Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “LENGTH”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

On entropic uncertainty relations in the presence of a minimal length

Entropic uncertainty relations for the position and momentum within the generalized uncertainty principle are examined. Studies of this principle are motivated by the existence of a minimal observable length. Then the position and momentum operators satisfy the modified commutation relation, for which more than one algebraic representation is known. One of them is described by auxiliary momentum so that the momentum and coordinate wave functions are connected by the Fourier transform. However, the probability density functions of the physically true and auxiliary momenta are different. As the corresponding entropies differ, known entropic uncertainty relations are changed. Using differential Shannon entropies, we give a state-dependent formulation with correction term. State-independent uncertainty relations are obtained in terms of the Rényi entropies and the Tsallis entropies with binning. Such relations allow one to take into account a finiteness of measurement resolution. - Highlights: • Entropic uncertainty bounds increase for position and physically true momentum. • Correction terms are always nonzero for wave packets of a finite width. • An increase of uncertainty bounds depends on acceptance functions of apparatuses.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

The E1 copper binding domain of full-length amyloid precursor protein mitigates copper-induced growth inhibition in brain metastatic prostate cancer DU145 cells

Highlights: • Copper levels are elevated in the tumour microenvironment. • APP mitigates copper-induced growth inhibition of DU145 prostate cancer (PCa) cells. • The APP intracellular domain is a prerequisite; soluble forms have no effect. • The E1 CuBD of APP is also a prerequisite. • APP copper binding potentially mitigates copper-induced PCa cell growth inhibition. - Abstract: Copper plays an important role in the aetiology and growth of tumours and levels of the metal are increased in the serum and tumour tissue of patients affected by a range of cancers including prostate cancer (PCa). The molecular mechanisms that enable cancer cells to proliferate in the presence of elevated copper levels are, therefore, of key importance in our understanding of tumour growth progression. In the current study, we have examined the role played by the amyloid precursor protein (APP) in mitigating copper-induced growth inhibition of the PCa cell line, DU145. A range of APP molecular constructs were stably over-expressed in DU145 cells and their effects on cell proliferation in the presence of copper were monitored. Our results show that endogenous APP expression was induced by sub-toxic copper concentrations in DU145 cells and over-expression of the wild-type protein was able to mitigate copper-induced growth inhibition via a mechanism involving the cytosolic and E1 copper binding domains of the full-length protein. APP likely represents one of a range of copper binding proteins that PCa cells employ in order to ensure efficient proliferation despite elevated concentrations of the metal within the tumour microenvironment. Targeting the expression of such proteins may contribute to therapeutic strategies for the treatment of cancers.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

The conserved Wdr8-hMsd1/SSX2IP complex localises to the centrosome and ensures proper spindle length and orientation

The centrosome plays a pivotal role in a wide range of cellular processes and its dysfunction is causally linked to many human diseases including cancer and developmental and neurological disorders. This organelle contains more than one hundred components, and yet many of them remain uncharacterised. Here we identified a novel centrosome protein Wdr8, based upon the structural conservation of the fission yeast counterpart. We showed that Wdr8 constitutively localises to the centrosome and super resolution microscopy uncovered that this protein is enriched at the proximal end of the mother centriole. Furthermore, we identified hMsd1/SSX2IP, a conserved spindle anchoring protein, as one of Wdr8 interactors by mass spectrometry. Wdr8 formed a complex and partially colocalised with hMsd1/SSX2IP. Intriguingly, knockdown of Wdr8 or hMsd1/SSX2IP displayed very similar mitotic defects, in which spindle microtubules became shortened and misoriented. Indeed, Wdr8 depletion resulted in the reduced recruitment of hMsd1/SSX2IP to the mitotic centrosome, though the converse is not true. Together, we propose that the conserved Wdr8-hMsd1/SSX2IP complex plays a critical role in controlling proper spindle length and orientation. - Highlights: • Human Wdr8 is a centrosomal protein enriched in the proximal end of the centriole. • Wdr8 and hMsd1/SSX2IP form a complex conserved in fungi. • Depletion of Wdr8 results in shorter, tilted spindle microtubules. • Depletion phenotypes of Wdr8 are very similar to those of hMsd1/SSX2IP knockdown.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Full-length RPB1 is required in two-step shoot regeneration

Highlights: • Mutations in RPB1 result in defects in callus formation in Arabidopsis. • Auxin gradient formation is disturbed in RPB1 mutants. • The frequency of shoot regeneration upon SIM is repressed in RPB1 mutants. • The cytokinin response receded during shoot regeneration. Regeneration is a complicated progress in plants and animals. Most multicellular organisms can regenerate new tissue when wounded, and plants excel most animals in their ability to regenerate whole new growth module from adult tissues. Regeneration in Arabidopsis includes two steps. Firstly, the explants from differentiated plant tissues such as roots or hypocotyls are induced to generate callus, then the shoots regenerate upon the callus. The phytohormone auxin and cytokinin play important parts in this process. And genes related to auxin and cytokinin siganls involved in the regeneration have been studied widely. As we reported before, in Arabidopsis the full-length CTD of RNA Polymerase II's largest subunit RPB1 is necessary in keeping normal cell cycling and maintaining stem cell niches. Here, we report that the mutants of card1s have significant defects in the regeneration progress both in the induction of callus and the formation of shoot. All the results further proved the importance of intact RPB1 from a distinctive perspective.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Shelterin differentially respond to oxidative stress induced by TiO2-NPs and regulate telomere length in human hepatocytes and hepatocarcinoma cells in vitro

Highlights: • Exposed to TiO{sub 2}-NPs caused telomere shortening and chromosome instability in normal cells but not in cancer cells. • The shelterin and Nrf-2 of normal and cancer cells differentially respond to oxidative stress induced by TiO{sub 2}-NPs. • The upregulation of Nrf-2 and shelterin protect telomere and chromosome stability against TiO{sub 2}-NPs exposure. Titanium dioxide nanoparticles (TiO{sub 2}-NPs) have raised serious attention for their widely use and potential adverse effects on human mainly due to producing ROS. However, the influence of TiO{sub 2}-NPs on telomere maintaining has not been studied clearly. Shelterin plays core roles in telomere length (TL) regulation. Abnormal TL are associated with chromosome instability (CIN) and high risk of diseases. This study investigated whether TiO{sub 2}-NPs affect TL to induce CIN through ROS generation and the possible mechanisms. Human hepatocyte L-02 and hepatocarcinoma cells QGY were exposed to TiO{sub 2}-NPs (0, 40, 80 μg/mL) for 72 h. The intracellular hydrogen dioxide (H{sub 2}O{sub 2}) concentration were measured. The TL, Nrf-2, and three core shelterin components (TRF1, TRF2, and POT1) transcription level were determined by quantitative real-time PCR. CIN was measured by cytokinesis-block micronucleus assay. TiO{sub 2}-NPs exposure increased intracellular H{sub 2}O{sub 2} in both L-02 and QGY cells, and induced Nrf-2, TRF1, TRF2, POT1 downregulated transcription compared with control (P P P P Nrf-2 to oxidative stress induced by TiO{sub 2}-NPs led to the weakened telomere protection in normal cells and effective telomere maintenance in cancer cells, respectively. The upregulation of Nrf-2 and shelterin could protect TL and chromosome stability against TiO{sub 2}-NPs exposure.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Exceptionally large migration length of carbon and topographically-facilitated self-limiting molecular beam epitaxial growth of graphene on hexagonal boron nitride

We demonstrate growth of single-layer graphene (SLG) on hexagonal boron nitride (h-BN) by molecular beam epitaxy (MBE), only limited in area by the finite size of the h-BN flakes. Using atomic force microscopy and micro-Raman spectroscopy, we show that for growth over a wide range of temperatures (500 °C – 1000 °C) the deposited carbon atoms spill off the edge of the h-BN flakes. We attribute this spillage to the very high mobility of the carbon atoms on the BN basal plane, consistent with van der Waals MBE. The h-BN flakes vary in size from 30 μm to 100 μm, thus demonstrating that the migration length of carbon atoms on h-BN is greater than 100 μm. When sufficient carbon is supplied to compensate for this loss, which is largely due to this fast migration of the carbon atoms to and off the edges of the h-BN flake, we find that the best growth temperature for MBE SLG on h-BN is ~950 °C. Self-limiting graphene growth appears to be facilitated by topographic h-BN surface features: We have thereby grown MBE self-limited SLG on an h-BN ridge. This opens up future avenues for precisely tailored fabrication of nano- and hetero-structures on pre-patterned h-BN surfaces for device applications.

Plaut, Annette S.↗
DOE OSTI2016

Crystal Structure of a Full-Length Human Tetraspanin Reveals a Cholesterol-Binding Pocket

Tetraspanins comprise a diverse family of four-pass transmembrane proteins that play critical roles in the immune, reproductive, genitourinary, and auditory systems. Despite their pervasive roles in human physiology, little is known about the structure of tetraspanins or the molecular mechanisms underlying their various functions. Here, we report the crystal structure of human CD81, a full-length tetraspanin. The transmembrane segments of CD81 pack as two largely separated pairs of helices, capped by the large extracellular loop (EC2) at the outer membrane leaflet. The two pairs of helices converge at the inner leaflet to create an intramembrane pocket with additional electron density corresponding to a bound cholesterol molecule within the cavity. Molecular dynamics simulations identify an additional conformation in which EC2 separates substantially from the transmembrane domain. As a result, cholesterol binding appears to modulate CD81 activity in cells, suggesting a potential mechanism for regulation of tetraspanin function.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2013

On the relevance of volume increase for the length changes of mortar bars in sulfate solutions

The ingress of sulfate ions into cementitious materials leads to the formation of ettringite, gypsum and other phases. The increase in solid volume through the formation of these phases is often assumed to be the only reason for expansion. In this paper we systematically compare the volume increase predicted by thermodynamic modeling to macroscopic expansion for mortars made with CEM I in different sulfate solutions and for mortars made with a range of blended cements in sodium sulfate solution. It is shown that the length changes cannot be explained by simple volume increase alone. A more plausible explanation of expansion lies in the theory of crystallization pressure, in which crystals forming from a supersaturated solution may exert pressure on their surroundings. It is observed that expansion occurs in systems where thermodynamic modeling predicts the co-existence of ettringite with gypsum. In such a case, if monosulfate and gypsum are both present locally, the solution can be highly supersaturated with respect to ettringite, whose formation in confined conditions (such as within C–S–H) can then exert expansive forces.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Bridging the gap between NMR measured mean silicate chain length and nano-scale silicate polymorphism of calcium silicate hydrates

Variable stoichiometry and silicate polymorphism in calcium-silicate-hydrates (C-S-H) has impeded the revelation of point defects distribution in the silicate tetrahedral network of C-S-H, which resembles tobermorite crystal structure with some bridging tetrahedra (BT) and paired tetrahedra (PT) vacancies in dreierketten chains. Here we use a computational approach to characterize silicate polymorphism by introducing the vacancy ratio of BT to PT (α) and establishing a three-term empirical mean chain length (MCL) formula for different calcium-to‑silicon ratios (Ca/Si) ranging from 1.2 to 2.3. The formula identifies BT and PT controls at low and high α respectively and allows an inverse mapping of polymorphic range based on NMR experiments. The proposed computational framework quantitatively describes silicate polymorphs and links NMR-measured MCL to C-S-H atomistic configurations at the molecular level.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Experimental investigation of the short-term creep recovery of hardened cement paste at micrometre length scale

This paper presents an experimental investigation on the short-term creep recovery of cement paste at micrometre length scale. Micro-cantilever beams were fabricated and tested with 8 different loading series using the nanoindenter. It is found that cement pastes show high recovery ratios (>80%) even subjected to very high stress levels. Relatively lower recovery ratios and non-linear creep were also observed for w/c 0.4 samples under high stress levels. A good agreement is found between the results predicted using the linear superposition principle and the experimental results except for the measured non-linear creep in w/c 0.4 samples. It is suggested that the short-term creep recovery may be associated with the microscale stress redistribution or the reversible internal water movement. The observed non-linear creep under the highest stress level may be due to the higher density of microcracks generated during the loading stage, which may further promote the water transfer.

36 MATERIALS SCIENCE↗
DOE OSTI2018

An arc-length method for controlled cohesive crack propagation using high-order XFEM and Irwin’s crack closure integral

Numerical modeling of cohesive crack growth in quasi-brittle materials is challenging, primarily due to the combination of (i) nonlinearity associated with the fracture process zone (FPZ), (ii) arbitrary directions to which a crack may propagate, and (iii) snap-back or snap-through instabilities encountered in the response of the structure. To address these challenges, here we propose a novel arc-length method that can follow the equilibrium path of cohesive crack propagation. The proposed approach is based on the extended finite element method (XFEM) with scalar high-order enrichment functions and Irwin’s crack closure integral, which allows for direct control of the applied loads necessary to propagate cohesive cracks. This is achieved by augmenting a constraint equation written in terms of stress intensity factors (SIFs), and expressed explicitly in terms of the enriched degrees of freedom, which is an attractive feature achieved with Irwin’s integral, since SIFs can be written in closed-form. Note that singular enrichments are active in an unstable crack propagation state and automatically vanish in stable crack configurations. Furthermore, to propagate cracks in arbitrary directions, we employ a maximum circumferential stress criterion implemented by (i) direct usage of the SIFs, and by (ii) a new stress-based nonlocal implementation of this principle. Various benchmark problems including pure mode I and mixed-mode fracture are solved to demonstrate the predictive capability of the present framework for cohesive crack modeling.

42 ENGINEERING↗
DOE OSTI2025

Extraction of high-purity medium-chain-length polyhydroxyalkanoates via combined mechanical treatment and mild oxidation

Polyhydroxyalkanoates (PHAs) are a class of polyester polymers of microbial origin and considered biodegradable alternatives to conventional plastics. To make PHAs cost-competitive with synthetic plastics, their production cost, including extraction cost, should be significantly reduced. Herein, this study aimed to develop an effective extraction method based on combined mechanical disruption and chemical treatment for the recovery of high-purity medium-chain-length PHAs (mcl-PHAs) at a lower cost. mcl-PHAs-accumulating Pseudomonas strains were used for PHA extraction via high-pressure homogenization (HPH) coupled with surfactant treatment and mild alkaline hydrogen peroxide oxidation. The mechanical-chemical method was found to have strong synergy for PHA extraction while minimizing PHA depolymerization. The optimized condition resulted in nearly 90 % mcl-PHA recovery with high purity (>91 %). The extracted high-purity PHAs exhibited thermal and mechanical properties suitable for downstream applications entailing flexible and elastomeric materials.

42 ENGINEERING↗
DOE OSTI2017

SPH with dynamical smoothing length adjustment based on the local flow kinematics

Due to the Lagrangian nature of Smoothed Particle Hydrodynamics (SPH), the adaptive resolution remains a challenging task. In this work, we first analyse the influence of the simulation parameters and the smoothing length on solution accuracy, in particular in high strain regions. Based on this analysis we develop a novel approach to dynamically adjust the kernel range for each SPH particle separately, accounting for the local flow kinematics. We use the Okubo–Weiss parameter that distinguishes the strain and vorticity dominated regions in the flow domain. The proposed development is relatively simple and implies only a moderate computational overhead. We validate the modified SPH algorithm for a selection of two-dimensional test cases: the Taylor–Green flow, the vortex spin-down, the lid-driven cavity and the dam-break flow against a sharp-edged obstacle. The simulation results show good agreement with the reference data and improvement of the long-term accuracy for unsteady flows. For the lid-driven cavity case, the proposed dynamical adjustment remedies the problem of tensile instability (particle clustering).

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Structure of the HIV-1 Full-Length Capsid Protein in a Conformationally Trapped Unassembled State Induced by Small-Molecule Binding

The capsid (CA) protein plays crucial roles in HIV infection and replication, essential to viral maturation. The absence of high-resolution structural data on unassembled CA hinders the development of antivirals effective in inhibiting assembly. Unlike enzymes that have targetable, functional substrate-binding sites, the CA does not have a known site that affects catalytic or other innate activity, which can be more readily targeted in drug development efforts. We report the crystal structure of the HIV-1 CA, revealing the domain organization in the context of the wild-type full-length (FL) unassembled CA. The FL CA adopts an antiparallel dimer configuration, exhibiting a domain organization sterically incompatible with capsid assembly. A small compound, generated in situ during crystallization, is bound tightly at a hinge site ('H site'), indicating that binding at this interdomain region stabilizes the ADP conformation. Electron microscopy studies on nascent crystals reveal both dimeric and hexameric lattices coexisting within a single condition, in agreement with the interconvertibility of oligomeric forms and supporting the feasibility of promoting assembly-incompetent dimeric states. Solution characterization in the presence of the H-site ligand shows predominantly unassembled dimeric CA, even under conditions that promote assembly. Our structure elucidation of the HIV-1 FL CA and characterization of a potential allosteric binding site provides three-dimensional views of an assembly-defective conformation, a state targeted in, and thus directly relevant to, inhibitor development. Based on our findings, we propose an unprecedented means of preventing CA assembly, by 'conformationally trapping' CA in assembly-incompetent conformational states induced by H-site binding.

Du, Shoucheng↗
DOE OSTI2017

Quantification of Dose-Volume and Dose-Length Parameters for Cervical Esophageal Stricture in Head and Neck Irradiation with the 3DCRT and IMRT Technique

To quantify and compare dose-volume and dose-length parameters of cervical esophagus between three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiation therapy (IMRT) and to correlate with incidence of cervical strictures in head and neck cancer irradiation with radical intent.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Impact of reduced dimensionality on the correlation length and magnetization dynamics of the spin chain cobaltite Ca 3 Co 2 O 6

We have recently applied the magnetic field and temperature dependence of magnetic entropy change as a probe of the magnetic states of a single crystal of Ca 3 Co 2 O 6 to establish a more comprehensive magnetic phase diagram for this exotic system. The results are consistent with the spin-density wave description of the ground state and indicate the suppression of the modulated state in favor of a ferrimagnetic up-up-down arrangement of the spin chains with the application of a moderate field. We demonstrate, in this study, that the features of the static magnetic phase diagram are preserved when the grain size of Ca 3 Co 2 O 6 is reduced to 440 nm (below the maximum c-axis correlation length of ~550 nm in Ca 3 Co 2 O 6 ), although the polycrystalline materials show a non-saturating behavior, rounded steps, and reduced magnetization when compared to the single crystal. Our new finding of the multiple low-temperature magnetization steps in the 440 nm sample, together with conflicting reports concerning such steps in nanostructured samples, suggests that correlations in the ab plane are more important than correlations along the c-axis in the appearance of the plateaus. The relaxation processes in the system are studied through the decay of remanent magnetization, ac susceptibility, and Argand diagrams. The introduction of grain boundaries in Ca 3 Co 2 O 6 weakens the slow-dynamic state, widens the low-temperature distribution of relaxation times, and lowers activation energies within the Arrhenius-like relaxation regime.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Flexibility of oxygen sublattice and hydrogen bond length predict proton mobility in ternary metal oxides

Discovery of fast proton conductors is important for advancing clean energy technologies. This requires a better understanding of proton migration mechanisms. While structural and chemical traits of ternary metal oxides have been related to proton migration barriers, lattice dynamical effects have not been resolved quantitatively. Here, in this work, we introduce a phonon-based dynamic descriptor, termed ‘‘thermal O…O fluctuation,’’ quantifying the flexibility of donor-acceptor oxide-ion pairs. This enables direct comparison of O-sublattice flexibility across diverse metal oxides. Using regression models, we ranked physical descriptors as predictors of proton mobility, finding that H-bond length and thermal O…O fluctuation were the strongest descriptors. Further analysis revealed a critical O…O spacing of 2.4 A˚ at the transition state, which is easier to reach by more flexible donor-acceptor pairs, enabling facile proton transfer. Our results demonstrate oxygen sublattice flexibility as a dynamic descriptor and provide guiding principles for enhancing proton mobility in ternary metal oxides.

diffusivity↗
DOE OSTI2020

Deformation behavior of metallic glass composites and plasticity accommodation at microstructural length-scales

Bulk metallic glass matrix composites represent a unique microstructural design strategy for overcoming the strength/ductility trade-off in structural alloys. Site-specific mechanical behavior of a Ti-based bulk metallic glass composite was evaluated at microstructural length-scale. The micro-pillars on the amorphous matrix showed on average a yield point of 1.9 GPa followed by serrated plastic deformation characteristic of shear banding. In contrast, micro-pillars on the crystalline dendritic phase showed a much lower yield strength of 0.72 GPa on average for the four different crystallographic orientations chosen, smooth plastic flow with no recognizable load burst, and stable strain-hardening after yield point. A number of micro-pillars were made at the interface between the glassy matrix and the crystalline dendrite. The mixed micro-pillars showed homogeneous deformation and greater plasticity which was attributed to their smaller stored elastic energy. Shear bands initiated in the amorphous matrix were arrested by the crystalline dendrite, which accommodated plasticity through slip bands and dislocations pile-ups. The interface remained intact after plastic deformation, with no observable signs of devitrification in the amorphous phase.

Bulk metallic glass matrix composite, Micro-pillar↗