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Li, Dan

Publications and source records attributed to Li, Dan.

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Isopiestic measurements of thermodynamic properties for the aqueous system LiBr–CaBr 2 –H 2 O at 373.15 K

In this study, the isopiestic molalities for the systems LiBr–H 2 O, CaBr 2 –H 2 O and LiBr–CaBr 2 –H 2 O were measured at 373.15 K with the isopiestic method using the Oak Ridge National Laboratory (ORNL) high–temperature gravimetric isopiestic apparatus. The osmotic coefficients were determined based on the lithium chloride and sodium chloride reference standards. The vapor pressure diagrams and osmotic coefficient diagrams at different mole fraction for LiBr were plotted. The calculated vapor pressure with water activities agree well with the experimental data. On the basis of Pitzer original and its extended model, the Pitzer binary parameters β (0) , β (1) C (0) and C (1) for the systems LiBr–H 2 O and CaBr 2 –H 2 O and mixing parameters of θ Li,Ca and ψ Li,Ca,Br were fitted with the measured osmotic coefficients. The calculated osmotic coefficients for systems LiBr–H 2 O and CaBr 2 –H 2 O agree well with the experimental data. The agreement between the calculated water activities and experimental results for the ternary system indicates that the parameters obtained in this work are reliable for water activity calculation. Finally, the thermodynamic data obtained in this study are essential for development of universal thermodynamic models for brine systems containing lithium bromide and calcium bromide.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Hepatitis B Virus X protein elevates Parkin-mediated mitophagy through Lon Peptidase in starvation

Highlights: • HBx induces the translocation of Parkin to partial mitochondria to elevate mitophagy. • HBx has diverse roles on mitochondrial and cytosolic LONP1 to enhance mitophagy. • HBx attenuates mitochondrial apoptosis in starvation through enhancing mitophagy. Hepatocellular Carcinoma (HCC) is the fifth most prevalent cancer worldwide. Specially, Hepatitis B viurs X protein (HBx) is a leading factor in the progression of Hepatitis B viurs-related HCC. Nutrient-deprived tumor microenvironment also contributes to tumor development. However, the role of HBx in nutrient-deprived HCC has received little investigation. Here, we show that HBx elevates PINK1-Parkin mediating mitophagy in starvation. HBx not only increases the PINK1/Parkin gene expression but also accelerates Parkin recruitment to partial mitochondria. Further analysis indicates that, HBx either promotes mitochondrial unfolded protein response, with remarkable mitochondrial LONP1 increases, or reduces LONP1 expression in cytosol inducing LONP1-Parkin pathway, both consequently enhancing mitophagy. Moreover, the enhanced mitophagy lowers mitochondrial apoptosis in starved hepatoma cells, and Bax is implied in the machinery. In addition, we define differential centrifuge, 3000 g or 12,000 g to pellet mitochondria, as an effective method to obtain distinct mitochondria. In collect, HBx regulates diverse aspects of LONP1 and Parkin, enhancing mitophagy in starvation. This study may shed new insights into the machinery development of hepatocellular carcinoma.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Distinct Turbulence Structures in Stably Stratified Boundary Layers With Weak and Strong Surface Shear

Turbulence structures and exchange of momentum and heat in the nocturnal stable boundary layer (SBL) show distinct features under different stability conditions prompting interest in their connection. Here eddy covariance data collected at four different heights on a 62-m meteorological tower over a large open flat terrain are used to characterize different SBL states and associated turbulence structures. In a SBL characterized by strong near-surface winds, turbulent eddy sizes scale with their observational heights and the SBL experiences enhanced turbulent mixing of momentum and heat throughout (a state hereafter referred to as a “coupled” state). Conversely, in a decoupled SBL, weak winds occur near the surface and turbulent eddies are depressed and detached from the boundary leading to suppressed vertical mixing and layered SBL profiles. Because the transport of momentum and heat to the surface across SBL layers is determined by turbulent eddies, cross-layer correlation and the aforementioned SBL coupling states can be delineated by distinct turbulence structures.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

The relation of magnetic properties and anomalous Hall behaviors in Mn4N (200) epitaxial films

Highlights: • Ferrimagnetic Mn4N(200) were grown on MgO(100) by plasma assisted molecular beam epitaxy. • We elucidate the relation of nitrogen vacancies and the magnetism by adjusting the growth pressure. • We state the relation of longitudinal resistivity and temperature as ρ{sub xx}∝T{sup 1.9994} (T ≤ 86K) and ρ{sub xx}∝T{sup 0.3068} (T > 86K) by data fitting. • We introduce a method to estimate the Debye temperature of Mn{sub 4}N materials and the residual resistance of 0 K. • We verify the linear relation between anomalou Hall resistivity (ρ{sub AH}) and magnetization at low magnetic field. - Abstract: The Mn{sub 4}N(200) films were grown on MgO(100) substrates by molecular beam epitaxy. The saturated magnetizations are 0.735 μB/f.u. and 0.892 μB/f.u. under pressure of 7.5 × 10{sup −6} mbar–9.5 × 10{sup −6} mbar. Increasing of growth pressure enhances the magnetism of Mn{sub 4}N due to the reduction of nitrogen vacancies. Debye temperature (T{sub D}) of Mn{sub 4}N is estimated to be 86 K. The longitudinal resistivity is linear to T{sup 1.9994} when T D , which coincides with electron-electron scattering of ferromagnetic coupling. The longitudinal resistivity originates from electron-electron scattering below T{sub D} since electron-phonon scattering is frozen. The longitudinal resistivity at 0 K is about 10% lower than 5 K as 7.085 μΩ cm. Mn{sub 4}N films show obvious anomalous Hall Effect in perpendicular magnetic fields. The anomalous Hall resistivity (ρ{sub AH}) of Mn{sub 4}N film is obtained by subtracting the ordinary Hall resistivity from transverse resistivity. The ρ{sub AH} is verified to be linear to magnetization at low magnetic field strength region (0–9 KOe).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Enhanced Temperature-Humidity Similarity Caused by Entrainment Processes With Increased Wind Shear

A number of studies already suggested that entrainment of warm/dry air from aloft degrades the similarity between air temperature (T) and specific humidity (q) in the atmospheric surface layer (ASL). Less is known about entrainment of cool/dry air on the ASL T-q similarity. Using eddy covariance measurements over a large inland water surface, enhanced T-q similarity with increased friction velocity (u*) was measured during daytime unstable conditions. Explaining this enhancement is the main goal of this work. Cool/dry air masses originating and advecting from land set the upper boundary condition on a quasi-equilibrated internal boundary layer embedding the warm/moist ASL over water. With increased u*, the entrainment velocity (dhI/dt ∝ u*) increases, thereby enhancing entrainment of cool/dry air originating from land, where t is time and hI is the internal boundary layer depth. By analyzing the scale-dependent (spectral) correlation coefficients, the enhanced T-q similarity with increased u* was shown to originate from spectral correlation coefficients in the middle- to low-frequency ranges (large eddies » z, the distance from the surface). With further increases in u*, similarity between T and q within large eddies was further enhanced and phase differences between T and q was reduced. Quadrant analysis showed large increases in flux and time fractions of downward large cool/dry eddies with increasing u*. These results provide evidence that enhanced entrainment of synchronized, large cool/dry eddies was a primary cause for the increased T-q similarity with increasing u*.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Intrinsic Constraints on Asymmetric Turbulent Transport of Scalars Within the Constant Flux Layer of the Lower Atmosphere: CONSTANT FLUX LAYER

A widely used assumption in boundary layer meteorology is the z independence of turbulent scalar fluxes F s throughout the atmospheric surface layer, where z is the distance from the boundary. This assumption is necessary for the usage of Monin-Obukhov Similarity Theory and for the interpretation of eddy covariance measurements of F s when using them to represent emissions or uptake from the surface. It is demonstrated here that the constant flux assumption offers intrinsic constraints on the third-order turbulent transport of F s in the unstable atmospheric surface layer. When enforcing z independence of F s on multilevel F s measurements collected above different surface cover types, it is shown that increasing instability leads to a novel and universal description of (i) the imbalance between ejecting and sweeping eddy contributions to F s and (ii) the ratio formed by a dimensionless turbulent transport of Fs and a dimensionless turbulent transport of scalar variance. When combined with structural models for the turbulent transport of F s , these two findings offer a new perspective on “closing” triple moments beyond conventional gradient diffusion schemes. A practical outcome is a diagnostic of the constant flux assumption from single-level F s measurements.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Tiam1 promotes thyroid carcinoma metastasis by modulating EMT via Wnt/β-catenin signaling

Aberrant expression of the guanine nucleotide exchange factor Tiam1 is implicated in the invasive phenotype of many cancers. However, its involvement in thyroid carcinoma and downstream molecular events remains largely undefined. Here, we examined the effects of Tiam1 on the invasiveness and metastasis of thyroid carcinoma in vitro and in vivo and explored the underlying mechanisms by investigating the regulation of Tiam1 expression and the downstream pathways affected. Our results showed that Tiam1 knockdown inhibited the migratory and invasive capacity of thyroid cancer cells, suppressed epithelial-mesenchymal transition (EMT), and inhibited Wnt/β-catenin signaling in vitro. Moreover, Tiam1 knockdown suppressed liver metastasis development in vivo. The effects of Tiam1 on metastasis and EMT mediated by the Wnt/β-catenin pathway were reversed by Rac1 silencing, suggesting that the prometastatic effect of Tiam1 is mediated by the activation of Rac1. These results indicate that Tiam1 may be a prognostic factor and potential therapeutic target for the treatment of thyroid cancers.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Modification of HBA/D230 Polymer for Stone Protection

By using poly(propylene glycol)bis(2-aminopropyl ether) (D230) as curing agent, we have prepared color-stable hydrogenated Bisphenol A (HBA) epoxy polymers, containing TiO{sub 2} nanoparticles. The loading and size of TiO{sub 2} nanoparticles (5 ~ 10, 21, 200 ~ 400 nm) are changed in order to investigate their photocatalytic effect on removing pollutants deposited on the surface of stone. HBA/D230 polymers containing different amounts of TiO{sub 2} nanomaterials were applied to methyl orange (MeO) on the limestone with exposure to the dry and wet environment, respectively. The results showed that the modification of HBA by addition of titanium dioxide particles substantially not only enhanced its protective efficiency but also rendered the treated stone surface self-cleaning ability. The photocatalytic degradation effect of MeO at the concentration of 0.001 M was the best when the size of TiO{sub 2} nanoparticles was between 200 ~ 400 nm. Compared to those in dry environment, the decrease of the content of MeO in samples exposed to wet environment was due to humidity on the surface of limestone.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Detection of Polarized Infrared Emission by Polycyclic Aromatic Hydrocarbons in the MWC 1080 Nebula

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in astrophysical environments, as revealed by their pronounced emission features at 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 μ m commonly ascribed to the C–H and C–C vibrational modes. Although these features have long been predicted to be polarized, previous searches for PAH polarization led to null or, at best, tentative detections. Here we report the definite detection of polarized PAH emission at 11.3 μ m in the nebula associated with the Herbig Be star MWC 1080. We measure a polarization degree of 1.9% ± 0.2%, which is unexpectedly high compared to models. This poses a challenge in the current understanding of the alignment of PAHs, which is required to polarize the PAH emission but thought to be substantially suppressed. PAH alignment with a magnetic field via a resonance paramagnetic relaxation process may account for such a high level of polarization.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

On the linkage between the k –5/3 spectral and k –7/3 cospectral scaling in high-Reynolds number turbulent boundary layers

Connections between the “–5/3” spectral and “–7/3” cospectral scaling exponents characterizing the inertial subranges of the wall-normal energy spectrum and the turbulent momentum flux cospectrum are explored in the equilibrium layer of high-Reynolds number turbulent boundary layers. Previous laboratory experiments and field measurements featured here in the atmospheric boundary layer show that the “–7/3” scaling in the momentum flux cospectrum F uw (k) commences at lower wavenumbers (around kz = 3) than the “–5/3” scaling in the wall-normal energy spectrum E ww (k) (around kz = 6), where k is the streamwise wavenumber and z is the distance from the surface. A satisfactory explanation as to why F uw (k) attains its “–7/3” inertial subrange scaling earlier than E ww (k) in wavenumber space remains elusive. A cospectral budget (CSB) model subject to several simplifications and closure schemes offers one viewpoint. In its simplest form, the CSB model assumes a balance at all k between the production term and a Rotta-like pressure decorrelation term with a prescribed wavenumber-dependent relaxation time scale. It predicts the “–7/3” scaling for F uw (k) from the “–5/3” scaling in E ww (k), thereby recovering earlier results derived from dimensional considerations. A finite flux transfer term was previously proposed to explain anomalous deviations from the “–7/3” cospectral scaling in the inertial subrange using a simplified spectral diffusion closure. However, this explanation is not compatible with an earlier commencement of the “–7/3” scaling in F uw (k). An alternative explanation that does not require a finite flux transfer is explored here. By linking the relaxation time scale in the slow-component of the Rotta model to the turbulent kinetic energy (TKE) spectrum, the earlier onset of the “–7/3” scaling in Fuw(k) is recovered without attainment of a “–5/3” scaling in E ww (k). In conclusion, the early onset of the “–7/3” scaling at smaller k is related to a slower than k–5/3 decay in the TKE spectrum at the crossover from production to inertial scales.

58 GEOSCIENCES↗
DOE OSTI2017

Anthelminthic drug niclosamide sensitizes the responsiveness of cervical cancer cells to paclitaxel via oxidative stress-mediated mTOR inhibition

Drug repurposing represents an alternative therapeutic strategy to cancer treatment. The potent anti-cancer activities of a FDA-approved anthelminthic drug niclosamide have been demonstrated in various cancers. However, whether niclosamide is active against cervical cancer is unknown. In this study, we investigated the effects of niclosamide alone and its combination with paclitaxel in cervical cancer in vitro and in vivo. We found that niclosamide significantly inhibited proliferation and induced apoptosis of a panel of cervical cancer cell lines, regardless of their cellular origin and genetic pattern. Niclosamide also inhibited tumor growth in cervical cancer xenograft mouse model. Importantly, niclosamide significantly enhanced the responsiveness of cervical cancer cell to paclitaxel. We further found that niclosamide induced mitochondrial dysfunctions via inhibiting mitochondrial respiration, complex I activity and ATP generation, which led to oxidative stress. ROS scavenge agent N-acetyl-L-cysteine (NAC) completely reversed the effects of niclosamide in increasing cellular ROS, inhibiting proliferation and inducing apoptosis, suggesting that oxidative stress induction is the mechanism of action of niclosamide in cervical cancer cells. In addition, niclosamide significantly inhibited mammalian target of rapamycin (mTOR) signaling pathway in cervical cancer cells and its inhibitory effect on mTOR is modulated by oxidative stress. Our work suggests that niclosamide is a useful addition to the treatment armamentarium for cervical cancer and induction of oxidative stress may be a potential therapeutic strategy in cervical cancer. - Highlights: • Niclosamide is active against cervical cancer cells in vitro and in vivo. • Niclosamide sensitizes cervical cancer cell response to paclitaxel. • Niclosamide induces mitochondrial dysfunction and oxidative damage. • Niclosamide inhibits mTOR signaling in an oxidative stress-dependent manner.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Fast and self-learning indoor airflow simulation based on in situ adaptive tabulation

Fast simulation for stratified indoor airflow distributions is desired for various applications, such as design of advanced indoor environments, emergency management, and coupled annual energy simulation for buildings with stratified air distributions. Reduced order models trained by pre-computed computational fluid dynamics results are fast, but their prediction may be inaccurate when applied for conditions outside the training domain. To overcome this limitation, we propose in this paper a fast and self-learning model based on an in situ adaptive tabulation (ISAT) algorithm, which is trained by a fast fluid dynamics (FFD) model as an example. The idea is that the ISAT will retrieve the solutions from an existing data set if the estimated prediction error is within a pre-defined tolerance. Otherwise, the ISAT will execute the FFD simulation, which is accelerated by running in parallel on a graphics processing unit, for a full-scale simulation. This paper systematically investigates the feasibility of the ISAT for indoor airflow simulations by presenting the ISAT-FFD implementation alongside results related to its overall performance. Using a stratified indoor airflow as an example, we evaluated how the training time of ISAT was impacted by four factors (training methods, error tolerances, number of inputs, and number of outputs). Then we demonstrated that a trained ISAT model can predict the key information for inputs both inside and outside the training domain. The ISAT was able to answer query points both inside and close to training domain using retrieve actions within a time less than 0.001 s for each query. In conclusion, we provided suggestions for using the ISAT for building applications.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2016

Closure Schemes for Stably Stratified Atmospheric Flows without Turbulence Cutoff

Two recently proposed turbulence closure schemes are compared against the conventional Mellor–Yamada (MY) model for stably stratified atmospheric flows. The Energy- and Flux-Budget (EFB) approach solves the budgets of turbulent momentum and heat fluxes and turbulent kinetic and potential energies. The Cospectral Budget (CSB) approach is formulated in wavenumber space and integrated across all turbulent scales to obtain flow variables in physical space. Unlike the MY model, which is subject to a “critical gradient Richardson number,” both EFB and CSB models allow turbulence to exist at any gradient Richardson number R i and predict a saturation of flux Richardson number ( R f → R fm ) at sufficiently large R i . The CSB approach further predicts the value of R fm and reveals a unique expression linking the Rotta and von Kármán constants. Hence, all constants in the CSB model are nontunable and stability independent. All models agree that the dimensionless sensible heat flux decays with increasing R i . However, the decay rate and subsequent cutoff in the MY model appear abrupt. The MY model further exhibits an abrupt cutoff in the turbulent stress normalized by vertical velocity variance, while the CSB and EFB models display increasing trends. The EFB model produces a rapid increase in the ratio of turbulent potential energy and vertical velocity variance as R fm is approached, suggesting a strong self-preservation mechanism. Vertical anisotropy in the turbulent kinetic energy is parameterized in different ways in MY and EFB, but this consideration is not required in CSB. Differences between EFB and CSB model predictions originate from how the vertical anisotropy is specified in the EFB model.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

AN ORDERED MAGNETIC FIELD IN THE PROTOPLANETARY DISK OF AB Aur REVEALED BY MID-INFRARED POLARIMETRY

Magnetic fields ( B -fields) play a key role in the formation and evolution of protoplanetary disks, but their properties are poorly understood due to the lack of observational constraints. Using CanariCam at the 10.4 m Gran Telescopio Canarias, we have mapped out the mid-infrared polarization of the protoplanetary disk around the Herbig Ae star AB Aur. We detect ∼0.44% polarization at 10.3 μ m from AB Aur's inner disk ( r < 80 au), rising to ∼1.4% at larger radii. Our simulations imply that the mid-infrared polarization of the inner disk arises from dichroic emission of elongated particles aligned in a disk B -field. The field is well ordered on a spatial scale, commensurate with our resolution (∼50 au), and we infer a poloidal shape tilted from the rotational axis of the disk. The disk of AB Aur is optically thick at 10.3 μ m, so polarimetry at this wavelength is probing the B -field near the disk surface. Our observations therefore confirm that this layer, favored by some theoretical studies for developing magneto-rotational instability and its resultant viscosity, is indeed very likely to be magnetized. At radii beyond ∼80 au, the mid-infrared polarization results primarily from scattering by dust grains with sizes up to ∼1 μ m, a size indicating both grain growth and, probably, turbulent lofting of the particles from the disk mid-plane.

79 ASTRONOMY AND ASTROPHYSICS↗