Rank one chaos in a class of planar systems with heteroclinic cycle.

PubMed

Chen, Fengjuan; Han, Maoan

2009-12-01

In this paper, we study rank one chaos in a class of planar systems with heteroclinic cycle. We first find a stable limit cycle inside the heteroclinic cycle. We then add an external periodic forcing to create rank one chaos. We follow a step-by-step procedure guided by the theory of rank one chaos to find experimental evidence of strange attractors with Sinai, Ruelle, and Bowen measures.

Electrical coupled Morris-Lecar neurons: From design to pattern analysis

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

Binczak, S.; Behdad, R.; Rossé, M.

2016-06-08

In this study, an experimental electronic neuron based on Morris-Lecar model is presented, able to become an experimental unit tool to study collective association of robust coupled neurons. The circuit design is given according to the ionic currents of this model. A weak coupling of such neurons under Multisim Software can generate clusters based on the boundary conditions of the neurons and their initial conditions. For this study, we work in the region close to the fold bifurcation of limit cycles. In this region two limit cycles exist, one of the cycles is stable and another one is unstable.

A limit cycle oscillator model for cycling mood variations of bipolar disorder patients derived from cellular biochemical reaction equations

NASA Astrophysics Data System (ADS)

Frank, T. D.

2013-08-01

We derive a nonlinear limit cycle model for oscillatory mood variations as observed in patients with cycling bipolar disorder. To this end, we consider two signaling pathways leading to the activation of two enzymes that play a key role for cellular and neural processes. We model pathway cross-talk in terms of an inhibitory impact of the first pathway on the second and an excitatory impact of the second on the first. The model also involves a negative feedback loop (inhibitory self-regulation) for the first pathway and a positive feedback loop (excitatory self-regulation) for the second pathway. We demonstrate that due to the cross-talk the biochemical dynamics is described by an oscillator equation. Under disease-free conditions the oscillatory system exhibits a stable fixed point. The breakdown of the self-inhibition of the first pathway at higher concentration levels is studied by means of a scalar control parameter ξ, where ξ equal to zero refers to intact self-inhibition at all concentration levels. Under certain conditions, stable limit cycle solutions emerge at critical parameter values of ξ larger than zero. These oscillations mimic pathological cycling mood variations that emerge due to a disease-induced bifurcation. Consequently, our modeling analysis supports the notion of bipolar disorder as a dynamical disease. In addition, our study establishes a connection between mechanistic biochemical modeling of bipolar disorder and phenomenological nonlinear oscillator approaches to bipolar disorder suggested in the literature.

Flutter, Postflutter, and Control of a Supersonic Wing Section

NASA Technical Reports Server (NTRS)

Marzocca, Piergiovanni; Librescu, Liviu; Silva, Walter A.

2002-01-01

A number of issues related to the flutter and postflutter of two-dimensional supersonic lifting surfaces are addressed. Among them there are the 1) investigation of the implications of the nonlinear unsteady aerodynamics and structural nonlinearities on the stable/unstable character of the limit cycle and 2) study of the implications of the incorporation of a control capability on both the flutter boundary and the postflutter behavior. To this end, a powerful methodology based on the Lyapunov first quantity is implemented. Such a treatment of the problem enables one to get a better understanding of the various factors involved in the nonlinear aeroelastic problem, including the stable and unstable limit cycle. In addition, it constitutes a first step toward a more general investigation of nonlinear aeroelastic phenomena of three-dimensional lifting surfaces.

Goodwin accelerator model revisited with fixed time delays

NASA Astrophysics Data System (ADS)

Matsumoto, Akio; Merlone, Ugo; Szidarovszky, Ferenc

2018-05-01

Dynamics of Goodwin's accelerator business cycle model is reconsidered. The model is characterized by a nonlinear accelerator and an investment time delay. The role of the nonlinearity for the birth of persistent oscillations is fully discussed in the existing literature. On the other hand, not much of the role of the delay has yet been revealed. The purpose of this paper is to show that the delay really matters. In the original framework of Goodwin [6], it is first demonstrated that there is a threshold value of the delay: limit cycles arise for smaller values than the threshold and so do sawtooth oscillations for larger values. In the extended framework in which a consumption or saving delay, in addition to the investment delay, is introduced, three main results are demonstrated under assumption of the identical length of investment and consumption delays. The dynamics with consumption delay is basically the same as that of the single delay model. Second, in the case of saving delay, the steady state can coexist with the stable and unstable limit cycles in the stable case. Third, in the unstable case, there is an interval of delay in which the limit cycle or the sawtooth oscillation emerges depending on the choice of the constant initial function.

[A review of water and carbon flux partitioning and coupling in SPAC using stable isotope techniques].

PubMed

Xu, Xiao Wu; Yu, Xin Xiao; Jia, Guo Dong; Li, Han Zhi; Lu, Wei Wei; Liu, Zi Qiang

2017-07-18

Soil-vegetation-atmosphere continuum (SPAC) is one of the important research objects in the field of terrestrial hydrology, ecology and global change. The process of water and carbon cycling, and their coupling mechanism are frontier issues. With characteristics of tracing, integration and indication, stable isotope techniques contribute to the estimation of the relationship between carbon sequestration and water consumption in ecosystems. In this review, based on a brief introduction of stable isotope principles and techniques, the applications of stable isotope techniques to water and carbon exchange in SPAC using optical stable isotope techniques were mainly explained, including: partitioning of net carbon exchange into photosynthesis and respiration; partitioning of evapotranspiration into transpiration and evaporation; coupling of water and carbon cycle at the ecosystem scale. Advanced techniques and methods provided long-term and high frequency measurements for isotope signals at the ecosystem scale, but the issues about the precision and accuracy for measurements, partitioning of ecosystem respiration, adaptability for models under non-steady state, scaling up, coupling mechanism of water and carbon cycles, were challenging. The main existing research findings, limitations and future research prospects were discussed, which might help new research and technology development in the field of stable isotope ecology.

High-Performance Cells Containing Lithium Metal Anodes, LiNi0.6Co0.2Mn0.2O2 (NCM 622) Cathodes, and Fluoroethylene Carbonate-Based Electrolyte Solution with Practical Loading.

PubMed

Salitra, Gregory; Markevich, Elena; Afri, Michal; Talyosef, Yosef; Hartmann, Pascal; Kulisch, Joern; Sun, Yang-Kook; Aurbach, Doron

2018-06-13

We report on the highly stable lithium metal|LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM 622) cells with practical electrodes' loading of 3.3 mA h g -1 , which can undergo many hundreds of stable cycles, demonstrating high rate capability. A key issue was the use of fluoroethylene carbonate (FEC)-based electrolyte solutions (1 M LiPF 6 in FEC/dimethyl carbonate). Li|NCM 622 cells can be cycled at 1.5 mA cm -2 for more than 600 cycles, whereas symmetric Li|Li cells demonstrate stable performance for more than 1000 cycles even at higher areal capacity and current density. We attribute the excellent performance of both Li|NCM and Li|Li cells to the formation of a stable and efficient solid electrolyte interphase (SEI) on the surface of the Li metal electrodes cycled in FEC-based electrolyte solutions. The composition of the SEI on the Li and the NCM electrodes is analyzed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. A drastic capacity fading of Li|NCM cells is observed, followed by spontaneous capacity recovery during prolonged cycling. This phenomenon depends on the current density and the amount of the electrolyte solution and relates to kinetic limitations because of SEI formation on the Li anodes in the FEC-based electrolyte solution.

Multiple attractors and boundary crises in a tri-trophic food chain.

PubMed

Boer, M P; Kooi, B W; Kooijman, S A

2001-02-01

The asymptotic behaviour of a model of a tri-trophic food chain in the chemostat is analysed in detail. The Monod growth model is used for all trophic levels, yielding a non-linear dynamical system of four ordinary differential equations. Mass conservation makes it possible to reduce the dimension by 1 for the study of the asymptotic dynamic behaviour. The intersections of the orbits with a Poincaré plane, after the transient has died out, yield a two-dimensional Poincaré next-return map. When chaotic behaviour occurs, all image points of this next-return map appear to lie close to a single curve in the intersection plane. This motivated the study of a one-dimensional bi-modal, non-invertible map of which the graph resembles this curve. We will show that the bifurcation structure of the food chain model can be understood in terms of the local and global bifurcations of this one-dimensional map. Homoclinic and heteroclinic connecting orbits and their global bifurcations are discussed also by relating them to their counterparts for a two-dimensional map which is invertible like the next-return map. In the global bifurcations two homoclinic or two heteroclinic orbits collide and disappear. In the food chain model two attractors coexist; a stable limit cycle where the top-predator is absent and an interior attractor. In addition there is a saddle cycle. The stable manifold of this limit cycle forms the basin boundary of the interior attractor. We will show that this boundary has a complicated structure when there are heteroclinic orbits from a saddle equilibrium to this saddle limit cycle. A homoclinic bifurcation to a saddle limit cycle will be associated with a boundary crisis where the chaotic attractor disappears suddenly when a bifurcation parameter is varied. Thus, similar to a tangent local bifurcation for equilibria or limit cycles, this homoclinic global bifurcation marks a region in the parameter space where the top-predator goes extinct. The 'Paradox of Enrichment' says that increasing the concentration of nutrient input can cause destabilization of the otherwise stable interior equilibrium of a bi-trophic food chain. For a tri-trophic food chain enrichment of the environment can even lead to extinction of the highest trophic level.

Extremely Stable Sodium Metal Batteries Enabled by Localized High-Concentration Electrolytes

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

Zheng, Jianming; Chen, Shuru; Zhao, Wengao

Sodium (Na) metal is a promising anode for Na ion batteries. However, the high reactivity of Na metal with electrolytes and the low Na metal cycling efficiency have limited its practical application in rechargeable Na metal batteries. High concentration electrolytes (HCE, ≥4 M) consisting of sodium bis(fluorosulfonyl)imide (NaFSI) and ether solvent could ensure the stable cycling of Na metal with high coulombic efficiency, but suffer from high viscosity, poor wetting ability, and high salt cost. Here, we report that the salt concentration could be significantly reduced (≤ 1.5 M) by diluting with a hydrofluoroether (HFE) as ‘inert’ diluent, which maintainsmore » the solvation structures of HCE, thereby forming a localized high concentration electrolyte (LHCE). A LHCE (2.1 M NaFSI/DME-BTFE (solvent molar ratio 1:2)) has been demonstrated to enable the dendrite-free Na deposition with high coulombic efficiency of > 99%, fast-charging (20C) and stable cycling (90.8% retention after 40,000 cycles) of Na||Na3V2(PO4)3 batteries.« less

Excitatory and Inhibitory Interactions in Localized Populations of Model Neurons

PubMed Central

Wilson, Hugh R.; Cowan, Jack D.

1972-01-01

Coupled nonlinear differential equations are derived for the dynamics of spatially localized populations containing both excitatory and inhibitory model neurons. Phase plane methods and numerical solutions are then used to investigate population responses to various types of stimuli. The results obtained show simple and multiple hysteresis phenomena and limit cycle activity. The latter is particularly interesting since the frequency of the limit cycle oscillation is found to be a monotonic function of stimulus intensity. Finally, it is proved that the existence of limit cycle dynamics in response to one class of stimuli implies the existence of multiple stable states and hysteresis in response to a different class of stimuli. The relation between these findings and a number of experiments is discussed. PMID:4332108

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.

A Resolution of the Paradox of Enrichment

NASA Astrophysics Data System (ADS)

Feng, Z. C.; Li, Y. Charles

2015-06-01

The paradox of enrichment was observed by Rosenzweig [1971] in a class of predator-prey models. Two of the parameters in the models are crucial for the paradox. These two parameters are the prey's carrying capacity and prey's half-saturation for predation. Intuitively, increasing the carrying capacity due to enrichment of the prey's environment should lead to a more stable predator-prey system. Analytically, it turns out that increasing the carrying capacity always leads to an unstable predator-prey system that is susceptible to extinction from environmental random perturbations. This is the so-called paradox of enrichment. Our resolution here rests upon a closer investigation on a dimensionless number H formed from the carrying capacity and the prey's half-saturation. By recasting the models into dimensionless forms, the models are in fact governed by a few dimensionless numbers including H. The effects of the two parameters: carrying capacity and half-saturation are incorporated into the number H. In fact, increasing the carrying capacity is equivalent (i.e. has the same effect on H) to decreasing the half-saturation which implies more aggressive predation. Since there is no paradox between more aggressive predation and instability of the predator-prey system, the paradox of enrichment is resolved. The so-called instability of the predator-prey system is characterized by the existence of a stable limit cycle in the phase plane, which gets closer and closer to the predator axis and prey axis. Due to random environmental perturbations, this can lead to extinction. We also further explore spatially dependent models for which the phase space is infinite-dimensional. The spatially independent limit cycle which is generated by a Hopf bifurcation from an unstable steady state, is linearly stable in the infinite-dimensional phase space. Numerical simulations indicate that the basin of attraction of the limit cycle is riddled. This shows that spatial perturbations can sometimes (neither always nor never) remove the paradox of enrichment near the limit cycle!

Self-sustained oscillations of a sinusoidally-deformed plate

NASA Astrophysics Data System (ADS)

Muriel, Diego F.; Cowen, Edwin A.

2015-11-01

Motivated by energy harvesting, the oscillatory motion of a deformed elastic material with aspect ratio Length/Width=2, immerse in an incompressible flow is studied experimentally. To induce the wave-like deformation a polycarbonate sheet is placed under longitudinal compression with external forcing provided by equispaced tension lines anchored in a frame. No additional constrains are placed in the material. Based on quantitative image-based edge detection, ADV, and PIV measurements, we document the existence of three natural states of motion. Bellow a critical velocity, a stable state presents a sinusoidal-like deformation with weak small perturbations. Above a critical velocity, instability appears in the form of a traveling wave with predictable dominant frequency accompanied by higher-order harmonics. As the flow velocity increases the instability converges faster to its limit cycle in the phase plane (e.g., vertical velocity and position), until the stable oscillatory mode transitions to chaos showing a broad energy spectrum and unstable limit cycle. The underlying objective is to induce the onset of the instability at lower critical velocities for higher bending rigidities, promoting possible energy extraction and increasing the range at which stable oscillations appear.

Emergent Oscillations in Networks of Stochastic Spiking Neurons

PubMed Central

van Drongelen, Wim; Cowan, Jack D.

2011-01-01

Networks of neurons produce diverse patterns of oscillations, arising from the network's global properties, the propensity of individual neurons to oscillate, or a mixture of the two. Here we describe noisy limit cycles and quasi-cycles, two related mechanisms underlying emergent oscillations in neuronal networks whose individual components, stochastic spiking neurons, do not themselves oscillate. Both mechanisms are shown to produce gamma band oscillations at the population level while individual neurons fire at a rate much lower than the population frequency. Spike trains in a network undergoing noisy limit cycles display a preferred period which is not found in the case of quasi-cycles, due to the even faster decay of phase information in quasi-cycles. These oscillations persist in sparsely connected networks, and variation of the network's connectivity results in variation of the oscillation frequency. A network of such neurons behaves as a stochastic perturbation of the deterministic Wilson-Cowan equations, and the network undergoes noisy limit cycles or quasi-cycles depending on whether these have limit cycles or a weakly stable focus. These mechanisms provide a new perspective on the emergence of rhythmic firing in neural networks, showing the coexistence of population-level oscillations with very irregular individual spike trains in a simple and general framework. PMID:21573105

Transition from homogeneous to inhomogeneous limit cycles: Effect of local filtering in coupled oscillators

NASA Astrophysics Data System (ADS)

Banerjee, Tanmoy; Biswas, Debabrata; Ghosh, Debarati; Bandyopadhyay, Biswabibek; Kurths, Jürgen

2018-04-01

We report an interesting symmetry-breaking transition in coupled identical oscillators, namely, the continuous transition from homogeneous to inhomogeneous limit cycle oscillations. The observed transition is the oscillatory analog of the Turing-type symmetry-breaking transition from amplitude death (i.e., stable homogeneous steady state) to oscillation death (i.e., stable inhomogeneous steady state). This novel transition occurs in the parametric zone of occurrence of rhythmogenesis and oscillation death as a consequence of the presence of local filtering in the coupling path. We consider paradigmatic oscillators, such as Stuart-Landau and van der Pol oscillators, under mean-field coupling with low-pass or all-pass filtered self-feedback and through a rigorous bifurcation analysis we explore the genesis of this transition. Further, we experimentally demonstrate the observed transition, which establishes its robustness in the presence of parameter fluctuations and noise.

Triggering of longitudinal combustion instabilities in solid rocket motors: Nonlinear combustion response

NASA Technical Reports Server (NTRS)

Wicker, J. M.; Greene, W. D.; Kim, S. I.; Yang, V.

1995-01-01

Pulsed oscillations in solid rocket motors are investigated with emphasis on nonlinear combustion response. The study employs a wave equation governing the unsteady motions in a two-phase flow, and a solution technique based on spatial- and time-averaging. A wide class of combustion response functions is studied to second-order in fluctuation amplitude to determine if, when, and how triggered instabilities arise. Conditions for triggering are derived from analysis of limit cycles, and regions of triggering are found in parametric space. Based on the behavior of model dynamical systems, introduction of linear cross-coupling and quadratic self-coupling among the acoustic modes appears to be the manner in which the nonlinear combustion response produces triggering to a stable limit cycle. Regions of initial conditions corresponding to stable pulses were found, suggesting that stability depends on initial phase angle and harmonic content, as well as the composite amplitude, of the pulse.

A limit-cycle self-organizing map architecture for stable arm control.

PubMed

Huang, Di-Wei; Gentili, Rodolphe J; Katz, Garrett E; Reggia, James A

2017-01-01

Inspired by the oscillatory nature of cerebral cortex activity, we recently proposed and studied self-organizing maps (SOMs) based on limit cycle neural activity in an attempt to improve the information efficiency and robustness of conventional single-node, single-pattern representations. Here we explore for the first time the use of limit cycle SOMs to build a neural architecture that controls a robotic arm by solving inverse kinematics in reach-and-hold tasks. This multi-map architecture integrates open-loop and closed-loop controls that learn to self-organize oscillatory neural representations and to harness non-fixed-point neural activity even for fixed-point arm reaching tasks. We show through computer simulations that our architecture generalizes well, achieves accurate, fast, and smooth arm movements, and is robust in the face of arm perturbations, map damage, and variations of internal timing parameters controlling the flow of activity. A robotic implementation is evaluated successfully without further training, demonstrating for the first time that limit cycle maps can control a physical robot arm. We conclude that architectures based on limit cycle maps can be organized to function effectively as neural controllers. Copyright © 2016 Elsevier Ltd. All rights reserved.

Trapping Phenomenon Attenuates the Consequences of Tipping Points for Limit Cycles

NASA Astrophysics Data System (ADS)

Medeiros, Everton S.; Caldas, Iberê L.; Baptista, Murilo S.; Feudel, Ulrike

2017-02-01

Nonlinear dynamical systems may be exposed to tipping points, critical thresholds at which small changes in the external inputs or in the system’s parameters abruptly shift the system to an alternative state with a contrasting dynamical behavior. While tipping in a fold bifurcation of an equilibrium is well understood, much less is known about tipping of oscillations (limit cycles) though this dynamics are the typical response of many natural systems to a periodic external forcing, like e.g. seasonal forcing in ecology and climate sciences. We provide a detailed analysis of tipping phenomena in periodically forced systems and show that, when limit cycles are considered, a transient structure, so-called channel, plays a fundamental role in the transition. Specifically, we demonstrate that trajectories crossing such channel conserve, for a characteristic time, the twisting behavior of the stable limit cycle destroyed in the fold bifurcation of cycles. As a consequence, this channel acts like a “ghost” of the limit cycle destroyed in the critical transition and instead of the expected abrupt transition we find a smooth one. This smoothness is also the reason that it is difficult to precisely determine the transition point employing the usual indicators of tipping points, like critical slowing down and flickering.

Predator interference and stability of predator-prey dynamics.

PubMed

Přibylová, Lenka; Berec, Luděk

2015-08-01

Predator interference, that is, a decline in the per predator consumption rate as predator density increases, is generally thought to promote predator-prey stability. Indeed, this has been demonstrated in many theoretical studies on predator-prey dynamics. In virtually all of these studies, the stabilization role is demonstrated as a weakening of the paradox of enrichment. With predator interference, stable limit cycles that appear as a result of environmental enrichment occur for higher values of the environmental carrying capacity of prey, and even a complete absence of the limit cycles can happen. Here we study predator-prey dynamics using the Rosenzweig-MacArthur-like model in which the Holling type II functional response has been replaced by a predator-dependent family which generalizes many of the commonly used descriptions of predator interference. By means of a bifurcation analysis we show that sufficiently strong predator interference may bring about another stabilizing mechanism. In particular, hysteresis combined with (dis)appearance of stable limit cycles imply abrupt increases in both the prey and predator densities and enhanced persistence and resilience of the predator-prey system. We encourage refitting the previously collected data on predator consumption rates as well as for conducting further predation experiments to see what functional response from the explored family is the most appropriate.

Sequential dynamics in the motif of excitatory coupled elements

NASA Astrophysics Data System (ADS)

Korotkov, Alexander G.; Kazakov, Alexey O.; Osipov, Grigory V.

2015-11-01

In this article a new model of motif (small ensemble) of neuron-like elements is proposed. It is built with the use of the generalized Lotka-Volterra model with excitatory couplings. The main motivation for this work comes from the problems of neuroscience where excitatory couplings are proved to be the predominant type of interaction between neurons of the brain. In this paper it is shown that there are two modes depending on the type of coupling between the elements: the mode with a stable heteroclinic cycle and the mode with a stable limit cycle. Our second goal is to examine the chaotic dynamics of the generalized three-dimensional Lotka-Volterra model.

Stable cycling in discrete-time genetic models.

PubMed

Hastings, A

1981-11-01

Examples of stable cycling are discussed for two-locus, two-allele, deterministic, discrete-time models with constant fitnesses. The cases that cycle were found by using numerical techniques to search for stable Hopf bifurcations. One consequence of the results is that apparent cases of directional selection may be due to stable cycling.

Non-Nuclear Validation Test Results of a Closed Brayton Cycle Test-Loop

NASA Astrophysics Data System (ADS)

Wright, Steven A.

2007-01-01

Both NASA and DOE have programs that are investigating advanced power conversion cycles for planetary surface power on the moon or Mars, or for next generation nuclear power plants on earth. Although open Brayton cycles are in use for many applications (combined cycle power plants, aircraft engines), only a few closed Brayton cycles have been tested. Experience with closed Brayton cycles coupled to nuclear reactors is even more limited and current projections of Brayton cycle performance are based on analytic models. This report describes and compares experimental results with model predictions from a series of non-nuclear tests using a small scale closed loop Brayton cycle available at Sandia National Laboratories. A substantial amount of testing has been performed, and the information is being used to help validate models. In this report we summarize the results from three kinds of tests. These tests include: 1) test results that are useful for validating the characteristic flow curves of the turbomachinery for various gases ranging from ideal gases (Ar or Ar/He) to non-ideal gases such as CO2, 2) test results that represent shut down transients and decay heat removal capability of Brayton loops after reactor shut down, and 3) tests that map a range of operating power versus shaft speed curve and turbine inlet temperature that are useful for predicting stable operating conditions during both normal and off-normal operating behavior. These tests reveal significant interactions between the reactor and balance of plant. Specifically these results predict limited speed up behavior of the turbomachinery caused by loss of load, the conditions for stable operation, and for direct cooled reactors, the tests reveal that the coast down behavior during loss of power events can extend for hours provided the ultimate heat sink remains available.

Highly selective luminescent sensing of picric acid based on a water-stable europium metal-organic framework

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

Xia, Tifeng; Zhu, Fengliang; Cui, Yuanjing, E-mail: cuiyj@zju.edu.cn

A water-stable metal-organic framework (MOF) EuNDC has been synthesized for selective detection of the well-known contaminant and toxicant picric acid (PA) in aqueous solution. Due to the photo-induced electron transfer and self-absorption mechanism, EuNDC displayed rapid, selective and sensitive detection of PA with a detection limit of 37.6 ppb. Recyclability experiments revealed that EuNDC retains its initial luminescent intensity and same quenching efficiency in each cycle, suggesting high photostability and reusability for long-term sensing applications. The excellent detection performance of EuNDC makes it a promising PA sensing material for practical applications. - Graphical abstract: A water-stable europium-based metal-organic framework hasmore » been reported for highly selective sensing of picric acid (PA) with a detection limit of 37.6 ppb in aqueous solution. - Highlights: • A water-stable metal-organic framework (MOF) EuNDC was synthesized. • The highly selective detection of picric acid with a detection limit of 37.6 ppb was realized. • The detection mechanism were also presented and discussed.« less

Air-stable and freestanding lithium alloy/graphene foil as an alternative to lithium metal anodes

NASA Astrophysics Data System (ADS)

Zhao, Jie; Zhou, Guangmin; Yan, Kai; Xie, Jin; Li, Yuzhang; Liao, Lei; Jin, Yang; Liu, Kai; Hsu, Po-Chun; Wang, Jiangyan; Cheng, Hui-Ming; Cui, Yi

2017-10-01

Developing high-capacity anodes is a must to improve the energy density of lithium batteries for electric vehicle applications. Alloy anodes are one promising option, but without pre-stored lithium, the overall energy density is limited by the low-capacity lithium metal oxide cathodes. Recently, lithium metal has been revived as a high-capacity anode, but faces several challenges owing to its high reactivity and uncontrolled dendrite growth. Here, we show a series of Li-containing foils inheriting the desirable properties of alloy anodes and pure metal anodes. They consist of densely packed LixM (M = Si, Sn, or Al) nanoparticles encapsulated by large graphene sheets. With the protection of graphene sheets, the large and freestanding LixM/graphene foils are stable in different air conditions. With fully expanded LixSi confined in the highly conductive and chemically stable graphene matrix, this LixSi/graphene foil maintains a stable structure and cyclability in half cells (400 cycles with 98% capacity retention). This foil is also paired with high-capacity Li-free V2O5 and sulfur cathodes to achieve stable full-cell cycling.

Air-stable and freestanding lithium alloy/graphene foil as an alternative to lithium metal anodes

DOE PAGES

Zhao, Jie; Zhou, Guangmin; Yan, Kai; ...

2017-07-10

Developing high-capacity anodes is a must to improve the energy density of lithium batteries for electric vehicle applications. Alloy anodes are one promising option, but without pre-stored lithium, the overall energy density is limited by the low-capacity lithium metal oxide cathodes. Recently, lithium metal has been revived as a high-capacity anode, but faces several challenges owing to its high reactivity and uncontrolled dendrite growth. Here, we show a series of Li-containing foils inheriting the desirable properties of alloy anodes and pure metal anodes. They consist of densely packed Li xM (M = Si, Sn, or Al) nanoparticles encapsulated by largemore » graphene sheets. With the protection of graphene sheets, the large and freestanding Li xM/graphene foils are stable in different air conditions. With fully expanded Li xSi confined in the highly conductive and chemically stable graphene matrix, this LixSi/graphene foil maintains a stable structure and cyclability in half cells (400 cycles with 98% capacity retention). As a result, this foil is also paired with high-capacity Li-free V 2O 5 and sulfur cathodes to achieve stable full-cell cycling.« less

Air-stable and freestanding lithium alloy/graphene foil as an alternative to lithium metal anodes

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

Zhao, Jie; Zhou, Guangmin; Yan, Kai

Developing high-capacity anodes is a must to improve the energy density of lithium batteries for electric vehicle applications. Alloy anodes are one promising option, but without pre-stored lithium, the overall energy density is limited by the low-capacity lithium metal oxide cathodes. Recently, lithium metal has been revived as a high-capacity anode, but faces several challenges owing to its high reactivity and uncontrolled dendrite growth. Here, we show a series of Li-containing foils inheriting the desirable properties of alloy anodes and pure metal anodes. They consist of densely packed Li xM (M = Si, Sn, or Al) nanoparticles encapsulated by largemore » graphene sheets. With the protection of graphene sheets, the large and freestanding Li xM/graphene foils are stable in different air conditions. With fully expanded Li xSi confined in the highly conductive and chemically stable graphene matrix, this LixSi/graphene foil maintains a stable structure and cyclability in half cells (400 cycles with 98% capacity retention). As a result, this foil is also paired with high-capacity Li-free V 2O 5 and sulfur cathodes to achieve stable full-cell cycling.« less

A variational method for analyzing limit cycle oscillations in stochastic hybrid systems

NASA Astrophysics Data System (ADS)

Bressloff, Paul C.; MacLaurin, James

2018-06-01

Many systems in biology can be modeled through ordinary differential equations, which are piece-wise continuous, and switch between different states according to a Markov jump process known as a stochastic hybrid system or piecewise deterministic Markov process (PDMP). In the fast switching limit, the dynamics converges to a deterministic ODE. In this paper, we develop a phase reduction method for stochastic hybrid systems that support a stable limit cycle in the deterministic limit. A classic example is the Morris-Lecar model of a neuron, where the switching Markov process is the number of open ion channels and the continuous process is the membrane voltage. We outline a variational principle for the phase reduction, yielding an exact analytic expression for the resulting phase dynamics. We demonstrate that this decomposition is accurate over timescales that are exponential in the switching rate ɛ-1 . That is, we show that for a constant C, the probability that the expected time to leave an O(a) neighborhood of the limit cycle is less than T scales as T exp (-C a /ɛ ) .

Quadrupedal galloping control for a wide range of speed via vertical impulse scaling.

PubMed

Park, Hae-Won; Kim, Sangbae

2015-03-25

This paper presents a bio-inspired quadruped controller that allows variable-speed galloping. The controller design is inspired by observations from biological runners. Quadrupedal animals increase the vertical impulse that is generated by ground reaction forces at each stride as running speed increases and the duration of each stance phase reduces, whereas the swing phase stays relatively constant. Inspired by this observation, the presented controller estimates the required vertical impulse at each stride by applying the linear momentum conservation principle in the vertical direction and prescribes the ground reaction forces at each stride. The design process begins with deriving a planar model from the MIT Cheetah 2 robot. A baseline periodic limit cycle is obtained by optimizing ground reaction force profiles and the temporal gait pattern (timing and duration of gait phases). To stabilize the optimized limit cycle, the obtained limit cycle is converted to a state feedback controller by representing the obtained ground reaction force profiles as functions of the state variable, which is monotonically increasing throughout the gait, adding impedance control around the height and pitch trajectories of the obtained limit cycle and introducing a finite state machine and a pattern stabilizer to enforce the optimized gait pattern. The controller that achieves a stable 3 m s(-1) gallop successfully adapts the speed change by scaling the vertical ground reaction force to match the momentum lost by gravity and adding a simple speed controller that controls horizontal speed. Without requiring additional gait optimization processes, the controller achieves galloping at speeds ranging from 3 m s(-1) to 14.9 m s(-1) while respecting the torque limit of the motor used in the MIT Cheetah 2 robot. The robustness of the controller is verified by demonstrating stable running during various disturbances, including 1.49 m step down and 0.18 m step up, as well as random ground height and model parameter variations.

Development of metal hydride composites

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

Congdon, J.W.

1992-12-01

Most of current hydride technology at Savannah River Site is based on beds of metal hydride powders; the expansion upon hydridation and the cycling results in continued breakdown into finer particles. Goal is to develop a composite which will contain the fines in a dimensionally stable matrix, for use in processes which require a stable gas flow through a hydride bed. Metal hydride composites would benefit the advanced Thermal Cycling Absorption process (hydrogen isotope separation), and the Replacement Tritium Facility (storage, pumping, compression, purification of hydrogen isotopes). These composites were fabricated by cold compaction of a mixture of metal hydridemore » granules and coarse copper powder; the porosity in the granules was introduced by means of ammonium carbonate. The composite pellets were cycled 138 times in hydrogen with the loss of LANA0.75 (LaNi{sub 4.25}Al{sub 0.75}) limited to the surface. Vacuum sintering can provide additional strength at the edges. Without a coating, the metal hydride particles exposed at the pellet surface can be removed by cycling several times in hydrogen.« less

Biologically enhanced cathode design for improved capacity and cycle life for lithium-oxygen batteries

NASA Astrophysics Data System (ADS)

Oh, Dahyun; Qi, Jifa; Lu, Yi-Chun; Zhang, Yong; Shao-Horn, Yang; Belcher, Angela M.

2013-11-01

Lithium-oxygen batteries have a great potential to enhance the gravimetric energy density of fully packaged batteries by two to three times that of lithium ion cells. Recent studies have focused on finding stable electrolytes to address poor cycling capability and improve practical limitations of current lithium-oxygen batteries. In this study, the catalyst electrode, where discharge products are deposited and decomposed, was investigated as it has a critical role in the operation of rechargeable lithium-oxygen batteries. Here we report the electrode design principle to improve specific capacity and cycling performance of lithium-oxygen batteries by utilizing high-efficiency nanocatalysts assembled by M13 virus with earth-abundant elements such as manganese oxides. By incorporating only 3-5 wt% of palladium nanoparticles in the electrode, this hybrid nanocatalyst achieves 13,350 mAh g-1c (7,340 mAh g-1c+catalyst) of specific capacity at 0.4 A g-1c and a stable cycle life up to 50 cycles (4,000 mAh g-1c, 400 mAh g-1c+catalyst) at 1 A g-1c.

Dynamics and Collapse in a Power System Model with Voltage Variation: The Damping Effect.

PubMed

Ma, Jinpeng; Sun, Yong; Yuan, Xiaoming; Kurths, Jürgen; Zhan, Meng

2016-01-01

Complex nonlinear phenomena are investigated in a basic power system model of the single-machine-infinite-bus (SMIB) with a synchronous generator modeled by a classical third-order differential equation including both angle dynamics and voltage dynamics, the so-called flux decay equation. In contrast, for the second-order differential equation considering the angle dynamics only, it is the classical swing equation. Similarities and differences of the dynamics generated between the third-order model and the second-order one are studied. We mainly find that, for positive damping, these two models show quite similar behavior, namely, stable fixed point, stable limit cycle, and their coexistence for different parameters. However, for negative damping, the second-order system can only collapse, whereas for the third-order model, more complicated behavior may happen, such as stable fixed point, limit cycle, quasi-periodicity, and chaos. Interesting partial collapse phenomena for angle instability only and not for voltage instability are also found here, including collapse from quasi-periodicity and from chaos etc. These findings not only provide a basic physical picture for power system dynamics in the third-order model incorporating voltage dynamics, but also enable us a deeper understanding of the complex dynamical behavior and even leading to a design of oscillation damping in electric power systems.

Thermodynamical analysis of a quantum heat engine based on harmonic oscillators.

PubMed

Insinga, Andrea; Andresen, Bjarne; Salamon, Peter

2016-07-01

Many models of heat engines have been studied with the tools of finite-time thermodynamics and an ensemble of independent quantum systems as the working fluid. Because of their convenient analytical properties, harmonic oscillators are the most frequently used example of a quantum system. We analyze different thermodynamical aspects with the final aim of the optimization of the performance of the engine in terms of the mechanical power provided during a finite-time Otto cycle. The heat exchange mechanism between the working fluid and the thermal reservoirs is provided by the Lindblad formalism. We describe an analytical method to find the limit cycle and give conditions for a stable limit cycle to exist. We explore the power production landscape as the duration of the four branches of the cycle are varied for short times, intermediate times, and special frictionless times. For short times we find a periodic structure with atolls of purely dissipative operation surrounding islands of divergent behavior where, rather than tending to a limit cycle, the working fluid accumulates more and more energy. For frictionless times the periodic structure is gone and we come very close to the global optimal operation. The global optimum is found and interestingly comes with a particular value of the cycle time.

Existence and stability of limit cycles in control of anti-lock braking systems with two boundaries via perturbation theory

NASA Astrophysics Data System (ADS)

Köppen, Thomas; Küpper, Tassilo; Makarenkov, Oleg

2017-05-01

This paper presents a two-phase control logic for anti-lock braking systems (ABS). ABS are by now a standard component in every modern car, preventing the wheels from going into a lock situation where the wheels are fixed by the brake and the stopping distances are greatly prolonged. There are different approaches to such control logics. An ABS design proposed in recent literature controls the wheel's slip by creating stable limit cycles in the corresponding phase space. This design is modified via an analytical approach that is derived from perturbation theory. Simulation results document shorter braking distance compared to available tests in the literature.

On the validity of Zeeman's classification for three dimensional competitive differential equations with linearly determined nullclines

NASA Astrophysics Data System (ADS)

Jiang, Jifa; Niu, Lei

2017-12-01

We study three dimensional competitive differential equations with linearly determined nullclines and prove that they always have 33 stable nullcline classes in total. Each class is given in terms of inequalities on the intrinsic growth rates and competitive coefficients and is independent of generating functions. The common characteristics are that every trajectory converges to an equilibrium in classes 1-25, that Hopf bifurcations do not occur within class 32, and that there is always a heteroclinic cycle in class 27. Nontrivial dynamical behaviors, such as the existence and multiplicity of limit cycles, only may occur in classes 26-33, but these nontrivial dynamical behaviors depend on generating functions. We show that Hopf bifurcation can occur within each of classes 26-31 for continuous-time Leslie/Gower system and Ricker system, the same as Lotka-Volterra system; but it only occurs in classes 26 and 27 for continuous-time Atkinson/Allen system and Gompertz system. There is an apparent distinction between Lotka-Volterra system and Leslie/Gower system, Ricker system, Atkinson/Allen system, and Gompertz system with the identical growth rate. Lotka-Volterra system with the identical growth rate has no limit cycle, but admits a center on the carrying simplex in classes 26 and 27. But Leslie/Gower system, Ricker system, Atkinson/Allen system, and Gompertz system with the identical growth rate do possess limit cycles. At last, we provide examples to show that Leslie/Gower system and Ricker system can also admit two limit cycles. This general classification greatly widens applications of Zeeman's method and makes it possible to investigate the existence and multiplicity of limit cycles, centers and stability of heteroclinic cycles for three dimensional competitive systems with linearly determined nullclines, as done in planar systems.

Hard-Soft Composite Carbon as a Long-Cycling and High-Rate Anode for Potassium-Ion Batteries

DOE PAGES

Jian, Zelang; Hwang, Sooyeon; Li, Zhifei; ...

2017-05-05

There exist tremendous needs for sustainable storage solutions for intermittent renewable energy sources, such as solar and wind energy. Thus, systems based on Earth-abundant elements deserve much attention. Potassium-ion batteries represent a promising candidate because of the abundance of potassium resources. As for the choices of anodes, graphite exhibits encouraging potassium-ion storage properties; however, it suffers limited rate capability and poor cycling stability. Here in this paper, nongraphitic carbons as K-ion anodes with sodium carboxymethyl cellulose as the binder are systematically investigated. Compared to hard carbon and soft carbon, a hard–soft composite carbon with 20 wt% soft carbon distributed inmore » the matrix phase of hard carbon microspheres exhibits highly amenable performance: high capacity, high rate capability, and very stable long-term cycling. In contrast, pure hard carbon suffers limited rate capability, while the capacity of pure soft carbon fades more rapidly.« less

Frequency domain optical parametric amplification

PubMed Central

Schmidt, Bruno E.; Thiré, Nicolas; Boivin, Maxime; Laramée, Antoine; Poitras, François; Lebrun, Guy; Ozaki, Tsuneyuki; Ibrahim, Heide; Légaré, François

2014-01-01

Today’s ultrafast lasers operate at the physical limits of optical materials to reach extreme performances. Amplification of single-cycle laser pulses with their corresponding octave-spanning spectra still remains a formidable challenge since the universal dilemma of gain narrowing sets limits for both real level pumped amplifiers as well as parametric amplifiers. We demonstrate that employing parametric amplification in the frequency domain rather than in time domain opens up new design opportunities for ultrafast laser science, with the potential to generate single-cycle multi-terawatt pulses. Fundamental restrictions arising from phase mismatch and damage threshold of nonlinear laser crystals are not only circumvented but also exploited to produce a synergy between increased seed spectrum and increased pump energy. This concept was successfully demonstrated by generating carrier envelope phase stable, 1.43 mJ two-cycle pulses at 1.8 μm wavelength. PMID:24805968

Hard-Soft Composite Carbon as a Long-Cycling and High-Rate Anode for Potassium-Ion Batteries

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

Jian, Zelang; Hwang, Sooyeon; Li, Zhifei

There exist tremendous needs for sustainable storage solutions for intermittent renewable energy sources, such as solar and wind energy. Thus, systems based on Earth-abundant elements deserve much attention. Potassium-ion batteries represent a promising candidate because of the abundance of potassium resources. As for the choices of anodes, graphite exhibits encouraging potassium-ion storage properties; however, it suffers limited rate capability and poor cycling stability. Here in this paper, nongraphitic carbons as K-ion anodes with sodium carboxymethyl cellulose as the binder are systematically investigated. Compared to hard carbon and soft carbon, a hard–soft composite carbon with 20 wt% soft carbon distributed inmore » the matrix phase of hard carbon microspheres exhibits highly amenable performance: high capacity, high rate capability, and very stable long-term cycling. In contrast, pure hard carbon suffers limited rate capability, while the capacity of pure soft carbon fades more rapidly.« less

Nitrogen isotope patterns in Alaskan black spruce reflect organic nitrogen sources and the activity of ectomycorrihizal fungi

Treesearch

Jordan R. Mayor; Edward A.G. Schuur; Michelle C. Mack; Teresa N. Hollingsworth; Erland Bääth

2012-01-01

Global patterns in soil, plant, and fungal stable isotopes of N (15N) show promise as integrated metrics of N cycling, particularly the activity of ectomycorrhizal (ECM) fungi. At small spatial scales, however, it remains difficult to differentiate the underlying causes of plant 15N variability and this limits the...

How to couple identical ring oscillators to get quasiperiodicity, extended chaos, multistability, and the loss of symmetry

NASA Astrophysics Data System (ADS)

Hellen, Edward H.; Volkov, Evgeny

2018-09-01

We study the dynamical regimes demonstrated by a pair of identical 3-element ring oscillators (reduced version of synthetic 3-gene genetic Repressilator) coupled using the design of the 'quorum sensing (QS)' process natural for interbacterial communications. In this work QS is implemented as an additional network incorporating elements of the ring as both the source and the activation target of the fast diffusion QS signal. This version of indirect nonlinear coupling, in cooperation with the reasonable extension of the parameters which control properties of the isolated oscillators, exhibits the formation of a very rich array of attractors. Using a parameter-space defined by the individual oscillator amplitude and the coupling strength, we found the extended area of parameter-space where the identical oscillators demonstrate quasiperiodicity, which evolves to chaos via the period doubling of either resonant limit cycles or complex antiphase symmetric limit cycles with five winding numbers. The symmetric chaos extends over large parameter areas up to its loss of stability, followed by a system transition to an unexpected mode: an asymmetric limit cycle with a winding number of 1:2. In turn, after long evolution across the parameter-space, this cycle demonstrates a period doubling cascade which restores the symmetry of dynamics by formation of symmetric chaos, which nevertheless preserves the memory of the asymmetric limit cycles in the form of stochastic alternating "polarization" of the time series. All stable attractors coexist with some others, forming remarkable and complex multistability including the coexistence of torus and limit cycles, chaos and regular attractors, symmetric and asymmetric regimes. We traced the paths and bifurcations leading to all areas of chaos, and presented a detailed map of all transformations of the dynamics.

Noise-induced extinction for a ratio-dependent predator-prey model with strong Allee effect in prey

NASA Astrophysics Data System (ADS)

Mandal, Partha Sarathi

2018-04-01

In this paper, we study a stochastically forced ratio-dependent predator-prey model with strong Allee effect in prey population. In the deterministic case, we show that the model exhibits the stable interior equilibrium point or limit cycle corresponding to the co-existence of both species. We investigate a probabilistic mechanism of the noise-induced extinction in a zone of stable interior equilibrium point. Computational methods based on the stochastic sensitivity function technique are applied for the analysis of the dispersion of random states near stable interior equilibrium point. This method allows to construct a confidence domain and estimate the threshold value of the noise intensity for a transition from the coexistence to the extinction.

High rate and stable cycling of lithium metal anode

PubMed Central

Qian, Jiangfeng; Henderson, Wesley A.; Xu, Wu; Bhattacharya, Priyanka; Engelhard, Mark; Borodin, Oleg; Zhang, Ji-Guang

2015-01-01

Lithium metal is an ideal battery anode. However, dendrite growth and limited Coulombic efficiency during cycling have prevented its practical application in rechargeable batteries. Herein, we report that the use of highly concentrated electrolytes composed of ether solvents and the lithium bis(fluorosulfonyl)imide salt enables the high-rate cycling of a lithium metal anode at high Coulombic efficiency (up to 99.1%) without dendrite growth. With 4 M lithium bis(fluorosulfonyl)imide in 1,2-dimethoxyethane as the electrolyte, a lithium|lithium cell can be cycled at 10 mA cm−2 for more than 6,000 cycles, and a copper|lithium cell can be cycled at 4 mA cm−2 for more than 1,000 cycles with an average Coulombic efficiency of 98.4%. These excellent performances can be attributed to the increased solvent coordination and increased availability of lithium ion concentration in the electrolyte. Further development of this electrolyte may enable practical applications for lithium metal anode in rechargeable batteries. PMID:25698340

Emulsifying conditions and processing parameters optimisation of kenaf seed oil-in-water nanoemulsions stabilised by ternary emulsifier mixtures.

PubMed

Cheong, Ai M; Tan, Chin P; Nyam, Kar L

2018-01-01

Kenaf ( Hibiscus cannabinus L.) seed oil has been proven for its multi-pharmacological benefits; however, its poor water solubility and stability have limited its industrial applications. This study was aimed to further improve the stability of pre-developed kenaf seed oil-in-water nanoemulsions by using food-grade ternary emulsifiers. The effects of emulsifier concentration (1, 5, 10, 15% w/w), homogenisation pressure (16,000, 22,000, 28,000 psi), and homogenisation cycles (three, four, five cycles) were studied to produce high stability of kenaf seed oil-in-water nanoemulsions using high pressure homogeniser. Generally, results showed that the emulsifier concentration and homogenisation conditions had great effect ( p < 0.05) on the particle sizes, polydispersity index and hence the physical stability of nanoemulsions. Homogenisation parameters at 28,000 psi for three cycles produced the most stable homogeneous nanoemulsions that were below 130 nm, below 0.16, and above -40 mV of particle size, polydispersity index, and zeta potential, respectively. Field emission scanning electron microscopy micrograph showed that the optimised nanoemulsions had a good distribution within nano-range. The optimised nanoemulsions were proved to be physically stable for up to six weeks of storage at room temperature. The results from this study also provided valuable information in producing stable kenaf seed oil nanoemulsions for the future application in food and nutraceutical industries.

Oscillatory dynamics in rock-paper-scissors games with mutations.

PubMed

Mobilia, Mauro

2010-05-07

We study the oscillatory dynamics in the generic three-species rock-paper-scissors games with mutations. In the mean-field limit, different behaviors are found: (a) for high mutation rate, there is a stable interior fixed point with coexistence of all species; (b) for low mutation rates, there is a region of the parameter space characterized by a limit cycle resulting from a Hopf bifurcation; (c) in the absence of mutations, there is a region where heteroclinic cycles yield oscillations of large amplitude (not robust against noise). After a discussion on the main properties of the mean-field dynamics, we investigate the stochastic version of the model within an individual-based formulation. Demographic fluctuations are therefore naturally accounted and their effects are studied using a diffusion theory complemented by numerical simulations. It is thus shown that persistent erratic oscillations (quasi-cycles) of large amplitude emerge from a noise-induced resonance phenomenon. We also analytically and numerically compute the average escape time necessary to reach a (quasi-)cycle on which the system oscillates at a given amplitude. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Rutile TiO2 Mesocrystals as Sulfur Host for High-Performance Lithium-Sulfur Batteries.

PubMed

Sun, Qingqing; Chen, Kaixiang; Liu, Yubin; Li, Yafeng; Wei, Mingdeng

2017-11-16

Although lithium-sulfur (Li-S) batteries are among the most promising rechargeable batteries in the field of energy-storage devices, their poor cycling performance restricts their potential applications. Polar materials can improve the cycling stability owing to their inherent strong chemical interaction with polysulfides. Herein, novel rutile TiO 2 mesocrystals (RTMs) are employed as the host for sulfur in Li-S batteries; the RTMs display a stable cycling performance with a capacity retention of 64 % and a small average capacity decay rate of 0.12 % per cycle over 300 cycles at 1 C rate. The good electrochemical properties are attributed to the interior ordered nanopores of the RTMs, which can effectively limit the dissolution of polysulfides, and the ultrafine nanowires in RTMs, which shorten the path for lithium-ion transport effectively. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Low cost space power generation

NASA Technical Reports Server (NTRS)

Olsen, Randall B.

1991-01-01

The success of this study has given a method of fabricating durable copolymer films without size limitations. Previously, only compression molded samples were durable enough to generate electrical energy. The strengthened specimens are very long lived materials. The lifetime was enhanced at least a factor of 1,300 in full pyroelectric conversion cycle experiments compared with extruded, non-strengthened film. The new techniques proved so successful that the lifetime of the resultant copolymer samples was not fully characterized. The lifetime of these new materials is so long that accelerated tests were devised to probe their durability. After a total of more than 67 million high voltage electrical cycles at 100 C, the electrical properties of a copolymer sample remained stable. The test was terminated without any detectable degradation to allow for other experiments. One must be cautious in extrapolating to power cycle performance, but 67 million electrical cycles correspond to 2 years of pyroelectric cycling at 1 Hz. In another series of experiments at reduced temperature and electrical stress, a specimen survived over one-third of a billion electrical cycles during nearly three months of continuous testing. The radiation-limited lifetimes of the copolymer were shown to range from several years to millions of years for most earth orbits. Thus, the pyroelectric copolymer has become a strong candidate for serious consideration for future spacecraft power supplies.

Universal route to optimal few- to single-cycle pulse generation in hollow-core fiber compressors.

PubMed

Conejero Jarque, E; San Roman, J; Silva, F; Romero, R; Holgado, W; Gonzalez-Galicia, M A; Alonso, B; Sola, I J; Crespo, H

2018-02-02

Gas-filled hollow-core fiber (HCF) pulse post-compressors generating few- to single-cycle pulses are a key enabling tool for attosecond science and ultrafast spectroscopy. Achieving optimum performance in this regime can be extremely challenging due to the ultra-broad bandwidth of the pulses and the need of an adequate temporal diagnostic. These difficulties have hindered the full exploitation of HCF post-compressors, namely the generation of stable and high-quality near-Fourier-transform-limited pulses. Here we show that, independently of conditions such as the type of gas or the laser system used, there is a universal route to obtain the shortest stable output pulse down to the single-cycle regime. Numerical simulations and experimental measurements performed with the dispersion-scan technique reveal that, in quite general conditions, post-compressed pulses exhibit a residual third-order dispersion intrinsic to optimum nonlinear propagation within the fiber, in agreement with measurements independently performed in several laboratories around the world. The understanding of this effect and its adequate correction, e.g. using simple transparent optical media, enables achieving high-quality post-compressed pulses with only minor changes in existing setups. These optimized sources have impact in many fields of science and technology and should enable new and exciting applications in the few- to single-cycle pulse regime.

A Supercompressible, Elastic, and Bendable Carbon Aerogel with Ultrasensitive Detection Limits for Compression Strain, Pressure, and Bending Angle.

PubMed

Zhuo, Hao; Hu, Yijie; Tong, Xing; Chen, Zehong; Zhong, Linxin; Lai, Haihong; Liu, Linxiang; Jing, Shuangshuang; Liu, Qingzhong; Liu, Chuanfu; Peng, Xinwen; Sun, Runcang

2018-05-01

Ultralight and compressible carbon materials have promising applications in strain and pressure detection. However, it is still difficult to prepare carbon materials with supercompressibility, elasticity, stable strain-electrical signal response, and ultrasensitive detection limits, due to the challenge in structural regulation. Herein, a new strategy to prepare a reduced graphene oxide (rGO)-based lamellar carbon aerogels with unexpected and integrated performances by designing wave-shape rGO layers and enhancing the interaction among the rGO layers is demonstrated. Addition of cellulose nanocrystalline and low-molecular-weight carbon precursors enhances the interaction among rGO layers and thus produces an ultralight, flexible, and superstable structure. The as-prepared carbon aerogel displays a supercompressibility (undergoing an extreme strain of 99%) and elasticity (100% height retention after 10 000 cycles at a strain of 30%), as well as stable strain-current response (at least 10 000 cycles). Particularly, the carbon aerogel is ultrasensitive for detecting tiny change in strain (0.012%) and pressure (0.25 Pa), which are the lowest detection limits for compressible carbon materials reported in the literature. Moreover, the carbon aerogel exhibits excellent bendable performance and can detect an ultralow bending angle of 0.052°. Additionally, the carbon aerogel also demonstrates its promising application as wearable devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Digital second-order phase-locked loop

NASA Technical Reports Server (NTRS)

Holes, J. K.; Carl, C.; Tegnelia, C. R. (Inventor)

1973-01-01

A digital second-order phase-locked loop is disclosed in which a counter driven by a stable clock pulse source is used to generate a reference waveform of the same frequency as an incoming waveform, and to sample the incoming waveform at zero-crossover points. The samples are converted to digital form and accumulated over M cycles, reversing the sign of every second sample. After every M cycles, the accumulated value of samples is hard limited to a value SGN = + or - 1 and multiplied by a value delta sub 1 equal to a number of n sub 1 of fractions of a cycle. An error signal is used to advance or retard the counter according to the sign of the sum by an amount equal to the sum.

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

Nandwana, Peeyush; Peter, William H.; Lowe, Larry E.

In this study, powder bed based additive manufacturing technologies offer a big advantage in terms of reusability of the powders over multiple cycles that result in cost savings. However, currently there are no standards to determine the factors that govern the powder reuse times. This work presents the results from a recyclability study conducted on Inconel 718 and Ti-6Al-4V powders. It has been found that the Inconel 718 powders are chemically stable over a large number of cycles and their reuse time is limited by physical characteristics of powders such as flowability. Ti-6Al-4V, on the other hand, finds its reusemore » time governed by the oxygen pick up that occurs during and in between build cycles. The detailed results have been presented.« less

Evolution of supersonic corner vortex in a hypersonic inlet/isolator model

NASA Astrophysics Data System (ADS)

Huang, He-Xia; Tan, Hui-Jun; Sun, Shu; Ling, Yu

2016-12-01

There are complex corner vortex flows in a rectangular hypersonic inlet/isolator. The corner vortex propagates downstream and interacts with the shocks and expansion waves in the isolator repeatedly. The supersonic corner vortex in a generic hypersonic inlet/isolator model is theoretically and numerically analyzed at a freestream Mach number of 4.92. The cross-flow topology of the corner vortex flow is found to obey Zhang's theory ["Analytical analysis of subsonic and supersonic vortex formation," Acta Aerodyn. Sin. 13, 259-264 (1995)] strictly, except for the short process with the vortex core situated in a subsonic flow which is surrounded by a supersonic flow. In general, the evolution history of the corner vortex under the influence of the background waves in the hypersonic inlet/isolator model can be classified into two types, namely, from the adverse pressure gradient region to the favorable pressure gradient region and the reversed one. For type 1, the corner vortex is a one-celled vortex with the cross-sectional streamlines spiraling inwards at first. Then the Hopf bifurcation occurs and the streamlines in the outer part of the limit cycle switch to spiraling outwards, yielding a two-celled vortex. The limit cycle shrinks gradually and finally vanishes with the streamlines of the entire corner vortex spiraling outwards. For type 2, the cross-sectional streamlines of the corner vortex spiral outwards first. Then a stable limit cycle is formed, yielding a two-celled vortex. The short-lived limit cycle forces the streamlines in the corner vortex to change the spiraling trends rapidly. Although it is found in this paper that there are some defects on the theoretical proof of the limit cycle, Zhang's theory is proven useful for the prediction and qualitative analysis of the complex corner vortex in a hypersonic inlet/isolator. In addition, three conservation laws inside the limit cycle are obtained.

Funneled potential and flux landscapes dictate the stabilities of both the states and the flow: Fission yeast cell cycle.

PubMed

Luo, Xiaosheng; Xu, Liufang; Han, Bo; Wang, Jin

2017-09-01

Using fission yeast cell cycle as an example, we uncovered that the non-equilibrium network dynamics and global properties are determined by two essential features: the potential landscape and the flux landscape. These two landscapes can be quantified through the decomposition of the dynamics into the detailed balance preserving part and detailed balance breaking non-equilibrium part. While the funneled potential landscape is often crucial for the stability of the single attractor networks, we have uncovered that the funneled flux landscape is crucial for the emergence and maintenance of the stable limit cycle oscillation flow. This provides a new interpretation of the origin for the limit cycle oscillations: There are many cycles and loops existed flowing through the state space and forming the flux landscapes, each cycle with a probability flux going through the loop. The limit cycle emerges when a loop stands out and carries significantly more probability flux than other loops. We explore how robustness ratio (RR) as the gap or steepness versus averaged variations or roughness of the landscape, quantifying the degrees of the funneling of the underlying potential and flux landscapes. We state that these two landscapes complement each other with one crucial for stabilities of states on the cycle and the other crucial for the stability of the flow along the cycle. The flux is directly related to the speed of the cell cycle. This allows us to identify the key factors and structure elements of the networks in determining the stability, speed and robustness of the fission yeast cell cycle oscillations. We see that the non-equilibriumness characterized by the degree of detailed balance breaking from the energy pump quantified by the flux is the cause of the energy dissipation for initiating and sustaining the replications essential for the origin and evolution of life. Regulating the cell cycle speed is crucial for designing the prevention and curing strategy of cancer.

Funneled potential and flux landscapes dictate the stabilities of both the states and the flow: Fission yeast cell cycle

PubMed Central

2017-01-01

Using fission yeast cell cycle as an example, we uncovered that the non-equilibrium network dynamics and global properties are determined by two essential features: the potential landscape and the flux landscape. These two landscapes can be quantified through the decomposition of the dynamics into the detailed balance preserving part and detailed balance breaking non-equilibrium part. While the funneled potential landscape is often crucial for the stability of the single attractor networks, we have uncovered that the funneled flux landscape is crucial for the emergence and maintenance of the stable limit cycle oscillation flow. This provides a new interpretation of the origin for the limit cycle oscillations: There are many cycles and loops existed flowing through the state space and forming the flux landscapes, each cycle with a probability flux going through the loop. The limit cycle emerges when a loop stands out and carries significantly more probability flux than other loops. We explore how robustness ratio (RR) as the gap or steepness versus averaged variations or roughness of the landscape, quantifying the degrees of the funneling of the underlying potential and flux landscapes. We state that these two landscapes complement each other with one crucial for stabilities of states on the cycle and the other crucial for the stability of the flow along the cycle. The flux is directly related to the speed of the cell cycle. This allows us to identify the key factors and structure elements of the networks in determining the stability, speed and robustness of the fission yeast cell cycle oscillations. We see that the non-equilibriumness characterized by the degree of detailed balance breaking from the energy pump quantified by the flux is the cause of the energy dissipation for initiating and sustaining the replications essential for the origin and evolution of life. Regulating the cell cycle speed is crucial for designing the prevention and curing strategy of cancer. PMID:28892489

Delay induced stability switch, multitype bistability and chaos in an intraguild predation model.

PubMed

Shu, Hongying; Hu, Xi; Wang, Lin; Watmough, James

2015-12-01

In many predator-prey models, delay has a destabilizing effect and induces oscillations; while in many competition models, delay does not induce oscillations. By analyzing a rather simple delayed intraguild predation model, which combines both the predator-prey relation and competition, we show that delay in intraguild predation models promotes very complex dynamics. The delay can induce stability switches exhibiting a destabilizing role as well as a stabilizing role. It is shown that three types of bistability are possible: one stable equilibrium coexists with another stable equilibrium (node-node bistability); one stable equilibrium coexists with a stable periodic solution (node-cycle bistability); one stable periodic solution coexists with another stable periodic solution (cycle-cycle bistability). Numerical simulations suggest that delay can also induce chaos in intraguild predation models.

Highly selective luminescent sensing of picric acid based on a water-stable europium metal-organic framework

NASA Astrophysics Data System (ADS)

Xia, Tifeng; Zhu, Fengliang; Cui, Yuanjing; Yang, Yu; Wang, Zhiyu; Qian, Guodong

2017-01-01

A water-stable metal-organic framework (MOF) EuNDC has been synthesized for selective detection of the well-known contaminant and toxicant picric acid (PA) in aqueous solution. Due to the photo-induced electron transfer and self-absorption mechanism, EuNDC displayed rapid, selective and sensitive detection of PA with a detection limit of 37.6 ppb. Recyclability experiments revealed that EuNDC retains its initial luminescent intensity and same quenching efficiency in each cycle, suggesting high photostability and reusability for long-term sensing applications. The excellent detection performance of EuNDC makes it a promising PA sensing material for practical applications.

Magnesium and calcium sulfate stabilities and the water budget of Mars

USGS Publications Warehouse

Chou, I.-Ming; Seal, R.R.

2007-01-01

Magnesium sulfate probably plays a dominant role in the water cycle of Mars away from the polar ice caps through hydration and dehydration reactions. This prominence is due to its abundance, its occurrence in numerous hydration states, and its ability to hydrate and dehydrate rapidly. New experimental studies on the metastable reaction between hexahydrite (MgSO4??6H2O) and starkeyite (MgSO4-4H2O) as a function of temperature and relative humidity, supplemented by recent investigations of the stable reaction between epsomite (MgSO4??7H2O) and hexahydrite and by phase equilibrium calculations, suggest that the most important magnesium sulfate phases involved in the Martian water cycle are MgSO4??11 H2O, epsomite, starkeyite, and possibly kieserite (MgSO4??H2O). Hexahydrite is not predicted to be stable on the surface of Mars. During diurnal variations in temperature and relative humidity, 1 kg of MgSO4 can release or remove from the atmosphere 1.5 kg of H2O by cycling between kieserite and MgSO4??11 H2O. Despite subequal abundances of calcium sulfate, calcium sulfates are not likely to be important in the water cycle of the planet because of sluggish rates of hydration and dehydration and a more limited range of H2O concentrations per kilogram of CaSO4 (0.00 to 0.26 kg kg-1). Modern or recent erosion on Mars attributed to liquid water may be due to the dehydration Of MgSO4??11 H2O because of the inferred abundance and likelihood of occurrence of this phase and its limited stability relative to known variations in temperature and relative humidity.

Effects of friction dampers on aerodynamically unstable rotor stages

NASA Technical Reports Server (NTRS)

Griffin, J. H.; Sinha, A.

1983-01-01

Attention is given to the physical concepts and mathematical techniques useful in the analysis of the stabilizing effect of friction on aerodynamically unstable rotor stages. Results are presented for three-, four-, and five-bladed disks. In the present multidegree-of-freedom model of an aerodynamically unstable rotor stage, a harmonic steady state solution due to the friction dampers may be either a stability limit, a stable cycle limit, or neither. A criterion is established in the form of an energy function which determines whether the solution is a stability limit. In the event that the initial displacement and velocity exeed those associated with the steady state solution corresponding to a stability limit, the reponse becomes unbounded.

Identification of FOPDT and SOPDT process dynamics using closed loop test.

PubMed

Bajarangbali, Raghunath; Majhi, Somanath; Pandey, Saurabh

2014-07-01

In this paper, identification of stable and unstable first order, second order overdamped and underdamped process dynamics with time delay is presented. Relay with hysteresis is used to induce a limit cycle output and using this information, unknown process model parameters are estimated. State space based generalized analytical expressions are derived to achieve accurate results. To show the performance of the proposed method expressions are also derived for systems with a zero. In real time systems, measurement noise is an important issue during identification of process dynamics. A relay with hysteresis reduces the effect of measurement noise, in addition a new multiloop control strategy is proposed to recover the original limit cycle. Simulation results are included to validate the effectiveness of the proposed method. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

A thermally regenerative ammonia battery with carbon-silver electrodes for converting low-grade waste heat to electricity

NASA Astrophysics Data System (ADS)

Rahimi, Mohammad; Kim, Taeyoung; Gorski, Christopher A.; Logan, Bruce E.

2018-01-01

Thermally regenerative ammonia batteries (TRABs) have shown great promise as a method to convert low-grade waste heat into electrical power, with power densities an order of magnitude higher than other approaches. However, previous TRABs based on copper electrodes suffered from unbalanced anode dissolution and cathode deposition rates during discharging cycles, limiting practical applications. To produce a TRAB with stable and reversible electrode reactions over many cycles, inert carbon electrodes were used with silver salts. In continuous flow tests, power production was stable over 100 discharging cycles, demonstrating excellent reversibility. Power densities were 23 W m-2-electrode area in batch tests, which was 64% higher than that produced in parallel tests using copper electrodes, and 30 W m-2 (net energy density of 490 Wh m-3-anolyte) in continuous flow tests. While this battery requires the use a precious metal, an initial economic analysis of the system showed that the cost of the materials relative to energy production was 220 per MWh, which is competitive with energy production from other non-fossil fuel sources. A substantial reduction in costs could be obtained by developing less expensive anion exchange membranes.

Stable isotope phenotyping via cluster analysis of NanoSIMS data as a method for characterizing distinct microbial ecophysiologies and sulfur-cycling in the environment

NASA Astrophysics Data System (ADS)

Dawson, K.; Scheller, S.; Dillon, J. G.; Orphan, V. J.

2016-12-01

Stable isotope probing (SIP) is a valuable tool for gaining insights into ecophysiology and biogeochemical cycling of environmental microbial communities by tracking isotopically labeled compounds into cellular macromolecules as well as into byproducts of respiration. SIP, in conjunction with nanoscale secondary ion mass spectrometry (NanoSIMS), allows for the visualization of isotope incorporation at the single cell level. In this manner, both active cells within a diverse population as well as heterogeneity in metabolism within a homogeneous population can be observed. The ecophysiological implications of these single cell stable isotope measurements are often limited to the taxonomic resolution of paired fluorescence in situ hybridization (FISH) microscopy. Here we introduce a taxonomy-independent method using multi-isotope SIP and NanoSIMS for identifying and grouping phenotypically similar microbial cells by their chemical and isotopic fingerprint. This method was applied to SIP experiments in a sulfur-cycling biofilm collected from sulfidic intertidal vents amended with 13C-acetate, 15N-ammonium, and 33S-sulfate. Using a cluster analysis technique based on fuzzy c-means to group cells according to their isotope (13C/12C, 15N/14N, and 33S/32S) and elemental ratio (C/CN and S/CN) profiles, our analysis partitioned 2200 cellular regions of interest (ROIs) into 5 distinct groups. These isotope phenotype groupings are reflective of the variation in labeled substrate uptake by cells in a multispecies metabolic network dominated by Gamma- and Deltaproteobacteria. Populations independently grouped by isotope phenotype were subsequently compared with paired FISH data, demonstrating a single coherent deltaproteobacterial cluster and multiple gammaproteobacterial groups, highlighting the distinct ecophysiologies of spatially-associated microbes within the sulfur-cycling biofilm from White Point Beach, CA.

Stable Isotope Phenotyping via Cluster Analysis of NanoSIMS Data As a Method for Characterizing Distinct Microbial Ecophysiologies and Sulfur-Cycling in the Environment

PubMed Central

Dawson, Katherine S.; Scheller, Silvan; Dillon, Jesse G.; Orphan, Victoria J.

2016-01-01

Stable isotope probing (SIP) is a valuable tool for gaining insights into ecophysiology and biogeochemical cycling of environmental microbial communities by tracking isotopically labeled compounds into cellular macromolecules as well as into byproducts of respiration. SIP, in conjunction with nanoscale secondary ion mass spectrometry (NanoSIMS), allows for the visualization of isotope incorporation at the single cell level. In this manner, both active cells within a diverse population as well as heterogeneity in metabolism within a homogeneous population can be observed. The ecophysiological implications of these single cell stable isotope measurements are often limited to the taxonomic resolution of paired fluorescence in situ hybridization (FISH) microscopy. Here we introduce a taxonomy-independent method using multi-isotope SIP and NanoSIMS for identifying and grouping phenotypically similar microbial cells by their chemical and isotopic fingerprint. This method was applied to SIP experiments in a sulfur-cycling biofilm collected from sulfidic intertidal vents amended with 13C-acetate, 15N-ammonium, and 33S-sulfate. Using a cluster analysis technique based on fuzzy c-means to group cells according to their isotope (13C/12C, 15N/14N, and 33S/32S) and elemental ratio (C/CN and S/CN) profiles, our analysis partitioned ~2200 cellular regions of interest (ROIs) into five distinct groups. These isotope phenotype groupings are reflective of the variation in labeled substrate uptake by cells in a multispecies metabolic network dominated by Gamma- and Deltaproteobacteria. Populations independently grouped by isotope phenotype were subsequently compared with paired FISH data, demonstrating a single coherent deltaproteobacterial cluster and multiple gammaproteobacterial groups, highlighting the distinct ecophysiologies of spatially-associated microbes within the sulfur-cycling biofilm from White Point Beach, CA. PMID:27303371

Phase I study of temozolomide in paediatric patients with advanced cancer. United Kingdom Children's Cancer Study Group.

PubMed Central

Estlin, E. J.; Lashford, L.; Ablett, S.; Price, L.; Gowing, R.; Gholkar, A.; Kohler, J.; Lewis, I. J.; Morland, B.; Pinkerton, C. R.; Stevens, M. C.; Mott, M.; Stevens, R.; Newell, D. R.; Walker, D.; Dicks-Mireaux, C.; McDowell, H.; Reidenberg, P.; Statkevich, P.; Marco, A.; Batra, V.; Dugan, M.; Pearson, A. D.

1998-01-01

A phase I study of temozolomide administered orally once a day, on 5 consecutive days, between 500 and 1200 mg m(-2) per 28-day cycle was performed. Children were stratified according to prior craniospinal irradiation or nitrosourea therapy. Sixteen of 20 patients who had not received prior craniospinal irradiation or nitrosourea therapy were evaluable. Myelosuppression was dose limiting, with Common Toxicity Criteria (CTC) grade 4 thrombocytopenia occurring in one of six patients receiving 1000 mg m(-2) per cycle, and two of four patients treated at 1200 mg m(-2) per cycle. Therefore, the maximum-tolerated dose (MTD) was 1000 mg m(-2) per cycle. The MTD was not defined for children with prior craniospinal irradiation because of poor recruitment. Plasma pharmacokinetic analyses showed temozolomide to be rapidly absorbed and eliminated, with linear increases in peak plasma concentrations and systemic exposure with increasing dose. Responses (CR and PR) were seen in two out of five patients with high-grade astrocytomas, and one patient had stable disease. One of ten patients with diffuse intrinsic brain stem glioma achieved a long-term partial response, and a further two patients had stable disease. Therefore, the dose recommended for phase II studies in patients who have not received prior craniospinal irradiation or nitrosoureas is 1000 mg m(-2) per cycle. Further evaluation in diffuse intrinsic brain stem gliomas and other high-grade astrocytomas is warranted. Images Figure 5 p658-b Figure 6 p659-b PMID:9744506

Climate stability of habitable Earth-like planets

NASA Astrophysics Data System (ADS)

Menou, Kristen

2015-11-01

The carbon-silicate cycle regulates the atmospheric CO2 content of terrestrial planets on geological timescales through a balance between the rates of CO2 volcanic outgassing and planetary intake from rock weathering. It is thought to act as an efficient climatic thermostat on Earth and, by extension, on other habitable planets. If, however, the weathering rate increases with the atmospheric CO2 content, as expected on planets lacking land vascular plants, the carbon-silicate cycle feedback can become severely limited. Here we show that Earth-like planets receiving less sunlight than current Earth may no longer possess a stable warm climate but instead repeatedly cycle between unstable glaciated and deglaciated climatic states. This has implications for the search for life on exoplanets in the habitable zone of nearby stars.

Stability analysis of nonlinear autonomous systems - General theory and application to flutter

NASA Technical Reports Server (NTRS)

Smith, L. L.; Morino, L.

1975-01-01

The analysis makes use of a singular perturbation method, the multiple time scaling. Concepts of stable and unstable limit cycles are introduced. The solution is obtained in the form of an asymptotic expansion. Numerical results are presented for the nonlinear flutter of panels and airfoils in supersonic flow. The approach used is an extension of a method for analyzing nonlinear panel flutter reported by Morino (1969).

Nonlinear resonance and synchronization in the ring of unidirectionally coupled Toda oscillators

NASA Astrophysics Data System (ADS)

Dvorak, Anton; Astakhov, Vladimir; Perlikowski, Przemyslaw; Kapitaniak, Tomasz

2016-11-01

In the ring of unidirectionally coupled Toda oscillators the nonlinear resonance and the synchronization are investigated. It is shown how the nonlinear resonance affects the structure of the main synchronization region. As a result of nonlinear resonance we observe the coexistence of two stable limit cycles near the resonant frequency, which leads to coexistence of periodic and quasi-periodic regimes within the synchronization region.

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

Rizwan-uddin

Recently, various branches of engineering and science have seen a rapid increase in the number of dynamical analyses undertaken. This modern phenomenon often obscures the fact that such analyses were sometimes carried out even before the current trend began. Moreover, these earlier analyses, which even now seem very ingenuous, were carried out at a time when the available information about dynamical systems was not as well disseminated as it is today. One such analysis, carried out in the early 1960s, showed the existence of stable limit cycles in a simple model for space-independent xenon dynamics in nuclear reactors. The authors,more » apparently unaware of the now well-known bifurcation theorem by Hopf, could not numerically discover unstable limit cycles, though they did find regions in parameter space where the fixed points are stable for small perturbations but unstable for very large perturbations. The analysis was carried out both analytically and numerically. As a tribute to these early nonlinear dynamicists in the field of nuclear engineering, in this paper, the Hopf theorem and its conclusions are briefly described, and then the solution of the space-independent xenon oscillation problem is presented, which was obtained using the bifurcation analysis BIFDD code. These solutions are presented along with a discussion of the earlier results.« less

An intermittent control model of flexible human gait using a stable manifold of saddle-type unstable limit cycle dynamics

PubMed Central

Fu, Chunjiang; Suzuki, Yasuyuki; Kiyono, Ken; Morasso, Pietro; Nomura, Taishin

2014-01-01

Stability of human gait is the ability to maintain upright posture during walking against external perturbations. It is a complex process determined by a number of cross-related factors, including gait trajectory, joint impedance and neural control strategies. Here, we consider a control strategy that can achieve stable steady-state periodic gait while maintaining joint flexibility with the lowest possible joint impedance. To this end, we carried out a simulation study of a heel-toe footed biped model with hip, knee and ankle joints and a heavy head-arms-trunk element, working in the sagittal plane. For simplicity, the model assumes a periodic desired joint angle trajectory and joint torques generated by a set of feed-forward and proportional-derivative feedback controllers, whereby the joint impedance is parametrized by the feedback gains. We could show that a desired steady-state gait accompanied by the desired joint angle trajectory can be established as a stable limit cycle (LC) for the feedback controller with an appropriate set of large feedback gains. Moreover, as the feedback gains are decreased for lowering the joint stiffness, stability of the LC is lost only in a few dimensions, while leaving the remaining large number of dimensions quite stable: this means that the LC becomes saddle-type, with a low-dimensional unstable manifold and a high-dimensional stable manifold. Remarkably, the unstable manifold remains of low dimensionality even when the feedback gains are decreased far below the instability point. We then developed an intermittent neural feedback controller that is activated only for short periods of time at an optimal phase of each gait stride. We characterized the robustness of this design by showing that it can better stabilize the unstable LC with small feedback gains, leading to a flexible gait, and in particular we demonstrated that such an intermittent controller performs better if it drives the state point to the stable manifold, rather than directly to the LC. The proposed intermittent control strategy might have a high affinity for the inverted pendulum analogy of biped gait, providing a dynamic view of how the step-to-step transition from one pendular stance to the next can be achieved stably in a robust manner by a well-timed neural intervention that exploits the stable modes embedded in the unstable dynamics. PMID:25339687

An intermittent control model of flexible human gait using a stable manifold of saddle-type unstable limit cycle dynamics.

PubMed

Fu, Chunjiang; Suzuki, Yasuyuki; Kiyono, Ken; Morasso, Pietro; Nomura, Taishin

2014-12-06

Stability of human gait is the ability to maintain upright posture during walking against external perturbations. It is a complex process determined by a number of cross-related factors, including gait trajectory, joint impedance and neural control strategies. Here, we consider a control strategy that can achieve stable steady-state periodic gait while maintaining joint flexibility with the lowest possible joint impedance. To this end, we carried out a simulation study of a heel-toe footed biped model with hip, knee and ankle joints and a heavy head-arms-trunk element, working in the sagittal plane. For simplicity, the model assumes a periodic desired joint angle trajectory and joint torques generated by a set of feed-forward and proportional-derivative feedback controllers, whereby the joint impedance is parametrized by the feedback gains. We could show that a desired steady-state gait accompanied by the desired joint angle trajectory can be established as a stable limit cycle (LC) for the feedback controller with an appropriate set of large feedback gains. Moreover, as the feedback gains are decreased for lowering the joint stiffness, stability of the LC is lost only in a few dimensions, while leaving the remaining large number of dimensions quite stable: this means that the LC becomes saddle-type, with a low-dimensional unstable manifold and a high-dimensional stable manifold. Remarkably, the unstable manifold remains of low dimensionality even when the feedback gains are decreased far below the instability point. We then developed an intermittent neural feedback controller that is activated only for short periods of time at an optimal phase of each gait stride. We characterized the robustness of this design by showing that it can better stabilize the unstable LC with small feedback gains, leading to a flexible gait, and in particular we demonstrated that such an intermittent controller performs better if it drives the state point to the stable manifold, rather than directly to the LC. The proposed intermittent control strategy might have a high affinity for the inverted pendulum analogy of biped gait, providing a dynamic view of how the step-to-step transition from one pendular stance to the next can be achieved stably in a robust manner by a well-timed neural intervention that exploits the stable modes embedded in the unstable dynamics.

Climate-mediated nitrogen and carbon dynamics in a tropical watershed

NASA Astrophysics Data System (ADS)

Ballantyne, A. P.; Baker, P. A.; Fritz, S. C.; Poulter, B.

2011-06-01

Climate variability affects the capacity of the biosphere to assimilate and store important elements, such as nitrogen and carbon. Here we present biogeochemical evidence from the sediments of tropical Lake Titicaca indicating that large hydrologic changes in response to global glacial cycles during the Quaternary were accompanied by major shifts in ecosystem state. During prolonged glacial intervals, lake level was high and the lake was in a stable nitrogen-limited state. In contrast, during warm dry interglacials lake level fell and rates of nitrogen concentrations increased by a factor of 4-12, resulting in a fivefold to 24-fold increase in organic carbon concentrations in the sediments due to increased primary productivity. Observed periods of increased primary productivity were also associated with an apparent increase in denitrification. However, the net accumulation of nitrogen during interglacial intervals indicates that increased nitrogen supply exceeded nitrogen losses due to denitrification, thereby causing increases in primary productivity. Although primary productivity in tropical ecosystems, especially freshwater ecosystems, tends to be nitrogen limited, our results indicate that climate variability may lead to changes in nitrogen availability and thus changes in primary productivity. Therefore some tropical ecosystems may shift between a stable state of nitrogen limitation and a stable state of nitrogen saturation in response to varying climatic conditions.

Systematic Effect for an Ultralong Cycle Lithium-Sulfur Battery.

PubMed

Wu, Feng; Ye, Yusheng; Chen, Renjie; Qian, Ji; Zhao, Teng; Li, Li; Li, Wenhui

2015-11-11

Rechargeable lithium-sulfur (Li-S) batteries are attractive candidates for energy storage devices because they have five times the theoretical energy storage of state-of-the-art Li-ion batteries. The main problems plaguing Li-S batteries are poor cycle life and limited rate capability, caused by the insulating nature of S and the shuttle effect associated with the dissolution of intermediate lithium polysulfides. Here, we report the use of biocell-inspired polydopamine (PD) as a coating agent on both the cathode and separator to address these problems (the "systematic effects"). The PD-modified cathode and separator play key roles in facilitating ion diffusion and keeping the cathode structure stable, leading to uniform lithium deposition and a solid electrolyte interphase. As a result, an ultralong cycle performance of more than 3000 cycles, with a capacity fade of only 0.018% per cycle, was achieved at 2 C. It is believed that the systematic modification of the cathode and separator for Li-S batteries is a new strategy for practical applications.

Eliminating Voltage Decay of Lithium-Rich Li 1.14Mn 0.54Ni 0.14Co 0.14O 2 Cathodes by Controlling the Electrochemical Process

DOE PAGES

Wei, Z.; Zhu, Y.; Zhang, W.; ...

2015-03-27

Lithium-rich material owns a particularly high capacity owing to the activation of electrochemical inactive Li 2MnO 3 phase. But at the same time, MnO 2 phase formed after Li 2MnO 3 activation confronts a severe problem of converting to spinel phase, and resulting in voltage decay. To our knowledge, this phenomenon is inherent property of layered manganese oxide materials and can hardly be overcome. Based on this, unlike previous reports, herein we design a method for the first time to accelerate the phase transformation by tuning the charge upper-limit voltage at a high value, so the phase transformation process canmore » be finished in a few cycles. Then material structure remains stable while cycling at a low upper-limit voltage. By this novel method voltage decay is eliminated significantly.« less

Image registration and analysis for quantitative myocardial perfusion: application to dynamic circular cardiac CT.

PubMed

Isola, A A; Schmitt, H; van Stevendaal, U; Begemann, P G; Coulon, P; Boussel, L; Grass, M

2011-09-21

Large area detector computed tomography systems with fast rotating gantries enable volumetric dynamic cardiac perfusion studies. Prospectively, ECG-triggered acquisitions limit the data acquisition to a predefined cardiac phase and thereby reduce x-ray dose and limit motion artefacts. Even in the case of highly accurate prospective triggering and stable heart rate, spatial misalignment of the cardiac volumes acquired and reconstructed per cardiac cycle may occur due to small motion pattern variations from cycle to cycle. These misalignments reduce the accuracy of the quantitative analysis of myocardial perfusion parameters on a per voxel basis. An image-based solution to this problem is elastic 3D image registration of dynamic volume sequences with variable contrast, as it is introduced in this contribution. After circular cone-beam CT reconstruction of cardiac volumes covering large areas of the myocardial tissue, the complete series is aligned with respect to a chosen reference volume. The results of the registration process and the perfusion analysis with and without registration are evaluated quantitatively in this paper. The spatial alignment leads to improved quantification of myocardial perfusion for three different pig data sets.

Delay-induced patterns in a two-dimensional lattice of coupled oscillators

PubMed Central

Kantner, Markus; Schöll, Eckehard; Yanchuk, Serhiy

2015-01-01

We show how a variety of stable spatio-temporal periodic patterns can be created in 2D-lattices of coupled oscillators with non-homogeneous coupling delays. The results are illustrated using the FitzHugh-Nagumo coupled neurons as well as coupled limit cycle (Stuart-Landau) oscillators. A “hybrid dispersion relation” is introduced, which describes the stability of the patterns in spatially extended systems with large time-delay. PMID:25687789

[Generalization of the Lotka-Volterra equation].

PubMed

Nazarenko, V G

1976-01-01

A complete qualitative study of Lotka--Volterra model with cooperative interactions in the system predator-prey is carried out. The model is as follows: (see abstract). The character of all possible stationary states is investigated in the first quadrant of the phase plane of the model variables depending on the system parameters. It is shown that for the generalized model considered unstable and stable limit cycles only of the infinite amplitude are possible in the first quadrant.

Seasonally Varying Predation Behavior and Climate Shifts Are Predicted to Affect Predator-Prey Cycles.

PubMed

Tyson, Rebecca; Lutscher, Frithjof

2016-11-01

The functional response of some predator species changes from a pattern characteristic for a generalist to that for a specialist according to seasonally varying prey availability. Current theory does not address the dynamic consequences of this phenomenon. Since season length correlates strongly with altitude and latitude and is predicted to change under future climate scenarios, including this phenomenon in theoretical models seems essential for correct prediction of future ecosystem dynamics. We develop and analyze a two-season model for the great horned owl (Bubo virginialis) and snowshoe hare (Lepus americanus). These species form a predator-prey system in which the generalist to specialist shift in predation pattern has been documented empirically. We study the qualitative behavior of this predator-prey model community as summer season length changes. We find that relatively small changes in summer season length can have a profound impact on the system. In particular, when the predator has sufficient alternative resources available during the summer season, it can drive the prey to extinction, there can be coexisting stable states, and there can be stable large-amplitude limit cycles coexisting with a stable steady state. Our results illustrate that the impacts of global change on local ecosystems can be driven by internal system dynamics and can potentially have catastrophic consequences.

SAMHD1 controls cell cycle status, apoptosis and HIV-1 infection in monocytic THP-1 cells

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

Bonifati, Serena; Daly, Michele B.; St Gelais, Corine

SAMHD1 limits HIV-1 infection in non-dividing myeloid cells by decreasing intracellular dNTP pools. HIV-1 restriction by SAMHD1 in these cells likely prevents activation of antiviral immune responses and modulates viral pathogenesis, thus highlighting a critical role of SAMHD1 in HIV-1 physiopathology. Here, we explored the function of SAMHD1 in regulating cell proliferation, cell cycle progression and apoptosis in monocytic THP-1 cells. Using the CRISPR/Cas9 technology, we generated THP-1 cells with stable SAMHD1 knockout. We found that silencing of SAMHD1 in cycling cells stimulates cell proliferation, redistributes cell cycle population in the G{sub 1}/G{sub 0} phase and reduces apoptosis. These alterationsmore » correlated with increased dNTP levels and more efficient HIV-1 infection in dividing SAMHD1 knockout cells relative to control. Our results suggest that SAMHD1, through its dNTPase activity, affects cell proliferation, cell cycle distribution and apoptosis, and emphasize a key role of SAMHD1 in the interplay between cell cycle regulation and HIV-1 infection.« less

Electrogram fractionation in murine HL-1 atrial monolayer model.

PubMed

Umapathy, Karthikeyan; Masse, Stephane; Kolodziejska, Karolina; Veenhuyzen, George D; Chauhan, Vijay S; Husain, Mansoor; Farid, Talha; Downar, Eugene; Sevaptsidis, Elias; Nanthakumar, Kumaraswamy

2008-07-01

Complex fractionated atrial electrograms have been suggested as important targets for catheter ablation of atrial fibrillation. The etiology and the mechanism of these signals have not been completely elucidated because of limitations of interpretation of these signals in relation to simultaneously acquired signals in the neighboring atrial tissue. This study sought to study the origin of electrogram fractionation under the conditions of rotor formation and wave fragmentation, using atrial monolayer preparations. We performed optical mapping of 45 atrial monolayer preparations using a complementary metal oxide semiconductor (CMOS) Brainvision Ultima camera system (SciMedia-Brainvision, Tokyo, Japan). We observed stable rotors in 32 of the 45 recordings. The derived bipolar electrograms did not show complex fractionation at the core of the rotor in any of the 32 recordings. We were also able to show that 2 bipolar electrodes placed adjacent to the core of a stable rotor in a zone where there is no wave break will record electrical activity for the majority of the rotor's cycle length. In 13 of the 45 recordings, wave break or wave collision events were present. Of these, 8 of 13 recordings showed complex fractionation. In 19 of the 27, simulation of meandering rotors also showed complex fractionation. Complex fractionated electrograms can be recorded at sites of migrating rotors and wave break. No fractionation occurs at the core of a stable rotor. Electrograms that span the rotor cycle length and alternate between 2 bipoles that straddle the core can identify site of a stable rotor.

High Voltage Magnesium-ion Battery Enabled by Nanocluster Mg3Bi2 Alloy Anode in Noncorrosive Electrolyte.

PubMed

Tan, Yi-Hong; Yao, Wei-Tang; Zhang, Tianwen; Ma, Tao; Lu, Lei-Lei; Zhou, Fei; Yao, Hong-Bin; Yu, Shu-Hong

2018-05-03

Currently, developing high voltage (beyond 2 V) rechargeable Mg-ion batteries still remains a great challenge owing to the limit of corrosive electrolyte and low compatibility of anode material. Here we report a facile one step solid state alloying route to synthesize nanoclustered Mg 3 Bi 2 alloy as a high-performance anode to build up a 2 V Mg-ion battery using noncorrosive electrolyte. The fabricated nanoclustered Mg 3 Bi 2 anode delivers a high reversible specific capacity (360 mAh g -1 ) with excellent stability (90.7% capacity retention over 200 cycles) and high Coulombic efficiency (average 98%) at 0.1 A g -1 . The good performance is attributed to the stable nanostructures, which effectively accommodate the reversible Mg 2+ ion insertion/deinsertion without losing electric contact among clusters. Significantly, the nanoclustered Mg 3 Bi 2 anode can be coupled with high voltage cathode Prussian Blue to assemble a full cell using noncorrosive electrolyte, showing a stable cycling (88% capacity retention over 200 cycles at 0.2 A g -1 ) and good rate capability (103 mAh g -1 at 0.1 A g -1 and 58 mAh g -1 at 2 A g -1 ). The energy and power density of the as-fabricated full cell can reach up to 81 Wh kg -1 and 2850 W kg -1 , respectively, which are both the highest values among the reported Mg-ion batteries using noncorrosive electrolytes. This study demonstrates a cost-effective route to fabricate stable and high voltage rechargeable Mg-ion battery potentially for grid-scale energy storage.

Chaotic Behavior of a Generalized Sprott E Differential System

NASA Astrophysics Data System (ADS)

Oliveira, Regilene; Valls, Claudia

A chaotic system with only one equilibrium, a stable node-focus, was introduced by Wang and Chen [2012]. This system was found by adding a nonzero constant b to the Sprott E system [Sprott, 1994]. The coexistence of three types of attractors in this autonomous system was also considered by Braga and Mello [2013]. Adding a second parameter to the Sprott E differential system, we get the autonomous system ẋ = ayz + b,ẏ = x2 - y,ż = 1 - 4x, where a,b ∈ ℝ are parameters and a≠0. In this paper, we consider theoretically some global dynamical aspects of this system called here the generalized Sprott E differential system. This polynomial differential system is relevant because it is the first polynomial differential system in ℝ3 with two parameters exhibiting, besides the point attractor and chaotic attractor, coexisting stable limit cycles, demonstrating that this system is truly complicated and interesting. More precisely, we show that for b sufficiently small this system can exhibit two limit cycles emerging from the classical Hopf bifurcation at the equilibrium point p = (1/4, 1/16, 0). We also give a complete description of its dynamics on the Poincaré sphere at infinity by using the Poincaré compactification of a polynomial vector field in ℝ3, and we show that it has no first integrals in the class of Darboux functions.

Continuous model for the rock-scissors-paper game between bacteriocin producing bacteria.

PubMed

Neumann, Gunter; Schuster, Stefan

2007-06-01

In this work, important aspects of bacteriocin producing bacteria and their interplay are elucidated. Various attempts to model the resistant, producer and sensitive Escherichia coli strains in the so-called rock-scissors-paper (RSP) game had been made in the literature. The question arose whether there is a continuous model with a cyclic structure and admitting an oscillatory dynamics as observed in various experiments. The May-Leonard system admits a Hopf bifurcation, which is, however, degenerate and hence inadequate. The traditional differential equation model of the RSP-game cannot be applied either to the bacteriocin system because it involves positive interaction terms. In this paper, a plausible competitive Lotka-Volterra system model of the RSP game is presented and the dynamics generated by that model is analyzed. For the first time, a continuous, spatially homogeneous model that describes the competitive interaction between bacteriocin-producing, resistant and sensitive bacteria is established. The interaction terms have negative coefficients. In some experiments, for example, in mice cultures, migration seemed to be essential for the reinfection in the RSP cycle. Often statistical and spatial effects such as migration and mutation are regarded to be essential for periodicity. Our model gives rise to oscillatory dynamics in the RSP game without such effects. Here, a normal form description of the limit cycle and conditions for its stability are derived. The toxicity of the bacteriocin is used as a bifurcation parameter. Exact parameter ranges are obtained for which a stable (robust) limit cycle and a stable heteroclinic cycle exist in the three-species game. These parameters are in good accordance with the observed relations for the E. coli strains. The roles of growth rate and growth yield of the three strains are discussed. Numerical calculations show that the sensitive, which might be regarded as the weakest, can have the longest sojourn times.

Mechanical measurements on lithium phosphorous oxynitride coated silicon thin film electrodes for lithium-ion batteries during lithiation and delithiation

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

Al-Obeidi, Ahmed, E-mail: alobeidi@mit.edu; Thompson, Carl V., E-mail: reiner.moenig@kit.edu, E-mail: cthomp@mit.edu; Kramer, Dominik, E-mail: dominik.kramer@kit.edu

2016-08-15

The development of large stresses during lithiation and delithiation drives mechanical and chemical degradation processes (cracking and electrolyte decomposition) in thin film silicon anodes that complicate the study of normal electrochemical and mechanical processes. To reduce these effects, lithium phosphorous oxynitride (LiPON) coatings were applied to silicon thin film electrodes. Applying a LiPON coating has two purposes. First, the coating acts as a stable artificial solid electrolyte interphase. Second, it limits mechanical degradation by retaining the electrode's planar morphology during cycling. The development of stress in LiPON-coated electrodes was monitored using substrate curvature measurements. LiPON-coated electrodes displayed highly reproducible cycle-to-cyclemore » behavior, unlike uncoated electrodes which had poorer coulombic efficiency and exhibited a continual loss in stress magnitude with continued cycling due to film fracture. The improved mechanical stability of the coated silicon electrodes allowed for a better investigation of rate effects and variations of mechanical properties during electrochemical cycling.« less

A simple method to generate stable cell lines for the analysis of transient protein-protein interactions.

PubMed

Savage, Emilia Elizabeth; Wootten, Denise; Christopoulos, Arthur; Sexton, Patrick Michael; Furness, Sebastian George Barton

2013-04-01

Transient protein-protein interactions form the basis of signal transduction pathways in addition to many other biological processes. One tool for studying these interactions is bioluminescence resonance energy transfer (BRET). This technique has been widely applied to study signaling pathways, in particular those initiated by G protein-coupled receptors (GPCRs). These assays are routinely performed using transient transfection, a technique that has limitations in terms of assay cost and variability, overexpression of interacting proteins, vector uptake limited to cycling cells, and non-homogenous expression across cells within the assay. To address these issues, we developed bicistronic vectors for use with Life Technology's Gateway and flpIN systems. These vectors provide a means to generate isogenic cell lines for comparison of interacting proteins. They have the advantage of stable, single copy, isogenic, homogeneous expression with low inter-assay variation. We demonstrate their utility by assessing ligand-induced interactions between GPCRs and arrestin proteins.

Nitrogen cycle in microbial mats: completely unknown?

NASA Astrophysics Data System (ADS)

Coban, O.; Bebout, B.

2015-12-01

Microbial mats are thought to have originated around 3.7 billion years ago, most likely in the areas around submarine hydrothermal vents, which supplied a source of energy in the form of reduced chemical species from the Earth's interior. Active hydrothermal vents are also believed to exist on Jupiter's moon Europa, Saturn's moon Enceladus, and on Mars, earlier in that planet's history. Microbial mats have been an important force in the maintenance of Earth's ecosystems and the first photosynthesis was also originated there. Microbial mats are believed to exhibit most, if not all, biogeochemical processes that exist in aquatic ecosystems, due to the presence of different physiological groups of microorganisms therein. While most microbially mediated biogeochemical transformations have been shown to occur within microbial mats, the nitrogen cycle in the microbial mats has received very little study in spite of the fact that nitrogen usually limits growth in marine environments. We will present the first results in the determination of a complete nitrogen budget for a photosynthetic microbial mat. Both in situ sources and sinks of nitrogen in photosynthetic microbial mats are being measured using stable isotope techniques. Our work has a particular focus on recently described, but poorly understood, processes, e.g., anammox and dissimilatory nitrate reduction, and an emphasis on understanding the role that nitrogen cycling may play in generating biogenic nitrogen isotopic signatures and biomarker molecules. Measurements of environmental controls on nitrogen cycling should offer insight into the nature of co-evolution of these microbial communities and their planets of origin. Identifying the spatial (microscale) as well as temporal (diel and seasonal) distribution of nitrogen transformations, e.g., rates of nitrification and denitrification, within mats, particularly with respect to the distribution of photosynthetically-produced oxygen, is anticipated. The results of this research, the first results of which will be presented here, will help us to improve our understanding of the cycle of the element most responsible for limiting the production of biomass on Earth and improved an ability to use stable isotopes of nitrogen, and nitrogen containing compounds, in our search for life elsewhere.

Recyclability study on Inconel 718 and Ti-6Al-4V powders for use in electron beam melting

DOE PAGES

Nandwana, Peeyush; Peter, William H.; Lowe, Larry E.; ...

2015-10-20

In this study, powder bed based additive manufacturing technologies offer a big advantage in terms of reusability of the powders over multiple cycles that result in cost savings. However, currently there are no standards to determine the factors that govern the powder reuse times. This work presents the results from a recyclability study conducted on Inconel 718 and Ti-6Al-4V powders. It has been found that the Inconel 718 powders are chemically stable over a large number of cycles and their reuse time is limited by physical characteristics of powders such as flowability. Ti-6Al-4V, on the other hand, finds its reusemore » time governed by the oxygen pick up that occurs during and in between build cycles. The detailed results have been presented.« less

Full cycle rapid scan EPR deconvolution algorithm.

PubMed

Tseytlin, Mark

2017-08-01

Rapid scan electron paramagnetic resonance (RS EPR) is a continuous-wave (CW) method that combines narrowband excitation and broadband detection. Sinusoidal magnetic field scans that span the entire EPR spectrum cause electron spin excitations twice during the scan period. Periodic transient RS signals are digitized and time-averaged. Deconvolution of absorption spectrum from the measured full-cycle signal is an ill-posed problem that does not have a stable solution because the magnetic field passes the same EPR line twice per sinusoidal scan during up- and down-field passages. As a result, RS signals consist of two contributions that need to be separated and postprocessed individually. Deconvolution of either of the contributions is a well-posed problem that has a stable solution. The current version of the RS EPR algorithm solves the separation problem by cutting the full-scan signal into two half-period pieces. This imposes a constraint on the experiment; the EPR signal must completely decay by the end of each half-scan in order to not be truncated. The constraint limits the maximum scan frequency and, therefore, the RS signal-to-noise gain. Faster scans permit the use of higher excitation powers without saturating the spin system, translating into a higher EPR sensitivity. A stable, full-scan algorithm is described in this paper that does not require truncation of the periodic response. This algorithm utilizes the additive property of linear systems: the response to a sum of two inputs is equal the sum of responses to each of the inputs separately. Based on this property, the mathematical model for CW RS EPR can be replaced by that of a sum of two independent full-cycle pulsed field-modulated experiments. In each of these experiments, the excitation power equals to zero during either up- or down-field scan. The full-cycle algorithm permits approaching the upper theoretical scan frequency limit; the transient spin system response must decay within the scan period. Separation of the interfering up- and down-field scan responses remains a challenge for reaching the full potential of this new method. For this reason, only a factor of two increase in the scan rate was achieved, in comparison with the standard half-scan RS EPR algorithm. It is important for practical use that faster scans not necessarily increase the signal bandwidth because acceleration of the Larmor frequency driven by the changing magnetic field changes its sign after passing the inflection points on the scan. The half-scan and full-scan algorithms are compared using a LiNC-BuO spin probe of known line-shape, demonstrating that the new method produces stable solutions when RS signals do not completely decay by the end of each half-scan. Copyright © 2017 Elsevier Inc. All rights reserved.

Full cycle rapid scan EPR deconvolution algorithm

NASA Astrophysics Data System (ADS)

Tseytlin, Mark

2017-08-01

Rapid scan electron paramagnetic resonance (RS EPR) is a continuous-wave (CW) method that combines narrowband excitation and broadband detection. Sinusoidal magnetic field scans that span the entire EPR spectrum cause electron spin excitations twice during the scan period. Periodic transient RS signals are digitized and time-averaged. Deconvolution of absorption spectrum from the measured full-cycle signal is an ill-posed problem that does not have a stable solution because the magnetic field passes the same EPR line twice per sinusoidal scan during up- and down-field passages. As a result, RS signals consist of two contributions that need to be separated and postprocessed individually. Deconvolution of either of the contributions is a well-posed problem that has a stable solution. The current version of the RS EPR algorithm solves the separation problem by cutting the full-scan signal into two half-period pieces. This imposes a constraint on the experiment; the EPR signal must completely decay by the end of each half-scan in order to not be truncated. The constraint limits the maximum scan frequency and, therefore, the RS signal-to-noise gain. Faster scans permit the use of higher excitation powers without saturating the spin system, translating into a higher EPR sensitivity. A stable, full-scan algorithm is described in this paper that does not require truncation of the periodic response. This algorithm utilizes the additive property of linear systems: the response to a sum of two inputs is equal the sum of responses to each of the inputs separately. Based on this property, the mathematical model for CW RS EPR can be replaced by that of a sum of two independent full-cycle pulsed field-modulated experiments. In each of these experiments, the excitation power equals to zero during either up- or down-field scan. The full-cycle algorithm permits approaching the upper theoretical scan frequency limit; the transient spin system response must decay within the scan period. Separation of the interfering up- and down-field scan responses remains a challenge for reaching the full potential of this new method. For this reason, only a factor of two increase in the scan rate was achieved, in comparison with the standard half-scan RS EPR algorithm. It is important for practical use that faster scans not necessarily increase the signal bandwidth because acceleration of the Larmor frequency driven by the changing magnetic field changes its sign after passing the inflection points on the scan. The half-scan and full-scan algorithms are compared using a LiNC-BuO spin probe of known line-shape, demonstrating that the new method produces stable solutions when RS signals do not completely decay by the end of each half-scan.

Soil mineralogy and microbes determine forest life history strategy and carbon cycling in humid tropical forests

NASA Astrophysics Data System (ADS)

Soong, J.; Verbruggen, E.; Peñuelas, J.; Janssens, I. A.; Grau, O.

2017-12-01

Tropical forests account for over one third of global terrestrial gross primary productivity and cycle more C than any other ecosystem on Earth. However, we still lack a mechanistic understanding of how such high productivity is maintained on the old, highly weathered and phosphorus depleted soils in the tropics. We hypothesized that heterogeneity in soil texture, mineralogy and microbial community composition may be the major drivers of differences in soil C storage and P limitation across tropical forests. We sampled 12 forest sites across a 200 km transect in the humid neo-tropics of French Guiana that varied in soil texture, precipitation and mineralogy. We found that soil texture was a major driver of soil carbon stocks and forest life history strategy, where sandy forests have lower soil C stocks, slower turnover and decomposition and a more closed nutrient cycle while clayey forests have higher soil C stocks, faster turnover and a more leaky nutrient cycle (using natural abundance stable isotope evidence). We found that although the presence of Al and Fe oxides in the clayey soils occludes soil organic matter and P, a greater abundance of arbuscular mycorrhizal fungi help forests to access occluded P in clayey soils fueling higher turnover and faster decomposition rates. Evidence from a laboratory incubation of tropical soils with nutrient additions further demonstrates the de-coupling of microbial P demands from C:N limitations providing further evidence for the need to examine microbial stoichiometry to explain C cycling in the P-limited tropics. We argue that microbial community composition and physiological demands, constrained within the limitations of soil mineralogical reactivity, largely controls nutrient and C cycling in tropical forest soils. Together our observational field study and laboratory incubation provide a unique dataset to shed light on the mineralogical and microbial controls on C and nutrient cycling in tropical soils. By integrating microbial, soil, litter and forest metrics we describe how microbes, minerals and soil organic matter act as an ecosystem property driving forest dynamics via microbial and plant stoichiometric constraints.

An advanced lithium-air battery exploiting an ionic liquid-based electrolyte.

PubMed

Elia, G A; Hassoun, J; Kwak, W-J; Sun, Y-K; Scrosati, B; Mueller, F; Bresser, D; Passerini, S; Oberhumer, P; Tsiouvaras, N; Reiter, J

2014-11-12

A novel lithium-oxygen battery exploiting PYR14TFSI-LiTFSI as ionic liquid-based electrolyte medium is reported. The Li/PYR14TFSI-LiTFSI/O2 battery was fully characterized by electrochemical impedance spectroscopy, capacity-limited cycling, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The results of this extensive study demonstrate that this new Li/O2 cell is characterized by a stable electrode-electrolyte interface and a highly reversible charge-discharge cycling behavior. Most remarkably, the charge process (oxygen oxidation reaction) is characterized by a very low overvoltage, enhancing the energy efficiency to 82%, thus, addressing one of the most critical issues preventing the practical application of lithium-oxygen batteries.

Adding stable carbon isotopes improves model representation of the role of microbial communities in peatland methane cycling

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

Deng, Jia; McCalley, Carmody K.; Frolking, Steve

Climate change is expected to have significant and uncertain impacts on methane (CH 4) emissions from northern peatlands. Biogeochemical models can extrapolate site-specific CH 4 measurements to larger scales and predict responses of CH 4 emissions to environmental changes. However, these models include considerable uncertainties and limitations in representing CH4 production, consumption, and transport processes. To improve predictions of CH 4 transformations, we incorporated acetate and stable carbon (C) isotopic dynamics associated with CH 4 cycling into a biogeochemistry model, DNDC. By including these new features, DNDC explicitly simulates acetate dynamics and the relative contribution of acetotrophic and hydrogenotrophic methanogenesismore » (AM and HM) to CH 4 production, and predicts the C isotopic signature (δ 13C) in soil C pools and emitted gases. When tested against biogeochemical and microbial community observations at two sites in a zone of thawing permafrost in a subarctic peatland in Sweden, the new formulation substantially improved agreement with CH 4 production pathways and δ 13C in emitted CH 4 (δ 13C-CH 4), a measure of the integrated effects of microbial production and consumption, and of physical transport. We also investigated the sensitivity of simulated δ 13C-CH 4 to C isotopic composition of substrates and, to fractionation factors for CH4 production (α AM and α HM), CH 4 oxidation (α MO), and plant-mediated CH 4 transport (α TP). The sensitivity analysis indicated that the δ13C-CH 4 is highly sensitive to the factors associated with microbial metabolism (α AM, α HM, and α MO). The model framework simulating stable C isotopic dynamics provides a robust basis for better constraining and testing microbial mechanisms in predicting CH 4 cycling in peatlands.« less

Divergence of feeding channels within the soil food web determined by ecosystem type.

PubMed

Crotty, Felicity V; Blackshaw, Rod P; Adl, Sina M; Inger, Richard; Murray, Philip J

2014-01-01

Understanding trophic linkages within the soil food web (SFW) is hampered by its opacity, diversity, and limited niche adaptation. We need to expand our insight between the feeding guilds of fauna and not just count biodiversity. The soil fauna drive nutrient cycling and play a pivotal, but little understood role within both the carbon (C) and nitrogen (N) cycles that may be ecosystem dependent. Here, we define the structure of the SFW in two habitats (grassland and woodland) on the same soil type and test the hypothesis that land management would alter the SFW in these habitats. To do this, we census the community structure and use stable isotope analysis to establish the pathway of C and N through each trophic level within the ecosystems. Stable isotope ratios of C and N from all invertebrates were used as a proxy for trophic niche, and community-wide metrics were obtained. Our empirically derived C/N ratios differed from those previously reported, diverging from model predictions of global C and N cycling, which was unexpected. An assessment of the relative response of the different functional groups to the change from agricultural grassland to woodland was performed. This showed that abundance of herbivores, microbivores, and micropredators were stimulated, while omnivores and macropredators were inhibited in the grassland. Differences between stable isotope ratios and community-wide metrics, highlighted habitats with similar taxa had different SFWs, using different basal resources, either driven by root or litter derived resources. Overall, we conclude that plant type can act as a top-down driver of community functioning and that differing land management can impact on the whole SFW.

Adding stable carbon isotopes improves model representation of the role of microbial communities in peatland methane cycling

DOE PAGES

Deng, Jia; McCalley, Carmody K.; Frolking, Steve; ...

2017-06-13

Climate change is expected to have significant and uncertain impacts on methane (CH 4) emissions from northern peatlands. Biogeochemical models can extrapolate site-specific CH 4 measurements to larger scales and predict responses of CH 4 emissions to environmental changes. However, these models include considerable uncertainties and limitations in representing CH4 production, consumption, and transport processes. To improve predictions of CH 4 transformations, we incorporated acetate and stable carbon (C) isotopic dynamics associated with CH 4 cycling into a biogeochemistry model, DNDC. By including these new features, DNDC explicitly simulates acetate dynamics and the relative contribution of acetotrophic and hydrogenotrophic methanogenesismore » (AM and HM) to CH 4 production, and predicts the C isotopic signature (δ 13C) in soil C pools and emitted gases. When tested against biogeochemical and microbial community observations at two sites in a zone of thawing permafrost in a subarctic peatland in Sweden, the new formulation substantially improved agreement with CH 4 production pathways and δ 13C in emitted CH 4 (δ 13C-CH 4), a measure of the integrated effects of microbial production and consumption, and of physical transport. We also investigated the sensitivity of simulated δ 13C-CH 4 to C isotopic composition of substrates and, to fractionation factors for CH4 production (α AM and α HM), CH 4 oxidation (α MO), and plant-mediated CH 4 transport (α TP). The sensitivity analysis indicated that the δ13C-CH 4 is highly sensitive to the factors associated with microbial metabolism (α AM, α HM, and α MO). The model framework simulating stable C isotopic dynamics provides a robust basis for better constraining and testing microbial mechanisms in predicting CH 4 cycling in peatlands.« less

Hydrodynamic interaction of two particles in confined linear shear flow at finite Reynolds number

NASA Astrophysics Data System (ADS)

Yan, Yiguang; Morris, Jeffrey F.; Koplik, Joel

2007-11-01

We discuss the hydrodynamic interactions of two solid bodies placed in linear shear flow between parallel plane walls in a periodic geometry at finite Reynolds number. The computations are based on the lattice Boltzmann method for particulate flow, validated here by comparison to previous results for a single particle. Most of our results pertain to cylinders in two dimensions but some examples are given for spheres in three dimensions. Either one mobile and one fixed particle or else two mobile particles are studied. The motion of a mobile particle is qualitatively similar in both cases at early times, exhibiting either trajectory reversal or bypass, depending upon the initial vector separation of the pair. At longer times, if a mobile particle does not approach a periodic image of the second, its trajectory tends to a stable limit point on the symmetry axis. The effect of interactions with periodic images is to produce nonconstant asymptotic long-time trajectories. For one free particle interacting with a fixed second particle within the unit cell, the free particle may either move to a fixed point or take up a limit cycle. Pairs of mobile particles starting from symmetric initial conditions are shown to asymptotically reach either fixed points, or mirror image limit cycles within the unit cell, or to bypass one another (and periodic images) indefinitely on a streamwise periodic trajectory. The limit cycle possibility requires finite Reynolds number and arises as a consequence of streamwise periodicity when the system length is sufficiently short.

High Energy Density Li-ion Cells for EV’s Based on Novel, High Voltage Cathode Material Systems

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

Kepler, Keith D.; Slater, Michael

This Li-ion cell technology development project had three objectives: to develop advanced electrode materials and cell components to enable stable high-voltage operation; to design and demonstrate a Li-ion cell using these materials that meets the PHEV40 performance targets; and to design and demonstrate a Li-ion cell using these materials that meets the EV performance targets. The major challenge to creating stable high energy cells with long cycle life is system integration. Although materials that can give high energy cells are known, stabilizing them towards long-term cycling in the presence of other novel cell components is a major challenge. The majormore » technical barriers addressed by this work include low cathode specific energy, poor electrolyte stability during high voltage operation, and insufficient capacity retention during deep discharge for Si-containing anodes. Through the course of this project, Farasis was able to improve capacity retention of NCM materials for 4.4+ V operation, through both surface treatment and bulk-doping approaches. Other material advances include increased rate capability and of HE-NCM materials through novel synthesis approach, doubling the relative capacity at 1C over materials synthesized using standard methods. Silicon active materials proved challenging throughout the project and ultimately were the limiting factor in the energy density vs. cycle life trade off. By avoiding silicon anodes for the lower energy PHEV design, we manufactured cells with intermediate energy density and long cycle life under high voltage operation for PHEV applications. Cells with high energy density for EV applications were manufactured targeting a 300 Wh/kg design and were able to achieve > 200 cycles.« less

Polymers for new battery technologies.

NASA Astrophysics Data System (ADS)

Singh, Mohit

2009-03-01

The chemical and electrochemical reactivity of the components comprising today's lithium batteries has severely limited their lifetime and stability, and attempts to push the limits on energy density have exacerbated these stability issues. The weakest link in terms of safety and stability of Li ion systems is the organic liquid electrolyte that facilitates the Li^+ ion transport between the electrodes. The electrolyte is flammable and electrochemically unstable against the graphitic anode. It is the continuous electrochemical degradation of the electrolyte at the electrodes that leads to poor cycle life of the batteries, and in some cases runaway reactions that lead to explosions. Dry polymer electrolytes alleviate the electrochemical stability problem by offering a stable electrode-electrolyte interface. The absence of flammable liquids prevents runaway reactions. The main hurdle that has prevented dry polymer electrolytes from being commercialized is low ionic conductivity, and challenges in interfacing with the electrode materials. We demonstrate a novel approach towards addressing these challenges that renders batteries with excellent cycle lives, and thermal stability.

Complex bifurcation patterns in a discrete predator-prey model with periodic environmental modulation

NASA Astrophysics Data System (ADS)

Harikrishnan, K. P.

2018-02-01

We consider the simplest model in the family of discrete predator-prey system and introduce for the first time an environmental factor in the evolution of the system by periodically modulating the natural death rate of the predator. We show that with the introduction of environmental modulation, the bifurcation structure becomes much more complex with bubble structure and inverse period doubling bifurcation. The model also displays the peculiar phenomenon of coexistence of multiple limit cycles in the domain of attraction for a given parameter value that combine and finally gets transformed into a single strange attractor as the control parameter is increased. To identify the chaotic regime in the parameter plane of the model, we apply the recently proposed scheme based on the correlation dimension analysis. We show that the environmental modulation is more favourable for the stable coexistence of the predator and the prey as the regions of fixed point and limit cycle in the parameter plane increase at the expense of chaotic domain.

Ultrathin dendrimer-graphene oxide composite film for stable cycling lithium-sulfur batteries.

PubMed

Liu, Wen; Jiang, Jianbing; Yang, Ke R; Mi, Yingying; Kumaravadivel, Piranavan; Zhong, Yiren; Fan, Qi; Weng, Zhe; Wu, Zishan; Cha, Judy J; Zhou, Henghui; Batista, Victor S; Brudvig, Gary W; Wang, Hailiang

2017-04-04

Lithium-sulfur batteries (Li-S batteries) have attracted intense interest because of their high specific capacity and low cost, although they are still hindered by severe capacity loss upon cycling caused by the soluble lithium polysulfide intermediates. Although many structure innovations at the material and device levels have been explored for the ultimate goal of realizing long cycle life of Li-S batteries, it remains a major challenge to achieve stable cycling while avoiding energy and power density compromises caused by the introduction of significant dead weight/volume and increased electrochemical resistance. Here we introduce an ultrathin composite film consisting of naphthalimide-functionalized poly(amidoamine) dendrimers and graphene oxide nanosheets as a cycling stabilizer. Combining the dendrimer structure that can confine polysulfide intermediates chemically and physically together with the graphene oxide that renders the film robust and thin (<1% of the thickness of the active sulfur layer), the composite film is designed to enable stable cycling of sulfur cathodes without compromising the energy and power densities. Our sulfur electrodes coated with the composite film exhibit very good cycling stability, together with high sulfur content, large areal capacity, and improved power rate.

Uniform Incorporation of Flocculent Molybdenum Disulfide Nanostructure into Three-Dimensional Porous Graphene as an Anode for High-Performance Lithium Ion Batteries and Hybrid Supercapacitors.

PubMed

Zhang, Fan; Tang, Yongbing; Liu, Hui; Ji, Hongyi; Jiang, Chunlei; Zhang, Jing; Zhang, Xiaolong; Lee, Chun-Sing

2016-02-01

Hybrid supercapacitors (HSCs) with lithium-ion battery-type anodes and electric double layer capacitor-type cathodes are attracting extensive attention and under wide investigation because of their combined merits of both high power and energy density. However, the performance of most HSCs is limited by low kinetics of the battery-type anode which cannot match the fast kinetics of the capacitor-type cathode. In this study, we have synthesized a three-dimensional (3D) porous composite with uniformly incorporated MoS2 flocculent nanostructure onto 3D graphene via a facile solution-processed method as an anode for high-performance HSCs. This composite shows significantly enhanced electrochemical performance due to the synergistic effects of the conductive graphene sheets and the interconnected porous structure, which exhibits a high rate capability of 688 mAh/g even at a high current density of 8 A/g and a stable cycling performance (997 mAh/g after 700 cycles at 2 A/g). Furthermore, by using this composite as the anode for HSCs, the HSC shows a high energy density of 156 Wh/kg at 197 W/kg, which also remains at 97 Wh/kg even at a high power density of 8314 W/kg with a stable cycling life, among the best results of the reported HSCs thus far.

Coexistence of Multiple Attractors in an Active Diode Pair Based Chua’s Circuit

NASA Astrophysics Data System (ADS)

Bao, Bocheng; Wu, Huagan; Xu, Li; Chen, Mo; Hu, Wen

This paper focuses on the coexistence of multiple attractors in an active diode pair based Chua’s circuit with smooth nonlinearity. With dimensionless equations, dynamical properties, including boundness of system orbits and stability distributions of two nonzero equilibrium points, are investigated, and complex coexisting behaviors of multiple kinds of disconnected attractors of stable point attractors, limit cycles and chaotic attractors are numerically revealed. The results show that unlike the classical Chua’s circuit, the proposed circuit has two stable nonzero node-foci for the specified circuit parameters, thereby resulting in the emergence of multistability phenomenon. Based on two general impedance converters, the active diode pair based Chua’s circuit with an adjustable inductor and an adjustable capacitor is made in hardware, from which coexisting multiple attractors are conveniently captured.

Bistability induces episodic spike communication by inhibitory neurons in neuronal networks.

PubMed

Kazantsev, V B; Asatryan, S Yu

2011-09-01

Bistability is one of the important features of nonlinear dynamical systems. In neurodynamics, bistability has been found in basic Hodgkin-Huxley equations describing the cell membrane dynamics. When the neuron is clamped near its threshold, the stable rest potential may coexist with the stable limit cycle describing periodic spiking. However, this effect is often neglected in network computations where the neurons are typically reduced to threshold firing units (e.g., integrate-and-fire models). We found that the bistability may induce spike communication by inhibitory coupled neurons in the spiking network. The communication is realized in the form of episodic discharges with synchronous (correlated) spikes during the episodes. A spiking phase map is constructed to describe the synchronization and to estimate basic spike phase locking modes.

Selection of stable scFv antibodies by phage display.

PubMed

Brockmann, Eeva-Christine

2012-01-01

ScFv fragments are popular recombinant antibody formats but often suffer from limited stability. Phage display is a powerful tool in antibody engineering and applicable also for stability selection. ScFv variants with improved stability can be selected from large randomly mutated phage displayed libraries with a specific antigen after the unstable variants have been inactivated by heat or GdmCl. Irreversible scFv denaturation, which is a prerequisite for efficient selection, is achieved by combining denaturation with reduction of the intradomain disulfide bonds. Repeated selection cycles of increasing stringency result in enrichment of stabilized scFv fragments. Procedures for constructing a randomly mutated scFv library by error-prone PCR and phage display selection for enrichment of stable scFv antibodies from the library are described here.

Influence of forest disturbance on stable nitrogen isotope ratios in soil and vegetation profiles

Treesearch

Jennifer D. Knoepp; Scott R. Taylor; Lindsay R. Boring; Chelcy F. Miniat

2015-01-01

Soil and plant stable nitrogen isotope ratios (15 N) are influenced by atmospheric nitrogen (N) inputs and processes that regulate organic matter (OM) transformation and N cycling. The resulting 15N patterns may be useful for discerning ecosystem differences in N cycling. We studied two ecosystems; longleaf pine wiregrass (...

Non-equilibrium thermodynamical description of rhythmic motion patterns of active systems: a canonical-dissipative approach.

PubMed

Dotov, D G; Kim, S; Frank, T D

2015-02-01

We derive explicit expressions for the non-equilibrium thermodynamical variables of a canonical-dissipative limit cycle oscillator describing rhythmic motion patterns of active systems. These variables are statistical entropy, non-equilibrium internal energy, and non-equilibrium free energy. In particular, the expression for the non-equilibrium free energy is derived as a function of a suitable control parameter. The control parameter determines the Hopf bifurcation point of the deterministic active system and describes the effective pumping of the oscillator. In analogy to the equilibrium free energy of the Landau theory, it is shown that the non-equilibrium free energy decays as a function of the control parameter. In doing so, a similarity between certain equilibrium and non-equilibrium phase transitions is pointed out. Data from an experiment on human rhythmic movements is presented. Estimates for pumping intensity as well as the thermodynamical variables are reported. It is shown that in the experiment the non-equilibrium free energy decayed when pumping intensity was increased, which is consistent with the theory. Moreover, pumping intensities close to zero could be observed at relatively slow intended rhythmic movements. In view of the Hopf bifurcation underlying the limit cycle oscillator model, this observation suggests that the intended limit cycle movements were actually more similar to trajectories of a randomly perturbed stable focus. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Quantifying the contribution of single microbial cells to nitrogen assimilation in aquatic environments

NASA Astrophysics Data System (ADS)

Musat, N.; Kuypers, M. M. M.

2009-04-01

Nitrogen is a primary productivity-limiting nutrient in the ocean. The nitrogen limitation of productivity may be overcome by organisms capable of converting dissolved N2 into fixed nitrogen available to the ecosystem. In many oceanic regions, growth of phytoplankton is nitrogen limited because fixation of N2 cannot make up for the removal of fixed inorganic nitrogen (NH4+, NO2-, NO3-) by anaerobic microbial processes. The amount of available fixed nitrogen in the ocean can be changed by the biological processes of heterotrophic denitrification, anaerobic ammonium oxidation and nitrogen fixation. For a complete understanding of nitrogen cycling in the ocean a link between the microbial and biogeochemical processes at the single cell level and their role in global biogeochemical cycles is essential. Here we report a recently developed method, Halogen In Situ Hybridization-Secondary Ion Mass Spectroscopy (HISH-SIMS) and its potential application to study the nitrogen-cycle processes in the ocean. The method allows simultaneous phylogenetic identification and quantitation of metabolic activities of single microbial cells in the environment. It uses horseradish-peroxidase-labeled oligonucleotide probes and fluorine-containing tyramides for the identification of microorganisms in combination with stable-isotope-labeling experiments for analyzing the metabolic function of single microbial cells. HISH-SIMS was successfully used to study nitrogen assimilation and nitrogen fixation by anaerobic phototrophs in a meromictic alpine lake. The HISH-SIMS method enables studies of the ecophysiology of individual, phylogenetically identified microorganisms involved in the N-cycle and allows us to track the flow of nitrogen within microbial communities.

Evolution of the global phosphorus cycle.

PubMed

Reinhard, Christopher T; Planavsky, Noah J; Gill, Benjamin C; Ozaki, Kazumi; Robbins, Leslie J; Lyons, Timothy W; Fischer, Woodward W; Wang, Chunjiang; Cole, Devon B; Konhauser, Kurt O

2017-01-19

The macronutrient phosphorus is thought to limit primary productivity in the oceans on geological timescales. Although there has been a sustained effort to reconstruct the dynamics of the phosphorus cycle over the past 3.5 billion years, it remains uncertain whether phosphorus limitation persisted throughout Earth's history and therefore whether the phosphorus cycle has consistently modulated biospheric productivity and ocean-atmosphere oxygen levels over time. Here we present a compilation of phosphorus abundances in marine sedimentary rocks spanning the past 3.5 billion years. We find evidence for relatively low authigenic phosphorus burial in shallow marine environments until about 800 to 700 million years ago. Our interpretation of the database leads us to propose that limited marginal phosphorus burial before that time was linked to phosphorus biolimitation, resulting in elemental stoichiometries in primary producers that diverged strongly from the Redfield ratio (the atomic ratio of carbon, nitrogen and phosphorus found in phytoplankton). We place our phosphorus record in a quantitative biogeochemical model framework and find that a combination of enhanced phosphorus scavenging in anoxic, iron-rich oceans and a nutrient-based bistability in atmospheric oxygen levels could have resulted in a stable low-oxygen world. The combination of these factors may explain the protracted oxygenation of Earth's surface over the last 3.5 billion years of Earth history. However, our analysis also suggests that a fundamental shift in the phosphorus cycle may have occurred during the late Proterozoic eon (between 800 and 635 million years ago), coincident with a previously inferred shift in marine redox states, severe perturbations to Earth's climate system, and the emergence of animals.

The Electrochemical Performance of Silicon Nanoparticles in Concentrated Electrolyte.

PubMed

Chang, Zeng-Hua; Wang, Jian-Tao; Wu, Zhao-Hui; Gao, Min; Wu, Shuai-Jin; Lu, Shi-Gang

2018-06-11

Silicon is a promising material for anodes in energy-storage devices. However, excessive growth of a solid-electrolyte interphase (SEI) caused by the severe volume change during the (de)lithiation processes leads to dramatic capacity fading. Here, we report a super-concentrated electrolyte composed of lithium bis(fluorosulfonyl)imide (LiFSI) and propylene carbonate (PC) with a molar ratio of 1:2 to improve the cycling performance of silicon nanoparticles (SiNPs). The SiNP electrode shows a remarkably improved cycling performance with an initial delithiation capacity of approximately 3000 mAh g -1 and a capacity of approximately 2000 mAh g -1 after 100 cycles, exhibiting about 6.8 times higher capacity than the cells with dilute electrolyte LiFSI-(PC) 8 . Raman spectra reveal that most of the PC solvent and FSI anions are complexed by Li + to form a specific solution structure like a fluid polymeric network. The reduction of FSI anions starts to play an important role owing to the increased concentration of contact ion pairs (CIPs) or aggregates (AGGs), which contribute to the formation of a more mechanically robust and chemically stable complex SEI layer. The complex SEI layer can effectively suppress the morphology evolution of silicon particles and self-limit the excessive growth, which mitigates the crack propagation of the silicon electrode and the deterioration of the kinetics. This study will provide a new direction for screening cycling-stable electrolytes for silicon-based electrodes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nonlinear dynamics of the rock-paper-scissors game with mutations.

PubMed

Toupo, Danielle F P; Strogatz, Steven H

2015-05-01

We analyze the replicator-mutator equations for the rock-paper-scissors game. Various graph-theoretic patterns of mutation are considered, ranging from a single unidirectional mutation pathway between two of the species, to global bidirectional mutation among all the species. Our main result is that the coexistence state, in which all three species exist in equilibrium, can be destabilized by arbitrarily small mutation rates. After it loses stability, the coexistence state gives birth to a stable limit cycle solution created in a supercritical Hopf bifurcation. This attracting periodic solution exists for all the mutation patterns considered, and persists arbitrarily close to the limit of zero mutation rate and a zero-sum game.

Chaotic and stable perturbed maps: 2-cycles and spatial models

NASA Astrophysics Data System (ADS)

Braverman, E.; Haroutunian, J.

2010-06-01

As the growth rate parameter increases in the Ricker, logistic and some other maps, the models exhibit an irreversible period doubling route to chaos. If a constant positive perturbation is introduced, then the Ricker model (but not the classical logistic map) experiences period doubling reversals; the break of chaos finally gives birth to a stable two-cycle. We outline the maps which demonstrate a similar behavior and also study relevant discrete spatial models where the value in each cell at the next step is defined only by the values at the cell and its nearest neighbors. The stable 2-cycle in a scalar map does not necessarily imply 2-cyclic-type behavior in each cell for the spatial generalization of the map.

Materials Compositions for Lithium Ion Batteries with Extended Thermal Stability

NASA Astrophysics Data System (ADS)

Kalaga, Kaushik

Advancements in portable electronics have generated a pronounced demand for rechargeable energy storage devices with superior capacity and reliability. Lithium ion batteries (LIBs) have evolved as the primary choice of portable power for several such applications. While multiple variations have been developed, safety concerns of commercial technologies limit them to atmospheric temperature operability. With several niche markets such as aerospace, defense and oil & gas demanding energy storage at elevated temperatures, there is a renewed interest in developing rechargeable batteries that could survive temperatures beyond 100°C. Instability of critical battery components towards extreme thermal and electrochemical conditions limit their usability at high temperatures. This study deals with developing material configurations for LIB components to stabilize them at such temperatures. Flammable organic solvent based electrolytes and low melting polymer based separators have been identified as the primary bottleneck for LIBs to survive increasing temperature. Furthermore, thermally activated degradation processes in oxide based electrodes have been identified as the reason for their limited lifetime. A quasi-solid composite comprising of room temperature ionic liquids (RTILs) and Clay was developed as an electrolyte/separator hybrid and tested to be stable up to 120°C. These composites facilitate complete reversible Li intercalation in lithium titanate (LTO) with a stable capacity of 120 mAh g-1 for several cycles of charge and discharge while simultaneously resisting severe thermal conditions. Modified phosphate based electrodes were introduced as a reliable alternative for operability at high temperatures in this study. These systems were shown to deliver stable reversible capacity for numerous charge/discharge cycles at elevated temperatures. Higher lithium intercalation potential of the developed cathode materials makes them interesting candidates for high voltage lithium batteries, which may be dubbed as the next generation devices. Architectural engineering of battery components to amplify the device performance is also discussed. 3D electrode structures developed using CVD and electrodeposition techniques demonstrated significant enhancement in performance when compared to their 2D analogues. The study has established the prospects of LIBs at high temperatures through material tuning and engineering approaches and envisage a scope for viable devices.

Powering up the future: radical polymers for battery applications.

PubMed

Janoschka, Tobias; Hager, Martin D; Schubert, Ulrich S

2012-12-18

Our society's dependency on portable electric energy, i.e., rechargeable batteries, which permit power consumption at any place and in any time, will eventually culminate in resource wars on limited commodities like lithium, cobalt, and rare earth metals. The substitution of conventional metals as means of electric charge storage by organic and polymeric materials, which may ultimately be derived from renewable resources, appears to be the only feasible way out. In this context, the novel class of organic radical batteries (ORBs) excelling in rate capability (i.e., charging speed) and cycling stability (>1000 cycles) sets new standards in battery research. This review examines stable nitroxide radical bearing polymers, their processing to battery systems, and their promising performance. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analytical Investigation of the Decrease in the Size of the Habitable Zone Due to a Limited CO2 Outgassing Rate

NASA Astrophysics Data System (ADS)

Abbot, Dorian S.

2016-08-01

The habitable zone concept is important because it focuses the scientific search for extraterrestrial life and aids the planning of future telescopes. Recent work has shown that planets near the outer edge of the habitable zone might not actually be able to stay warm and habitable if CO2 outgassing rates are not large enough to maintain high CO2 partial pressures against removal by silicate weathering. In this paper, I use simple equations for the climate and CO2 budget of a planet in the habitable zone that can capture the qualitative behavior of the system. With these equations I derive an analytical formula for an effective outer edge of the habitable zone, including limitations imposed by the CO2 outgassing rate. I then show that climate cycles between a snowball state and a warm climate are only possible beyond this limit if the weathering rate in the snowball climate is smaller than the CO2 outgassing rate (otherwise stable snowball states result). I derive an analytical solution for the climate cycles including a formula for their period in this limit. This work allows us to explore the qualitative effects of weathering processes on the effective outer edge of the habitable zone, which is important because weathering parameterizations are uncertain.

Analytical Investigation of the Decrease in the Size of the Habitable Zone due to Limited CO2 Outgassing Rate

NASA Astrophysics Data System (ADS)

Abbot, D. S.

2016-12-01

The habitable zone concept is important because it focuses the scientific search for extraterrestrial life and aids the planning of future telescopes. Recent work has shown that planets near the outer edge of the habitable zone might not actually be able to stay warm and habitable if CO2 outgassing rates are not large enough to maintain high CO2 partial pressures against removal by silicate weathering. I use simple equations for the climate and CO2 budget of a planet in the habitable zone that can capture the qualitative behavior of the system. With these equations I derive an analytical formula for an effective outer edge of the habitable zone, including limitations imposed by the CO2 outgassing rate. I then show that climate cycles between a Snowball state and a warm climate are only possible beyond this limit if the weathering rate in the Snowball climate is smaller than the CO2 outgassing rate (otherwise stable Snowball states result). I derive an analytical solution for the climate cycles including a formula for their period in this limit. This work allows us to explore the qualitative effects of weathering processes on the effective outer edge of the habitable zone, which is important because weathering parameterizations are uncertain.

A Magnesium-Activated Carbon Hybrid Capacitor

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

Yoo, HD; Shterenberg, I; Gofer, Y

2013-12-11

Prototype cells of hybrid capacitor were developed, comprising activated carbon (AC) cloth and magnesium (Mg) foil as the positive and negative electrodes, respectively. The electrolyte solution included ether solvent (TBF) and a magnesium organo-halo-aluminate complex 0.25 M Mg2Cl3+-Ph2AlCl2-. In this solution Mg can be deposited/dissolved reversibly for thousands of cycles with high reversibility (100% cycling efficiency). The main barrier for integrating porous AC electrodes with this electrolyte solution was the saturation of the pores with the large ions in the AC prior to reaching the potential limit. This is due to the existence of bulky Mg and Al based ionicmore » complexes consisting Cl, alkyl or aryl (R), and THF ligands. This problem was resolved by adding 0.5 M of lithium chloride (LiCl), thus introducing smaller ionic species to the solution. This Mg hybrid capacitor system demonstrated a stable cycle performance for many thousands of cycles with a specific capacitance of 90 Fg(-1) for the AC positive electrodes along a potential range of 2.4 V. (C) 2014 The Electrochemical Society. All rights reserved.« less

Stability and robustness analysis of cooperation cycles driven by destructive agents in finite populations

NASA Astrophysics Data System (ADS)

Requejo, Rubén J.; Camacho, Juan; Cuesta, José A.; Arenas, Alex

2012-08-01

The emergence and promotion of cooperation are two of the main issues in evolutionary game theory, as cooperation is amenable to exploitation by defectors, which take advantage of cooperative individuals at no cost, dooming them to extinction. It has been recently shown that the existence of purely destructive agents (termed jokers) acting on the common enterprises (public goods games) can induce stable limit cycles among cooperation, defection, and destruction when infinite populations are considered. These cycles allow for time lapses in which cooperators represent a relevant fraction of the population, providing a mechanism for the emergence of cooperative states in nature and human societies. Here we study analytically and through agent-based simulations the dynamics generated by jokers in finite populations for several selection rules. Cycles appear in all cases studied, thus showing that the joker dynamics generically yields a robust cyclic behavior not restricted to infinite populations. We also compute the average time in which the population consists mostly of just one strategy and compare the results with numerical simulations.

Powering Lithium-Sulfur Battery Performance by Propelling Polysulfide Redox at Sulfiphilic Hosts.

PubMed

Yuan, Zhe; Peng, Hong-Jie; Hou, Ting-Zheng; Huang, Jia-Qi; Chen, Cheng-Meng; Wang, Dai-Wei; Cheng, Xin-Bing; Wei, Fei; Zhang, Qiang

2016-01-13

Lithium-sulfur (Li-S) battery system is endowed with tremendous energy density, resulting from the complex sulfur electrochemistry involving multielectron redox reactions and phase transformations. Originated from the slow redox kinetics of polysulfide intermediates, the flood of polysulfides in the batteries during cycling induced low sulfur utilization, severe polarization, low energy efficiency, deteriorated polysulfide shuttle, and short cycling life. Herein, sulfiphilic cobalt disulfide (CoS2) was incorporated into carbon/sulfur cathodes, introducing strong interaction between lithium polysulfides and CoS2 under working conditions. The interfaces between CoS2 and electrolyte served as strong adsorption and activation sites for polar polysulfides and therefore accelerated redox reactions of polysulfides. The high polysulfide reactivity not only guaranteed effective polarization mitigation and promoted energy efficiency by 10% but also promised high discharge capacity and stable cycling performance during 2000 cycles. A slow capacity decay rate of 0.034%/cycle at 2.0 C and a high initial capacity of 1368 mAh g(-1) at 0.5 C were achieved. Since the propelling redox reaction is not limited to Li-S system, we foresee the reported strategy herein can be applied in other high-power devices through the systems with controllable redox reactions.

A stable organic-inorganic hybrid layer protected lithium metal anode for long-cycle lithium-oxygen batteries

NASA Astrophysics Data System (ADS)

Zhu, Jinhui; Yang, Jun; Zhou, Jingjing; Zhang, Tao; Li, Lei; Wang, Jiulin; Nuli, Yanna

2017-10-01

A stable organic-inorganic hybrid layer (OIHL) is direct fabricated on lithium metal surface by the interfacial reaction of lithium metal foil with 1-chlorodecane and oxygen/carbon dioxide mixed gas. This favorable OIHL is approximately 30 μm thick and consists of lithium alkyl carbonate and lithium chloride. The lithium-oxygen batteries with OIHL protected lithium metal anode exhibit longer cycle life (340 cycles) than those with bare lithium metal anode (50 cycles). This desirable performance can be ascribed to the robust OIHL which prevents the growth of lithium dendrites and the corrosion of lithium metal.

Reference intervals for orotic acid in urine, plasma and dried blood spot using hydrophilic interaction liquid chromatography-tandem mass spectrometry.

PubMed

D'Apolito, Oceania; Garofalo, Daniela; la Marca, Giancarlo; Dello Russo, Antonio; Corso, Gaetano

2012-02-01

Orotic acid (OA), a marker of hereditary orotic aciduria, is usually used for the differential diagnosis of some hyperammonemic inherited defects of urea cycle and of basic amino acid transporters. This study was aimed to establish age related reference intervals of OA in urine, and for the first time in plasma, and dried blood spot (DBS) from 229 apparently healthy subjects aged from three days to 40 years. The quantification of OA was performed by a previously implemented method, using a stable isotope dilution with 1,3-[(15)N(2)]-orotic acid and hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS). The method has proved to be sensitive and accurate for a quantitative analysis of OA also in DBS and plasma. According to previous studies, urinary OA levels (mmol/mol of creatinine) decrease significantly with age. The upper limits (as 99th %ile) were of 3.44 and 1.30 in groups aged from three days to 1 year (group 1) and from 1 year to 12 years (group 2), respectively; in teenagers (from 13 to 19 years; group 3) and adults (from 20 to 40 years; group 4) urinary levels became more stable and the upper limits were of 0.64 and 1.21, respectively. Furthermore, OA levels in DBS (μM) also resulted significantly higher in subjects of group 1 (upper limit of 0.89) than in subjects of groups 2, 3 and 4 (upper limits of 0.24, 0.21, and 0.29, respectively). OA levels in plasma (μM) were significantly lower in subjects of group 3 (upper limit of 0.30) than in subjects of groups 1, 2, and 4 (upper limits of 0.59, 0.48, and 0.77, respectively). This method was also employed for OA quantification in plasma and DBS of 17 newborns affected by urea cycle defects, resulting sensitive and specific enough to screen these disorders. Copyright © 2011 Elsevier B.V. All rights reserved.

Effect on dynamic mechanical stability and interfragmentary movement of angle-stable locking of intramedullary nails in unstable distal tibia fractures: a biomechanical study.

PubMed

Gueorguiev, Boyko; Wähnert, Dirk; Albrecht, Daniel; Ockert, Ben; Windolf, Markus; Schwieger, Karsten

2011-02-01

Unstable distal tibia fractures are challenging injuries that require surgery. Increasingly, intramedullary nails are being used. However, fracture site anatomy may cause distal-fragment stabilization and fixation problems and lead to malunion/nonunion. We studied the influence of angle-stable nail locking on fracture gap movement and other biomechanical parameters. Eight pairs of fresh human cadaver tibiae were used. The bone mineral density (BMD) was determined. All tibiae were nailed with a Synthes Expert tibial nail. Within each pair, one tibia was randomized to receive conventional locking screws; the other, angle-stable screws with sleeves. A 7-mm osteotomy was created 10 mm above the upper distal locking screw, to simulate an AO 42-A3 fracture. Biomechanical testing involved nondestructive mediolateral and anteroposterior pure bending, followed by cyclic combined axial and torsional loading to catastrophic failure. The neutral zone was determined. Fracture gap movement was monitored with 3-D motion tracking. The angle-stable locked constructs had a significantly smaller mediolateral neutral zone (mean: 0.04 degree; p=0.039) and significantly smaller fracture gap angulation (p=0.043). The number of cycles to failure did not differ significantly between the locking configurations. BMD was a significant covariate affecting the number of cycles to failure (p=0.008). However, over the first 20,000 cycles, there was no significant correlation in the angle-stable construct. Angle-stable locking of the Expert tibial nail was associated with a significant reduction in the mediolateral neutral zone and in fracture gap movement. Angle-stable fixation also reduced the influence of BMD over the first 20,000 cycles.

Angle-stable and compressed angle-stable locking for tibiotalocalcaneal arthrodesis with retrograde intramedullary nails. Biomechanical evaluation.

PubMed

Mückley, Thomas; Hoffmeier, Konrad; Klos, Kajetan; Petrovitch, Alexander; von Oldenburg, Geert; Hofmann, Gunther O

2008-03-01

Retrograde intramedullary nailing is an established procedure for tibiotalocalcaneal arthrodesis. The goal of this study was to evaluate the effects of angle-stable locking or compressed angle-stable locking on the initial stability of the nails and on the behavior of the constructs under cyclic loading conditions. Tibiotalocalcaneal arthrodesis was performed in fifteen third-generation synthetic bones and twenty-four fresh-frozen cadaver legs with use of retrograde intramedullary nailing with three different locking modes: a Stryker nail with compressed angle-stable locking, a Stryker nail with angle-stable locking, and a statically locked Biomet nail. Analyses were performed of the initial stability of the specimens (range of motion) and the laxity of the constructs (neutral zone) in dorsiflexion/plantar flexion, varus/valgus, and external rotation/internal rotation. Cyclic testing up to 100,000 cycles was also performed. The range of motion and the neutral zone in dorsiflexion/plantar flexion at specific cycle increments were determined. In both bone models, the intramedullary nails with compressed angle-stable locking and those with angle-stable locking were significantly superior, in terms of a smaller range of motion and neutral zone, to the statically locked nails. The compressed angle-stable nails were superior to the angle-stable nails only in the synthetic bone model, in external/internal rotation. Cyclic testing showed the nails with angle-stable locking and those with compressed angle-stable locking to have greater stability in both models. In the synthetic bone model, compressed angle-stable locking was significantly better than angle-stable locking; in the cadaver bone model, there was no significant difference between these two locking modes. During cyclic testing, five statically locked nails in the cadaver bone model failed, whereas one nail with angle-stable locking and one with compressed angle-stable locking failed. Regardless of the bone model, the nails with angle-stable or compressed angle-stable locking had better initial stability and better stability following cycling than did the nails with static locking.

From Genes to Protein Mechanics on a Chip

PubMed Central

Milles, Lukas F.; Verdorfer, Tobias; Pippig, Diana A.; Nash, Michael A.; Gaub, Hermann E.

2014-01-01

Single-molecule force spectroscopy enables mechanical testing of individual proteins, however low experimental throughput limits the ability to screen constructs in parallel. We describe a microfluidic platform for on-chip protein expression and measurement of single-molecule mechanical properties. We constructed microarrays of proteins covalently attached to a chip surface, and found that a single cohesin-modified cantilever that bound to the terminal dockerin-tag of each protein remained stable over thousands of pulling cycles. The ability to synthesize and mechanically probe protein libraries presents new opportunities for high-throughput mechanical phenotyping. PMID:25194847

A Control Framework for Anthropomorphic Biped Walking Based on Stabilizing Feedforward Trajectories.

PubMed

Rezazadeh, Siavash; Gregg, Robert D

2016-10-01

Although dynamic walking methods have had notable successes in control of bipedal robots in the recent years, still most of the humanoid robots rely on quasi-static Zero Moment Point controllers. This work is an attempt to design a highly stable controller for dynamic walking of a human-like model which can be used both for control of humanoid robots and prosthetic legs. The method is based on using time-based trajectories that can induce a highly stable limit cycle to the bipedal robot. The time-based nature of the controller motivates its use to entrain a model of an amputee walking, which can potentially lead to a better coordination of the interaction between the prosthesis and the human. The simulations demonstrate the stability of the controller and its robustness against external perturbations.

Silicon oxycarbide glass-graphene composite paper electrode for long-cycle lithium-ion batteries.

PubMed

David, Lamuel; Bhandavat, Romil; Barrera, Uriel; Singh, Gurpreet

2016-03-30

Silicon and graphene are promising anode materials for lithium-ion batteries because of their high theoretical capacity; however, low volumetric energy density, poor efficiency and instability in high loading electrodes limit their practical application. Here we report a large area (approximately 15 cm × 2.5 cm) self-standing anode material consisting of molecular precursor-derived silicon oxycarbide glass particles embedded in a chemically-modified reduced graphene oxide matrix. The porous reduced graphene oxide matrix serves as an effective electron conductor and current collector with a stable mechanical structure, and the amorphous silicon oxycarbide particles cycle lithium-ions with high Coulombic efficiency. The paper electrode (mass loading of 2 mg cm(-2)) delivers a charge capacity of ∼588 mAh g(-1)electrode (∼393 mAh cm(-3)electrode) at 1,020th cycle and shows no evidence of mechanical failure. Elimination of inactive ingredients such as metal current collector and polymeric binder reduces the total electrode weight and may provide the means to produce efficient lightweight batteries.

Simulations of the HDO and H2O-18 atmospheric cycles using the NASA GISS general circulation model - Sensitivity experiments for present-day conditions

NASA Technical Reports Server (NTRS)

Jouzel, Jean; Koster, R. D.; Suozzo, R. J.; Russell, G. L.; White, J. W. C.

1991-01-01

Incorporating the full geochemical cycles of stable water isotopes (HDO and H2O-18) into an atmospheric general circulation model (GCM) allows an improved understanding of global delta-D and delta-O-18 distributions and might even allow an analysis of the GCM's hydrological cycle. A detailed sensitivity analysis using the NASA/Goddard Institute for Space Studies (GISS) model II GCM is presented that examines the nature of isotope modeling. The tests indicate that delta-D and delta-O-18 values in nonpolar regions are not strongly sensitive to details in the model precipitation parameterizations. This result, while implying that isotope modeling has limited potential use in the calibration of GCM convection schemes, also suggests that certain necessarily arbitrary aspects of these schemes are adequate for many isotope studies. Deuterium excess, a second-order variable, does show some sensitivity to precipitation parameterization and thus may be more useful for GCM calibration.

Solar signals detected within neutral atmospheric and ionospheric parameters

NASA Astrophysics Data System (ADS)

Koucka Knizova, Petra; Georgieva, Katya; Mosna, Zbysek; Kozubek, Michal; Kouba, Daniel; Kirov, Boian; Potuzníkova, Katerina; Boska, Josef

2018-06-01

We have analyzed time series of solar data together with the atmospheric and ionospheric measurements for solar cycles 19 till 23 according to particular data availability. For the analyses we have used long term data with 1-day sampling. By mean of Continuous Wavelet Transform (CWT) we have found common spectral domains within solar and atmospheric and ionospheric time series. Further we have identified terms when particular pairs of signals show high coherence applying Wavelet Transform Coherence (WTC). Despite wide oscillation ranges detected in particular time series CWT spectra we found only limited domains with high coherence by mean of WTC. Wavelet Transform Coherence reveals significant high power domains with stable phase difference for periods 1 month, 2 months, 6 months, 1 year, 2 years and 3-4 years between pairs of solar data and atmospheric and ionospheric data. The occurence of the detected domains vary significantly during particular solar cycle (SC) and from cycle to the following one. It indicates the changing solar forcing and/or atmospheric sensitivity with time.

Every apple has a voice: using stable isotopes to teach about food sourcing and the water cycle

DOE PAGES

Oerter, Erik; Malone, Molly; Putman, Annie; ...

2017-01-01

Agricultural crops such as fruits take up irrigation and meteoric water and incorporate it into their tissue (fruit water) during growth, and the geographic origin of a fruit may be traced by comparing the H and O stable isotope composition ( δ 2H and δ 18O values) of fruit water to the global geospatial distribution of H and O stable isotopes in precipitation. This connection between common fruits and the global water cycle provides an access point to connect with a variety of demographic groups to educate about isotope hydrology and the water cycle. Within the context of a 1-daymore » outreach activity designed for a wide spectrum of participants (high school students, undergraduate students, high school science teachers) we developed introductory lecture materials, in-class participatory demonstrations of fruit water isotopic measurement in real time, and a computer lab exercise to couple actual fruit water isotope data with open-source online geospatial analysis software. Here, we assessed learning outcomes with pre- and post-tests tied to learning objectives, as well as participant feedback surveys. Results indicate that this outreach activity provided effective lessons on the basics of stable isotope hydrology and the water cycle. But, the computer lab exercise needs to be more specifically tailored to the abilities of each participant group. This pilot study provides a foundation for further development of outreach materials that can effectively engage a range of participant groups in learning about the water cycle and the ways in which humans modify the water cycle through agricultural activity.« less

Every apple has a voice: using stable isotopes to teach about food sourcing and the water cycle

NASA Astrophysics Data System (ADS)

Oerter, Erik; Malone, Molly; Putman, Annie; Drits-Esser, Dina; Stark, Louisa; Bowen, Gabriel

2017-07-01

Agricultural crops such as fruits take up irrigation and meteoric water and incorporate it into their tissue (fruit water) during growth, and the geographic origin of a fruit may be traced by comparing the H and O stable isotope composition (δ2H and δ18O values) of fruit water to the global geospatial distribution of H and O stable isotopes in precipitation. This connection between common fruits and the global water cycle provides an access point to connect with a variety of demographic groups to educate about isotope hydrology and the water cycle. Within the context of a 1-day outreach activity designed for a wide spectrum of participants (high school students, undergraduate students, high school science teachers) we developed introductory lecture materials, in-class participatory demonstrations of fruit water isotopic measurement in real time, and a computer lab exercise to couple actual fruit water isotope data with open-source online geospatial analysis software. We assessed learning outcomes with pre- and post-tests tied to learning objectives, as well as participant feedback surveys. Results indicate that this outreach activity provided effective lessons on the basics of stable isotope hydrology and the water cycle. However, the computer lab exercise needs to be more specifically tailored to the abilities of each participant group. This pilot study provides a foundation for further development of outreach materials that can effectively engage a range of participant groups in learning about the water cycle and the ways in which humans modify the water cycle through agricultural activity.

Every apple has a voice: using stable isotopes to teach about food sourcing and the water cycle

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

Oerter, Erik; Malone, Molly; Putman, Annie

Agricultural crops such as fruits take up irrigation and meteoric water and incorporate it into their tissue (fruit water) during growth, and the geographic origin of a fruit may be traced by comparing the H and O stable isotope composition ( δ 2H and δ 18O values) of fruit water to the global geospatial distribution of H and O stable isotopes in precipitation. This connection between common fruits and the global water cycle provides an access point to connect with a variety of demographic groups to educate about isotope hydrology and the water cycle. Within the context of a 1-daymore » outreach activity designed for a wide spectrum of participants (high school students, undergraduate students, high school science teachers) we developed introductory lecture materials, in-class participatory demonstrations of fruit water isotopic measurement in real time, and a computer lab exercise to couple actual fruit water isotope data with open-source online geospatial analysis software. Here, we assessed learning outcomes with pre- and post-tests tied to learning objectives, as well as participant feedback surveys. Results indicate that this outreach activity provided effective lessons on the basics of stable isotope hydrology and the water cycle. But, the computer lab exercise needs to be more specifically tailored to the abilities of each participant group. This pilot study provides a foundation for further development of outreach materials that can effectively engage a range of participant groups in learning about the water cycle and the ways in which humans modify the water cycle through agricultural activity.« less

[The effect of the light schedule on biochemical indicators in the blood, serum and urine of heifers during their estrus cycle].

PubMed

Urbanová, J; Drybcák, J; Vĕzník, Z; Vojtísek, B; Alexa, P; Holcák, V; Kaláb, P; Pecka, F

1983-10-01

The dynamics of 38 biochemical parameters of blood, serum and urine was studied in ten heifers during their oestrous cycle in a light house (80-340 lux) and a dark small house (10-40 lux). In the light stable a significant influence (P less than 0.05) was found to be exerted on five parameters and in the dark stable nine parameters, four being influenced in the same way in both houses: haematocrit value and haemoglobin in blood and cholesterol and progesterone in serum; the relationship of progesterone content in serum to the days of oestrous cycle was particularly high in the light house. The comparison of the parameters between the groups demonstrated a significant (P less than 0.05) influence of light regime, exerted on some days of the oestrous cycle upon the levels of inorganic phosphorus, total protein and aspartate aminotransferase activity (AST) in serum and upon haematocrit, haemoglobin and ketone bodies in the blood of heifers. However, the light regime did not influence the levels of progesterone which were somewhat higher in the light house but with no statistically significant difference from the dark house. A significant difference between the groups was obtained in the levels of sodium and phosphorus in urine (P less than 0.05) between the first and tenth days of the oestrous cycle. No differences in the oestrous cycle between the heifers in the light and dark stables were recorded. Neither was the duration of heat influenced significantly; it was only less manifest in the dark stable.

The dynamics of a harvested predator-prey system with Holling type IV functional response.

PubMed

Liu, Xinxin; Huang, Qingdao

2018-05-31

The paper aims to investigate the dynamical behavior of a predator-prey system with Holling type IV functional response in which both the species are subject to capturing. We mainly consider how the harvesting affects equilibria, stability, limit cycles and bifurcations in this system. We adopt the method of qualitative and quantitative analysis, which is based on the dynamical theory, bifurcation theory and numerical simulation. The boundedness of solutions, the existence and stability of equilibrium points of the system are further studied. Based on the Sotomayor's theorem, the existence of transcritical bifurcation and saddle-node bifurcation are derived. We use the normal form theorem to analyze the Hopf bifurcation. Simulation results show that the first Lyapunov coefficient is negative and a stable limit cycle may bifurcate. Numerical simulations are performed to make analytical studies more complete. This work illustrates that using the harvesting effort as control parameter can change the behaviors of the system, which may be useful for the biological management. Copyright © 2018 Elsevier B.V. All rights reserved.

A highly resilient mesoporous SiOx lithium storage material engineered by oil-water templating.

PubMed

Park, Eunjun; Park, Min-Sik; Lee, Jaewoo; Kim, Ki Jae; Jeong, Goojin; Kim, Jung Ho; Kim, Young-Jun; Kim, Hansu

2015-02-01

Mesoporous silicon-based materials gained considerable attention as high-capacity lithium-storage materials. However, the practical use is still limited by the complexity and limited number of available synthetic routes. Here, we report carbon-coated porous SiOx as high capacity lithium storage material prepared by using a sol-gel reaction of hydrogen silsesquioxane and oil-water templating. A hydrophobic oil is employed as a pore former inside the SiOx matrix and a precursor for carbon coating on the SiOx . The anode exhibits a high capacity of 730 mAh g(-1) and outstanding cycling performance over 100 cycles without significant dimensional changes. Carbon-coated porous SiOx also showed highly stable thermal reliability comparable to that of graphite. These promising properties come from the mesopores in the SiOx matrix, which ensures reliable operation of lithium storage in SiOx . The scalable sol-gel process presented here can open up a new avenue for the versatile preparation of porous SiOx lithium storage materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced cycling performance of a Li metal anode in a dimethylsulfoxide-based electrolyte using highly concentrated lithium salt for a lithium-oxygen battery

NASA Astrophysics Data System (ADS)

Togasaki, Norihiro; Momma, Toshiyuki; Osaka, Tetsuya

2016-03-01

Stable charge-discharge cycling behavior for a lithium metal anode in a dimethylsulfoxide (DMSO)-based electrolyte is strongly desired of lithium-oxygen batteries, because the Li anode is rapidly exhausted as a result of side reactions during cycling in the DMSO solution. Herein, we report a novel electrolyte design for enhancing the cycling performance of Li anodes by using a highly concentrated DMSO-based electrolyte with a specific Li salt. Lithium nitrate (LiNO3), which forms an inorganic compound (Li2O) instead of a soluble product (Li2S) on a lithium surface, exhibits a >20% higher coulombic efficiency than lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium perchlorate, regardless of the loading current density. Moreover, the stable cycling of Li anodes in DMSO-based electrolytes depends critically on the salt concentration. The highly concentrated electrolyte 4.0 M LiNO3/DMSO displays enhanced and stable cycling performance comparable to that of carbonate-based electrolytes, which had not previously been achieved. We suppose this enhancement is due to the absence of free DMSO solvent in the electrolyte and the promotion of the desolvation of Li ions on the solid electrolyte interphase surface, both being consequences of the unique structure of the electrolyte.

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

Wei, Xiaoliang; Xu, Wu; Huang, Jinhua

Nonaqueous redox flow batteries hold the promise to achieve higher energy density ascribed to the broader voltage window than their aqueous counterparts, but their current performance is limited by low redox material concentration, poor cell efficiency, and inferior cycling stability. We report a new nonaqueous total-organic flow battery based on high concentrations of 9-fluorenone as negative and 2,5-di-tert-butyl-1-methoxy-4-[2’-methoxyethoxy]benzene as positive redox materials. The supporting electrolytes are found to greatly affect the cycling stability of flow cells through varying chemical stabilities of the charged radical species, especially the 9-fluorenone radical anions, as confirmed by electron spin resonance. Such an electrolyte optimizationmore » sheds light on mechanistic understandings of capacity fading in flow batteries employing organic radical-based redox materials and demonstrates that rational design of supporting electrolyte is vital for stable cyclability.« less

The effect of climate variations on the dynamics of pasture–livestock interactions under cooperative and noncooperative management

PubMed Central

Brekke, Kjell Arne; Øksendal, Bernt; Stenseth, Nils Chr.

2007-01-01

It is well known from Hardin's “Tragedy of the Commons” [Hardin G (1968) Science 162:1243–1248] that, if open access is allowed, overgrazing typically results. Hardin, and most authors of the subsequent literature, adopted a static view of the underlying ecosystem. Here we extend this tragedy of the commons to consider the dynamics of the involved ecosystem as well. We consider a general model that allows for a variable carrying capacity of the pastures (due to variation in precipitation) and a stimulating effect on plant growth due to grazing. Our analysis further emphasizes the tragedy; in addition to overgrazing, the ecosystem may approach limit cycles. Thus, unless the pastoralists are able to coordinate themselves, the human capability of long-term planning will generally not stabilize the system. Although numerical optimization shows that a cooperative optimum would yield a high and stable harvest, the open-access system may produce limit cycles, in which even the peak harvest may be below the stable cooperative optimal harvest. Such fluctuations cause both losses in biomass production and utility losses. Our dynamic analysis also demonstrates that, in the absence of cooperation between herders, too much rain in an otherwise dry area might (temporally) destabilize the ecological grazing system through overstocking, subsequently leading to further overgrazing (which will be observed in, but not caused by, the typically dry conditions of landscapes where pastoralism is practiced). In short, through this study we have brought time (and temporal dynamics) into the Hardin's tragedy of the commons and show that the tragedy might be profoundly worsened. PMID:17804790

The effect of climate variations on the dynamics of pasture-livestock interactions under cooperative and noncooperative management.

PubMed

Brekke, Kjell Arne; Øksendal, Bernt; Stenseth, Nils Chr

2007-09-11

It is well known from Hardin's "Tragedy of the Commons" [Hardin G (1968) Science 162:1243-1248] that, if open access is allowed, overgrazing typically results. Hardin, and most authors of the subsequent literature, adopted a static view of the underlying ecosystem. Here we extend this tragedy of the commons to consider the dynamics of the involved ecosystem as well. We consider a general model that allows for a variable carrying capacity of the pastures (due to variation in precipitation) and a stimulating effect on plant growth due to grazing. Our analysis further emphasizes the tragedy; in addition to overgrazing, the ecosystem may approach limit cycles. Thus, unless the pastoralists are able to coordinate themselves, the human capability of long-term planning will generally not stabilize the system. Although numerical optimization shows that a cooperative optimum would yield a high and stable harvest, the open-access system may produce limit cycles, in which even the peak harvest may be below the stable cooperative optimal harvest. Such fluctuations cause both losses in biomass production and utility losses. Our dynamic analysis also demonstrates that, in the absence of cooperation between herders, too much rain in an otherwise dry area might (temporally) destabilize the ecological grazing system through overstocking, subsequently leading to further overgrazing (which will be observed in, but not caused by, the typically dry conditions of landscapes where pastoralism is practiced). In short, through this study we have brought time (and temporal dynamics) into the Hardin's tragedy of the commons and show that the tragedy might be profoundly worsened.

Diversification of Nitrogen Sources in Various Tundra Vegetation Types in the High Arctic

PubMed Central

Skrzypek, Grzegorz; Wojtuń, Bronisław; Richter, Dorota; Jakubas, Dariusz; Wojczulanis-Jakubas, Katarzyna; Samecka-Cymerman, Aleksandra

2015-01-01

Low nitrogen availability in the high Arctic represents a major constraint for plant growth, which limits the tundra capacity for carbon retention and determines tundra vegetation types. The limited terrestrial nitrogen (N) pool in the tundra is augmented significantly by nesting seabirds, such as the planktivorous Little Auk (Alle alle). Therefore, N delivered by these birds may significantly influence the N cycling in the tundra locally and the carbon budget more globally. Moreover, should these birds experience substantial negative environmental pressure associated with climate change, this will adversely influence the tundra N-budget. Hence, assessment of bird-originated N-input to the tundra is important for understanding biological cycles in polar regions. This study analyzed the stable nitrogen composition of the three main N-sources in the High Arctic and in numerous plants that access different N-pools in ten tundra vegetation types in an experimental catchment in Hornsund (Svalbard). The percentage of the total tundra N-pool provided by birds, ranged from 0–21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by atmospheric N2-fixation. The stable nitrogen isotope mixing mass balance, in contrast to direct methods that measure actual deposition, indicates the ratio between the actual N-loads acquired by plants from different N-sources. Our results enhance our understanding of the importance of different N-sources in the Arctic tundra and the used methodological approach can be applied elsewhere. PMID:26376204

Diversification of Nitrogen Sources in Various Tundra Vegetation Types in the High Arctic.

PubMed

Skrzypek, Grzegorz; Wojtuń, Bronisław; Richter, Dorota; Jakubas, Dariusz; Wojczulanis-Jakubas, Katarzyna; Samecka-Cymerman, Aleksandra

2015-01-01

Low nitrogen availability in the high Arctic represents a major constraint for plant growth, which limits the tundra capacity for carbon retention and determines tundra vegetation types. The limited terrestrial nitrogen (N) pool in the tundra is augmented significantly by nesting seabirds, such as the planktivorous Little Auk (Alle alle). Therefore, N delivered by these birds may significantly influence the N cycling in the tundra locally and the carbon budget more globally. Moreover, should these birds experience substantial negative environmental pressure associated with climate change, this will adversely influence the tundra N-budget. Hence, assessment of bird-originated N-input to the tundra is important for understanding biological cycles in polar regions. This study analyzed the stable nitrogen composition of the three main N-sources in the High Arctic and in numerous plants that access different N-pools in ten tundra vegetation types in an experimental catchment in Hornsund (Svalbard). The percentage of the total tundra N-pool provided by birds, ranged from 0-21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by atmospheric N2-fixation. The stable nitrogen isotope mixing mass balance, in contrast to direct methods that measure actual deposition, indicates the ratio between the actual N-loads acquired by plants from different N-sources. Our results enhance our understanding of the importance of different N-sources in the Arctic tundra and the used methodological approach can be applied elsewhere.

Testing the limits in a greenhouse ocean: Did low nitrogen availability limit marine productivity during the end-Triassic mass extinction?

NASA Astrophysics Data System (ADS)

Schoepfer, Shane D.; Algeo, Thomas J.; Ward, Peter D.; Williford, Kenneth H.; Haggart, James W.

2016-10-01

The end-Triassic mass extinction has been characterized as a 'greenhouse extinction', related to rapid atmospheric warming and associated changes in ocean circulation and oxygenation. The response of the marine nitrogen cycle to these oceanographic changes, and the extent to which mass extinction intervals represent a deviation in nitrogen cycling from other ice-free 'greenhouse' periods of Earth history, remain poorly understood. The well-studied Kennecott Point section in Haida Gwaii, British Columbia, Canada, was deposited in the open Panthalassic Ocean, and is used here as a test case to better understand changes in the nitrogen cycle and marine productivity from the pre-crisis greenhouse of the Rhaetian to the latest-Rhaetian crisis interval. We estimated marine productivity from the late Norian to the early Hettangian using TOC- and P-based paleoproductivity transform equations, and then compared these estimates to records of sedimentary nitrogen isotopes, redox-sensitive trace elements, and biomarker data. Major negative excursions in δ15N (to ≤ 0 ‰) correspond to periods of depressed marine productivity. During these episodes, the development of a stable pycnocline below the base of the photic zone suppressed vertical mixing and limited N availability in surface waters, leading to low productivity and increased nitrogen fixation, as well as ecological stresses in the photic zone. The subsequent shoaling of euxinic waters into the ocean surface layer was fatal for most Triassic marine fauna, although the introduction of regenerated NH4+ into the photic zone may have allowed phytoplankton productivity to recover. These results indicate that the open-ocean nitrogen cycle was influenced by climatic changes during the latest Triassic, despite having existed in a greenhouse state for over 50 million years previously, and that low N availability limited marine productivity for hundreds of thousands of years during the end-Triassic crisis.

Life cycle as a stable trait in the evaluation of diversity of Nostoc from biofilms in rivers.

PubMed

Mateo, Pilar; Perona, Elvira; Berrendero, Esther; Leganés, Francisco; Martín, Marta; Golubić, Stjepko

2011-05-01

The diversity within the genus Nostoc is still controversial and more studies are needed to clarify its heterogeneity. Macroscopic species have been extensively studied and discussed; however, the microscopic forms of the genus, especially those from running waters, are poorly known and likely represented by many more species than currently described. Nostoc isolates from biofilms of two Spanish calcareous rivers were characterized comparing the morphology and life cycle in two culture media with different levels of nutrients and also comparing the 16S rRNA gene sequences. The results showed that trichome shape and cellular dimensions varied considerably depending on the culture media used, whereas the characteristics expressed in the course of the life cycle remained stable for each strain independent of the culture conditions. Molecular phylogenetic analysis confirmed the distinction between the studied strains established on morphological grounds. A balanced approach to the evaluation of diversity of Nostoc in the service of autecological studies requires both genotypic information and the evaluation of stable traits. The results of this study show that 16S rRNA gene sequence similarity serves as an important criterion for characterizing Nostoc strains and is consistent with stable attributes, such as the life cycle. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Diel CO2 cycles reduce severity of behavioural abnormalities in coral reef fish under ocean acidification.

PubMed

Jarrold, Michael D; Humphrey, Craig; McCormick, Mark I; Munday, Philip L

2017-08-31

Elevated CO 2 levels associated with ocean acidification (OA) have been shown to alter behavioural responses in coral reef fishes. However, all studies to date have used stable pCO 2 treatments, not considering the substantial diel pCO 2 variation that occurs in shallow reef habitats. Here, we reared juvenile damselfish, Acanthochromis polyacanthus, and clownfish, Amphiprion percula, at stable and diel cycling pCO 2 treatments in two experiments. As expected, absolute lateralization of A. polyacanthus and response to predator cue of Am. percula were negatively affected in fish reared at stable, elevated pCO 2 in both experiments. However, diel pCO 2 fluctuations reduced the negative effects of OA on behaviour. Importantly, in experiment two, behavioural abnormalities that were present in fish reared at stable 750 µatm CO 2 were largely absent in fish reared at 750 ± 300 µatm CO 2 . Overall, we show that diel pCO 2 cycles can substantially reduce the severity of behavioural abnormalities caused by elevated CO 2 . Thus, past studies may have over-estimated the impacts of OA on the behavioural performance of coral reef fishes. Furthermore, our results suggest that diel pCO 2 cycles will delay the onset of behavioural abnormalities in natural populations.

Evidence of Microbial Regulation of Biogeochemical Cycles from a Study on Methane Flux and Land Use Change

PubMed Central

Nazaries, Loïc; Pan, Yao; Bodrossy, Levente; Baggs, Elizabeth M.; Millard, Peter; Murrell, J. Colin

2013-01-01

Microbes play an essential role in ecosystem functions, including carrying out biogeochemical cycles, but are currently considered a black box in predictive models and all global biodiversity debates. This is due to (i) perceived temporal and spatial variations in microbial communities and (ii) lack of ecological theory explaining how microbes regulate ecosystem functions. Providing evidence of the microbial regulation of biogeochemical cycles is key for predicting ecosystem functions, including greenhouse gas fluxes, under current and future climate scenarios. Using functional measures, stable-isotope probing, and molecular methods, we show that microbial (community diversity and function) response to land use change is stable over time. We investigated the change in net methane flux and associated microbial communities due to afforestation of bog, grassland, and moorland. Afforestation resulted in the stable and consistent enhancement in sink of atmospheric methane at all sites. This change in function was linked to a niche-specific separation of microbial communities (methanotrophs). The results suggest that ecological theories developed for macroecology may explain the microbial regulation of the methane cycle. Our findings provide support for the explicit consideration of microbial data in ecosystem/climate models to improve predictions of biogeochemical cycles. PMID:23624469

Stable isotope probing to study functional components of complex microbial ecosystems.

PubMed

Mazard, Sophie; Schäfer, Hendrik

2014-01-01

This protocol presents a method of dissecting the DNA or RNA of key organisms involved in a specific biochemical process within a complex ecosystem. Stable isotope probing (SIP) allows the labelling and separation of nucleic acids from community members that are involved in important biochemical transformations, yet are often not the most numerically abundant members of a community. This pure culture-independent technique circumvents limitations of traditional microbial isolation techniques or data mining from large-scale whole-community metagenomic studies to tease out the identities and genomic repertoires of microorganisms participating in biological nutrient cycles. SIP experiments can be applied to virtually any ecosystem and biochemical pathway under investigation provided a suitable stable isotope substrate is available. This versatile methodology allows a wide range of analyses to be performed, from fatty-acid analyses, community structure and ecology studies, and targeted metagenomics involving nucleic acid sequencing. SIP experiments provide an effective alternative to large-scale whole-community metagenomic studies by specifically targeting the organisms or biochemical transformations of interest, thereby reducing the sequencing effort and time-consuming bioinformatics analyses of large datasets.

Resistive switching characteristics of solution-processed Al-Zn-Sn-O films annealed by microwave irradiation

NASA Astrophysics Data System (ADS)

Kim, Tae-Wan; Baek, Il-Jin; Cho, Won-Ju

2018-02-01

In this study, we employed microwave irradiation (MWI) at low temperature in the fabrication of solution-processed AlZnSnO (AZTO) resistive random access memory (ReRAM) devices with a structure of Ti/AZTO/Pt and compared the memory characteristics with the conventional thermal annealing (CTA) process. Typical bipolar resistance switching (BRS) behavior was observed in AZTO ReRAM devices treated with as-deposited (as-dep), CTA and MWI. In the low resistance state, the Ohmic conduction mechanism describes the dominant conduction of these devices. On the other hand, the trap-controlled space charge limited conduction (SCLC) mechanism predominates in the high resistance state. The AZTO ReRAM devices processed with MWI showed larger memory windows, uniform distribution of resistance state and operating voltage, stable DC durability (>103 cycles) and stable retention characteristics (>104 s). In addition, the AZTO ReRAM devices treated with MWI exhibited multistage storage characteristics by modulating the amplitude of the reset bias, and eight distinct resistance levels were obtained with stable retention capability.

Nitrogen doped graphene - Silver nanowire hybrids: An excellent anode material for lithium ion batteries

NASA Astrophysics Data System (ADS)

Nair, Anju K.; Elizabeth, Indu; S, Gopukumar; Thomas, Sabu; M. S, Kala; Kalarikkal, Nandakumar

2018-01-01

We present an in-situ polyol assisted synthesis approach for the preparation of silver nanowires (AgNW) over the nitrogen doped graphene (NG) sheets and has been tested as a viable LIBs anode material for the first time. The use of NG serves as nucleation sites, thereby facilitating the growth of AgNWs. The specific material design of the as-prepared NG-AgNW hybrids involves some advantages, including a continuous AgNW-graphene conducting network. Since AgNWs are electrically conductive, it provides an electrical contact with NG sheets which can effectively help the charge transport process and limit the variations in volume during the lithiation/de-lithiation processes. Apart from this, the insertion of metallic Ag nanowires into a percolated NG network increases the interlayer distance of NG sheets and prevent its restacking. Moreover, the more porous nature of the hybrid structure accommodating the large volume changes of AgNWs. As an anode material for LIBs, the NG-AgNW hybrid displays a remarkable initial discharge capacity of 1215 mAh g-1 and attains a stable capacity of 724 mAh g-1 at a current density of 100 mA g-1 after 50 cycles. The electrode exhibits a stable reversible capacity of 714, 634, 550 and 464 mA h g-1 at 0.1, 0.2, 0.5, 1 Ag-1 respectively. The reversible capacity (710 mAh g-1) at 0.1 Ag-1 is recovered after the cycling at various current densities confirming outstanding rate performance of the material. In addition, the coulombic efficiency, the NG-AgNW anode retains nearly 99% after the second cycle, further indicating its excellent reversibility. The hybrid material exhibits better cycling stability, greater rate capability, capacity retention and superior reversible capacity than that of bare AgNW and NG sheets. Our smart design will pave way for the development of efficient electrode materials for high capacity and long cycle life LIBs.

Analysis of the stability of nonlinear suspension system with slow-varying sprung mass under dual-excitation

NASA Astrophysics Data System (ADS)

Yao, Jun; Zhang, Jinqiu; Zhao, Mingmei; Li, Xin

2018-07-01

This study investigated the stability of vibration in a nonlinear suspension system with slow-varying sprung mass under dual-excitation. A mathematical model of the system was first established and then solved using the multi-scale method. Finally, the amplitude-frequency curve of vehicle vibration, the solution's stable region and time-domain curve in Hopf bifurcation were derived. The obtained results revealed that an increase in the lower excitation would reduce the system's stability while an increase in the upper excitation can make the system more stable. The slow-varying sprung mass will change the system's damping from negative to positive, leading to the appearance of limit cycle and Hopf bifurcation. As a result, the vehicle's vibration state is forced to change. The stability of this system is extremely fragile under the effect of dynamic Hopf bifurcation as well as static bifurcation.

Multistability in Chua's circuit with two stable node-foci

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

Bao, B. C.; Wang, N.; Xu, Q.

2016-04-15

Only using one-stage op-amp based negative impedance converter realization, a simplified Chua's diode with positive outer segment slope is introduced, based on which an improved Chua's circuit realization with more simpler circuit structure is designed. The improved Chua's circuit has identical mathematical model but completely different nonlinearity to the classical Chua's circuit, from which multiple attractors including coexisting point attractors, limit cycle, double-scroll chaotic attractor, or coexisting chaotic spiral attractors are numerically simulated and experimentally captured. Furthermore, with dimensionless Chua's equations, the dynamical properties of the Chua's system are studied including equilibrium and stability, phase portrait, bifurcation diagram, Lyapunov exponentmore » spectrum, and attraction basin. The results indicate that the system has two symmetric stable nonzero node-foci in global adjusting parameter regions and exhibits the unusual and striking dynamical behavior of multiple attractors with multistability.« less

Nb-doped SrTiO3 glass-ceramics as high temperature stable n-type oxide thermoelectrics

NASA Astrophysics Data System (ADS)

Lingner, Julian; Jakob, Gerhard; Letz, Martin

2012-06-01

Niobium doped SrTiO3 is known for its high potential as an oxide thermoelectric material and is one of the possible candidates for the n-type site in an oxidic thermoelectric module. The high thermal conductivity [1] and the lack of high-temperature stability of the oxygen vacancies [2] limit its properties in the ceramic systems. Glass-ceramics are intrinsic nano-structured systems and provide crystal phases densely embedded in a glass matrix which prevents the material from detoriation at high temperatures. In particular, the glass-matrix prevents an uncontrolled reoxidization as well as an uncontrolled grain growth therefore retaining the nano-structure even at high temperatures. Here, measurements and results of first glass-ceramic systems are presented, which show a low thermal conductivity due to the residue glass phase. Furthermore a stable thermal cycling up to 650 °C is demonstrated.

Every Apple has a Voice: Using Stable Isotope Hydrology to Teach about Food Sourcing and the Water Cycle

NASA Astrophysics Data System (ADS)

Oerter, E.; Malone, M.; Putman, A.; Stark, L. A.; Bowen, G. J.

2016-12-01

Agricultural crops such as fruits take up irrigation and meteoric water and incorporate it into their tissue ("fruit water") during growth, and the geographic origin of a fruit may be traced by comparing the H and O stable isotope composition (δ2H and δ18O values) of fruit water to the global geospatial distribution of H and O stable isotopes in precipitation. This connection between common fruits and the global water cycle provides an access point to connect with a variety of demographic groups to educate about isotope hydrology and the water cycle. Within the context of a one-day outreach activity designed for a wide spectrum of participants (high school students, undergraduate students, high school science teachers) we developed introductory lecture materials, in-class participatory demonstrations of fruit water isotopic measurement in real time, and a computer lab exercise to couple actual fruit water isotope data with open-source on-line geospatial analysis software. We assessed learning outcomes with pre- and post-tests tied to learning objectives, as well as participant feedback surveys. Results indicate that this outreach activity provided effective lessons on the basics of stable isotope hydrology and the water cycle. The introductory lecture and demonstration components were received, on average, uniformly well by the various participant groups. However, the computer lab exercise needs to be more specifically tailored to the abilities of each demographic group. This pilot study provides a foundation for further development of outreach materials that can effectively engage a range of participant groups in learning about the water cycle and the ways in which humans modify the water cycle through agricultural activity.

Electrodeposited Structurally Stable V2O5 Inverse Opal Networks as High Performance Thin Film Lithium Batteries.

PubMed

Armstrong, Eileen; McNulty, David; Geaney, Hugh; O'Dwyer, Colm

2015-12-09

High performance thin film lithium batteries using structurally stable electrodeposited V2O5 inverse opal (IO) networks as cathodes provide high capacity and outstanding cycling capability and also were demonstrated on transparent conducting oxide current collectors. The superior electrochemical performance of the inverse opal structures was evaluated through galvanostatic and potentiodynamic cycling, and the IO thin film battery offers increased capacity retention compared to micron-scale bulk particles from improved mechanical stability and electrical contact to stainless steel or transparent conducting current collectors from bottom-up electrodeposition growth. Li(+) is inserted into planar and IO structures at different potentials, and correlated to a preferential exposure of insertion sites of the IO network to the electrolyte. Additionally, potentiodynamic testing quantified the portion of the capacity stored as surface bound capacitive charge. Raman scattering and XRD characterization showed how the IO allows swelling into the pore volume rather than away from the current collector. V2O5 IO coin cells offer high initial capacities, but capacity fading can occur with limited electrolyte. Finally, we demonstrate that a V2O5 IO thin film battery prepared on a transparent conducting current collector with excess electrolyte exhibits high capacities (∼200 mAh g(-1)) and outstanding capacity retention and rate capability.

On Takens’ last problem: tangencies and time averages near heteroclinic networks

NASA Astrophysics Data System (ADS)

Labouriau, Isabel S.; Rodrigues, Alexandre A. P.

2017-05-01

We obtain a structurally stable family of smooth ordinary differential equations exhibiting heteroclinic tangencies for a dense subset of parameters. We use this to find vector fields C 2-close to an element of the family exhibiting a tangency, for which the set of solutions with historic behaviour contains an open set. This provides an affirmative answer to Takens’ last problem (Takens 2008 Nonlinearity 21 T33-6). A limited solution with historic behaviour is one for which the time averages do not converge as time goes to infinity. Takens’ problem asks for dynamical systems where historic behaviour occurs persistently for initial conditions in a set with positive Lebesgue measure. The family appears in the unfolding of a degenerate differential equation whose flow has an asymptotically stable heteroclinic cycle involving two-dimensional connections of non-trivial periodic solutions. We show that the degenerate problem also has historic behaviour, since for an open set of initial conditions starting near the cycle, the time averages approach the boundary of a polygon whose vertices depend on the centres of gravity of the periodic solutions and their Floquet multipliers. We illustrate our results with an explicit example where historic behaviour arises C 2-close of a \\mathbf{SO}(2) -equivariant vector field.

The origin, source, and cycling of methane in deep crystalline rock biosphere.

PubMed

Kietäväinen, Riikka; Purkamo, Lotta

2015-01-01

The emerging interest in using stable bedrock formations for industrial purposes, e.g., nuclear waste disposal, has increased the need for understanding microbiological and geochemical processes in deep crystalline rock environments, including the carbon cycle. Considering the origin and evolution of life on Earth, these environments may also serve as windows to the past. Various geological, chemical, and biological processes can influence the deep carbon cycle. Conditions of CH4 formation, available substrates and time scales can be drastically different from surface environments. This paper reviews the origin, source, and cycling of methane in deep terrestrial crystalline bedrock with an emphasis on microbiology. In addition to potential formation pathways of CH4, microbial consumption of CH4 is also discussed. Recent studies on the origin of CH4 in continental bedrock environments have shown that the traditional separation of biotic and abiotic CH4 by the isotopic composition can be misleading in substrate-limited environments, such as the deep crystalline bedrock. Despite of similarities between Precambrian continental sites in Fennoscandia, South Africa and North America, where deep methane cycling has been studied, common physicochemical properties which could explain the variation in the amount of CH4 and presence or absence of CH4 cycling microbes were not found. However, based on their preferred carbon metabolism, methanogenic microbes appeared to have similar spatial distribution among the different sites.

The origin, source, and cycling of methane in deep crystalline rock biosphere

PubMed Central

Kietäväinen, Riikka; Purkamo, Lotta

2015-01-01

The emerging interest in using stable bedrock formations for industrial purposes, e.g., nuclear waste disposal, has increased the need for understanding microbiological and geochemical processes in deep crystalline rock environments, including the carbon cycle. Considering the origin and evolution of life on Earth, these environments may also serve as windows to the past. Various geological, chemical, and biological processes can influence the deep carbon cycle. Conditions of CH4 formation, available substrates and time scales can be drastically different from surface environments. This paper reviews the origin, source, and cycling of methane in deep terrestrial crystalline bedrock with an emphasis on microbiology. In addition to potential formation pathways of CH4, microbial consumption of CH4 is also discussed. Recent studies on the origin of CH4 in continental bedrock environments have shown that the traditional separation of biotic and abiotic CH4 by the isotopic composition can be misleading in substrate-limited environments, such as the deep crystalline bedrock. Despite of similarities between Precambrian continental sites in Fennoscandia, South Africa and North America, where deep methane cycling has been studied, common physicochemical properties which could explain the variation in the amount of CH4 and presence or absence of CH4 cycling microbes were not found. However, based on their preferred carbon metabolism, methanogenic microbes appeared to have similar spatial distribution among the different sites. PMID:26236303

Coupled replicator equations for the dynamics of learning in multiagent systems

NASA Astrophysics Data System (ADS)

Sato, Yuzuru; Crutchfield, James P.

2003-01-01

Starting with a group of reinforcement-learning agents we derive coupled replicator equations that describe the dynamics of collective learning in multiagent systems. We show that, although agents model their environment in a self-interested way without sharing knowledge, a game dynamics emerges naturally through environment-mediated interactions. An application to rock-scissors-paper game interactions shows that the collective learning dynamics exhibits a diversity of competitive and cooperative behaviors. These include quasiperiodicity, stable limit cycles, intermittency, and deterministic chaos—behaviors that should be expected in heterogeneous multiagent systems described by the general replicator equations we derive.

Growth of a delta-doped silicon layer by molecular beam epitaxy on a charge-coupled device for reflection-limited ultraviolet quantum efficiency

NASA Technical Reports Server (NTRS)

Hoenk, Michael E.; Grunthaner, Paula J.; Grunthaner, Frank J.; Terhune, R. W.; Fattahi, Masoud; Tseng, Hsin-Fu

1992-01-01

Low-temperature silicon molecular beam epitaxy is used to grow a delta-doped silicon layer on a fully processed charge-coupled device (CCD). The measured quantum efficiency of the delta-doped backside-thinned CCD is in agreement with the reflection limit for light incident on the back surface in the spectral range of 260-600 nm. The 2.5 nm silicon layer, grown at 450 C, contained a boron delta-layer with surface density of about 2 x 10 exp 14/sq cm. Passivation of the surface was done by steam oxidation of a nominally undoped 1.5 nm Si cap layer. The UV quantum efficiency was found to be uniform and stable with respect to thermal cycling and illumination conditions.

Characteristics of NO cycle coupling with urea cycle in non-hyperammonemic carriers of ornithine transcarbamylase deficiency.

PubMed

Nagasaka, Hironori; Yorifuji, Tohru; Egawa, Hiroto; Inui, Ayano; Fujisawa, Tomoo; Komatsu, Haruki; Tsukahara, Hirokazu; Uemoto, Shinji; Inomata, Yukihiro

2013-07-01

Urea cycle deficient patients with prominent hyperammonemic often exhibit abnormal production of nitric oxide (NO), which reduces vascular tone, along with amino acid abnormalities. However, information related to the metabolic changes in heterozygotes of ornithine transcarbamylase deficiency (OTCD) lacking overt hyperammonemia is quite limited. We examined vascular mediators and amino acids in non-hyperammonemic heterozygotes. Twenty-four heterozygous OTCD adult females without hyperammonemic bouts, defined as non-hyperammonemic carriers, were enrolled. We measured blood amino acids constituting urea cycle and nitric oxide (NO) cycle. Blood concentrations of nitrate/nitrite (NOx) as stable NO-metabolites, asymmetric dimethylarginine (ADMA) inhibiting NO synthesis, and endothelin-1 (ET-1) raising vascular tone were also determined. NOx concentrations were significantly lower in non-hyperammonemic carriers (p < 0.01). However, ADMA and ET-1 levels in this group were comparable to those in the age-matched control group. Arginine and citrulline levels were also significantly lower in non-hyperammonemic carriers than in controls (p < 0.01). Of the 24 non-hyperammonemic carriers, 10 often developed headaches. Their daily NOx and arginine levels were significantly lower than those in headache-free carriers (p < 0.05). In three carriers receiving oral l-arginine, blood NOx concentrations were significantly higher. In two of those three, the occurrence of headaches was decreased. These results suggest that NO cycle coupling with the urea cycle is altered substantially even in non-hyperammonemic OTCD carriers, predisposing them to headaches. Copyright © 2013 Elsevier Inc. All rights reserved.

A biomimetic redox flow battery based on flavin mononucleotide

PubMed Central

Orita, Akihiro; Verde, Michael G.; Sakai, Masanori; Meng, Ying Shirley

2016-01-01

The versatility in design of redox flow batteries makes them apt to efficiently store energy in large-scale applications at low cost. The discovery of inexpensive organic electroactive materials for use in aqueous flow battery electrolytes is highly attractive, but is thus far limited. Here we report on a flow battery using an aqueous electrolyte based on the sodium salt of flavin mononucleotide. Flavins are highly versatile electroactive molecules, which catalyse a multitude of redox reactions in biological systems. We use nicotinamide (vitamin B3) as a hydrotropic agent to enhance the water solubility of flavin mononucleotide. A redox flow battery using flavin mononucleotide negative and ferrocyanide positive electrolytes in strong base shows stable cycling performance, with over 99% capacity retention over the course of 100 cycles. We hypothesize that this is enabled due to the oxidized and reduced forms of FMN-Na being stabilized by resonance structures. PMID:27767026

Design, fabrication, and performance of foil journal bearing for the brayton rotating unit

NASA Technical Reports Server (NTRS)

Licht, L.; Branger, M.

1973-01-01

Foil bearings were designed and manufactured to replace pivoted-shoe journal bearings in an existing Brayton Cycle turbo-alternator-compressor. The design of this unconventional rotor support was accomplished within the constraints and space limitations imposed by the present machine, and the substitution of foil bearings was effected without changes or modification other machine components. A housing and a test rig were constructed to incorporate the new foil-bearing support into a unified assemble with an air-driven rotor and the gimbal-mounted thrust bearing, seals, and shrouds of an actual Brayton Rotating Unit. The foil bearing required no external pressure source, and stable self-acting rotation was achieved at all speeds up to 43,200 rpm. Excellent wipe-wear characteristics of the foil bearing permitted well over 1000 start-stop cycles with no deterioriation of performance in the entire speed range.

An improved high-performance lithium-air battery.

PubMed

Jung, Hun-Gi; Hassoun, Jusef; Park, Jin-Bum; Sun, Yang-Kook; Scrosati, Bruno

2012-06-10

Although dominating the consumer electronics markets as the power source of choice for popular portable devices, the common lithium battery is not yet suited for use in sustainable electrified road transport. The development of advanced, higher-energy lithium batteries is essential in the rapid establishment of the electric car market. Owing to its exceptionally high energy potentiality, the lithium-air battery is a very appealing candidate for fulfilling this role. However, the performance of such batteries has been limited to only a few charge-discharge cycles with low rate capability. Here, by choosing a suitable stable electrolyte and appropriate cell design, we demonstrate a lithium-air battery capable of operating over many cycles with capacity and rate values as high as 5,000 mAh g(carbon)(-1) and 3 A g(carbon)(-1), respectively. For this battery we estimate an energy density value that is much higher than those offered by the currently available lithium-ion battery technology.

Understanding Voltage Decay in Lithium-Rich Manganese-Based Layered Cathode Materials by Limiting Cutoff Voltage.

PubMed

Yang, Jingsong; Xiao, Lifen; He, Wei; Fan, Jiangwei; Chen, Zhongxue; Ai, Xinping; Yang, Hanxi; Cao, Yuliang

2016-07-27

The effect of the cutoff voltages on the working voltage decay and cyclability of the lithium-rich manganese-based layered cathode (LRMO) was investigated by electrochemical measurements, electrochemical impedance spectroscopy, ex situ X-ray diffraction, transmission electron microscopy, and energy dispersive spectroscopy line scan technologies. It was found that both lower (2.0 V) and upper (4.8 V) cutoff voltages cause severe voltage decay with cycling due to formation of the spinel phase and migration of the transition metals inside the particles. Appropriate cutoff voltage between 2.8 and 4.4 V can effectively inhibit structural variation as the electrode demonstrates 92% capacity retention and indiscernible working voltage decay over 430 cycles. The results also show that phase transformation not only on high charge voltage but also on low discharge voltage should be addressed to obtain highly stable LRMO materials.

A biomimetic redox flow battery based on flavin mononucleotide

NASA Astrophysics Data System (ADS)

Orita, Akihiro; Verde, Michael G.; Sakai, Masanori; Meng, Ying Shirley

2016-10-01

The versatility in design of redox flow batteries makes them apt to efficiently store energy in large-scale applications at low cost. The discovery of inexpensive organic electroactive materials for use in aqueous flow battery electrolytes is highly attractive, but is thus far limited. Here we report on a flow battery using an aqueous electrolyte based on the sodium salt of flavin mononucleotide. Flavins are highly versatile electroactive molecules, which catalyse a multitude of redox reactions in biological systems. We use nicotinamide (vitamin B3) as a hydrotropic agent to enhance the water solubility of flavin mononucleotide. A redox flow battery using flavin mononucleotide negative and ferrocyanide positive electrolytes in strong base shows stable cycling performance, with over 99% capacity retention over the course of 100 cycles. We hypothesize that this is enabled due to the oxidized and reduced forms of FMN-Na being stabilized by resonance structures.

A biomimetic redox flow battery based on flavin mononucleotide.

PubMed

Orita, Akihiro; Verde, Michael G; Sakai, Masanori; Meng, Ying Shirley

2016-10-21

The versatility in design of redox flow batteries makes them apt to efficiently store energy in large-scale applications at low cost. The discovery of inexpensive organic electroactive materials for use in aqueous flow battery electrolytes is highly attractive, but is thus far limited. Here we report on a flow battery using an aqueous electrolyte based on the sodium salt of flavin mononucleotide. Flavins are highly versatile electroactive molecules, which catalyse a multitude of redox reactions in biological systems. We use nicotinamide (vitamin B3) as a hydrotropic agent to enhance the water solubility of flavin mononucleotide. A redox flow battery using flavin mononucleotide negative and ferrocyanide positive electrolytes in strong base shows stable cycling performance, with over 99% capacity retention over the course of 100 cycles. We hypothesize that this is enabled due to the oxidized and reduced forms of FMN-Na being stabilized by resonance structures.

Coordination Chemistry in magnesium battery electrolytes: how ligands affect their performance

DOE PAGES

Shao, Yuyan; Liu, Tianbiao L.; Li, Guosheng; ...

2013-11-04

Magnesium battery is potentially a safe, cost-effective, and high energy density technology for large scale energy storage. However, the development of magnesium battery has been hindered by the limited performance and the lack of fundamental understandings of electrolytes. Here, we present a coordination chemistry study of Mg(BH 4) 2 in ethereal solvents. The O donor denticity, i.e. ligand strength of the ethereal solvents which act as ligands to form solvated Mg complexes, plays a significant role in enhancing coulombic efficiency of the corresponding solvated Mg complex electrolytes. A new and safer electrolyte is developed based on Mg(BH4)2, diglyme and optimizedmore » LiBH4 additive. The new electrolyte demonstrates 100% coulombic efficiency, no dendrite formation, and stable cycling performance with the cathode capacity retention of ~90% for 300 cycles in a prototype magnesium battery.« less

Layered sulfur/PEDOT:PSS nano composite electrodes for lithium sulfur cell applications

NASA Astrophysics Data System (ADS)

Anilkumar, K. M.; Jinisha, B.; Manoj, M.; Pradeep, V. S.; Jayalekshmi, S.

2018-06-01

Lithium-Sulfur (Li-S) cells are emerging as the next generation energy storage devices owing to their impressive electrochemical properties with high theoretical specific capacity of 1675 mAh/g. Lack of electronic conductivity of sulfur, its volume expansion during high lithium intake and the shuttling effect due to the formation of soluble polysulfides are the main limitations, delaying the commercialization of this technology. To address these challenges, in the present work, the conducting polymer PEDOT:PSS is used as the covering matrix over the sulfur particles to improve their Li storage properties. The sulfur/PEDOT:PSS nanocomposite is synthesised using the hydrothermal process and its formation with the polymer coating over sulfur nanoparticles is established from the XRD, Raman spectroscopy, FE-SEM and TEM studies. The electrochemical studies show that the cells assembled using the sulfur/PEDOT:PSS nanocomposite as the cathode, with the components taken in the weight ratio of 9:1, offer a reversible capacity of 1191 mAh g-1 at 0.1C rate. These cells display stable electrochemical capacities over 200 cycles at gradually increasing current rates. The polymer layer facilitates electronic conduction and suppresses the polysulfide formation and the volume expansion of sulfur. A reversible capacity of 664 mAh g-1 is observed after 200 cycles at 1C rate with the capacity retention of 75 % of the initial stable capacity. The highlight of the present work is the possibility to achieve high discharge capacities at high C rates and the retention of a good percentage of the initial capacity over 200 cycles, for these Li-S cells.

Habitable planets with high obliquities

NASA Technical Reports Server (NTRS)

Williams, D. M.; Kasting, J. F.

1997-01-01

Earth's obliquity would vary chaotically from 0 degrees to 85 degrees were it not for the presence of the Moon (J. Laskar, F. Joutel, and P. Robutel, 1993, Nature 361, 615-617). The Moon itself is thought to be an accident of accretion, formed by a glancing blow from a Mars-sized planetesimal. Hence, planets with similar moons and stable obliquities may be extremely rare. This has lead Laskar and colleagues to suggest that the number of Earth-like planets with high obliquities and temperate, life-supporting climates may be small. To test this proposition, we have used an energy-balance climate model to simulate Earth's climate at obliquities up to 90 degrees. We show that Earth's climate would become regionally severe in such circumstances, with large seasonal cycles and accompanying temperature extremes on middle- and high-latitude continents which might be damaging to many forms of life. The response of other, hypothetical, Earth-like planets to large obliquity fluctuations depends on their land-sea distribution and on their position within the habitable zone (HZ) around their star. Planets with several modest-sized continents or equatorial supercontinents are more climatically stable than those with polar supercontinents. Planets farther out in the HZ are less affected by high obliquities because their atmospheres should accumulate CO2 in response to the carbonate-silicate cycle. Dense, CO2-rich atmospheres transport heat very effectively and therefore limit the magnitude of both seasonal cycles and latitudinal temperature gradients. We conclude that a significant fraction of extrasolar Earth-like planets may still be habitable, even if they are subject to large obliquity fluctuations.

Enhanced performance of graphite anode materials by AlF3 coating for lithium-ion batteries

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

Ding, Fei; Xu, Wu; Choi, Daiwon

2012-04-27

In order to form the stable surface film and to further enhance the long-term cycling stability of the graphite anodes of lithium-ion batteries, the surface of graphite powders has been modified by AlF3 coating through chemical precipitation method. The AlF3-coated graphite shows no evident changes in the bulk structure and a thin AlF3-coating layer of about 2 nm thick is found to uniformly cover the graphite particles with 2 wt% AlF3 content. However, it delivers a higher initial discharge capacity and largely improved rate performances compared to the pristine graphite. Remarkably, AlF3 coated graphite demonstrated a much better cycle life.more » After 300 cycles, AlF3 coated graphite and uncoated graphite show capacity retention of 92% and 81%, respectively. XPS measurement shows that a more conductive solid electrode interface (SEI) layer was formed on AlF3 coated graphite as compared to uncoated graphite. SEM monograph also reveals that the AlF3-coated graphite particles have a much more stable surface morphology after long-term cycling. Therefore, the improved electrochemical performance of AlF3 coated graphite can be attributed to a more stable and conductive SEI formed on coated graphite anode during cycling process.« less

Silicon oxycarbide glass-graphene composite paper electrode for long-cycle lithium-ion batteries

PubMed Central

David, Lamuel; Bhandavat, Romil; Barrera, Uriel; Singh, Gurpreet

2016-01-01

Silicon and graphene are promising anode materials for lithium-ion batteries because of their high theoretical capacity; however, low volumetric energy density, poor efficiency and instability in high loading electrodes limit their practical application. Here we report a large area (approximately 15 cm × 2.5 cm) self-standing anode material consisting of molecular precursor-derived silicon oxycarbide glass particles embedded in a chemically-modified reduced graphene oxide matrix. The porous reduced graphene oxide matrix serves as an effective electron conductor and current collector with a stable mechanical structure, and the amorphous silicon oxycarbide particles cycle lithium-ions with high Coulombic efficiency. The paper electrode (mass loading of 2 mg cm−2) delivers a charge capacity of ∼588 mAh g−1electrode (∼393 mAh cm−3electrode) at 1,020th cycle and shows no evidence of mechanical failure. Elimination of inactive ingredients such as metal current collector and polymeric binder reduces the total electrode weight and may provide the means to produce efficient lightweight batteries. PMID:27025781

High-dose ifosfamide by infusion with Mesna in advanced refractory sarcomas.

PubMed

Güllü, I; Yalçin, S; Tekuzman, G; Barişta, I; Alkiş, N; Celik, I; Zengin, N; Güler, N; Kars, A; Baltali, E

1996-01-01

Twenty patients with advanced sarcomas entered a pilot study with ifosfamide (IF) and mercaptoethane sulfonate sodium (Mesna) as a second-line treatment for six planned cycles. All patients had received prior doxorubicin- and cyclophosphamide-based chemotherapies. IF was administered at a dose of 3 g/m2 given as continuous intravenous infusion for 24 hr on day 1-5 with Mesna. In the absence of disease progression, chemotherapy was planned to be repeated every 4 weeks for six consecutive cycles. Following chemotherapy, only 2 patients (11%) achieved partial response with response durations of 6 and 9 months. There was no complete response. When considered for only high-grade tumors, the response rate reached up to 22%. Toxicity was reported for 48 cycles and the dose-limiting toxicities were myelosuppression (22%) and encephalopathy (17%). Chemotherapy protocol was changed after two or three courses in 16 patients with stable or progressive disease. IF/Mesna chemotherapy at this dose and schedule was not found to be very promising in refractory sarcomas as a second-line chemotherapy.

Phase 1/2 study of cyclin-dependent kinase (CDK)4/6 inhibitor palbociclib (PD-0332991) with bortezomib and dexamethasone in relapsed/refractory multiple myeloma.

PubMed

Niesvizky, Ruben; Badros, Ashraf Z; Costa, Luciano J; Ely, Scott A; Singhal, Seema B; Stadtmauer, Edward A; Haideri, Nisreen A; Yacoub, Abdulraheem; Hess, Georg; Lentzsch, Suzanne; Spicka, Ivan; Chanan-Khan, Asher A; Raab, Marc S; Tarantolo, Stefano; Vij, Ravi; Zonder, Jeffrey A; Huang, Xiangao; Jayabalan, David; Di Liberto, Maurizio; Huang, Xin; Jiang, Yuqiu; Kim, Sindy T; Randolph, Sophia; Chen-Kiang, Selina

2015-01-01

This phase 1/2 study was the first to evaluate the safety and efficacy of the cyclin-dependent kinase (CDK) 4/6-specific inhibitor palbociclib (PD-0332991) in sequential combination with bortezomib and dexamethasone in relapsed/refractory multiple myeloma. The recommended phase 2 dose was palbociclib 100 mg orally once daily on days 1-12 of a 21-day cycle with bortezomib 1.0 mg/m2 (intravenous) and dexamethasone 20 mg (orally 30 min pre-bortezomib dosing) on days 8 and 11 (early G1 arrest) and days 15 and 18 (cell cycle resumed). Dose-limiting toxicities were primarily cytopenias; most other treatment-related adverse events were grade≤3. At a bortezomib dose lower than that in other combination therapy studies, antitumor activity was observed (phase 1). In phase 2, objective responses were achieved in 5 (20%) patients; 11 (44%) achieved stable disease. Biomarker and pharmacodynamic assessments demonstrated that palbociclib inhibited CDK4/6 and the cell cycle initially in most patients.

Closed-Cycle, Frequency-Stable CO2 Laser Technology

NASA Technical Reports Server (NTRS)

Batten, Carmen E. (Editor); Miller, Irvin M. (Editor); Wood, George M., Jr. (Editor); Willetts, David V. (Editor)

1987-01-01

These proceedings contain a collection of papers and comments presented at a workshop on technology associated with long-duration closed-cycle operation of frequency-stable, pulsed carbon dioxide lasers. This workshop was held at the NASA Langley Research Center June 10 to 12, 1986. The workshop, jointly sponsored by the National Aeronautics and Space Administration (NASA) and the Royal Signals and Radar Establishment (RSRE), was attended by 63 engineers and scientists from the United States and the United Kingdom. During the 2 1/2 days of the workshop, a number of issues relating to obtaining frequency-stable operation and to the catalytic control of laser gas chemistry were discussed, and specific recommendations concerning future activities were drafted.

Oxidatively-Stable Linear Poly(propylenimine)-Containing Adsorbents for CO2 Capture from Ultra-Dilute Streams.

PubMed

Pang, Simon H; Lively, Ryan P; Jones, Christopher W

2018-05-29

Aminopolymer-based solid sorbents have been widely investigated for CO2 capture from dilute streams such as flue gas or ambient air. However, the oxidative stability of the most well-studied aminopolymer, poly(ethylenimine) (PEI), is limited, causing it to lose its CO2 capture capacity after exposure to oxygen at elevated temperatures. Here we demonstrate the use of linear poly(propylenimine) (PPI), synthesized via a simple cationic ring-opening polymerization, as a more oxidatively-stable alternative to PEI with high CO2 capacity and amine efficiency. The performance of linear PPI/SBA-15 composites is investigated over a range of CO2 capture conditions (CO2 partial pressure, adsorption temperature) to examine the trade-off between adsorption capacity and sorption site accessibility, which may be expected to be more limited in linear polymers relative to the prototypical hyperbranched PEI. Linear PPI/SBA-15 composites are more efficient at CO2 capture and retain 65-83% of their CO2 capacity after exposure to a harsh oxidative treatment, compared to 20-40% retention for linear PEI. Additionally, we demonstrate long-term stability of linear PPI sorbents over 50 adsorption/desorption cycles with no loss in performance. Combined with other strategies for improving oxidative stability and adsorption kinetics, linear PPI may play a role as a component of stable, solid adsorbents in commercial applications for CO2 capture. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

15N indicates an active N-cycling microbial community in low carbon, freshwater sediments.

NASA Astrophysics Data System (ADS)

Sheik, C.

2017-12-01

Earth's large lakes are unique aquatic ecosystems, but we know little of the microbial life driving sedimentary biogeochemical cycles and ultimately the isotopic record. In several of these large lakes, water column productivity is constrained by element limitation, such as phosphorus and iron, creating oligotrophic water column conditions that drive low organic matter content in sediments. Yet, these sediments are biogeochemically active and have been shown to have oxygen consumption rates akin to pelagic ocean sediments and complex sulfur cycling dynamics. Thus, large oligotrophic lakes provide unique and interesting biogeochemical contrast to highly productive freshwater and coastal marine systems. Using Lake Superior as our study site, we found microbial community structure followed patterns in bulk sediment carbon and nitrogen concentrations. These observed patterns were loosely driven by land proximity, as some stations are more coastal and have higher rates of sedimentation, allochthonous carbon inputs and productivity than pelagic sites. Interestingly, upper sediment carbon and nitrogen stable isotopes were quite different from water column. Sediment carbon and nitrogen isotopes correlated significantly with microbial community structure. However, 15N showed much stronger correlation than 13C, and became heavier with core depth. Coinciding with the increase in 15N values, we see evidence of both denitrification and anammox processes in 16S rRNA gene libraries and metagenome assembled genomes. Given that microorganisms prefer light isotopes and that these N-cycling processes both contribute to N2 production and efflux from the sediment, the increase in 15N with sediment depth suggests microbial turnover. Abundance of these genomes also varies with depth suggesting these novel microorganisms are partitioning into specific sediment geochemical zones. Additionally, several of these genomes contain genes involved in sulphur cycling, suggesting a dual biogeochemical role and potential for a cryptic sulfur cycle. Together, Lake Superior sediments offer a glimpse into microbial metabolism in carbon limited environments. Further the pervasiveness of co-metabolic pathways suggests interpretation of isotopic records may be messier than previously thought.

Bifurcation analysis of an automatic dynamic balancing mechanism for eccentric rotors

NASA Astrophysics Data System (ADS)

Green, K.; Champneys, A. R.; Lieven, N. J.

2006-04-01

We present a nonlinear bifurcation analysis of the dynamics of an automatic dynamic balancing mechanism for rotating machines. The principle of operation is to deploy two or more masses that are free to travel around a race at a fixed distance from the hub and, subsequently, balance any eccentricity in the rotor. Mathematically, we start from a Lagrangian description of the system. It is then shown how under isotropic conditions a change of coordinates into a rotating frame turns the problem into a regular autonomous dynamical system, amenable to a full nonlinear bifurcation analysis. Using numerical continuation techniques, curves are traced of steady states, limit cycles and their bifurcations as parameters are varied. These results are augmented by simulations of the system trajectories in phase space. Taking the case of a balancer with two free masses, broad trends are revealed on the existence of a stable, dynamically balanced steady-state solution for specific rotation speeds and eccentricities. However, the analysis also reveals other potentially attracting states—non-trivial steady states, limit cycles, and chaotic motion—which are not in balance. The transient effects which lead to these competing states, which in some cases coexist, are investigated.

Natural abundance N stable isotopes in plants and soils as an indicator of N deposition hotspots in urban environments

NASA Astrophysics Data System (ADS)

Trammell, T. L.

2017-12-01

The natural abundance of stable isotopes in plants and soils has been utilized to understand ecological phenomenon. Foliar δ15N is an integrator of soil δ15N, atmospheric N sources, and fractionation processes that occur during plant N uptake, plant N assimilation, and mycorrhizal associations. The amount of reactive N in the environment has greatly increased due to human activities, and urban ecosystems experience excess N deposition that can have cascading effects on plants and soils. Foliar δ15N has been shown to increase with increasing N deposition and nitrification rates suggesting increased foliar δ15N occurs with greater N inputs as a result of accelerated soil N cycling. Thus, foliar δ15N can be an indication of soil N availability for plant uptake and soil N cycling rates, since high N availability results in increased soil N cycling and subsequent loss of 14N. Limited research has utilized foliar and soil δ15N in urban forests to assess the importance of plant uptake of atmospheric N deposition and to gain insight about ecosystem processes. Previous investigations found foliar δ15N of mature trees in urban forests is not only related to elevated pollutant-derived N deposition, but also to soil N availability and soil N cycling rates. Similarly, enriched foliar δ15N of urban saplings was attributed to soil characteristics that indicated higher nitrification, thus, greater nitrate leaching and low N retention in the urban soils. These studies demonstrate the need for measuring the δ15N of various plant and soil N sources while simultaneously measuring soil N processes (e.g., net nitrification rates) in order to use natural abundance δ15N of plants and soils to assess N sources and cycling in urban forests. A conceptual framework that illustrates biogenic and anthropogenic controls on nitrogen isotope composition in urban plants and soils will be presented along with foliar and soil δ15N from urban forests across several cities as a proof of concept. Foliar and soil 15N can be extremely useful when N sources are isotopically distinct, patterns are detectable, or multiple tools are used simultaneously to understand N cycling. N cycles tightly in most ecosystems, thus δ15N in plants and soils can provide information about N source and availability to ecosystems.

Composite lithium metal anode by melt infusion of lithium into a 3D conducting scaffold with lithiophilic coating.

PubMed

Liang, Zheng; Lin, Dingchang; Zhao, Jie; Lu, Zhenda; Liu, Yayuan; Liu, Chong; Lu, Yingying; Wang, Haotian; Yan, Kai; Tao, Xinyong; Cui, Yi

2016-03-15

Lithium metal-based battery is considered one of the best energy storage systems due to its high theoretical capacity and lowest anode potential of all. However, dendritic growth and virtually relative infinity volume change during long-term cycling often lead to severe safety hazards and catastrophic failure. Here, a stable lithium-scaffold composite electrode is developed by lithium melt infusion into a 3D porous carbon matrix with "lithiophilic" coating. Lithium is uniformly entrapped on the matrix surface and in the 3D structure. The resulting composite electrode possesses a high conductive surface area and excellent structural stability upon galvanostatic cycling. We showed stable cycling of this composite electrode with small Li plating/stripping overpotential (<90 mV) at a high current density of 3 mA/cm(2) over 80 cycles.

A Novel and Rapid Method to Determine Doxycycline in Human Plasma by Liquid Chromatography Tandem Mass Spectrometry

PubMed Central

Krishna, A. Chaitanya; Sathiyaraj, M.; Saravanan, R. S.; Chelladurai, R.; Vignesh, R.

2012-01-01

A simple, rapid, specific and sensitive liquid chromatography tandem mass spectrometric method has been developed and validated for the determination of doxycycline from the human plasma. Doxycycline is extracted from human plasma by solid phase extraction. Demeclocycline was used as an internal standard. Detection was performed at transitions of 444.800→428.200 for doxycycline and 464.700→448.100 for demeclocycline using mass spectrometry. Chromatographic separation of analyte and internal standard were carried out using a reverse phase C18, column at 0.500 ml/min flow. The assay of doxycycline is linear over the range of 0.055-7.612 μg/ml, with a precision <14.83%, regression coefficient (r2)=0.9961 and the limit of quantification in plasma for doxycycline was 0.055 μg/ml. Mean extraction recovery obtained was 95.55%. Samples are stable at room temperature for 6 h, processed samples were stable at least for 30.20 h and also stable at three freeze-thaw cycles. The method has been used to perform pharmacokinetic and bioequivalence studies in human plasma. PMID:23798780

Atomic Layer Deposition of Stable LiAlF4 Lithium Ion Conductive Interfacial Layer for Stable Cathode Cycling.

PubMed

Xie, Jin; Sendek, Austin D; Cubuk, Ekin D; Zhang, Xiaokun; Lu, Zhiyi; Gong, Yongji; Wu, Tong; Shi, Feifei; Liu, Wei; Reed, Evan J; Cui, Yi

2017-07-25

Modern lithium ion batteries are often desired to operate at a wide electrochemical window to maximize energy densities. While pushing the limit of cutoff potentials allows batteries to provide greater energy densities with enhanced specific capacities and higher voltage outputs, it raises key challenges with thermodynamic and kinetic stability in the battery. This is especially true for layered lithium transition-metal oxides, where capacities can improve but stabilities are compromised as wider electrochemical windows are applied. To overcome the above-mentioned challenges, we used atomic layer deposition to develop a LiAlF 4 solid thin film with robust stability and satisfactory ion conductivity, which is superior to commonly used LiF and AlF 3 . With a predicted stable electrochemical window of approximately 2.0 ± 0.9 to 5.7 ± 0.7 V vs Li + /Li for LiAlF 4 , excellent stability was achieved for high Ni content LiNi 0.8 Mn 0.1 Co 0.1 O 2 electrodes with LiAlF 4 interfacial layer at a wide electrochemical window of 2.75-4.50 V vs Li + /Li.

Interfacial Engineered Polyaniline/Sulfur-Doped TiO2 Nanotube Arrays for Ultralong Cycle Lifetime Fiber-Shaped, Solid-State Supercapacitors.

PubMed

Li, Chun; Wang, Zhuanpei; Li, Shengwen; Cheng, Jianli; Zhang, Yanning; Zhou, Jingwen; Yang, Dan; Tong, Dong-Ge; Wang, Bin

2018-05-30

Fiber-shaped supercapacitors (FSCs) have great promises in wearable electronics applications. However, the limited specific surface area and inadequate structural stability caused by the weak interfacial interactions of the electrodes result in relatively low specific capacitance and unsatisfactory cycle lifetime. Herein, solid-state FSCs with high energy density and ultralong cycle lifetime based on polyaniline (PANI)/sulfur-doped TiO 2 nanotube arrays (PANI/S-TiO 2 ) are fabricated by interfacial engineering. The experimental results and ab initio calculations reveal that S doping can effectively promote the conductivity of titania nanotubes and increase the binding energy of PANI anchored on the electrode surface, leading to a much stronger binding of PANI on the surface of the electrode and excellent electrode structure stability. As a result, the FSCs using the PANI/S-TiO 2 electrodes deliver a high specific capacitance of 91.9 mF cm -2 , a capacitance retention of 93.78% after 12 000 charge-discharge cycles, and an areal energy density of 3.2 μW h cm -2 . Meanwhile, the all-solid-state FSC device retains its excellent flexibility and stable electrochemical capacitance even after bending 150 cycles. The enhanced performances of FSCs could be attributed to the large surface area, reduced ion diffusion path, improved electrical conductivity, and engineered interfacial interaction of the rationally designed electrodes.

Seasonal controls of the short term variability of pCO2 at the Scotian Shelf

NASA Astrophysics Data System (ADS)

Thomas, H.; Craig, S.; Greenan, B. J. W.; Burt, W.; Herndl, G. J.; Higginson, S.; Salt, L.; Shadwick, E. H.; Urrego-Blanco, J.

2012-04-01

Much of the surface ocean carbon cycle variability can be attributed to the availability of sunlight, through processes such as heat fluxes or photosynthesis, which regulate the ocean carbon cycle over a wide range of time scales. The critical processes occurring on timescales of a day or less, however, have undergone few investigations, and most of those have been limited to a time span of several days to months, or exceptionally, for longer periods. Optical methods have helped to infer short-term biological variability, however lacking corresponding investigations of oceanic CO2 system. Here, we employ high-frequency CO2 system and optical observations covering the full seasonal cycle on the Scotian Shelf, Northwestern Atlantic Ocean, in order to unravel daily periodicity of the surface ocean carbon cycle and its effects on annual budgets. We show that significant daily periodicity occurs only if the water column is sufficiently stable as observed during seasonal warming. During that time biological CO2 drawdown, or net community production (NCP), is delayed for several hours relative to the daylight cycle due the daily build-up of essential Chlorophyll a, to cell physiology and to grazing effects, all restricting or hindering photosynthesis in the early morning hours. NCP collapses in summer by more than 90%, when the mixed layer depth reaches the seasonal minimum, which eventually makes the observed daily periodicity of the CO2 system vanish.

High rate and stable cycling of lithium metal anode

DOE PAGES

Qian, Jiangfeng; Henderson, Wesley A.; Xu, Wu; ...

2015-02-20

Lithium (Li) metal is an ideal anode material for rechargeable batteries. However, dendritic Li growth and limited Coulombic efficiency (CE) during repeated Li deposition/stripping processes have prevented the application of this anode in rechargeable Li metal batteries, especially for use at high current densities. Here, we report that the use of highly concentrated electrolytes composed of ether solvents and the lithium bis(fluorosulfonyl)imide (LiFSI) salt enables the high rate cycling of a Li metal anode at high CE (up to 99.1 %) without dendrite growth. With 4 M LiFSI in 1,2-dimethoxyethane (DME) as the electrolyte, a Li|Li cell can be cycledmore » at high rates (10 mA cm -2) for more than 6000 cycles with no increase in the cell impedance, and a Cu|Li cell can be cycled at 4 mA cm-2 for more than 1000 cycles with an average CE of 98.4%. These excellent high rate performances can be attributed to the increased solvent coordination and increased availability of Li+ concentration in the electrolyte. Lastly, further development of this electrolyte may lead to practical applications for Li metal anode in rechargeable batteries. The fundamental mechanisms behind the high rate ion exchange and stability of the electrolytes also shine light on the stability of other electrochemical systems.« less

Bulk Bismuth as a High-Capacity and Ultralong Cycle-Life Anode for Sodium-Ion Batteries by Coupling with Glyme-Based Electrolytes.

PubMed

Wang, Chenchen; Wang, Liubin; Li, Fujun; Cheng, Fangyi; Chen, Jun

2017-09-01

Sodium-ion batteries (SIBs) have attracted great interest for large-scale electric energy storage in recent years. However, anodes with long cycle life and large reversible capacities are still lacking and therefore limiting the development of SIBs. Here, a bulk Bi anode with surprisingly high Na storage performance in combination with glyme-based electrolytes is reported. This study shows that the bulk Bi electrode is gradually developed into a porous integrity during initial cycling, which is totally different from that in carbonate-based electrolytes and ensures facile Na + transport and structural stability. The achievable capacity of bulk Bi in the NaPF 6 -diglyme electrolyte is high up to 400 mAh g -1 , and the capacity retention is 94.4% after 2000 cycles, corresponding to a capacity loss of 0.0028% per cycle. It exhibits two flat discharge/charge plateaus at 0.67/0.77 and 0.46/0.64 V, ascribed to the typical two-phase reactions of Bi ↔ NaBi and NaBi ↔ Na 3 Bi, respectively. The excellent performance is attributed to the unique porous integrity, stable solid electrolyte interface, and good electrode wettability of glymes. This interplay between electrolyte and electrode to boost Na storage performance will pave a new pathway for high-performance SIBs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-power parametric amplification of 11.8-fs laser pulses with carrier-envelope phase control.

PubMed

Zinkstok, R Th; Witte, S; Hogervorst, W; Eikema, K S E

2005-01-01

Phase-stable parametric chirped-pulse amplification of ultrashort pulses from a carrier-envelope phase-stabilized mode-locked Ti:sapphire oscillator (11.0 fs) to 0.25 mJ/pulse at 1 kHz is demonstrated. Compression with a grating compressor and a LCD shaper yields near-Fourier-limited 11.8-fs pulses with an energy of 0.12 mJ. The amplifier is pumped by 532-nm pulses from a synchronized mode-locked laser, Nd:YAG amplifier system. This approach is shown to be promising for the next generation of ultrafast amplifiers aimed at producing terawatt-level phase-controlled few-cycle laser pulses.

Seasonal variations in the stable carbon isotopic signature of biogenic methane in a coastal sediment

NASA Technical Reports Server (NTRS)

Martens, C. S.; Green, C. D.; Blair, N. E.; Des Marais, D. J.

1986-01-01

Systematic seasonal variations in the stable carbon isotopic signature of methane gas occur in the anoxic sediments of Cape Lookout Bight, a lagoonal basin on North Carolina's Outer Banks. Values for the carbon isotope ratio of methane range from -57.3 per mil during summer to -68.5 per mil during winter in gas bubbles with an average methane content of 95 percent. The variations are hypothesized to result from changes in the pathways of microbial methane production and cycling of key substrates including acetate and hydrogen. The use of stable isotopic signatures to investigate the global methane cycle through mass balance calculations, involving various sediment and soil biogenic sources, appears to require seasonally averaged data from individual sites.

Fabrication and lithium storage performance of sugar apple-shaped SiOx@C nanocomposite spheres

NASA Astrophysics Data System (ADS)

Li, Mingqi; Zeng, Ying; Ren, Yurong; Zeng, Chunmei; Gu, Jingwei; Feng, Xiaofang; He, Hongyan

2015-08-01

Nonstoichiometric SiOx is a kind of very attractive anode material for high-energy lithium-ion batteries because of a high specific capacity and facile synthesis. However, the poor electrical conductivity and unstable electrode structure of SiOx severely limit its electrochemical performance as anode in lithium-ion batteries. In this work, highly durable sugar apple-shaped SiOx@C nanocomposite spheres are fabricated to achieve significantly improved electrochemical performance. The composite is synthesized by homogenous one-pot synthesis, using ethyltriethoxysilanes (EtSi(OEt)3) and resorcinol/formaldehyde (RF) as starting materials. The morphology, composition and structure of the composite are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analysis (EA) and X-ray photoelectron spectroscopy (XPS). At a current density of 50 mA g-1, the sugar apple-shaped SiOx@C spheres exhibit a stable discharge capacity of about 630 mAh g-1 calculated on the total mass of both SiOx and C. At a current density of 100 mA g-1, a stable discharge capacity of about 550 mAh g-1 is obtained and the capacity has been kept up to 400 cycles. The excellent cycling performance is attributed to the homogeneous dispersion of SiOx in disordered carbon at the nanometer scale and the unique structure of the composite.

Melatonin Decreases Glucose Metabolism in Prostate Cancer Cells: A 13C Stable Isotope-Resolved Metabolomic Study.

PubMed

Hevia, David; Gonzalez-Menendez, Pedro; Fernandez-Fernandez, Mario; Cueto, Sergio; Rodriguez-Gonzalez, Pablo; Garcia-Alonso, Jose I; Mayo, Juan C; Sainz, Rosa M

2017-07-26

The pineal neuroindole melatonin exerts an exceptional variety of systemic functions. Some of them are exerted through its specific membrane receptors type 1 and type 2 (MT1 and MT2) while others are mediated by receptor-independent mechanisms. A potential transport of melatonin through facilitative glucose transporters (GLUT/ SLC2A ) was proposed in prostate cancer cells. The prostate cells have a particular metabolism that changes during tumor progression. During the first steps of carcinogenesis, oxidative phosphorylation is reactivated while the switch to the "Warburg effect" only occurs in advanced tumors and in the metastatic stage. Here, we investigated whether melatonin might change prostate cancer cell metabolism. To do so, 13 C stable isotope-resolved metabolomics in androgen sensitive LNCaP and insensitive PC-3 prostate cancer cells were employed. In addition to metabolite 13 C-labeling, ATP/AMP levels, and lactate dehydrogenase or pentose phosphate pathway activity were measured. Melatonin reduces lactate labeling in androgen-sensitive cells and it also lowers 13 C-labeling of tricarboxylic acid cycle metabolites and ATP production. In addition, melatonin reduces lactate 13 C-labeling in androgen insensitive prostate cancer cells. Results demonstrated that melatonin limits glycolysis as well as the tricarboxylic acid cycle and pentose phosphate pathway in prostate cancer cells, suggesting that the reduction of glucose uptake is a major target of the indole in this tumor type.

A novel device based on smart textile to control heart's activity during exercise.

PubMed

Romagnoli, Marco; Alis, Rafael; Guillen, Javier; Basterra, Javier; Villacastin, J P; Guillen, Sergio

2014-06-01

In recent years, several systems have been developed to control cardiac function during exercise, and some are also capable of recording RR data to provide heart rate variability (HRV) analyses. In this study we compare time between heart beats and HRV parameters obtained with a smart textile system (GOW; Weartech sl., Spain) and an electrocardiogram machine commonly used in hospitals during continuous cycling tests. Twelve cardiology patients performed a 30-min cycling test at stable submaximal intensity. RR interval data were recorded during the test by both systems. 3-min RR segments were taken to compare the time intervals between beats and HRV variables using Bland-Altman analyses and intraclass correlation coefficients. Limits of agreement (LoAs) on RR intervals were stable at around 3 ms (widest LoAs -5.754 to 6.094 ms, tightest LoAs -2.557 to 3.105 ms, medium LoAs -3.638 ± 0.812 to 3.145 ± 0.539 ms). HRV parameters related to short-term change presented wide LoAs (RMSSD -0.17 to 18.41 %, HF -17.64 to 33.21 %, SD1 -0.50 to 17.54 %) as an effect of the error measurement of the GOW system. The GOW system is a valid tool for controlling HR during physical activity, although its use as a clinical tool for HRV cannot be supported.

Free-anchored Nb2O5@graphene networks for ultrafast-stable lithium storage.

PubMed

Deng, Qinglin; Li, Mengjiao; Wang, Junyong; Jiang, Kai; Hu, Zhigao; Chu, Junhao

2018-05-04

Orthorhombic Nb 2 O 5 (T-Nb 2 O 5 ) has structural merit but poor electrical conductivity, limiting their applications in energy storage. Although graphene is frequently adopted to effectively improve its electrochemical properties, the ordinary modified methods cannot meet the growing demands for high-performance. Here, we demonstrate that different graphene modified routes play a vital role in affecting the electrochemical performances of T-Nb 2 O 5 . By only manual shaking within one minute, Nb 2 O 5 nano-particles can be rapidly adsorbed onto graphene, then the free-anchored T-Nb 2 O 5 @graphene three-dimensional networks can be successfully prepared based on hydrogel method. As for the application in lithium-ion batteries, it performs outstanding rate character (129 mA h g -1 (25C rate), 110 mA h g -1 (50C rate) and 90 mA h g -1 (100C rate), correspond to 79%, 67% and 55% capacity of 0.5C rate, respectively) and excellent long-term cycling feature (∼70% capacity retention after 20000 cycles). Moreover, it still maintains similar ultrafast-stable lithium storage performances when Cu foil is substituted by Al foil as current collector. In addition, relevant kinetics mechanisms are also expounded. This work provides a versatile strategy for the preparation of graphene modified Nb 2 O 5 or other types of nanoparticles.

Free-anchored Nb2O5@graphene networks for ultrafast-stable lithium storage

NASA Astrophysics Data System (ADS)

Deng, Qinglin; Li, Mengjiao; Wang, Junyong; Jiang, Kai; Hu, Zhigao; Chu, Junhao

2018-05-01

Orthorhombic Nb2O5 (T-Nb2O5) has structural merit but poor electrical conductivity, limiting their applications in energy storage. Although graphene is frequently adopted to effectively improve its electrochemical properties, the ordinary modified methods cannot meet the growing demands for high-performance. Here, we demonstrate that different graphene modified routes play a vital role in affecting the electrochemical performances of T-Nb2O5. By only manual shaking within one minute, Nb2O5 nano-particles can be rapidly adsorbed onto graphene, then the free-anchored T-Nb2O5@graphene three-dimensional networks can be successfully prepared based on hydrogel method. As for the application in lithium-ion batteries, it performs outstanding rate character (129 mA h g-1 (25C rate), 110 mA h g-1 (50C rate) and 90 mA h g-1 (100C rate), correspond to 79%, 67% and 55% capacity of 0.5C rate, respectively) and excellent long-term cycling feature (˜70% capacity retention after 20000 cycles). Moreover, it still maintains similar ultrafast-stable lithium storage performances when Cu foil is substituted by Al foil as current collector. In addition, relevant kinetics mechanisms are also expounded. This work provides a versatile strategy for the preparation of graphene modified Nb2O5 or other types of nanoparticles.

Agricultural Nutrient Cycling at the Strawberry Creek Watershed: Insights Into Processes Using Stable Isotope Analysis

NASA Astrophysics Data System (ADS)

Thuss, E.; English, M. C.; Spoelstra, J.

2009-05-01

When nitrogen availability exceeds biological demand, excess nitrogen, especially nitrate, may subsequently pollute ground and surface water. Agricultural practices in Southern Ontario typically supplement soils with organic and inorganic nutrients to aid in crop development, and employ various management techniques to limit nutrient loss. Excess nitrogen has several potential fates, which are controlled by the net effects of numerous nitrogen cycling reactions in the soil that are often difficult to measure directly. Nitrogen cycling in soils is controlled in large part by soil moisture, as it affects microbial activity and soil redox conditions. Stable isotope geochemistry is a powerful tool that provides information on nitrogen sources and processes. This study uses crop nitrogen and carbon isotope ratios to provide insights into the net effects of soil nitrogen cycling and nitrogen fate. This research was conducted at the Strawberry Creek Watershed (SCW), an agricultural research watershed located between Kitchener-Waterloo and Guelph, Ontario. The SCW exhibits elevated nitrate concentrations in groundwater, tile discharge, and the stream itself. Previous isotopic work revealed that this nitrate is largely derived from chemical fertilizer and manure applications. Field-scale hydrological processes lead to areas where the fate of applied nitrogen differs, which has an isotopic effect on the residual nitrogen that is available to plants. Results of this study indicate significant patterns in the isotopic signature of plant tissue, in both temporal and spatial scales. At the plot-scale where soil conditions are similar, there is little to no variation in foliar isotope values, but at the field-scale there appears to be a significant amount of variability related to soil moisture and nitrogen loss. This relationship can potentially provide insight into ideal conditions for nitrogen uptake efficiency. Reducing agricultural nitrogen leaching to ground and surface water requires a better understanding of nitrogen fate in the soil zone, and will result in more effective agricultural nutrient management.

Role of intermediate phase for stable cycling of Na7V4(P2O7)4PO4 in sodium ion battery

PubMed Central

Lim, Soo Yeon; Kim, Heejin; Chung, Jaehoon; Lee, Ji Hoon; Kim, Byung Gon; Choi, Jeon-Jin; Chung, Kyung Yoon; Cho, Woosuk; Kim, Seung-Joo; Goddard, William A.; Jung, Yousung; Choi, Jang Wook

2014-01-01

Sodium ion batteries offer promising opportunities in emerging utility grid applications because of the low cost of raw materials, yet low energy density and limited cycle life remain critical drawbacks in their electrochemical operations. Herein, we report a vanadium-based ortho-diphosphate, Na7V4(P2O7)4PO4, or VODP, that significantly reduces all these drawbacks. Indeed, VODP exhibits single-valued voltage plateaus at 3.88 V vs. Na/Na+ while retaining substantial capacity (>78%) over 1,000 cycles. Electronic structure calculations reveal that the remarkable single plateau and cycle life originate from an intermediate phase (a very shallow voltage step) that is similar both in the energy level and lattice parameters to those of fully intercalated and deintercalated states. We propose a theoretical scheme in which the reaction barrier that arises from lattice mismatches can be evaluated by using a simple energetic consideration, suggesting that the presence of intermediate phases is beneficial for cell kinetics by buffering the differences in lattice parameters between initial and final phases. We expect these insights into the role of intermediate phases found for VODP hold in general and thus provide a helpful guideline in the further understanding and design of battery materials. PMID:24379365

Construction of Metal-Organic Framework/Conductive Polymer Hybrid for All-Solid-State Fabric Supercapacitor.

PubMed

Qi, Kai; Hou, Ruizuo; Zaman, Shahid; Qiu, Yubing; Xia, Bao Yu; Duan, Hongwei

2018-05-30

Metal-organic frameworks (MOFs) hold promising potential in energy storage but are limited by poor conductivity. In this work, a metal-organic framework/polypyrrole hybrid is constructed by a facile one-pot electrodeposition method in the presence of dopamine. An all-solid-state fabric supercapacitor based on this hybrid demonstrates excellent electrochemical energy-storage performance, which achieves a specific capacitance of 10 mF cm -1 (206 mF cm -2 ), a power density of 132 μW cm -1 (2102 μW cm -2 ), and an energy density of 0.8 μWh cm -1 (12.8 μWh cm -2 ). The stable cycling life and excellent mechanical flexibility over a wide range of working temperature are also achieved, which maintains a capacitance retention of 89% over 10 000 charging/discharging cycles, a capacitance decrease of only 4% after 1000 frizzy (360° bending) cycles, and no obvious capacitance loss under 100 repeated heating (100 °C)/cooling (-15 °C) cycles. This fibrous supercapacitor displays promising potential in wearable textile electronics as it can be easily woven into common cotton cloth. Our strategy may shed some valuable light on the construction of MOF-based hybrids for flexible energy-storage electronics.

Role of intermediate phase for stable cycling of Na7V4(P2O7)4PO4 in sodium ion battery.

PubMed

Lim, Soo Yeon; Kim, Heejin; Chung, Jaehoon; Lee, Ji Hoon; Kim, Byung Gon; Choi, Jeon-Jin; Chung, Kyung Yoon; Cho, Woosuk; Kim, Seung-Joo; Goddard, William A; Jung, Yousung; Choi, Jang Wook

2014-01-14

Sodium ion batteries offer promising opportunities in emerging utility grid applications because of the low cost of raw materials, yet low energy density and limited cycle life remain critical drawbacks in their electrochemical operations. Herein, we report a vanadium-based ortho-diphosphate, Na7V4(P2O7)4PO4, or VODP, that significantly reduces all these drawbacks. Indeed, VODP exhibits single-valued voltage plateaus at 3.88 V vs. Na/Na(+) while retaining substantial capacity (>78%) over 1,000 cycles. Electronic structure calculations reveal that the remarkable single plateau and cycle life originate from an intermediate phase (a very shallow voltage step) that is similar both in the energy level and lattice parameters to those of fully intercalated and deintercalated states. We propose a theoretical scheme in which the reaction barrier that arises from lattice mismatches can be evaluated by using a simple energetic consideration, suggesting that the presence of intermediate phases is beneficial for cell kinetics by buffering the differences in lattice parameters between initial and final phases. We expect these insights into the role of intermediate phases found for VODP hold in general and thus provide a helpful guideline in the further understanding and design of battery materials.

Effects of thermal cycling on graphie-fiber-reinforced 6061 aluminum

NASA Technical Reports Server (NTRS)

Dries, G. A.; Tompkins, S. S.

1986-01-01

Graphite-reinforced aluminum alloy metal-matrix composites are among materials being considered for structural components in dimensionally stable space structures. This application requires materials with low values of thermal expansions and high specific stiffnesses. They must remain stable during exposures to the space environment for periods extending to 20 years. The effects of thermal cycling on the thermal expansion behavior and mechanical properties of Thornel P100 graphite 6061 aluminum composites, as fabricated and after thermal processing to eliminate thermal strain hysteresis, have been investigated. Two groups of composites were studied: one was fabricated by hot roll bonding and the other by diffusion bonding. Processing significantly reduced strain hysteresis during thermal cycling in both groups and improved the ultimate tensile strength and modulus in the diffusion-bonded composites. Thermal cycling stabilized the as-fabricated composites by reducing the residual fabrication stress and increased the matrix strength by metallurgical aging. Thermal expansion behavior of both groups after processing was insensitive to thermal cycling. Data scatter was too large to determine effects of thermal cycling on the mechanical properties. The primary effects of processing and thermal cycling can be attributed to changes in the metallurgical condition and stress state of the matrix.

Period doubling cascades of limit cycles in cardiac action potential models as precursors to chaotic early Afterdepolarizations.

PubMed

Kügler, Philipp; Bulelzai, M A K; Erhardt, André H

2017-04-04

Early afterdepolarizations (EADs) are pathological voltage oscillations during the repolarization phase of cardiac action potentials (APs). EADs are caused by drugs, oxidative stress or ion channel disease, and they are considered as potential precursors to cardiac arrhythmias in recent attempts to redefine the cardiac drug safety paradigm. The irregular behaviour of EADs observed in experiments has been previously attributed to chaotic EAD dynamics under periodic pacing, made possible by a homoclinic bifurcation in the fast subsystem of the deterministic AP system of differential equations. In this article we demonstrate that a homoclinic bifurcation in the fast subsystem of the action potential model is neither a necessary nor a sufficient condition for the genesis of chaotic EADs. We rather argue that a cascade of period doubling (PD) bifurcations of limit cycles in the full AP system paves the way to chaotic EAD dynamics across a variety of models including a) periodically paced and spontaneously active cardiomyocytes, b) periodically paced and non-active cardiomyocytes as well as c) unpaced and spontaneously active cardiomyocytes. Furthermore, our bifurcation analysis reveals that chaotic EAD dynamics may coexist in a stable manner with fully regular AP dynamics, where only the initial conditions decide which type of dynamics is displayed. EADs are a potential source of cardiac arrhythmias and hence are of relevance both from the viewpoint of drug cardiotoxicity testing and the treatment of cardiomyopathies. The model-independent association of chaotic EADs with period doubling cascades of limit cycles introduced in this article opens novel opportunities to study chaotic EADs by means of bifurcation control theory and inverse bifurcation analysis. Furthermore, our results may shed new light on the synchronization and propagation of chaotic EADs in homogeneous and heterogeneous multicellular and cardiac tissue preparations.

Three-dimensional stable lithium metal anode with nanoscale lithium islands embedded in ionically conductive solid matrix

PubMed Central

Lin, Dingchang; Zhao, Jie; Sun, Jie; Yao, Hongbin; Liu, Yayuan; Yan, Kai; Cui, Yi

2017-01-01

Rechargeable batteries based on lithium (Li) metal chemistry are attractive for next-generation electrochemical energy storage. Nevertheless, excessive dendrite growth, infinite relative dimension change, severe side reactions, and limited power output severely impede their practical applications. Although exciting progress has been made to solve parts of the above issues, a versatile solution is still absent. Here, a Li-ion conductive framework was developed as a stable “host” and efficient surface protection to address the multifaceted problems, which is a significant step forward compared with previous host concepts. This was fulfilled by reacting overstoichiometry of Li with SiO. The as-formed LixSi–Li2O matrix would not only enable constant electrode-level volume, but also protect the embedded Li from direct exposure to electrolyte. Because uniform Li nucleation and deposition can be fulfilled owing to the high-density active Li domains, the as-obtained nanocomposite electrode exhibits low polarization, stable cycling, and high-power output (up to 10 mA/cm2) even in carbonate electrolytes. The Li–S prototype cells further exhibited highly improved capacity retention under high-power operation (∼600 mAh/g at 6.69 mA/cm2). The all-around improvement on electrochemical performance sheds light on the effectiveness of the design principle for developing safe and stable Li metal anodes. PMID:28416664

Composite lithium metal anode by melt infusion of lithium into a 3D conducting scaffold with lithiophilic coating

PubMed Central

Liang, Zheng; Lin, Dingchang; Zhao, Jie; Lu, Zhenda; Liu, Yayuan; Liu, Chong; Lu, Yingying; Wang, Haotian; Yan, Kai; Tao, Xinyong; Cui, Yi

2016-01-01

Lithium metal-based battery is considered one of the best energy storage systems due to its high theoretical capacity and lowest anode potential of all. However, dendritic growth and virtually relative infinity volume change during long-term cycling often lead to severe safety hazards and catastrophic failure. Here, a stable lithium–scaffold composite electrode is developed by lithium melt infusion into a 3D porous carbon matrix with “lithiophilic” coating. Lithium is uniformly entrapped on the matrix surface and in the 3D structure. The resulting composite electrode possesses a high conductive surface area and excellent structural stability upon galvanostatic cycling. We showed stable cycling of this composite electrode with small Li plating/stripping overpotential (<90 mV) at a high current density of 3 mA/cm2 over 80 cycles. PMID:26929378

Comparative proteomics of two life cycle stages of stable isotope-labeled Trypanosoma brucei reveals novel components of the parasite's host adaptation machinery.

PubMed

Butter, Falk; Bucerius, Ferdinand; Michel, Margaux; Cicova, Zdenka; Mann, Matthias; Janzen, Christian J

2013-01-01

Trypanosoma brucei developed a sophisticated life cycle to adapt to different host environments. Although developmental differentiation of T. brucei has been the topic of intensive research for decades, the mechanisms responsible for adaptation to different host environments are not well understood. We developed stable isotope labeling by amino acids in cell culture in trypanosomes to compare the proteomes of two different life cycle stages. Quantitative comparison of 4364 protein groups identified many proteins previously not known to be stage-specifically expressed. The identification of stage-specific proteins helps to understand how parasites adapt to different hosts and provides new insights into differences in metabolism, gene regulation, and cell architecture. A DEAD-box RNA helicase, which is highly up-regulated in the bloodstream form of this parasite and which is essential for viability and proper cell cycle progression in this stage is described as an example.

Towards High-Performance Aqueous Sodium-Ion Batteries: Stabilizing the Solid/Liquid Interface for NASICON-Type Na2 VTi(PO4 )3 using Concentrated Electrolytes.

PubMed

Zhang, Huang; Jeong, Sangsik; Qin, Bingsheng; Vieira Carvalho, Diogo; Buchholz, Daniel; Passerini, Stefano

2018-04-25

Aqueous Na-ion batteries may offer a solution to the cost and safety issues of high-energy batteries. However, substantial challenges remain in the development of electrode materials and electrolytes enabling high performance and long cycle life. Herein, we report the characterization of a symmetric Na-ion battery with a NASICON-type Na 2 VTi(PO 4 ) 3 electrode material in conventional aqueous and "water-in-salt" electrolytes. Extremely stable cycling performance for 1000 cycles at a high rate (20 C) is found with the highly concentrated aqueous electrolytes owing to the formation of a resistive but protective interphase between the electrode and electrolyte. These results provide important insight for the development of aqueous Na-ion batteries with stable long-term cycling performance for large-scale energy storage. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Time-varying economic dominance in financial markets: A bistable dynamics approach

NASA Astrophysics Data System (ADS)

He, Xue-Zhong; Li, Kai; Wang, Chuncheng

2018-05-01

By developing a continuous-time heterogeneous agent financial market model of multi-assets traded by fundamental and momentum investors, we provide a potential mechanism for generating time-varying dominance between fundamental and non-fundamental in financial markets. We show that investment constraints lead to the coexistence of a locally stable fundamental steady state and a locally stable limit cycle around the fundamental, characterized by a Bautin bifurcation. This provides a mechanism for market prices to switch stochastically between the two persistent but very different market states, leading to the coexistence and time-varying dominance of seemingly controversial efficient market and price momentum over different time periods. The model also generates other financial market stylized facts, such as spillover effects in both momentum and volatility, market booms, crashes, and correlation reduction due to cross-sectional momentum trading. Empirical evidence based on the U.S. market supports the main findings. The mechanism developed in this paper can be used to characterize time-varying economic dominance in economics and finance in general.

Time-varying economic dominance in financial markets: A bistable dynamics approach.

PubMed

He, Xue-Zhong; Li, Kai; Wang, Chuncheng

2018-05-01

By developing a continuous-time heterogeneous agent financial market model of multi-assets traded by fundamental and momentum investors, we provide a potential mechanism for generating time-varying dominance between fundamental and non-fundamental in financial markets. We show that investment constraints lead to the coexistence of a locally stable fundamental steady state and a locally stable limit cycle around the fundamental, characterized by a Bautin bifurcation. This provides a mechanism for market prices to switch stochastically between the two persistent but very different market states, leading to the coexistence and time-varying dominance of seemingly controversial efficient market and price momentum over different time periods. The model also generates other financial market stylized facts, such as spillover effects in both momentum and volatility, market booms, crashes, and correlation reduction due to cross-sectional momentum trading. Empirical evidence based on the U.S. market supports the main findings. The mechanism developed in this paper can be used to characterize time-varying economic dominance in economics and finance in general.

Better Bet-Hedging with coupled positive and negative feedback loops

NASA Astrophysics Data System (ADS)

Narula, Jatin; Igoshin, Oleg

2011-03-01

Bacteria use the phenotypic heterogeneity associated with bistable switches to distribute the risk of activating stress response strategies like sporulation and persistence. However bistable switches offer little control over the timing of phenotype switching and first passage times (FPT) for individual cells are found to be exponentially distributed. We show that a genetic circuit consisting of interlinked positive and negative feedback loops allows cells to control the timing of phenotypic switching. Using a mathematical model we find that in this system a stable high expression state and stable low expression limit cycle coexist and the FPT distribution for stochastic transitions between them shows multiple peaks at regular intervals. A multimodal FPT distribution allows cells to detect the persistence of stress and control the rate of phenotype transition of the population. We further show that extracellular signals from cell-cell communication that change the strength of the feedback loops can modulate the FPT distribution and allow cells even greater control in a bet-hedging strategy.

How a small noise generates large-amplitude oscillations of volcanic plug and provides high seismicity

NASA Astrophysics Data System (ADS)

Alexandrov, Dmitri V.; Bashkirtseva, Irina A.; Ryashko, Lev B.

2015-04-01

A non-linear behavior of dynamic model of the magma-plug system under the action of N-shaped friction force and stochastic disturbances is studied. It is shown that the deterministic dynamics essentially depends on the mutual arrangement of an equilibrium point and the friction force branches. Variations of this arrangement imply bifurcations, birth and disappearance of stable limit cycles, changes of the stability of equilibria, system transformations between mono- and bistable regimes. A slope of the right increasing branch of the friction function is responsible for the formation of such regimes. In a bistable zone, the noise generates transitions between small and large amplitude stochastic oscillations. In a monostable zone with single stable equilibrium, a new dynamic phenomenon of noise-induced generation of large amplitude stochastic oscillations in the plug rate and pressure is revealed. A beat-type dynamics of the plug displacement under the influence of stochastic forcing is studied as well.

Cyclic variations of fuel-droplet distribution during the early intake stroke of a lean-burn stratified-charge spark-ignition engine

NASA Astrophysics Data System (ADS)

Aleiferis, P. G.; Hardalupas, Y.; Taylor, A. M. K. P.; Ishii, K.; Urata, Y.

2005-11-01

Lean-burn spark-ignition engines exhibit higher efficiency and lower specific emissions in comparison with stoichiometrically charged engines. However, as the air-to-fuel (A/F) ratio of the mixture is made leaner than stoichiometric, cycle-by-cycle variations in the early stages of in-cylinder combustion, and subsequent indicated mean effective pressure (IMEP), become more pronounced and limit the range of lean-burn operation. Viable lean-burn engines promote charge stratification, the mixture near the spark plug being richer than the cylinder volume averaged value. Recent work has shown that cycle-by-cycle variations in the early stages of combustion in a stratified-charge engine can be associated with variations in both the local value of A/F ratio near the spark plug around ignition timing, as well as in the volume averaged value of the A/F ratio. The objective of the current work was to identify possible sources of such variability in A/F ratio by studying the in-cylinder field of fuel-droplet distribution during the early intake stroke. This field was visualised in an optical single-cylinder 4-valve pentroof-type spark-ignition engine by means of laser-sheet illumination in planes parallel to the cylinder head gasket 6 and 10 mm below the spark plug. The engine was run with port-injected isooctane at 1500 rpm with 30% volumetric efficiency and air-to-fuel ratio corresponding to both stoichiometric firing (A/F=15, Φ =1.0) and mixture strength close to the lean limit of stable operation (A/F=22, Φ =0.68). Images of Mie intensity scattered by the cloud of fuel droplets were acquired on a cycle-by-cycle basis. These were studied in order to establish possible correlations between the cyclic variations in size, location and scattered-light intensity of the cloud of droplets with the respective variations in IMEP. Because of the low level of Mie intensity scattered by the droplets and because of problems related to elastic scattering on the walls of the combustion chamber, as well as problems related to engine “rocking” at the operating conditions close to the misfire limit, the acquired images were processed for background subtraction by using a PIV-based data correction algorithm. After this processing, the arrival and leaving timings of fuel droplets into the illuminated plane were found not to vary significantly on a cycle-by-cycle basis but the recorded cycle-by-cycle variations in Mie intensity suggested that the amount of fuel in the cylinder could have been 6 26% greater for the “strong” cycles with IMEP 115% higher than the average IMEP, than the ones imaged for “weak” cycles at less than 85% the average IMEP. This would correspond to a maximum cyclic variability in the in-cylinder equivalence ratio Φ of the order of 0.17.

A Search for Charged Massive Stable Particles at D0

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

Eads, Michael Terry

2005-08-01

A search for charged massive stable particles has been performed with the D0 detector at the Fermilab Tevatron. The signature is two particles reconstructed as muons, but with speed and invariant mass inconsistent with beam-produced muons. No excess of events is observed and limits are set on the production cross-section for pair-produced stable stau sleptons based on 390 pb -1 of data. Limits vary from 0.06 pb to 0.62 pb, depending on the stau mass, and are the strictest Tevatron limits to date. Mass limits are also set for stable charginos. The limits are 140 GeV/c 2 for a higgsino-likemore » chargino and 174 GeV/c 2 for a gaugino-like chargino. These are currently the best limits to date for stable charginos.« less

New type of synchronization of oscillators with hard excitation

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

Kovaleva, M. A., E-mail: margo.kovaleva@gmail.com; Manevich, L. I., E-mail: manevichleonid3@gmail.com; Pilipchuk, V. N.

2013-08-15

It is shown that stable limiting cycles corresponding to nonlinear beats with complete energy exchange between oscillators can exist in a system of two weakly coupled active oscillators (generators). The oscillatory regime of this type, which implements a new type of synchronization in an active system, is an alternative to the well-studied synchronization in a regime close to a nonlinear normal mode. In this case, the ranges of dissipative parameters corresponding to different types of synchronization do not intersect. The analytic description of attractors revealed in analysis is based on the concept of limiting phase trajectories, which was developed earliermore » by one of the authors for conservative systems. A transition (in the parametric space) from the complete energy exchange between oscillators to predominant localization of energy in one of the oscillators can be naturally described using this concept. The localized normal mode is an attractor in the range of parameters in which neither the limiting phase trajectory nor any of the collective normal modes is an attractor.« less

Stability branching induced by collective atomic recoil in an optomechanical ring cavity

NASA Astrophysics Data System (ADS)

Ian, Hou

2017-02-01

In a ring cavity filled with an atomic condensate, self-bunching of atoms due to the cavity pump mode produce an inversion that re-emits into the cavity probe mode with an exponential gain, forming atomic recoil lasing. An optomechanical ring cavity is formed when one of the reflective mirrors is mounted on a mechanical vibrating beam. In this paper, we extend studies on the stability of linear optomechanical cavities to such ring cavities with two counter-propagating cavity modes, especially when the forward propagating pump mode is taken to its weak coupling limit. We find that when the atomic recoil is in action, stable states of the mechanical mode of the mirror converge into branch cuts, where the gain produced by the recoiling strikes balance with the multiple decay sources, such as cavity leakage in the optomechanical system. This balance is obtained when the propagation delay in the dispersive atomic medium matches in a periodic pattern to the frequencies and linewidths of the cavity mode and the collective bosonic mode of the atoms. We show an input-output hysteresis cycle between the atomic mode and the cavity mode to verify the multi-valuation of the stable states after branching at the weak coupling limit.

H, C, O, and N stable isotopes to decipher climate feedbacks in a mountainous watershed (East River, Colorado)

NASA Astrophysics Data System (ADS)

Bill, M.; Conrad, M. E.; Beller, H. R.; Bouskill, N.; Brodie, E.; Brown, W.; Carroll, R. W. H.; Kim, Y.; Nico, P. S.; Sorensen, P. O.; Tokunaga, T. K.; Wan, J.; Williams, K. H.

2017-12-01

Temperature and precipitation variability in response to climate change affects water cycling of a watershed and can potentially impact water quality, water availability, elemental and molecular fluxes, and biogeochemical processes. Here we report the application of light stable isotopic analysis to a large multidisciplinary project addressing watershed function. The study area is charaterized by a snow-dominated headwater catchment of the Colorado River (East River, Colorado). We are measuring H, C, O, and N stable isotopes in an effort to differentiate natural and climate induced perturbations to the hydrologic cycle on C and N cycling in a moutainous watershed. Water H and O stable isotopes of rain, snow, ground and surface water are being used to constrain source contributions to streamflow. H and O isotopes of water together with elemental concentations were used in end-member mixing analysis (EMMA) to chararacterize and quantify downstream flow. Results indicate runoff is dominated by snowmelt (66±13%) and to a lessor extent groundwater (26±11%) with sources moving toward near equal contributions during baseflow (45%). We are also using C and N stable isotopes in conjunction with elemental concentations to characterize leaf litter and to estimate nutrient inputs and decomposition rates. C and N isotopes are being used to characterize watershed soils, soil biomass, and sedimentary rocks to constrain carbon fluxes to the rivers and the atmosphere. We are analyzing variations of C, O, and N stable isotopes of CO2, N2O and CH4 greenhouse gases in different temperature, precipitation, and hydrological regimes to connect climate change with biogeochemical fluxes between the watershed and the atmosphere.

Shortening tobacco life cycle accelerates functional gene identification in genomic research.

PubMed

Ning, G; Xiao, X; Lv, H; Li, X; Zuo, Y; Bao, M

2012-11-01

Definitive allocation of function requires the introduction of genetic mutations and analysis of their phenotypic consequences. Novel, rapid and convenient techniques or materials are very important and useful to accelerate gene identification in functional genomics research. Here, over-expression of PmFT (Prunus mume), a novel FT orthologue, and PtFT (Populus tremula) lead to shortening of the tobacco life cycle. A series of novel short life cycle stable tobacco lines (30-50 days) were developed through repeated self-crossing selection breeding. Based on the second transformation via a gusA reporter gene, the promoter from BpFULL1 in silver birch (Betula pendula) and the gene (CPC) from Arabidopsis thaliana were effectively tested using short life cycle tobacco lines. Comparative analysis among wild type, short life cycle tobacco and Arabidopsis transformation system verified that it is optional to accelerate functional gene studies by shortening host plant material life cycle, at least in these short life cycle tobacco lines. The results verified that the novel short life cycle transgenic tobacco lines not only combine the advantages of economic nursery requirements and a simple transformation system, but also provide a robust, effective and stable host system to accelerate gene analysis. Thus, shortening tobacco life cycle strategy is feasible to accelerate heterologous or homologous functional gene identification in genomic research. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

The recommended Threshold Limit Values for heat exposure fail to maintain body core temperature within safe limits in older working adults.

PubMed

Lamarche, Dallon T; Meade, Robert D; D'Souza, Andrew W; Flouris, Andreas D; Hardcastle, Stephen G; Sigal, Ronald J; Boulay, Pierre; Kenny, Glen P

2017-09-01

The American Conference of Governmental and Industrial Hygienists (ACGIH®) Threshold Limit Values (TLV® guidelines) for work in the heat consist of work-rest (WR) allocations designed to ensure a stable core temperature that does not exceed 38°C. However, the TLV® guidelines have not been validated in older workers. This is an important shortcoming given that adults as young as 40 years demonstrate impairments in their ability to dissipate heat. We therefore evaluated body temperature responses in older adults during work performed in accordance to the TLV® recommended guidelines. On three occasions, 9 healthy older (58 ± 5 years) males performed a 120-min work-simulated protocol in accordance with the TLV® guidelines for moderate-to-heavy intensity work (360 W fixed rate of heat production) in different wet-bulb globe temperatures (WBGT). The first was 120 min of continuous (CON) cycling at 28.0°C WBGT (CON[28°C]). The other two protocols were 15-min intermittent work bouts performed with different WR cycles and WBGT: (i) WR of 3:1 at 29.0°C (WR3:1[29°C]) and (ii) WR of 1:1 at 30.0°C (WR1:1[30°C]). Rectal temperature was measured continuously. The rate of change in mean body temperature was determined via thermometry (weighting coefficients: rectal, 0.9; mean skin temperature, 0.1) and direct calorimetry. Rectal temperature exceeded 38°C in all participants in CON[28°C] and WR3:1[29°C] whereas a statistically similar proportion of workers exceeded 38°C in WR1:1[30°C] (χ 2 ; P = 0.32). The average time for rectal temperature to reach 38°C was: CON[28°C], 53 ± 7; WR3:1[29°C], 79 ± 11; and WR1:1[30°C], 100 ± 29 min. Finally, while a stable mean body temperature was not achieved in any work condition as measured by thermometry (i.e., >0°C·min -1 ; all P<0.01), heat balance as determined by direct calorimetry was achieved in WR3:1[29°C] and WR1:1[30°C] (both P ≥ 0.08). Our findings indicate that the TLV® guidelines do not prevent body core temperature from exceeding 38°C in older workers. Furthermore, a stable core temperature was not achieved within safe limits (i.e., ≤38°C) indicating that the TLV® guidelines may not adequately protect all individuals during work in hot conditions.

“Ni-Less” Cathodes for High Energy Density, Intermediate Temperature Na-NiCl 2 Batteries

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

Chang, Hee-Jung; Lu, Xiaochuan; Bonnett, Jeffery F.

Among various battery technologies being considered for stationary energy storage applications, sodium-metal halide (Na-MH) batteries have become one of the most attractive candidates because of the abundance of raw materials, long cycle life, high energy density, and superior safety. However, one of issues limiting its practical application is the relatively expensive nickel (Ni) used in the cathode. In the present work, we focus on of efforts to develop new Ni-based cathodes, and demonstrate that a much higher specific energy density of 405 Wh/kg (23% higher than state-of-the-art Na-MH batteries) can be achieved at an operating temperature of 190oC. Furthermore, 15%more » less Ni is used in the new cathode than that in conventional Na-NiCl2 batteries. Long-term cycling tests also show stable electrochemical performance for over 300 cycles with excellent capacity retention (~100%). The results in this work indicate that these advances can significantly reduce the raw material cost associated with Ni (a 31% reduction) and promote practical applications of Na-MH battery technologies in stationary energy storage systems.« less

Identifying mantle lithosphere inheritance in controlling intraplate orogenesis

NASA Astrophysics Data System (ADS)

Heron, Philip J.; Pysklywec, Russell N.; Stephenson, Randell

2016-09-01

Crustal inheritance is often considered important in the tectonic evolution of the Wilson Cycle. However, the role of the mantle lithosphere is usually overlooked due to its difficulty to image and uncertainty in rheological makeup. Recently, increased resolution in lithosphere imaging has shown potential scarring in continental mantle lithosphere to be ubiquitous. In our study, we analyze intraplate deformation driven by mantle lithosphere heterogeneities from ancient Wilson Cycle processes and compare this to crustal inheritance deformation. We present 2-D numerical experiments of continental convergence to generate intraplate deformation, exploring the limits of continental rheology to understand the dominant lithosphere layer across a broad range of geological settings. By implementing a "jelly sandwich" rheology, common in stable continental lithosphere, we find that during compression the strength of the mantle lithosphere is integral in generating deformation from a structural anomaly. We posit that if the continental mantle is the strongest layer within the lithosphere, then such inheritance may have important implications for the Wilson Cycle. Furthermore, our models show that deformation driven by mantle lithosphere scarring can produce tectonic patterns related to intraplate orogenesis originating from crustal sources, highlighting the need for a more formal discussion of the role of the mantle lithosphere in plate tectonics.

Putting one step before the other: distinct activation pathways for Cdk1 and Cdk2 bring order to the mammalian cell cycle

PubMed Central

Merrick, Karl A.; Fisher, Robert P.

2010-01-01

Eukaryotic cell division is controlled by the activity of cyclin-dependent kinases (CDKs). Cdk1 and Cdk2, which function at different stages of the mammalian cell cycle, both require cyclin-binding and phosphorylation of the activation (T-) loop for full activity, but differ with respect to the order in which the two steps occur in vivo. To form stable complexes with either of its partners—cyclins A and B—Cdk1 must be phosphorylated on its T-loop, but that phosphorylation in turn depends on the presence of cyclin. Cdk2 can follow a kinetically distinct path to activation in which T-loop phosphorylation precedes cyclin-binding, and thereby out-compete the more abundant Cdk1 for limiting amounts of cyclin A. Mathematical modeling suggests this could be a principal basis for the temporal ordering of CDK activation during S phase, which may dictate the sequence in which replication origins fire. Still to be determined are how: 1) the activation machinery discriminates between closely related CDKs, and 2) coordination of the cell cycle is affected when this mechanism of pathway insulation breaks down. PMID:20139727

Suppressing Manganese Dissolution from Lithium Manganese Oxide Spinel Cathodes with Single-Layer Graphene

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

Jaber-Ansari, Laila; Puntambekar, Kanan P.; Kim, Soo

2015-06-24

Spinel-structured LiMn 2 O 4 (LMO) is a desirable cathode material for Li-ion batteries due to its low cost, abundance, and high power capability. However, LMO suffers from limited cycle life that is triggered by manganese dissolution into the electrolyte during electrochemical cycling. Here, it is shown that single-layer graphene coatings suppress manganese dissolution, thus enhancing the performance and lifetime of LMO cathodes. Relative to lithium cells with uncoated LMO cathodes, cells with graphene-coated LMO cathodes provide improved capacity retention with enhanced cycling stability. X-ray photoelectron spectroscopy reveals that graphene coatings inhibit manganese depletion from the LMO surface. Additionally, transmissionmore » electron microscopy demonstrates that a stable solid electrolyte interphase is formed on graphene, which screens the LMO from direct contact with the electrolyte. Density functional theory calculations provide two mechanisms for the role of graphene in the suppression of manganese dissolution. First, common defects in single-layer graphene are found to allow the transport of lithium while concurrently acting as barriers for manganese diffusion. Second, graphene can chemically interact with Mn 3+ at the LMO electrode surface, promoting an oxidation state change to Mn 4+ , which suppresses dissolution.« less

Few Atomic Layered Lithium Cathode Materials to Achieve Ultrahigh Rate Capability in Lithium-Ion Batteries.

PubMed

Tai, Zhixin; Subramaniyam, Chandrasekar M; Chou, Shu-Lei; Chen, Lingna; Liu, Hua-Kun; Dou, Shi-Xue

2017-09-01

The most promising cathode materials, including LiCoO 2 (layered), LiMn 2 O 4 (spinel), and LiFePO 4 (olivine), have been the focus of intense research to develop rechargeable lithium-ion batteries (LIBs) for portable electronic devices. Sluggish lithium diffusion, however, and unsatisfactory long-term cycling performance still limit the development of present LIBs for several applications, such as plug-in/hybrid electric vehicles. Motivated by the success of graphene and novel 2D materials with unique physical and chemical properties, herein, a simple shear-assisted mechanical exfoliation method to synthesize few-layered nanosheets of LiCoO 2 , LiMn 2 O 4 , and LiFePO 4 is used. Importantly, these as-prepared nanosheets with preferred orientations and optimized stable structures exhibit excellent C-rate capability and long-term cycling performance with much reduced volume expansion during cycling. In particular, the zero-strain insertion phenomenon could be achieved in 2-3 such layers of LiCoO 2 electrode materials, which could open up a new way to the further development of next-generation long-life and high-rate batteries. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Integrative molecular and microanalytical studies of syntrophic partnerships linking C, S, and N cycles in anoxic environments

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

Orphan, Victoria

2016-07-15

Syntrophy and other forms of symbiotic associations between microorganisms are central to carbon and nutrient cycling in the environment. However, the inherent interdependence of these interactions, dynamic behavior, and frequent existence at thermodynamic limits has hindered our ability to both recognize syntrophic partnerships in nature and effectively study their behavior in the laboratory. To characterize and understand the underlying factors influencing syntrophic associations within complex communities requires a suite of tools that extend beyond basic molecular identification and cultivation. This specifically includes methods that preserve the natural spatial relationships between metabolically interdependent microorganisms while allowing downstream geochemical and/or molecular analysis.more » With support from this award, we have developed and applied new combinations of molecular, microscopy, and stable isotope-based methodologies that enable the characterization of fundamental links between phylogenetically-identified microorganisms and their specific metabolic activities and interactions in the environment. Through the coupling of fluorescence in situ hybridization (FISH) with cell capture and targeted metagenomics (Magneto-FISH), and FISH + secondary ion mass spectrometry (i.e. FISH-SIMS or FISH-nanoSIMS), we have defined new microbial interactions and the ecophysiology of anaerobic microorganisms involved in environmental methane cycling.« less

Tin anode for sodium-ion batteries using natural wood fiber as a mechanical buffer and electrolyte reservoir.

PubMed

Zhu, Hongli; Jia, Zheng; Chen, Yuchen; Weadock, Nicholas; Wan, Jiayu; Vaaland, Oeyvind; Han, Xiaogang; Li, Teng; Hu, Liangbing

2013-07-10

Sodium (Na)-ion batteries offer an attractive option for low cost grid scale storage due to the abundance of Na. Tin (Sn) is touted as a high capacity anode for Na-ion batteries with a high theoretical capacity of 847 mAh/g, but it has several limitations such as large volume expansion with cycling, slow kinetics, and unstable solid electrolyte interphase (SEI) formation. In this article, we demonstrate that an anode consisting of a Sn thin film deposited on a hierarchical wood fiber substrate simultaneously addresses all the challenges associated with Sn anodes. The soft nature of wood fibers effectively releases the mechanical stresses associated with the sodiation process, and the mesoporous structure functions as an electrolyte reservoir that allows for ion transport through the outer and inner surface of the fiber. These properties are confirmed experimentally and computationally. A stable cycling performance of 400 cycles with an initial capacity of 339 mAh/g is demonstrated; a significant improvement over other reported Sn nanostructures. The soft and mesoporous wood fiber substrate can be utilized as a new platform for low cost Na-ion batteries.

Durability of template-free Fe-N-C foams for electrochemical oxygen reduction in alkaline solution

NASA Astrophysics Data System (ADS)

Mufundirwa, Albert; Harrington, George F.; Smid, Břetislav; Cunning, Benjamin V.; Sasaki, Kazunari; Lyth, Stephen M.

2018-01-01

Due to the high cost and limited availability of platinum, the development of non-platinum-group metals (non-PGM) catalysts is of paramount importance. A promising alternative to Pt are Fe-N-C-based materials. Here we present the synthesis, characterization and electrochemistry of a template-free nitrogen-doped carbon foam, impregnated with iron. This low-cost and gram-scale method results in materials with micron-scale pore size and large surface area (1600 m2g-1). When applied as an oxygen reduction reaction (ORR) electrocatalyst in alkaline solution, the Fe-N-C foams display extremely high initial activity, slightly out-performing commercially available non-PGM catalysts (NCP-2000, Pajarito Powder). The load-cycle durability in alkaline solution is investigated, and the performance steadily degrades over 60,000 potential cycles, whilst the commercial catalyst is remarkably stable. The post-operation catalyst microstructure is elucidated by transmission electron microscopy (TEM), to provide insight into the degradation processes. The resulting images suggest that potential cycling leads to leaching of atomically dispersed Fe-N2/4 sites in all the catalysts, whereas encapsulated iron nanoparticles are protected.

DMSO-Li2O2 Interface in the Rechargeable Li-O2 Battery Cathode: Theoretical and Experimental Perspectives on Stability.

PubMed

Schroeder, Marshall A; Kumar, Nitin; Pearse, Alexander J; Liu, Chanyuan; Lee, Sang Bok; Rubloff, Gary W; Leung, Kevin; Noked, Malachi

2015-06-03

One of the greatest obstacles for the realization of the nonaqueous Li-O2 battery is finding a solvent that is chemically and electrochemically stable under cell operating conditions. Dimethyl sulfoxide (DMSO) is an attractive candidate for rechargeable Li-O2 battery studies; however, there is still significant controversy regarding its stability on the Li-O2 cathode surface. We performed multiple experiments (in situ XPS, FTIR, Raman, and XRD) which assess the stability of the DMSO-Li2O2 interface and report perspectives on previously published studies. Our electrochemical experiments show long-term stable cycling of a DMSO-based operating Li-O2 cell with a platinum@carbon nanotube core-shell cathode fabricated via atomic layer deposition, specifically with >45 cycles of 40 h of discharge per cycle. This work is complemented by density functional theory calculations of DMSO degradation pathways on Li2O2. Both experimental and theoretical evidence strongly suggests that DMSO is chemically and electrochemically stable on the surface of Li2O2 under the reported operating conditions.

Fumarate Reductase Activity Maintains an Energized Membrane in Anaerobic Mycobacterium tuberculosis

PubMed Central

Watanabe, Shinya; Zimmermann, Michael; Goodwin, Michael B.; Sauer, Uwe; Barry, Clifton E.; Boshoff, Helena I.

2011-01-01

Oxygen depletion of Mycobacterium tuberculosis engages the DosR regulon that coordinates an overall down-regulation of metabolism while up-regulating specific genes involved in respiration and central metabolism. We have developed a chemostat model of M. tuberculosis where growth rate was a function of dissolved oxygen concentration to analyze metabolic adaptation to hypoxia. A drop in dissolved oxygen concentration from 50 mmHg to 0.42 mmHg led to a 2.3 fold decrease in intracellular ATP levels with an almost 70-fold increase in the ratio of NADH/NAD+. This suggests that re-oxidation of this co-factor becomes limiting in the absence of a terminal electron acceptor. Upon oxygen limitation genes involved in the reverse TCA cycle were upregulated and this upregulation was associated with a significant accumulation of succinate in the extracellular milieu. We confirmed that this succinate was produced by a reversal of the TCA cycle towards the non-oxidative direction with net CO2 incorporation by analysis of the isotopomers of secreted succinate after feeding stable isotope (13C) labeled precursors. This showed that the resulting succinate retained both carbons lost during oxidative operation of the TCA cycle. Metabolomic analyses of all glycolytic and TCA cycle intermediates from 13C-glucose fed cells under aerobic and anaerobic conditions showed a clear reversal of isotope labeling patterns accompanying the switch from normoxic to anoxic conditions. M. tuberculosis encodes three potential succinate-producing enzymes including a canonical fumarate reductase which was highly upregulated under hypoxia. Knockout of frd, however, failed to reduce succinate accumulation and gene expression studies revealed a compensatory upregulation of two homologous enzymes. These major realignments of central metabolism are consistent with a model of oxygen-induced stasis in which an energized membrane is maintained by coupling the reductive branch of the TCA cycle to succinate secretion. This fermentative process may offer unique targets for the treatment of latent tuberculosis. PMID:21998585

Growth of the European abalone ( Haliotis tuberculata L.) in situ: Seasonality and ageing using stable oxygen isotopes

NASA Astrophysics Data System (ADS)

Roussel, Sabine; Huchette, Sylvain; Clavier, Jacques; Chauvaud, Laurent

2011-02-01

The ormer, Haliotis tuberculata is the only European abalone species commercially exploited. The determination of growth and age in the wild is an important tool for fisheries and aquaculture management. However, the ageing technique used in the past in the field is unreliable. The stable oxygen isotope composition ( 18O/ 16O) of the shell depends on the temperature and oxygen isotope composition of the ambient sea water. The stable oxygen isotope technique, developed to study paleoclimatological changes in shellfish, was applied to three H. tuberculata specimens collected in north-west Brittany. For the specimens collected, the oxygen isotope ratios of the shell reflected the seasonal cycle in the temperature. From winter-to-winter cycles, estimates of the age and the annual growth increment, ranging from 13 to 55 mm per year were obtained. This study shows that stable oxygen isotopes can be a reliable tool for ageing and growth studies of this abalone species in the wild, and for validating other estimates.

Fire-extinguishing organic electrolytes for safe batteries

NASA Astrophysics Data System (ADS)

Wang, Jianhui; Yamada, Yuki; Sodeyama, Keitaro; Watanabe, Eriko; Takada, Koji; Tateyama, Yoshitaka; Yamada, Atsuo

2018-01-01

Severe safety concerns are impeding the large-scale employment of lithium/sodium batteries. Conventional electrolytes are highly flammable and volatile, which may cause catastrophic fires or explosions. Efforts to introduce flame-retardant solvents into the electrolytes have generally resulted in compromised battery performance because those solvents do not suitably passivate carbonaceous anodes. Here we report a salt-concentrated electrolyte design to resolve this dilemma via the spontaneous formation of a robust inorganic passivation film on the anode. We demonstrate that a concentrated electrolyte using a salt and a popular flame-retardant solvent (trimethyl phosphate), without any additives or soft binders, allows stable charge-discharge cycling of both hard-carbon and graphite anodes for more than 1,000 cycles (over one year) with negligible degradation; this performance is comparable or superior to that of conventional flammable carbonate electrolytes. The unusual passivation character of the concentrated electrolyte coupled with its fire-extinguishing property contributes to developing safe and long-lasting batteries, unlocking the limit toward development of much higher energy-density batteries.

Reduced Graphene Oxide-Hybridized Polymeric High-Internal Phase Emulsions for Highly Efficient Removal of Polycyclic Aromatic Hydrocarbons from Water Matrix.

PubMed

Huang, Yipeng; Zhang, Wenjuan; Ruan, Guihua; Li, Xianxian; Cong, Yongzheng; Du, Fuyou; Li, Jianping

2018-03-27

Reduced graphene oxide (RGO)-hybridized polymeric high-internal phase emulsions (RGO/polyHIPEs) with an open-cell structure and hydrophobicity have been successfully prepared using 2-ethylhexyl acrylate and ethylene glycol dimethacrylate as the monomer and the cross-linker, respectively. The adsorption mechanism and performance of this RGO/polyHIPEs to polycyclic aromatic hydrocarbons (PAHs) were investigated. Adsorption isotherms of PAHs on RGO/polyHIPEs show that the saturated adsorption capacity is 47.5 mg/g and the equilibrium time is 8 h. Cycling tests show that the adsorption capacity of RGO/polyHIPEs remains stable in 10 adsorption-desorption cycles without observable structure change in RGO/polyHIPEs. Moreover, the PAH residues in water samples after being purified by RGO/polyHIPEs are lower than the limit values in drinking water set by the European Food Safety Authority. These results demonstrate that the RGO/polyHIPEs have great potentiality in PAH removal and water purification.

A Continuous Labour Supply Model in Microsimulation: A Life-Cycle Modelling Approach with Heterogeneity and Uncertainty Extension

PubMed Central

Li, Jinjing; Sologon, Denisa Maria

2014-01-01

This paper advances a structural inter-temporal model of labour supply that is able to simulate the dynamics of labour supply in a continuous setting and addresses two main drawbacks of most existing models. The first limitation is the inability to incorporate individual heterogeneity as every agent is sharing the same parameters of the utility function. The second one is the strong assumption that individuals make decisions in a world of perfect certainty. Essentially, this paper offers an extension of marginal-utility-of-wealth-constant labour supply functions known as “Frisch functions” under certainty and uncertainty with homogenous and heterogeneous preferences. The lifetime models based on the fixed effect vector decomposition yield the most stable simulation results, under both certain and uncertain future wage assumptions. Due to its improved accuracy and stability, this lifetime labour supply model is particularly suitable for enhancing the performance of the life cycle simulation models, thus providing a better reference for policymaking. PMID:25391021

Multistability and hidden attractors in a relay system with hysteresis

NASA Astrophysics Data System (ADS)

Zhusubaliyev, Zhanybai T.; Mosekilde, Erik; Rubanov, Vasily G.; Nabokov, Roman A.

2015-06-01

For nonlinear dynamic systems with switching control, the concept of a "hidden attractor" naturally applies to a stable dynamic state that either (1) coexists with the stable switching cycle or (2), if the switching cycle is unstable, has a basin of attraction that does not intersect with the neighborhood of that cycle. We show how the equilibrium point of a relay system disappears in a boundary-equilibrium bifurcation as the system enters the region of autonomous switching dynamics and demonstrate experimentally how a relay system can exhibit large amplitude chaotic oscillations at high values of the supply voltage. By investigating a four-dimensional model of the experimental relay system we finally show how a variety of hidden periodic, quasiperiodic and chaotic attractors arise, transform and disappear through different bifurcations.

Polyhydroxyalkanoate production as a side stream process on a municipal waste water treatment plant.

PubMed

Pittmann, T; Steinmetz, H

2014-09-01

This work describes the production of polyhydroxyalkanoates (PHAs) as a side stream process on a municipal waste water treatment plant (WWTP) at different operation conditions. Therefore various tests were conducted regarding a high PHA production and stable PHA composition. Influence of substrate concentration, temperature, pH and cycle time of an installed feast/famine-regime were investigated. The results demonstrated a strong influence of the operating conditions on the PHA production. Lower substrate concentration, 20°C, neutral pH-value and a 24h cycle time are preferable for high PHA production up to 28.4% of cell dry weight (CDW). PHA composition was influenced by cycle time only and a stable PHA composition was reached. Copyright © 2014 Elsevier Ltd. All rights reserved.

A flexible and qualitatively stable model for cell cycle dynamics including DNA damage effects.

PubMed

Jeffries, Clark D; Johnson, Charles R; Zhou, Tong; Simpson, Dennis A; Kaufmann, William K

2012-01-01

This paper includes a conceptual framework for cell cycle modeling into which the experimenter can map observed data and evaluate mechanisms of cell cycle control. The basic model exhibits qualitative stability, meaning that regardless of magnitudes of system parameters its instances are guaranteed to be stable in the sense that all feasible trajectories converge to a certain trajectory. Qualitative stability can also be described by the signs of real parts of eigenvalues of the system matrix. On the biological side, the resulting model can be tuned to approximate experimental data pertaining to human fibroblast cell lines treated with ionizing radiation, with or without disabled DNA damage checkpoints. Together these properties validate a fundamental, first order systems view of cell dynamics. Classification Codes: 15A68.

High-flux solar-driven thermochemical dissociation of CO2 and H2O using nonstoichiometric ceria.

PubMed

Chueh, William C; Falter, Christoph; Abbott, Mandy; Scipio, Danien; Furler, Philipp; Haile, Sossina M; Steinfeld, Aldo

2010-12-24

Because solar energy is available in large excess relative to current rates of energy consumption, effective conversion of this renewable yet intermittent resource into a transportable and dispatchable chemical fuel may ensure the goal of a sustainable energy future. However, low conversion efficiencies, particularly with CO(2) reduction, as well as utilization of precious materials have limited the practical generation of solar fuels. By using a solar cavity-receiver reactor, we combined the oxygen uptake and release capacity of cerium oxide and facile catalysis at elevated temperatures to thermochemically dissociate CO(2) and H(2)O, yielding CO and H(2), respectively. Stable and rapid generation of fuel was demonstrated over 500 cycles. Solar-to-fuel efficiencies of 0.7 to 0.8% were achieved and shown to be largely limited by the system scale and design rather than by chemistry.

Empirical evidence for stability of the 405-kiloyear Jupiter-Venus eccentricity cycle over hundreds of millions of years.

PubMed

Kent, Dennis V; Olsen, Paul E; Rasmussen, Cornelia; Lepre, Christopher; Mundil, Roland; Irmis, Randall B; Gehrels, George E; Giesler, Dominique; Geissman, John W; Parker, William G

2018-06-12

The Newark-Hartford astrochronostratigraphic polarity timescale (APTS) was developed using a theoretically constant 405-kiloyear eccentricity cycle linked to gravitational interactions with Jupiter-Venus as a tuning target and provides a major timing calibration for about 30 million years of Late Triassic and earliest Jurassic time. While the 405-ky cycle is both unimodal and the most metronomic of the major orbital cycles thought to pace Earth's climate in numerical solutions, there has been little empirical confirmation of that behavior, especially back before the limits of orbital solutions at about 50 million years before present. Moreover, the APTS is anchored only at its younger end by U-Pb zircon dates at 201.6 million years before present and could even be missing a number of 405-ky cycles. To test the validity of the dangling APTS and orbital periodicities, we recovered a diagnostic magnetic polarity sequence in the volcaniclastic-bearing Chinle Formation in a scientific drill core from Petrified Forest National Park (Arizona) that provides an unambiguous correlation to the APTS. New high precision U-Pb detrital zircon dates from the core are indistinguishable from ages predicted by the APTS back to 215 million years before present. The agreement shows that the APTS is continuous and supports a stable 405-kiloyear cycle well beyond theoretical solutions. The validated Newark-Hartford APTS can be used as a robust framework to help differentiate provinciality from global temporal patterns in the ecological rise of early dinosaurs in the Late Triassic, amongst other problems.

The mantle lithosphere and the Wilson Cycle

NASA Astrophysics Data System (ADS)

Heron, Philip; Pysklywec, Russell; Stephenson, Randell

2017-04-01

In the view of the conventional theory of plate tectonics (e.g., the Wilson Cycle), crustal inheritance is often considered important in tectonic evolution. However, the role of the mantle lithosphere is usually overlooked due to its difficulty to image and uncertainty in rheological makeup. Deep seismic imaging has shown potential scarring in continental mantle lithosphere to be ubiquitous. Recent studies have interpreted mantle lithosphere heterogeneities to be pre-existing structures, and as such linked to the Wilson Cycle and inheritance. In our study, we analyze intraplate deformation driven by mantle lithosphere heterogeneities from ancient Wilson Cycle processes and compare this to crustal inheritance deformation. We present 2-D numerical experiments of continental convergence to generate intraplate deformation, exploring the limits of continental rheology to understand the dominant lithosphere layer across a broad range of geological settings. By implementing a "jelly sandwich" rheology, characteristic of stable continental lithosphere, we find that during compression the strength of the mantle lithosphere is integral in controlling deformation from a structural anomaly. We posit that if the continental mantle is the strongest layer within the lithosphere, then such inheritance may have important implications for the Wilson Cycle. Furthermore, our models show that deformation driven by mantle lithosphere scarring can produce tectonic patterns related to intraplate orogenesis originating from crustal sources, highlighting the need for a more formal discussion of the role of the mantle lithosphere in plate tectonics. We outline the difficulty in unravelling the causes of tectonic deformation, alongside discussing the role of deep lithosphere processes in plate tectonics.

Improved Statistical Methods Enable Greater Sensitivity in Rhythm Detection for Genome-Wide Data

PubMed Central

Hutchison, Alan L.; Maienschein-Cline, Mark; Chiang, Andrew H.; Tabei, S. M. Ali; Gudjonson, Herman; Bahroos, Neil; Allada, Ravi; Dinner, Aaron R.

2015-01-01

Robust methods for identifying patterns of expression in genome-wide data are important for generating hypotheses regarding gene function. To this end, several analytic methods have been developed for detecting periodic patterns. We improve one such method, JTK_CYCLE, by explicitly calculating the null distribution such that it accounts for multiple hypothesis testing and by including non-sinusoidal reference waveforms. We term this method empirical JTK_CYCLE with asymmetry search, and we compare its performance to JTK_CYCLE with Bonferroni and Benjamini-Hochberg multiple hypothesis testing correction, as well as to five other methods: cyclohedron test, address reduction, stable persistence, ANOVA, and F24. We find that ANOVA, F24, and JTK_CYCLE consistently outperform the other three methods when data are limited and noisy; empirical JTK_CYCLE with asymmetry search gives the greatest sensitivity while controlling for the false discovery rate. Our analysis also provides insight into experimental design and we find that, for a fixed number of samples, better sensitivity and specificity are achieved with higher numbers of replicates than with higher sampling density. Application of the methods to detecting circadian rhythms in a metadataset of microarrays that quantify time-dependent gene expression in whole heads of Drosophila melanogaster reveals annotations that are enriched among genes with highly asymmetric waveforms. These include a wide range of oxidation reduction and metabolic genes, as well as genes with transcripts that have multiple splice forms. PMID:25793520

Patterns in stable isotope ratios of particulate material from the eastern US continental shelf

EPA Science Inventory

Stable isotope measurements of nitrogen and carbon (δ15N, δ13C) in estuarine, nearshore, and open ocean ecosystems are often utilized in order to characterize human influences, elucidate food web dynamics, or better understand nitrogen cycling. Reliable information a...

Limit cycles in piecewise-affine gene network models with multiple interaction loops

NASA Astrophysics Data System (ADS)

Farcot, Etienne; Gouzé, Jean-Luc

2010-01-01

In this article, we consider piecewise affine differential equations modelling gene networks. We work with arbitrary decay rates, and under a local hypothesis expressed as an alignment condition of successive focal points. The interaction graph of the system may be rather complex (multiple intricate loops of any sign, multiple thresholds, etc.). Our main result is an alternative theorem showing that if a sequence of region is periodically visited by trajectories, then under our hypotheses, there exists either a unique stable periodic solution, or the origin attracts all trajectories in this sequence of regions. This result extends greatly our previous work on a single negative feedback loop. We give several examples and simulations illustrating different cases.

Collective phase description of oscillatory convection

NASA Astrophysics Data System (ADS)

Kawamura, Yoji; Nakao, Hiroya

2013-12-01

We formulate a theory for the collective phase description of oscillatory convection in Hele-Shaw cells. It enables us to describe the dynamics of the oscillatory convection by a single degree of freedom which we call the collective phase. The theory can be considered as a phase reduction method for limit-cycle solutions in infinite-dimensional dynamical systems, namely, stable time-periodic solutions to partial differential equations, representing the oscillatory convection. We derive the phase sensitivity function, which quantifies the phase response of the oscillatory convection to weak perturbations applied at each spatial point, and analyze the phase synchronization between two weakly coupled Hele-Shaw cells exhibiting oscillatory convection on the basis of the derived phase equations.

Piecewise adiabatic following in non-Hermitian cycling

NASA Astrophysics Data System (ADS)

Gong, Jiangbin; Wang, Qing-hai

2018-05-01

The time evolution of periodically driven non-Hermitian systems is in general nonunitary but can be stable. It is hence of considerable interest to examine the adiabatic following dynamics in periodically driven non-Hermitian systems. We show in this work the possibility of piecewise adiabatic following interrupted by hopping between instantaneous system eigenstates. This phenomenon is first observed in a computational model and then theoretically explained, using an exactly solvable model, in terms of the Stokes phenomenon. In the latter case, the piecewise adiabatic following is shown to be a genuine critical behavior and the precise phase boundary in the parameter space is located. Interestingly, the critical boundary for piecewise adiabatic following is found to be unrelated to the domain for exceptional points. To characterize the adiabatic following dynamics, we also advocate a simple definition of the Aharonov-Anandan (AA) phase for nonunitary cyclic dynamics, which always yields real AA phases. In the slow driving limit, the AA phase reduces to the Berry phase if adiabatic following persists throughout the driving without hopping, but oscillates violently and does not approach any limit in cases of piecewise adiabatic following. This work exposes the rich features of nonunitary dynamics in cases of slow cycling and should stimulate future applications of nonunitary dynamics.

The missing biology in land carbon models (Invited)

NASA Astrophysics Data System (ADS)

Prentice, I. C.; Cornwell, W.; Dong, N.; Maire, V.; Wang, H.; Wright, I.

2013-12-01

Models of terrestrial carbon cycling give divergent results, and recent developments - notably the inclusion of nitrogen-carbon cycle coupling - have apparently made matters worse. More extensive benchmarking of models would be highly desirable, but is not a panacea. Problems with current models include overparameterization (assigning separate sets of parameter values for each plant functional type can easily obscure more fundamental model limitations), and the widespread persistence of incorrect paradigms to describe plant responses to environment. Next-generation models require a more sound basis in observations and theory. A possible way forward will be outlined. It will be shown how the principle of optimization by natural selection can yield testable, general hypotheses about plant function. A specific optimality hypothesis about the control of CO2 drawdown versus water loss by leaves will be shown to yield global and quantitatively verifable predictions of plant behaviour as demonstrated in field gas-exchange measurements across species from different environments, and in the global pattern of stable carbon isotope discrimination by plants. Combined with the co-limitation hypothesis for the control of photosynthetic capacity and an economic approach to the costs of nutrient acquisition, this hypothesis provides a potential foundation for a comprehensive predictive understanding of the controls of primary production on land.

Metformin directly acts on mitochondria to alter cellular bioenergetics

PubMed Central

2014-01-01

Background Metformin is widely used in the treatment of diabetes, and there is interest in ‘repurposing’ the drug for cancer prevention or treatment. However, the mechanism underlying the metabolic effects of metformin remains poorly understood. Methods We performed respirometry and stable isotope tracer analyses on cells and isolated mitochondria to investigate the impact of metformin on mitochondrial functions. Results We show that metformin decreases mitochondrial respiration, causing an increase in the fraction of mitochondrial respiration devoted to uncoupling reactions. Thus, cells treated with metformin become energetically inefficient, and display increased aerobic glycolysis and reduced glucose metabolism through the citric acid cycle. Conflicting prior studies proposed mitochondrial complex I or various cytosolic targets for metformin action, but we show that the compound limits respiration and citric acid cycle activity in isolated mitochondria, indicating that at least for these effects, the mitochondrion is the primary target. Finally, we demonstrate that cancer cells exposed to metformin display a greater compensatory increase in aerobic glycolysis than nontransformed cells, highlighting their metabolic vulnerability. Prevention of this compensatory metabolic event in cancer cells significantly impairs survival. Conclusions Together, these results demonstrate that metformin directly acts on mitochondria to limit respiration and that the sensitivity of cells to metformin is dependent on their ability to cope with energetic stress. PMID:25184038

Population trends in Vermivora warblers are linked to strong migratory connectivity

USGS Publications Warehouse

Kramer, Gunnar R.; Andersen, David; Buehler, David A.; Wood, Petra B.; Peterson, Sean M.; Lehman, Justin A.; Aldinger, Kyle R.; Bulluck, Lesley P.; Harding, Sergio R.; Jones, John A.; Loegering, John P.; Smalling, Curtis G.; Vallender, Rachel; Streby, Henry M.

2018-01-01

Migratory species can experience limiting factors at different locations and during different periods of their annual cycle. In migratory birds, these factors may even occur in different hemispheres. Therefore, identifying the distribution of populations throughout their annual cycle (i.e., migratory connectivity) can reveal the complex ecological and evolutionary relationships that link species and ecosystems across the globe and illuminate where and how limiting factors influence population trends. A growing body of literature continues to identify species that exhibit weak connectivity wherein individuals from distinct breeding areas co-occur during the nonbreeding period. A detailed account of a broadly distributed species exhibiting strong migratory connectivity in which nonbreeding isolation of populations is associated with differential population trends remains undescribed. Here, we present a range-wide assessment of the nonbreeding distribution and migratory connectivity of two broadly dispersed Nearctic-Neotropical migratory songbirds. We used geolocators to track the movements of 70 Vermivora warblers from sites spanning their breeding distribution in eastern North America and identified links between breeding populations and nonbreeding areas. Unlike blue-winged warblers (Vermivora cyanoptera), breeding populations of golden-winged warblers (Vermivora chrysoptera) exhibited strong migratory connectivity, which was associated with historical trends in breeding populations: stable for populations that winter in Central America and declining for those that winter in northern South America.

Polyethylene oxide film coating enhances lithium cycling efficiency of an anode-free lithium-metal battery.

PubMed

Assegie, Addisu Alemayehu; Cheng, Ju-Hsiang; Kuo, Li-Ming; Su, Wei-Nien; Hwang, Bing-Joe

2018-03-29

The practical implementation of an anode-free lithium-metal battery with promising high capacity is hampered by dendrite formation and low coulombic efficiency. Most notably, these challenges stem from non-uniform lithium plating and unstable SEI layer formation on the bare copper electrode. Herein, we revealed the homogeneous deposition of lithium and effective suppression of dendrite formation using a copper electrode coated with a polyethylene oxide (PEO) film in an electrolyte comprising 1 M LiTFSI, DME/DOL (1/1, v/v) and 2 wt% LiNO3. More importantly, the PEO film coating promoted the formation of a thin and robust SEI layer film by hosting lithium and regulating the inevitable reaction of lithium with the electrolyte. The modified electrode exhibited stable cycling of lithium with an average coulombic efficiency of ∼100% over 200 cycles and low voltage hysteresis (∼30 mV) at a current density of 0.5 mA cm-2. Moreover, we tested the anode-free battery experimentally by integrating it with an LiFePO4 cathode into a full-cell configuration (Cu@PEO/LiFePO4). The new cell demonstrated stable cycling with an average coulombic efficiency of 98.6% and capacity retention of 30% in the 200th cycle at a rate of 0.2C. These impressive enhancements in cycle life and capacity retention result from the synergy of the PEO film coating, high electrode-electrolyte interface compatibility, stable polar oligomer formation from the reduction of 1,3-dioxolane and the generation of SEI-stabilizing nitrite and nitride upon lithium nitrate reduction. Our result opens up a new route to realize anode-free batteries by modifying the copper anode with PEO to achieve ever more demanding yet safe interfacial chemistry and control of dendrite formation.

Periodic or chaotic bursting dynamics via delayed pitchfork bifurcation in a slow-varying controlled system

NASA Astrophysics Data System (ADS)

Yu, Yue; Zhang, Zhengdi; Han, Xiujing

2018-03-01

In this work, we aim to demonstrate the novel routes to periodic and chaotic bursting, i.e., the different bursting dynamics via delayed pitchfork bifurcations around stable attractors, in the classical controlled Lü system. First, by computing the corresponding characteristic polynomial, we determine where some critical values about bifurcation behaviors appear in the Lü system. Moreover, the transition mechanism among different stable attractors has been introduced including homoclinic-type connections or chaotic attractors. Secondly, taking advantage of the above analytical results, we carry out a study of the mechanism for bursting dynamics in the Lü system with slowly periodic variation of certain control parameter. A distinct delayed supercritical pitchfork bifurcation behavior can be discussed when the control item passes through bifurcation points periodically. This delayed dynamical behavior may terminate at different parameter areas, which leads to different spiking modes around different stable attractors (equilibriums, limit cycles, or chaotic attractors). In particular, the chaotic attractor may appear by Shilnikov connections or chaos boundary crisis, which leads to the occurrence of impressive chaotic bursting oscillations. Our findings enrich the study of bursting dynamics and deepen the understanding of some similar sorts of delayed bursting phenomena. Finally, some numerical simulations are included to illustrate the validity of our study.

The detection and stabilisation of limit cycle for deterministic finite automata

NASA Astrophysics Data System (ADS)

Han, Xiaoguang; Chen, Zengqiang; Liu, Zhongxin; Zhang, Qing

2018-04-01

In this paper, the topological structure properties of deterministic finite automata (DFA), under the framework of the semi-tensor product of matrices, are investigated. First, the dynamics of DFA are converted into a new algebraic form as a discrete-time linear system by means of Boolean algebra. Using this algebraic description, the approach of calculating the limit cycles of different lengths is given. Second, we present two fundamental concepts, namely, domain of attraction of limit cycle and prereachability set. Based on the prereachability set, an explicit solution of calculating domain of attraction of a limit cycle is completely characterised. Third, we define the globally attractive limit cycle, and then the necessary and sufficient condition for verifying whether all state trajectories of a DFA enter a given limit cycle in a finite number of transitions is given. Fourth, the problem of whether a DFA can be stabilised to a limit cycle by the state feedback controller is discussed. Criteria for limit cycle-stabilisation are established. All state feedback controllers which implement the minimal length trajectories from each state to the limit cycle are obtained by using the proposed algorithm. Finally, an illustrative example is presented to show the theoretical results.

Phase Restructuring in Transition Metal Dichalcogenides for Highly Stable Energy Storage.

PubMed

Leng, Kai; Chen, Zhongxin; Zhao, Xiaoxu; Tang, Wei; Tian, Bingbing; Nai, Chang Tai; Zhou, Wu; Loh, Kian Ping

2016-09-28

Achieving homogeneous phase transition and uniform charge distribution is essential for good cycle stability and high capacity when phase conversion materials are used as electrodes. Herein, we show that chemical lithiation of bulk 2H-MoS 2 distorts its crystalline domains in three primary directions to produce mosaic-like 1T' nanocrystalline domains, which improve phase and charge uniformity during subsequent electrochemical phase conversion. 1T'-Li x MoS 2 , a macroscopic dense material with interconnected nanoscale grains, shows excellent cycle stability and rate capability in a lithium rechargeable battery compared to bulk or exfoliated-restacked MoS 2 . Transmission electron microscopy studies reveal that the interconnected MoS 2 nanocrystals created during the phase change process are reformable even after multiple cycles of galvanostatic charging/discharging, which allows them to play important roles in the long term cycling performance of the chemically intercalated TMD materials. These studies shed light on how bulk TMDs can be processed into quasi-2D nanophase material for stable energy storage.

Interior Fracture Mechanism Analysis and Fatigue Life Prediction of Surface-Hardened Gear Steel under Axial Loading.

PubMed

Li, Wei; Deng, Hailong; Liu, Pengfei

2016-10-18

The interior defect-induced fracture of surface-hardened metallic materials in the long life region has become a key issue on engineering design. In the present study, the axial loading test with fully reversed condition was performed to examine the fatigue property of a surface-carburized low alloy gear steel in the long life region. Results show that this steel represents the duplex S-N (stress-number of cycles) characteristics without conventional fatigue limit related to 10⁷ cycles. Fatigue cracks are all originated from the interior inclusions in the matrix region due to the inhabitation effect of carburized layer. The inclusion induced fracture with fisheye occurs in the short life region below 5 × 10⁵ cycles, whereas the inclusion induced fracture with fine granular area (FGA) and fisheye occurs in the long life region beyond 10⁶ cycles. The stress intensity factor range at the front of FGA can be regarded as the threshold value controlling stable growth of interior long crack. The evaluated maximum inclusion size in the effective damage volume of specimen is about 27.29 μm. Considering the size relationships between fisheye and FGA, and inclusion, the developed life prediction method involving crack growth can be acceptable on the basis of the good agreement between the predicted and experimental results.

Phase I trial of volasertib, a Polo-like kinase inhibitor, plus platinum agents in solid tumors: safety, pharmacokinetics and activity.

PubMed

Awada, Ahmad; Dumez, Herlinde; Aftimos, Philippe G; Costermans, Jo; Bartholomeus, Sylvie; Forceville, Kathleen; Berghmans, Thierry; Meeus, Marie-Anne; Cescutti, Jessica; Munzert, Gerd; Pilz, Korinna; Liu, Dan; Schöffski, Patrick

2015-06-01

This trial evaluated the maximum tolerated dose (MTD), safety, pharmacokinetics, and activity of volasertib, a selective Polo-like kinase 1 inhibitor that induces mitotic arrest and apoptosis, combined with cisplatin or carboplatin in patients with advanced/metastatic solid tumors (NCT00969761; 1230.6). Sequential patient cohorts (3 + 3 dose-escalation design) received a single infusion of volasertib (100-350 mg) with cisplatin (60-100 mg/m(2)) or carboplatin (area under the concentration versus time curve [AUC]4-AUC6) on day 1 every 3 weeks for up to six cycles. Sixty-one patients received volasertib/cisplatin (n = 30) or volasertib/carboplatin (n = 31) for a median of 3.5 (range, 1-6) and 2.0 (range, 1-6) treatment cycles, respectively. The most common cycle 1 dose-limiting toxicities (DLTs) were thrombocytopenia, neutropenia and fatigue. MTDs (based on cycle 1 DLTs) were determined to be volasertib 300 mg plus cisplatin 100 mg/m(2) and volasertib 300 mg plus carboplatin AUC6. Co-administration did not affect the pharmacokinetics of each drug. Partial responses were observed in two patients in each arm. Stable disease was achieved in 11 and six patients treated with volasertib/cisplatin and volasertib/carboplatin, respectively. Volasertib plus cisplatin or carboplatin at full single-agent doses was generally manageable and demonstrated activity in heavily pretreated patients with advanced solid tumors.

Long term stability of Li-S batteries using high concentration lithium nitrate electrolytes

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

Adams, Brian D.; Carino, Emily V.; Connell, Justin G.

Lithium-sulfur (Li-S) battery is a very promising candidate for the next generation of energy storage systems required for electrical vehicles and grid energy storage applications due to its very high theoretical specific energy (2500 W h kg-1). However, the low coulombic efficiency (CE) during repeated Li plating/stripping of these processes have limited practical application of rechargeable Li-S batteries. In this work, a new electrolyte system based on high concentration of LiNO3 in diglyme solvent is developed which enables high CE of Li metal plating/stripping and high stability of Li anode in the sulfur containing electrolyte. Tailoring of electrolyte properties formore » the Li negative electrode has proven to be a successful strategy for improving the capacity retention and cycle life of Li-S batteries. This electrolyte provides a CE for Li plating/stripping of greater than 99% for over 200 cycles. In contrast, Li metal cycles for only less than 35 cycles at high CE in the standard 1 M LiTFSI + 2wt% LiNO3 in DOL:DME electrolyte under the same conditions. The stable Li metal anode enabled by the new electrolyte may accelerate the applications of high energy density Li-S batteries in both electrical vehicles and large-scale grid energy storage markets.« less

Li3PO4 Matrix Enables a Long Cycle Life and High Energy Efficiency Bismuth-Based Battery.

PubMed

Sun, Chuan-Fu; Hu, Junkai; Wang, Peng; Cheng, Xi-Yuan; Lee, Sang Bok; Wang, YuHuang

2016-09-14

Bismuth is a lithium-ion battery anode material that can operate at an equilibrium potential higher than graphite and provide a capacity twice as high as that of Li4Ti5O12, making it intrinsically free from lithium plating that may cause catastrophic battery failure. However, the potential of bismuth is hampered by its inferior cyclability (limited to tens of cycles). Here, we propose an "ion conductive solid-state matrix" approach to address this issue. By homogeneously confining bismuth nanoparticles in a solid-state γ-Li3PO4 matrix that is electrochemically formed in situ, the resulting composite anode exhibits a reversible capacity of 280 mA hours per gram (mA h/g) at a rate of 100 mA/g and a record cyclability among bismuth-based anodes up to 500 cycles with a capacity decay rate of merely 0.071% per cycle. We further show that full-cell batteries fabricated from this composite anode and commercial LiFePO4 cathode deliver a stable cell voltage of ∼2.5 V and remarkable energy efficiency up to 86.3%, on par with practical batteries (80-90%). This work paves a way for harnessing bismuth-based battery chemistry for the design of high capacity, safer lithium-ion batteries to meet demanding applications such as electric vehicles.

Local neuropeptide signaling modulates serotonergic transmission to shape the temporal organization of C. elegans egg-laying behavior

PubMed Central

Banerjee, Navonil; Bhattacharya, Raja; Francis, Michael M.

2017-01-01

Animal behaviors are often composed of distinct alternating behavioral states. Neuromodulatory signals are thought to be critical for establishing stable behavioral states and for orchestrating transitions between them. However, we have only a limited understanding of how neuromodulatory systems act in vivo to alter circuit performance and shape behavior. To address these questions, we have investigated neuromodulatory signaling in the context of Caenorhabditis elegans egg-laying. Egg-laying activity cycles between discrete states–short bursts of egg deposition (active phases) that alternate with prolonged quiescent periods (inactive phases). Here using genetic, pharmacological and optogenetic approaches for cell-specific activation and inhibition, we show that a group of neurosecretory cells (uv1) located in close spatial proximity to the egg-laying neuromusculature direct the temporal organization of egg-laying by prolonging the duration of inactive phases. We demonstrate that the modulatory effects of the uv1 cells are mediated by peptides encoded by the nlp-7 and flp-11 genes that act locally to inhibit circuit activity, primarily by inhibiting vesicular release of serotonin from HSN motor neurons. This peptidergic inhibition is achieved, at least in part, by reducing synaptic vesicle abundance in the HSN motor neurons. By linking the in vivo actions of specific neuropeptide signaling systems with the generation of stable behavioral outcomes, our study reveals how cycles of neuromodulation emanating from non-neuronal cells can fundamentally shape the organization of a behavioral program. PMID:28384151

USE OF THE COMPOSITION AND STABLE CARBONIISOTOPE RATIO OF MICROBIAL FATTY ACIDS TO STUDY CARBON CYCLING

EPA Science Inventory

We use measurements of the concentration and stable carbon isotopic ratio (*13C) of individual microbial phospholipid fatty acids (PLFAs) in soils and sediments as indicators of live microbial biomass levels and microbial carbon source. For studies of soil organic matter (SOM) cy...

FATTY ACID STABLE ISOTOPE INDICATORS OF MICROBIAL CARBON SOURCE IN TROPICAL SOILS

EPA Science Inventory

The soil microbial community plays an important role in tropical ecosystem functioning because of its importance in the soil organic matter (SOM) cycle. We have measured the stable carbon isotopic ratio (delta13C) of individual phospholipid fatty acids (PLFAs) in a variety of tr...

40 CFR 86.140-94 - Exhaust sample analysis.

Code of Federal Regulations, 2011 CFR

2011-07-01

...-cycle and methanol-fueled, natural gas-fueled and liquefied petroleum gas-fueled (if non-heated FID option is used) diesel vehicle HC: (1) Zero the analyzers and obtain a stable zero reading. Recheck after...: (1) Zero HFID analyzer and obtain a stable zero reading. (2) Introduce span gas and set instrument...

40 CFR 86.140-94 - Exhaust sample analysis.

Code of Federal Regulations, 2010 CFR

2010-07-01

...-cycle and methanol-fueled, natural gas-fueled and liquefied petroleum gas-fueled (if non-heated FID option is used) diesel vehicle HC: (1) Zero the analyzers and obtain a stable zero reading. Recheck after...: (1) Zero HFID analyzer and obtain a stable zero reading. (2) Introduce span gas and set instrument...

Physiological effects of environmentally relevant, multi-day thermal stress on wild juvenile Atlantic salmon (Salmo salar).

PubMed

Corey, Emily; Linnansaari, Tommi; Cunjak, Richard A; Currie, Suzanne

2017-01-01

The frequency of extreme thermal events in temperate freshwater systems is expected to increase alongside global surface temperature. The Miramichi River, located in eastern Canada, is a prominent Atlantic salmon ( Salmo salar ) river where water temperatures can exceed the proposed upper thermal limit for the species (~27°C). Current legislation closes the river to recreational angling when water temperatures exceed 20°C for two consecutive nights. We aimed to examine how natural thermal variation, representative of extreme high thermal events, affected the thermal tolerance and physiology of wild, juvenile Atlantic salmon. We acclimated fish to four thermal cycles, characteristic of real-world thermal conditions while varying daily thermal minima (16°C, 18°C, 20°C or 22°C) and diel thermal fluctuation (e.g. Δ5°C-Δ9°C). In each cycling condition, we assessed the role that thermal minima played on the acute thermal tolerance (critical thermal maximum, (CTMax)), physiological (e.g. heat shock protein 70 (HSP70), ubiquitin) and energetic (e.g. hepatic glycogen, blood glucose and lactate) status of juvenile Atlantic salmon throughout repeated thermal cycles. Exposure to 16-21°C significantly increased CTMax (+0.9°C) compared to a stable acclimation temperature (16°C), as did exposure to diel thermal fluctuations of 18-27°C, 20-27°C and 22-27°C, yet repeated exposure provided no further increases in acute thermal tolerance. In comparison to the reference condition (16-21°C), consecutive days of high temperature cycling with different thermal minima resulted in significant increases in HSP70 and ubiquitin, a significant decrease in liver glycogen, and no significant cumulative effect on either blood glucose or lactate. However, comparison between thermally taxed treatments suggested the diel thermal minima had little influence on the physiological or energetic response of juvenile salmon, despite the variable thermal cycling condition. Our results suggest that relatively cooler night temperatures in the summer months may play a limited role in mitigating physiological stress throughout warm diel cycle events.

Impact of the Diurnal Cycle of the Atmospheric Boundary Layer on Wind-Turbine Wakes: A Numerical Modelling Study

NASA Astrophysics Data System (ADS)

Englberger, Antonia; Dörnbrack, Andreas

2018-03-01

The wake characteristics of a wind turbine for different regimes occurring throughout the diurnal cycle are investigated systematically by means of large-eddy simulation. Idealized diurnal cycle simulations of the atmospheric boundary layer are performed with the geophysical flow solver EULAG over both homogeneous and heterogeneous terrain. Under homogeneous conditions, the diurnal cycle significantly affects the low-level wind shear and atmospheric turbulence. A strong vertical wind shear and veering with height occur in the nocturnal stable boundary layer and in the morning boundary layer, whereas atmospheric turbulence is much larger in the convective boundary layer and in the evening boundary layer. The increased shear under heterogeneous conditions changes these wind characteristics, counteracting the formation of the night-time Ekman spiral. The convective, stable, evening, and morning regimes of the atmospheric boundary layer over a homogeneous surface as well as the convective and stable regimes over a heterogeneous surface are used to study the flow in a wind-turbine wake. Synchronized turbulent inflow data from the idealized atmospheric boundary-layer simulations with periodic horizontal boundary conditions are applied to the wind-turbine simulations with open streamwise boundary conditions. The resulting wake is strongly influenced by the stability of the atmosphere. In both cases, the flow in the wake recovers more rapidly under convective conditions during the day than under stable conditions at night. The simulated wakes produced for the night-time situation completely differ between heterogeneous and homogeneous surface conditions. The wake characteristics of the transitional periods are influenced by the flow regime prior to the transition. Furthermore, there are different wake deflections over the height of the rotor, which reflect the incoming wind direction.

The Pleistocene evolution of the East Antarctic Ice Sheet in the Prydz bay region: Stable isotopic evidence from ODP Site 1167

USGS Publications Warehouse

Theissen, K.M.; Dunbar, R.B.; Cooper, A. K.; Mucciarone, D.A.; Hoffmann, D.

2003-01-01

Ocean Drilling Program Leg 188, Prydz Bay, East Antarctica is part of a larger initiative to explore the Cenozoic history of the Antarctic Ice Sheet through direct drilling and sampling of the continental margins. In this paper, we present stable isotopic results from Ocean Drilling Program (ODP) Site 1167 located on the Prydz Channel Trough Mouth Fan (TMF), the first Antarctic TMF to be drilled. The foraminifer-based ??18O record is interpreted along with sedimentary and downhole logging evidence to reconstruct the Quaternary glacial history of Prydz Bay and the adjacent Lambert Glacier Amery Ice Shelf System (LGAISS). We report an electron spin resonance age date of 36. 9 ?? 3.3 ka at 0.45 m below sea floor and correlate suspected glacial-interglacial cycles with the global isotopic stratigraphy to improve the chronology for Site 1167. The ??18O record based on planktonic (Neogloboquadrina pachyderma (s.)) and limited benthic results (Globocassidulina crassa), indicates a trend of ice sheet expansion that was interrupted by a period of reduced ice volume and possibly warmer conditions during the early-mid-Pleistocene (0.9-1.38 Ma). An increase in ?? 18O values after ??? 900 ka appears to coincide with the mid-Pleistocene climate transition and the expansion of the northern hemisphere ice sheet. The ??18O record in the upper 50 m of the stratigraphic section indicates as few as three glacial-interglacial cycles, tentatively assigned as marine isotopic stages (MIS) 16-21, are preserved since the Brunhes/Matuyama paleomagnetic reversal (780 ka). This suggests that there is a large unconformity near the top of the section and/or that there may have been few extreme advances of the ice sheet since the mid-Pleistocene climate transition resulting in lowered sedimentation rates on the Prydz Channel TMF. The stable isotopic record from Site 1167 is one of the few available from the area south of the Antarctic Polar Front that has been linked with the global isotopic stratigraphy. Our results suggest the potential for the recovery of useful stable isotopic records in other TMFs. ?? 2003 Elsevier B.V. All rights reserved.

Reversible Self-Assembly of Glutathione-Coated Gold Nanoparticle Clusters via pH-Tunable Interactions

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

Moaseri, Ehsan; Bollinger, Jonathan A.; Changalvaie, Behzad

In this study, nanoparticle (NP) clusters with diameters ranging from 20 to 100 nm are reversibly assembled from 5 nm gold (Au) primary particles coated with glutathione (GSH) in aqueous solution as a function of pH in the range of 5.4 to 3.8. As the pH is lowered, the GSH surface ligands become partially zwitterionic and form interparticle hydrogen bonds that drive the self-limited assembly of metastable clusters in <1 min. Whereas clusters up to 20 nm in size are stable against cluster–cluster aggregation for up to 1 day, clusters up to 80 nm in size can be stabilized overmore » this period via the addition of citrate to the solution in equal molarity with GSH molecules. The cluster diameter may be cycled reversibly by tuning pH to manipulate the colloidal interactions; however, modest background cluster–cluster aggregation occurs during cycling. Cluster sizes can be stabilized for at least 1 month via the addition of PEG-thiol as a grafted steric stabilizer, where PEG-grafted clusters dissociate back to starting primary NPs at pH 7 in fewer than 3 days. Whereas the presence of excess citrate has little effect on the initial size of the metastable clusters, it is necessary for both the cycling and dissociation to mediate the GSH–GSH hydrogen bonds. In conclusion, these metastable clusters exhibit significant characteristics of equilibrium self-limited assembly between primary particles and clusters on time scales where cluster–cluster aggregation is not present.« less

Reversible Self-Assembly of Glutathione-Coated Gold Nanoparticle Clusters via pH-Tunable Interactions

DOE PAGES

Moaseri, Ehsan; Bollinger, Jonathan A.; Changalvaie, Behzad; ...

2017-10-06

In this study, nanoparticle (NP) clusters with diameters ranging from 20 to 100 nm are reversibly assembled from 5 nm gold (Au) primary particles coated with glutathione (GSH) in aqueous solution as a function of pH in the range of 5.4 to 3.8. As the pH is lowered, the GSH surface ligands become partially zwitterionic and form interparticle hydrogen bonds that drive the self-limited assembly of metastable clusters in <1 min. Whereas clusters up to 20 nm in size are stable against cluster–cluster aggregation for up to 1 day, clusters up to 80 nm in size can be stabilized overmore » this period via the addition of citrate to the solution in equal molarity with GSH molecules. The cluster diameter may be cycled reversibly by tuning pH to manipulate the colloidal interactions; however, modest background cluster–cluster aggregation occurs during cycling. Cluster sizes can be stabilized for at least 1 month via the addition of PEG-thiol as a grafted steric stabilizer, where PEG-grafted clusters dissociate back to starting primary NPs at pH 7 in fewer than 3 days. Whereas the presence of excess citrate has little effect on the initial size of the metastable clusters, it is necessary for both the cycling and dissociation to mediate the GSH–GSH hydrogen bonds. In conclusion, these metastable clusters exhibit significant characteristics of equilibrium self-limited assembly between primary particles and clusters on time scales where cluster–cluster aggregation is not present.« less

Effect of repeated drying-wetting-freezing-thawing cycles on the active soil organic carbon pool

NASA Astrophysics Data System (ADS)

Semenov, V. M.; Kogut, B. M.; Lukin, S. M.

2014-04-01

Samples of soddy-podzolic soil (long-term overgrown fallow and continuous bare fallow), gray forest soil (forest, farming agrocenosis), and a typical chernozem (virgin steppe, forest area, farming agrocenosis, continuous bare fallow) have been incubated under stable conditions; other samples of these soils have been subjected to six drying-wetting-incubation-freezing-thawing-incubation cycles during 136 days. The wetting of dried soils and the thawing of frozen soils result in an abrupt but short increase in the emission rate of C-CO2 by 2.7-12.4 and 1.6-2.7 times, respectively, compared to the stable incubation conditions. As the soil is depleted in potentially mineralizable organic matter, the rate of the C-CO2 emission pulses initiated by disturbing impacts decreases. The cumulative extra production of C-CO2 by soils of natural lands for six cycles makes up 21-40% of that in the treatments with stable incubation conditions; the corresponding value for cultivated soils, including continuous clean fallow, is in the range of 45-82%. The content of potentially mineralizable organic matter in the soils subjected to recurrent drying-wetting-freezingthawing cycles decreased compared to the soils without disturbing impacts by 1.6-4.4 times, and the mineralization constants decreased by 1.9-3.6 times. It has been emphasized that the cumulative effect of drying-wetting-freezing-thawing cycles is manifested not only in the decrease in the total Corg from the soil but also in the reduction of the mineralization potential of the soil organic matter.

Comparison of the quench and fault current limiting characteristics of the flux-coupling type SFCL with single and three-phase transformer

NASA Astrophysics Data System (ADS)

Jung, Byung Ik; Cho, Yong Sun; Park, Hyoung Min; Chung, Dong Chul; Choi, Hyo Sang

2013-01-01

The South Korean power grid has a network structure for the flexible operation of the system. The continuously increasing power demand necessitated the increase of power facilities, which decreased the impedance in the power system. As a result, the size of the fault current in the event of a system fault increased. As this increased fault current size is threatening the breaking capacity of the circuit breaker, the main protective device, a solution to this problem is needed. The superconducting fault current limiter (SFCL) has been designed to address this problem. SFCL supports the stable operation of the circuit breaker through its excellent fault-current-limiting operation [1-5]. In this paper, the quench and fault current limiting characteristics of the flux-coupling-type SFCL with one three-phase transformer were compared with those of the same SFCL type but with three single-phase transformers. In the case of the three-phase transformers, both the superconducting elements of the fault and sound phases were quenched, whereas in the case of the single-phase transformer, only that of the fault phase was quenched. For the fault current limiting rate, both cases showed similar rates for the single line-to-ground fault, but for the three-wire earth fault, the fault current limiting rate of the single-phase transformer was over 90% whereas that of the three-phase transformer was about 60%. It appears that when the three-phase transformer was used, the limiting rate decreased because the fluxes by the fault current of each phase were linked in one core. When the power loads of the superconducting elements were compared by fault type, the initial (half-cycle) load was great when the single-phase transformer was applied, whereas for the three-phase transformer, its power load was slightly lower at the initial stage but became greater after the half fault cycle.

47 CFR 27.50 - Power limits and duty cycle.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 2 2010-10-01 2010-10-01 false Power limits and duty cycle. 27.50 Section 27... MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES Technical Standards § 27.50 Power limits and duty cycle. (a) The... duty cycle must not exceed 38 percent; for WCS CPE using FDD technology, the duty cycle must not exceed...

Reliability improvements in tunable Pb1-xSnxSe diode lasers

NASA Technical Reports Server (NTRS)

Linden, K. J.; Butler, J. F.; Nill, K. W.; Reeder, R. E.

1980-01-01

Recent developments in the technology of Pb-salt diode lasers which have led to significant improvements in reliability and lifetime, and to improved operation at very long wavelengths are described. A combination of packaging and contacting-metallurgy improvements has led to diode lasers that are stable both in terms of temperature cycling and shelf-storage time. Lasers cycled over 500 times between 77 K and 300 K have exhibited no measurable changes in either electrical contact resistance or threshold current. Utilizing metallurgical contacting process, both lasers and experimental n-type and p-type bulk materials are shown to have electrical contact resistance values that are stable for shelf storage periods well in excess of one year. Problems and experiments which have led to devices with improved performance stability are discussed. Stable device configurations achieved for material compositions yielding lasers which operate continuously at wavelengths as long as 30.3 micrometers are described.

Encapsulated monoclinic sulfur for stable cycling of li-s rechargeable batteries.

PubMed

Moon, San; Jung, Young Hwa; Jung, Wook Ki; Jung, Dae Soo; Choi, Jang Wook; Kim, Do Kyung

2013-12-03

Monoclinic S8 , an uncommon allotrope of sulfur at room temperature, can be formed when common orthorhombic S8 is heat-treated under enclosed environments in nanometer dimensions. Monoclinic S8 prevents the formation of soluble polysulfides during battery operation, resulting in unprecedented cycling performance over 1000 cycles under the highest sulfur content to date. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dynamics and control of the vortex flow behind a slender conical forebody by a pair of plasma actuators

NASA Astrophysics Data System (ADS)

Meng, Xuanshi; Long, Yuexiao; Wang, Jianlei; Liu, Feng; Luo, Shijun

2018-02-01

Detailed particle-image-velocimetry (PIV) and surface pressure measurements are presented to study the vortex flow behind a slender conical forebody at high angles of attack. The results confirm the existence of two randomly appearing mirror imaged asymmetric bi-stable states of the separation vortices, giving rise to large side force and moment. A pair of carefully designed dielectric barrier discharge plasma actuators mounted near the apex and on both sides of the conical body are used to manipulate the vortex flow and thus provide control of the side forces on the body without using flaps. By making use of a duty-cycle actuation scheme that alternately actuates the port and starboard plasma actuators and optimizing the duty-cycle frequency, the present work demonstrates the feasibility of achieving a nearly perfect linear proportional control of the side force and moment in response to the duty-cycle ratio. Phase-locked PIV and surface pressure measurements are used to study the unsteady dynamic evolution of the flow within one duty-cycle actuation to reveal the flow control mechanism. It is found that under the duty-cycle actuation with the optimized frequency, the vortex flow essentially follows the plasma actuation by alternating between the two bi-stable states controlled directly by the duty-cycle ratio.

Evolutionary behaviour, trade-offs and cyclic and chaotic population dynamics.

PubMed

Hoyle, Andy; Bowers, Roger G; White, Andy

2011-05-01

Many studies of the evolution of life-history traits assume that the underlying population dynamical attractor is stable point equilibrium. However, evolutionary outcomes can change significantly in different circumstances. We present an analysis based on adaptive dynamics of a discrete-time demographic model involving a trade-off whose shape is also an important determinant of evolutionary behaviour. We derive an explicit expression for the fitness in the cyclic region and consequently present an adaptive dynamic analysis which is algebraic. We do this fully in the region of 2-cycles and (using a symbolic package) almost fully for 4-cycles. Simulations illustrate and verify our results. With equilibrium population dynamics, trade-offs with accelerating costs produce a continuously stable strategy (CSS) whereas trade-offs with decelerating costs produce a non-ES repellor. The transition to 2-cycles produces a discontinuous change: the appearance of an intermediate region in which branching points occur. The size of this region decreases as we move through the region of 2-cycles. There is a further discontinuous fall in the size of the branching region during the transition to 4-cycles. We extend our results numerically and with simulations to higher-period cycles and chaos. Simulations show that chaotic population dynamics can evolve from equilibrium and vice-versa.

MULTIPLE STABLE PERIODIC SOLUTIONS IN A MODEL FOR THE HORMONAL REGULATION OF THE MENSTRUAL CYCLE

EPA Science Inventory

ABSTRACT

The pituitary hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and the ovarian hormones, estradiol (E2), progesterone (P4), and inhibin (Ih), are five hormones important for the regulation and maintenance of the human menstrual cycle. The...

Kinetic control on Zn isotope signatures recorded in marine diatoms

NASA Astrophysics Data System (ADS)

Köbberich, Michael; Vance, Derek

2017-08-01

Marine diatoms dominate the oceanic cycle of the essential micronutrient zinc (Zn). The stable isotopes of zinc and other metals are increasingly used to understand trace metal micronutrient cycling in the oceans. One clear feature of the early isotope data is the heavy Zn isotope signature of the average oceanic dissolved pool relative to the inputs, potentially driven by uptake of light isotopes into phytoplankton cells and export to sediments. However, despite the fact that diatoms strip Zn from surface waters across the Antarctic polar front in the Southern Ocean, the local upper ocean is not isotopically heavy. Here we use culturing experiments to quantify the extent of Zn isotope fractionation by diatoms and to elucidate the mechanisms driving it. We have cultured two different open-ocean diatom species (T. oceanica and Chaetoceros sp.) in a series of experiments at constant medium Zn concentration but at bioavailable medium Fe ranging from limiting to replete. We find that T. oceanica can maintain high growth rates and Zn uptake rates over the full range of bioavailable iron (Fe) investigated, and that the Zn taken up has a δ66Zn that is unfractionated relative to that of the bioavailable free Zn in the medium. The studied representative of the genus Chaetoceros, on the other hand, shows more significantly reduced Zn uptake rates at low Fe and records more variable biomass δ66Zn signatures, of up to 0.85‰ heavier than the medium. We interpret the preferential uptake of heavy isotopes at extremely low Zn uptake rates as potentially due to either of the following two mechanisms. First, the release of extracellular polymeric substances (EPS), at low Fe levels, may preferentially scavenge heavy Zn isotopes. Second, the Zn uptake rate may be slow enough to establish pseudo-equilibrium conditions at the transporter site, with heavy Zn isotopes forming more stable surface complexes. Thus we find that, in our experiments, Fe-limitation exerts a key control that not only limits diatom growth, but also affects the Zn uptake physiology of diatoms. Uptake of heavy isotopes occurs under Fe-limiting conditions that drive extremely low Zn uptake rates. On the other hand, more rapid Zn uptake rates result in biomass that is indistinguishable from the external bioavailable free Zn pool. These experimental results can, in principle, explain the range of Zn isotopic compositions found in the real surface ocean, given the geographically variable interplay between Fe-limitation, Zn uptake rates, and the degree of organic complexation of oceanic Zn.

USE OF THE COMPOSITION AND STABLE CARBON ISOTOPE RATIO OF MICROBIAL FATTY ACIDS TO STUDY CARBON CYCLING

EPA Science Inventory

We use measurements of the concentration and stable carbon isotopic ratio (Gamma 13C) of individual microbial phospholipid fatty acids (PLFAS) in soils and sediments as indicators of live microbial biomass levels and microbial carbon source. For studies of soil organic matter (SO...

Bifurcation of small limit cycles in cubic integrable systems using higher-order analysis

NASA Astrophysics Data System (ADS)

Tian, Yun; Yu, Pei

2018-05-01

In this paper, we present a method of higher-order analysis on bifurcation of small limit cycles around an elementary center of integrable systems under perturbations. This method is equivalent to higher-order Melinikov function approach used for studying bifurcation of limit cycles around a center but simpler. Attention is focused on planar cubic polynomial systems and particularly it is shown that the system studied by Żoła¸dek (1995) [24] can indeed have eleven limit cycles under perturbations at least up to 7th order. Moreover, the pattern of numbers of limit cycles produced near the center is discussed up to 39th-order perturbations, and no more than eleven limit cycles are found.

Sulfur isotope biogeochemistry of soils from an episodically flooded coastal wetland, southern Baltic Sea

NASA Astrophysics Data System (ADS)

Fernández Fernández, Luz Eva; Westphal, Julia; Schmiedinger, Iris; Kreuzburg, Matthias; Bahlo, Reiner; Koebsch, Franziska; Böttcher, Michael E.

2017-04-01

Coastal wetlands are under dynamic impact both from fresh water and salt water sources, thereby experiencing temporarily sulfur-excess and -limiting conditions. In the present study, nine up to 10 meter long sediment cores from a recently rewetted fen (Hütelmoor, southern Baltic Sea) which has been under impact by episodic flooding with brackish waters were investigated (isotope) geochemically. The sites are positioned at different distances to the Baltic Sea coastline. The soils were analyzed for the elemental composition (CNS), reactive iron and sedimentary sulfur contents, iron sulfide micro-textures, as well as the stable sulfur isotope composition of inorganic and organic sulfur fractions to understand signal development for the biogeochemical carbon-sulfur cycles in such a dynamic ecosystem. We found evidence for the activity of dissimilatory sulfate-reducing microorganisms and the associated formation of pyrite with different textures (framboids, single euhedral crystals and clusters) and sulfurization of organic matter. Sedimentary sulfur fractions and their stable isotope signatures are controlled by the availability of dissolved organic matter or methane, reactive iron, and in particular dissolved sulfate and thereby from the relative position to the coast line and the given lithology. d34S values in the pyrite fraction vary in a wide range between -21 and +15 per mil versus VCDT, in agreement with spatial and temporal dynamics in the extend of sulfate-limiting conditions during the oxidation of reduced carbon.

Exploring the nonlinear cloud and rain equation

NASA Astrophysics Data System (ADS)

Koren, Ilan; Tziperman, Eli; Feingold, Graham

2017-01-01

Marine stratocumulus cloud decks are regarded as the reflectors of the climate system, returning back to space a significant part of the income solar radiation, thus cooling the atmosphere. Such clouds can exist in two stable modes, open and closed cells, for a wide range of environmental conditions. This emergent behavior of the system, and its sensitivity to aerosol and environmental properties, is captured by a set of nonlinear equations. Here, using linear stability analysis, we express the transition from steady to a limit-cycle state analytically, showing how it depends on the model parameters. We show that the control of the droplet concentration (N), the environmental carrying-capacity (H0), and the cloud recovery parameter (τ) can be linked by a single nondimensional parameter (μ=√{N }/(ατH0) ) , suggesting that for deeper clouds the transition from open (oscillating) to closed (stable fixed point) cells will occur for higher droplet concentration (i.e., higher aerosol loading). The analytical calculations of the possible states, and how they are affected by changes in aerosol and the environmental variables, provide an enhanced understanding of the complex interactions of clouds and rain.

Performance evaluation of a non-woven lithium ion battery separator prepared through a paper-making process

NASA Astrophysics Data System (ADS)

Huang, Xiaosong

2014-06-01

Porous separator functions to electrically insulate the negative and positive electrodes yet communicate lithium ions between the two electrodes when infiltrated with a liquid electrolyte. The separator must fulfill numerous requirements (e.g. permeability, wettability, and thermal stability) in order to optimize the abuse tolerance and electrochemical performance of a battery. Non-woven mat separators have advantages such as high porosity and heat resistance. However, their applications in lithium ion batteries are very limited as their inadequate pore structures could cause accelerated battery performance degradation and even internal short. This work features the development of thermally stable non-woven composite separators using a low cost paper-making process. The composite separators offer significantly improved thermal dimensional stability and exhibit superior wettability by the liquid electrolyte compared to a conventional polypropylene separator. The open porous structures of the non-woven composite separators also resulted in high effective ionic conductivities. The electrochemical performance of the composite separators was tested in coin cells. Stable cycle performances and improved rate capabilities have been observed for the coin cells with these composite separators.

Architecture-Dependent Robustness and Bistability in a Class of Genetic Circuits

PubMed Central

Zhang, Jiajun; Yuan, Zhanjiang; Li, Han-Xiong; Zhou, Tianshou

2010-01-01

Understanding the relationship between genotype and phenotype is a challenge in systems biology. An interesting yet related issue is why a particular circuit topology is present in a cell when the same function can supposedly be obtained from an alternative architecture. Here we analyzed two topologically equivalent genetic circuits of coupled positive and negative feedback loops, named NAT and ALT circuits, respectively. The computational search for the oscillation volume of the entire biologically reasonable parameter region through large-scale random samplings shows that the NAT circuit exhibits a distinctly larger fraction of the oscillatory region than the ALT circuit. Such a global robustness difference between two circuits is supplemented by analyzing local robustness, including robustness to parameter perturbations and to molecular noise. In addition, detailed dynamical analysis shows that the molecular noise of both circuits can induce transient switching of the different mechanism between a stable steady state and a stable limit cycle. Our investigation on robustness and dynamics through examples provides insights into the relationship between network architecture and its function. PMID:20712986

Noise-induced transitions and shifts in a climate-vegetation feedback model.

PubMed

Alexandrov, Dmitri V; Bashkirtseva, Irina A; Ryashko, Lev B

2018-04-01

Motivated by the extremely important role of the Earth's vegetation dynamics in climate changes, we study the stochastic variability of a simple climate-vegetation system. In the case of deterministic dynamics, the system has one stable equilibrium and limit cycle or two stable equilibria corresponding to two opposite (cold and warm) climate-vegetation states. These states are divided by a separatrix going across a point of unstable equilibrium. Some possible stochastic scenarios caused by different externally induced natural and anthropogenic processes inherit properties of deterministic behaviour and drastically change the system dynamics. We demonstrate that the system transitions across its separatrix occur with increasing noise intensity. The climate-vegetation system therewith fluctuates, transits and localizes in the vicinity of its attractor. We show that this phenomenon occurs within some critical range of noise intensities. A noise-induced shift into the range of smaller global average temperatures corresponding to substantial oscillations of the Earth's vegetation cover is revealed. Our analysis demonstrates that the climate-vegetation interactions essentially contribute to climate dynamics and should be taken into account in more precise and complex models of climate variability.

A Consideration of Stable Operating Power Limits of HVDC System Composed of Voltage Source Converters

NASA Astrophysics Data System (ADS)

Konishi, Hiroo; Takahashi, Choei; Kishibe, Hideto; Sato, Hiromichi

The stable operating power limits of a small scale HVDC system composed of voltage source converters (VSC-HVDC system) are analyzed with a simple model. The VSC-HVDC system could operate where the AC system must be somewhat larger in capacity than the VSC-HVDC system capacity. The stable operating power limits were between one and two times the SCR (short circuit ratio). When the inverter of the VSC-HVDC system was operated with lead reactive (capacitive) power control conditions, the stable operating limits were increased through AC voltage stabilization. When the inverter was a STATCOM operation, it could operate regardless of the SCR but regions within allowable AC voltage variations.

Sea-Sponge-like Structure of Nano-Fe3O4 on Skeleton-C with Long Cycle Life under High Rate for Li-Ion Batteries.

PubMed

Chen, Shipei; Wu, Qingnan; Wen, Ming; Wu, Qingsheng; Li, Jiaqi; Cui, Yi; Pinna, Nicola; Fan, Yafei; Wu, Tong

2018-06-13

To meet the demands of long cycle life under high rate for lithium-ion batteries, the advancement of anode materials with stable structural properties is necessarily demanded. Such promotion needs to design reasonable structure to facilitate the transportation of electron and lithium ions (Li + ). Herein, a novel C/Fe 3 O 4 sea-sponge-like structure was synthesized by ultrasonic spray pyrolysis following thermal decomposition process. On the basis of sea-sponge carbon (SSC) excellences in electronic conductivity and short Li + diffusion pathway, nano-Fe 3 O 4 anchored on stable SSC skeleton can deliver high electrochemical performance with long cycle life under high rate. During electrochemical cycling, well-dispersed nano-Fe 3 O 4 in ∼6 nm not only averts excessive pulverization and is enveloped by solid electrolyte interphase film, but also increases Li + diffusion efficiency. The much improved electrochemical properties showed a capacity of around 460 mAh g -1 at a high rate of 1.5C with a retention rate of 93%, which is maintained without degradation up to 1000 cycles (1C = 1000 mA g -1 ).

High performance sulfur graphite full cell for next generation sulfur Li-ion battery

NASA Astrophysics Data System (ADS)

Wu, Yunwen; Momma, Toshiyuki; Yokoshima, Tokihiko; Nara, Hiroki; Osaka, Tetsuya

2018-06-01

Sulfur (S) Li-ion battery which use the metallic Li free anode is deemed as a promising solution to conquer the hazards originating from Li metal. However, stable cycling performance and low production price of the S Li-ion battery still remain challenging. Here, we propose a S-LixC full cell system by paring a S cathode and a pre-lithiated graphite anode which is cheap and commercially available. It shows stable cycling performance with a capacity around 1300 mAh (g-S)-1 at 0.2 C-rate and 1000 mAh (g-S)-1 at 0.5 C-rate. In addition, 0.1% per cycle capacity fading rate with a capacity retention of 880 mAh (g-S)-1 after 400 cycles at 0.2 C-rate has been achieved. The pre-formed solid electrolyte interphase (SEI) layer on the pre-lithaited graphite anode largely contributes to the high capacity performance. Notably, a 10-times-enlarged scale of S-LixC laminate type full cell has been assembled with high capacity performance (around 1000 mAh (g-S)-1) even after high rate cycling.

Electromyographic amplitude variability of chewing cycles in deaf individuals.

PubMed

de Oliveira, A Siriani; Vitti, M; Chaves, T C; Bevilaqua-Grossi, D; Zuccolotto, M C C; Regalo, S C H

2006-09-01

This study had the goal of determining if the amplitude of the surface electromyograph signals changes in terms of time of analysis and subjects, deaf or normal listeners, when estimated in a 250 ms of length window, visually determined, considering the most stable signal period from the center of the chewing cycle. In order to do this, groups with control subjects, listeners and deaf individuals, who made use of the Brazilian sign language (LIBRAS), were studied. All participants performed continuous 5 s of chewing for the electromyographic recording of the temporalis and masseter muscles. The normalized RMS values of three chewing cycles were compared between and among groups. The results from the Kruskall-Wallis test did not show any statistically significant differences (p > 0.05) between the normalized RMS values obtained in the three individual chewing cycles, for each of the two completed and evaluated cycles, in both groups studied. The Mann-Whitney test showed that the mean normalized RMS values obtained in the first chewing cycle were higher for the control group when compared to the mean amplitude values of the first chewing cycle of the group of deaf volunteers. It can be concluded that, in these experimental conditions, the RMS values obtained from the select windows of 250 ms length duration, in relatively stable periods of the electromyographic signal of chewing cycles did not suffer any changes in terms of EMG register duration, in both studied groups, but does give evidence of the differences among the groups.

Nonlinear Dynamic Models in Advanced Life Support

NASA Technical Reports Server (NTRS)

Jones, Harry

2002-01-01

To facilitate analysis, ALS systems are often assumed to be linear and time invariant, but they usually have important nonlinear and dynamic aspects. Nonlinear dynamic behavior can be caused by time varying inputs, changes in system parameters, nonlinear system functions, closed loop feedback delays, and limits on buffer storage or processing rates. Dynamic models are usually cataloged according to the number of state variables. The simplest dynamic models are linear, using only integration, multiplication, addition, and subtraction of the state variables. A general linear model with only two state variables can produce all the possible dynamic behavior of linear systems with many state variables, including stability, oscillation, or exponential growth and decay. Linear systems can be described using mathematical analysis. Nonlinear dynamics can be fully explored only by computer simulations of models. Unexpected behavior is produced by simple models having only two or three state variables with simple mathematical relations between them. Closed loop feedback delays are a major source of system instability. Exceeding limits on buffer storage or processing rates forces systems to change operating mode. Different equilibrium points may be reached from different initial conditions. Instead of one stable equilibrium point, the system may have several equilibrium points, oscillate at different frequencies, or even behave chaotically, depending on the system inputs and initial conditions. The frequency spectrum of an output oscillation may contain harmonics and the sums and differences of input frequencies, but it may also contain a stable limit cycle oscillation not related to input frequencies. We must investigate the nonlinear dynamic aspects of advanced life support systems to understand and counter undesirable behavior.

Stable interstitial layer to alleviate fatigue fracture of high nickel cathode for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Yang, Chengkai; Shao, Ruiwen; Mi, Yingying; Shen, Lanyao; Zhao, Binglu; wang, Qian; Wu, Kai; Lui, Wen; Gao, Peng; Zhou, Henghui

2018-02-01

High nickel cathodes can deliver higher capacity with lower cost than conventional LiCoO2, however, the irreversible structural and morphology degradation with long-term cycling hinder their further application. In this paper, LiNi0.815Co0.15Al0.035O2 agglomerates are treated by LiNi0.333Co0.333Mn0.333O2 coating to get a stable interstitial layer without capacity loss. The interstitial layer is about 10 nm in thickness and has a layered (R-3m) structure, which can improve the chemical and mechanical stability of cathode materials with capacity retention of 88.5% after 200 cycles. The structural analysis and in-situ compression test proves that the morphology degradation is a fatigue process within long-term electrochemical reaction, and the coated sample has an excellent elastic recovery capacity thus leading to long cycle life.

Highly deformation-tolerant carbon nanotube sponges as supercapacitor electrodes.

PubMed

Li, Peixu; Kong, Chuiyan; Shang, Yuanyuan; Shi, Enzheng; Yu, Yuntao; Qian, Weizhong; Wei, Fei; Wei, Jinquan; Wang, Kunlin; Zhu, Hongwei; Cao, Anyuan; Wu, Dehai

2013-09-21

Developing flexible and deformable supercapacitor electrodes based on porous materials is of high interest in energy related fields. Here, we show that carbon nanotube sponges, consisting of highly porous conductive networks, can serve as compressible and deformation-tolerant supercapacitor electrodes in aqueous or organic electrolytes. In aqueous electrolytes, the sponges maintain a similar specific capacitance (>90% of the original value) under a predefined compressive strain of 50% (corresponding to a volume reduction of 50%), and retain more than 70% of the original capacitance under 80% strain while the volume normalized capacitance increases by 3-fold. The sponge electrode maintains a stable performance after 1000 large strain compression cycles. A coin-shaped cell assembled with these sponges shows excellent stability over 15,000 charging cycles with negligible degradation after 500 cycles. Our results indicate that carbon nanotube sponges have the potential to fabricate deformable supercapacitor electrodes with stable performance.

Novel Stable Gel Polymer Electrolyte: Toward a High Safety and Long Life Li-Air Battery.

PubMed

Yi, Jin; Liu, Xizheng; Guo, Shaohua; Zhu, Kai; Xue, Hailong; Zhou, Haoshen

2015-10-28

Nonaqueous Li-air battery, as a promising electrochemical energy storage device, has attracted substantial interest, while the safety issues derived from the intrinsic instability of organic liquid electrolytes may become a possible bottleneck for the future application of Li-air battery. Herein, through elaborate design, a novel stable composite gel polymer electrolyte is first proposed and explored for Li-air battery. By use of the composite gel polymer electrolyte, the Li-air polymer batteries composed of a lithium foil anode and Super P cathode are assembled and operated in ambient air and their cycling performance is evaluated. The batteries exhibit enhanced cycling stability and safety, where 100 cycles are achieved in ambient air at room temperature. The feasibility study demonstrates that the gel polymer electrolyte-based polymer Li-air battery is highly advantageous and could be used as a useful alternative strategy for the development of Li-air battery upon further application.

Impact of unusual fatty acid synthesis on futile cycling through beta-oxidation and on gene expression in transgenic plants.

PubMed

Moire, Laurence; Rezzonico, Enea; Goepfert, Simon; Poirier, Yves

2004-01-01

Arabidopsis expressing the castor bean (Ricinus communis) oleate 12-hydroxylase or the Crepis palaestina linoleate 12-epoxygenase in developing seeds typically accumulate low levels of ricinoleic acid and vernolic acid, respectively. We have examined the presence of a futile cycle of fatty acid degradation in developing seeds using the synthesis of polyhydroxyalkanoate (PHA) from the intermediates of the peroxisomal beta-oxidation cycle. Both the quantity and monomer composition of the PHA synthesized in transgenic plants expressing the 12-epoxygenase and 12-hydroxylase in developing seeds revealed the presence of a futile cycle of degradation of the corresponding unusual fatty acids, indicating a limitation in their stable integration into lipids. The expression profile of nearly 200 genes involved in fatty acid biosynthesis and degradation has been analyzed through microarray. No significant changes in gene expression have been detected as a consequence of the activity of the 12-epoxygenase or the 12-hydroxylase in developing siliques. Similar results have also been obtained for transgenic plants expressing the Cuphea lanceolata caproyl-acyl carrier protein thioesterase and accumulating high amounts of caproic acid. Only in developing siliques of the tag1 mutant, deficient in the accumulation of triacylglycerols and shown to have a substantial futile cycling of fatty acids toward beta-oxidation, have some changes in gene expression been detected, notably the induction of the isocitrate lyase gene. These results indicate that analysis of peroxisomal PHA is a better indicator of the flux of fatty acid through beta-oxidation than the expression profile of genes involved in lipid metabolism.

Impact of Unusual Fatty Acid Synthesis on Futile Cycling through β-Oxidation and on Gene Expression in Transgenic Plants1[w

PubMed Central

Moire, Laurence; Rezzonico, Enea; Goepfert, Simon; Poirier, Yves

2004-01-01

Arabidopsis expressing the castor bean (Ricinus communis) oleate 12-hydroxylase or the Crepis palaestina linoleate 12-epoxygenase in developing seeds typically accumulate low levels of ricinoleic acid and vernolic acid, respectively. We have examined the presence of a futile cycle of fatty acid degradation in developing seeds using the synthesis of polyhydroxyalkanoate (PHA) from the intermediates of the peroxisomal β-oxidation cycle. Both the quantity and monomer composition of the PHA synthesized in transgenic plants expressing the 12-epoxygenase and 12-hydroxylase in developing seeds revealed the presence of a futile cycle of degradation of the corresponding unusual fatty acids, indicating a limitation in their stable integration into lipids. The expression profile of nearly 200 genes involved in fatty acid biosynthesis and degradation has been analyzed through microarray. No significant changes in gene expression have been detected as a consequence of the activity of the 12-epoxygenase or the 12-hydroxylase in developing siliques. Similar results have also been obtained for transgenic plants expressing the Cuphea lanceolata caproyl-acyl carrier protein thioesterase and accumulating high amounts of caproic acid. Only in developing siliques of the tag1 mutant, deficient in the accumulation of triacylglycerols and shown to have a substantial futile cycling of fatty acids toward β-oxidation, have some changes in gene expression been detected, notably the induction of the isocitrate lyase gene. These results indicate that analysis of peroxisomal PHA is a better indicator of the flux of fatty acid through β-oxidation than the expression profile of genes involved in lipid metabolism. PMID:14671017

Species differences in nitrogen cycling in a humid sub-tropical forest inferred from 15N natural abundance

NASA Astrophysics Data System (ADS)

Abdisa Gurmesa, Geshere; Lu, Xiankai; Gundersen, Per; Mao, Qinggong; Zhou, Kaijun; Mo, Jiangming

2017-04-01

Studies of natural abundance of stable nitrogen isotope (δ15N) of ecosystems can provide integrated information about N status and N cycling rates within the ecosystems. Plant species with different N cycling traits can affect ecosystem δ15N, but such differences are poorly explored in tropical forests. This study evaluates the extent of variation in plant δ15N among co-occurring sub-tropical tropical tree species in old-growth mixed broadleaved forest in southern China. We compared leaf δ15N values among five co-occurring tree species under ambient deposition (control plots), and variation in plant δ15N response to a decade of N addition (N-plots) and to a one-year enriched 15N addition to both treatments in the study forest. We found significant differences in leaf δ15N values among tree species (up to 3‰) both in control and N-plots. Responses of leaf δ15N to N and 15N addition also differ among the tree species. These differences are explained by differences in N acquisition strategies (dependence on soil N and/or deposition N among the plant species) that is partly related to differences in mycorrhizal association among the studied plants. Our results indicate that plant species in N-rich tropical forests could have distinct N cycling traits as observed in many predominantly N-limited temperate and boreal forests. The finding, therefore, highlights the importance of considering tree species variation in studying N cycling in N-rich tropical forests.

Chloride-reinforced carbon nanofiber host as effective polysulfide traps in lithium-sulfur batteries

DOE PAGES

Fan, Lei; Zhuang, Houlong; Zhang, Kaihang; ...

2016-01-01

Lithium-sulfur (Li-S) battery is one of the most promising alternatives for the current state-of-art lithium-ion batteries (LIBs) due to its high theoretical energy density and lower production cost from the use of earth abundant element - sulfur. However, the commercialization of Li-S batteries has been so far limited to the cyclability and the retention of active sulfur materials. Using co-electrospinning and physical vapor deposition procedures, we created a class of chloride-carbon nanofiber composites, and studied their effectiveness on polysulfides sequestration. By trapping sulfur reduction products in the modified-cathode through both chemical and physical confinements in a conductive host, these chloride-coatedmore » cathodes are shown to remarkably suppress the polysulfide dissolution and shuttling between lithium and sulfur electrodes. We show that not only the binding energy but also the electronic conductivity of the host plays an important role on the reversibility of sulfur-based cathode upon repeated cycles. Electrochemical analysis of the chloride-modified cathodes over hundreds of cycles indicates that too strong binding of the sulfur species may lead to the decay of Coulombic efficiency. Cells containing indium chloride-modified carbon nanofiber outperform cells with other halogenated salt modifications, delivering an average specific capacity of above 1200mAh g-1 at 0.2C over 200 cycles. Once loaded with high S content, it shows stable capacity retention with only 0.019% decay per cycle from 5th to 650th cycle. It also shows stabilized cyclability and enhanced Coulombic efficiency in the absence of traditional anode stabilizer lithium nitrite.« less

Tropical dendrochemistry: A novel approach to estimate age and growth from ringless trees

NASA Astrophysics Data System (ADS)

Poussart, P. M.; Myneni, S. C. B.; Lanzirotti, A.

2006-09-01

Although tropical forests play an active role in the global carbon cycle and climate, their growth history remains poorly characterized compared to other ecosystems on the planet. Trees are prime candidates for the extraction of paleoclimate archives as they can be probed sub-annually, are widely distributed and can live for over 1400 years [Chambers et al., 1998]. However, dendrochronological techniques have found limited applications in the tropics because trees often lack visible growth rings (Whitmore, 1990). Alternative methods exist (dendrometry (DaSilva et al., 2002), radio- and stable isotopes (Evans and Schrag, 2004; Poussart et al., 2004; Poussart and Schrag, 2005), but the derived records are either of short-duration, lack seasonal resolution or are prohibitively labor intensive to produce. Here, we show the first X-ray microprobe synchrotron record of calcium (Ca) from a ringless Miliusa velutina tree from Thailand and use it to estimate the tree's age and growth history. The Ca age model agrees within <=2 years of bomb-radiocarbon age estimates and confirms that the cycles are seasonal. The amplitude of the Ca annual cycle is correlated significantly with growth and annual Ca maxima correlate with the amount of dry season rainfall. Synchrotron measurements are fast and producing sufficient numbers of replicated multi-century tropical dendrochemical climate records now seems analytically feasible.

High rate psychrophilic anaerobic digestion of high solids (35%) dairy manure in sequence batch reactor.

PubMed

Saady, Noori M Cata; Massé, Daniel I

2015-06-01

Zero liquid discharge is increasingly adopted as an objective for waste treatment process. The objective of this study was to increase the feed total solids (TS) and the organic loading rate (OLR) fed to a novel psychrophilic (20°C) dry anaerobic digestion (PDAD). Duplicate laboratory-scale bioreactors were fed cow feces and wheat straw (35% TS in feed) at OLR of 6.0 g TCOD kg(-1) inoculum d(-1) during long-term operation (147 days consisting of 7 successive cycles). An overall average specific methane yield (SMY) of 151.8±7.9 N L CH4 kg(-1) VS fed with an averaged volatile solids removal of 42.4±4.3% were obtained at a volatile solids-based inoculum-to-substrate ratio (ISR) of 2.13±0.2. The operation was stable as indicated by biogas and VFAs profiles and the results were reproducible in successive cycles; a maximum SMY of 163.3±5.7 N L CH4 kg(-1) VS fed was obtained. Hydrolysis was the reaction limiting step. High rate PDAD of 35% TS dairy manure is possible in sequential batch reactor within 21 days treatment cycle length. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Pituitary, ovarian and additional contraceptive effects of an estradiol-based combined oral contraceptive: results of a randomized, open-label study.

PubMed

Endrikat, Jan; Parke, Susanne; Trummer, Dietmar; Serrani, Marco; Duijkers, Ingrid; Klipping, Christine

2013-02-01

The estrogen step-down/progestogen step-up 28-day estradiol valerate/dienogest (E(2)V/DNG) oral contraceptive effectively inhibits ovulation; however, limited data are available regarding its effects on estradiol (E2), progesterone, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) or its additional extraovarian contraceptive effects. In this secondary analysis, 100 women received E(2)V 3 mg on days 1-2, E(2)V 2 mg/DNG 2 mg on days 3-7, E(2)V 2 mg/DNG 3 mg on days 8-24, E(2)V 1 mg on days 25-26 and placebo on days 27-28 for one treatment cycle. Measures included the presence/absence of cervical mucus; endometrial thickness; and serum E2, progesterone, and gonadotropin levels. E2, progesterone, LH and FSH levels did not exhibit the typical ovulatory increase and remained relatively stable during the cycle. E(2)V/DNG reduced mean maximal endometrial thickness and proportion of women with visible cervical mucus. All parameters returned to pretreatment levels during the posttreatment cycle. E(2)V/DNG provides extraovarian contraceptive effects (reducing endometrial thickness and cervical mucus production) in addition to inhibiting ovulation, assuring contraceptive efficacy. Copyright © 2013 Elsevier Inc. All rights reserved.

Application of the unsteady vortex-lattice method to the nonlinear two-degree-of-freedom aeroelastic equations

NASA Technical Reports Server (NTRS)

Strganac, T. W.; Mook, D. T.

1986-01-01

A means of numerically simulating flutter is established by implementing a predictor-corrector algorithm to solve the equations of motion. Aerodynamic loads are provided by the unsteady vortex lattice method (UVLM). This method is illustrated via the obtainment of stable and unstable responses to initial disturbances in the case of two-degree-of-freedom motion. It was found that for some angles of attack and dynamic pressure, the initial disturbance decays, for others it grows (flutter). When flutter occurs, the solution yields the amplitude and period of the resulting limit cycle. The preliminaray results attest to the feasibility of this method for studying flutter in cases that would be difficult to treat using a classical approach.

Collective phase description of oscillatory convection

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

Kawamura, Yoji, E-mail: ykawamura@jamstec.go.jp; Nakao, Hiroya

We formulate a theory for the collective phase description of oscillatory convection in Hele-Shaw cells. It enables us to describe the dynamics of the oscillatory convection by a single degree of freedom which we call the collective phase. The theory can be considered as a phase reduction method for limit-cycle solutions in infinite-dimensional dynamical systems, namely, stable time-periodic solutions to partial differential equations, representing the oscillatory convection. We derive the phase sensitivity function, which quantifies the phase response of the oscillatory convection to weak perturbations applied at each spatial point, and analyze the phase synchronization between two weakly coupled Hele-Shawmore » cells exhibiting oscillatory convection on the basis of the derived phase equations.« less

Core–Shell Nanoparticle Coating as an Interfacial Layer for Dendrite-Free Lithium Metal Anodes

DOE PAGES

Liu, Wei; Li, Weiyang; Zhuo, Denys; ...

2017-02-08

Lithium metal based batteries represent a major challenge and opportunity in enabling a variety of devices requiring high-energy-density storage. However, dendritic lithium growth has limited the practical application of lithium metal anodes. Here we report a nanoporous, flexible and electrochemically stable coating of silica@poly(methyl methacrylate) (SiO 2@PMMA) core–shell nanospheres as an interfacial layer on lithium metal anode. This interfacial layer is capable of inhibiting Li dendrite growth while sustaining ionic flux through it, which is attributed to the nanoscaled pores formed among the nanospheres. Lastly, enhanced Coulombic efficiencies during lithium charge/discharge cycles have been achieved at various current densities andmore » areal capacities.« less

Core–Shell Nanoparticle Coating as an Interfacial Layer for Dendrite-Free Lithium Metal Anodes

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

Liu, Wei; Li, Weiyang; Zhuo, Denys

Lithium metal based batteries represent a major challenge and opportunity in enabling a variety of devices requiring high-energy-density storage. However, dendritic lithium growth has limited the practical application of lithium metal anodes. Here we report a nanoporous, flexible and electrochemically stable coating of silica@poly(methyl methacrylate) (SiO 2@PMMA) core–shell nanospheres as an interfacial layer on lithium metal anode. This interfacial layer is capable of inhibiting Li dendrite growth while sustaining ionic flux through it, which is attributed to the nanoscaled pores formed among the nanospheres. Lastly, enhanced Coulombic efficiencies during lithium charge/discharge cycles have been achieved at various current densities andmore » areal capacities.« less

YORP on tumbling asteroids

NASA Astrophysics Data System (ADS)

Rozek, A.; Breiter, S.; Vokrouhlicky, D.

2011-10-01

A semi-analytical model of the Yarkovsky-O'Keefe- Radzievskii-Paddack (YORP) effect on an asteroid spin in non principal axis rotation state is presented. Assuming zero conductivity, the YORP torque is represented by spherical harmonics series with vector coefficients, allowing to use any degree and order of approximation. Within the quadrupole approximation of the illumination function we find the same first integrals involving rotational momentum, obliquity and dynamical inertia that were obtained by Cicaló and Scheeres [1]. The integrals do not exist when higher degree terms of illumination function are included and then the asymptotic states known from Vokrouhlický et al. [2] appear. This resolves an apparent contradiction between earlier results. Averaged equations of motion admit stable and unstable limit cycle solutions that were not detected previously.

Winnerless competition principle and prediction of the transient dynamics in a Lotka-Volterra model

NASA Astrophysics Data System (ADS)

Afraimovich, Valentin; Tristan, Irma; Huerta, Ramon; Rabinovich, Mikhail I.

2008-12-01

Predicting the evolution of multispecies ecological systems is an intriguing problem. A sufficiently complex model with the necessary predicting power requires solutions that are structurally stable. Small variations of the system parameters should not qualitatively perturb its solutions. When one is interested in just asymptotic results of evolution (as time goes to infinity), then the problem has a straightforward mathematical image involving simple attractors (fixed points or limit cycles) of a dynamical system. However, for an accurate prediction of evolution, the analysis of transient solutions is critical. In this paper, in the framework of the traditional Lotka-Volterra model (generalized in some sense), we show that the transient solution representing multispecies sequential competition can be reproducible and predictable with high probability.

Winnerless competition principle and prediction of the transient dynamics in a Lotka-Volterra model.

PubMed

Afraimovich, Valentin; Tristan, Irma; Huerta, Ramon; Rabinovich, Mikhail I

2008-12-01

Predicting the evolution of multispecies ecological systems is an intriguing problem. A sufficiently complex model with the necessary predicting power requires solutions that are structurally stable. Small variations of the system parameters should not qualitatively perturb its solutions. When one is interested in just asymptotic results of evolution (as time goes to infinity), then the problem has a straightforward mathematical image involving simple attractors (fixed points or limit cycles) of a dynamical system. However, for an accurate prediction of evolution, the analysis of transient solutions is critical. In this paper, in the framework of the traditional Lotka-Volterra model (generalized in some sense), we show that the transient solution representing multispecies sequential competition can be reproducible and predictable with high probability.

Oscillating dynamo in the presence of a fossil magnetic field - The solar cycle

NASA Technical Reports Server (NTRS)

Levy, E. H.; Boyer, D.

1982-01-01

Hydromagnetic dynamo generation of oscillating magnetic fields in the presence of an external, ambient magnetic field introduces a marked polarity asymmetry between the two halves of the magnetic cycle. The principle of oscillating dynamo interaction with external fields is developed, and a tentative application to the sun is described. In the sun a dipole moment associated with the stable fluid beneath the convection zone would produce an asymmetrical solar cycle.

Suppression of Dendritic Lithium Growth by in Situ Formation of a Chemically Stable and Mechanically Strong Solid Electrolyte Interphase.

PubMed

Wan, Guojia; Guo, Feihu; Li, Hui; Cao, Yuliang; Ai, Xinping; Qian, Jiangfeng; Li, Yangxing; Yang, Hanxi

2018-01-10

The growth and proliferation of Li dendrites during repeated Li cycling has long been a crucial issue that hinders the development of secondary Li-metal batteries. Building a stable and robust solid state electrolyte interphase (SEI) on the Li-anode surface is regarded as a promising strategy to overcome the dendrite issues. In this work, we report a simple strategy to engineer the interface chemistry of Li-metal anodes by using tiny amounts of dimethyl sulfate (DMS, C 2 H 6 SO 4 ) as the SEI-forming additive. With the preferential reduction of DMS, an SEI layer composed of Li 2 S/Li 2 O forms on the Li surface. This inorganic SEI layer features high structural modulus and low interfacial resistant, enabling a dense and dendrite-free Li deposition as evidenced by scanning electron microscopy, atomic force microscopy, and in situ optical images. In addition, this SEI layer can prevent the deposited Li from direct contact with corrosive electrolytes, thus rendering an improved cycling stability of Li anodes with an average Coulombic efficiency of 97% for up to 150 cycles. When the DMS additive is introduced into a Li/NCM full cell, the cycle life of Li-metal batteries can be also improved significantly. This work demonstrates a feasible route to suppress Li dendrite growth by designing appropriate film-forming additives to regulate the interfacial properties of the SEI layer, and also the sulfonyl-based derivatives revealed in this work represent a large variety of new film-forming molecules, providing a broad selectivity for constructing high efficiency and cycle-stable Li anodes to address the intrinsic problems of rechargeable Li-metal batteries.

Elucidating the nutritional dynamics of fungi using stable isotopes

Treesearch

Jordan R. Mayor; Edward A.G. Schuur; Terry W. Henkel

2009-01-01

Mycorrhizal and saprotrophic (SAP) fungi are essential to terrestrial element cycling due to their uptake of mineral nutrients and decomposition of detritus. Linking these ecological roles to specific fungi is necessary to improve our understanding of global nutrient cycling, fungal ecophysiology, and forest ecology. Using discriminant analyses of nitrogen and carbon...

Fire, climate change, and forest resilience in interior Alaska

Treesearch

Jill F. Johnstone; F. Stuart Chapin; Teresa N. Hollingsworth; Michelle C. Mack; Vladimir Romanovsky; Merritt Turetsky

2010-01-01

In the boreal forests of interior Alaska, feedbacks that link forest soils, fire characteristics, and plant traits have supported stable cycles of forest succession for the past 6000 years. This high resilience of forest stands to fire disturbance is supported by two interrelated feedback cycles: (i) interactions among disturbance regime and plant-soil-microbial...

Teacher Career Stages: Implications for Staff Development. Fastback 214.

ERIC Educational Resources Information Center

Burke, Peter J.; And Others

Literature on adult life stages and career development is synthesized and placed within the perspective of a career cycle model for teachers as adult learners. The teacher career cycle is viewed as a progression affected by personal and environmental factors. The stages a teacher's career proceeds through (e.g., preservice, entry, growing, stable,…

Phase restructuring in transition metal dichalcogenides for highly stable energy storage

DOE PAGES

Leng, Kai; Chen, Zhongxin; Zhao, Xiaoxu; ...

2016-09-16

Achieving homogeneous phase transition and uniform charge distribution is essential for good cycle stability and high capacity when phase conversion materials are used as electrodes. Herein, we show that chemical lithiation of bulk 2H-MoS 2 distorts its crystalline domains in three primary directions to produce mosaic-like 1T' nanocrystalline domains, which improve phase and charge uniformity during subsequent electrochemical phase conversion. 1T'-Li xMoS 2, a macroscopic dense material with interconnected nanoscale grains, shows excellent cycle stability and rate capability in a lithium rechargeable battery compared to bulk or exfoliated-restacked MoS 2. Transmission electron microscopy studies reveal that the interconnected MoS 2more » nanocrystals created during the phase change process are reformable even after multiple cycles of galvanostatic charging/discharging, which allows them to play important roles in the long term cycling performance of the chemically intercalated TMD materials. Finally, these studies shed light on how bulk TMDs can be processed into quasi-2D nanophase material for stable energy storage.« less

Universal quinone electrodes for long cycle life aqueous rechargeable batteries

NASA Astrophysics Data System (ADS)

Liang, Yanliang; Jing, Yan; Gheytani, Saman; Lee, Kuan-Yi; Liu, Ping; Facchetti, Antonio; Yao, Yan

2017-08-01

Aqueous rechargeable batteries provide the safety, robustness, affordability, and environmental friendliness necessary for grid storage and electric vehicle operations, but their adoption is plagued by poor cycle life due to the structural and chemical instability of the anode materials. Here we report quinones as stable anode materials by exploiting their structurally stable ion-coordination charge storage mechanism and chemical inertness towards aqueous electrolytes. Upon rational selection/design of quinone structures, we demonstrate three systems that coupled with industrially established cathodes and electrolytes exhibit long cycle life (up to 3,000 cycles/3,500 h), fast kinetics (>=20C), high anode specific capacity (up to 200-395 mAh g-1), and several examples of state-of-the-art specific energy/energy density (up to 76-92 Wh kg-1/ 161-208 Wh l-1) for several operational pH values (-1 to 15), charge carrier species (H+, Li+, Na+, K+, Mg2+), temperature (-35 to 25 °C), and atmosphere (with/without O2), making them a universal anode approach for any aqueous battery technology.

Organosulfide-plasticized solid-electrolyte interphase layer enables stable lithium metal anodes for long-cycle lithium-sulfur batteries

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

Li, Guoxing; Gao, Yue; He, Xin

Lithium metal is a promising anode candidate for the next-generation rechargeable battery due to its highest specific capacity (3860 mA h g -1) and lowest potential, but low Coulombic efficiency and formation of lithium dendrites hinder its practical application. Here, we report a self-formed flexible hybrid solid-electrolyte interphase layer through co-deposition of organosulfides/organopolysulfides and inorganic lithium salts using sulfur-containing polymers as an additive in the electrolyte. The organosulfides/organopolysulfides serve as “plasticizer” in the solid-electrolyte interphase layer to improve its mechanical flexibility and toughness. The as-formed robust solid-electrolyte interphase layers enable dendrite-free lithium deposition and significantly improve Coulombic efficiency (99% overmore » 400 cycles at a current density of 2mAcm -2). A lithium-sulfur battery based on this strategy exhibits long cycling life (1000 cycles) and good capacity retention. This study reveals an avenue to effectively fabricate stable solid-electrolyte interphase layer for solving the issues associated with lithium metal anodes.« less

An experimental study on pseudoelasticity of a NiTi-based damper for civil applications

NASA Astrophysics Data System (ADS)

Nespoli, Adelaide; Bassani, Enrico; Della Torre, Davide; Donnini, Riccardo; Villa, Elena; Passaretti, Francesca

2017-10-01

In this work, a pseudoelastic damper composed by NiTi wires is tested at 0.5, 1 and 2 Hz for 1000 mechanical cycles. The damping performances were evaluated by three key parameters: the damping capacity, the dissipated energy per cycle and the maximum force. During testing, the temperature of the pseudoelastic elements was registered as well. Results show that the damper assures a bi-directional motion throughout the 1000 cycles together with the maintenance of the recentering. It was observed a stabilization process in the first 50 mechanical cycles, where the key parameters reach stable values; in particular it was found that the damping capacity and the dissipated energy both decrease with frequency. Besides, the mean temperature of the pseudoleastic elements reaches a stable value during tests and confirms the different response of the pseudoelastic wires accordingly with the specific length and stain. Finally, interesting thermal effects were observed at 1 and 2 Hz: at these frequencies and at high strains, the maximum force increases but the temperature of the NiTi wire decreases being in contraddiction with the Clausius-Clapeyron law.

Organosulfide-plasticized solid-electrolyte interphase layer enables stable lithium metal anodes for long-cycle lithium-sulfur batteries

DOE PAGES

Li, Guoxing; Gao, Yue; He, Xin; ...

2017-10-11

Lithium metal is a promising anode candidate for the next-generation rechargeable battery due to its highest specific capacity (3860 mA h g -1) and lowest potential, but low Coulombic efficiency and formation of lithium dendrites hinder its practical application. Here, we report a self-formed flexible hybrid solid-electrolyte interphase layer through co-deposition of organosulfides/organopolysulfides and inorganic lithium salts using sulfur-containing polymers as an additive in the electrolyte. The organosulfides/organopolysulfides serve as “plasticizer” in the solid-electrolyte interphase layer to improve its mechanical flexibility and toughness. The as-formed robust solid-electrolyte interphase layers enable dendrite-free lithium deposition and significantly improve Coulombic efficiency (99% overmore » 400 cycles at a current density of 2mAcm -2). A lithium-sulfur battery based on this strategy exhibits long cycling life (1000 cycles) and good capacity retention. This study reveals an avenue to effectively fabricate stable solid-electrolyte interphase layer for solving the issues associated with lithium metal anodes.« less

Advanced Sodium Ion Battery Anode Constructed via Chemical Bonding between Phosphorus, Carbon Nanotube, and Cross-Linked Polymer Binder.

PubMed

Song, Jiangxuan; Yu, Zhaoxin; Gordin, Mikhail L; Li, Xiaolin; Peng, Huisheng; Wang, Donghai

2015-12-22

Maintaining structural stability is a great challenge for high-capacity conversion electrodes with large volume change but is necessary for the development of high-energy-density, long-cycling batteries. Here, we report a stable phosphorus anode for sodium ion batteries by the synergistic use of chemically bonded phosphorus-carbon nanotube (P-CNT) hybrid and cross-linked polymer binder. The P-CNT hybrid was synthesized through ball-milling of red phosphorus and carboxylic group functionalized carbon nanotubes. The P-O-C bonds formed in this process help maintain contact between phosphorus and CNTs, leading to a durable hybrid. In addition, cross-linked carboxymethyl cellulose-citric acid binder was used to form a robust electrode. As a result, this anode delivers a stable cycling capacity of 1586.2 mAh/g after 100 cycles, along with high initial Coulombic efficiency of 84.7% and subsequent cycling efficiency of ∼99%. The unique electrode framework through chemical bonding strategy reported here is potentially inspirable for other electrode materials with large volume change in use.

In situ analysis of capacity fade in thin-film anodes for high performance Li-ion all-solid-state batteries

NASA Astrophysics Data System (ADS)

Leite, Marina S.; Gong, Chen; Ruzmetov, Dmitry; Talin, A. Alec

There is still a pressing need to understand how the solid-interfaces in Li-ion all-solid-batteries form, including their chemical composition and electrical characteristics. In order to resolve the origin of the degradation mechanism in Al anodes, we combine in situ scanning electron microscopy in ultra-high vacuum with electrochemical cycling, in addition to ex situ characterization of the morphological, chemical, and electrical changes of the Al anodes upon lithiation. An AlLi alloy capped by a stable Al-Li-O is formed on the top surface of the anode, trapping Li, which results in the capacity fade, from 48.0 to 41.5 μ.Ah/cm2 in two cycles. The addition of a Cu capping layer is insufficient to prevent the device degradation because of the fast Li diffusion within Al. Yet, Si present extremely stable cycling: >92% of capacity retention after 100 cycles, with average Coulombic efficiency of 98%. Our in situ measurements represent a new platform for probing the real-time degradation of electrodes in all-solid-state batteries for energy storage devices.

Characterization of Fast-Scan Cyclic Voltammetric Electrodes Using Paraffin as an Effective Sealant with In Vitro and In Vivo Applications.

PubMed

Ramsson, Eric S; Cholger, Daniel; Dionise, Albert; Poirier, Nicholas; Andrus, Avery; Curtiss, Randi

2015-01-01

Fast-scan cyclic voltammetry (FSCV) is a powerful technique for measuring sub-second changes in neurotransmitter levels. A great time-limiting factor in the use of FSCV is the production of high-quality recording electrodes; common recording electrodes consist of cylindrical carbon fiber encased in borosilicate glass. When the borosilicate is heated and pulled, the molten glass ideally forms a tight seal around the carbon fiber cylinder. It is often difficult, however, to guarantee a perfect seal between the glass and carbon. Indeed, much of the time spent creating electrodes is in an effort to find a good seal. Even though epoxy resins can be useful in this regard, they are irreversible (seals are permanent), wasteful (epoxy cannot be reused once hardener is added), hazardous (hardeners are often caustic), and require curing. Herein we characterize paraffin as an electrode sealant for FSCV microelectrodes. Paraffin boasts the advantages of near-immediate curing times, simplicity in use, long shelf-life and stable waterproof seals capable of withstanding extended cycling. Borosilicate electrode tips were left intact or broken and dipped in paraffin embedding wax. Excess wax was removed from the carbon surface with xyelenes or by repeated cycling at an extended waveform (-0.4 to 1.4V, 400 V/s, 60 Hz). Then, the waveform was switched to a standard waveform (-0.4 to 1.3V, 400 V/s, 10 Hz) and cycled until stable. Wax-sealing does not inhibit electrode sensitivity, as electrodes detected linear changes in dopamine before and after wax (then xylenes) exposure. Paraffin seals are intact after 11 days of implantation in the mouse, and still capable of measuring transient changes in in vivo dopamine. From this it is clear that paraffin wax is an effective sealant for FSCV electrodes that provides a convenient substitute to epoxy sealants.

Characterization of Fast-Scan Cyclic Voltammetric Electrodes Using Paraffin as an Effective Sealant with In Vitro and In Vivo Applications

PubMed Central

Ramsson, Eric S.; Cholger, Daniel; Dionise, Albert; Poirier, Nicholas; Andrus, Avery; Curtiss, Randi

2015-01-01

Fast-scan cyclic voltammetry (FSCV) is a powerful technique for measuring sub-second changes in neurotransmitter levels. A great time-limiting factor in the use of FSCV is the production of high-quality recording electrodes; common recording electrodes consist of cylindrical carbon fiber encased in borosilicate glass. When the borosilicate is heated and pulled, the molten glass ideally forms a tight seal around the carbon fiber cylinder. It is often difficult, however, to guarantee a perfect seal between the glass and carbon. Indeed, much of the time spent creating electrodes is in an effort to find a good seal. Even though epoxy resins can be useful in this regard, they are irreversible (seals are permanent), wasteful (epoxy cannot be reused once hardener is added), hazardous (hardeners are often caustic), and require curing. Herein we characterize paraffin as an electrode sealant for FSCV microelectrodes. Paraffin boasts the advantages of near-immediate curing times, simplicity in use, long shelf-life and stable waterproof seals capable of withstanding extended cycling. Borosilicate electrode tips were left intact or broken and dipped in paraffin embedding wax. Excess wax was removed from the carbon surface with xyelenes or by repeated cycling at an extended waveform (-0.4 to 1.4V, 400 V/s, 60 Hz). Then, the waveform was switched to a standard waveform (-0.4 to 1.3V, 400 V/s, 10 Hz) and cycled until stable. Wax-sealing does not inhibit electrode sensitivity, as electrodes detected linear changes in dopamine before and after wax (then xylenes) exposure. Paraffin seals are intact after 11 days of implantation in the mouse, and still capable of measuring transient changes in in vivo dopamine. From this it is clear that paraffin wax is an effective sealant for FSCV electrodes that provides a convenient substitute to epoxy sealants. PMID:26505195

Self-organizing maps based on limit cycle attractors.

PubMed

Huang, Di-Wei; Gentili, Rodolphe J; Reggia, James A

2015-03-01

Recent efforts to develop large-scale brain and neurocognitive architectures have paid relatively little attention to the use of self-organizing maps (SOMs). Part of the reason for this is that most conventional SOMs use a static encoding representation: each input pattern or sequence is effectively represented as a fixed point activation pattern in the map layer, something that is inconsistent with the rhythmic oscillatory activity observed in the brain. Here we develop and study an alternative encoding scheme that instead uses sparsely-coded limit cycles to represent external input patterns/sequences. We establish conditions under which learned limit cycle representations arise reliably and dominate the dynamics in a SOM. These limit cycles tend to be relatively unique for different inputs, robust to perturbations, and fairly insensitive to timing. In spite of the continually changing activity in the map layer when a limit cycle representation is used, map formation continues to occur reliably. In a two-SOM architecture where each SOM represents a different sensory modality, we also show that after learning, limit cycles in one SOM can correctly evoke corresponding limit cycles in the other, and thus there is the potential for multi-SOM systems using limit cycles to work effectively as hetero-associative memories. While the results presented here are only first steps, they establish the viability of SOM models based on limit cycle activity patterns, and suggest that such models merit further study. Copyright © 2014 Elsevier Ltd. All rights reserved.

Facile synthesis of 3D MnNi-layered double hydroxides (LDH)/graphene composites from directly graphites for pseudocapacitor and their electrochemical analysis

NASA Astrophysics Data System (ADS)

Lee, Ilbok; Jeong, Gyoung Hwa; An, Soyeon; Kim, Sang-Wook; Yoon, Songhun

2018-01-01

Herein, MnNi-layered double hydroxides (LDH) were imbibed within the interlayers of graphene nanosheets. The anionic surfactant, sodium dodecyl sulfate played a role of graphite exfoliator adding interaction with metal cations. Using this process, layered MnNi-LDH-graphene nanocomposite was prepared without formation of graphene oxide. When applied into pseudocapacitor electrode, LDH-graphene with optimal ratio between Mn and Ni exhibited very stable cycle with 90% at 1400 cycles and high energy 47.29 Wh kg-1 at the power density of 7473 W kg-1, which was attributed to highly stable layered LDH structure within conductive graphene layers.

Survival and reversion of a stable L form in soil

NASA Technical Reports Server (NTRS)

Horwitz, A. H.; Casida, L. E., Jr.

1978-01-01

The stable L form of Agromyces ramosus reverted to a bacterial form when incubated in sterilized soil. The cellular and colonial morphology of this bacterial form resembled that of the original parent bacterial form. The two forms differed, however, in that the revertant maintained its bacterial form when transferred onto a low-salt (NaCl) medium but was virtually completely induced into the L-form state on a high-salt medium. The original parent bacterial form was not sensitive to salt. The possibility is discussed that an L-form - bacterial-form cycle for this bacterium might occur naturally in soil. This cycle would be mediated by fluctuations in local salt concentrations in the soil.

Complete In Vitro Life Cycle of Trypanosoma congolense: Development of Genetic Tools

PubMed Central

Plazolles, Nicolas; Baltz, Théo

2010-01-01

Background Animal African trypanosomosis, a disease mainly caused by the protozoan parasite Trypanosoma congolense, is a major constraint to livestock productivity and has a significant impact in the developing countries of Africa. RNA interference (RNAi) has been used to study gene function and identify drug and vaccine targets in a variety of organisms including trypanosomes. However, trypanosome RNAi studies have mainly been conducted in T. brucei, as a model for human infection, largely ignoring livestock parasites of economical importance such as T. congolense, which displays different pathogenesis profiles. The whole T. congolense life cycle can be completed in vitro, but this attractive model displayed important limitations: (i) genetic tools were currently limited to insect forms and production of modified infectious BSF through differentiation was never achieved, (ii) in vitro differentiation techniques lasted several months, (iii) absence of long-term bloodstream forms (BSF) in vitro culture prevented genomic analyses. Methodology/Principal Findings We optimized culture conditions for each developmental stage and secured the differentiation steps. Specifically, we devised a medium adapted for the strenuous development of stable long-term BSF culture. Using Amaxa nucleofection technology, we greatly improved the transfection rate of the insect form and designed an inducible transgene expression system using the IL3000 reference strain. We tested it by expression of reporter genes and through RNAi. Subsequently, we achieved the complete in vitro life cycle with dramatically shortened time requirements for various wild type and transgenic strains. Finally, we established the use of modified strains for experimental infections and underlined a host adaptation phase requirement. Conclusions/Significance We devised an improved T. congolense model, which offers the opportunity to perform functional genomics analyses throughout the whole life cycle. It represents a very useful tool to understand pathogenesis mechanisms and to study potential therapeutic targets either in vitro or in vivo using a mouse model. PMID:20209144

Computational analysis of sedimentation of two particles in a narrow channel

NASA Astrophysics Data System (ADS)

Aidun, Cyrus K.; Ding, Ejiang

1998-11-01

The motion and interaction of two spherical bodies of diameter d in a narrow channel (width 4d) is simulated by Lattice-Boltzmann method at Reynolds numbers between 0 and 10. The initial positions of the particles are midway between the centerline of the channel and the side wall while one particle is 2d above the other. At low Reynolds numbers, the particles oscillate around the centerline of the channel while they approach each other, and eventually settle in contact. At higher Reynolds numbers, the trailing particle approaches the leading one; jointly, the particles enter into a damping oscillation without contacting each other. This motion has been described as drafting, kissing and tumbling (Hu, Joseph, and Crochet, Theoret. Comput. Fluid Dyn. 3 1992; Feng, Hu, and Joseph, J. Fluid Mech. 261 1994). In the phase space, constructed by the distances between each particle and the side wall, the attractor is a fixed point, representing a steady state. At even higher Reynolds number the dynamics changes into a stable limit cycle. The amplitude of the limit cycle increases as the Reynolds number increases in value. As Reynolds number increases further the motion becomes more complex. The trajectory in the phase space suggests the existence of a strange attractor. The dynamics of two particle sedimentation at this range of Reynolds number will be presented.

A 1 GeV CW FFAG High Intensity Proton Driver

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

Johnstone, C.; Sheehy, S. L.

2012-05-01

The drive for high beam power, high duty cycle, and reliable beams at reasonable cost has focused world attention on fixed-field accelerators, notably Fixed-Field Alternating Gradient accelerators (FFAGs). High-intensity GeV proton drivers are of particular interest, as these encounter duty cycle and space-charge limits in the synchrotron and machine size concerns in the weaker-focusing cyclotron. Recently, the concept of isochronous orbits has been explored and developed for non-scaling FFAGs using powerful new methodologies in FFAG accelerator design. These new breeds of FFAGs have been identified by international collaborations for serious study thanks to their potential applications including Accelerator Driven Subcriticalmore » Reactors (ADS) a nd Accelerator Transmutation of Waste. The extreme reliability requirements for ADS mandate CW operation capability and the FFAG s strong focusing, particularly in the vertical, will serve to mitigate the effect of space charge (as compared with the weak- focusing cyclotron). This paper reports on these new advances in FFAG accelerator technology and presents a stable, 0.25-1GeV isochronous FFAG for an accelerator driven subcritical reactor.« less

Experimental Demonstration of the Thermochemical Reduction of Ceria in a Solar Aerosol Reactor

PubMed Central

2016-01-01

We report on the experimental demonstration of an aerosol solar reactor for the thermal reduction of ceria, as part of a thermochemical redox cycle for splitting H2O and CO2. The concept utilizes a cavity-receiver enclosing an array of alumina tubes, each containing a downward gravity-driven aerosol flow of ceria particles countercurrent to an inert sweep gas flow for intrinsic separation of reduced ceria and oxygen. A 2 kWth lab-scale prototype with a single tube was tested under radiative fluxes approaching 4000 suns, yielding reaction extents of up to 53% of the thermodynamic equilibrium at 1919 K within residence times below 1 s. Upon thermal redox cycling, fresh primary particles of 2.44 μm mean size initially formed large agglomerates of 1000 μm mean size, then sintered into stable particles of 150 μm mean size. The reaction extent was primarily limited by heat transfer for large particles/agglomerates (mean size > 200 μm) and by the gas phase advection of product O2 for smaller particles. PMID:27853339

Experimental Demonstration of the Thermochemical Reduction of Ceria in a Solar Aerosol Reactor.

PubMed

Welte, Michael; Barhoumi, Rafik; Zbinden, Adrian; Scheffe, Jonathan R; Steinfeld, Aldo

2016-10-12

We report on the experimental demonstration of an aerosol solar reactor for the thermal reduction of ceria, as part of a thermochemical redox cycle for splitting H 2 O and CO 2 . The concept utilizes a cavity-receiver enclosing an array of alumina tubes, each containing a downward gravity-driven aerosol flow of ceria particles countercurrent to an inert sweep gas flow for intrinsic separation of reduced ceria and oxygen. A 2 kW th lab-scale prototype with a single tube was tested under radiative fluxes approaching 4000 suns, yielding reaction extents of up to 53% of the thermodynamic equilibrium at 1919 K within residence times below 1 s. Upon thermal redox cycling, fresh primary particles of 2.44 μm mean size initially formed large agglomerates of 1000 μm mean size, then sintered into stable particles of 150 μm mean size. The reaction extent was primarily limited by heat transfer for large particles/agglomerates (mean size > 200 μm) and by the gas phase advection of product O 2 for smaller particles.

Fatigue limit and Hysteresis Behavior of Type 304L Stainless Steel in Air and PWR Water, at 150°C and 300°C

NASA Astrophysics Data System (ADS)

Solomon, H. D.; Amzallag, C.; Vallee, A. J.; DeLair, R. E.

This is a study of the 107 cycle fatigue limit of Type 304L Stainless Steel, as measured in fully reversed (R=-1) load-controlled tests, at 150°C and 300°C, in air and PWR water. The staircase method was used to determine the fatigue limit. The tests run here utilized a cycle frequency of 1.818Hz and are compared to other tests from the literature that were run at 30Hz. The fatigue limit measured in the tests run at the high frequency was higher than that measured here. This is explained by measurements of the strain developed during cycling, using the different cycle frequencies. The tests run at the higher frequencies yielded lower strains for a given stress and, as expected, this resulted in higher fatigue limits. Using 107 cycles to define a run-out also led to a lower fatigue limit. These results are important as most previous fatigue limit measurements utilized 106 cycles or less to define a run-out, and when lives as long as 107 cycles are used the tests are generally run at high cycle frequencies, thus leading to higher fatigue limits than those measured here.

ALD of Al2O3 for Highly Improved Performance in Li-Ion Batteries

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

Dillon, A.; Jung, Y. S.; Ban, C.

2012-01-01

Significant advances in energy density, rate capability and safety will be required for the implementation of Li-ion batteries in next generation electric vehicles. We have demonstrated atomic layer deposition (ALD) as a promising method to enable superior cycling performance for a vast variety of battery electrodes. The electrodes range from already demonstrated commercial technologies (cycled under extreme conditions) to new materials that could eventually lead to batteries with higher energy densities. For example, an Al2O3 ALD coating with a thickness of ~ 8 A was able to stabilize the cycling of unexplored MoO3 nanoparticle anodes with a high volume expansion.more » The ALD coating enabled stable cycling at C/2 with a capacity of ~ 900 mAh/g. Furthermore, rate capability studies showed the ALD-coated electrode maintained a capacity of 600 mAh/g at 5C. For uncoated electrodes it was only possible to observe stable cycling at C/10. Also, we recently reported that a thin ALD Al2O3 coating with a thickness of ~5 A can enable natural graphite (NG) electrodes to exhibit remarkably durable cycling at 50 degrees C. The ALD-coated NG electrodes displayed a 98% capacity retention after 200 charge-discharge cycles. In contrast, bare NG showed a rapid decay. Additionally, Al2O3 ALD films with a thickness of 2 to 4 A have been shown to allow LiCoO2 to exhibit 89% capacity retention after 120 charge-discharge cycles performed up to 4.5 V vs Li/Li+. Bare LiCoO2 rapidly deteriorated in the first few cycles. The capacity fade is likely caused by oxidative decomposition of the electrolyte at higher potentials or perhaps cobalt dissolution. Interestingly, we have recently fabricated full cells of NG and LiCoO2 where we coated both electrodes, one or the other electrode as well as neither electrode. In creating these full cells, we observed some surprising results that lead us to obtain a greater understanding of the ALD coatings. We have also recently coated a binder free LiNi0.04Mn0.04Co02O2 electrode containing 5 wt% single-walled carbon nanotubes as the conductive additive and demonstrated both high rate capability as well as the ability to cycle the cathode to 5 V vrs. Li/Li+. Finally, we coated a Celgard (TM) separator and enabled stable cycling in a high dielectric electrolyte. These results will be presented in detail.« less

Long term stability of Li-S batteries using high concentration lithium nitrate electrolytes

DOE PAGES

Adams, Brian D.; Carino, Emily V.; Connell, Justin G.; ...

2017-09-08

The lithium-sulfur (Li-S) battery is a very promising candidate for the next generation of energy storage systems required for electrical vehicles and grid energy storage applications due to its very high theoretical specific energy (2500 W h kg -1). However, low Coulombic efficiency (CE) during repeated Li metal plating/stripping has severely limited the practical application of rechargeable Li-S batteries. In this work, a new electrolyte system based on a high concentration of LiNO 3 in diglyme (G2) solvent is developed which enables an exceptionally high CE for Li metal plating/stripping and thus high stability of the Li anode in themore » sulfur-containing electrolyte. The tailoring of electrolyte properties for the Li anode has proven to be a highly successful strategy for improving the capacity retention and cycle life of Li-S batteries. This electrolyte provides a CE of greater than 99% for over 200 cycles of Li plating/stripping. In contrast, the Li anode cycles for less than 35 cycles (with a high CE) in the state-of-the-art 1 M LiTFSI + 0.3 M LiNO 3 in 1,3-dioxolane:1,2-dimethoxyethane (DOL:DME) electrolyte under the same conditions. Lastly, the stable Li anode enabled by the new electrolyte may accelerate the applications of high energy density Li-S batteries in both electrical vehicles and large-scale grid energy storage markets.« less

Electrochemical performance and interfacial investigation on Si composite anode for lithium ion batteries in full cell

NASA Astrophysics Data System (ADS)

Shobukawa, Hitoshi; Alvarado, Judith; Yang, Yangyuchen; Meng, Ying Shirley

2017-08-01

Lithium ion batteries (LIBs) containing silicon (Si) as a negative electrode have gained much attention recently because they deliver high energy density. However, the commercialization of LIBs with Si anode is limited due to the unstable electrochemical performance associated with expansion and contraction during electrochemical cycling. This study investigates the electrochemical performance and degradation mechanism of a full cell containing Si composite anode and LiFePO4 (lithium iron phosphate (LFP)) cathode. Enhanced electrochemical cycling performance is observed when the full cell is cycled with fluoroethylene carbonate (FEC) additive compared to the standard electrolyte. To understand the improvement in the electrochemical performance, x-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) are used. Based on the electrochemical behavior, FEC improves the reversibility of lithium ion diffusion into the solid electrolyte interphase (SEI) on the Si composite anode. Moreover, XPS analysis demonstrates that the SEI composition generated from the addition of FEC consists of a large amount of LiF and less carbonate species, which leads to better capacity retention over 40 cycles. The effective SEI successively yields more stable capacity retention and enhances the reversibility of lithium ion diffusion through the interphase of the Si anode, even at higher discharge rate. This study contributes to a basic comprehension of electrochemical performance and SEI formation of LIB full cells with a high loading Si composite anode.

Testing Urey's carbonate-silicate cycle using the calcium isotopic composition of sedimentary carbonates

NASA Astrophysics Data System (ADS)

Blättler, Clara L.; Higgins, John A.

2017-12-01

Carbonate minerals constitute a major component of the sedimentary geological record and an archive of a fraction of the carbon and calcium cycled through the Earth's surface reservoirs for over three billion years. For calcium, carbonate minerals constitute the ultimate sink for almost all calcium liberated during continental and submarine weathering of silicate minerals. This study presents >500 stable isotope ratios of calcium in Precambrian carbonate sediments, both limestones and dolomites, in an attempt to characterize the isotope mass balance of the sedimentary carbonate reservoir through time. The mean of the dataset is indistinguishable from estimates of the calcium isotope ratio of bulk silicate Earth, consistent with the Urey cycle being the dominant mechanism exchanging calcium among surface reservoirs. The variability in bulk sediment calcium isotope ratios within each geological unit does not reflect changes in the global calcium cycle, but rather highlights the importance of local mineralogical and/or diagenetic effects in the carbonate record. This dataset demonstrates the potential for calcium isotope ratios to help assess these local effects, such as the former presence of aragonite, even in rocks with a history of neomorphism and recrystallization. Additionally, 29 calcium isotope measurements are presented from ODP (Ocean Drilling Program) Site 801 that contribute to the characterization of altered oceanic crust as an additional sink for calcium, and whose distinct isotopic signature places a limit on the importance of this subduction flux over Earth history.

Long term stability of Li-S batteries using high concentration lithium nitrate electrolytes

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

Adams, Brian D.; Carino, Emily V.; Connell, Justin G.

The lithium-sulfur (Li-S) battery is a very promising candidate for the next generation of energy storage systems required for electrical vehicles and grid energy storage applications due to its very high theoretical specific energy (2500 W h kg -1). However, low Coulombic efficiency (CE) during repeated Li metal plating/stripping has severely limited the practical application of rechargeable Li-S batteries. In this work, a new electrolyte system based on a high concentration of LiNO 3 in diglyme (G2) solvent is developed which enables an exceptionally high CE for Li metal plating/stripping and thus high stability of the Li anode in themore » sulfur-containing electrolyte. The tailoring of electrolyte properties for the Li anode has proven to be a highly successful strategy for improving the capacity retention and cycle life of Li-S batteries. This electrolyte provides a CE of greater than 99% for over 200 cycles of Li plating/stripping. In contrast, the Li anode cycles for less than 35 cycles (with a high CE) in the state-of-the-art 1 M LiTFSI + 0.3 M LiNO 3 in 1,3-dioxolane:1,2-dimethoxyethane (DOL:DME) electrolyte under the same conditions. Lastly, the stable Li anode enabled by the new electrolyte may accelerate the applications of high energy density Li-S batteries in both electrical vehicles and large-scale grid energy storage markets.« less

Long term stability of Li-S batteries using high concentration lithium nitrate electrolytes

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

Adams, Brian D.; Carino, Emily V.; Connell, Justin G.

The lithium-sulfur (Li-S) battery is a very promising candidate for the next generation of energy storage systems required for electrical vehicles and grid energy storage applications due to its very high theoretical specific energy (2500 W h kg(-1)). However, low Coulombic efficiency (CE) during repeated Li metal plating/stripping has severely limited the practical application of rechargeable Li-S batteries. In this work, a new electrolyte system based on a high concentration of LiNO3 in diglyme (G2) solvent is developed which enables an exceptionally high CE for Li metal plating/stripping and thus high stability of the Li anode in the sulfur-containing electrolyte.more » The tailoring of electrolyte properties for the Li anode has proven to be a highly successful strategy for improving the capacity retention and cycle life of Li-S batteries. This electrolyte provides a CE of greater than 99% for over 200 cycles of Li plating/stripping. In contrast, the Li anode cycles for less than 35 cycles (with a high CE) in the state-of-the-art 1 M LiTFSI + 0.3 M LiNO3 in 1,3-dioxolane: 1,2-dimethoxyethane (DOL:DME) electrolyte under the same conditions. The stable Li anode enabled by the new electrolyte may accelerate the applications of high energy density Li-S batteries in both electrical vehicles and large-scale grid energy storage markets.« less

Cell cycle-dependent transcription factors control the expression of yeast telomerase RNA.

PubMed

Dionne, Isabelle; Larose, Stéphanie; Dandjinou, Alain T; Abou Elela, Sherif; Wellinger, Raymund J

2013-07-01

Telomerase is a specialized ribonucleoprotein that adds repeated DNA sequences to the ends of eukaryotic chromosomes to preserve genome integrity. Some secondary structure features of the telomerase RNA are very well conserved, and it serves as a central scaffold for the binding of associated proteins. The Saccharomyces cerevisiae telomerase RNA, TLC1, is found in very low copy number in the cell and is the limiting component of the known telomerase holoenzyme constituents. The reasons for this low abundance are unclear, but given that the RNA is very stable, transcriptional control mechanisms must be extremely important. Here we define the sequences forming the TLC1 promoter and identify the elements required for its low expression level, including enhancer and repressor elements. Within an enhancer element, we found consensus sites for Mbp1/Swi4 association, and chromatin immunoprecipitation (ChIP) assays confirmed the binding of Mbp1 and Swi4 to these sites of the TLC1 promoter. Furthermore, the enhancer element conferred cell cycle-dependent regulation to a reporter gene, and mutations in the Mbp1/Swi4 binding sites affected the levels of telomerase RNA and telomere length. Finally, ChIP experiments using a TLC1 RNA-binding protein as target showed cell cycle-dependent transcription of the TLC1 gene. These results indicate that the budding yeast TLC1 RNA is transcribed in a cell cycle-dependent fashion late in G1 and may be part of the S phase-regulated group of genes involved in DNA replication.

The effect of frequency on atmospheric pressure glow discharge in a pin-to-plate gap sustained by a resonant power supply

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

Wang, Yong Sheng; Ding, Wei Dong; Wang, Ya Nan

More and more researchers have been attracted to the research of atmospheric pressure glow discharge (APGD) because of its great prospect in numerous industrial applications. Nevertheless, almost all of the industrial applications are based on achievement of stable, large-volume, and uniform APGD. In a previous study, stable filamentary APGD was obtained by applying a resonant power supply between pin-to-plate electrodes which could limit the peak value of discharge current to supress the glow-to-arc transition through a series-wound resonance principle. The filamentary APGD is centimeter-level in the length but only several millimeters in diameter. Therefore, in order to obtain large-volume andmore » uniform APGD, it is significant to study how to diffuse filamentary APGD in radial direction. With the increasing resonant frequency of alternating current discharge, excited particles (mainly including energetic electrons and trapped ions left from the previous half-cycle discharge) in the electrodes gap increase, which benefits obtaining stable self-sustaining APGD. In this paper, mechanism and law of the influence of resonant frequency on the diffusion of filamentary APGD in ambient air were studied. By comparing the photos of discharge plasma and waveforms of the discharge voltage and current, it is found that the volume of the glow discharge plasma enlarges as the resonant frequency of the power supply increases. It is very significant and anticipating to study how to obtain stable, large-volume, and uniform APGD in ambient air by the resonant power supply.« less

Stable and Flexible CuInS2/ZnS:Al-TiO2 Film for Solar-Light-Driven Photodegradation of Soil Fumigant.

PubMed

Yan, Lili; Li, Zhichun; Sun, Mingxing; Shen, Guoqing; Li, Liang

2016-08-10

Semiconductor quantum dots (QDs) are suitable light absorbers for photocatalysis because of their unique properties. However, QDs generally suffer from poor photochemical stability against air, limiting their applications in photocatalysis. In this study, a stable solar-light-driven QDs-containing photocatalytic film was developed to facilitate photocatalytic degradation of the soil fumigant 1,3-dichloropropene (1,3-D). Highly stable CuInS2/ZnS:Al core/shell QDs (CIS/ZnS:Al QDs) were synthesized by doping Al into the ZnS shell and controlling ZnS:Al shell thickness; the CIS/ZnS:Al QDs were subsequently combined with TiO2 to form a CIS/ZnS:Al-TiO2 photocatalyst. The optimized ZnS:Al shell thickness for 1,3-D photodegradation was approximately 1.3 nm, which guaranteed and balanced the good photocatalytic activity and stability of the CIS/ZnS:Al-TiO2 photocatalyst. The photodegradation efficiency of 1,3-D can be maintained up to more than 80% after five cycles during recycling experiment. When CIS/ZnS:Al-TiO2 was deposited as photocatalytic film on a flexible polyethylene terephthalate substrate, over 99% of cis-1,3-D and 98% of trans-1,3-D were depleted as they passed through the film during 15 h of irradiation under natural solar light. This study demonstrated that the stable CIS/ZnS:Al-TiO2 photocatalyst both in powder and film form is a promising agent for photodegradation and emission reduction of soil fumigants.

EDTA improves stability of whole blood C-peptide and insulin to over 24 hours at room temperature.

PubMed

McDonald, Timothy J; Perry, Mandy H; Peake, Roy W A; Pullan, Nicola J; O'Connor, John; Shields, Beverley M; Knight, Beatrice A; Hattersley, Andrew T

2012-01-01

C-peptide and insulin measurements in blood provide useful information regarding endogenous insulin secretion. Conflicting evidence on sample stability and handling procedures continue to limit the widespread clinical use of these tests. We assessed the factors that altered the stability of insulin and C-peptide in blood. We investigated the impact of preservative type, time to centrifugation, storage conditions and duration of storage on the stability of C-peptide and insulin on three different analytical platforms. C-peptide was stable for at least 24 hours at room temperature in both centrifuged and whole blood collected in K(+)-EDTA and serum gel tubes, with the exception of whole blood serum gel, which decreased to 78% of baseline at 24 hours, (p = 0.008). Insulin was stable at room temperature for 24 hours in both centrifuged and whole blood collected in K(+)-EDTA tubes. In contrast insulin levels decreased in serum gel tubes both centrifuged and whole blood (66% of baseline, p = 0.01 and 76% of baseline p = 0.01, by 24 hours respectively). C-peptide and insulin remained stable after 6 freeze-thaw cycles. The stability of C-peptide and insulin in whole blood K(+)-EDTA tubes negates the need to conform to strict sample handling procedures for these assays, greatly increasing their clinical utility.

Explaining pathological changes in axonal excitability through dynamical analysis of conductance-based models

NASA Astrophysics Data System (ADS)

Coggan, Jay S.; Ocker, Gabriel K.; Sejnowski, Terrence J.; Prescott, Steven A.

2011-10-01

Neurons rely on action potentials, or spikes, to relay information. Pathological changes in spike generation likely contribute to certain enigmatic features of neurological disease, like paroxysmal attacks of pain and muscle spasm. Paroxysmal symptoms are characterized by abrupt onset and short duration, and are associated with abnormal spiking although the exact pathophysiology remains unclear. To help decipher the biophysical basis for 'paroxysmal' spiking, we replicated afterdischarge (i.e. continued spiking after a brief stimulus) in a minimal conductance-based axon model. We then applied nonlinear dynamical analysis to explain the dynamical basis for initiation and termination of afterdischarge. A perturbation could abruptly switch the system between two (quasi-)stable attractor states: rest and repetitive spiking. This bistability was a consequence of slow positive feedback mediated by persistent inward current. Initiation of afterdischarge was explained by activation of the persistent inward current forcing the system to cross a saddle point that separates the basins of attraction associated with each attractor. Termination of afterdischarge was explained by the attractor associated with repetitive spiking being destroyed. This occurred when ultra-slow negative feedback, such as intracellular sodium accumulation, caused the saddle point and stable limit cycle to collide; in that regard, the active attractor is not truly stable when the slowest dynamics are taken into account. The model also explains other features of paroxysmal symptoms, including temporal summation and refractoriness.

Partitioning of Evapotranspiration Using a Stable Water Isotope Technique in a High Temperature Agricultural Production System

NASA Astrophysics Data System (ADS)

Lu, X.; Liang, L.; Wang, L.; Jenerette, D.; Grantz, D. A.

2015-12-01

Agricultural production in the hot and arid low desert systems of southern California relies heavily on irrigation. A better understanding of how much and to what extent the irrigation water is transpired by crops relative to being lost through evaporation will contribute to better management of increasingly limited agricultural water resources. In this study, we examined the evapotranspiration (ET) partitioning over a field of forage sorghum (S. bicolor) during a growing season with several irrigation cycles. In several field campaigns we used continuous measurements of near-surface variations in the stable isotopic composition of water vapor (δ2H). We employed custom built transparent chambers coupled with a laser-based isotope analyzer and used Keeling plot and mass balance methods for surface flux partitioning. The preliminary results show that δT is more enriched than δE in the early growing season, and becomes less enriched than δE later in the season as canopy cover increases. There is an increase in the contribution of transpiration to ET as (1) leaf area index increases, and (2) as soil surface moisture declines. These results are consistent with theory, and extend these measurements to an environment that experiences extreme soil surface temperatures. The data further support the use of chamber based methods with stable isotopic analysis for characterization of ET partitioning in challenging field environments.

Pseudo-simple heteroclinic cycles in R4

NASA Astrophysics Data System (ADS)

Chossat, Pascal; Lohse, Alexander; Podvigina, Olga

2018-06-01

We study pseudo-simple heteroclinic cycles for a Γ-equivariant system in R4 with finite Γ ⊂ O(4) , and their nearby dynamics. In particular, in a first step towards a full classification - analogous to that which exists already for the class of simple cycles - we identify all finite subgroups of O(4) admitting pseudo-simple cycles. To this end we introduce a constructive method to build equivariant dynamical systems possessing a robust heteroclinic cycle. Extending a previous study we also investigate the existence of periodic orbits close to a pseudo-simple cycle, which depends on the symmetry groups of equilibria in the cycle. Moreover, we identify subgroups Γ ⊂ O(4) , Γ ⊄ SO(4) , admitting fragmentarily asymptotically stable pseudo-simple heteroclinic cycles. (It has been previously shown that for Γ ⊂ SO(4) pseudo-simple cycles generically are completely unstable.) Finally, we study a generalized heteroclinic cycle, which involves a pseudo-simple cycle as a subset.

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

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

Mao, Chengyu; Wood, Marissa; David, Lamuel Abraham

Here, most lithium-ion batteries still rely on intercalation-type graphite materials for anodes, so it is important to consider their role in full cells for applications in electric vehicles. Here, we systematically evaluate the chemical and physical properties of six commercially-available natural and synthetic graphites to establish which factors have the greatest impact on the cycling stability of full cells with nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. Electrochemical data and post-mortem characterization explain the origin of capacity fade. The NMC811 cathode shows large irreversible capacity loss and impedance growth, accounting for much of full cell degradation. However, six graphite anodes demonstrate significant differencesmore » with respect to structural change, surface area, impedance growth, and SEI chemistry, which impact overall capacity retention. We found long cycle life correlated most strongly with stable graphite crystallite size. In addition, graphites with lower surface area generally had higher coulombic efficiencies during formation cycles, which led to more stable long-term cycling. The best graphite screened here enables a capacity retention around 90% in full pouch cells over extensive long-term cycling compared to only 82% for cells with the lowest performing graphite. The results show that optimal graphite selection improves cycling stability of high energy lithium-ion cells.« less

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

DOE PAGES

Mao, Chengyu; Wood, Marissa; David, Lamuel Abraham; ...

2018-06-16

Here, most lithium-ion batteries still rely on intercalation-type graphite materials for anodes, so it is important to consider their role in full cells for applications in electric vehicles. Here, we systematically evaluate the chemical and physical properties of six commercially-available natural and synthetic graphites to establish which factors have the greatest impact on the cycling stability of full cells with nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. Electrochemical data and post-mortem characterization explain the origin of capacity fade. The NMC811 cathode shows large irreversible capacity loss and impedance growth, accounting for much of full cell degradation. However, six graphite anodes demonstrate significant differencesmore » with respect to structural change, surface area, impedance growth, and SEI chemistry, which impact overall capacity retention. We found long cycle life correlated most strongly with stable graphite crystallite size. In addition, graphites with lower surface area generally had higher coulombic efficiencies during formation cycles, which led to more stable long-term cycling. The best graphite screened here enables a capacity retention around 90% in full pouch cells over extensive long-term cycling compared to only 82% for cells with the lowest performing graphite. The results show that optimal graphite selection improves cycling stability of high energy lithium-ion cells.« less

Electrochemical performance evaluations and safety investigations of pentafluoro(phenoxy)cyclotriphosphazene as a flame retardant electrolyte additive for application in lithium ion battery systems using a newly designed apparatus for improved self-extinguishing time measurements

NASA Astrophysics Data System (ADS)

Dagger, Tim; Lürenbaum, Constantin; Schappacher, Falko M.; Winter, Martin

2017-02-01

A modified self-extinguishing time (SET) device which enhances the reproducibility of the results is presented. Pentafluoro(phenoxy)cyclotriphosphazene (FPPN) is investigated as flame retardant electrolyte additive for lithium ion batteries (LIBs) in terms of thermal stability and electrochemical performance. SET measurements and adiabatic reaction calorimetry are applied to determine the flammability and the reactivity of a standard LIB electrolyte containing 5% FPPN. The results reveal that the additive-containing electrolyte is nonflammable for 10 s whereas the commercially available reference electrolyte inflames instantaneously after 1 s of ignition. The onset temperature of the safety enhanced electrolyte is delayed by ≈ 21 °C. Compatibility tests in half cells show that the electrolyte is reductively stable while the cyclic voltammogram indicates oxidative decomposition during the first cycle. Cycling experiments in full cells show improved cycling performance and rate capability, which can be attributed to cathode passivation during the first cycle. Post-mortem analysis of the electrolyte by gas chromatography-mass spectrometry confirms the presence of the additive in high amounts after 501 cycles which ensures enhanced safety of the electrolyte. The investigations present FPPN as stable electrolyte additive that improves the intrinsic safety of the electrolyte and its cycling performance at the same time.

Long noncoding RNA PANDA and scaffold-attachment-factor SAFA control senescence entry and exit.

PubMed

Puvvula, Pavan Kumar; Desetty, Rohini Devi; Pineau, Pascal; Marchio, Agnés; Moon, Anne; Dejean, Anne; Bischof, Oliver

2014-11-19

Cellular senescence is a stable cell cycle arrest that limits the proliferation of pre-cancerous cells. Here we demonstrate that scaffold-attachment-factor A (SAFA) and the long noncoding RNA PANDA differentially interact with polycomb repressive complexes (PRC1 and PRC2) and the transcription factor NF-YA to either promote or suppress senescence. In proliferating cells, SAFA and PANDA recruit PRC complexes to repress the transcription of senescence-promoting genes. Conversely, the loss of SAFA-PANDA-PRC interactions allows expression of the senescence programme. Accordingly, we find that depleting either SAFA or PANDA in proliferating cells induces senescence. However, in senescent cells where PANDA sequesters transcription factor NF-YA and limits the expression of NF-YA-E2F-coregulated proliferation-promoting genes, PANDA depletion leads to an exit from senescence. Together, our results demonstrate that PANDA confines cells to their existing proliferative state and that modulating its level of expression can cause entry or exit from senescence.

Integration of concentrated solar power (CSP) and circulating fluidized bed (CFB) power plants - final results of the COMBO-CFB project

NASA Astrophysics Data System (ADS)

Suojanen, Suvi; Hakkarainen, Elina; Kettunen, Ari; Kapela, Jukka; Paldanius, Juha; Tuononen, Minttu; Selek, Istvan; Kovács, Jenö; Tähtinen, Matti

2017-06-01

Hybridization of solar energy together with another energy source is an option to provide heat and power reliably on demand. Hybridization allows decreasing combustion related fuel consumption and emissions, assuring stable grid connection and cutting costs of concentrated solar power technology due to shared power production equipment. The research project "Integration of Concentrated Solar Power (CSP) and Circulating Fluidized Bed (CFB) Power Plants" (COMBO-CFB) has been carried out to investigate the technical possibilities and limitations of the concept. The main focus was on the effect of CSP integration on combustion dynamics and on the joint power cycle, and on the interactions of subsystems. The research provides new valuable experimental data and knowhow about dynamic behaviour of CFB combustion under boundary conditions of the hybrid system. Limiting factors for maximum solar share in different hybridization schemes and suggestions for enhancing the performance of the hybrid system are derived.

Active and stable Ir@Pt core–shell catalysts for electrochemical oxygen reduction

DOE PAGES

Strickler, Alaina L.; Jackson, Ariel; Jaramillo, Thomas F.

2016-12-28

Electrochemical oxygen reduction is an important reaction for many sustainable energy technologies, such as fuel cells and metal–air batteries. Kinetic limitations of this reaction, expensive electrocatalysts, and catalyst instability, however, limit the commercial viability of such devices. Herein, we report an active Ir@Pt core–shell catalyst that combines platinum overlayers with nanostructure effects to tune the oxygen binding to the Pt surface, thereby achieving enhanced activity and stability for the oxygen reduction reaction. Ir@Pt nanoparticles with several shell thicknesses were synthesized in a scalable, inexpensive, one-pot polyol method. Electrochemical analysis demonstrates the activity and stability of the Ir@Pt catalyst, with specificmore » and mass activities increasing to 2.6 and 1.8 times that of commercial Pt/C (TKK), respectively, after 10 000 stability cycles. Furthermore, activity enhancement of the Ir@Pt catalyst is attributed to weakening of the oxygen binding to the Pt surface induced by the Ir core.« less

Significance of Phosphoenolpyruvate Carboxylase during Ammonium Assimilation: Carbon Isotope Discrimination in Photosynthesis and Respiration by the N-Limited Green Alga Selenastrum minutum.

PubMed

Guy, R D; Vanlerberghe, G C; Turpin, D H

1989-04-01

The effect of N-assimilation on the partitioning of carbon fixation between phosphoenolpyruvate carboxylase (PEPcase) and ribulose bisphosphate carboxylase/oxygenase (Rubisco) was determined by measuring stable carbon isotope discrimination during photosynthesis by an N-limited green alga, Selenastrum minutum (Naeg.) Collins. This was facilitated by a two process model accounting for simultaneous CO(2) fixation and respiratory CO(2) release. Discrimination by control cells was consistent with the majority of carbon being fixed by Rubisco. During nitrogen assimilation however, discrimination was greatly reduced indicating an enhanced flux through PEPcase which accounted for upward of 70% of total carbon fixation. This shift toward anaplerotic metabolism supports a large increase in tricarboxylic acid cycle activity primarily between oxaloacetate and alpha-ketoglutarate thereby facilitating the provision of carbon skeletons for amino acid synthesis. This provides an example of a unique set of conditions under which anaplerotic carbon fixation by PEPcase exceeds photosynthetic carbon fixation by Rubisco in a C(3) organism.

A phase I/II study of carfilzomib 2-10-min infusion in patients with advanced solid tumors.

PubMed

Papadopoulos, Kyriakos P; Burris, Howard A; Gordon, Michael; Lee, Peter; Sausville, Edward A; Rosen, Peter J; Patnaik, Amita; Cutler, Richard E; Wang, Zhengping; Lee, Susan; Jones, Suzanne F; Infante, Jeffery R

2013-10-01

Tolerability, pharmacokinetics (PK), pharmacodynamics, and antitumor activity of carfilzomib, a selective proteasome inhibitor, administered twice weekly by 2-10-min intravenous (IV) infusion on days 1, 2, 8, 9, 15, and 16 in 28-day cycles, were assessed in patients with advanced solid tumors in this phase I/II study. Adult patients with solid tumors progressing after ≥1 prior therapies were enrolled. The dose was 20 mg/m(2) in week 1 of cycle 1 and 20, 27, or 36 mg/m(2) thereafter. The maximum tolerated dose or protocol-defined maximum planned dose (MPD) identified during dose escalation was administered to an expansion cohort and to patients with small cell lung, non-small cell lung, ovarian, and renal cancer in phase II tumor-specific cohorts. Fourteen patients received carfilzomib during dose escalation. The single dose-limiting toxicity at 20/36 mg/m(2) was grade 3 fatigue, establishing the MPD as the expansion and phase II dose. Sixty-five additional patients received carfilzomib at the MPD. Adverse events included fatigue, nausea, anorexia, and dyspnea. Carfilzomib PK was dose proportional with a half-life <1 h. All doses resulted in at least 80 % proteasome inhibition in blood. Partial responses occurred in two patients in phase I, with 21.5 % stable disease after four cycles in evaluable patients in the expansion and phase II cohorts. Carfilzomib 20/36 mg/m(2) was well tolerated when administered twice weekly by 2-10-min IV infusion. At this dose and infusion rate, carfilzomib inhibited the proteasome in blood but demonstrated limited antitumor activity in patients with advanced solid tumors.

A Slowed Cell Cycle Stabilizes the Budding Yeast Genome.

PubMed

Vinton, Peter J; Weinert, Ted

2017-06-01

During cell division, aberrant DNA structures are detected by regulators called checkpoints that slow division to allow error correction. In addition to checkpoint-induced delay, it is widely assumed, though rarely shown, that merely slowing the cell cycle might allow more time for error detection and correction, thus resulting in a more stable genome. Fidelity by a slowed cell cycle might be independent of checkpoints. Here we tested the hypothesis that a slowed cell cycle stabilizes the genome, independent of checkpoints, in the budding yeast Saccharomyces cerevisiae We were led to this hypothesis when we identified a gene ( ERV14 , an ER cargo membrane protein) that when mutated, unexpectedly stabilized the genome, as measured by three different chromosome assays. After extensive studies of pathways rendered dysfunctional in erv14 mutant cells, we are led to the inference that no particular pathway is involved in stabilization, but rather the slowed cell cycle induced by erv14 stabilized the genome. We then demonstrated that, in genetic mutations and chemical treatments unrelated to ERV14 , a slowed cell cycle indeed correlates with a more stable genome, even in checkpoint-proficient cells. Data suggest a delay in G2/M may commonly stabilize the genome. We conclude that chromosome errors are more rarely made or are more readily corrected when the cell cycle is slowed (even ∼15 min longer in an ∼100-min cell cycle). And, some chromosome errors may not signal checkpoint-mediated responses, or do not sufficiently signal to allow correction, and their correction benefits from this "time checkpoint." Copyright © 2017 by the Genetics Society of America.

Assessment of serum HE4 levels throughout the normal menstrual cycle.

PubMed

Moore, Richard G; Plante, Beth; Hartnett, Erin; Mitchel, Jessica; Raker, Christine A; Vitek, Wendy; Eklund, Elizabeth; Lambert-Messerlian, Geralyn

2017-07-01

Human epididymis protein 4 is a serum biomarker to aid in differentiating benign and malignant disease in women with a pelvic mass. Interpretation of human epididymis protein 4 results relies on robust normative data. The purpose of this study was to evaluate whether human epididymis protein 4 levels are variable in women during the normal menstrual cycle. Healthy women, 18-45 years old, with regular menstrual cycles were recruited from community gynecologic practices in Rhode Island. Women consented to enroll and to participate by the donation of blood and urine samples at 5 specific times over the course of each cycle. Levels of reproductive hormones and human epididymis protein 4 were determined. Data were analyzed with the use of linear regression after log transformation. Among 74 enrolled cycles, 53 women had confirmed ovulation during the menstrual cycle and completed all 5 sample collections. Levels of estradiol, progesterone, and luteinizing hormone displayed the expected menstrual cycle patterns. Levels of human epididymis protein 4 in serum were relatively stable across the menstrual cycle, except for a small ovulatory (median, 37.0 pM) increase. Levels of human epididymis protein 4 in urine, after correction for creatinine, displayed the same pattern of secretion observed in serum. Serum human epididymis protein 4 levels are relatively stable across the menstrual cycle of reproductive-aged women and can be determined on any day to evaluate risk of ovarian malignancy. A slight increase is expected at ovulation; but even with this higher human epididymis protein 4 level, results are well within the healthy reference range for women (<120 pM). Levels of human epididymis protein 4 in urine warrant further investigation for use in clinical practice as a simple and convenient sample. Copyright © 2017 Elsevier Inc. All rights reserved.

USE OF SLACK-WATER ENVIRONMENTS BY COHO SALMON JUVENILES IN A COASTAL OREGON STREAM AS INDICATED BY 34S STABLE ISOTOPE ANALYSIS

EPA Science Inventory

Stable isotopes of sulfur are rarely used in studies of elemental cycling, trophic position or use of marine-derived nutrients by salmonids. The main reason for this probably is the reluctance on the part of isotope labs to expose their instruments to SO2 (because of its corrosi...

Biological factors of natural and artificial ecosystems stable (unstable) functioning

NASA Astrophysics Data System (ADS)

Pechurkin, Nikolai S.

The problem of sustainable development of humanity on Earth and the problem of supporting human life in space have the same scientific and methodological bases. The key to solve both problems is a long term maintenance of balanced material cycle. As a whole, natural or artificial ecosystems are to be more closed than open, but their elements (links of systems) are to be substantially open in interactions with each other. Prolonged stable interactions of different links have to have unique joint results - closed material cycling or biotic turnover. It is necessary to include, at least, three types of main links into any system to support real material cycling: producers, consumers, reducers. Producer links are now under studies in many laboratories. It is evident that the higher productivity of link, the lower link stability. Especially, it concerns with parasite impact to plants. As usual, artificial ecosystems are more simple (incomplete) than natural ecosystems, sometimes, they have not enough links for prolonged stable functioning. For example, life support system for space flight can be incomplete in consumer link, having only some crew persons, instead of interacting populations of consumers. As for reducer link, it is necessary to "organize" a special coordinated work of microbial biocenoses to fulfill proper cycling. Possible evolution of links, their self development is a matter of special attention for the maintenance of prolonged stable functioning. It's the most danger for systems with populations of quickly reproducing, so-called, R - strategists, according to symbols of logistic equation. From another side, quick reproduction of R - strategists is able to increase artificial ecosystems and their links functioning. After some damages of system, R - strategist's link can be quickly "self repaired" up to level of normal functioning. Some experimental data of this kind and mathematical models are to be discussed in the paper. This work is supported by grant, Yenissey, 07-04-96806

Membrane Resonance Enables Stable and Robust Gamma Oscillations

PubMed Central

Moca, Vasile V.; Nikolić, Danko; Singer, Wolf; Mureşan, Raul C.

2014-01-01

Neuronal mechanisms underlying beta/gamma oscillations (20–80 Hz) are not completely understood. Here, we show that in vivo beta/gamma oscillations in the cat visual cortex sometimes exhibit remarkably stable frequency even when inputs fluctuate dramatically. Enhanced frequency stability is associated with stronger oscillations measured in individual units and larger power in the local field potential. Simulations of neuronal circuitry demonstrate that membrane properties of inhibitory interneurons strongly determine the characteristics of emergent oscillations. Exploration of networks containing either integrator or resonator inhibitory interneurons revealed that: (i) Resonance, as opposed to integration, promotes robust oscillations with large power and stable frequency via a mechanism called RING (Resonance INduced Gamma); resonance favors synchronization by reducing phase delays between interneurons and imposes bounds on oscillation cycle duration; (ii) Stability of frequency and robustness of the oscillation also depend on the relative timing of excitatory and inhibitory volleys within the oscillation cycle; (iii) RING can reproduce characteristics of both Pyramidal INterneuron Gamma (PING) and INterneuron Gamma (ING), transcending such classifications; (iv) In RING, robust gamma oscillations are promoted by slow but are impaired by fast inputs. Results suggest that interneuronal membrane resonance can be an important ingredient for generation of robust gamma oscillations having stable frequency. PMID:23042733

Resting states are resting traits--an FMRI study of sex differences and menstrual cycle effects in resting state cognitive control networks.

PubMed

Hjelmervik, Helene; Hausmann, Markus; Osnes, Berge; Westerhausen, René; Specht, Karsten

2014-01-01

To what degree resting state fMRI is stable or susceptible to internal mind states of the individual is currently an issue of debate. To address this issue, the present study focuses on sex differences and investigates whether resting state fMRI is stable in men and women or changes within relative short-term periods (i.e., across the menstrual cycle). Due to the fact that we recently reported menstrual cycle effects on cognitive control based on data collected during the same sessions, the current study is particularly interested in fronto-parietal resting state networks. Resting state fMRI was measured in sixteen women during three different cycle phases (menstrual, follicular, and luteal). Fifteen men underwent three sessions in corresponding time intervals. We used independent component analysis to identify four fronto-parietal networks. The results showed sex differences in two of these networks with women exhibiting higher functional connectivity in general, including the prefrontal cortex. Menstrual cycle effects on resting states were non-existent. It is concluded that sex differences in resting state fMRI might reflect sexual dimorphisms in the brain rather than transitory activating effects of sex hormones on the functional connectivity in the resting brain.

Resting States Are Resting Traits – An fMRI Study of Sex Differences and Menstrual Cycle Effects in Resting State Cognitive Control Networks

PubMed Central

Hjelmervik, Helene; Hausmann, Markus; Osnes, Berge; Westerhausen, René; Specht, Karsten

2014-01-01

To what degree resting state fMRI is stable or susceptible to internal mind states of the individual is currently an issue of debate. To address this issue, the present study focuses on sex differences and investigates whether resting state fMRI is stable in men and women or changes within relative short-term periods (i.e., across the menstrual cycle). Due to the fact that we recently reported menstrual cycle effects on cognitive control based on data collected during the same sessions, the current study is particularly interested in fronto-parietal resting state networks. Resting state fMRI was measured in sixteen women during three different cycle phases (menstrual, follicular, and luteal). Fifteen men underwent three sessions in corresponding time intervals. We used independent component analysis to identify four fronto-parietal networks. The results showed sex differences in two of these networks with women exhibiting higher functional connectivity in general, including the prefrontal cortex. Menstrual cycle effects on resting states were non-existent. It is concluded that sex differences in resting state fMRI might reflect sexual dimorphisms in the brain rather than transitory activating effects of sex hormones on the functional connectivity in the resting brain. PMID:25057823

University students' cognitive performance under temperature cycles induced by direct load control events.

PubMed

Zhang, F; de Dear, R

2017-01-01

As one of the most common strategies for managing peak electricity demand, direct load control (DLC) of air-conditioners involves cycling the compressors on and off at predetermined intervals. In university lecture theaters, the implementation of DLC induces temperature cycles which might compromise university students' learning performance. In these experiments, university students' learning performance, represented by four cognitive skills of memory, concentration, reasoning, and planning, was closely monitored under DLC-induced temperature cycles and control conditions simulated in a climate chamber. In Experiment 1 with a cooling set point temperature of 22°C, subjects' cognitive performance was relatively stable or even slightly promoted by the mild heat intensity and short heat exposure resulting from temperature cycles; in Experiment 2 with a cooling set point of 24°C, subjects' reasoning and planning performance observed a trend of decline at the higher heat intensity and longer heat exposure. Results confirm that simpler cognitive tasks are less susceptible to temperature effects than more complex tasks; the effect of thermal variations on cognitive performance follows an extended-U relationship with performance being relatively stable across a range of temperatures. DLC appears to be feasible in university lecture theaters if DLC algorithms are implemented judiciously. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Bifurcation of Limit Cycles in a Near-Hamiltonian System with a Cusp of Order Two and a Saddle

NASA Astrophysics Data System (ADS)

Bakhshalizadeh, Ali; Zangeneh, Hamid R. Z.; Kazemi, Rasool

In this paper, the asymptotic expansion of first-order Melnikov function of a heteroclinic loop connecting a cusp of order two and a hyperbolic saddle for a planar near-Hamiltonian system is given. Next, we consider the limit cycle bifurcations of a hyper-elliptic Liénard system with this kind of heteroclinic loop and study the least upper bound of limit cycles bifurcated from the period annulus inside the heteroclinic loop, from the heteroclinic loop itself and the center. We find that at most three limit cycles can be bifurcated from the period annulus, also we present different distributions of bifurcated limit cycles.

Trace elements retained in washed nuclear fuel reprocessing solvents

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

Gray, L.W.; MacMurdo, K.W.

1979-09-01

Analysis of purified TBP extractant from solvent extraction processes at Savannah River Plant showed several stable elements and several long-lived radioisotopes. Stable elements Al, Na, Br, Ce, Hg, and Sm are found in trace quantities in the solvent. The only stable metallic element consistently found in the solvent was Al, with a concentration which varies from about 30 ppM to about 10 ppM. The halogens Br and Cl appear to be found in the solvent systems as organo halides. Radionuclides found were principally /sup 106/Ru, /sup 129/I, /sup 3/H, /sup 235/U, and /sup 239/Pu. The /sup 129/I concentration was aboutmore » 1 ppM in the first solvent extraction cycle of each facility. In the other cycles, /sup 129/I concentration varied from about 0.1 to 0.5 ppM. Both /sup 129/I and /sup 3/H appear to be in the organic solvent as a result of exchange with hydrogen.« less

Silicon algae with carbon topping as thin-film anodes for lithium-ion microbatteries by a two-step facile method

NASA Astrophysics Data System (ADS)

Biserni, E.; Xie, M.; Brescia, R.; Scarpellini, A.; Hashempour, M.; Movahed, P.; George, S. M.; Bestetti, M.; Li Bassi, A.; Bruno, P.

2015-01-01

Silicon-based electrodes for Li-ion batteries (LIB) attract much attention because of their high theoretical capacity. However, their large volume change during lithiation results in poor cycling due to mechanical cracking. Moreover, silicon can hardly form a stable solid electrolyte interphase (SEI) layer with common electrolytes. We present a safe, innovative strategy to prepare nanostructured silicon-carbon anodes in a two-step process. The nanoporosity of Si films accommodates the volume expansion while a disordered graphitic C layer on top promotes the formation of a stable SEI. This approach shows its promises: carbon-coated porous silicon anodes perform in a very stable way, reaching the areal capacity of ∼175 μAh cm-2, and showing no decay for at least 1000 cycles. With requiring only a two-step deposition process at moderate temperatures, this novel very simple cell concept introduces a promising way to possibly viable up-scaled production of next-generation nanostructured Si anodes for lithium-ion microbatteries.

A siloxane-incorporated copolymer as an in situ cross-linkable binder for high performance silicon anodes in Li-ion batteries

NASA Astrophysics Data System (ADS)

Jeena, M. T.; Bok, Taesoo; Kim, Si Hoon; Park, Sooham; Kim, Ju-Young; Park, Soojin; Ryu, Ja-Hyoung

2016-04-01

The electrochemical performance of Li-ion batteries (LIBs) can be highly tuned by various factors including the morphology of the anode material, the nature of the electrolyte, the binding material, and the percentage of conducting materials. Binding materials have been of particular interest to researchers over the decades as a means to further improve the cycle durability and columbic efficiency of LIBs. Such approaches include the introduction of different polymeric binders such as poly(acrylic acid) (PAA), carboxymethyl cellulose (CMC), and alginic acid (Alg) into the Si anode of LIBs. To achieve a better efficiency of LIBs, herein, we introduce a novel copolymer, poly(tert-butyl acrylate-co-triethoxyvinylsilane) (TBA-TEVS), as an efficient binder with stable cycle retention and excellent specific capacity. The binder forms a highly interconnected three-dimensional network upon thermal treatment as a result of de-protection of the tert-butyl group and the consequent inter-intra condensation reaction, which minimizes pulverization of the Si nanoparticles. Moreover, the siloxane group is expected to promote the formation of stable solid-electrolyte-interface (SEI) layers. A series of random copolymers were synthesized by varying the molar ratio of tert-butyl acrylate and triethoxyvinylsilane. Twenty-one percent of TEVS in the TBS-TEVS copolymer gave rise to a superior performance as a binder for Si anodes, where the anodes showed a stable specific capacity of 2551 mA h g-1 over hundreds of cycles and an initial columbic efficiency (ICE) of 81.8%.The electrochemical performance of Li-ion batteries (LIBs) can be highly tuned by various factors including the morphology of the anode material, the nature of the electrolyte, the binding material, and the percentage of conducting materials. Binding materials have been of particular interest to researchers over the decades as a means to further improve the cycle durability and columbic efficiency of LIBs. Such approaches include the introduction of different polymeric binders such as poly(acrylic acid) (PAA), carboxymethyl cellulose (CMC), and alginic acid (Alg) into the Si anode of LIBs. To achieve a better efficiency of LIBs, herein, we introduce a novel copolymer, poly(tert-butyl acrylate-co-triethoxyvinylsilane) (TBA-TEVS), as an efficient binder with stable cycle retention and excellent specific capacity. The binder forms a highly interconnected three-dimensional network upon thermal treatment as a result of de-protection of the tert-butyl group and the consequent inter-intra condensation reaction, which minimizes pulverization of the Si nanoparticles. Moreover, the siloxane group is expected to promote the formation of stable solid-electrolyte-interface (SEI) layers. A series of random copolymers were synthesized by varying the molar ratio of tert-butyl acrylate and triethoxyvinylsilane. Twenty-one percent of TEVS in the TBS-TEVS copolymer gave rise to a superior performance as a binder for Si anodes, where the anodes showed a stable specific capacity of 2551 mA h g-1 over hundreds of cycles and an initial columbic efficiency (ICE) of 81.8%. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01559j

Limit-cycle-based control of the myogenic wingbeat rhythm in the fruit fly Drosophila

PubMed Central

Bartussek, Jan; Mutlu, A. Kadir; Zapotocky, Martin; Fry, Steven N.

2013-01-01

In many animals, rhythmic motor activity is governed by neural limit cycle oscillations under the control of sensory feedback. In the fruit fly Drosophila melanogaster, the wingbeat rhythm is generated myogenically by stretch-activated muscles and hence independently from direct neural input. In this study, we explored if generation and cycle-by-cycle control of Drosophila's wingbeat are functionally separated, or if the steering muscles instead couple into the myogenic rhythm as a weak forcing of a limit cycle oscillator. We behaviourally tested tethered flying flies for characteristic properties of limit cycle oscillators. To this end, we mechanically stimulated the fly's ‘gyroscopic’ organs, the halteres, and determined the phase relationship between the wing motion and stimulus. The flies synchronized with the stimulus for specific ranges of stimulus amplitude and frequency, revealing the characteristic Arnol'd tongues of a forced limit cycle oscillator. Rapid periodic modulation of the wingbeat frequency prior to locking demonstrates the involvement of the fast steering muscles in the observed control of the wingbeat frequency. We propose that the mechanical forcing of a myogenic limit cycle oscillator permits flies to avoid the comparatively slow control based on a neural central pattern generator. PMID:23282849

Response of an oscillatory differential delay equation to a single stimulus.

PubMed

Mackey, Michael C; Tyran-Kamińska, Marta; Walther, Hans-Otto

2017-04-01

Here we analytically examine the response of a limit cycle solution to a simple differential delay equation to a single pulse perturbation of the piecewise linear nonlinearity. We construct the unperturbed limit cycle analytically, and are able to completely characterize the perturbed response to a pulse of positive amplitude and duration with onset at different points in the limit cycle. We determine the perturbed minima and maxima and period of the limit cycle and show how the pulse modifies these from the unperturbed case.

Determining the N and O isotope effects of microbial nitrite reduction: the global N cycle implications of an enzyme-dependent isotope effect

NASA Astrophysics Data System (ADS)

Martin, T. S.; Casciotti, K. L.

2014-12-01

The marine nitrogen (N) cycle is a dynamic system of critical importance, since nitrogen is the limiting nutrient in over half of the world's oceans. Denitrification and anammox, the main N loss processes from the ocean, have different effects on carbon cycling and greenhouse gas emission. Understanding the balance between the two processes is vital to understanding the role of the N cycle in global climate change. One approach for investigating these processes is by using stable isotope analysis to estimate the relative magnitudes of N fluxes, particularly for biologically mediated processes. In order to make the most of the currently available isotope analysis techniques, it is necessary to know the isotope effects for each processes occurring in the environment. Nitrite reduction is an important step in denitrification. Previous work had begun to explore the N isotope effects for nitrite reduction, but no oxygen (O) isotope effect has been measured. Additionally, no consideration has been given to the type of nitrite reductase carrying out the reaction. There are two main types of respiratory nitrite reductase, one that is Cu-based and another that is Fe-based. We performed batch culture experiments with denitrifier strains possessing either a Cu-type or Fe-type nitrite reductase. Both N and O isotope effects for nitrite reduction were determined for each of these experiments by measuring the NO2- concentration, as well as the N and O isotopes of nitrite and applying a Rayleigh fractionation model. Both the N and O isotope effects were found to be significantly different between the two types of enzymes. This enzyme-linked difference in isotope effects emphasizes the importance of microbial community composition within the global N cycle.

Rational design of anode materials based on Group IVA elements (Si, Ge, and Sn) for lithium-ion batteries.

PubMed

Wu, Xing-Long; Guo, Yu-Guo; Wan, Li-Jun

2013-09-01

Lithium-ion batteries (LIBs) represent the state-of-the-art technology in rechargeable energy-storage devices and they currently occupy the prime position in the marketplace for powering an increasingly diverse range of applications. However, the fast development of these applications has led to increasing demands being placed on advanced LIBs in terms of higher energy/power densities and longer life cycles. For LIBs to meet these requirements, researchers have focused on active electrode materials, owing to their crucial roles in the electrochemical performance of batteries. For anode materials, compounds based on Group IVA (Si, Ge, and Sn) elements represent one of the directions in the development of high-capacity anodes. Although these compounds have many significant advantages when used as anode materials for LIBs, there are still some critical problems to be solved before they can meet the high requirements for practical applications. In this Focus Review, we summarize a series of rational designs for Group IVA-based anode materials, in terms of their chemical compositions and structures, that could address these problems, that is, huge volume variations during cycling, unstable surfaces/interfaces, and invalidation of transport pathways for electrons upon cycling. These designs should at least include one of the following structural benefits: 1) Contain a sufficient number of voids to accommodate the volume variations during cycling; 2) adopt a "plum-pudding"-like structure to limit the volume variations during cycling; 3) facilitate an efficient and permanent transport pathway for electrons and lithium ions; or 4) show stable surfaces/interfaces to stabilize the in situ formed SEI layers. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development and validation of a stability-indicating gas chromatographic method for quality control of residual solvents in blonanserin: a novel atypical antipsychotic agent.

PubMed

Peng, Ming; Liu, Jin; Lu, Dan; Yang, Yong-Jian

2012-09-01

Blonanserin is a novel atypical antipsychotic agent for the treatment of schizophrenia. Ethyl alcohol, isopropyl alcohol and toluene are utilized in the synthesis route of this bulk drug. A new validated gas chromatographic (GC) method for the simultaneous determination of residual solvents in blonanserin is described in this paper. Blonanserin was dissolved in N, N-dimethylformamide to make a sample solution that was directly injected into a DB-624 column. A postrun oven temperature at 240°C for approximately 2 h after the analysis cycle was performed to wash out blonanserin residue in the GC column. Quantitation was performed by external standard analyses and the validation was carried out according to International Conference on Harmonization validation guidelines Q2A and Q2B. The method was shown to be specific (no interference in the blank solution), linear (correlation coefficients ≥0.99998, n = 10), accurate (average recoveries between 94.1 and 101.7%), precise (intra-day and inter-day precision ≤2.6%), sensitive (limit of detection ≤0.2 ng, and limit of quantitation ≤0.7 ng), robust (small variations of carrier gas flow, initial oven temperature, temperature ramping rate, injector and detector temperatures did not significantly affect the system suitability test parameters and peak areas) and stable (reference standard and sample solutions were stable over 48 h). This extensively validated method is ready to be used for the quality control of blonanserin.

A 2-DOF model of an elastic rocket structure excited by a follower force

NASA Astrophysics Data System (ADS)

Brejão, Leandro F.; da Fonseca Brasil, Reyolando Manoel L. R.

2017-10-01

We present a two degree of freedom model of an elastic rocket structure excited by the follower force given by the motor thrust that is supposed to be always in the direction of the tangent to the deformed shape of the device at its lower tip. The model comprises two massless rigid pinned bars, initially in vertical position, connected by rotational springs. Lumped masses and dampers are considered at the connections. The generalized coordinates are the angular displacements of the bars with respect to the vertical. We derive the equations of motion via Lagrange’s equations and simulate its time evolution using Runge-Kutta 4th order time step-by-step numerical integration algorithm. Results indicate possible occurrence of stable and unstable vibrations, such as limit cycles.

Complex dynamics of a nonlinear voter model with contrarian agents

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

Tanabe, Shoma; Masuda, Naoki, E-mail: masuda@mist.i.u-tokyo.ac.jp

2013-12-15

We investigate mean-field dynamics of a nonlinear opinion formation model with congregator and contrarian agents. Each agent assumes one of the two possible states. Congregators imitate the state of other agents with a rate that increases with the number of other agents in the opposite state, as in the linear voter model and nonlinear majority voting models. Contrarians flip the state with a rate that increases with the number of other agents in the same state. The nonlinearity controls the strength of the majority voting and is used as a main bifurcation parameter. We show that the model undergoes amore » rich bifurcation scenario comprising the egalitarian equilibrium, two symmetric lopsided equilibria, limit cycle, and coexistence of different types of stable equilibria with intertwining attractive basins.« less

Engineering Hollow Carbon Architecture for High-Performance K-Ion Battery Anode.

PubMed

Bin, De-Shan; Lin, Xi-Jie; Sun, Yong-Gang; Xu, Yan-Song; Zhang, Ke; Cao, An-Min; Wan, Li-Jun

2018-05-31

K-ion batteries (KIBs) are now drawing increasing research interest as an inexpensive alternative to Li-ion batteries (LIBs). However, due to the large size of K + , stable electrode materials capable of sustaining the repeated K + intercalation/deintercalation cycles are extremely deficient especially if a satisfactory reversible capacity is expected. Herein, we demonstrated that the structural engineering of carbon into a hollow interconnected architecture, a shape similar to the neuron-cell network, promised high conceptual and technological potential for a high-performance KIB anode. Using melamine-formaldehyde resin as the starting material, we identify an interesting glass blowing effect of this polymeric precursor during its carbonization, which features a skeleton-softening process followed by its spontaneous hollowing. When used as a KIB anode, the carbon scaffold with interconnected hollow channels can ensure a resilient structure for a stable potassiation/depotassiation process and deliver an extraordinary capacity (340 mAh g -1 at 0.1 C) together with a superior cycling stability (no obvious fading over 150 cycles at 0.5 C).

Stitching h-BN by atomic layer deposition of LiF as a stable interface for lithium metal anode

PubMed Central

Xie, Jin; Liao, Lei; Gong, Yongji; Li, Yanbin; Shi, Feifei; Pei, Allen; Sun, Jie; Zhang, Rufan; Kong, Biao; Subbaraman, Ram; Christensen, Jake; Cui, Yi

2017-01-01

Defects are important features in two-dimensional (2D) materials that have a strong influence on their chemical and physical properties. Through the enhanced chemical reactivity at defect sites (point defects, line defects, etc.), one can selectively functionalize 2D materials via chemical reactions and thereby tune their physical properties. We demonstrate the selective atomic layer deposition of LiF on defect sites of h-BN prepared by chemical vapor deposition. The LiF deposits primarily on the line and point defects of h-BN, thereby creating seams that hold the h-BN crystallites together. The chemically and mechanically stable hybrid LiF/h-BN film successfully suppresses lithium dendrite formation during both the initial electrochemical deposition onto a copper foil and the subsequent cycling. The protected lithium electrodes exhibit good cycling behavior with more than 300 cycles at relatively high coulombic efficiency (>95%) in an additive-free carbonate electrolyte. PMID:29202031

Stitching h-BN by atomic layer deposition of LiF as a stable interface for lithium metal anode

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

Xie, Jin; Liao, Lei; Gong, Yongji

Defects are important features in two-dimensional (2D) materials that have a strong influence on their chemical and physical properties. Through the enhanced chemical reactivity at defect sites (point defects, line defects, etc.), one can selectively functionalize 2D materials via chemical reactions and thereby tune their physical properties. We demonstrate the selective atomic layer deposition of LiF on defect sites of h-BN prepared by chemical vapor deposition. The LiF deposits primarily on the line and point defects of h-BN, thereby creating seams that hold the h-BN crystallites together. The chemically and mechanically stable hybrid LiF/h-BN film successfully suppresses lithium dendrite formationmore » during both the initial electrochemical deposition onto a copper foil and the subsequent cycling. In conclusion, the protected lithium electrodes exhibit good cycling behavior with more than 300 cycles at relatively high coulombic efficiency (>95%) in an additive-free carbonate electrolyte.« less

Highly stable carbon coated Mg2Si intermetallic nanoparticles for lithium-ion battery anode

NASA Astrophysics Data System (ADS)

Tamirat, Andebet Gedamu; Hou, Mengyan; Liu, Yao; Bin, Duan; Sun, Yunhe; Fan, Long; Wang, Yonggang; Xia, Yongyao

2018-04-01

Silicon is an ideal candidate anode material for Li-ion batteries (LIBs). However, it suffers from rapid capacity fading due to large volume expansion upon lithium insertion. Herein, we design and fabricate highly stable carbon coated porous Mg2Si intermetallic anode material using facile mechano-thermal technique followed by carbon coating using thermal vapour deposition (TVD), toluene as carbon source. The electrode exhibits an excellent first reversible capacity of 726 mAh g-1 at a rate of 100 mA g-1. More importantly, the electrode demonstrates high rate capability (380 mAh g-1 at high rate of 2 A g-1) as well as high cycle stability, with capacity retentions of 65% over 500 cycles. These improvements are attributable to both Mg supporting medium and the uniform carbon coating, which can effectively increase the conductivity and electronic contact of the active material and protects large volume alterations during the electrochemical cycling process.

Comparative study on the freeze stability of yeast and chemical leavened steamed bread dough.

PubMed

Wang, Pei; Yang, Runqiang; Gu, Zhenxin; Xu, Xueming; Jin, Zhengyu

2017-04-15

The present study comparatively evaluated the evolution of yeast and chemical leavened steamed bread dough (YLD/CLD) quality during freeze/thaw (FT) cycles. The steamed bread quality of CLD was more freeze-stable than that of the YLD after 3 FT cycles. Decreased yeast viability contributed to the loss of gassing power in YLD while no significant differences were observed for CLD during FT cycles. However, faster gas release rate in frozen CLD indicated gas retention loss due to the distortion of gluten network. Glutenin macropolymers (GMP) depolymerization via breakage of inter-chain disulfide (SS) bonds and conversions of α-helix and β-turn to β-sheet structures were the main indicators of gluten deterioration. Gluten network was more vulnerable in frozen YLD, resulting in detectable loss of viscoelasticity. The results suggested that supplement of chemical leavener contributed to a more freeze-tolerant gluten network besides its stable gassing power. Copyright © 2016 Elsevier Ltd. All rights reserved.

Stitching h-BN by atomic layer deposition of LiF as a stable interface for lithium metal anode

DOE PAGES

Xie, Jin; Liao, Lei; Gong, Yongji; ...

2017-11-29

Defects are important features in two-dimensional (2D) materials that have a strong influence on their chemical and physical properties. Through the enhanced chemical reactivity at defect sites (point defects, line defects, etc.), one can selectively functionalize 2D materials via chemical reactions and thereby tune their physical properties. We demonstrate the selective atomic layer deposition of LiF on defect sites of h-BN prepared by chemical vapor deposition. The LiF deposits primarily on the line and point defects of h-BN, thereby creating seams that hold the h-BN crystallites together. The chemically and mechanically stable hybrid LiF/h-BN film successfully suppresses lithium dendrite formationmore » during both the initial electrochemical deposition onto a copper foil and the subsequent cycling. In conclusion, the protected lithium electrodes exhibit good cycling behavior with more than 300 cycles at relatively high coulombic efficiency (>95%) in an additive-free carbonate electrolyte.« less

Composite of K-doped (NH4)2V3O8/graphene as an anode material for sodium-ion batteries.

PubMed

Liu, Xin; Li, Zhiwei; Fei, Hailong; Wei, Mingdeng

2015-11-21

A layer structured K-doped (NH4)2V3O8/graphene (K-NVG) was prepared via a hydrothermal route and then used as an anode material for sodium-ion batteries for the first time. The K-NVG nanosheets have a diameter in the range of 200-500 nm. The K-NVG electrode exhibited stable cycling and a good rate performance with a reversible capacity of 235.4 mA h g(-1), which is much higher than the 90.5 mA h g(-1) value of the (NH4)2V3O8/graphene electrode after 100 cycles at a current density of 100 mA g(-1). Simultaneously, the retention rate was maintained at 82% even after 250 cycles at the current density of 300 mA g(-1). Such good electrochemical properties may be attributed to the K-NVG's stable layered structure.

Limit Cycle Bifurcations by Perturbing a Piecewise Hamiltonian System with a Double Homoclinic Loop

NASA Astrophysics Data System (ADS)

Xiong, Yanqin

2016-06-01

This paper is concerned with the bifurcation problem of limit cycles by perturbing a piecewise Hamiltonian system with a double homoclinic loop. First, the derivative of the first Melnikov function is provided. Then, we use it, together with the analytic method, to derive the asymptotic expansion of the first Melnikov function near the loop. Meanwhile, we present the first coefficients in the expansion, which can be applied to study the limit cycle bifurcation near the loop. We give sufficient conditions for this system to have 14 limit cycles in the neighborhood of the loop. As an application, a piecewise polynomial Liénard system is investigated, finding six limit cycles with the help of the obtained method.

Local linear approximation of the Jacobian matrix better captures phase resetting of neural limit cycle oscillators.

PubMed

Oprisan, Sorinel Adrian

2014-01-01

One effect of any external perturbations, such as presynaptic inputs, received by limit cycle oscillators when they are part of larger neural networks is a transient change in their firing rate, or phase resetting. A brief external perturbation moves the figurative point outside the limit cycle, a geometric perturbation that we mapped into a transient change in the firing rate, or a temporal phase resetting. In order to gain a better qualitative understanding of the link between the geometry of the limit cycle and the phase resetting curve (PRC), we used a moving reference frame with one axis tangent and the others normal to the limit cycle. We found that the stability coefficients associated with the unperturbed limit cycle provided good quantitative predictions of both the tangent and the normal geometric displacements induced by external perturbations. A geometric-to-temporal mapping allowed us to correctly predict the PRC while preserving the intuitive nature of this geometric approach.

New insights on ecosystem mercury cycling revealed by stable isotopes of mercury in water flowing from a headwater peatland catchment

Treesearch

Glenn E. Woerndle; Martin Tsz-Ki Tsui; Stephen D. Sebestyen; Joel D. Blum; Xiangping Nie; Randall K. Kolka

2018-01-01

Stable isotope compositions of mercury (Hg) were measured in the outlet stream and in soil cores at different landscape positions in a 9.7-ha boreal upland-peatland catchment. An acidic permanganate/persulfate digestion procedure was validated for water samples with high dissolved organic matter (DOM) concentrations through Hg spike addition analysis. We report a...

Na2Ti6O13: a potential anode for grid-storage sodium-ion batteries.

PubMed

Rudola, Ashish; Saravanan, Kuppan; Devaraj, Sappani; Gong, Hao; Balaya, Palani

2013-08-28

The ultra-fast (30C or 2 min) rate capability and impressive long cycle life (>5000 cycles) of Na2Ti6O13 are reported. A stable 2.5 V sodium-ion battery full cell is demonstrated. In addition, the sodium storage mechanism and thermal stability of Na2Ti6O13 are discussed.

Is overprotection of the sulfur cathode good for Li-S batteries?

PubMed

Gao, Tian; Shao, Jie; Li, Xingxing; Zhu, Guobin; Lu, Qiujian; Han, Yuyao; Qu, Qunting; Zheng, Honghe

2015-08-11

How to restrain the dissolution of polysulfides from the sulfur cathode is the current research focus of Li-S batteries. Here, we find that moderate dissolution of polysulfides is of great importance for high-efficiency and stable discharge/charge cycling. Both overprotection and inadequate protection of the sulfur cathode are unfavorable for the cycling of Li-S batteries.

Large and stable reversible lithium-ion storages from mesoporous SnO2 nanosheets with ultralong lifespan over 1000 cycles

NASA Astrophysics Data System (ADS)

Zhang, Xiao; Jiang, Bin; Guo, Jinxue; Xie, Yaping; Tang, Lin

2014-12-01

The major challenge to promote the commercialization of SnO2 anode materials is to construct unique structures and/or composites that could alleviate the volume effect and extend the lifespan. This study develops an efficient synthetic solution for the preparation of mesoporous SnO2 nanosheets, which involves an evaporation-induced selfassembly process and the following thermal treatment. Surfactant F127 is used as the soft template to form abundant cores. The as-prepared sample intrinsically inherits flexible sheet-like structure and porous features, as characterized with XRD, SEM, TEM and BET techniques. Based on these combining structural benefits, the sample is utilized as anode materials for lithium-ion batteries and exhibits excellent Li+ storage performance such as large and stable reversible capacity, good rate capability, and especially the outstanding durable cycling life of over 1000 cycles, which meets the demands of practical applications. The structural changes of SnO2 nanosheets are observed from the decomposed electrodes after different electrochemical cycles. Moreover, this synthesis strategy may offer an alternative and universal approach for synthesis of other transitional metal oxides or their binary composites as high-performance anode materials for lithium-ion batteries.

Measuring influenza RNA quantity after prolonged storage or multiple freeze/thaw cycles.

PubMed

Granados, Andrea; Petrich, Astrid; McGeer, Allison; Gubbay, Jonathan B

2017-09-01

In this study, we aim to determine what effects prolonged storage and repeated freeze/thaw cycles have on the stability of influenza A(H1N1)pdm09 (influenza A/H1N1)RNA. Cloned influenza A/H1N1 RNA transcripts were serially diluted from 8.0-1.0 log 10 copies/μl. RT-qPCR was used to measure RNA loss in transcripts stored at -80°C, -20°C, 4°C and 25°C for up to 84days or transcripts undergoing a total of 10 freeze/thaw cycles. Viral load was measured in clinical specimens stored at-80°C for three years (n=89 influenza A RNA extracts; n=35 primary specimens) and in 10 clinical specimens from the 2015/2016 influenza season that underwent 7 freeze/thaw cycles. RNA stored at -80°C, -20°C, 4°C and 25°C is stable for up to 56, 56, 21, and 7days respectively or up to 9 freeze/thaw cycles when stored at -80°C. There is no difference in viral load in clinical specimens that have been stored for up to three years at -80°C if they are re-extracted. Similarly, clinical specimens undergoing up to 7 freeze/thaw cycles are stable if they are re-extracted between cycles. Influenza specimens can be stored for up to three years at -80°C or undergo up to 7 freeze/thaw cycles without loss of RNA quantity if re-extracted. Copyright © 2017 Elsevier B.V. All rights reserved.

The role of moisture in the nest thermoregulation of social wasps.

PubMed

Klingner, R; Richter, K; Schmolz, E; Keller, B

2005-09-01

Paper nests of social wasps are intriguing constructions for both, biologists and engineers. We demonstrate that moisture and latent heat significantly influence the thermal performance of the nest construction. Two colonies of the hornet Vespa crabro were investigated in order to clarify the relation of the temperature and the moisture regime inside the nest. Next to fairly stable nest temperatures the hornets maintain a high relative humidity inside the nest. We found that in consequence a partial vapor-pressure gradient between nest and ambient drives a constant vapor flux through the envelope. The vapor flux is limited by the diffusion resistance of the envelope. The driving force of vapor flux is heat, which is consumed through evaporation inside the nest. The colony has to compensate this loss with metabolic heat production in order to maintain a stable nest temperature. However, humidity fluctuations inside the nest induce circadian adsorption and desorption cycles, which stabilize the nest temperature and thus contribute significantly to temperature homeostasis. Our study demonstrates that both mechanisms influence nest thermoregulation and need to be considered to understand the thermodynamic behavior of nests of wasps and social insects in general.

On the origin of reproducible sequential activity in neural circuits

NASA Astrophysics Data System (ADS)

Afraimovich, V. S.; Zhigulin, V. P.; Rabinovich, M. I.

2004-12-01

Robustness and reproducibility of sequential spatio-temporal responses is an essential feature of many neural circuits in sensory and motor systems of animals. The most common mathematical images of dynamical regimes in neural systems are fixed points, limit cycles, chaotic attractors, and continuous attractors (attractive manifolds of neutrally stable fixed points). These are not suitable for the description of reproducible transient sequential neural dynamics. In this paper we present the concept of a stable heteroclinic sequence (SHS), which is not an attractor. SHS opens the way for understanding and modeling of transient sequential activity in neural circuits. We show that this new mathematical object can be used to describe robust and reproducible sequential neural dynamics. Using the framework of a generalized high-dimensional Lotka-Volterra model, that describes the dynamics of firing rates in an inhibitory network, we present analytical results on the existence of the SHS in the phase space of the network. With the help of numerical simulations we confirm its robustness in presence of noise in spite of the transient nature of the corresponding trajectories. Finally, by referring to several recent neurobiological experiments, we discuss possible applications of this new concept to several problems in neuroscience.

On the origin of reproducible sequential activity in neural circuits.

PubMed

Afraimovich, V S; Zhigulin, V P; Rabinovich, M I

2004-12-01

Robustness and reproducibility of sequential spatio-temporal responses is an essential feature of many neural circuits in sensory and motor systems of animals. The most common mathematical images of dynamical regimes in neural systems are fixed points, limit cycles, chaotic attractors, and continuous attractors (attractive manifolds of neutrally stable fixed points). These are not suitable for the description of reproducible transient sequential neural dynamics. In this paper we present the concept of a stable heteroclinic sequence (SHS), which is not an attractor. SHS opens the way for understanding and modeling of transient sequential activity in neural circuits. We show that this new mathematical object can be used to describe robust and reproducible sequential neural dynamics. Using the framework of a generalized high-dimensional Lotka-Volterra model, that describes the dynamics of firing rates in an inhibitory network, we present analytical results on the existence of the SHS in the phase space of the network. With the help of numerical simulations we confirm its robustness in presence of noise in spite of the transient nature of the corresponding trajectories. Finally, by referring to several recent neurobiological experiments, we discuss possible applications of this new concept to several problems in neuroscience.

Melt quenched vanadium oxide embedded in graphene oxide sheets as composite electrodes for amperometric dopamine sensing and lithium ion battery applications

NASA Astrophysics Data System (ADS)

Sreejesh, M.; Shenoy, Sulakshana; Sridharan, Kishore; Kufian, D.; Arof, A. K.; Nagaraja, H. S.

2017-07-01

Electrochemical sensors and lithium-ion batteries are two important topics in electrochemistry that have attracted much attention owing to their extensive applications in enzyme-free biosensors and portable electronic devices. Herein, we report a simple hydrothermal approach for synthesizing composites of melt quenched vanadium oxide embedded on graphene oxide of equal proportion (MVGO50) for the fabrication of electrodes for nonenzymatic amperometic dopamine sensor and lithium-ion battery applications. The sensing performance of MVGO50 electrodes through chronoamperometry studies in 0.1 M PBS solution (at pH 7) over a wide range of dopamine concentration exhibited a highest sensitivity of 25.02 μA mM-1 cm-2 with the lowest detection limit of 0.07 μM. In addition, the selective sensing capability of MVGO50 was also tested through chronoamperometry studies by the addition of a very small concentration of dopamine (10 μM) in the presence of a fairly higher concentration of uric acid (10 mM) as the interfering species. Furthermore, the reversible lithium cycling properties of MVGO50 are evaluated by galvanostatic charge-discharge cycling studies. MVGO50 electrodes exhibited enhanced rate capacity of up to 200 mAhg-1 at a current of 0.1C rate and remained stable during cycling. These results indicate that MVGO composites are potential candidates for electrochemical device applications.

Phase I Trial of a Pathotropic Retroviral Vector Expressing a Cytocidal Cyclin G1 Construct (Rexin-G) in Patients With Advanced Pancreatic Cancer

PubMed Central

Galanis, Evanthia; Carlson, Stephanie K; Foster, Nathan R; Lowe, Val; Quevedo, Fernando; McWilliams, Robert R; Grothey, Axel; Jatoi, Aminah; Alberts, Steven R; Rubin, Joseph

2009-01-01

Rexin-G is a pathotropic retroviral vector displaying a von Willebrand factor–targeting motif and expressing a dominant negative cyclin G1 gene. We undertook a phase I trial of intravenous (IV) administration of Rexin-G in patients with gemcitabine refractory, metastatic pancreatic adenocarcinoma. Twelve patients were treated. Dose escalation was performed from a dose of 1 × 1011 colony forming units (CFU) per cycle to 6 × 1011 CFU per cycle. The treatment was well tolerated. One dose-limiting toxicity (DLT) at dose level 2 (1.5 × 1011 CFU per cycle) was observed, consisting of grade 3 transaminitis. There was no detection of replication-competent virus in patients’ peripheral blood mononuclear cells (PBMCs) or viral integration in DNA obtained from PBMCs, and no development of neutralizing antibodies. No evidence of antitumor activity was observed. The best objective response was progressive disease in 11 of the 12 study patients, while 1 patient showed radiographically stable disease with clinical deterioration and increase in the CA19.9 tumor marker. Median time to progression was 32 days. The median duration of survival of the study patients was 3.5 months from treatment initiation. Rexin-G is well tolerated in doses up to 6 × 1011 CFU in patients with recurrent pancreatic cancer, but there was no evidence of clinical antitumor activity. PMID:18388964

Estimating the boundaries of a limit cycle in a 2D dynamical system using renormalization group

NASA Astrophysics Data System (ADS)

Dutta, Ayan; Das, Debapriya; Banerjee, Dhruba; Bhattacharjee, Jayanta K.

2018-04-01

While the plausibility of formation of limit cycle has been a well studied topic in context of the Poincare-Bendixson theorem, studies on estimates in regard to the possible size and shape of the limit cycle seem to be scanty in the literature. In this paper we present a pedagogical study of some aspects of the size of this limit cycle using perturbative renormalization group by doing detailed and explicit calculations upto second order for the Selkov model for glycolytic oscillations. This famous model is well known to lead to a limit cycle for certain ranges of values of the parameters involved in the problem. Within the tenets of the approximations made, reasonable agreement with the numerical plots can be achieved.

High-energy green supercapacitor driven by ionic liquid electrolytes as an ultra-high stable next-generation energy storage device

NASA Astrophysics Data System (ADS)

Thangavel, Ranjith; Kannan, Aravindaraj G.; Ponraj, Rubha; Thangavel, Vigneysh; Kim, Dong-Won; Lee, Yun-Sung

2018-04-01

Development of supercapacitors with high energy density and long cycle life using sustainable materials for next-generation applications is of paramount importance. The ongoing challenge is to elevate the energy density of supercapacitors on par with batteries, while upholding the power and cyclability. In addition, attaining such superior performance with green and sustainable bio-mass derived compounds is very crucial to address the rising environmental concerns. Herein, we demonstrate the use of watermelon rind, a bio-waste from watermelons, towards high energy, and ultra-stable high temperature green supercapacitors with a high-voltage ionic liquid electrolyte. Supercapacitors assembled with ultra-high surface area, hierarchically porous carbon exhibits a remarkable performance both at room temperature and at high temperature (60 °C) with maximum energy densities of ∼174 Wh kg-1 (25 °C), and 177 Wh kg-1 (60 °C) - based on active mass of both electrodes. Furthermore, an ultra-high specific power of ∼20 kW kg-1 along with an ultra-stable cycling performance with 90% retention over 150,000 cycles has been achieved even at 60 °C, outperforming supercapacitors assembled with other carbon based materials. These results demonstrate the potential to develop high-performing, green energy storage devices using eco-friendly materials for next generation electric vehicles and other advanced energy storage systems.

Assessment of diel chemical and isotopic techniques to investigate biogeochemical cycles in the upper Klamath River, Oregon, USA

USGS Publications Warehouse

Poulson, S.R.; Sullivan, A.B.

2009-01-01

The upper Klamath River experiences a cyanobacterial algal bloom and poor water quality during the summer. Diel chemical and isotopic techniques have been employed in order to investigate the rates of biogeochemical processes. Four diel measurements of field parameters (temperature, pH, dissolved oxygen concentrations, and alkalinity) and stable isotope compositions (dissolved oxygen-??18O and dissolved inorganic carbon-??13C) have been performed between June 2007 and August 2008. Significant diel variations of pH, dissolved oxygen (DO) concentration, and DO-??18O were observed, due to varying rates of primary productivity vs. respiration vs. gas exchange with air. Diel cycles are generally similar to those previously observed in river systems, although there are also differences compared to previous studies. In large part, these different diel signatures are the result of the low turbulence of the upper Klamath River. Observed changes in the diel signatures vs. sampling date reflect the evolution of the status of the algal bloom over the course of the summer. Results indicate the potential utility of applying diel chemical and stable isotope techniques to investigate the rates of biogeochemical cycles in slow-moving rivers, lakes, and reservoirs, but also illustrate the increased complexity of stable isotope dynamics in these low-turbulence systems compared to well-mixed aquatic systems. ?? 2009 Elsevier B.V.

In situ monitoring of H and O stable isotopes in soil water reveals ecohydrologic dynamics in managed soil systems [Urban ecohydrologic dynamics revealed by in situ monitoring of H and O stable isotopes in soil water

DOE PAGES

Oerter, Erik J.; Bowen, Gabriel

2017-04-12

The water cycle in urban and hydrologically managed settings is subject to perturbations that are dynamic on small spatial and temporal scales; the effects of which may be especially profound in soils. We deploy a membrane inlet-based laser spectroscopy system in conjunction with soil moisture and temperature sensors to monitor soil water dynamics and H and O stable isotope ratios (δ 2H and δ 18O values) in a seasonally irrigated urban-landscaped garden soil over the course of 9 months between the cessation of irrigation in the autumn and the onset of irrigation through the summer. Here, we find that soilmore » water δ 2H and δ 18O values predominately reflect seasonal precipitation and irrigation inputs. A comparison of total soil water by cryogenic extraction and mobile soil water measured by in situ water vapor probes reveals that initial infiltration events after long periods of soil drying (the autumn season in this case) emplace water into the soil matrix that is not easily replaced by, or mixed with, successive pulses of infiltrating soil water. Tree stem xylem water H and O stable isotope composition did not match that of available water sources. Our findings suggest that partitioning of soil water into mobile and immobile “pools” and resulting ecohydrologic separation may occur in engineered and hydrologically managed soils and not be limited to natural settings. Furthermore, the laser spectroscopy method detailed here has potential to yield insights in a variety of critical zone and vadose zone studies, potential that is heightened by the simplicity and portability of the system.« less

In situ monitoring of H and O stable isotopes in soil water reveals ecohydrologic dynamics in managed soil systems [Urban ecohydrologic dynamics revealed by in situ monitoring of H and O stable isotopes in soil water

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

Oerter, Erik J.; Bowen, Gabriel

The water cycle in urban and hydrologically managed settings is subject to perturbations that are dynamic on small spatial and temporal scales; the effects of which may be especially profound in soils. We deploy a membrane inlet-based laser spectroscopy system in conjunction with soil moisture and temperature sensors to monitor soil water dynamics and H and O stable isotope ratios (δ 2H and δ 18O values) in a seasonally irrigated urban-landscaped garden soil over the course of 9 months between the cessation of irrigation in the autumn and the onset of irrigation through the summer. Here, we find that soilmore » water δ 2H and δ 18O values predominately reflect seasonal precipitation and irrigation inputs. A comparison of total soil water by cryogenic extraction and mobile soil water measured by in situ water vapor probes reveals that initial infiltration events after long periods of soil drying (the autumn season in this case) emplace water into the soil matrix that is not easily replaced by, or mixed with, successive pulses of infiltrating soil water. Tree stem xylem water H and O stable isotope composition did not match that of available water sources. Our findings suggest that partitioning of soil water into mobile and immobile “pools” and resulting ecohydrologic separation may occur in engineered and hydrologically managed soils and not be limited to natural settings. Furthermore, the laser spectroscopy method detailed here has potential to yield insights in a variety of critical zone and vadose zone studies, potential that is heightened by the simplicity and portability of the system.« less

Conducting Polymers Crosslinked with Sulfur as Cathode Materials for High-Rate, Ultralong-Life Lithium-Sulfur Batteries.

PubMed

Zeng, Shuaibo; Li, Ligui; Xie, Lihong; Zhao, Dengke; Wang, Nan; Chen, Shaowei

2017-09-11

Low electrical conductivity and a lack of chemical confinement are two major factors that limit the rate performances and cycling stabilities of cathode materials in lithium-sulfur (Li-S) batteries. Herein, sulfur is copolymerized with poly(m-aminothiophenol) (PMAT) nanoplates through inverse vulcanization to form the highly crosslinked copolymer cp(S-PMAT) in which approximately 80 wt % of the feed sulfur is bonded chemically to the thiol groups of PMAT. A cp(S-PMAT)/C-based cathode exhibits a high discharge capacity of 1240 mAh g -1 at 0.1 C and remarkable rate capacities of 880 mAh g -1 at 1 C and 600 mAh g -1 at 5 C. Moreover, it can retain a capacity of 495 mAh g -1 after 1000 deep discharge-charge cycles at 2 C; this corresponds to a retention of 66.9 % and a decay rate of only 0.040 % per cycle. Such a remarkable rate performance is attributed to the highly conductive pathways of PMAT nanoplates, and the excellent cycling stability is ascribed mainly to the chemical confinement of sulfur through a large number of stable covalent bonds between sulfur and the thiol groups of PMAT. The results suggest that this strategy is a viable paradigm for the design and engineering of conducting polymers with reactive functional groups as effective electrode materials for high-performance Li-S batteries. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Triggered instabilities in rocket motors and active combustion control for an incinerator afterburner

NASA Astrophysics Data System (ADS)

Wicker, Josef M.

1999-11-01

Two branches of research are conducted in this thesis. The first deals with nonlinear combustion response as a mechanism for triggering combustion instabilities in solid rocket motors. A nonlinear wave equation is developed to study a wide class of combustion response functions to second-order in fluctuation amplitude. Conditions for triggering are derived from analysis of limit cycles, and regions of triggering are found in parametric space. Introduction of linear cross-coupling and quadratic self-coupling among the acoustic modes appears to be how the nonlinear combustion response produces triggering to a stable limit cycle. Regions of initial conditions corresponding to stable pulses were found, suggesting that stability depends on initial phase angle and harmonic content, as well as the composite amplitude, of the pulse. Also, dependence of nonlinear stability upon system parameters is considered. The second part of this thesis presents research for a controller to improve the emissions of an incinerator afterburner. The developed controller was experimentally tested at the Naval Air Warfare Center (NAWC), on a 50kW-scale model of an afterburner for Naval shipboard incinerator applications. Acoustic forcing of the combustor's reacting shear layer is used to control the formation of coherent vortical structures, within which favorable fuel-air mixing and efficient combustion can occur. Laser-based measurements of CO emissions are used as the performance indicator for the combustor. The controller algorithm is based on the downhill simplex method and adjusts the shear layer forcing parameters in order to minimize the CO emissions. The downhill simplex method was analyzed with respect to its behavior in the face of time-variation of the plant and noise in the sensor signal, and was modified to account for these difficulties. The control system has experimentally demonstrated the ability (1) to find optimal control action for single- and multi-variable control, (2) to maintain optimal control for time-varying operating states, and (3) to automatically adjust auxiliary fuel in response to changing stoichiometry of the incoming waste pyrolysis gas. Also presented but not tested in the experiments are an expert-type model-guidance feature to aid convergence of the controller to optimum control, and methodology for maintaining flammability.

Conical Euler analysis and active roll suppression for unsteady vortical flows about rolling delta wings

NASA Technical Reports Server (NTRS)

Lee-Rausch, Elizabeth M.; Batina, John T.

1993-01-01

A conical Euler code was developed to study unsteady vortex-dominated flows about rolling, highly swept delta wings undergoing either forced motions or free-to-roll motions that include active roll suppression. The flow solver of the code involves a multistage, Runge-Kutta time-stepping scheme that uses a cell-centered, finite-volume, spatial discretization of the Euler equations on an unstructured grid of triangles. The code allows for the additional analysis of the free to-roll case by simultaneously integrating in time the rigid-body equation of motion with the governing flow equations. Results are presented for a delta wing with a 75 deg swept, sharp leading edge at a free-stream Mach number of 1.2 and at 10 deg, 20 deg, and 30 deg angle of attack alpha. At the lower angles of attack (10 and 20 deg), forced-harmonic analyses indicate that the rolling-moment coefficients provide a positive damping, which is verified by free-to-roll calculations. In contrast, at the higher angle of attack (30 deg), a forced-harmonic analysis indicates that the rolling-moment coefficient provides negative damping at the small roll amplitudes. A free-to-roll calculation for this case produces an initially divergent response, but as the amplitude of motion grows with time, the response transitions to a wing-rock type of limit cycle oscillation, which is characteristic of highly swept delta wings. This limit cycle oscillation may be actively suppressed through the use of a rate-feedback control law and antisymmetrically deflected leading-edge flaps. Descriptions of the conical Euler flow solver and the free-to roll analysis are included in this report. Results are presented that demonstrate how the systematic analysis of the forced response of the delta wing can be used to predict the stable, neutrally stable, and unstable free response of the delta wing. These results also give insight into the flow physics associated with unsteady vortical flows about delta wings undergoing forced motions and free-to-roll motions, including the active suppression of the wing-rock type phenomenon. The conical Euler methodology developed is directly extend able to three-dimensional calculations.

Controllable embedding of sulfur in high surface area nitrogen doped three dimensional reduced graphene oxide by solution drop impregnation method for high performance lithium-sulfur batteries

NASA Astrophysics Data System (ADS)

Zegeye, Tilahun Awoke; Tsai, Meng-Che; Cheng, Ju-Hsiang; Lin, Ming-Hsien; Chen, Hung-Ming; Rick, John; Su, Wei-Nien; Kuo, Chung-Feng Jeffrey; Hwang, Bing-Joe

2017-06-01

High capacity lithium-sulfur batteries with stable cycle performance and sulfur loadings greater than 70 wt% are regarded as promising candidates for energy storage devices. However, it has been challenged to achieving practical application of sulfur cathode because of low loading of active sulfur and poor cycle performance. Herein, we design novel nanocomposite cathode materials consist of sulfur (80 wt%) embedded within nitrogen doped three-dimensional reduced graphene oxide (N-3D-rGO) by controllable sulfur-impregnation method. Nitrogen doping helps increase the surface area by ten times from pristine graphene, and pore volume by seven times. These structural features allow the cathode to hold more sulfur. It also adsorbs polysulfides and prevents their detachment from the host materials; thereby achieving stable cycle performance. The solution drop sulfur-impregnation method provides uniform distribution of nano-sulfur in controlled manner. The material delivers a high initial discharge capacity of 1042 mAhg-1 and 916 mAhg-1 with excellent capacity retention of 94.8% and 81.9% at 0.2 C and 0.5 C respectively after 100 cycles. Thus, the combination of solution drop and nitrogen doping opens a new chapter for resolving capacity fading as well as long cycling problems and creates a new strategy to increase sulfur loading in controlled mechanism.

Rotor Stability Separates Sustained Ventricular Fibrillation From Self-Terminating Episodes in Humans

PubMed Central

Krummen, David E.; Hayase, Justin; Morris, David J.; Ho, Jeffrey; Smetak, Miriam R.; Clopton, Paul; Rappel, Wouter-Jan; Narayan, Sanjiv M.

2014-01-01

Objective We mapped human ventricular fibrillation (VF) to define mechanistic differences between episodes requiring defibrillation versus those that spontaneously terminate. Background VF is a leading cause of mortality, yet episodes may also self-terminate. We hypothesized that the initial maintenance of human VF is dependent upon the formation and stability of VF rotors. Methods We enrolled 26 consecutive patients (age 64±10 years, n=13 with LV dysfunction) during ablation procedures for ventricular arrhythmias, using 64-electrode basket catheters in both ventricles to map VF prior to prompt defibrillation per IRB-approved protocol. Fifty-two inductions were attempted and 36 VF episodes were observed. Phase analysis was applied to identify bi-ventricular rotors in the first 10 seconds or until VF terminated, whichever came first (11.4±2.9 seconds to defibrillator charging). Results Rotors were present in 16 of 19 patients with VF, and in all patients with sustained VF. Sustained, but not self-limiting VF, was characterized by greater rotor stability: (1) rotors were present in 68±17% of cycles in sustained versus 11±18% of cycles in self-limiting VF (p<0.001); with (2) maximum continuous rotations greater in sustained (17±11, range 7–48) versus self-limiting VF (1.1±1.4, range 0–4, p<0.001). Additionally, biventricular rotor locations in sustained VF were conserved across multiple inductions (7/7 patients, p=0.025). Conclusions In patients with and without structural heart disease, the formation of stable rotors identifies individuals whose VF requires defibrillation from those in whom VF spontaneously self-terminates. Future work should define the mechanisms that stabilize rotors and evaluate whether rotor modulation may reduce subsequent VF risk. PMID:24794115

An observational constraint on stomatal function in forests: evaluating coupled carbon and water vapor exchange with carbon isotopes in the Community Land Model (CLM4.5)

NASA Astrophysics Data System (ADS)

Raczka, Brett; Duarte, Henrique F.; Koven, Charles D.; Ricciuto, Daniel; Thornton, Peter E.; Lin, John C.; Bowling, David R.

2016-09-01

Land surface models are useful tools to quantify contemporary and future climate impact on terrestrial carbon cycle processes, provided they can be appropriately constrained and tested with observations. Stable carbon isotopes of CO2 offer the potential to improve model representation of the coupled carbon and water cycles because they are strongly influenced by stomatal function. Recently, a representation of stable carbon isotope discrimination was incorporated into the Community Land Model component of the Community Earth System Model. Here, we tested the model's capability to simulate whole-forest isotope discrimination in a subalpine conifer forest at Niwot Ridge, Colorado, USA. We distinguished between isotopic behavior in response to a decrease of δ13C within atmospheric CO2 (Suess effect) vs. photosynthetic discrimination (Δcanopy), by creating a site-customized atmospheric CO2 and δ13C of CO2 time series. We implemented a seasonally varying Vcmax model calibration that best matched site observations of net CO2 carbon exchange, latent heat exchange, and biomass. The model accurately simulated observed δ13C of needle and stem tissue, but underestimated the δ13C of bulk soil carbon by 1-2 ‰. The model overestimated the multiyear (2006-2012) average Δcanopy relative to prior data-based estimates by 2-4 ‰. The amplitude of the average seasonal cycle of Δcanopy (i.e., higher in spring/fall as compared to summer) was correctly modeled but only when using a revised, fully coupled An - gs (net assimilation rate, stomatal conductance) version of the model in contrast to the partially coupled An - gs version used in the default model. The model attributed most of the seasonal variation in discrimination to An, whereas interannual variation in simulated Δcanopy during the summer months was driven by stomatal response to vapor pressure deficit (VPD). The model simulated a 10 % increase in both photosynthetic discrimination and water-use efficiency (WUE) since 1850 which is counter to established relationships between discrimination and WUE. The isotope observations used here to constrain CLM suggest (1) the model overestimated stomatal conductance and (2) the default CLM approach to representing nitrogen limitation (partially coupled model) was not capable of reproducing observed trends in discrimination. These findings demonstrate that isotope observations can provide important information related to stomatal function driven by environmental stress from VPD and nitrogen limitation. Future versions of CLM that incorporate carbon isotope discrimination are likely to benefit from explicit inclusion of mesophyll conductance.

Design and Construction of Multi-Variable Vortex-Ring Bubble Generator for Use in Interactive Exhibit

DTIC Science & Technology

2013-12-01

providing the opportunity to teach complex subjects related to stable and unstable equilibrium, stochastic systems, and conservation laws. The...bubbles through adjustment of three variables. The seal pressure, actuating pressure, and cycle time of the triggering solenoid valve each contribute to...stable and unstable equilibrium, stochastic systems, and conservation laws. The diaphragm valve designed in this thesis provides the centerpiece for

Subsurface iron and arsenic removal for shallow tube well drinking water supply in rural Bangladesh.

PubMed

van Halem, D; Olivero, S; de Vet, W W J M; Verberk, J Q J C; Amy, G L; van Dijk, J C

2010-11-01

Subsurface iron and arsenic removal has the potential to be a cost-effective technology to provide safe drinking water in rural decentralized applications, using existing shallow tube wells. A community-scale test facility in Bangladesh was constructed for injection of aerated water (∼1 m(3)) into an anoxic aquifer with elevated iron (0.27 mmolL(-1)) and arsenic (0.27μmolL(-1)) concentrations. The injection (oxidation) and abstraction (adsorption) cycles were monitored at the test facility and simultaneously simulated in the laboratory with anoxic column experiments. Dimensionless retardation factors (R) were determined to represent the delayed arrival of iron or arsenic in the well compared to the original groundwater. At the test facility the iron removal efficacies increased after every injection-abstraction cycle, with retardation factors (R(Fe)) up to 17. These high removal efficacies could not be explained by the theory of adsorptive-catalytic oxidation, and therefore other ((a)biotic or transport) processes have contributed to the system's efficacy. This finding was confirmed in the anoxic column experiments, since the mechanism of adsorptive-catalytic oxidation dominated in the columns and iron removal efficacies did not increase with every cycle (stable at R(Fe)=∼8). R(As) did not increase after multiple cycles, it remained stable around 2, illustrating that the process which is responsible for the effective iron removal did not promote the co-removal of arsenic. The columns showed that subsurface arsenic removal was an adsorptive process and only the freshly oxidized adsorbed iron was available for the co-adsorption of arsenic. This indicates that arsenic adsorption during subsurface treatment is controlled by the amount of adsorbed iron that is oxidized, and not by the amount of removed iron. For operational purposes this is an important finding, since apparently the oxygen concentration of the injection water does not control the subsurface arsenic removal, but rather the injection volume. Additionally, no relation has been observed in this study between the amount of removed arsenic at different molar Fe:As ratios (28, 63, and 103) of the groundwater. It is proposed that the removal of arsenic was limited by the presence of other anions, such as phosphate, competing for the same adsorption sites. Copyright © 2010 Elsevier Ltd. All rights reserved.

Water quality, isoscapes and stoichioscapes of seagrasses indicate general P limitation and unique N cycling in shallow water benthos of Bermuda

NASA Astrophysics Data System (ADS)

Fourqurean, J. W.; Manuel, S. A.; Coates, K. A.; Kenworthy, W. J.; Boyer, J. N.

2015-07-01

Striking spatial patterns in stable isotope ratios (isoscapes) and elemental ratios (stoichioscapes) of seagrass leaves and the water column nutrients indicate general P-limitation of both water column and benthic primary productivity on the Bermuda Platform, and they highlight the role of the Bermuda Islands as a source of N and P. We found consistent differences among the four seagrass species (Syringodium filiforme, Thalassia testudinum, Halodule sp. and Halophila decipiens) in the N, P, δ13C and δ15N of leaf tissues. The δ15N of seagrass leaves was especially variable, with values from -10.1 to 8.8‰, greatly expanding the reported range of values for all seagrass species globally. Spatial patterns from both the water column and the seagrass leaves indicated that P availability was higher near shore, and δ15N values suggest this was likely a result of human waste disposal. Spatially-contiguous areas of extremely depleted seagrass δ15N suggest unique N sources and cycling compared to other seagrass-dominated environments. Seagrass N : P values were not as far from the stoichiometric balance between N and P availability as in the water column, and there were no strong relationships between the water column N : P and the seagrass N : P. Such isoscapes and stoichioscapes provide valuable ecogeochemical tools to infer ecosystem processes as well as provide information that can inform food web and animal movement studies.

Water quality, isoscapes and stoichioscapes of seagrasses indicate general P limitation and unique N cycling in shallow water benthos of Bermuda

NASA Astrophysics Data System (ADS)

Fourqurean, J. W.; Manuel, S. A.; Coates, K. A.; Kenworthy, W. J.; Boyer, J. N.

2015-10-01

Striking spatial patterns in stable isotope ratios (isoscapes) and elemental ratios (stoichioscapes) of seagrass leaves and the water column nutrients indicate general P-limitation of both water column and benthic primary productivity on the Bermuda Platform, and they highlight the role of the Bermuda Islands as a source of N and P. We found consistent differences among the four seagrass species (Syringodium filiforme, Thalassia testudinum, Halodule sp. and Halophila decipiens) in the N, P, δ13C and δ15N of leaf tissues. The δ15N of seagrass leaves was especially variable, with values from -10.1 to 8.8 ‰, greatly expanding the reported range of values for all seagrass species globally. Spatial patterns from both the water column and the seagrass leaves indicated that P availability was higher near shore, and δ15N values suggest this was likely a result of human waste disposal. Spatially contiguous areas of extremely depleted seagrass 15N suggest unique N sources and cycling compared to other seagrass-dominated environments. Seagrass N : P values were not as far from the stoichiometric balance between N and P availability as in the water column, and there were no strong relationships between the water column N : P and the seagrass N : P. Such isoscapes and stoichioscapes provide valuable ecogeochemical tools to infer ecosystem processes as well as provide information that can inform food web and animal movement studies.

Does natural weathering change the stable isotope composition (²H, ¹³C, ¹⁵N, ¹⁸O and ³⁴S) of cattle hair?

PubMed

Auerswald, Karl; Rossmann, Andreas; Schäufele, Rudi; Schwertl, Michael; Monahan, Frank J; Schnyder, Hans

2011-12-30

Stable isotope analysis of hair has found applications in many fields of science because it provides a temporally resolved, fairly stable isotopic archive of mammalian individuals. We investigated whether this hair archive is modified by natural weathering while attached to a living animal. We analyzed the tail switch hairs of one suckler cow, sampled seven times over a period of four annual summer pasture-winter stall feeding cycles. We compared relative isotope ratios (δ²H, δ¹³C, δ¹⁵N, δ¹⁸O and δ³⁴S) of sections of hair that grew simultaneously but were exposed to natural weathering conditions over different periods of time. Natural wear caused a loss of mass of approx. 0.13% day⁻¹, with no apparent effect of environmental conditions. Changes in δ²H, δ¹³C, δ¹⁵N and δ¹⁸O were below the detection limit, indicating that hair is a reliable archive for the isotopes of these elements. In contrast, δ³⁴S values increased during the grazing period by about 1‰, with exposure to UV radiation appearing to have a major influence on this result. The δ³⁴S values decreased during the subsequent stall period, probably due to abrasion. Seasonal variation in δ³⁴S may indicate alternating environments that differ in their weathering conditions.

Conducting polymer nanostructures for photocatalysis under visible light

NASA Astrophysics Data System (ADS)

Ghosh, Srabanti; Kouamé, Natalie A.; Ramos, Laurence; Remita, Samy; Dazzi, Alexandre; Deniset-Besseau, Ariane; Beaunier, Patricia; Goubard, Fabrice; Aubert, Pierre-Henri; Remita, Hynd

2015-05-01

Visible-light-responsive photocatalysts can directly harvest energy from solar light, offering a desirable way to solve energy and environment issues. Here, we show that one-dimensional poly(diphenylbutadiyne) nanostructures synthesized by photopolymerization using a soft templating approach have high photocatalytic activity under visible light without the assistance of sacrificial reagents or precious metal co-catalysts. These polymer nanostructures are very stable even after repeated cycling. Transmission electron microscopy and nanoscale infrared characterizations reveal that the morphology and structure of the polymer nanostructures remain unchanged after many photocatalytic cycles. These stable and cheap polymer nanofibres are easy to process and can be reused without appreciable loss of activity. Our findings may help the development of semiconducting-based polymers for applications in self-cleaning surfaces, hydrogen generation and photovoltaics.

SAFT nickel hydrogen cell cycling status

NASA Technical Reports Server (NTRS)

Borthomieu, Yannick; Duquesne, Didier

1994-01-01

An overview of the NiH2 cell development is given. The NiH2 SAFT system is an electrochemical (single or dual) stack (IPV). The stack is mounted in an hydroformed Inconel 718 vessel operating at high pressure, equipped with 'rabbit ears' ceramic brazed electrical feedthroughs. The cell design is described: positive electrode, negative electrode, and stack configuration. Overviews of low earth orbit and geostationary earth orbit cyclings are provided. DPA results are also provided. The cycling and DPA results demonstrate that SAFT NiH2 is characterized by high reliability and very stable performances.

Optimization of Turbine Engine Cycle Analysis with Analytic Derivatives

NASA Technical Reports Server (NTRS)

Hearn, Tristan; Hendricks, Eric; Chin, Jeffrey; Gray, Justin; Moore, Kenneth T.

2016-01-01

A new engine cycle analysis tool, called Pycycle, was recently built using the OpenMDAO framework. This tool uses equilibrium chemistry based thermodynamics, and provides analytic derivatives. This allows for stable and efficient use of gradient-based optimization and sensitivity analysis methods on engine cycle models, without requiring the use of finite difference derivative approximation methods. To demonstrate this, a gradient-based design optimization was performed on a multi-point turbofan engine model. Results demonstrate very favorable performance compared to an optimization of an identical model using finite-difference approximated derivatives.

Investigating wind turbine impacts on near-wake flow using profiling Lidar data and large-eddy simulations with an actuator disk model

DOE PAGES

Mirocha, Jeffrey D.; Rajewski, Daniel A.; Marjanovic, Nikola; ...

2015-08-27

In this study, wind turbine impacts on the atmospheric flow are investigated using data from the Crop Wind Energy Experiment (CWEX-11) and large-eddy simulations (LESs) utilizing a generalized actuator disk (GAD) wind turbine model. CWEX-11 employed velocity-azimuth display (VAD) data from two Doppler lidar systems to sample vertical profiles of flow parameters across the rotor depth both upstream and in the wake of an operating 1.5 MW wind turbine. Lidar and surface observations obtained during four days of July 2011 are analyzed to characterize the turbine impacts on wind speed and flow variability, and to examine the sensitivity of thesemore » changes to atmospheric stability. Significant velocity deficits (VD) are observed at the downstream location during both convective and stable portions of four diurnal cycles, with large, sustained deficits occurring during stable conditions. Variances of the streamwise velocity component, σ u, likewise show large increases downstream during both stable and unstable conditions, with stable conditions supporting sustained small increases of σ u , while convective conditions featured both larger magnitudes and increased variability, due to the large coherent structures in the background flow. Two representative case studies, one stable and one convective, are simulated using LES with a GAD model at 6 m resolution to evaluate the compatibility of the simulation framework with validation using vertically profiling lidar data in the near wake region. Virtual lidars were employed to sample the simulated flow field in a manner consistent with the VAD technique. Simulations reasonably reproduced aggregated wake VD characteristics, albeit with smaller magnitudes than observed, while σu values in the wake are more significantly underestimated. The results illuminate the limitations of using a GAD in combination with coarse model resolution in the simulation of near wake physics, and validation thereof using VAD data.« less

Patterns of expression and normalized levels of the five Arabidopsis phytochromes.

PubMed

Sharrock, Robert A; Clack, Ted

2002-09-01

Using monoclonal antibodies specific for each apoprotein and full-length purified apoprotein standards, the levels of the five Arabidopsis phytochromes and their patterns of expression in seedlings and mature plants and under different light conditions have been characterized. Phytochrome levels are normalized to the DNA content of the various tissue extracts to approximate normalization to the number of cells in the tissue. One phytochrome, phytochrome A, is highly light labile. The other four phytochromes are much more light stable, although among these, phytochromes B and C are reduced 4- to 5-fold in red- or white-light-grown seedlings compared with dark-grown seedlings. The total amount of extractable phytochrome is 23-fold lower in light-grown than dark-grown tissues, and the percent ratios of the five phytochromes, A:B:C:D:E, are measured as 85:10:2:1.5:1.5 in etiolated seedlings and 5:40:15:15:25 in seedlings grown in continuous white light. The four light-stable phytochromes are present at nearly unchanging levels throughout the course of development of mature rosette and reproductive-stage plants and are present in leaves, stems, roots, and flowers. Phytochrome protein expression patterns over the course of seed germination and under diurnal and circadian light cycles are also characterized. Little cycling in response to photoperiod is observed, and this very low amplitude cycling of some phytochrome proteins is out of phase with previously reported cycling of PHY mRNA levels. These studies indicate that, with the exception of phytochrome A, the family of phytochrome photoreceptors in Arabidopsis constitutes a quite stable and very broadly distributed array of sensory molecules.

Estimating exercise capacity from walking tests in elderly individuals with stable coronary artery disease.

PubMed

Mandic, Sandra; Walker, Robert; Stevens, Emily; Nye, Edwin R; Body, Dianne; Barclay, Leanne; Williams, Michael J A

2013-01-01

Compared with symptom-limited cardiopulmonary exercise test (CPET), timed walking tests are cheaper, well-tolerated and simpler alternative for assessing exercise capacity in coronary artery disease (CAD) patients. We developed multivariate models for predicting peak oxygen consumption (VO2peak) from 6-minute walk test (6MWT) distance and peak shuttle walk speed for elderly stable CAD patients. Fifty-eight CAD patients (72 SD 6 years, 66% men) completed: (1) CPET with expired gas analysis on a cycle ergometer, (2) incremental 10-meter shuttle walk test, (3) two 6MWTs, (4) anthropometric assessment and (5) 30-second chair stands. Linear regression models were developed for estimating VO2peak from 6MWT distance and peak shuttle walk speed as well as demographic, anthropometric and functional variables. Measured VO2peak was significantly related to 6MWT distance (r = 0.719, p < 0.001) and peak shuttle walk speed (r = 0.717, p < 0.001). The addition of demographic (age, gender), anthropometric (height, weight, body mass index, body composition) and functional characteristics (30-second chair stands) increased the accuracy of predicting VO2peak from both 6MWT distance and peak shuttle walk speed (from 51% to 73% of VO2peak variance explained). Addition of demographic, anthropometric and functional characteristics improves the accuracy of VO2peak estimate based on walking tests in elderly individuals with stable CAD. Implications for Rehabilitation Timed walking tests are cheaper, well-tolerated and simpler alternative for assessing exercise capacity in cardiac patients. Walking tests could be used to assess individual's functional capacity and response to therapeutic interventions when symptom-limited cardiopulmonary exercise testing is not practical or not necessary for clinical reasons. Addition of demographic, anthropometric and functional characteristics improves the accuracy of peak oxygen consumption estimate based on 6-minute walk test distance and peak shuttle walk speed in elderly patients with coronary artery disease.

Advanced binary geothermal power plants: Limits of performance

NASA Astrophysics Data System (ADS)

Bliem, C. J.; Mines, G. L.

1991-01-01

The Heat Cycle Research Program is investigating potential improvements to power cycles utilizing moderate temperature geothermal resources to produce electrical power. Investigations have specifically examined Rankine cycle binary power systems. Binary Rankine cycles are more efficient than the flash steam cycles at moderate resource temperature, achieving a higher net brine effectiveness. At resource conditions similar to those at the Heber binary plant, it has been shown that mixtures of saturated hydrocarbons (alkanes) or halogenated hydrocarbons operating in a supercritical Rankine cycle gave improved performance over Rankine cycles with the pure working fluids executing single or dual boiling cycles or supercritical cycles. Recently, other types of cycles have been proposed for binary geothermal service. The feasible limits on efficiency of a plant given practical limits on equipment performance is explored and the methods used in these advanced concept plants to achieve the maximum possible efficiency are discussed. (Here feasible is intended to mean reasonably achievable and not cost effective.) No direct economic analysis was made because of the sensitivity of economic results to site specific input. The limit of performance of three advanced plants were considered. The performance predictions were taken from the developers of each concept. The advanced plants considered appear to be approaching the feasible limit of performance. Ultimately, the plant designer must weigh the advantages and disadvantages of the the different cycles to find the best plant for a given service. In addition, a standard is presented of comparison of the work which has been done in the Heat Cycle Research Program and in the industrial sector by Exergy, Inc. and Polythermal Technologies.

Chaos and generalised multistability in a mesoscopic model of the electroencephalogram

NASA Astrophysics Data System (ADS)

Dafilis, Mathew P.; Frascoli, Federico; Cadusch, Peter J.; Liley, David T. J.

2009-06-01

We present evidence for chaos and generalised multistability in a mesoscopic model of the electroencephalogram (EEG). Two limit cycle attractors and one chaotic attractor were found to coexist in a two-dimensional plane of the ten-dimensional volume of initial conditions. The chaotic attractor was found to have a moderate value of the largest Lyapunov exponent (3.4 s -1 base e) with an associated Kaplan-Yorke (Lyapunov) dimension of 2.086. There are two different limit cycles appearing in conjunction with this particular chaotic attractor: one multiperiodic low amplitude limit cycle whose largest spectral peak is within the alpha band (8-13 Hz) of the EEG; and another multiperiodic large-amplitude limit cycle which may correspond to epilepsy. The cause of the coexistence of these structures is explained with a one-parameter bifurcation analysis. Each attractor has a basin of differing complexity: the large-amplitude limit cycle has a basin relatively uncomplicated in its structure while the small-amplitude limit cycle and chaotic attractor each have much more finely structured basins of attraction, but none of the basin boundaries appear to be fractal. The basins of attraction for the chaotic and small-amplitude limit cycle dynamics apparently reside within each other. We briefly discuss the implications of these findings in the context of theoretical attempts to understand the dynamics of brain function and behaviour.

Pulsar wind model for the spin-down behavior of intermittent pulsars

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

Li, L.; Tong, H.; Yan, W. M.

Intermittent pulsars are part-time radio pulsars. They have higher slow down rates in the on state (radio-loud) than in the off state (radio-quiet). This gives evidence that particle wind may play an important role in pulsar spindown. The effect of particle acceleration is included in modeling the rotational energy loss rate of the neutron star. Applying the pulsar wind model to the three intermittent pulsars (PSR B1931+24, PSR J1841–0500, and PSR J1832+0029) allows their magnetic fields and inclination angles to be calculated simultaneously. The theoretical braking indices of intermittent pulsars are also given. In the pulsar wind model, the densitymore » of the particle wind can always be the Goldreich-Julian density. This may ensure that different on states of intermittent pulsars are stable. The duty cycle of particle wind can be determined from timing observations. It is consistent with the duty cycle of the on state. Inclination angle and braking index observations of intermittent pulsars may help to test different models of particle acceleration. At present, the inverse Compton scattering induced space charge limited flow with field saturation model can be ruled out.« less

Highly-Stable Li₄Ti₅O12 Anodes Obtained by Atomic-Layer-Deposited Al₂O₃.

PubMed

Yoon, Jae Kook; Nam, Seunghoon; Shim, Hyung Cheoul; Park, Kunwoo; Yoon, Taeho; Park, Hyung Sang; Hyun, Seungmin

2018-05-16

LTO (Li₄Ti₅O 12 ) has been highlighted as anode material for next-generation lithium ion secondary batteries due to advantages such as a high rate capability, excellent cyclic performance, and safety. However, the generation of gases from undesired reactions between the electrode surface and the electrolyte has restricted the application of LTO as a negative electrode in Li-ion batteries in electric vehicles (EVs) and energy storage systems (ESS). As the generation of gases from LTO tends to be accelerated at high temperatures (40⁻60 °C), the thermal stability of LTO should be maintained during battery discharge, especially in EVs. To overcome these technical limitations, a thin layer of Al₂O₃ (~2 nm thickness) was deposited on the LTO electrode surface by atomic layer deposition (ALD), and an electrochemical charge-discharge cycle test was performed at 60 °C. The capacity retention after 500 cycles clearly shows that Al₂O₃-coated LTO outperforms the uncoated one, with a discharge capacity retention of ~98%. TEM and XPS analyses indicate that the surface reactions of Al₂O₃-coated LTO are suppressed, while uncoated LTO undergoes the (111) to (222) phase transformation, as previously reported in the literature.

Signal-off Electrochemiluminescence Biosensor Based on Phi29 DNA Polymerase Mediated Strand Displacement Amplification for MicroRNA Detection.

PubMed

Chen, Anyi; Gui, Guo-Feng; Zhuo, Ying; Chai, Ya-Qin; Xiang, Yun; Yuan, Ruo

2015-06-16

A target induced cycling strand displacement amplification (SDA) mediated by phi29 DNA polymerase (phi29) was first investigated and applied in a signal-off electrochemiluminescence (ECL) biosensor for microRNA (miRNA) detection. Herein, the target miRNA triggered the phi29-mediated SDA which could produce amounts of single-stranded DNA (assistant probe) with accurate and comprehensive nucleotide sequence. Then, the assistant probe hybridized with the capture probe and the ferrocene-labeled probe (Fc-probe) to form a ternary "Y" structure for ECL signal quenching by ferrocene. Therefore, the ECL intensity would decrease with increasing concentration of the target miRNA, and the sensitivity of biosensor would be promoted on account of the efficient signal amplification of the target induced cycling reaction. Besides, a self-enhanced Ru(II) ECL system was designed to obtain a stable and strong initial signal to further improve the sensitivity. The ECL assay for miRNA-21 detection is developed with excellent sensitivity of a concentration variation from 10 aM to 1.0 pM and limit of detection down to 3.3 aM.

Probing the characteristics of casein as green binder for non-aqueous electrochemical double layer capacitors' electrodes

NASA Astrophysics Data System (ADS)

Varzi, Alberto; Raccichini, Rinaldo; Marinaro, Mario; Wohlfahrt-Mehrens, Margret; Passerini, Stefano

2016-09-01

Casein from bovine milk is evaluated in this work as binding agent for electrochemical double layer capacitors (EDLCs) electrodes. It is demonstrated that casein provides excellent adhesion strength to the current collector (1187 kPa compared to 51 kPa achieved with PVdF), thus leading to mechanically stable electrodes. At the same time, it offers high thermal stability (above 200 °C) and electrochemical stability in organic electrolytes. Apparently though, the casein-based electrodes offer lower electronic conductivity than those based on other state-of-the-art binders, which can limit the rate performance of the resulting EDLC. In the attempt of improving the electrochemical performance, it is found that the application of a pressing step can solve this issue, leading to excellent rate capability (up to 84% capacitance retention at 50 mA cm-2) and cycling stability (96.8% after 10,000 cycles at 10 mA cm-2) in both PC- and ACN-based electrolytes. Although the adhesive power casein is known since ancient times, this report presents the first proof of concept of its employment in electrochemical power sources.

Centennial-scale reductions in nitrogen availability in temperate forests of the United States

USGS Publications Warehouse

McLauchlan, Kendra K.; Gerhart, Laci M.; Battles, John J.; Craine, Joseph M.; Elmore, Andrew J.; Higuera, Phil E.; Mack, Michelle M; McNeil, Brendan E.; Nelson, David M.; Pederson, Neil; Perakis, Steven

2017-01-01

Forests cover 30% of the terrestrial Earth surface and are a major component of the global carbon (C) cycle. Humans have doubled the amount of global reactive nitrogen (N), increasing deposition of N onto forests worldwide. However, other global changes—especially climate change and elevated atmospheric carbon dioxide concentrations—are increasing demand for N, the element limiting primary productivity in temperate forests, which could be reducing N availability. To determine the long-term, integrated effects of global changes on forest N cycling, we measured stable N isotopes in wood, a proxy for N supply relative to demand, on large spatial and temporal scales across the continental U.S.A. Here, we show that forest N availability has generally declined across much of the U.S. since at least 1850 C.E. with cool, wet forests demonstrating the greatest declines. Across sites, recent trajectories of N availability were independent of recent atmospheric N deposition rates, implying a minor role for modern N deposition on the trajectory of N status of North American forests. Our results demonstrate that current trends of global changes are likely to be consistent with forest oligotrophication into the foreseeable future, further constraining forest C fixation and potentially storage.

Room-Temperature, Ambient-Pressure Chemical Synthesis of Amine-Functionalized Hierarchical Carbon-Sulfur Composites for Lithium-Sulfur Battery Cathodes.

PubMed

Chae, Changju; Kim, Jinmin; Kim, Ju Young; Ji, Seulgi; Lee, Sun Sook; Kang, Yongku; Choi, Youngmin; Suk, Jungdon; Jeong, Sunho

2018-02-07

Recently, the achievement of newly designed carbon-sulfur composite materials has attracted a tremendous amount of attention as high-performance cathode materials for lithium-sulfur batteries. To date, sulfur materials have been generally synthesized by a sublimation technique in sealed containers. This is a well-developed technique for the synthesizing of well-ordered sulfur materials, but it is limited when used to scale up synthetic procedures for practical applications. In this study, we suggest an easily scalable, room-temperature/ambient-pressure chemical pathway for the synthesis of highly functioning cathode materials using electrostatically assembled, amine-terminated carbon materials. It is demonstrated that stable cycling performance outcomes are achievable with a capacity of 730 mAhg -1 at a current density of 1 C with good cycling stability by a virtue of the characteristic chemical/physical properties (a high conductivity for efficient charge conduction and the presence of a number of amine groups that can interact with sulfur atoms during electrochemical reactions) of composite materials. The critical roles of conductive carbon moieties and amine functional groups inside composite materials are clarified with combinatorial analyses by X-ray photoelectron spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy.

Montreal electronic artificial urinary sphincters: Our futuristic alternatives to the AMS800™.

PubMed

Biardeau, Xavier; Hached, Sami; Loutochin, Oleg; Campeau, Lysanne; Sawan, Mohamad; Corcos, Jacques

2017-10-01

We aimed to present three novel remotely controlled hydromechanical artificial urinary sphincters (AUSs) and report their in-vitro and ex-vivo results. We successively developed three distinct hydromechanical AUSs on the basis of the existing AMS800 ™ device by incorporating an electronic pump. No changes were made to the cuff and balloon. The AUS#1 was designed as an electromagnetically controlled device. The AUS#2 and AUS#3 were conceived as Bluetooth 2.1 remotely controlled and Bluetooth 4.0 remotely-controlled, adaptive devices, respectively. In-vitro experiments profiled occlusive cuff pressure (OCP) during a complete device cycle, with different predetermined OCP. Ex-vivo experiments were performed on a fresh pig bladder with 4 cm cuff placed around the urethra. Leak point pressure with different predetermined OCP values was successively measured during cystometry via a catheter at the bladder dome. Our in-vitro and ex-vivo experiments demonstrated that these three novel AUSs provided stable and predetermined OCP - within the physiological range - and completely deflated the cuff, when required, in a limited time compatible with physiological voiding cycles. Our three novel, remotely controlled AUSs showed promising results that should be confirmed by in-vivo experiments focusing on efficacy and safety.

Pulsar Wind Model for the Spin-down Behavior of Intermittent Pulsars

NASA Astrophysics Data System (ADS)

Li, L.; Tong, H.; Yan, W. M.; Yuan, J. P.; Xu, R. X.; Wang, N.

2014-06-01

Intermittent pulsars are part-time radio pulsars. They have higher slow down rates in the on state (radio-loud) than in the off state (radio-quiet). This gives evidence that particle wind may play an important role in pulsar spindown. The effect of particle acceleration is included in modeling the rotational energy loss rate of the neutron star. Applying the pulsar wind model to the three intermittent pulsars (PSR B1931+24, PSR J1841-0500, and PSR J1832+0029) allows their magnetic fields and inclination angles to be calculated simultaneously. The theoretical braking indices of intermittent pulsars are also given. In the pulsar wind model, the density of the particle wind can always be the Goldreich-Julian density. This may ensure that different on states of intermittent pulsars are stable. The duty cycle of particle wind can be determined from timing observations. It is consistent with the duty cycle of the on state. Inclination angle and braking index observations of intermittent pulsars may help to test different models of particle acceleration. At present, the inverse Compton scattering induced space charge limited flow with field saturation model can be ruled out.

The impact of moisture sources on the oxygen isotope composition of precipitation at a continental site in central Europe

NASA Astrophysics Data System (ADS)

Krklec, Kristina; Domínguez-Villar, David; Lojen, Sonja

2018-06-01

The stable isotope composition of precipitation records processes taking place within the hydrological cycle. Potentially, moisture sources are important controls on the stable isotope composition of precipitation, but studies focused on this topic are still scarce. We studied the moisture sources contributing to precipitation at Postojna (Slovenia) from 2009 to 2013. Back trajectory analyses were computed for the days with precipitation at Postojna. The moisture uptake locations were identified along these trajectories using standard hydrometeorological formulation. The moisture uptake locations were integrated in eight source regions to facilitate its comparison to the monthly oxygen isotope composition (δ18O values) of precipitation. Nearly half of the precipitation originated from continental sources (recycled moisture), and >40% was from central and western Mediterranean. Results show that moisture sources do not have a significant impact on the oxygen isotope composition at this site. We suggest that the large proportion of recycled moisture originated from transpiration rather than evaporation, which produced water vapour with less negative δ18O values. Thus the difference between the oceanic and local vapour source was reduced, which prevented the distinction of the moisture sources based on their oxygen isotope signature. Nevertheless, δ18O values of precipitation are partially controlled by climate parameters, which is of major importance for paleoclimate studies. We found that the main climate control on Postojna δ18O values of precipitation is the surface temperature. Amount effect was not recorded at this site, and the winter North Atlantic Oscillation (NAO) does not impact the δ18O values of precipitation. The Western Mediterranean Oscillation (WeMO) was correlated to oxygen stable isotope composition, although this atmospheric pattern was not a control. Instead we found that the link to δ18O values results from synoptic scenarios affecting WeMO index as well as temperature. Therefore, interpretation of δ18O values of precipitation in terms of climate is limited to surface temperature, although at least half of the variability observed still depends on unknown controls of the hydrological cycle.

Year-round shotgun metagenomes reveal stable microbial communities in agricultural soils and novel ammonia oxidizers responding to fertilization.

PubMed

Orellana, Luis H; Chee-Sanford, Joanne C; Sanford, Robert A; Löffler, Frank E; Konstantinidis, Konstantinos T

2017-11-03

The dynamics of individual microbial populations and their gene functions in agricultural soils, especially after major activities such as nitrogen (N) fertilization, remain elusive but are important for better understanding nutrient cycling. Here, we analyzed 20 short-read metagenomes collected at four time points across one year from two depths (0-5 and 20-30 cm) in two Midwestern agricultural sites representing contrasting soil textures (sandy versus silty-loam), with similar cropping histories. Although microbial community taxonomic and functional compositions differed between the two locations and depths, they were more stable within a depth/site throughout the year than communities in natural water-based ecosystems. For example, among the 69 population genomes assembled from the metagenomes, 75% showed less than 2-fold change in abundance between any two sampling points. Interestingly, six deep-branching Thaumarchaeota and three complete ammonia oxidizer (comammox) Nitrospira populations increased up to 5-fold in abundance upon the addition of N fertilizer. These results indicated that indigenous archaeal ammonia oxidizers may respond faster (more copiotrophic) to N fertilization than previously thought. None of 29 recovered putative denitrifier genomes encoded the complete denitrification pathway, suggesting that denitrification is carried out by a collection of different populations. Altogether, our study identified novel microbial populations and genes responding to seasonal and human-induced perturbations in agricultural soils that should facilitate future monitoring efforts and N-related studies. Importance Even though the impact of agricultural management on the microbial community structure has already been recognized, understanding of the dynamics of individual microbial populations and what functions each population encodes are limited. Yet, this information is important for better understanding nutrient cycling, with potentially important implications for preserving nitrogen in soils and sustainability. Here we show that reconstructed metagenome-assembled genomes (MAGs) are relatively stable in their abundance and functional gene content year-round, and seasonal nitrogen fertilization has selected for novel Thaumarchaeota and comammox Nitrospira nitrifiers that are potentially less oligotrophic compared to their marine counterparts previously studied. Copyright © 2017 American Society for Microbiology.

Diel biogeochemical processes in terrestrial waters

USGS Publications Warehouse

Nimick, David A.; Gammons, Christopher H.

2011-01-01

Many biogeochemical processes in rivers and lakes respond to the solar photocycle and produce persistent patterns of measureable phenomena that exhibit a day–night, or 24-h, cycle. Despite a large body of recent literature, the mechanisms responsible for these diel fluctuations are widely debated, with a growing consensus that combinations of physical, chemical, and biological processes are involved. These processes include streamflow variation, photosynthesis and respiration, plant assimilation, and reactions involving photochemistry, adsorption and desorption, and mineral precipitation and dissolution. Diel changes in streamflow and water properties such as temperature, pH, and dissolved oxygen concentration have been widely recognized, and recently, diel studies have focused more widely by considering other constituents such as dissolved and particulate trace metals, metalloids, rare earth elements, mercury, organic matter, dissolved inorganic carbon (DIC), and nutrients. The details of many diel processes are being studied using stable isotopes, which also can exhibit diel cycles in response to microbial metabolism, photosynthesis and respiration, or changes in phase, speciation, or redox state. In addition, secondary effects that diel cycles might have, for example, on biota or in the hyporheic zone are beginning to be considered.This special issue is composed primarily of papers presented at the topical session “Diurnal Biogeochemical Processes in Rivers, Lakes, and Shallow Groundwater” held at the annual meeting of the Geological Society of America in October 2009 in Portland, Oregon. This session was organized because many of the growing number of diel studies have addressed just a small part of the full range of diel cycling phenomena found in rivers and lakes. This limited focus is understandable because (1) fundamental aspects of many diel processes are poorly understood and require detailed study, (2) the interests and expertise of individual scientists typically do not encompass the wide diversity and range of processes that produce diel cycles, and (3) the logistics of making field measurements for 24-h periods has limited recognition and understanding of these important cycles. Thus, the topical session brought together hydrologists, biologists, geochemists, and ecologists to discuss field studies, laboratory experiments, theoretical modeling, and measurement techniques related to diel cycling. Hopefully with the cross-disciplinary synergy developed at the session as well as by this special issue, a more comprehensive understanding of the interrelationships between the diel processes will be developed. Needless to say, understanding diel processes is critical for regulatory agencies and the greater scientific community. And perhaps more importantly, expanded knowledge of biogeochemical cycling may lead to better predictions of how aquatic ecosystems might react to changing conditions of contaminant loading, eutrophication, climate change, drought, industrialization, development, and other variables.

Identification of limit cycles in multi-nonlinearity, multiple path systems

NASA Technical Reports Server (NTRS)

Mitchell, J. R.; Barron, O. L.

1979-01-01

A method of analysis which identifies limit cycles in autonomous systems with multiple nonlinearities and multiple forward paths is presented. The FORTRAN code for implementing the Harmonic Balance Algorithm is reported. The FORTRAN code is used to identify limit cycles in multiple path and nonlinearity systems while retaining the effects of several harmonic components.

Tracking heterotrophic and autotrophic carbon cycling by magnetotactic bacteria in freshwater sediments using DNA stable isotope probing

NASA Astrophysics Data System (ADS)

Kürşat Coşkun, Ömer; Roud, Sophie; He, Kuang; Petersen, Nikolai; Gilder, Stuart; Orsi, William D.

2017-04-01

Magnetotactic bacteria (MTB) are diverse, widespread, motile prokaryotes which biomineralize nanosize magnetic minerals, either magnetite or gregite, under highly conserved genetic control and have magnetotaxis to align their position in aquatic environment according to Earth's magnetic field. They play important roles on some geobiological cycle of important minerals such as iron, sulphur, nitrogen and carbon. Yet, to date, their importance in carbon cycle and carbon source in their natural environment have not been previously studied. In this study, we focused on freshwater benthic carbon cycling of MTB and total bacteria using DNA stable isotope probing (DNA-SIP) technique coupled with quantitative PCR (qPCR). Pond sediments from Unterlippach (Germany) were amended with 13C-labelled sodium bicarbonate and 13C-labelled organic matter, and incubated in the dark over a two week time period. Applying separate qPCR assays specific for total bacteria and MTB, respectively, allowed us to estimate the contribution of MTB to total heterotrophic and autotrophic carbon cycling via DNA-SIP. After one week, there was a slight degree of autotrophic activity which increased markedly after two weeks. Comparing total DNA to the qPCR data revealed that changes in the buoyant density of DNA was due mainly to autotrophic bacterial production. DNA-SIP also identified heterotrophic utilization of 13C-labelled organic matter by MTB after 1 week. The qPCR data also allowed us to estimate uptake rates based on the incubation times for heterotrophic and autotrophic MTB. High-throughput DNA sequencing of 16S rRNA genes showed that most of the MTB involved in carbon cycling were related to the Magnetococcus genus. This study sheds light on the carbon sources for MTB in a natural environment and helps unravel their ecological role in the carbon cycle.

Sequential measurements of serum matrix metalloproteinase 9 to monitor chemotherapy responses in patients with advanced non-small-cell lung cancer.

PubMed

Qiao, Xiaojuan; Zhai, Xiaoran; Wang, Jinghui; Zhao, Xiaoting; Yang, Xinjie; Lv, Jialin; Ma, Li; Zhang, Lina; Wang, Yue; Zhang, Shucai; Yue, Wentao

2016-01-01

Matrix metalloproteinase 9 (MMP-9) plays an important role in tumor invasion and metastasis, including lung cancer. However, whether variations in serum MMP-9 levels can serve as a biomarker for monitoring chemotherapy curative effect remains unclear. This study was designed to investigate the association between variations in serum MMP-9 levels and chemotherapy curative effect in patients with lung cancer. A total of 82 patients with advanced lung cancer were included. All newly diagnosed patients were treated with platinum-based doublet chemotherapy. Serial measurements of serum MMP-9 levels were performed by enzyme-linked immunosorbent assay. In this manner, we chose four time points to examine the association, including before chemotherapy, and 3 weeks after the beginning of the first, second, and fourth cycles of chemotherapy. Compared with the serum level of MMP-9 before progressive disease, patients with progressive disease had elevated serum levels of MMP-9. Compared with the previous time point of collecting specimens, the serum levels of MMP-9 in the patients with a complete response/partial response/stable disease decreased or were maintained stable. The differences of variation in serum MMP-9 levels in patients with different chemotherapy curative effects were all statistically significant after one cycle, two cycles, and four cycles (after one cycle: P<0.001; after two cycles: P<0.001; after four cycles: P=0.01). However, patients with small-cell lung cancer did not exhibit similar test results. The variation in serum MMP-9 levels in patients with non-small-cell lung cancer during chemotherapy was closely related to chemotherapy curative effect and could be useful to monitor chemotherapy curative effect for a small portion of patients.

Planetary resonances, bi-stable oscillation modes, and solar activity cycles

NASA Technical Reports Server (NTRS)

Sleeper, H. P., Jr.

1972-01-01

The natural resonance structure of the planets in the solar system yields resonance periods of 11.08 and 180 years. The 11.08 year period is due to resonance of the sidereal periods of the three inner planets. The 180-year period is due to synodic resonances of the four major planets. These periods are also observed in the sunspot time series. The 11-year sunspot cycles from 1 to 19 are separated into categories of positive and negative cycles, Mode 1 and Mode 2 cycles, and typical and anomalous cycles. Each category has a characteristic shape, magnitude, or duration, so that statistical prediction techniques are improved when a cycle can be classified in a given category. These categories provide evidence for bistable modes of solar oscillation. The next minimum is expected in 1977 and the next maximum in 1981 or later. These epoch values are 2.5 years later than those based on typical cycle characteristics.

Exploring water cycle dynamics by sampling multiple stable water isotope pools in a developed landscape in Germany

NASA Astrophysics Data System (ADS)

Orlowski, Natalie; Kraft, Philipp; Pferdmenges, Jakob; Breuer, Lutz

2016-09-01

A dual stable water isotope (δ2H and δ18O) study was conducted in the developed (managed) landscape of the Schwingbach catchment (Germany). The 2-year weekly to biweekly measurements of precipitation, stream, and groundwater isotopes revealed that surface and groundwater are isotopically disconnected from the annual precipitation cycle but showed bidirectional interactions between each other. Apparently, snowmelt played a fundamental role for groundwater recharge explaining the observed differences to precipitation δ values. A spatially distributed snapshot sampling of soil water isotopes at two soil depths at 52 sampling points across different land uses (arable land, forest, and grassland) revealed that topsoil isotopic signatures were similar to the precipitation input signal. Preferential water flow paths occurred under forested soils, explaining the isotopic similarities between top- and subsoil isotopic signatures. Due to human-impacted agricultural land use (tilling and compression) of arable and grassland soils, water delivery to the deeper soil layers was reduced, resulting in significant different isotopic signatures. However, the land use influence became less pronounced with depth and soil water approached groundwater δ values. Seasonally tracing stable water isotopes through soil profiles showed that the influence of new percolating soil water decreased with depth as no remarkable seasonality in soil isotopic signatures was obvious at depths > 0.9 m and constant values were observed through space and time. Since classic isotope evaluation methods such as transfer-function-based mean transit time calculations did not provide a good fit between the observed and calculated data, we established a hydrological model to estimate spatially distributed groundwater ages and flow directions within the Vollnkirchener Bach subcatchment. Our model revealed that complex age dynamics exist within the subcatchment and that much of the runoff must has been stored for much longer than event water (average water age is 16 years). Tracing stable water isotopes through the water cycle in combination with our hydrological model was valuable for determining interactions between different water cycle components and unravelling age dynamics within the study area. This knowledge can further improve catchment-specific process understanding of developed, human-impacted landscapes.

Coral-algal Reef Complex of Vigoleno, Piacenza, Northern Italy

NASA Astrophysics Data System (ADS)

Russo, Antonio; Artoni, Andrea; Scarponi, Daniele; Serventi, Paolo

2017-12-01

During the late Miocene, reef complexes characterised by poorly diversified coral associations (mainly Porites, occasionally associated with Tarbellastraea and/or Siderastraea), became widespread in the Mediterranean area. One of these complexes crops out at Vigoleno (Castell’Arquato, Piacenza, Northern Italy). According to the regional palaeogeographic and palinspastic reconstructions, it can be considered up to now the northernmost late Miocene (Tortonian-Messinian) reef of the Mediterranean area. Despite the limited outcropping and the faulting, the multidisciplinary investigations reveal the anatomy of this reef complex along two reference sections. In addition, a marked cyclicity characterises both carbonate and siliciclastic deposits of the Vigoleno wedge-top basin. At present, the lack of reliable geochronological markers and unsuitability of the material for stable isotope analyses are not sufficient to constrain the time-span and the main controlling environmental factors of these depositional cycles.

Financing Renewable Energy Projects in Developing Countries: A Critical Review

NASA Astrophysics Data System (ADS)

Donastorg, A.; Renukappa, S.; Suresh, S.

2017-08-01

Access to clean and stable energy, meeting sustainable development goals, the fossil fuel dependency and depletion are some of the reasons that have impacted developing countries to transform the business as usual economy to a more sustainable economy. However, access and availability of finance is a major challenge for many developing countries. Financing renewable energy projects require access to significant resources, by multiple parties, at varying points in the project life cycles. This research aims to investigate sources and new trends in financing RE projects in developing countries. For this purpose, a detail and in-depth literature review have been conducted to explore the sources and trends of current RE financial investment and projects, to understand the gaps and limitations. This paper concludes that there are various internal and external sources of finance available for RE projects in developing countries.

Pattern formation in superdiffusion Oregonator model

NASA Astrophysics Data System (ADS)

Feng, Fan; Yan, Jia; Liu, Fu-Cheng; He, Ya-Feng

2016-10-01

Pattern formations in an Oregonator model with superdiffusion are studied in two-dimensional (2D) numerical simulations. Stability analyses are performed by applying Fourier and Laplace transforms to the space fractional reaction-diffusion systems. Antispiral, stable turing patterns, and travelling patterns are observed by changing the diffusion index of the activator. Analyses of Floquet multipliers show that the limit cycle solution loses stability at the wave number of the primitive vector of the travelling hexagonal pattern. We also observed a transition between antispiral and spiral by changing the diffusion index of the inhibitor. Project supported by the National Natural Science Foundation of China (Grant Nos. 11205044 and 11405042), the Research Foundation of Education Bureau of Hebei Province, China (Grant Nos. Y2012009 and ZD2015025), the Program for Young Principal Investigators of Hebei Province, China, and the Midwest Universities Comprehensive Strength Promotion Project.

Engineering the surface of LiCoO 2 electrodes using atomic layer deposition for stable high-voltage lithium ion batteries

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

Xie, Jin; Zhao, Jie; Liu, Yayuan

Here, developing advanced technologies to stabilize positive electrodes of lithium ion batteries under high-voltage operation is becoming increasingly important, owing to the potential to achieve substantially enhanced energy density for applications such as portable electronics and electrical vehicles. Here, we deposited chemically inert and ionically conductive LiAlO 2 interfacial layers on LiCoO 2 electrodes using the atomic layer deposition technique. During prolonged cycling at high-voltage, the LiAlO 2 coating not only prevented interfacial reactions between the LiCoO 2 electrode and electrolyte, as confirmed by electrochemical impedance spectroscopy and Raman characterizations, but also allowed lithium ions to freely diffuse into LiCoOmore » 2 without sacrificing the power density. As a result, a capacity value close to 200 mA·h·g –1 was achieved for the LiCoO 2 electrodes with commercial level loading densities, cycled at the cut-off potential of 4.6 V vs. Li +/Li for 50 stable cycles; this represents a 40% capacity gain, compared with the values obtained for commercial samples cycled at the cut-off potential of 4.2 V vs. Li +/Li.« less

Porous α-Fe2O3 nanostructures and their lithium storage properties as full cell configuration against LiFePO4

NASA Astrophysics Data System (ADS)

Veluri, P. S.; Shaligram, A.; Mitra, S.

2015-10-01

A two step approach for synthesis of porous α-Fe2O3 nanostructures has been realized via polyol method by complexing iron oxalate with ethylene glycol. Crystalline Fe2O3 samples with different porosities are obtained by calcination of Fe-Ethylene glycol complex at various temperatures. The as-prepared porous Fe2O3 structures exhibit promising lithium storage performance at high current rates. It is observed that the calcination temperature and the resultant porosity have a significant effect on capacity and cycling stability. Samples calcined at high temperature (600 °C) demonstrates stable cycle life with capacity retention of 1077 mAh g-1 at 500 mA g-1 current rate after 50 charge-discharge cycles. Samples calcined at temperatures of 500 and 600 °C display stable cycle life and high rate capability with reversible capacity of 930 mAh g-1 and 688 mAh g-1 at 5 A g-1, respectively. Impregnation of electrodes with electrolyte before cell fabrication shows enhanced electrochemical performance. The viability of Fe2O3 porous nanostructures as prospective anode material examined against commercial LiFePO4 cathode shows promising electrochemical performance.

Engineering the surface of LiCoO 2 electrodes using atomic layer deposition for stable high-voltage lithium ion batteries

DOE PAGES

Xie, Jin; Zhao, Jie; Liu, Yayuan; ...

2017-07-25

Here, developing advanced technologies to stabilize positive electrodes of lithium ion batteries under high-voltage operation is becoming increasingly important, owing to the potential to achieve substantially enhanced energy density for applications such as portable electronics and electrical vehicles. Here, we deposited chemically inert and ionically conductive LiAlO 2 interfacial layers on LiCoO 2 electrodes using the atomic layer deposition technique. During prolonged cycling at high-voltage, the LiAlO 2 coating not only prevented interfacial reactions between the LiCoO 2 electrode and electrolyte, as confirmed by electrochemical impedance spectroscopy and Raman characterizations, but also allowed lithium ions to freely diffuse into LiCoOmore » 2 without sacrificing the power density. As a result, a capacity value close to 200 mA·h·g –1 was achieved for the LiCoO 2 electrodes with commercial level loading densities, cycled at the cut-off potential of 4.6 V vs. Li +/Li for 50 stable cycles; this represents a 40% capacity gain, compared with the values obtained for commercial samples cycled at the cut-off potential of 4.2 V vs. Li +/Li.« less

Binder-free graphene foams for O2 electrodes of Li-O2 batteries.

PubMed

Zhang, Wenyu; Zhu, Jixin; Ang, Huixiang; Zeng, Yi; Xiao, Ni; Gao, Yiben; Liu, Weiling; Hng, Huey Hoon; Yan, Qingyu

2013-10-21

We report a novel method to prepare bind-free graphene foams as O2 electrodes for Li-O2 batteries. The graphene foams are synthesized by electrochemical leavening of the graphite papers, followed by annealing in inert gas to control the amount of structural defects in the graphene foams. It was found that the structural defects were detrimental to the processes of the ORR and OER in Li-O2 batteries. The round-trip efficiencies and the cycling stabilities of the graphene foams were undermined by the structural defects. For example, the as-prepared graphene foam with a high defect level (ID/IG = 0.71) depicted a round-trip efficiency of only 0.51 and a 20(th)-cycle discharge capacity of only 340 mA h g(-1) at a current density of 100 mA g(-1). By contrast, the graphene foam electrode annealed at 800 °C with ID/IG = 0.07 delivered a round-trip efficiency of up to 80% with a stable discharge voltage at ~2.8 V and a stable charge voltage below 3.8 V for 20 cycles. According to the analysis on the electrodes after 20 cycles, the structural defects led to the quickened decay of the graphene foams and boosted the formation of side products.

Controllable Electrochemical Fabrication of KO2-Decorated Binder-Free Cathodes for Rechargeable Lithium-Oxygen Batteries.

PubMed

Yu, Wei; Wang, Huwei; Qin, Lei; Hu, Junyang; Liu, Liang; Li, Baohua; Zhai, Dengyun; Kang, Feiyu

2018-05-23

Understanding the electrochemical property of superoxides in alkali metal oxygen batteries is critical for the design of a stable oxygen battery with high capacity and long cycle performance. In this work, a KO 2 -decorated binder-free cathode is fabricated by a simple and efficient electrochemical strategy. KO 2 nanoparticles are uniformly coated on the carbon nanotube film (CNT-f) through a controllable discharge process in the K-O 2 battery, and the KO 2 -decorated CNT-f is innovatively introduced into the Li-O 2 battery as the O 2 diffusion electrode. The Li-O 2 battery based on the KO 2 -decorated CNT-f cathode can deliver enhanced discharge capacity, reduced charge overpotential, and more stable cycle performance compared with the battery in the absence of KO 2 . In situ formed KO 2 particles on the surface of CNT-f cathode assist to form Li 2 O 2 nanosheets in the Li-O 2 battery, which contributes to the improvement of discharge capacity and cycle life. Interestingly, the analysis of KO 2 -decorated CNT-f cathodes, after discharge and cycle tests, reveals that the electrochemically synthesized KO 2 seems not a conventional electrocatalyst but a partially dissolvable and decomposable promoter in Li-O 2 batteries.

Electrochemical properties of monolithic nickel sulfide electrodes for use in sodium batteries

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

Go, Dae-Yeon; Park, Jinsoo, E-mail: jsp@ikw.ac.kr; Noh, Pan-Jin

2014-10-15

Highlights: • We succeeded in preparing monolithic Ni{sub 3}S{sub 2} integrated electrode through the sulfuration. • The sulfuration is a facile and useful method to synthesize metal sulfides with nanostructure. • As-prepared monolithic Ni{sub 3}S{sub 2} electrodes showed very stable and cycle performance over charge/discharge cycling. - Abstract: Monolithic nickel sulfide electrodes were prepared using a facile synthesis method, sulfuration and annealing. As-prepared Ni{sub 3}S{sub 2} electrodes were characterized by X-ray diffractometry and field emission scanning electron microscopy. Thermal stability was determined by thermal gravimetric analysis and differential scanning calorimetry. Electrochemical properties were measured by galvanostatic charge and discharge cyclingmore » for Na-ion batteries. Three kinds of Ni{sub 3}S{sub 2} electrodes were prepared by varying the sulfuration time (5, 15 and 25 min). The electrochemical results indicated that the capacities increased with an increase in sulfuration time and the cycle performance was stable as a result of monolithic integration of nanostructured Ni{sub 3}S{sub 2} on Ni plates, leading to low interfacial resistance.« less

Integrated time-lapse and single-cell transcription studies highlight the variable and dynamic nature of human hematopoietic cell fate commitment

PubMed Central

Moussy, Alice; Cosette, Jérémie; Parmentier, Romuald; da Silva, Cindy; Corre, Guillaume; Richard, Angélique; Gandrillon, Olivier; Stockholm, Daniel

2017-01-01

Individual cells take lineage commitment decisions in a way that is not necessarily uniform. We address this issue by characterising transcriptional changes in cord blood-derived CD34+ cells at the single-cell level and integrating data with cell division history and morphological changes determined by time-lapse microscopy. We show that major transcriptional changes leading to a multilineage-primed gene expression state occur very rapidly during the first cell cycle. One of the 2 stable lineage-primed patterns emerges gradually in each cell with variable timing. Some cells reach a stable morphology and molecular phenotype by the end of the first cell cycle and transmit it clonally. Others fluctuate between the 2 phenotypes over several cell cycles. Our analysis highlights the dynamic nature and variable timing of cell fate commitment in hematopoietic cells, links the gene expression pattern to cell morphology, and identifies a new category of cells with fluctuating phenotypic characteristics, demonstrating the complexity of the fate decision process (which is different from a simple binary switch between 2 options, as it is usually envisioned). PMID:28749943

Centromere Transcription: Means and Motive.

PubMed

Duda, Zachary; Trusiak, Sarah; O'Neill, Rachel

2017-01-01

The chromosome biology field at large has benefited from studies of the cell cycle components, protein cascades and genomic landscape that are required for centromere identity, assembly and stable transgenerational inheritance. Research over the past 20 years has challenged the classical descriptions of a centromere as a stable, unmutable, and transcriptionally silent chromosome component. Instead, based on studies from a broad range of eukaryotic species, including yeast, fungi, plants, and animals, the centromere has been redefined as one of the more dynamic areas of the eukaryotic genome, requiring coordination of protein complex assembly, chromatin assembly, and transcriptional activity in a cell cycle specific manner. What has emerged from more recent studies is the realization that the transcription of specific types of nucleic acids is a key process in defining centromere integrity and function. To illustrate the transcriptional landscape of centromeres across eukaryotes, we focus this review on how transcripts interact with centromere proteins, when in the cell cycle centromeric transcription occurs, and what types of sequences are being transcribed. Utilizing data from broadly different organisms, a picture emerges that places centromeric transcription as an integral component of centromere function.

Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

NASA Astrophysics Data System (ADS)

An, Hyosung; Mike, Jared; Smith, Kendall; Swank, Lisa; Lin, Yen-Hao; Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie

Structural energy storage materials combining load-bearing mechanical properties and high energy storage performance are desired for applications in wearable devices or flexible displays. Vanadium pentoxide (V2O5) is a promising cathode material for possible use in flexible battery electrodes, but it remains limited by low Li+ diffusion coefficient and electronic conductivity, severe volumetric changes upon cycling, and limited mechanical flexibility. Here, we demonstrate a route to address these challenges by blending a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT- b-PEO), with V2O5 to form a mechanically flexible, electro-mechanically stable hybrid electrode. V2O5 layers were arranged parallel in brick-and-mortar-like fashion held together by the P3HT- b-PEO binder. This unique structure significantly enhances mechanical flexibility, toughness and cyclability without sacrificing capacity. Electrodes comprised of 10 wt% polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes.

Tunable, stable source of femtosecond pulses near 2 μm via supercontinuum of an Erbium mode-locked laser.

PubMed

Klose, Andrew; Ycas, Gabriel; Maser, Daniel L; Diddams, Scott A

2014-11-17

A source of ultrashort pulses of light in the 2 μm region was constructed using supercontinuum broadening from an erbium mode-locked laser. The output spectrum spanned 1000 nm to 2200 nm with an average power of 250 mW. A pulse width of 39 fs for part of the spectrum in the 2000 nm region, corresponding to less than six optical cycles, was achieved. A heterodyne measurement of the free-running mode-locked laser with a narrow-linewidth continuous wave laser resulted in a near shot noise-limited beat note with a signal-to-noise ratio of 45 dB in a 10 kHz resolution bandwidth. The relative intensity noise of the broadband system was investigated over the entire supercontinuum, and the integrated relative intensity noise of the 2000 nm portion of the spectrum was 1.7 × 10(-3). The long-term stability of the system was characterized, and intensity fluctuations in the spectrum were found to be highly correlated throughout the supercontinuum. Spectroscopic limitations due to the laser noise characteristics are discussed.

Phase I/II study of the novel proteasome inhibitor delanzomib (CEP-18770) for relapsed and refractory multiple myeloma.

PubMed

Vogl, Dan T; Martin, Thomas G; Vij, Ravi; Hari, Parameswaran; Mikhael, Joseph R; Siegel, David; Wu, Ka Lung; Delforge, Michel; Gasparetto, Cristina

2017-08-01

Delanzomib (CEP-18770), a reversible P2 threonine boronic acid proteasome (β5/β1 subunits) inhibitor that showed promising anti-myeloma effects in preclinical studies, was investigated in a single-agent multicenter phase I/II study in patients with relapsed/refractory myeloma. Sixty-one patients (17 during dose escalation; 44 in the expansion cohort) received delanzomib on days 1, 8, and 15 in 28-d cycles; 47 received the maximum tolerated dose (MTD), 2.1 mg/m 2 . Dose-limiting toxicities (DLTs) at 2.4 mg/m 2 were rash and thrombocytopenia. At the MTD, the most prominent adverse events were nausea, vomiting, anorexia, fatigue, and pyrexia; grade 3/4 thrombocytopenia and neutropenia occurred in 53 and 23% of patients, respectively. Peripheral neuropathy (21%) was limited to grades 1/2. At the MTD, 26 patients (55%) had stable disease and four (9%) had a partial response (PR). Median time to progression (TTP) was 2.5 months across the cohort. Based upon the efficacy results, development of delanzomib for myeloma was discontinued.

Perturbation analysis of the limit cycle of the free van der Pol equation

NASA Technical Reports Server (NTRS)

Dadfar, M. B.; Geer, J.; Anderson, C. M.

1983-01-01

A power series expansion in the damping parameter, epsilon, of the limit cycle of the free van der Pol equation is constructed and analyzed. Coefficients in the expansion are computed in exact rational arithmetic using the symbolic manipulation system MACSYMA and using a FORTRAN program. The series is analyzed using Pade approximants. The convergence of the series for the maximum amplitude of the limit cycle is limited by two pair of complex conjugate singularities in the complex epsilon-plane. A new expansion parameter is introduced which maps these singularities to infinity and leads to a new expansion for the amplitude which converges for all real values of epsilon. Amplitudes computed from this transformed series agree very well with reported numerical and asymptotic results. For the limit cycle itself, convergence of the series expansion is limited by three pair of complex conjugate branch point singularities. Two pair remain fixed throughout the cycle, and correspond to the singularities found in the maximum amplitude series, while the third pair moves in the epsilon-plane as a function of t from one of the fixed pairs to the other. The limit cycle series is transformed using a new expansion parameter, which leads to a new series that converges for larger values of epsilon.

Novel Conjugated Ladder-Structured Oligomer Anode with High Lithium Storage and Long Cycling Capability.

PubMed

Xie, Jian; Rui, Xianhong; Gu, Peiyang; Wu, Jiansheng; Xu, Zhichuan J; Yan, Qingyu; Zhang, Qichun

2016-07-06

Herein we report the development of nanostructured poly(1,4-dihydro-11H-pyrazino[2',3':3,4]cyclopenta[1,2-b]quinoxalin-11-one) (PPCQ), a novel conjugated ladderlike oligomer with the presence of a rich amount of heteroatoms, as the anode material. Beyond its remarkable lithium storage of 972 mAh g(-1) after 120 cycles, the superior cycle life and stable capacity performance of 489 mAh g(-1) revealed by ultralong testing of 1000 cycles (with an average Coulombic efficiency 99.8%) at a high current density of 2.5 A g(-1) indicate its excellent electrochemical stability to be promisingly applied for high-performance lithium-ion batteries (LIBs).

Childhood-Limited versus Persistent Antisocial Behavior: Why Do Some Recover and Others Do Not? The TRAILS Study

ERIC Educational Resources Information Center

Veenstra, Rene; Lindenberg, Siegwart; Verhulst, Frank C.; Ormel, Johan

2009-01-01

Possible differences between childhood-limited antisocial youth and their stable high-antisocial counterparts were examined. Children were 11 years old at wave 1 (T1) and 13.5 at wave 2 (T2). At both waves, the same parent, teacher, and self-reports of antisocial behavior were used. Stable highs and childhood-limited antisocial youth differed…

Toward a stable solid-electrolyte-interfaces on nickel-rich cathodes: LiPO2F2 salt-type additive and its working mechanism for LiNi0.5Mn0.25Co0.25O2 cathodes

NASA Astrophysics Data System (ADS)

Zhao, Weimin; Zheng, Guorui; Lin, Min; Zhao, Wengao; Li, Dongjiang; Guan, Xiaoyun; Ji, Yajuan; Ortiz, Gregorio F.; Yang, Yong

2018-03-01

Although the LiNi0.5Mn0.25Co0.25O2 holds the merits of high theoretical capacities and a relatively high operating voltage, the battery performance suffers from the severe cycling decay due to the unstable solid electrolyte interface on the cathode. Herein, we present LiPO2F2 as a salt-type electrolyte additive to enhance the cycling stability of large-size crystallite LiNi0.5Mn0.25Co0.25O2 cathodes. Results demonstrate that 1 wt% LiPO2F2 can significantly improve not only the initial coulombic efficiency by 3%, but also the cycling stability and rate capability at 25 °C. Furthermore, the discharge capacity of LiNi0.5Mn0.25Co0.25O2 cathodes still maintain 156 mAh g-1 after 100 cycles even when the temperature increases to 55 °C. In-depth experimental characterization and theoretical calculation indicate that a new stable and thin (e.g. 15-20 nm) film formed on the surface of the cathodes, with composition of LiPO2F2, LiF, etc., which significantly reduces charge transfer impedance of the electrodes, and therefore significantly improves the cycling and rate performance of LiNi0.5Mn0.25Co0.25O2.

Electropolymerization of high stable poly(3,4-ethylenedioxythiophene) in ionic liquids and its potential applications in electrochemical capacitor

NASA Astrophysics Data System (ADS)

Liu, Keke; Hu, Zhenglong; Xue, Rong; Zhang, Jianrong; Zhu, Junjie

2008-05-01

Poly(3,4-ethylenedioxythiophene) (PEDOT) has been successfully electropolymerized using a purified 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) as both the growth medium and the supporting electrolyte. The electrochemical performance of the PEDOT thin film was investigated in 1 mol L-1 H2SO4 solution. It possesses nearly ideal capacitive property, and its specific capacitance is about 130 F g-1. Compared with other conducting polymers, enhanced cycling lifetime (up to 70,000 cycles), which is close to that of active carbon materials, was observed on repetitive redox cycling.

Cycling and floating performance of symmetric supercapacitor derived from coconut shell biomass

NASA Astrophysics Data System (ADS)

Barzegar, Farshad; Khaleed, Abubakar A.; Ugbo, Faith U.; Oyeniran, Kabir O.; Momodu, Damilola Y.; Bello, Abdulhakeem; Dangbegnon, Julien K.; Manyala, Ncholu

2016-11-01

This work present two-step synthesizes route to low-cost mesoporous carbon from coconut shell. The electrochemical characterization of the coconut shell based activated carbon (CSAC) material as electrode for supercapacitor showed a specific capacitance of 186 F g-1, energy density of ˜11 Wh kg-1 and power density of 325 W kg-1 at a 0.5 A g-1 with an excellent stability after floating for 100 h and cycling for 10000 cycles in polymer gel electrolyte. The CSAC showed very good potential as a stable material for supercapacitors desirable for high power applications.

Stereoselective Syntheses of Soman Analog

DTIC Science & Technology

1993-04-28

only one pseudorotatomer cycle exists. Surprisingly. la-f are hydrolytically stable in the absence of acid ; phosphorane lb, for example, remained...unchanged in CDCl3 for at least 2 weeks even in the presence of water or 0.1 N NaOH at room temperature. However, la-f are extremely labile to aqueous acids ...1 and 2 are hydrolytically stable in neutral and basic conditions, but extremely labile to aqueous acids : they remained unchanged for at least 3 days

Alternative Stable States, Coral Reefs, and Smooth Dynamics with a Kick.

PubMed

Ippolito, Stephen; Naudot, Vincent; Noonburg, Erik G

2016-03-01

We consider a computer simulation, which was found to be faithful to time series data for Caribbean coral reefs, and an analytical model to help understand the dynamics of the simulation. The analytical model is a system of ordinary differential equations (ODE), and the authors claim this model demonstrates the existence of alternative stable states. The existence of an alternative stable state should consider a sudden shift in coral and macroalgae populations, while the grazing rate remains constant. The results of such shifts, however, are often confounded by changes in grazing rate. Although the ODE suggest alternative stable states, the ODE need modification to explicitly account for shifts or discrete events such as hurricanes. The goal of this paper will be to study the simulation dynamics through a simplified analytical representation. We proceed by modifying the original analytical model through incorporating discrete changes into the ODE. We then analyze the resulting dynamics and their bifurcations with respect to changes in grazing rate and hurricane frequency. In particular, a "kick" enabling the ODE to consider impulse events is added. Beyond adding a "kick" we employ the grazing function that is suggested by the simulation. The extended model was fit to the simulation data to support its use and predicts the existence cycles depending nonlinearly on grazing rates and hurricane frequency. These cycles may bring new insights into consideration for reef health, restoration and dynamics.

A comparison between rate-and-state friction and microphysical models, based on numerical simulations of fault slip

NASA Astrophysics Data System (ADS)

van den Ende, M. P. A.; Chen, J.; Ampuero, J.-P.; Niemeijer, A. R.

2018-05-01

Rate-and-state friction (RSF) is commonly used for the characterisation of laboratory friction experiments, such as velocity-step tests. However, the RSF framework provides little physical basis for the extrapolation of these results to the scales and conditions of natural fault systems, and so open questions remain regarding the applicability of the experimentally obtained RSF parameters for predicting seismic cycle transients. As an alternative to classical RSF, microphysics-based models offer means for interpreting laboratory and field observations, but are generally over-simplified with respect to heterogeneous natural systems. In order to bridge the temporal and spatial gap between the laboratory and nature, we have implemented existing microphysical model formulations into an earthquake cycle simulator. Through this numerical framework, we make a direct comparison between simulations exhibiting RSF-controlled fault rheology, and simulations in which the fault rheology is dictated by the microphysical model. Even though the input parameters for the RSF simulation are directly derived from the microphysical model, the microphysics-based simulations produce significantly smaller seismic event sizes than the RSF-based simulation, and suggest a more stable fault slip behaviour. Our results reveal fundamental limitations in using classical rate-and-state friction for the extrapolation of laboratory results. The microphysics-based approach offers a more complete framework in this respect, and may be used for a more detailed study of the seismic cycle in relation to material properties and fault zone pressure-temperature conditions.

[Development of Audio Indicator System for Respiratory Dynamic CT Imaging].

PubMed

Muramatsu, Shun; Moriya, Hiroshi; Tsukagoshi, Shinsuke; Yamada, Norikazu

We created the device, which can conduct a radiological technologist's voice to a subject during CT scanning. For 149 lung cancer, dynamic respiratory CT were performed. 92 cases were performed using this device, the others were without this device. The respiratory cycle and respiratory amplitude were analyzed from the lung density. A stable respirating cycle was obtained by using the audio indicator system. The audio indicator system is useful for respiratory dynamic CT.

Advanced Thermally Stable Coal-Based Jet Fuels

DTIC Science & Technology

2008-02-01

of hydrotreated refined chemical oil derived jet fuels in the pyrolytic regime. Preprints of Papers-American Chemical Society Division of Fuel...hydrogenation of a mixture of light cycle oil and refined chemical oil met or exceeded all but four JP-8 specifications. The fuel has excellent low-temperature...mixture of light cycle oil and refined chemical oil met or exceeded all but four JP-8 specifications. The fuel has excellent low-temperature viscosity

Continental Growth and Mantle Hydration as Earth System Feedback Cycles and possible Effects of the Biosphere

NASA Astrophysics Data System (ADS)

Höning, D.; Spohn, T.

2016-12-01

The evolution of Earth is charcterized by intertwined feedback cycles. We focus on two feedback cycles that include the mantle water budget and the continental crust and study possible effects of the Earth's biosphere. The first feedback loop includes cycling of water into the mantle at subduction zones and outgassing at volcanic chains and mid-ocean ridges. Water will reduce the viscosity of mantle rock, and therefore the speed of mantle convection and plate subduction will increase with the mantle water concentration, eventually enhancing the rates of mantle water regassing and outgassing. A second feedback loop includes the production and erosion of continental crust. Continents grow by volcanism above subduction zones, whose total length is determined by the total area of the continents. Furthermore, the erosion rate of the continents is proportional to the total surface area of continental crust. The rate of sediment subduction affects the rate of transport of water to the mantle and the production rate of new continental crust. We present a model that includes both cycles and show how the system develops stable and unstable fixed points in a plane defined by mantle water concentration and surface are of continents. The stable points represent either an Earth mostly covered by continents and a wet mantle or an Earth mostly covered by oceans with a dry mantle. The presently observed Earth is inbetween these extreme states but the state is intrinsically unstable. We couple the feedback model to a parameterized thermal evolution model. We show how Earth evolved towards its present unstable state. We argue that other feedback cycles such as the carbonate silicate cycle may act to stabilize the present state, however. By enhancing continental weathering and erosion, and eventually the sediment transport into subduction zones, the biosphere impacts both feedback cycles and might play a crucial role in regulating Earth's system and keep continental crust coverage and mantle water budget at its present day state.

[Research advances in identifying nitrate pollution sources of water environment by using nitrogen and oxygen stable isotopes].

PubMed

Mao, Wei; Liang, Zhi-wei; Li, Wei; Zhu, Yao; Yanng, Mu-yi; Jia, Chao-jie

2013-04-01

Water body' s nitrate pollution has become a common and severe environmental problem. In order to ensure human health and water environment benign evolution, it is of great importance to effectively identify the nitrate pollution sources of water body. Because of the discrepant composition of nitrogen and oxygen stable isotopes in different sources of nitrate in water body, nitrogen and oxygen stable isotopes can be used to identify the nitrate pollution sources of water environment. This paper introduced the fractionation factors of nitrogen and oxygen stable isotopes in the main processes of nitrogen cycling and the composition of these stable isotopes in main nitrate sources, compared the advantages and disadvantages of five pre-treatment methods for analyzing the nitrogen and oxygen isotopes in nitrate, and summarized the research advances in this aspect into three stages, i. e. , using nitrogen stable isotope alone, using nitrogen and oxygen stable isotopes simultaneously, and combining with mathematical models. The future research directions regarding the nitrate pollution sources identification of water environment were also discussed.

Effects of pyriproxyfen and buprofezin on immature development, female oviposition, and egg-hatching in the stable fly

USDA-ARS?s Scientific Manuscript database

The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), is one of the most economically significant biting flies affecting cattle. Use of traditional insecticides have only limited success in control of stable flies largely due to the stable fly’s unique feeding behaviors and immature developm...

Phase I Trial of Anti-CS1 Monoclonal Antibody Elotuzumab in Combination With Bortezomib in the Treatment of Relapsed/Refractory Multiple Myeloma

PubMed Central

Jakubowiak, Andrzej J.; Benson, Don M.; Bensinger, William; Siegel, David S.D.; Zimmerman, Todd M.; Mohrbacher, Ann; Richardson, Paul G.; Afar, Daniel E.H.; Singhal, Anil K.; Anderson, Kenneth C.

2012-01-01

Purpose To evaluate the maximum-tolerated dose (MTD), safety, and efficacy of elotuzumab in combination with bortezomib in patients with relapsed or relapsed and refractory multiple myeloma (MM). Patients and Methods Elotuzumab (2.5, 5.0, 10, or 20 mg/kg intravenously [IV]) and bortezomib (1.3 mg/m2 IV) were administered on days 1 and 11 and days 1, 4, 8, and 11, respectively, in 21-day cycles by using a 3 + 3 dose-escalation design. Patients with stable disease or better after four cycles could continue treatment until disease progression or unexpected toxicity. Responses were assessed during each cycle by using European Group for Blood and Marrow Transplantation (EBMT) criteria. Results Twenty-eight patients with a median of two prior therapies were enrolled; three patients each received 2.5, 5.0, and 10 mg/kg of elotuzumab and 19 received 20 mg/kg (six during dose escalation and 13 during an expansion phase). No dose-limiting toxicities were observed during cycle 1 of the dose-escalation phase, and the MTD was not reached up to the maximum planned dose of 20 mg/kg. The most frequent grade 3 to 4 adverse events (AEs) were lymphopenia (25%) and fatigue (14%). Two elotuzumab-related serious AEs of chest pain and gastroenteritis occurred in one patient. An objective response (a partial response or better) was observed in 13 (48%) of 27 evaluable patients and in two (67%) of three patients refractory to bortezomib. Median time to progression was 9.46 months. Conclusion The combination of elotuzumab and bortezomib was generally well-tolerated and showed encouraging activity in patients with relapsed/refractory MM. PMID:22291084

Investigational Aurora A kinase inhibitor alisertib (MLN8237) as an enteric-coated tablet formulation in non-hematologic malignancies: Phase 1 dose-escalation study

PubMed Central

Falchook, Gerald; Kurzrock, Razelle; Gouw, Launce; Hong, David; McGregor, Kimberly A.; Zhou, Xiaofei; Shi, Hongliang; Fingert, Howard; Sharma, Sunil

2014-01-01

Background This phase 1b study evaluated an enteric-coated tablet (ECT) formulation of the investigational Aurora A kinase inhibitor, alisertib (MLN8237). Methods Patients with advanced, non-hematologic malignancies received oral alisertib ECT for 7 days BID followed by 14 days treatment-free (21-day cycles; 3+3 dose escalation schema). Objectives were to assess safety, pharmacokinetics, and antitumor activity, and to define a recommended phase 2 dose (RP2D) of alisertib. Results 24 patients were treated. Median age was 57 years. Patients received a median of 2 cycles (range 1–12). The RP2D was determined as 50 mg BID for 7 days (21-day cycles). A cycle 1 dose-limiting toxicity of grade 4 febrile neutropenia was observed in 1 of 13 patients at RP2D. The most common drug-related adverse event (AE) was neutropenia (50%). At doses ≥40 mg BID, 7 patients had drug-related AEs that were serious but largely reversible/manageable by dose reduction and supportive care, including 3 with febrile neutropenia. Pharmacokinetic data were available in 24 patients. Following administration of alisertib ECT, the plasma peak concentration of alisertib was achieved at ~3 h; systemic exposure increased with increasing dose over 10–60 mg BID. Mean t½ was ~21 h following multiple dosing. Renal clearance was negligible. Nine patients achieved stable disease (3.98*, 5.59, 1.28*, 2.56, 5.45*, 3.48, 3.15, 8.31, and 6.93* months; *censored). Conclusions Alisertib ECT was generally well tolerated in adults with advanced, non-hematologic malignancies. The RP2D is 50 mg BID for 7 days and is being evaluated in ongoing phase 2 studies. PMID:24879333

Fast "Feast/Famine" Cycles for Studying Microbial Physiology Under Dynamic Conditions: A Case Study with Saccharomyces cerevisiae.

PubMed

Suarez-Mendez, Camilo A; Sousa, Andre; Heijnen, Joseph J; Wahl, Aljoscha

2014-05-15

Microorganisms are constantly exposed to rapidly changing conditions, under natural as well as industrial production scale environments, especially due to large-scale substrate mixing limitations. In this work, we present an experimental approach based on a dynamic feast/famine regime (400 s) that leads to repetitive cycles with moderate changes in substrate availability in an aerobic glucose cultivation of Saccharomyces cerevisiae. After a few cycles, the feast/famine produced a stable and repetitive pattern with a reproducible metabolic response in time, thus providing a robust platform for studying the microorganism's physiology under dynamic conditions. We found that the biomass yield was slightly reduced (-5%) under the feast/famine regime, while the averaged substrate and oxygen consumption as well as the carbon dioxide production rates were comparable. The dynamic response of the intracellular metabolites showed specific differences in comparison to other dynamic experiments (especially stimulus-response experiments, SRE). Remarkably, the frequently reported ATP paradox observed in single pulse experiments was not present during the repetitive perturbations applied here. We found that intracellular dynamic accumulations led to an uncoupling of the substrate uptake rate (up to 9-fold change at 20 s.) Moreover, the dynamic profiles of the intracellular metabolites obtained with the feast/famine suggest the presence of regulatory mechanisms that resulted in a delayed response. With the feast famine setup many cellular states can be measured at high frequency given the feature of reproducible cycles. The feast/famine regime is thus a versatile platform for systems biology approaches, which can help us to identify and investigate metabolite regulations under realistic conditions (e.g., large-scale bioreactors or natural environments).

Fast “Feast/Famine” Cycles for Studying Microbial Physiology Under Dynamic Conditions: A Case Study with Saccharomyces cerevisiae

PubMed Central

Suarez-Mendez, Camilo A.; Sousa, Andre; Heijnen, Joseph J.; Wahl, Aljoscha

2014-01-01

Microorganisms are constantly exposed to rapidly changing conditions, under natural as well as industrial production scale environments, especially due to large-scale substrate mixing limitations. In this work, we present an experimental approach based on a dynamic feast/famine regime (400 s) that leads to repetitive cycles with moderate changes in substrate availability in an aerobic glucose cultivation of Saccharomyces cerevisiae. After a few cycles, the feast/famine produced a stable and repetitive pattern with a reproducible metabolic response in time, thus providing a robust platform for studying the microorganism’s physiology under dynamic conditions. We found that the biomass yield was slightly reduced (−5%) under the feast/famine regime, while the averaged substrate and oxygen consumption as well as the carbon dioxide production rates were comparable. The dynamic response of the intracellular metabolites showed specific differences in comparison to other dynamic experiments (especially stimulus-response experiments, SRE). Remarkably, the frequently reported ATP paradox observed in single pulse experiments was not present during the repetitive perturbations applied here. We found that intracellular dynamic accumulations led to an uncoupling of the substrate uptake rate (up to 9-fold change at 20 s.) Moreover, the dynamic profiles of the intracellular metabolites obtained with the feast/famine suggest the presence of regulatory mechanisms that resulted in a delayed response. With the feast famine setup many cellular states can be measured at high frequency given the feature of reproducible cycles. The feast/famine regime is thus a versatile platform for systems biology approaches, which can help us to identify and investigate metabolite regulations under realistic conditions (e.g., large-scale bioreactors or natural environments). PMID:24957030

A phase I trial of the novel farnesyl protein transferase inhibitor, BMS-214662, in combination with paclitaxel and carboplatin in patients with advanced cancer.

PubMed

Dy, Grace K; Bruzek, Laura M; Croghan, Gary A; Mandrekar, Sumithra; Erlichman, Charles; Peethambaram, Prema; Pitot, Henry C; Hanson, Lorelei J; Reid, Joel M; Furth, Alfred; Cheng, Shinta; Martell, Robert E; Kaufmann, Scott H; Adjei, Alex A

2005-03-01

This phase I study was conducted to determine the toxicities, pharmacokinetics, and pharmacodynamics of BMS-214662, a farnesyl transferase inhibitor, in combination with paclitaxel and carboplatin, in patients with advanced solid tumors. Patients with solid tumors received one of six escalating dose levels of BMS-214662 infused over 1 hour given following paclitaxel and carboplatin on the first day of a 21-day cycle. Toxicities were graded by the National Cancer Institute common toxicity criteria and recorded as maximum grade per patient for each treatment cycle. Inhibition of farnesyl transferase activity in peripheral blood mononuclear cells (PBMCs) was evaluated. Accumulation of unfarnesylated HDJ-2 in PBMCs of patients was evaluated as a marker of farnesyl transferase inhibition by BMS-214662. Thirty patients received 141 cycles of treatment through six dose levels. Dose-limiting toxicities were neutropenia, thrombocytopenia, nausea, and vomiting. There was no pharmacokinetic interaction between BMS-214662 and paclitaxel. The maximum tolerated dose was established as BMS-214662 (160 mg/m(2)), paclitaxel (225 mg/m(2)) and carboplatin (area under the curve = 6 on day 1), every 21 days. Inhibition of HDJ-2 farnesylation in PBMCs of patients was shown. One measurable partial response was observed in a patient with taxane-resistant esophageal cancer. There was partial regression of evaluable disease in two other patients (endometrial and ovarian cancer). Stable disease (> 4 cycles) occurred in eight other patients. The combination of BMS-214662 with paclitaxel and carboplatin was well tolerated, with broad activity in solid tumors. There was no correlation between dose level and accumulation of unfarnesylated HDJ-2 in PBMCs nor tumor response.

Physics in the laundromat

NASA Astrophysics Data System (ADS)

McDonald, Kirk T.

1998-03-01

The spin cycle of a washing machine involves motion that is stabilized by the Coriolis force, similar to the case of the motion of shafts of large turbines. This system is an example of a stable inverted pendulum.

Crack propagation at stresses below the fatigue limit.

NASA Technical Reports Server (NTRS)

Holden, F. C.; Hyler, W. S.; Marschall, C. W.

1967-01-01

Crack propagation for stainless steel and Ti alloy at stresses below fatigue limit, noting of alternating stress cycles crack propagation for stainless steel and Ti alloy at stresses below fatigue limit, noting role of alternating stress cycles

Combinatorial explosion in model gene networks

NASA Astrophysics Data System (ADS)

Edwards, R.; Glass, L.

2000-09-01

The explosive growth in knowledge of the genome of humans and other organisms leaves open the question of how the functioning of genes in interacting networks is coordinated for orderly activity. One approach to this problem is to study mathematical properties of abstract network models that capture the logical structures of gene networks. The principal issue is to understand how particular patterns of activity can result from particular network structures, and what types of behavior are possible. We study idealized models in which the logical structure of the network is explicitly represented by Boolean functions that can be represented by directed graphs on n-cubes, but which are continuous in time and described by differential equations, rather than being updated synchronously via a discrete clock. The equations are piecewise linear, which allows significant analysis and facilitates rapid integration along trajectories. We first give a combinatorial solution to the question of how many distinct logical structures exist for n-dimensional networks, showing that the number increases very rapidly with n. We then outline analytic methods that can be used to establish the existence, stability and periods of periodic orbits corresponding to particular cycles on the n-cube. We use these methods to confirm the existence of limit cycles discovered in a sample of a million randomly generated structures of networks of 4 genes. Even with only 4 genes, at least several hundred different patterns of stable periodic behavior are possible, many of them surprisingly complex. We discuss ways of further classifying these periodic behaviors, showing that small mutations (reversal of one or a few edges on the n-cube) need not destroy the stability of a limit cycle. Although these networks are very simple as models of gene networks, their mathematical transparency reveals relationships between structure and behavior, they suggest that the possibilities for orderly dynamics in such networks are extremely rich and they offer novel ways to think about how mutations can alter dynamics.

Combinatorial explosion in model gene networks.

PubMed

Edwards, R.; Glass, L.

2000-09-01

The explosive growth in knowledge of the genome of humans and other organisms leaves open the question of how the functioning of genes in interacting networks is coordinated for orderly activity. One approach to this problem is to study mathematical properties of abstract network models that capture the logical structures of gene networks. The principal issue is to understand how particular patterns of activity can result from particular network structures, and what types of behavior are possible. We study idealized models in which the logical structure of the network is explicitly represented by Boolean functions that can be represented by directed graphs on n-cubes, but which are continuous in time and described by differential equations, rather than being updated synchronously via a discrete clock. The equations are piecewise linear, which allows significant analysis and facilitates rapid integration along trajectories. We first give a combinatorial solution to the question of how many distinct logical structures exist for n-dimensional networks, showing that the number increases very rapidly with n. We then outline analytic methods that can be used to establish the existence, stability and periods of periodic orbits corresponding to particular cycles on the n-cube. We use these methods to confirm the existence of limit cycles discovered in a sample of a million randomly generated structures of networks of 4 genes. Even with only 4 genes, at least several hundred different patterns of stable periodic behavior are possible, many of them surprisingly complex. We discuss ways of further classifying these periodic behaviors, showing that small mutations (reversal of one or a few edges on the n-cube) need not destroy the stability of a limit cycle. Although these networks are very simple as models of gene networks, their mathematical transparency reveals relationships between structure and behavior, they suggest that the possibilities for orderly dynamics in such networks are extremely rich and they offer novel ways to think about how mutations can alter dynamics. (c) 2000 American Institute of Physics.

Accreditation status of U.S. military graduate medical education programs.

PubMed

De Lorenzo, Robert A

2008-07-01

Military graduate medical education (GME) comprises a substantial fraction of U.S. physician training capacity. The wars in Iraq and Afghanistan have placed substantial stress on military medicine, and lay and professional press accounts have raised awareness of the effects on military GME. To date, however, objective data on military GME quality remains sparse. Determine the accreditation status of U.S. military GME programs. Additionally, military GME program data will be compared to national (U.S.) accreditation lengths. Retrospective review of Accreditation Council for Graduate Medical Education (ACGME) data. All military-sponsored core programs in specialties with at least three residencies were included. Military-affiliated but civilian-sponsored programs were excluded. The current and past cycle data were used for the study. For each specialty, the current mean accreditation length and the net change in cycle was calculated. National mean accreditation lengths by specialty for 2005 to 2006 were obtained from the ACGME. Comparison between the overall mean national and military accreditation lengths was performed with a z test. All other comparisons employed descriptive statistics. Ninety-nine military programs in 15 specialties were included in the analysis. During the study period, 1 program was newly accredited, and 6 programs had accreditation withdrawn or were closed. The mean accreditation length of the military programs was 4.0 years. The overall national mean for the same specialties is 3.5 years (p < 0.01). In previous cycles, 68% of programs had accreditation of 4 years or longer, compared to 70% in the current cycle, while 13% had accreditation of 2 years or less in the previous cycle compared to 14% in the current cycle. Ten (68%) of the military specialties had mean accreditation lengths greater than the national average, while 5 (33%) were below it. Ten (68%) specialties had stable or improving cycle lengths when compared to previous cycles. Military GME accreditation cycle lengths are, overall, longer than national averages. Trends show many military programs are experiencing either stable or slightly lengthening accreditation compared to previous cycles. A few specialties show a declining trend. There has been a modest 5% decline in the number of military core residency programs since 2000.

Titanium Disulfide Coated Carbon Nanotube Hybrid Electrodes Enable High Energy Density Symmetric Pseudocapacitors.

PubMed

Zang, Xining; Shen, Caiwei; Kao, Emmeline; Warren, Roseanne; Zhang, Ruopeng; Teh, Kwok Siong; Zhong, Junwen; Wei, Minsong; Li, Buxuan; Chu, Yao; Sanghadasa, Mohan; Schwartzberg, Adam; Lin, Liwei

2018-02-01

While electrochemical supercapacitors often show high power density and long operation lifetimes, they are plagued by limited energy density. Pseudocapacitive materials, in contrast, operate by fast surface redox reactions and are shown to enhance energy storage of supercapacitors. Furthermore, several reported systems exhibit high capacitance but restricted electrochemical voltage windows, usually no more than 1 V in aqueous electrolytes. Here, it is demonstrated that vertically aligned carbon nanotubes (VACNTs) with uniformly coated, pseudocapacitive titanium disulfide (TiS 2 ) composite electrodes can extend the stable working range to over 3 V to achieve a high capacitance of 195 F g -1 in an Li-rich electrolyte. A symmetric cell demonstrates an energy density of 60.9 Wh kg -1 -the highest among symmetric pseudocapacitors using metal oxides, conducting polymers, 2D transition metal carbides (MXene), and other transition metal dichalcogenides. Nanostructures prepared by an atomic layer deposition/sulfurization process facilitate ion transportation and surface reactions to result in a high power density of 1250 W kg -1 with stable operation over 10 000 cycles. A flexible solid-state supercapacitor prepared by transferring the TiS 2 -VACNT composite film onto Kapton tape is demonstrated to power a 2.2 V light emitting diode (LED) for 1 min. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Long-Term Stable Adhesion for Conducting Polymers in Biomedical Applications: IrOx and Nanostructured Platinum Solve the Chronic Challenge.

PubMed

Boehler, Christian; Oberueber, Felix; Schlabach, Sabine; Stieglitz, Thomas; Asplund, Maria

2017-01-11

Conducting polymers (CPs) have frequently been described as outstanding coating materials for neural microelectrodes, providing significantly reduced impedance or higher charge injection compared to pure metals. Usability has until now, however, been limited by poor adhesion of polymers like poly(3,4-ethylenedioxythiophene) (PEDOT) to metallic substrates, ultimately precluding long-term applications. The aim of this study was to overcome this weakness of CPs by introducing two novel adhesion improvement strategies that can easily be integrated with standard microelectrode fabrication processes. Iridium Oxide (IrOx) demonstrated exceptional stability for PEDOT coatings, resulting in polymer survival over 10 000 redox cycles and 110 days under accelerated aging conditions at 60 °C. Nanostructured Pt was furthermore introduced as a purely mechanical adhesion promoter providing 10-fold adhesion improvement compared to smooth Pt substrates by simply altering the morphology of Pt. This layer can be realized in a very simple process that is compatible with any electrode design, turning nanostructured Pt into a universal adhesion layer for CP coatings. By the introduction of these adhesion-promoting strategies, the weakness of CP-based neural probes can ultimately be eliminated and true long-term stable use of PEDOT on neural probes will be possible in future electrode generations.

State diagram of a three-sphere microswimmer in a channel

NASA Astrophysics Data System (ADS)

Daddi-Moussa-Ider, Abdallah; Lisicki, Maciej; Mathijssen, Arnold J. T. M.; Hoell, Christian; Goh, Segun; Bławzdziewicz, Jerzy; Menzel, Andreas M.; Löwen, Hartmut

2018-06-01

Geometric confinements are frequently encountered in soft matter systems and in particular significantly alter the dynamics of swimming microorganisms in viscous media. Surface-related effects on the motility of microswimmers can lead to important consequences in a large number of biological systems, such as biofilm formation, bacterial adhesion and microbial activity. On the basis of low-Reynolds-number hydrodynamics, we explore the state diagram of a three-sphere microswimmer under channel confinement in a slit geometry and fully characterize the swimming behavior and trajectories for neutral swimmers, puller- and pusher-type swimmers. While pushers always end up trapped at the channel walls, neutral swimmers and pullers may further perform a gliding motion and maintain a stable navigation along the channel. We find that the resulting dynamical system exhibits a supercritical pitchfork bifurcation in which swimming in the mid-plane becomes unstable beyond a transition channel height while two new stable limit cycles or fixed points that are symmetrically disposed with respect to the channel mid-height emerge. Additionally, we show that an accurate description of the averaged swimming velocity and rotation rate in a channel can be captured analytically using the method of hydrodynamic images, provided that the swimmer size is much smaller than the channel height.

Long-time behavior and Turing instability induced by cross-diffusion in a three species food chain model with a Holling type-II functional response.

PubMed

Haile, Dawit; Xie, Zhifu

2015-09-01

In this paper, we study a strongly coupled reaction-diffusion system describing three interacting species in a food chain model, where the third species preys on the second one and simultaneously the second species preys on the first one. An intra-species competition b2 among the second predator is introduced to the food chain model. This parameter produces some very interesting result in linear stability and Turing instability. We first show that the unique positive equilibrium solution is locally asymptotically stable for the corresponding ODE system when the intra-species competition exists among the second predator. The positive equilibrium solution remains linearly stable for the reaction diffusion system without cross diffusion, hence it does not belong to the classical Turing instability scheme. But it becomes linearly unstable only when cross-diffusion also plays a role in the reaction-diffusion system, hence the instability is driven solely from the effect of cross diffusion. Our results also exhibit some interesting combining effects of cross-diffusion, intra-species competitions and inter-species interactions. Numerically, we conduct a one parameter analysis which illustrate how the interactions change the existence of stable equilibrium, limit cycle, and chaos. Some interesting dynamical phenomena occur when we perform analysis of interactions in terms of self-production of prey and intra-species competition of the middle predator. By numerical simulations, it illustrates the existence of nonuniform steady solutions and new patterns such as spot patterns, strip patterns and fluctuations due to the diffusion and cross diffusion in two-dimension. Published by Elsevier Inc.

Weight Fluctuation and Cancer Risk in Post-Menopausal Women: The Women’s Health Initiative

PubMed Central

Welti, Laura M.; Beavers, Daniel P.; Caan, Bette J.; Sangi-Haghpeykar, Haleh; Vitolins, Mara Z.; Beavers, Kristen M.

2017-01-01

Background Weight cycling, defined by an intentional weight loss and subsequent regain, commonly occurs in overweight and obese women and is associated with some negative health outcomes. We examined the role of various weight-change patterns during early to mid- adulthood and associated risk of highly prevalent, obesity-related cancers (breast, endometrial, colorectal) in postmenopausal women. Methods 80,943 postmenopausal women (age: 63.4±7.4 years) in the Women’s Health Initiative Observational Study were categorized by self-reported weight change (weight stable; weight gain; lost weight; weight cycled [1–3, 4–6, 7–10, >10 times]) during early to mid- adulthood (18–50 years). Three site-specific associations were investigated using Cox proportional hazard models (age, race/ethnicity, income, education, smoking, alcohol, physical activity, hormone therapy, diet, BMI). Results 7,464 (breast=5,564; endometrial=788; colorectal=1,290) incident cancer cases were identified between September 1994 and August 2014. Compared with weight stability, weight gain was significantly associated with risk of breast cancer (HR=1.11, 1.03–1.20) after adjustment for BMI. Similarly, weight cycling was significantly associated with risk of endometrial cancer (HR=1.23, 1.01–1.49). Weight cycling “4–6 times” was most consistently associated with cancer risk, showing a 38% increased risk for endometrial cancer (95% CI: 1.08–1.76) compared to weight stable women. Conclusions Weight gain and weight cycling were positively associated with risk of breast and endometrial cancer, respectively. Impact These data suggest weight cycling and weight gain increase risk of prevalent cancers in postmenopausal women. Adopting ideal body weight maintenance practices before and after weight loss should be encouraged to reduce risk of incident breast and endometrial cancers. PMID:28069684

Annealing texture of nanostructured IF steel

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

Jamaati, Roohollah, E-mail: jamaati@nit.ac.ir

In the present work, the evolution of annealing texture in nanostructured interstitial free steel fabricated via accumulative roll bonding (ARB) process was investigated. Textural evolution after post-annealing of ARB-processed samples was evaluated using X-ray diffraction. There were several texture transitions in the γ-fiber and ζ-fiber during ARB and post-annealing treatment. It was found that with increasing the number of ARB cycles, the volume fraction of the low angle grain boundary decreased and the high angle grain boundary fraction increased. Also, the shear texture was dominant after the first cycle, while for other samples, the rolling texture was dominant. The one-cyclemore » sample clearly indicated a weak α-fiber and γ-fiber and a relatively strong ζ-fiber. In addition, during the recrystallization and before the grain growth, the intensity of α-fiber and γ-fiber decreased, the intensity of ζ-fiber increased, and the intensity of (011)〈100〉 orientation in the ε-fiber and η-fiber increased. Moreover, it was concluded that the transition from the rolling texture to the shear one was a sign of occurrence of the recrystallization (before the grain growth). Finally, with increasing the number of ARB cycles, the intensity of rolling and shear textures saturated and a stable texture formed. - Highlights: • There were texture transitions in the γ-fiber and ζ-fiber. • When the number of cycles increased, the low angle grain boundaries decreased. • The shear texture was dominant after the first cycle. • Transition from rolling texture to shear one was a sign of recrystallization. • With increasing the number of ARB cycles, a stable texture formed.« less

Cell cycle dynamics in a response/signalling feedback system with a gap.

PubMed

Gong, Xue; Buckalew, Richard; Young, Todd; Boczko, Erik

2014-01-01

We consider a dynamical model of cell cycles of n cells in a culture in which cells in one specific phase (S for signalling) of the cell cycle produce chemical agents that influence the growth/cell cycle progression of cells in another phase (R for responsive). In the case that the feedback is negative, it is known that subpopulations of cells tend to become clustered in the cell cycle; while for a positive feedback, all the cells tend to become synchronized. In this paper, we suppose that there is a gap between the two phases. The gap can be thought of as modelling the physical reality of a time delay in the production and action of the signalling agents. We completely analyse the dynamics of this system when the cells are arranged into two cell cycle clusters. We also consider the stability of certain important periodic solutions in which clusters of cells have a cyclic arrangement and there are just enough clusters to allow interactions between them. We find that the inclusion of a small gap does not greatly alter the global dynamics of the system; there are still large open sets of parameters for which clustered solutions are stable. Thus, we add to the evidence that clustering can be a robust phenomenon in biological systems. However, the gap does effect the system by enhancing the stability of the stable clustered solutions. We explain this phenomenon in terms of contraction rates (Floquet exponents) in various invariant subspaces of the system. We conclude that in systems for which these models are reasonable, a delay in signalling is advantageous to the emergence of clustering.

Insect seasonality: circle map analysis of temperature-driven life cycles.

PubMed

Powell, James A; Logan, Jesse A

2005-05-01

Maintaining an adaptive seasonality, with life cycle events occurring at appropriate times of year and in synchrony with cohorts and ephemeral resources, is a basic ecological requisite for many cold-blooded organisms. There are many mechanisms for synchronizing developmental milestones, such as egg laying (oviposition), egg hatching, cocoon opening, and the emergence of adults. These are often irreversible, specific to particular life stages, and include diapause, an altered physiological state which can be reversed by some synchronizing environmental cue (e.g. photoperiod). However, many successful organisms display none of these mechanisms for maintaining adaptive seasonality. In this paper, we briefly review the mathematical relationship between environmental temperatures and developmental timing and discuss the consequences of viewing these models as circle maps from the cycle of yearly oviposition dates and temperatures to oviposition dates for subsequent generations. Of particular interest biologically are life cycles which are timed to complete in exactly 1 year, or univoltine cycles. Univoltinism, associated with reproductive success for many temperate species, is related to stable fixed points of the developmental circle map. Univoltine fixed points are stable and robust in broad temperature bands, but lose stability suddenly to maladaptive cycles at the edges of these bands. Adaptive seasonality may therefore break down with little warning with constantly increasing or decreasing temperature change, as in scenarios for global warming. These ideas are illustrated and explored in the context of Mountain Pine Beetle (Dendroctonus ponderosae Hopkins) occurring in the marginal thermal habitat of central Idaho's Rocky Mountains. Applications of these techniques have not been widely explored by the applied math community, but are likely to provide great insight into the response of biological systems to climate change.

Electrons, life and the evolution of Earth's oxygen cycle.

PubMed

Falkowski, Paul G; Godfrey, Linda V

2008-08-27

The biogeochemical cycles of H, C, N, O and S are coupled via biologically catalysed electron transfer (redox) reactions. The metabolic processes responsible for maintaining these cycles evolved over the first ca 2.3 Ga of Earth's history in prokaryotes and, through a sequence of events, led to the production of oxygen via the photobiologically catalysed oxidation of water. However, geochemical evidence suggests that there was a delay of several hundred million years before oxygen accumulated in Earth's atmosphere related to changes in the burial efficiency of organic matter and fundamental alterations in the nitrogen cycle. In the latter case, the presence of free molecular oxygen allowed ammonium to be oxidized to nitrate and subsequently denitrified. The interaction between the oxygen and nitrogen cycles in particular led to a negative feedback, in which increased production of oxygen led to decreased fixed inorganic nitrogen in the oceans. This feedback, which is supported by isotopic analyses of fixed nitrogen in sedimentary rocks from the Late Archaean, continues to the present. However, once sufficient oxygen accumulated in Earth's atmosphere to allow nitrification to out-compete denitrification, a new stable electron 'market' emerged in which oxygenic photosynthesis and aerobic respiration ultimately spread via endosymbiotic events and massive lateral gene transfer to eukaryotic host cells, allowing the evolution of complex (i.e. animal) life forms. The resulting network of electron transfers led a gas composition of Earth's atmosphere that is far from thermodynamic equilibrium (i.e. it is an emergent property), yet is relatively stable on geological time scales. The early coevolution of the C, N and O cycles, and the resulting non-equilibrium gaseous by-products can be used as a guide to search for the presence of life on terrestrial planets outside of our Solar System.

[The new magnetic therapy TAMMEF in the treatment of simple shoulder pain].

PubMed

Battisti, E; Bianciardi, L; Albanese, A; Piazza, E; Rigato, M; Galassi, G; Giordano, N

2007-01-01

Numerous studies have demonstrated the utility of extremely low frequencies (ELF) electromagnetic fields in the treatment of pain. Moreover, the effects of these fields seems to depend on their respective codes (frequency, intensity, waveform). In our study we want to assess the effects of the TAMMEF (Therapeutic Application of a Musically Modulated Electromagnetic Field) system, whose field is piloted by a musical signal and its parameters (frequency, intensity, waveform) are modified in time, randomly varying within the respective ranges, so that all possible codes can occur during a single application. Sixty subjects, affected by shoulder periarthritis were enrolled in the study and randomly divided into three groups of 20 patients each: A exposed to TAMMEF, B exposed to ELF, C exposed to a simulated field. All subjects underwent a cycle of 15 daily sessions of 30 minutes each and a clinical examination upon enrollment, after 7 days of therapy, at the end of the cycle and at a follow-up 30 days later. All the patients of groups A and B completed the therapy without the appearance of side effects: they presented a significant improvement of the subjective pain and the functional limitation, which remained stable at the follow-up examination. In group C, there was no improvement of the pain symptoms or articular functionality. This study suggests that the TAMMEF system is efficacious in the control of pain symptoms and in the reduction of functional limitation in patients with shoulder periarthritis. Moreover, the effects of the TAMMEF system cover those produced by the ELF field.

A novel curcumin derivative which inhibits P-glycoprotein, arrests cell cycle and induces apoptosis in multidrug resistance cells.

PubMed

Lopes-Rodrigues, Vanessa; Oliveira, Ana; Correia-da-Silva, Marta; Pinto, Madalena; Lima, Raquel T; Sousa, Emília; Vasconcelos, M Helena

2017-01-15

Cancer multidrug resistance (MDR) is a major limitation to the success of cancer treatment and is highly associated with the overexpression of drug efflux pumps such as P-glycoprotein (P-gp). In order to achieve more effective chemotherapeutic treatments, it is important to develop P-gp inhibitors to block/decrease its activity. Curcumin (1) is a secondary metabolite isolated from the turmeric of Curcuma longa L.. Diverse biological activities have been identified for this compound, particularly, MDR modulation in various cancer cell models. However, curcumin (1) has low chemical stability, which severely limits its application. In order to improve stability and P-gp inhibitory effect, two potential more stable curcumin derivatives were synthesized as building blocks, followed by several curcumin derivatives. These compounds were then analyzed in terms of antitumor and anti-P-gp activity, in two MDR and sensitive tumor lines (from chronic myeloid leukemia and non-small cell lung cancer). We identified from a series of curcumin derivatives a novel curcumin derivative (1,7-bis(3-methoxy-4-(prop-2-yn-1-yloxy)phenyl)hepta-1,6-diene-3,5-dione, 10) with more potent antitumor and anti-P-gp activity than curcumin (1). This compound (10) was shown to promote cell cycle arrest (at the G2/M phase) and induce apoptosis in the MDR chronic myeloid leukemia cell line. Therefore it is a really interesting P-gp inhibitor due to its ability to inhibit both P-gp function and expression. Copyright © 2016 Elsevier Ltd. All rights reserved.

Oxygen reduction reaction catalyzed by platinum nanonetwork prepared by template free one step synthesis for polymer electrolyte membrane fuel cells

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

Narayanamoorthy, B.; Kumar, B.V.V.S. Pavan; Eswaramoorthy, M.

2014-07-01

Highlights: • Supportless Pt nanonetwork (Pt NN) synthesized by novel template free one step method as per our earlier reported procedure. • Electrocatalytic activity of Pt NN studied taking oxygen reduction reaction in acid medium. • Kinetic and thermodynamic parameters were deduced under hydrodynamic conditions. • ORR mechanistic pathway was proposed based on kinetic rate constants. • ADT analysis found enhanced stability (5000 cycles) for Pt NN than Pt NN/VC and reported Pt/C. - Abstract: The reduction reaction of molecular oxygen (ORR) was investigated using supportless Pt nanonetwork (Pt NN) electrocatalyst in sulfuric acid medium. Pt NN was prepared bymore » template free borohydride reduction. The transmission electron microscope images revealed a network like nano-architecture having an average cluster size of 30 nm. The electrochemical characterization of supportless and Vulcan carbon supported Pt NN (Pt NN/VC) was carried out using rotating disc and ring disc electrodes at various temperatures. Kinetic and thermodynamic parameters were estimated under hydrodynamic conditions and compared with Pt NN/VC and reported Pt/C catalysts. The accelerated durability test revealed that supportless Pt NN is quite stable for 5000 potential cycles with 22% reduction in electrochemical surface area (ECSA). While the initial limiting current density has in fact increased by 11.6%, whereas Pt NN/VC suffered nearly 55% loss in ECSA and 13% loss in limiting current density confirming an enhanced stability of supportless Pt NN morphology for ORR compared to conventional Pt/C ORR catalysts in acid medium.« less

Speed and efficiency limits of multilevel incoherent heat engines.

PubMed

Mukherjee, V; Niedenzu, W; Kofman, A G; Kurizki, G

2016-12-01

We present a comprehensive theory of heat engines (HE) based on a quantum-mechanical "working fluid" (WF) with periodically modulated energy levels. The theory is valid for any periodicity of driving Hamiltonians that commute with themselves at all times and do not induce coherence in the WF. Continuous and stroke cycles arise in opposite limits of this theory, which encompasses hitherto unfamiliar cycle forms, dubbed here hybrid cycles. The theory allows us to discover the speed, power, and efficiency limits attainable by incoherently operating multilevel HE depending on the cycle form and the dynamical regimes.

Orbital pacing of carbon fluxes by a ∼9-My eccentricity cycle during the Mesozoic.

PubMed

Martinez, Mathieu; Dera, Guillaume

2015-10-13

Eccentricity, obliquity, and precession are cyclic parameters of the Earth's orbit whose climatic implications have been widely demonstrated on recent and short time intervals. Amplitude modulations of these parameters on million-year time scales induce "grand orbital cycles," but the behavior and the paleoenvironmental consequences of these cycles remain debated for the Mesozoic owing to the chaotic diffusion of the solar system in the past. Here, we test for these cycles from the Jurassic to the Early Cretaceous by analyzing new stable isotope datasets reflecting fluctuations in the carbon cycle and seawater temperatures. Our results document a prominent cyclicity of ∼9 My in the carbon cycle paced by changes in the seasonal dynamics of hydrological processes and long-term sea level fluctuations. These paleoenvironmental changes are linked to a great eccentricity cycle consistent with astronomical solutions. The orbital forcing signal was mainly amplified by cumulative sequestration of organic matter in the boreal wetlands under greenhouse conditions. Finally, we show that the ∼9-My cycle faded during the Pliensbachian, which could either reflect major paleoenvironmental disturbances or a chaotic transition affecting this cycle.

Quantum correlations and limit cycles in the driven-dissipative Heisenberg lattice

NASA Astrophysics Data System (ADS)

Owen, E. T.; Jin, J.; Rossini, D.; Fazio, R.; Hartmann, M. J.

2018-04-01

Driven-dissipative quantum many-body systems have attracted increasing interest in recent years as they lead to novel classes of quantum many-body phenomena. In particular, mean-field calculations predict limit cycle phases, slow oscillations instead of stationary states, in the long-time limit for a number of driven-dissipative quantum many-body systems. Using a cluster mean-field and a self-consistent Mori projector approach, we explore the persistence of such limit cycles as short range quantum correlations are taken into account in a driven-dissipative Heisenberg model.

Stable metallization for diamond and other materials

NASA Technical Reports Server (NTRS)

Bachli, Andreas (Inventor); Kolawa, Elzbieta (Inventor); Nicolet, Marc-Aurele (Inventor); Vandersande, Jan W. (Inventor)

2000-01-01

An adherent and metallurgically stable metallization system for diamond is presented. The big improvement in metallurgical stability is attributed to the use of a ternary, amorphous Ti--Si--N diffusion barrier. No diffusion between the layers and no delamination of the metallization was observed after annealing the schemes at 400.degree. C. for 100 hours and at 900.degree. C. for 30 minutes. Thermal cycling experiments in air from -65 to 155.degree. C. and adhesion tests were performed. Various embodiments are disclosed.

Reduction of capacity decay in vanadium flow batteries by an electrolyte-reflow method

NASA Astrophysics Data System (ADS)

Wang, Ke; Liu, Le; Xi, Jingyu; Wu, Zenghua; Qiu, Xinping

2017-01-01

Electrolyte imbalance is a major issue with Vanadium flow batteries (VFBs) as it has a significant impact on electrolyte utilization and cycle life over extended charge-discharge cycling. This work seeks to reduce capacity decay and prolong cycle life of VFBs by adopting a novel electrolyte-reflow method. Different current density and various start-up time of the method are investigated in the charge-discharge tests. The results show that the capacity decay rate is reduced markedly and the cycle life is prolonged substantially by this method. In addition, the coulomb efficiency, voltage efficiency and energy efficiency remain stable during the whole cycle life test, which indicates this method has little impact on the long lifetime performance of the VFBs. The method is low-cost, simple, effective, and can be applied in industrial VFB productions.

Statistics of stable marriages

NASA Astrophysics Data System (ADS)

Dzierzawa, Michael; Oméro, Marie-José

2000-11-01

In the stable marriage problem N men and N women have to be matched by pairs under the constraint that the resulting matching is stable. We study the statistical properties of stable matchings in the large N limit using both numerical and analytical methods. Generalizations of the model including singles and unequal numbers of men and women are also investigated.

Stable graphene-polyoxometalate nanomaterials for application in hybrid supercapacitors.

PubMed

Suárez-Guevara, Jullieth; Ruiz, Vanesa; Gómez-Romero, Pedro

2014-10-14

We report the synthesis of hybrid supercapacitor electrodes by a novel reduction of GO with simultaneous incorporation of polyoxometalate. These hybrids show a 30% increase in specific capacitance and excellent stability after 10,000 cycles.

A Hollow-Structured Manganese Oxide Cathode for Stable Zn-MnO₂ Batteries.

PubMed

Guo, Xiaotong; Li, Jianming; Jin, Xu; Han, Yehu; Lin, Yue; Lei, Zhanwu; Wang, Shiyang; Qin, Lianjie; Jiao, Shuhong; Cao, Ruiguo

2018-05-05

Aqueous rechargeable zinc-manganese dioxide (Zn-MnO₂) batteries are considered as one of the most promising energy storage devices for large scale-energy storage systems due to their low cost, high safety, and environmental friendliness. However, only a few cathode materials have been demonstrated to achieve stable cycling for aqueous rechargeable Zn-MnO₂ batteries. Here, we report a new material consisting of hollow MnO₂ nanospheres, which can be used for aqueous Zn-MnO₂ batteries. The hollow MnO₂ nanospheres can achieve high specific capacity up to ~405 mAh g −1 at 0.5 C. More importantly, the hollow structure of birnessite-type MnO₂ enables long-term cycling stability for the aqueous Zn-MnO₂ batteries. The excellent performance of the hollow MnO₂ nanospheres should be due to their unique structural properties that enable the easy intercalation of zinc ions.

Stable prevalence of Powassan virus in Ixodes scapularis in a northern Wisconsin focus.

PubMed

Brackney, Doug E; Nofchissey, Robert A; Fitzpatrick, Kelly A; Brown, Ivy K; Ebel, Gregory D

2008-12-01

Deer tick virus (DTV), a variant of Powassan virus (POWV), appears to be maintained in nature in an enzootic cycle between Ixodes scapularis ticks and small mammals. Although POWV infection of human beings is rare, a recent report suggests increasing incidence and the possibility that POWV may be an emerging tick-borne zoonosis. Therefore, we assessed the long-term stability of the POWV transmission cycle in northwestern Wisconsin. Adult I. scapularis and Dermacentor variabilis were collected from Hayward and Spooner, Wisconsin, screened for infection by reverse transcriptase polymerase chain reaction (RT-PCR), and virus was isolated. Seventeen of 1,335 (1.3%) of I. scapularis and 0 of 222 (0%) of D. variabilis ticks were infected. All isolated virus belonged to the DTV genotype of POWV. These findings suggest stable transmission of POWV in this focus over ten years and highlight the potential for this agent to emerge as a public health concern.

Confined silicon nanospheres by biomass lignin for stable lithium ion battery.

PubMed

Niu, Xiaoying; Zhou, Jinqiu; Qian, Tao; Wang, Mengfan; Yan, Chenglin

2017-10-06

Biomass lignin, as a significant renewable resource, is one of the most abundant natural polymers in the world. Here, we report a novel silicon-based material, in which lignin-derived functional conformal network crosslinks the silicon nanoparticles via self-assembly. This newly-developed material could greatly solve the problems of large volume change during lithiation/delithiation process and the formation of unstable solid electrolyte interphase layers on the silicon surface. With this anode, the battery demonstrates a high capacity of ∼3000 mA h g -1 , a highly stable cycling retention (∼89% after 100 cycles at 300 mA g -1 ) and an excellent rate capability (∼800 mA h g -1 at 9 A g -1 ). Moreover, the feasibility of full lithium-ion batteries with the novel silicon-based material would provide wide range of applications in the field of flexible energy storage systems for wearable electronic devices.

A novel iron-lead redox flow battery for large-scale energy storage

NASA Astrophysics Data System (ADS)

Zeng, Y. K.; Zhao, T. S.; Zhou, X. L.; Wei, L.; Ren, Y. X.

2017-04-01

The redox flow battery (RFB) is one of the most promising large-scale energy storage technologies for the massive utilization of intermittent renewables especially wind and solar energy. This work presents a novel redox flow battery that utilizes inexpensive and abundant Fe(II)/Fe(III) and Pb/Pb(II) redox couples as redox materials. Experimental results show that both the Fe(II)/Fe(III) and Pb/Pb(II) redox couples have fast electrochemical kinetics in methanesulfonic acid, and that the coulombic efficiency and energy efficiency of the battery are, respectively, as high as 96.2% and 86.2% at 40 mA cm-2. Furthermore, the battery exhibits stable performance in terms of efficiencies and discharge capacities during the cycle test. The inexpensive redox materials, fast electrochemical kinetics and stable cycle performance make the present battery a promising candidate for large-scale energy storage applications.

Confined silicon nanospheres by biomass lignin for stable lithium ion battery

NASA Astrophysics Data System (ADS)

Niu, Xiaoying; Zhou, Jinqiu; Qian, Tao; Wang, Mengfan; Yan, Chenglin

2017-10-01

Biomass lignin, as a significant renewable resource, is one of the most abundant natural polymers in the world. Here, we report a novel silicon-based material, in which lignin-derived functional conformal network crosslinks the silicon nanoparticles via self-assembly. This newly-developed material could greatly solve the problems of large volume change during lithiation/delithiation process and the formation of unstable solid electrolyte interphase layers on the silicon surface. With this anode, the battery demonstrates a high capacity of ˜3000 mA h g-1, a highly stable cycling retention (˜89% after 100 cycles at 300 mA g-1) and an excellent rate capability (˜800 mA h g-1 at 9 A g-1). Moreover, the feasibility of full lithium-ion batteries with the novel silicon-based material would provide wide range of applications in the field of flexible energy storage systems for wearable electronic devices.

Limit cycle vibrations in turbomachinery

NASA Technical Reports Server (NTRS)

Ryan, S. G.

1991-01-01

The focus is on an examination of rotordynamic systems which are simultaneously susceptible to limit cycle instability and subharmonic response. Characteristics of each phenomenon are determined as well as their interrelationship. A normalized, single mass rotor model is examined as well as a complex model of the high pressure fuel turbopump and the Space Shuttle Main Engine. Entrainment of limit cycle instability by subharmonic response is demonstrated for both models. The nonuniqueness of the solution is also demonstrated.

Standalone BISON Fuel Performance Results for Watts Bar Unit 1, Cycles 1-3

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

Clarno, Kevin T.; Pawlowski, Roger; Stimpson, Shane

2016-03-07

The Consortium for Advanced Simulation of Light Water Reactors (CASL) is moving forward with more complex multiphysics simulations and increased focus on incorporating fuel performance analysis methods. The coupled neutronics/thermal-hydraulics capabilities within the Virtual Environment for Reactor Applications Core Simulator (VERA-CS) have become relatively stable, and major advances have been made in analysis efforts, including the simulation of twelve cycles of Watts Bar Nuclear Unit 1 (WBN1) operation. While this is a major achievement, the VERA-CS approaches for treating fuel pin heat transfer have well-known limitations that could be eliminated through better integration with the BISON fuel performance code. Severalmore » approaches are being implemented to consider fuel performance, including a more direct multiway coupling with Tiamat, as well as a more loosely coupled one-way approach with standalone BISON cases. Fuel performance typically undergoes an independent analysis using a standalone fuel performance code with manually specified input defined from an independent core simulator solution or set of assumptions. This report summarizes the improvements made since the initial milestone to execute BISON from VERA-CS output. Many of these improvements were prompted through tighter collaboration with the BISON development team at Idaho National Laboratory (INL). A brief description of WBN1 and some of the VERA-CS data used to simulate it are presented. Data from a small mesh sensitivity study are shown, which helps justify the mesh parameters used in this work. The multi-cycle results are presented, followed by the results for the first three cycles of WBN1 operation, particularly the parameters of interest to pellet-clad interaction (PCI) screening (fuel-clad gap closure, maximum centerline fuel temperature, maximum/minimum clad hoop stress, and cumulative damage index). Once the mechanics of this capability are functioning, future work will target cycles with known or suspected PCI failures to determine how well they can be estimated.« less

A phase 2 study of the oral mammalian target of rapamycin inhibitor, everolimus, in patients with recurrent endometrial carcinoma.

PubMed

Slomovitz, Brian M; Lu, Karen H; Johnston, Taren; Coleman, Robert L; Munsell, Mark; Broaddus, Russell R; Walker, Cheryl; Ramondetta, Lois M; Burke, Thomas W; Gershenson, David M; Wolf, Judith

2010-12-01

Dysregulation of phosphatase and tensin homolog (PTEN) and the gene that encodes the p110α catalytic subunit of phosphatidylinositol-3-kinase (PI3K), PIK3CA, are the most common mutations in endometrial carcinoma (EC). Loss of PTEN or activation of PIK3CA results in constitutive activation of AKT, which leads to up-regulation of mammalian target of rapamycin (mTOR). Everolimus is an oral rapamycin analog that acts by selectively inhibiting mTOR. A single-institution, open-labeled, phase 2 study of everolimus in patients with measurable recurrent EC who had failed at least 1 and no more than 2 prior chemotherapeutic regimens was performed. Everolimus was administered at a dose of 10 mg orally daily for 28-day cycles. Patients were treated until disease progression or toxicity. The primary endpoint was clinical benefit response (CBR), defined as a confirmed complete or partial response or prolonged stable disease (SD) (≥8 weeks). Inclusion was limited to patients with endometrioid histology. A total of 35 patients were enrolled (median age, 58 years; range, 38-81 years). A total of 81 cycles were administered. Twelve of 28 (43%) evaluable patients had not developed disease progression at the time of the first objective evaluation (8 weeks). All these patients had SD (median, 4.5 cycles; range, 2-10 cycles). Six of the 28 (21%) patients had a confirmed CBR at 20 weeks of therapy. Patients with CBR discontinued treatment because of toxicity (6 patients), disease progression (5 patients), and noncompliance (1 patient). Seven patients were unevaluable after receiving ≤1 cycle because of toxicity (5 patients) or noncompliance (2 patients). The most common drug-related toxicities were fatigue, anemia, pain, lymphopenia, and nausea. Everolimus demonstrated encouraging single-agent CBR in pretreated patients with recurrent endometrioid EC. Future studies will evaluate this agent in combination with hormonal and/or cytotoxic therapy. Copyright © 2010 American Cancer Society.

Tropical cloud forest climate variability and the demise of the Monteverde golden toad

PubMed Central

Anchukaitis, Kevin J.; Evans, Michael N.

2010-01-01

Widespread amphibian extinctions in the mountains of the American tropics have been blamed on the interaction of anthropogenic climate change and a lethal pathogen. However, limited meteorological records make it difficult to conclude whether current climate conditions at these sites are actually exceptional in the context of natural variability. We use stable oxygen isotope measurements from trees without annual rings to reconstruct a century of hydroclimatology in the Monteverde Cloud Forest of Costa Rica. High-resolution measurements reveal coherent isotope cycles that provide annual chronological control and paleoclimate information. Climate variability is dominated by interannual variance in dry season moisture associated with El Niño Southern Oscillation events. There is no evidence of a trend associated with global warming. Rather, the extinction of the Monteverde golden toad (Bufo periglenes) appears to have coincided with an exceptionally dry interval caused by the 1986–1987 El Niño event. PMID:20194772

Irreversible thermodynamic analysis and application for molecular heat engines

NASA Astrophysics Data System (ADS)

Lucia, Umberto; Açıkkalp, Emin

2017-09-01

Is there a link between the macroscopic approach to irreversibility and microscopic behaviour of the systems? Consumption of free energy keeps the system away from a stable equilibrium. Entropy generation results from the redistribution of energy, momentum, mass and charge. This concept represents the essence of the thermodynamic approach to irreversibility. Irreversibility is the result of the interaction between systems and their environment. The aim of this paper is to determine lost works in a molecular engine and compare results with macro (classical) heat engines. Firstly, irreversible thermodynamics are reviewed for macro and molecular cycles. Secondly, irreversible thermodynamics approaches are applied for a quantum heat engine with -1/2 spin system. Finally, lost works are determined for considered system and results show that macro and molecular heat engines obey same limitations. Moreover, a quantum thermodynamic approach is suggested in order to explain the results previously obtained from an atomic viewpoint.

Adiabatic pumping solutions in global AdS

NASA Astrophysics Data System (ADS)

Carracedo, Pablo; Mas, Javier; Musso, Daniele; Serantes, Alexandre

2017-05-01

We construct a family of very simple stationary solutions to gravity coupled to a massless scalar field in global AdS. They involve a constantly rising source for the scalar field at the boundary and thereby we name them pumping solutions. We construct them numerically in D = 4. They are regular and, generically, have negative mass. We perform a study of linear and nonlinear stability and find both stable and unstable branches. In the latter case, solutions belonging to different sub-branches can either decay to black holes or to limiting cycles. This observation motivates the search for non-stationary exactly timeperiodic solutions which we actually construct. We clarify the role of pumping solutions in the context of quasistatic adiabatic quenches. In D = 3 the pumping solutions can be related to other previously known solutions, like magnetic or translationally-breaking backgrounds. From this we derive an analytic expression.

Dynamics in a three species food-web system

NASA Astrophysics Data System (ADS)

Gupta, K.; Gakkhar, S.

2016-04-01

In this paper, the dynamics of a three species food-web system is discussed. The food-web comprises of one predator and two logistically growing competing species. The predator species is taking food from one of the competitors with Holling type II functional response. Another competitor is the amensal species for the predator of first species. The system is shown to be positive and bounded. The stability of various axial points, boundary points and interior point has been investigated. The persistence of the system has been studied. Numerical simulation has been performed to show the occurrence of Hopf bifurcation and stable limit cycle about the interior point. The presence of second competitor and its interaction with predator gives more complex dynamics than the simple prey-predator system. The existence of transcritical bifurcation has been established about two axial points. The existence of periodic attractor having period-2 solution has been shown, when amensal coefficient is chosen as bifurcation parameter.