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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Shocks, Rarefaction Waves, and Current Fluctuations for Anharmonic Chains

The nonequilibrium dynamics of anharmonic chains is studied by imposing an initial domain-wall state, in which the two half lattices are prepared in equilibrium with distinct parameters. Here, we analyse the Riemann problem for the corresponding Euler equations and, in specific cases, compare with molecular dynamics. Additionally, the fluctuations of time-integrated currents are investigated. In analogy with the KPZ equation, their typical fluctuations should be of size t 1/3 and have a Tracy–Widom GUE distributed amplitude. The proper extension to anharmonic chains is explained and tested through molecular dynamics. Our results are calibrated against the stochastic LeRoux lattice gas.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Optimal Linear Responses for Markov Chains and Stochastically Perturbed Dynamical Systems

The linear response of a dynamical system refers to changes to properties of the system when small external perturbations are applied. We consider the little-studied question of selecting an optimal perturbation so as to (i) maximise the linear response of the equilibrium distribution of the system, (ii) maximise the linear response of the expectation of a specified observable, and (iii) maximise the linear response of the rate of convergence of the system to the equilibrium distribution. We also consider the inhomogeneous, sequential, or time-dependent situation where the governing dynamics is not stationary and one wishes to select a sequence of small perturbations so as to maximise the overall linear response at some terminal time. We develop the theory for finite-state Markov chains, provide explicit solutions for some illustrative examples, and numerically apply our theory to stochastically perturbed dynamical systems, where the Markov chain is replaced by a matrix representation of an approximate annealed transfer operator for the random dynamical system.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Perturbation Bounds for Markov Chains with General State Space

The aim of this paper is to investigate the stability of Markov chains with general state space. We present new conditions for the strong stability of Markov chains after a small perturbation of their transition kernels. Also, we obtain perturbation bounds with respect to different quantities.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

The Berry–Esseen Bound for General Markov Chains

A rate of convergence in the CLT is studied for recurrent Markov chains. The Berry–Esseen type bound is obtained with explicit dependence on parameters of the chain. The method of the proof is purely analytical. It is based on the complex analysis of generating functions.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Nanoparticle using parallel split rings and implementation of chain for creating Fano resonance with polarization independence for energy harvesting in mid-infrared

In optical devices, the polarization of the incident wave affects the Nano particle characteristics. Therefore, designing a polarization-independent device is significant in the process of designing optical structures. On the other hand, the concept of Fano resonance and dark mode has been utilized for achieving more energy enhancement. In this paper, we have developed a symmetrical Nano antenna by employing Fano resonance, which is independent of the incident wave polarization. The proposed Nano antenna is modified in mid infrared regime for biosensing and energy harvesting applications. The designed metamaterial antenna is made by Nano split ring resonators with etched capacitive gaps, which are utilized for concentrating energy. The introduced Nano antenna has a bright and dark mode with a weak enhancement of electric field. The effect of the incident wave polarization is investigated at wave incident angles between 0° and 45° to illustrate the independency of the polarization due to the symmetrical shape of the Nano antenna. In order to trigger the dark mode and enhance the electric field, a Nano chain is incorporated in the final structure. This arrangement has led to increasing of electric field drastically. Furthermore, the figure of merit has been calculated as an advantageous factor in sensing the surrounding materials with various refractive indices. Our findings illustrated that the chain arrangement has caused a peak in the linear form of the extinction cross section of the Nano antenna. This in turn has resulted in the appearance of Fano resonance with no impact on the resonance frequency that has been originally adjusted by capacitive gaps and inductive strips.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Charge Transfer Dissociation (CTD) Mass Spectrometry of Peptide Cations: Study of Charge State Effects and Side-Chain Losses

1+, 2+, and 3+ precursors of substance P and bradykinin were subjected to helium cation irradiation in a 3D ion trap mass spectrometer. Charge exchange with the helium cations produces a variety of fragment ions, the number and type of which are dependent on the charge state of the precursor ions. For 1+ peptide precursors, fragmentation is generally restricted to C−CO backbone bonds (a and x ions), whereas for 2+ and 3+ peptide precursors, all three backbone bonds (C−CO, C−N, and N−Cα) are cleaved. The type of backbone bond cleavage is indicative of possible dissociation channels involved in CTD process, including high-energy, kinetic-based, and ETD-like pathways. In addition to backbone cleavages, amino acid side-chain cleavages are observed in CTD, which are consistent with other high-energy and radical-mediated techniques. The unique dissociation pattern and supplementary information available from side-chain cleavages make CTD a potentially useful activation method for the structural study of gas-phase biomolecules. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Analytical solutions for quantum walks on 1D chain with different shift operators

In this paper, we study the discrete-time quantum walks on 1D Chain with the moving and swapping shift operators. We derive analytical solutions for the eigenvalues and eigenstates of the evolution operator U{sup -hat} using the Chebyshev polynomial technique, and calculate the long-time averaged probabilities for the two different shift operators respectively. It is found that the probability distributions for the moving and swapping shift operators display completely different characteristics. For the moving shift operator, the probability distribution exhibits high symmetry where the probabilities at mirror positions are equal. The probabilities are inversely proportional to the system size N and approach to zero as N→∞. On the contrary, for the swapping shift operator, the probability distribution is not symmetric, the probability distribution approaches to a power-law stationary distribution as N→∞ under certain coin parameter condition. We show that such power-law stationary distribution is determined by the eigenstates of the eigenvalues ±1 and calculate the intrinsic probability for different starting positions. Our findings suggest that the eigenstates corresponding to eigenvalues ±1 play an important role for the swapping shift operator. - Highlights: • QWs on 1D chain with the moving and swapping operators are studied for the first time. • We derive analytical results for the probability distribution for the two operators. •We compare the dynamics of QWs with two different shift operators. • We find the particular eigenvalues ±1 play an important role for the dynamics. • We use the Chebyshev technique to treat the problem.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Universal scheme for finite-probability perfect transfer of arbitrary multispin states through spin chains

In combination with the theories of open system and quantum recovering measurement, we propose a quantum state transfer scheme using spin chains by performing two sequential operations: a projective measurement on the spins of ‘environment’ followed by suitably designed quantum recovering measurements on the spins of interest. The scheme allows perfect transfer of arbitrary multispin states through multiple parallel spin chains with finite probability. Our scheme is universal in the sense that it is state-independent and applicable to any model possessing spin–spin interactions. We also present possible methods to implement the required measurements taking into account the current experimental technologies. As applications, we consider two typical models for which the probabilities of perfect state transfer are found to be reasonably high at optimally chosen moments during the time evolution. - Highlights: • Scheme that can achieve perfect quantum state transfer is devised. • The scheme is state-independent and applicable to any spin-interaction models. • The scheme allows perfect transfer of arbitrary multispin states. • Applications to two typical models are considered in detail.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Entanglement dynamics in critical random quantum Ising chain with perturbations

We simulate the entanglement dynamics in a critical random quantum Ising chain with generic perturbations using the time-evolving block decimation algorithm. Starting from a product state, we observe super-logarithmic growth of entanglement entropy with time. The numerical result is consistent with the analytical prediction of Vosk and Altman using a real-space renormalization group technique. - Highlights: • We study the dynamical quantum phase transition between many-body localized phases. • We simulate the dynamics of a very long random spin chain with matrix product states. • We observe numerically super-logarithmic growth of entanglement entropy with time.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Excitations of breathers and rogue wave in the Heisenberg spin chain

Highlights: • The breathers and rogue wave are demonstrated in spin chain system. • The corresponding existence conditions based on the perturbation wave number K and magnon number N are presented explicitly. • The magnetic moment distribution of these nonlinear waves are characterized in detail. • These instable nonlinear waves can convert into stable soliton structure under different critical conditions. - Abstract: We study the excitations of breathers and rogue wave in a classical Heisenberg spin chain with twist interaction, which is governed by a fourth-order integrable nonlinear Schrödinger equation. The dynamics of these waves have been extracted from an exact solution. In particular, the corresponding existence conditions based on the parameters of perturbation wave number K, magnon number N, background wave vector k{sub s} and amplitude c are presented explicitly. Furthermore, the characteristics of magnetic moment distribution corresponding to these nonlinear waves are also investigated in detail. Finally, we discussed the state transition of three types nonlinear localized waves under the different excitation conditions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Carbachol ameliorates lipopolysaccharide-induced intestinal epithelial tight junction damage by down-regulating NF-{kappa}{beta} and myosin light-chain kinase pathways

Highlights: Black-Right-Pointing-Pointer Carbachol reduced the lipopolysaccharide-induced intestinal barrier breakdown. Black-Right-Pointing-Pointer Carbachol ameliorated the lipopolysaccharide-induced ileal tight junction damage. Black-Right-Pointing-Pointer Carbachol prevented the LPS-induced NF-{kappa}{beta} and myosin light-chain kinase activation. Black-Right-Pointing-Pointer Carbachol exerted its beneficial effects in an {alpha}7 nicotinic receptor-dependent manner. -- Abstract: Carbachol is a cholinergic agonist that protects the intestines after trauma or burn injury. The present study determines the beneficial effects of carbachol and the mechanisms by which it ameliorates the lipopolysaccharide (LPS)-induced intestinal barrier breakdown. Rats were injected intraperitoneally with 10 mg/kg LPS. Results showed that the gut barrier permeability was reduced, the ultrastructural disruption of tight junctions (TJs) was prevented, the redistribution of zonula occludens-1 and claudin-2 proteins was partially reversed, and the nuclear factor-kappa beta (NF-{kappa}{beta}) and myosin light-chain kinase (MLCK) activation in the intestinal epithelium were suppressed after carbachol administration in LPS-exposed rats. Pretreatment with the {alpha}7 nicotinic acetylcholine receptor ({alpha}7nAchR) antagonist {alpha}-bungarotoxin blocked the protective action of carbachol. These results suggested that carbachol treatment can protect LPS-induced intestinal barrier dysfunction. Carbachol exerts its beneficial effect on the amelioration of the TJ damage by inhibiting the NF-{kappa}{beta} and MLCK pathways in an {alpha}7nAchR-dependent manner.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Dissect Kif5b in nuclear positioning during myogenesis: The light chain binding domain and the autoinhibitory peptide are both indispensable

Highlights: ► Kif5b localizes at myonuclear membrane and is responsible for nuclear dispersion. ► Kif5b stalk/tail domain contains signal for nuclear membrane targeting. ► Kif5b stalk/tail domain directly binds to a nesprin 4 in vitro. ► KLC binding domain and autoinhibitory peptide are both functionally indispensable. -- Abstract: The microtubule motor kinesin-1 is responsible for the nuclear positioning during myogenesis. Here we show that the coiled-coil stalk/tail domain containing the kinesin light chain (KLC) binding sites targets to the perinuclear region like endogenous Kif5b, while the globular tail domain cannot. To investigate which fragments of kinesin heavy chain (Kif5b) is responsible for the myonuclear positioning, we transfect Kif5b expression constructs into Kif5b deficient myoblasts and test their ability to rescue the myonuclear phenotype. We find that the KLC binding domain and the autoinhibitory peptide in the globular tail region are both indispensable for the nuclear membrane localization of Kif5b and the kinesin-1-mediated myonuclear positioning. These results suggest that while the KLC binding domain may directly targets Kif5b to the myonuclear membrane, the autoinhibitory peptide may play an indirect role in regulating the kinesin-1-mediated myonuclear positioning.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Heptachlor induced mitochondria-mediated cell death via impairing electron transport chain complex III

Highlights: •Heptachlor inhibited mitochondrial electron transport chain complex III activity. •Heptachlor promoted generation of reactive oxygen species. •Heptachlor induced Bax activation. •Heptachlor induced mitochondria-mediated and caspase-dependent apoptosis. -- Abstract: Environmental toxins like pesticides have been implicated in the pathogenesis of Parkinson’s disease (PD). Epidemiological studies suggested that exposures to organochlorine pesticides have an association with an increased PD risk. In the present study, we examined the mechanism of toxicity induced by an organochlorine pesticide heptachlor. In a human dopaminergic neuroblastoma SH-SY5Y cells, heptachlor induced both morphological and functional damages in mitochondria. Interestingly, the compound inhibited mitochondrial electron transport chain complex III activity. Rapid generation of reactive oxygen species and the activation of Bax were then detected. Subsequently, mitochondria-mediated, caspase-dependent apoptosis followed. Our results raise a possibility that an organochlorine pesticide heptachlor can act as a neurotoxicant associated with PD.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

The N-terminal strand modulates immunoglobulin light chain fibrillogenesis

Highlights: •We evaluated the impact of mutations in the N-terminal strand of 6aJL2 protein. •Mutations destabilized the protein in a position-dependent manner. •Destabilizing mutations accelerated the fibrillogenesis by shortening the lag time. •The effect on the kinetic of fibril elongation by seeding was of different nature. •The N-terminal strand is buried in the fibrillar state of 6aJL2 protein. -- Abstract: It has been suggested that the N-terminal strand of the light chain variable domain (V{sub L}) protects the molecule from aggregation by hindering spurious intermolecular contacts. We evaluated the impact of mutations in the N-terminal strand on the thermodynamic stability and kinetic of fibrillogenesis of the V{sub L} protein 6aJL2. Mutations in this strand destabilized the protein in a position-dependent manner, accelerating the fibrillogenesis by shortening the lag time; an effect that correlated with the extent of destabilization. In contrast, the effect on the kinetics of fibril elongation, as assessed in seeding experiments was of different nature, as it was not directly dependant on the degree of destabilization. This finding suggests different factors drive the nucleation-dependent and elongation phases of light chain fibrillogenesis. Finally, taking advantage of the dependence of the Trp fluorescence upon environment, four single Trp substitutions were made in the N-terminal strand, and changes in solvent exposure during aggregation were evaluated by acrylamide-quenching. The results suggest that the N-terminal strand is buried in the fibrillar state of 6aJL2 protein. This finding suggest a possible explanation for the modulating effect exerted by the mutations in this strand on the aggregation behavior of 6aJL2 protein.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Lead discovery for mammalian elongation of long chain fatty acids family 6 using a combination of high-throughput fluorescent-based assay and RapidFire mass spectrometry assay

A high-throughput RapidFire mass spectrometry assay is described for elongation of very long-chain fatty acids family 6 (Elovl6). Elovl6 is a microsomal enzyme that regulates the elongation of C12-16 saturated and monounsaturated fatty acids. Elovl6 may be a new therapeutic target for fat metabolism disorders such as obesity, type 2 diabetes, and nonalcoholic steatohepatitis. To identify new Elovl6 inhibitors, we developed a high-throughput fluorescence screening assay in 1536-well format. However, a number of false positives caused by fluorescent interference have been identified. To pick up the real active compounds among the primary hits from the fluorescence assay, we developed a RapidFire mass spectrometry assay and a conventional radioisotope assay. These assays have the advantage of detecting the main products directly without using fluorescent-labeled substrates. As a result, 276 compounds (30%) of the primary hits (921 compounds) in a fluorescence ultra-high-throughput screening method were identified as common active compounds in these two assays. It is concluded that both methods are very effective to eliminate false positives. Compared with the radioisotope method using an expensive {sup 14}C-labeled substrate, the RapidFire mass spectrometry method using unlabeled substrates is a high-accuracy, high-throughput method. In addition, some of the hit compounds selected from the screening inhibited cellular fatty acid elongation in HEK293 cells expressing Elovl6 transiently. This result suggests that these compounds may be promising lead candidates for therapeutic drugs. Ultra-high-throughput fluorescence screening followed by a RapidFire mass spectrometry assay was a suitable strategy for lead discovery against Elovl6. - Highlights: • A novel assay for elongation of very-long-chain fatty acids 6 (Elovl6) is proposed. • RapidFire mass spectrometry (RF-MS) assay is useful to select real screening hits. • RF-MS assay is proved to be beneficial because of its high-throughput and accuracy. • A combination of fluorescent and RF-MS assays is effective for Elovl6 inhibitors.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Ferritin heavy chain controls the HIF-driven hypoxic response by activating the asparaginyl hydroxylase FIH

Highlights: • Ferritin Heavy Chain (FTH1) directly interacts with Factor Inhibiting HIF (FIH). • FTH1 facilitates the FIH-mediated Asn803 hydroxylation in HIF-1α. • FTH1 prevents the recruitment of p300 to HIF-1α through the Asn803 hydroxylation. • FTH1 represses the HIF-driven gene expression under either normoxic or hypoxic conditions. Hypoxia-inducible factor 1 (HIF-1) is a key player in cellular response to hypoxia. The stability and transcriptional activity of this protein are oxygen-dependently regulated by the prolyl hydroxylases PHD1-3 and the asparaginyl hydroxylase FIH. Recently, ferritin heavy chain (FTH1) has been characterized to reinforce the HIF-1 signaling pathway in an indirect way through the inhibition of PHD activity by depleting the free iron pool in the cytoplasm. In the present study, we addressed the role of FTH1 in the FIH control of HIF-1 activity. Unexpectedly, immunoprecipitation analyses revealed that FTH1 directly interacted with FIH. In an in vitro hydroxylation assay, FTH1 was found to facilitate the FIH-mediated Asn803 hydroxylation in HIF-1α. As expected, FTH1 prevented the recruitment of p300 to HIF-1α through the Asn803 hydroxylation. In luciferase reporter analyses, FTH1 was found to repress the transcriptional activity of HIF-1α in HCT116 cells under either normoxic or hypoxic conditions. Consequently, FTH1 downregulated the expression of the HIF-1 target genes, such as VEGF, CA9 and GLUT1. Our results suggest a new role of FTH1 as a co-regulator for the FIH-mediated oxygen sensing pathway. Since HIF-1α is involved in pathogenesis of diverse hypoxia-associated diseases, we propose that FTH1 be a potential target in developing new therapeutic strategies against such diseases.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

A novel 1-acyl-sn-glycerol-3-phosphate O-acyltransferase homolog for the synthesis of membrane phospholipids with a branched-chain fatty acyl group in Shewanella livingstonensis Ac10

Highlights: • A new 1-acyl-sn-glycerol-3-phosphate O-acyltransferase (PlsC) was discovered. • The enzyme introduces a branched-chain fatty acyl group into membrane phospholipids. • The substrate specificity of the enzyme is unprecedented in the PlsC family enzymes. • Multiple PlsC homologs contribute to generation of membrane phospholipid diversity. 1-Acyl-sn-glycerol-3-phosphate O-acyltransferase (PlsC) plays an essential role in the formation of phosphatidic acid, a precursor of various membrane phospholipids (PLs), in bacteria by catalyzing the introduction of an acyl group into the sn-2 position of lysophosphatidic acid. Various bacteria produce more than one PlsC. However, the physiological significance of the occurrence of multiple PlsCs is poorly understood. A psychrotrophic bacterium, Shewanella livingstonensis Ac10, which produces eicosapentaenoic acid at low temperatures, has five putative PlsCs (PlsC1-5). We previously showed that PlsC1 is responsible for the production of PLs containing an eicosapentaenoyl group. Here, we characterized another putative PlsC of this bacterium named PlsC4. We generated a plsC4-disrupted mutant and found that PLs containing 13:0 found in the parental strain were almost completely absent in the mutant. The loss of these PLs was suppressed by introduction of a plsC4-expression plasmid. PLs containing 15:0 were also drastically decreased by plsC4 disruption. Gas chromatography-mass spectrometry analysis of fatty acyl methyl esters derived from PLs of the parental strain showed that the 13:0 and 15:0 groups were an 11-methyllauroyl group and a 13-methylmyristoyl group, respectively. Phospholipase A2 treatment revealed that these fatty acyl groups were linked to the sn-2 position of PLs. Thus, PlsC4 is a new type of PlsC homolog that is responsible for the synthesis of PLs containing a branched-chain fatty acyl group at the sn-2 position and plays a clearly different role from that of PlsC1 in vivo.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Ca2+-dependent inhibition of branched-chain α-ketoacid dehydrogenase kinase by thiamine pyrophosphate

Catabolism of the branched-chain amino acids (BCAAs: leucine, isoleucine, and valine) is regulated by the branched-chain α-ketoacid dehydrogenase (BCKDH) complex, which in turn is regulated by phosphorylation catalyzed by BCKDH kinase (BDK). Thiamine pyrophosphate (TPP) is required as a coenzyme for the E1 component of the BCKDH complex and can also bring about activation of the complex by inhibiting BDK. The present study shows that free Ca{sup 2+} in the physiological range greatly increases the sensitivity of BDK to inhibition by TPP (IC{sub 50} of 2.5 μM in the presence of 1 μM free Ca{sup 2+}). This novel mechanism may be responsible for the stimulation of BCAA oxidation by conditions that increase mitochondrial free Ca{sup 2+} levels, e.g. in skeletal muscle during exercise.

60 APPLIED LIFE SCIENCES↗