular Mechanisms of Interface Buildup and Stability in Porous Si/Eumelanin Hybrids

PubMed Central

Pinna, Elisa; Melis, Claudio; Antidormi, Aleandro; Cardia, Roberto; Sechi, Elisa; Cappellini, Giancarlo; Colombo, Luciano

2017-01-01

Porous Si/eumelanin hybrids are a novel class of organic–inorganic hybrid materials that hold considerable promise for photovoltaic applications. Current progress toward device setup is, however, hindered by photocurrent stability issues, which require a detailed understanding of the mechanisms underlying the buildup and consolidation of the eumelanin–silicon interface. Herein we report an integrated experimental and computational study aimed at probing interface stability via surface modification and eumelanin manipulation, and at modeling the organic–inorganic interface via formation of a 5,6-dihydroxyindole (DHI) tetramer and its adhesion to silicon. The results indicated that mild silicon oxidation increases photocurrent stability via enhancement of the DHI–surface interaction, and that higher oxidation states in DHI oligomers create more favorable conditions for the efficient adhesion of growing eumelanin. PMID:28753933

Issues with Strong Compression of Plasma Target by Stabilized Imploding Liner

NASA Astrophysics Data System (ADS)

Turchi, Peter; Frese, Sherry; Frese, Michael

2017-10-01

Strong compression (10:1 in radius) of an FRC by imploding liquid metal liners, stabilized against Rayleigh-Taylor modes, using different scalings for loss based on Bohm vs 100X classical diffusion rates, predict useful compressions with implosion times half the initial energy lifetime. The elongation (length-to-diameter ratio) near peak compression needed to satisfy empirical stability criterion and also retain alpha-particles is about ten. The present paper extends these considerations to issues of the initial FRC, including stability conditions (S*/E) and allowable angular speeds. Furthermore, efficient recovery of the implosion energy and alpha-particle work, in order to reduce the necessary nuclear gain for an economical power reactor, is seen as an important element of the stabilized liner implosion concept for fusion. We describe recent progress in design and construction of the high energy-density prototype of a Stabilized Liner Compressor (SLC) leading to repetitive laboratory experiments to develop the plasma target. Supported by ARPA-E ALPHA Program.

Proton Distribution in Heavy Nuclei

DOE R&D Accomplishments Database

Johnson, M. H; Teller, E.

1953-11-13

It is reasoned that, from considerations connected with beta-decay stability and Coulomb repulsion forces, a neutron excess is developed on the surface of heavy nuclei. Several consequences of this qualitative analysis in nucleon interactions are briefly noted. (K.S.)

Integrated Learning Systems: A Primer.

ERIC Educational Resources Information Center

Wilson, Judy

1990-01-01

An overview of integrated learning systems (ILS) is provided. Twelve companies marketing products under the term ILS are identified. Philosophical approaches, curriculum areas, management systems, costs, and company stability are discussed as important considerations for schools considering these companies. (CW)

Some Effects of Roll Rate on the Longitudinal Stability Characteristics of a Cruciform Missile Configuration as Determined from Flight Test for a Mach Number Range of 1.1 to 1.8

NASA Technical Reports Server (NTRS)

Barber, H. T., Jr.; Lundstrom, R. R.

1956-01-01

A model of a cruciform missile configuration having a low-aspectratio wing equipped with flap-type controls was flight tested in order to determine stability and control characteristics while rolling at about 5 radians per second. Comparison is made with results from a similar model which rolled at a much lower rate. Results showed that, if the ratio of roll rate to natural circular frequency in pitch is not greater than about 0.3, the motion following a step disturbance in pitch essentially remains in a plane in space. The slope of normal-force coefficient against angle of attack C(sub N(sub A)) was the same as for the slowly rolling model at O deg control deflection but C(sub N(sub A)) was much higher for the faster rolling model at about 5 deg control deflection. The slope of pitching-moment coefficient against angle of attack & same for both models at 0 deg control deflection but was lower for the faster rolling model at about 5 deg control deflection. Damping data for the faster rolling model showed considerably more scatter than for the slowly rolling model.

Alginate/sodium caseinate aqueous-core capsules: a pH-responsive matrix.

PubMed

Ben Messaoud, Ghazi; Sánchez-González, Laura; Jacquot, Adrien; Probst, Laurent; Desobry, Stéphane

2015-02-15

Alginate capsules have several applications. Their functionality depends considerably on their permeability, chemical and mechanical stability. Consequently, the creation of composite system by addition of further components is expected to control mechanical and release properties of alginate capsules. Alginate and alginate-sodium caseinate composite liquid-core capsules were prepared by a simple extrusion. The influence of the preparation pH and sodium caseinate concentration on capsules physico-chemical properties was investigated. Results showed that sodium caseinate influenced significantly capsules properties. As regards to the membrane mechanical stability, composite capsules prepared at pH below the isoelectric point of sodium caseinate exhibited the highest surface Young's modulus, increasing with protein content, explained by potential electrostatic interactions between sodium caseinate amino-groups and alginate carboxylic group. The kinetic of cochineal red A release changed significantly for composite capsules and showed a pH-responsive release. Sodium caseinate-dye mixture studied by absorbance and fluorescence spectroscopy confirmed complex formation at pH 2 by electrostatic interactions between sodium caseinate tryptophan residues and cochineal red sulfonate-groups. Consequently, the release mechanism was explained by membrane adsorption process. This global approach is useful to control release mechanism from macro and micro-capsules by incorporating guest molecules which can interact with the entrapped molecule under specific conditions. Copyright © 2014 Elsevier Inc. All rights reserved.

High Performance Solid Polymer Electrolytes for Rechargeable Batteries: A Self-Catalyzed Strategy toward Facile Synthesis.

PubMed

Cui, Yanyan; Liang, Xinmiao; Chai, Jingchao; Cui, Zili; Wang, Qinglei; He, Weisheng; Liu, Xiaochen; Liu, Zhihong; Cui, Guanglei; Feng, Jiwen

2017-11-01

It is urgent to seek high performance solid polymer electrolytes (SPEs) via a facile chemistry and simple process. The lithium salts are composed of complex anions that are stabilized by a Lewis acid agent. This Lewis acid can initiate the ring opening polymerization. Herein, a self-catalyzed strategy toward facile synthesis of crosslinked poly(ethylene glycol) diglycidyl ether-based solid polymer electrolyte (C-PEGDE) is presented. It is manifested that the poly(ethylene glycol) diglycidyl ether-based solid polymer electrolyte possesses a superior electrochemical stability window up to 4.5 V versus Li/Li + and considerable ionic conductivity of 8.9 × 10 -5 S cm -1 at ambient temperature. Moreover, the LiFePO 4 /C-PEGDE/Li batteries deliver stable charge/discharge profiles and considerable rate capability. It is demonstrated that this self-catalyzed strategy can be a very effective approach for high performance solid polymer electrolytes.

Soybean-derived biofuels and home heating fuels.

PubMed

Mushrush, George W; Wynne, James H; Willauer, Heather D; Lloyd, Christopher L

2006-01-01

It is environmentally enticing to consider replacing or blending petroleum derived heating fuels with biofuels for many reasons. Major considerations include the soaring worldwide price of petroleum products, especially home heating oil, the toxicity of the petroleum-derived fuels and the environmental damage that leaking petroleum tanks afford. For these reasons, it has been suggested that domestic renewable energy sources be considered as replacements, or at the least, as blending stocks for home heating fuels. If recycled soy restaurant cooking oils could be employed for this purpose, this would represent an environmental advantage. Renewable plant sources of energy tend to be less toxic than their petroleum counterparts. This is an important consideration when tank leakage occurs. Home fuel oil storage tanks practically always contain some bottom water. This water environment has a pH value that factors into heating fuel stability. Therefore, the question is: would the biofuel help or exacerbate fuel stability and furnace maintenance issues?

Selection considerations between ZERODUR® and silicon carbide for dimensionally-stable spaceborne optical telescopes in two-earth-orbits

NASA Astrophysics Data System (ADS)

Hull, Tony; Westerhoff, Thomas; Weidmann, Gunter

2015-09-01

A key consideration in defining a space telescope mission is definition of the optical materials. This selection defines both the performance of the system and system complexity and cost. Optimal material selection for system stability must consider the thermal environment and its variation. Via numerical simulations, we compare the thermal and structural-mechanical behavior of ZERODUR® and SiC as mirror substrates for telescope assemblies in space. SiC has significantly larger CTE values then ZERODUR®, but also its thermal diffusivity k/(ρcp) is larger, and that helps to homogenize thermal gradients in the mirror. Therefore it is not obvious at first glance which material performs with better dimensional stability under realistic unsteady, inhomogeneous thermal loads. We specifically examine the telescope response to transient, gradient driving, thermal environments representative of low- and high-earth- orbits.

Differential stability of therapeutic peptides with different proteolytic cleavage sites in blood, plasma and serum.

PubMed

Böttger, Roland; Hoffmann, Ralf; Knappe, Daniel

2017-01-01

Proteolytic degradation of peptide-based drugs is often considered as major weakness limiting systemic therapeutic applications. Therefore, huge efforts are typically devoted to stabilize sequences against proteases present in serum or plasma, obtained as supernatants after complete blood coagulation or centrifugation of blood supplemented with anticoagulants, respectively. Plasma and serum are reproducibly obtained from animals and humans allowing consistent for clinical analyses and research applications. However, the spectrum of active or activated proteases appears to vary depending on the activation of proteases and cofactors during coagulation (serum) or inhibition of such enzymes by anticoagulants (plasma), such as EDTA (metallo- and Ca2+-dependent proteases) and heparin (e.g. thrombin, factor Xa). Here, we studied the presumed effects on peptide degradation by taking blood via cardiac puncture of CD-1 mice using a syringe containing a peptide solution. Due to absence of coagulation activators (e.g. glass surfaces and damaged cells), visible blood clotting was prevented allowing to study peptide degradation for one hour. The remaining peptide was quantified and the degradation products were identified using mass spectrometry. When the degradation rates (half-life times) were compared to serum derived freshly from the same animal and commercial serum and plasma samples, peptides of three different families showed indeed considerably different stabilities. Generally, peptides were faster degraded in serum than in plasma, but surprisingly all peptides were more stable in fresh blood and the order of degradation rates among the peptides varied among the six different incubation experiments. This indicates, that proteolytic degradation of peptide-based therapeutics may often be misleading stimulating efforts to stabilize peptides at degradation sites relevant only in vitro, i.e., for serum or plasma stability assays, but of lower importance in vivo.

Replica Exchange Molecular Dynamics Study of Dimerization in Prion Protein: Multiple Modes of Interaction and Stabilization.

PubMed

Chamachi, Neharika G; Chakrabarty, Suman

2016-08-04

The pathological forms of prions are known to be a result of misfolding, oligomerization, and aggregation of the cellular prion. While the mechanism of misfolding and aggregation in prions has been widely studied using both experimental and computational tools, the structural and energetic characterization of the dimer form have not garnered as much attention. On one hand dimerization can be the first step toward a nucleation-like pathway to aggregation, whereas on the other hand it may also increase the conformational stability preventing self-aggregation. In this work, we have used extensive all-atom replica exchange molecular dynamics simulations of both monomer and dimer forms of a mouse prion protein to understand the structural, dynamic, and thermodynamic stability of dimeric prion as compared to the monomeric form. We show that prion proteins can dimerize spontaneously being stabilized by hydrophobic interactions as well as intermolecular hydrogen bonding and salt bridge formation. We have computed the conformational free energy landscapes for both monomer and dimer forms to compare the thermodynamic stability and misfolding pathways. We observe large conformational heterogeneity among the various modes of interactions between the monomers and the strong intermolecular interactions may lead to as high as 20% β-content. The hydrophobic regions in helix-2, surrounding coil regions, terminal regions along with the natively present β-sheet region appear to actively participate in prion-prion intermolecular interactions. Dimerization seems to considerably suppress the inherent dynamic instability observed in monomeric prions, particularly because the regions of structural frustration constitute the dimer interface. Further, we demonstrate an interesting reversible coupling between the Q160-G131 interaction (which leads to inhibition of β-sheet extension) and the G131-V161 H-bond formation.

Impact of formulation and particle size on stability and immunogenicity of oil-in-water emulsion adjuvants

PubMed Central

Iyer, Vidyashankara; Cayatte, Corinne; Guzman, Bernardo; Schneider-Ohrum, Kirsten; Matuszak, Ryan; Snell, Angie; Rajani, Gaurav Manohar; McCarthy, Michael P; Muralidhara, Bilikallahalli

2015-01-01

Oil-in-water emulsions have gained consideration as vaccine adjuvants in recent years due to their ability to elicit a differentiated immunogenic response compared to traditional aluminum salt adjuvants. Squalene, a cholesterol precursor, is a natural product with immunostimulatory properties, making it an ideal candidate for such oil-in-water emulsions. Particle size is a key parameter of these emulsions and its relationship to stability and adjuvanticity has not been extensively studied. This study evaluates the effect of particle size on the stability and immunogenicity of squalene emulsions. We investigated the effect of formulation parameters such as surfactant concentration on particle size, resulting in particles with average diameter of 80 nm, 100 nm, 150 nm, 200 nm, or 250 nm. Emulsions were exposed to shear and temperature stresses, and stability parameters such as pH, osmolarity, size, and in-depth visual appearance were monitored over time. In addition, adjuvanticity of different particle size was assessed in a mouse model using Respiratory Syncytial Virus Fusion protein (RSV-F) as a model antigen. Temperature dependent phase separation appeared to be the most common route of degradation occurring in the higher particle sizes emulsions. The emulsions below 150 nm size maintained stability at either 5°C or 25°C, and the 80 nm diameter ones showed no measurable changes in size even after one month at 40°C. In vivo studies using the emulsions as an adjuvant with RSV F antigen revealed that superior immunogenicity could be achieved with the 80 nm particle size emulsion. PMID:26090563

Effects of copyrolysis of sludge with calcium carbonate and calcium hydrogen phosphate on chemical stability of carbon and release of toxic elements in the resultant biochars.

PubMed

Xu, Xuebin; Hu, Xin; Ding, Zhuhong; Chen, Yijun

2017-12-01

The potential release of toxic elements and the stability of carbon in sludge-based biochars are important on their application in soil remediation and wastewater treatment. In this study, municipal sludge was co-pyrolyzed with calcium carbonate (CaCO 3 ) and calcium dihydrogen phosphate [Ca(H 2 PO 4 ) 2 ] under 300 and 600 °C, respectively. The basic physicochemical properties of the resultant biochars were characterized and laboratory chemical oxidation and leaching experiments of toxic elements were conducted to evaluate the chemical stability of carbon in biochars and the potential release of toxic elements from biochars. Results show that the exogenous minerals changed the physico-chemical properties of the resultant biochars greatly. Biochars with exogenous minerals, especially Ca(H 2 PO 4 ) 2 , decreased the release of Zn, Cr, Ni, Cu, Pb, and As and the release ratios were less than 1%. Tessier's sequential extraction analysis revealed that labile toxic elements were transferred to residual fraction in the biochars with high pyrolysis temperature (600 °C) and exogenous minerals. Low risks for biochar-bound Pb, Zn, Cd, As, Cr, and Cu were confirmed according to risk assessment code (RAC) while the potential ecological risk index (PERI) revealed that the exogenous Ca(H 2 PO 4 ) 2 significantly decreased the risks from considerable to moderate level. Moreover, the exogenous minerals significantly increased the chemical stability of carbon in 600 °C-pyrolyzed biochars by 10-20%. These results indicated that the copyrolysis of sludge with phosphate and carbonate, especially phosphate, were effective methods to prepare the sludge-based biochars with immobilized toxic elements and enhanced chemical stability of carbon. Copyright © 2017 Elsevier Ltd. All rights reserved.

Robust SMES controller design for stabilization of inter-area oscillation considering coil size and system uncertainties

NASA Astrophysics Data System (ADS)

Ngamroo, Issarachai

2010-12-01

It is well known that the superconducting magnetic energy storage (SMES) is able to quickly exchange active and reactive power with the power system. The SMES is expected to be the smart storage device for power system stabilization. Although the stabilizing effect of SMES is significant, the SMES is quite costly. Particularly, the superconducting magnetic coil size which is the essence of the SMES, must be carefully selected. On the other hand, various generation and load changes, unpredictable network structure, etc., cause system uncertainties. The power controller of SMES which is designed without considering such uncertainties, may not tolerate and loses stabilizing effect. To overcome these problems, this paper proposes the new design of robust SMES controller taking coil size and system uncertainties into account. The structure of the active and reactive power controllers is the 1st-order lead-lag compensator. No need for the exact mathematical representation, system uncertainties are modeled by the inverse input multiplicative perturbation. Without the difficulty of the trade-off of damping performance and robustness, the optimization problem of control parameters is formulated. The particle swarm optimization is used for solving the optimal parameters at each coil size automatically. Based on the normalized integral square error index and the consideration of coil current constraint, the robust SMES with the smallest coil size which still provides the satisfactory stabilizing effect, can be achieved. Simulation studies in the two-area four-machine interconnected power system show the superior robustness of the proposed robust SMES with the smallest coil size under various operating conditions over the non-robust SMES with large coil size.

Stability Impact on Wake Development in Moderately Complex Terrain

NASA Astrophysics Data System (ADS)

Infield, D.; Zorzi, G.

2017-05-01

This paper uses a year of SCADA data from Whitelee Wind Farm near Glasgow to investigate wind turbine wake development in moderately complex terrain. Atmospheric stability measurements in terms of Richardson number from a met mast at an adjoining site have been obtained and used to assess the impact of stability on wake development. Considerable filtering of these data has been undertaken to ensure that all turbines are working normally and are well aligned with the wind direction. A group of six wind turbines, more or less in a line, have been selected for analysis, and winds within a 2 degree direction sector about this line are used to ensure, as far as possible, that all the turbines investigated are fully immersed in the wake/s of the upstream turbine/s. Results show how the terrain effects combine with the wake effects, with both being of comparable importance for the site in question. Comparison has been made with results from two commercial CFD codes for neutral stability, and reasonable agreement is demonstrated. Richardson number has been plotted against wind shear and turbulence intensity at a met mast on the wind farm that for the selected wind direction is not in the wake of any turbines. Good correlations are found indicating that the Richardson numbers obtained are reliable. The filtered data used for wake analysis were split according to Richardson number into two groups representing slightly stable to neutral, and unstable conditions. Very little difference in wake development is apparent. A greater difference can be observed when the data are separated simply by turbulence intensity, suggesting that, although turbulence intensity is correlated with stability, of the two it is the parameter that most directly impacts on wake development through mixing of ambient and wake flows.

Stability of miscible core?annular flows with viscosity stratification

NASA Astrophysics Data System (ADS)

Selvam, B.; Merk, S.; Govindarajan, Rama; Meiburg, E.

The linear stability of variable viscosity, miscible core-annular flows is investigated. Consistent with pipe flow of a single fluid, the flow is stable at any Reynolds number when the magnitude of the viscosity ratio is less than a critical value. This is in contrast to the immiscible case without interfacial tension, which is unstable at any viscosity ratio. Beyond the critical value of the viscosity ratio, the flow can be unstable even when the more viscous fluid is in the core. This is in contrast to plane channel flows with finite interface thickness, which are always stabilized relative to single fluid flow when the less viscous fluid is in contact with the wall. If the more viscous fluid occupies the core, the axisymmetric mode usually dominates over the corkscrew mode. It is demonstrated that, for a less viscous core, the corkscrew mode is inviscidly unstable, whereas the axisymmetric mode is unstable for small Reynolds numbers at high Schmidt numbers. For the parameters under consideration, the switchover occurs at an intermediate Schmidt number of about 500. The occurrence of inviscid instability for the corkscrew mode is shown to be consistent with the Rayleigh criterion for pipe flows. In some parameter ranges, the miscible flow is seen to be more unstable than its immiscible counterpart, and the physical reasons for this behaviour are discussed.A detailed parametric study shows that increasing the interface thickness has a uniformly stabilizing effect. The flow is least stable when the interface between the two fluids is located at approximately 0.6 times the tube radius. Unlike for channel flow, there is no sudden change in the stability with radial location of the interface. The instability originates mainly in the less viscous fluid, close to the interface.

High temperature microstructural stability and recrystallization mechanisms in 14YWT alloys

DOE PAGES

Aydogan, E.; El-Atwani, O.; Takajo, S.; ...

2018-02-09

In-situ neutron diffraction experiments were performed on room temperature compressed 14YWT nanostructured ferritic alloys at 1100°C and 1150°C to understand their thermally activated static recrystallization mechanisms. The existence of high density of Y-Ti-O rich nano-oxides (<5 nm) shift the recrystallization temperature up due to Zener pinning of the grain boundaries, making these materials attractive for high temperature applications. This study serves to quantify the texture evolution in-situ and understand the effect of particles on the recrystallization mechanisms in 14YWT alloys. We have shown, both experimentally and theoretically, that there is considerable recovery in the 20% compressed sample after 6.5 hmore » annealing at 1100°C while recrystallization occurs within an hour of annealing at 1100°C and 1150°C in the 60% compressed samples. Moreover, the 60% compressed samples show {112}<110> and {112}<111> texture components during annealing, in contrast to the conventional recrystallization textures in body centered cubic alloys. Furthermore, nano-oxide size, shape, density and distribution are considerably different in unrecrystallized and abnormally grown grains. Transmission electron microscopy analysis shows that oxide particles having a size between 5 and 30 nm play a critical role for recrystallization mechanisms in 14YWT nanostructured ferritic alloys.« less

High temperature microstructural stability and recrystallization mechanisms in 14YWT alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aydogan, E.; El-Atwani, O.; Takajo, S.

In-situ neutron diffraction experiments were performed on room temperature compressed 14YWT nanostructured ferritic alloys at 1100°C and 1150°C to understand their thermally activated static recrystallization mechanisms. The existence of high density of Y-Ti-O rich nano-oxides (<5 nm) shift the recrystallization temperature up due to Zener pinning of the grain boundaries, making these materials attractive for high temperature applications. This study serves to quantify the texture evolution in-situ and understand the effect of particles on the recrystallization mechanisms in 14YWT alloys. We have shown, both experimentally and theoretically, that there is considerable recovery in the 20% compressed sample after 6.5 hmore » annealing at 1100°C while recrystallization occurs within an hour of annealing at 1100°C and 1150°C in the 60% compressed samples. Moreover, the 60% compressed samples show {112}<110> and {112}<111> texture components during annealing, in contrast to the conventional recrystallization textures in body centered cubic alloys. Furthermore, nano-oxide size, shape, density and distribution are considerably different in unrecrystallized and abnormally grown grains. Transmission electron microscopy analysis shows that oxide particles having a size between 5 and 30 nm play a critical role for recrystallization mechanisms in 14YWT nanostructured ferritic alloys.« less

The effect of Al intermediate layer on thermal resistance of EB-PVD yttria-stabilized zirconia coatings on titanium substrate

NASA Astrophysics Data System (ADS)

Panin, Alexey; Panin, Victor; Kazachenok, Marina; Shugurov, Artur; Sinyakova, Elena; Martynov, Sergey; Rusyaev, Andrey; Kasterov, Artur

2017-12-01

The yttria-stabilized zirconia coatings sprayed on titanium substrates by the electron beam physical vapor deposition were subjected to thermal annealing in air at 1000°C for 1, 30 and 60 min. The delamination and fracture of the coatings are studied by the scanning electron microscopy and X-ray diffraction. It is shown that a magnetron sputtered Al interlayer between the coating and the substrate considerably improves the thermal resistance of ceramic coatings.

In vitro degradation of ribosomes.

PubMed

Mora, G; Rivas, A

1976-12-01

The cytoplasmic ribosomes from Euglena gracilis var. bacillaris are found to be of two types taking into consideration their stability "in vitro". In the group of unstable ribosomes the large subunit is degraded. The other group apparently does not suffer any degradation under the conditions described. However the RNAs extracted from both types of ribosomes are degraded during sucrose density gradients. The degradation of the largest RNA species has been reported previously, but no comment has been made about the stability of the ribosome itself.

Physically-based landslide assessment for railway infrastructure

NASA Astrophysics Data System (ADS)

Heyerdahl, Håkon; Høydal, Øyvind

2017-04-01

A new high-speed railway line in Eastern Norway passes through areas with Quaternary soil deposits where stability of natural slopes poses considerable challenges. The ground typically consist of thick layers of marine clay deposits, overlain by 8-10 m of silt and sand. Both shallow landslides in the top layers of silt and sand and deep-seated failures in clay must be accounted for. In one section of the railway, the potential for performing stabilizing measures is limited due to existing cultural heritage on top of the slope. Hence, the stability of a steep top section of the slope needs to be evaluated. Assessment of the slope stability for rainfall-triggered slides relies on many parameters. An approach based only on empirical relations will not comply with the design criteria, which only allows deterministic safety margins. From a classic geotechnical approach, the slope would also normally be considered unsafe. However, considerable suction is assumed to exist in the silty and sandy deposits above ground-water level, which will improve the stability. The stabilizing effect however is highly dependent on rainfall, infiltration and soil moisture, and thereby varies continuously. An unsaturated geomechanical approach was taken to assess the slope stability. Soil moisture sensors were installed to monitor changes of in situ water content in the vadose zone. Retention curves for silt/sand specimens samples were measured by pressure plate tests. Some triaxial tests soil strength were performed to check the effect of suction on soil shear strength (performed as drained constant water content tests on compacted specimens). Based on the performed laboratory tests, the unsaturated response of the slope will be modelled numerically and compared with measured soil moisture in situ. Work is still on-going. Initial conditions after respectively dry and wet periods need to be coupled with selected rainfall intensities and duration to see the effect on slope stability. The aim of the work is to reach a result informing the client about the probability of a landslide in the slope, based on expected critical rainfall. A strictly deterministic criterion for minimum safety margin may need to be replaced by scenarios for probability and geometry of potential failures for given return periods and rainfall events.

Investigation of process variables and intensification effects of ultrasound applied in oxidative desulfurization of model diesel over MoO3/Al2O3 catalyst.

PubMed

Akbari, Azam; Omidkhah, Mohammadreza; Darian, Jafar Towfighi

2014-03-01

A new heterogeneous sonocatalytic system consisting of a MoO3/Al2O3 catalyst and H2O2 combined with ultrasonication was studied to improve and accelerate the oxidation of model sulfur compounds of diesel, resulting in a significant enhancement in the process efficiency. The influence of ultrasound on properties, activity and stability of the catalyst was studied in detail by means of GC-FID, PSD, SEM and BET techniques. Above 98% conversion of DBT in model diesel containing 1000 μg/g sulfur was obtained by new ultrasound-assisted desulfurization at H2O2/sulfur molar ratio of 3, temperature of 318 K and catalyst dosage of 30 g/L after 30 min reaction, contrary to the 55% conversion obtained during the silent process. This improvement was considerably affected by operation parameters and catalyst properties. The effects of main process variables were investigated using response surface methodology in silent process compared to ultrasonication. Ultrasound provided a good dispersion of catalyst and oxidant by breakage of hydrogen bonding and deagglomeration of them in the oil phase. Deposition of impurities on the catalyst surface caused a quick deactivation in silent experiments resulting only 5% of DBT oxidation after 6 cycles of silent reaction by recycled catalyst. Above 95% of DBT was oxidized after 6 ultrasound-assisted cycles showing a great improvement in stability by cleaning the surface during ultrasonication. A considerable particle size reduction was also observed after 3 h sonication that could provide more dispersion of catalyst in model fuel.

Considerations for opto-mechanical vs. digital stabilization in surveillance systems

NASA Astrophysics Data System (ADS)

Kowal, David

2015-05-01

Electro-optical surveillance and reconnaissance systems are frequently mounted on unstable or vibrating platforms such as ships, vehicles, aircraft and masts. Mechanical coupling between the platform and the cameras leads to angular vibration of the line of sight. Image motion during detector and eye integration times leads to image smear and a resulting loss of resolution. Additional effects are wavy images for detectors based on a rolling shutter mechanism and annoying movement of the image at low frequencies. A good stabilization system should yield sub-pixel stabilization errors and meet cost and size requirements. There are two main families of LOS stabilization methods: opto-mechanical stabilization and electronic stabilization. Each family, or a combination of both, can be implemented by a number of different techniques of varying complexity, size and cost leading to different levels of stabilization. Opto-mechanical stabilization is typically based on gyro readings, whereas electronic stabilization is typically based on gyro readings or image registration calculations. A few common stabilization techniques, as well as options for different gimbal arrangements will be described and analyzed. The relative merits and drawbacks of the different techniques and their applicability to specific systems and environments will be discussed. Over the years Controp has developed a large number of stabilized electro-optical payloads. A few examples of payloads with unique stabilization mechanisms will be described.

A novel synthesis of a new thorium (IV) metal organic framework nanostructure with well controllable procedure through ultrasound assisted reverse micelle method.

PubMed

Sargazi, Ghasem; Afzali, Daryoush; Mostafavi, Ali

2018-03-01

Reverse micelle (RM) and ultrasound assisted reverse micelle (UARM) were applied to the synthesis of novel thorium nanostructures as metal organic frameworks (MOFs). Characterization with different techniques showed that the Th-MOF sample synthesized by UARM method had higher thermal stability (354°C), smaller mean particle size (27nm), and larger surface area (2.02×10 3 m 2 /g). Besides, in this novel approach, the nucleation of crystals was found to carry out in a shorter time. The synthesis parameters of UARM method were designed by 2 k-1 factorial and the process control was systematically studied using analysis of variance (ANOVA) and response surface methodology (RSM). ANOVA showed that various factors, including surfactant content, ultrasound duration, temperature, ultrasound power, and interaction between these factors, considerably affected different properties of the Th-MOF samples. According to the 2 k-1 factorial design, the determination coefficient (R 2 ) of the model is 0.999, with no significant lack of fit. The F value of 5432, implied that the model was highly significant and adequate to represent the relationship between the responses and the independent variables, also the large R-adjusted value indicates a good relationship between the experimental data and the fitted model. RSM predicted that it would be possible to produce Th-MOF samples with the thermal stability of 407°C, mean particle size of 13nm, and surface area of 2.20×10 3 m 2 /g. The mechanism controlling the Th-MOF properties was considerably different from the conventional mechanisms. Moreover, the MOF sample synthesized using UARM exhibited higher capacity for nitrogen adsorption as a result of larger pore sizes. It is believed that the UARM method and systematic studies developed in the present work can be considered as a new strategy for their application in other nanoscale MOF samples. Copyright © 2017 Elsevier B.V. All rights reserved.

A Coarse-Grained Elastic Network Atom Contact Model and Its Use in the Simulation of Protein Dynamics and the Prediction of the Effect of Mutations

PubMed Central

Frappier, Vincent; Najmanovich, Rafael J.

2014-01-01

Normal mode analysis (NMA) methods are widely used to study dynamic aspects of protein structures. Two critical components of NMA methods are coarse-graining in the level of simplification used to represent protein structures and the choice of potential energy functional form. There is a trade-off between speed and accuracy in different choices. In one extreme one finds accurate but slow molecular-dynamics based methods with all-atom representations and detailed atom potentials. On the other extreme, fast elastic network model (ENM) methods with Cα−only representations and simplified potentials that based on geometry alone, thus oblivious to protein sequence. Here we present ENCoM, an Elastic Network Contact Model that employs a potential energy function that includes a pairwise atom-type non-bonded interaction term and thus makes it possible to consider the effect of the specific nature of amino-acids on dynamics within the context of NMA. ENCoM is as fast as existing ENM methods and outperforms such methods in the generation of conformational ensembles. Here we introduce a new application for NMA methods with the use of ENCoM in the prediction of the effect of mutations on protein stability. While existing methods are based on machine learning or enthalpic considerations, the use of ENCoM, based on vibrational normal modes, is based on entropic considerations. This represents a novel area of application for NMA methods and a novel approach for the prediction of the effect of mutations. We compare ENCoM to a large number of methods in terms of accuracy and self-consistency. We show that the accuracy of ENCoM is comparable to that of the best existing methods. We show that existing methods are biased towards the prediction of destabilizing mutations and that ENCoM is less biased at predicting stabilizing mutations. PMID:24762569

The Impact of Temperatures on the Stability of Rocks Surrounding a Single Fracture

NASA Astrophysics Data System (ADS)

Zhang, Yan; Li, Ning; Dai, Jun

2018-05-01

Research on the influence of temperature and the accompanying stress on the stability of the rocks surrounding an underground tunnel has become ever more important. This paper constructs a geometric model of a single-fracture tunnel by combining a high-temperature underground tunnel as the object of study with an example that uses a high-temperature tunnel segment in the water diversion tunnel of a hydropower station in Xinjiang. Based on the relevant theoretical analysis, with the consideration of different working conditions, a numerical experimental analysis was conducted to determine the two-dimensional transient temperature field distribution of the tunnel rock mass by using a numerical analysis software. The experimental data was consistent with the measured data. The calculated results show the following: a. when the temperature difference is greater, the stress concentration is higher near the fracture of the surrounding rock; b. the degree of the stress concentration in the crack tip region is not positively correlated to the distance, and there is a sensitive region where the stress varies.

High Yield Production and Radiochemical Isolation of Isotopically Pure Arsenic-72 and Novel Radioarsenic Labeling Strategies for the Development of Theranostic Radiopharmaceuticals.

PubMed

Ellison, Paul A; Barnhart, Todd E; Chen, Feng; Hong, Hao; Zhang, Yin; Theuer, Charles P; Cai, Weibo; Nickles, Robert J; DeJesus, Onofre T

2016-01-20

Radioisotopes of arsenic are of considerable interest to the field of nuclear medicine with unique nuclear and chemical properties making them well-suited for use in novel theranostic radiopharmaceuticals. However, progress must still be made in the production of isotopically pure radioarsenic and in its stable conjugation to biological targeting vectors. This work presents the production and irradiation of isotopically enriched (72)Ge(m) discs in an irrigation-cooled target system allowing for the production of isotopically pure (72)As with capability on the order of 10 GBq. A radiochemical separation procedure isolated the reactive trivalent radioarsenic in a small volume buffered aqueous solution, while reclaiming (72)Ge target material. The direct thiol-labeling of a monoclonal antibody resulted in a conjugate exhibiting exceptionally poor in vivo stability in a mouse model. This prompted further investigations to alternative radioarsenic labeling strategies, including the labeling of the dithiol-containing chelator dihydrolipoic acid, and thiol-modified mesoporous silica nanoparticles (MSN-SH). Radioarsenic-labeled MSN-SH showed exceptional in vivo stability toward dearsenylation.

High Yield Production and Radiochemical Isolation of Isotopically Pure Arsenic-72 and Novel Radioarsenic Labeling Strategies for the Development of Theranostic Radiopharmaceuticals

PubMed Central

Ellison, Paul A.; Barnhart, Todd E.; Chen, Feng; Hong, Hao; Zhang, Yin; Theuer, Charles P.; Cai, Weibo; Nickles, Robert J.; DeJesus, Onofre T.

2016-01-01

Radioisotopes of arsenic are of considerable interest to the field of nuclear medicine with unique nuclear and chemical properties making them well-suited for use in novel theranostic radiopharmaceuticals. However, progress must still be made in the production of isotopically pure radioarsenic and in its stable conjugation to biological targeting vectors. This work presents the production and irradiation of isotopically enriched 72Ge(m) discs in an irrigation-cooled target system allowing for the production of isotopically pure 72As with capability on the order of 10 GBq. A radiochemical separation procedure isolated the reactive trivalent radioarsenic in a small volume buffered aqueous solution, while reclaiming 72Ge target material. The direct thiol-labeling of a monoclonal antibody resulted in a conjugate exhibiting exceptionally poor in vivo stability in a mouse model. This prompted further investigations to alternative radioarsenic labeling strategies, including the labeling of the dithiol-containing chelator dihydrolipoic acid, and thiol-modified mesoporous silica nanoparticles (MSN-SH). Radioarsenic-labeled MSN-SH showed exceptional in vivo stability toward dearsenylation. PMID:26646989

Early Onset of Nucleate Boiling on Gas-covered Biphilic Surfaces.

PubMed

Shen, Biao; Yamada, Masayuki; Hidaka, Sumitomo; Liu, Jiewei; Shiomi, Junichiro; Amberg, Gustav; Do-Quang, Minh; Kohno, Masamichi; Takahashi, Koji; Takata, Yasuyuki

2017-05-17

For phase-change cooling schemes for electronics, quick activation of nucleate boiling helps safeguard the electronics components from thermal shocks associated with undesired surface superheating at boiling incipience, which is of great importance to the long-term system stability and reliability. Previous experimental studies show that bubble nucleation can occur surprisingly early on mixed-wettability surfaces. In this paper, we report unambiguous evidence that such unusual bubble generation at extremely low temperatures-even below the boiling point-is induced by a significant presence of incondensable gas retained by the hydrophobic surface, which exhibits exceptional stability even surviving extensive boiling deaeration. By means of high-speed imaging, it is revealed that the consequently gassy boiling leads to unique bubble behaviour that stands in sharp contrast with that of pure vapour bubbles. Such findings agree qualitatively well with numerical simulations based on a diffuse-interface method. Moreover, the simulations further demonstrate strong thermocapillary flows accompanying growing bubbles with considerable gas contents, which is associated with heat transfer enhancement on the biphilic surface in the low-superheat region.

Radiometric correction of atmospheric path length fluctuations in interferometric experiments. [in radio astronomy

NASA Technical Reports Server (NTRS)

Resch, G. M.; Hogg, D. E.; Napier, P. J.

1984-01-01

To support very long baseline interferometric experiments, a system has been developed for estimating atmospheric water vapor path delay. The system consists of dual microwave radiometers, one operating at 20.7 GHz and the other at 31.4 GHz. The measured atmospheric brightness temperatures at these two frequencies yield the estimate of the precipitable water present in both vapor and droplets. To determine the accuracy of the system, a series of observations were undertaken, comparing the outputs of two water vapor radiometers with the phase variation observed with two connected elements of the very large array (VLA). The results show that: (1) water vapor fluctuations dominate the residual VLA phase and (2) the microwave radiometers can measure and correct these effects. The rms phase error after correction is typically 15 deg at a wavelength of 6 cm, corresponding to an uncertainty in the path delay of 0.25 cm. The residual uncertainty is consistent with the stability of the microwave radiometer but is still considerably larger than the stability of the VLA. The technique is less successful under conditions of heavy cloud.

Rainwater as a chemical agent of geologic processes; a review

USGS Publications Warehouse

Carroll, Dorothy

1962-01-01

Chemical analyses of the rainwater collected at several localities are given to show the variations of the principal constitutents. In rock weathering and soil-forming processes, the chemical composition of rainwater has an important effect which has been evaluated for only a few arid areas. In humid regions the important amounts of calcium, magnesium, sodium, and potassium added yearly by rain may be expected to influence the composition of the soil water and thereby the cations in the exchange positions of soil clay minerals. The acquisition of cations by clay minerals may slow down chemical weathering. The stability of soil clay minerals is influenced by the constant accession of cations from rainwater. Conversely, the clay minerals modify the amounts and kinds of cations that are leached out by drainage waters. The stability of micaceous minerals in soils may be partly due to accessions of K +1 ions from rainwater. The pH of rainwater in any area varies considerably and seems to form a seasonal and regional pattern. The recorded pH values range from 3.0 to 9.8.

Mechanism of DNA-binding enhancement by the human T-cell leukaemia virus transactivator Tax.

PubMed

Baranger, A M; Palmer, C R; Hamm, M K; Giebler, H A; Brauweiler, A; Nyborg, J K; Schepartz, A

1995-08-17

Tax protein activates transcription of the human T-cell leukaemia virus type I (HTLV-I) genome through three imperfect cyclic AMP-responsive element (CRE) target sites located within the viral promoter. Previous work has shown that Tax interacts with the bZIP element of proteins that bind the CRE target site to promote peptide dimerization, suggesting an association between Tax and bZIP coiled coil. Here we show that the site of interaction with Tax is not the coiled coil, but the basic segment. This interaction increases the stability of the GCN4 bZIP dimer by 1.7 kcal mol-1 and the DNA affinity of the dimer by 1.9 kcal mol-1. The differential effect of Tax on several bZip-DNA complexes that differ in peptide sequence or DNA conformation suggests a model for Tax action based on stabilization of a distinct DNA-bound protein structure. This model may explain how Tax interacts with transcription factors of considerable sequence diversity to alter patterns of gene expression.

Differential stability of photosynthetic membranes and fatty acid composition at elevated temperature in Symbiodinium

NASA Astrophysics Data System (ADS)

Díaz-Almeyda, E.; Thomé, P. E.; El Hafidi, M.; Iglesias-Prieto, R.

2011-03-01

Coral reefs are threatened by increasing surface seawater temperatures resulting from climate change. Reef-building corals symbiotic with dinoflagellates in the genus Symbiodinium experience dramatic reductions in algal densities when exposed to temperatures above the long-term local summer average, leading to a phenomenon called coral bleaching. Although the temperature-dependent loss in photosynthetic function of the algal symbionts has been widely recognized as one of the early events leading to coral bleaching, there is considerable debate regarding the actual damage site. We have tested the relative thermal stability and composition of membranes in Symbiodinium exposed to high temperature. Our results show that melting curves of photosynthetic membranes from different symbiotic dinoflagellates substantiate a species-specific sensitivity to high temperature, while variations in fatty acid composition under high temperature rather suggest a complex process in which various modifications in lipid composition may be involved. Our results do not support the role of unsaturation of fatty acids of the thylakoid membrane as being mechanistically involved in bleaching nor as being a dependable tool for the diagnosis of thermal susceptibility of symbiotic reef corals.

Possible bicollinear nematic state with monoclinic lattice distortions in iron telluride compounds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bishop, Christopher B.; Herbrych, Jacek W.; Dagotto, Elbio R.

2017-07-15

Here, iron telluride (FeTe) is known to display bicollinear magnetic order at low temperatures together with a monoclinic lattice distortion. Because the bicollinear order can involve two different wave vectors (π/2,π/2) and (π/2,–π/2), symmetry considerations allow for the possible stabilization of a nematic state with short-range bicollinear order coupled to monoclinic lattice distortions at a T S higher than the temperature T N where long-range bicollinear order fully develops. As a concrete example, the three-orbital spin-fermion model for iron telluride is studied with an additional coupling ˜λ 12 between the monoclinic lattice strain and an orbital-nematic order parameter with Bmore » 2g symmetry. Monte Carlo simulations show that with increasing ˜λ 12 the first-order transition characteristic of FeTe splits and bicollinear nematicity is stabilized in a (narrow) temperature range. In this new regime, the lattice is monoclinically distorted and short-range spin and orbital order breaks rotational invariance. A discussion of possible realizations of this exotic state is provided.« less

Classical and quantum stability in putative landscapes

DOE PAGES

Dine, Michael

2017-01-18

Landscape analyses often assume the existence of large numbers of fields, N, with all of the many couplings among these fields (subject to constraints such as local supersymmetry) selected independently and randomly from simple (say Gaussian) distributions. We point out that unitarity and perturbativity place significant constraints on behavior of couplings with N, eliminating otherwise puzzling results. In would-be flux compactifications of string theory, we point out that in order that there be large numbers of light fields, the compactification radii must scale as a positive power of N; scaling of couplings with N may also be necessary for perturbativity.more » We show that in some simple string theory settings with large numbers of fields, for fixed R and string coupling, one can bound certain sums of squares of couplings by order one numbers. This may argue for strong correlations, possibly calling into question the assumption of uncorrelated distributions. Finally, we consider implications of these considerations for classical and quantum stability of states without supersymmetry, with low energy supersymmetry arising from tuning of parameters, and with dynamical breaking of supersymmetry.« less

In vitro and in vivo biotransformation of WMS-1410, a potent GluN2B selective NMDA receptor antagonist.

PubMed

Falck, Evamaria; Begrow, Frank; Verspohl, Eugen J; Wünsch, Bernhard

2014-06-01

Structural modification of the GluN2B selective NMDA receptor antagonist ifenprodil led to the 3-benzazepine WMS-1410 with similar GluN2B affinity but higher receptor selectivity. Herein the in vitro and in vivo biotransformation of WMS-1410 is reported. Incubation of WMS-1410 with rat liver microsomes and different cofactors resulted in four hydroxylated phase I metabolites, two phase II metabolites and five combined phase I/II metabolites. With exception of catechol 4, these metabolites were also identified in the urine of a rat treated with WMS-1410. However the metabolites 7, 8 and 12 clearly show that the catechol metabolite 4 was also formed in vivo. As shown for ifenprodil the phenol of WMS-1410 represents the metabolically most reactive structural element. The biotransformation of WMS-1410 is considerably slower than the biotransformation of ifenprodil indicating a higher metabolic stability. From the viewpoint of metabolic stability the bioisosteric replacement of the phenol of WMS-1410 by a metabolically more stable moiety should be favourable. Copyright © 2014 Elsevier B.V. All rights reserved.

Epitaxial strain effect in perovskite RENiO3 films (RE = La-Eu) prepared by metal organic decomposition

NASA Astrophysics Data System (ADS)

Ikeda, Ai; Manabe, Takaaki; Naito, Michio

2014-10-01

We report the synthesis of perovskite RENiO3 films (RE = La, Pr, Nd, Sm, and Eu) by metal organic decomposition (MOD). The RENiO3 family is an ideal system for studying the metal-insulator transition due to the simplicity of the materials. One of the drawbacks is that the bulk synthesis of the RENiO3 requires processing at high oxygen pressures to stabilize Ni3+. Fundamentally, MOD is similar to solid-state reaction, but it turned out that the MOD synthesis tends to stabilize RENiO3 without the need for high oxygen pressure. The films prepared by MOD show high crystallinity and low resistivity. Furthermore, we have investigated the epitaxial strain effect and observed a dramatic effect in PrNiO3 and NdNiO3 films on LaAlO3 substrates. The metal-insulator transition in the PrNiO3 films on LaAlO3 is fully suppressed, whereas the metal-insulator transition temperature is considerably lowered in the NdNiO3 films on LaAlO3.

Classical and quantum stability in putative landscapes

NASA Astrophysics Data System (ADS)

Dine, Michael

2017-01-01

Landscape analyses often assume the existence of large numbers of fields, N , with all of the many couplings among these fields (subject to constraints such as local supersymmetry) selected independently and randomly from simple (say Gaussian) distributions. We point out that unitarity and perturbativity place significant constraints on behavior of couplings with N , eliminating otherwise puzzling results. In would-be flux compactifications of string theory, we point out that in order that there be large numbers of light fields, the compactification radii must scale as a positive power of N ; scaling of couplings with N may also be necessary for perturbativity. We show that in some simple string theory settings with large numbers of fields, for fixed R and string coupling, one can bound certain sums of squares of couplings by order one numbers. This may argue for strong correlations, possibly calling into question the assumption of uncorrelated distributions. We consider implications of these considerations for classical and quantum stability of states without supersymmetry, with low energy supersymmetry arising from tuning of parameters, and with dynamical breaking of supersymmetry.

Protective Action of Spermine and Spermidine against Photoinhibition of Photosystem I in Isolated Thylakoid Membranes

PubMed Central

Yaakoubi, Hnia; Hamdani, Saber; Bekalé, Laurent; Carpentier, Robert

2014-01-01

The photo-stability of photosystem I (PSI) is of high importance for the photosynthetic processes. For this reason, we studied the protective action of two biogenic polyamines (PAs) spermine (Spm) and spermidine (Spd) on PSI activity in isolated thylakoid membranes subjected to photoinhibition. Our results show that pre-loading thylakoid membranes with Spm and Spd reduced considerably the inhibition of O2 uptake rates, P700 photooxidation and the accumulation of superoxide anions (O2 −) induced by light stress. Spm seems to be more effective than Spd in preserving PSI photo-stability. The correlation of the extent of PSI protection, photosystem II (PSII) inhibition and O2 − generation with increasing Spm doses revealed that PSI photo-protection is assumed by two mechanisms depending on the PAs concentration. Given their antioxidant character, PAs scavenge directly the O2 − generated in thylakoid membranes at physiological concentration (1 mM). However, for non-physiological concentration, the ability of PAs to protect PSI is due to their inhibitory effect on PSII electron transfer. PMID:25420109

Effects of sulphur on the performance of an anaerobic membrane bioreactor: Biological stability, trace organic contaminant removal, and membrane fouling.

PubMed

Song, Xiaoye; Luo, Wenhai; McDonald, James; Khan, Stuart J; Hai, Faisal I; Guo, Wenshan; Ngo, Hao H; Nghiem, Long D

2018-02-01

This study investigated the impact of sulphur content on the performance of an anaerobic membrane bioreactor (AnMBR) with an emphasis on the biological stability, contaminant removal, and membrane fouling. Removal of 38 trace organic contaminants (TrOCs) that are ubiquitously present in municipal wastewater by AnMBR was evaluated. Results show that basic biological performance of AnMBR regarding biomass growth and the removal of chemical oxygen demand (COD) was not affected by sulphur addition when the influent COD/SO 4 2- ratio was maintained higher than 10. Nevertheless, the content of hydrogen sulphate in the produced biogas increased significantly and membrane fouling was exacerbated with sulphur addition. Moreover, the increase in sulphur content considerably affected the removal of some hydrophilic TrOCs and their residuals in the sludge phase during AnMBR operation. By contrast, no significant impact on the removal of hydrophobic TrOCs was noted with sulphur addition to AnMBR. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Effect of sound on boundary layer stability

NASA Technical Reports Server (NTRS)

Saric, William S. (Principal Investigator); Spencer, Shelly Anne

1993-01-01

Experiments are conducted in the Arizona State University Unsteady Wind Tunnel with a zero-pressure-gradient flat-plate model that has a 67:1 elliptical leading edge. Boundary-layer measurements are made of the streamwise fluctuating-velocity component in order to identify the amplified T-S waves that are forced by downstream-travelling, sound waves. Measurements are taken with circular 3-D roughness elements placed at the Branch 1 neutral stability point for the frequency under consideration, and then with the roughness element downstream of Branch 1. These roughness elements have a principal chord dimension equal to 2(lambda)(sub TS)/pi, of the T-S waves under study and are 'stacked' in order to resemble a Gaussian height distribution. Measurements taken just downstream of the roughness (with leading-edge T-S waves, surface roughness T-S waves, instrumentation sting vibrations and the Stokes wave subtracted) show the generation of 3-D-T-S waves, but not in the characteristic heart-shaped disturbance field predicted by 3-D asymptotic theory. Maximum disturbance amplitudes are found on the roughness centerline. However, some near-field characteristics predicted by numerical modelling are observed.

Effect of sound on boundary layer stability

NASA Technical Reports Server (NTRS)

Saric, William S.; Spencer, Shelly Anne

1993-01-01

Experiments are conducted in the Arizona State University Unsteady Wind Tunnel with a zero-pressure-gradient flat-plate model that has a 67:1 elliptical leading edge. Boundary-layer measurements are made of the streamwise fluctuating-velocity component in order to identify the amplified T-S waves that are forced by downstream-traveling sound waves. Measurements are taken with circular 3-D roughness elements placed at the Branch 1 neutral stability point for the frequency under consideration, and then with the roughness element downstream of Branch 1. These roughness elements have a principal chord dimension equal to 2 lambda(sub TS)/pi of the T-S waves under study and are 'stacked' in order to resemble a Gaussian height distribution. Measurements taken just downstream of the roughness (with leading-edge T-S waves, surface roughness T-S waves, instrumentation sting vibrations, and the Stokes wave subtracted) show the generation of 3-D T-S waves, but not in the characteristic heart-shaped disturbance field predicted by 3-D asymptotic theory. Maximum disturbance amplitudes are found on the roughness centerline. However, some near-field characteristics predicted by numerical modeling are observed.

Growth of streptomycetes in soil and their impact on bioremediation.

PubMed

Schütze, Eileen; Klose, Michael; Merten, Dirk; Nietzsche, Sandor; Senftleben, Dominik; Roth, Martin; Kothe, Erika

2014-02-28

The impact of the extremely heavy metal resistant actinomycete Streptomyces mirabilis P16B-1 on heavy metal mobilization/stabilization, phytoremediation and stress level of plants was analyzed in the presence and absence of Sorghum bicolor in sterile microcosms containing highly metal contaminated or control soil. For control, a metal sensitive S. lividans TK24 was used. The metal contents with respect to the mobile and specifically adsorbed fractions of the contaminated soil were considerably decreased by addition of both, living and dead biomass of the strains, with the heavy metal resistant S. mirabilis P16B-1 showing considerably higher impact. Both strains could grow in control soil, while only S. mirabilis P16B-1 formed new tip growth in the metal contaminated soil. A plant growth promoting effect was visible for S. mirabilis P16B-1 in contaminated soil enhancing the dry weight of inoculated Sorghum plants. Thus, metal resistant strains like S. mirabilis P16B-1 are able to enhance phytoremediation of heavy metal contaminated soils. Copyright © 2013 Elsevier B.V. All rights reserved.

Thermodynamic and Mechanic Consideration on the stability of Anti-symmetric Schaefer’s equation

NASA Astrophysics Data System (ADS)

Suriamihardja, D. A.; Amiruddin; Saaduddin

2018-03-01

Schaefer’s equation relates an interaction between population of fishes and the number of units of fishing effort. The population growth of fishes is reduced by the number of units of fishing effort, while the population growth of units of fishing effort depends on the existence of fishes. This paper aims to examine the stability of an anti-symmetric Schaefer’s equation through thermodynamic and mechanic procedure using a formula of entropy production near equilibrium which is recognized as Onsager’s relation. The results confirm that entropic approach (thermodynamics) and dissipative approach (mechanics) are usable to be applied as Lyapunov’s procedure in examining the stability of systems of differential equations.

Perspective—Localized Corrosion: Passive Film Breakdown vs Pit Growth Stability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frankel, G. S.; Li, Tianshu; Scully, J. R.

2017-02-24

A debate about the critical step in localized corrosion has raged for decades. Some researchers focus on the composition and structure of the passive film associated with the initial breakdown of the film, whereas others consider that the susceptibility to pitting is controlled by the pit growth kinetics and the stabilization of pit growth. The basis for a unified theory of pitting is presented here in which pit stability considerations are controlling under aggressive conditions (harsh electrolytes and extreme environments and/or susceptible microstructures) and the passive film properties and protectiveness are the critical factors in less extreme environments and/or formore » less susceptible alloys.« less

Influence of Heat Treatments on the Microstructural Evolution and Resultant Mechanical Properties in a Low Carbon Medium Mn Heavy Steel Plate

NASA Astrophysics Data System (ADS)

Chen, Jun; Lv, Meng-yang; Liu, Zhen-yu; Wang, Guo-dong

2016-05-01

In this study, the microstructural evolution and resultant mechanical properties in a low carbon medium Mn heavy steel plate were investigated in detail. The results show that the introduction of medium manganese alloy design in the heavy steel plate has been shown to achieve the outstanding combination of strength, ductility, low-temperature impact toughness, and strain hardening capacity. It has been found that the austenite phase mainly displays at martensitic lath boundaries and shows lath shape for the heat treating at 873 K (600 °C) for 1 to 10 hours or 893 K (620 °C) for 2 hours, and not all the austenite phase obeys the K-S or N-W orientation relationship with respect to abutting martensitic lath. Although the microstructure in the steel after heat treating at 873 K (600 °C) for 1 to 10 hours is similar to each other, the resultant mechanical properties are very different because the volume fraction and stability of retained austenite vary with the heat treatments. The best low-temperature impact toughness is achieved after heat treating at 873 K (600 °C) for 2 hours due to the formation of a considerable volume fraction of retained austenite with relatively high stability, but the strain hardening capacity and ductility are disappointing because of insufficient TRIP effect. Based on enhancing TRIP effect, the two methods have been suggested. One is to increase the isothermal holding temperature to 893 K (620 °C), and the other one is to prolong the isothermal holding time to 10 hours at 873 K (600 °C). The two methods can significantly increase strain hardening capacity and ductility nearly without harming low-temperature impact toughness. In addition, the stability of retained austenite has been discussed by the quantitative analysis and it has been demonstrated that the stability of retained austenite is related to the chemical composition, size, and morphology. Moreover, the isothermal holding temperature has a great effect on the stability of retained austenite, while the effect of the isothermal holding time is relatively poor.

Study of Reactive Melt Processing Behavior of Externally Plasticized Cellulose Acetate in Presence of Isocyanate

PubMed Central

Erdmann, Rafael; Kabasci, Stephan; Kurek, Joanna; Zepnik, Stefan

2014-01-01

Two types of externally plasticized cellulose acetate (CA) were chemically modified using 4,4'-methylene diphenyl diisocyanate (MDI) as crosslinking agent. Crosslinking was performed in the molten state by means of melt mixing in an internal mixer. The viscoelastic properties of the non-crosslinked, externally plasticized CA show typical temperature dependence, similar to conventional thermoplastics. A strong increase in storage modulus is observed with increasing crosslink density indicating that the crosslinked compounds exhibit predominately elastic response. The complex viscosity also increases considerably with increasing crosslink density and does not reach the typical Newtonian plateau at low radial frequencies any more. The viscoelastic properties correlate well with the data recorded online during reactive melt processing in the internal mixer. In comparison to the non-crosslinked CA, the crosslinked compounds show higher glass transition temperature, higher VICAT softening temperatures, improved thermal stability and lower plasticizer evaporation at evaluated temperatures. PMID:28788273

Properties of jet engine combustion particles during the PartEmis experiment: Microphysics and Chemistry

NASA Astrophysics Data System (ADS)

Petzold, A.; Stein, C.; Nyeki, S.; Gysel, M.; Weingartner, E.; Baltensperger, U.; Giebl, H.; Hitzenberger, R.; Döpelheuer, A.; Vrchoticky, S.; Puxbaum, H.; Johnson, M.; Hurley, C. D.; Marsh, R.; Wilson, C. W.

2003-07-01

The particles emitted from an aircraft engine combustor were investigated in the European project PartEmis. Measured aerosol properties were mass and number concentration, size distribution, mixing state, thermal stability of internally mixed particles, hygroscopicity, and cloud condensation nuclei (CCN) activation potential. The combustor operation conditions corresponded to modern and older engine gas path temperatures at cruise altitude, with fuel sulphur contents (FSC) of 50, 410, and 1270 μg g-1. Operation conditions and FSC showed only a weak influence on the microphysical aerosol properties, except for hygroscopic and CCN properties. Particles of size D >= 30 nm were almost entirely internally mixed. Particles of sizes D < 20 nm showed a considerable volume fraction of compounds that volatilise at 390 K (10-15%) and 573 K (4-10%), while respective fractions decreased to <5% for particles of size D >= 50 nm.

Study of Reactive Melt Processing Behavior of Externally Plasticized Cellulose Acetate in Presence of Isocyanate.

PubMed

Erdmann, Rafael; Kabasci, Stephan; Kurek, Joanna; Zepnik, Stefan

2014-12-04

Two types of externally plasticized cellulose acetate (CA) were chemically modified using 4,4'-methylene diphenyl diisocyanate (MDI) as crosslinking agent. Crosslinking was performed in the molten state by means of melt mixing in an internal mixer. The viscoelastic properties of the non-crosslinked, externally plasticized CA show typical temperature dependence, similar to conventional thermoplastics. A strong increase in storage modulus is observed with increasing crosslink density indicating that the crosslinked compounds exhibit predominately elastic response. The complex viscosity also increases considerably with increasing crosslink density and does not reach the typical Newtonian plateau at low radial frequencies any more. The viscoelastic properties correlate well with the data recorded online during reactive melt processing in the internal mixer. In comparison to the non-crosslinked CA, the crosslinked compounds show higher glass transition temperature, higher VICAT softening temperatures, improved thermal stability and lower plasticizer evaporation at evaluated temperatures.

Preparation and characteristics of epoxy/clay/B4C nanocomposite at high concentration of boron carbide for neutron shielding application

NASA Astrophysics Data System (ADS)

Kiani, Mohammad Amin; Ahmadi, Seyed Javad; Outokesh, Mohammad; Adeli, Ruhollah; Mohammadi, Aghil

2017-12-01

In this research, the characteristics of the prepared samples in epoxy matrix by means of X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), as well as scanning electron microscope (SEM) are evaluated. Meanwhile, the obtained mechanical properties of the specimen are investigated. Thermogravimetric analysis (TGA) is also employed to evaluate the thermal degradation of manufactured nanocomposites. The thermal neutron absorption properties of nanocomposites containing 3 wt% of montmorillonite nanoclay (closite30B) have been studied experimentally, using an Am-Be point source. Mechanical tests reveal that the higher B4C concentrations, the more tensile strengths, but lower Young's modulus in all samples under consideration. TGA analysis also shows that thermal stability of the nanocomposite, increases in presence of B4C. Finally, neutron absorption analysis shows that increasing the B4C concentration leads to a nonlinearly build-up of neutron absorption cross section.

Modified EVA Encapsulant Formulations for Low Temperature Processing: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mei, Z.; Pern, F. J.; Glick, S. H.

2001-10-01

Presented at the 2001 NCPV Program Review Meeting: We have developed several new ethylene-vinyl acetate (EVA) formulations modified on the basis of NREL patented EVA formulations [1]. The new formulations can be cured to a desired gel content of {approx}80% in the ambient at temperatures 20-30 C lower than the typical conditions in vacuum (i.e. {approx}150 C). Glass/glass laminates showed transmittance spectra that are essentially the same as that of EVA 15295P in the visible and NIR regions but higher in the UV region. Results of fluorescence analysis of the ambient-processed new EVA formulations showed the concentrations of the curing-generatedmore » {alpha},{beta}-unsaturated carbonyl chromophores, which are responsible for the UV induced EVA discoloration and photodegradation, were considerably lower than that of EVA 15295P, therefore suggesting a better photochemical stability of new EVA formulations.« less

Engineering Lipases: walking the fine line between activity and stability

NASA Astrophysics Data System (ADS)

Dasetty, Siva; Blenner, Mark A.; Sarupria, Sapna

2017-11-01

Lipases are enzymes that hydrolyze lipids and have several industrial applications. There is a tremendous effort in engineering the activity, specificity and stability of lipases to render them functional in a variety of environmental conditions. In this review, we discuss the recent experimental and simulation studies focused on engineering lipases. Experimentally, mutagenesis studies have demonstrated that the activity, stability, and specificity of lipases can be modulated by mutations. It has been particularly challenging however, to elucidate the underlying mechanisms through which these mutations affect the lipase properties. We summarize results from experiments and molecular simulations highlighting the emerging picture to this end. We end the review with suggestions for future research which underscores the delicate balance of various facets in the lipase that affect their activity and stability necessitating the consideration of the enzyme as a network of interactions.

The Geopolitics of Nuclear Waste.

ERIC Educational Resources Information Center

Marshall, Eliot

1991-01-01

The controversy surrounding the potential storage of nuclear waste at Yucca Mountain, Nevada, is discussed. Arguments about the stability of the site and the groundwater situation are summarized. The role of the U.S. Department of Energy and other political considerations are described. (CW)

Simulating the Stability of Colloidal Amorphous Iron Oxide in Natural Water

EPA Science Inventory

Considerable uncertainty exists as to whether existing thermodynamic equilibrium solid/water partitioning paradigms can be used to assess the mobility of insoluble manufactured nanomaterials in the aquatic environment. In this work, the traditional Derjaguin–Landau–Verwey–Overbee...

The Tropopause Inversion Layer: New Observations, New Theories

NASA Astrophysics Data System (ADS)

Tandon, N.; Randel, W. J.; Pan, L.; Son, S.; Polvani, L. M.

2009-12-01

There is now great interest in the tropopause inversion inversion layer (TIL), a 1-2 km region just above the tropopause where there is a spike in static stability. Radio occultation data from the COSMIC GPS mission are providing an unprecedented level of spatial and temporal resolution with which to analyze the TIL. We start by showing the agreement between GPS data and radiosondes. We then examine the causes and consequences of the TIL. Observations from the ACE satellite and fixed dynamical heating calculations suggest strong roles for water vapor and ozone in the formation and modulation of the TIL. This agrees with observations showing a large TIL in the polar winter, where water vapor levels are persistently high. It is also clear that TIL strength is related to vorticity, but observations and models have important differences that need to be reconciled. These dynamical considerations dovetail with observations showing high TIL variability in the storm-track regions. Finally there is evidence from ozonesonde data that the TIL may be coupled to transport across the tropopause.

Homeostatic synaptic depression is achieved through a regulated decrease in presynaptic calcium channel abundance

PubMed Central

Gaviño, Michael A; Ford, Kevin J; Archila, Santiago; Davis, Graeme W

2015-01-01

Homeostatic signaling stabilizes synaptic transmission at the neuromuscular junction (NMJ) of Drosophila, mice, and human. It is believed that homeostatic signaling at the NMJ is bi-directional and considerable progress has been made identifying mechanisms underlying the homeostatic potentiation of neurotransmitter release. However, very little is understood mechanistically about the opposing process, homeostatic depression, and how bi-directional plasticity is achieved. Here, we show that homeostatic potentiation and depression can be simultaneously induced, demonstrating true bi-directional plasticity. Next, we show that mutations that block homeostatic potentiation do not alter homeostatic depression, demonstrating that these are genetically separable processes. Finally, we show that homeostatic depression is achieved by decreased presynaptic calcium channel abundance and calcium influx, changes that are independent of the presynaptic action potential waveform. Thus, we identify a novel mechanism of homeostatic synaptic plasticity and propose a model that can account for the observed bi-directional, homeostatic control of presynaptic neurotransmitter release. DOI: http://dx.doi.org/10.7554/eLife.05473.001 PMID:25884248

Unraveling protein stabilization mechanisms: vitrification and water replacement in a glass transition temperature controlled system.

PubMed

Grasmeijer, N; Stankovic, M; de Waard, H; Frijlink, H W; Hinrichs, W L J

2013-04-01

The aim of this study was to elucidate the role of the two main mechanisms used to explain the stabilization of proteins by sugar glasses during drying and subsequent storage: the vitrification and the water replacement theory. Although in literature protein stability is often attributed to either vitrification or water replacement, both mechanisms could play a role and they should be considered simultaneously. A model protein, alkaline phosphatase, was incorporated in either inulin or trehalose by spray drying. To study the storage stability at different glass transition temperatures, a buffer which acts as a plasticizer, ammediol, was incorporated in the sugar glasses. At low glass transition temperatures (<50°C), the enzymatic activity of the protein strongly decreased during storage at 60°C. Protein stability increased when the glass transition temperature was raised considerably above the storage temperature. This increased stability could be attributed to vitrification. A further increase of the glass transition temperature did not further improve stability. In conclusion, vitrification plays a dominant role in stabilization at glass transition temperatures up to 10 to 20°C above storage temperature, depending on whether trehalose or inulin is used. On the other hand, the water replacement mechanism predominantly determines stability at higher glass transition temperatures. Copyright © 2013 Elsevier B.V. All rights reserved.

Assessment of read and write stability for 6T SRAM cell based on charge plasma DLTFET

NASA Astrophysics Data System (ADS)

Anju; Yadav, Shivendra; Sharma, Dheeraj

2018-03-01

To overcome the process variations due to random dopant fluctuations (RDFs) and complex annealing techniques a charge plasma based doping less TFET (CP-DLTFET) device has been proposed for designing of 6T SRAM cell. The proposed device also benefited by subthreshold slope, low leakage current, and low power supply. In this paper, to avoid the dependency of stability parameters of SRAM cell to supply voltage (Vdd), here N-curve metrics has been analyzed to determine read and write stability. Because N-curve provides stability analysis in terms of voltage and current as well as it gives combine stability analysis with the facility of an inline tester. Further, analyzing the N-curve metrics for different Vdd, cell ratio, and pull-up ratio assist in designing the configuration of transistors for the better read and write stability. Power metrics of N-curve gives the knowledge about read and write stability instead of using four metrics (SINM, SVNM, WTV, and WTI) of N-curve. Finally, in the 6T CP-DLTFET SRAM cell, read and write stability is tested by the interface trap charges (ITCs). The performance parameter of the 6T CP-DLTFET SRAM cell provides considerable read and write stability with less fabrication complexity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, W.; Tuleya, R.E.; Ginis, I.

In this study, the effect of thermodynamic environmental changes on hurricane intensity is extensively investigated with the National Oceanic and Atmospheric Administration Geophysical Fluid Dynamics Laboratory hurricane model for a suite of experiments with different initial upper-tropospheric temperature anomalies up to {+-}4 C and sea surface temperatures ranging from 26 to 31 C given the same relative humidity profile. The results indicate that stabilization in the environmental atmosphere and sea surface temperature (SST) increase cause opposing effects on hurricane intensity. The offsetting relationship between the effects of atmospheric stability increase (decrease) and SST increase (decrease) is monotonic and systematic inmore » the parameter space. This implies that hurricane intensity increase due to a possible global warming associated with increased CO{sub 2} is considerably smaller than that expected from warming of the oceanic waters alone. The results also indicate that the intensity of stronger (weaker) hurricanes is more (less) sensitive to atmospheric stability and SST changes. The model-attained hurricane intensity is found to be well correlated with the maximum surface evaporation and the large-scale environmental convective available potential energy. The model-attained hurricane intensity if highly correlated with the energy available from wet-adiabatic ascent near the eyewall relative to a reference sounding in the undisturbed environment for all the experiments. Coupled hurricane-ocean experiments show that hurricane intensity becomes less sensitive to atmospheric stability and SST changes since the ocean coupling causes larger (smaller) intensity reduction for stronger (weaker) hurricanes. This implies less increase of hurricane intensity related to a possible global warming due to increased CO{sub 2}.« less

Intraprocedural left ventricular free wall rupture diagnosed by left ventriculogram in a patient with infero-posterior myocardial infarction and severe aortic stenosis.

PubMed

Konishi, Takao; Funayama, Naohiro; Yamamoto, Tadashi; Nishihara, Hiroshi; Hotta, Daisuke; Kikuchi, Kenjiro; Yokoyama, Hideo; Ohori, Katsumi

2016-06-06

Left ventricular wall rupture remains a major lethal complication of acute myocardial infarction and hypertension is a well-known predisposing factor of cardiac rupture after myocardial infarction. An 87-year-old man was admitted to our hospital, diagnosed as acute myocardial infarction (AMI). The echocardiogram showed 0.67-cm(2) aortic valve, consistent with severe aortic stenosis (AS). A coronary angiography showed a chronic occlusion of the proximal left circumflex artery and a 99 % stenosis and thrombus in the mid right coronary artery. During percutaneous angioplasty of the latter, transient hypotension and bradycardia developed at the time of balloon inflation, and low doses of noradrenaline and etilefrine were intravenously administered as needed. The patient suddenly lost consciousness and developed electro-mechanical dissociation. Cardio-pulmonary resuscitation followed by insertion of an intra-aortic balloon pump (IABP) and percutaneous cardiopulmonary support were initiated. The echocardiogram revealed moderate pericardial effusion, though the site of free wall rupture was not distinctly visible. A left ventriculogram clearly showed an infero-posterior apical wall rupture. Surgical treatment was withheld because of the interim development of brain death. In this patient, who presented with severe AS, the administration of catecholamine to stabilize the blood pressure probably increased the intraventricular pressures considerably despite apparently normal measurements of the central aortic pressure. IABP, temporary pacemaker, or both are recommended instead of intravenous catecholamines for patients with AMI complicated with significant AS to stabilize hemodynamic function during angioplasty.

Liposome-containing Hibiscus sabdariffa calyx extract formulations with increased antioxidant activity, improved dermal penetration and reduced dermal toxicity.

PubMed

Pinsuwan, Sirirat; Amnuaikit, Thanaporn; Ungphaiboon, Suwipa; Itharat, Arunporn

2010-12-01

Hibiscus sabdariffa Linn, or Roselle, is a medicinal plant used extensively in traditional Thai medicine since ancient times. The extracts of Roselle calyces possess antioxidant activity and have potential for development as active ingredients in cosmetic products. However the limitations of using Roselle extracts in cosmetics are its low skin permeation and dermal irritation. Liposome technology is an obvious approach that might overcome these problems. Liposome formulations of standardized Roselle extracts were developed with various lipid components. The formulation showing the highest entrapment efficiency was selected for stability, skin permeation and dermal irritability studies. The liposome formulation with the highest entrapment efficiency (83%) and smalôlest particle size (332 mm) was formulated with phosphatidylcholine from soybean (SPC): Tween 80: deoxycholic acid (DA); 84:16:2.5 weight ratio, total lipid of 200 g/mL and 10% w/v Roselle extract in final liposomal preparation. This liposome formulation was found to be stable after storage at 4 degrees C, protected from light, for 2 months. The in vitro skin permeation studies, using freshly excised pig skin and modified Franz-diffusion cells, showed that the liposome formulation was able to considerably increased the rate of permeation of active compounds in Roselle extracts compared to the Roselle extract solution. The in vivo dermal irritability testing on rabbit skin showed that the liposome formulation dramatically decreased skin irritability compared to the unformulated extract. These results showed that the liposomes containing Roselle extracts had good stability, high entrapment efficacy, increased skin permeation and low skin irritation.

Computational and Experimental Study of the Transient Transport Phenomena in a Full-Scale Twin-Roll Continuous Casting Machine

NASA Astrophysics Data System (ADS)

Xu, Mianguang; Li, Zhongyang; Wang, Zhaohui; Zhu, Miaoyong

2017-02-01

To gain a fundamental understanding of the transient fluid flow in twin-roll continuous casting, the current paper applies both large eddy simulation (LES) and full-scale water modeling experiments to investigate the characteristics of the top free surface, stirring effect of the roll rotation, boundary layer fluctuations, and backflow stability. The results show that, the characteristics of the top free surface and the flow field in the wedge-shaped pool region are quite different with/without the consideration of the roll rotation. The roll rotation decreases the instantaneous fluctuation range of the top free surface, but increases its horizontal velocity. The stirring effect of the roll rotating makes the flow field more homogenous and there exists clear shear flow on the rotating roll surface. The vortex shedding induced by the Kármán Vortex Street from the submerged entry nozzle (SEN) causes the "velocity magnitude wave" and strongly influences the boundary layer stability and the backflow stability. The boundary layer fluctuations or the "velocity magnitude wave" induced by the vortex shedding could give rise to the internal porosity. In strip continuous casting process, the vortex shedding phenomenon indicates that the laminar flow can give rise to instability and that it should be made important in the design of the feeding system and the setting of the operating parameters.

Mass size distribution of particle-bound water

NASA Astrophysics Data System (ADS)

Canepari, S.; Simonetti, G.; Perrino, C.

2017-09-01

The thermal-ramp Karl-Fisher method (tr-KF) for the determination of PM-bound water has been applied to size-segregated PM samples collected in areas subjected to different environmental conditions (protracted atmospheric stability, desert dust intrusion, urban atmosphere). This method, based on the use of a thermal ramp for the desorption of water from PM samples and the subsequent analysis by the coulometric KF technique, had been previously shown to differentiate water contributes retained with different strength and associated to different chemical components in the atmospheric aerosol. The application of the method to size-segregated samples has revealed that water showed a typical mass size distribution in each one of the three environmental situations that were taken into consideration. A very similar size distribution was shown by the chemical PM components that prevailed during each event: ammonium nitrate in the case of atmospheric stability, crustal species in the case of desert dust, road-dust components in the case of urban sites. The shape of the tr-KF curve varied according to the size of the collected particles. Considering the size ranges that better characterize the event (fine fraction for atmospheric stability, coarse fraction for dust intrusion, bi-modal distribution for urban dust), this shape is coherent with the typical tr-KF shape shown by water bound to the chemical species that predominate in the same PM size range (ammonium nitrate, crustal species, secondary/combustion species - road dust components).

Stabilization study on a wet-granule tableting method for a compression-sensitive benzodiazepine receptor agonist.

PubMed

Fujita, Megumi; Himi, Satoshi; Iwata, Motokazu

2010-03-01

SX-3228, 6-benzyl-3-(5-methoxy-1,3,4-oxadiazol-2-yl)-5,6,7,8-tetrahydro-1,6-naphthyridin-2(1H)-one, is a newly-synthesized benzodiazepine receptor agonist intended to be developed as a tablet preparation. This compound, however, becomes chemically unstable due to decreased crystallinity when it undergoes mechanical treatments such as grinding and compression. A wet-granule tableting method, where wet granules are compressed before being dried, was therefore investigated as it has the advantage of producing tablets of sufficient hardness at quite low compression pressures. The results of the stability testing showed that the drug substance was chemically considerably more stable in wet-granule compression tablets compared to conventional tablets. Furthermore, the drug substance was found to be relatively chemically stable in wet-granule compression tablets even when high compression pressure was used and the effect of this pressure was small. After investigating the reason for this excellent stability, it became evident that near-isotropic pressure was exerted on the crystals of the drug substance because almost all the empty spaces in the tablets were occupied with water during the wet-granule compression process. Decreases in crystallinity of the drug substance were thus small, making the drug substance chemically stable in the wet-granule compression tablets. We believe that this novel approach could be useful for many other compounds that are destabilized by mechanical treatments.

Navigating in foldonia: Using accelerated molecular dynamics to explore stability, unfolding and self-healing of the β-solenoid structure formed by a silk-like polypeptide

PubMed Central

Zhao, Binwu

2017-01-01

The β roll molecules with sequence (GAGAGAGQ)10 stack via hydrogen bonding to form fibrils which have been themselves been used to make viral capsids of DNA strands, supramolecular nanotapes and pH-responsive gels. Accelerated molecular dynamics (aMD) simulations are used to investigate the unfolding of a stack of two β roll molecules, (GAGAGAGQ)10, to shed light on the folding mechanism by which silk-inspired polypeptides form fibrils and to identify the dominant forces that keep the silk-inspired polypeptide in a β roll configuration. Our study shows that a molecule in a stack of two β roll molecules unfolds in a step-wise fashion mainly from the C terminal. The bottom template is found to play an important role in stabilizing the β roll structure of the molecule on top by strengthening the hydrogen bonds in the layer that it contacts. Vertical hydrogen bonds within the β roll structure are considerably weaker than lateral hydrogen bonds, signifying the importance of lateral hydrogen bonds in stabilizing the β roll structure. Finally, an intermediate structure was found containing a β hairpin and an anti-parallel β sheet consisting of strands from the top and bottom molecules, revealing the self-healing ability of the β roll stack. PMID:28329017

Scalable explicit implementation of anisotropic diffusion with Runge-Kutta-Legendre super-time stepping

NASA Astrophysics Data System (ADS)

Vaidya, Bhargav; Prasad, Deovrat; Mignone, Andrea; Sharma, Prateek; Rickler, Luca

2017-12-01

An important ingredient in numerical modelling of high temperature magnetized astrophysical plasmas is the anisotropic transport of heat along magnetic field lines from higher to lower temperatures. Magnetohydrodynamics typically involves solving the hyperbolic set of conservation equations along with the induction equation. Incorporating anisotropic thermal conduction requires to also treat parabolic terms arising from the diffusion operator. An explicit treatment of parabolic terms will considerably reduce the simulation time step due to its dependence on the square of the grid resolution (Δx) for stability. Although an implicit scheme relaxes the constraint on stability, it is difficult to distribute efficiently on a parallel architecture. Treating parabolic terms with accelerated super-time-stepping (STS) methods has been discussed in literature, but these methods suffer from poor accuracy (first order in time) and also have difficult-to-choose tuneable stability parameters. In this work, we highlight a second-order (in time) Runge-Kutta-Legendre (RKL) scheme (first described by Meyer, Balsara & Aslam 2012) that is robust, fast and accurate in treating parabolic terms alongside the hyperbolic conversation laws. We demonstrate its superiority over the first-order STS schemes with standard tests and astrophysical applications. We also show that explicit conduction is particularly robust in handling saturated thermal conduction. Parallel scaling of explicit conduction using RKL scheme is demonstrated up to more than 104 processors.

Effect of body aerodynamics on the dynamic flight stability of the hawkmoth Manduca sexta.

PubMed

Nguyen, Anh Tuan; Han, Jong-Seob; Han, Jae-Hung

2016-12-14

This study explores the effects of the body aerodynamics on the dynamic flight stability of an insect at various different forward flight speeds. The insect model, whose morphological parameters are based on measurement data from the hawkmoth Manduca sexta, is treated as an open-loop six-degree-of-freedom dynamic system. The aerodynamic forces and moments acting on the insect are computed by an aerodynamic model that combines the unsteady panel method and the extended unsteady vortex-lattice method. The aerodynamic model is then coupled to a multi-body dynamic code to solve the system of motion equations. First, the trimmed flight conditions of insect models with and without consideration of the body aerodynamics are obtained using a trim search algorithm. Subsequently, the effects of the body aerodynamics on the dynamic flight stability are analysed through modal structures, i.e., eigenvalues and eigenvectors in this case, which are based on linearized equations of motion. The solutions from the nonlinear and linearized equations of motion due to gust disturbances are obtained, and the effects of the body aerodynamics are also investigated through these solutions. The results showed the important effect of the body aerodynamics at high-speed forward flight (in this paper at 4.0 and 5.0 m s -1 ) and the movement trends of eigenvalues when the body aerodynamics is included.

Toward Dendrite-Free Lithium Deposition via Structural and Interfacial Synergistic Effects of 3D Graphene@Ni Scaffold.

PubMed

Xie, Keyu; Wei, Wenfei; Yuan, Kai; Lu, Wei; Guo, Min; Li, Zhihua; Song, Qiang; Liu, Xingrui; Wang, Jian-Gan; Shen, Chao

2016-10-05

Owing to its ultrahigh specific capacity and low electrochemical potential, lithium (Li) metal is regarded as one of the most attractive anode materials for next-generation lithium batteries. Nevertheless, the commercialization of Li-metal-based rechargeable batteries (LiMBs) has been retarded by the uncontrollable growth of Li dendrites, as well as the resulting poor cycle stability and safety hazards. In this work, a 3D graphene@Ni scaffold has been proposed to accomplish dendrite-free Li deposition via structural and interfacial synergistic effects. Due to the intrinsic high surface area used to reduce the effective electrode current density and the surface-coated graphene working as an artificial protection layer to provide high cycle stability as well as suppress the growth of Li dendrites, the Coulombic efficiencies of Li deposition on 3D graphene@Ni foam after 100 cycles can be sustained as high as 96, 98, and 92% at the current densities of 0.25, 0.5, and 1.0 mA cm -2 , respectively, which shows more excellent cycle stability than that of its planar Cu foil and bare Ni foam counterparts. The results obtained here demonstrate that the comprehensive consideration of multiaspect factors could be more help to enhance the performance of Li metal anode so as to achieve its real application in next-generation LiMBs.

Integrated analysis on static/dynamic aeroelasticity of curved panels based on a modified local piston theory

NASA Astrophysics Data System (ADS)

Yang, Zhichun; Zhou, Jian; Gu, Yingsong

2014-10-01

A flow field modified local piston theory, which is applied to the integrated analysis on static/dynamic aeroelastic behaviors of curved panels, is proposed in this paper. The local flow field parameters used in the modification are obtained by CFD technique which has the advantage to simulate the steady flow field accurately. This flow field modified local piston theory for aerodynamic loading is applied to the analysis of static aeroelastic deformation and flutter stabilities of curved panels in hypersonic flow. In addition, comparisons are made between results obtained by using the present method and curvature modified method. It shows that when the curvature of the curved panel is relatively small, the static aeroelastic deformations and flutter stability boundaries obtained by these two methods have little difference, while for curved panels with larger curvatures, the static aeroelastic deformation obtained by the present method is larger and the flutter stability boundary is smaller compared with those obtained by the curvature modified method, and the discrepancy increases with the increasing of curvature of panels. Therefore, the existing curvature modified method is non-conservative compared to the proposed flow field modified method based on the consideration of hypersonic flight vehicle safety, and the proposed flow field modified local piston theory for curved panels enlarges the application range of piston theory.

pH-Cleavable Nucleoside Lipids: A New Paradigm for Controlling the Stability of Lipid-Based Delivery Systems.

PubMed

Oumzil, Khalid; Benizri, Sébastien; Tonelli, Giovanni; Staedel, Cathy; Appavoo, Ananda; Chaffanet, Max; Navailles, Laurence; Barthélémy, Philippe

2015-11-01

Lipid-based delivery systems are an established technology with considerable clinical acceptance and several applications in human. Herein, we report the design, synthesis and evaluation of novel orthoester nucleoside lipids (ONLs) for the modulation of liposome stability. The ONLs contain head groups with 3'-orthoester nucleoside derivatives featuring positive or negative charges. The insertion of the orthoester function in the NL structures allows the formation of pH-sensitive liposomes. ONL-based liposomes can be hydrolyzed to provide nontoxic products, including nucleoside derivatives and hexadecanol. To allow the release to be tunable at different hydrolysis rates, the charge of the polar head structure is modulated, and the head group can be released at a biologically relevant pH. Crucially, when ONLs are mixed with natural phosphocholine lipids (PC), the resultant liposome evolves toward the formation of a hexadecanol/PC lamellar system. Biological evaluation shows that stable nucleic acid lipid particles (SNALPs) formulated with ONLs and siRNAs can effectively enter into tumor cells and release their nucleic acid payload in response to an intracellular acidic environment. This results in a much higher antitumor activity than conventional SNALPs. The ability to use pH-cleavable nucleolipids to control the stability of lipid-based delivery systems represents a promising approach for the intracellular delivery of drug cargos. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stability-indicating RP-HPLC Method for the Simultaneous Determination of Sitagliptin and Simvastatin in Tablets

PubMed Central

Ramalingam, P.; Bhaskar, V. Udaya; Reddy, Y. Padmanabha; Kumar, K. Vinod

2014-01-01

A new stability-indicating high-performance liquid chromatographic method for simultaneous analysis of sitagliptin and simvastatin in pharmaceutical dosage form was developed and validated. The mobile phase consisted of methanol and water (70:30, v/v) with 0.2 % of n-heptane sulfonic acid adjusted to pH 3.0 with ortho phosphoric acid was used. Retentions of sitagliptin and simvastatin were 4.3 min and 30.4 min, respectively with a flow rate of 1 ml/min on C8 (Qualisil BDS, 250×4.6 mm, 5 μ). Eluents were detected at 253 nm using photodiode diode array detector. The linear regression analysis data for the linearity plot showed correlation coefficient values of 0.9998 and 0.9993 for sitagliptin and simvastatin, with respective concentration ranges of 20-150 μg/ml and 8-60 μg/ml. The relative standard deviation for inter-day precision was lower than 2.0%. The assay of sitagliptin and simvastatin was determined in tablet dosage form was found to be within limits. Both drugs were subjected to a variety of stress conditions such as acidic, basic, oxidation, photolytic, neutral and thermal stress in order to achieve adequate degradation. Results revealed that considerable degradation was found in all stress conditions except oxidative degradations. The method has proven specificity for stability indicating assay method. PMID:25425754

A flight investigation of the effect of mass distribution and control setting on the spinning of the XN2Y-1 airplane

NASA Technical Reports Server (NTRS)

Scudder, N F

1935-01-01

The investigation of the effect of mass distribution on the spinning of airplanes initiated with tests on the NY-1 airplane has been continued by tests on another airplane in order to increase the scope of the information and to observe particularly the behavior of an airplane that shows considerable change in sideslip angle for its various conditions of spinning. The XN2Y-1 naval training biplane was used for the present tests in which changes of ballast along the longitudinal and lateral axes and changes of aileron, stabilizer, and elevator settings were made. The effects of these changes on the steady spin were measured in flight.

PURDU-WINCOF: A computer code for establishing the performance of a fan-compressor unit with water ingestion

NASA Technical Reports Server (NTRS)

Leonardo, M.; Tsuchiya, T.; Murthy, S. N. B.

1982-01-01

A model for predicting the performance of a multi-spool axial-flow compressor with a fan during operation with water ingestion was developed incorporating several two-phase fluid flow effects as follows: (1) ingestion of water, (2) droplet interaction with blades and resulting changes in blade characteristics, (3) redistribution of water and water vapor due to centrifugal action, (4) heat and mass transfer processes, and (5) droplet size adjustment due to mass transfer and mechanical stability considerations. A computer program, called the PURDU-WINCOF code, was generated based on the model utilizing a one-dimensional formulation. An illustrative case serves to show the manner in which the code can be utilized and the nature of the results obtained.

Preparation and characterizations of EGDE crosslinked chitosan electrospun membranes.

PubMed

Aqil, A; Tchemtchoua, V T; Colige, A; Atanasova, G; Poumay, Y; Jérôme, C

2015-01-01

Composite Crosslinked nanofibrous membranes of chitosan, ethylene glycol diglycidyl ether (EGDE) and polyethylene oxide was successfully prepared with bead free morphology via electrospinning technique followed by heat mediated chemical crosslinking. Architectural stability of nanofiber mat in aqueous medium was achieved by chemical crosslinking of only 1% EGDE, and tensile strength tests revealed that increasing EGDE content has considerably enhance the elastic modulus of nanofibers. The structure, morphology and mechanical properties of nanofibers were characterized by Attenuated Total Reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and Instron machine, respectively. Skin fibroblasts and endothelial cells showed good attachment, proliferation and viability on crosslinked electrospun membranes. The results indicate a good biocompatibility and non-toxic nature of the resulted membrane.

One-Pot Synthesis of D-Phenylalanine-Functionalized Multi-Walled Carbon Nanotubes: a Metal-Free Chiral Material for the Asymmetric Electroreduction of Aromatic Ketones.

PubMed

Yue, Ying-Na; Zeng, Sheng; Wang, Hui; Wang, Shuo; Wang, Huan; Lu, Jia-Xing

2018-06-19

A simple protocol to synthesize D-phenylalanine (D-PHE)-functionalized multi-walled carbon nanotubes (MWCNTs) via one-pot method was established by grafting D-PHE onto MWCNTs to obtain D-PHE-MWCNTs under mild reaction conditions. The resulting D-PHE-MWCNTs were detailedly characterized via spectroscopy and surface analysis. The electroreduction of 2,2,2-trifluoroacetophenone at D-PHE-MWCNTs cathode afforded (S)-α-(trifluoromethyl) benzyl alcohol whose yield was 65% and the enantiomeric excess was 40%. No extra catalysts were required in this electrochemical reaction solution compared with other reactions requiring homogeneous catalysis. The metal-free chiral material also showed acceptable asymmetric electroreduction performance, considerable stability and favorable reusability.

Study on antibacterial alginate-stabilized copper nanoparticles by FT-IR and 2D-IR correlation spectroscopy

PubMed Central

Díaz-Visurraga, Judith; Daza, Carla; Pozo, Claudio; Becerra, Abraham; von Plessing, Carlos; García, Apolinaria

2012-01-01

Background The objective of this study was to clarify the intermolecular interaction between antibacterial copper nanoparticles (Cu NPs) and sodium alginate (NaAlg) by Fourier transform infrared spectroscopy (FT-IR) and to process the spectra applying two-dimensional infrared (2D-IR) correlation analysis. To our knowledge, the addition of NaAlg as a stabilizer of copper nanoparticles has not been previously reported. It is expected that the obtained results will provide valuable additional information on: (1) the influence of reducing agent ratio on the formation of copper nanoparticles in order to design functional nanomaterials with increased antibacterial activity, and (2) structural changes related to the incorporation of Cu NPs into the polymer matrix. Methods Cu NPs were prepared by microwave heating using ascorbic acid as reducing agent and NaAlg as stabilizing agent. The characterization of synthesized Cu NPs by ultraviolet visible spectroscopy, transmission electron microscopy (TEM), electron diffraction analysis, X-ray diffraction (XRD), and semiquantitative analysis of the weight percentage composition indicated that the average particle sizes of Cu NPs are about 3–10 nm, they are spherical in shape, and consist of zerovalent Cu and Cu2O. Also, crystallite size and relative particle size of stabilized Cu NPs were calculated by XRD using Scherrer’s formula and FT from the X-ray diffraction data. Thermogravimetric analysis, differential thermal analysis, differential scanning calorimetry (DSC), FT-IR, second-derivative spectra, and 2D-IR correlation analysis were applied to studying the stabilization mechanism of Cu NPs by NaAlg molecules. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of stabilized Cu NPs against five bacterial strains (Staphylococccus aureus ATCC 6538P, Escherichia coli ATCC 25922 and O157: H7, and Salmonella enterica serovar Typhimurium ATCC 13311 and 14028) were evaluated with macrodilution, agar dilution plate count, and well-diffusion methods. Results On the basis of the semiquantitative analysis, there was a direct correlation between the reducing agent ratio and the percentage of zerovalent Cu. This was confirmed with the statistical analysis of population of Cu NPs from TEM micrographs. At lower reducing agent ratios, two phases coexist (Cu2O and zerovalent Cu) due to incomplete reduction of copper ions by the reducing agent; however, at higher reducing agent ratios, the Cu NPs consist mainly of zerovalent Cu. Crystallite size and relative particle size of stabilized Cu NPs showed considerable differences in results and tendencies in respect to TEM analysis. However, the relative particle size values obtained from FT of XRD data agreed well with the histograms from the TEM observations. From FT results, the relative particle size and reducing agent ratio of stabilized Cu NPs showed an inverse correlation. The incomplete reduction of copper ions at lower reducing agent ratios was also confirmed by DSC studies. FT-IR and 2D-IR correlation spectra analysis suggested the first event involved in the stabilization of Cu NPs is their electrostatic interaction with –C=O of carboxylate groups of NaAlg, followed by the interaction with the available O–C–O−, and finally with the –OH groups. Bacterial susceptibility to stabilized nanoparticles was found to vary depending on the bacterial strains. The lowest MIC and MBC of stabilized Cu NPs ranged between 2 mg/L and 8 mg/L for all studied strains. Disk-diffusion studies with both E. coli strains revealed greater effectiveness of the stabilized Cu NPs compared to the positive controls (cloxacillin, amoxicillin, and nitrofurantoin). S. aureus showed the highest sensitivity to stabilized Cu NPs compared to the other studied strains. Conclusion Cu NPs were successfully synthesized via chemical reduction assisted with microwave heating. Average particle size, polydispersity, and phase composition of Cu NPs depended mainly on the reducing agent ratio. Likewise, thermal stability and antibacterial activity of stabilized Cu NPs were affected by their phase composition. Because of the carboxylate groups in polymer chains, the structural changes of stabilized Cu NPs are different from those of NaAlg. NaAlg acted as a size controller and stabilizing agent of Cu NPs, due to their ability to bind strongly to the metal surface. Our study on the stabilizing agent–dependent structural changes of stabilized NPs is helpful for wide application of NaAlg as an important biopolymer. PMID:22848180

Impact of lysozyme on stability mechanism of nanozirconia aqueous suspension

NASA Astrophysics Data System (ADS)

Szewczuk-Karpisz, Katarzyna; Wiśniewska, Małgorzata

2016-08-01

The effect of lysozyme (LSZ) presence on the zirconium(IV) oxide (ZrO2) aqueous suspension stability was examined. The applied zirconia contains mesopores (with a diameter about 30 nm) and its mean particle size is about 100 nm. To determine the stability mechanism of ZrO2 suspension in the biopolymer presence, the adsorption and electrokinetic (surface charge density and zeta potential) measurements were performed in the pH range 3-10. The lysozyme adsorption on the nanozirconia surface proceeds mainly through electrostatic forces. Under solid-polymer repulsion conditions, there is no adsorption of lysozyme (pH < 6, CNaCl 0.01 mol/dm3). The increase of solution ionic strength to 0.2 mol/dm3 causes screening of unfavourable forces and biopolymer adsorption becomes possible. The LSZ addition to the ZrO2 suspension influences its stability. At pH 3, 4.6 and 7.6, slight improvement of the system stability was obtained. In turn, at pH 9 considerable destabilization of nanozirconia particles covered by polymeric layers occurs.

A colloidal singularity reveals the crucial role of colloidal stability for nanomaterials in-vitro toxicity testing: nZVI-microalgae colloidal system as a case study.

PubMed

Gonzalo, Soledad; Llaneza, Veronica; Pulido-Reyes, Gerardo; Fernández-Piñas, Francisca; Bonzongo, Jean Claude; Leganes, Francisco; Rosal, Roberto; García-Calvo, Eloy; Rodea-Palomares, Ismael

2014-01-01

Aggregation raises attention in Nanotoxicology due to its methodological implications. Aggregation is a physical symptom of a more general physicochemical condition of colloidal particles, namely, colloidal stability. Colloidal stability is a global indicator of the tendency of a system to reduce its net surface energy, which may be achieved by homo-aggregation or hetero-aggregation, including location at bio-interfaces. However, the role of colloidal stability as a driver of ENM bioactivity has received little consideration thus far. In the present work, which focuses on the toxicity of nanoscaled Fe° nanoparticles (nZVI) towards a model microalga, we demonstrate that colloidal stability is a fundamental driver of ENM bioactivity, comprehensively accounting for otherwise inexplicable differential biological effects. The present work throws light on basic aspects of Nanotoxicology, and reveals a key factor which may reconcile contradictory results on the influence of aggregation in bioactivity of ENMs.

The effect of implant design of linked total elbow arthroplasty on stability and stress: a finite element analysis.

PubMed

Willing, Ryan; King, Graham J W; Johnson, James A

2014-01-01

Several linked total elbow arthroplasty designs exist, which function similar to a loose hinge joint. Constraint behaviour is an important design consideration, as it affects joint stability, or how much secondary [e.g. varus-valgus (VV)] motion is permitted. Implant durability is also a concern, as bearing failures have been reported. This finite element analysis investigates the constraint characteristics and ultra high molecular weight polyethylene bearing stresses of three linked elbow design concepts [cylindrical (CY), hourglass (HG) and concave cylinder (CC)]. The bearing of the CY design was subjected to elevated Von Mises stresses (2.1-5.4 times higher than the HG and CC designs) due to edge loading. The HG design maintained low stresses, but was unable to provide consistent VV stability. The CC design also maintained low stresses while providing consistent VV stability. These results suggest that CC designs may provide better stability characteristics and durability in vivo, compared to the other two designs.

Effect of surface charge alteration on stability of L-asparaginase II from Escherichia sp.

PubMed

Vidya, Jalaja; Ushasree, Mrudula Vasudevan; Pandey, Ashok

2014-03-05

Escherichia coli L-asparaginases have great significance in the treatment of leukemia. Consequently, there is considerable interest in engineering this enzyme for improving its stability. In this work, the effect of surface charge on the stability of the enzyme l-asparaginase II was studied by site-directed mutagenesis of the cloned ansB gene from Escherichia sp. Replacement of two positively charged residues (K139 and K207) on the surface loops with neutral and reverse charges resulted in altered thermo stability in designed variants. Neutral charge substitutions (K139A and K207A) retained greater tolerance and stability followed by negative charge substitutions (K139D and K207D) compared to control mutant K139R and wild enzyme. From the results, it was concluded that the optimization of surface charge contributed much to the thermal properties of proteins without affecting the structure. Copyright © 2013 Elsevier Inc. All rights reserved.

A Colloidal Singularity Reveals the Crucial Role of Colloidal Stability for Nanomaterials In-Vitro Toxicity Testing: nZVI-Microalgae Colloidal System as a Case Study

PubMed Central

Fernández-Piñas, Francisca; Bonzongo, Jean Claude; Leganes, Francisco; Rosal, Roberto; García-Calvo, Eloy; Rodea-Palomares, Ismael

2014-01-01

Aggregation raises attention in Nanotoxicology due to its methodological implications. Aggregation is a physical symptom of a more general physicochemical condition of colloidal particles, namely, colloidal stability. Colloidal stability is a global indicator of the tendency of a system to reduce its net surface energy, which may be achieved by homo-aggregation or hetero-aggregation, including location at bio-interfaces. However, the role of colloidal stability as a driver of ENM bioactivity has received little consideration thus far. In the present work, which focuses on the toxicity of nanoscaled Fe° nanoparticles (nZVI) towards a model microalga, we demonstrate that colloidal stability is a fundamental driver of ENM bioactivity, comprehensively accounting for otherwise inexplicable differential biological effects. The present work throws light on basic aspects of Nanotoxicology, and reveals a key factor which may reconcile contradictory results on the influence of aggregation in bioactivity of ENMs. PMID:25340509

Transient Stability and Frequency Response of the US Western Interconnection Under Conditions of High Wind and Solar Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, Nicholas W.; Shao, Miaolei; Pajic, Slobodan

The addition of large amounts of wind and solar generation to bulk power systems that are traditionally subject to operating constraints set by transient stability and frequency response limitations is the subject of considerable concern in the industry. The US Western Interconnection (WI) is expected to experience substantial additional growth in both wind and solar generation. These plants will, to some extent, displace large central station thermal generation, both coal and gas-fired, which have traditionally helped maintain stability. This paper reports the results of a study that investigated the transient stability and frequency response of the WI with high penetrationsmore » of wind and solar generation. The main goals of this work were to (1) create a realistic, baseline model of the WI, (2) test selected transient stability and frequency events, (3) investigate the impact of large amounts of wind and solar generation, and (4) examine means to improve performance.« less

Transient Stability and Frequency Response of the Us Western Interconnection Under Conditions of High Wind and Solar Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, Kara; Miller, Nicholas W.; Shao, Miaolei

Adding large amounts of wind and solar generation to bulk power systems that are traditionally subject to operating constraints set by transient stability and frequency response limitations is the subject of considerable concern in the industry. The US Western Interconnection (WI) is expected to experience substantial additional growth in both wind and solar generation. These plants will, to some extent, displace large central station thermal generation, both coal and gas-fired, which have traditionally helped maintain stability. Our paper reports the results of a study that investigated the transient stability and frequency response of the WI with high penetrations of windmore » and solar generation. Moreover, the main goals of this work were to (1) create a realistic, baseline model of the WI, (2) test selected transient stability and frequency events, (3) investigate the impact of large amounts of wind and solar generation, and (4) examine means to improve performance.« less

The lightest organic radical cation for charge storage in redox flow batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Jinhua; Pan, Baofei; Duan, Wentao

2016-08-25

Electrochemically reversible fluids of high energy density are promising materials for capturing the electrical energy generated from intermittent sources like solar and wind. To meet this technological challenge there is a need to understand the fundamental limits and interplay of electrochemical potential, stability and solubility in “lean” derivatives of redox-active molecules. Here we describe the process of molecular pruning, illustrated for 2,5-di-tert-butyl-1,4-bis(2-methoxyethoxy)benzene, a molecule known to produce a persistently stable, high-potential radical cation. By systematically shedding molecular fragments considered important for radical cation steric stabilization, we discovered a minimalistic structure that retains long-term stability in its oxidized form. Interestingly, wemore » find the tert-butyl groups are unnecessary; high stability of the radical cation and high solubility are both realized in derivatives having appropriately positioned arene methyl groups. These stability trends are rationalized by mechanistic considerations of the postulated decomposition pathways. We suggest that the molecular pruning approach will uncover lean redox active derivatives for electrochemical energy storage leading to materials with long-term stability and high intrinsic capacity.« less

Postural stability and vehicle kinematics during an evasive lane change manoeuvre: a driver training study.

PubMed

Petersen, Andrew; Barrett, Rod

2009-05-01

The purpose of this study was to investigate the effect of a 2-day driver-training course that emphasised postural stability maintenance during critical driving situations on postural stability and vehicle kinematics during an evasive lane change manoeuvre. Following training, the trainee group experienced enhanced postural stability during specific phases of the task. In terms of vehicle kinematics, the main adaptation to training was that trained drivers reduced the extent to which they experienced vehicle decelerations during rapid turning compared to controls. Such a strategy may confer a safety benefit due to the increased risks associated with simultaneous braking while turning during an evasive manoeuvre. The newly learned strategy was consistent with the strategy used by a group of highly skilled drivers (driving instructors). Taken together, the results of the study suggest postural stability may be a useful variable to consider in relation to the skill-based component of hierarchical driver training programmes. The findings of this study provide some preliminary evidence to suggest that postural stability may be an important consideration when instructing individuals on how to safely negotiate obstacles during driving.

Learning discriminative functional network features of schizophrenia

NASA Astrophysics Data System (ADS)

Gheiratmand, Mina; Rish, Irina; Cecchi, Guillermo; Brown, Matthew; Greiner, Russell; Bashivan, Pouya; Polosecki, Pablo; Dursun, Serdar

2017-03-01

Associating schizophrenia with disrupted functional connectivity is a central idea in schizophrenia research. However, identifying neuroimaging-based features that can serve as reliable "statistical biomarkers" of the disease remains a challenging open problem. We argue that generalization accuracy and stability of candidate features ("biomarkers") must be used as additional criteria on top of standard significance tests in order to discover more robust biomarkers. Generalization accuracy refers to the utility of biomarkers for making predictions about individuals, for example discriminating between patients and controls, in novel datasets. Feature stability refers to the reproducibility of the candidate features across different datasets. Here, we extracted functional connectivity network features from fMRI data at both high-resolution (voxel-level) and a spatially down-sampled lower-resolution ("supervoxel" level). At the supervoxel level, we used whole-brain network links, while at the voxel level, due to the intractably large number of features, we sampled a subset of them. We compared statistical significance, stability and discriminative utility of both feature types in a multi-site fMRI dataset, composed of schizophrenia patients and healthy controls. For both feature types, a considerable fraction of features showed significant differences between the two groups. Also, both feature types were similarly stable across multiple data subsets. However, the whole-brain supervoxel functional connectivity features showed a higher cross-validation classification accuracy of 78.7% vs. 72.4% for the voxel-level features. Cross-site variability and heterogeneity in the patient samples in the multi-site FBIRN dataset made the task more challenging compared to single-site studies. The use of the above methodology in combination with the fully data-driven approach using the whole brain information have the potential to shed light on "biomarker discovery" in schizophrenia.

Preliminary Assessment of Various Additives on the Specific Reactivity of Anti- rHBsAg Monoclonal Antibodies

PubMed Central

Yazdani, Yaghoub; Mohammadi, Saeed; Yousefi, Mehdi; Shokri, Fazel

2015-01-01

Background: Antibodies have a wide application in diagnosis and treatment. In order to maintain optimal stability of various functional parts of antibodies such as antigen binding sites, several approaches have been suggested. Using additives such as polysaccharides and polyols is one of the main methods in protecting antibodies against aggregation or degradation in the formulation. The aim of this study was to evaluate the protective effect of various additives on the specific reactivity of monoclonal antibodies (mAbs) against recombinant HBsAg (rHBsAg) epitopes. Methods: To estimate the protective effect of different additives on the stability of antibody against conformational epitopes (S3 antibody) and linear epitopes (S7 and S11 antibodies) of rHBsAg, heat shock at 37°C was performed in liquid and solid phases. Environmental factors were considered to be constant. The specific reactivity of antibodies was evaluated using ELISA method. The data were analyzed using SPSS software by Mann-Whitney nonparametric test with the confidence interval of 95%. Results: Our results showed that 0.25 M sucrose, 0.04 M trehalose and 0.5% BSA had the most protective effect on maintaining the reactivity of mAbs (S3) against conformational epitopes of rHBsAg. Results obtained from S7 and S11 mAbs against linear characteristics showed minor differences. The most efficient protective additives were 0.04 M trehalose and 1 M sucrose. Conclusion: Nowadays, application of appropriate additives is important for increasing the stability of antibodies. It was concluded that sucrose, trehalose and BSA have considerable effects on the specific reactivity of anti rHBsAg mAbs during long storage. PMID:26605008

Preliminary Assessment of Various Additives on the Specific Reactivity of Anti- rHBsAg Monoclonal Antibodies.

PubMed

Yazdani, Yaghoub; Mohammadi, Saeed; Yousefi, Mehdi; Shokri, Fazel

2015-01-01

Antibodies have a wide application in diagnosis and treatment. In order to maintain optimal stability of various functional parts of antibodies such as antigen binding sites, several approaches have been suggested. Using additives such as polysaccharides and polyols is one of the main methods in protecting antibodies against aggregation or degradation in the formulation. The aim of this study was to evaluate the protective effect of various additives on the specific reactivity of monoclonal antibodies (mAbs) against recombinant HBsAg (rHBsAg) epitopes. To estimate the protective effect of different additives on the stability of antibody against conformational epitopes (S3 antibody) and linear epitopes (S7 and S11 antibodies) of rHBsAg, heat shock at 37°C was performed in liquid and solid phases. Environmental factors were considered to be constant. The specific reactivity of antibodies was evaluated using ELISA method. The data were analyzed using SPSS software by Mann-Whitney nonparametric test with the confidence interval of 95%. Our results showed that 0.25 M sucrose, 0.04 M trehalose and 0.5% BSA had the most protective effect on maintaining the reactivity of mAbs (S3) against conformational epitopes of rHBsAg. Results obtained from S7 and S11 mAbs against linear characteristics showed minor differences. The most efficient protective additives were 0.04 M trehalose and 1 M sucrose. Nowadays, application of appropriate additives is important for increasing the stability of antibodies. It was concluded that sucrose, trehalose and BSA have considerable effects on the specific reactivity of anti rHBsAg mAbs during long storage.

Impact of linker and conjugation chemistry on antigen binding, Fc receptor binding and thermal stability of model antibody-drug conjugates

PubMed Central

Acchione, Mauro; Kwon, Hyewon; Jochheim, Claudia M.; Atkins, William M.

2012-01-01

Antibody-drug conjugates (ADCs) with biotin as a model cargo tethered to IgG1 mAbs via different linkers and conjugation methods were prepared and tested for thermostability and ability to bind target antigen and Fc receptor. Most conjugates demonstrated decreased thermostability relative to unconjugated antibody, based on DSC, with carbohydrate and amine coupled ADCs showing the least effect compared with thiol coupled conjugates. A strong correlation between biotin-load and loss of stability is observed with thiol conjugation to one IgG scaffold, but the stability of a second IgG scaffold is relatively insensitive to biotin load. The same correlation for amine coupling was less significant. Binding of antibody to antigen and Fc receptor was investigated using surface plasmon resonance. None of the conjugates exhibited altered antigen affinity. Fc receptor FcγIIb (CD32b) interactions were investigated using captured antibody conjugate. Protein G and Protein A, known inhibitors of Fc receptor (FcR) binding to IgG, were also used to extend the analysis of the impact of conjugation on Fc receptor binding. H10NPEG4 was the only conjugate to show significant negative impact to FcR binding, which is likely due to higher biotin-load compared with the other ADCs. The ADC aHISNLC and aHISTPEG8 demonstrated some loss in affinity for FcR, but to much lower extent. The general insensitivity of target binding and effector function of the IgG1 platform to conjugation highlight their utility. The observed changes in thermostability require consideration for the choice of conjugation chemistry, depending on the system being pursued and particular application of the conjugate. PMID:22531451

Laboratory and 3-D distinct element analysis of the failure mechanism of a slope under external surcharge

NASA Astrophysics Data System (ADS)

Li, N.; Cheng, Y. M.

2015-01-01

Landslide is a major disaster resulting in considerable loss of human lives and property damages in hilly terrain in Hong Kong, China and many other countries. The factor of safety and the critical slip surface for slope stabilization are the main considerations for slope stability analysis in the past, while the detailed post-failure conditions of the slopes have not been considered in sufficient detail. There is however increasing interest in the consequences after the initiation of failure that includes the development and propagation of the failure surfaces, the amount of failed mass and runoff and the affected region. To assess the development of slope failure in more detail and to consider the potential danger of slopes after failure has initiated, the slope stability problem under external surcharge is analyzed by the distinct element method (DEM) and a laboratory model test in the present research. A more refined study about the development of failure, microcosmic failure mechanisms and the post-failure mechanisms of slopes will be carried out. The numerical modeling method and the various findings from the present work can provide an alternate method of analysis of slope failure, which can give additional information not available from the classical methods of analysis.

Laboratory and 3-D-distinct element analysis of failure mechanism of slope under external surcharge

NASA Astrophysics Data System (ADS)

Li, N.; Cheng, Y. M.

2014-09-01

Landslide is a major disaster resulting in considerable loss of human lives and property damages in hilly terrain in Hong Kong, China and many other countries. The factor of safety and the critical slip surface for slope stabilization are the main considerations for slope stability analysis in the past, while the detailed post-failure conditions of the slopes have not been considered in sufficient details. There are however increasing interest on the consequences after the initiation of failure which includes the development and propagation of the failure surfaces, the amount of failed mass and runoff and the affected region. To assess the development of slope failure in more details and to consider the potential danger of slopes after failure has initiated, the slope stability problem under external surcharge is analyzed by the distinct element method (DEM) and laboratory model test in the present research. A more refined study about the development of failure, microcosmic failure mechanism and the post-failure mechanism of slope will be carried out. The numerical modeling method and the various findings from the present work can provide an alternate method of analysis of slope failure which can give additional information not available from the classical methods of analysis.

Artificial in-plane ordering of textured YBa2Cu3O(7-x) films deposited on polycrystalline yttria-stabilized zirconia substrates

NASA Astrophysics Data System (ADS)

Harshavardhan, K. S.; Rajeswari, M.; Hwang, D. M.; Chen, C. Y.; Sands, T. D.; Venkatesan, T.; Tkaczyk, J. E.; Lay, K. W.; Safari, A.; Johnson, L.

1992-12-01

Anisotropic surface texturing of the polycrystalline yttria-stabilized zirconia substrates, prior to YBa2Cu3O(7-x) film deposition, is shown to promote in-plane (basal plane) ordering of the film growth in addition to the c-axis texturing. The Jc's of the films in the weak-link-dominated low-field regime are enhanced considerably, and this result is attributed to the reduction of weak links resulting from a reduction in the number of in-plane large-angle grain boundaries.

A History of Nanobubbles.

PubMed

Alheshibri, Muidh; Qian, Jing; Jehannin, Marie; Craig, Vincent S J

2016-11-01

We follow the history of nanobubbles from the earliest experiments pointing to their existence to recent years. We cover the effect of Laplace pressure on the thermodynamic stability of nanobubbles and why this implies that nanobubbles are thermodynamically never stable. Therefore, understanding bubble stability becomes a consideration of the rate of bubble dissolution, so the dominant approach to understanding this is discussed. Bulk nanobubbles (or fine bubbles) are treated separately from surface nanobubbles as this reflects their separate histories. For each class of nanobubbles, we look at the early evidence for their existence, methods for the production and characterization of nanobubbles, evidence that they are indeed gaseous, or otherwise, and theories for their stability. We also look at applications of both surface and bulk nanobubbles.

Some problems of the solar wind interaction with Venus

NASA Astrophysics Data System (ADS)

Breus, T. K.; Krymskii, A. M.

1987-09-01

The aim of this paper is to analyze the effect of solar wind mass-loading due to hot-oxygen Venus corona photoionization on the plasma flow parameters in the nose part of the magnetosheath and the flow stability, taking into consideration the axial symmetry of the flow. The analysis has shown that the mass-loading effect increases the distance between the shock front and the ionopause and reduces the maximum magnetic field strength in the magnetic barrier in the vicinity of the stagnation region of the ionopause. The axial symmetry of the stream stabilizes the ionopause disturbances in the nose part. For shorter wavelengths the instability problem should be investigated numerically and should account for the stabilizing effect of the finite Larmor ion radius.

Post landing design and testing of an ACRV model. [Assured Crew Return Vehicles

NASA Technical Reports Server (NTRS)

Hosterman, Kenneth C.; Anderson, Loren A.

1991-01-01

Consideration is given to a 1990-1991 program concentrated on the design, building, and testing of a one-fifth scale model of the egress and stabilization systems for an Apollo Command Module (ACM)-based assured crew return vehicle (ACRV). The program is aimed at determining the feasibility of 1) stabilizing the ACRV out of the range of motions which cause space sickness and 2) the safe and rapid removaling of a sick or injured crewmember from the ACRV. Research have been conducted in the following areas: ACRV model construction, water test facility identification, and stabilization control systems. The fidelity of the model has been established from geometric and dynamic characteristic tests performed on the model.

H∞ control problem of linear periodic piecewise time-delay systems

NASA Astrophysics Data System (ADS)

Xie, Xiaochen; Lam, James; Li, Panshuo

2018-04-01

This paper investigates the H∞ control problem based on exponential stability and weighted L2-gain analyses for a class of continuous-time linear periodic piecewise systems with time delay. A periodic piecewise Lyapunov-Krasovskii functional is developed by integrating a discontinuous time-varying matrix function with two global terms. By applying the improved constraints to the stability and L2-gain analyses, sufficient delay-dependent exponential stability and weighted L2-gain criteria are proposed for the periodic piecewise time-delay system. Based on these analyses, an H∞ control scheme is designed under the considerations of periodic state feedback control input and iterative optimisation. Finally, numerical examples are presented to illustrate the effectiveness of our proposed conditions.

Stability of hydrogenated graphene: a first-principles study

DOE PAGES

Yi, Ding; Yang, Liu; Xie, Shijie; ...

2015-02-10

In order to explain the disagreement between present theoretical and experimental investigations on the stability of hydrogenated graphene, we have systematically studied hydrogenated graphene with different configurations from the consideration of single-side and double-side adsorption using first-principles calculations. Both binding energy and formation energy are calculated to characterize the stability of the system. It is found that single-side hydrogenated graphene is always unstable. However, for double-side hydrogenation, some configurations are stable due to the increased carbon–carbon sp 3 hybridization compared to single-side hydrogenation. Furthermore, it is found that the system is energetically favorable when an equal number of hydrogen atomsmore » are adsorbed on each side of the graphene.« less

Some design considerations for a synthetic aperture optical telescope array

NASA Astrophysics Data System (ADS)

Scott, P. W.

1984-01-01

Several design considerations inherent in the configuration of phased array transmission of multiwavelength laser beams are discussed. Attention is focused on the U.S.A.F. phased array (PHASAR) demonstration project, where problems have been encountered in dividing the beam(s), controlling the optical path differences between subapertures, and expanding individual beams.A piston-driven path length adjustment mechanism has been selected, along with an active control system and proven components for stability maintenance. The necessity of developing broadband, high reflectivity low phase shift coatings for the system mirrors is stressed.

Temperature effect on the structural stabilities and electronic properties of X22H28 (X=C, Si and Ge) nanocrystals: A first-principles study

NASA Astrophysics Data System (ADS)

Deng, Xiao-Lin; Zhao, Yu-Jun; Wang, Ya-Ting; Liao, Ji-Hai; Yang, Xiao-Bao

2016-12-01

Based on ab initio molecular dynamic simulations, we have theoretically investigated the structural stabilities and electronic properties of X22H28 (X=C, Si, and Ge) nanocrystals, as a function of temperature with consideration of vibrational entropy effects. To compare the relative stabilities of X22H28 isomers, the vibration free energies are obtained according to the calculated phonon spectrum, where the typical modes are shown to be dominant to the structural stabilities. In addition, there is a significant gap reduction as the temperature increases from 0 K to 300 K, where the decrements are 0.2 /0.5 /0.6eV for C/Si/Ge nanocrystals, respectively. The dependence of energy gap on the variance of bond length is also analyzed according to the corresponding atomic attributions to the HOMO and LUMO levels.

Cation-Induced Stabilization and Denaturation of DNA Origami Nanostructures in Urea and Guanidinium Chloride.

PubMed

Ramakrishnan, Saminathan; Krainer, Georg; Grundmeier, Guido; Schlierf, Michael; Keller, Adrian

2017-11-01

The stability of DNA origami nanostructures under various environmental conditions constitutes an important issue in numerous applications, including drug delivery, molecular sensing, and single-molecule biophysics. Here, the effect of Na + and Mg 2+ concentrations on DNA origami stability is investigated in the presence of urea and guanidinium chloride (GdmCl), two strong denaturants commonly employed in protein folding studies. While increasing concentrations of both cations stabilize the DNA origami nanostructures against urea denaturation, they are found to promote DNA origami denaturation by GdmCl. These inverse behaviors are rationalized by a salting-out of Gdm + to the hydrophobic DNA base stack. The effect of cation-induced DNA origami denaturation by GdmCl deserves consideration in the design of single-molecule studies and may potentially be exploited in future applications such as selective denaturation for purification purposes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Management of failed instability surgery: how to get it right the next time.

PubMed

Boone, Julienne L; Arciero, Robert A

2010-07-01

Traumatic anterior shoulder dislocations are the most frequent type of joint dislocation and affect approximately 1.7% of the general population. The literature supports the consideration of primary stabilization in high-risk patients because of reported recurrences as high as 80% to 90% with nonoperative treatment regimens. Successful stabilization of anterior glenohumeral instability relies on not only good surgical techniques but also careful patient selection. Failure rates after open and arthroscopic stabilization have been reported to range from 2% to 8% and 4% to 13%, respectively. Recurrent shoulder instability leads to increased morbidity to the patient, increased pain, decreased activity level, prolonged time away from work and sports, and a general decrease in quality of life. This article reviews the potential pitfalls in anterior shoulder stabilization and discusses appropriate methods of addressing them in revision surgery. Copyright 2010 Elsevier Inc. All rights reserved.

Development and Testing of a High Stability Engine Control (HISTEC) System

NASA Technical Reports Server (NTRS)

Orme, John S.; DeLaat, John C.; Southwick, Robert D.; Gallops, George W.; Doane, Paul M.

1998-01-01

Flight tests were recently completed to demonstrate an inlet-distortion-tolerant engine control system. These flight tests were part of NASA's High Stability Engine Control (HISTEC) program. The objective of the HISTEC program was to design, develop, and flight demonstrate an advanced integrated engine control system that uses measurement-based, real-time estimates of inlet airflow distortion to enhance engine stability. With improved stability and tolerance of inlet airflow distortion, future engine designs may benefit from a reduction in design stall-margin requirements and enhanced reliability, with a corresponding increase in performance and decrease in fuel consumption. This paper describes the HISTEC methodology, presents an aircraft test bed description (including HISTEC-specific modifications) and verification and validation ground tests. Additionally, flight test safety considerations, test plan and technique design and approach, and flight operations are addressed. Some illustrative results are presented to demonstrate the type of analysis and results produced from the flight test program.

Overview of waste stabilization with cement.

PubMed

Batchelor, B

2006-01-01

Cement can treat a variety of wastes by improving physical characteristics (solidification) and reducing the toxicity and mobility of contaminants (stabilization). Potentially adverse waste-binder interactions are an important consideration because they can limit solidification. Stabilization occurs when a contaminant is converted from the dissolved (mobile) phase to a solid (immobile) phase by reactions, such as precipitation, sorption, or substitution. These reactions are often strongly affected by pH, so the presence of components of the waste that control pH are critical to stabilization reactions. Evaluating environmental impacts can be accomplished in a tiered strategy in which simplest approach would be to measure the maximum amount of contaminant that could be released. Alternatively, the sequence of release can be determined, either by microcosm tests that attempt to simulate conditions in the disposal zone or by mechanistic models that attempt to predict behavior using fundamental characteristics of the treated waste.

Transient Stability of the US Western Interconnection with High Wind and Solar Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, Kara; Miller, Nicholas W.; Shao, Miaolei

The addition of large amounts of wind and solar generation to bulk power systems that are traditionally subject to operating constraints set by transient limitations is the subject of considerable concern in the industry. The US Western Interconnection (WI) is expected to experience substantial additional growth in both wind and solar generation. These plants will, to some extent, displace large central station thermal generation, both coal and gas-fired, which have traditionally helped maintain stability. This paper reports the results of a study that investigated the transient stability of the WI with high penetrations of wind and solar generation. The mainmore » goals of this work were to (1) create a realistic, baseline model of the WI, (2) test selected transient stability events, (3) investigate the impact of large amounts of wind and solar generation, and (4) examine means to improve performance.« less

Microbalance accurately measures extremely small masses

NASA Technical Reports Server (NTRS)

Patashnick, H.

1970-01-01

Oscillating fiber microbalance has a vibrating quartz fiber as balance arm to hold the mass to be weighed. Increasing fiber weight decreases its resonant frequency. Scaler and timer measure magnitude of the shift. This instrument withstands considerable physical abuse and has calibration stability at normal room temperatures.

Just Right

ERIC Educational Resources Information Center

Wendell, Kristen B.

2012-01-01

Structural engineering can be a rich and exciting context for exploring and learning about the properties of materials. Even a structure as commonplace as a house requires careful consideration of important properties such as strength, stability, and insulation. As a former engineer and current elementary science teacher educator, the author has…

Evaluation of interaction properties of geosynthetics in cohesive soils : lab and field pullout tests.

DOT National Transportation Integrated Search

2004-01-01

The considerable increase of using geosynthetics in mechanically stabilized earth (MSE) walls has raised the need to evaluate their interface shear strength and pullout properties in various types of backfills. This report investigates the use of a m...

Thermodynamic considerations in the support of life for long space voyages

NASA Technical Reports Server (NTRS)

Iberall, A. S.; Cardon, S. Z.

1979-01-01

The essential requirements for the maintenance of life, particularly human life, on isolated space missions of long duration were investigated through the study of extended irreversible thermodynamics. The characterization of a four trophic level system was developed. Questions of stability are discussed.

COMMENTS ON THE PAPER 'ON THE STABILITY OF TRIANGULAR LAGRANGIAN POINTS IN THE RESTRICTED THREE-BODY PROBLEM' (2008, AJ, 135, 187)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanov, A. P.

2009-06-15

In the referenced paper an analytical approach was introduced, which allows one to demonstrate the instability in linearly stable systems, specifically, in a classical three-body problem. These considerations are disproved here.

Youth Exposed to Violence: Stability, Co-Occurrence, and Context

ERIC Educational Resources Information Center

Margolin, Gayla; Vickerman, Katrina A.; Ramos, Michelle C.; Serrano, Sarah Duman; Gordis, Elana B.; Iturralde, Esti; Oliver, Pamella H.; Spies, Lauren A.

2009-01-01

With considerable literature establishing how separate types of violence disrupt the lives of children, there is emerging interest in examining violence across multiple interpersonal domains. This article examines four commonly occurring and frequently researched domains of violence exposure: marital physical aggression, mother-to-youth…

A proposed new generation of intact stability criteria for assessment of ship stability in longitudinal waves

NASA Astrophysics Data System (ADS)

Andrei, C.

2017-08-01

Intact ship stability assessment to prevent stability failure in heavy weather conditions is of paramount importance on board vessel. The possibility of assessment the causes that can lead to loss of ship’s stability as well as the assessment of intact stability in heavy seas is a important problem and has attracted a huge interest of the national and international regulatory authorities. Despite the regulations in force, referring to intact ship stability, many ships continued to lose the stability and or capsize due to failure modes that presently are not covered by such regulations. Based on this aspect has been identified the necessity of modelling an updated criteria for assessment of ship’s stability taking into consideration actual possible situations for loss of stability in heavy seas as a measure of increasing she safety of ships. In this respect, the goal of this paper is to illustrate a possible criteria for assessment ship’s stability in heavy seas through a method of determination the possible problems in a form of dynamic stability criteria. A new intact stability criteria is proposed and developed based on separate levels for assessment of vulnerability and susceptibility of ships in situations of parametric rolling and pure loss of stability encountered in extreme sea conditions. Mathematical models correlated with ship’s construction particulars and weather conditions were developed for every separate level in order to assess the ship’s stability. The objective of the proposed criteria is to bring to officers on board ships the possibility of assessment the ship’s intact stability, as a measure of prevention and improvement of safety during the voyage.

Stabilization of Polar Nanoregions in Pb-free Ferroelectrics

DOE PAGES

Pramanick, A.; Dmowski, Wojciech; Egami, Takeshi; ...

2018-05-18

In this study, the formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba(Zr,Ti)O 3. It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomicmore » displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.« less

Stabilization of Polar Nanoregions in Pb-free Ferroelectrics

NASA Astrophysics Data System (ADS)

Pramanick, A.; Dmowski, W.; Egami, T.; Budisuharto, A. Setiadi; Weyland, F.; Novak, N.; Christianson, A. D.; Borreguero, J. M.; Abernathy, D. L.; Jørgensen, M. R. V.

2018-05-01

The formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba (Zr ,Ti )O3 . It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomic displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.

High Performance Solid Polymer Electrolytes for Rechargeable Batteries: A Self‐Catalyzed Strategy toward Facile Synthesis

PubMed Central

Cui, Yanyan; Liang, Xinmiao; Chai, Jingchao; Cui, Zili; Wang, Qinglei; He, Weisheng; Liu, Xiaochen; Feng, Jiwen

2017-01-01

Abstract It is urgent to seek high performance solid polymer electrolytes (SPEs) via a facile chemistry and simple process. The lithium salts are composed of complex anions that are stabilized by a Lewis acid agent. This Lewis acid can initiate the ring opening polymerization. Herein, a self‐catalyzed strategy toward facile synthesis of crosslinked poly(ethylene glycol) diglycidyl ether‐based solid polymer electrolyte (C‐PEGDE) is presented. It is manifested that the poly(ethylene glycol) diglycidyl ether‐based solid polymer electrolyte possesses a superior electrochemical stability window up to 4.5 V versus Li/Li+ and considerable ionic conductivity of 8.9 × 10−5 S cm−1 at ambient temperature. Moreover, the LiFePO4/C‐PEGDE/Li batteries deliver stable charge/discharge profiles and considerable rate capability. It is demonstrated that this self‐catalyzed strategy can be a very effective approach for high performance solid polymer electrolytes. PMID:29201612

Stabilization of Polar Nanoregions in Pb-free Ferroelectrics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pramanick, A.; Dmowski, Wojciech; Egami, Takeshi

In this study, the formation of polar nanoregions through solid-solution additions is known to enhance significantly the functional properties of ferroelectric materials. Despite considerable progress in characterizing the microscopic behavior of polar nanoregions (PNR), understanding their real-space atomic structure and dynamics of their formation remains a considerable challenge. Here, using the method of dynamic pair distribution function, we provide direct insights into the role of solid-solution additions towards the stabilization of polar nanoregions in the Pb-free ferroelectric of Ba(Zr,Ti)O 3. It is shown that for an optimum level of substitution of Ti by larger Zr ions, the dynamics of atomicmore » displacements for ferroelectric polarization are slowed sufficiently below THz frequencies, which leads to increased local correlation among dipoles within PNRs. The dynamic pair distribution function technique demonstrates a unique capability to obtain insights into locally correlated atomic dynamics in disordered materials, including new Pb-free ferroelectrics, which is necessary to understand and control their functional properties.« less

Examination of molecular mechanism for the enhanced thermal stability of anthocyanins by metal cations and polysaccharides.

PubMed

Tachibana, Noriko; Kimura, Yukihiro; Ohno, Takashi

2014-01-15

Anthocyanins exhibit colour variation over wide pH range but the colour stability is relatively low at the physiological pH. To improve the stability of anthocyanins in neutral to weakly acidic pH region, effects of metal cations and polysaccharides on the colour stability of cyanidin-3-glucoside (C3G) were examined by ultraviolet-visible and resonance Raman spectroscopies. C3G was thermally stabilized by the addition of Fe(3+) but formed aggregation. However, further addition of anionic polysaccharides enhanced the thermal stability of C3G without aggregation. Similar stabilisation was confirmed for delphinidin-3-glucoside (D3G) but not for pelargonidin-3-glucoside. The stability of anthocyanins considerably varied depending on pHs and kinds of metal cations, polysaccharides and buffer molecules. The characteristic resonance Raman bands of C3G-Fe(3+) and D3G-Fe(3+) complexes were significantly affected by the addition of alginate, (18)O/(16)O-isotope substitution, and Fe(2+)/Fe(3+)-replacement. These results suggest that alginate associates with C3G through Fe(3+) to form a stable complex, which enhances the thermal stability of C3G. Copyright © 2013 Elsevier Ltd. All rights reserved.

Investigation of the n  =  1 resistive wall modes in the ITER high-mode confinement

NASA Astrophysics Data System (ADS)

Zheng, L. J.; Kotschenreuther, M. T.; Valanju, P.

2017-06-01

The n  =  1 resistive wall mode (RWM) stability of ITER high-mode confinement is investigated with bootstrap current included for equilibrium, together with the rotation and diamagnetic drift effects for stability. Here, n is the toroidal mode number. We use the CORSICA code for computing the free boundary equilibrium and AEGIS code for stability. We find that the inclusion of bootstrap current for equilibrium is critical. It can reduce the local magnetic shear in the pedestal, so that the infernal mode branches can develop. Consequently, the n  =  1 modes become unstable without a stabilizing wall at a considerably lower beta limit, driven by the steep pressure gradient in the pedestal. Typical values of the wall position stabilize the ideal mode, but give rise to the ‘pedestal’ resistive wall modes. We find that the rotation can contribute a stabilizing effect on RWMs and the diamagnetic drift effects can further improve the stability in the co-current rotation case. But, generally speaking, the rotation stabilization effects are not as effective as the case without including the bootstrap current effects on equilibrium. We also find that the diamagnetic drift effects are actually destabilizing when there is a counter-current rotation.

Biodiversity and ecosystem stability in a decade-long grassland experiment.

PubMed

Tilman, David; Reich, Peter B; Knops, Johannes M H

2006-06-01

Human-driven ecosystem simplification has highlighted questions about how the number of species in an ecosystem influences its functioning. Although biodiversity is now known to affect ecosystem productivity, its effects on stability are debated. Here we present a long-term experimental field test of the diversity-stability hypothesis. During a decade of data collection in an experiment that directly controlled the number of perennial prairie species, growing-season climate varied considerably, causing year-to-year variation in abundances of plant species and in ecosystem productivity. We found that greater numbers of plant species led to greater temporal stability of ecosystem annual aboveground plant production. In particular, the decadal temporal stability of the ecosystem, whether measured with intervals of two, five or ten years, was significantly greater at higher plant diversity and tended to increase as plots matured. Ecosystem stability was also positively dependent on root mass, which is a measure of perenniating biomass. Temporal stability of the ecosystem increased with diversity, despite a lower temporal stability of individual species, because of both portfolio (statistical averaging) and overyielding effects. However, we found no evidence of a covariance effect. Our results indicate that the reliable, efficient and sustainable supply of some foods (for example, livestock fodder), biofuels and ecosystem services can be enhanced by the use of biodiversity.

Synthesis of cuprous oxide epoxy nanocomposite as an environmentally antimicrobial coating.

PubMed

M El Saeed, Ashraf; Abd El-Fattah, M; Azzam, Ahmed M; Dardir, M M; Bader, Magd M

2016-08-01

Cuprous oxide is commonly used as a pigment; paint manufacturers begin to employ cuprous oxide as booster biocides in their formulations, to replace the banned organotins as the principal antifouling compounds. Epoxy coating was reinforced with cuprous oxide nanoparticles (Cu2O NPs). The antibacterial as well as antifungal activity of Cu2O epoxy nanocomposite (Cu2O EN) coating films was investigated. Cu2O NPs were also experimented for antibiofilm and time-kill assay. The thermal stability and the mechanical properties of Cu2O EN coating films were also investigated. The antimicrobial activity results showed slowdown, the growth of organisms on the Cu2O EN coating surface. TGA results showed that incorporating Cu2O NPs into epoxy coating considerably enhanced the thermal stability and increased the char residue. The addition of Cu2O NPs at lower concentration into epoxy coating also led to an improvement in the mechanical resistance such as scratch and abrasion. Cu2O NPs purity was confirmed by XRD. The TEM photograph demonstrated that the synthesized Cu2O NPs were of cubic shape and the average diameter of the crystals was around 25nm. The resulting perfect dispersion of Cu2O NPs in epoxy coating revealed by SEM ensured white particles embedded in the epoxy matrix. Copyright © 2016 Elsevier B.V. All rights reserved.

3-Methoxylphenylpropyl amides as novel receptor subtype-selective melatoninergic ligands: characterization of physicochemical and pharmacokinetic properties.

PubMed

Zhu, Jing; Hu, Yueqing; Ho, Maurice K C; Wong, Yung H

2011-01-01

Developing subtype-selective melatoninergic ligands has been a subject of considerable interest in drug discovery. A series of 3-methoxyphenylpropyl amide derivatives showing selective binding capacity to type 2 melatonin receptor with subnanomolar range of affinities has been identified recently by our laboratory. In the present study, their physicochemical properties, Caco-2 cell and mdr1-MDCK cell permeability, plasma protein binding, and metabolic stability were investigated. The selected compounds are lipophilic in nature, exhibiting aqueous solubility ranging from 40 to 200 microg/mL. Cell permeability studies on Caco-2 and mdr1-MDCK model revealed that they were readily transported through intestinal epithelium and possessed high penetration potential through blood-brain barrier, implying good oral absorption and central nervous system (CNS) distribution potential. They also showed substantial binding to human plasma protein ranging from 78.5% to 92.3%. These compounds were, however, subjected to rapid cytochrome P450-mediated degradation in rat and human liver microsomes with in vitro half-life of 9.5-31.9 min in rat and 5.5-66.7 min in human, which were much shorter than that of melatonin (approximately 73 min). Metabolite profiling unveiled that C6-ether linkage and methoxy substituents were likely the major metabolic soft spots in their structures, which provided important information for further improvement of their structural stability.

The psychosocial burden of childhood overweight and obesity: evidence for persisting difficulties in boys and girls.

PubMed

Gibson, Lisa Y; Allen, Karina L; Davis, Elizabeth; Blair, Eve; Zubrick, Stephen R; Byrne, Susan M

2017-07-01

There is evidence that overweight and obese children tend to remain overweight or obese into adolescence and adulthood. However, little is known about the long-term psychosocial outcomes of childhood overweight and obesity. This study aimed to investigate the course of psychosocial difficulties over a 2-year period for children who were overweight or obese at baseline, and a sample of children who were a healthy weight at baseline. Participants were 212 children aged 8 to 13 years at baseline, who were participating in the Childhood Growth and Development (GAD) Study. Questionnaire and interview measures were used to assess children's self-esteem, depressive symptoms, body image, eating disorder symptoms, experiences with bullying, family satisfaction and quality of life. Linear mixed models were used to consider longitudinal changes in psychosocial variables. Overweight and obese children reported greater psychosocial distress than healthy weight children, and these differences were more pronounced for girls than boys. Weight and psychosocial impairment showed stability from baseline to 2-year follow-up. The results of this study suggest that psychosocial difficulties show considerable stability in childhood, for overweight/obese and healthy weight children. What is Known: • Childhood obesity tracks into adolescence and adulthood. • Physical health problems associated with childhood obesity also persist to adulthood. What is New: • Overweight and obese children are at risk of ongoing psychosocial distress from childhood into early adolescence.

Some Effects of Roll Rate on the Longitudinal Stability Characteristics of a Cruciform Missile Configuration as Determined from Flight Test for a Mach Number Range of 1.1. to 1.8

NASA Technical Reports Server (NTRS)

Lundstrom, Reginald R; Baber, Hal T , Jr

1956-01-01

A model of a cruciform missile configuration having a low-aspect-ratio wing equipped with flap-type controls was flight tested in order to determine stability and control characteristics while rolling at about 5 radians per second. Comparison is made with results from a similar model which rolled at a much lower rate. Results showed that, if the ratio of roll rate to natural circular frequency in pitch is not greater than about 0.3, the motion following a step disturbance in pitch essentially remains in a plane in space. The slope of normal- force coefficient against angle of attack C(sub N(sub alpha)) was the same as for the slowly rolling model at 0 degrees control deflection but C(sub N(sub alpha)) was much higher for the faster rolling model at about 5 degrees control deflection. The slope of pitching-moment coefficient against angle of attack C(sub m(sub alpha)) as determined from the model period of oscillation was the same for both models at 0 degrees control deflection but was lower for the faster rolling model at about 5 degrees control deflection. Damping data for the faster rolling model showed considerably more scatter than for the slowly rolling model.

Optimization of nanostructured lipid carriers for topical delivery of nimesulide using Box-Behnken design approach.

PubMed

Moghddam, Seyedeh Marziyeh Mahdavi; Ahad, Abdul; Aqil, Mohd; Imam, Syed Sarim; Sultana, Yasmin

2017-05-01

The aim of the present study was to develop and optimize topically applied nimesulide-loaded nanostructured lipid carriers. Box-Behnken experimental design was applied for optimization of nanostructured lipid carriers. The independent variables were ratio of stearic acid: oleic acid (X 1 ), poloxamer 188 concentration (X 2 ) and lecithin concentration (X 3 ) while particle size (Y 1 ) and entrapment efficiency (Y 2 ) were the chosen responses. Further, skin penetration study, in vitro release, confocal laser scanning microscopy and stability study were also performed. The optimized nanostructured lipid carriers of nimesulide provide reasonable particle size, flux, and entrapment efficiency. Optimized formulation (F9) with mean particle size of 214.4 ± 11 nm showed 89.4 ± 3.40% entrapment efficiency and achieved mean flux 2.66 ± 0.09 μg/cm 2 /h. In vitro release study showed prolonged drug release from the optimized formulation following Higuchi release kinetics with R 2 value of 0.984. Confocal laser scanning microscopy revealed an enhanced penetration of Rhodamine B-loaded nanostructured lipid carriers to the deeper layers of the skin. The stability study confirmed that the optimized formulation was considerably stable at refrigerator temperature as compared to room temperature. Our results concluded that nanostructured lipid carriers are an efficient carrier for topical delivery of nimesulide.

Semantic Stability is More Pleasurable in Unstable Episodic Contexts. On the Relevance of Perceptual Challenge in Art Appreciation.

PubMed

Muth, Claudia; Raab, Marius H; Carbon, Claus-Christian

2016-01-01

Research in the field of psychological aesthetics points to the appeal of stimuli which defy easy recognition by being "semantically unstable" but which still allow for creating meaning-in the ongoing process of elaborative perception or as an end product of the entire process. Such effects were reported for hidden images (Muth and Carbon, 2013) as well as Cubist artworks concealing detectable-although fragmented-objects (Muth et al., 2013). To test the stability of the relationship between semantic determinacy and appreciation across different episodic contexts, 30 volunteers evaluated an artistic movie continuously on visual determinacy or liking via the Continuous Evaluation Procedure (CEP, Muth et al., 2015b). The movie consisted of five episodes with emerging Gestalts. In the first between-participants condition, the hidden Gestalts in the movie episodes were of increasing determinacy, in the second condition, the episodes showed decreasing determinacies of hidden Gestalts. In the increasing-determinacy group, visual determinacy was rated higher and showed better predictive quality for liking than in the decreasing-determinacy group. Furthermore, when the movie started with low visual determinacy of hidden Gestalts, unexpectedly strong increases in visual determinacy had a bigger effect on liking than in the condition which allowed for weaker Gestalt recognition after having started with highly determinate Gestalts. The resulting pattern calls for consideration of the episodic context when examining art appreciation.

Historical nectar assessment reveals the fall and rise of floral resources in Britain.

PubMed

Baude, Mathilde; Kunin, William E; Boatman, Nigel D; Conyers, Simon; Davies, Nancy; Gillespie, Mark A K; Morton, R Daniel; Smart, Simon M; Memmott, Jane

2016-02-04

There is considerable concern over declines in insect pollinator communities and potential impacts on the pollination of crops and wildflowers. Among the multiple pressures facing pollinators, decreasing floral resources due to habitat loss and degradation has been suggested as a key contributing factor. However, a lack of quantitative data has hampered testing for historical changes in floral resources. Here we show that overall floral rewards can be estimated at a national scale by combining vegetation surveys and direct nectar measurements. We find evidence for substantial losses in nectar resources in England and Wales between the 1930s and 1970s; however, total nectar provision in Great Britain as a whole had stabilized by 1978, and increased from 1998 to 2007. These findings concur with trends in pollinator diversity, which declined in the mid-twentieth century but stabilized more recently. The diversity of nectar sources declined from 1978 to 1990 and thereafter in some habitats, with four plant species accounting for over 50% of national nectar provision in 2007. Calcareous grassland, broadleaved woodland and neutral grassland are the habitats that produce the greatest amount of nectar per unit area from the most diverse sources, whereas arable land is the poorest with respect to amount of nectar per unit area and diversity of nectar sources. Although agri-environment schemes add resources to arable landscapes, their national contribution is low. Owing to their large area, improved grasslands could add substantially to national nectar provision if they were managed to increase floral resource provision. This national-scale assessment of floral resource provision affords new insights into the links between plant and pollinator declines, and offers considerable opportunities for conservation.

Historical nectar assessment reveals the fall and rise of floral resources in Britain

NASA Astrophysics Data System (ADS)

Baude, Mathilde; Kunin, William E.; Boatman, Nigel D.; Conyers, Simon; Davies, Nancy; Gillespie, Mark A. K.; Morton, R. Daniel; Smart, Simon M.; Memmott, Jane

2016-02-01

There is considerable concern over declines in insect pollinator communities and potential impacts on the pollination of crops and wildflowers. Among the multiple pressures facing pollinators, decreasing floral resources due to habitat loss and degradation has been suggested as a key contributing factor. However, a lack of quantitative data has hampered testing for historical changes in floral resources. Here we show that overall floral rewards can be estimated at a national scale by combining vegetation surveys and direct nectar measurements. We find evidence for substantial losses in nectar resources in England and Wales between the 1930s and 1970s; however, total nectar provision in Great Britain as a whole had stabilized by 1978, and increased from 1998 to 2007. These findings concur with trends in pollinator diversity, which declined in the mid-twentieth century but stabilized more recently. The diversity of nectar sources declined from 1978 to 1990 and thereafter in some habitats, with four plant species accounting for over 50% of national nectar provision in 2007. Calcareous grassland, broadleaved woodland and neutral grassland are the habitats that produce the greatest amount of nectar per unit area from the most diverse sources, whereas arable land is the poorest with respect to amount of nectar per unit area and diversity of nectar sources. Although agri-environment schemes add resources to arable landscapes, their national contribution is low. Owing to their large area, improved grasslands could add substantially to national nectar provision if they were managed to increase floral resource provision. This national-scale assessment of floral resource provision affords new insights into the links between plant and pollinator declines, and offers considerable opportunities for conservation.

Immobilization of infant fecal microbiota and utilization in an in vitro colonic fermentation model.

PubMed

Cinquin, C; Le Blay, G; Fliss, I; Lacroix, C

2004-07-01

Bacteria isolated from infant feces were immobilized in polysaccharide gel beads (2.5% gellan gum, 0.25% xanthan gum) using a two-phase dispersion process. A 52-day continuous culture was carried out in a single-stage chemostat containing precolonized beads and fed with a medium formulated to approximate the composition of infant chyme. Different dilution rates and pH conditions were tested to simulate the proximal (PCS), transverse (TCS), and distal (DCS) colons. Immobilization preserved all nine bacterial groups tested with survival rates between 3 and 56%. After 1 week fermentation, beads were highly colonized with all populations tested (excepted Staphylococcus spp. present in low numbers), which remained stable throughout the 7.5 weeks of fermentation, with variations below 1 log unit. However, free-cell populations in the circulating liquid medium, produced by immobilized cell growth, cell-release activity from gel beads, and free-cell growth, were altered considerably by culture conditions. Compared to the stabilization period, PCS was characterized by a considerable and rapid increase in Bifidobacterium spp. concentrations (7.4 to 9.6 log CFU/mL), whereas Bifidobacterium spp., Lactobacillus spp., and Clostridium spp. concentrations decreased and Staphylococcus spp. and coliforms increased during TCS and DCS. Under pseudo-steady-state conditions, the community structure developed in the chemostat reflected the relative proportions of viable bacterial numbers and metabolites generally encountered in infant feces. This work showed that a complex microbiota such as infant fecal bacteria can be immobilized and used in a continuous in vitro intestinal fermentation model to reproduce the high bacterial concentration and bacterial diversity of the feces inoculum, at least at the genera level, with a high stability during long-term experiment.

Storm track response to climate change: Insights from simulations using an idealized dry GCM.

NASA Astrophysics Data System (ADS)

Mbengue, Cheikh; Schneider, Tapio

2013-04-01

The midlatitude storm tracks, where the most intense extratropical cyclones are found, are an important fixture in the general circulation. They are instrumental in balancing the Earth's heat, momentum, and moisture budgets and are responsible for the weather and climatic patterns over large regions of the Earth's surface. As a result, the midlatitude storm tracks are the subject of a considerable amount of scientific research to understand their response to global warming. This has produced the robust result showing that the storm tracks migrate poleward with global warming. However, the dynamical mechanisms responsible for this migration remain unclear. Our work seeks to broaden understanding of the dynamical mechanisms responsible for storm track migration. Competing mechanisms present in the comprehensive climate models often used to study storm track dynamics make it difficult to determine the primary mechanisms responsible for storm track migration. We are thus prompted to study storm track dynamics from a simplified and idealized framework, which enables the decoupling of mean temperature effects from the effects of static stability and of tropical from extratropical effects. Using a statistically zonally symmetric, dry general circulation model (GCM), we conduct a series of numerical simulations to help understand the storm track response to global mean temperatures and to the tropical convective static stability, which we can vary independently. We define storm tracks as regions of zonally and temporally averaged maxima of barotropic eddy kinetic energy (EKE). This storm track definition also allows us to use previously found scalings between the magnitude of bulk measures of mean available potential energy (MAPE) and EKE, to decompose MAPE, and to obtain some mechanistic understanding of the storm track response in our simulations. These simulations provide several insights, which enable us to extend upon existing theories on the mechanisms driving the poleward migration of the storm tracks. We demonstrate a poleward migration of the midlatitude storm tracks in dry atmospheres with fixed pole-equator temperature contrast and increasing radiative equilibrium mean temperature, without changes in convective static stability. We also show scalings between the location of maxima of surface MAPE and of barotropic EKE. In the simulations where we independently vary tropical convective static stability, we find a marked poleward migration of the storm tracks. However, our decomposition shows that meridional temperature gradients, and not static stability, determine the location and the intensity of the storm tracks. This suggests that although the storm tracks are sensitive to tropical convective static stability, it influences them indirectly. Furthermore, our simulations show that the storm tracks generally migrate in tandem with the terminus of the Hadley cell. Therefore, we hypothesize that it is possible that the Hadley cell provides the tropical-extratropical communication necessary to generate the storm track response to tropical convective static stability we observe in the simulations. The results contained herein could be used to supplement ongoing storm track research in moist atmospheres using comparatively more comprehensive GCMs to understand storm track dynamics in earth-like environments.

A Systematic Approach Toward Stabilization of CagL, a Protein Antigen from Helicobacter pylori That Is a Candidate Subunit Vaccine

PubMed Central

Choudhari, Shyamal P.; Pendleton, Kirk P.; Ramsey, Joshua D.; Blanchard, Thomas G.; Picking, William D.

2013-01-01

An important consideration in the development of subunit vaccines is loss of activity caused by physical instability of the protein. Such instability often results from suboptimal solution conditions related to pH and temperature. Excipients can help to stabilize vaccines, but it is important to screen and identify excipients that adequately contribute to stabilization of a given formulation. CagL is a protein present in strains of Helicobacter pylori that possess type IV secretion systems. It contributes to bacterial adherence via α5β1 integrin, thereby making it an attractive subunit vaccine candidate. We characterized the stability of CagL in different pH and temperature conditions using a variety of spectroscopic techniques. Stability was assessed in terms of transition temperature (Tm) with the accumulated data then incorporated into an empirical phase diagram (EPD) that provided an overview of CagL physical stability. These analyses indicated maximum CagL stability at pH 4–6 up to 40 °C in the absence of excipient. Using this EPD analysis, aggregation assays were developed to screen a panel of excipients with some found to inhibit CagL aggregation. Candidate stabilizers were selected to confirm their enhanced stabilizing effect. These analyses will help in the formulation of a stable vaccine against H. pylori. PMID:23794457

Preserving enzymatic activity and enhancing biochemical stability of glutathione transferase by soluble additives under free and tethered conditions.

PubMed

Karamitros, Christos S; Labrou, Nikolaos E

2017-09-01

In the present study, we report the effect of four different soluble additives (sucrose, lactitol, superfloc c577, and dextran sulfate) on the stability of glutathione transferase 1 enzyme from Zea mays (ZmGSTF1-1) under free and tethered conditions at 4 and 25 °C. Among all additives, the best stabilizing effects were observed in the case of superfloc c577 and sucrose at both tested temperatures, yet at distinct concentrations at each condition. Those two stabilizing agents were further combined and potential positive synergistic effects were investigated. In addition, we assessed the long-term storage and operational stability of ZmGSTF1-1 under tethered conditions in the presence of additives, which provided the most conducive effects on its stability under free conditions. Our results strongly suggest that the presence of additives may be beneficial to the stability of the enzyme under both free and tethered conditions. Thermodynamic analysis of the free enzyme in the presence of sucrose, which exhibited the best stabilizing effect at both temperatures, shed light on the possible mechanism of action. Given the considerable importance of the development of GST-based biosensors with prolonged stability, the present work may be of general interest to researchers in the field of applied enzymology. © 2016 International Union of Biochemistry and Molecular Biology, Inc.

Moral Education in a Plural Society: A Singapore Case Study.

ERIC Educational Resources Information Center

Gopinathan, S.

1980-01-01

This article examines moral education in the schools of Singapore, a highly complex society with considerable pluralism plus rapid urbanization and industrialization. Analysis of recent government reports indicates an inadequate response to moral education issues--concern for political stability and ethnic sensibilities promote generalizations…

Exploring the electrochemical properties of hole transport materials with spiro-cores for efficient perovskite solar cells from first-principles.

PubMed

Chi, Wei-Jie; Li, Quan-Song; Li, Ze-Sheng

2016-03-21

Perovskite solar cells (PSCs) with organic small molecules as hole transport materials (HTMs) have attracted considerable attention due to their power conversion efficiencies as high as 20%. In the present work, three new spiro-type hole transport materials with spiro-cores, i.e. Spiro-F1, Spiro-F2 and Spiro-F3, are investigated by using density functional theory combined with the Marcus theory and Einstein relation. Based on the calculated and experimental highest occupied molecular orbital (HOMO) levels of 30 reference molecules, an empirical equation, which can predict the HOMO levels of hole transport materials accurately, is proposed. Moreover, a simplified method, in which the hole transport pathways are simplified to be one-dimensional, is presented and adopted to qualitatively compare the molecular hole mobilities. The calculated results show that the perovskite solar cells with the new hole transport materials can have higher open-circuit voltages due to the lower HOMO levels of Spiro-F1 (-5.31 eV), Spiro-F2 (-5.42 eV) and Spiro-F3 (-5.10 eV) compared with that of Spiro-OMeTAD (-5.09 eV). Furthermore, the hole mobilities of Spiro-F1 (1.75 × 10(-2) cm(2) V(-1) s(-1)) and Spiro-F3 (7.59 × 10(-3) cm(2) V(-1) s(-1)) are 3.1 and 1.4 times that of Spiro-OMeTAD (5.65 × 10(-3) cm(2) V(-1) s(-1)) respectively, due to small reorganization energies and large transfer integrals. Interestingly, the stability properties of Spiro-F1 and Spiro-F2 are shown to be comparable to that of Spiro-OMeTAD, and the dimers of Spiro-F2 and Spiro-F3 possess better stability than that of Spiro-OMeTAD. Taking into consideration the appropriate HOMO level, improved hole mobility and enhanced stability, Spiro-F1 and Spiro-F3 may become the most promising alternatives to Spiro-OMeTAD. The present work offers a new design strategy and reliable calculation methods towards the development of excellent organic small molecules as HTMs for highly efficient and stable PSCs.

The Three-Dimensional (3D) Numerical Stability Analysis of Hyttemalmen Open-Pit

NASA Astrophysics Data System (ADS)

Cała, Marek; Kowalski, Michał; Stopkowicz, Agnieszka

2014-10-01

The purpose of this paper was to perform the 3D numerical calculations allowing slope stability analysis of Hyttemalmen open pit (location Kirkenes, Finnmark Province, Norway). After a ramp rock slide, which took place in December 2010, as well as some other small-scale rock slope stability problems, it proved necessary to perform a serious stability analyses. The Hyttemalmen open pit was designed with a depth up to 100 m, a bench height of 24 m and a ramp width of 10 m. The rock formation in the iron mining district of Kirkenes is called the Bjornevaten Group. This is the most structurally complicated area connected with tectonic process such as folding, faults and metamorphosis. The Bjornevaten Group is a volcano-sedimentary sequence. Rock slope stability depends on the mechanical properties of the rock, hydro-geological conditions, slope topography, joint set systems and seismic activity. However, rock slope stability is mainly connected with joint sets. Joints, or general discontinuities, are regarded as weak planes within rock which have strength reducing consequences with regard to rock strength. Discontinuities within the rock mass lead to very low tensile strength. Several simulations were performed utilising the RocLab (2007) software to estimate the gneiss cohesion for slopes of different height. The RocLab code is dedicated to estimate rock mass strength using the Hoek-Brown failure criterion. Utilising both the GSI index and the Hoek-Brown strength criterion the equivalent Mohr-Coulomb parameters (cohesion and angle of internal friction) can be calculated. The results of 3D numerical calculations (with FLA3D code) show that it is necessary to redesign the slope-bench system in the Hyttemalmen open pit. Changing slope inclination for lower stages is recommended. The minimum factor of safety should be equal 1.3. At the final planned stage of excavation, the factor of safety drops to 1.06 with failure surface ranging through all of the slopes. In the case of a slope angle 70° for lower stages, FS = 1.26, which is not enough to provide slope stability. Another series of calculations were therefore performed taking water table lowering into consideration, which increases the global safety factor. It was finally evaluated, that for a water table level of 72 m the factor of safety equals 1.3, which is enough to assure global open-pit stability.

pH-Dependent Binding of Chloride to a Marine Alkaline Phosphatase Affects the Catalysis, Active Site Stability, and Dimer Equilibrium.

PubMed

Hjörleifsson, Jens G; Ásgeirsson, Bjarni

2017-09-26

The effect of ionic strength on enzyme activity and stability varies considerably between enzymes. Ionic strength is known to affect the catalytic activity of some alkaline phosphatases (APs), such as Escherichia coli AP, but how ions affect APs is debated. Here, we studied the effect of various ions on a cold-adapted AP from Vibrio splendidus (VAP). Previously, we have found that the active form of VAP is extremely unstable at low ionic strengths. Here we show that NaCl increased the activity and stability of VAP and that the effect was pH-dependent in the range of pH 7-10. The activity profile as a function of pH formed two maxima, indicating a possible conformational change. Bringing the pH from the neutral to the alkaline range was accompanied by a large increase in both the K i for inorganic phosphate (product inhibition) and the K M for p-nitrophenyl phosphate. The activity transitions observed as the pH was varied correlated with structural changes as monitored by tryptophan fluorescence. Thermal and urea-induced inactivation was shown to be accompanied by neither dissociation of the active site metal ions nor dimer dissociation. This would suggest that the inactivation involved subtle changes in active site conformation. Furthermore, the VAP dimer equilibrium was studied for the first time and shown to highly favor dimerization, which was dependent on pH and NaCl concentration. Taken together, the data support a model in which anions bind to some specific acceptor in the active site of VAP, resulting in great stabilization and catalytic rate enhancement, presumably through a different mechanism.

Regulation of oxidative DNA damage repair by DNA polymerase λ and MutYH by cross-talk of phosphorylation and ubiquitination

PubMed Central

Markkanen, Enni; van Loon, Barbara; Ferrari, Elena; Parsons, Jason L.; Dianov, Grigory L.; Hübscher, Ulrich

2012-01-01

It is of pivotal importance for genome stability that repair DNA polymerases (Pols), such as Pols λ and β, which all exhibit considerably reduced fidelity when replicating undamaged DNA, are tightly regulated, because their misregulation could lead to mutagenesis. Recently, we found that the correct repair of the abundant and highly miscoding oxidative DNA lesion 7,8-dihydro-8-oxo-2′-deoxyguanine (8-oxo-G) is performed by an accurate repair pathway that is coordinated by the MutY glycosylase homologue (MutYH) and Pol λ in vitro and in vivo. Pol λ is phosphorylated by Cdk2/cyclinA in late S and G2 phases of the cell cycle, promoting Pol λ stability by preventing it from being targeted for proteasomal degradation by ubiquitination. However, it has remained a mystery how the levels of Pol λ are controlled, how phosphorylation promotes its stability, and how the engagement of Pol λ in active repair complexes is coordinated. Here, we show that the E3 ligase Mule mediates the degradation of Pol λ and that the control of Pol λ levels by Mule has functional consequences for the ability of mammalian cells to deal with 8-oxo-G lesions. Furthermore, we demonstrate that phosphorylation of Pol λ by Cdk2/cyclinA counteracts its Mule-mediated degradation by promoting recruitment of Pol λ to chromatin into active 8-oxo-G repair complexes through an increase in Pol λ’s affinity to chromatin-bound MutYH. Finally, MutYH appears to promote the stability of Pol λ by binding it to chromatin. In contrast, Pol λ not engaged in active repair on chromatin is subject for proteasomal degradation. PMID:22203964

Technical Stability and Biological Variability in MicroRNAs from Dried Blood Spots: A Lung Cancer Therapy-Monitoring Showcase.

PubMed

Kahraman, Mustafa; Laufer, Thomas; Backes, Christina; Schrörs, Hannah; Fehlmann, Tobias; Ludwig, Nicole; Kohlhaas, Jochen; Meese, Eckart; Wehler, Thomas; Bals, Robert; Keller, Andreas

2017-09-01

Different work flows have been proposed to use miRNAs as blood-borne biomarkers. In particular, the method used for collecting blood from patients can considerably influence the diagnostic results. We explored whether dried blood spots (DBSs) facilitate stable miRNA measurements and compared its technical stability with biological variability. First, we tested the stability of DBS samples by generating from 1 person 18 whole-genome-wide miRNA profiles of DBS samples that were exposed to different temperature and humidity conditions. Second, we investigated technical reproducibility by performing 7 replicates of DBS again from 1 person. Third, we investigated DBS samples from 53 patients with lung cancer undergoing different therapies. Across these 3 stages, 108 genome-wide miRNA profiles from DBS were generated and evaluated biostatistically. In the stability analysis, we observed that temperature and humidity had an overall limited influence on the miRNomes (average correlation between the different conditions of 0.993). Usage of a silica gel slightly diminished DBS' technical reproducibility. The 7 technical replicates had an average correlation of 0.996. The correlation with whole-blood PAXGene miRNomes of the same individual was remarkable (correlation of 0.88). Finally, evaluation of the samples from the 53 patients with lung cancer exposed to different therapies showed that the biological variations exceeded the technical variability significantly ( P < 0.0001), yielding 51 dysregulated miRNAs. We present a stable work flow for profiling of whole miRNomes on the basis of samples collected from DBS. Biological variations exceeded technical variations significantly. DBS-based miRNA profiles will potentially further the translational character of miRNA biomarker studies. © 2017 American Association for Clinical Chemistry.

Contrasting frictional behaviour of fault gouges containing Mg-rich phyllosilicates

NASA Astrophysics Data System (ADS)

Sanchez Roa, C.; Faulkner, D.; Jimenez Millan, J.; Nieto, F.

2015-12-01

The clay mineralogy of fault gouges has important implications on frictional properties and stability of fault planes. We studied the specific case of the Galera fault zone where fault gouges containing Mg-rich phyllosilicates appear as hydrothermal deposits related to high salinity fluids enriched in Mg2+. These deposits are dominated by sepiolite and palygorskite, both fibrous clay minerals with similar composition to Mg-smectite. The frictional strengths of sepiolite and palygorskite have not yet been determined, however, as they are part of the clay mineral group, it has been assumed that their frictional behaviour would be in line with platy clay minerals. We performed frictional sliding experiments on powdered pure standards and fault rocks in order to establish the frictional behaviour of sepiolite and palygorskite using a triaxial deformation apparatus with a servo-controlled axial loading system and fluid pressure pump. Friction coefficients for palygorskite and sepiolite as monomineralic samples were found to be 0.65 to 0.7 for dry experiments, and 0.45 to 0.5 for water-saturated experiments. Although these fibrous minerals are part of the phyllosilicates group, they show higher friction coefficients and their mechanical behaviour is less stable than platy clay minerals. This difference is a consequence of their stronger structural framework and the discontinuity of water layers. Our results present a contrast in mechanical behaviour between Mg-rich fibrous and platy clay minerals in fault gouges, where smectite is known to considerably reduce friction coefficients and to increase the stability of the fault plane leading to creeping processes. Transformations between saponite and sepiolite have been previously observed and could modify the deformation regime of a fault zone. Constraining the stability conditions and possible mineral reactions or transformations in fault gouges could help us understand the general role of clay minerals in fault stability.

Comparative evaluation of the effectiveness of the implantation in the lateral part of the mandible between short tissue level (TE) and bone level (BL) implant systems.

PubMed

Hadzik, Jakub; Botzenhart, Ute; Krawiec, Maciej; Gedrange, Tomasz; Heinemann, Friedhelm; Vegh, Andras; Dominiak, Marzena

2017-09-01

Short dental implants can be an alternative method of treatment to a vertical bone augmentation procedure at sites of reduced alveolar height. However, for successful treatment, an implant system that causes a minimal marginal bone loss (MBL) should be taken into consideration. The aim of the study has been to evaluate implantation effectiveness for bone level and tissue level short implants provided in lateral aspects of partially edentulous mandible and limited alveolar ridge height. The MBL and primary as well as secondary implant stability were determined in the study. Patients were randomly divided into two groups according to the method of treatment provided. Sixteen short Bone Level Implants (OsseoSpeed TX, Astra tech) and 16 short Tissue Level Implants (RN SLActive ® , Straumann) were successfully placed in the edentulous part of the mandible. The determination of the marginal bone level was based on radiographic evaluation after 12 and 36 weeks. Implant stability was measured immediately after insertion and after 12 weeks. The marginal bone level of Bone Level Implants was significantly lower compared to Tissue Level Implants. Furthermore, the Bone Level Implants had greater primary and secondary stability in comparison with Tissue Level Implants (Primary: 77.8 ISQ versus 66.5 ISQ; Secondary: 78.9 ISQ versus 73.9 ISQ, respectively). Since short Bone Level Implants showed a significantly decreased MBL 12 and 36 weeks after implantation as well as better results for the primary stability compared to Tissue Level Implants, they should preferentially be used for this mentioned indication. Copyright © 2017 Elsevier GmbH. All rights reserved.

Direct force measurements reveal that protein Tau confers short-range attractions and isoform-dependent steric stabilization to microtubules

PubMed Central

Chung, Peter J.; Choi, Myung Chul; Miller, Herbert P.; Feinstein, H. Eric; Raviv, Uri; Li, Youli; Wilson, Leslie; Feinstein, Stuart C.; Safinya, Cyrus R.

2015-01-01

Microtubules (MTs) are hollow cytoskeletal filaments assembled from αβ-tubulin heterodimers. Tau, an unstructured protein found in neuronal axons, binds to MTs and regulates their dynamics. Aberrant Tau behavior is associated with neurodegenerative dementias, including Alzheimer’s. Here, we report on a direct force measurement between paclitaxel-stabilized MTs coated with distinct Tau isoforms by synchrotron small-angle X-ray scattering (SAXS) of MT-Tau mixtures under osmotic pressure (P). In going from bare MTs to MTs with Tau coverage near the physiological submonolayer regime (Tau/tubulin-dimer molar ratio; ΦTau = 1/10), isoforms with longer N-terminal tails (NTTs) sterically stabilized MTs, preventing bundling up to PB ∼ 10,000–20,000 Pa, an order of magnitude larger than bare MTs. Tau with short NTTs showed little additional effect in suppressing the bundling pressure (PB ∼ 1,000–2,000 Pa) over the same range. Remarkably, the abrupt increase in PB observed for longer isoforms suggests a mushroom to brush transition occurring at 1/13 < ΦTau < 1/10, which corresponds to MT-bound Tau with NTTs that are considerably more extended than SAXS data for Tau in solution indicate. Modeling of Tau-mediated MT–MT interactions supports the hypothesis that longer NTTs transition to a polyelectrolyte brush at higher coverages. Higher pressures resulted in isoform-independent irreversible bundling because the polyampholytic nature of Tau leads to short-range attractions. These findings suggest an isoform-dependent biological role for regulation by Tau, with longer isoforms conferring MT steric stabilization against aggregation either with other biomacromolecules or into tight bundles, preventing loss of function in the crowded axon environment. PMID:26542680

Conservation of Oxidative Protein Stabilization in an Insect Homologue of Parkinsonism-Associated Protein DJ-1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Jiusheng; Prahlad, Janani; Wilson, Mark A.

2012-08-21

DJ-1 is a conserved, disease-associated protein that protects against oxidative stress and mitochondrial damage in multiple organisms. Human DJ-1 contains a functionally essential cysteine residue (Cys106) whose oxidation is important for regulating protein function by an unknown mechanism. This residue is well-conserved in other DJ-1 homologues, including two (DJ-1{alpha} and DJ-1{beta}) in Drosophila melanogaster. Because D. melanogaster is a powerful model system for studying DJ-1 function, we have determined the crystal structure and impact of cysteine oxidation on Drosophila DJ-1{beta}. The structure of D. melanogaster DJ-1{beta} is similar to that of human DJ-1, although two important residues in the humanmore » protein, Met26 and His126, are not conserved in DJ-1{beta}. His126 in human DJ-1 is substituted with a tyrosine in DJ-1{beta}, and this residue is not able to compose a putative catalytic dyad with Cys106 that was proposed to be important in the human protein. The reactive cysteine in DJ-1 is oxidized readily to the cysteine-sulfinic acid in both flies and humans, and this may regulate the cytoprotective function of the protein. We show that the oxidation of this conserved cysteine residue to its sulfinate form (Cys-SO{sub 2{sup -}}) results in considerable thermal stabilization of both Drosophila DJ-1{beta} and human DJ-1. Therefore, protein stabilization is one potential mechanism by which cysteine oxidation may regulate DJ-1 function in vivo. More generally, most close DJ-1 homologues are likely stabilized by cysteine-sulfinic acid formation but destabilized by further oxidation, suggesting that they are biphasically regulated by oxidative modification.« less

Synthesis and characterization of polyaniline coated gold nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zuber, Siti Nurzulaiha Mohd; Kamarun, Dzaraini; Zaki, Hamizah

2015-08-28

Considerable attention has been drawn during the last two decades to prepare nanocomposites consists of conducting polymer and noble metal due to their potential ability to generate a new class of material with novel optical, chemical, electronic or mechanical properties for various applications. In this work, an attempt has been made to synthesize nanocomposite of polyaniline (PANI) coated with gold nanoparticles (AuNPs) chemically with various types of surfactants such as polyvinylpyrrolidone (PVP), and sodium dodecyl sulphate (SDS) which act as stabilizing agents to help in stabilization of the PANI/Gold nanocomposites system. The synthesized nanocomposites were characterized by UV-Visible, field emissionmore » scanning electron microscope (FESEM) and particle size analyzer (PSA). The formation of finger like structure can be seen in the FESEM images when the AuNPs were incorporated into the polymer matrix. The EDX data showed that 18.66% and 12.67% of AuNPs atoms were present in the composite system thus proved the incorporation of AuNPs into the polymer matrix. A small red shift of the absorption peak in the UV-Vis of both PANI/AuNPs composites system may be due to the incorporation of AuNPs in the PANI matrix.« less

Borders and Modal Articulations. Semiotic Constructs of Sensemaking Processes Enabling a Fecund Dialogue Between Cultural Psychology and Clinical Psychology.

PubMed

De Luca Picione, Raffaele; Freda, Maria Francesca

2016-03-01

The notion of the border is an interesting advancement in research on the processes of meaning making within the cultural psychology. The development of this notion in semiotic key allows to handle with adequate complexity construction, transformation, stability and the breakup of the relationship between person/world/otherness. These semiotic implications have already been widely discussed and exposed by authors such Valsiner (2007, 2014), Neuman (2003, 2008), Simão (Culture & Psychology, 9, 449-459, 2003, Theory & Psychology, 15, 549-574, 2005, 2015), with respect to issues of identity/relatedness, inside/outside, stability/change in the irreversible flow of the time. In this work, after showing some of the basics of such semiotic notion of border, we discuss the processes of construction and transformation of borders through the modal articulation, defined as the contextual positioning that the person assumes with respect to the establishment of a boundary in terms of necessity, obligation, willingness, possibility, permission, ability. This modal subjective positioning acquires considerable interest from the clinical point of view since its degree of plasticity vs that of rigidity is the basis of processes of development or stiffening of relations between person/world/otherness.

Wine Resveratrol: From the Ground Up

PubMed Central

Bavaresco, Luigi; Lucini, Luigi; Busconi, Matteo; Flamini, Riccardo; De Rosso, Mirko

2016-01-01

The ability of the grapevine to activate defense mechanisms against some pathogens has been shown to be linked to the synthesis of resveratrol and other stilbenes by the plant (inducible viniferins). Metabolized viniferins may also be produced or modified by extracellular enzymes released by the pathogen in an attempt to eliminate undesirable toxic compounds. Because of the important properties of resveratrol, there is increasing interest in producing wines with higher contents of this compound and a higher nutritional value. Many biotic and abiotic elicitors can trigger the resveratrol synthesis in the berries, and some examples are reported. Under the same elicitation pressure, viticultural and enological factors can substantially affect the resveratrol concentration in the wine. The production of high resveratrol-containing grapes and wines relies on quality-oriented viticulture (suitable terroirs and sustainable cultural practices) and winemaking technologies that avoid degradation of the compound. In general, the oenological practices commonly used to stabilize wine after fermentation do not affect resveratrol concentration, which shows considerable stability. Finally the paper reports on two sirtuin genes (SIRT) expressed in grapevine leaves and berries and the role of resveratrol on the deacetylation activity of the encoded enzymes. PMID:27089363

Stability of selected serum proteins after long-term storage in the Janus Serum Bank.

PubMed

Gislefoss, Randi E; Grimsrud, Tom K; Mørkrid, Lars

2009-01-01

Human serum from biobanks is frequently used in prospective epidemiological studies. Long-term storage may modify its composition. A better understanding of the stability of the serum components may improve the interpretation of future studies. The concentrations of selected proteins; immunoglobulins, carrier proteins and enzymes in samples stored at -25 degrees C for 25 years and 2 years were compared with 1-month-old samples. For each length of storage time, 130 specimens were randomly selected from apparently healthy male blood donors aged 40-49 years. We examined the distribution of values, compared dispersion and localization of central tendency, and established reference intervals for each component. The study demonstrated non-significant or numerically small group differences in the concentrations of albumin, aspartate amino transferase, cystatin C, immunoglobulin E, immunoglobulin G, and sex hormone binding globulin. Mean values between fresh and 25-year-old samples suggested larger differences during storage for alanine amino transferase (-73.4%), creatinine kinase (-96.1%), insulin C-peptide (-98.7%), ferritin (-18.5%) and transferrin (+8.2%). The findings showed that long-term storage can introduce a considerable bias for vulnerable components.

Docetaxel-loaded multilayer nanoparticles with nanodroplets for cancer therapy.

PubMed

Oh, Keun Sang; Kim, Kyungim; Yoon, Byeong Deok; Lee, Hye Jin; Park, Dal Yong; Kim, Eun-Yeong; Lee, Kiho; Seo, Jae Hong; Yuk, Soon Hong

2016-01-01

A mixture of docetaxel (DTX) and Solutol(®) HS 15 (Solutol) transiently formed nanodroplets when it was suspended in an aqueous medium. However, nanodroplets that comprised DTX and Solutol showed a rapid precipitation of DTX because of their unstable characteristics in the aqueous medium. The incorporation of nanodroplets that comprised DTX and Solutol through vesicle fusion and subsequent stabilization was designed to prepare multilayer nanoparticles (NPs) with a DTX-loaded Solutol nanodroplet (as template NPs) core for an efficient delivery of DTX as a chemotherapeutic drug. As a result, the DTX-loaded Solutol nanodroplets (~11.7 nm) were observed to have an increased average diameter (from 11.7 nm to 156.1 nm) and a good stability of the hydrated NPs without precipitation of DTX by vesicle fusion and multilayered structure, respectively. Also, a long circulation of the multilayer NPs was observed, and this was due to the presence of Pluronic F-68 on the surface of the multilayer NPs. This led to an improved antitumor efficacy based on the enhanced permeation and retention effect. Therefore, this study indicated that the multilayer NPs have a considerable potential as a drug delivery system with an enhanced therapeutic efficacy by blood circulation and with low side effects.

Low-dimensional organization of angular momentum during walking on a narrow beam.

PubMed

Chiovetto, Enrico; Huber, Meghan E; Sternad, Dagmar; Giese, Martin A

2018-01-08

Walking on a beam is a challenging motor skill that requires the regulation of upright balance and stability. The difficulty in beam walking results from the reduced base of support compared to that afforded by flat ground. One strategy to maintain stability and hence avoid falling off the beam is to rotate the limb segments to control the body's angular momentum. The aim of this study was to examine the coordination of the angular momentum variations during beam walking. We recorded movement kinematics of participants walking on a narrow beam and computed the angular momentum contributions of the body segments with respect to three different axes. Results showed that, despite considerable variability in the movement kinematics, the angular momentum was characterized by a low-dimensional organization based on a small number of segmental coordination patterns. When the angular momentum was computed with respect to the beam axis, the largest fraction of its variation was accounted for by the trunk segment. This simple organization was robust and invariant across all participants. These findings support the hypothesis that control strategies for complex balancing tasks might be easier to understand by investigating angular momentum instead of the segmental kinematics.

Facile one-step construction of covalently networked, self-healable, and transparent superhydrophobic composite films

NASA Astrophysics Data System (ADS)

Lee, Yujin; You, Eun-Ah; Ha, Young-Geun

2018-07-01

Despite the considerable demand for bioinspired superhydrophobic surfaces with highly transparent, self-cleaning, and self-healable properties, a facile and scalable fabrication method for multifunctional superhydrophobic films with strong chemical networks has rarely been established. Here, we report a rationally designed facile one-step construction of covalently networked, transparent, self-cleaning, and self-healable superhydrophobic films via a one-step preparation and single-reaction process of multi-components. As coating materials for achieving the one-step fabrication of multifunctional superhydrophobic films, we included two different sizes of Al2O3 nanoparticles for hierarchical micro/nano dual-scale structures and transparent films, fluoroalkylsilane for both low surface energy and covalent binding functions, and aluminum nitrate for aluminum oxide networked films. On the basis of stability tests for the robust film composition, the optimized, covalently linked superhydrophobic composite films with a high water contact angle (>160°) and low sliding angle (<1°) showed excellent thermal stability (up to 400 °C), transparency (≈80%), self-healing, self-cleaning, and waterproof abilities. Therefore, the rationally designed, covalently networked superhydrophobic composite films, fabricated via a one-step solution-based process, can be further utilized for various optical and optoelectronic applications.

Engineering glycoside hydrolase stability by the introduction of zinc binding

DOE PAGES

Ellinghaus, Thomas L.; Pereira, Jose H.; McAndrew, Ryan P.; ...

2018-06-27

The development of robust enzymes, in particular cellulases, is a key step in the success of biological routes to `second-generation' biofuels. The typical sources of the enzymes used to degrade biomass include mesophilic and thermophilic organisms. The endoglucanase J30 from glycoside hydrolase family 9 was originally identified through metagenomic analyses of compost-derived bacterial consortia. These studies, which were tailored to favor growth on targeted feedstocks, have already been shown to identify cellulases with considerable thermal tolerance. The amino-acid sequence of J30 shows comparably low identity to those of previously analyzed enzymes. As an enzyme that combines a well measurable activitymore » with a relatively low optimal temperature (50°C) and a modest thermal tolerance, it offers the potential for structural optimization aimed at increased stability. Here, the crystal structure of wild-type J30 is presented along with that of a designed triple-mutant variant with improved characteristics for industrial applications. Through the introduction of a structural Zn 2+ site, the thermal tolerance was increased by more than 10°C and was paralleled by an increase in the catalytic optimum temperature by more than 5°C.« less

Engineering glycoside hydrolase stability by the introduction of zinc binding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ellinghaus, Thomas L.; Pereira, Jose H.; McAndrew, Ryan P.

The development of robust enzymes, in particular cellulases, is a key step in the success of biological routes to `second-generation' biofuels. The typical sources of the enzymes used to degrade biomass include mesophilic and thermophilic organisms. The endoglucanase J30 from glycoside hydrolase family 9 was originally identified through metagenomic analyses of compost-derived bacterial consortia. These studies, which were tailored to favor growth on targeted feedstocks, have already been shown to identify cellulases with considerable thermal tolerance. The amino-acid sequence of J30 shows comparably low identity to those of previously analyzed enzymes. As an enzyme that combines a well measurable activitymore » with a relatively low optimal temperature (50°C) and a modest thermal tolerance, it offers the potential for structural optimization aimed at increased stability. Here, the crystal structure of wild-type J30 is presented along with that of a designed triple-mutant variant with improved characteristics for industrial applications. Through the introduction of a structural Zn 2+ site, the thermal tolerance was increased by more than 10°C and was paralleled by an increase in the catalytic optimum temperature by more than 5°C.« less

Stability and optimised H∞ control of tripped and untripped vehicle rollover

NASA Astrophysics Data System (ADS)

Jin, Zhilin; Zhang, Lei; Zhang, Jiale; Khajepour, Amir

2016-10-01

Vehicle rollover is a serious traffic accident. In order to accurately evaluate the possibility of untripped and some special tripped vehicle rollovers, and to prevent vehicle rollover under unpredictable variations of parameters and harsh driving conditions, a new rollover index and an anti-roll control strategy are proposed in this paper. Taking deflections of steering and suspension induced by the roll at the axles into consideration, a six degrees of freedom dynamic model is established, including lateral, yaw, roll, and vertical motions of sprung and unsprung masses. From the vehicle dynamics theory, a new rollover index is developed to predict vehicle rollover risk under both untripped and special tripped situations. This new rollover index is validated by Carsim simulations. In addition, an H-infinity controller with electro hydraulic brake system is optimised by genetic algorithm to improve the anti-rollover performance of the vehicle. The stability and robustness of the active rollover prevention control system are analysed by some numerical simulations. The results show that the control system can improve the critical speed of vehicle rollover obviously, and has a good robustness for variations in the number of passengers and longitude position of the centre of gravity.

Extended Solids of Carbon Monoxide formed from Re2(CO)12

NASA Astrophysics Data System (ADS)

Ciezak-Jenkins, Jennifer

Extended solids are formed from simple molecular gases under extreme P/T and are of considerable interest as high-energy-density materials. It has been postulated that a transformation from a single-bonded polymeric-like material back to the more stable triply-bonded diatomic phase would be a highly exothermic process yielding large amounts of energy. The extended polymeric solid of CO was first reported and recovered from high pressure conditions in 2005. Although the material was found to have potentially interesting energetic properties, it showed a number of stability issues, degrading into CO2 and graphitic carbon over 3 to 5 days. As such, our lab has been focused on the identification of methods to increase the metastability of the recovered solid. Metal carbonyls offer one such route for stabilization. In this talk, our progress in the study of the synthesis, characterization, and recovery of extended solids of CO starting from Re2(CO)12\\ to pressures near 50 GPa will be presented. I will discuss the analysis and the implications of these results. New opportunities and challenges that have arisen in the course of our studies that will be pursued in the future will also be presented. Ref

Initial Computations of Vertical Displacement Events with NIMROD

NASA Astrophysics Data System (ADS)

Bunkers, Kyle; Sovinec, C. R.

2014-10-01

Disruptions associated with vertical displacement events (VDEs) have potential for causing considerable physical damage to ITER and other tokamak experiments. We report on initial computations of generic axisymmetric VDEs using the NIMROD code [Sovinec et al., JCP 195, 355 (2004)]. An implicit thin-wall computation has been implemented to couple separate internal and external regions without numerical stability limitations. A simple rectangular cross-section domain generated with the NIMEQ code [Howell and Sovinec, CPC (2014)] modified to use a symmetry condition at the midplane is used to test linear and nonlinear axisymmetric VDE computation. As current in simulated external coils for large- R / a cases is varied, there is a clear n = 0 stability threshold which lies below the decay-index criterion for the current-loop model of a tokamak to model VDEs [Mukhovatov and Shafranov, Nucl. Fusion 11, 605 (1971)]; a scan of wall distance indicates the offset is due to the influence of the conducting wall. Results with a vacuum region surrounding a resistive wall will also be presented. Initial nonlinear computations show large vertical displacement of an intact simulated tokamak. This effort is supported by U.S. Department of Energy Grant DE-FG02-06ER54850.

Trans-sinusal maxillary distraction for correction of midfacial hypoplasia: long-term clinical results.

PubMed

Nadjmi, N; Schutyser, F; Van Erum, R

2006-10-01

Maxillary distraction osteogenesis is indicated in severe angle class III malocclusions, and severe maxillary hypoplasia among some cleft patients and other craniofacial deformities. Twenty patients, aged 8-48 years (mean 17.8+/-10.5 SD) with maxillary and midfacial hypoplasia were treated. The follow-up period was 13-65 months (mean 35+/-16.3 SD). A trans-sinusal maxillary distractor was placed intraorally at each side of the maxilla. The distraction vector was predicted using specialist software, and was transferred to the patients using stereolithographic models and individual templates. A (high) Le Fort I type osteotomy was performed. The amount of activation varied from 8 to 17.5 mm (mean 13.1+/-2.9 SD). Soft and hard tissue formation resulted in complete healing across the distraction gaps. The distractors are almost completely submerged, and can be left in place as long as necessary to avoid relapse. Wit's appraisal was used to measure the stability of the long-term distraction results. Results up to 5 years after distraction showed considerable maxillary advancement with long-term stability. Ongoing growth of the facial skeleton must be considered when distraction osteogenesis is chosen in growing patients.

Probing Transition-Metal Silicides as PGM-Free Catalysts for Hydrogen Oxidation and Evolution in Acidic Medium

PubMed Central

Mittermeier, Thomas; Madkikar, Pankaj; Wang, Xiaodong; Gasteiger, Hubert A.; Piana, Michele

2017-01-01

In this experimental study, we investigate various transition-metal silicides as platinum-group-metal-(PGM)-free electrocatalysts for the hydrogen oxidation reaction (HOR), and for the hydrogen evolution reaction (HER) in acidic environment for the first time. Using cyclic voltammetry in 0.1 M HClO4, we first demonstrate that the tested materials exhibit sufficient stability against dissolution in the relevant potential window. Further, we determine the HOR and HER activities for Mo, W, Ta, Ni and Mo-Ni silicides in rotating disk electrode experiments. In conclusion, for the HOR only Ni2Si shows limited activity, and the HER activity of the investigated silicides is considerably lower compared to other PGM-free HER catalysts reported in the literature. PMID:28773022

Sensor-Aware Recognition and Tracking for Wide-Area Augmented Reality on Mobile Phones

PubMed Central

Chen, Jing; Cao, Ruochen; Wang, Yongtian

2015-01-01

Wide-area registration in outdoor environments on mobile phones is a challenging task in mobile augmented reality fields. We present a sensor-aware large-scale outdoor augmented reality system for recognition and tracking on mobile phones. GPS and gravity information is used to improve the VLAD performance for recognition. A kind of sensor-aware VLAD algorithm, which is self-adaptive to different scale scenes, is utilized to recognize complex scenes. Considering vision-based registration algorithms are too fragile and tend to drift, data coming from inertial sensors and vision are fused together by an extended Kalman filter (EKF) to achieve considerable improvements in tracking stability and robustness. Experimental results show that our method greatly enhances the recognition rate and eliminates the tracking jitters. PMID:26690439

Improved radial segregation via the destabilizing vertical Bridgman configuration

NASA Astrophysics Data System (ADS)

Sonda, Paul; Yeckel, Andrew; Daoutidis, Prodromos; Derby, Jeffrey J.

2004-01-01

We employ a computational model to revisit the classic crystal growth experiments conducted by Kim et al. (J. Electrochem. Soc. 119 (1972) 1218) and Müller et al. (J. Crystal Growth 70 (1984) 78), which were among the first to clearly document the effects of flow transitions on segregation. Analysis of the growth of tellerium-doped indium antimonide within a destabilizing vertical Bridgman configuration reveals the existence of multiple states, each of which can be reached by feasible paths of process operation. Transient growth simulations conducted on the different solution branches reveal striking differences in hydrodynamic and segregation behavior. We show that crystals grown in the destabilizing configuration exhibit considerably better radial segregation than those grown in the stabilizing configuration, a result which challenges conventional wisdom and practice.

Sensor-Aware Recognition and Tracking for Wide-Area Augmented Reality on Mobile Phones.

PubMed

Chen, Jing; Cao, Ruochen; Wang, Yongtian

2015-12-10

Wide-area registration in outdoor environments on mobile phones is a challenging task in mobile augmented reality fields. We present a sensor-aware large-scale outdoor augmented reality system for recognition and tracking on mobile phones. GPS and gravity information is used to improve the VLAD performance for recognition. A kind of sensor-aware VLAD algorithm, which is self-adaptive to different scale scenes, is utilized to recognize complex scenes. Considering vision-based registration algorithms are too fragile and tend to drift, data coming from inertial sensors and vision are fused together by an extended Kalman filter (EKF) to achieve considerable improvements in tracking stability and robustness. Experimental results show that our method greatly enhances the recognition rate and eliminates the tracking jitters.

Diaqua­(2,2′-bipyridine-κ2 N,N′)bis­(perchlorato-κO)copper(II)

PubMed Central

Damous, Maamar; Hamlaoui, Meriem; Bouacida, Sofiane; Merazig, Hocine; Daran, Jean-Claude

2011-01-01

The central CuN2O4 motif of the title compound, [Cu(ClO4)2(C10H8N2)(H2O)2], exhibits a Jahn–Teller-distorted octa­hedral geometry around the metal atom, showing a considerably long Cu—O bond distance of 2.5058 (12) Å towards the second perchlorate group, giving a (4 + 1+1)-type coordination mode. In the crystal, the components are linked via inter­molecular O—H⋯O hydrogen bonds, forming layers parallel to (001). Additional stabilization within these layers is provided by π–π [centroid–centroid distances of 3.7848 (9)–4.4231 (9) Å] stacking inter­actions. PMID:21754328

The Transition from Stiff to Compliant Materials in Squid Beaks

PubMed Central

Miserez, Ali; Schneberk, Todd; Sun, Chengjun; Zok, Frank W.; Waite, J. Herbert

2009-01-01

The beak of the Humboldt squid Dosidicus gigas represents one of the hardest and stiffest wholly organic materials known. As it is deeply embedded within the soft buccal envelope, the manner in which impact forces are transmitted between beak and envelope is a matter of considerable scientific interest. Here, we show that the hydrated beak exhibits a large stiffness gradient, spanning two orders of magnitude from the tip to the base. This gradient is correlated with a chemical gradient involving mixtures of chitin, water, and His-rich proteins that contain 3,4-dihydroxyphenyl-l-alanine (dopa) and undergo extensive stabilization by histidyl-dopa cross-link formation. These findings may serve as a foundation for identifying design principles for attaching mechanically mismatched materials in engineering and biological applications. PMID:18369144

The transition from stiff to compliant materials in squid beaks.

PubMed

Miserez, Ali; Schneberk, Todd; Sun, Chengjun; Zok, Frank W; Waite, J Herbert

2008-03-28

The beak of the Humboldt squid Dosidicus gigas represents one of the hardest and stiffest wholly organic materials known. As it is deeply embedded within the soft buccal envelope, the manner in which impact forces are transmitted between beak and envelope is a matter of considerable scientific interest. Here, we show that the hydrated beak exhibits a large stiffness gradient, spanning two orders of magnitude from the tip to the base. This gradient is correlated with a chemical gradient involving mixtures of chitin, water, and His-rich proteins that contain 3,4-dihydroxyphenyl-L-alanine (dopa) and undergo extensive stabilization by histidyl-dopa cross-link formation. These findings may serve as a foundation for identifying design principles for attaching mechanically mismatched materials in engineering and biological applications.

The Transition from Stiff to Compliant Materials in Squid Beaks

NASA Astrophysics Data System (ADS)

Miserez, Ali; Schneberk, Todd; Sun, Chengjun; Zok, Frank W.; Waite, J. Herbert

2008-03-01

The beak of the Humboldt squid Dosidicus gigas represents one of the hardest and stiffest wholly organic materials known. As it is deeply embedded within the soft buccal envelope, the manner in which impact forces are transmitted between beak and envelope is a matter of considerable scientific interest. Here, we show that the hydrated beak exhibits a large stiffness gradient, spanning two orders of magnitude from the tip to the base. This gradient is correlated with a chemical gradient involving mixtures of chitin, water, and His-rich proteins that contain 3,4-dihydroxyphenyl-L-alanine (dopa) and undergo extensive stabilization by histidyl-dopa cross-link formation. These findings may serve as a foundation for identifying design principles for attaching mechanically mismatched materials in engineering and biological applications.

A knitted glove sensing system with compression strain for finger movements

NASA Astrophysics Data System (ADS)

Ryu, Hochung; Park, Sangki; Park, Jong-Jin; Bae, Jihyun

2018-05-01

Development of a fabric structure strain sensor has received considerable attention due to its broad application in healthcare monitoring and human–machine interfaces. In the knitted textile structure, it is critical to understand the surface structural deformation from a different body motion, inducing the electrical signal characteristics. Here, we report the electromechanical properties of the knitted glove sensing system focusing on the compressive strain behavior. Compared with the electrical response of the tensile strain, the compressive strain shows much higher sensitivity, stability, and linearity via different finger motions. Additionally, the sensor exhibits constant electrical properties after repeated cyclic tests and washing processes. The proposed knitted glove sensing system can be readily extended to a scalable and cost-effective production due to the use of a commercialized manufacturing system.

Crystalline liquids: the blue phases

NASA Astrophysics Data System (ADS)

Wright, David C.; Mermin, N. David

1989-04-01

The blue phases of cholesteric liquid crystals are liquids that exhibit orientational order characterized by crystallographic space-group symmetries. We present here a pedagogical introduction to the current understanding of the equilibrium structure of these phases accompanied by a general overview of major experimental results. Using the Ginzburg-Landau free energy appropriate to the system, we first discuss in detail the character and stability of the usual helical phase of cholesterics, showing that for certain parameter ranges the helical phase is unstable to the appearance of one or more blue phases. The two principal models for the blue phases are two limiting cases of the Ginzburg-Landau theory. We explore each limit and conclude with some general considerations of defects in both models and an exact minimization of the free energy in a curved three-dimensional space.

Synthesis, spectroscopic characterization and structural investigations of new adduct compound of carbazole with picric acid: DNA binding and antimicrobial studies

NASA Astrophysics Data System (ADS)

Saravanabhavan, Munusamy; Sathya, Krishnan; Puranik, Vedavati G.; Sekar, Marimuthu

2014-01-01

Carbazole picrate (CP), a new organic compound has been synthesized, characterized by various analytical and spectroscopic technique such as FT-IR, UV-Vis, 1H and 13C NMR spectroscopy. An orthorhombic geometry was proposed based on single crystal XRD study. The thermal stability of the crystal was studied by using thermo-gravimetric and differential thermal analyses and found that it was stable up to 170 °C. Further, the newly synthesized title compound was tested for its in vitro antibacterial and antifungal activity against various bacterial and fungal species. Also, the compound was tested for its binding activity with Calf thymus (CT) DNA and the results show a considerable interaction between CP and CT-DNA.

Structural and semiconductor-to-metal transitions of double-perovskite cobalt oxide Sr2-xLaxCoTiO6-δ with enhanced thermoelectric capability

NASA Astrophysics Data System (ADS)

Sugahara, Tohru; Ohtaki, Michitaka

2011-08-01

The thermoelectric properties of double-perovskite oxide Sr2-xLaxCoTiO6-δ were revealed to vary anomalously with the La concentration, plausibly due to a structural transition found in this study. Although the temperature dependence of the resistivity and thermopower of the present oxide showed a semiconductor-to-metal transition similar to those observed for other perovskite-related Co oxides such as Sr1-xYxCoO3-δ, the transition temperature was more than 350 K higher, implying considerable stabilization of the low-spin state of Co ions in the double-perovskite oxide. Consequently, the operating temperature range of the oxide for potential thermoelectric applications was significantly expanded toward higher temperatures.

Grammatical Gender in American Norwegian Heritage Language: Stability or Attrition?

PubMed Central

Lohndal, Terje; Westergaard, Marit

2016-01-01

This paper investigates possible attrition/change in the gender system of Norwegian heritage language spoken in America. Based on data from 50 speakers in the Corpus of American Norwegian Speech (CANS), we show that the three-gender system is to some extent retained, although considerable overgeneralization of the masculine (the most frequent gender) is attested. This affects both feminine and neuter gender forms, while declension class markers such as the definite suffix remain unaffected. We argue that the gender category is vulnerable due to the lack of transparency of gender assignment in Norwegian. Furthermore, unlike incomplete acquisition, which may result in a somewhat different or reduced gender system, attrition is more likely to lead to general erosion, eventually leading to complete loss of gender. PMID:27014151

International Agreements and Cooperation in Environmental Conservation and Resource Management.

ERIC Educational Resources Information Center

Thacher, Peter S.

1991-01-01

Considerations regarding stabilizing the greenhouse effect (global warming) emphasize the difficulties in launching a comprehensive plan to deal with aspects of global change. Experience gained in dealing with atmospheric issues will help in developing a process that links management and research in solving global problems. (SLD)

48 CFR 17.207 - Exercise of options.

Code of Federal Regulations, 2010 CFR

2010-10-01

... period specified in the contract. (b) When the contract provides for economic price adjustment and the... consideration such factors as market stability and comparison of the time since award with the usual duration of... that is subject to an economic price adjustment provision; or (5) A specific price that is subject to...

Rethinking the International Financial System: Views from the South.

ERIC Educational Resources Information Center

Zhou, Yiping, Ed.

1999-01-01

Considerable resources have been spent to rescue a few countries from crises caused by dramatic shifts in financial inflows and outflows. Measures should be sought to render the institutions and mechanisms of international financial transactions more transparent, accountable, and supportive of the delicate balance between short-term stability and…

Stabilization of lead and copper by biochar amendments in arms range soils: Influence of biochar characteristics, soil property, and equilibrium conditions

USDA-ARS?s Scientific Manuscript database

Soil amendment of char products (biochar) from thermochemical processing (slow/fast pyrolysis and gasification) of biomass for biofuel production has received considerable interests for contaminant sorption, soil fertilization, and carbon sequestration. Of potential sites for biochar application, h...

Predicting velocity in bendway weir eddy fields

Treesearch

Kristoph-Dietrich Kinzli; Christopher I. Thornton

2010-01-01

Rehabilitation of the Middle Rio Grande (MRG) in central New Mexico has become necessary because of changes in morphology resulting from the installation of dams, and because of habitat restoration considerations for the endangered Rio Grande silvery minnow (Hybognathus amarus). Bendway weirs are erosion control and channel-stabilization structures placed transverse to...

46 CFR 170.295 - Special consideration for free surface of passive roll stabilization tanks.

Code of Federal Regulations, 2010 CFR

2010-10-01

...) The factor (K) must be calculated as follows: (1) Plot (I/d)tan T on Graph 170.295 where— (i) (I) is... the roll tank; and (iii) (T) is the angle of heel. (2) Plot the moments of transference of the liquid...

Regulating Approaches to Learning: Testing Learning Strategy Convergences across a Year at University

ERIC Educational Resources Information Center

Fryer, Luke K.; Vermunt, Jan D.

2018-01-01

Background: Contemporary models of student learning within higher education are often inclusive of processing and regulation strategies. Considerable research has examined their use over time and their (person-centred) convergence. The longitudinal stability/variability of learning strategy use, however, is poorly understood, but essential to…

Quick, easy to prepare freeze-dried soups

NASA Technical Reports Server (NTRS)

Ramirez, R. V.; Larson, R. W.

1972-01-01

Major advantages of soups are that they totally rehydrate in less than five minutes in water at approximately 150 deg F, maintain flavor and quality stability for two weeks in a 100 F environment, and remain stable for considerably longer at ambient temperatures. They are suitable for either household or field use.

SEABEE Pretest Results of the Joint Logistics-over-the-Shore (LOTS) Test and Evaluation Program.

DTIC Science & Technology

1977-12-07

in the harbor. None of the equipment required extensive shoring. Some chocks and * wedges were placed on the equipment to increase its stability. P...incident. A subsequent examination revealed considerable structural damage to *the Peck & Hale tie-downs. Evidently one of the latching devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Jinhua; Pan, Baofei; Duan, Wentao

In advanced electrical grids of the future, electrochemically rechargeable fluids of high energy density will capture the power generated from intermittent sources like solar and wind. To meet this outstanding technological demand there is a need to understand the fundamental limits and interplay of electrochemical potential, stability, and solubility in low-weight redox-active molecules. By generating a combinatorial set of 1,4-dimethoxybenzene derivatives with different arrangements of substituents, we discovered a mini-malistic structure that combines exceptional long-term stability in its oxidized form and a record-breaking intrinsic capacity of 161 mAh/g. The nonaqueous redox flow battery has been demonstrated that uses this moleculemore » as a catholyte material and operated stably for 100 charge/discharge cycles. Furthermore, the observed stability trends are rationalized by mechanistic considerations of the reaction pathways.« less

An experimental study of energy loss mechanisms and efficiency consideration in the low power dc arcjet

NASA Technical Reports Server (NTRS)

Curran, F. M.

1985-01-01

The potential utility of the low power dc arcjet in auxiliary propulsion was investigated. It was indicated that improvements in the areas of stability, energy efficiency, reliability, and electrode erosion are necessary to obtain a useful device. A water-cooled arcjet simulator was tested to investigate both the energy loss mechanisms at the electrodes and the stability of different conventional arcjet configurations in the presence of a vortex flow field. It is shown that in certain configurations only 25 to 30% of the input energy is lost to the electrodes. It is also shown that vortex stabilization is not difficult to obtain in many cases at the flow rates used and that a careful starting procedure is effective in minimizing electrode damage.

An experimental study of energy loss mechanisms and efficiency considerations in the low power dc arcjet

NASA Technical Reports Server (NTRS)

Curran, F. M.

1985-01-01

The potential utility of the low power dc arcjet in auxiliary propulsion was investigated. It was indicated that improvements in the areas of stability, energy efficiency, reliability, and electrode erosion are necessary to obtain a useful device. A water-cooled arcjet simulator was tested to investigate both the energy loss mechanisms at the electrodes and the stability of different conventional arcjet configurations in the presence of a vortex flow field. It is shown that in certain configurations only 25 to 30 percent of the input energy is lost to the electrodes. It is also shown that vortex stabilization is not difficult to obtain in many cases at the flow rates used and that a careful starting procedure is effective in minimizing electrode damage.

A study of the problem of designing airplanes with satisfactory inherent damping of the dutch roll oscillation

NASA Technical Reports Server (NTRS)

Campbell, John P; Mckinney, Marion O , Jr

1954-01-01

Considerable interest has recently been shown in means of obtaining satisfactory stability of the dutch roll oscillation for modern high-performance airplanes without resort to complicated artificial stabilizing devices. One approach to this problem is to lay out the airplane in the earliest stages of design so that it will have the greatest practicable inherent stability of the lateral oscillation. The present report presents some preliminary results of a theoretical analysis to determine the design features that appear most promising in providing adequate inherent stability. These preliminary results cover the case of fighter airplanes at subsonic speeds. The investigation indicated that it is possible to design fighter airplanes to have substantially better inherent stability than most current designs. Since the use of low-aspect-ratio swept-back wings is largely responsible for poor dutch roll stability, it is important to design the airplane with the maximum aspect ratio and minimum sweep that will permit attainment of the desired performance. The radius of gyration in roll should be kept as low as possible and the nose-up inclination of the principal longitudinal axis of inertia should be made as great as practicable. (author)

Hexagonal MoTe2 with Amorphous BN Passivation Layer for Improved Oxidation Resistance and Endurance of 2D Field Effect Transistors.

PubMed

Sirota, Benjamin; Glavin, Nicholas; Krylyuk, Sergiy; Davydov, Albert V; Voevodin, Andrey A

2018-06-06

Environmental and thermal stability of two-dimensional (2D) transition metal dichalcogenides (TMDs) remains a fundamental challenge towards enabling robust electronic devices. Few-layer 2H-MoTe 2 with an amorphous boron nitride (a-BN) covering layer was synthesized as a channel for back-gated field effect transistors (FET) and compared to uncovered MoTe 2 . A systematic approach was taken to understand the effects of heat treatment in air on the performance of FET devices. Atmospheric oxygen was shown to negatively affect uncoated MoTe 2 devices while BN-covered FETs showed considerably enhanced chemical and electronic characteristic stability. Uncapped MoTe 2 FET devices, which were heated in air for one minute, showed a polarity switch from n- to p-type at 150 °C, while BN-MoTe 2 devices switched only after 200 °C of heat treatment. Time-dependent experiments at 100 °C showed that uncapped MoTe 2 samples exhibited the polarity switch after 15 min of heat treatment while the BN-capped device maintained its n-type conductivity for the maximum 60 min duration of the experiment. X-ray photoelectron spectroscopy (XPS) analysis suggests that oxygen incorporation into MoTe 2 was the primary doping mechanism for the polarity switch. This work demonstrates the effectiveness of an a-BN capping layer in preserving few-layer MoTe 2 material quality and controlling its conductivity type at elevated temperatures in an atmospheric environment.

Long-term Stability and Reliability of Baseline Cognitive Assessments in High School Athletes Using ImPACT at 1-, 2-, and 3-year Test-Retest Intervals.

PubMed

Brett, Benjamin L; Smyk, Nathan; Solomon, Gary; Baughman, Brandon C; Schatz, Philip

2016-08-18

The ImPACT (Immediate Post-Concussion Assessment and Cognitive Testing) neurocognitive testing battery is a widely used tool used for the assessment and management of sports-related concussion. Research on the stability of ImPACT in high school athletes at a 1- and 2-year intervals have been inconsistent, requiring further investigation. We documented 1-, 2-, and 3-year test-retest reliability of repeated ImPACT baseline assessments in a sample of high school athletes, using multiple statistical methods for examining stability. A total of 1,510 high school athletes completed baseline cognitive testing using online ImPACT test battery at three time periods of approximately 1- (N = 250), 2- (N = 1146), and 3-year (N = 114) intervals. No participant sustained a concussion between assessments. Intraclass correlation coefficients (ICCs) ranged in composite scores from 0.36 to 0.90 and showed little change as intervals between assessments increased. Reliable change indices and regression-based measures (RBMs) examining the test-retest stability demonstrated a lack of significant change in composite scores across the various time intervals, with very few cases (0%-6%) falling outside of 95% confidence intervals. The results suggest ImPACT composites scores remain considerably stability across 1-, 2-, and 3-year test-retest intervals in high school athletes, when considering both ICCs and RBM. Annually ascertaining baseline scores continues to be optimal for ensuring accurate and individualized management of injury for concussed athletes. For instances in which more recent baselines are not available (1-2 years), clinicians should seek to utilize more conservative range estimates in determining the presence of clinically meaningful change in cognitive performance. © The Author 2016. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

The use of alkanethiol self-assembled monolayers on 316L stainless steel for coronary artery stent nanomedicine applications: an oxidative and in vitro stability study.

PubMed

Mahapatro, Anil; Johnson, Dave M; Patel, Devang N; Feldman, Marc D; Ayon, Arturo A; Agrawal, C Mauli

2006-09-01

The use of self-assembled monolayers (SAMs) on medical devices offers a methodology for the incorporation of nanotechnology into medicine. SAMs are highly ordered nanosized molecular coatings, adding 1 to 10 nm thickness to a surface. This work is part of an overall goal to deliver therapeutic drugs from the surface of metal coronary stents using SAMs. In this study the oxidative and in vitro stability of functional alkylthiol SAMs on 316L stainless steel (SS) has been demonstrated. SAMs of 11-mercaptoundecanoic acid (-COOH SAM) and 11-mercapto-1-undecanol (-OH SAM) were formed on 316L SS. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and contact angle (CA) measurements collectively confirmed the formation of functional alkylthiol SAMs on 316L SS. Well-formed SAMs (CA: 82 deg +/- 9 deg) were achieved within 48 hours of immersion in ethanolic solutions, after which no significant improvement in CA was observed. The ratio of the thiolate peak (163.5 eV) to the oxidized sulfur (sulfonates) peak (166.5 eV) gives us an indication of the percentage SAMs that would bind to the metal and serve as a drug reservoir in vivo; which in turn represents the stability and viability of these SAMs, keeping in mind the cardiovascular application under consideration. Oxidative and in vitro stability studies showed that alkanethiol SAMs oxidized completely within 14 days. The SAMs tend to desorb and leave the metal surface after longer time periods (21 days) in phosphate-buffered saline (PBS) immersion, whereas for oxidative exposure the SAMs continue to remain on the metal surface in the form of sulfonates. Although the chemistry of bonding of alkylthiol with the 316L SS is not well understood, the nanosized alkylthiol SAMs demonstrate sufficient stability to justify further study on these systems for potential in vivo drug delivery in the chosen coronary artery stent applications.

Thermophysical properties of plasma sprayed coatings

NASA Technical Reports Server (NTRS)

Wilkes, K. E.; Lagedrost, J. F.

1973-01-01

Thermophysical properties of plasma sprayed materials were determined for the following plasma sprayed materials: CaO - stabilized ZrO2, Y2O3 - stabilized ZerO2, Al2O3, HfO2 Mo, nichrome, NiAl, Mo-ZrO2, and MoAl2O3 mixtures. In all cases the thermal conductivity of the as-sprayed materials was found to be considerably lower than that of the bulk material. The flash-laser thermal diffusivity technique was used both for diffusivity determination of single-layer materials and to determine the thermal contact resistance at the interface of two-layer specimens.

THE FUEL ELEMENT GRAPHITE. Project DRAGON.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, L.W.; Price, M.S.T.

1963-01-15

The main requirements of a fuel element graphite for reactors based on the Dragon concept are low transmission coefficient for fission products, dimensional stability under service conditions, high strength, high thermal conductivity, high purity, and high resistance to oxidation. Since conclusions reached in early 1960, a considerable amount of information has accumulated concerning the likely behaviour of graphites in high temperature reactor systems, particularly data on dimensional stability under irradiation. The influence of this new knowledge on the development of fuel element graphite with the Dragon Project is discussed in detail in the final section of this paper.

Aircraft empennage structural detail design

NASA Technical Reports Server (NTRS)

Meholic, Greg; Brown, Rhonda; Hall, Melissa; Harvey, Robert; Singer, Michael; Tella, Gustavo

1993-01-01

This project involved the detailed design of the aft fuselage and empennage structure, vertical stabilizer, rudder, horizontal stabilizer, and elevator for the Triton primary flight trainer. The main design goals under consideration were to illustrate the integration of the control systems devices used in the tail surfaces and their necessary structural supports as well as the elevator trim, navigational lighting system, electrical systems, tail-located ground tie, and fuselage/cabin interface structure. Accommodations for maintenance, lubrication, adjustment, and repairability were devised. Weight, fabrication, and (sub)assembly goals were addressed. All designs were in accordance with the FAR Part 23 stipulations for a normal category aircraft.

Aerogel Insulation Systems for Space Launch Applications

NASA Technical Reports Server (NTRS)

Fesmire, James E.

2005-01-01

New developments in materials science in the areas of solution gelation processes and nanotechnology have led to the recent commercial production of aerogels. Concurrent with these advancements has been the development of new approaches to cryogenic thermal insulation systems. For example, thermal and physical characterizations of aerogel beads under cryogenic-vacuum conditions have been performed at the Cryogenics Test Laboratory of the NASA Kennedy Space Center. Aerogel-based insulation system demonstrations have also been conducted to improve performance for space launch applications. Subscale cryopumping experiments show the thermal insulating ability of these fully breathable nanoporous materials. For a properly executed thermal insulation system, these breathable aerogel systems are shown to not cryopump beyond the initial cooldown and thermal stabilization phase. New applications are being developed to augment the thermal protection systems of space launch vehicles, including the Space Shuttle External Tank. These applications include a cold-boundary temperature of 90 K with an ambient air environment in which both weather and flight aerodynamics are important considerations. Another application is a nitrogen-purged environment with a cold-boundary temperature of 20 K where both initial cooldown and launch ascent profiles must be considered. Experimental results and considerations for these flight system applications are discussed.

Modelling approaches: the case of schizophrenia.

PubMed

Heeg, Bart M S; Damen, Joep; Buskens, Erik; Caleo, Sue; de Charro, Frank; van Hout, Ben A

2008-01-01

Schizophrenia is a chronic disease characterized by periods of relative stability interrupted by acute episodes (or relapses). The course of the disease may vary considerably between patients. Patient histories show considerable inter- and even intra-individual variability. We provide a critical assessment of the advantages and disadvantages of three modelling techniques that have been used in schizophrenia: decision trees, (cohort and micro-simulation) Markov models and discrete event simulation models. These modelling techniques are compared in terms of building time, data requirements, medico-scientific experience, simulation time, clinical representation, and their ability to deal with patient heterogeneity, the timing of events, prior events, patient interaction, interaction between co-variates and variability (first-order uncertainty). We note that, depending on the research question, the optimal modelling approach should be selected based on the expected differences between the comparators, the number of co-variates, the number of patient subgroups, the interactions between co-variates, and simulation time. Finally, it is argued that in case micro-simulation is required for the cost-effectiveness analysis of schizophrenia treatments, a discrete event simulation model is best suited to accurately capture all of the relevant interdependencies in this chronic, highly heterogeneous disease with limited long-term follow-up data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pradeepkumar, Aiswarya; Mishra, Neeraj; Kermany, Atieh Ranjbar

Epitaxial cubic silicon carbide on silicon is of high potential technological relevance for the integration of a wide range of applications and materials with silicon technologies, such as micro electro mechanical systems, wide-bandgap electronics, and graphene. The hetero-epitaxial system engenders mechanical stresses at least up to a GPa, pressures making it extremely challenging to maintain the integrity of the silicon carbide/silicon interface. In this work, we investigate the stability of said interface and we find that high temperature annealing leads to a loss of integrity. High–resolution transmission electron microscopy analysis shows a morphologically degraded SiC/Si interface, while mechanical stress measurementsmore » indicate considerable relaxation of the interfacial stress. From an electrical point of view, the diode behaviour of the initial p-Si/n-SiC junction is catastrophically lost due to considerable inter-diffusion of atoms and charges across the interface upon annealing. Temperature dependent transport measurements confirm a severe electrical shorting of the epitaxial silicon carbide to the underlying substrate, indicating vast predominance of the silicon carriers in lateral transport above 25 K. This finding has crucial consequences on the integration of epitaxial silicon carbide on silicon and its potential applications.« less

Stability Calculation Method of Slope Reinforced by Prestressed Anchor in Process of Excavation

PubMed Central

Li, Zhong; Wei, Jia; Yang, Jun

2014-01-01

This paper takes the effect of supporting structure and anchor on the slope stability of the excavation process into consideration; the stability calculation model is presented for the slope reinforced by prestressed anchor and grillage beam, and the dynamic search model of the critical slip surface also is put forward. The calculation model of the optimal stability solution of each anchor tension of the whole process is also given out, through which the real-time analysis and checking of slope stability in the process of excavation can be realized. The calculation examples indicate that the slope stability is changed with the dynamic change of the design parameters of anchor and grillage beam. So it is relatively more accurate and reasonable by using dynamic search model to determine the critical slip surface of the slope reinforced by prestressed anchor and grillage beam. Through the relationships of each anchor layout and the slope height of various stages of excavation, and the optimal stability solution of prestressed bolt tension design value in various excavation stages can be obtained. The arrangement of its prestressed anchor force reflects that the layout of the lower part of bolt and the calculation of slope reinforcement is in line with the actual. These indicate that the method is reasonable and practical. PMID:24683319

Stability calculation method of slope reinforced by prestressed anchor in process of excavation.

PubMed

Li, Zhong; Wei, Jia; Yang, Jun

2014-01-01

This paper takes the effect of supporting structure and anchor on the slope stability of the excavation process into consideration; the stability calculation model is presented for the slope reinforced by prestressed anchor and grillage beam, and the dynamic search model of the critical slip surface also is put forward. The calculation model of the optimal stability solution of each anchor tension of the whole process is also given out, through which the real-time analysis and checking of slope stability in the process of excavation can be realized. The calculation examples indicate that the slope stability is changed with the dynamic change of the design parameters of anchor and grillage beam. So it is relatively more accurate and reasonable by using dynamic search model to determine the critical slip surface of the slope reinforced by prestressed anchor and grillage beam. Through the relationships of each anchor layout and the slope height of various stages of excavation, and the optimal stability solution of prestressed bolt tension design value in various excavation stages can be obtained. The arrangement of its prestressed anchor force reflects that the layout of the lower part of bolt and the calculation of slope reinforcement is in line with the actual. These indicate that the method is reasonable and practical.

Initial Edge Stability Observations in the PEGASUS Toroidal Experiment

NASA Astrophysics Data System (ADS)

Bongard, M. W.; Battaglia, D. J.; Garstka, G. D.; Sontag, A. C.; Unterberg, E. A.

2007-11-01

Edge stability is an important consideration for design of fusion experiments, as transient heat loads generated by edge instabilities may damage the first wall. Such instabilities are now believed to include peeling (current driven) and ballooning (pressure driven) components. Peeling instability may be expected for high values of edge j||/B and low edge pressure gradient. This matches the operating space of Pegasus, with typical ˜100 kA/m^2, |B|˜ 0.01 T, and an L-mode edge. A new camera system has observed filamentary structures in the edge of nearly all ohmically-heated discharges. Ideal stability analysis of these discharges with DCON indicates marginal stability to resistive interchange for ψN>= 0.95. Modification of triangularity during startup is observed to delay instability onset. A plasma control system based on that used on DIII-D will allow study of the influence of plasma shaping on mode stability characteristics. An array of magnetic probes capable of insertion into the scrape-off layer and plasma edge is being developed to provide a local constraint on the edge current profile.

Physicochemical properties and storage stability of soybean protein nanoemulsions prepared by ultra-high pressure homogenization.

PubMed

Xu, Jing; Mukherjee, Dipaloke; Chang, Sam K C

2018-02-01

This study investigated the effects of the ultrahigh pressure homogenization (pressure, protein concentration, oil phase fraction, pH, temperature, and ionic strength) and storage on the properties of nanoemulsions (100-500nm range), which were stabilized by laboratory-prepared soybean protein isolate (SPI), β-conglycinin (7S) and glycinin (11S). The nanoemulsions made with SPI, 7S and 11S proteins exhibited considerable stability over various ionic strengths (0-500mM NaCl), pH (<4 or >7), thermal treatments (30-60°C) and storage (0-45days). The far-UV spectra of SPI, 7S, 11S dispersions, and SPI-, 7S-, 11S protein-stabilized nanoemulsions were analyzed for the protein structural changes following lipid removal. The ultra-high pressure homogenization changed the secondary structure of SPI, 7S, 11S proteins in the nanoemulsions, and enhanced their stability. This study demonstrated that SPI, 7S, and 11S proteins can be used as effective emulsifiers in nanoemulsions prepared by ultra-high pressure homogenization. Copyright © 2017. Published by Elsevier Ltd.

Significant improvement of thermal stability of glucose 1-dehydrogenase by introducing disulfide bonds at the tetramer interface.

PubMed

Ding, Haitao; Gao, Fen; Liu, Danfeng; Li, Zeli; Xu, Xiaohong; Wu, Min; Zhao, Yuhua

2013-12-10

Rational design was applied to glucose 1-dehydrogenase (LsGDH) from Lysinibacillus sphaericus G10 to improve its thermal stability by introduction of disulfide bridges between subunits. One out of the eleven mutants, designated as DS255, displayed significantly enhanced thermal stability with considerable soluble expression and high specific activity. It was extremely stable at pH ranging from 4.5 to 10.5, as it retained nearly 100% activity after incubating at different buffers for 1h. Mutant DS255 also exhibited high thermostability, having a half-life of 9900min at 50°C, which was 1868-fold as that of its wild type. Moreover, both of the increased free energy of denaturation and decreased entropy of denaturation of DS255 suggested that the enzyme structure was stabilized by the engineered disulfide bonds. On account of its robust stability, mutant DS255 would be a competitive candidate in practical applications of chiral chemicals synthesis, biofuel cells and glucose biosensors. Copyright © 2013 Elsevier Inc. All rights reserved.

Toward a better understanding of helicopter stability derivatives

NASA Technical Reports Server (NTRS)

Hansen, R. S.

1982-01-01

An amended six degree of freedom helicopter stability and control derivative model was developed in which body acceleration and control rate derivatives were included in the Taylor series expansion. These additional derivatives were derived from consideration of the effects of the higher order rotor flapping dynamics, which are known to be inadequately represented in the conventional six degree of freedom, quasistatic stability derivative model. The amended model was a substantial improvement over the conventional model, effectively doubling the unsable bandwidth and providing a more accurate representation of the short period and cross axis characteristics. Further investigations assessed the applicability of the two stability derivative model structures for flight test parameter identification. Parameters were identified using simulation data generated from a higher order base line model having sixth order rotor tip path plane dynamics. Three lower order models were identified: one using the conventional stability derivative model structure, a second using the amended six degree of freedom model structure, and a third model having eight degrees of freedom that included a simplified rotor tip path plane tilt representation.

Key issues in application of composites to transport aircraft

NASA Technical Reports Server (NTRS)

Stone, M.

1978-01-01

The application of composite materials to transport aircraft was identified and reviewed including the major contributing disciplines of design, manufacturing, and processing. Factors considered include: crashworthiness considerations (structural integrity, postcrash fires, and structural fusing), electrical/avionics subsystems integration, lightning, and P-static protection design; manufacturing development, evaluation, selection, and refining of tooling and curing procedures; and major joint design considerations. Development of the DC-10 rudder, DC-10 vertical stabilizer, and the DC-9 wing study project was reviewed. The Federal Aviation Administration interface and the effect on component design of compliance with Federal Aviation Regulation 25 Composite Guidelines are discussed.

Decomposition of heterogeneous organic matterand its long-term stabilization in soils

USGS Publications Warehouse

Sierra, Carlos A.; Harmon, Mark E.; Perakis, Steven S.

2011-01-01

Soil organic matter is a complex mixture of material with heterogeneous biological, physical, and chemical properties. Decomposition models represent this heterogeneity either as a set of discrete pools with different residence times or as a continuum of qualities. It is unclear though, whether these two different approaches yield comparable predictions of organic matter dynamics. Here, we compare predictions from these two different approaches and propose an intermediate approach to study organic matter decomposition based on concepts from continuous models implemented numerically. We found that the disagreement between discrete and continuous approaches can be considerable depending on the degree of nonlinearity of the model and simulation time. The two approaches can diverge substantially for predicting long-term processes in soils. Based on our alternative approach, which is a modification of the continuous quality theory, we explored the temporal patterns that emerge by treating substrate heterogeneity explicitly. The analysis suggests that the pattern of carbon mineralization over time is highly dependent on the degree and form of nonlinearity in the model, mostly expressed as differences in microbial growth and efficiency for different substrates. Moreover, short-term stabilization and destabilization mechanisms operating simultaneously result in long-term accumulation of carbon characterized by low decomposition rates, independent of the characteristics of the incoming litter. We show that representation of heterogeneity in the decomposition process can lead to substantial improvements in our understanding of carbon mineralization and its long-term stability in soils.

Stability of operational taxonomic units: an important but neglected property for analyzing microbial diversity.

PubMed

He, Yan; Caporaso, J Gregory; Jiang, Xiao-Tao; Sheng, Hua-Fang; Huse, Susan M; Rideout, Jai Ram; Edgar, Robert C; Kopylova, Evguenia; Walters, William A; Knight, Rob; Zhou, Hong-Wei

2015-01-01

The operational taxonomic unit (OTU) is widely used in microbial ecology. Reproducibility in microbial ecology research depends on the reliability of OTU-based 16S ribosomal subunit RNA (rRNA) analyses. Here, we report that many hierarchical and greedy clustering methods produce unstable OTUs, with membership that depends on the number of sequences clustered. If OTUs are regenerated with additional sequences or samples, sequences originally assigned to a given OTU can be split into different OTUs. Alternatively, sequences assigned to different OTUs can be merged into a single OTU. This OTU instability affects alpha-diversity analyses such as rarefaction curves, beta-diversity analyses such as distance-based ordination (for example, Principal Coordinate Analysis (PCoA)), and the identification of differentially represented OTUs. Our results show that the proportion of unstable OTUs varies for different clustering methods. We found that the closed-reference method is the only one that produces completely stable OTUs, with the caveat that sequences that do not match a pre-existing reference sequence collection are discarded. As a compromise to the factors listed above, we propose using an open-reference method to enhance OTU stability. This type of method clusters sequences against a database and includes unmatched sequences by clustering them via a relatively stable de novo clustering method. OTU stability is an important consideration when analyzing microbial diversity and is a feature that should be taken into account during the development of novel OTU clustering methods.

ASSESSMENT OF A STABLE COSMETIC PREPARATION BASED ON ENZYMATIC INTERESTERIFIED FAT, PROPOSED IN THE PREVENTION OF ATOPIC DERMATITIS.

PubMed

Kowalska, Malgorzata; Mendrycka, Mariola; Zbikowska, Anna; Kowalska, Dorota

2017-03-01

Atopic dermatitis is one of the most common skin disorders seen in infants, children and adults. Proper prevention might slow the atopic symptoms. The purpose of the work was a sensory analysis, an evaluation of moistening properties and stability of emulsions based on an enzymatic interesterified fat blend (mutton tallow and walnut oil) and homogenized at different revolutions and different contents of thickener. The emulsions were evaluated with respect to sensory and skin moisturizing properties by 78 respondents. Stability tests, particle size, distribution, dispersity index, morphology structure of the emulsions were determinated too. Taking into consideration all properties of the emulsions, emulsion IV (containing 0.9 g carboxymethyl cellulose and homogenized at 18000 rpm) and emulsion V (1.5 g of carboxymethyl cellulose and homogenized at 24000 rpm) were found to be of optimum composition. The emulsions exhibited good stability, were highly rated in sensory terms and displayed optimum moistening properties. It has been proven that model emulsions based on interesterified fats containing partial acylglicerols, with optimum carboxymethyl cellulose content and specific revolutions at the time of homogenization are an opportunity for developing preparations targeted at skins requiring special care (e.g., with atopic dermatitis or psoriasis). The work proved the use of enzymatic process to create the emulsifier, which represents the innovative contribution of this work. Also it showed an additional application of enzymatic interesterified fats which since has been used only in food industries.

Separating method factors and higher order traits of the Big Five: a meta-analytic multitrait-multimethod approach.

PubMed

Chang, Luye; Connelly, Brian S; Geeza, Alexis A

2012-02-01

Though most personality researchers now recognize that ratings of the Big Five are not orthogonal, the field has been divided about whether these trait intercorrelations are substantive (i.e., driven by higher order factors) or artifactual (i.e., driven by correlated measurement error). We used a meta-analytic multitrait-multirater study to estimate trait correlations after common method variance was controlled. Our results indicated that common method variance substantially inflates trait correlations, and, once controlled, correlations among the Big Five became relatively modest. We then evaluated whether two different theories of higher order factors could account for the pattern of Big Five trait correlations. Our results did not support Rushton and colleagues' (Rushton & Irwing, 2008; Rushton et al., 2009) proposed general factor of personality, but Digman's (1997) α and β metatraits (relabeled by DeYoung, Peterson, and Higgins (2002) as Stability and Plasticity, respectively) produced viable fit. However, our models showed considerable overlap between Stability and Emotional Stability and between Plasticity and Extraversion, raising the question of whether these metatraits are redundant with their dominant Big Five traits. This pattern of findings was robust when we included only studies whose observers were intimately acquainted with targets. Our results underscore the importance of using a multirater approach to studying personality and the need to separate the causes and outcomes of higher order metatraits from those of the Big Five. We discussed the implications of these findings for the array of research fields in which personality is studied.

Thermodynamics of the variable modified Chaplygin gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panigrahi, D.; Chatterjee, S., E-mail: dibyendupanigrahi@yahoo.co.in, E-mail: chat_sujit1@yahoo.com

A cosmological model with a new variant of Chaplygin gas obeying an equation of state (EoS), P = A ρ − B /ρ{sup α} where B = B {sub 0} a {sup n} is investigated in the context of its thermodynamical behaviour. Here B {sub 0} and n are constants and a is the scale factor. We show that the equation of state of this 'Variable Modified Chaplygin gas' (VMCG) can describe the current accelerated expansion of the universe. Following standard thermodynamical criteria we mainly discuss the classical thermodynamical stability of the model and find that the new parameter, nmore » introduced in VMCG plays a crucial role in determining the stability considerations and should always be negative. We further observe that although the earlier model of Lu explains many of the current observational findings of different probes it fails the desirable tests of thermodynamical stability. We also note that for 0 n < our model points to a phantom type of expansion which, however, is found to be compatible with current SNe Ia observations and CMB anisotropy measurements. Further the third law of thermodynamics is obeyed in our case. Our model is very general in the sense that many of earlier works in this field may be obtained as a special case of our solution. An interesting point to note is that the model also apparently suggests a smooth transition from the big bang to the big rip in its whole evaluation process.« less

Residues in the alternative reading frame tumor suppressor that influence its stability and p53-independent activities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tommaso, Anne di; Hagen, Jussara; Tompkins, Van

2009-04-15

The Alternative Reading Frame (ARF) protein suppresses tumorigenesis through p53-dependent and p53-independent pathways. Most of ARF's anti-proliferative activity is conferred by sequences in its first exon. Previous work showed specific amino acid changes occurred in that region during primate evolution, so we programmed those changes into human p14ARF to assay their functional impact. Two human p14ARF residues (Ala{sup 14} and Thr{sup 31}) were found to destabilize the protein while two others (Val{sup 24} and Ala{sup 41}) promoted more efficient p53 stabilization and activation. Despite those effects, all modified p14ARF forms displayed robust p53-dependent anti-proliferative activity demonstrating there are no significantmore » biological differences in p53-mediated growth suppression associated with simian versus human p14ARF residues. In contrast, p53-independent p14ARF function was considerably altered by several residue changes. Val{sup 24} was required for p53-independent growth suppression whereas multiple residues (Val{sup 24}, Thr{sup 31}, Ala{sup 41} and His{sup 60}) enabled p14ARF to block or reverse the inherent chromosomal instability of p53-null MEFs. Together, these data pinpoint specific residues outside of established p14ARF functional domains that influence its expression and signaling activities. Most intriguingly, this work reveals a novel and direct role for p14ARF in the p53-independent maintenance of genomic stability.« less

Step-wise addition of disulfide bridge in firefly luciferase controls color shift through a flexible loop: a thermodynamic perspective.

PubMed

Nazari, Mahboobeh; Hosseinkhani, Saman; Hassani, Leila

2013-02-01

Multi-color bioluminescence is developed using the introduction of single/double disulfide bridges in firefly luciferase. The bioluminescence reaction, which uses luciferin, Mg(2+)-ATP and molecular oxygen to yield an electronically excited oxyluciferin, is carried out by the luciferase and emits visible light. The bioluminescence color of firefly luciferases is determined by the luciferase sequence and assay conditions. It has been proposed that the stability of a protein may increase through the introduction of a disulfide bridge that decreases the configurational entropy of unfolding. Single and double disulfide bridges are introduced into Photinus pyralis firefly luciferase to make separate mutant enzymes with a single/double bridge (C(81)-A(105)C, L(306)C-L(309)C, P(451)C-V(469)C; C(81)-A(105)C/P(451)C-V(469)C, and A(296)C-A(326)C/P(451)C-V(469)C). By introduction of disulfide bridges using site-directed mutagenesis in Photinus pyralis luciferase the color of emitted light was changed to red or kept in different extents. The bioluminescence color shift occurred with displacement of a critical loop in the luciferase structure without any change in green emitter mutants. Thermodynamic analysis revealed that among mutants, L(306)C-L(309)C shows a remarkable stability against urea denaturation and also a considerable increase in kinetic stability and a clear shift in bioluminescence spectra towards red.

Achieving high capacity and rate capability in layered lithium transition metal oxide cathodes for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Ahn, Juhyeon; Susanto, Dieky; Noh, Jae-Kyo; Ali, Ghulam; Cho, Byung Won; Chung, Kyung Yoon; Kim, Jong Hak; Oh, Si Hyoung

2017-08-01

In this study, we target to find a new composition for a layered mixed metal oxide, which has a high structural stability and a good electrochemical performance. Our strategy is to alter the transition metal composition focusing on the relative amounts of redox active Ni and Co to the inactive Mn, based on highly-stabilized LiNi1/3Co1/3Mn1/3O2. X-ray absorption near-edge structure and X-ray diffraction analyses show that the degree of cation disorder decreases on increasing the ratio of Ni and Co to Mn, by the presence of Ni3+, suggesting that slightly higher Ni and Co contents lead to improved structural stability. Electrochemical studies demonstrate that LiNi0.4Co0.4Mn0.2O2 cathodes exhibit considerable improvements in both the reversible capacity and the rate capabilities at a voltage range of 2.5-4.6 V. In situ XRD measurements reveal that LiNi0.4Co0.4Mn0.2O2 maintains a single-phase and undergoes lesser structural variations compared to controlled compositions during a delithiation process up to 4.6 V, while achieving a high reversible capacity over 200 mAh g-1. As a result, LiNi0.4Co0.4Mn0.2O2 experiences fewer structural degradations during electrochemical cycling, which explains the excellent long-term cycling performance.

Effects of Ti and Ta addition on microstructure stability and tensile properties of reduced activation ferritic/martensitic steel for nuclear fusion reactors

NASA Astrophysics Data System (ADS)

Kim, Han Kyu; Lee, Ji Won; Moon, Joonoh; Lee, Chang Hoon; Hong, Hyun Uk

2018-03-01

The effects of Ti and Ta addition on microstructure stability and tensile properties of a reduced activation ferritic/martensitic (RAFM) steel have been investigated. Ti addition of 0.06 wt% to conventional RAFM reference base steel (Fe-9.3Cr-0.93W-0.22V-0.094Ta-0.1C) was intended to promote the precipitation of nano-sized (Ti,W) carbides with a high resistance to coarsening. In addition, the Ti addition was substituted for 0.094 wt% Ta. The Ti-added RAFM steel (Ti-RAFM) exhibited a higher yield strength (ΔYS = 32 MPa) at 600 °C than the reference base steel due to additional precipitation hardening by (Ti,W)-rich MX with an average size of 6.1 nm and the area fraction of 2.39%. However, after thermal exposure at 600 °C for 1000 h, this Ti-RAFM was more susceptible to degradation than the reference base steel; the block width increased by 77.6% in Ti-RAFM after thermal exposure while the reference base steel showed only 9.1% increase. In order to suppress diffusion rate during thermal exposure, the large-sized Ta element with low activation was added to Ti-RAFM. The Ta-added Ti-RAFM steel exhibited good properties with outstanding microstructure stability. Quantitative comparison in microstructures was discussed with a consideration of Ti and Ta addition.

The Human Vertical Translation Vestibulo-ocular Reflex (tVOR): Normal and Abnormal Responses

PubMed Central

Liao, Ke; Walker, Mark F.; Joshi, Anand; Reschke, Millard; Strupp, Michael; Leigh, R. John

2010-01-01

Geometric considerations indicate that the human translational vestibulo-ocular reflex (tVOR) should have substantially different properties than the angular vestibulo-ocular reflex (aVOR). Specifically, tVOR cannot simultaneously stabilize images of distant and near objects on the retina. Most studies make the tacit assumption that tVOR acts to stabilize foveal images even though, in humans, tVOR is reported to compensate for less than 60% of foveal image motion. We have determined that the compensation gain (eye rotational velocity / required eye rotational velocity to maintain foveal target fixation) of tVOR is held steady at ~ 0.6 during viewing of either near or distant targets during vertical (bob) translations in ambient illumination. We postulate that tVOR evolved not to stabilize the image of the target on the fovea, but rather to minimize retinal image motion between objects lying in different depth planes, in order to optimize motion parallax information. Such behavior is optimized when binocular visual cues of both far and distant targets are available in ambient light. Patients with progressive supranuclear palsy or cerebellar ataxia show impaired ability to increase tVOR responses appropriately when they view near targets. In cerebellar patients, impaired ability to adjust tVOR responses to viewing conditions occurs despite intact ability to converge at near. Loss of the ability to adjust tVOR according to viewing conditions appears to represent a distinct disorder of vestibular function. PMID:19645882

Measuring the emulsification dynamics and stability of self-emulsifying drug delivery systems.

PubMed

Vasconcelos, Teófilo; Marques, Sara; Sarmento, Bruno

2018-02-01

Self-emulsifying drug delivery systems (SEDDS) are one of the most promising technologies in the drug delivery field, particularly for addressing solubility and bioavailability issues of drugs. The development of these drug carriers excessively relies in visual observations and indirect determinations. The present manuscript intended to describe a method able to measure the emulsification of SEDDS, both micro and nano-emulsions, able to measure the droplet size and to evaluate the physical stability of these formulations. Additionally, a new process to evaluate the physical stability of SEDDS after emulsification was also proposed, based on a cycle of mechanical stress followed by a resting period. The use of a multiparameter continuous evaluation during the emulsification process and stability was of upmost value to understand SEDDS emulsification process. Based on this method, SEDDS were classified as fast and slow emulsifiers. Moreover, emulsification process and stabilization of emulsion was subject of several considerations regarding the composition of SEDDS as major factor that affects stability to physical stress and the use of multicomponent with different properties to develop a stable and robust SEDDS formulation. Drug loading level is herein suggested to impact droplets size of SEDDS after dispersion and SEDDS stability to stress conditions. The proposed protocol allows an online measurement of SEDDS droplet size during emulsification and a rationale selection of excipients based on its emulsification and stabilization performance. Copyright © 2017. Published by Elsevier B.V.

Control of human gait stability through foot placement.

PubMed

Bruijn, Sjoerd M; van Dieën, Jaap H

2018-06-01

During human walking, the centre of mass (CoM) is outside the base of support for most of the time, which poses a challenge to stabilizing the gait pattern. Nevertheless, most of us are able to walk without substantial problems. In this review, we aim to provide an integrative overview of how humans cope with an underactuated gait pattern. A central idea that emerges from the literature is that foot placement is crucial in maintaining a stable gait pattern. In this review, we explore this idea; we first describe mechanical models and concepts that have been used to predict how foot placement can be used to control gait stability. These concepts, such as for instance the extrapolated CoM concept, the foot placement estimator concept and the capture point concept, provide explicit predictions on where to place the foot relative to the body at each step, such that gait is stabilized. Next, we describe empirical findings on foot placement during human gait in unperturbed and perturbed conditions. We conclude that humans show behaviour that is largely in accordance with the aforementioned concepts, with foot placement being actively coordinated to body CoM kinematics during the preceding step. In this section, we also address the requirements for such control in terms of the sensory information and the motor strategies that can implement such control, as well as the parts of the central nervous system that may be involved. We show that visual, vestibular and proprioceptive information contribute to estimation of the state of the CoM. Foot placement is adjusted to variations in CoM state mainly by modulation of hip abductor muscle activity during the swing phase of gait, and this process appears to be under spinal and supraspinal, including cortical, control. We conclude with a description of how control of foot placement can be impaired in humans, using ageing as a primary example and with some reference to pathology, and we address alternative strategies available to stabilize gait, which include modulation of ankle moments in the stance leg and changes in body angular momentum, such as rapid trunk tilts. Finally, for future research, we believe that especially the integration of consideration of environmental constraints on foot placement with balance control deserves attention. © 2018 The Authors.

Comparison of the partitioning behaviours of yttrium, rare earth elements, and titanium between hydrogenetic marine ferromanganese crusts and seawater

USGS Publications Warehouse

Bau, M.; Koschinsky, A.; Dulski, P.; Hein, J.R.

1996-01-01

In order to evaluate details of the partitioning behaviours of Y, rare earth elements (REEs), and Ti between inorganic metal oxide surfaces and seawater, we studied the distribution of these elements in hydrogenetic marine ferromanganese (Fe-Mn) crusts from the Central Pacific Ocean. Nonphosphatized Fe-Mn crusts display shale-normalized rare earths and yttrium (REYSN) patterns (Y inserted between Dy and Ho) that are depleted in light REEs (LREEs) and which show negative anomalies for YSN, and positive anomalies for LaSN, EuSN, GdSN, and in most cases, CeSN. They show considerably smaller Y/ Ho ratios than seawater or common igneous and clastic rocks, indicating that Y and Ho are fractionated in the marine environment. Compared to P-poor crusts, REYSN patterns of phosphatized Fe-Mn crusts are similar, but yield pronounced positive YSN anomalies, stronger positive LaSN anomalies, and enrichment of the HREEs relative to the MREEs. The data suggest modification of REY during phosphatization and indicate that studies requiring primary REY distributions or isotopic ratios should be restricted to nonphosphatized (layers of) Fe-Mn crusts. Apparent bulk coefficients, KMD, describing trace metal partitioning between nonphosphatized hydrogenetic Fe-Mn crusts and seawater, are similar for Pr to Eu and decrease for Eu to Yb. Exceptionally high values of KCeD, which are similar to those of Ti, result from oxidative scavenging of Ce and support previous suggestions that Ce(IV) is a hydroxide-dominated element in seawater. Yttrium and Gd show lower KD values than their respective neighbours in the REY series. Results of modelling the exchange equilibrium between REY dissolved in seawater and REY sorbed on hydrous Fe-Mn oxides corroborate previous studies that suggested the surface complexation of REY can be approximated by their first hydroxide binding constant. Negative "anomalies" occur for stabilities of bulk surface complexes of Gd, La, and particularly Y. The differences in inorganic surface complex stability between Y and Ho and between Gd and its REE neighbours are similar to those shown by the stabilities of complexes with aminocarboxylic acids and are significantly larger than those shown by stabilities of complexes with carboxylic acids. Hence, sorption of Y and REEs onto hydrous Fe-Mn oxides may contribute significantly to the positive YSN and GdSN anomalies in seawater.

Enhanced gastric stability of esomeprazole by molecular interaction and modulation of microenvironmental pH with alkalizers in solid dispersion.

PubMed

Van Nguyen, Hien; Baek, Namhyun; Lee, Beom-Jin

2017-05-15

Due to the instability of esomeprazole magnesium dihydrate (EPM), a proton pump inhibitor, in gastric fluid, enteric-coated dosage form is commonly used for therapeutic application. In this study, we prepared new gastric fluid resistant solid dispersions (SDs) containing alkalizers. Then, new mechanistic evidence regarding the effects of pharmaceutical alkalizers on the aqueous stability of EPM in simulated gastric fluid was investigated. The alkalizer-loaded SD were prepared by dissolving or dispersing EPM, hydroxypropyl methylcellulose (HPMC) 6 cps, and an alkalizer, in ethanol 50% (v/v) followed by spray drying. Nine different alkalizers were assessed for in vitro stability in two media, simulated gastric fluid (pH 1.2 buffer) and simulated intestinal fluid (pH 6.8 buffer). The microenvironmental pH (pH M ) was measured to evaluate the effect of the alkalizer on the pH M of SDs. Drug crystallinity and morphology of the SDs were also examined by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM). The interactions among EPM, the polymer, and the alkalizer were elucidated by Fourier transform infrared (FTIR) spectroscopy. The in vivo absorption studies of the optimized alkalizer-containing SD and the enteric-coated reference tablet Nexium ® were then conducted in beagle dogs. Among alkalizers, MgO loaded in SDs proved to be the best alkalizer to stabilize EPM in simulated gastric fluid. pH M values of the alkalizer-containing SDs were significantly higher than that of the SD without alkalizer. The pH M values decreased in the following order: MgO, Na 2 CO 3 , Ca(OH) 2 , and no alkalizer. DSC and PXRD data exhibited a change in the drug crystallinity of the SDs from crystalline to amorphous form. SEM data showed a relatively spherical shape of the MgO-loaded SD compared to the less-defined shape of pure drug. FTIR indicated a strong molecular interaction among EPM, alkalizer and polymer; in particular, MgO showed the strongest interaction with EPM. It was evident that alkalizer interacts with benzimidazole ring and/or sulfonyl group of EPM for enhancing EPM stability in gastric fluid. Regarding the in vivo absorption studies in beagle dogs, the optimized SD (C16) was bioequivalent to the reference Nexium ® and had a considerable greater absorption at the early stages. The current alkalizer-containing SD could provide a promising approach for aqueous stabilization of acid-labile drugs without using enteric coating method. Copyright © 2017 Elsevier B.V. All rights reserved.