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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 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

The enlargement of high reflectance range in ultra-narrow bandpass filter with disordered one-dimensional photonic crystal

The conventional ultra-narrow bandpass filter structure has only a very limited width of high-reflectance range. This study, by introducing disorder into one-dimensional (1D) photonic crystal, attempts to enlarge the width of high-reflectance range while keeping the ultra-narrow bandpass. Enlargement by 46.8% was obtained after theoretical design. Since this structure contains some degree of disorder already, it has a strong tolerance of the variation of layer thicknesses. Unlike studies using conventional periodic structures, theoretical statistical results in this study demonstrate that high quality remains even after allowing for ±5% variation of layer thicknesses. This indicates that only a very low thickness control precision is required in the future and the production difficulty is immensely lowered. To put the construction to test, a structure has been developed and demonstrated by a magnetron reactive sputtering coating system, which agrees with the theoretical result very well. By introducing disorder into the periodic 1D photonic crystal structure, the high-reflectance range is significantly extended by 37%, with an ultra-narrow pass band of 0.8 nm and intensity of 82%.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Structural and dynamic mechanisms of GABA A receptor modulators with opposing activities

γ-Aminobutyric acid type A (GABA A ) receptors are pentameric ligand-gated ion channels abundant in the central nervous system and are prolific drug targets for treating anxiety, sleep disorders and epilepsy. Diverse small molecules exert a spectrum of effects on γ-aminobutyric acid type A (GABA A ) receptors by acting at the classical benzodiazepine site. They can potentiate the response to GABA, attenuate channel activity, or counteract modulation by other ligands. Structural mechanisms underlying the actions of these drugs are not fully understood. Here we present two high-resolution structures of GABA A receptors in complex with zolpidem, a positive allosteric modulator and heavily prescribed hypnotic, and DMCM, a negative allosteric modulator with convulsant and anxiogenic properties. These two drugs share the extracellular benzodiazepine site at the α/γ subunit interface and two transmembrane sites at β/α interfaces. Structural analyses reveal a basis for the subtype selectivity of zolpidem that underlies its clinical success. Molecular dynamics simulations provide insight into how DMCM switches from a negative to a positive modulator as a function of binding site occupancy. Together, these findings expand our understanding of how GABA A receptor allosteric modulators acting through a common site can have diverging activities.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2011

Crystal Structure of the Dimeric Oct6 (Pou3fl) POU Domain Bound to Palindromic MORE DNA

POU domains (named after their identification in Pit1, Oct1 unc86) are found in around 15 transcription factors encoded in mammalian genomes many of which feature prominently as key regulators at development bifurcations. For example, the POU III class Octamer binding protein 6 (Oct6) is expressed in embryonic stem cells and during neural development and drives the differentia5tion of myelinated cells in the central and peripheral nervous system. Defects in oct6 expression levels are linked to neurological disorders such as schizophrenia. POU proteins contain a bi-partite DNA binding domain that assembles on various DNA motifs with differentially configured subdomains. Intriguingly, alternative configurations of POU domains on different DNA sites were shown to affect the subsequent recruitment of transcriptional coactivators. Namely, binding of Oct1 to a Palindromic Oct-factor Recognition Element (PORE) was shown to facilitate the recruitment of the OBF1 coactivator whereas More of PORE (MORE) bound Oct1 does not. Moreover, Pit1 was shown to recruit the corepressor N-CoR only when bound to a variant MORE motif with a 2 bp half-site spacing. Therefore, POU proteins are seen as a paradigm for DNA induced allosteric effects on transcription factors modulating their regulatory potential. However, a big unresolved conundrum for the POU class and for most if not all other transcription factor classes is how highly similar proteins regulate different sets of genes causing fundamentally different biological responses. Ultimately, there must be subtle features enabling those factors to engage in contrasting molecular interactions in the cell. Thus, the dissection of the molecular details of the transcription-DNA recognition in general, and the formation of multimeric regulatory complexes, in particular, is highly desirable. To contribute to these efforts they solved the 2.05 {angstrom} crystal structure of Oct6 bound as a symmetrical homodimer to palindromic MORE DNA.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Subcellular distribution of cyclin-dependent kinase-like 5 (CDKL5) is regulated through phosphorylation by dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A)

Cyclin-dependent kinase-like 5 (CDKL5) is a Ser/Thr protein kinase primarily expressed in the central nervous system and is known to cause X-linked neurodevelopmental disorders such as Rett syndrome. However, the mechanisms regulating CDKL5 have not yet been fully clarified. Therefore, in this study, we investigated the protein kinase that directly phosphorylates CDKL5, identifying it as dual specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A), an enzyme binding to and phosphorylating CDKL5. We showed that subcellular distribution of CDKL5 was regulated by its phosphorylation by DYRK1A. In mouse neuroblastoma Neuro2a cells, CDKL5 was localized in both the cytosol and nucleus, whereas DYRK1A showed a typical nuclear localization. When CDKL5 and DYRK1A were co-expressed, the cytosolic localization of CDKL5 was significantly increased. Results of site-directed mutagenesis revealed that the phosphorylation site was Ser-308, in the vicinity of the nuclear localization signal. A mutation mimicking the phosphorylated serine residue by aspartate substitution (S308D) changed CDKL5 localization to the cytosol, whereas the corresponding alanine-substituted analog, CDKL5(S308A), was primarily localized to the nucleus. Taken together, these results strongly suggested that DYRK1A bound to CDKL5 and phosphorylated it on Ser-308, thus interfering with its nuclear localization. - Highlights: • We investigated the mechanism regulating subcellular localization of CDKL5. • DYRK1A was identified as an enzyme that bound to and phosphorylated CDKL5. • The phosphorylation site of CDKL5 was Ser-308, in the vicinity of the NLS. • When DYRK1A was co-expressed, the cytosolic CDKL5 was significantly increased. • In conclusion, DYRK1A regulates CDKL5 localization via phosphorylation on Ser-308.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Unlocking the brain's mysteries: Meet the bioengineers behind next-generation neural devices

Bioengineers in the Neural Technologies Group at Lawrence Livermore are creating the next generation of clinical- and research-quality neural interfaces. The goal is to gain a fundamental understanding of neuroscience, treat a variety of debilitating neurological disorders (such as Parkinson's, depression, and epilepsy), and restore lost neural functions such as sight, hearing, and mobility.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1998

Abnormalities of the QT interval in primary disorders of autonomic failure

BACKGROUND: Experimental evidence shows that activation of the autonomic nervous system influences ventricular repolarization and, therefore, the QT interval on the ECG. To test the hypothesis that the QT interval is abnormal in autonomic dysfunction, we examined ECGs in patients with severe primary autonomic failure and in patients with congenital dopamine beta-hydroxylase (DbetaH) deficiency who are unable to synthesize norepinephrine and epinephrine. SUBJECTS AND METHODS: Maximal QT and rate-corrected QT (QTc) intervals and adjusted QTc dispersion [(maximal QTc - minimum QTc on 12 lead ECG)/square root of the number of leads measured] were determined in blinded fashion from ECGs of 67 patients with primary autonomic failure (36 patients with multiple system atrophy [MSA], and 31 patients with pure autonomic failure [PAF]) and 17 age- and sex-matched healthy controls. ECGs of 5 patients with congenital DbetaH deficiency and 6 age- and sex-matched controls were also analyzed. RESULTS: Patients with MSA and PAF had significantly prolonged maximum QTc intervals (492+/-58 ms(1/2) and 502+/-61 ms(1/2) [mean +/- SD]), respectively, compared with controls (450+/-18 ms(1/2), P < .05 and P < .01, respectively). A similar but not significant trend was observed for QT. QTc dispersion was also increased in MSA (40+/-20 ms(1/2), P < .05 vs controls) and PAF patients (32+/-19 ms(1/2), NS) compared with controls (21+/-5 ms(1/2)). In contrast, patients with congenital DbetaH deficiency did not have significantly different RR, QT, QTc intervals, or QTc dispersion when compared with controls. CONCLUSIONS: Patients with primary autonomic failure who have combined parasympathetic and sympathetic failure have abnormally prolonged QT interval and increased QT dispersion. However, QT interval in patients with congenital DbetaH deficiency was not significantly different from controls. It is possible, therefore, that QT abnormalities in patients with primary autonomic failure are not solely caused by lesions of the sympathetic nervous system, and that the parasympathetic nervous system is likely to have a modulatory role in ventricular repolarization.

Non-NASA Center↗
NASA NTRS1994

Video Game Adapts To Brain Waves

Electronic training system based on video game developed to help children afflicted with attention-deficit disorder (ADD) learn to prolong their attention spans. Uses combination of electroencephalography (EEG) and adaptive control to encourage attentiveness. Monitors trainee's brain-wave activity: if EEG signal indicates attention is waning, system increases difficulty of game, forcing trainee to devote more attention to it. Game designed to make trainees want to win and, in so doing, learn to pay attention for longer times.

Pope, Alan T.↗
DOE OSTI2021

From hard spheres to hard-core spins

A system of hard spheres exhibits physics that is controlled only by their density. This comes about because the interaction energy is either infinite or zero, so all allowed configurations have exactly the same energy. The low-density phase is liquid, while the high-density phase is crystalline, an example of “order by disorder” as it is driven purely by entropic considerations. Here we study a family of hard spin models, which we call hard-core spin models, where we replace the translational degrees of freedom of hard spheres with the orientational degrees of freedom of lattice spins. Their hard-core interaction serves analogously to divide configurations of the many spin system into allowed and disallowed sectors. We present detailed results on the square lattice in d = 2 for a set of models with $\mathbb{Z}_n$ symmetry, which generalize Potts models, and their U(1) limits, for ferromagnetic and antiferromagnetic senses of the interaction, which we refer to as exclusion and inclusion models. As the exclusion and inclusion angles are varied, we find a Kosterlitz-Thouless phase transition between a disordered phase and an ordered phase with quasi-long-ranged order, which is the form order by disorder takes in these systems. These results follow from a set of height representations, an ergodic cluster algorithm, and transfer matrix calculations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Thermodynamic coarsening arrested by viscous fingering in partially miscible binary mixtures

We view the evolution of binary mixtures far from equilibrium, and demonstrate that the interplay between phase separation and hydrodynamic instability can arrest the Ostwald ripening process characteristic of nonflowing mixtures. We describe a model binary system in a Hele-Shaw cell using a phase-field approach with explicit dependence of both phase fraction and mass concentration. When the viscosity contrast between phases is large (as is the case for gas and liquid phases), an imposed background flow leads to viscous fingering, phase branching, and pinch off. This dynamic flow disorder limits phase growth and arrests thermodynamic coarsening. Because of this, the system reaches a regime of statistical steady state in which the binary mixture is permanently driven away from equilibrium.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Ovarian Artery Embolization in Patients With Collateral Supply to Symptomatic Uterine Leiomyomata

Purpose: To evaluate the safety and outcome of ovarian artery embolization (OAE) in patients with collateral supply to symptomatic uterine leiomyomata. Materials and Methods: Thirteen patients with relevant leiomyoma perfusion by way of enlarged ovarian arteries underwent additional OAE during the same (N = 10) or a second procedure (N = 3). Uterine artery embolization (UAE) was performed bilaterally in 10 and unilaterally in 2 patients with a single artery. One patient had no typical uterine arteries but bilaterally enlarged ovarian arteries, prompting bilateral OAE. OAE was accomplished with coil embolization in one and particle embolization in 12 patients. Symptoms before therapy and clinical outcome were assessed using a standardized questionnaire. Contrast-enhanced magnetic resonance (MR) imaging after embolization was available in 11 of 13 patients and was used to determine the percentage of fibroid infarction. Results: UAE and OAE were technically successful in all patients. One patient experienced prolonged irritation at the puncture site. Median clinical follow-up time was 16 months (range 4-37). Ten of 13 patients showed improvement or complete resolution of clinical symptoms. One patient reported only slight improvement of her symptoms. These women presented with regular menses. Two patients (15%), 47 and 48 years, both with unilateral OAE, reported permanent amenorrhea directly after embolization. Their symptoms completely resolved. Seven patients showed complete and 4 showed >90% fibroid infarction after embolization therapy. Conclusions: OAE is technically safe and effective in patients with ovarian artery collateral supply to symptomatic uterine leiomyomata. The risk of permanent amenorrhea observed in this study is similar to the reported incidence after UAE.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2024

Generalized representative structures for atomistic systems

A new method is presented to generate atomic structures that reproduce the essential characteristics of arbitrary material systems, phases, or ensembles. Previous methods allow one to reproduce the essential characteristics (e.g. the chemical disorder) of a large random alloy within a small crystal structure. The ability to generate small representations of random alloys, along with the restriction to crystal systems, results from using the fixed-lattice cluster correlations to describe structural characteristics. A more general description of the structural characteristics of atomic systems is obtained using complete sets of atomic environment descriptors. These are used within for generating representative atomic structures without restriction to fixed lattices. A general data-driven approach is provided here utilizing the atomic cluster expansion (ACE) basis. The N-body ACE descriptors are a complete set of atomic environment descriptors that span both chemical and spatial degrees of freedom and are used within for describing atomic structures. The generalized representative structure (GRS) method presented within generates small atomic structures that reproduce ACE descriptor distributions corresponding to arbitrary structural and chemical complexity. It is shown that systematically improvable representations of crystalline systems on fixed parent lattices, amorphous materials, liquids, and ensembles of atomic structures may be produced efficiently through optimization algorithms. With the GRS method, we highlight reduced representations of atomistic machine-learning training datasets that contain similar amounts of information and small 40–72 atom representations of liquid phases. The ability to use GRS methodology as a driver for informed novel structure generation is also demonstrated. The advantages over other data-driven methods and state-of-the-art methods restricted to high-symmetry systems are highlighted.

atomic cluster expansion↗
DOE OSTI2018

Differential effects of voluntary wheel running and toy rotation on the mRNA expression of neurotrophic factors and FKBP5 in a post-traumatic stress disorder rat model with the shuttle-box task

Highlights: • Running wheel or toy rotation produces almost the same behavioral effects. • The running wheel might alter PTSD-like behaviors via neurotrophic factors. • Toy rotation might alter PTSD-like behaviors via the HPA system. Life-threatening experiences can result in the development of post-traumatic stress disorder. We have developed an animal model for post-traumatic stress disorder (PTSD) using a shuttle box in rats. In this paradigm, the rats were exposed to inescapable foot-shock stress (IS) in a shuttle box, and then an avoidance/escape task was performed in the same box 2 weeks after IS. A previous study using this paradigm revealed that environmental enrichment (EE) ameliorated avoidance/numbing-like behaviors, but not hyperarousal-like behaviors, and EE also elevated hippocampal brain-derived neurotrophic factor (BDNF) expression. However, the differential effects of EE components, i.e., running wheel (RW) or toy rotation, on PTSD-like behaviors has remained unclear. In this experiment, we demonstrated that RW, toy rotation, and EE (containing RW and toy rotation) ameliorated avoidance/numbing-like behaviors, induced learning of avoidance responses, and improved depressive-like behaviors in traumatized rats. The RW increased the hippocampal mRNA expression of neurotrophic factors, especially BDNF and glial-cell derived neurotrophic factor. Toy rotation influenced FK506 binding protein 5 mRNA expression, which is believed to be a regulator of the hypothalamic-pituitary-adrenal (HPA)-axis system, in the hippocampus and amygdala. This is the first report to elucidate the differential mechanistic effects of RW and toy rotation. The former appears to exert its effects via neurotrophic factors, while the latter exerts its effects via the HPA axis. Further studies will lead to a better understanding of the influence of environmental factors on PTSD.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Colloquium : Anomalous metals: Failed superconductors

The observation of metallic ground states in a variety of two-dimensional electronic systems poses a fundamental challenge for the theory of electron fluids. Here evidence is analyzed for the existence of a regime, called the “anomalous metal regime,” in diverse 2D superconducting systems driven through a quantum superconductor to metal transition by tuning physical parameters such as the magnetic field, the gate voltage in the case of systems with a metal-oxide semiconductor field-effect transistor (MOSFET) geometry, or the degree of disorder. The principal phenomenological observation is that in the anomalous metal, as a function of decreasing temperature, the resistivity first drops as if the system were approaching a superconducting ground state, but then saturates at low temperatures to a value that can be orders of magnitude smaller than the Drude value. The anomalous metal also shows a giant positive magnetoresistance. Thus, it behaves as if it were a “failed superconductor.” This behavior is observed in a broad range of parameters. It will be moreover exhibited, by theoretical solution of a model of superconducting grains embedded in a metallic matrix, that as a matter of principle such anomalous metallic behavior can occur in the neighborhood of a quantum superconductor to metal transition. Furthermore, it will be also argued that the robustness and ubiquitous nature of the observed phenomena are difficult to reconcile with any existing theoretical treatment and speculate about the character of a more fundamental theoretical framework.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Quantum Fluctuations and Multifractally enhanced Superconductivity in Disordered Thin Films

The interplay between electron–electron interactions and weak localization (or anti-localization) phenomena in two-dimensional systems can significantly enhance the superconducting transition temperature. For this work, we develop the theory of quantum fluctuations within such multifractally enhanced superconducting states in thin films. In conditions of weak disorder, we employ the Finkel’stein nonlinear sigma model to derive an effective action for the superconducting order parameter and the quasiclassical Green’s function, meticulously accounting for the influence of quantum fluctuations. This effective action, applicable for interactions of any strength, reveals the critical role of well-known collective modes in a dirty superconductor, and its saddle-point analysis leads to modified Usadel and gap equations. These equations comprehensively incorporate the renormalizations stemming from the interplay between interactions and disorder, resulting in the non-trivial energy dependence of the gap function. Notably, our analysis establishes a direct relation between the self-consistent gap equation at the superconducting transition temperature and the known renormalization group equations for interaction parameters in the normal state.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Understanding Heterogeneities in Quantum Materials

Quantum materials are usually heterogeneous, with structural defects, impurities, surfaces, edges, interfaces, and disorder. These heterogeneities are sometimes viewed as liabilities within conventional systems; however, their electronic and magnetic structures often define and affect the quantum phenomena such as coherence, interaction, entanglement, and topological effects in the host system. Therefore, a critical need is to understand the roles of heterogeneities in order to endow materials with new quantum functions for energy and quantum information science applications. In this article, several representative examples are reviewed on the recent progress in connecting the heterogeneities to the quantum behaviors of real materials. Specifically, three intertwined topic areas are assessed: i) Reveal the structural, electronic, magnetic, vibrational, and optical degrees of freedom of heterogeneities. ii) Understand the effect of heterogeneities on the behaviors of quantum states in host material systems. iii) Control heterogeneities for new quantum functions. This progress is achieved by establishing the atomistic-level structure-property relationships associated with heterogeneities in quantum materials. Finally, the understanding of the interactions between electronic, magnetic, photonic, and vibrational states of heterogeneities enables the design of new quantum materials, including topological matter and quantum light emitters based on heterogenous 2D materials.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Glassy Phenomena and Precursors in the Lattice Dynamics

Broad classes of functional materials exhibit glass-like phenomena originating with the frustration of a soft phonon driven phase transition, including relaxor ferroelectrics and shape memory strain glasses. While the soft phonon mechanism is mostly understood, how this mechanism becomes frustrated in the presence of disorder remains intensely debated. A common structural feature of the frustrated state is nanoscale regions of local ferroic displacements that form well above the ordering temperature; these are called polar nanoregions (PNRs) in relaxor ferroelectrics and ferroelastic nanodomains (FND) in the strain glasses. The existence of these small regions provides a basis to explain glass-like slow relaxation phenomena, which can manifest in the lattice dynamics as phonon over damping. However, this does not explain why the long-range order becomes localized into PNRs or FNDs, or why this happens specifically at the nanoscale. Recent scattering experiments and theories suggest an exciting new way to think about these problems in terms of the physics of lattice vibrations in chemically disordered crystals. More generally, probing the lattice dynamics of these systems sheds new light on the microscopic origin of the nanoregions, glassy behavior, and enhanced functional properties.

Manley, Michael E.↗
DOE OSTI2024

Multiomic Network Analysis Identifies Dysregulated Neurobiological Pathways in Opioid Addiction

BACKGROUND: Opioid addiction is a worldwide public health crisis. In the United States, for example, opioids cause more drug overdose deaths than any other substance. However, opioid addiction treatments have limited efficacy, meaning that additional treatments are needed. METHODS: To help address this problem, we used network-based machine learning techniques to integrate results from genome-wide association studies of opioid use disorder and problematic prescription opioid misuse with transcriptomic, proteomic, and epigenetic data from the dorsolateral prefrontal cortex of people who died of opioid overdose and control individuals. RESULTS: Here we identified 211 highly interrelated genes identified by genome-wide association studies or dysregulation in the dorsolateral prefrontal cortex of people who died of opioid overdose that implicated the Akt, BDNF (brain-derived neurotrophic factor), and ERK (extracellular signal-regulated kinase) pathways, identifying 414 drugs targeting 48 of these opioid addiction–associated genes. Some of the identified drugs are approved to treat other substance use disorders or depression. CONCLUSIONS: Our synthesis of multiomics using a systems biology approach revealed key gene targets that could contribute to drug repurposing, genetics-informed addiction treatment, and future discovery.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Topological Hall effect in magnetic topological insulator films

Geometric Berry phase can be induced either by spin–orbit coupling, giving rise to the anomalous Hall effect in ferromagnetic materials, or by chiral spin texture, such as skyrmions, leading to the topological Hall effect. Recent experiments have revealed that both phenomena can occur in topological insulator films with magnetic doping, thus providing us with an intriguing platform to study the interplay between these two phenomena. In this work, we report on a numerical simulation of the anomalous Hall and topological Hall effects in a four-band model that can properly describe the quantum well states in the magnetic topological insulator films by combining Landauer–Büttiker formula and the iterative Green’s function method. Our numerical results suggest that spin–orbit coupling in this model plays a different role in the quantum transport in the clean and disordered limits. In the clean limit, spin–orbit coupling mainly influences the longitudinal transport but does not have much effect on topological Hall conductance. In the disordered limit, the longitudinal transport is determined by disorder scattering and spin–orbit coupling is found to affect strongly the topological Hall conductance. Here, this sharp contrast unveils a dramatic interplay between spin–orbit coupling and disorder effect in topological Hall effect in magnetic topological insulator systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗