Distributed Capacitive Sensor for Sample Mass Measurement

NASA Technical Reports Server (NTRS)

Toda, Risaku; McKinney, Colin; Jackson, Shannon P.; Mojarradi, Mohammad; Manohara, Harish; Trebi-Ollennu, Ashitey

2011-01-01

Previous robotic sample return missions lacked in situ sample verification/ quantity measurement instruments. Therefore, the outcome of the mission remained unclear until spacecraft return. In situ sample verification systems such as this Distributed Capacitive (DisC) sensor would enable an unmanned spacecraft system to re-attempt the sample acquisition procedures until the capture of desired sample quantity is positively confirmed, thereby maximizing the prospect for scientific reward. The DisC device contains a 10-cm-diameter pressure-sensitive elastic membrane placed at the bottom of a sample canister. The membrane deforms under the weight of accumulating planetary sample. The membrane is positioned in close proximity to an opposing rigid substrate with a narrow gap. The deformation of the membrane makes the gap narrower, resulting in increased capacitance between the two parallel plates (elastic membrane and rigid substrate). C-V conversion circuits on a nearby PCB (printed circuit board) provide capacitance readout via LVDS (low-voltage differential signaling) interface. The capacitance method was chosen over other potential approaches such as the piezoelectric method because of its inherent temperature stability advantage. A reference capacitor and temperature sensor are embedded in the system to compensate for temperature effects. The pressure-sensitive membranes are aluminum 6061, stainless steel (SUS) 403, and metal-coated polyimide plates. The thicknesses of these membranes range from 250 to 500 m. The rigid substrate is made with a 1- to 2-mm-thick wafer of one of the following materials depending on the application requirements glass, silicon, polyimide, PCB substrate. The glass substrate is fabricated by a microelectromechanical systems (MEMS) fabrication approach. Several concentric electrode patterns are printed on the substrate. The initial gap between the two plates, 100 m, is defined by a silicon spacer ring that is anodically bonded to the glass substrate. The fabricated proof-of-concept devices have successfully demonstrated tens to hundreds of picofarads of capacitance change when a simulated sample (100 g to 500 g) is placed on the membrane.

Biochemistry Students' Ideas about How an Enzyme Interacts with a Substrate

ERIC Educational Resources Information Center

Linenberger, Kimberly J.; Bretz, Stacey Lowery

2015-01-01

Enzyme-substrate interactions are a fundamental concept of biochemistry that is built upon throughout multiple biochemistry courses. Central to understanding enzyme-substrate interactions is specific knowledge of exactly how an enzyme and substrate interact. Within this narrower topic, students must understand the various binding sites on an…

Effect of substrate temperature and V/III flux ratio on In incorporation for InGaN/GaN heterostructures grown by plasma-assisted molecular-beam epitaxy

NASA Astrophysics Data System (ADS)

O'Steen, M. L.; Fedler, F.; Hauenstein, R. J.

1999-10-01

Reflection high-energy electron diffraction (RHEED) and laterally spatially resolved high resolution x-ray diffraction (HRXRD) have been used to identify and characterize rf plasma-assisted molecular-beam epitaxial growth factors which strongly affect the efficiency of In incorporation into InxGa1-xN epitaxial materials. HRXRD results for InxGa1-xN/GaN superlattices reveal a particularly strong dependence of average alloy composition x¯ upon both substrate growth temperature and incident V/III flux ratio. For fixed flux ratio, results reveal a strong thermally activated behavior, with over an order-of-magnitude decrease in x¯ with increasing growth temperature within the narrow range 590-670 °C. Within this same range, a further strong dependence upon V/III flux ratio is observed. The decreased In incorporation at elevated substrate temperatures is tentatively attributed to In surface-segregation and desorption processes. RHEED observations support this segregation/desorption interpretation to account for In loss.

An expert-based model for selecting the most suitable substrate material type for antenna circuits

NASA Astrophysics Data System (ADS)

AL-Oqla, Faris M.; Omar, Amjad A.

2015-06-01

Quality and properties of microwave circuits depend on all the circuit components. One of these components is the substrate. The process of substrate material selection is a decision-making problem that involves multicriteria with objectives that are diverse and conflicting. The aim of this work was to select the most suitable substrate material type to be used in antennas in the microwave frequency range that gives best performance and reliability of the substrate. For this purpose, a model was built to ease the decision-making that includes hierarchical alternatives and criteria. The substrate material type options considered were limited to fiberglass-reinforced epoxy laminates (FR4 εr = 4.8), aluminium (III) oxide (alumina εr = 9.6), gallium arsenide III-V compound (GaAs εr = 12.8) and PTFE composites reinforced with glass microfibers (Duroid εr = 2.2-2.3). To assist in building the model and making decisions, the analytical hierarchy process (AHP) was used. The decision-making process revealed that alumina substrate material type was the most suitable choice for the antennas in the microwave frequency range that yields best performance and reliability. In addition, both the size of the circuit and the loss tangent of the substrates were found to be the most contributing subfactors in the antenna circuit specifications criterion. Experimental assessments were conducted utilising The Expert Choice™ software. The judgments were tested and found to be precise, consistent and justifiable, and the marginal inconsistency values were found to be very narrow. A sensitivity analysis was also presented to demonstrate the confidence in the drawn conclusions.

Finding pathways to prepare Fe4N thin films at low substrate temperature

NASA Astrophysics Data System (ADS)

Seema, Gupta, Nitiand Mukul

2018-04-01

In Fe-N phase diagram the formation of Fe4N thin films occur in a very narrow region, specially below 573 K. Above this, the range of homogeneity for formation of Fe4N start to increase yielding more favorable conditions for formation of single phase Fe4N. However, when deposited at high substrate temperature (Ts) typically above 650 K, nitrogen (N) tends to diffuse out of the system yielding a N deficient phase. In this work, we attempt to find pathways to deposit Fe4N thin films at low Ts and successfully prepared single phase Fe4N thin films at Ts as low as 423 K. This was achieved by utilizing an underlayer of CrN. We find that such underlayer not only has close lattice matching with Fe4N, it also acts as a diffusion barrier for the film-substrate interface.

Growth of heterostructures on InAs for high mobility device applications

NASA Astrophysics Data System (ADS)

Contreras-Guerrero, R.; Wang, S.; Edirisooriya, M.; Priyantha, W.; Rojas-Ramirez, J. S.; Bhuwalka, K.; Doornbos, G.; Holland, M.; Oxland, R.; Vellianitis, G.; Van Dal, M.; Duriez, B.; Passlack, M.; Diaz, C. H.; Droopad, R.

2013-09-01

The growth of heterostructures lattice matched to InAs(100) substrates for high mobility electronic devices has been investigated. The oxide removal process and homoepitaxial nucleation depends on the deposition parameters to avoid the formation of surface defects that can propagate through the structure during growth which can result in degraded device performance. The growth parameters for InAs homoepitaxy were found to be within an extremely narrow range when using As4 with a slight increase using As2. High structural quality lattice matched AlAsxSb1-x buffer layer was grown on InAs(100) substrates using a digital growth technique with the AlAs mole fraction adjusted by varying the incident As flux. Using the AlAsxSb1-x buffer layer, the transport properties of thin InAs channel layers were determined on conducting native substrates.

Rapid change with depth in megabenthic structure-forming communities of the Makapu'u deep-sea coral bed

NASA Astrophysics Data System (ADS)

Long, Dustin J.; Baco, Amy R.

2014-01-01

Seamounts are largely unexplored undersea mountains rising abruptly from the ocean floor, which can support an increased abundance and diversity of organisms. Deep-sea corals are important benthic structure-formers on current-swept hard substrates in these habitats. While depth is emerging as a factor structuring the fauna of seamounts on a large spatial scale, most work addressing deep-sea coral and seamount community structure has not considered the role of small-scale variation in species distributions. Video from six ROV dives over a depth range of ~320-530 m were analyzed to assess the diversity and density of benthic megafaunal invertebrates across the Makapu'u deep-sea coral bed, offshore of Oahu, Hawaii. At the same time, the physical environment along the dive track was surveyed to relate biotic patterns with abiotic variables including depth, aspect, rugosity, substrate, slope and relief to test the factors structuring community assemblages. Despite the narrow range examined, depth was found to be the strongest structuring gradient, and six unique macrobenthic communities were found, with a 93% faunal dissimilarity over the depth surveyed. Relief, rugosity and slope were also factors in the final model. Alcyonacean octocorals were the dominant macrofaunal invertebrates at all but the deepest depth zone. The commercially harvested precious coral C. secundum was the dominant species at depths 370-470 m, with a distribution that is on average deeper than similar areas. This may be artificial due to the past harvesting of this species on the shallower portion of its range. Primnoid octocorals were the most abundant octocoral family overall. This work yields new insight on the spatial ecology of seamounts, pointing out that community changes can occur over narrow depth ranges and that communities can be structured by small-scale physiography.

Deposition of vanadium oxide films by direct-current magnetron reactive sputtering

NASA Astrophysics Data System (ADS)

Kusano, E.; Theil, J. A.; Thornton, John A.

1988-06-01

It is demonstrated here that thin films of vanadium oxide can be deposited at modest substrate temperatures by dc reactive sputtering from a vanadium target in an O2-Ar working gas using a planar magnetron source. Resistivity ratios of about 5000 are found between a semiconductor phase with a resistivity of about 5 Ohm cm and a metallic phase with a resistivity of about 0.001 Ohm cm for films deposited onto borosilicate glass substrates at about 400 C. X-ray diffraction shows the films to be single-phase VO2 with a monoclinic structure. The VO2 films are obtained for a narrow range of O2 injection rates which correspond to conditions where cathode poisoning is just starting to occur.

Deposition of vanadium oxide films by direct-current magnetron reactive sputtering

NASA Technical Reports Server (NTRS)

Kusano, E.; Theil, J. A.; Thornton, John A.

1988-01-01

It is demonstrated here that thin films of vanadium oxide can be deposited at modest substrate temperatures by dc reactive sputtering from a vanadium target in an O2-Ar working gas using a planar magnetron source. Resistivity ratios of about 5000 are found between a semiconductor phase with a resistivity of about 5 Ohm cm and a metallic phase with a resistivity of about 0.001 Ohm cm for films deposited onto borosilicate glass substrates at about 400 C. X-ray diffraction shows the films to be single-phase VO2 with a monoclinic structure. The VO2 films are obtained for a narrow range of O2 injection rates which correspond to conditions where cathode poisoning is just starting to occur.

On the Correlation Between the Self-Organized Island Pattern and Substrate Elastic Anisotropy

DTIC Science & Technology

2007-04-01

eters would be most useful to experimentalists. The kinetic Monte Carlo KMC has been proposed re- cently to study QD island self-organization by many...time ti. 21,25 Based on a proposed coupled KMC , the authors simu- lated the island ordering and narrow size distribution in two dimensions and further...100, 013527 2006pattern has not been studied so far within the coupled KMC algorithm where the long-range strain energy field is in- cluded

Controlling nested wrinkle morphology through the boundary effect on narrow-band thin films

NASA Astrophysics Data System (ADS)

Xu, Hanyang; Shi, Tielin; Liao, Guanglan; Xia, Qi

2017-07-01

We describe the formation of nested wrinkles created by the thermal mismatch between a narrow-band thin film and a compliant substrate. When a film is described as "narrow-band", it literally means that the film band width is much shorter than its length; more precisely, it means that the width is comparable with the wavelength of the wrinkles. A silicon mask was used during film sputtering to create narrow-band films on poly (dimethylsiloxane) substrate, thus creating regular boundaries to steer local stresses and control wrinkle morphology. Disordered nano-scale wrinkles were found nested within highly ordered micro-scale sinusoidal wrinkles. The formation of nested wrinkles was explained through the amplitude and wavelength saturation of nano-scale wrinkles. The disordered morphology of nano-scale wrinkles and the highly ordered morphology of micro-scale wrinkles were explained by using the boundary effect.

Long-range dielectric-loaded surface plasmon polariton waveguides operating at telecommunication wavelengths.

PubMed

Volkov, Valentyn S; Han, Zhanghua; Nielsen, Michael G; Leosson, Kristjan; Keshmiri, Hamid; Gosciniak, Jacek; Albrektsen, Ole; Bozhevolnyi, Sergey I

2011-11-01

We report on the realization of long-range dielectric-loaded surface plasmon polariton waveguides (LR-DLSPPWs) consisting of straight and bent subwavelength dielectric ridges deposited on thin and narrow metal stripes supported by a dielectric buffer layer covering a low-index substrate. Using imaging with a near-field optical microscope and end-fire coupling with a tapered fiber connected to a tunable laser at telecommunication wavelengths (1425-1545 nm), we demonstrate low-loss (propagation length ∼500 μm) and well-confined (mode width ∼1 μm) LR-DLSPPW mode guiding and determine the propagation and bend loss.

Plasmonic and silicon spherical nanoparticle antireflective coatings

NASA Astrophysics Data System (ADS)

Baryshnikova, K. V.; Petrov, M. I.; Babicheva, V. E.; Belov, P. A.

2016-03-01

Over the last decade, plasmonic antireflecting nanostructures have been extensively studied to be utilized in various optical and optoelectronic systems such as lenses, solar cells, photodetectors, and others. The growing interest to all-dielectric photonics as an alternative optical technology along with plasmonics motivates us to compare antireflective properties of plasmonic and all-dielectric nanoparticle coatings based on silver and crystalline silicon respectively. Our simulation results for spherical nanoparticles array on top of amorphous silicon show that both silicon and silver coatings demonstrate strong antireflective properties in the visible spectral range. For the first time, we show that zero reflectance from the structure with silicon coatings originates from the destructive interference of electric- and magnetic-dipole responses of nanoparticle array with the wave reflected from the substrate, and we refer to this reflection suppression as substrate-mediated Kerker effect. We theoretically compare the silicon and silver coating effectiveness for the thin-film photovoltaic applications. Silver nanoparticles can be more efficient, enabling up to 30% increase of the overall absorbance in semiconductor layer. Nevertheless, silicon coatings allow up to 64% absorbance increase in the narrow band spectral range because of the substrate-mediated Kerker effect, and band position can be effectively tuned by varying the nanoparticles sizes.

Plasmonic and silicon spherical nanoparticle antireflective coatings

PubMed Central

Baryshnikova, K. V.; Petrov, M. I.; Babicheva, V. E.; Belov, P. A.

2016-01-01

Over the last decade, plasmonic antireflecting nanostructures have been extensively studied to be utilized in various optical and optoelectronic systems such as lenses, solar cells, photodetectors, and others. The growing interest to all-dielectric photonics as an alternative optical technology along with plasmonics motivates us to compare antireflective properties of plasmonic and all-dielectric nanoparticle coatings based on silver and crystalline silicon respectively. Our simulation results for spherical nanoparticles array on top of amorphous silicon show that both silicon and silver coatings demonstrate strong antireflective properties in the visible spectral range. For the first time, we show that zero reflectance from the structure with silicon coatings originates from the destructive interference of electric- and magnetic-dipole responses of nanoparticle array with the wave reflected from the substrate, and we refer to this reflection suppression as substrate-mediated Kerker effect. We theoretically compare the silicon and silver coating effectiveness for the thin-film photovoltaic applications. Silver nanoparticles can be more efficient, enabling up to 30% increase of the overall absorbance in semiconductor layer. Nevertheless, silicon coatings allow up to 64% absorbance increase in the narrow band spectral range because of the substrate-mediated Kerker effect, and band position can be effectively tuned by varying the nanoparticles sizes. PMID:26926602

Low work function, stable compound clusters and generation process

DOEpatents

Dinh, Long N.; Balooch, Mehdi; Schildbach, Marcus A.; Hamza, Alex V.; McLean, II, William

2000-01-01

Low work function, stable compound clusters are generated by co-evaporation of a solid semiconductor (i.e., Si) and alkali metal (i.e., Cs) elements in an oxygen environment. The compound clusters are easily patterned during deposition on substrate surfaces using a conventional photo-resist technique. The cluster size distribution is narrow, with a peak range of angstroms to nanometers depending on the oxygen pressure and the Si source temperature. Tests have shown that compound clusters when deposited on a carbon substrate contain the desired low work function property and are stable up to 600.degree. C. Using the patterned cluster containing plate as a cathode baseplate and a faceplate covered with phosphor as an anode, one can apply a positive bias to the faceplate to easily extract electrons and obtain illumination.

Luminescence properties of ZnxMg1-xSe layers

NASA Astrophysics Data System (ADS)

Bala, Waclaw; Firszt, Franciszek; Dzik, Janusz; Gapinski, Adam; Glowacki, Grzegorz

1995-10-01

This work deals with the study of luminescence properties of ZnxMg1-xSe layers prepared by different methods. ZnxMg1-xSe mixed crystal layers were obtained by: (a) thermal diffusion of Mg metal in the temperature range 1050 K - 1200 K into ZnSe single crystal grown by Bridgman method, and (b) epitaxial growth on (001) GaAs and (111) ZnTe substrates by MBE using elemental Zn, Se and Mg sources. The luminescence spectra of ZnxMg1-xSe layers grown on (001) GaAs and (111) ZnTe substrates are dominated by narrow blue and violet emission bands with maxima positioned at about 3.05 - 3.28 eV, 2.88 - 3.04 eV, and 2.81 - 2.705 eV.

Fabrication of Ag nanostructures with remarkable narrow plasmonic resonances by glancing angle deposition

NASA Astrophysics Data System (ADS)

Abbasian, Sara; Moshaii, Ahmad; Vayghan, Nader Sobhkhiz; Nikkhah, Maryam

2018-05-01

Glancing angle deposition (GLAD) is an efficient and inexpensive method to fabricate nanostructures with diverse complexities. However, this method has a limitation in fabrication of plasmonic nanostructures with narrow resonance peaks causing that the GLAD-nanostructures have rarely been used for refractive-index sensing. In this work, we proposed two approaches to overcome this limitation of GLAD and to fabricate Ag nanostructures with narrow plasmonic peaks. In the first approach, we introduce an effective method for seeding modification of the substrate and then growing the Ag nanocolumns on such seeded layer. The optical characterization shows that such pre-seeding of the substrate leads to nearly 40% narrowing of the plasmonic peak. In another approach, the nanostructures are grown by GLAD on a bare substrate and then are annealed at 200-400 °C. Such annealing converts the nanostructures to nanodomes with large inter-particle distances and about 60% reduction of their plasmonic width. Also, the annealing of the nanostructures at 400 °C provides a twofold improvement in figure of merit of sensing of the nanostructures. This improvement makes the GLAD comparative to other expensive alternate methods for fabrication of plasmonic sensors. In addition, the experimental plasmonic peaks are reproduced in a proper numerical simulation for similar nanostructures.

Monitoring substrate enables real-time regulation of a protein localization pathway.

PubMed

Ito, Koreaki; Mori, Hiroyuki; Chiba, Shinobu

2018-06-01

Protein localization machinery supports cell survival and physiology, suggesting the potential importance of its expression regulation. Here, we summarize a remarkable scheme of regulation, which allows real-time feedback regulation of the machinery expression. A class of regulatory nascent polypeptides, called monitoring substrates, undergoes force-sensitive translation arrest. The resulting ribosome stalling on the mRNA then affects mRNA folding to expose the ribosome-binding site of the downstream target gene and upregulate its translation. The target gene encodes a component of the localization machinery, whose physical action against the monitoring substrate leads to arrest cancellation. Thus, this scheme of feedback loop allows the cell to adjust the amount of the machinery to correlate inversely with the effectiveness of the process at a given moment. The system appears to have emerged late in evolution, in which a narrow range of organisms selected a distinct monitoring substrate-machinery combination. Currently, regulatory systems of SecM-SecA, VemP-SecDF2 and MifM-YidC2 are known to occur in different bacterial species.

The ‘Goldilocks’ effect: preservation bias in vertebrate track assemblages

PubMed Central

Falkingham, P. L.; Bates, K. T.; Margetts, L.; Manning, P. L.

2011-01-01

Finite-element analysis was used to investigate the extent of bias in the ichnological fossil record attributable to body mass. Virtual tracks were simulated for four dinosaur taxa of different sizes (Struthiomimus, Tyrannosaurus, Brachiosaurus and Edmontosaurus), in a range of substrate conditions. Outlines of autopodia were generated based upon osteology and published soft-tissue reconstructions. Loads were applied vertically to the feet equivalent to the weight of the animal, and distributed accordingly to fore- and hindlimbs where relevant. Ideal, semi-infinite elastic–plastic substrates displayed a ‘Goldilocks’ quality where only a narrow range of loads could produce tracks, given that small animals failed to indent the substrate, and larger animals would be unable to traverse the area without becoming mired. If a firm subsurface layer is assumed, a more complete assemblage is possible, though there is a strong bias towards larger, heavier animals. The depths of fossil tracks within an assemblage may indicate thicknesses of mechanically distinct substrate layers at the time of track formation, even when the lithified strata appear compositionally homogeneous. This work increases the effectiveness of using vertebrate tracks as palaeoenvironmental indicators in terms of inferring substrate conditions at the time of track formation. Additionally, simulated undertracks are examined, and it is shown that complex deformation beneath the foot may not be indicative of limb kinematics as has been previously interpreted, but instead ridges and undulations at the base of a track may be a function of sediment displacement vectors and pedal morphology. PMID:21233145

Using spectral information in forensic imaging.

PubMed

Miskelly, Gordon M; Wagner, John H

2005-12-20

Improved detection of forensic evidence by combining narrow band photographic images taken at a range of wavelengths is dependent on the substance of interest having a significantly different spectrum from the underlying substrate. While some natural substances such as blood have distinctive spectral features which are readily distinguished from common colorants, this is not true for visualization agents commonly used in forensic science. We now show that it is possible to select reagents with narrow spectral features that lead to increased visibility using digital cameras and computer image enhancement programs even if their coloration is much less intense to the unaided eye than traditional reagents. The concept is illustrated by visualising latent fingermarks on paper with the zinc complex of Ruhemann's Purple, cyanoacrylate-fumed fingerprints with Eu(tta)(3)(phen), and soil prints with 2,6-bis(benzimidazol-2-yl)-4-[4'-(dimethylamino)phenyl]pyridine [BBIDMAPP]. In each case background correction is performed at one or two wavelengths bracketing the narrow absorption or emission band of these compounds. However, compounds with sharp spectral features would also lead to improved detection using more advanced algorithms such as principal component analysis.

Mapping the Substrate Binding Site of Phenylacetone Monooxygenase from Thermobifida fusca by Mutational Analysis▿†

PubMed Central

Dudek, Hanna M.; de Gonzalo, Gonzalo; Torres Pazmiño, Daniel E.; Stępniak, Piotr; Wyrwicz, Lucjan S.; Rychlewski, Leszek; Fraaije, Marco W.

2011-01-01

Baeyer-Villiger monooxygenases catalyze oxidations that are of interest for biocatalytic applications. Among these enzymes, phenylacetone monooxygenase (PAMO) from Thermobifida fusca is the only protein showing remarkable stability. While related enzymes often present a broad substrate scope, PAMO accepts only a limited number of substrates. Due to the absence of a substrate in the elucidated crystal structure of PAMO, the substrate binding site of this protein has not yet been defined. In this study, a structural model of cyclopentanone monooxygenase, which acts on a broad range of compounds, has been prepared and compared with the structure of PAMO. This revealed 15 amino acid positions in the active site of PAMO that may account for its relatively narrow substrate specificity. We designed and analyzed 30 single and multiple mutants in order to verify the role of these positions. Extensive substrate screening revealed several mutants that displayed increased activity and altered regio- or enantioselectivity in Baeyer-Villiger reactions and sulfoxidations. Further substrate profiling resulted in the identification of mutants with improved catalytic properties toward synthetically attractive compounds. Moreover, the thermostability of the mutants was not compromised in comparison to that of the wild-type enzyme. Our data demonstrate that the positions identified within the active site of PAMO, namely, V54, I67, Q152, and A435, contribute to the substrate specificity of this enzyme. These findings will aid in more dedicated and effective redesign of PAMO and related monooxygenases toward an expanded substrate scope. PMID:21724896

High resolution on-chip optical filter array based on double subwavelength grating reflectors

DOE PAGES

Horie, Yu; Arbabi, Amir; Han, Seunghoon; ...

2015-11-05

An optical filter array consisting of vertical narrow-band Fabry-Pèrot (FP) resonators formed by two highly reflective high contrast subwavelength grating mirrors is reported. The filters are designed to cover a wide range of operation wavelengths ( Δλ/λ=5%) just by changing the in-plane grating parameters while the device thickness is maintained constant. In conclusion, operation in the telecom band with transmission efficiencies greater than 40% and quality factors greater than 1,000 are measured experimentally for filters fabricated on the same substrate.

High resolution on-chip optical filter array based on double subwavelength grating reflectors

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

Horie, Yu; Arbabi, Amir; Han, Seunghoon

An optical filter array consisting of vertical narrow-band Fabry-Pèrot (FP) resonators formed by two highly reflective high contrast subwavelength grating mirrors is reported. The filters are designed to cover a wide range of operation wavelengths ( Δλ/λ=5%) just by changing the in-plane grating parameters while the device thickness is maintained constant. In conclusion, operation in the telecom band with transmission efficiencies greater than 40% and quality factors greater than 1,000 are measured experimentally for filters fabricated on the same substrate.

Selectively Plasmon-Enhanced Second-Harmonic Generation from Monolayer Tungsten Diselenide on Flexible Substrates.

PubMed

Wang, Zhuo; Dong, Zhaogang; Zhu, Hai; Jin, Lei; Chiu, Ming-Hui; Li, Lain-Jong; Xu, Qing-Hua; Eda, Goki; Maier, Stefan A; Wee, Andrew T S; Qiu, Cheng-Wei; Yang, Joel K W

2018-02-27

Monolayer two-dimensional transition-metal dichalcogenides (2D TMDCs) exhibit promising characteristics in miniaturized nonlinear optical frequency converters, due to their inversion asymmetry and large second-order nonlinear susceptibility. However, these materials usually have very short light interaction lengths with the pump laser because they are atomically thin, such that second-harmonic generation (SHG) is generally inefficient. In this paper, we fabricate a judiciously structured 150 nm-thick planar surface consisting of monolayer tungsten diselenide and sub-20 nm-wide gold trenches on flexible substrates, reporting ∼7000-fold SHG enhancement without peak broadening or background in the spectra as compared to WSe 2 on as-grown sapphire substrates. Our proof-of-concept experiment yields effective second-order nonlinear susceptibility of 2.1 × 10 4 pm/V. Three orders of magnitude enhancement is maintained with pump wavelength ranging from 800 to 900 nm, breaking the limitation of narrow pump wavelength range for cavity-enhanced SHG. In addition, SHG amplitude can be dynamically controlled via selective excitation of the lateral gap plasmon by rotating the laser polarization. Such a fully open, flat, and ultrathin profile enables a great variety of functional samples with high SHG from one patterned silicon substrate, favoring scalable production of nonlinear converters. The surface accessibility also enables integration with other optical components for information processing in an ultrathin and flexible form.

Growth behavior of carbon nanotubes on multilayered metal catalyst film in chemical vapor deposition

NASA Astrophysics Data System (ADS)

Cui, H.; Eres, G.; Howe, J. Y.; Puretkzy, A.; Varela, M.; Geohegan, D. B.; Lowndes, D. H.

2003-06-01

The temperature and time dependences of carbon nanotube (CNT) growth by chemical vapor deposition are studied using a multilayered Al/Fe/Mo catalyst on silicon substrates. Within the 600-1100 °C temperature range of these studies, narrower temperature ranges were determined for the growth of distinct types of aligned multi-walled CNTs and single-walled CNTs by using high-resolution transmission electron microscopy and Raman spectroscopy. At 900 °C, in contrast to earlier work, double-walled CNTs are found more abundant than single-walled CNTs. Defects also are found to accumulate faster than the ordered graphitic structure if the growth of CNTs is extended to long durations.

Optical filters for UV to near IR space applications

NASA Astrophysics Data System (ADS)

Begou, T.; Krol, H.; Hecquet, Christophe; Bondet, C.; Lumeau, J.; Grèzes-Besset, C.; Lequime, M.

2017-11-01

We present hereafter the results on the fabrication of complex optical filters within the Institut Fresnel in close collaboration with CILAS. Bandpass optical filters dedicated to astronomy and space applications, with central wavelengths ranging from ultraviolet to near infrared, were deposited on both sides of glass substrates with performances in very good congruence with theoretical designs. For these applications, the required functions are particularly complex as they must present a very narrow bandwidth as well as a high level of rejection over a broad spectral range. In addition to those severe optical performances, insensitivity to environmental conditions is necessary. For this purpose, robust solutions with particularly stable performances have to be proposed.

Use of CdS quantum dot-functionalized cellulose nanocrystal films for anti-counterfeiting applications

NASA Astrophysics Data System (ADS)

Chen, L.; Lai, C.; Marchewka, R.; Berry, R. M.; Tam, K. C.

2016-07-01

Structural colors and photoluminescence have been widely used for anti-counterfeiting and security applications. We report for the first time the use of CdS quantum dot (QD)-functionalized cellulose nanocrystals (CNCs) as building blocks to fabricate nanothin films via layer-by-layer (LBL) self-assembly for anti-counterfeiting applications. Both negatively- and positively-charged CNC/QD nanohybrids with a high colloidal stability and a narrow particle size distribution were prepared. The controllable LBL coating process was characterized by scanning electron microscopy and ellipsometry. The rigid structure of CNCs leads to nanoporous structured films on poly(ethylene terephthalate) (PET) substrates with high transmittance (above 70%) over the entire range of visible light and also resulted in increased hydrophilicity (contact angles of ~40 degrees). Nanothin films on PET substrates showed good flexibility and enhanced stability in both water and ethanol. The modified PET films with structural colors from thin-film interference and photoluminescence from QDs can be used in anti-counterfeiting applications.Structural colors and photoluminescence have been widely used for anti-counterfeiting and security applications. We report for the first time the use of CdS quantum dot (QD)-functionalized cellulose nanocrystals (CNCs) as building blocks to fabricate nanothin films via layer-by-layer (LBL) self-assembly for anti-counterfeiting applications. Both negatively- and positively-charged CNC/QD nanohybrids with a high colloidal stability and a narrow particle size distribution were prepared. The controllable LBL coating process was characterized by scanning electron microscopy and ellipsometry. The rigid structure of CNCs leads to nanoporous structured films on poly(ethylene terephthalate) (PET) substrates with high transmittance (above 70%) over the entire range of visible light and also resulted in increased hydrophilicity (contact angles of ~40 degrees). Nanothin films on PET substrates showed good flexibility and enhanced stability in both water and ethanol. The modified PET films with structural colors from thin-film interference and photoluminescence from QDs can be used in anti-counterfeiting applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr03039d

Selective epitaxy using the gild process

DOEpatents

Weiner, Kurt H.

1992-01-01

The present invention comprises a method of selective epitaxy on a semiconductor substrate. The present invention provides a method of selectively forming high quality, thin GeSi layers in a silicon circuit, and a method for fabricating smaller semiconductor chips with a greater yield (more error free chips) at a lower cost. The method comprises forming an upper layer over a substrate, and depositing a reflectivity mask which is then removed over selected sections. Using a laser to melt the unmasked sections of the upper layer, the semiconductor material in the upper layer is heated and diffused into the substrate semiconductor material. By varying the amount of laser radiation, the epitaxial layer is formed to a controlled depth which may be very thin. When cooled, a single crystal epitaxial layer is formed over the patterned substrate. The present invention provides the ability to selectively grow layers of mixed semiconductors over patterned substrates such as a layer of Ge.sub.x Si.sub.1-x grown over silicon. Such a process may be used to manufacture small transistors that have a narrow base, heavy doping, and high gain. The narrowness allows a faster transistor, and the heavy doping reduces the resistance of the narrow layer. The process does not require high temperature annealing; therefore materials such as aluminum can be used. Furthermore, the process may be used to fabricate diodes that have a high reverse breakdown voltage and a low reverse leakage current.

Specificity of a protein-protein interface: local dynamics direct substrate recognition of effector caspases.

PubMed

Fuchs, Julian E; von Grafenstein, Susanne; Huber, Roland G; Wallnoefer, Hannes G; Liedl, Klaus R

2014-04-01

Proteases are prototypes of multispecific protein-protein interfaces. Proteases recognize and cleave protein and peptide substrates at a well-defined position in a substrate binding groove and a plethora of experimental techniques provide insights into their substrate recognition. We investigate the caspase family of cysteine proteases playing a key role in programmed cell death and inflammation, turning caspases into interesting drug targets. Specific ligand binding to one particular caspase is difficult to achieve, as substrate specificities of caspase isoforms are highly similar. In an effort to rationalize substrate specificity of two closely related caspases, we investigate the substrate promiscuity of the effector Caspases 3 and 7 by data mining (cleavage entropy) and by molecular dynamics simulations. We find a strong correlation between binding site rigidity and substrate readout for individual caspase subpockets explaining more stringent substrate readout of Caspase 7 via its narrower conformational space. Caspase 3 subpockets S3 and S4 show elevated local flexibility explaining the more unspecific substrate readout of that isoform in comparison to Caspase 7. We show by in silico exchange mutations in the S3 pocket of the proteases that a proline residue in Caspase 7 contributes to the narrowed conformational space of the binding site. These findings explain the substrate specificities of caspases via a mechanism of conformational selection and highlight the crucial importance of binding site local dynamics in substrate recognition of proteases. Proteins 2014; 82:546-555. © 2013 Wiley Periodicals, Inc. Copyright © 2013 The Authors Proteins: Structure, Function, and Bioinformatics Published by Wiley Periodicals, Inc.

Self-organized micro-holes on titania based sol-gel films under continuous direct writing with a continuous wave ultraviolet laser

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

Bakhti, S.; Destouches, N.; Gamet, E.

The microstructuring of titania based sol-gel films is investigated by direct writing with a continuous wave ultraviolet laser beam emitting at 244 nm. Depending on the exposure conditions, the films exhibit a volume expansion, a volume shrinkage, a self-shaped delamination, or are damaged. This paper is mainly focused on the regime where spontaneous local delamination occurs, which corresponds to a narrow range of laser irradiances and writing speeds. In this regime, self-organized round-shape micro-holes opened on the substrate are generated.

Narrow energy band gap gallium arsenide nitride semi-conductors and an ion-cut-synthesis method for producing the same

DOEpatents

Weng, Xiaojun; Goldman, Rachel S.

2006-06-06

A method for forming a semi-conductor material is provided that comprises forming a donor substrate constructed of GaAs, providing a receiver substrate, implanting nitrogen into the donor substrate to form an implanted layer comprising GaAs and nitrogen. The implanted layer is bonded to the receiver substrate and annealed to form GaAsN and nitrogen micro-blisters in the implanted layer. The micro-blisters allow the implanted layer to be cleaved from the donor substrate.

Integrating gastrocnemius force-length properties, in vivo activation and operating lengths reveals how Anolis deal with ecological challenges.

PubMed

Foster, Kathleen L; Higham, Timothy E

2017-03-01

A central question in biology is how animals successfully behave under complex natural conditions. Although changes in locomotor behaviour, motor control and force production in relation to incline are commonly examined, a wide range of other factors, including a range of perch diameters, pervades arboreal habitats. Moving on different substrate diameters requires considerable alteration of body and limb posture, probably causing significant shifts in the lengths of the muscle-tendon units powering locomotion. Thus, how substrate shape impacts in vivo muscle function remains an important but neglected question in ecophysiology. Here, we used high-speed videography, electromyography, in situ contractile experiments and morphology to examine gastrocnemius muscle function during arboreal locomotion in the Cuban knight anole, Anolis equestris The gastrocnemius contributes more to the propulsive effort on broad surfaces than on narrow surfaces. Surprisingly, substrate inclination affected the relationship between the maximum potential force and fibre recruitment; the trade-off that was present between these variables on horizontal surfaces became a positive relationship on inclined surfaces. Finally, the biarticular nature of the gastrocnemius allows it to generate force isometrically, regardless of substrate diameter and incline, despite the fact that the tendons are incapable of stretching during cyclical locomotion. Our results emphasize the importance of considering ecology and muscle function together, and the necessity of examining both mechanical and physiological properties of muscles to understand how animals move in their environment. © 2017. Published by The Company of Biologists Ltd.

Temporal behavior of RHEED intensity oscillations during molecular beam epitaxial growth of GaAs and AlGaAs on (111)B GaAs substrates

NASA Astrophysics Data System (ADS)

Yen, Ming Y.; Haas, T. W.

1990-10-01

We present the temporal behavior of intensity oscillations in reflection high-energy electron diffraction (RHEED) during molecular beam epitaxial (MBE) growth of GaAs and A1GaAs on (1 1 1)B GaAs substrates. The RHEED intensity oscillations were examined as a function of growth parameters in order to provide the insight into the dynamic characteristics and to identify the optimal condition for the two-dimensional layer-by-layer growth. The most intense RHEED oscillation was found to occur within a very narrow temperature range which seems to optimize the surface migration kinetics of the arriving group III elements and the molecular dissodiative reaction of the group V elements. The appearance of an initial transient of the intensity upon commencement of the growth and its implications are described.

Voltage control of magnetism in NiZn ferrite/mica/PMNPT heterostructure with giant tunability and narrow linewidth

NASA Astrophysics Data System (ADS)

Wang, Xinjun; Chen, Yunpeng; Chen, Huaihao; Gao, Yuan; He, Yifan; Li, Menghui; Lin, Hwaider; Sun, Neville; Sun, Nian

2018-05-01

Recently, large magnetoelectric coupling of a spinel/piezoelectric heterostructure has been reported. However, the linewidth of the spinel is very large due to lattice mismatch when ferrite is directly deposited on piezoelectric substrates. This indicates a large magnetic loss, which impedes the spinel/piezoelectric heterostructure from useful device applications. Mica is a well-known 2D material, which can be split manually layer by layer without the substrate clamping effect. In this report, NiZn ferrite was deposited on a mica substrate by a spin-spray deposition technique. Spin-spray deposition is a wet chemical synthesis technique involving several chemical reactions for generating high-quality crystalline spinel ferrite films with various compositions directly from an aqueous solution. The thickness of ferrite is 2 μm, and the linewidth of the ferromagnetic resonance (FMR) is 115 Oe which is suitable for RF/microwave devices. The large FMR field tuning of 605 Oe was observed in NiZn ferrite/mica/PMN-PT heterostructures with minimal substrate clamping effect by reducing the thickness of the mica substrate. These multiferroic heterostructures exhibiting combined giant magnetoelectric coupling and narrow ferromagnetic resonance linewidth offer great opportunities for flexible RF magnetic devices.

InP Based Ternary And Quaternary Thin Film Structures On Large Areas Grown By LP-MOVPE

NASA Astrophysics Data System (ADS)

Schmitz, D.; Strauch, , G.; Jurgensen, H.; Heyen, M.; Harde, P.

1989-11-01

Using low pressure MOVPE and higher linear flow velocities high purity GalnAs/lnP and GalnAsP heterostructures can be prepared. Excellent homogeneity in thickness, composition, and doping on a 2" InP substrate can be realized by this approach for optimized conditions. The low growth rates required for the deposition of very narrow well structures are achieved by selecting reduced pressures of the group III and group V compounds used for deposition. The method yields structures with high electron mobilities of the two dimensional electron gas in the well and narrow PL (i.e. 2.2 meV for 20 nm wells) line widths, which is indicative of low impurity incorporation and abrupt heterojunctions. The observed energy shifts (up to 528 meV) demonstrate the large range of bandgap variation attainable by this method. A study of dopant incorporation shows, that Zn yields steep transitions in InGaAs.

Buried nanoantenna arrays: versatile antireflection coating.

PubMed

Kabiri, Ali; Girgis, Emad; Capasso, Federico

2013-01-01

Reflection is usually a detrimental phenomenon in many applications such as flat-panel-displays, solar cells, photodetectors, infrared sensors, and lenses. Thus far, to control and suppress the reflection from a substrate, numerous techniques including dielectric interference coatings, surface texturing, adiabatic index matching, and scattering from plasmonic nanoparticles have been investigated. A new technique is demonstrated to manage and suppress reflection from lossless and lossy substrates. It provides a wider flexibility in design versus previous methods. Reflection from a surface can be suppressed over a narrowband, wideband, or multiband frequency range. The antireflection can be dependent or independent of the incident wave polarization. Moreover, antireflection at a very wide incidence angle can be attained. The reflection from a substrate is controlled by a buried nanoantenna array, a structure composed of (1) a subwavelength metallic array and (2) a dielectric cover layer referred to as a superstrate. The material properties and thickness of the superstrate and nanoantennas' geometry and periodicity control the phase and intensity of the wave circulating inside the superstrate cavity. A minimum reflectance of 0.02% is achieved in various experiments in the mid-infrared from a silicon substrate. The design can be integrated in straightforward way in optical devices. The proposed structure is a versatile AR coating to optically impedance matches any substrate to free space in selected any narrow and broadband spectral response across the entire visible and infrared spectrum.

Dynamic locomotor capabilities revealed by early dinosaur trackmakers from southern Africa.

PubMed

Wilson, Jeffrey A; Marsicano, Claudia A; Smith, Roger M H

2009-10-06

A new investigation of the sedimentology and ichnology of the Early Jurassic Moyeni tracksite in Lesotho, southern Africa has yielded new insights into the behavior and locomotor dynamics of early dinosaurs. The tracksite is an ancient point bar preserving a heterogeneous substrate of varied consistency and inclination that includes a ripple-marked riverbed, a bar slope, and a stable algal-matted bar top surface. Several basal ornithischian dinosaurs and a single theropod dinosaur crossed its surface within days or perhaps weeks of one another, but responded to substrate heterogeneity differently. Whereas the theropod trackmaker accommodated sloping and slippery surfaces by gripping the substrate with its pedal claws, the basal ornithischian trackmakers adjusted to the terrain by changing between quadrupedal and bipedal stance, wide and narrow gauge limb support (abduction range = 31 degrees ), and plantigrade and digitigrade foot posture. The locomotor adjustments coincide with changes in substrate consistency along the trackway and appear to reflect 'real time' responses to a complex terrain. It is proposed that these responses foreshadow important locomotor transformations characterizing the later evolution of the two main dinosaur lineages. Ornithischians, which shifted from bipedal to quadrupedal posture at least three times in their evolutionary history, are shown to have been capable of adopting both postures early in their evolutionary history. The substrate-gripping behavior demonstrated by the early theropod, in turn, is consistent with the hypothesized function of pedal claws in bird ancestors.

Motor-substrate interactions in mycoplasma motility explains non-Arrhenius temperature dependence.

PubMed

Chen, Jing; Neu, John; Miyata, Makoto; Oster, George

2009-12-02

Mycoplasmas exhibit a novel, substrate-dependent gliding motility that is driven by approximately 400 "leg" proteins. The legs interact with the substrate and transmit the forces generated by an assembly of ATPase motors. The velocity of the cell increases linearly by nearly 10-fold over a narrow temperature range of 10-40 degrees C. This corresponds to an Arrhenius factor that decreases from approximately 45 k(B)T at 10 degrees C to approximately 10 k(B)T at 40 degrees C. On the other hand, load-velocity curves at different temperatures extrapolate to nearly the same stall force, suggesting a temperature-insensitive force-generation mechanism near stall. In this article, we propose a leg-substrate interaction mechanism that explains the intriguing temperature sensitivity of this motility. The large Arrhenius factor at low temperature comes about from the addition of many smaller energy barriers arising from many substrate-binding sites at the distal end of the leg protein. The Arrhenius dependence attenuates at high temperature due to two factors: 1), the reduced effective multiplicity of energy barriers intrinsic to the multiple-site binding mechanism; and 2), the temperature-sensitive weakly facilitated leg release that curtails the power stroke. The model suggests an explanation for the similar steep, sub-Arrhenius temperature-velocity curves observed in many molecular motors, such as kinesin and myosin, wherein the temperature behavior is dominated not by the catalytic biochemistry, but by the motor-substrate interaction.

Motor-Substrate Interactions in Mycoplasma Motility Explains Non-Arrhenius Temperature Dependence

PubMed Central

Chen, Jing; Neu, John; Miyata, Makoto; Oster, George

2009-01-01

Abstract Mycoplasmas exhibit a novel, substrate-dependent gliding motility that is driven by ∼400 “leg” proteins. The legs interact with the substrate and transmit the forces generated by an assembly of ATPase motors. The velocity of the cell increases linearly by nearly 10-fold over a narrow temperature range of 10–40°C. This corresponds to an Arrhenius factor that decreases from ∼45 kBT at 10°C to ∼10 kBT at 40°C. On the other hand, load-velocity curves at different temperatures extrapolate to nearly the same stall force, suggesting a temperature-insensitive force-generation mechanism near stall. In this article, we propose a leg-substrate interaction mechanism that explains the intriguing temperature sensitivity of this motility. The large Arrhenius factor at low temperature comes about from the addition of many smaller energy barriers arising from many substrate-binding sites at the distal end of the leg protein. The Arrhenius dependence attenuates at high temperature due to two factors: 1), the reduced effective multiplicity of energy barriers intrinsic to the multiple-site binding mechanism; and 2), the temperature-sensitive weakly facilitated leg release that curtails the power stroke. The model suggests an explanation for the similar steep, sub-Arrhenius temperature-velocity curves observed in many molecular motors, such as kinesin and myosin, wherein the temperature behavior is dominated not by the catalytic biochemistry, but by the motor-substrate interaction. PMID:19948122

Free-Flow Zone Electrophoresis of Peptides and Proteins in PDMS Microchip for Narrow pI Range Sample Prefractionation Coupled with Mass Spectrometry

PubMed Central

Song, Yong-Ak; Chan, Michael; Celio, Chris; Tannenbaum, Steven R.; Wishnok, John S.; Han, Jongyoon

2010-01-01

In this paper, we are evaluating the strategy of sorting peptides / proteins based on the charge to mass without resorting to ampholytes and / or isoelectric focusing, using a single- and two-step free-flow zone electrophoresis. We developed a simple fabrication method to create a salt bridge for free-flow zone electrophoresis in PDMS chips by surface printing a hydrophobic layer on a glass substrate. Since the surface-printed hydrophobic layer prevents plasma bonding between the PDMS chip and the substrate, an electrical junction gap can be created for free-flow zone electrophoresis. With this device, we demonstrated a separation of positive and negative peptides and proteins at a given pH in standard buffer systems, and validated the sorting result with LC/MS. Furthermore, we coupled two sorting steps via off-chip titration, and isolated peptides within specific pI ranges from sample mixtures, where the pI range was simply set by the pH values of the buffer solutions. This free-flow zone electrophoresis sorting device, with its simplicity of fabrication, and a sorting resolution of 0.5 pH unit, can potentially be a high-throughput sample fractionation tool for targeted proteomics using LC/MS. PMID:20163146

Radiative transfer modeling of dust-coated Pancam calibration target materials: Laboratory visible/near-infrared spectrogoniometry

USGS Publications Warehouse

Johnson, J. R.; Sohl-Dickstein, J.; Grundy, W.M.; Arvidson, R. E.; Bell, J.F.; Christensen, P.R.; Graff, T.; Guinness, E.A.; Kinch, K.; Morris, Robert; Shepard, M.K.

2006-01-01

Laboratory visible/near-infrared multispectral observations of Mars Exploration Rover Pancam calibration target materials coated with different thicknesses of Mars spectral analog dust were acquired under variable illumination geometries using the Bloomsburg University Goniometer. The data were fit with a two-layer radiative transfer model that combines a Hapke formulation for the dust with measured values of the substrate interpolated using a He-Torrance approach. We first determined the single-scattering albedo, phase function, opposition effect width, and amplitude for the dust using the entire data set (six coating thicknesses, three substrates, four wavelengths, and phase angles 3??-117??). The dust exhibited single-scattering albedo values similar to other Mars analog soils and to Mars Pathfinder dust and a dominantly forward scattering behavior whose scattering lobe became narrower at longer wavelengths. Opacity values for each dust thickness corresponded well to those predicted from the particles sizes of the Mars analog dust. We then restricted the number of substrates, dust thicknesses, and incidence angles input to the model. The results suggest that the dust properties are best characterized when using substrates whose reflectances are brighter and darker than those of the deposited dust and data that span a wide range of dust thicknesses. The model also determined the dust photometric properties relatively well despite limitations placed on the range of incidence angles. The model presented here will help determine the photometric properties of dust deposited on the MER rovers and to track the multiple episodes of dust deposition and erosion that have occurred at both landing sites. Copyright 2006 by the American Geophysical Union.

Ordered alternating binary polymer nanodroplet array by sequential spin dewetting.

PubMed

Bhandaru, Nandini; Das, Anuja; Salunke, Namrata; Mukherjee, Rabibrata

2014-12-10

We report a facile technique for fabricating an ordered array of nearly equal-sized mesoscale polymer droplets of two constituent polymers (polystyrene, PS and poly(methyl methacrylate), PMMA) arranged in an alternating manner on a topographically patterned substrate. The self-organized array of binary polymers is realized by sequential spin dewetting. First, a dilute solution of PMMA is spin-dewetted on a patterned substrate, resulting in an array of isolated PMMA droplets arranged along the substrate grooves due to self-organization during spin coating itself. The sample is then silanized with octadecyltrichlorosilane (OTS), and subsequently, a dilute solution of PS is spin-coated on to it, which also undergoes spin dewetting. The spin-dewetted PS drops having a size nearly equal to the pre-existing PMMA droplets position themselves between two adjacent PMMA drops under appropriate conditions, forming an alternating binary polymer droplet array. The alternating array formation takes place for a narrow range of solution concentration for both the polymers and depends on the geometry of the substrate. The size of the droplets depends on the extent of confinement, and droplets as small as 100 nm can be obtained by this method, on a suitable template. The findings open up the possibility of creating novel surfaces having ordered multimaterial domains with a potential multifunctional capability.

Single-mode surface plasmon distributed feedback lasers.

PubMed

Karami Keshmarzi, Elham; Tait, R Niall; Berini, Pierre

2018-03-29

Single-mode surface plasmon distributed feedback (DFB) lasers are realized in the near infrared using a two-dimensional non-uniform long-range surface plasmon polariton structure. The surface plasmon mode is excited onto a 20 nm-thick, 1 μm-wide metal stripe (Ag or Au) on a silica substrate, where the stripe is stepped in width periodically, forming a 1st order Bragg grating. Optical gain is provided by optically pumping a 450 nm-thick IR-140 doped PMMA layer as the top cladding, which covers the entire length of the Bragg grating, thus creating a DFB laser. Single-mode lasing peaks of very narrow linewidth were observed for Ag and Au DFBs near 882 nm at room temperature. The narrow linewidths are explained by the low spontaneous emission rate into the surface plasmon lasing mode as well as the high quality factor of the DFB structure. The lasing emission is exclusively TM polarized. Kinks in light-light curves accompanied by spectrum narrowing were observed, from which threshold pump power densities can be clearly identified (0.78 MW cm-2 and 1.04 MW cm-2 for Ag and Au DFB lasers, respectively). The Schawlow-Townes linewidth for our Ag and Au DFB lasers is estimated and very narrow linewidths are predicted for the lasers. The lasers are suitable as inexpensive, recyclable and highly coherent sources of surface plasmons, or for integration with other surface plasmon elements of similar structure.

Lasing characteristics of InAs quantum dot laers on InP substrate

NASA Technical Reports Server (NTRS)

Yang, Y.; Qiu, D.; Uhl, R.; Chacon, R.

2003-01-01

Single-stack InAs self-assembled quantum dots (QD) lasers based on InP substrate have been grown by metalorganic vapor phase epitaxy. The narrow ridge waveguide lasers lased up to 260 K in continuous wave operation, and near room temperature in pulsed mode, with wavelengths between 1.59 to 1.74 mu m.

Age-0 Lost River sucker and shortnose sucker nearshore habitat use in Upper Klamath Lake, Oregon: A patch occupancy approach

USGS Publications Warehouse

Burdick, S.M.; Hendrixson, H.A.; VanderKooi, S.P.

2008-01-01

We examined habitat use by age-0 Lost River suckers Deltistes luxatus and shortnose suckers Chasmistes brevirostris over six substrate classes and in vegetated and nonvegetated areas of Upper Klamath Lake, Oregon. We used a patch occupancy approach to model the effect of physical habitat and water quality conditions on habitat use. Our models accounted for potential inconsistencies in detection probability among sites and sampling occasions as a result of differences in fishing gear types and techniques, habitat characteristics, and age-0 fish size and abundance. Detection probability was greatest during mid- to late summer, when water temperatures were highest and age-0 suckers were the largest. The proportion of sites used by age-0 suckers was inversely related to depth (range = 0.4-3.0 m), particularly during late summer. Age-0 suckers were more likely to use habitats containing small substrate (64 mm) and habitats with vegetation than those without vegetation. Relatively narrow ranges in dissolved oxygen, temperature, and pH prevented us from detecting effects of these water quality features on age-0 sucker nearshore habitat use.

Surface study of graphene ink for fine solid lines printed on BOPP Substrate in micro-flexographic printing using XPS analysis technique

NASA Astrophysics Data System (ADS)

Hassan, S.; Yusof, M. S.; Embong, Z.; Ding, S.; Maksud, M. I.

2018-01-01

Micro-flexographic printing is a combination of flexography and micro-contact printing technique. It is a new printing method for fine solid lines printing purpose. Graphene material has been used as depositing agent or printing ink in other printing technique like inkjet printing. This graphene ink is printed on biaxially oriented polypropylene (BOPP) by using Micro-flexographic printing technique. The choose of graphene as a printing ink is due to its wide application in producing electronic and micro-electronic devices such as Radio-frequency identification (RFID) and printed circuit board. The graphene printed on the surface of BOPP substrate was analyzed using X-Ray Photoelectron Spectroscopy (XPS). The positions for each synthetic component in the narrow scan are referred to the electron binding energy (eV). This research is focused on two narrow scan regions which are C 1s and O 1s. Further discussion of the narrow scan spectrum will be explained in detail. From the narrow scan analysis, it is proposed that from the surface adhesive properties of graphene, it is suitable as an alternative printing ink medium for Micro-flexographic printing technique in printing multiple fine solid lines at micro to nano scale feature.

Background correction in forensic photography. I. Photography of blood under conditions of non-uniform illumination or variable substrate color--theoretical aspects and proof of concept.

PubMed

Wagner, John H; Miskelly, Gordon M

2003-05-01

The combination of photographs taken at two or three wavelengths at and bracketing an absorbance peak indicative of a particular compound can lead to an image with enhanced visualization of the compound. This procedure works best for compounds with absorbance bands that are narrow compared with "average" chromophores. If necessary, the photographs can be taken with different exposure times to ensure that sufficient light from the substrate is detected at all three wavelengths. The combination of images is readily performed if the images are obtained with a digital camera and are then processed using an image processing program. Best results are obtained if linear images at the peak maximum, at a slightly shorter wavelength, and at a slightly longer wavelength are used. However, acceptable results can also be obtained under many conditions if non-linear photographs are used or if only two wavelengths (one of which is at the peak maximum) are combined. These latter conditions are more achievable by many "mid-range" digital cameras. Wavelength selection can either be by controlling the illumination (e.g., by using an alternate light source) or by use of narrow bandpass filters. The technique is illustrated using blood as the target analyte, using bands of light centered at 395, 415, and 435 nm. The extension of the method to detection of blood by fluorescence quenching is also described.

Bilayer Metasurfaces for Dual- and Broadband Optical Antireflection

DOE PAGES

Huang, Li; Chang, Chun-Chieh; Zeng, Beibei; ...

2017-08-09

Optical antireflection has long been pursued for a wide range of applications, but existing approaches encounter issues in the performance, bandwidth, and structure complexity, particularly in the long-wavelength infrared regime. Here we present the demonstration of bilayer metasurfaces that accomplish dual- and broadband optical antireflection in the terahertz and mid-infrared spectral ranges. Furthermore, by simply tailoring the structural geometry and dimensions, here we show that subwavelength metal/dielectric structures enable dramatic reduction of Fresnel reflection and significant enhancement of transmission at a substrate surface, operating either at two discrete narrow bands or over a broad bandwidth up to 28%. We alsomore » use a semianalytical interference model to interpret the obtained results, in which we find that the dispersion of the constituent structures plays a critical role in achieving the observed broadband optical antireflection.« less

Growth and Properties of Lattice Matched GaAsSbN Epilayer on GaAs for Solar Cell Applications

NASA Technical Reports Server (NTRS)

Bharatan, Sudhakar; Iyer, Shanthi; Matney, Kevin; Collis, Ward J.; Nunna Kalyan; Li, Jia; Wu, Liangjin; McGuire, Kristopher; McNeil, Laurie E.

2006-01-01

The growth and properties of GaAsSbN single quantum wells (SQWs) are investigated in this work. The heterostructures were grown on GaAs substrates in an elemental solid source molecular beam epitaxy (MBE) system assisted with a RF plasma nitrogen source. A systematic study has been carried out to determine the influence of various growth conditions, such as the growth temperature and the source shutter-opening sequence, on the quality of the grown layers and the incorporation of N and Sb. The effects of ex situ and in situ annealing under As overpressure on the optical properties of the layers have also been investigated. Substrate temperature in the range of 450-470 C was found to be optimum. Simultaneous opening of the source shutters was found to yield sharper QW interfaces. N and Sb incorporations were found to depend strongly upon substrate temperatures and source shutter opening sequences. A significant increase in PL intensity with a narrowing of PL line shape and blue shift in emission energy were observed on annealing the GaAsSbN/GaAs SQW, with in situ annealing under As overpressure providing better results, compared to ex situ annealing.

Measurements of the absorption coefficient of stratospheric aerosols

NASA Technical Reports Server (NTRS)

Ogren, J. A.; Ahlquist, N. C.; Clarke, A. D.; Charlson, R. J.

1981-01-01

The absorption coefficients of stratospheric aerosols are measured using a variation on the integrating plate method. The technique is based on the decrease in the transparency of a substrate when an absorbing aerosol is deposited on it. A Lambert scatterer is placed behind the substrate to integrate forward scattered light and minimize the effect of scattering on the measurement. The low pressure in the stratosphere is used for the direct impaction of particles onto a narrow strip of opal glass. The eight samples collected had a median value of 4 x 10 to the -9th m with an uncertainty of + or - 5 x 10 to the -9th m. If this absorption is due to graphitic carbon, then its concentration is estimated at about 0.4 ng/cu m, or about 0.25% of the total aerosol mass concentration. Estimates of the aerosol scattering coefficients based on satellite extinction inversions result in an aerosol single-scattering albedo in the range of 0.96-1.0.

Terahertz radiation in graphene hyperbolic medium excited by an electric dipole.

PubMed

Feng, Xiaodong; Gong, Sen; Zhong, Renbin; Zhao, Tao; Hu, Min; Zhang, Chao; Liu, Shenggang

2018-03-01

In this Letter, the enhanced and directional radiation in a wide terahertz (THz) frequency range in a graphene hyperbolic medium excited by an electric dipole is presented. The numerical simulations and theoretical analyses indicate that the enhanced radiation comes from the strong surface plasmon couplings in the graphene hyperbolic medium, consisting of alternative graphene and dielectric substrate layers. The simulation results also show that the peak power flow of the enhanced THz radiation in the graphene hyperbolic medium is dramatically enhanced by more than 1 order of magnitude over that in a general medium within a certain distance from the dipole, and the electromagnetic fields are strongly concentrated in a narrow angle. Also, the radiation fields can be manipulated, and the fields' angular distributions can be tuned by adjusting the dielectric permittivity and thickness of the substrates, and the chemical potential of graphene. Accordingly, it provides a good opportunity for developing miniature, integratable, high-power-density, and tunable radiation sources in the THz band at room temperature.

A metal-insulator transition study of VO 2 thin films grown on sapphire substrates

DOE PAGES

Yu, Shifeng; Wang, Shuyu; Lu, Ming; ...

2017-12-15

In this paper, vanadium thin films were deposited on sapphire substrates by DC magnetron sputtering and then oxidized in a tube furnace filled with oxygen under different temperatures and oxygen flow rates. The significant influence of the oxygen flow rate and oxidation temperature on the electrical and structural properties of the vanadium oxide thin films were investigated systematically. It shows the pure vanadium dioxide (VO 2) state can only be obtained in a very narrow temperature and oxygen flow rate range. The resistivity change during the metal-insulator transition varies from 0.2 to 4 orders of magnitude depending on the oxidationmore » condition. Large thermal hysteresis during the metal-insulator phase transition was observed during the transition compared to the results in literature. Proper oxidation conditions can significantly reduce the thermal hysteresis. Finally, the fabricated VO 2 thin films showed the potential to be applied in the development of electrical sensors and other smart devices.« less

Growth characteristics of (100)HgCdTe layers in low-temperature MOVPE with ditertiarybutyltelluride

NASA Astrophysics Data System (ADS)

Yasuda, K.; Hatano, H.; Ferid, T.; Minamide, M.; Maejima, T.; Kawamoto, K.

1996-09-01

Low-temperature growth of (100)HgCdTe (MCT) layers in MOVPE has been studied using ditertiarybutyltelluride (DtBTe), dimethylcadmium (DMCd), and elementary mercury as precursors. MCT layers were grown at 275°C on (100)GaAs substrates. Growths were carried out in a vertical growth cell which has a narrow spacing between the substrate and cell ceiling. Using the growth cell, the Cd-composition ( x) of MCT layers was controlled over a wide range from 0 to 0.98 by the DMCd flow. The growth rate of the MCT layers was constant at 5 μm h -1 for the increased DMCd flow. Preferential Cd-incorporation into MCT layers and an increase of the growth rate were observed in the presence of mercury vapor. The growth characteristics were considered to be due to the alkyl-exchange reaction between DMCd and mercury. The electrical properties and crystallinity of grown layers were also evaluated, which showed that layers with high quality can be grown at 275°C.

Electrical characterizations of MIS structures based on variable-gap n(p)-HgCdTe grown by MBE on Si(0 1 3) substrates

NASA Astrophysics Data System (ADS)

Voitsekhovskii, A. V.; Nesmelov, S. N.; Dzyadukh, S. M.; Varavin, V. S.; Dvoretskii, S. A.; Mikhailov, N. N.; Yakushev, M. V.; Sidorov, G. Yu.

2017-12-01

Metal-insulator-semiconductor (MIS) structures based on n(p)-Hg1-xCdxTe (x = 0.22-0.40) with near-surface variable-gap layers were grown by the molecular-beam epitaxy (MBE) technique on the Si (0 1 3) substrates. Electrical properties of MIS structures were investigated experimentally at various temperatures (9-77 K) and directions of voltage sweep. The ;narrow swing; technique was used to determine the spectra of fast surface states with the exception of hysteresis effects. It is established that the density of fast surface states at the MCT/Al2O3 interface at a minimum does not exceed 3 × 1010 eV-1 × cm-2. For MIS structures based on n-MCT/Si(0 1 3), the differential resistance of the space-charge region in strong inversion mode in the temperature range 50-90 K is limited by the Shockley-Read-Hall generation in the space-charge region.

Use of CdS quantum dot-functionalized cellulose nanocrystal films for anti-counterfeiting applications.

PubMed

Chen, L; Lai, C; Marchewka, R; Berry, R M; Tam, K C

2016-07-21

Structural colors and photoluminescence have been widely used for anti-counterfeiting and security applications. We report for the first time the use of CdS quantum dot (QD)-functionalized cellulose nanocrystals (CNCs) as building blocks to fabricate nanothin films via layer-by-layer (LBL) self-assembly for anti-counterfeiting applications. Both negatively- and positively-charged CNC/QD nanohybrids with a high colloidal stability and a narrow particle size distribution were prepared. The controllable LBL coating process was characterized by scanning electron microscopy and ellipsometry. The rigid structure of CNCs leads to nanoporous structured films on poly(ethylene terephthalate) (PET) substrates with high transmittance (above 70%) over the entire range of visible light and also resulted in increased hydrophilicity (contact angles of ∼40 degrees). Nanothin films on PET substrates showed good flexibility and enhanced stability in both water and ethanol. The modified PET films with structural colors from thin-film interference and photoluminescence from QDs can be used in anti-counterfeiting applications.

Angle resolved x-ray photoelectron spectroscopy (ARXPS) analysis of lanthanum oxide for micro-flexography printing

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

Hassan, S., E-mail: suhaimihas@uthm.edu.my; Yusof, M. S., E-mail: mdsalleh@uthm.edu.my; Maksud, M. I., E-mail: midris1973@gmail.com

2016-01-22

Micro-flexography printing was developed in patterning technique from micron to nano scale range to be used for graphic, electronic and bio-medical device on variable substrates. In this work, lanthanum oxide (La{sub 2}O{sub 3}) has been used as a rare earth metal candidate as depositing agent. This metal deposit was embedded on Carbon (C) and Silica (Si) wafer substrate using Magnetron Sputtering technique. The choose of Lanthanum as a target is due to its wide application in producing electronic devices such as thin film battery and printed circuit board. The La{sub 2}O{sub 3} deposited on the surface of Si wafer substratemore » was then analyzed using Angle Resolve X-Ray Photoelectron Spectroscopy (ARXPS). The position for each synthetic component in the narrow scan of Lanthanum (La) 3d and O 1s are referred to the electron binding energy (eV). The La 3d narrow scan revealed that the oxide species of this particular metal is mainly contributed by La{sub 2}O{sub 3} and La(OH){sub 3}. The information of oxygen species, O{sup 2-} component from O 1s narrow scan indicated that there are four types of species which are contributed from the bulk (O{sup 2−}), two chemisorb component (La{sub 2}O{sub 3}) and La(OH){sub 3} and physisorp component (OH). Here, it is proposed that from the adhesive and surface chemical properties of La, it is suitable as an alternative medium for micro-flexography printing technique in printing multiple fine solid lines at nano scale. Hence, this paper will describe the capability of this particular metal as rare earth metal for use in of micro-flexography printing practice. The review of other parameters contributing to print fine lines will also be described later.« less

Stiffness of hyaluronic acid gels containing liver extracellular matrix supports human hepatocyte function and alters cell morphology.

PubMed

Deegan, Daniel B; Zimmerman, Cynthia; Skardal, Aleksander; Atala, Anthony; Shupe, Thomas D

2015-03-01

Tissue engineering and cell based liver therapies have utilized primary hepatocytes with limited success due to the failure of hepatocytes to maintain their phenotype in vitro. In order to overcome this challenge, hyaluronic acid (HA) cell culture substrates were formulated to closely mimic the composition and stiffness of the normal liver cellular microenvironment. The stiffness of the substrate was modulated by adjusting HA hydrogel crosslinking. Additionally, the repertoire of bioactive molecules within the HA substrate was bolstered by supplementation with normal liver extracellular matrix (ECM). Primary human hepatocyte viability and phenotype were determined over a narrow physiologically relevant range of substrate stiffnesses from 600 to 4600Pa in both the presence and absence of liver ECM. Cell attachment, viability, and organization of the actin cytoskeleton improved with increased stiffness up to 4600Pa. These differences were not evident in earlier time points or substrates containing only HA. However, gene expression for the hepatocyte markers hepatocyte nuclear factor 4 alpha (HNF4α) and albumin significantly decreased on the 4600Pa stiffness at day 7 indicating that cells may not have maintained their phenotype long-term at this stiffness. Function, as measured by albumin secretion, varied with both stiffness and time in culture and peaked at day 7 at the 1200Pa stiffness, slightly below the stiffness of normal liver ECM at 3000Pa. Overall, gel stiffness affected primary human hepatocyte cell adhesion, functional marker expression, and morphological characteristics dependent on both the presence of liver ECM in gel substrates and time in culture. Copyright © 2015 Elsevier Ltd. All rights reserved.

Neural activity underlying motor-action preparation and cognitive narrowing in approach-motivated goal states.

PubMed

Gable, Philip A; Threadgill, A Hunter; Adams, David L

2016-02-01

High-approach-motivated (pre-goal) positive affect states encourage tenacious goal pursuit and narrow cognitive scope. As such, high approach-motivated states likely enhance the neural correlates of motor-action preparation to aid in goal acquisition. These neural correlates may also relate to the cognitive narrowing associated with high approach-motivated states. In the present study, we investigated motor-action preparation during pre-goal and post-goal states using an index of beta suppression over the motor cortex. The results revealed that beta suppression was greatest in pre-goal positive states, suggesting that higher levels of motor-action preparation occur during high approach-motivated positive states. Furthermore, beta and alpha suppression in the high approach-motivated positive states predicted greater cognitive narrowing. These results suggest that approach-motivated pre-goal states engage the neural substrates of motor-action preparation and cognitive narrowing. Individual differences in motor-action preparation relate to the degree of cognitive narrowing.

Trace metal bioavailability: Modeling chemical and biological interactions of sediment-bound zinc

USGS Publications Warehouse

Luoma, S. N.; Bryan, G.W.; Jenne, Everett A.

1979-01-01

Extractable concentrations of sediment-bound Zn, as modified by the physicochemical form of the metal in the sediments, controlled Zn concentrations in the deposit-feeding bivalvesScrobicularia plana (collected from 40 stations in 17 estuaries in southwest England) andMacoma balthica (from 28 stations in San Francisco Bay). Over a wide range of concentrations, a significant correlation was found between ammonium acetate-soluble concentrations of Zn in sediments and Zn concentrations in Scrobicularia. This correlation was insufficiently precise to be of predictive value for Scrobicularia, and did not hold for Macoma over the narrower range of Zn concentrations observed in San Francisco Bay. Strong correlation of Zn concentrations inScrobicularia and the bioavailability of sediment-bound Zn to Macoma with ratios of sorption substrate (oxides of iron and manganese, organic carbon, carbonates, humic materials) concentrations in sediments were found in both the English and San Francisco Bay study areas. These correlations were attributed to substrate competition for sorption of Zn within sediments, assuming: 1) competition for sorption of Zn was largely controlled by the relative concentrations of substrates present in the sediments and 2) the bioavailability of Zn to the deposit feeders was determined by the partitioning of Zn among the substrates. The correlations indicated that the availability of Zn to the bivalves increased when concentrations of either amorphous inorganic oxides or humic substances increased in sediments. Availability was reduced at increased concentrations of organic carbon and, in San Francisco Bay, ammonium acetate-soluble Mn. Concentrations of biologically available Zn in solution and low salinities may also have enhanced Zn uptake, although the roles of these variables were less obvious from the statistical analysis.

Thickness dependent band gap of Bi{sub 2-x}Sb{sub x}Te{sub 3} (x = 0, 0.05, 0.1) thin films

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

Patel, M. M.; Soni, P. H., E-mail: phsoni-msu@yahoo.com; Desai, C. F.

2016-05-23

Thin films of Bi{sub 2}Te{sub 3}(Sb) were prepared on alkali halide crystal substrates. Sb content and the film thickness were varied. Bi{sub 2}Te{sub 3} is a narrow gap semiconductor. Bi-Sb is a continuous solid solution of substitutional type and Sb therefore was used to test its effect on the band gap. The film thickness variation was also taken up. The infra-red absorption spectra were used in the wave number range 400 cm{sup −1} to 4000 cm{sup −1}. The band gap obtained from the absorption data was found to increase with decreasing thickness since the thickness range used was from 30more » nm to 170 nm. This is a range corresponding to nanostructures and hence quantum size effect was observed as expected. The band gap also exhibited Sb content dependence. The detail results are have been reported and explained.« less

Growth behavior of carbon nanotubes on multilayered metal catalyst film (Al/Fe/Mo) in chemical vapor deposition

NASA Astrophysics Data System (ADS)

Cui, H.; Eres, G.; Howe, J. Y.; Puretzky, A.; Varela, M.; Geohegan, D. B.; Lowndes, D. H.

2003-03-01

The temperature- and time- dependences of carbon nanotube (CNT) growth by chemical vapor deposition are studied using a multilayered Al/Fe/Mo catalyst on silicon substrates. Within the 600 - 1100 ^oC temperature range in these studies, narrower temperature ranges were determined for the growth of aligned multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs). Aligned MWCNT growth is favored at lower temperatures ( ˜700 ^oC). At 900 ^oC, in contrast to earlier work, double-walled carbon nanotubes (DWCNTs) are found more abundant than SWCNTs. At further elevated temperature, highly defective carbon structures are produced. Defects also are found to accumulate faster than the ordered graphitic structure if the growth of CNTs is extended to long growth durations. Atomic force microscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy, and Raman spectroscopy are used to characterize the catalyst and various types of CNTs.

Structural and optical properties of PbS thin films grown by chemical bath deposition

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

Seghaier, S.; Kamoun, N.; Guasch, C.

2007-09-19

Lead sulphide thin films are grown on glass substrates at various deposition times tD, in the range of 40-60 min per step of 2 min, using the chemical bath deposition technique. X-ray diffraction and atomic force microscopy are used to characterize the film structure. The surface composition is analysed by Auger electron spectroscopy. It appears that the as-prepared thin films are polycrystalline with cubic structure. Nanometric scale crystallites are uniformly distributed on the surface. They exhibit almost a stoechiometric composition with a [Pb]/[S] ratio equal to 1.10. Optical properties are studied in the range of 300-3300 nm by spectrophotometric measurements.more » Analysis of the optical absorption data of lead sulphide thin layers reveals a narrow optical direct band gap equal to 0.46 eV for the layer corresponding to a deposition time equal to 60 min.« less

Background correction in forensic photography. II. Photography of blood under conditions of non-uniform illumination or variable substrate color--practical aspects and limitations.

PubMed

Wagner, John H; Miskelly, Gordon M

2003-05-01

The combination of photographs taken at wavelengths at and bracketing the peak of a narrow absorbance band can lead to enhanced visualization of the substance causing the narrow absorbance band. This concept can be used to detect putative bloodstains by division of a linear photographic image taken at or near 415 nm with an image obtained by averaging linear photographs taken at or near 395 and 435 nm. Nonlinear images can also be background corrected by substituting subtraction for the division. This paper details experimental applications and limitations of this technique, including wavelength selection of the illuminant and at the camera. Characterization of a digital camera to be used in such a study is also detailed. Detection limits for blood using the three wavelength correction method under optimum conditions have been determined to be as low as 1 in 900 dilution, although on strongly patterned substrates blood diluted more than twenty-fold is difficult to detect. Use of only the 435 nm photograph to estimate the background in the 415 nm image lead to a twofold improvement in detection limit on unpatterned substrates compared with the three wavelength method with the particular camera and lighting system used, but it gave poorer background correction on patterned substrates.

Multi-scale ordering of self-assembled InAs/GaAs(001) quantum dots

PubMed Central

Songmuang, R; Rastelli, A; Heidemeyer, H; Schmidt, OG

2006-01-01

Ordering phenomena related to the self-assembly of InAs quantum dots (QD) grown on GaAs(001) substrates are experimentally investigated on different length scales. On the shortest length-scale studied here, we examine the QD morphology and observe two types of QD shapes, i.e., pyramids and domes. Pyramids are elongated along the [1-10] directions and are bounded by {137} facets, while domes have a multi-facetted shape. By changing the growth rates, we are able to control the size and size homogeneity of freestanding QDs. QDs grown by using low growth rate are characterized by larger sizes and a narrower size distribution. The homogeneity of buried QDs is measured by photoluminescence spectroscopy and can be improved by low temperature overgrowth. The overgrowth induces the formation of nanostructures on the surface. The fabrication of self-assembled nanoholes, which are used as a template to induce short-range positioning of QDs, is also investigated. The growth of closely spaced QDs (QD molecules) containing 2–6 QDs per QD molecule is discussed. Finally, the long-range positioning of self-assembled QDs, which can be achieved by the growth on patterned substrates, is demonstrated. Lateral QD replication observed during growth of three-dimensional QD crystals is reported.

Magnetic properties and thermal stability of Ti-doped CrO2 films

NASA Astrophysics Data System (ADS)

Zhang, Z.; Cheng, M.; Lu, Z.; Yu, Z.; Liu, S.; Liang, R.; Liu, Y.; Shi, J.; Xiong, R.

2018-04-01

Chromium dioxide (CrO2) is a striking half metal material which may have important applications in the field of spintronics. However, pure CrO2 film is metastable at room temperature and the synthesis process can be only performed in a narrow temperature range of 390-410 °C with TiO2 used as substrate material. Here, we report the preparation and investigation of (1 0 0) oriented Ti-doped CrO2 films on TiO2 substrates. It is found that Ti-doped films can maintain pure rutile phase even after a 510 °C post-annealing, showing much better thermal stability than pure CrO2 films. Ti-doped films can be prepared in a wider temperature window (390-470 °C), which may be attributed to the improvement of thermal stability. The broadening of process window may be beneficial for further improvement of film quality by optimizing growth temperature in a larger range. In addition to the improvement of thermal stability, the magnetic properties of Ti-doped CrO2 are also found to be tuned by Ti doping: saturation magnetizations of Ti-doped films at room temperature are significantly lower, and magnetic anisotropy decreases as the Ti-concentration increases, which is beneficial for decreasing switching current density in STT-based spintronic devices.

Designing PolyHEMA Substrates that Mimic the Viscoelastic Response of Soft Tissue

PubMed Central

Holt, Brian; Tripathi, Anubhav; Morgan, Jeffrey R.

2011-01-01

Matching the mechanical properties of a biomaterial to soft tissue is often overlooked despite the fact that it’s well known that cells respond to and are capable of changing their mechanical environment. In this paper, we used NaCl and alginate beads as porogens to make a series of micro- and macro-porous pHEMA substrates [poly(2-hydroxyethly methacrylate)] and quantified their mechanical behavior under low-magnitude shear loads over physiologically relevant frequencies. Using a stress-controlled rheometer, we performed isothermal (37°C) frequency response experiments between 0.628 and 75.4 rad/s [0.01–12Hz] at 0.1% strain. Both micro- and macro-porous pHEMA substrates were predominately elastic in nature with a narrow range of G′ and G″ values that mimicked the response of human skin. The magnitude of the G′ and G″ values of the macro-porous substrates were designed to closely match human skin. To determine how cell growth might alter their mechanical properties, pHEMA substrates were functionalized and human skin fibroblasts grown on them for fourteen days. As a result of cell growth, the magnitude of G′ and G″ increased at low frequencies while also altering the degree of high frequency dependence, indicating that cellular interactions with the micro-pore infrastructure has a profound effect on the viscoelastic behavior of the substrates. These data could be fit to a mathematical model describing a soft solid. A quantitative understanding of the mechanical behavior of biomaterials in regimes that are physiologically relevant and how these mechanics may change after implantation may aid in the design of new materials. PMID:21496821

Electronic structure of uranium overlayers on magnesium and aluminium

NASA Astrophysics Data System (ADS)

Gouder, T.

1997-06-01

We studied U overlayers on polycrystalline Mg and Al by X-ray and ultra-violet photoelectron spectroscopies (XPS and UPS, respectively), and compared the mode of growth and the evolution of the electronic structure as a function of coverage. The goal of this work was to detect localization, or at least correlation effects, in U overlayers and U substrate near surface alloys, which were expected to occur because of the reduced U 5f bandwidth in these systems. On Mg, U deposits as a pure overlayer without any interdiffusion, while on Al spontaneous interdiffusion takes place. The U 4f spectra of {U}/{Mg} show only weak correlation satellites. Nevertheless, the asymmetrical shape of the U 4f peak indicates 5f band narrowing. On Al, strong correlation satellites are observed in addition to plasmon loss features. It seems that U-substrate interactions promote correlation effects, while the reduced coordination in overlayers plays a less important role. UPS valence-band (VB) spectra of the two systems look remarkably similar. They do not show any correlation satellites. With decreasing overlayer thickness the 5f peak narrows, which is attributed to 5f band narrowing at the surface.

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

Bahl, C.; Morisseau, C; Bomberger, J

Cystic fibrosis transmembrane conductance regulator (CFTR) inhibitory factor (Cif) is a virulence factor secreted by Pseudomonas aeruginosa that reduces the quantity of CFTR in the apical membrane of human airway epithelial cells. Initial sequence analysis suggested that Cif is an epoxide hydrolase (EH), but its sequence violates two strictly conserved EH motifs and also is compatible with other {alpha}/{beta} hydrolase family members with diverse substrate specificities. To investigate the mechanistic basis of Cif activity, we have determined its structure at 1.8-{angstrom} resolution by X-ray crystallography. The catalytic triad consists of residues Asp129, His297, and Glu153, which are conserved across themore » family of EHs. At other positions, sequence deviations from canonical EH active-site motifs are stereochemically conservative. Furthermore, detailed enzymatic analysis confirms that Cif catalyzes the hydrolysis of epoxide compounds, with specific activity against both epibromohydrin and cis-stilbene oxide, but with a relatively narrow range of substrate selectivity. Although closely related to two other classes of {alpha}/{beta} hydrolase in both sequence and structure, Cif does not exhibit activity as either a haloacetate dehalogenase or a haloalkane dehalogenase. A reassessment of the structural and functional consequences of the H269A mutation suggests that Cif's effect on host-cell CFTR expression requires the hydrolysis of an extended endogenous epoxide substrate.« less

Sub-5 nm, globally aligned graphene nanoribbons on Ge(001)

DOE PAGES

Kiraly, Brian; Mannix, Andrew J.; Jacobberger, Robert M.; ...

2016-05-23

Graphene nanoribbons (GNRs) hold great promise for future electronics because of their edge and width dependent electronic bandgaps and exceptional transport properties. While significant progress toward such devices has been made, the field has been limited by difficulties achieving narrow widths, global alignment, and atomically pristine GNR edges on technologically relevant substrates. A recent advance has challenged these limits by using Ge(001) substrates to direct the bottom-up growth of GNRs with nearly pristine armchair edges and widths near ~10 nm via atmospheric pressure chemical vapor deposition. In this work, we extend the growth of GNRs on Ge(001) to ultra-high vacuummore » conditions and realize GNRs narrower than 5 nm. Armchair graphene nanoribbons directed along the Ge <110> surface directions are achieved with excellent width control and relatively large bandgaps. As a result, the bandgap magnitude and electronic uniformity make these new materials excellent candidates for future developments in nanoelectronics.« less

Fabrication and characterization of multi-stopband Fabry-Pérot filter array for nanospectrometers in the VIS range using SCIL nanoimprint technology

NASA Astrophysics Data System (ADS)

Shen, Yannan; Istock, André; Zaman, Anik; Woidt, Carsten; Hillmer, Hartmut

2018-05-01

Miniaturization of optical spectrometers can be achieved by Fabry-Pérot (FP) filter arrays. Each FP filter consists of two parallel highly reflecting mirrors and a resonance cavity in between. Originating from different individual cavity heights, each filter transmits a narrow spectral band (transmission line) with different wavelengths. Considering the fabrication efficiency, plasma enhanced chemical vapor deposition (PECVD) technology is applied to implement the high-optical-quality distributed Bragg reflectors (DBRs), while substrate conformal imprint lithography (one type of nanoimprint technology) is utilized to achieve the multiple cavities in just a single step. The FP filter array fabricated by nanoimprint combined with corresponding detector array builds a so-called "nanospectrometer". However, the silicon nitride and silicon dioxide stacks deposited by PECVD result in a limited stopband width of DBR (i.e., < 100 nm), which then limits the sensing range of filter arrays. However, an extension of the spectral range of filter arrays is desired and the topic of this investigation. In this work, multiple DBRs with different central wavelengths (λ c) are structured, deposited, and combined on a single substrate to enlarge the entire stopband. Cavity arrays are successfully aligned and imprinted over such terrace like surface in a single step. With this method, small chip size of filter arrays can be preserved, and the fabrication procedure of multiple resonance cavities is kept efficient as well. The detecting range of filter arrays is increased from roughly 50 nm with single DBR to 163 nm with three different DBRs.

A review of gradient stiffness hydrogels used in tissue engineering and regenerative medicine.

PubMed

Xia, Tingting; Liu, Wanqian; Yang, Li

2017-06-01

Substrate stiffness is known to impact characteristics including cell differentiation, proliferation, migration and apoptosis. Hydrogels are polymeric materials distinguished by high water content and diverse physical properties. Gradient stiffness hydrogels are designed by the need to develop biologically friendly materials as extracellular matrix (ECM) alternatives to replace the separated and narrow-ranged hydrogel substrates. Important new discoveries in cell behaviors have been realized with model gradient stiffness hydrogel systems from the two-dimensional (2D) to three-dimensional (3D) scale. Basic and clinical applications for gradient stiffness hydrogels in tissue engineering and regenerative medicine continue to drive the development of stiffness and structure varied hydrogels. Given the importance of gradient stiffness hydrogels in basic research and biomedical applications, there is a clear need for systems for gradient stiffness hydrogel design strategies and their applications. This review will highlight past work in the field of gradient stiffness hydrogels fabrication methods, mechanical property test, applications as well as areas for future study. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1799-1812, 2017. © 2017 Wiley Periodicals, Inc.

Preparation of atomically flat rutile TiO 2(001) surfaces for oxide film growth

DOE PAGES

Wang, Yang; Lee, Shinbuhm; Vilmercati, P.; ...

2016-01-01

The availability of low-index rutile TiO 2 single crystal substrates with atomically flat surfaces is essential for enabling epitaxialgrowth of rutile transition metal oxide films. The high surface energy of the rutile (001) surface often leads to surface faceting, which precludes the sputter and annealing treatment commonly used for the preparation of clean and atomically flat TiO 2(110) substrate surfaces. In this work, we reveal that stable and atomically flat rutile TiO 2(001) surfaces can be prepared with an atomically ordered reconstructedsurface already during a furnace annealing treatment in air. We tentatively ascribe this result to the decrease in surfacemore » energy associated with the surface reconstruction, which removes the driving force for faceting. Despite the narrow temperature window where this morphology can initially be formed, we demonstrate that it persists in homoepitaxialgrowth of TiO 2(001) thin films. The stabilization of surface reconstructions that prevent faceting of high-surface-energy crystal faces may offer a promising avenue towards the realization of a wider range of high quality epitaxial transition metal oxide heterostructures.« less

Development of a self-packaged 2D MEMS thermal wind sensor for low power applications

NASA Astrophysics Data System (ADS)

Zhu, Yan-qing; Chen, Bei; Qin, Ming; Huang, Jian-qiu; Huang, Qing-an

2015-08-01

This article describes the design, fabrication, and testing of a self-packaged 2D thermal wind sensor. The sensor consists of four heaters and nine thermistors. A central thermistor senses the average heater temperature, whereas the other eight, which are distributed symmetrically around the heaters, measure the temperature differences between the upstream and downstream surface of the sensor. The sensor was realized on one side of a silicon-in-glass (SIG) substrate. Vertical silicon vias in the substrate ensure good thermal contact between the sensor and the airflow and the glass effectively isolates the heaters from the thermistors. The substrate was fabricated by using a glass reflow process, after which the sensor was realized by a lift-off process. The sensor’s geometry was investigated with the help of simulations. These show that narrow heaters, moderate heater spacing, and thin substrates all improve the sensor’s sensitivity. Finally, the sensor was tested and calibrated in a wind tunnel by using a linear interpolation algorithm. At a constant heating power of 24.5 mW, measurement results show that the sensor can detect airflow speeds of up to 25 m s-1, with an accuracy of 0.1 m s-1 at low speeds and 0.5 m s-1 at high speeds. Airflow direction can be determined in a range of 360° with an accuracy of ±6°.

CT demonstration of pharyngeal narrowing in adult obstructive sleep apnea

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

Bohlman, M.E.; Haponik, E.F.; Smith, P.L.

Sleep apnea is a major cause of daytime hypersomnolence. Among the proposed etiologies, focal obstruction of the airways at the level of the pharynx has been suggested but not proven. Using computed tomography, the cross-sectional area of the airway can be readily assessed. Thirty-three adults with clinically proven sleep apnea and 12 normal adults underwent systematic computed tomography of the neck. Significant airway narrowing was demonstrated in all the patients with obstructive sleep apnea, whereas no such narrowing was seen in the controls. In 11, the narrowing was at a single level, whereas in 22 patients two or more levelsmore » were affected. This study has shown that a structurally abnormal airway may serve as an anatomic substrate for the development of sleep apnea. On the basis of this evidence, uvulopalatopharyngoplasty has been performed in two patients with relief of symptoms in one.« less

Substrate-Specific Differential Gene Expression and RNA editing in the Brown Rot Fungus Fomitopsis pinicola.

PubMed

Wu, Baojun; Gaskell, Jill; Held, Benjamin W; Toapanta, Cristina; Vuong, Thu; Ahrendt, Steven; Lipzen, Anna; Zhang, Jiwei; Schilling, Jonathan S; Master, Emma; Grigoriev, Igor V; Blanchette, Robert A; Cullen, Dan; Hibbett, David S

2018-06-08

Wood-decaying fungi tend to have characteristic substrate ranges that partly define their ecological niche. Fomitopsis pinicola is a brown rot species of Polyporales that is reported on 82 species of softwoods and 42 species of hardwoods. We analyzed gene expression levels and RNA editing profiles of F. pinicola from submerged cultures with ground wood powder (sampled at five days) or solid wood wafers (sampled at ten and thirty days), using aspen, pine, and spruce substrates (aspen was used only in submerged cultures). Fomitopsis pinicola expressed similar sets of wood-degrading enzymes typical of brown rot fungi across all culture conditions and timepoints. Nevertheless, differential gene expression and RNA editing were observed across all pairwise comparisons of substrates and timepoints. Genes exhibiting differential expression and RNA editing encode diverse enzymes with known or potential function in brown rot decay, including laccase, benzoquinone reductase, aryl alcohol oxidase, cytochrome P450s, and various glycoside hydrolases. There was no overlap between differentially expressed and differentially edited genes, suggesting that these may provide F. pinicola with independent mechanisms for responding to different conditions. Comparing transcriptomes from submerged cultures and wood wafers, we found that culture conditions had a greater impact on global expression profiles than substrate wood species. In contrast, the suites of genes subject to RNA editing were much less affected by culture conditions. These findings highlight the need for standardization of culture conditions in studies of gene expression in wood-decaying fungi. IMPORTANCE All species of wood-decaying fungi occur on a characteristic range of substrates (host plants), which may be broad or narrow. Understanding the mechanisms that allow fungi to grow on particular substrates is important for both fungal ecology and applied uses of different feedstocks in industrial processes. We grew the wood-decaying polypore Fomitopsis pinicola on three different wood species, aspen, pine and spruce, under various culture conditions. We examined both gene expression (transcription levels) and RNA editing (post-transcriptional modification of RNA, which can potentially yield different proteins from the same gene). We found that F. pinicola is able to modify both gene expression and RNA editing profiles across different substrate species and culture conditions. Many of the genes involved encode enzymes with known or predicted functions in wood decay. This work provides clues to how wood-decaying fungi may adjust their arsenal of decay enzymes to accommodate different host substrates. Copyright © 2018 American Society for Microbiology.

Leveraging Crystal Anisotropy for Deterministic Growth of InAs Quantum Dots with Narrow Optical Linewidths

DTIC Science & Technology

2013-08-29

similar layer thicknesses. This offset indicates that the electric field profile of our Schottky diode is different than for unpatterned samples, implying...sacrificing uniformity by further optimizing the substrate Figure 3. (a) Schematic of the Schottky diode heterostructure, indicating the patterned substrate...and negative (X−) trions are indicated . (c) Distribution of linewidths for 80 PL lines from dots grown in high density arrays such as those in Figure 2b

Specific features of the spectra and relaxation kinetics of long-wavelength photoconductivity in narrow-gap HgCdTe epitaxial films and heterostructures with quantum wells

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

Rumyantsev, V. V., E-mail: rumyantsev@ipmras.ru; Ikonnikov, A. V.; Antonov, A. V.

2013-11-15

The spectra and relaxation kinetics of interband photoconductivity are investigated in narrow-gap Hg{sub 1-x}Cd{sub x}Te epitaxial films with x = 0.19-0.23 and in structures with HgCdTe-based quantum wells (QWs), having an interband-transition energy in the range of 30-90 meV, grown by molecular-beam epitaxy on GaAs (013) substrates. A long-wavelength sensitivity band caused by impurities or defects is found in the spectra of the structures with quantum wells in addition to the interband photoconductivity. It is shown that the lifetimes of nonequilibrium carriers in the structures with QWs is less than in bulk samples at the same optical-transition energy. From themore » measured carrier lifetimes, the ampere-watt responsivity and the equivalent noise power for a film with x = 0.19 at a wavelength of 19 {mu}m are estimated. When investigating the relaxation kinetics of the photoconductivity at 4.2 K in high excitation regime, it is revealed that radiative recombination is dominant over other mechanisms of nonequilibrium-carrier recombination.« less

Carbonaceous film coating

DOEpatents

Maya, L.

1988-04-27

A method of making a carbonaceous film comprising heating tris(1,3,2-benzodiazaborolo)borazine or dodecahydro tris(1,3,2)diazaborine(1,2-a:1'2'-c:1''2''-e)borazine in an inert atmosphere in the presence of a substrate to a temperature at which the borazine compound decomposes, and the decomposition products deposit onto the substrate to form a thin, tenacious, highly reflective conductive coating having a narrow band gap which is susceptible of modification and a relatively low coefficient of friction.

Carbonaceous film coating

DOEpatents

Maya, Leon

1989-01-01

A method of making a carbonaceous film comprising heating tris(1,3,2-benzodiazaborolo)borazine or dodecahydro tris[1,3,2]diazaborine[1,2-a:1'2'-c:1"2"-e]borazine in an inert atmosphere in the presence of a substrate to a temperature at which the borazine compound decomposes, and the decomposition products deposit onto the substrate to form a thin, tenacious, highly reflective conductive coating having a narrow band gap which is susceptible of modification and a relatively low coefficient of friction.

Surface-assisted laser desorption/ionization time-of-flight mass spectrometry of small drug molecules and high molecular weight synthetic/biological polymers using electrospun composite nanofibers.

PubMed

Bian, Juan; Olesik, Susan V

2017-03-27

Polyacrylonitrile/Nafion®/carbon nanotube (PAN/Nafion®/CNT) composite nanofibers were prepared using electrospinning. These electrospun nanofibers were studied as possible substrates for surface-assisted laser desorption/ionization (SALDI) and matrix-enhanced surface-assisted laser desorption/ionization time-of-flight mass spectrometry (ME-SALDI/TOF-MS) for the first time in this paper. Electrospinning provides this novel substrate with a uniform morphology and a narrow size distribution, where CNTs were evenly and firmly immobilized on polymeric nanofibers. The results show that PAN/Nafion®/CNT nanofibrous mats are good substrates for the analysis of both small drug molecules and high molecular weight polymers with high sensitivity. Markedly improved reproducibility was observed relative to MALDI. Due to the composite formation between the polymers and the CNTs, no contamination of the carbon nanotubes to the mass spectrometer was observed. Furthermore, electrospun nanofibers used as SALDI substrates greatly extended the duration of ion signals of target analytes compared to the MALDI matrix. The proposed SALDI approach was successfully used to quantify small drug molecules with no interference in the low mass range. The results show that verapamil could be detected with a surface concentration of 220 femtomoles, indicating the high detection sensitivity of this method. Analysis of peptides and proteins with the electrospun composite substrate using matrix assisted-SALDI was improved and a low limit of detection of approximately 6 femtomoles was obtained for IgG. Both SALDI and ME-SALDI analyses displayed high reproducibility with %RSD ≤ 9% for small drug molecules and %RSD ≤ 14% for synthetic polymers and proteins.

Environmental resistance of oxide tags fabricated on 304L stainless steel via nanosecond pulsed laser irradiation

DOE PAGES

Lawrence, Samantha Kay; Adams, David P.; Bahr, David F.; ...

2015-11-14

Nanosecond pulsed laser irradiation was used to fabricate colored, mechanically robust oxide “tags” on 304L stainless steel. Immersion in simulated seawater solution, salt fog exposure, and anodic polarization in a 3.5% NaCl solution were employed to evaluate the environmental resistance of these oxide tags. Single layer oxides outside a narrow thickness range (~ 100–150 nm) are susceptible to dissolution in chloride containing environments. The 304L substrates immediately beneath the oxides corrode severely—attributed to Cr-depletion in the melt zone during laser processing. For the first time, multilayered oxides were fabricated with pulsed laser irradiation in an effort to expand the protectivemore » thickness range while also increasing the variety of film colors attainable in this range. Layered films grown using a laser scan rate of 475 mm/s are more resistant to both localized and general corrosion than oxides fabricated at 550 mm/s. Furthermore, in the absence of pre-processing to mitigate Cr-depletion, layered films can enhance environmental stability of the system.« less

Ultrathin Terahertz Quarter-wave plate based on Split Ring Resonator and Wire Grating hybrid Metasurface.

PubMed

Nouman, Muhammad Tayyab; Hwang, Ji Hyun; Jang, Jae-Hyung

2016-12-13

Planar metasurface based quarter-wave plates offer various advantages over conventional waveplates in terms of compactness, flexibility and simple fabrication; however they offer very narrow bandwidth of operation. Here, we demonstrate a planar terahertz (THz) metasurface capable of linear to circular polarization conversion and vice versa in a wide frequency range. The proposed metasurface is based on horizontally connected split ring resonators and is realized on an ultrathin (0.05λ) zeonor substrate. The fabricated quarter waveplate realizes linear to circular polarization conversion in two broad frequency bands comprising 0.64-0.82 THz and 0.96-1.3 THz with an insertion loss ranging from -3.9 to -10 dB. By virtue of ultrathin sub wavelength thickness, the proposed waveplate design is well suited for application in near field THz optical systems. Additionally, the proposed metasurface design offers novel transmission phase characteristics that present further opportunities to realize dynamic polarization control of incident waves.

Ultrathin Terahertz Quarter-wave plate based on Split Ring Resonator and Wire Grating hybrid Metasurface

PubMed Central

Nouman, Muhammad Tayyab; Hwang, Ji Hyun; Jang, Jae-Hyung

2016-01-01

Planar metasurface based quarter-wave plates offer various advantages over conventional waveplates in terms of compactness, flexibility and simple fabrication; however they offer very narrow bandwidth of operation. Here, we demonstrate a planar terahertz (THz) metasurface capable of linear to circular polarization conversion and vice versa in a wide frequency range. The proposed metasurface is based on horizontally connected split ring resonators and is realized on an ultrathin (0.05λ) zeonor substrate. The fabricated quarter waveplate realizes linear to circular polarization conversion in two broad frequency bands comprising 0.64–0.82 THz and 0.96–1.3 THz with an insertion loss ranging from −3.9 to −10 dB. By virtue of ultrathin sub wavelength thickness, the proposed waveplate design is well suited for application in near field THz optical systems. Additionally, the proposed metasurface design offers novel transmission phase characteristics that present further opportunities to realize dynamic polarization control of incident waves. PMID:27958358

Fabrication and performance of polymer-nanocomposite anti-reflective thin films deposited by RIR-MAPLE

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

Singaravelu, S.; Mayo, D. C.; Park, H-. K.

2014-07-01

Design of polymer anti-reflective (AR) optical coatings for plastic substrates is challenging because polymers exhibit a relatively narrow range of refractive indices. Here, we report synthesis of a four-layer AR stack using hybrid polymer: nanoparticle materials deposited by resonant infrared matrix-assisted pulsed laser evaporation. An Er: YAG laser ablated frozen solutions of a high-index composite containing TiO2 nanoparticles and poly(methylmethacrylate) (PMMA), alternating with a layer of PMMA. The optimized AR coatings, with thicknesses calculated using commercial software, yielded a coating for polycarbonate with transmission over 97 %, scattering <3 %, and a reflection coefficient below 0.5 % across the visiblemore » range, with a much smaller number of layers than would be predicted by a standard thin film calculation. The TiO2 nanoparticles contribute more to the enhanced refractive index of the high-index layers than can be accounted for by an effective medium model of the nanocomposite.« less

Low acclimation capacity of narrow-ranging thermal specialists exposes susceptibility to global climate change.

PubMed

Markle, Tricia M; Kozak, Kenneth H

2018-05-01

Thermal acclimation is hypothesized to offer a selective advantage in seasonal habitats and may underlie disparities in geographic range size among closely-related species with similar ecologies. Understanding this relationship is also critical for identifying species that are more sensitive to warming climates. Here, we study North American plethodontid salamanders to investigate whether acclimation ability is associated with species' latitudinal extents and the thermal range of the environments they inhabit. We quantified variation in thermal physiology by measuring standard metabolic rate (SMR) at different test and acclimation temperatures for 16 species of salamanders with varying latitudinal extents. A phylogenetically-controlled Markov chain Monte Carlo generalized linear mixed model (MCMCglmm) was then employed to determine whether there are differences in SMR between wide- and narrow-ranging species at different acclimation temperatures. In addition, we tested for a relationship between the acclimation ability of species and the environmental temperature ranges they inhabit. Further, we investigated if there is a trade-off between critical thermal maximum (CTMax) and thermal acclimation ability. MCMCglmm results show a significant difference in acclimation ability between wide and narrow-ranging temperate salamanders. Salamanders with wide latitudinal distributions maintain or slightly increase SMR when subjected to higher test and acclimation temperatures, whereas several narrow-ranging species show significant metabolic depression. We also found significant, positive relationships between acclimation ability and environmental thermal range, and between acclimation ability and CTMax. Wide-ranging salamander species exhibit a greater capacity for thermal acclimation than narrow-ranging species, suggesting that selection for acclimation ability may have been a key factor enabling geographic expansion into areas with greater thermal variability. Further, given that narrow-ranging salamanders are found to have both poor acclimation ability and lower tolerance to warm temperatures, they are likely to be more susceptible to environmental warming associated with anthropogenic climate change.

Biochemistry students' ideas about how an enzyme interacts with a substrate.

PubMed

Linenberger, Kimberly J; Bretz, Stacey Lowery

2015-01-01

Enzyme-substrate interactions are a fundamental concept of biochemistry that is built upon throughout multiple biochemistry courses. Central to understanding enzyme-substrate interactions is specific knowledge of exactly how an enzyme and substrate interact. Within this narrower topic, students must understand the various binding sites on an enzyme and be able to reason from simplistic lock and key or induced fit models to the more complex energetics model of transition state theory. Learning to understand these many facets of enzyme-substrate interactions and reasoning from multiple models present challenges where students incorrectly make connections between concepts or make no connection at all. This study investigated biochemistry students' understanding of enzyme-substrate interactions through the use of clinical interviews and a national administration (N = 707) of the Enzyme-Substrate Interactions Concept Inventory. Findings include misconceptions regarding the nature of enzyme-substrate interactions, naïve ideas about the active site, a lack of energetically driven interactions, and an incomplete understanding of the specificity pocket. © 2015 by the International Union of Biochemistry and Molecular Biology.

Samarium electrodeposited acetate and oxide thin films on stainless steel substrate characterized by XPS

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

Myhre, Kristian; Burns, Jonathan; Meyer, Harry

Characterization of a samarium thin film deposited on a stainless steel substrate using molecular electrodeposition was carried out using a Thermo Scientific K-Alpha X-ray photoelectron spectrometer. We studied two types of samarium electrodeposition samples, one as-deposited and one heated to 700 °C in an air flow. Survey scans include peaks coming from the stainless steel substrate, such as Fe and Cr. An X-ray photoelectron spectroscopy (XPS) survey spectrum, Sm 3d, C 1s, and O 1s narrow scans are shown. It was determined that the heating process decomposed the deposited Sm acetate to Sm 2O 3 using XPS.

Samarium electrodeposited acetate and oxide thin films on stainless steel substrate characterized by XPS

DOE PAGES

Myhre, Kristian; Burns, Jonathan; Meyer, Harry; ...

2016-06-01

Characterization of a samarium thin film deposited on a stainless steel substrate using molecular electrodeposition was carried out using a Thermo Scientific K-Alpha X-ray photoelectron spectrometer. We studied two types of samarium electrodeposition samples, one as-deposited and one heated to 700 °C in an air flow. Survey scans include peaks coming from the stainless steel substrate, such as Fe and Cr. An X-ray photoelectron spectroscopy (XPS) survey spectrum, Sm 3d, C 1s, and O 1s narrow scans are shown. It was determined that the heating process decomposed the deposited Sm acetate to Sm 2O 3 using XPS.

Regulation of the Deposition Morphology of Inkjet-Printed Crystalline Materials via Polydopamine Functional Coatings for Highly Uniform and Electrically Conductive Patterns.

PubMed

Liu, Liang; Ma, Siyuan; Pei, Yunheng; Xiong, Xiao; Sivakumar, Preeth; Singler, Timothy J

2016-08-24

We report a method to achieve highly uniform inkjet-printed silver nitrate (AgNO3) and a reactive silver precursor patterns on rigid and flexible substrates functionalized with polydopamine (PDA) coatings. The printed AgNO3 patterns on PDA-coated substrates (glass and polyethylene terephthalate (PET)) exhibit a narrow thickness distribution ranging between 0.9 and 1 μm in the line transverse direction and uniform deposition profiles in the line axial direction. The deposited reactive silver precursor patterns on PDA-functionalized substrates also show "dome-shaped" morphology without "edge-thickened" structure due to "coffee-stain" effect. We posit that the highly uniform functional ink deposits formed on PDA-coated substrates are attributable to the strong binding interaction between the abundant catecholamine moieties at the PDA surface and the metallic silver cations (Ag(+) or Ag(NH3)(2+)) in the solutal inks. During printing of the ink rivulet and solvent evaporation, the substrate-liquid ink (S-L) interface is enriched with the silver-based cations and a solidification at the S/L interface is induced. The preferential solidification initiated at the S-L interface is further verified by the in situ visualization of the dynamic solidification process during solvent evaporation, and results suggest an enhanced crystal nucleation and growth localized at the S-L interface on PDA functionalized substrates. This interfacial interaction mediates solute transport in the liquid phase, resulting in the controlled enrichment of solute at the S-L interface and mitigated solute precipitation in both the contact line region and the liquid ink-vapor (L-V) interface due to evaporation. This mediated transport contributes to the final uniform solid deposition for both types of ink systems. This technique provides a complementary strategy for achieving highly uniform inkjet-printed crystalline structures, and can serve as an innovative foundation for high-precision additive delivery of functional materials.

Human Viperin Causes Radical SAM-Dependent Elongation of Escherichia coli, Hinting at Its Physiological Role.

PubMed

Nelp, Micah T; Young, Anthony P; Stepanski, Branden M; Bandarian, Vahe

2017-08-01

Viperin (virus inhibitory protein, endoplasmic reticulum-associated, interferon-inducible) is a widely distributed protein that is expressed in response to infection and causes antiviral effects against a broad spectrum of viruses. Viperin is a member of the radical S-adenosyl-l-methionine (SAM) superfamily of enzymes, which typically employ a 4Fe-4S cluster to reductively cleave SAM to initiate chemistry. Though the specific reaction catalyzed by viperin remains unknown, it has been shown that expression of viperin causes an increase in the fluidity of lipid membranes, which impedes the budding of nascent viral particles from the membrane inhibiting propagation of the infection. Herein, we show that expression of the human viperin homologue induces a dramatically elongated morphology of the host Escherichia coli cells. Mutation of an essential cysteine that coordinates the radical SAM cluster abrogates this effect. Thus, the native radical SAM activity of viperin is likely occurring in the host bacteria, indicating the elusive substrate is shared between both bacteria and humans, significantly narrowing the range of potential candidate substrates and providing a convenient bacterial platform from which future studies can occur.

Transparent, Weakly Conductive Films for Space Applications

NASA Technical Reports Server (NTRS)

Griffin, John; Morgan, Ashraf; Hambourger, Paul D.

2004-01-01

Electrically insulating spacecraft surfaces are vulnerable to nonuniform charge buildup due to particles emitted by the sun. On Mars, insulating surfaces of exploration vehicles and structures will be affected by dust coatings possibly held in place by triboelectric surface charge. Application of a conductive film may be a solution to the charging problem, but the coating must be highly transparent if used on solar panels, lenses, etc. Sheet resistivity requirements depend on the application and are in the range 10(exp 2) - 10(exp 8) ohms/square. Co-deposited indium tin oxide (ITO) and MgF2 is promising, with high transparency, tailorable electrical properties, and durability to atomic oxygen. Due to ITO's relatively narrow bandgap (approximately 3.5 eV), the film might absorb enough ultraviolet to protect polymeric substrates. Recent work on dual-magnetron-sputtered ITO-MgF2 showed that a variety of polymeric substrates can be coated at room temperature. However, the sheet resistivity is very sensitive to composition, suggestive of a percolation transition. This could be a serious problem for large-scale coating production. We will report on attempts to control film composition by plasma emission monitoring of the ITO and MgF2 guns.

Self-biased magnetoelectric charge coupling in transducer of SmFe2, Pb(Zr,Ti)O3 stack, and stepped horn substrate with multi-frequency effect

NASA Astrophysics Data System (ADS)

Tang, Chengpei; Lu, Caijiang; Gao, Hongli; Fu, Guoqiang

2017-10-01

This paper presents a broadband, self-biased magnetoelectric (ME) charge coupling in a transducer comprising of a negative magnetostrictive SmFe2 plate, a piezoelectric Pb(Zr,Ti)O3 (PZT) stack, and a stepped horn substrate. By using the SmFe2 plate with a large anisotropic field, an outstanding self-biased piezomagnetic effect is realized. The horn serves as a waveguide with multiple resonances and converges vibrating energy excited by the SmFe2 plate from the wide side to the narrow side, which results in a higher vibrating magnification at the position of the PZT-stack. Then, a strong mechanical-electric coupling is realized by the use of the PZT-stack with high capacitance. Consequently, several large peaks of ME charge response with magnitudes of 1.02-18.99 nC/Oe in the 0.1-50 kHz range are observed at zero-biased magnetic field. This demonstrates that the proposed broadband self-biased structure may be useful for multifunctional devices such as low frequency AC magnetic field sensors or multi-frequency energy harvesters.

Enhanced Switchable Ferroelectric Photovoltaic Effects in Hexagonal Ferrite Thin Films via Strain Engineering.

PubMed

Han, Hyeon; Kim, Donghoon; Chu, Kanghyun; Park, Jucheol; Nam, Sang Yeol; Heo, Seungyang; Yang, Chan-Ho; Jang, Hyun Myung

2018-01-17

Ferroelectric photovoltaics (FPVs) are being extensively investigated by virtue of switchable photovoltaic responses and anomalously high photovoltages of ∼10 4 V. However, FPVs suffer from extremely low photocurrents due to their wide band gaps (E g ). Here, we present a promising FPV based on hexagonal YbFeO 3 (h-YbFO) thin-film heterostructure by exploiting its narrow E g . More importantly, we demonstrate enhanced FPV effects by suitably exploiting the substrate-induced film strain in these h-YbFO-based photovoltaics. A compressive-strained h-YbFO/Pt/MgO heterojunction device shows ∼3 times enhanced photovoltaic efficiency than that of a tensile-strained h-YbFO/Pt/Al 2 O 3 device. We have shown that the enhanced photovoltaic efficiency mainly stems from the enhanced photon absorption over a wide range of the photon energy, coupled with the enhanced polarization under a compressive strain. Density functional theory studies indicate that the compressive strain reduces E g substantially and enhances the strength of d-d transitions. This study will set a new standard for determining substrates toward thin-film photovoltaics and optoelectronic devices.

Temporal and spectral properties of the songs of the southern green stink bug Nezara viridula (L.) from Slovenia.

PubMed

Cokl, A; Virant-Doberlet, M; Stritih, N

2000-01-01

Substrate born songs of the southern green stinkbug Nezara viridula (L.) from Slovenia were recorded and analysed. The male calling song is composed of narrow-band regularly repeated single pulses and of broad-band frequency modulated pulses grouped into pulse trains. The female calling song is characterised by broad-band pulsed and narrow-band non-pulsed pulse trains. A frequency modulated pre-pulse precedes the narrow-band pulse train. A frequency-modulated post-pulse usually follows the pulse train of the male courtship song. The male calling song triggers broad-band pulse trains of the female courtship song. The female also produces a repelling low-frequency vibration that inhibits male calling and courtship. The male rival song is characterised by prolonged pulses with a typical frequency modulation.

Raman imaging using fixed bandpass filter

NASA Astrophysics Data System (ADS)

Landström, L.; Kullander, F.; Lundén, H.; Wästerby, P.

2017-05-01

By using fixed narrow band pass optical filtering and scanning the laser excitation wavelength, hyperspectral Raman imaging could be achieved. Experimental, proof-of-principle results from the Chemical Warfare Agent (CWA) tabun (GA) as well as the common CWA simulant tributyl phosphate (TBP) on different surfaces/substrates are presented and discussed.

Experimental band structure of potassium as measured by angle-resolved photoemission

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

Itchkawitz, B.S.; Lyo, I.; Plummer, E.W.

1990-04-15

The bulk band structure of potassium along the (110) direction was measured using angle-resolved photoemission from an epitaxial potassium film several thousand angstroms thick grown on a Ni(100) substrate. We find the occupied bandwidth to be 1.60{plus minus}0.05 eV, which is narrower than the free-electron bandwidth of 2.12 eV and agrees with recent calculations of the quasiparticle self-energy. A narrow peak near the Fermi level which did not disperse with photon energy was observed for photon energies which, according to the nearly-free-electron model, should yield no direct transitions. A comparison of the binding energy and intensity of the anomalous peakmore » as functions of photon energy is made to the calculations of Shung and Mahan (Phys. Rev. B 38, 3856 (1988)). The discrepancies found are discussed in terms of an enhanced surface photoeffect in the photon energy range 20{le}{h bar}{omega}{le}30 eV. For low photon energies, a bulk peak was also observed due to a surface umklapp process with an intensity comparable to the standard bulk (110) peak. The possible contributions to this strong surface umklapp process from a shear instability at the first few (110) atomic planes is discussed.« less

Al x Ga1‑ x N-based semipolar deep ultraviolet light-emitting diodes

NASA Astrophysics Data System (ADS)

Akaike, Ryota; Ichikawa, Shuhei; Funato, Mitsuru; Kawakami, Yoichi

2018-06-01

Deep ultraviolet (UV) emission from Al x Ga1‑ x N-based light-emitting diodes (LEDs) fabricated on semipolar (1\\bar{1}02) (r-plane) AlN substrates is presented. The growth conditions are optimized. A high NH3 flow rate during metalorganic vapor phase epitaxy yields atomically flat Al y Ga1‑ y N (y > x) on which Al x Ga1‑ x N/Al y Ga1‑ y N multiple quantum wells with abrupt interfaces and good periodicity are fabricated. The fabricated r-Al x Ga1‑ x N-based LED emits at 270 nm, which is in the germicidal wavelength range. Additionally, the emission line width is narrow, and the peak wavelength is stable against the injection current, so the semipolar LED shows promise as a UV emitter.

Molluscan extinction patterns across the Cenomanian-Turonian stage boundary in the western interior of the United States

USGS Publications Warehouse

Elder, W.P.

1989-01-01

High-resolution stratigraphic analysis of 18 sections spanning the Cenomanian-Turonian Stage boundary in the western interior of the United States has allowed determination of the magnitude and pattern of molluscan extinction and disruption. Composite range data from all sections show that the faunal turnover across the stage boundary occurs in a series of narrow stratigraphic zones, defined by multiple first and last occurrences, separated by intervals displaying little or no taxonomic turnover. Two of the apparent extinction steps (bottom and top of the Neocardioceras juddii Zone) may be intercontinentally developed. The additional steps apparently reflect cyclic changes in water mass and substrate characteristics in the western interior basin produced in response to orbital forcing of climate. The most affected mollusks were those having intercontinental distributions. -Author

116 years of misplaced management: Portballintrae, Northern Ireland

NASA Astrophysics Data System (ADS)

Jackson, D. W. T.

2012-04-01

Portballintrae has had a protracted history of human interference ranging from small-scale sand removal to hard coastal engineering. A small, horse shoe embayment and a once popular seaside destination on the north coast of Northern Ireland, it has suffered from progressive sediment loss over the last 116 years. From a once sediment abundant system, with a wide sandy beach, it now contains only a limited amount of sand draped over bedrock and/or gravel substrate and a relatively narrow beach. Installation of an obtrusive pier in its western section is thought to have interrupted the natural hydrody-namics and set in motion a progressive longshore transport and re-moval of sand into deeper water. Successive hard engineering 'solutions' prompted through public pressure and engineers keen to do business, have been largely ineffectual, located within a sediment-starved beach system.

Evidence for filamentary superconductivity up to 220 K in oriented multiphase Y-Ba-Cu-O thin films

NASA Astrophysics Data System (ADS)

Schönberger, R.; Otto, H. H.; Brunner, B.; Renk, K. F.

1991-02-01

We report on the observation of filamentary superconductivity up to 220 K in multiphase Y-Ba-Cu-O materials that are deposited as highly oriented thin films on (110)-SrTiO 3 substrates by laser ablation from ceramic targets. The high temperature zero resistivity states are reproducible after temperature cycling down to 80 K for samples treated by a special oxygenation and ozonization process at 340 K and measured in a pure oxygen atmosphere. Our results on thin films confirm former experiments of J.T. Chen and co-workers obtained on ceramic samples with preferred crystallite orientation. A close connection between superconductivity and structural instabilities of most likely ferroic nature, which are observed more often for YBa 2Cu 3O 7 in a narrow temperature range near 220 K, is suggested.

Vibration-tolerant narrow-linewidth semiconductor disk laser using novel frequency-stabilisation schemes

NASA Astrophysics Data System (ADS)

Hunter, Craig R.; Jones, Brynmor E.; Schlosser, Peter; Sørensen, Simon Toft; Strain, Michael J.; McKnight, Loyd J.

2018-02-01

This paper will present developments in narrow-linewidth semiconductor-disk-laser systems using novel frequencystabilisation schemes for reduced sensitivity to mechanical vibrations, a critical requirement for mobile applications. Narrow-linewidth single-frequency lasers are required for a range of applications including metrology and highresolution spectroscopy. Stabilisation of the laser was achieved using a monolithic fibre-optic ring resonator with free spectral range of 181 MHz and finesse of 52 to act as passive reference cavity for the laser. Such a cavity can operate over a broad wavelength range and is immune to a wide band of vibrational frequency noise due to its monolithic implementation. The frequency noise of the locked system has been measured and compared to typical Fabry-Perotlocked lasers using vibration equipment to simulate harsh environments, and analysed here. Locked linewidths of < 40 kHz have been achieved. These developments offer a portable, narrow-linewidth laser system for harsh environments that can be flexibly designed for a range of applications.

Dry season distribution of land crabs, Gecarcinus quadratus (Crustacea: Gecarcinidae), in Corcovado National Park, Costa Rica.

PubMed

Griffiths, Megan E; Mohammad, Basma A; Vega, Andres

2007-03-01

The land crab Gecarcinus quadratus is an engineering species that controls nutrient cycling in tropical forests. Factors regulating their coastal distribution are not fully understood. We quantified land crab distribution during the dry season at Sirena Field Station in Corcovado National Park, Costa Rica, and found that land crab burrow density decreases with increasing distance from the ocean. Leaf litter depth and tree seedling density are negatively correlated with land crab burrow density. Burrows are strongly associated with sand substrate and burrow density is comparatively low in clay substrate. Results suggest that G. quadratus is limited to a narrow coastal zone with sand substrate, and this distribution could have profound effects on plant community structure.

Effects of chemical structure on the thermodynamic efficiency of radical chain carriers for organic synthesis.

PubMed

Lin, Ching Yeh; Peh, Jessie; Coote, Michelle L

2011-03-18

The chain carrier index (CCI), defined as the ratio of the bond dissociation free energies (BDFE) of corresponding chain carrier halides and hydrides, is proposed as a measure of the thermodynamic efficiency of chain carriers for radical dehalogenation. The larger this value is relative to the corresponding value of the organic substrate, the more thermodynamically efficient the process. The chloride and bromide CCIs were evaluated at the G3(MP2)-RAD(+) level of theory for 120 different R-groups, covering a broad range of carbon-centered and noncarbon-centered species; the effects of solvent and temperature have also been studied. The broad finding from this work is that successful chain carriers generally maximize the strength of their halide (versus hydride bonds) through charge-shift bonding. As a result, the thermodynamic efficiency of a chain carrier tends to increase down the periodic table, and also with the inclusion of stronger electron donating substituents. The CCIs of carbon-centered species fall into a relatively narrow range so that, even when the CCI is maximized through inclusion of lone pair donor OMe or NMe(2) groups, the thermodynamic driving force for dehalogenation of other organic substrates is modest at best, and the process is likely to be kinetically hampered. Among the noncarbon-centered species studied, bismuth- and borane-centered compounds have some of the highest CCI values and, although their kinetics requires further optimization, these classes of compounds would be worth further investigation as tin-free radical reducing agents.

Molecular Beam Epitaxy Growth of High Crystalline Quality LiNbO3

NASA Astrophysics Data System (ADS)

Tellekamp, M. Brooks; Shank, Joshua C.; Goorsky, Mark S.; Doolittle, W. Alan

2016-12-01

Lithium niobate is a multi-functional material with wide reaching applications in acoustics, optics, and electronics. Commercial applications for lithium niobate require high crystalline quality currently limited to bulk and ion sliced material. Thin film lithium niobate is an attractive option for a variety of integrated devices, but the research effort has been stagnant due to poor material quality. Both lattice matched and mismatched lithium niobate are grown by molecular beam epitaxy and studied to understand the role of substrate and temperature on nucleation conditions and material quality. Growth on sapphire produces partially coalesced columnar grains with atomically flat plateaus and no twin planes. A symmetric rocking curve shows a narrow linewidth with a full width at half-maximum (FWHM) of 8.6 arcsec (0.0024°), which is comparable to the 5.8 arcsec rocking curve FWHM of the substrate, while the film asymmetric rocking curve is 510 arcsec FWHM. These values indicate that the individual grains are relatively free of long-range disorder detectable by x-ray diffraction with minimal measurable tilt and twist and represents the highest structural quality epitaxial material grown on lattice mismatched sapphire without twin planes. Lithium niobate is also grown on lithium tantalate producing high quality coalesced material without twin planes and with a symmetric rocking curve of 193 arcsec, which is nearly equal to the substrate rocking curve of 194 arcsec. The surface morphology of lithium niobate on lithium tantalate is shown to be atomically flat by atomic force microscopy.

Obtaining a Low and Wide Atomic Layer Deposition Window (150-275 °C) for In2 O3 Films Using an InIII Amidinate and H2 O.

PubMed

Kim, Sang Bok; Jayaraman, Ashwin; Chua, Danny; Davis, Luke M; Zheng, Shao-Liang; Zhao, Xizhu; Lee, Sunghwan; Gordon, Roy G

2018-06-05

Indium oxide is a major component of many technologically important thin films, most notably the transparent conductor indium tin oxide (ITO). Despite being pyrophoric, homoleptic indium(III) alkyls do not allow atomic layer deposition (ALD) of In 2 O 3 using water as a co-precursor at substrate temperatures below 200 °C. Several alternative indium sources have been developed, but none allows ALD at lower temperatures except in the presence of oxidants such as O 2 or O 3 , which are not compatible with some substrates or alloying processes. We have synthesized a new indium precursor, tris(N,N'-diisopropylformamidinato)indium(III), compound 1, which allows ALD of pure, carbon-free In 2 O 3 films using H 2 O as the only co-reactant, on substrates in the temperature range 150-275 °C. In contrast, replacing just the H of the anionic iPrNC(H)NiPr ligand with a methyl group (affording the known tris(N,N'-diisopropylacetamidinato)indium(III), compound 2) results in a considerably higher and narrower ALD window in the analogous reaction with H 2 O (225-300 °C). Kinetic studies demonstrate that a higher rate of surface reactions in both parts of the ALD cycle gives rise to this difference in the ALD windows. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tuning the metal-insulator transition of VO2 by introducing W dopants via a combinatorial approach

NASA Astrophysics Data System (ADS)

Liang, Yangang; Lee, Seunghun; Zhang, Xiaohang; Takeuchi, Ichiro

We have systematically studied the structural phase transition and the electronic properties of composition spread V1-xWxO2 (0 <= x <= 0.037) thin films fabricated on silicon (001) and c-cut sapphire substrates through combinatorial pulsed laser deposition of a V2O5 target and a WO3 target. Our in-situ temperature-dependent x-ray diffraction measurements reveal a gradual change in the film structure from a monoclinic phase to a tetragonal phase via an intermediate mixture of the two as the concentration of tungsten increases from 0% to 3.7% at 300 K. At 358 K, the film is found to be in a tetragonal phase for the entire composition range we studied. The results also suggest that the volume of the unit cell increases as the concentration of tungsten increases. Electrical transport results further show that both the phase transition temperature and the width of the hysteresis loop decrease with the increasing of the concentration of tungsten. Especially, epitaxial V1-xWxO2 films fabricated on c-cut sapphire substrates show narrower hysteresis loop compared to textured V1-xWxO2 films fabricated on Si (100) substrates. In addition, the Hall effect measurements on the epitaxial V1-xWxO2 thin films at various temperature points provide important information for the change in the electronic structure upon increasing the concentration of tungsten. This work was supported by CNAM.

Efficient low-temperature transparent electrocatalytic layers based on graphene oxide nanosheets for dye-sensitized solar cells.

PubMed

Seo, Seon Hee; Jeong, Eun Ji; Han, Joong Tark; Kang, Hyon Chol; Cha, Seung I; Lee, Dong Yoon; Lee, Geon-Woong

2015-05-27

Electrocatalytic materials with a porous structure have been fabricated on glass substrates, via high-temperature fabrication, for application as alternatives to platinum in dye-sensitized solar cells (DSCs). Efficient, nonporous, nanometer-thick electrocatalytic layers based on graphene oxide (GO) nanosheets were prepared on plastic substrates using electrochemical control at low temperatures of ≤100 °C. Single-layer, oxygen-rich GO nanosheets prepared on indium tin oxide (ITO) substrates were electrochemically deoxygenated in acidic medium within a narrow scan range in order to obtain marginally reduced GO at minimum expense of the oxygen groups. The resulting electrochemically reduced GO (E-RGO) had a high density of residual alcohol groups with high electrocatalytic activity toward the positively charged cobalt-complex redox mediators used in DSCs. The ultrathin, alcohol-rich E-RGO layer on ITO-coated poly(ethylene terephthalate) was successfully applied as a lightweight, low-temperature counter electrode with an extremely high optical transmittance of ∼97.7% at 550 nm. A cobalt(II/III)-mediated DSC employing the highly transparent, alcohol-rich E-RGO electrode exhibited a photovoltaic power conversion efficiency of 5.07%. This is superior to that obtained with conventionally reduced GO using hydrazine (3.94%) and even similar to that obtained with platinum (5.10%). This is the first report of a highly transparent planar electrocatalytic layer based on carbonaceous materials fabricated on ITO plastics for application in DSCs.

van der Waals epitaxy of Ge films on mica

NASA Astrophysics Data System (ADS)

Littlejohn, A. J.; Xiang, Y.; Rauch, E.; Lu, T.-M.; Wang, G.-C.

2017-11-01

To date, many materials have been successfully grown on substrates through van der Waals epitaxy without adhering to the constraint of lattice matching as is required for traditional chemical epitaxy. However, for elemental semiconductors such as Ge, this has been challenging and therefore it has not been achieved thus far. In this paper, we report the observation of Ge epitaxially grown on mica at a narrow substrate temperature range around 425 °C. Despite the large lattice mismatch (23%) and the lack of high in-plane symmetry in the mica surface, an epitaxial Ge film with [111] out-of-plane orientation is observed. Crystallinity and electrical properties degrade upon deviation from the ideal growth temperature, as shown by Raman spectroscopy, X-ray diffraction, and Hall effect measurements. X-ray pole figure analysis reveals that there exist multiple rotational domains in the epitaxial Ge film with dominant in-plane orientations between Ge [" separators="|1 ¯10 ] and mica[100] of (20 n )°, where n = 0, 1, 2, 3, 4, 5. A superlattice area mismatch model was used to account for the likelihood of the in-plane orientation formation and was found to be qualitatively consistent with the observed dominant orientations. Our observation of Ge epitaxy with one out-of-plane growth direction through van der Waals forces is a step toward the growth of single crystal Ge films without the constraint in the lattice and symmetry matches with the substrates.

Influence of Panax ginseng on Cytochrome P450 (CYP)3A and P-glycoprotein (Pgp) Activity in Healthy Subjects

PubMed Central

Malati, Christine Y.; Robertson, Sarah M.; Hunt, Jennifer D.; Chairez, Cheryl; Alfaro, Raul M.; Kovacs, Joseph A.; Penzak, Scott R.

2012-01-01

A number of herbal preparations have been shown to interact with prescription medications secondary to modulation of cytochrome P450 (CYP) and/or P-glycoprotein (P-gp). The purpose of this study was to determine the influence of Panax ginseng on CYP3A and P-gp function using the probe substrates midazolam and fexofenadine, respectively. Twelve healthy subjects (8 males) completed this open label, single sequence pharmacokinetic study. Healthy volunteers received single oral doses of midazolam 8 mg and fexofenadine 120 mg, before and after 28 days of P. ginseng 500 mg twice daily. Midazolam and fexofenadine pharmacokinetic parameter values were calculated and compared pre-and post P. ginseng administration. Geometric mean ratios (post-ginseng/pre-ginseng) for midazolam area under the concentration vs. time curve from zero to infinity (AUC0-∞), half life (T1/2), and maximum concentration (Cmax) were significantly reduced at 0.66 (0.55 – 0.78), 0.71 (0.53 – 0.90), and 0.74 (0.56 – 0.93), respectively. Conversely, fexofenadine pharmacokinetics were unaltered by P. ginseng administration. Based on these results, Panax ginseng appeared to induce CYP3A activity in the liver and possibly the gastrointestinal tract. Patients taking Panax ginseng in combination with CYP3A substrates with narrow therapeutic ranges should be monitored closely for adequate therapeutic response to the substrate medication. PMID:21646440

Total ionizing dose effect in an input/output device for flash memory

NASA Astrophysics Data System (ADS)

Liu, Zhang-Li; Hu, Zhi-Yuan; Zhang, Zheng-Xuan; Shao, Hua; Chen, Ming; Bi, Da-Wei; Ning, Bing-Xu; Zou, Shi-Chang

2011-12-01

Input/output devices for flash memory are exposed to gamma ray irradiation. Total ionizing dose has been shown great influence on characteristic degradation of transistors with different sizes. In this paper, we observed a larger increase of off-state leakage in the short channel device than in long one. However, a larger threshold voltage shift is observed for the narrow width device than for the wide one, which is well known as the radiation induced narrow channel effect. The radiation induced charge in the shallow trench isolation oxide influences the electric field of the narrow channel device. Also, the drain bias dependence of the off-state leakage after irradiation is observed, which is called the radiation enhanced drain induced barrier lowing effect. Finally, we found that substrate bias voltage can suppress the off-state leakage, while leading to more obvious hump effect.

Between Scylla and Charybdis: Hydrophobic Graphene-Guided Water Diffusion on Hydrophilic Substrates

PubMed Central

Kim, Jin-Soo; Choi, Jin Sik; Lee, Mi Jung; Park, Bae Ho; Bukhvalov, Danil; Son, Young-Woo; Yoon, Duhee; Cheong, Hyeonsik; Yun, Jun-Nyeong; Jung, Yousung; Park, Jeong Young; Salmeron, Miquel

2013-01-01

The structure of water confined in nanometer-sized cavities is important because, at this scale, a large fraction of hydrogen bonds can be perturbed by interaction with the confining walls. Unusual fluidity properties can thus be expected in the narrow pores, leading to new phenomena like the enhanced fluidity reported in carbon nanotubes. Crystalline mica and amorphous silicon dioxide are hydrophilic substrates that strongly adsorb water. Graphene, on the other hand, interacts weakly with water. This presents the question as to what determines the structure and diffusivity of water when intercalated between hydrophilic substrates and hydrophobic graphene. Using atomic force microscopy, we have found that while the hydrophilic substrates determine the structure of water near its surface, graphene guides its diffusion, favouring growth of intercalated water domains along the C-C bond zigzag direction. Molecular dynamics and density functional calculations are provided to help understand the highly anisotropic water stripe patterns observed. PMID:23896759

Ecosystem and physiological controls over methane production in northern wetlands

NASA Technical Reports Server (NTRS)

Valentine, David W.; Holland, Elisabeth A.; Schimel, David S.

1994-01-01

Peat chemistry appears to exert primary control over methane production rates in the Canadian Northern Wetlands Study (NOWES) area. We determined laboratory methane production rate potentials in anaerobic slurries of samples collected from a transect of sites through the NOWES study area. We related methane production rates to indicators of resistance to microbial decay (peat C: N and lignin: N ratios) and experimentally manipulated substrate availability for methanogenesis using ethanol (EtOH) and plant litter. We also determined responses of methane production to pH and temperature. Methane production potentials declined along the gradient of sites from high rates in the coastal fens to low rates in the interior bogs and were generally highest in surface layers. Strong relationships between CH4 production potentials and peat chemistry suggested that methanogenesis was limited by fermentation rates. Methane production at ambient pH responded strongly to substrate additions in the circumneutral fens with narrow lignin: N and C: N ratios (delta CH4/delta EtOH = 0.9-2.3 mg/g) and weakly in the acidic bogs with wide C: N and lignin: N ratios (delta CH4/delta EtOH = -0.04-0.02 mg/g). Observed Q(sub 10) values ranged from 1.7 to 4.7 and generally increased with increasing substrate availability, suggesting that fermentation rates were limiting. Titration experiments generally demonstrated inhibition of methanogenesis by low pH. Our results suggest that the low rates of methane emission observed in interior bogs during NOWES likely resulted from pH and substrate quality limitation of the fermentation step in methane production and thus reflect intrinsically low methane production potentials. Low methane emission rates observed during NOWES will likely be observed in other northern wetland regions with similar vegetation chemistry.

Conceptual development of the Laser Beam Manifold (LBM)

NASA Technical Reports Server (NTRS)

Campbell, W.; Owen, R. B.

1979-01-01

The laser beam manifold, a device for transforming a single, narrow, collimated beam of light into several beams of desired intensity ratios is described. The device consists of a single optical substrate with a metallic coating on both optical surfaces. By changing the entry point, the number of outgoing beams can be varied.

Ridge-width dependence of the threshold of long wavelength (λ ≈ 14 µm) Quantum Cascade lasers with sloped and vertical sidewalls.

PubMed

Huang, Xue; Chiu, Yenting; Charles, William O; Gmachl, Claire

2012-01-30

We investigate the ridge-width dependence of the threshold of Quantum Cascade lasers fabricated by wet and dry etching, respectively. The sloped sidewalls resulting from wet etching affect the threshold in two ways as the ridge gets narrower. First, the transverse modes are deeper in the substrate, hence reducing the optical confinement factor. Second, more important, a non-negligible field exists in the lossy SiO2 insulation layer, as a result of transverse magnetic mode coupling to the surface plamon mode at the insulator/metal surface, which increases the waveguide loss. By contrast, dry etching is anisotropic and leads to waveguides with vertical sidewalls, which avoids the shift of the modes to the substrate layer and coupling to the surface plasmons, resulting in improved threshold compared with wet-etched lasers, e.g., for narrow ridge widths below 20 µm, the threshold of a 14 µm wide λ ≈ 14 µm laser by dry etching is ~60% lower than that of a wet-etched laser of the same width, at 80 K.

Experimental and theoretical study of the buckling of narrow thin plates on an elastic foundation under compression

NASA Astrophysics Data System (ADS)

Kurguzov, V. D.; Demeshkin, A. G.

2016-05-01

The paper describes the processes of elastic deformation of thin films under mechanical loading. The film is modeled longitudinally by a compressed plate arranged on an elastic foundation. A computer model of the buckling of the narrow thin plate with a delamination portion located on an elastic foundation is constructed. This paper also touches upon the supercritical behavior of the plate-substrate system. The experiments on the axial compression of a metal strip adhered to a rubber plate are performed, and 2 to 7 buckling modes are obtained therein. The critical loads and buckling modes obtained in the numerical calculations are compared with the experimental data. It is shown that there is the possibility of progressive delamination of the metal plate from the foundation if the critical load is exceeded. It is found that the use of the proposed approach, which, in contrast to other approaches, accounts for the elastic deformation of the substrate, causes the dependence between the critical bending stress and the stiffness of the foundation.

Group-III nitride VCSEL structures grown by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Ng, HockMin; Moustakas, Theodore D.

2000-07-01

III-nitride VCSEL structures designed for electron-beam pumping have been grown by molecular beam epitaxy (MBE). The structures consist of a sapphire substrate on which an AlN/GaN distributed Bragg reflector (DBR) with peak reflectance >99% at 402 nm is deposited. The active region consists of a 2-(lambda) cavity with 25 In0.1Ga0.9N/GaN multiquantum wells (MQWs) whose emission coincides with the high reflectance region of the DBR. The thicknesses of the InGaN wells and the GaN barriers are 35 angstrom and 75 angstrom respectively. The top reflector consists of a silver metallic mirror which prevents charging effects during electron-beam pumping. The structure was pumped from the top- side with a cw electron-beam using a modified cathodoluminescence (CL) system mounted on a scanning electron microscope chamber. Light output was collected from the polished sapphire substrate side. Measurements performed at 100 K showed intense emission at 407 nm with narrowing of the linewidth with increasing beam current. A narrow emission linewidth of 0.7 nm was observed indicating the onset of stimulated emission.

Narrow-headed garter snake (Thamnophis rufipunctatus)

USGS Publications Warehouse

Nowak, Erika M.

2006-01-01

The narrow-headed garter snake is a harmless, nonvenomous snake that is distinguished by its elongated, triangular-shaped head and the red or dark spots on its olive to tan body. Today, the narrow-headed garter snake is a species of special concern in the United States because of its decline over much of its historic range. Arizona's Oak Creek has historically contained the largest population of narrow-headed garter snakes in the United States. The U.S. Geological Survey (USGS) and the Arizona Game and Fish Department jointly funded research by USGS scientists in Oak Creek to shed light on the factors causing declining population numbers. The research resulted in better understanding of the snake's habitat needs, winter and summer range, and dietary habits. Based on the research findings, the U.S. Forest Service has developed recommendations that visitors and local residents can adopt to help slow the decline of the narrow-headed garter snake in Oak Creek.

Thin noble metal films on Si (111) investigated by optical second-harmonic generation and photoemission

NASA Astrophysics Data System (ADS)

Pedersen, K.; Kristensen, T. B.; Pedersen, T. G.; Morgen, P.; Li, Z.; Hoffmann, S. V.

2002-05-01

Thin noble metal films (Ag, Au and Cu) on Si (111) have been investigated by optical second-harmonic generation (SHG) in combination with synchrotron radiation photoemission spectroscopy. The valence band spectra of Ag films show a quantization of the sp-band in the 4-eV energy range from the Fermi level down to the onset of the d-bands. For Cu and Au the corresponding energy range is much narrower and quantization effects are less visible. Quantization effects in SHG are observed as oscillations in the signal as a function of film thickness. The oscillations are strongest for Ag and less pronounced for Cu, in agreement with valence band photoemission spectra. In the case of Au, a reacted layer floating on top of the Au film masks the observation of quantum well levels by photoemission. However, SHG shows a well-developed quantization of levels in the Au film below the reacted layer. For Ag films, the relation between film thickness and photon energy of the SHG resonances indicates different types of resonances, some of which involve both quantum well and substrate states.

Estimation of mercury background values in sediment and biota of the Bijagós archipelago, Guinea-Bissau.

PubMed

Coelho, J P; Monteiro, R J R; Catry, T; Lourenço, P M; Catry, P; Regalla, A; Catry, I; Figueira, P; Pereira, E; Vale, C; P Granadeiro, José

2016-10-15

This work evaluates the mercury (Hg) contamination status (sediments and biota) of the Bijagós archipelago, off the coast of Guinea-Bissau. Sediments exhibited very low concentrations (<1-12ngg(-1)), pointing to negligible sources of anthropogenic Hg in the region. Nevertheless, Hg is well correlated to the fine fraction, aluminium, and loss on ignition, indicating the effect of grain size and organic matter content on the presence of Hg in sediments. Mercury in the bivalves Tagelus adansoni and Senilia senilis did not vary considerably among sites, ranging within narrow intervals (0.09-0.12 and 0.12-0.14μgg(-1) (dry weight), respectively). Divergent substrate preferences/feeding tactics may justify slight differences between species. The value 11ngg(-1) is proposed as the sediment background concentration for this West-African coastal region, and concentrations within the interval 8-10ngg(-1) (wet weight) may be considered as reference range for S. senilis and T. adansoni in future monitoring studies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Controllable electrodeposition of ZnO nanorod arrays on flexible stainless steel mesh substrate for photocatalytic degradation of Rhodamine B

NASA Astrophysics Data System (ADS)

Lu, Hui; Zhang, Mei; Guo, Min

2014-10-01

Well-aligned single-crystalline ZnO nanorod arrays (ZNRAs) were prepared on flexible stainless steel mesh (SSM) substrate in large-scale by using a direct electrodeposition method. The effects of electrochemical parameters, such as applied potential, applied nucleation potential time, substrate pretreatment, electrodeposition duration and times, on the orientation, morphology and density of ZNRAs were systematically studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and the selected area electron diffraction (SAED). The results showed that ZNRAs on SSM substrate with [0 0 1] preferred orientation and well crystallization were obtained by controlling the applied potential in the range of -0.9 to -1.1 V. The density of ZNRAs could be increased obviously by applying a nucleation potential (-1.3 V for more than 10 s before deposition) or by means of substrate pretreatment (the SSM immersed in zinc acetate colloid for more than 10 min before deposition), meanwhile, the deposited ZNRAs also had small average diameter (<46 ± 4 nm), narrow size distribution and good orientation. In addition, it was also found that the average diameter of ZNRAs could be increased from 89 to 201 ± 5 nm by extending the electrodeposition duration from 1800 to 7200 s, and the length of rods was from 0.8 to 2.2 ± 0.1 μm when the times of the electrodeposition from one to six times. Furthermore, the band gap energy (Eg) of as-prepared ZNTAs was not closely related to the electrodeposition times (only changed from 3.30 to 3.32 eV). The ZNRAs prepared with more electrodeposition times showed enhanced photocatalytic performance under the UV-lamp for degradation of Rhodamine B. The degradation efficiency of ZNRAs improved from 89.4% to 98.3% with the deposition times from one to six times.

Substrate Specificity of Cysteine Proteases Beyond the S2 Pocket: Mutagenesis and Molecular Dynamics Investigation of Fasciola hepatica Cathepsins L

PubMed Central

Corvo, Ileana; Ferraro, Florencia; Merlino, Alicia; Zuberbühler, Kathrin; O'Donoghue, Anthony J.; Pastro, Lucía; Pi-Denis, Natalia; Basika, Tatiana; Roche, Leda; McKerrow, James H.; Craik, Charles S.; Caffrey, Conor R.; Tort, José F.

2018-01-01

Cysteine proteases are widespread in all life kingdoms, being central to diverse physiological processes based on a broad range of substrate specificity. Paralogous Fasciola hepatica cathepsin L proteases are essential to parasite invasion, tissue migration and reproduction. In spite of similarities in their overall sequence and structure, these enzymes often exhibit different substrate specificity. These preferences are principally determined by the amino acid composition of the active site's S2 subsite (pocket) of the enzyme that interacts with the substrate P2 residue (Schetcher and Berger nomenclature). Although secreted FhCL1 accommodates aliphatic residues in the S2 pocket, FhCL2 is also efficient in cleaving proline in that position. To understand these differences, we engineered the FhCL1 S2 subsite at three amino acid positions to render it identical to that present in FhCL2. The substitutions did not produce the expected increment in proline accommodation in P2. Rather, they decreased the enzyme's catalytic efficiency toward synthetic peptides. Nonetheless, a change in the P3 specificity was associated with the mutation of Leu67 to Tyr, a hinge residue between the S2 and S3 subsites that contributes to the accommodation of Gly in S3. Molecular dynamic simulations highlighted changes in the spatial distribution and secondary structure of the S2 and S3 pockets of the mutant FhCL1 enzymes. The reduced affinity and catalytic efficiency of the mutant enzymes may be due to a narrowing of the active site cleft that hinders the accommodation of substrates. Because the variations in the enzymatic activity measured could not be exclusively allocated to those residues lining the active site, other more external positions might modulate enzyme conformation, and, therefore, catalytic activity. PMID:29725596

Resonances of nanoparticles with poor plasmonic metal tips

NASA Astrophysics Data System (ADS)

Ringe, Emilie; Desantis, Christopher J.; Collins, Sean M.; Duchamp, Martial; Dunin-Borkowski, Rafal E.; Skrabalak, Sara E.; Midgley, Paul A.

2015-11-01

The catalytic and optical properties of metal nanoparticles can be combined to create platforms for light-driven chemical energy storage and enhanced in-situ reaction monitoring. However, the heavily damped plasmon resonances of many catalytically active metals (e.g. Pt, Pd) prevent this dual functionality in pure nanostructures. The addition of catalytic metals at the surface of efficient plasmonic particles thus presents a unique opportunity if the resonances can be conserved after coating. Here, nanometer resolution electron-based techniques (electron energy loss, cathodoluminescence, and energy dispersive X-ray spectroscopy) are used to show that Au particles incorporating a catalytically active but heavily damped metal, Pd, sustain multiple size-dependent localized surface plasmon resonances (LSPRs) that are narrow and strongly localized at the Pd-rich tips. The resonances also couple with a dielectric substrate and other nanoparticles, establishing that the full range of plasmonic behavior is observed in these multifunctional nanostructures despite the presence of Pd.

Emission Testing Results of Thermally Stable, Metamaterial, Selective-Emitters for Thermophotovoltaics

NASA Astrophysics Data System (ADS)

Levinson, Katherine; Naka, Norihito; Pfiester, Nicole; Licht, Abigail; Vandervelde, Tom

2015-03-01

In thermophotovoltaics, the energy from a heated emitter is converted to electricity by a photovoltaic diode. A selective emitter can be used to emit a narrow band of wavelengths tailored to the bandgap of the photovoltaic diode. This spectral shaping improves the conversion efficiency of the diode and reduces undesirable diode heating. In our research, we study selective emitters based on metamaterials composed of repeating nanoscale structures. The emission characteristics of these materials vary based on the compositional structure, allowing the emitted spectrum to be tunable. Simulations were performed with CST Microwave Studio to design emitters with peak wavelengths ranging from 1-10 microns. The structures were then fabricated using physical vapor deposition and electron beam lithography on a sapphire substrate. Emitter materials studied include gold, platinum, and iridium. Here we report on the emission spectra of the selective emitters and the post-heating structural integrity.

Lattice-Matched Epitaxial Graphene Grown on Boron Nitride.

PubMed

Davies, Andrew; Albar, Juan D; Summerfield, Alex; Thomas, James C; Cheng, Tin S; Korolkov, Vladimir V; Stapleton, Emily; Wrigley, James; Goodey, Nathan L; Mellor, Christopher J; Khlobystov, Andrei N; Watanabe, Kenji; Taniguchi, Takashi; Foxon, C Thomas; Eaves, Laurence; Novikov, Sergei V; Beton, Peter H

2018-01-10

Lattice-matched graphene on hexagonal boron nitride is expected to lead to the formation of a band gap but requires the formation of highly strained material and has not hitherto been realized. We demonstrate that aligned, lattice-matched graphene can be grown by molecular beam epitaxy using substrate temperatures in the range 1600-1710 °C and coexists with a topologically modified moiré pattern with regions of strained graphene which have giant moiré periods up to ∼80 nm. Raman spectra reveal narrow red-shifted peaks due to isotropic strain, while the giant moiré patterns result in complex splitting of Raman peaks due to strain variations across the moiré unit cell. The lattice-matched graphene has a lower conductance than both the Frenkel-Kontorova-type domain walls and also the topological defects where they terminate. We relate these results to theoretical models of band gap formation in graphene/boron nitride heterostructures.

Growth and magnetic properties of multiferroic LaxBi1-xMnO3 thin films

NASA Astrophysics Data System (ADS)

Gajek, M.; Bibes, M.; Wyczisk, F.; Varela, M.; Fontcuberta, J.; Barthélémy, A.

2007-05-01

A comparative study of LaxBi1-xMnO3 thin films grown on SrTiO3 substrates is reported. It is shown that these films grow epitaxially in a narrow pressure-temperature range. A detailed structural and compositional characterization of the films is performed within the growth window. The structure and the magnetization of this system are investigated. We find a clear correlation between the magnetization and the unit-cell volume that we ascribe to Bi deficiency and the resultant introduction of a mixed valence on the Mn ions. On these grounds, we show that the reduced magnetization of LaxBi1-xMnO3 thin films compared to the bulk can be explained quantitatively by a simple model, taking into account the deviation from nominal composition and the Goodenough-Kanamori-Anderson rules of magnetic interactions.

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

Yu, Shifeng; Wang, Shuyu; Lu, Ming

In this paper, vanadium thin films were deposited on sapphire substrates by DC magnetron sputtering and then oxidized in a tube furnace filled with oxygen under different temperatures and oxygen flow rates. The significant influence of the oxygen flow rate and oxidation temperature on the electrical and structural properties of the vanadium oxide thin films were investigated systematically. It shows the pure vanadium dioxide (VO 2) state can only be obtained in a very narrow temperature and oxygen flow rate range. The resistivity change during the metal-insulator transition varies from 0.2 to 4 orders of magnitude depending on the oxidationmore » condition. Large thermal hysteresis during the metal-insulator phase transition was observed during the transition compared to the results in literature. Proper oxidation conditions can significantly reduce the thermal hysteresis. Finally, the fabricated VO 2 thin films showed the potential to be applied in the development of electrical sensors and other smart devices.« less

Biocatalysts for the pharmaceutical industry created by structure-guided directed evolution of stereoselective enzymes.

PubMed

Li, Guangyue; Wang, Jian-Bo; Reetz, Manfred T

2018-04-01

Enzymes have been used for a long time as catalysts in the asymmetric synthesis of chiral intermediates needed in the production of therapeutic drugs. However, this alternative to man-made catalysts has suffered traditionally from distinct limitations, namely the often observed wrong or insufficient enantio- and/or regioselectivity, low activity, narrow substrate range, and insufficient thermostability. With the advent of directed evolution, these problems can be generally solved. The challenge is to develop and apply the most efficient mutagenesis methods which lead to highest-quality mutant libraries requiring minimal screening. Structure-guided saturation mutagenesis and its iterative form have emerged as the method of choice for evolving stereo- and regioselective mutant enzymes needed in the asymmetric synthesis of chiral intermediates. The number of (industrial) applications in the preparation of chiral pharmaceuticals is rapidly increasing. This review features and analyzes typical case studies. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electrografting of diazonium-functionalized polyoxometalates: synthesis, immobilisation and electron-transfer characterisation from glassy carbon.

PubMed

Rinfray, Corentin; Izzet, Guillaume; Pinson, Jean; Gam Derouich, Sarra; Ganem, Jean-Jacques; Combellas, Catherine; Kanoufi, Frédéric; Proust, Anna

2013-10-04

Polyoxometalates (POMs) are attractive candidates for the rational design of multi-level charge-storage materials because they display reversible multi-step reduction processes in a narrow range of potentials. The functionalization of POMs allows for their integration in hybrid complementary metal oxide semiconductor (CMOS)/molecular devices, provided that fine control of their immobilisation on various substrates can be achieved. Owing to the wide applicability of the diazonium route to surface modification, a functionalized Keggin-type POM [PW11 O39 {Ge(p-C6 H4 -CC-C6 H4 -${{\\rm N}{{+\\hfill \\atop 2\\hfill}}}$)}](3-) bearing a pending diazonium group was prepared and subsequently covalently anchored onto a glassy carbon electrode. Electron transfer with the immobilised POM was thoroughly investigated and compared to that of the free POM in solution. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Landscape heterogeneity-biodiversity relationship: effect of range size.

PubMed

Katayama, Naoki; Amano, Tatsuya; Naoe, Shoji; Yamakita, Takehisa; Komatsu, Isamu; Takagawa, Shin-ichi; Sato, Naoto; Ueta, Mutsuyuki; Miyashita, Tadashi

2014-01-01

The importance of landscape heterogeneity to biodiversity may depend on the size of the geographic range of species, which in turn can reflect species traits (such as habitat generalization) and the effects of historical and contemporary land covers. We used nationwide bird survey data from Japan, where heterogeneous landscapes predominate, to test the hypothesis that wide-ranging species are positively associated with landscape heterogeneity in terms of species richness and abundance, whereas narrow-ranging species are positively associated with landscape homogeneity in the form of either open or forest habitats. We used simultaneous autoregressive models to explore the effects of climate, evapotranspiration, and landscape heterogeneity on the richness and abundance of breeding land-bird species. The richness of wide-ranging species and the total species richness were highest in heterogeneous landscapes, where many wide-ranging species showed the highest abundance. In contrast, the richness of narrow-ranging species was not highest in heterogeneous landscapes; most of those species were abundant in either open or forest landscapes. Moreover, in open landscapes, narrow-ranging species increased their species richness with decreasing temperature. These results indicate that heterogeneous landscapes are associated with rich bird diversity but that most narrow-ranging species prefer homogeneous landscapes--particularly open habitats in colder regions, where grasslands have historically predominated. There is a need to reassess the generality of the heterogeneity-biodiversity relationship, with attention to the characteristics of species assemblages determined by environments at large spatiotemporal scales.

Landscape Heterogeneity–Biodiversity Relationship: Effect of Range Size

PubMed Central

Katayama, Naoki; Amano, Tatsuya; Naoe, Shoji; Yamakita, Takehisa; Komatsu, Isamu; Takagawa, Shin-ichi; Sato, Naoto; Ueta, Mutsuyuki; Miyashita, Tadashi

2014-01-01

The importance of landscape heterogeneity to biodiversity may depend on the size of the geographic range of species, which in turn can reflect species traits (such as habitat generalization) and the effects of historical and contemporary land covers. We used nationwide bird survey data from Japan, where heterogeneous landscapes predominate, to test the hypothesis that wide-ranging species are positively associated with landscape heterogeneity in terms of species richness and abundance, whereas narrow-ranging species are positively associated with landscape homogeneity in the form of either open or forest habitats. We used simultaneous autoregressive models to explore the effects of climate, evapotranspiration, and landscape heterogeneity on the richness and abundance of breeding land-bird species. The richness of wide-ranging species and the total species richness were highest in heterogeneous landscapes, where many wide-ranging species showed the highest abundance. In contrast, the richness of narrow-ranging species was not highest in heterogeneous landscapes; most of those species were abundant in either open or forest landscapes. Moreover, in open landscapes, narrow-ranging species increased their species richness with decreasing temperature. These results indicate that heterogeneous landscapes are associated with rich bird diversity but that most narrow-ranging species prefer homogeneous landscapes—particularly open habitats in colder regions, where grasslands have historically predominated. There is a need to reassess the generality of the heterogeneity-biodiversity relationship, with attention to the characteristics of species assemblages determined by environments at large spatiotemporal scales. PMID:24675969

Linear variable narrow bandpass optical filters in the far infrared (Conference Presentation)

NASA Astrophysics Data System (ADS)

Rahmlow, Thomas D.

2017-06-01

We are currently developing linear variable filters (LVF) with very high wavelength gradients. In the visible, these filters have a wavelength gradient of 50 to 100 nm/mm. In the infrared, the wavelength gradient covers the range of 500 to 900 microns/mm. Filter designs include band pass, long pass and ulta-high performance anti-reflection coatings. The active area of the filters is on the order of 5 to 30 mm along the wavelength gradient and up to 30 mm in the orthogonal, constant wavelength direction. Variation in performance along the constant direction is less than 1%. Repeatable performance from filter to filter, absolute placement of the filter relative to a substrate fiducial and, high in-band transmission across the full spectral band is demonstrated. Applications include order sorting filters, direct replacement of the spectrometer and hyper-spectral imaging. Off-band rejection with an optical density of greater than 3 allows use of the filter as an order sorting filter. The linear variable order sorting filters replaces other filter types such as block filters. The disadvantage of block filters is the loss of pixels due to the transition between filter blocks. The LVF is a continuous gradient without a discrete transition between filter wavelength regions. If the LVF is designed as a narrow band pass filter, it can be used in place of a spectrometer thus reducing overall sensor weight and cost while improving the robustness of the sensor. By controlling the orthogonal performance (smile) the LVF can be sized to the dimensions of the detector. When imaging on to a 2 dimensional array and operating the sensor in a push broom configuration, the LVF spectrometer performs as a hyper-spectral imager. This paper presents performance of LVF fabricated in the far infrared on substrates sized to available detectors. The impact of spot size, F-number and filter characterization are presented. Results are also compared to extended visible LVF filters.

Fabrication of a novel aluminum surface covered by numerous high-aspect-ratio anodic alumina nanofibers

NASA Astrophysics Data System (ADS)

Nakajima, Daiki; Kikuchi, Tatsuya; Natsui, Shungo; Sakaguchi, Norihito; Suzuki, Ryosuke O.

2015-11-01

The formation behavior of anodic alumina nanofibers via anodizing in a concentrated pyrophosphoric acid under various conditions was investigated using electrochemical measurements and SEM/TEM observations. Pyrophosphoric acid anodizing at 293 K resulted in the formation of numerous anodic alumina nanofibers on an aluminum substrate through a thin barrier oxide and honeycomb oxide with narrow walls. However, long-term anodizing led to the chemical dissolution of the alumina nanofibers. The density of the anodic alumina nanofibers decreased as the applied voltage increased in the 10-75 V range. However, active electrochemical dissolution of the aluminum substrate occurred at a higher voltage of 90 V. Low temperature anodizing at 273 K resulted in the formation of long alumina nanofibers measuring several micrometers in length, even though a long processing time was required due to the low current density during the low temperature anodizing. In contrast, high temperature anodizing easily resulted in the formation and chemical dissolution of alumina nanofibers. The structural nanofeatures of the anodic alumina nanofibers were controlled by choosing of the appropriate electrochemical conditions, and numerous high-aspect-ratio alumina nanofibers (>100) can be successfully fabricated. The anodic alumina nanofibers consisted of a pure amorphous aluminum oxide without anions from the employed electrolyte.

Influence of laser power on the penetration depth and geometry of scanning tracks in selective laser melting

NASA Astrophysics Data System (ADS)

Stopyra, Wojciech; Kurzac, Jarosław; Gruber, Konrad; Kurzynowski, Tomasz; Chlebus, Edward

2016-12-01

SLM technology allows production of a fully functional objects from metal and ceramic powders, with true density of more than 99,9%. The quality of manufactured items in SLM method affects more than 100 parameters, which can be divided into fixed and variable. Fixed parameters are those whose value before the process should be defined and maintained in an appropriate range during the process, e.g. chemical composition and morphology of the powder, oxygen level in working chamber, heating temperature of the substrate plate. In SLM technology, five parameters are variables that optimal set allows to produce parts without defects (pores, cracks) and with an acceptable speed. These parameters are: laser power, distance between points, time of exposure, distance between lines and layer thickness. To develop optimal parameters thin walls or single track experiments are performed, to select the best sets narrowed to three parameters: laser power, exposure time and distance between points. In this paper, the effect of laser power on the penetration depth and geometry of scanned single track was shown. In this experiment, titanium (grade 2) substrate plate was used and scanned by fibre laser of 1064 nm wavelength. For each track width, height and penetration depth of laser beam was measured.

Effect of self-organization, defects, impurities, and autocatalytic processes on the parameters of ZnO films and nanorods

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

Mezdrogina, M. M., E-mail: Margaret.M@mail.ioffe.ru; Eremenko, M. V.; Levitskii, V. S.

The effects of the parameters of ZnO-film deposition onto different substrates using the method of ac magnetron sputtering in a gas mixture of argon and oxygen hare studied. The phenomenon of self-organization is observed, which leads to invariability of the surface morphology of the ZnO films upon a variation in the substrate materials and deposition parameters. The parameters of the macro- and micro-photoluminescence spectra of the films differ insignificantly from the parameters of the photoluminescence spectra of bulk ZnO crystals obtained by the method of hydrothermal growth. The presence of intense emission with a narrow full-width at half-maximum (FWHM) inmore » different regions of the spectrum allows ZnO films obtained by magnetron sputtering doped with rare-earth metal impurities (REIs) to be considered as a promising material for the creation of optoelectronic devices working in a broad spectral range. The possibility of the implementation of magnetic ordering upon legierung with REIs significantly broadens the functional possibilities of ZnO films. The parameters of the photoluminescence spectra of ZnO nanorods are determined by their geometrical parameters and by the concentration and type of the impurities introduced.« less

Cationic flocculants carrying hydrophobic functionalities: applications for solid/liquid separation.

PubMed

Schwarz, S; Jaeger, W; Paulke, B-R; Bratskaya, S; Smolka, N; Bohrisch, J

2007-07-26

The flocculation behaviors of three series of polycations with narrow molecular weight distributions carrying hydrophobic substituents on their backbones [poly(N-vinylbenzyl-N,N,N-trimethylammonium chloride), poly(N-vinylbenzyl-N,N-dimethyl-N-butylammonium chloride), and poly(N-vinylbenzylpyridinium chloride)] were investigated in dispersions of monodisperse polystyrene latexes and kaolin. Apparently, the charge density of the polycations decreases with increasing substituent hydrophobicity and increasing molecular weight of the polyelectrolytes. The necessary amount of flocculant for phase separation in dispersions with high substrate surface charge densities increases with increasing hydrophobicity of the polyelectrolyte. Nevertheless, the introduction of hydrophobic functionalities is beneficial, resulting in a substantial broadening of the range between the minimum and maximum amounts of flocculant necessary for efficient flocculation (flocculation window). An increase in ionic strength supports this effect. When the substrate has a low charge density, the hydrophobic interactions play a much more significant role in the flocculation process. Here, the minimum efficient doses remained the same for all three polyelectrolytes investigated, but the width of the flocculation window increased as the polycation hydrophobicity and the molecular weight increased. The necessary amount of flocculant increased with an increase in particle size at constant solid content of the dispersion, as well as with a decreasing number of particles at a constant particle size.

Production of human milk fat analogue containing docosahexaenoic and arachidonic acids.

PubMed

Turan, Dilek; Sahin Yeşilçubuk, Neşe; Akoh, Casimir C

2012-05-02

Human milk fat (HMF) analogue containing docosahexaenoic acid (DHA) and arachidonic acid (ARA) at sn-1,3 positions and palmitic acid (PA) at sn-2 position was produced. Novozym 435 lipase was used to produce palmitic acid-enriched hazelnut oil (EHO). EHO was then used to produce the final structured lipid (SL) through interesterification reactions using Lipozyme RM IM. Reaction variables for 3 h reactions were temperature, substrate mole ratio, and ARASCO/DHASCO (A:D) ratio. After statistical analysis of DHA, ARA, total PA, and PA content at sn-2 position, a large-scale production was performed at 60 °C, 3:2 A:D ratio, and 1:0.1 substrate mole ratio. For the SL, those results were determined as 57.3 ± 0.4%, 2.7 ± 0.0%, 2.4 ± 0.1%, and 66.1 ± 2.2%, respectively. Tocopherol contents were 84, 19, 85, and 23 μg/g oil for α-, β-, γ-, and δ-tocopherol. Melting range of SL was narrower than that of EHO. Oxidative stability index (OSI) value of SL (0.80 h) was similar to that of EHO (0.88 h). This SL can be used in infant formulas to provide the benefits of ARA and DHA.

Electrodeposition of Zn-Co-Mo Alloy on the Steel Substrate from Citrate Bath and Its Corrosion Behavior in the Chloride Media

NASA Astrophysics Data System (ADS)

Keyvani, A.; Yeganeh, M.; Rezaeyan, H.

2017-04-01

In this study, Zn-Co-Mo coatings were deposited on the steel substrate from a citrate bath after adjusting pH, concentration, and current density. The morphology, the content of alloying elements, and the thickness of deposits were studied. Deposition behavior of these ternary coatings was examined by cathodic polarization and cyclic voltammetry (CV) techniques. The synthesized deposits were investigated by scanning electron microscopy (SEM), energy-dispersive x-ray (EDX) analysis, x-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization methods. The results showed that the deposition potential of Zn-Co-Mo alloy was feasible in negative potentials higher than about -1.25 V versus Ag/AgCl. Moreover, the corrosion behavior of these coatings was found to be related to the extent of Mo as well as the local anodes and cathodes. The amount of molybdenum in the Zn-Co-Mo coating varied from 2.6 to 14 wt.% as a result of changing the pH. Based on the experimental findings, a narrow range of pH values between 5 and 5.5 could contribute to the high quality of coating in conjunction with the corrosion resistant alloy. Besides, the coatings with Mo element could show a passive-like behavior in the anodic region.

Japanese and Chinese Learners' Acquisition of the Narrow-Range Rules for the Dative Alternation in English.

ERIC Educational Resources Information Center

Inagaki, Shunji

1997-01-01

Investigated the acquisition of narrow-range rules governing the dative alternation by adult learners of English as a Second Language, native English speakers, and Japanese and Chinese speakers. Suggests that the Japanese and Chinese learners' acquisition of the dative alternation in English is governed by the properties of an equivalent structure…

Growth of HgCdTe by Modified Molecular Beam Epitaxy

DTIC Science & Technology

1981-06-01

more commonly available substrates, e.g., silicon and germa - nium. If successful, this approach may by-pass the need for large size CdTe technology...the cooling rate is quite slow. 14 C3239A/bw SC5202. 11FR U) I- CL 0 00 CL 6 uiV CLC W- ( n EU (zw*/M) In A1LISN~a H3MOd U 0 4.- rwo 4- CC L- 01a...7 and Fig. 8. The angular distribution of the splashed particles is narrower. By placing the substrate at a wide 22 C3239A/bw ř N SC5202. 11FR I-x

An experimental investigation of high temperature superconducting microstrip antennas at K- and Ka-band frequencies. Ph.D. Thesis Final Report

NASA Technical Reports Server (NTRS)

Richard, Mark A.

1993-01-01

The recent discovery of high temperature superconductors (HTS) has generated a substantial amount of interest in microstrip antenna applications. However, the high permittivity of substrates compatible with HTS results in narrow bandwidths and high patch edge impedances of such antennas. To investigate the performance of superconducting microstrip antennas, three antenna architectures at K and Ka-band frequencies are examined. Superconducting microstrip antennas that are directly coupled, gap coupled, and electromagnetically coupled to a microstrip transmission line were designed and fabricated on lanthanum aluminate substrates using YBa2Cu3O7 superconducting thin films. For each architecture, a single patch antenna and a four element array were fabricated. Measurements from these antennas, including input impedance, bandwidth, patterns, efficiency, and gain are presented. The measured results show usable antennas can be constructed using any of the architectures. All architectures show excellent gain characteristics, with less than 2 dB of total loss in the four element arrays. Although the direct and gap coupled antennas are the simplest antennas to design and fabricate, they suffer from narrow bandwidths. The electromagnetically coupled antenna, on the other hand, allows the flexibility of using a low permittivity substrate for the patch radiator, while using HTS for the feed network, thus increasing the bandwidth while effectively utilizing the low loss properties of HTS. Each antenna investigated in this research is the first of its kind reported.

Motivation Matters: Differing Effects of Pre-Goal and Post-Goal Emotions on Attention and Memory

PubMed Central

Kaplan, Robin L.; Van Damme, Ilse; Levine, Linda J.

2012-01-01

People often show enhanced memory for information that is central to emotional events and impaired memory for peripheral details. The intensity of arousal elicited by an emotional event is commonly held to be the mechanism underlying memory narrowing, with the implication that all sources of emotional arousal should have comparable effects. Discrete emotions differ in their effects on memory, however, with some emotions broadening rather than narrowing the range of information attended to and remembered. Thus, features of emotion other than arousal appear to play a critical role in memory narrowing. We review theory and research on emotional memory narrowing and argue that motivation matters. Recent evidence suggests that emotions experienced prior to goal attainment or loss lead to memory narrowing whereas emotions experienced after goal attainment or loss broaden the range of information encoded in memory. The motivational component of emotion is an important but understudied feature that can help to clarify the conditions under which emotions enhance and impair attention and memory. PMID:23162490

Motivation matters: differing effects of pre-goal and post-goal emotions on attention and memory.

PubMed

Kaplan, Robin L; Van Damme, Ilse; Levine, Linda J

2012-01-01

People often show enhanced memory for information that is central to emotional events and impaired memory for peripheral details. The intensity of arousal elicited by an emotional event is commonly held to be the mechanism underlying memory narrowing, with the implication that all sources of emotional arousal should have comparable effects. Discrete emotions differ in their effects on memory, however, with some emotions broadening rather than narrowing the range of information attended to and remembered. Thus, features of emotion other than arousal appear to play a critical role in memory narrowing. We review theory and research on emotional memory narrowing and argue that motivation matters. Recent evidence suggests that emotions experienced prior to goal attainment or loss lead to memory narrowing whereas emotions experienced after goal attainment or loss broaden the range of information encoded in memory. The motivational component of emotion is an important but understudied feature that can help to clarify the conditions under which emotions enhance and impair attention and memory.

Cost-Effective Mapping of Benthic Habitats in Inland Reservoirs through Split-Beam Sonar, Indicator Kriging, and Historical Geologic Data

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

Venteris, Erik R.; May, Cassandra

2014-04-23

Because bottom substrate composition is an important control on the temporal and spatial location of the aquatic community, accurate maps of benthic habitats of inland lakes and reservoirs provide valuable information to managers, recreational users, and scientists. Therefore, we collected vertical, split-beam sonar data (roughness [E1], hardness [E2], and bathymetry) and sediment samples to make such maps. Statistical calibration between sonar parameters and sediment classes was problematic because the E1:E2 ratios for soft (muck and clay) sediments overlapped a lower and narrower range for hard (gravel) substrates. Thus, we used indicator kriging (IK) to map the probability that unsampled locationsmore » did not contain coarse sediments. To overcome the calibration issue we tested proxies for the natural processes and anthropogenic history of the reservoir as potential predictive variables. Of these, a geologic map proved to be the most useful. The central alluvial valley and mudflats contained mainly muck and organic-rich clays. The surrounding glacial till and shale bedrock uplands contained mainly poorly sorted gravels. Anomalies in the sonar data suggested that the organic-rich sediments also contained trapped gases, presenting additional interpretive issues for the mapping. We extended the capability of inexpensive split-beam sonar units through the incorporation of historic geologic maps and other records as well as validation with dredge samples. Through the integration of information from multiple data sets, were able to objectively identify bottom substrate and provide reservoir users with an accurate map of available benthic habitat.« less

Cost-Effective Mapping of Benthic Habitats in Inland Reservoirs through Split-Beam Sonar, Indicator Kriging, and Historical Geologic Data

PubMed Central

Venteris, Erik R.; May, Cassandra J.

2014-01-01

Because bottom substrate composition is an important control on the temporal and spatial location of the aquatic community, accurate maps of benthic habitats of inland lakes and reservoirs provide valuable information to managers, recreational users, and scientists. Therefore, we collected vertical, split-beam sonar data (roughness [E1], hardness [E2], and bathymetry) and sediment samples to make such maps. Statistical calibration between sonar parameters and sediment classes was problematic because the E1:E2 ratios for soft (muck and clay) sediments overlapped a lower and narrower range for hard (gravel) substrates. Thus, we used indicator kriging (IK) to map the probability that unsampled locations did not contain coarse sediments. To overcome the calibration issue we tested proxies for the natural processes and anthropogenic history of the reservoir as potential predictive variables. Of these, a geologic map proved to be the most useful. The central alluvial valley and mudflats contained mainly muck and organic-rich clays. The surrounding glacial till and shale bedrock uplands contained mainly poorly sorted gravels. Anomalies in the sonar data suggested that the organic-rich sediments also contained trapped gases, presenting additional interpretive issues for the mapping. We extended the capability of inexpensive split-beam sonar units through the incorporation of historic geologic maps and other records as well as validation with dredge samples. Through the integration of information from multiple data sets, were able to objectively identify bottom substrate and provide reservoir users with an accurate map of available benthic habitat. PMID:24759834

Cost-effective mapping of benthic habitats in inland reservoirs through split-beam sonar, indicator kriging, and historical geologic data.

PubMed

Venteris, Erik R; May, Cassandra J

2014-01-01

Because bottom substrate composition is an important control on the temporal and spatial location of the aquatic community, accurate maps of benthic habitats of inland lakes and reservoirs provide valuable information to managers, recreational users, and scientists. Therefore, we collected vertical, split-beam sonar data (roughness [E1], hardness [E2], and bathymetry) and sediment samples to make such maps. Statistical calibration between sonar parameters and sediment classes was problematic because the E1:E2 ratios for soft (muck and clay) sediments overlapped a lower and narrower range for hard (gravel) substrates. Thus, we used indicator kriging (IK) to map the probability that unsampled locations did not contain coarse sediments. To overcome the calibration issue we tested proxies for the natural processes and anthropogenic history of the reservoir as potential predictive variables. Of these, a geologic map proved to be the most useful. The central alluvial valley and mudflats contained mainly muck and organic-rich clays. The surrounding glacial till and shale bedrock uplands contained mainly poorly sorted gravels. Anomalies in the sonar data suggested that the organic-rich sediments also contained trapped gases, presenting additional interpretive issues for the mapping. We extended the capability of inexpensive split-beam sonar units through the incorporation of historic geologic maps and other records as well as validation with dredge samples. Through the integration of information from multiple data sets, were able to objectively identify bottom substrate and provide reservoir users with an accurate map of available benthic habitat.

Ultra-hard amorphous AlMgB14 films RF sputtered onto curved substrates

NASA Astrophysics Data System (ADS)

Grishin, A. M.; Putrolaynen, V. V.; Yuzvyuk, M. H.

2017-03-01

Recently, hard AlMgB14 (BAM) coatings were deposited for the first time by RF magnetron sputtering using a single stoichiometric ceramic target. High target sputtering power and sufficiently short target-to-substrate distance were found to be critical processing conditions. They enabled fabrication of stoichiometric in-depth compositionally homogeneous films with the peak values of nanohardness 88 GPa and Young’s modulus 517 GPa at the penetration depth of 26 nm and, respectively, 35 GPa and 275 GPa at 200 nm depth in 2 µm thick film (Grishin et al 2014 JETP Lett. 100 680). The narrow range of sufficiently short target-to-substrate distance makes impossible to coat non flat specimens. To achieve ultimate BAM films’ characteristics onto curved surfaces we developed two-step sputtering process. The first thin layer is deposited as a template at low RF power that facilitates a layered Frank van der Merwe mode growth of smooth film occurs. The next layer is grown at high RF target sputtering power. The affinity of subsequent flow of sputtered atoms to already evenly condensed template fosters the development of smooth film surface. As an example, we made BAM coating onto hemispherical 5 mm in diameter ball made from a hard tool steel and used as a head of a special gauge. Very smooth (6.6 nm RMS surface roughness) and hard AlMgB14 films fabricated onto commercial ball-shaped items enhance hardness of tool steel specimens by a factor of four.

Growth of InN on Ge substrate by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Trybus, Elaissa; Namkoong, Gon; Henderson, Walter; Doolittle, W. Alan; Liu, Rong; Mei, Jin; Ponce, Fernando; Cheung, Maurice; Chen, Fei; Furis, Madalina; Cartwright, Alexander

2005-06-01

InN epitaxial growth on a (1 1 1)-oriented, Ga-doped germanium substrate using molecular beam epitaxy is described. X-ray diffraction and transmission electron microscopy investigations have shown that the InN epitaxial layer consists of a wurtzite structure, which has the epitaxial relationship of (0 0 0 1) InN∥(1 1 1) Ge. Transmission electron microscopy shows an intermediate layer at the interface between the InN/Ge substrate. Consistent with recent reports implying a narrow bandgap of InN [Phys. Stat Sol. B 229 (2002) R1, Appl. Phys. Lett. 80 (2002) 3967], a strong photoluminescence with peak energy of 0.69 eV at 15 K was observed for this InN epilayer, in contrast to the peak energy of 0.71 eV for Ga-doped Ge under the same measurement conditions.

X-ray probe of GaN thin films grown on InGaN compliant substrates

NASA Astrophysics Data System (ADS)

Xu, Xiaoqing; Li, Yang; Liu, Jianming; Wei, Hongyuan; Liu, Xianglin; Yang, Shaoyan; Wang, Zhanguo; Wang, Huanhua

2013-04-01

GaN thin films grown on InGaN compliant substrates were characterized by several X-ray technologies: X-ray reciprocal space mapping (RSM), grazing incidence X-ray diffraction (GIXRD), and X-ray photoemission spectrum (XPS). Narrow Lorentz broadening and stress free state were observed for GaN grown on InGaN compliant substrate, while mosaic structure and large tensile stress were observed at the presence of residual indium atoms. RSM disclosed the mosaicity, and the GIXRD was conducted to investigate the depth dependences of crystal quality and strain states. XPS depth profile of indium contents indicated that residual indium atoms deteriorated the crystal quality of GaN not only by producing lattice mismatch at the interface of InGaN and GaN but also by diffusing into GaN overlayers. Accordingly, two solutions were proposed to improve the efficiency of self-patterned lateral epitaxial overgrowth method. This research goes a further step in resolving the urgent substrate problem in GaN fabrication.

Effect of nonsinusoidal bias waveforms on ion energy distributions and fluorocarbon plasma etch selectivity

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

Agarwal, Ankur; Kushner, Mark J.; Iowa State University, Department of Electrical and Computer Engineering, 104 Marston Hall, Ames, Iowa 50011-2151

2005-09-15

The distributions of ion energies incident on the wafer significantly influence feature profiles and selectivity during plasma etching. Control of ion energies is typically obtained by varying the amplitude or frequency of a radio frequency sinusoidal bias voltage applied to the substrate. The resulting ion energy distribution (IED), though, is generally broad. Controlling the width and shape of the IED can potentially improve etch selectivity by distinguishing between threshold energies of surface processes. In this article, control of the IED was computationally investigated by applying a tailored, nonsinusoidal bias waveform to the substrate of an inductively coupled plasma. The waveformmore » we investigated, a quasi-dc negative bias having a short positive pulse each cycle, produced a narrow IED whose width was controllable based on the length of the positive spike and frequency. We found that the selectivity between etching Si and SiO{sub 2} in fluorocarbon plasmas could be controlled by adjusting the width and energy of the IED. Control of the energy of a narrow IED enables etching recipes that transition between speed and selectivity without change of gas mixture.« less

M-shaped grating by nanoimprinting: a replicable, large-area, highly active plasmonic surface-enhanced Raman scattering substrate with nanogaps.

PubMed

Zhu, Zhendong; Bai, Benfeng; Duan, Huigao; Zhang, Haosu; Zhang, Mingqian; You, Oubo; Li, Qunqing; Tan, Qiaofeng; Wang, Jia; Fan, Shoushan; Jin, Guofan

2014-04-24

Plasmonic nanostructures separated by nanogaps enable strong electromagnetic-field confinement on the nanoscale for enhancing light-matter interactions, which are in great demand in many applications such as surface-enhanced Raman scattering (SERS). A simple M-shaped nanograting with narrow V-shaped grooves is proposed. Both theoretical and experimental studies reveal that the electromagnetic field on the surface of the M grating can be pronouncedly enhanced over that of a grating without such grooves, due to field localization in the nanogaps formed by the narrow V grooves. A technique based on room-temperature nanoimprinting lithography and anisotropic reactive-ion etching is developed to fabricate this device, which is cost-effective, reliable, and suitable for fabricating large-area nanostructures. As a demonstration of the potential application of this device, the M grating is used as a SERS substrate for probing Rhodamine 6G molecules. Experimentally, an average SERS enhancement factor as high as 5×10⁸ has been achieved, which verifies the greatly enhanced light-matter interaction on the surface of the M grating over that of traditional SERS surfaces. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and characterization of nano-sized zirconia powder synthesized by single emulsion-assisted direct precipitation.

PubMed

Chandra, Navin; Singh, Deepesh Kumar; Sharma, Meenakshi; Upadhyay, Ravi Kant; Amritphale, S S; Sanghi, S K

2010-02-15

For the first time, single reverse microemulsion-assisted direct precipitation route has been successfully used to synthesize tetragonal zirconia nanoparticles in narrow size range. The synthesized powder was characterized using FT-IR, XRD and HRTEM techniques. The zirconia nanoparticles obtained were spherical in shape and has narrow particle size distribution in the range of 13-31nm and crystallite size in the range of 13-23nm. Copyright 2009 Elsevier Inc. All rights reserved.

Winter Precipitation Efficiency of Mountain Ranges in the Colorado Rockies Under Climate Change

NASA Astrophysics Data System (ADS)

Eidhammer, Trude; Grubišić, Vanda; Rasmussen, Roy; Ikdea, Kyoko

2018-03-01

Orographic precipitation depends on the environmental conditions and the barrier shape. In this study we examine the sensitivity of the precipitation efficiency (i.e., drying ratio (DR)), defined as the ratio of precipitation to incoming water flux, to mountain shape, temperature, stability, and horizontal velocity of the incoming air mass. Furthermore, we explore how the DR of Colorado mountain ranges might change under warmer and moister conditions in the future. For given environmental conditions, we find the DR to be primarily dependent on the upwind slope for mountain ranges wider than about 70 km and on both the slope and width for narrower ranges. Temperature is found to exert an influence on the DR for all Colorado mountain ranges, with DR decreasing with increasing temperature, under both the current and future climate conditions. The decrease of DR with temperature under warmer climate was found to be stronger for wider mountains than the narrower ones. We attribute this asymmetry to the sensitivity of DR to reduced horizontal velocity under warmer conditions. Specifically, while DR for wider mountains shows no sensitivity to changes in horizontal velocity, the DR for narrow ranges increases as the horizontal velocity decreases and more time is provided for precipitation to form. Thus, for narrower ranges, the horizontal velocity appears to offset the temperature effect slightly. The percentagewise decrease of DR for all examined mountain ranges is about 4%K-1. In comparison, the increase in precipitation is about 6%K-1 while the vapor flux increase is about 9%K-1.

Low-temperature synthesis of single-walled carbon nanotubes with a narrow diameter distribution using size-classified catalyst nanoparticles

NASA Astrophysics Data System (ADS)

Kondo, Daiyu; Sato, Shintaro; Awano, Yuji

2006-05-01

Single-walled carbon nanotubes (SWNTs) with a narrow diameter distribution have been synthesized by hot-filament chemical vapor deposition using acetylene at 590 °C. Iron nanoparticles with diameters of 1.6, 2.0, 2.5, 5.0 and 10 nm (standard deviation: ≈10%) obtained with a differential mobility analyzer were used as a catalyst without any supporting materials on a substrate. SWNTs were obtained from 2.0 nm or smaller particles. The ratio of G band to D band in Raman spectra was as high as 35 without purification, indicating that high-quality SWNTs were synthesized. The SWNT diameters correlated with the particle diameters, demonstrating diameter-controlled SWNT growth.

Recipient luminophoric mediums having narrow spectrum luminescent materials and related semiconductor light emitting devices and methods

DOEpatents

LeToquin, Ronan P; Tong, Tao; Glass, Robert C

2014-12-30

Light emitting devices include a light emitting diode ("LED") and a recipient luminophoric medium that is configured to down-convert at least some of the light emitted by the LED. In some embodiments, the recipient luminophoric medium includes a first broad-spectrum luminescent material and a narrow-spectrum luminescent material. The broad-spectrum luminescent material may down-convert radiation emitted by the LED to radiation having a peak wavelength in the red color range. The narrow-spectrum luminescent material may also down-convert radiation emitted by the LED into the cyan, green or red color range.

Comparative analysis of Beggiatoa from hypersaline and marine environments.

PubMed

de Albuquerque, Julia Peixoto; Keim, Carolina Neumann; Lins, Ulysses

2010-07-01

The main criterion to classify a microorganism as belonging to the genus Beggiatoa is its morphology. All multicellular, colorless, gliding bacterial filaments containing sulfur globules described so far belong to this genus. At the ultrastructural level, they show also a very complex cell envelope structure. Here we describe uncultured vacuolated and non-vacuolated bacteria from two different environments showing all characteristics necessary to assign a bacterium to the genus Beggiatoa. We also intended to investigate whether narrow and vacuolate Beggiatoa do differ morphologically as much as they do phylogenetically. Both large, vacuolated trichomes and narrow filaments devoid of vacuoles were observed. We confirmed the identity of the narrow filaments by 16S rRNA phylogenetic analysis. The diameters of the trichomes ranged from 2.4 to 34 microm, and their lengths ranged from 10 microm to over 30 mm. Narrow trichomes moved by gliding at 3.0 microm/s; large filaments moved at 1.5 microm/s. Periplasmic sulfur inclusions were observed in both types of filaments, whereas phosphorus-rich bodies were found only in narrow trichomes. On the other hand, nitrate vacuoles were observed only in large trichomes. Ultra-thin section transmission electron microscopy showed differences between the cell ultrastructure of narrow (non-vacuolated) and large (vacuolated) Beggiatoa. We observed that cell envelopes from narrow Beggiatoa consist of five layers, whereas cell envelopes from large trichomes contain four layers. Copyright 2010 Elsevier Ltd. All rights reserved.

Three-Body Recombination near a Narrow Feshbach Resonance in Li 6

NASA Astrophysics Data System (ADS)

Li, Jiaming; Liu, Ji; Luo, Le; Gao, Bo

2018-05-01

We experimentally measure and theoretically analyze the three-atom recombination rate, L3, around a narrow s -wave magnetic Feshbach resonance of Li 6 - Li 6 at 543.3 G. By examining both the magnetic field dependence and, especially, the temperature dependence of L3 over a wide range of temperatures from a few μ K to above 200 μ K , we show that three-atom recombination through a narrow resonance follows a universal behavior determined by the long-range van der Waals potential and can be described by a set of rate equations in which three-body recombination proceeds via successive pairwise interactions. We expect the underlying physical picture to be applicable not only to narrow s wave resonances, but also to resonances in nonzero partial waves, and not only at ultracold temperatures, but also at much higher temperatures.

Condensing Heat Exchanger with Hydrophilic Antimicrobial Coating

NASA Technical Reports Server (NTRS)

Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor)

2014-01-01

A multi-layer antimicrobial hydrophilic coating is applied to a substrate of anodized aluminum, although other materials may form the substrate. A silver layer is sputtered onto a thoroughly clean anodized surface of the aluminum to about 400 nm thickness. A layer of crosslinked, silicon-based macromolecular structure about 10 nm thickness overlies the silver layer, and the outermost surface of the layer of crosslinked, silicon-based macromolecular structure is hydroxide terminated to produce a hydrophilic surface with a water drop contact angle of less than 10.degree.. The coated substrate may be one of multiple fins in a condensing heat exchanger for use in the microgravity of space, which has narrow channels defined between angled fins such that the surface tension of condensed water moves water by capillary flow to a central location where it is pumped to storage. The antimicrobial coating prevents obstruction of the capillary passages.

Tearing as a test for mechanical characterization of thin adhesive films

NASA Astrophysics Data System (ADS)

Hamm, Eugenio; Reis, Pedro; Leblanc, Michael; Roman, Benoit; Cerda, Enrique

2008-05-01

Thin adhesive films have become increasingly important in applications involving packaging, coating or for advertising. Once a film is adhered to a substrate, flaps can be detached by tearing and peeling, but they narrow and collapse in pointy shapes. Similar geometries are observed when peeling ultrathin films grown or deposited on a solid substrate, or skinning the natural protective cover of a ripe fruit. Here, we show that the detached flaps have perfect triangular shapes with a well-defined vertex angle; this is a signature of the conversion of bending energy into surface energy of fracture and adhesion. In particular, this triangular shape of the tear encodes the mechanical parameters related to these three forms of energy and could form the basis of a quantitative assay for the mechanical characterization of thin adhesive films, nanofilms deposited on substrates or fruit skin.

Tearing as a test for mechanical characterization of thin adhesive films.

PubMed

Hamm, Eugenio; Reis, Pedro; LeBlanc, Michael; Roman, Benoit; Cerda, Enrique

2008-05-01

Thin adhesive films have become increasingly important in applications involving packaging, coating or for advertising. Once a film is adhered to a substrate, flaps can be detached by tearing and peeling, but they narrow and collapse in pointy shapes. Similar geometries are observed when peeling ultrathin films grown or deposited on a solid substrate, or skinning the natural protective cover of a ripe fruit. Here, we show that the detached flaps have perfect triangular shapes with a well-defined vertex angle; this is a signature of the conversion of bending energy into surface energy of fracture and adhesion. In particular, this triangular shape of the tear encodes the mechanical parameters related to these three forms of energy and could form the basis of a quantitative assay for the mechanical characterization of thin adhesive films, nanofilms deposited on substrates or fruit skin.

Lateral epitaxial overgowth of GaAs by organometallic chemical vapor deposition

NASA Technical Reports Server (NTRS)

Gale, R. P.; Mcclelland, R. W.; Fan, J. C. C.; Bozler, C. O.

1982-01-01

Lateral epitaxial overgrowth of GaAs by organometallic chemical vapor deposition has been demonstrated. Pyrolytic decomposition of trimethylgallium and arsine, without the use of HCl, was used to deposit GaAs on substrates prepared by coating (110) GaAs wafers with SiO2, then using photolithography to open narrow stripes in the oxide. Lateral overgrowth was seeded by epitaxial deposits formed on the GaAs surfaces exposed by the stripe openings. The extent of lateral overgrowth was investigated as a function of stripe orientation and growth temperature. Ratios of lateral to vertical growth rates greater than five have been obtained. The lateral growth is due to surface-kinetic control for the two-dimensional growth geometry studied. A continuous epitaxial GaAs layer 3 microns thick has been grown over a patterned mask on a GaAs substrate and then cleaved from the substrate.

Interlocking-based attachment during locomotion in the beetle Pachnoda marginata (Coleoptera, Scarabaeidae)

PubMed Central

Bußhardt, Philipp; Kunze, Daniel; Gorb, Stanislav N.

2014-01-01

The attachment function of tibial spurs and pretarsal claws in the beetle Pachnoda marginata (Coleoptera, Scarabaeidae) during locomotion was examined in this study. First, we measured the angle, at which the beetles detached from substrates with different roughness. At a surface roughness of 12 μm and higher, intact animals were able to cling to a completely tilted platform (180°). Second, we estimated the forces the beetles could exert in walking on smooth and rough cylinders of different diameters, on a plane and also between two plates. To elucidate the role of the individual structures, we ablated them consecutively. We found tibial spurs not to be in use in walking on flat substrates. On some of the curved substrates, ablation of tibial spurs caused an effect. A clear effect of tibial spurs was revealed in walking between two plates. Thus, these structures are probably used for generating propulsion in narrowed spaces. PMID:25385502

Development of a microbalance suitable for space application. [mass measurement device for particulate and vapor deposition measurements

NASA Technical Reports Server (NTRS)

Patashnick, H.; Rupprecht, G.

1977-01-01

The tapered element oscillating microbalance (TEOM), an ultrasensitive mass measurement device which is suitable for both particulate and vapor deposition measurements is described. The device can be used in contamination measurements, surface reaction studies, particulate monitoring systems or any microweighing activity where either laboratory or field monitoring capability is desired. The active element of the TEOM consists of a tube or reed constructed of a material with high mechanical quality factor and having a special taper. The element is firmly mounted at the wide end while the other end supports a substrate surface which can be composed of virtually any material. The tapered element with the substrate at the free (narrow) end is set into oscillation in a clamped free mode. A feedback system maintains the oscillation whose natural frequency will change in relation to the mass deposited on the substrate.

A technique for production of nanocrystalline cellulose with a narrow size distribution

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

Bai, Wen; Holbery, James D.; Li, Kaichang

2009-02-01

Nanocrystalline cellulose (NCC) was prepared by sulfuric acid hydrolysis of microcrystalline cellulose. A differential centrifugation technique was studied to obtain NCC whiskers with a narrow size distribution. It was shown that the volume of NCC in different fractions had an inverse relationship with relative centrifugal force (RCF). The length of NCC whiskers was also fractionized by differential RCF. The aspect ratio of NCC in different fractions had a relatively narrow range. This technique provides an easy way of producing NCC whiskers with a narrow size distribution.

ARC-1986-A86-7024

NASA Image and Video Library

1986-01-24

P-29508BW Range: 1.12 million kilometers (690,000 miles) This clear-filter view of the Uranian rings delta, gamma, eta, beta and alpha (from top) was taken with Voyager 2's narrow-angle camera and clearly illustrates the broad outer component and narrow inner component of the eta ring, which orbits Uranus at a radius of some 47,000 km (29,000 mi). The broad component is considerably more transparent than the dense, narrow inner eta component, as well as the other narrow rings shown. Resolution here is about 10 km (6 mi).

Optical properties of InGaN thin films in the entire composition range

NASA Astrophysics Data System (ADS)

Kazazis, S. A.; Papadomanolaki, E.; Androulidaki, M.; Kayambaki, M.; Iliopoulos, E.

2018-03-01

The optical properties of thick InGaN epilayers, with compositions spanning the entire ternary range, are studied in detail. High structural quality, single phase InxGa1-xN (0001) films were grown heteroepitaxially by radio-frequency plasma assisted molecular-beam epitaxy on freestanding GaN substrates. Their emission characteristics were investigated by low temperature photoluminescence spectroscopy, whereas variable angle spectroscopic ellipsometry was applied to determine the complex dielectric function of the films, in the 0.55-4.0 eV photon range. Photoluminescence lines were intense and narrow, in the range of 100 meV for Ga-rich InGaN films (x < 0.3), around 150 meV for mid-range composition films (0.3 < x < 0.6), and in the range of 50 meV for In-rich alloys (x > 0.6). The composition dependence of the strain-free emission energy was expressed by a bowing parameter of b = 2.70 ± 0.12 eV. The films' optical dielectric function dispersion was obtained by the analysis of the ellipsometric data employing a Kramers-Kronig consistent parameterized optical model. The refractive index dispersion was obtained for alloys in the entire composition range, and the corresponding values at the band edge show a parabolic dependence on the InN mole fraction expressed by a bowing parameter of b = 0.81 ± 0.04. The bowing parameter describing the fundamental energy bandgap was deduced to be equal to 1.66 ± 0.07 eV, consistent with the ab initio calculations for statistically random (non-clustered) InGaN alloys.

Mass production of holographic transparent components for augmented and virtual reality applications

NASA Astrophysics Data System (ADS)

Russo, Juan Manuel; Dimov, Fedor; Padiyar, Joy; Coe-Sullivan, Seth

2017-06-01

Diffractive optics such as holographic optical elements (HOEs) can provide transparent and narrow band components with arbitrary incident and diffracted angles for near-to-eye commercial electronic products for augmented reality (AR), virtual reality (VR), and smart glass applications. In this paper, we will summarize the operational parameters and general optical geometries relevant for near-to-eye displays, the holographic substrates available for these applications, and their performance characteristics and ease of manufacture. We will compare the holographic substrates available in terms of fabrication, manufacturability, and end-user performance characteristics. Luminit is currently emplacing the manufacturing capacity to serve this market, and this paper will discuss the capabilities and limitations of this unique facility.

Synthesis of cobalt nanoparticles on Si (100) by swift heavy ion irradiation

PubMed Central

2013-01-01

We report the growth and characterization of uniform-sized nanoparticles of cobalt on n-type silicon (100) substrates by swift heavy ion (SHI) irradiation. The Co thin films of 25-nm thicknesses were grown by e-beam evaporation and irradiated with two different types of ions, 45-MeV Li3+ and 100-MeV O7+ ions with fluences ranging from 1 × 1011 to 1 × 1013 ions/cm2. SHI irradiation, with the beam rastered over the area of the film, resulted in the restructuring of the film into a dense array of Co nanostructures. Surface topography studied by atomic force microscopy revealed narrowed size distributions, with particle sizes ranging from 20 to 50 nm, formed through a self-organized process. Ion fluence-dependent changes in crystallinity of the Co nanostructures were determined by glancing angle X-ray diffraction. Rutherford backscattering spectroscopy analysis showed the absence of beam-induced mixing in this system. Surface restructuring and beam-induced crystallization are the dominant effects, with the nanoparticle size and density being dependent on the ion fluence. Results are analyzed in the context of molecular dynamics calculations of electron-lattice energy transfer. PMID:24138985

High-resolution TEM Studies of Carbon Nanotubes and Catalyst Nanoparticles Produced During CVD from Metal Multilayer Films

NASA Astrophysics Data System (ADS)

Howe, Jane Y.; Puretzky, Alex A.; Geohegan, David B.; Cui, Hongtao; Eres, Varela; Maria, Alex A.; Lowndes, Douglas H.

2003-03-01

The structure of single-wall and multiwall carbon nanotubes and associated metal catalyst nanoparticles produced during chemical vapor deposition from multilayered metal films deposited on Si and Mo substrates were studied by high-resolution TEM and EDS. Electron beam-evaporated metal multilayer films (e.g. Al-Fe-Mo, typically 11-50 nm total thickness) roughen upon heat treatment to form a variety of catalyst particle sizes suitable for carbon nanotube growth by chemical vapor deposition using acetylene, hydrogen, and argon flow gases. This study investigates these nanoparticles, the type of nanotubes grown, their wall, tip, and basal structures, as well as the associated amounts of amorphous carbon deposited on their walls in different temperature and pressure ranges. Mixtures of SWNT and MWNT are found even for low growth temperatures (650-700 C), while rapid growth of vertically-aligned multiwall nanotubes (VA-MWNTs) predominate in a narrow temperature range at a given pressure. Arrested growth experiments were performed to determine the time periods for SWNT vs. MWNT growth. The nature of the catalyst nanoparticles, their support structure, and insights on the mechanisms of growth will be discussed.

Synthesis of cobalt nanoparticles on Si (100) by swift heavy ion irradiation.

PubMed

Attri, Asha; Kumar, Ajit; Verma, Shammi; Ojha, Sunil; Asokan, Kandasami; Nair, Lekha

2013-10-18

We report the growth and characterization of uniform-sized nanoparticles of cobalt on n-type silicon (100) substrates by swift heavy ion (SHI) irradiation. The Co thin films of 25-nm thicknesses were grown by e-beam evaporation and irradiated with two different types of ions, 45-MeV Li3+ and 100-MeV O7+ ions with fluences ranging from 1 × 1011 to 1 × 1013 ions/cm2. SHI irradiation, with the beam rastered over the area of the film, resulted in the restructuring of the film into a dense array of Co nanostructures. Surface topography studied by atomic force microscopy revealed narrowed size distributions, with particle sizes ranging from 20 to 50 nm, formed through a self-organized process. Ion fluence-dependent changes in crystallinity of the Co nanostructures were determined by glancing angle X-ray diffraction. Rutherford backscattering spectroscopy analysis showed the absence of beam-induced mixing in this system. Surface restructuring and beam-induced crystallization are the dominant effects, with the nanoparticle size and density being dependent on the ion fluence. Results are analyzed in the context of molecular dynamics calculations of electron-lattice energy transfer.

Synthesis of cobalt nanoparticles on Si (100) by swift heavy ion irradiation

NASA Astrophysics Data System (ADS)

Attri, Asha; Kumar, Ajit; Verma, Shammi; Ojha, Sunil; Asokan, Kandasami; Nair, Lekha

2013-10-01

We report the growth and characterization of uniform-sized nanoparticles of cobalt on n-type silicon (100) substrates by swift heavy ion (SHI) irradiation. The Co thin films of 25-nm thicknesses were grown by e-beam evaporation and irradiated with two different types of ions, 45-MeV Li3+ and 100-MeV O7+ ions with fluences ranging from 1 × 1011 to 1 × 1013 ions/cm2. SHI irradiation, with the beam rastered over the area of the film, resulted in the restructuring of the film into a dense array of Co nanostructures. Surface topography studied by atomic force microscopy revealed narrowed size distributions, with particle sizes ranging from 20 to 50 nm, formed through a self-organized process. Ion fluence-dependent changes in crystallinity of the Co nanostructures were determined by glancing angle X-ray diffraction. Rutherford backscattering spectroscopy analysis showed the absence of beam-induced mixing in this system. Surface restructuring and beam-induced crystallization are the dominant effects, with the nanoparticle size and density being dependent on the ion fluence. Results are analyzed in the context of molecular dynamics calculations of electron-lattice energy transfer.

Supercritical fluid molecular spray thin films and fine powders

DOEpatents

Smith, Richard D.

1988-01-01

Solid films are deposited, or fine powders formed, by dissolving a solid material into a supercritical fluid solution at an elevated pressure and then rapidly expanding the solution through a short orifice into a region of relatively low pressure. This produces a molecular spray which is directed against a substrate to deposit a solid thin film thereon, or discharged into a collection chamber to collect a fine powder. The solvent is vaporized and pumped away. Solution pressure is varied to determine, together with flow rate, the rate of deposition and to control in part whether a film or powder is produced and the granularity of each. Solution temperature is varied in relation to formation of a two-phase system during expansion to control porosity of the film or powder. A wide variety of film textures and powder shapes are produced of both organic and inorganic compounds. Films are produced with regular textural feature dimensions of 1.0-2.0 .mu.m down to a range of 0.01 to 0.1 .mu.m. Powders are formed in very narrow size distributions, with average sizes in the range of 0.02 to 5 .mu.m.

Oviposition Substrate of the Mountain Fly Drosophila nigrosparsa (Diptera: Drosophilidae)

PubMed Central

Tratter, Magdalena; Bächli, Gerhard; Kirchmair, Martin; Kaufmann, Rüdiger; Arthofer, Wolfgang; Schlick-Steiner, Birgit C.; Steiner, Florian M.

2016-01-01

The survival of insect larvae often depends on the mother’s choice of oviposition substrate, and thus, this choice is an essential part of an insect species’ ecology. Especially species with narrow substrate preferences may suffer from changes in substrate availability triggered by, for example, climate change. Recent climate warming is affecting species directly (e.g., physiology) but also indirectly (e.g., biological interactions) leading to mismatching phenologies and distributions. However, the preferred oviposition substrate is still unknown for many drosophilid species, especially for those at higher elevations. In this study, we investigated the oviposition-substrate preference of the montane-alpine fly Drosophila nigrosparsa in rearing and multiple-choice experiments using natural substrates in the laboratory. Insect emergence from field-collected substrates was tested. More than 650 insects were reared from natural substrates, among them 152 drosophilids but no individual of D. nigrosparsa. In the multiple-choice experiments, D. nigrosparsa preferred ovipositing on mushrooms (> 93% of eggs); additionally, a few eggs were laid on berries but none on other substrates such as cow faeces, rotten plant material, and soil. The flies laid 24 times more eggs per day when mushrooms were included in the substrates than when they were excluded. We infer that D. nigrosparsa is a mushroom breeder with some variation in oviposition choice. The flies favoured some mushrooms over others, but they were not specialised on a single fungal taxon. Although it is unclear if and how climate change will affect D. nigrosparsa, our results indicate that this species will not be threatened by oviposition-substrate limitations in the near future because of the broad altitudinal distribution of the mushrooms considered here, even if the flies will have to shift upwards to withstand increasing temperatures. PMID:27788257

Purification and Characterization of Allophanate Hydrolase (AtzF) from Pseudomonas sp. Strain ADP

PubMed Central

Shapir, Nir; Sadowsky, Michael J.; Wackett, Lawrence P.

2005-01-01

AtzF, allophanate hydrolase, is a recently discovered member of the amidase signature family that catalyzes the terminal reaction during metabolism of s-triazine ring compounds by bacteria. In the present study, the atzF gene from Pseudomonas sp. strain ADP was cloned and expressed as a His-tagged protein, and the protein was purified and characterized. AtzF had a deduced subunit molecular mass of 66,223, based on the gene sequence, and an estimated holoenzyme molecular mass of 260,000. The active protein did not contain detectable metals or organic cofactors. Purified AtzF hydrolyzed allophanate with a kcat/Km of 1.1 × 104 s−1 M−1, and 2 mol of ammonia was released per mol allophanate. The substrate range of AtzF was very narrow. Urea, biuret, hydroxyurea, methylcarbamate, and other structurally analogous compounds were not substrates for AtzF. Only malonamate, which strongly inhibited allophanate hydrolysis, was an alternative substrate, with a greatly reduced kcat/Km of 21 s−1 M−1. Data suggested that the AtzF catalytic cycle proceeds through a covalent substrate-enzyme intermediate. AtzF reacts with malonamate and hydroxylamine to generate malonohydroxamate, potentially derived from hydroxylamine capture of an enzyme-tethered acyl group. Three putative catalytically important residues, one lysine and two serines, were altered by site-directed mutagenesis, each with complete loss of enzyme activity. The identity of a putative serine nucleophile was probed using phenyl phosphorodiamidate that was shown to be a time-dependent inhibitor of AtzF. Inhibition was due to phosphoroamidation of Ser189 as shown by liquid chromatography/matrix-assisted laser desorption ionization mass spectrometry. The modified residue corresponds in sequence alignments to the nucleophilic serine previously identified in other members of the amidase signature family. Thus, AtzF affects the cleavage of three carbon-to-nitrogen bonds via a mechanism similar to that of enzymes catalyzing single-amide-bond cleavage reactions. AtzF orthologs appear to be widespread among bacteria. PMID:15901697

Densification behavior of ceramic and crystallizable glass materials constrained on a rigid substrate

NASA Astrophysics Data System (ADS)

Calata, Jesus N.

2005-11-01

Constrained sintering is an important process for many applications. The sintering process almost always involves some form of constraint, both internal and external, such as rigid particles, reinforcing fibers and substrates to which the porous body adheres. The densification behavior of zinc oxide and cordierite-base crystallizable glass constrained on a rigid substrate was studied to add to the understanding of the behavior of various materials undergoing sintering when subjected to external substrate constraint. Porous ZnO films were isothermally sintered at temperatures between 900°C and 1050°C. The results showed that the densification of films constrained on substrates is severely reduced. This was evident in the sintered microstructures where the particles are joined together by narrower necks forming a more open structure, instead of the equiaxed grains with wide grain boundaries observed in the freestanding films. The calculated activation energies of densification were also different. For the density range of 60 to 64%, the constrained film had an activation energy of 391 +/- 34 kJ/mole compared to 242 +/- 21 kJ/mole for the freestanding film, indicating a change in the densification mechanism. In-plane stresses were observed during the sintering of the constrained films. Yielding of the films, in which the stresses dropped slight or remained unchanged, occurred at relative densities below 60% before the stresses climbed linearly with increasing density followed by a gradual relaxation. A substantial amount of the stresses remained after cooling. Free and constrained films of the cordierite-base crystallizable glass (glass-ceramic) were sintered between 900°C and 1000°C. The substrate constraint did not have a significant effect on the densification rate but the constrained films eventually underwent expansion. Calculations of the densification activation energy showed that, on average, it was close to 1077 kJ/mole, the activation energy of the glass, indicating that the prevailing mechanism was still viscous flow. The films expanded earlier and faster with increasing sintering temperature. The expansion was traced to the formation of pores at the interface with the silicon substrate and to a lesser extent on aluminum nitride. It was significantly reduced when the silicon substrate was pre-oxidized at 900°C, leading to the conclusion that the pore formation at the interface was due to poor wetting, which in turn was caused by the loss of the thin oxide layer through a reaction with the glass.

Ultra-narrow surface lattice resonances in plasmonic metamaterial arrays for biosensing applications.

PubMed

Danilov, Artem; Tselikov, Gleb; Wu, Fan; Kravets, Vasyl G; Ozerov, Igor; Bedu, Frederic; Grigorenko, Alexander N; Kabashin, Andrei V

2018-05-01

When excited over a periodic metamaterial lattice of gold nanoparticles (~ 100nm), localized plasmon resonances (LPR) can be coupled by a diffraction wave propagating along the array plane, which leads to a drastic narrowing of plasmon resonance lineshapes (down to a few nm full-width-at-half-maximum) and the generation of singularities of phase of reflected light. These phenomena look very promising for the improvement of performance of plasmonic biosensors, but conditions of implementation of such diffractively coupled plasmonic resonances, also referred to as plasmonic surface lattice resonances (PSLR), are not always compatible with biosensing arrangement implying the placement of the nanoparticles between a glass substrate and a sample medium (air, water). Here, we consider conditions of excitation and properties of PSLR over arrays of glass substrate-supported single and double Au nanoparticles (~ 100-200nm), arranged in a periodic metamaterial lattice, in direct and Attenuated Total Reflection (ATR) geometries, and assess their sensitivities to variations of refractive index (RI) of the adjacent sample dielectric medium. First, we identify medium (PSLR air , PSLR wat for air and water, respectively) and substrate (PSLR sub ) modes corresponding to the coupling of individual plasmon oscillations at medium- and substrate-related diffraction cut-off edges. We show that spectral sensitivity of medium modes to RI variations is determined by the lattice periodicity in both direct and ATR geometries (~ 320nm per RIU change in our case), while substrate mode demonstrates much lower sensitivity. We also show that phase sensitivity of PSLR can exceed 10 5 degrees of phase shift per RIU change and thus outperform the relevant parameter for all other plasmonic sensor counterparts. We finally demonstrate the applicability of surface lattice resonances in plasmonic metamaterial arrays to biosensing using standard streptavidin-biotin affinity model. Combining advantages of nanoscale architectures, including drastic concentration of electric field, possibility of manipulation at the nanoscale etc, and high phase and spectral sensitivities, PSLRs promise the advancement of current state-of-the-art plasmonic biosensing technology toward single molecule label-free detection. Copyright © 2017 Elsevier B.V. All rights reserved.

Nanocomposites for high-speed optical modulators and plasmonic thermal mid-infrared emitters

NASA Astrophysics Data System (ADS)

Demir, Veysi

Demand for high-speed optical modulators and narrow-bandwidth infrared thermal emitters for numerous applications continues to rise and new optical devices are needed to deal with massive data flows, processing powers, and fabrication costs. Conventional techniques are usually hindered by material limitations or electronic interconnects and advances in organic nanocomposite materials and their integration into photonic integrated circuits (PICs) have been acknowledged as a promising alternative to single crystal techniques. The work presented in this thesis uses plasmonic and magneto-optic effects towards the development of novel optical devices for harnessing light and generating high bandwidth signals (>40GHz) at room and cryogenic temperatures (4.2°K). Several publications have resulted from these efforts and are listed at the end of the abstract. In our first published research we developed a narrow-bandwidth mid-infrared thermal emitter using an Ag/dielectric/Ag thin film structure arranged in hexagonal planar lattice structures. PECVD produced nanoamorphous carbon (NAC) is used as a dielectric layer. Spectrally tunable (>2 mum) and narrow bandwidth (<0.5 mum) emission peaks in the range of 4-7 mum were demonstrated by decreasing the resistivity of NAC from 1012 and 109 O.cm with an MoSi2 dopant and increasing the emitter lattice constant from 4 to 7 mum. This technique offers excellent flexibility for developing cost-effective mid-IR sources as compared to costly fiber and quantum cascade lasers (QCLs). Next, the effect of temperature on the Verdet constant for cobalt-ferrite polymer nanocomposites was measured for a series of temperatures ranging from 40 to 200°K with a Faraday rotation polarimeter. No visual change was observed in the films during thermal cycling, and ˜4x improvement was achieved at 40°K. The results are promising and further analysis is merited at 4.2°K to assess the performance of this material for cryogenic magneto-optic modulators for supercomputers. Finally, the dielectric constant and loss tangent of MAPTMS sol-gel films were measured over a wide range of microwave frequencies. The test structures were prepared by spin-coating sol-gel films onto metallized glass substrates. The dielectric properties of the sol-gel were probed with several different sets of coplanar waveguides (CPWs) electroplated onto sol-gel films. The dielectric constant and loss-tangent of these films were determined to be ˜3.1 and 3 x 10-3 at 35GHz. These results are very promising indicating that sol-gels are viable cladding materials for high-speed electro-optic polymer modulators (>40GHz).

129Xe on Ir(111): NMR study of xenon on a metal single crystal surface

PubMed Central

Jänsch, H. J.; Gerhard, P.; Koch, M.

2004-01-01

NMR experiments of 129Xe adsorbed on an iridium single crystal surface are reported. Very high nuclear polarization (Pz ≈ 0.7) makes the experiment possible. A coverage of less then one monolayer is investigated on the Ir(111) surface with an area of 0.8 cm2. The observed resonance line shifts are very large and highly anisotropic. We find σiso = 1,032 ± 11 ppm and σan = 291 ± 33 ppm, which are far above the typical range of physisorption. The highly ordered substrate leads to homogeneous conditions for the xenon atoms, as seen in the narrow linewidth of 20 ppm. Chemical shifts under physisorption conditions are not large enough to totally explain the results. Knight shift can clearly be identified as the cause of the findings. This shift shows the presence of conduction electrons of the metallic substrate at the xenon nucleus and thus the mixing of metallic and atomic states at the Fermi level. Such mixing is in accordance with recent Hartree–Fock and density functional calculations of similar van der Waals adsorption systems. Quantitative comparisons, however, fail completely. The size and ratio of σan and σiso are pure ground-state properties in a structurally simple system. They are accessible to theory and provide detailed local information that can serve as a benchmark for theory. PMID:15361579

Thermal ecology of montane Atelopus (Anura: Bufonidae): A study of intrageneric diversity.

PubMed

Rueda Solano, Luis Alberto; Navas, Carlos A; Carvajalino-Fernández, Juan Manuel; Amézquita, Adolfo

2016-05-01

Harlequin frogs (Bufonidae: Atelopus) are among the most threatened frog genus in the world and reach very high elevations in the tropical Andes and the Sierra Nevada de Santa Marta (SNSM). Learning about their thermal ecology is essential to infer sensitivity to environmental changes, particularly climate warming. We report on the activity temperature and thermoregulatory behavior of three high-elevation species of harlequin frogs, Atelopus nahumae, Atelopus laetissimus and Atelopus carrikeri. The first two mentioned live in streams in Andean rain forests, whereas A. carrikeri inhabits paramo streams in the SNSM. We studied the thermal ecology of these species in tree localities differing in altitude, and focused on activity body, operative, substrate and air temperature. A main trend was lower body temperature as elevation increased, so that differences among species were largely explained by differences in substrate temperature. However, this temperature variation was much lower in forest species than paramo species. The Atelopus species included in this work proved to be thermoconformers, a trend that not extended to all congenerics at high elevation. This diversity in thermal ecology poses important questions when discussing the impact of climate warming for high-elevation harlequin frogs. For example, forest species show narrow thermal ranges and, if highly specialized, may be more susceptible to temperature change. Paramo species such as A. carrikeri, in contrast, may be more resilient to temperature change. Copyright © 2016 Elsevier Ltd. All rights reserved.

Transparent, Weakly Conductive Films for Space Applications

NASA Astrophysics Data System (ADS)

Griffin, John; Morgan, Ashraf; Hambourger, Paul

2004-10-01

Electrically insulating spacecraft surfaces are vulnerable to nonuniform charge buildup due to particles emitted by the sun. On Mars, insulating surfaces of exploration vehicles and structures will be affected by dust coatings possibly held in place by triboelectric surface charge. Application of a conductive film may be a solution to the charging problem, but the coating must be highly transparent if used on solar panels, lenses, etc. Sheet resistivity requirements depend on the application and are in the range 10^2-10^8 ohms/square. Co-deposited indium tin oxide (ITO) and MgF2 is promising, with high transparency, tailorable electrical properties, and durability to atomic oxygen.(Joyce A. Dever et al., NASA TM 1998-208499 (August 1998).) Due to ITO's relatively narrow bandgap ( ˜3.5 eV), the film might absorb enough ultraviolet to protect polymeric substrates. Recent work on dual-magnetron-sputtered ITO-MgF2 showed that a variety of polymeric substrates can be coated at room temperature.(Thomas Cashman et al., Vacuum Technology & Coating, September 2003, p. 38.) However, the sheet resistivity is very sensitive to composition, suggestive of a percolation transition. This could be a serious problem for large-scale coating production. We will report on attempts to control film composition by plasma emission monitoring of the ITO and MgF2 guns. Supported by NASA Glenn Research Center, Cooperative Agreements NCC3-1033 and NCC3-1065.

Kinetics of self-induced nucleation and optical properties of GaN nanowires grown by plasma-assisted molecular beam epitaxy on amorphous Al{sub x}O{sub y}

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

Sobanska, M., E-mail: sobanska@ifpan.edu.pl; Zytkiewicz, Z. R.; Klosek, K.

Nucleation kinetics of GaN nanowires (NWs) by molecular beam epitaxy on amorphous Al{sub x}O{sub y} buffers deposited at low temperature by atomic layer deposition is analyzed. We found that the growth processes on a-Al{sub x}O{sub y} are very similar to those observed on standard Si(111) substrates, although the presence of the buffer significantly enhances nucleation rate of GaN NWs, which we attribute to a microstructure of the buffer. The nucleation rate was studied vs. the growth temperature in the range of 720–790 °C, which allowed determination of nucleation energy of the NWs on a-Al{sub x}O{sub y} equal to 6 eV. Thismore » value is smaller than 10.2 eV we found under the same conditions on nitridized Si(111) substrates. Optical properties of GaN NWs on a-Al{sub x}O{sub y} are analyzed as a function of the growth temperature and compared with those on Si(111) substrates. A significant increase of photoluminescence intensity and much longer PL decay times, close to those on silicon substrates, are found for NWs grown at the highest temperature proving their high quality. The samples grown at high temperature have very narrow PL lines. This allowed observation that positions of donor-bound exciton PL line in the NWs grown on a-Al{sub x}O{sub y} are regularly lower than in samples grown directly on silicon suggesting that oxygen, instead of silicon, is the dominant donor. Moreover, PL spectra suggest that total concentration of donors in GaN NWs grown on a-Al{sub x}O{sub y} is lower than in those grown under similar conditions on bare Si. This shows that the a-Al{sub x}O{sub y} buffer efficiently acts as a barrier preventing uptake of silicon from the substrate to GaN.« less

Enhancement of thickness uniformity of thin films grown by pulsed laser deposition

NASA Technical Reports Server (NTRS)

Fernandez, Felix E.

1995-01-01

A peculiarity of the pulsed laser deposition technique of thin-film growth which limits its applicability is the very rapid drop of resulting film thickness as a function of distance from the deposition axis. This is due to the narrow forward peaking of the emission plume characteristic of the laser ablation process. The plume is usually modeled by a cos(sup n) theta function with n greater, and in some cases, much higher, than 1. Based on this behavior, a method is presented to substantially enhance coverage uniformity in substrate zones of the order of the target-substrate distance h, and to within a specified thickness tolerance. Essentially, target irradiation is caused to form an annular emission source instead of the usual spot. By calculating the resulting thickness profiles, an optimum radius s is found for the annular source, corresponding to a given power in the emission characteristic and a given value of h. The radius of this annulus scales with h. Calculated numerical results for optimal s/h ratios corresponding to a wide range of values for n are provided for the case of +/- 1% tolerance in deviation from the thickness at deposition axis. Manners of producing annular illumination of the target by means of conic optics are presented for the case of a laser beam with radially symmetric profile. The region of uniform coverage at the substrate can be further augmented by extension of the method to multiple concentric annular sources. By using a conic optic of novel design, it is shown also how a single-laser beam can be focused onto a target in the required manner. Applicability of the method would be limited in practice by the available laser power. On the other hand, the effective emitting area can be large, which favors extremely high growth rates, and since growth can occur uniformly over the whole substrate for each laser pulse, single-shot depositions with substantial thicknesses are possible. In addition, the simultaneity of growth over the complete substrate is desirable when monitoring the growth in situ.

Influences of W Content on the Phase Transformation Properties and the Associated Stress Change in Thin Film Substrate Combinations Studied by Fabrication and Characterization of Thin Film V1- xW xO2 Materials Libraries.

PubMed

Wang, Xiao; Rogalla, Detlef; Ludwig, Alfred

2018-04-09

The mechanical stress change of VO 2 film substrate combinations during their reversible phase transformation makes them promising for applications in micro/nanoactuators. V 1- x W x O 2 thin film libraries were fabricated by reactive combinatorial cosputtering to investigate the effects of the addition of W on mechanical and other transformation properties. High-throughput characterization methods were used to systematically determine the composition spread, crystalline structure, surface topography, as well as the temperature-dependent phase transformation properties, that is, the hysteresis curves of the resistance and stress change. The study indicates that as x in V 1- x W x O 2 increases from 0.007 to 0.044 the crystalline structure gradually shifts from the VO 2 (M) phase to the VO 2 (R) phase. The transformation temperature decreases by 15 K/at. % and the resistance change is reduced to 1 order of magnitude, accompanied by a wider transition range and a narrower hysteresis with a minimal value of 1.8 K. A V 1- x W x O 2 library deposited on a Si 3 N 4 /SiO 2 -coated Si cantilever array wafer was used to study simultaneously the temperature-dependent stress change σ( T) of films with different W content through the phase transformation. Compared with σ( T) of ∼700 MPa of a VO 2 film, σ( T) in V 1- x W x O 2 films decreases to ∼250 MPa. Meanwhile, σ( T) becomes less abrupt and occurs over a wider temperature range with decreased transformation temperatures.

Natronobiforma cellulositropha gen. nov., sp. nov., a novel haloalkaliphilic member of the family Natrialbaceae (class Halobacteria) from hypersaline alkaline lakes.

PubMed

Sorokin, Dimitry Y; Khijniak, Tatiana V; Kostrikina, Nadezhda A; Elcheninov, Alexander G; Toshchakov, Stepan V; Bale, Nicole J; Damsté, Jaap S Sinninghe; Kublanov, Ilya V

2018-04-27

Six strains of extremely halophilic and alkaliphilic euryarchaea were enriched and isolated in pure culture from surface brines and sediments of hypersaline alkaline lakes in various geographical locations with various forms of insoluble cellulose as growth substrate. The cells are mostly flat motile rods with a thin monolayer cell wall while growing on cellobiose. In contrast, the cells growing with cellulose are mostly nonmotile cocci covered with a thick external EPS layer. The isolates, designated AArcel, are obligate aerobic heterotrophs with a narrow substrate spectrum. All strains can use insoluble celluloses, cellobiose, a few soluble glucans and xylan as their carbon and energy source. They are extreme halophiles, growing within the range from 2.5 to 4.8M total Na + (optimum at 4M) and obligate alkaliphiles, with the pH range for growth from 7.5 to 9.9 (optimum at 8.5-9). The core archaeal lipids of strain AArcel5 T were dominated by C 20 -C 20 dialkyl glycerol ether (DGE) (i.e. archaeol) and C 20 -C 25 DGE in nearly equal proportion. The 16S rRNA gene analysis indicated that all six isolates belong to a single genomic species mostly related to the genera Saliphagus-Natribaculum-Halovarius. Taking together a substantial phenotypic difference of the new isolates from the closest relatives and the phylogenetic distance, it is concluded that the AArcel group represents a novel genus-level branch within the family Natrialbaceae for which the name Natronobiforma cellulositropha gen. nov., sp. nov. is proposed with AArcel5 T as the type strain (JCM 31939 T =UNIQEM U972 T ). Copyright © 2018 The Authors. Published by Elsevier GmbH.. All rights reserved.

Structure-based Analysis to Hu-DNA Binding

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

Swinger,K.; Rice, P.

2007-01-01

HU and IHF are prokaryotic proteins that induce very large bends in DNA. They are present in high concentrations in the bacterial nucleoid and aid in chromosomal compaction. They also function as regulatory cofactors in many processes, such as site-specific recombination and the initiation of replication and transcription. HU and IHF have become paradigms for understanding DNA bending and indirect readout of sequence. While IHF shows significant sequence specificity, HU binds preferentially to certain damaged or distorted DNAs. However, none of the structurally diverse HU substrates previously studied in vitro is identical with the distorted substrates in the recently publishedmore » Anabaena HU(AHU)-DNA cocrystal structures. Here, we report binding affinities for AHU and the DNA in the cocrystal structures. The binding free energies for formation of these AHU-DNA complexes range from 10-14.5 kcal/mol, representing K{sub d} values in the nanomolar to low picomolar range, and a maximum stabilization of at least 6.3 kcal/mol relative to complexes with undistorted, non-specific DNA. We investigated IHF binding and found that appropriate structural distortions can greatly enhance its affinity. On the basis of the coupling of structural and relevant binding data, we estimate the amount of conformational strain in an IHF-mediated DNA kink that is relieved by a nick (at least 0.76 kcal/mol) and pinpoint the location of the strain. We show that AHU has a sequence preference for an A+T-rich region in the center of its DNA-binding site, correlating with an unusually narrow minor groove. This is similar to sequence preferences shown by the eukaryotic nucleosome.« less

Gold nanoparticles-decorated electrospun poly(N-vinyl-2-pyrrolidone) nanofibers with tunable size and coverage density for nanomolar detection of single and binary component dyes by surface-enhanced raman spectroscopy

NASA Astrophysics Data System (ADS)

Kurniawan, Alfin; Wang, Meng-Jiy

2017-09-01

The application of the electrospun nanomaterials to surface-enhanced Raman spectroscopy (SERS) is a rapidly evolving field which holds potential for future developments in the generation of portable plasmonic-based detection platforms. In this study, a simple approach to fabricate electrospun poly(N-vinylpyrrolidone) (PVP) mats decorated with gold nanoparticles (AuNPs) by combining electrospinning and calcination was presented. AuNPs were decorated on the fiber mat surface through electrostatic interactions between positively charged aminosilane groups and negatively charged AuNPs. The size and coverage density of AuNPs on the fiber mats could be tuned by varying the calcination temperature. Calcination of AuNPs-decorated PVP fibers at 500 °C-700 °C resulted in the uniform decoration of high density AuNPs with very narrow gaps on every single fiber, which in turn contribute to strong electromagnetic SERS enhancement. The robust free-standing AuNPs-decorated mat which calcined at 500 °C (500/AuNPs-F) exhibited high SERS activity toward cationic (methylene blue, MB) and anionic (methyl orange, MO) dyes in single and binary systems with a detection range from tens of nM to a few hundred μM. The fabricated SERS substrate demonstrated high reproducibility with the spot-to-spot variation in SERS signal intensities was ±10% and ±12% for single and binary dye systems, respectively. The determination of MB and MO in spiked river water and tap water with 500/AuNPs-F substrate gave satisfactory results in terms of the percent spike recoveries (ranging from 92.6%-96.6%) and reproducibility (%RSD values less than 15 for all samples).

A dense grid of narrow bandpass steep edge filters for the JST/T250 telescope: summary of results

NASA Astrophysics Data System (ADS)

Brauneck, U.; Sprengard, R.; Bourquin, S.; Marín-Franch, A.

2017-09-01

On the Javalambre mountain in Spain, the Centro de Estudios de Fisica del Cosmos de Aragon (CEFCA) has setup a new wide field telescope, the JST/T250: a 2.55 m telescope with a plate scale of 22.67"/mm and a 3° diameter field of view. To conduct a photometric sky survey, a large format mosaic camera made of 14 individual CCDs is used in combination with filter trays containing 14 filters each of theses 101.7 x 96.5 mm in size. For this instrument, SCHOTT manufactured 56 specially designed steep edged bandpass interference filters which were recently completed. The filter set consists of bandpass filters in the range between 348,5 nm and 910 nm and a longpass filter at 915 nm. Most of the filters have FWHM of 14.5 nm and a blocking between 250 and 1050 nm with optical density of OD5. Absorptive color glass substrates in combination with interference filters were used to minimize residual reflection in order to avoid ghost images. Inspite of containing absorptive elements, the filters show the maximum possible transmission. This was achieved by using magnetron sputtering for the filter coating process. The most important requirement for the continuous photometric survey is the tight tolerancing of the central wavelengths and FWHM of the filters. This insures each bandpass having a defined overlap with its neighbors. In addition, the blocking of the filters is better than OD5 in the range 250-1050 nm. A high image quality required a low transmitted wavefront error (

Band gap engineering of N-alloyed Ga{sub 2}O{sub 3} thin films

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

Song, Dongyu; Li, Bingsheng, E-mail: libingsheng@hit.edu.cn, E-mail: ashen@ccny.cuny.edu; Sui, Yu

2016-06-15

The authors report the tuning of band gap of GaON ternary alloy in a wide range of 2.75 eV. The samples were prepared by a two-step nitridation method. First, the samples were deposited on 2-inch fused silica substrates by megnetron sputtering with NH{sub 3} and Ar gas for 60 minutes. Then they were annealed in NH{sub 3} ambience at different temperatures. The optical band gap energies are calculated from transmittance measurements. With the increase of nitridation temperature, the band gap gradually decreases from 4.8 eV to 2.05 eV. X-ray diffraction results indicate that as-deposited amorphous samples can crystallize into monoclinicmore » and hexagonal structures after they were annealed in oxygen or ammonia ambience, respectively. The narrowing of the band gap is attributed to the enhanced repulsion of N2p -Ga3d orbits and formation of hexagonal structure.« less

Demonstration of a Monolithic Micro-Spectrometer System

NASA Technical Reports Server (NTRS)

Rajic, S.; Egert, C. M.

1995-01-01

The starting design of a spectrometer based on a modified Czerny-Turner configuration containing five precision surfaces encapsulated in a monolithic structure is described. Since the purpose at the early stages of the development was to demonstrate the feasibility of the technology and not an attempt to address a specific sensing problem, the first substrate material chosen was optical quality polymethyl methacrylate (PMMA). The final system design decision was narrowed down to two possible configurations containing five and six precision surfaces. The five surface design was chosen since it contained one less precision optical surface, yet included multiple off-axis spheres. In this particular design and material system, the mass was kept below 7 g. The wavelength range (bandpass) design goal was 1 micrometer (0.6 - 1.6 micrometers). The PMMA is particularly transparent in this wavelength region and there are interesting effects to monitor within this band. The optical system was designed and optimized using the ZEMAX optical design software program to be entirely alignment free (self aligning).

Plant response to nutrient availability across variable bedrock geologies

USGS Publications Warehouse

Castle, S.C.; Neff, J.C.

2009-01-01

We investigated the role of rock-derived mineral nutrient availability on the nutrient dynamics of overlying forest communities (Populus tremuloides and Picea engelmanni-Abies lasiocarpa v. arizonica) across three parent materials (andesite, limestone, and sandstone) in the southern Rocky Mountains of Colorado. Broad geochemical differences were observed between bedrock materials; however, bulk soil chemistries were remarkably similar between the three different sites. In contrast, soil nutrient pools were considerably different, particularly for P, Ca, and Mg concentrations. Despite variations in nutrient stocks and nutrient availability in soils, we observed relatively inflexible foliar concentrations and foliar stoichiometries for both deciduous and coniferous species. Foliar nutrient resorption (P and K) in the deciduous species followed patterns of nutrient content across substrate types, with higher resorption corresponding to lower bedrock concentrations. Work presented here indicates a complex plant response to available soil nutrients, wherein plant nutrient use compensates for variations in supply gradients and results in the maintenance of a narrow range in foliar stoichiometry. ?? 2008 Springer Science+Business Media, LLC.

Investigation of phase-change coatings for variable thermal control of spacecraft

NASA Technical Reports Server (NTRS)

Kelliher, W. C.; Young, P. R.

1972-01-01

An investigation was conducted to determine the feasibility of producing a spacecraft coating system that could vary the ratio of its solar absorptance to thermal emittance to adjust automatically for changes in the thermal balance of a spacecraft. This study resulted in a new concept called the phase-change effect which uses the change that occurs in the optical properties of many materials during the phase transition from a crystalline solid to an amorphous material. A series of two-component model coatings was developed which, when placed on a highly reflecting substrate, exhibited a sharp decrease in solar absorptance within a narrow temperature range. A variable thermal control coating can have a significant amount of temperature regulation with the phase-change effect. Data are presented on several crystallite-polymer formulations, their physical and optical properties, and associated phase-change temperatures. Aspects pertaining to their use in a space environment and an example of the degree of thermal regulation attainable with these coatings is also given.

Adhesion signals of phospholipid vesicles at an electrified interface.

PubMed

DeNardis, Nadica Ivošević; Žutić, Vera; Svetličić, Vesna; Frkanec, Ruža

2012-09-01

General adhesion behavior of phospholipid vesicles was examined in a wide range of potentials at the mercury electrode by recording time-resolved adhesion signals. It was demonstrated that adhesion-based detection is sensitive to polar headgroups in phospholipid vesicles. We identified a narrow potential window around the point of zero charge of the electrode where the interaction of polar headgroups of phosphatidylcholine vesicles with the substrate is manifested in the form of bidirectional signals. The bidirectional signal is composed of the charge flow due to the nonspecific interaction of vesicle adhesion and spreading and of the charge flow due to a specific interaction of the negatively charged electrode and the most exposed positively charged choline headgroups. These signals are expected to appear only when the electrode surface charge density is less than the surface charge density of the choline groups at the contact interface. In comparison, for the negatively charged phosphatidylserine vesicles, we identified the potential window at the mercury electrode where charge compensation takes place, and bidirectional signals were not detected.

Drosophila Regulate Yeast Density and Increase Yeast Community Similarity in a Natural Substrate

PubMed Central

Stamps, Judy A.; Yang, Louie H.; Morales, Vanessa M.; Boundy-Mills, Kyria L.

2012-01-01

Drosophila melanogaster adults and larvae, but especially larvae, had profound effects on the densities and community structure of yeasts that developed in banana fruits. Pieces of fruit exposed to adult female flies previously fed fly-conditioned bananas developed higher yeast densities than pieces of the same fruits that were not exposed to flies, supporting previous suggestions that adult Drosophila vector yeasts to new substrates. However, larvae alone had dramatic effects on yeast density and species composition. When yeast densities were compared in pieces of the same fruits assigned to different treatments, fruits that developed low yeast densities in the absence of flies developed significantly higher yeast densities when exposed to larvae. Across all of the fruits, larvae regulated yeast densities within narrow limits, as compared to a much wider range of yeast densities that developed in pieces of the same fruits not exposed to flies. Larvae also affected yeast species composition, dramatically reducing species diversity across fruits, reducing variation in yeast communities from one fruit to the next (beta diversity), and encouraging the consistent development of a yeast community composed of three species of yeast (Candida californica, C. zemplinina, and Pichia kluvyeri), all of which were palatable to larvae. Larvae excreted viable cells of these three yeast species in their fecal pools, and discouraged the growth of filamentous fungi, processes which may have contributed to their effects on the yeast communities in banana fruits. These and other findings suggest that D. melanogaster adults and their larval offspring together engage in ‘niche construction’, facilitating a predictable microbial environment in the fruit substrates in which the larvae live and develop. PMID:22860093

Characterization of Hybrid Toluate and Benzoate Dioxygenases

PubMed Central

Ge, Yong; Eltis, Lindsay D.

2003-01-01

Toluate dioxygenase of Pseudomonas putida mt-2 (TADOmt2) and benzoate dioxygenase of Acinetobacter calcoaceticus ADP1 (BADOADP1) catalyze the 1,2-dihydroxylation of different ranges of benzoates. The catalytic component of these enzymes is an oxygenase consisting of two subunits. To investigate the structural determinants of substrate specificity in these ring-hydroxylating dioxygenases, hybrid oxygenases consisting of the α subunit of one enzyme and the β subunit of the other were prepared, and their respective specificities were compared to those of the parent enzymes. Reconstituted BADOADP1 utilized four of the seven tested benzoates in the following order of apparent specificity: benzoate > 3-methylbenzoate > 3-chlorobenzoate > 2-methylbenzoate. This is a significantly narrower apparent specificity than for TADOmt2 (3-methylbenzoate > benzoate ∼ 3-chlorobenzoate > 4-methylbenzoate ∼ 4-chlorobenzoate ≫ 2-methylbenzoate ∼ 2-chlorobenzoate [Y. Ge, F. H. Vaillancourt, N. Y. Agar, and L. D. Eltis, J. Bacteriol. 184:4096-4103, 2002]). The apparent substrate specificity of the αBβT hybrid oxygenase for these benzoates corresponded to that of BADOADP1, the parent from which the α subunit originated. In contrast, the apparent substrate specificity of the αTβB hybrid oxygenase differed slightly from that of TADOmt2 (3-chlorobenzoate > 3-methylbenzoate > benzoate ∼ 4-methylbenzoate > 4-chlorobenzoate > 2-methylbenzoate > 2-chlorobenzoate). Moreover, the αTβB hybrid catalyzed the 1,6-dihydroxylation of 2-methylbenzoate, not the 1,2-dihydroxylation catalyzed by the TADOmt2 parent. Finally, the turnover of this ortho-substituted benzoate was much better coupled to O2 utilization in the hybrid than in the parent. Overall, these results support the notion that the α subunit harbors the principal determinants of specificity in ring-hydroxylating dioxygenases. However, they also demonstrate that the β subunit contributes significantly to the enzyme's function. PMID:12949084

Development of Bioactive Ceramic Coating on Titanium Alloy substrate for Biomedical Application Using Dip Coating Method

NASA Astrophysics Data System (ADS)

Asmawi, R.; Ibrahim, M. H. I.; Amin, A. M.; Mustafa, N.; Noranai, Z.

2017-08-01

Bioactive apatite, such as hydroxyapatite ceramic (HA), [Ca10(PO4)6(OH)2] has been extensively investigated for biomedical applications due to its excellent biocompatibility and tissue bioactivity properties. Its bioactivity provides direct bonding to the bone tissue. Because of its similarity in chemical composition to the inorganic matrix of bone, HA is widely used as implant materials for bone. Unfortunately, because of its poor mechanical properties,. this bioactive material is not suitable for load bearing applications. In this study, by the assistance of dip-coating technique, HA coatings were deposited on titanium alloy substrates by employing hydrothermal derived HA powder. The produced coatings then were oven-dried at 130°C for 1 hour and calcined at various temperature over the range of 200-800°C for 1 hour. XRD measurement showed that HA was the only phase present in the coatings. However coatings calcined at 800°C comprised a mixture of HA and tri-calcium phosphate (TCP). FTIR measurement showed the existence of hydroxyl, phosphate, and carbonate bands. PO4 - band became sharper and narrower with the increased of calcination temperature. FESEM observation showed that the coating is polycrystalline with individual particles of nano to submicron size and has an average particle size of 35 nm. The thickness of the coating are direcly propotional with the viscosity of coating slurry. It was shown that the more viscous coating slurry would produce a thicker ceramic coating. Mechanical properties of the coating were measured in term of adhesion strength using a Micro Materials Nano Test microscratch testing machine. The result revealed that the coating had a good adhesion to the titanium alloy substrate.

Effects of electrical conductivity of substrate materials on microstructure of diamond-like carbon films prepared by bipolar-type plasma based ion implantation

NASA Astrophysics Data System (ADS)

Nakao, S.; Sonoda, T.

2013-03-01

Diamond-like carbon (DLC) films are prepared by a bipolar-type plasma based ion implantation, and the structural differences between DLC films deposited on different electrical conductive substrates, i.e., conductive Si wafers and insulating glass plates are examined by Raman spectroscopy and x-ray photo emission spectroscopy (XPS). In the Raman measurements, graphite (G) and disorder (D) peaks are observed for both samples. However, the additional photo luminescence is overlapped on the spectra in the case of on-glass sample. To elucidate the structural difference, the intensity ratio of D to G peak (I(D)/I(G)), G peak position and full width at half maximum (FWHM) are obtained by curve fitting using Gaussian function and linear baseline. It is found that the I(D)/I(G) is lower, G peak position is higher and FWHM of G peak is narrower for on-glass sample than for on-Si sample. According to Robertson [1], lower I(D)/I(G) seems more sp3 C-C bonding in amount for on-glass sample. In contrast, higher G peak position and narrower FWHM of G peak suggest less sp3 C-C bonding in amount for on-glass sample. The results of XPS analysis with C1s spectra reveal that sp3 ratio, i.e., the intensity ratio of sp3/(sp3+sp2) is smaller for on-glass sample than for on-Si sample. The inconsistency of the trend between I(D)/I(G) and other parameters (G peak position and FWHM of G peak) might be caused by the overlap of photo luminescence signal on Raman spectrum as to on-glass sample. From these results, it is considered that sp3 C-C bonding is reduced in amount when using insulating substrate in comparison with conductive substrate.

Anisotropic relaxation behavior of InGaAs/GaAs selectively grown in narrow trenches on (001) Si substrates

NASA Astrophysics Data System (ADS)

Guo, W.; Mols, Y.; Belz, J.; Beyer, A.; Volz, K.; Schulze, A.; Langer, R.; Kunert, B.

2017-07-01

Selective area growth of InGaAs inside highly confined trenches on a pre-patterned (001) Si substrate has the potential of achieving a high III-V crystal quality due to high aspect ratio trapping for improved device functionalities in Si microelectronics. If the trench width is in the range of the hetero-layer thickness, the relaxation mechanism of the mismatched III-V layer is no longer isotropic, which has a strong impact on the device fabrication and performance if not controlled well. The hetero-epitaxial nucleation of InxGa1-xAs on Si can be simplified by using a binary nucleation buffer such as GaAs. A pronounced anisotropy in strain release was observed for the growth of InxGa1-xAs on a fully relaxed GaAs buffer with a (001) surface inside 20 and 100 nm wide trenches, exploring the full composition range from GaAs to InAs. Perpendicular to the trench orientation (direction of high confinement), the strain release in InxGa1-xAs is very efficiently caused by elastic relaxation without defect formation, although a small compressive force is still induced by the trench side walls. In contrast, the strain release along the trenches is governed by plastic relaxation once the vertical film thickness has clearly exceeded the critical layer thickness. On the other hand, the monolithic deposition of mismatched InxGa1-xAs directly into a V-shaped trench bottom with {111} Si planes leads instantly to a pronounced nucleation of misfit dislocations along the {111} Si/III-V interfaces. In this case, elastic relaxation no longer plays a role as the strain release is ensured by plastic relaxation in both directions. Hence, using a ternary seed layer facilitates the integration of InxGa1-xAs covering the full composition range.

Extensive peptide and natural protein substrate screens reveal that mouse caspase-11 has much narrower substrate specificity than caspase-1

PubMed Central

Ramirez, Monica L. Gonzalez; Poreba, Marcin; Snipas, Scott J.; Groborz, Katarzyna; Drag, Marcin; Salvesen, Guy S.

2018-01-01

Inflammatory cell death, or pyroptosis, is triggered by pathogenic infections or events. It is executed by caspase-1 (in the canonical pyroptosis pathway) or caspase-11 (noncanonical pathway), each via production of a cell-lytic domain from the pyroptosis effector protein gasdermin D through specific and limited proteolysis. Pyroptosis is accompanied by the release of inflammatory mediators, including the proteolytically processed forms of interleukin-1β (IL-1β) and IL-18. Given the similar inflammatory outcomes of the canonical and noncanonical pyroptosis pathways, we hypothesized that caspase-1 and -11 should have very similar activities and substrate specificities. To test this hypothesis, we purified recombinant murine caspases and analyzed their primary specificities by massive hybrid combinatorial substrate library (HyCoSuL) screens. We correlated the substrate preferences of each caspase with their activities on the recombinant natural substrates IL-1β, IL-18, and gasdermin D. Although we identified highly selective and robust peptidyl substrates for caspase-1, we were unable to do so for caspase-11, because caspase-1 cleaved even the best caspase-11 substrates equally well. Caspase-1 rapidly processed pro-IL-1β and -18, but caspase-11 processed these two pro-ILs extremely poorly. However, both caspase-1 and -11 efficiently produced the cell-lytic domain from the gasdermin D precursor. We hypothesize that caspase-11 may have evolved a specific exosite to selectively engage pyroptosis without directly activating pro-IL-1β or -18. In summary, comparing the activities of caspase-1 and -11 in HyCoSuL screens and with three endogenous protein substrates, we conclude that caspase-11 has highly restricted substrate specificity, preferring gasdermin D over all other substrates examined. PMID:29414788

Meniscus-force-mediated layer transfer technique using single-crystalline silicon films with midair cavity: Application to fabrication of CMOS transistors on plastic substrates

NASA Astrophysics Data System (ADS)

Sakaike, Kohei; Akazawa, Muneki; Nakagawa, Akitoshi; Higashi, Seiichiro

2015-04-01

A novel low-temperature technique for transferring a silicon-on-insulator (SOI) layer with a midair cavity (supported by narrow SiO2 columns) by meniscus force has been proposed, and a single-crystalline Si (c-Si) film with a midair cavity formed in dog-bone shape was successfully transferred to a poly(ethylene terephthalate) (PET) substrate at its heatproof temperature or lower. By applying this proposed transfer technique, high-performance c-Si-based complementary metal-oxide-semiconductor (CMOS) transistors were successfully fabricated on the PET substrate. The key processes are the thermal oxidation and subsequent hydrogen annealing of the SOI layer on the midair cavity. These processes ensure a good MOS interface, and the SiO2 layer works as a “blocking” layer that blocks contamination from PET. The fabricated n- and p-channel c-Si thin-film transistors (TFTs) on the PET substrate showed field-effect mobilities of 568 and 103 cm2 V-1 s-1, respectively.

Three new species and the molecular phylogeny of Antipathozoanthus from the Indo-Pacific Ocean (Anthozoa, Hexacorallia, Zoantharia).

PubMed

Kise, Hiroki; Fujii, Takuma; Masucci, Giovanni Diego; Biondi, Piera; Reimer, James Davis

2017-01-01

In this study, three new species of macrocnemic zoantharians (Hexacorallia, Zoantharia) are described from localities in the Indo-Pacific Ocean including the Red Sea, the Maldives, Palau, and southern Japan: Antipathozoanthus obscurus sp. n. , A. remengesaui sp. n. , and A. cavernus sp. n. Although the genus Antipathozoanthus is currently restricted to species living on antipatharians, A. obscurus sp. n. is not associated with any living substrate and instead is found on coral reef carbonate substrate within narrow caves or cracks. The two new species that have association with antipatharians, A. remengesaui sp. n. and A. cavernus sp. n. , can be distinguished by their relative coenenchyme development and the antipatharian species that each uses as substrate. Additionally, all new species described in this study have unique nuclear internal transcribed spacer region of ribosomal DNA (ITS-rDNA) sequences. Our results indicate that more phylogenetic studies focusing on increasing the numbers of species examined within each of the genera of Parazoanthidae are required in order to better understand the evolutionary history of substrate specificity within the family Parazoanthidae.

Three new species and the molecular phylogeny of Antipathozoanthus from the Indo-Pacific Ocean (Anthozoa, Hexacorallia, Zoantharia)

PubMed Central

Kise, Hiroki; Fujii, Takuma; Masucci, Giovanni Diego; Biondi, Piera; Reimer, James Davis

2017-01-01

Abstract In this study, three new species of macrocnemic zoantharians (Hexacorallia, Zoantharia) are described from localities in the Indo-Pacific Ocean including the Red Sea, the Maldives, Palau, and southern Japan: Antipathozoanthus obscurus sp. n., A. remengesaui sp. n., and A. cavernus sp. n. Although the genus Antipathozoanthus is currently restricted to species living on antipatharians, A. obscurus sp. n. is not associated with any living substrate and instead is found on coral reef carbonate substrate within narrow caves or cracks. The two new species that have association with antipatharians, A. remengesaui sp. n. and A. cavernus sp. n., can be distinguished by their relative coenenchyme development and the antipatharian species that each uses as substrate. Additionally, all new species described in this study have unique nuclear internal transcribed spacer region of ribosomal DNA (ITS-rDNA) sequences. Our results indicate that more phylogenetic studies focusing on increasing the numbers of species examined within each of the genera of Parazoanthidae are required in order to better understand the evolutionary history of substrate specificity within the family Parazoanthidae. PMID:29362542

Chromogenic Detection of Dipeptidyl Peptidase IV (DPP-IV) Activity using Peptide-Functionalized Gold Nanoparticles

NASA Astrophysics Data System (ADS)

Abul-Huda, Yasin Mohammad

Metal nanoparticles offer a useful platform for a wide range of biological applications especially for biosensing, bioimaging and drug delivery. This thesis presents a body of original research describing the synthesis, characterisation and development of a novel and convenient biosensing assay for detection of dipeptidyl peptidase IV (DPP-IV) enzyme activity using peptide functionalized gold nanoparticles. The distinctive optical and physical properties of gold nanoparticles (Au NP) were harnessed for the development of a colorimetric assay for rapid sensing of DPP-IV activities and screening DPP-IV inhbitors. The citrate reduction method for Au NPs synthesis was optimised and several potential peptide substrates (GPDC, VP-EN-DC, C/G dipeptide, GPG-EN-PEG4-LA, GPDCALNNC) were designed to provide substrates that mimic the DPP-IV natural substrates. The performances of the substrate functionalized Au NPs were assessed for their appropriateness for the detection of the enzyme activity. Addition of DPP-IV to the solutions containing the functionalized Au NPs resulted in cleavage of the substrate and thus causing the aggregation of the Au NPs which in turn led to a shift of the surface plasmon peak toward longer wavelengths, and a change of the colour of the colloidal suspension from red to blue. Overall, real-time detection of DPP-IV activity over a broader range (0-40 U/L) with high selectivity and stability was obtained, thus providing a method that can be used to determine the levels of DPP-IV/CD26 in biological fluids such as serum and plasma. Further assay developments were conducted to overcome limitations encountered with the original Au NP assay, especially the narrow dynamic linear range and stability in high ionic strength solutions. Validation and comparison of the Au NP assay developed has revealed that this method is highly correlated to the gold standard chromogenic Gly-Pro-pNA method for detection of enzyme activity in biological samples. Very good recoveries (in the range 83.6 -114.9%) were obtained in spiked serum samples, which indicate that this assay could provide a suitable alternative for enzyme activity detection with the naked eye and without the need for sophisticated instruments. Investigations into the effects of incorporating different stabilizers in order to improve the stability of the peptide functionalized Au NP in high ionic strength solutions were also investigated. Gold nanoparticles have different shapes and structures and an alternative approach for detection of DPP-IV activity using gold nanorods due to their higher refractive index sensitivities was explored. As a conclusion, three out of five approaches, all utilising Au NP-ligand conjugates were demonstrated useful for the detection of the DPP-IV activity. The system developed here is portable and would permit on-site analysis of samples, which offers a real alternative approach from traditional assays and reduces the need for laboratory testing. The logical next step in this research would be the continuation of experiments to transform this test into a point of care testing device that could offer an early detection tool for disease management.

Studies to reveal the nature of interactions between catalase and curcumin using computational methods and optical techniques.

PubMed

Mofidi Najjar, Fayezeh; Ghadari, Rahim; Yousefi, Reza; Safari, Naser; Sheikhhasani, Vahid; Sheibani, Nader; Moosavi-Movahedi, Ali Akbar

2017-02-01

Curcumin is an important antioxidant compound, and is widely reported as an effective component for reducing complications of many diseases. However, the detailed mechanisms of its activity remain poorly understood. We found that curcumin can significantly increase catalase activity of BLC (bovine liver catalase). The mechanism of curcumin action was investigated using a computational method. We suggested that curcumin may activate BLC by modifying the bottleneck of its narrow channel. The molecular dynamic simulation data showed that placing curcumin on the structure of enzyme can increase the size of the bottleneck in the narrow channel of BLC, and readily allow the access of substrate to the active site. Because of the increase of the distance between amino acids of the bottleneck in the presence of curcumin, the entrance space of substrate increased from 250Å 3 to 440Å 3 . In addition, the increase in emission of intrinsic fluorescence of BLC in presence of curcumin demonstrated changes in tertiary structure of catalase, and possibility of less quenching. We also used circular dichroism (CD) spectropolarimetry to determine how curcumin may alter the enzyme secondary structure. Catalase spectra in the presence of various concentrations of curcumin showed an increase in the amount of α-helix content. Copyright © 2016 Elsevier B.V. All rights reserved.

Perovskite nanocrystals: across-dimensional attachment, film-scale assembly on a flexible substrate and their fluorescence properties

NASA Astrophysics Data System (ADS)

Huang, Wenyi; Liu, Jiajia; Bai, Bing; Huang, Liu; Xu, Meng; Liu, Jia; Rong, Hongpan; Zhang, Jiatao

2018-03-01

Perovskite nanocrystals (NCs), which are a good fluorescence candidate with excellent photoelectric properties, have opened new avenues in the fabrication of highly efficient solar cells, light-emitting diodes (LEDs), and other optoelectronic devices. Further advances will rely on the multitude of compositional, structural variants that enable the formation of lower-dimensionality layered and three-dimensional (3D) perovskites with architectural innovations. In this work, the perovskite film was fabricated on a flexible substrate using simple dip-coating technology and 3D assemblies of perovskite NCs were obtained through an attachment process. Original perovskite NCs had a rectangular or square morphology with high particle uniformity and the narrow and symmetric fluorescence emission peak was adjustable at 515-527 nm. The controllable self-assembly of the micron size cuboid-like 3D assembly had an apparent enhancement on peak (111) in the x-ray diffraction (XRD) pattern. Surface ligands not only play a role in the attachment process but also keep the independence of each NC in 3D assemblies. Such assembly of the perovskite film maintained the original perovskite NCs fluorescence emission peak and narrow full width at the half-maximum (FWHM), which is of great importance for the investigation of future devices.

The evolution of environmental tolerance and range size: a comparison of geographically restricted and widespread Mimulus.

PubMed

Sheth, Seema N; Angert, Amy L

2014-10-01

The geographic ranges of closely related species can vary dramatically, yet we do not fully grasp the mechanisms underlying such variation. The niche breadth hypothesis posits that species that have evolved broad environmental tolerances can achieve larger geographic ranges than species with narrow environmental tolerances. In turn, plasticity and genetic variation in ecologically important traits and adaptation to environmentally variable areas can facilitate the evolution of broad environmental tolerance. We used five pairs of western North American monkeyflowers to experimentally test these ideas by quantifying performance across eight temperature regimes. In four species pairs, species with broader thermal tolerances had larger geographic ranges, supporting the niche breadth hypothesis. As predicted, species with broader thermal tolerances also had more within-population genetic variation in thermal reaction norms and experienced greater thermal variation across their geographic ranges than species with narrow thermal tolerances. Species with narrow thermal tolerance may be particularly vulnerable to changing climatic conditions due to lack of plasticity and insufficient genetic variation to respond to novel selection pressures. Conversely, species experiencing high variation in temperature across their ranges may be buffered against extinction due to climatic changes because they have evolved tolerance to a broad range of temperatures. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

A new lime material for container substrates

USDA-ARS?s Scientific Manuscript database

The primary component in greenhouse potting substrates is sphagnum peatmoss. Substrate solution pH of non-amended peatmoss ranges from 4.0 to 4.5. Ideal pH for most greenhouse floriculture crops ranges from 5.8 to 6.2. Dolomitic lime is most often used to elevate substrate pH in peatmoss-based me...

Virial series expansion and Monte Carlo studies of equation of state for hard spheres in narrow cylindrical pores

NASA Astrophysics Data System (ADS)

Mon, K. K.

2018-05-01

In this paper, the virial series expansion and constant pressure Monte Carlo method are used to study the longitudinal pressure equation of state for hard spheres in narrow cylindrical pores. We invoke dimensional reduction and map the model into an effective one-dimensional fluid model with interacting internal degrees of freedom. The one-dimensional model is extensive. The Euler relation holds, and longitudinal pressure can be probed with the standard virial series expansion method. Virial coefficients B2 and B3 were obtained analytically, and numerical quadrature was used for B4. A range of narrow pore widths (2 Rp) , Rp<(√{3 }+2 ) /4 =0.9330 ... (in units of the hard sphere diameter) was used, corresponding to fluids in the important single-file formations. We have also computed the virial pressure series coefficients B2', B3', and B4' to compare a truncated virial pressure series equation of state with accurate constant pressure Monte Carlo data. We find very good agreement for a wide range of pressures for narrow pores. These results contribute toward increasing the rather limited understanding of virial coefficients and the equation of state of hard sphere fluids in narrow cylindrical pores.

Wide-angle Spectrally Selective Perfect Absorber by Utilizing Dispersionless Tamm Plasmon Polaritons

PubMed Central

Xue, Chun-hua; Wu, Feng; Jiang, Hai-tao; Li, Yunhui; Zhang, Ye-wen; Chen, Hong

2016-01-01

We theoretically investigate wide-angle spectrally selective absorber by utilizing dispersionless Tamm plasmon polaritons (TPPs) under TM polarization. TPPs are resonant tunneling effects occurring on the interface between one-dimensional photonic crystals (1DPCs) and metal slab, and their dispersion properties are essentially determined by that of 1DPCs. Our investigations show that dispersionless TPPs can be excited in 1DPCs containing hyperbolic metamaterials (HMMs) on metal substrate. Based on dispersionless TPPs, electromagnetic waves penetrate into metal substrate and are absorbed entirely by lossy metal, exhibiting a narrow-band and wide-angle perfect absorption for TM polarization. Our results exhibit nearly perfect absorption with a value over 98% in the angle of incidence region of 0–80 degree. PMID:27991565

Robust lanthanide emitters in polyelectrolyte thin films for photonic applications

NASA Astrophysics Data System (ADS)

Greenspon, Andrew S.; Marceaux, Brandt L.; Hu, Evelyn L.

2018-02-01

Trivalent lanthanides provide stable emission sources at wavelengths spanning the ultraviolet through the near infrared with uses in telecommunications, lighting, and biological sensing and imaging. We describe a method for incorporating an organometallic lanthanide complex within polyelectrolyte multilayers, producing uniform, optically active thin films on a variety of substrates. These films demonstrate excellent emission with narrow linewidths, stable over a period of months, even when bound to metal substrates. Utilizing different lanthanides such as europium and terbium, we are able to easily tune the resulting wavelength of emission of the thin film. These results demonstrate the suitability of this platform as a thin film emitter source for a variety of photonic applications such as waveguides, optical cavities, and sensors.

ARC-1986-A86-7011

NASA Image and Video Library

1986-01-14

Range : 2.52 million miles (1.56 million miles) P-29481B/W Voyager 2 returned this photograph with all nine known Uranus rings visible from a 15 sec. exposure through the narrow angle camera. The rings are quite dark and very narrow. The most prominent and outermost of the nine, Epsilon, is seen at top. The next three in toward Uranus, called Delta, Gamma, and Eta, are much fainter and more narrow than Epsilon ring. Then come Beta and Alpha rings, and finally, the innermost grouping, known simply as the 4,5, & 6 rings. The last three are very faint and are at the limit of detection for the Voyager camera. Uranus' rings range in width from about 100 km. (60 mi.) at the widest part of the Epsilon ring, to only a few kilometers for most of the others. this iamge was processed to enhance narrow features; the bright dots are imperfections on the camera detector. The resolution scale is about 50 km. (30 mi.)

X-ray structures of the Pseudomonas cichorii D-tagatose 3-epimerase mutant form C66S recognizing deoxy sugars as substrates.

PubMed

Yoshida, Hiromi; Yoshihara, Akihide; Ishii, Tomohiko; Izumori, Ken; Kamitori, Shigehiro

2016-12-01

Pseudomonas cichorii D-tagatose 3-epimerase (PcDTE), which has a broad substrate specificity, efficiently catalyzes the epimerization of not only D-tagatose to D-sorbose but also D-fructose to D-psicose (D-allulose) and also recognizes the deoxy sugars as substrates. In an attempt to elucidate the substrate recognition and catalytic reaction mechanisms of PcDTE for deoxy sugars, the X-ray structures of the PcDTE mutant form with the replacement of Cys66 by Ser (PcDTE_C66S) in complexes with deoxy sugars were determined. These X-ray structures showed that substrate recognition by the enzyme at the 1-, 2-, and 3-positions is responsible for enzymatic activity and that substrate-enzyme interactions at the 4-, 5-, and 6-positions are not essential for the catalytic reaction of the enzyme leading to the broad substrate specificity of PcDTE. They also showed that the epimerization site of 1-deoxy 3-keto D-galactitol is shifted from C3 to C4 and that 1-deoxy sugars may bind to the catalytic site in the inhibitor-binding mode. The hydrophobic groove that acts as an accessible surface for substrate binding is formed through the dimerization of PcDTE. In PcDTE_C66S/deoxy sugar complex structures, bound ligand molecules in both the linear and ring forms were detected in the hydrophobic groove, while bound ligand molecules in the catalytic site were in the linear form. This result suggests that the sugar-ring opening of a substrate may occur in the hydrophobic groove and also that the narrow channel of the passageway to the catalytic site allows a substrate in the linear form to pass through.

Design and Test of Passively Operated Heat Switches for 0.2 to 15 K

NASA Technical Reports Server (NTRS)

DiPirro, M. J.; Shirron, P. J.; Canavan, E. R.; Francis, J. J.; Tuttle, J. G.

2003-01-01

Heat switches have many uses in cryogenics, from regulating heat flow between refrigeration stages to thermally isolating components once they have cooled to low temperature. Among the techniques one can use for thermal switching, the gas-gap technique has the advantages of wide operating temperature range, high switching ratio, and no moving parts. The traditional gas-gap switch uses copper conductors separated by a small gap and an external getter. The switch is activated by heating and cooling the getter by moving gas into and out of the gap, turning the switch on and off. We have designed, built and tested heat switches that use an internal getter to passively turn off at temperatures between 0.2 and 15 K. The getter is thermally anchored to one side of the switch, and when that side of the switch cools through a transition region, gas adsorbs onto the getter and the switch turns off. The challenges are to make the transition region very narrow and tailorable to a wide range of applications, and to achieve high gas conductance when the switch is on. We have made switches using He-3, He-4, hydrogen, and neon gas, and have used charcoal and various metal substrates as getters. Switching ratios range from 1000 to over 10,000. Design and performance of these switches will be discussed in detail.

Heavy-ion dominance near Cluster perigees

NASA Astrophysics Data System (ADS)

Ferradas, C. P.; Zhang, J.-C.; Kistler, L. M.; Spence, H. E.

2015-12-01

Time periods in which heavy ions dominate over H+ in the energy range of 1-40 keV were observed by the Cluster Ion Spectrometry (CIS)/COmposition DIstribution Function (CODIF) instrument onboard Cluster Spacecraft 4 at L values less than 4. The characteristic feature is a narrow flux peak at around 10 keV that extends into low L values, with He+ and/or O+ dominating. In the present work we perform a statistical study of these events and examine their temporal occurrence and spatial distribution. The observed features, both the narrow energy range and the heavy-ion dominance, can be interpreted using a model of ion drift from the plasma sheet, subject to charge exchange losses. The narrow energy range corresponds to the only energy range that has direct drift access from the plasma sheet during quiet times. The drift time to these locations from the plasma sheet is > 30 h, so that charge exchange has a significant impact on the population. We show that a simple drift/loss model can explain the dependence on L shell and MLT of these heavy-ion-dominant time periods.

The oligomeric architecture of the archaeal exosome is important for processive and efficient RNA degradation.

PubMed

Audin, Maxime J C; Wurm, Jan Philip; Cvetkovic, Milos A; Sprangers, Remco

2016-04-07

The exosome plays an important role in RNA degradation and processing. In archaea, three Rrp41:Rrp42 heterodimers assemble into a barrel like structure that contains a narrow RNA entrance pore and a lumen that contains three active sites. Here, we demonstrate that this quaternary structure of the exosome is important for efficient RNA degradation. We find that the entrance pore of the barrel is required for nM substrate affinity. This strong interaction is crucial for processive substrate degradation and prevents premature release of the RNA from the enzyme. Using methyl TROSY NMR techniques, we establish that the 3' end of the substrate remains highly flexible inside the lumen. As a result, the RNA jumps between the three active sites that all equally participate in substrate degradation. The RNA jumping rate is, however, much faster than the cleavage rate, indicating that not all active site:substrate encounters result in catalysis. Enzymatic turnover therefore benefits from the confinement of the active sites and substrate in the lumen, which ensures that the RNA is at all times bound to one of the active sites. The evolution of the exosome into a hexameric complex and the optimization of its catalytic efficiency were thus likely co-occurring events. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

Development of Sample Verification System for Sample Return Missions

NASA Technical Reports Server (NTRS)

Toda, Risaku; McKinney, Colin; Jackson, Shannon P.; Mojarradi, Mohammad; Trebi-Ollennu, Ashitey; Manohara, Harish

2011-01-01

This paper describes the development of a proof of-concept sample verification system (SVS) for in-situ mass measurement of planetary rock and soil sample in future robotic sample return missions. Our proof-of-concept SVS device contains a 10 cm diameter pressure sensitive elastic membrane placed at the bottom of a sample canister. The membrane deforms under the weight of accumulating planetary sample. The membrane is positioned in proximity to an opposing substrate with a narrow gap. The deformation of the membrane makes the gap to be narrower, resulting in increased capacitance between the two nearly parallel plates. Capacitance readout circuitry on a nearby printed circuit board (PCB) transmits data via a low-voltage differential signaling (LVDS) interface. The fabricated SVS proof-of-concept device has successfully demonstrated approximately 1pF/gram capacitance change

Photo-Detection on Narrow-Bandgap High-Mobility 2D Semiconductors

NASA Astrophysics Data System (ADS)

Charnas, Adam; Qiu, Gang; Deng, Yexin; Wang, Yixiu; Du, Yuchen; Yang, Lingming; Wu, Wenzhuo; Ye, Peide

Photo-detection and energy harvesting device concepts have been demonstrated widely in 2D materials such as graphene, TMDs, and black phosphorus. In this work, we demonstrate anisotropic photo-detection achieved using devices fabricated from hydrothermally grown narrow-bandgap high-mobility 2D semiconductor. Back-gated FETs were fabricated by transferring the 2D flakes onto a Si/SiO2 substrate and depositing various metal contacts across the flakes to optimize the access resistance for optoelectronic devices. Photo-responsivity was measured and mapped by slightly biasing the devices and shining a laser spot at different locations of the device to observe and map the resulting photo-generated current. Optimization of the Schottky barrier height for both n and p at the metal-2D interfaces using asymmetric contact engineering was performed to improve device performance.

Compact MEMS external cavity tunable laser with ultra-narrow linewidth for coherent detection.

PubMed

Zhang, Di; Zhao, Jianyi; Yang, Qi; Liu, Wen; Fu, Yanfeng; Li, Chao; Luo, Ming; Hu, Shenglei; Hu, Qianggao; Wang, Lei

2012-08-27

A compact and ultra-narrow linewidth tunable laser with an external cavity based on a simple single-axis-MEMS mirror is presented in this paper. We discuss the simulation of this tunable laser using a two-step hybrid analysis method to obtain an optimal design of the device. A wide wavelength tuning range about 40 nm in C-band with a narrow linewidth of less than 50 kHz and wavelength accuracy of ± 1 GHz over the entire tuning range can be achieved experimentally. We also conduct several experiments under different conditions to test the tunable laser. This device shows an excellent performance in both single-carrier polarization-multiplexed quadrature phase-shift keying (PM-QPSK) and multi-carrier orthogonal frequency division multiplexing (OFDM) coherent systems.

Stabilizing new bismuth compounds in thin film form [Stabilizing new thin film materials in bismuth compounds

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

Chen, Aiping; Zhou, Honghui; Zhu, Yuanyuan

2016-11-10

Growth of unexpected phases from a composite target of BiFeO 3:BiMnO 3 and/or BiFeO 3:BiCrO 3 has been explored using pulsed laser deposition. The Bi 2FeMnO 6 tetragonal phase can be grown directly on SrTiO 3 (STO) substrate, while two phases (S1 and S2) were found to grow on LaAlO 3 (LAO) substrates with narrow growth windows. However, introducing a thin CeO 2 buffer layer effectively broadens the growth window for the pure S1 phase, regardless of the substrate. Moreover, we discovered two new phases (X1 and X2) when growing on STO substrates using a BiFeO 3:BiCrO 3 target. Puremore » X2 phase can be obtained on CeO 2-buffered STO and LAO substrates. This work demonstrates that some unexpected phases can be stabilized in a thin film form by using composite perovskite BiRO 3 (R = Cr, Mn, Fe, Co, Ni) targets. Moreover, it also indicates that CeO 2 can serve as a general template for the growth of bismuth compounds with potential room-temperature multiferroicity.« less

Theory of electric resonance in the neocortical apical dendrite.

PubMed

Kasevich, Ray S; LaBerge, David

2011-01-01

Pyramidal neurons of the neocortex display a wide range of synchronous EEG rhythms, which arise from electric activity along the apical dendrites of neocortical pyramidal neurons. Here we present a theoretical description of oscillation frequency profiles along apical dendrites which exhibit resonance frequencies in the range of 10 to 100 Hz. The apical dendrite is modeled as a leaky coaxial cable coated with a dielectric, in which a series of compartments act as coupled electric circuits that gradually narrow the resonance profile. The tuning of the peak frequency is assumed to be controlled by the average amplitude of voltage-gated outward currents, which in turn are regulated by the subthreshold noise in the thousands of synaptic spines that are continuously bombarded by local circuits. The results of simulations confirmed the ability of the model both to tune the peak frequency in the 10-100 Hz range and to gradually narrow the resonance profile. Considerable additional narrowing of the resonance profile is provided by repeated looping through the apical dendrite via the corticothalamocortical circuit, which reduced the width of each resonance curve (at half-maximum) to approximately 1 Hz. Synaptic noise in the neural circuit is discussed in relation to the ways it can influence the narrowing process.

Theory of Electric Resonance in the Neocortical Apical Dendrite

PubMed Central

Kasevich, Ray S.; LaBerge, David

2011-01-01

Pyramidal neurons of the neocortex display a wide range of synchronous EEG rhythms, which arise from electric activity along the apical dendrites of neocortical pyramidal neurons. Here we present a theoretical description of oscillation frequency profiles along apical dendrites which exhibit resonance frequencies in the range of 10 to 100 Hz. The apical dendrite is modeled as a leaky coaxial cable coated with a dielectric, in which a series of compartments act as coupled electric circuits that gradually narrow the resonance profile. The tuning of the peak frequency is assumed to be controlled by the average amplitude of voltage-gated outward currents, which in turn are regulated by the subthreshold noise in the thousands of synaptic spines that are continuously bombarded by local circuits. The results of simulations confirmed the ability of the model both to tune the peak frequency in the 10–100 Hz range and to gradually narrow the resonance profile. Considerable additional narrowing of the resonance profile is provided by repeated looping through the apical dendrite via the corticothalamocortical circuit, which reduced the width of each resonance curve (at half-maximum) to approximately 1 Hz. Synaptic noise in the neural circuit is discussed in relation to the ways it can influence the narrowing process. PMID:21853129

Spectroscopic properties of triangular silver nanoplates immobilized on polyelectrolyte multilayer-modified glass substrates

NASA Astrophysics Data System (ADS)

Rabor, Janice B.; Kawamura, Koki; Muko, Daiki; Kurawaki, Junichi; Niidome, Yasuro

2017-07-01

Fabrication of surface-immobilized silver nanostructures with reproducible plasmonic properties by dip-coating technique is difficult due to shape alteration. To address this challenge, we used a polyelectrolyte multilayer to promote immobilization of as-received triangular silver nanoplates (TSNP) on a glass substrate through electrostatic interaction. The substrate-immobilized TSNP were characterized by absorption spectrophotometry and scanning electron microscopy. The bandwidth and peak position of localized surface plasmon resonance (LSPR) bands can be tuned by simply varying the concentration of the colloidal solution and immersion time. TSNP immobilized from a higher concentration of colloidal solution with longer immersion time produced broadened LSPR bands in the near-IR region, while a lower concentration with shorter immersion time produced narrower bands in the visible region. The shape of the nanoplates was retained even at long immersion time. Analysis of peak positions and bandwidths also revealed the point at which the main species of the immobilization had been changed from isolates to aggregates.

Catalytic nanoporous membranes

DOEpatents

Pellin, Michael J [Naperville, IL; Hryn, John N [Naperville, IL; Elam, Jeffrey W [Elmhurst, IL

2009-12-01

A nanoporous catalytic membrane which displays several unique features including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity.

Kinetics of Mixed Microbial Assemblages Enhance Removal of Highly Dilute Organic Substrates

PubMed Central

Lewis, David L.; Hodson, Robert E.; Hwang, Huey-Min

1988-01-01

Our experiments with selected organic substrates reveal that the rate-limiting process governing microbial degradation rates changes with substrate concentration, S, in such a manner that substrate removal is enhanced at lower values of S. This enhancement is the result of the dominance of very efficient systems for substrate removal at low substrate concentrations. The variability of dominant kinetic parameters over a range of S causes the kinetics of complex assemblages to be profoundly dissimilar to those of systems possessing a single set of kinetic parameters; these findings necessitate taking a new approach to predicting substrate removal rates over wide ranges of S. PMID:16347715

InGaP solar cell on Ge-on-Si virtual substrate for novel solar power conversion

NASA Astrophysics Data System (ADS)

Kim, T. W.; Albert, B. R.; Kimerling, L. C.; Michel, J.

2018-02-01

InGaP single-junction solar cells are grown on lattice-matched Ge-on-Si virtual substrates using metal-organic chemical vapor deposition. Optoelectronic simulation results indicate that the optimal collection length for InGaP single-junction solar cells with a carrier lifetime range of 2-5 ns is wider than approximately 1 μm. Electron beam-induced current measurements reveal that the threading dislocation density (TDD) of InGaP solar cells fabricated on Ge and Ge-on-Si substrates is in the range of 104-3 × 107 cm-2. We demonstrate that the open circuit voltage (Voc) of InGaP solar cells is not significantly influenced by TDDs less than 2 × 106 cm-2. Fabricated InGaP solar cells grown on a Ge-on-Si virtual substrate and a Ge substrate exhibit Voc in the range of 0.96 to 1.43 V under an equivalent illumination in the range of ˜0.5 Sun. The estimated efficiency of the InGaP solar cell fabricated on the Ge-on-Si virtual substrate (Ge substrate) at room temperature for the limited incident spectrum spanning the photon energy range of 1.9-2.4 eV varies from 16.6% to 34.3%.

Resonant cavity light-emitting diodes based on dielectric passive cavity structures

NASA Astrophysics Data System (ADS)

Ledentsov, N.; Shchukin, V. A.; Kropp, J.-R.; Zschiedrich, L.; Schmidt, F.; Ledentsov, N. N.

2017-02-01

A novel design for high brightness planar technology light-emitting diodes (LEDs) and LED on-wafer arrays on absorbing substrates is proposed. The design integrates features of passive dielectric cavity deposited on top of an oxide- semiconductor distributed Bragg reflector (DBR), the p-n junction with a light emitting region is introduced into the top semiconductor λ/4 DBR period. A multilayer dielectric structure containing a cavity layer and dielectric DBRs is further processed by etching into a micrometer-scale pattern. An oxide-confined aperture is further amended for current and light confinement. We study the impact of the placement of the active region into the maximum or minimum of the optical field intensity and study an impact of the active region positioning on light extraction efficiency. We also study an etching profile composed of symmetric rings in the etched passive cavity over the light emitting area. The bottom semiconductor is an AlGaAs-AlAs multilayer DBR selectively oxidized with the conversion of the AlAs layers into AlOx to increase the stopband width preventing the light from entering the semiconductor substrate. The approach allows to achieve very high light extraction efficiency in a narrow vertical angle keeping the reasonable thermal and current conductivity properties. As an example, a micro-LED structure has been modeled with AlGaAs-AlAs or AlGaAs-AlOx DBRs and an active region based on InGaAlP quantum well(s) emitting in the orange spectral range at 610 nm. A passive dielectric SiO2 cavity is confined by dielectric Ta2O5/SiO2 and AlGaAs-AlOx DBRs. Cylindrically-symmetric structures with multiple ring patterns are modeled. It is demonstrated that the extraction coefficient of light to the air can be increased from 1.3% up to above 90% in a narrow vertical angle (full width at half maximum (FWHM) below 20°). For very small oxide-confined apertures 100nm the narrowing of the FWHM for light extraction can be reduced down to 5°. Consequently high efficiency high brightness arrays of micro-LEDs becomes possible. For single emitters the approach is particularly interesting for oscillator strength engineering allowing high speed data transmission and for single photonics applying single quantum dot (QD) emitters and allowing >90% coupling of the emission into single mode fiber. We also note that for longer wavelength ( 1300nm) QDs the thickness of the layers and surface patterns significantly increase allowing greatly reduced processing tolerances and applying further simplifications due to the possibility of using high contrast GaAs-AlOx DBRs.

Advances in OLED/OPD-based sensors and spectrometer-on-a-chip (Conference Presentation)

NASA Astrophysics Data System (ADS)

Shinar, Joseph; Kaudal, Rajiv; Manna, Eeshita; Fungura, Fadzai; Shinar, Ruth

2016-09-01

We describe ongoing advances toward achieving all-organic optical sensors and a spectrometer on a chip. Two-dimensional combinatorial arrays of microcavity OLEDs (μcOLEDs) with systematically varying optical cavity lengths are fabricated on a single chip by changing the thickness of different organic and/or spacer layers sandwiched between two metal electrodes (one very thin) that form the cavity. The broad spectral range is achieved by utilizing materials that result in white OLEDs (WOLEDs) when fabricated on a standard ITO substrate. The tunable and narrower emissions from the μcOLEDs serve as excitation sources in luminescent sensors and in monitoring light absorption. For each wavelength, the light from the μcOLED is partially absorbed by a sample under study and the light emitted by an electronically excited sample, or the transmitted light is detected by a photodetector (PD). To obtain a compact monitor, an organic PD (OPD) or a perovskite-based PD is integrated with the μcOLED array. We show the potential of encompassing a broader wavelength range by using WOLED materials to fabricate the μcOLEDs. The utility of the all-organic analytical devices is demonstrated by monitoring oxygen, and bioanalytes based on oxygen detection, as well as the absorption spectra of dyes.

Gradients, vegetation and climate: spatial and temporal dynamics in the Olympic Mountains, USA

USGS Publications Warehouse

Peterson, David L.; Schreiner, Edward G.; Buckingham, Nelsa M.

1997-01-01

The steep environmental gradients of mountains result in the juxtaposition of diverse vegetation associations with narrow ecotones because life zones are compressed. Variation in geologic substrate, landforms, and soils, in combination with steep environmental gradients, create habitat diversity across spatial scales from 106 ha to <10 m2. This leads to higher biodiversity in a smaller space than in landscapes with less topographic variation. Mountains are often considered to be refuges for biological diversity at the regional scale, although variation in landscape features creates refuges at a fine scale as well. Mountains should also be considered a source of biological diversity, because they provide the germplasm for migration into lowland areas following glacial recession. Many taxa are distributed over a broad range of elevations and habitats, which maximizes the potential to respond to environmental perturbations. Reorganization of species distribution and abundance as a result of climatic change may be impacted considerably by human-caused fragmentation of landscape features, especially at lower elevations. This paper uses palaeoecological and biogeographical data to investigate the spatial and temporal vegetation dynamics of a steep maritime range, the Olympic Mountains (USA). The role of resource management in protecting vegetation in a fragmented landscape is discussed, with emphasis on how to address uncertainties such as climatic change.

Wideband electromagnetic energy harvesting from ambient vibrations

NASA Astrophysics Data System (ADS)

Mallick, Dhiman; Podder, Pranay; Roy, Saibal

2015-06-01

Different bandwidth widening schemes of electromagnetic energy harvesters have been reported in this work. The devices are fabricated on FR4 substrate using laser micromachining techniques. The linear device operate in a narrow band around the resonance; in order to tune resonant frequency of the device electrically, two different types of complex load topologies are adopted. Using capacitive load, the resonant frequency is tuned in the low frequency direction whereas using inductive load, the resonant frequency is tuned in the high frequency direction. An overall tuning range of ˜2.4 Hz is obtained at 0.3g though the output power dropped significantly over the tuning range. In order to improve the off-resonance performance, nonlinear oscillation based systems are adopted. A specially designed spring arm with fixed-guided configuration produced single well nonlinear monostable configuration. With increasing input acceleration, wider bandwidth is obtained with such a system as large displacement, stretching nonlinearity comes into play and 9.55 Hz bandwidth is obtained at 0.5g. The repulsive force between one static and one vibrating oppositely polarized magnets are used to generate bistable nonlinear potential system. The distance between the mentioned magnets is varied between 4 to 10 mm to produce tunable nonlinearity with a maximum half power bandwidth over 3 Hz at 0.5g.

Stabilizing Ir(001) Epitaxy on Yttria-Stabilized Zirconia Using a Thin Ir Seed Layer Grown by Pulsed Laser Deposition

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

Fan, Lisha; Jacobs, Christopher B.; Rouleau, Christopher M.

In this paper, we demonstrate the reproducible epitaxial growth of 100 nm thick Ir(001) films on a heteroepitaxial stack consisting of 5 nm Ir and 100 nm yttria-stabilized zirconia (YSZ) grown on Si(001) substrates. It is shown that a 5 nm thick Ir layer grown by pulsed laser deposition in the same chamber as the YSZ film without breaking the vacuum is the key to stabilizing Ir(001) epitaxial growth. Growth of the Ir seed layer with pure (001) orientation occurs only in a narrow growth temperature window from 550 to 750 °C, and the fraction of Ir(111) increases at substratemore » temperatures outside of this window. The Ir seed layer prevents exposure of the YSZ film to air during sample transfer and enables highly reproducible Ir(001) heteroepitaxy on YSZ buffered Si(001). In contrast, if Ir is grown directly on a bare YSZ layer that was exposed to ambient conditions, the films are prone to change orientation to (111). These results reveal that preserving the chemical and structural purity of the YSZ surface is imperative for achieving Ir(001) epitaxy. The narrow range of the mosaic spread values from eight experiments demonstrates the high yield and high reproducibility of Ir(001) heteroepitaxy by this approach. Lastly, the improved Ir(001) epitaxial growth method is of great significance for integrating a variety of technologically important materials such as diamond, graphene, and functional oxides on a Si platform.« less

Stabilizing Ir(001) Epitaxy on Yttria-Stabilized Zirconia Using a Thin Ir Seed Layer Grown by Pulsed Laser Deposition

DOE PAGES

Fan, Lisha; Jacobs, Christopher B.; Rouleau, Christopher M.; ...

2016-11-18

In this paper, we demonstrate the reproducible epitaxial growth of 100 nm thick Ir(001) films on a heteroepitaxial stack consisting of 5 nm Ir and 100 nm yttria-stabilized zirconia (YSZ) grown on Si(001) substrates. It is shown that a 5 nm thick Ir layer grown by pulsed laser deposition in the same chamber as the YSZ film without breaking the vacuum is the key to stabilizing Ir(001) epitaxial growth. Growth of the Ir seed layer with pure (001) orientation occurs only in a narrow growth temperature window from 550 to 750 °C, and the fraction of Ir(111) increases at substratemore » temperatures outside of this window. The Ir seed layer prevents exposure of the YSZ film to air during sample transfer and enables highly reproducible Ir(001) heteroepitaxy on YSZ buffered Si(001). In contrast, if Ir is grown directly on a bare YSZ layer that was exposed to ambient conditions, the films are prone to change orientation to (111). These results reveal that preserving the chemical and structural purity of the YSZ surface is imperative for achieving Ir(001) epitaxy. The narrow range of the mosaic spread values from eight experiments demonstrates the high yield and high reproducibility of Ir(001) heteroepitaxy by this approach. Lastly, the improved Ir(001) epitaxial growth method is of great significance for integrating a variety of technologically important materials such as diamond, graphene, and functional oxides on a Si platform.« less

Molecular cloning and catalytic characterization of a recombinant tropine biosynthetic tropinone reductase from Withania coagulans leaf.

PubMed

Kushwaha, Amit K; Sangwan, Neelam S; Tripathi, Sandhya; Sangwan, Rajender S

2013-03-10

Tropinone reductases (TRs) are small proteins belonging to the SDR (short chain dehydrogenase/reductase) family of enzymes. TR-I and TR-II catalyze the conversion of tropinone into tropane alcohols (tropine and pseudotropine, respectively). The steps are intermediary enroute to biosynthesis of tropane esters of medicinal importance, hyoscyamine/scopolamine, and calystegins, respectively. Biosynthesis of tropane alkaloids has been proposed to occur in roots. However, in the present report, a tropine forming tropinone reductase (TR-I) cDNA was isolated from the aerial tissue (leaf) of a medicinal plant, Withania coagulans. The ORF was deduced to encode a polypeptide of 29.34 kDa. The complete cDNA (WcTRI) was expressed in E. coli and the recombinant His-tagged protein was purified for functional characterization. The enzyme had a narrow pH range of substantial activity with maxima at 6.6. Relatively superior thermostability of the enzyme (30% retention of activity at 60 °C) was catalytic novelty in consonance with the desert area restricted habitat of the plant. The in vitro reaction kinetics predominantly favoured the forward reaction. The enzyme had wide substrate specificity but did not cover the substrates of other well-known plant SDR related to menthol metabolism. To our knowledge, this pertains to be the first report on any gene and enzyme of secondary metabolism from the commercially and medicinally important vegetable rennet species. Copyright © 2012 Elsevier B.V. All rights reserved.

Multicolor Bioluminescence Boosts Malaria Research: Quantitative Dual-Color Assay and Single-Cell Imaging in Plasmodium falciparum Parasites

PubMed Central

2015-01-01

New reliable and cost-effective antimalarial drug screening assays are urgently needed to identify drugs acting on different stages of the parasite Plasmodium falciparum, and particularly those responsible for human-to-mosquito transmission, that is, the P. falciparum gametocytes. Low Z′ factors, narrow dynamic ranges, and/or extended assay times are commonly reported in current gametocyte assays measuring gametocyte-expressed fluorescent or luciferase reporters, endogenous ATP levels, activity of gametocyte enzymes, or redox-dependent dye fluorescence. We hereby report on a dual-luciferase gametocyte assay with immature and mature P. falciparum gametocyte stages expressing red and green-emitting luciferases from Pyrophorus plagiophthalamus under the control of the parasite sexual stage-specific pfs16 gene promoter. The assay was validated with reference antimalarial drugs and allowed to quantitatively and simultaneously measure stage-specific drug effects on parasites at different developmental stages. The optimized assay, requiring only 48 h incubation with drugs and using a cost-effective luminogenic substrate, significantly reduces assay cost and time in comparison to state-of-the-art analogous assays. The assay had a Z′ factor of 0.71 ± 0.03, and it is suitable for implementation in 96- and 384-well microplate formats. Moreover, the use of a nonlysing d-luciferin substrate significantly improved the reliability of the assay and allowed one to perform, for the first time, P. falciparum bioluminescence imaging at single-cell level. PMID:25102353

Post-fabrication voltage controlled resonance tuning of nanoscale plasmonic antennas.

PubMed

Lumdee, Chatdanai; Toroghi, Seyfollah; Kik, Pieter G

2012-07-24

Voltage controlled wavelength tuning of the localized surface plasmon resonance of gold nanoparticles on an aluminum film is demonstrated in single particle microscopy and spectroscopy measurements. Anodization of the Al film after nanoparticle deposition forms an aluminum oxide spacer layer between the gold particles and the Al film, modifying the particle-substrate interaction. Darkfield microscopy reveals ring-shaped scattering images from individual Au nanoparticles, indicative of plasmon resonances with a dipole moment normal to the substrate. Single particle scattering spectra show narrow plasmon resonances that can be tuned from ~580 to ~550 nm as the anodization voltage increases to 12 V. All observed experimental trends could be reproduced in numerical simulations. The presented approach could be used as a general postfabrication resonance optimization step of plasmonic nanoantennas and devices.

Stresses and Temperature Stability of Dense Wavelength Division Multiplexing Filters Prepared by Reactive Ion-Assisted E-Gun Evaporation

NASA Astrophysics Data System (ADS)

Wei, Chao-Tsang; Shieh, Han-Ping D.

2005-10-01

In this paper, we report the in situ measurement of the temperature stability of narrow-band-pass filters on different types of substrate, for dense wavelength division multiplexing (DWDM) filters in optical-fiber transmission systems. The DWDM filters were designed as all-dielectric Fabry-Perot filters and fabricated by reactive ion-assisted deposition. Ta2O5 and SiO2 were used as high- and low-refractive-index layers, respectively, for constructing the DWDM filters. The accuracy and stability of the coating process were evaluated for fabricating the DWDM filters for the temperature stability of the center wavelength. The center wavelength shift was determined to be greatly dependent on the coefficient of thermal expansion of the substrate on which the filter is deposited.

Room-temperature continuous operation of InAsSb quantum-dot lasers near 2 mu m based on (100) InP substrate

NASA Technical Reports Server (NTRS)

Qui, Y.; Uhl, D.; Keo, S.

2003-01-01

Single-stack InAsSb self-assembled quantum-dot lasers based on (001) InP substrate have been grown by metalorganic vapor-phase epitaxy. The narrow ridge waveguide lasers lased at wavelengths near 2 mu m up to 25 degrees C in continuous-wave operation. At room temperature, a differential quantum efficiency of 13 percent is obtained and the maximum output optical power reaches 3 mW per facet with a threshold current density of 730 A/cm(sup 2). With increasing temperature the emission wavelength is extremely temperature stable, and a very low wavelength temperature sensitivity of 0.05 nm/degrees C is measured, which is even lower than that caused by the refractive index change.

Obtaining Thickness-Limited Electrospray Deposition for 3D Coating.

PubMed

Lei, Lin; Kovacevich, Dylan A; Nitzsche, Michael P; Ryu, Jihyun; Al-Marzoki, Kutaiba; Rodriguez, Gabriela; Klein, Lisa C; Jitianu, Andrei; Singer, Jonathan P

2018-04-04

Electrospray processing utilizes the balance of electrostatic forces and surface tension within a charged spray to produce charged microdroplets with a narrow dispersion in size. In electrospray deposition, each droplet carries a small quantity of suspended material to a target substrate. Past electrospray deposition results fall into two major categories: (1) continuous spray of films onto conducting substrates and (2) spray of isolated droplets onto insulating substrates. A crossover regime, or a self-limited spray, has only been limitedly observed in the spray of insulating materials onto conductive substrates. In such sprays, a limiting thickness emerges, where the accumulation of charge repels further spray. In this study, we examined the parametric spray of several glassy polymers to both categorize past electrospray deposition results and uncover the critical parameters for thickness-limited sprays. The key parameters for determining the limiting thickness were (1) field strength and (2) spray temperature, related to (i) the necessary repulsive field and (ii) the ability for the deposited materials to swell in the carrier solvent vapor and redistribute charge. These control mechanisms can be applied to the uniform or controllably-varied microscale coating of complex three-dimensional objects.

High rate DC-reactive sputter deposition of Y 2O 3 film on the textured metal substrate for the superconducting coated conductor

NASA Astrophysics Data System (ADS)

Kim, Ho-Sup; Park, Chan; Ko, Rock-Kil; Shi, Dongqui; Chung, Jun-Ki; Ha, Hong-Soo; Park, Yu-Mi; Song, Kyu-Jeong; Youm, Do-Jun

2005-10-01

Y2O3 film was directly deposited on Ni-3at%W substrate by DC reactive sputtering. DC reactive sputtering was carried out using metallic Y target and water vapor for oxidizing the elements of metallic target on the substrate. The detailed conditions of DC reactive sputtering for depositions of Y2O3 films were investigated. The window of water vapor for proper growth of Y2O3 films was determined by sufficient oxidations of the Y2O3 films and the non-oxidation of the target surface, which was required for high rate sputtering. The window turned out to be fairly wide in the chamber used. As the sputtering power was raised, the deposition rate increased without narrowing the window. The fabricated Y2O3 films showed good texture qualities and surface morphologies. The YBCO film deposited directly on the Y2O3 buffered Ni-3at%W substrate showed Tc, Ic (77 K, self field), and Jc (77 K, self field) of 89 K, 64 A/cm and 1.1 MA/cm2, respectively.

Enhancing elastic stress relaxation in SiGe/Si heterostructures by Si pillar necking

NASA Astrophysics Data System (ADS)

Isa, F.; Salvalaglio, M.; Arroyo Rojas Dasilva, Y.; Jung, A.; Isella, G.; Erni, R.; Timotijevic, B.; Niedermann, P.; Gröning, P.; Montalenti, F.; von Känel, H.

2016-10-01

We demonstrate that the elastic stress relaxation mechanism in micrometre-sized, highly mismatched heterostructures may be enhanced by employing patterned substrates in the form of necked pillars, resulting in a significant reduction of the dislocation density. Compositionally graded Si1-xGex crystals were grown by low energy plasma enhanced chemical vapour deposition, resulting in tens of micrometres tall, three-dimensional heterostructures. The patterned Si(001) substrates consist of micrometre-sized Si pillars either with the vertical {110} or isotropically under-etched sidewalls resulting in narrow necks. The structural properties of these heterostructures were investigated by defect etching and transmission electron microscopy. We show that the dislocation density, and hence the competition between elastic and plastic stress relaxation, is highly influenced by the shape of the substrate necks and their proximity to the mismatched epitaxial material. The SiGe dislocation density increases monotonically with the crystal width but is significantly reduced by the substrate under-etching. The drop in dislocation density is interpreted as a direct effect of the enhanced compliance of the under-etched Si pillars, as confirmed by the three-dimensional finite element method simulations of the elastic energy distribution.

Thermokinetics of heterogeneous droplet nucleation on conically textured substrates.

PubMed

Singha, Sanat K; Das, Prasanta K; Maiti, Biswajit

2015-11-28

Within the framework of the classical theory of heterogeneous nucleation, a thermokinetic model is developed for line-tension-associated droplet nucleation on conical textures considering growth or shrinkage of the formed cluster due to both interfacial and peripheral monomer exchange and by considering different geometric configurations. Along with the principle of free energy extremization, Katz kinetic approach has been employed to study the effect of substrate conicity and wettability on the thermokinetics of heterogeneous water droplet nucleation. Not only the peripheral tension is found to have a considerable effect on the free energy barrier but also the substrate hydrophobicity and hydrophilicity are observed to switch over their roles between conical crest and trough for different growth rates of the droplet. Besides, the rate of nucleation increases and further promotes nucleation for negative peripheral tension as it diminishes the free energy barrier appreciably. Moreover, nucleation inhibition can be achievable for positive peripheral tension due to the enhancement of the free energy barrier. Analyzing all possible geometric configurations, the hydrophilic narrower conical cavity is found to be the most preferred nucleation site. These findings suggest a physical insight into the context of surface engineering for the promotion or the suppression of nucleation on real or engineered substrates.

Electrochemical photovoltaic cell having ternary alloy film

DOEpatents

Russak, Michael A.

1984-01-01

A thin film compound semiconductor electrode comprising CdSe.sub.1-x Te.sub.x (0.ltoreq.x.ltoreq.1) is deposited on a transparent conductive substrate. An electrolyte contacts the film to form a photoactive site. The semiconductor material has a narrow energy bandgap permitting high efficiency for light conversion. The film may be fabricated by: (1) co-evaporation of two II-VI group compounds with a common cation, or (2) evaporation of three elements, concurrenty.

Extensive peptide and natural protein substrate screens reveal that mouse caspase-11 has much narrower substrate specificity than caspase-1.

PubMed

Ramirez, Monica L Gonzalez; Poreba, Marcin; Snipas, Scott J; Groborz, Katarzyna; Drag, Marcin; Salvesen, Guy S

2018-05-04

Inflammatory cell death, or pyroptosis, is triggered by pathogenic infections or events. It is executed by caspase-1 (in the canonical pyroptosis pathway) or caspase-11 (noncanonical pathway), each via production of a cell-lytic domain from the pyroptosis effector protein gasdermin D through specific and limited proteolysis. Pyroptosis is accompanied by the release of inflammatory mediators, including the proteolytically processed forms of interleukin-1β (IL-1β) and IL-18. Given the similar inflammatory outcomes of the canonical and noncanonical pyroptosis pathways, we hypothesized that caspase-1 and -11 should have very similar activities and substrate specificities. To test this hypothesis, we purified recombinant murine caspases and analyzed their primary specificities by massive hybrid combinatorial substrate library (HyCoSuL) screens. We correlated the substrate preferences of each caspase with their activities on the recombinant natural substrates IL-1β, IL-18, and gasdermin D. Although we identified highly selective and robust peptidyl substrates for caspase-1, we were unable to do so for caspase-11, because caspase-1 cleaved even the best caspase-11 substrates equally well. Caspase-1 rapidly processed pro-IL-1β and -18, but caspase-11 processed these two pro-ILs extremely poorly. However, both caspase-1 and -11 efficiently produced the cell-lytic domain from the gasdermin D precursor. We hypothesize that caspase-11 may have evolved a specific exosite to selectively engage pyroptosis without directly activating pro-IL-1β or -18. In summary, comparing the activities of caspase-1 and -11 in HyCoSuL screens and with three endogenous protein substrates, we conclude that caspase-11 has highly restricted substrate specificity, preferring gasdermin D over all other substrates examined. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Fabrication of superconducting nanowires from ultrathin MgB2 films via focused ion beam milling

NASA Astrophysics Data System (ADS)

Zhang, Chen; Wang, Da; Liu, Zheng-Hao; Zhang, Yan; Ma, Ping; Feng, Qing-Rong; Wang, Yue; Gan, Zi-Zhao

2015-02-01

High quality superconducting nanowires were fabricated from ultrathin MgB2 films by a focused ion beam milling technique. The precursor MgB2 films in 10 nm thick were grown on MgO substrates by using a hybrid physical-chemical vapor deposition method. The nanowires, in widths of about 300-600 nm and lengths of 1 or 10 μm, showed high superconducting critical temperatures (Tc's) above 34 K and narrow superconducting transition widths (ΔTc's) of 1-3 K. The superconducting critical current density Jc of the nanowires was above 5 × 107 A/cm2 at 20 K. The high Tc, narrow ΔTc, and high Jc of the nanowires offered the possibility of making MgB2-based nano-devices such as hot-electron bolometers and superconducting nanowire single-photon detectors with high operating temperatures at 15-20 K.

Microstrip patch antenna receiving array operating in the Ku band

NASA Technical Reports Server (NTRS)

Walcher, Douglas A.

1996-01-01

Microstrip patch antennas were first investigated from the idea that it would be highly advantageous to fabricate radiating elements (antennas) on the same dielectric substrate as RF circuitry and transmission lines. Other advantages were soon discovered to be its lightweight, low profile, conformability to shaped surfaces, and low manufacturing costs. Unfortunately, these same patches continually exhibit narrow bandwidths, wide beamwidths, and low antenna gain. This thesis will present the design and experimental results of a microstrip patch antenna receiving array operating in the Ku band. An antenna array will be designed in an attempt to improve its performance over a single patch. Most Ku band information signals are either wide band television images or narrow band data and voice channels. An attempt to improve the gain of the array by introducing parasitic patches on top of the array will also be presented in this thesis.

Method for preparing high temperature superconductor

DOEpatents

Balachandran, Uthamalingam; Chudzik, Michael P.

2002-01-01

A method of depositing a biaxially textured metal oxide on a substrate defining a plane in which metal oxide atoms are vaporized from a source to form a plume of metal oxide atoms. Atoms in the plume disposed at a selected angle in a predetermined range of angles to the plane of the substrate are allowed to contact the substrate while preventing atoms outside a selected angle from reaching the substrate. The preferred range of angles is 40.degree.-70.degree. and the preferred angle is 60.degree..+-.5.degree.. A moving substrate is disclosed.

Long range wetting transparency on top of layered metal dielectric substrates

DTIC Science & Technology

2015-11-20

multi-layered stacks were deposited onto glass substrates ( silica -based Micro cover glass , 22mmx22mm from VWR (48366-067), index of refraction n...necessarily endorsed by the United States Government. Long-range wetting transparency on top of layered metal-dielectric substrates M. A...as far as ~100 nm beneath the water/MgF2 interface. We refer to this phenomenon as long range wetting transparency . The latter effect cannot be

Tunable narrow linewidth all-fiber thulium-doped fiber laser in a 2 µm-band using two Hi-Bi fiber optical loop mirrors

NASA Astrophysics Data System (ADS)

Posada-Ramírez, B.; Durán-Sánchez, M.; Álvarez-Tamayo, R. I.; Ibarra-Escamilla, B.; Hernández-Arriaga, M. V.; Sánchez-de-la-Llave, D.; Kuzin, E. A.

2017-08-01

We propose an all-fiber Tm-doped fiber laser with a tunable and narrow laser line generated in a wavelength region of 2 µm. A single laser line with a linewidth below 0.05 nm, tunable in a wavelength range of 44.25 nm, is obtained. The laser linewidth and the discrete wavelength tuning range depend on the characteristics of the two fiber optical loop mirrors with high birefringence in the loop that forms the cavity. Dual-wavelength laser operation is also observed at tuning range limits with a wavelength separation of 47 nm. Alternate wavelength switching is also observed.

Preliminary Results Obtained from Flight Test of a Rocket Model Having the Tail Only of the Grumman XF10F Airplane Configuration, TED No. NACA DE 354

NASA Technical Reports Server (NTRS)

Gardner, William N.; Edmondson, James L.

1950-01-01

A flight test was made to determine the servoplane effectiveness and stability characteristics of the free-floating horizontal stabilizer to be used on the XF10F airplane. The results of this test indicate that servoplane effectiveness is practically constant through the speed range up to a Mach number of 1.15, and the stabilizer static stability is satisfactory. A loss of damping occurs over a narrow Mach number range near M = 1.0, resulting in dynamic instability of the stabilizer in this narrow range. Above M = 1.0 there is a gradual positive trim change of the stabilizer.

Deposition of device quality, low hydrogen content, hydrogenated amorphous silicon at high deposition rates with increased stability using the hot wire filament technique

DOEpatents

Molenbroek, Edith C.; Mahan, Archie Harvin; Gallagher, Alan C.

2000-09-26

A method or producing hydrogenated amorphous silicon on a substrate, comprising the steps of: positioning the substrate in a deposition chamber at a distance of about 0.5 to 3.0 cm from a heatable filament in the deposition chamber; maintaining a pressure in said deposition chamber in the range of about 10 to 100 millitorr and pressure times substrate-filament spacing in the range of about 10 to 100 millitorr-cm, heating the filament to a temperature in the range of about 1,500 to 2,000.degree. C., and heating the substrate to a surface temperature in the range of about 280 to 475.degree. C.; and flowing silicohydride gas into the deposition chamber with said heated filament, decomposing said silicohydride gas into silicon and hydrogen atomic species and allowing products of gas reactions between said atomic species and the silicohydride gas to migrate to and deposit on said substrate while adjusting and maintaining said pressure times substrate-filament spacing in said deposition chamber at a value in said 10 to 100 millitorr range to produce statistically about 3 to 50 atomic collisions between the silicon and hydrogen atomic species migrating to said substrate and undecomposed molecules of the silane or other silicohydride gas in the deposition chamber.

Strain relaxation in nm-thick Cu and Cu-alloy films bonded to a rigid substrate

NASA Astrophysics Data System (ADS)

Herrmann, Ashley Ann Elizabeth

In the wide scope of modern technology, nm-thick metallic films are increasingly used as lubrication layers, optical coatings, plating seeds, diffusion barriers, adhesion layers, metal contacts, reaction catalyzers, etc. A prominent example is the use of nm-thick Cu films as electroplating seed layers in the manufacturing of integrated circuits (ICs). These high density circuits are linked by on-chip copper interconnects, which are manufactured by filling Cu into narrow trenches by electroplating. The Cu fill by electroplating requires a thin Cu seed deposited onto high-aspect-ratio trenches. In modern ICs, these trenches are approaching 10 nm or less in width, and the seed layers less than 1 nm in thickness. Since nm-thick Cu seed layers are prone to agglomeration or delamination, achieving uniform, stable and highly-conductive ultra-thin seeds has become a major manufacturing challenge. A fundamental understanding of the strain behavior and thermal stability of nm-thick metal films adhered to a rigid substrate is thus critically needed. In this study, we focus on understanding the deformation modes of nm-thick Cu and Cu-alloy films bonded to a rigid Si substrate and under compressive stress. The strengthening of Cu films through alloying is also studied. In-situ transport measurements are used to monitor the deformation of such films as they are heated from room temperature to 400 °C. Ex-situ AFM is then used to help characterize the mode of strain relaxation. The relaxation modes are known to be sensitive to the wetting and adhesive properties of the film-substrate interface. We use four different liners (Ta, Ru, Mo and Co), interposed between the film and substrate to provide a wide range of interfacial properties to study their effect on the film's thermal stability. Our measurements indicate that when the film/liner interfacial energy is low, grain growth is the dominant relaxation mechanism. As the interface energy increases, grain growth is suppressed, and the strain is relaxed through hillock/island formation instead. The kinetics-limiting parameters for these relaxation modes are identified and used to simulate their kinetics, and a deformation map is then constructed to delineate the conditions under which each mode would prevail. Such a deformation map would prove useful when one seeks to optimize the thermal stability or other mechanical properties in any ultra-thin film system.

A Chandra Survey of high-redshift (0.7 < z < 0.8) clusters selected in the 100 deg^2 SPT-Pol Deep Field

NASA Astrophysics Data System (ADS)

Garmire, Gordon

2016-09-01

We propose to observe a complete sample of 10 galaxy clusters at 1e14 < M500 < 5e14 and 0.7 < z < 0.8. These systems were selected from the 100 deg^2 deep field of the SPT-Pol SZ survey. This survey are has significant complementary data, including uniform depth ATCA, Herschel, Spitzer, and DES imaging, enabling a wide variety of astrophysical and cosmological studies. This sample complements the successful SPT-XVP survey, which has a broad redshift range and a narrow mass range, by including clusters over a narrow redshift range and broad mass range. These systems are such low mass and high redshift that they will not be detected in the eRosita all-sky survey.

A tale of seven narrow spikes and a long trough: constraining the timing of the percolation of H II bubbles at the tail end of reionization with ULAS J1120+0641

NASA Astrophysics Data System (ADS)

Chardin, Jonathan; Haehnelt, Martin G.; Bosman, Sarah E. I.; Puchwein, Ewald

2018-01-01

High signal-to-noise observations of the Ly α forest transmissivity in the z = 7.085 quasi-stellar object (QSO) ULAS J1120+0641 show seven narrow transmission spikes followed by a long 240 cMpc h-1 trough. Here, we use radiative transfer simulations of cosmic reionization previously calibrated to match a wider range of Ly α forest data to show that the occurrence of seven transmission spikes in the narrow redshift range z = 5.85-6.1 is very sensitive to the exact timing of reionization. Occurrence of the spikes requires the most underdense regions of the intergalactic medium to be already fully ionized. The rapid onset of a long trough at z = 6.12 requires a strong decrease of the photoionization rate Γ at z ≳ 6.1 in this line of sight, consistent with the end of percolation at this redshift. The narrow range of reionization histories that we previously found to be consistent with a wider range of Ly α forest data have a reasonable probability of showing seven spikes and the mock absorption spectra provide an excellent match to the spikes and the trough in the observed spectrum of ULAS J1120+0641. Larger samples of high signal-to-noise searches for rare Ly α transmission spikes at z > 5.8 should therefore provide important further insights into the exact timing of the percolation of H II bubbles at the tail end of reionization.

Conserved and narrow temperature limits in alpine insects: Thermal tolerance and supercooling points of the ice-crawlers, Grylloblatta (Insecta: Grylloblattodea: Grylloblattidae).

PubMed

Schoville, Sean D; Slatyer, Rachel A; Bergdahl, James C; Valdez, Glenda A

2015-07-01

For many terrestrial species, habitat associations and range size are dependent on physiological limits, which in turn may influence large-scale patterns of species diversity. The temperature range experienced by individuals is considered to shape the breadth of the thermal niche, with species occupying temporally and/or geographically stable climates tolerating a narrow temperature range. High-elevation environments experience large temperature fluctuations, with frequent periods below 0 °C, but Grylloblatta (Grylloblattodea: Grylloblattidae) occupy climatically stable microhabitats within this region. Here we test critical thermal limits and supercooling points for five Grylloblatta populations from across a large geographic area, to examine whether the stable microhabitats of this group are associated with a narrow thermal niche and assess their capacity to tolerate cold conditions. Thermal limits are highly conserved in Grylloblatta, despite substantial genetic divergence among populations spanning 1500 m elevation and being separated by over 500 km. Further, Grylloblatta show exceptionally narrow thermal limits compared to other insect taxa with little capacity to improve cold tolerance via plasticity. In contrast, upper thermal limits were significantly depressed by cold acclimation. Grylloblatta maintain coordinated movement until they freeze, and they die upon freezing. Convergence of the critical thermal minima, supercooling point and lower lethal limits point to adaptation to a cold but, importantly, constant thermal environment. These physiological data provide an explanation for the high endemism and patchy distribution of Grylloblatta, which relies on subterranean retreats to accommodate narrow thermal limits. These retreats are currently buffered from temperature fluctuations by snow cover, and a declining snowpack thus places Grylloblatta at risk of exposure to temperatures beyond its tolerance capacity. Copyright © 2015 Elsevier Ltd. All rights reserved.

High performance millimeter-wave microstrip circulators and isolators

NASA Technical Reports Server (NTRS)

Shih, Ming; Pan, J. J.

1990-01-01

Millimeter wave systems, phased array antennas, and high performance components all require wideband circulators (and isolators) to perform diplexing and switching, to improve isolation and Voltage Standing Wave Ratio (VSWR), and to construct IMPATT diode reflection amplifiers. Presently, most of the millimeter-wave circulators and isolators are available in the configurations of waveguide or stripline, both of which suffer from the shortcomings of bulky size/weight, narrow bandwidth, and poor compatibility with monolithic millimeter-wave integrated circuits (MMIC). MMW microstrip circulators/isolators can eliminate or improve these shortcomings. Stub-tuned microstrip circulator configuration were developed utilizing the electromagnetic fields perturbation technique, the adhesion problems of microstrip metallization on new ferrite substrate were overcome, the fabrication, assembly, packaging techniques were improved, and then successfully designed, fabricated a Ka band circulator which has isolation and return loss of greater than 16dB, insertion loss less than 0.7dB. To assess the steady and reliable performance of the circulator, a temperature cycling test was done over the range of -20 to +50 C for 3 continuous cycles and found no significant impact or variation of circulator performance.

FudC, a protein primarily responsible for furfural detoxification in Corynebacterium glutamicum.

PubMed

Tsuge, Yota; Kudou, Motonori; Kawaguchi, Hideo; Ishii, Jun; Hasunuma, Tomohisa; Kondo, Akihiko

2016-03-01

Lignocellulosic hydrolysates contain compounds that inhibit microbial growth and fermentation, thereby decreasing the productivity of biofuel and biochemical production. In particular, the heterocyclic aldehyde furfural is one of the most toxic compounds found in these hydrolysates. We previously demonstrated that Corynebacterium glutamicum converts furfural into the less toxic compounds furfuryl alcohol and 2-furoic acid. To date, however, the genes involved in these oxidation and reduction reactions have not been identified in the C. glutamicum genome. Here, we show that Cgl0331 (designated FudC) is mainly responsible for the reduction of furfural into furfuryl alcohol in C. glutamicum. Deletion of the gene encoding FudC markedly diminished the in vivo reduction of furfural to furfuryl alcohol. Purified His-tagged FudC protein from Escherichia coli was also shown to convert furfural into furfuryl alcohol in an in vitro reaction utilizing NADPH, but not NADH, as a cofactor. Kinetic measurements demonstrated that FudC has a high affinity for furfural but has a narrow substrate range for other aldehydes compared to the protein responsible for furfural reduction in E. coli.

Ultra-wideband optical leaky-wave slot antennas.

PubMed

Wang, Yan; Helmy, Amr S; Eleftheriades, George V

2011-06-20

We propose and investigate an ultra-wideband leaky-wave antenna that operates at optical frequencies for the purpose of efficient energy coupling between localized nanoscale optical circuits and the far-field. The antenna consists of an optically narrow aluminum slot on a silicon substrate. We analyze its far-field radiation pattern in the spectral region centered around 1550 nm with a 50% bandwidth ranging from 2000 nm to 1200 nm. This plasmonic leaky-wave slot produces a maximum far-field radiation angle at 32° and a 3 dB beamwidth of 24° at its center wavelength. The radiation pattern is preserved within the 50% bandwidth suffering only insignificant changes in both the radiation angle and the beamwidth. This wide-band performance is quite unique when compared to other optical antenna designs. Furthermore, the antenna effective length for radiating 90% and 99.9% of the input power is only 0.5λ(0) and 1.5λ(0) respectively at 1550 nm. The versatility and simplicity of the proposed design along with its small footprint makes it extremely attractive for integration with nano-optical components using existing technologies.

Highly Enhanced Raman Scattering on Carbonized Polymer Films.

PubMed

Yoon, Jong-Chul; Hwang, Jongha; Thiyagarajan, Pradheep; Ruoff, Rodney S; Jang, Ji-Hyun

2017-06-28

We have discovered a carbonized polymer film to be a reliable and durable carbon-based substrate for carbon enhanced Raman scattering (CERS). Commercially available SU8 was spin coated and carbonized (c-SU8) to yield a film optimized to have a favorable Fermi level position for efficient charge transfer, which results in a significant Raman scattering enhancement under mild measurement conditions. A highly sensitive CERS (detection limit of 10 -8 M) that was uniform over a large area was achieved on a patterned c-SU8 film and the Raman signal intensity has remained constant for 2 years. This approach works not only for the CMOS-compatible c-SU8 film but for any carbonized film with the correct composition and Fermi level, as demonstrated with carbonized-PVA (poly(vinyl alcohol)) and carbonized-PVP (polyvinylpyrollidone) films. Our study certainly expands the rather narrow range of Raman-active material platforms to include robust carbon-based films readily obtained from polymer precursors. As it uses broadly applicable and cheap polymers, it could offer great advantages in the development of practical devices for chemical/bio analysis and sensors.

Engineering of Pyranose Dehydrogenase for Increased Oxygen Reactivity

PubMed Central

Krondorfer, Iris; Lipp, Katharina; Brugger, Dagmar; Staudigl, Petra; Sygmund, Christoph; Haltrich, Dietmar; Peterbauer, Clemens K.

2014-01-01

Pyranose dehydrogenase (PDH), a member of the GMC family of flavoproteins, shows a very broad sugar substrate specificity but is limited to a narrow range of electron acceptors and reacts extremely slowly with dioxygen as acceptor. The use of substituted quinones or (organo)metals as electron acceptors is undesirable for many production processes, especially of food ingredients. To improve the oxygen reactivity, site-saturation mutagenesis libraries of twelve amino acids around the active site of Agaricus meleagris PDH were expressed in Saccharomyces cerevisiae. We established high-throughput screening assays for oxygen reactivity and standard dehydrogenase activity using an indirect Amplex Red/horseradish peroxidase and a DCIP/D-glucose based approach. The low number of active clones confirmed the catalytic role of H512 and H556. Only one position was found to display increased oxygen reactivity. Histidine 103, carrying the covalently linked FAD cofactor in the wild-type, was substituted by tyrosine, phenylalanine, tryptophan and methionine. Variant H103Y was produced in Pichia pastoris and characterized and revealed a five-fold increase of the oxygen reactivity. PMID:24614932

Fabrication and characterization of the noble metal nanostructures on the GaAs surface

NASA Astrophysics Data System (ADS)

Gladskikh, Polina V.; Gladskikh, Igor A.; Toropov, Nikita A.; Vartanyan, Tigran A.

2016-04-01

Self-assembled silver, gold, and copper nanostructures on the monocrystalline GaAs (100) wafer surface were obtained via physical vapor deposition and characterized by optical reflection spectroscopy, scanning electron microscopy, and current-voltage curve measurements. Reflection spectra of the samples with Ag equivalent thicknesses of 2, 5, 7.5, and 10 nm demonstrated wide plasmonic bands in the visible range of spectra. Thermal annealing of the nanostructures led to narrowing of the plasmonic bands of Au and Ag nanostructures caused by major transformations of the film morphology. While the as prepared films predominantly had a small scale labyrinth structure, after annealing well-separated nanoislands are formed on the gallium arsenide surface. A clear correlation between films morphology and their optical and electrical properties is elucidated. Annealing of the GaAs substrate with Ag nanostructures at 100 °C under control of the resistivity allowed us to obtain and fix the structure at the percolation threshold. It is established that the samples at the percolation threshold possess the properties of resistance switching and hysteresis.

Site-specific deposition of single gold nanoparticles by individual growth in electrohydrodynamically-printed attoliter droplet reactors.

PubMed

Schneider, Julian; Rohner, Patrik; Galliker, Patrick; Raja, Shyamprasad N; Pan, Ying; Tiwari, Manish K; Poulikakos, Dimos

2015-06-07

Gold nanoparticles with unique electronic, optical and catalytic properties can be efficiently synthesized in colloidal suspensions and are of broad scientific and technical interest and utility. However, their orderly integration on functional surfaces and devices remains a challenge. Here we show that single gold nanoparticles can be directly grown in individually printed, stabilized metal-salt ink attoliter droplets, using a nanoscale electrohydrodynamic printing method with a stable high-frequency dripping mode. This enables controllable sessile droplet nanoreactor formation and sustenance on non-wetting substrates, despite simultaneous rapid evaporation. The single gold nanoparticles can be formed inside such reactors in situ or by subsequent thermal annealing and plasma ashing. With this non-contact technique, single particles with diameters tunable in the range of 5-35 nm and with narrow size distribution, high yield and alignment accuracy are generated on demand and patterned into arbitrary arrays. The nanoparticles feature good catalytic activity as shown by the exemplary growth of silicon nanowires from the nanoparticles and the etching of nanoholes by the printed nanoparticles.

Conformal dual-band near-perfectly absorbing mid-infrared metamaterial coating.

PubMed

Jiang, Zhi Hao; Yun, Seokho; Toor, Fatima; Werner, Douglas H; Mayer, Theresa S

2011-06-28

Metamaterials offer a new approach to create surface coatings with highly customizable electromagnetic absorption from the microwave to the optical regimes. Thus far, efficient metamaterial absorbers have been demonstrated at microwave frequencies, with recent efforts aimed at much shorter terahertz and infrared wavelengths. The present infrared absorbers have been constructed from arrays of nanoscale metal resonators with simple circular or cross-shaped geometries, which provide a single band response. In this paper, we demonstrate a conformal metamaterial absorber with a narrow band, polarization-independent absorptivity of >90% over a wide ±50° angular range centered at mid-infrared wavelengths of 3.3 and 3.9 μm. The highly efficient dual-band metamaterial was realized by using a genetic algorithm to identify an array of H-shaped nanoresonators with an effective electric and magnetic response that maximizes absorption in each wavelength band when patterned on a flexible Kapton and Au thin film substrate stack. This conformal metamaterial absorber maintains its absorption properties when integrated onto curved surfaces of arbitrary materials, making it attractive for advanced coatings that suppress the infrared reflection from the protected surface.

Outcrop Geomorphology and Sediment Characterization in Killary Harbour, Ireland

NASA Astrophysics Data System (ADS)

Crouse, L. E.; Sautter, L.

2016-02-01

Killary Harbour in western Ireland is one of three fjards found in the country. A fjard is formed by glacial carving, but differs from fjords in being shallower, shorter, and broader in profile. The Harbour is located near the border of County Mayo and County Galway. The Marine Institute of Ireland, The Geological Survey of Ireland, and the INFOMAR project, led by chief scientist Kevin Sheehan, conducted bathymetric surveys in Killary Harbour, Ireland during July and August of 2014 aboard the R/V Celtic Voyager. A Kongsberg EM2040 multi-beam sonar was utilized to acquire the raw data, which was post-processed using CARIS HIPS and SIPS 9.0. The area of study is shallow harbor seafloor depths ranging from 15 to 60 m. An abundance of rocky outcrops and narrow channels are present in the North-Western section of the study area. Backscatter data collected during acquisition were used to determine the relative hardness of seafloor sediments and rocky outcrops. Characterization of the bathymetric terrain and sediments of the harbour could prove to be useful in finding hardbottom substrate for ideal fish habitat.

Fabrication and characterization of microstructures created in thermally deposited arsenic trisulfide by multiphoton lithography

NASA Astrophysics Data System (ADS)

Schwarz, Casey M.; Grabill, Chris N.; Richardson, Gerald D.; Labh, Shreya; Lewis, Anna M.; Vyas, Aadit; Gleason, Benn; Rivero-Baleine, Clara; Richardson, Kathleen A.; Pogrebnyakov, Alexej; Mayer, Theresa S.; Kuebler, Stephen M.

2017-04-01

A detailed study of multiphoton lithography (MPL) in arsenic trisulfide (As2S3) films and the effects on nanoscale morphology, chemical networking, and the appearance of the resulting features by the chemical composition, deposition rate, etch processing, and inclusion of an antireflection (AR) layer of As2Se3 between the substrate and the As2S3 layer is reported. MPL was used to photo-pattern nanostructured arrays in single- and multilayer films. The variation in chemical composition for laser-exposed, UV-exposed, and unexposed films is correlated with the etch response, nanostructure formation, and deposition conditions. Reflection of the focused beam at the substrate back into the film produces standing wave interference that modulates the exposure with distance from the substrate and produces nanobead structures. The interference and the modulation can be controlled by the addition of an AR layer of As2Se3 deposited between the substrate and the As2S3 film. Relative to structures produced in a single-layer As2S3 film having no AR layer, photo-patterning in the multilayer As2S3-on-As2Se3 film yields pillar-shaped structures that are closer to the targeted shape and are narrower (120 versus 320 nm), more uniform, and better adhering to the substrate. Processing methods are demonstrated for fabricating large-area arrays with diffractive optical function.

Giant Electric Field Control of Magnetism and Narrow Ferromagnetic Resonance Linewidth in FeCoSiB/Si/SiO2/PMN PT Multiferroic Heterostructures (Open Access Author’s Manuscript)

DTIC Science & Technology

2016-06-06

the widely used lead zirconate titanate ceramics which have a typical piezoelectric coefficient d31 of ~- 200pC/N, PMN-PT single crystals used in...substrate clamping effect, therefore, a relatively giant tunability can be obtained. However, the normally large roughness of piezoelectric layer...is the saturation magnetostriction constant, Y the Young’s modulus of the magnetic film, deff the effective piezoelectric coefficient, E

Optical humidity sensor

DOEpatents

Tarvin, Jeffrey A.

1987-01-01

An optical dielectric humidity sensor which includes a dielectric mirror having multiple alternating layers of two porous water-adsorbent dielectric materials with differing indices of refraction carried by a translucent substrate. A narrow-band polarized light source is positioned to direct light energy onto the mirror, and detectors are positioned to receive light energy transmitted through and reflected by the mirror. A ratiometer indicates humidity in the atmosphere which surrounds the dielectric mirror as a function of a ratio of light energies incident on the detectors.

Optical humidity sensor

DOEpatents

Tarvin, J.A.

1987-02-10

An optical dielectric humidity sensor is disclosed which includes a dielectric mirror having multiple alternating layers of two porous water-adsorbent dielectric materials with differing indices of refraction carried by a translucent substrate. A narrow-band polarized light source is positioned to direct light energy onto the mirror, and detectors are positioned to receive light energy transmitted through and reflected by the mirror. A ratiometer indicates humidity in the atmosphere which surrounds the dielectric mirror as a function of a ratio of light energies incident on the detectors. 2 figs.

Linewidth Narrowing and Purcell Enhancement in Photonic Crystal Cavities on an Er-Doped Silicon Nitride Platform

DTIC Science & Technology

2010-02-01

Low noise superconducting single photon detectors on silicon,” Appl. Phys. Lett. 93, 131101 (2008). 20. M. T. Tanner, C. M. Natarajan, V. K... wavelength sensitivity in NbTiN superconducting nanowire single-photon detectors fabricated on oxidized silicon substrates,” Proceedings of Single...cavity resonance wavelength and Q-factor for the PC cavity are shown in Figure 3. The data are taken both at low (0.050 mW) pump power and high (30 mW

Vertical force and torque analysis during mechanical preparation of extracted teeth using hand ProTaper instruments.

PubMed

Glavičić, Snježana; Anić, Ivica; Braut, Alen; Miletić, Ivana; Borčić, Josipa

2011-08-01

The purpose was to measure and analyse the vertical force and torque developed in the wider and narrower root canals during hand ProTaper instrumentation. Twenty human incisors were divided in two groups. Upper incisors were experimental model for the wide, while the lower incisors for the narrow root canals. Measurements of the force and torque were done by a device constructed for this purpose. Differences between the groups were statistically analysed by Mann-Whitney U-test with the significance level set to P<0.05. Vertical force in the upper incisors ranged 0.25-2.58 N, while in the lower incisors 0.38-6.94 N. Measured torque in the upper incisors ranged 0.53-12.03 Nmm, while in the lower incisor ranged 0.94-10.0 Nmm. Vertical force and torque were higher in the root canals of smaller diameter. The increase in the contact surface results in increase of the vertical force and torque as well in both narrower and wider root canals. © 2010 The Authors. Australian Endodontic Journal © 2010 Australian Society of Endodontology.

A protein-dye hybrid system as a narrow range tunable intracellular pH sensor.

PubMed

Anees, Palapuravan; Sudheesh, Karivachery V; Jayamurthy, Purushothaman; Chandrika, Arunkumar R; Omkumar, Ramakrishnapillai V; Ajayaghosh, Ayyappanpillai

2016-11-18

Accurate monitoring of pH variations inside cells is important for the early diagnosis of diseases such as cancer. Even though a variety of different pH sensors are available, construction of a custom-made sensor array for measuring minute variations in a narrow biological pH window, using easily available constituents, is a challenge. Here we report two-component hybrid sensors derived from a protein and organic dye nanoparticles whose sensitivity range can be tuned by choosing different ratios of the components, to monitor the minute pH variations in a given system. The dye interacts noncovalently with the protein at lower pH and covalently at higher pH, triggering two distinguishable fluorescent signals at 700 and 480 nm, respectively. The pH sensitivity region of the probe can be tuned for every unit of the pH window resulting in custom-made pH sensors. These narrow range tunable pH sensors have been used to monitor pH variations in HeLa cells using the fluorescence imaging technique.

Ultra-narrow pulse generator with precision-adjustable pulse width

NASA Astrophysics Data System (ADS)

Fu, Zaiming; Liu, Hanglin

2018-05-01

In this paper, a novel ultra-narrow pulse generation approach is proposed. It is based on the decomposition and synthesis of pulse edges. Through controlling their relative delay, an ultra-narrow pulse could be generated. By employing field programmable gate array digital synthesis technology, the implemented pulse generator is with programmable ability. The amplitude of pulse signals is controlled by the radio frequency amplifiers and bias tees, and high precision can be achieved. More importantly, the proposed approach can break through the limitation of device's propagation delay and optimize the resolution and the accuracy of the pulse width significantly. The implemented pulse generator has two channels, whose minimum pulse width, frequency range, and amplitude range are 100 ps, 15 MHz-1.5 GHz, and 0.1 Vpp-1.8 Vpp, respectively. Both resolution of pulse width and channel delay are 1 ps, and amplitude resolution is 10 mVpp.

Intersession reliability of self-selected and narrow stance balance testing in older adults.

PubMed

Riemann, Bryan L; Piersol, Kelsey

2017-10-01

Despite the common practice of using force platforms to assess balance of older adults, few investigations have examined the reliability of postural screening tests in this population. We sought to determine the test-retest reliability of self-selected and narrow stance balance testing with eyes open and eyes closed in healthy older adults. Thirty older adults (>65 years) completed 45 s trials of eyes open and eyes closed stability tests using self-selected and narrow stances on two separate days (1.9 ± .7 days). Average medial-lateral center of pressure velocity was computed. The ICC results ranged from .74 to .86, and no significant systematic changes (P < .05) occurred between the testing sessions for any of the tests. The standard error of measurement ranged from 15.9 to 23.6%. Reliability estimates were similar between the two stances and visual conditions assessed. Slightly higher coefficients were identified for the self-selected stances compared to the narrow stances under both visual conditions; however, there were negligible differences between the sessions. The within subject session-to-session variability provides a basis for further research to consider differences between fallers and non-fallers. Reliability for eyes open and closed balance testing using self-selected and narrow stances in older adults was established which should provide a foundation for the development of fall risk screening tests.

80-GHz MMIC HEMT Voltage-Controlled Oscillator

NASA Technical Reports Server (NTRS)

Samoska, Lorene; Radisic, Vesna; Micovic, Miro; Hu, Ming; Janke, Paul; Ngo, Catherine; Nguyen, Loi

2003-01-01

A voltage-controlled oscillator (VCO) that operates in the frequency range from 77.5 to 83.5 GHz has been constructed in the form of a monolithic microwave integrated circuit (MMIC) that includes high-electron-mobility transistors (HEMTs). This circuit is a prototype of electronically tunable signal sources in the 75-to-110-GHz range, needed for communication, imaging, and automotive radar applications, among others. This oscillator (see Figure 1) includes two AlInAs/GaInAs/InP HEMTs. One HEMT serves mainly as an oscillator gain element. The other HEMT serves mainly as a varactor for controlling the frequency: the frequency-control element is its gate-to-source capacitance, which is varied by changing its gate supply voltage. The gain HEMT is biased for class-A operation (meaning that current is conducted throughout the oscillation cycle). Grounded coplanar waveguides are used as impedance-matching transmission lines, the input and output matching being chosen to sustain oscillation and maximize output power. Air bridges are placed at discontinuities to suppress undesired slot electromagnetic modes. A high density of vias is necessary for suppressing a parallel-plate electromagnetic mode that is undesired because it can propagate energy into the MMIC substrate. Previous attempts at constructing HEMT-based oscillators yielded circuits with relatively low levels of output power and narrow tuning ranges. For example, one HEMT VCO reported in the literature had an output power of 7 dBm (.5 mW) and a tuning range 2-GHz wide centered approximately at a nominal frequency of 77 GHz. In contrast, as shown in Figure 2, the present MMIC HEMT VCO puts out a power of 12.5 dBm (.18 mW) or more over the 6-GHz-wide frequency range from 77.5 to 83.5 GHz

Effect of same-temperature GaN cap layer on the InGaN/GaN multiquantum well of green light-emitting diode on silicon substrate.

PubMed

Zheng, Changda; Wang, Li; Mo, Chunlan; Fang, Wenqing; Jiang, Fengyi

2013-01-01

GaN green LED was grown on Si (111) substrate by MOCVD. To enhance the quality of InGaN/GaN MQWs, same-temperature (ST) GaN protection layers with different thickness of 8 Å, 15 Å, and 30 Å were induced after the InGaN quantum wells (QWs) layer. Results show that a relative thicker cap layer is benefit to get InGaN QWs with higher In percent at fixed well temperature and obtain better QW/QB interface. As the cap thickness increases, the indium distribution becomes homogeneous as verified by fluorescence microscope (FLM). The interface of MQWs turns to be abrupt from XRD analysis. The intensity of photoluminescence (PL) spectrum is increased and the FWHM becomes narrow.

Oriented graphene nanoribbons embedded in hexagonal boron nitride trenches

PubMed Central

Chen, Lingxiu; He, Li; Wang, Hui Shan; Wang, Haomin; Tang, Shujie; Cong, Chunxiao; Xie, Hong; Li, Lei; Xia, Hui; Li, Tianxin; Wu, Tianru; Zhang, Daoli; Deng, Lianwen; Yu, Ting; Xie, Xiaoming; Jiang, Mianheng

2017-01-01

Graphene nanoribbons (GNRs) are ultra-narrow strips of graphene that have the potential to be used in high-performance graphene-based semiconductor electronics. However, controlled growth of GNRs on dielectric substrates remains a challenge. Here, we report the successful growth of GNRs directly on hexagonal boron nitride substrates with smooth edges and controllable widths using chemical vapour deposition. The approach is based on a type of template growth that allows for the in-plane epitaxy of mono-layered GNRs in nano-trenches on hexagonal boron nitride with edges following a zigzag direction. The embedded GNR channels show excellent electronic properties, even at room temperature. Such in-plane hetero-integration of GNRs, which is compatible with integrated circuit processing, creates a gapped channel with a width of a few benzene rings, enabling the development of digital integrated circuitry based on GNRs. PMID:28276532

Supported inorganic membranes

DOEpatents

Sehgal, Rakesh; Brinker, Charles Jeffrey

1998-01-01

Supported inorganic membranes capable of molecular sieving, and methods for their production, are provided. The subject membranes exhibit high flux and high selectivity. The subject membranes are substantially defect free and less than about 100 nm thick. The pores of the subject membranes have an average critical pore radius of less than about 5 .ANG., and have a narrow pore size distribution. The subject membranes are prepared by coating a porous substrate with a polymeric sol, preferably under conditions of low relative pressure of the liquid constituents of the sol. The coated substrate is dried and calcined to produce the subject supported membrane. Also provided are methods of derivatizing the surface of supported inorganic membranes with metal alkoxides. The subject membranes find use in a variety of applications, such as the separation of constituents of gaseous streams, as catalysts and catalyst supports, and the like.

All-Printed, Self-Aligned Carbon Nanotube Thin-Film Transistors on Imprinted Plastic Substrates.

PubMed

Song, Donghoon; Zare Bidoky, Fazel; Hyun, Woo Jin; Walker, S Brett; Lewis, Jennifer A; Frisbie, C Daniel

2018-05-09

We present a self-aligned process for printing thin-film transistors (TFTs) on plastic with single-walled carbon nanotube (SWCNT) networks as the channel material. The SCALE (self-aligned capillarity-assisted lithography for electronics) process combines imprint lithography with inkjet printing. Specifically, inks are jetted into imprinted reservoirs, where they then flow into narrow device cavities due to capillarity. Here, we incorporate a composite high- k gate dielectric and an aligned conducting polymer gate electrode in the SCALE process to enable a smaller areal footprint than prior designs that yields low-voltage SWCNT TFTs with average p-type carrier mobilities of 4 cm 2 /V·s and ON/OFF current ratios of 10 4 . Our work demonstrates the promising potential of the SCALE process to fabricate SWCNT-based TFTs with favorable I- V characteristics on plastic substrates.

Improved measurement of extracellular enzymatic activities in subsurface sediments using competitive desorption treatment

NASA Astrophysics Data System (ADS)

Hoarfrost, Adrienne; Snider, Rachel; Arnosti, Carol

2017-02-01

Extracellular enzymatic activities initiate microbially-driven heterotrophic carbon cycling in subsurface sediments. While measurement of hydrolytic activities in sediments is fundamental to our understanding of carbon cycling, these measurements are often technically difficult due to sorption of organic substrates to the sediment matrix. Most methods that measure hydrolysis of organic substrates in sediments rely on recovery of a fluorophore or fluorescently-labeled target substrate from a sediment incubation. The tendency for substrates to sorb to sediments results in lower recovery of an added substrate, and can result in data that are unusable or difficult to interpret. We developed a treatment using competitive desorption of a fluorescently-labeled, high molecular weight organic substrate that improves recovery of the labeled substrate from sediment subsamples. Competitive desorption treatment improved recovery of the fluorescent substrate by a median of 66%, expanded the range of sediments for which activity measurements could be made, and was effective in sediments from a broad range of geochemical contexts. More reliable measurements of hydrolytic activities in sediments will yield usable and more easily interpretable data from a wider range of sedimentary environments, enabling better understanding of microbially-catalyzed carbon cycling in subsurface environments.

Effects of low energy E-beam irradiation on graphene and graphene field effect transistors and raman metrology of graphene on split gate test structures

NASA Astrophysics Data System (ADS)

Rao, Gayathri S.

2011-12-01

Apart from its compelling performance in conventional nanoelectronic device geometries, graphene is an appropriate candidate to study certain interesting phenomenon (e.g. the Veselago lens effect) predicted on the basis of its linear electron dispersion relation. A key requirement for the observation of such phenomenon in graphene and for its use in conventional field-effect transistor (FET) devices is the need to minimize defects such as consisting of -- or resulting from -- adsorbates and lattice non-uniformities, and reduce deleterious substrate effects. Consequently the investigation of the origin and interaction of defects in the graphene lattice is essential to improve and tailor graphene-based device performance. In this thesis, optical spectroscopic studies on the influence of low-energy electron irradiation on adsorbate-induced defectivity and doping for substrate supported and suspended graphene were carried out along with spectroscopic and transport measurements on graphene FETs. A comparative investigation of the effects of single-step versus multi-step, low-energy electron irradiation (500 eV) on suspended, substrate supported graphene and on graphene FETs is reported. E-beam irradiation (single-step and multi-step) of substrate-supported graphene resulted in an increase in the Raman ID/IG ratio largely from hydrogenation due to radiolysis of the interfacial water layer between the graphene and the SiO2 substrate and from irradiated surface adsorbates. GFETs subjected to single and multi-step irradiation showed n-doping from CNP (charge neutrality point) shift of ˜ -8 and ˜ -16 V respectively. Correlation of this data with Raman analysis of suspended and supported graphene samples implied a strong role of the substrate and irradiation sequence in determining the level of doping. A correspondingly higher reduction in mobility per incident electron was also observed for GFETs subjected to multi-step irradiation compared to single step, in line with measured Raman ID/IG ratios. Additionally, the Raman G-band DeltaFWHM variation was strongly dependent on the nature of the e-beam irradiation and the presence of the substrate. Single-step irradiated, substrate-supported graphene exhibited substantial broadening while multi-step irradiation resulted in G-band narrowing. This behavior was not observed for suspended graphene which indicated the addition or elimination of substrate-induced phonon-relaxation mechanisms in response to each type of irradiation. The narrowing of the FWHM (G) in the multi-step case is attributed to doping consistent with the Dirac point shift of ˜ -16V and the removal of Landau phonon damping above Ef > ℏwG2 . In strong contrast, single step irradiation of substrate supported graphene yielded a broadening of the FWHM (G) accompanied by a CNP shift of ˜ -8V indicating appreciable n-doping. This reveals the presence of alternate phonon decay channels even when Landau damping above Ef > ℏwG2 is removed. It is proposed in this dissertation that this phenomenon is linked to hybridization of silicon oxide defect states (induced by single-step e-beam irradiation) and graphene electron states. This hybridization promotes a graphene phonon decay channel distinct from Landau damping, the latter being forbidden under sufficient doping. It is proposed that the alternate phonon decay channel involves two-component inelastic scattering, wherein the graphene phonons transfer energy to the carriers in the lattice which in turn couple to the polar phonons of the substrate resulting in mobility reduction. Furthermore, it is proposed that this defect-induced, graphene phonon decay channel is inhibited in multi-step e-beam irradiation due to the presence of adsorbates on the graphene introduced during ambient exposure between radiation cycles. On e-beam irradiation the adsorbates induce polar orientation of water dipoles at the graphene/SiO2 interface. This polar layer shifts the hybridized defect bands closer to the graphene Dirac bands thereby reducing the inelastic scattering and inhibiting the phonon decay medicated by SiO2 surface polar phonons (SPP). This model also explains the enhancement of n-type doping in GFETS observed for multi-step irradiation. These results highlight the impact of substrate defects and interaction of induced defectivity with the e-beam along with the role of interfacial water in impacting graphene device performance. The thesis also presents data on Raman-based characterization of graphene including layer number determination and carrier concentration measurement. Determination of layer number for graphene exfoliates focused on the splitting of the 2D Raman band. In addition, an alternate Raman-based thickness metrology was evaluated for CVD-based, polycrystalline graphene. Both were carried out on split gate test structures as a method for monolayer or bilayer confirmation in device geometries. In addition, carrier concentration measurements of exfoliates on 300nm SiO2 and split-gate test structure substrate have also been characterized with back gate biasing. These measurements made use of the stiffening of the Raman G-band with doping and the narrowing of the G-band FWHM. These results were important for validating conclusions from the e-beam irradiation experiments mentioned above regarding carrier doping.

Narrow Angle Wide Spectral Range Radiometer Design FEANICS/REEFS Radiometer Design Report

NASA Technical Reports Server (NTRS)

Camperchioli, William

2005-01-01

A critical measurement for the Radiative Enhancement Effects on Flame Spread (REEFS) microgravity combustion experiment is the net radiative flux emitted from the gases and from the solid fuel bed. These quantities are measured using a set of narrow angle, wide spectral range radiometers. The radiometers are required to have an angular field of view of 1.2 degrees and measure over the spectral range of 0.6 to 30 microns, which presents a challenging design effort. This report details the design of this radiometer system including field of view, radiometer response, radiometric calculations, temperature effects, error sources, baffling and amplifiers. This report presents some radiometer specific data but does not present any REEFS experiment data.

Steady-state turbulence with a narrow inertial range

NASA Technical Reports Server (NTRS)

Weatherall, J. C.; Nicholson, D. R.; Goldman, M. V.

1983-01-01

Coupled two-dimensional wave equations are solved on a computer to model Langmuir wave turbulence excited by a weak electron beam. The model includes wave growth due to beam-plasma interaction, and dissipation by Landau damping. The inertial range is limited to a relatively small number of modes such as could occur when the ratio of masses between the negative and positive ions is larger than in a hydrogen plasma, or when there is damping in long wavelength Langmuir waves. A steady state is found consisting of quasistable, collapsed wave packets. The effects of different beam parameters and the assumed narrow inertial range are considered. The results may be relevant to plasma turbulence observed in connection with type III solar bursts.

Catalytic nanoporous membranes

DOEpatents

Pellin, Michael J; Hryn, John N; Elam, Jeffrey W

2013-08-27

A nanoporous catalytic membrane which displays several unique features Including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity. Also provided is a method for producing a catalytic membrane having flow-through pores and discreet catalytic clusters adhering to the inside surfaces of the pores.

Structure and substrate ion binding in the sodium/proton antiporter PaNhaP

PubMed Central

Wöhlert, David; Kühlbrandt, Werner; Yildiz, Özkan

2014-01-01

Sodium/proton antiporters maintain intracellular pH and sodium levels. Detailed structures of antiporters with bound substrate ions are essential for understanding how they work. We have resolved the substrate ion in the dimeric, electroneutral sodium/proton antiporter PaNhaP from Pyrococcus abyssi at 3.2 Å, and have determined its structure in two different conformations at pH 8 and pH 4. The ion is coordinated by three acidic sidechains, a water molecule, a serine and a main-chain carbonyl in the unwound stretch of trans-membrane helix 5 at the deepest point of a negatively charged cytoplasmic funnel. A second narrow polar channel may facilitate proton uptake from the cytoplasm. Transport activity of PaNhaP is cooperative at pH 6 but not at pH 5. Cooperativity is due to pH-dependent allosteric coupling of protomers through two histidines at the dimer interface. Combined with comprehensive transport studies, the structures of PaNhaP offer unique new insights into the transport mechanism of sodium/proton antiporters. DOI: http://dx.doi.org/10.7554/eLife.03579.001 PMID:25426802

Improving performance of armchair graphene nanoribbon field effect transistors via boron nitride doping

NASA Astrophysics Data System (ADS)

Goharrizi, A. Yazdanpanah; Sanaeepur, M.; Sharifi, M. J.

2015-09-01

Device performance of 10 nm length armchair graphene nanoribbon field effect transistors with 1.5 nm and 4 nm width (13 and 33 atoms in width respectively) are compared in terms of Ion /Ioff , trans-conductance, and sub-threshold swing. While narrow devices suffer from edge roughness wider devices are subject to more substrate surface roughness and reduced bandgap. Boron Nitride doping is employed to compensate reduced bandgap in wider devices. Simultaneous effects of edge and substrate surface roughness are considered. Results show that in the presence of both the edge and substrate surface roughness the 4 nm wide device with boron nitride doping shows improved performance with respect to the 1.5 nm one (both of which incorporate the same bandgap AGNR as channel material). Electronic simulations are performed via NEGF method along with tight-binding Hamiltonian. Edge and surface roughness are created by means of one and two dimensional auto correlation functions respectively. Electronic characteristics are averaged over a large number of devices due to statistic nature of both the edge and surface roughness.

Influence of deposition temperature on WTiN coatings tribological performance

NASA Astrophysics Data System (ADS)

Londoño-Menjura, R. F.; Ospina, R.; Escobar, D.; Quintero, J. H.; Olaya, J. J.; Mello, A.; Restrepo-Parra, E.

2018-01-01

WTiN films were grown on silicon and stainless-steel substrates using the DC magnetron sputtering technique. The substrate temperature was varied taking values of 100 °C, 200 °C, 300 °C, and 400 °C. X-ray diffraction analysis allowed us to identify a rock salt-type face centered cubic (FCC) structure, with a lattice parameter of approximately 4.2 nm, a relatively low microstrain (deformations at microscopy level, between 4.7% and 6.7%), and a crystallite size of a few nanometers (11.6 nm-31.5 nm). The C1s, N1s, O1s, Ti2p, W4s, W4p, W4d and W4f narrow spectra were obtained using X-ray photoelectron spectroscopy (XPS) and depending on the substrate temperature, the deconvoluted spectra presented different binding energies. Grain sizes and roughness (approximately 4 nm) of films were determined using atomic force microscopy. Scratch and pin on disc tests were conducted, showing better performance of the film grown at 200 °C. This sample exhibited a lower roughness, coefficient of friction, and wear rate.

Wettability of partially suspended graphene

DOE PAGES

Ondarçuhu, Thierry; Thomas, Vincent; Nuñez, Marc; ...

2016-04-13

Dependence on the wettability of graphene on the nature of the underlying substrate remains only partially understood. We systematically investigate the role of liquid-substrate interactions on the wettability of graphene by varying the area fraction of suspended graphene from 0 to 95% by means of nanotextured substrates. We find that completely suspended graphene exhibits the highest water contact angle (85° ± 5°) compared to partially suspended or supported graphene, regardless of the hydrophobicity (hydrophilicity) of the substrate. Moreover, 80% of the long-range water-substrate interactions are screened by the graphene monolayer, the wettability of which is primarily determined by short-range graphene-liquidmore » interactions. By its well-defined chemical and geometrical properties, supported graphene therefore provides a model system to elucidate the relative contribution of short and long range interactions to the macroscopic contact angle.« less

A Chandra Survey of low-mass clusters at 0.8 < z < 0.9 selected in the 100 deg^2 SPT-Pol Deep Field

NASA Astrophysics Data System (ADS)

Kraft, Ralph

2016-09-01

We propose to observe a complete sample of 4 galaxy clusters at 1e14 < M500 < 3e14 and 0.8 < z < 0.9. These systems were selected from the 100 deg^2 deep field of the SPT-Pol SZ survey. This survey are has significant complementary data, including uniform depth ATCA, Herschel, Spitzer, and DES imaging, enabling a wide variety of astrophysical and cosmological studies. This sample complements the successful SPT-XVP survey, which has a broad redshift range and a narrow mass range, by including clusters over a narrow redshift range and broad mass range. These systems are such low mass and high redshift that they will not be detected in the eRosita all-sky survey.

A Chandra Survey of low-mass clusters at 0.7 < z < 0.8 selected in the 100 deg^2 SPT-Pol Deep Field

NASA Astrophysics Data System (ADS)

Kraft, Ralph

2016-09-01

We propose to observe a complete sample of 4 galaxy clusters at 1e14 < M500 < 3e14 and 0.7 < z < 0.8. These systems were selected from the 100 deg^2 deep field of the SPT-Pol SZ survey. This survey are has significant complementary data, including uniform depth ATCA, Herschel, Spitzer, and DES imaging, enabling a wide variety of astrophysical and cosmological studies. This sample complements the successful SPT-XVP survey, which has a broad redshift range and a narrow mass range, by including clusters over a narrow redshift range and broad mass range. These systems are such low mass and high redshift that they will not be detected in the eRosita all-sky survey.

Stress development in thin yttrium films on hard substrates during hydrogen loading

NASA Astrophysics Data System (ADS)

Dornheim, M.; Pundt, A.; Kirchheim, R.; Molen, S. J. v. d.; Kooij, E. S.; Kerssemakers, J.; Griessen, R.; Harms, H.; Geyer, U.

2003-06-01

Polycrystalline (0002)-textured yttrium (Y) films of 50-500 nm thickness on sapphire substrates were loaded electrolytically with hydrogen (H). The stresses which build up in these films were measured in situ using curvature measurements. The results are compared to the behavior of bulk Y-H. A linear elastic model is used to predict the behavior of clamped thin films. Basic properties of the bulk Y-H phase diagram and elastic constants resemble the measured values of the thin films. Compressive stress builds up during H-loading in the α-Y phase and in the (α-Y+β-YH2) two-phase field, showing an initial stress increase of -1.3 GPa per hydrogen concentration XH (compressive stress). While bulk Y-H samples are known to show a contraction in the β-YH2 phase during H loading, thin films show no evidence for such a contraction during the first loading cycle of the film. The stress remains constant in the bulk β-phase concentration range (ΔXH=0.1 H/Y). This is attributed to the narrow β-phase field (ΔXH=0.02 H/Y) of the thin film during the first loading. Only samples which have been kept at a hydrogen concentration of about 1.5 H/Y for weeks show tensile stress in the concentration range of the bulk β phase. Amazingly a stress increase of about +0.5 GPa/XH (tensile stress) is measured in the β+γ two-phase field. This is attributed to the smaller in-plane nearest-neighbor distance in the γ phase compared to the β phase. In the γ-phase field compressive stress is built up again, compensating the tensile stress. It increases by -1.3 GPa/XH. In total, the net stress in Y-H films remains comparably small. This could be a reason for the good mechanical stability of such Y-H switchable mirrors during H cycling.

Normal range of human dietary sodium intake: a perspective based on 24-hour urinary sodium excretion worldwide.

PubMed

McCarron, David A; Kazaks, Alexandra G; Geerling, Joel C; Stern, Judith S; Graudal, Niels A

2013-10-01

The recommendation to restrict dietary sodium for management of hypertensive cardiovascular disease assumes that sodium intake exceeds physiologic need, that it can be significantly reduced, and that the reduction can be maintained over time. In contrast, neuroscientists have identified neural circuits in vertebrate animals that regulate sodium appetite within a narrow physiologic range. This study further validates our previous report that sodium intake, consistent with the neuroscience, tracks within a narrow range, consistent over time and across cultures. Peer-reviewed publications reporting 24-hour urinary sodium excretion (UNaV) in a defined population that were not included in our 2009 publication were identified from the medical literature. These datasets were combined with those in our previous report of worldwide dietary sodium consumption. The new data included 129 surveys, representing 50,060 participants. The mean value and range of 24-hour UNaV in each of these datasets were within 1 SD of our previous estimate. The combined mean and normal range of sodium intake of the 129 datasets were nearly identical to that we previously reported (mean = 158.3±22.5 vs. 162.4±22.4 mmol/d). Merging the previous and new datasets (n = 190) yielded sodium consumption of 159.4±22.3 mmol/d (range = 114-210 mmol/d; 2,622-4,830mg/d). Human sodium intake, as defined by 24-hour UNaV, is characterized by a narrow range that is remarkably reproducible over at least 5 decades and across 45 countries. As documented here, this range is determined by physiologic needs rather than environmental factors. Future guidelines should be based on this biologically determined range.

Temporal intensity interferometry for characterization of very narrow spectral lines

NASA Astrophysics Data System (ADS)

Tan, P. K.; Kurtsiefer, C.

2017-08-01

Some stellar objects exhibit very narrow spectral lines in the visible range additional to their blackbody radiation. Natural lasing has been suggested as a mechanism to explain narrow lines in Wolf-Rayet stars. However, the spectral resolution of conventional astronomical spectrographs is still about two orders of magnitude too low to test this hypothesis. We want to resolve the linewidth of narrow spectral emissions in starlight. A combination of spectral filtering with single-photon-level temporal correlation measurements breaks the resolution limit of wavelength-dispersing spectrographs by moving the linewidth measurement into the time domain. We demonstrate in a laboratory experiment that temporal intensity interferometry can determine a 20-MHz-wide linewidth of Doppler-broadened laser light and identify a coherent laser light contribution in a blackbody radiation background.

Pharmacogenomics of CYP2C9: Functional and Clinical Considerations†

PubMed Central

Rettie, Allan E.; Fowler, Douglas M.; Miners, John O.

2017-01-01

CYP2C9 is the most abundant CYP2C subfamily enzyme in human liver and the most important contributor from this subfamily to drug metabolism. Polymorphisms resulting in decreased enzyme activity are common in the CYP2C9 gene and this, combined with narrow therapeutic indices for several key drug substrates, results in some important issues relating to drug safety and efficacy. CYP2C9 substrate selectivity is detailed and, based on crystal structures for the enzyme, we describe how CYP2C9 catalyzes these reactions. Factors relevant to clinical response to CYP2C9 substrates including inhibition, induction and genetic polymorphism are discussed in detail. In particular, we consider the issue of ethnic variation in pattern and frequency of genetic polymorphisms and clinical implications. Warfarin is the most well studied CYP2C9 substrate; recent work on use of dosing algorithms that include CYP2C9 genotype to improve patient safety during initiation of warfarin dosing are reviewed and prospects for their clinical implementation considered. Finally, we discuss a novel approach to cataloging the functional capabilities of rare ‘variants of uncertain significance’, which are increasingly detected as more exome and genome sequencing of diverse populations is conducted. PMID:29283396

Process optimization of ultrasonic spray coating of polymer films.

PubMed

Bose, Sanjukta; Keller, Stephan S; Alstrøm, Tommy S; Boisen, Anja; Almdal, Kristoffer

2013-06-11

In this work we have performed a detailed study of the influence of various parameters on spray coating of polymer films. Our aim is to produce polymer films of uniform thickness (500 nm to 1 μm) and low roughness compared to the film thickness. The coatings are characterized with respect to thickness, roughness (profilometer), and morphology (optical microscopy). Polyvinylpyrrolidone (PVP) is used to do a full factorial design of experiments with selected process parameters such as temperature, distance between spray nozzle and substrate, and speed of the spray nozzle. A mathematical model is developed for statistical analysis which identifies the distance between nozzle and substrate as the most significant parameter. Depending on the drying of the sprayed droplets on the substrate, we define two broad regimes, "dry" and "wet". The optimum condition of spraying lies in a narrow window between these two regimes, where we obtain a film of desired quality. Both with increasing nozzle-substrate distance and temperature, the deposition moves from a wet state to a dry regime. Similar results are also achieved for solvents with low boiling points. Finally, we study film formation during spray coating with poly (D,L-lactide) (PDLLA). The results confirm the processing knowledge obtained with PVP and indicate that the observed trends are identical for spraying of other polymer films.

Why some plant species are rare.

PubMed

Wieger Wamelink, G W; Wamelink, G W Weiger; Goedhart, Paul W; Frissel, Joep; Frissel, Josep Y

2014-01-01

Biodiversity, including plant species diversity, is threatened worldwide as a result of anthropogenic pressures such as an increase of pollutants and climate change. Rare species in particular are on the verge of becoming extinct. It is still unclear as to why some plant species are rare and others are not. Are they rare due to: intrinsic reasons, dispersal capacity, the effects of management or abiotic circumstances? Habitat preference of rare plant species may play an important role in determining why some species are rare. Based on an extensive data set of soil parameters we investigated if rarity is due to a narrow habitat preference for abiotic soil parameters. For 23 different abiotic soil parameters, of which the most influential were groundwater-table, soil-pH and nutrient-contents, we estimated species responses for common and rare species. Based on the responses per species we calculated the range of occurrence, the range between the 5 and 95 percentile of the response curve giving the habitat preference. Subsequently, we calculated the average response range for common and rare species. In addition, we designed a new graphic in order to provide a better means for presentation of the results. The habitat preferences of rare species for abiotic soil conditions are significantly narrower than for common species. Twenty of the twenty-three abiotic parameters showed on average significantly narrower habitat preferences for rare species than for common species; none of the abiotic parameters showed on average a narrower habitat preference for common species. The results have major implications for the conservation of rare plant species; accordingly management and nature development should be focussed on the maintenance and creation of a broad range of environmental conditions, so that the requirements of rare species are met. The conservation of (abiotic) gradients within ecosystems is particularly important for preserving rare species.

Erroneous Arrhenius: Modified Arrhenius model best explains the temperature dependence of ectotherm fitness

PubMed Central

Knies, Jennifer L.; Kingsolver, Joel G.

2013-01-01

The initial rise of fitness that occurs with increasing temperature is attributed to Arrhenius kinetics, in which rates of reaction increase exponentially with increasing temperature. Models based on Arrhenius typically assume single rate-limiting reaction(s) over some physiological temperature range for which all the rate-limiting enzymes are in 100% active conformation. We test this assumption using datasets for microbes that have measurements of fitness (intrinsic rate of population growth) at many temperatures and over a broad temperature range, and for diverse ectotherms that have measurements at fewer temperatures. When measurements are available at many temperatures, strictly Arrhenius kinetics is rejected over the physiological temperature range. However, over a narrower temperature range, we cannot reject strictly Arrhenius kinetics. The temperature range also affects estimates of the temperature dependence of fitness. These results indicate that Arrhenius kinetics only apply over a narrow range of temperatures for ectotherms, complicating attempts to identify general patterns of temperature dependence. PMID:20528477

Erroneous Arrhenius: modified arrhenius model best explains the temperature dependence of ectotherm fitness.

PubMed

Knies, Jennifer L; Kingsolver, Joel G

2010-08-01

The initial rise of fitness that occurs with increasing temperature is attributed to Arrhenius kinetics, in which rates of reaction increase exponentially with increasing temperature. Models based on Arrhenius typically assume single rate-limiting reactions over some physiological temperature range for which all the rate-limiting enzymes are in 100% active conformation. We test this assumption using data sets for microbes that have measurements of fitness (intrinsic rate of population growth) at many temperatures and over a broad temperature range and for diverse ectotherms that have measurements at fewer temperatures. When measurements are available at many temperatures, strictly Arrhenius kinetics are rejected over the physiological temperature range. However, over a narrower temperature range, we cannot reject strictly Arrhenius kinetics. The temperature range also affects estimates of the temperature dependence of fitness. These results indicate that Arrhenius kinetics only apply over a narrow range of temperatures for ectotherms, complicating attempts to identify general patterns of temperature dependence.

Magnetization behavior of RE123 bulk magnets bearing twin seed-crystals in pulsed field magnetization processes

NASA Astrophysics Data System (ADS)

Oka, T.; Miyazaki, T.; Ogawa, J.; Fukui, S.; Sato, T.; Yokoyama, K.; Langer, M.

2016-02-01

Melt-textured Y-Ba-Cu-O high temperature superconducting bulk magnets were fabricated by the cold seeding method with using single or twin-seed crystals composed of Nd-Ba-Cu-O thin films on MgO substrates. The behavior of the magnetic flux penetration into anisotropic-grown bulk magnets thus fabricated was precisely evaluated during and after the pulsed field magnetization operated at 35 K. These seed crystals were put on the top surfaces of the precursors to grow large grains during the melt-processes. Although we know the magnetic flux motion is restricted by the enhanced pinning effect in temperature ranges lower than 77 K, we observed that flux invasion occurred at applied fields of 3.3 T when the twin seeds were used. This is definitely lower than those of 3.7 T when the single-seeds were employed. This means that the magnetic fluxes are capable of invading into twin-seeded bulk magnets more easily than single-seeded ones. The twin seeds form the different grain growth regions, the narrow-GSR (growth sector region) and wide-GSR, according to the different grain growth directions which are parallel and normal to the rows of seed crystals, respectively. The invading flux measurements revealed that the magnetic flux invades the sample from the wide-GSR prior to the narrow-GSR. It suggests that such anisotropic grain growth leads to different distributions of pinning centers, variations of J c values, and the formation of preferential paths for the invading magnetic fluxes. Using lower applied fields definitely contributed to lowering the heat generation during the PFM process, which, in turn, led to enhanced trapped magnetic fluxes.

Electronic, Magnetic, and Transport Properties of Polyacrylonitrile-Based Carbon Nanofibers of Various Widths: Density-Functional Theory Calculations

NASA Astrophysics Data System (ADS)

Partovi-Azar, P.; Panahian Jand, S.; Kaghazchi, P.

2018-01-01

Edge termination of graphene nanoribbons is a key factor in determination of their physical and chemical properties. Here, we focus on nitrogen-terminated zigzag graphene nanoribbons resembling polyacrylonitrile-based carbon nanofibers (CNFs) which are widely studied in energy research. In particular, we investigate magnetic, electronic, and transport properties of these CNFs as functions of their widths using density-functional theory calculations together with the nonequilibrium Green's function method. We report on metallic behavior of all the CNFs considered in this study and demonstrate that the narrow CNFs show finite magnetic moments. The spin-polarized electronic states in these fibers exhibit similar spin configurations on both edges and result in spin-dependent transport channels in the narrow CNFs. We show that the partially filled nitrogen dangling-bond bands are mainly responsible for the ferromagnetic spin ordering in the narrow samples. However, the magnetic moment becomes vanishingly small in the case of wide CNFs where the dangling-bond bands fall below the Fermi level and graphenelike transport properties arising from the π orbitals are recovered. The magnetic properties of the CNFs as well as their stability have also been discussed in the presence of water molecules and the hexagonal boron nitride substrate.

Low-loss interference filter arrays made by plasma-assisted reactive magnetron sputtering (PARMS) for high-performance multispectral imaging

NASA Astrophysics Data System (ADS)

Broßmann, Jan; Best, Thorsten; Bauer, Thomas; Jakobs, Stefan; Eisenhammer, Thomas

2016-10-01

Optical remote sensing of the earth from air and space typically utilizes several channels in the visible and near infrared spectrum. Thin-film optical interference filters, mostly of narrow bandpass type, are applied to select these channels. The filters are arranged in filter wheels, arrays of discrete stripe filters mounted in frames, or patterned arrays on a monolithic substrate. Such multi-channel filter assemblies can be mounted close to the detector, which allows a compact and lightweight camera design. Recent progress in image resolution and sensor sensitivity requires improvements of the optical filter performance. Higher demands placed on blocking in the UV and NIR and in between the spectral channels, in-band transmission and filter edge steepness as well as scattering lead to more complex filter coatings with thicknesses in the range of 10 - 25μm. Technological limits of the conventionally used ion-assisted evaporation process (IAD) can be overcome only by more precise and higher-energetic coating technologies like plasma-assisted reactive magnetron sputtering (PARMS) in combination with optical broadband monitoring. Optics Balzers has developed a photolithographic patterning process for coating thicknesses up to 15μm that is fully compatible with the advanced PARMS coating technology. This provides the possibility of depositing multiple complex high-performance filters on a monolithic substrate. We present an overview of the performance of recently developed filters with improved spectral performance designed for both monolithic filter-arrays and stripe filters mounted in frames. The pros and cons as well as the resulting limits of the filter designs for both configurations are discussed.

Cyclopentanoid analogs of phosphatidylcholine: susceptibility to phospholipase A2.

PubMed

Lister, M D; Hancock, A J

1988-10-01

Six isomers of dipalmitoylcyclopentanetriol phosphocholine (cyclopentano-lecithin) were tested as potential substrates for phospholipase A2. Since each of these analogs possesses a configuration that mimics a narrow range of conformations of a glycerophospholipid molecule, the analogs were used to assess the enzyme's conformational requirements. Studies showed that all of the analogs containing the phosphocholine at the C-1 (or C-3) position could be hydrolyzed, while only one of the three analogs that contains the polar head group at the C-2 position was susceptible. Kinetic studies, however, revealed that only the all-trans-(1,3/2-1P)-cyclopentano-lecithin gave initial rates of hydrolysis that were measurable by pH-stat. Acyl group specificity of the enzyme towards the all-trans isomer was determined with an analog was acyl groups were distinguishable. The synthesis of this mixed-acid-cyclopentano-PC is described herein. When this analog was enzymatically assayed, results unequivocally showed the enzyme to be specific for C-2 acyl hydrolysis. This specificity, and data showing that the all-trans analog is stereospecifically hydrolyzed, indicate that it is acted on in an analogous manner to dipalmitoylphosphatidylcholine. These studies indicate that although the configuration of the analog is not necessarily a prerequisite for hydrolysis, there does appear to be an optimal spatial orientation for enzymatic activity. The analogy between the susceptibilities of all-trans-(1,3/2-1P)-cyclopentano-lecithin and glycero-lecithin suggests that the conformation of the glycero-lecithin during phospholipase A2-mediated hydrolysis may be best simulated by the all-trans orientation of C-O bonds in the artificial substrate.

Investigations of different doping concentration of phosphorus and boron into silicon substrate on the variable temperature Raman characteristics

NASA Astrophysics Data System (ADS)

Li, Xiaoli; Ding, Kai; Liu, Jian; Gao, Junxuan; Zhang, Weifeng

2018-01-01

Different doped silicon substrates have different device applications and have been used to fabricate solar panels and large scale integrated circuits. The thermal transport in silicon substrates are dominated by lattice vibrations, doping type, and doping concentration. In this paper, a variable-temperature Raman spectroscopic system is applied to record the frequency and linewidth changes of the silicon peak at 520 cm-1 in five chips of silicon substrate with different doping concentration of phosphorus and boron at the 83K to 1473K temperature range. The doping has better heat sensitive to temperature on the frequency shift over the low temperature range from 83K to 300K but on FWHM in high temperature range from 300K to 1473K. The results will be helpful for fundamental study and practical applications of silicon substrates.

Decreased airway narrowing and smooth muscle contraction in hyperresponsive pigs.

PubMed

Turner, Debra J; Noble, Peter B; Lucas, Matthew P; Mitchell, Howard W

2002-10-01

Increased smooth muscle contractility or reduced smooth muscle mechanical loads could account for the excessive airway narrowing and hyperresponsiveness seen in asthma. These mechanisms were investigated by using an allergen-induced porcine model of airway hyperresponsiveness. Airway narrowing to electric field stimulation was measured in isolated bronchial segments, over a range of transmural pressures (0-20 cmH(2)O). Contractile responses to ACh were measured in bronchial segments and in isolated tracheal smooth muscle strips isolated from control and test (ovalbumin sensitized and challenged) pigs. Test airways narrowed less than controls (P < 0.0001). Test pigs showed reduced contractility to ACh, both in isolated bronchi (P < 0.01) and smooth muscle strips (P < 0.01). Thus isolated airways from pigs exhibiting airway hyperresponsiveness in vivo are hyporesponsive in vitro. The decreased narrowing in bronchi from hyperresponsive pigs may be related to decreased smooth muscle contractility. These data suggest that mechanisms external to the airway wall may be important to the hyperresponsive nature of sensitized lungs.

Relationship between relative lens position and appositional closure in eyes with narrow angles.

PubMed

Otori, Yasumasa; Tomita, Yuki; Hamamoto, Ayumi; Fukui, Kanae; Usui, Shinichi; Tatebayashi, Misako

2011-03-01

To investigate the relationship between relative lens position (RLP) and appositional closure in eyes with narrow angles. Ultrasound biomicroscopy (UBM) was used to measure anterior chamber depth (ACD) and lens thickness (LT), and the IOLMaster to measure axial length (AL). The number of quadrants with appositional closure was assessed by UBM under dark conditions. The RLP was calculated thus: RLP = 10 × (ACD + 0.5 LT) /AL. This study comprised 30 consecutive patients (30 eyes) with narrow-angle eyes defined as Shaffer grade 2 or lower and without peripheral anterior synechiae (24 women, 6 men; mean age ± SD, 67.3 ± 10.4 years; range, 42-87 years). Under dark conditions, 66.7% of the eyes with narrow angles showed appositional closure in at least one quadrant. Of the various ocular biometric parameters, only the RLP significantly decreased with appositional closure in at least one quadrant (P = 0.005). A decrease in the RLP can be predictive of appositional closure for narrow-angle eyes under dark conditions.

Microwave-assisted intramolecular dehydrogenative Diels-Alder reactions for the synthesis of functionalized naphthalenes/solvatochromic dyes.

PubMed

Kocsis, Laura S; Benedetti, Erica; Brummond, Kay M

2013-04-01

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable. The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts. The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields.

Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes

PubMed Central

Kocsis, Laura S.; Benedetti, Erica; Brummond, Kay M.

2013-01-01

Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable. The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts. The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields. PMID:23609566

Effect of Annealing Temperature on Structural and Optical Properties of Sol-Gel-Derived ZnO Thin Films

NASA Astrophysics Data System (ADS)

Arif, Mohd.; Sanger, Amit; Vilarinho, Paula M.; Singh, Arun

2018-04-01

Nanocrystalline ZnO thin films were deposited on glass substrate via sol-gel dip-coating technique then annealed at 300°C, 400°C, and 500°C for 1 h. Their optical, structural, and morphological properties were studied using ultraviolet-visible (UV-Vis) spectrophotometry, x-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM). XRD diffraction revealed that the crystalline nature of the thin films increased with increasing annealing temperature. The c-axis orientation improved, and the grain size increased, as indicated by increased intensity of the (002) plane peak at 2θ = 34.42° corresponding to hexagonal ZnO crystal. The average crystallite size of the thin films ranged from 13 nm to 23 nm. Increasing the annealing temperature resulted in larger crystallite size and higher crystallinity with increased surface roughness. The grain size according to SEM analysis was in good agreement with the x-ray diffraction data. The optical bandgap of the thin films narrowed with increasing annealing temperature, lying in the range of 3.14 eV to 3.02 eV. The transmission of the thin films was as high as 94% within the visible region. The thickness of the thin films was 400 nm, as measured by ellipsometry, after annealing at the different temperatures of 300°C, 400°C, and 500°C.

Unmasking tandem site interaction in human acetylcholinesterase. Substrate activation with a cationic acetanilide substrate.

PubMed

Johnson, Joseph L; Cusack, Bernadette; Davies, Matthew P; Fauq, Abdul; Rosenberry, Terrone L

2003-05-13

Acetylcholinesterase (AChE) contains a narrow and deep active site gorge with two sites of ligand binding, an acylation site (or A-site) at the base of the gorge, and a peripheral site (or P-site) near the gorge entrance. The P-site contributes to catalytic efficiency by transiently binding substrates on their way to the acylation site, where a short-lived acyl enzyme intermediate is produced. A conformational interaction between the A- and P-sites has recently been found to modulate ligand affinities. We now demonstrate that this interaction is of functional importance by showing that the acetylation rate constant of a substrate bound to the A-site is increased by a factor a when a second molecule of substrate binds to the P-site. This demonstration became feasible through the introduction of a new acetanilide substrate analogue of acetylcholine, 3-(acetamido)-N,N,N-trimethylanilinium (ATMA), for which a = 4. This substrate has a low acetylation rate constant and equilibrates with the catalytic site, allowing a tractable algebraic solution to the rate equation for substrate hydrolysis. ATMA affinities for the A- and P-sites deduced from the kinetic analysis were confirmed by fluorescence titration with thioflavin T as a reporter ligand. Values of a >1 give rise to a hydrolysis profile called substrate activation, and the AChE site-specific mutant W86F, and to a lesser extent wild-type human AChE itself, showed substrate activation with acetylthiocholine as the substrate. Substrate activation was incorporated into a previous catalytic scheme for AChE in which a bound P-site ligand can also block product dissociation from the A-site, and two additional features of the AChE catalytic pathway were revealed. First, the ability of a bound P-site ligand to increase the substrate acetylation rate constant varied with the structure of the ligand: thioflavin T accelerated ATMA acetylation by a factor a(2) of 1.3, while propidium failed to accelerate. Second, catalytic rate constants in the initial intermediate formed during acylation (EAP, where EA is the acyl enzyme and P is the alcohol leaving group cleaved from the ester substrate) may be constrained such that the leaving group P must dissociate before hydrolytic deacylation can occur.

Narrowing beam-walking is a clinically feasible approach for assessing balance ability in lower-limb prosthesis users.

PubMed

Sawers, Andrew; Hafner, Brian J

2018-05-08

Challenging clinical balance tests are needed to expose balance deficits in lower-limb prost-hesis users. This study examined whether narrowing beam-walking could overcome conceptual and practical limitations identified in fixed-width beam-walking. Cross-sectional. Unilateral lower-limb prosthesis users. Participants walked 10 times along a low, narrowing beam. Performance was quantified using the normalized distance walked. Heuristic rules were applied to determine whether the narrowing beam task was "too easy," "too hard," or "appropriately challenging" for each participant. Linear regression and Bland-Altman plots were used to determine whether combinations of the first 5 trials could predict participants' stable beam-walking performance. Forty unilateral lower-limb prosthesis users participated. Narrowing beam-walking was appropriately challenging for 98% of participants. Performance stabilized for 93% of participants within 5 trials, while 62% were stable across all trials. The mean of trials 3-5 accurately predicted stable performance. A clinical narrowing beam-walking test is likely to challenge a range of lower-limb prosthesis users, have minimal administrative burden, and exhibit no floor or ceiling effects. Narrowing beam-walking is therefore a clinically viable method to evaluate lower-limb prosthesis users' balance ability, but requires psychometric testing before it is used to assess fall risk.

Acquisition and visualization techniques for narrow spectral color imaging.

PubMed

Neumann, László; García, Rafael; Basa, János; Hegedüs, Ramón

2013-06-01

This paper introduces a new approach in narrow-band imaging (NBI). Existing NBI techniques generate images by selecting discrete bands over the full visible spectrum or an even wider spectral range. In contrast, here we perform the sampling with filters covering a tight spectral window. This image acquisition method, named narrow spectral imaging, can be particularly useful when optical information is only available within a narrow spectral window, such as in the case of deep-water transmittance, which constitutes the principal motivation of this work. In this study we demonstrate the potential of the proposed photographic technique on nonunderwater scenes recorded under controlled conditions. To this end three multilayer narrow bandpass filters were employed, which transmit at 440, 456, and 470 nm bluish wavelengths, respectively. Since the differences among the images captured in such a narrow spectral window can be extremely small, both image acquisition and visualization require a novel approach. First, high-bit-depth images were acquired with multilayer narrow-band filters either placed in front of the illumination or mounted on the camera lens. Second, a color-mapping method is proposed, using which the input data can be transformed onto the entire display color gamut with a continuous and perceptually nearly uniform mapping, while ensuring optimally high information content for human perception.

Improving Control in a Joule-Thomson Refrigerator

NASA Technical Reports Server (NTRS)

Borders, James; Pearson, David; Prina, Mauro

2005-01-01

A report discusses a modified design of a Joule-Thomson (JT) refrigerator under development to be incorporated into scientific instrumentation aboard a spacecraft. In most other JT refrigerators (including common household refrigerators), the temperature of the evaporator (the cold stage) is kept within a desired narrow range by turning a compressor on and off as needed. This mode of control is inadequate for the present refrigerator because a JT-refrigerator compressor performs poorly when the flow from its evaporator varies substantially, and this refrigerator is required to maintain adequate cooling power. The proposed design modifications include changes in the arrangement of heat exchangers, addition of a clamp that would afford a controlled heat leak from a warmer to a cooler stage to smooth out temperature fluctuations in the cooler stage, and incorporation of a proportional + integral + derivative (PID) control system that would regulate the heat leak to maintain the temperature of the evaporator within a desired narrow range while keeping the amount of liquid in the evaporator within a very narrow range in order to optimize the performance of the compressor. Novelty lies in combining the temperature- and cooling-power-regulating controls into a single control system.

Precursor of superfluidity in a strongly interacting Fermi gas with negative effective range

NASA Astrophysics Data System (ADS)

Tajima, Hiroyuki

2018-04-01

We investigate theoretically the effects of pairing fluctuations in an ultracold Fermi gas near a Feshbach resonance with a negative effective range. By employing a many-body T -matrix theory with a coupled fermion-boson model, we show that the single-particle density of states exhibits the so-called pseudogap phenomenon, which is a precursor of superfluidity induced by strong pairing fluctuations. We clarify the region where strong pairing fluctuations play a crucial role in single-particle properties, from the broad-resonance region to the narrow-resonance limit at the divergent two-body scattering length. We also extrapolate the effects of pairing fluctuations to the positive-effective-range region from our results near the narrow Feshbach resonance. Results shown in this paper are relevant to the connection between ultracold Fermi gases and low-density neutron matter from the viewpoint of finite-effective-range corrections.

Narrow pH Range of Surface Water Bodies Receiving Pesticide Input in Europe.

PubMed

Bundschuh, Mirco; Weyers, Arnd; Ebeling, Markus; Elsaesser, David; Schulz, Ralf

2016-01-01

Fate and toxicity of the active ingredients (AI's) of plant protection products in surface waters is often influenced by pH. Although a general range of pH values is reported in literature, an evaluation targeting aquatic ecosystems with documented AI inputs is lacking at the larger scale. Results show 95% of European surface waters (n = 3075) with a documented history of AI exposure fall within a rather narrow pH range, between 7.0 and 8.5. Spatial and temporal variability in the data may at least be partly explained by the calcareous characteristics of parental rock material, the affiliation of the sampling site to a freshwater ecoregion, and the photosynthetic activity of macrophytes (i.e., higher pH values with photosynthesis). Nonetheless, the documented pH range fits well with the standard pH of most ecotoxicological test guidelines, confirming the fate and ecotoxicity of AIs are usually adequately addressed.

Longitudinal waves in a perpendicular collisionless plasma shock. IV - Gradient B.

NASA Technical Reports Server (NTRS)

Gary, S. P.

1972-01-01

The consideration of elastic waves in a Vlasov plasma of unmagnetized ions and magnetized electrons undergoing E x B electron drift and gradient B drift, pursued in the earlier three parts, is brought to conclusion in this last part of the longitudinal wave study in a collisionless plasma shock. Detailed calculations of the effects of the beta sub e dimensionless parameter on the E x B electron drift instability are presented. It is shown that the range of propagation of the elastic waves about the perpendicular remains quite narrow, and that, for oblique propagation, the already narrow angular range of unstable waves is decreased by increases in the value of the beta sub e dimensionless parameter. Also, increases in wave number generally reduce the growth rate and the angular range of propagation.

van der Waals epitaxy of CdTe thin film on graphene

NASA Astrophysics Data System (ADS)

Mohanty, Dibyajyoti; Xie, Weiyu; Wang, Yiping; Lu, Zonghuan; Shi, Jian; Zhang, Shengbai; Wang, Gwo-Ching; Lu, Toh-Ming; Bhat, Ishwara B.

2016-10-01

van der Waals epitaxy (vdWE) facilitates the epitaxial growth of materials having a large lattice mismatch with the substrate. Although vdWE of two-dimensional (2D) materials on 2D materials have been extensively studied, the vdWE for three-dimensional (3D) materials on 2D substrates remains a challenge. It is perceived that a 2D substrate passes little information to dictate the 3D growth. In this article, we demonstrated the vdWE growth of the CdTe(111) thin film on a graphene buffered SiO2/Si substrate using metalorganic chemical vapor deposition technique, despite a 46% large lattice mismatch between CdTe and graphene and a symmetry change from cubic to hexagonal. Our CdTe films produce a very narrow X-ray rocking curve, and the X-ray pole figure analysis showed 12 CdTe (111) peaks at a chi angle of 70°. This was attributed to two sets of parallel epitaxy of CdTe on graphene with a 30° relative orientation giving rise to a 12-fold symmetry in the pole figure. First-principles calculations reveal that, despite the relatively small energy differences, the graphene buffer layer does pass epitaxial information to CdTe as the parallel epitaxy, obtained in the experiment, is energetically favored. The work paves a way for the growth of high quality CdTe film on a large area as well as on the amorphous substrates.

Dynamic Locomotor Capabilities Revealed by Early Dinosaur Trackmakers from Southern Africa

PubMed Central

Wilson, Jeffrey A.; Marsicano, Claudia A.; Smith, Roger M. H.

2009-01-01

Background A new investigation of the sedimentology and ichnology of the Early Jurassic Moyeni tracksite in Lesotho, southern Africa has yielded new insights into the behavior and locomotor dynamics of early dinosaurs. Methodology/Principal Findings The tracksite is an ancient point bar preserving a heterogeneous substrate of varied consistency and inclination that includes a ripple-marked riverbed, a bar slope, and a stable algal-matted bar top surface. Several basal ornithischian dinosaurs and a single theropod dinosaur crossed its surface within days or perhaps weeks of one another, but responded to substrate heterogeneity differently. Whereas the theropod trackmaker accommodated sloping and slippery surfaces by gripping the substrate with its pedal claws, the basal ornithischian trackmakers adjusted to the terrain by changing between quadrupedal and bipedal stance, wide and narrow gauge limb support (abduction range = 31°), and plantigrade and digitigrade foot posture. Conclusions/Significance The locomotor adjustments coincide with changes in substrate consistency along the trackway and appear to reflect ‘real time’ responses to a complex terrain. It is proposed that these responses foreshadow important locomotor transformations characterizing the later evolution of the two main dinosaur lineages. Ornithischians, which shifted from bipedal to quadrupedal posture at least three times in their evolutionary history, are shown to have been capable of adopting both postures early in their evolutionary history. The substrate-gripping behavior demonstrated by the early theropod, in turn, is consistent with the hypothesized function of pedal claws in bird ancestors. PMID:19806213

Microfluidic transmission surface plasmon resonance enhancement for biosensor applications

NASA Astrophysics Data System (ADS)

Lertvachirapaiboon, Chutiparn; Baba, Akira; Ekgasit, Sanong; Shinbo, Kazunari; Kato, Keizo; Kaneko, Futao

2017-01-01

The microfluidic transmission surface plasmon resonance (MTSPR) constructed by assembling a gold-coated grating substrate with a microchannel was employed for biosensor application. The transmission surface plasmon resonance spectrum obtained from the MTSPR sensor chip showed a strong and narrow surface plasmon resonance (SPR) peak located between 650 and 800 nm. The maximum SPR excitation was observed at an incident angle of 35°. The MTSPR sensor chip was employed for glucose sensor application. Gold-coated grating substrates were functionalized using 3-mercapto-1-propanesulfonic acid sodium salt and subsequently functionalized using a five-bilayer poly(allylamine hydrochloride)/poly(sodium 4-styrenesulfonate) to facilitate the coupling/decoupling of the surface plasmon and to prepare a uniform surface for sensing. The detection limit of our developed system for glucose was 2.31 mM. This practical platform represents a high possibility of further developing several biomolecules, multiplex systems, and a point-of-care assay for practical biosensor applications.

Stable aqueous based Cu nanoparticle ink for printing well-defined highly conductive features on a plastic substrate.

PubMed

Jeong, Sunho; Song, Hae Chun; Lee, Won Woo; Lee, Sun Sook; Choi, Youngmin; Son, Wonil; Kim, Eui Duk; Paik, Choon Hoon; Oh, Seok Heon; Ryu, Beyong-Hwan

2011-03-15

With the aim of inkjet printing highly conductive and well-defined Cu features on plastic substrates, aqueous based Cu ink is prepared for the first time using water-soluble Cu nanoparticles with a very thin surface oxide layer. Owing to the specific properties, high surface tension and low boiling point, of water, the aqueous based Cu ink endows a variety of advantages over conventional Cu inks based on organic solvents in printing narrow conductive patterns without irregular morphologies. It is demonstrated how the design of aqueous based ink affects the basic properties of printed conductive features such as surface morphology, microstructure, conductivity, and line width. The long-term stability of aqueous based Cu ink against oxidation is analyzed through an X-ray photoelectron spectroscopy (XPS) based investigation on the evolution of the surface oxide layer in the aqueous based ink.

Stackable multi-port gas nozzles

DOEpatents

Poppe, Steve; Rozenzon, Yan; Ding, Peijun

2015-03-03

One embodiment provides a reactor for material deposition. The reactor includes a chamber and at least one gas nozzle. The chamber includes a pair of susceptors, each having a front side and a back side. The front side mounts a number of substrates. The susceptors are positioned vertically so that the front sides of the susceptors face each other, and the vertical edges of the susceptors are in contact with each other, thereby forming a substantially enclosed narrow channel between the substrates mounted on different susceptors. The gas nozzle includes a gas-inlet component situated in the center and a detachable gas-outlet component stacked around the gas-inlet component. The gas-inlet component includes at least one opening coupled to the chamber, and is configured to inject precursor gases into the chamber. The detachable gas-outlet component includes at least one opening coupled to the chamber, and is configured to output exhaust gases from the chamber.

Controlling the interparticle spacing of Au-salt loaded micelles and Au nanoparticles on flat surfaces.

PubMed

Bansmann, J; Kielbassa, S; Hoster, H; Weigl, F; Boyen, H G; Wiedwald, U; Ziemann, P; Behm, R J

2007-09-25

The self-organization of diblock copolymers into micellar structures in an appropriate solvent allows the deposition of well ordered arrays of pure metal and alloy nanoparticles on flat surfaces with narrow distributions in particle size and interparticle spacing. Here we investigated the influence of the materials (substrate and polymer) and deposition parameters (temperature and emersion velocity) on the deposition of metal salt loaded micelles by dip-coating from solution and on the order and inter-particle spacing of the micellar deposits and thus of the metal nanoparticle arrays resulting after plasma removal of the polymer shell. For identical substrate and polymer, variation of the process parameters temperature and emersion velocity enables the controlled modification of the interparticle distance within a certain length regime. Moreover, also the degree of hexagonal order of the final array depends sensitively on these parameters.

Quality improvements of ZnxCdyMg1-x-ySe layers grown on InP substrates by a thin ZnCdSe interfacial layer

NASA Astrophysics Data System (ADS)

Zeng, L.; Yang, B. X.; Tamargo, M. C.; Snoeks, E.; Zhao, L.

1998-03-01

The quality of lattice-matched ZnxCdyMg1-x-ySe epitaxial layers grown on (001) InP substrates with a III-V buffer layer has been improved by initially growing a ZnCdSe interfacial layer (50 Å) at low temperature. The widths of double crystal x-ray rocking curves for ZnxCdyMg1-x-ySe epilayers with band gaps as high as 3.05 eV were reduced to about 70 arcsec. The defect density evaluated from etch pit density and plan-view transmission electron microscopy measurements was reduced by two orders of magnitude, to 106-107cm-2. The photoluminescence band edge emission became more symmetric and slightly narrower. It is proposed that an initial two-dimensional growth mode has been achieved by incorporating such a lattice-matched ZnCdSe layer.

Effect of Same-Temperature GaN Cap Layer on the InGaN/GaN Multiquantum Well of Green Light-Emitting Diode on Silicon Substrate

PubMed Central

Zheng, Changda; Wang, Li; Mo, Chunlan; Fang, Wenqing; Jiang, Fengyi

2013-01-01

GaN green LED was grown on Si (111) substrate by MOCVD. To enhance the quality of InGaN/GaN MQWs, same-temperature (ST) GaN protection layers with different thickness of 8 Å, 15 Å, and 30 Å were induced after the InGaN quantum wells (QWs) layer. Results show that a relative thicker cap layer is benefit to get InGaN QWs with higher In percent at fixed well temperature and obtain better QW/QB interface. As the cap thickness increases, the indium distribution becomes homogeneous as verified by fluorescence microscope (FLM). The interface of MQWs turns to be abrupt from XRD analysis. The intensity of photoluminescence (PL) spectrum is increased and the FWHM becomes narrow. PMID:24369453

Sonoelectrochemical one-pot synthesis of Pt - Carbon black nanocomposite PEMFC electrocatalyst.

PubMed

Karousos, Dionysios S; Desdenakis, Kostantinos I; Sakkas, Petros M; Sourkouni, Georgia; Pollet, Bruno G; Argirusis, Christos

2017-03-01

Simultaneous electrocatalytic Pt-nanoparticle synthesis and decoration of Vulcan XC-72 carbon black substrate was achieved in a novel one-step-process, combining galvanostatic pulsed electrodeposition and pulsed ultrasonication with high power, low-frequency (20kHz) ultrasound. Aqueous chloroplatinic acid precursor baths, as well as carbon black suspensions in the former, were examined and decoration was proven by a combination of characterization methods, namely: dynamic light scattering, transmission electron microscopy, scanning electron microscopy with EDX-analysis and cyclic voltammetry. In particular, PVP was shown to have a beneficial stabilizing effect against free nanoparticle aggregation, ensuring narrow size distributions of the nanoparticles synthesized, but is also postulated to prevent the establishment of a strong metal-substrate interaction. Current pulse amplitude was identified as the most critical nanoparticle size-determining parameters, while only small size particles, under 10nm, appeared to be attached to carbon black. Copyright © 2016 Elsevier B.V. All rights reserved.

Two dimensional radial gas flows in atmospheric pressure plasma-enhanced chemical vapor deposition

NASA Astrophysics Data System (ADS)

Kim, Gwihyun; Park, Seran; Shin, Hyunsu; Song, Seungho; Oh, Hoon-Jung; Ko, Dae Hong; Choi, Jung-Il; Baik, Seung Jae

2017-12-01

Atmospheric pressure (AP) operation of plasma-enhanced chemical vapor deposition (PECVD) is one of promising concepts for high quality and low cost processing. Atmospheric plasma discharge requires narrow gap configuration, which causes an inherent feature of AP PECVD. Two dimensional radial gas flows in AP PECVD induces radial variation of mass-transport and that of substrate temperature. The opposite trend of these variations would be the key consideration in the development of uniform deposition process. Another inherent feature of AP PECVD is confined plasma discharge, from which volume power density concept is derived as a key parameter for the control of deposition rate. We investigated deposition rate as a function of volume power density, gas flux, source gas partial pressure, hydrogen partial pressure, plasma source frequency, and substrate temperature; and derived a design guideline of deposition tool and process development in terms of deposition rate and uniformity.

Using multivalency to tailor the superselective binding of polymers on substrates

NASA Astrophysics Data System (ADS)

Tito, Nicholas; Frenkel, Daan

2014-03-01

Multivalency is a microscopic design concept in which a single nanoscopic entity contains multiple ligands, each of which may bind to multiple receptors on another entity. A useful property of many multivalent systems is ``superselectivity,'' where the fraction of the multivalent species bound to their complementary receptors grows sharply with the total number of receptors available. For example in the past two decades, multivalency has been exploited to develop DNA-coated nanoparticles that self-assemble into aggregates over an extremely narrow temperature window. In this talk, we use analytic and self-consistent field theories to explore the binding of multivalent polymers to receptors on a flat substrate. Discussion will focus on how the sequence, number, and binding strength of ligands along the polymer chain can be used to tune the superselectivity of the system. Comparison with recent experiments on model systems will be presented as time permits. We wish to thank ERC Advanced Grant 227758.

Imbibition with swelling: Capillary rise in thin deformable porous media

NASA Astrophysics Data System (ADS)

Kvick, Mathias; Martinez, D. Mark; Hewitt, Duncan R.; Balmforth, Neil J.

2017-07-01

The imbibition of a liquid into a thin deformable porous substrate driven by capillary suction is considered. The substrate is initially dry and has uniform porosity and thickness. Two-phase flow theory is used to describe how the liquid flows through the pore space behind the wetting front when out-of-plane deformation of the solid matrix is considered. Neglecting gravity and evaporation, standard shallow-layer scalings are used to construct a reduced model of the dynamics. The model predicts convergence to a self-similar behavior in all regions except near the wetting front, where a boundary layer arises whose structure narrows with the advance of the front. Over time, the rise height approaches the similarity scaling of t1 /2, as in the classical Washburn or BCLW law. The results are compared with a series of laboratory experiments using cellulose paper sheets, which provide qualitative agreement.

Electronic characterization of defects in narrow gap semiconductors

NASA Technical Reports Server (NTRS)

Patterson, James D.

1993-01-01

The study of point defects in semiconductors has a long and honorable history. In particular, the detailed understanding of shallow defects in common semiconductors traces back to the classic work of Kohn and Luttinger. However, the study of defects in narrow gap semiconductors represents a much less clear story. Here, both shallow defects (caused by long range potentials) and deep defects (from short range potentials) are far from being completely understood. In this study, all results are calculational and our focus is on the chemical trend of deep levels in narrow gap semiconductors. We study substitutional (including antisite), interstitial and ideal vacancy defects. For substitutional and interstitial impurities, the efects of relaxation are included. For materials like Hg(1-x)Cd(x)Te, we study how the deep levels vary with x, of particular interest is what substitutional and interstitial atoms yield energy levels in the gap i.e. actually produce deep ionized levels. Also, since the main technique utilized is Green's functions, we include some summary of that method.

AC Loss Minimization in High Temperature Superconductors - U.K.

DTIC Science & Technology

2003-11-07

high currents in high magnetic fields. The DC properties are very attractive, but to reduce the AC losses it is necessary to use a narrow conductor... NiFe in the whole magnetic field region (goHext=0.01 T - 6 T) roughly by a factor of 2, reflecting the sample Jc(B) dependencies. Also the magnetic ...ratio of the tape, there is no visible effect in a parallel magnetic field. Hysteresis losses in metallic substrates - CeO2:Pd/ NiFe and CeO2:Pd/NiCrW

High-Resolution Printing of 3D Structures Using an Electrohydrodynamic Inkjet with Multiple Functional Inks.

PubMed

An, Byeong Wan; Kim, Kukjoo; Lee, Heejoo; Kim, So-Yun; Shim, Yulhui; Lee, Dae-Young; Song, Jun Yeob; Park, Jang-Ung

2015-08-05

Electrohydrodynamic-inkjet-printed high-resolution complex 3D structures with multiple functional inks are demonstrated. Printed 3D structures can have a variety of fine patterns, such as vertical or helix-shaped pillars and straight or rounded walls, with high aspect ratios (greater than ≈50) and narrow diameters (≈0.7 μm). Furthermore, the formation of freestanding, bridge-like Ag wire structures on plastic substrates suggests substantial potentials as high-precision, flexible 3D interconnects. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A hydrodynamic microchip for formation of continuous cell chains

NASA Astrophysics Data System (ADS)

Khoshmanesh, Khashayar; Zhang, Wei; Tang, Shi-Yang; Nasabi, Mahyar; Soffe, Rebecca; Tovar-Lopez, Francisco J.; Rajadas, Jayakumar; Mitchell, Arnan

2014-05-01

Here, we demonstrate the unique features of a hydrodynamic based microchip for creating continuous chains of model yeast cells. The system consists of a disk shaped microfluidic structure, containing narrow orifices that connect the main channel to an array of spoke channels. Negative pressure provided by a syringe pump draws fluid from the main channel through the narrow orifices. After cleaning process, a thin layer of water is left between the glass substrate and the polydimethylsiloxane microchip, enabling leakage beneath the channel walls. A mechanical clamp is used to adjust the operation of the microchip. Relaxing the clamp allows leakage of liquid beneath the walls in a controllable fashion, leading to formation of a long cell chain evenly distributed along the channel wall. The unique features of the microchip are demonstrated by creating long chains of yeast cells and model 15 μm polystyrene particles along the side wall and analysing the hydrogen peroxide induced death of patterned cells.

Narrowing of the middle cerebral artery: artificial intelligence methods and comparison of transcranial color coded duplex sonography with conventional TCD.

PubMed

Swiercz, Miroslaw; Swiat, Maciej; Pawlak, Mikolaj; Weigele, John; Tarasewicz, Roman; Sobolewski, Andrzej; Hurst, Robert W; Mariak, Zenon D; Melhem, Elias R; Krejza, Jaroslaw

2010-01-01

The goal of the study was to compare performances of transcranial color-coded duplex sonography (TCCS) and transcranial Doppler sonography (TCD) in the diagnosis of the middle cerebral artery (MCA) narrowing in the same population of patients using statistical and nonstatistical intelligent models for data analysis. We prospectively collected data from 179 consecutive routine digital subtraction angiography (DSA) procedures performed in 111 patients (mean age 54.17+/-14.4 years; 59 women, 52 men) who underwent TCD and TCCS examinations simultaneously. Each patient was examined independently using both ultrasound techniques, 267 M1 segments of MCA were assessed and narrowings were classified as < or =50% and >50% lumen reduction. Diagnostic performance was estimated by two statistical and two artificial neural networks (ANN) classification methods. Separate models were constructed for the TCD and TCCS sonographic data, as well as for detection of "any narrowing" and "severe narrowing" of the MCA. Input for each classifier consisted of the peak-systolic, mean and end-diastolic velocities measured with each sonographic method; the output was MCA narrowing. Arterial narrowings less or equal 50% of lumen reduction were found in 55 and >50% narrowings in 26 out of 267 arteries, as indicated by DSA. In the category of "any narrowing" the rate of correct assignment by all models was 82% to 83% for TCCS and 79% to 81% for TCD. In the diagnosis of >50% narrowing the overall classification accuracy remained in the range of 89% to 90% for TCCS data and 90% to 91% for TCD data. For the diagnosis of any narrowing, the sensitivity of the TCCS was significantly higher than that of the TCD, while for diagnosis of >50% MCA narrowing, sensitivity of the TCCS was similar to sensitivity of the TCD. Our study showed that TCCS outperforms conventional TCD in detection of < or =50% MCA narrowing, whereas no significant difference in accuracy between both methods was found in the diagnosis of >50% MCA narrowing. (E-mail: jaroslaw.krejza@uphs.upenn.edu).

Substrate for thin silicon solar cells

DOEpatents

Ciszek, Theodore F.

1998-01-01

A substrate for a photovoltaic device wherein the substrate is the base upon which photosensitive material is to be grown and the substrate comprises an alloy having boron in a range from 0.1 atomic % of the alloy to 1.3 atomic % of the alloy and the substrate has a resistivity less than 3.times.10.sup.-3 ohm-cm.

Weak Broadband Electromagnetic Fields are More Disruptive to Magnetic Compass Orientation in a Night-Migratory Songbird (Erithacus rubecula) than Strong Narrow-Band Fields

PubMed Central

Schwarze, Susanne; Schneider, Nils-Lasse; Reichl, Thomas; Dreyer, David; Lefeldt, Nele; Engels, Svenja; Baker, Neville; Hore, P. J.; Mouritsen, Henrik

2016-01-01

Magnetic compass orientation in night-migratory songbirds is embedded in the visual system and seems to be based on a light-dependent radical pair mechanism. Recent findings suggest that both broadband electromagnetic fields ranging from ~2 kHz to ~9 MHz and narrow-band fields at the so-called Larmor frequency for a free electron in the Earth’s magnetic field can disrupt this mechanism. However, due to local magnetic fields generated by nuclear spins, effects specific to the Larmor frequency are difficult to understand considering that the primary sensory molecule should be organic and probably a protein. We therefore constructed a purpose-built laboratory and tested the orientation capabilities of European robins in an electromagnetically silent environment, under the specific influence of four different oscillating narrow-band electromagnetic fields, at the Larmor frequency, double the Larmor frequency, 1.315 MHz or 50 Hz, and in the presence of broadband electromagnetic noise covering the range from ~2 kHz to ~9 MHz. Our results indicated that the magnetic compass orientation of European robins could not be disrupted by any of the relatively strong narrow-band electromagnetic fields employed here, but that the weak broadband field very efficiently disrupted their orientation. PMID:27047356

On the relative magnitudes of photosynthesis, respiration, growth and carbon storage in vegetation

NASA Astrophysics Data System (ADS)

van Oijen, M.

2012-04-01

• Background and Aims. The carbon balance of vegetation is dominated by the two large fluxes of photosynthesis (P) and respiration (R). Mechanistic models have attempted to simulate the two fluxes separately, each with their own set of internal and external controls. This has led to model predictions where environmental change causes R to exceed P, with consequent dieback of vegetation. However, empirical evidence suggests that the R:P ratio is constrained to a narrow range of about 0.4-0.5. Physiological explanations for the narrow range are not conclusive. We aim to introduce a novel perspective by theoretical study of the quantitative relationship between the four carbon fluxes of P, R, growth and storage (or its inverse, remobilisation). • Methods. Starting from the law of conservation of mass - in this case carbon - we derive equations for the relative magnitudes of all carbon fluxes which depend on only two parameters: the R:P ratio and the relative rate of storage of carbon into remobilisable reserves. The equations are used to explain observed flux ratios and to analyse incomplete data sets of carbon fluxes. • Key Results. Storage rate is shown to be a freely varying parameter, whereas R:P is narrowly constrained. This explains the constancy of the ratio reported in the literature. With the information thus gained, a data set of R and P in grassland was analysed, and flux estimates could be derived for the periods after cuts in which plant growth is dominated by remobilisation before photosynthesis takes over. • Conclusions. We conclude that the relative magnitudes of photosynthesis, respiration, growth and substrate storage are indeed tightly constrained, but because of mass conservation rather than for physiological reasons. This facilitates analysis of incomplete data sets. Mechanistic models, as the embodiment of physiological mechanisms, need to show consistency with the constraints. • Reference. Van Oijen, M., Schapendonk, A. & Höglind, M. (2010). On the relative magnitudes of photosynthesis, respiration, growth and carbon storage in vegetation. Annals of Botany 105: 793-797.

Properties of Silica-Based Aerogel Substrates and Application to C-Band Circular Patch Antenna

NASA Astrophysics Data System (ADS)

Abdel-Rahman, Mohamed; Haraz, Osama M.; Ashraf, Nadeem; Zia, Muhammad Fakhar; Khaled, Usama; Elsahfiey, Ibrahim; Alshebeili, Saleh; Sebak, Abdel Razik

2018-03-01

Silica aerogel is a lightweight and low-permittivity dielectric material that possesses attractive features for use as an antenna substrate. In this paper, we characterize the radio frequency and microwave dielectric permittivity properties of substrates composed of silica aerogel encapsulated in polymer aerogel in the frequency range from 10 MHz to 8.5 GHz. Characterized silica-based aerogel substrates show relative permittivity values varying between 1.055 and 1.25 and loss tangent values ranging from 5.08 × 10-4 to 0.0206. Silica-based aerogel substrates thus have the potential of use in designing antennas with high gain and large bandwidth. Validation is presented by characterizing the performance of a manufactured C-band circular patch antenna on silica-based aerogel substrate. The performance is also compared to a design that uses Rogers Duroid RT5880 substrate. The results reveal that the silica aerogel substrate antenna at 7.2 GHz provides 1.5 dB increase in gain, 88% enhancement in bandwidth and 68.5% reduction in mass, in comparison with the antenna on RT5880 substrate.

Living Shorelines: Coastal Resilience with a Blue Carbon Benefit

PubMed Central

Davis, Jenny L.; Currin, Carolyn A.; O’Brien, Colleen; Raffenburg, Craig; Davis, Amanda

2015-01-01

Living shorelines are a type of estuarine shoreline erosion control that incorporates native vegetation and preserves native habitats. Because they provide the ecosystem services associated with natural coastal wetlands while also increasing shoreline resilience, living shorelines are part of the natural and hybrid infrastructure approach to coastal resiliency. Marshes created as living shorelines are typically narrow (< 30 m) fringing marshes with sandy substrates that are well flushed by tides. These characteristics distinguish living shorelines from the larger meadow marshes in which most of the current knowledge about created marshes was developed. The value of living shorelines for providing both erosion control and habitat for estuarine organisms has been documented but their capacity for carbon sequestration has not. We measured carbon sequestration rates in living shorelines and sandy transplanted Spartina alterniflora marshes in the Newport River Estuary, North Carolina. The marshes sampled here range in age from 12 to 38 years and represent a continuum of soil development. Carbon sequestration rates ranged from 58 to 283 g C m-2 yr-1 and decreased with marsh age. The pattern of lower sequestration rates in older marshes is hypothesized to be the result of a relative enrichment of labile organic matter in younger sites and illustrates the importance of choosing mature marshes for determination of long-term carbon sequestration potential. The data presented here are within the range of published carbon sequestration rates for S. alterniflora marshes and suggest that wide-scale use of the living shoreline approach to shoreline management may come with a substantial carbon benefit. PMID:26569503

Living Shorelines: Coastal Resilience with a Blue Carbon Benefit.

PubMed

Davis, Jenny L; Currin, Carolyn A; O'Brien, Colleen; Raffenburg, Craig; Davis, Amanda

2015-01-01

Living shorelines are a type of estuarine shoreline erosion control that incorporates native vegetation and preserves native habitats. Because they provide the ecosystem services associated with natural coastal wetlands while also increasing shoreline resilience, living shorelines are part of the natural and hybrid infrastructure approach to coastal resiliency. Marshes created as living shorelines are typically narrow (< 30 m) fringing marshes with sandy substrates that are well flushed by tides. These characteristics distinguish living shorelines from the larger meadow marshes in which most of the current knowledge about created marshes was developed. The value of living shorelines for providing both erosion control and habitat for estuarine organisms has been documented but their capacity for carbon sequestration has not. We measured carbon sequestration rates in living shorelines and sandy transplanted Spartina alterniflora marshes in the Newport River Estuary, North Carolina. The marshes sampled here range in age from 12 to 38 years and represent a continuum of soil development. Carbon sequestration rates ranged from 58 to 283 g C m-2 yr-1 and decreased with marsh age. The pattern of lower sequestration rates in older marshes is hypothesized to be the result of a relative enrichment of labile organic matter in younger sites and illustrates the importance of choosing mature marshes for determination of long-term carbon sequestration potential. The data presented here are within the range of published carbon sequestration rates for S. alterniflora marshes and suggest that wide-scale use of the living shoreline approach to shoreline management may come with a substantial carbon benefit.

Cyclooxygenase Reaction Mechanism of PGHS ------- Evidence for a Reversible Transition between a Pentadienyl Radical and a New Tyrosyl Radical by Nitric Oxide Trapping

PubMed Central

Lü, Jian-Ming; Rogge, Corina E.; Wu, Gang; Kulmacz, Richard J.; van der Donk, Wilfred A.; Tsai, Ah-lim

2011-01-01

Incubation of prostaglandin H synthase-1 (PGHS-1) under anaerobic conditions with peroxide and arachidonic acid leads to two major radical species: a pentadienyl radical and a radical with a narrow EPR spectrum. The proportions of the two radicals are sensitive to temperature, favoring the narrow radical species at 22 °C. The EPR characteristics of this latter radical are somewhat similar to the previously reported narrow-singlet tyrosine radical NS1a and are insensitive to deuterium labeling of AA. To probe the origin and structure of this radical, we combined EPR analysis with nitric oxide (NO) trapping of tyrosine and substrate derived radicals for both PGHS-1 and -2. Formation of 3-nitrotyrosine in the proteins was analyzed by immunoblotting, whereas NO adducts to AA and AA metabolites were analyzed by mass spectrometry and by chromatography of 14C-labeled products. The results indicate that both nitrated tyrosine residues and NO-AA adducts formed upon NO trapping. The NO-AA adduct was predominantly an oxime at C11 of AA with three conjugated double bonds, as indicated by absorption at 275 nm and by mass spectral analysis. This adduct amounted to 10% and 20% of the heme concentration of PGHS-1 and -2, respectively. For PGHS-1, the yield of NO-AA adduct matched the yield of the narrow radical signal obtained in parallel EPR experiments. High frequency EPR characterization of this narrow radical, reported in an accompanying paper, supports assignment to a new tyrosyl radical, NS1c, rather than an AA-based radical. To reconcile the results from EPR and NO-trapping studies, we propose that the NS1c is in equilibrium with an AA pentadienyl radical, and that the latter reacts preferentially with NO. PMID:21403766

Aggradation and degradation of alluvial sand deposits, 1965 to 1986, Colorado River, Grand Canyon National Park, Arizona

USGS Publications Warehouse

Schmidt, John C.; Graf, Julia B.

1990-01-01

Alluvial sand deposits along the Colorado River in Grand Canyon National Park are used as campsites and are substrate for vegetation. The largest and most numerous of these deposits are formed in zones of recirculating current that are created downstream from where the channel is constricted by debris fans at tributary mouths. Alluvial sand deposits are classified by location and form. Separation and reattachment deposits are downstream from constrictions within recirculation zones. Separation deposits are near the point of flow separation and typically mantle large debris fans. Reattachment deposits are near the point of flow reattachment and project upstream beneath much of the zone of recirculating current. Upper-pool deposits are upstream from a constriction and are associated with backwaters. Channel-margin deposits line the channel and have the form of terraces. Some are created in small recirculation zones. Reattachment and channel-margin deposits are largest and most numerous in wide reaches, although small channel-margin deposits are used as campsites in the narrow Muav Gorge. Separation deposits are more uniformly distributed throughout Grand Canyon National Park than are other types of deposits. In some narrow reaches where the number of alluvial sand deposits used as campsites is small, separation deposits are a high percentage of the total. During high flows, both separation and reattachment deposits are initially scoured but are subsequently redeposited during flow recession. Sand is also exchanged between the main channel and recirculation zones. The rate of recession of high flows can affect the elevation of alluvial deposits that are left exposed after a flood has passed. Fluctuating flows that follow a period of steady discharge cause initial erosion of separation and reattachment deposits. A part of this eroded sand is transported to the main channel. Therefore, sand is exchanged between the main channel and recirculation zones and redistributed within recirculation zones over a broad range of discharges. Comparison of aerial photographs and reinterpretation of published data concerning changes of alluvial sand deposits following recession of high flows in 1983 and 1984 indicate that sand was eroded from recirculation zones in narrow reaches. In wide reaches, however, aggradation in recirculation zones may have occurred. In narrow reaches, the decrease of reattachment deposits was greater than that of separation deposits. In all reaches, the percentage of separation deposits that maintained a constant area was greater than for other deposits. Separation deposits, therefore, appear to be the most stable of the deposit types. Fluctuating flows between October 1985 and January 1986, which followed the higher and steadier flows of 1983 to 1985, caused erosion throughout the park. For separation deposits, erosion was greatest at those sites where deposition from the 1983 high flows had been greatest. The existing pattern of low campsite availability in narrow reaches and high campsite availability in wide reaches was thus accentuated by the sequence of flows between 1983 and 1985.

Adaption of a microwave plasma source for low temperature diamond deposition

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

Ulczynski, M.; Reinhard, D.K.; Asmussen, J.

1996-12-31

This report describes the adaption of a microwave plasma reactor for low temperature diamond deposition. The reactor is of a resonant cavity design. Three approaches have been taken to establish plasma conditions for diamond deposition on substrates which are in the range of 450 C to 550 C. In the first, the substrate is heated only by the plasma and the source is operated at pressures on the order of 10 torr, such that the volumetric power density is sufficiently low to achieve these temperatures. In the second, the plasma pressure and microwave input power were reduced and a substratemore » heater was used to maintain the desired deposition temperatures. In the third approach, the plasma pressure and microwave power were increased and a substrate cooler was used to keep the substrate temperature in the desired range. Reactor performance and deposition results will be described for the three configurations. For the plasma heated substrate assembly, substrate dimensions were up to 10 cm diameter. For the heated and cooled substrate assemblies, substrate dimensions were up to 7.5 cm diameter. Deposition results on a variety of substrates will be reported including low-temperature substrates such as borosilicate glass.« less

Latent fingermark development on a range of porous substrates using ninhydrin analogs--a comparison with ninhydrin and 1,8-diazofluoren.

PubMed

Berdejo, Stephanie; Rowe, Mark; Bond, John W

2012-03-01

Three relatively new reagents for developing latent fingermarks on porous substrates, 1,2-indandione (IND), 5-methylthioninhydrin (5-MTN), and lawsone, are compared with the more widely used ninhydrin and 1,8-diazofluoren (DFO). Developed latent fingermark visualization on 10 different substrates comprising colored papers, cardboard, and cellophane rather than conventional printer and writing/notepad paper is assessed using latent fingermark deposits from 48 donors. Results show improved fluorescent fingermark visualization using IND compared with DFO on a range of colored cardboards and thick white paper, thus extending the range of substrates known to yield improved visualization with IND. Adding zinc chloride to IND failed to yield any further improvement in fluorescent fingermark visualization. 5-MTN (with and without zinc chloride posttreatment) showed no improvement in visualization compared with ninhydrin and DFO although visible fingermarks were developed. Lawsone produced fluorescent visible fingermarks only with white substrates, which were inferior to those produced with DFO. © 2011 American Academy of Forensic Sciences.

Discovery of a narrow line quasar

NASA Technical Reports Server (NTRS)

Stocke, J.; Liebert, J.; Maccacaro, T.; Griffiths, R. E.; Steiner, J. E.

1982-01-01

A stellar object is reported which, while having X-ray and optical luminosities typical of quasars, has narrow permitted and forbidden emission lines over the observed spectral range. The narrow-line spectrum is high-excitation, the Balmer lines seem to be recombinational, and a redder optical spectrum than that of most quasars is exhibited, despite detection as a weak radio source. The object does not conform to the relationships between H-beta parameters and X-ray flux previously claimed for a large sample of the active galactic nuclei. Because reddish quasars with narrow lines, such as the object identified, may not be found by the standard techniques for the discovery of quasars, the object may be a prototype of a new class of quasars analogous to high-luminosity Seyfert type 2 galaxies. It is suggested that these objects cannot comprise more than 10% of all quasars.

Dynamic film thickness between bubbles and wall in a narrow channel

NASA Astrophysics Data System (ADS)

Ito, Daisuke; Damsohn, Manuel; Prasser, Horst-Michael; Aritomi, Masanori

2011-09-01

The present paper describes a novel technique to characterize the behavior of the liquid film between gas bubbles and the wall in a narrow channel. The method is based on the electrical conductance. Two liquid film sensors are installed on both opposite walls in a narrow rectangular channel. The liquid film thickness underneath the gas bubbles is recorded by the first sensor, while the void fraction information is obtained by measuring the conductance between the pair of opposite sensors. Both measurements are taken on a large two-dimensional domain and with a high speed. This makes it possible to obtain the two-dimensional distribution of the dynamic liquid film between the bubbles and the wall. In this study, this method was applied to an air-water flow ranging from bubbly to churn regimes in the narrow channel with a gap width of 1.5 mm.

Perfect narrow band absorber for sensing applications.

PubMed

Luo, Shiwen; Zhao, Jun; Zuo, Duluo; Wang, Xinbing

2016-05-02

We design and numerically investigate a perfect narrow band absorber based on a metal-metal-dielectric-metal structure which consists of periodic metallic nanoribbon arrays. The absorber presents an ultra narrow absorption band of 1.11 nm with a nearly perfect absorption of over 99.9% in the infrared region. For oblique incidence, the absorber shows an absorption more than 95% for a wide range of incident angles from 0 to 50°. Structure parameters to the influence of the performance are investigated. The structure shows high sensing performance with a high sensitivity of 1170 nm/RIU and a large figure of merit of 1054. The proposed structure has great potential as a biosensor.

The safety of lumacaftor and ivacaftor for the treatment of cystic fibrosis.

PubMed

Talamo Guevara, Maria; McColley, Susanna A

2017-11-01

Lumacaftor-ivacaftor is indicated for treatment of cystic fibrosis (CF) in patients homozygous for the Phe-508del cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations. In clinical trials, treated patients showed improved pulmonary function, reduced pulmonary exacerbations, and other benefits. This article reviews safety of this therapy. Areas covered: Safety findings in ivacaftor, lumacaftor and combined therapy trials, and reported subsequently through post-approval evaluation, were accessed by PubMed and Google searches using key words 'VX-770', 'ivacaftor', 'VX-809', and 'lumacaftor'. Transaminitis was seen in ivacaftor and combination trials. Non-congenital cataracts were seen in pre-clinical animal studies and in children taking ivacaftor and combined therapy. Dyspnea occurs in some patients taking lumacaftor and combined therapy and usually resolves without stopping treatment. Lumacaftor is a strong inducer of CYP3A while ivacaftor is a CYP3A sensitive substrate. Combination therapy can decrease systemic exposure of medications that are substrates of CYP3A, decreasing therapeutic effect. Co-administration of lumacaftor-ivacaftor with sensitive CYP3A substrates or CYP3A substrates with narrow therapeutic index is not recommended. Expert opinion: Lumacaftor-ivacaftor therapy may be associated with ocular and hepatic side effects. Specific recommendations for monitoring are available. Dyspnea occurs, especially during initiation of treatment. Potential drug interactions should be evaluated in patients taking combination therapy. The risk benefit ratio of lumacaftor-ivacaftor favors therapy.

Interplay of catalysis, fidelity, threading, and processivity in the exo- and endonucleolytic reactions of human exonuclease I

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

Shi, Yuqian; Hellinga, Homme W.; Beese, Lorena S.

Human exonuclease 1 (hExo1) is a member of the RAD2/XPG structure-specific 5'-nuclease superfamily. Its dominant, processive 5'–3' exonuclease and secondary 5'-flap endonuclease activities participate in various DNA repair, recombination, and replication processes. A single active site processes both recessed ends and 5'-flap substrates. By initiating enzyme reactions in crystals, we have trapped hExo1 reaction intermediates that reveal structures of these substrates before and after their exo- and endonucleolytic cleavage, as well as structures of uncleaved, unthreaded, and partially threaded 5' flaps. Their distinctive 5' ends are accommodated by a small, mobile arch in the active site that binds recessed endsmore » at its base and threads 5' flaps through a narrow aperture within its interior. A sequence of successive, interlocking conformational changes guides the two substrate types into a shared reaction mechanism that catalyzes their cleavage by an elaborated variant of the two-metal, in-line hydrolysis mechanism. Coupling of substrate-dependent arch motions to transition-state stabilization suppresses inappropriate or premature cleavage, enhancing processing fidelity. The striking reduction in flap conformational entropy is catalyzed, in part, by arch motions and transient binding interactions between the flap and unprocessed DNA strand. At the end of the observed reaction sequence, hExo1 resets without relinquishing DNA binding, suggesting a structural basis for its processivity.« less

Interplay of catalysis, fidelity, threading, and processivity in the exo- and endonucleolytic reactions of human exonuclease I.

PubMed

Shi, Yuqian; Hellinga, Homme W; Beese, Lorena S

2017-06-06

Human exonuclease 1 (hExo1) is a member of the RAD2/XPG structure-specific 5'-nuclease superfamily. Its dominant, processive 5'-3' exonuclease and secondary 5'-flap endonuclease activities participate in various DNA repair, recombination, and replication processes. A single active site processes both recessed ends and 5'-flap substrates. By initiating enzyme reactions in crystals, we have trapped hExo1 reaction intermediates that reveal structures of these substrates before and after their exo- and endonucleolytic cleavage, as well as structures of uncleaved, unthreaded, and partially threaded 5' flaps. Their distinctive 5' ends are accommodated by a small, mobile arch in the active site that binds recessed ends at its base and threads 5' flaps through a narrow aperture within its interior. A sequence of successive, interlocking conformational changes guides the two substrate types into a shared reaction mechanism that catalyzes their cleavage by an elaborated variant of the two-metal, in-line hydrolysis mechanism. Coupling of substrate-dependent arch motions to transition-state stabilization suppresses inappropriate or premature cleavage, enhancing processing fidelity. The striking reduction in flap conformational entropy is catalyzed, in part, by arch motions and transient binding interactions between the flap and unprocessed DNA strand. At the end of the observed reaction sequence, hExo1 resets without relinquishing DNA binding, suggesting a structural basis for its processivity.

Highly Efficient Antibacterial Surfaces Based on Bacterial/Cell Size Selective Microporous Supports.

PubMed

Vargas-Alfredo, Nelson; Santos-Coquillat, Ana; Martínez-Campos, Enrique; Dorronsoro, Ane; Cortajarena, Aitziber L; Del Campo, Adolfo; Rodríguez-Hernández, Juan

2017-12-27

We report on the fabrication of efficient antibacterial substrates selective for bacteria, i.e., noncytotoxic against mammalian cells. The strategy proposed is based on the different size of bacteria (1-4 μm) in comparison with mammalian cells (above 20 μm) that permit the bacteria to enter in contact with the inner part of micrometer-sized pores where the antimicrobial functionality are placed. On the contrary, mammalian cells, larger in terms of size, remain at the top surface, thus reducing adverse cytotoxic effects and improving the biocompatibility of the substrates. For this purpose, we fabricated well-ordered functional microporous substrates (3-5 μm) using the breath figures approach that enabled the selective functionalization of the pore cavity, whereas the rest of the surface remained unaffected. Microporous surfaces were prepared from polymer blends comprising a homopolymer (i.e., polystyrene) and a block copolymer (either polystyrene-b-poly(dimethylaminoethyl methacrylate) (PDMAEMA) or a quaternized polystyrene-b-poly(dimethylaminoethyl methacrylate)). As a result, porous surfaces with a narrow size distribution and a clear enrichment of the PDMAEMA or the quaternized PDMAEMA block inside the pores were obtained that, in the case of the quaternized PDMAEMA, provided an excellent antimicrobial activity to the films.

Selective Binding, Self-Assembly and Nanopatterning of the Creutz-Taube Ion on Surfaces

PubMed Central

Wang, Yuliang; Lieberman, Marya; Hang, Qingling; Bernstein, Gary

2009-01-01

The surface attachment properties of the Creutz-Taube ion, i.e., [(NH3)5Ru(pyrazine)Ru(NH3)5]5+, on both hydrophilic and hydrophobic types of surfaces were investigated using X-ray photoelectron spectroscopy (XPS). The results indicated that the Creutz-Taube ions only bound to hydrophilic surfaces, such as SiO2 and –OH terminated organic SAMs on gold substrates. No attachment of the ions on hydrophobic surfaces such as –CH3 terminated organic SAMs and poly(methylmethacrylate) (PMMA) thin films covered gold or SiO2 substrates was observed. Further ellipsometric, atomic force microscopy (AFM) and time-dependent XPS studies suggested that the attached cations could form an inorganic analog of the self-assembled monolayer on SiO2 substrate with a “lying-down” orientation. The strong electrostatic interaction between the highly charged cations and the anionic SiO2 surface was believed to account for these observations. Based on its selective binding property, patterning of wide (∼200 nm) and narrow (∼35 nm) lines of the Creutz-Taube ions on SiO2 surface were demonstrated through PMMA electron resist masks written by electron beam lithography (EBL). PMID:19333420

Clinical evaluation of P-glycoprotein inhibition by venetoclax: a drug interaction study with digoxin.

PubMed

Chiney, Manoj S; Menon, Rajeev M; Bueno, Orlando F; Tong, Bo; Salem, Ahmed Hamed

2018-09-01

1. Venetoclax is a novel, small molecule B-cell lymphoma-2 (BCL-2) inhibitor that has demonstrated clinical efficacy in a variety of haematological malignancies. Since venetoclax is an inhibitor of P glycoprotein (P-gp) transporter, a study was conducted in healthy, female volunteers to evaluate the effect of venetoclax on the pharmacokinetics of digoxin, a P-gp probe substrate. 2. Volunteers received a single oral dose of digoxin (0.5 mg) with or without a single oral dose of venetoclax (100  mg). Serial blood samples were obtained for pharmacokinetic assessments of digoxin and venetoclax and serial urine samples were obtained for measurement of digoxin concentrations. Safety was assessed throughout the study. 3. Coadministration of digoxin and venetoclax increased digoxin maximum observed plasma concentration (C max ) by 35% and area under the plasma-concentration time curve (AUC 0-∞) by 9%. Digoxin half-life, renal clearance and the fraction excreted unchanged in urine remained relatively similar. The results of this study indicate that venetoclax can increase the concentrations of P-gp substrates. Narrow therapeutic index P-gp substrates should be administered six hours prior to venetoclax to minimise the potential interaction.

Optical properties of nanocrystalline Y2O3 thin films grown on quartz substrates by electron beam deposition

NASA Astrophysics Data System (ADS)

Wiktorczyk, Tadeusz; Biegański, Piotr; Serafińczuk, Jarosław

2016-09-01

Yttrium oxide thin films of a thickness 221-341 nm were formed onto quartz substrates by reactive physical vapor deposition in an oxygen atmosphere. An electron beam gun was applied as a deposition source. The effect of substrate temperature during film deposition (in the range of 323-673 K) on film structure, surface morphology and optical properties was investigated. The surface morphology studies (with atomic force microscopy and diffuse spectra reflectivity) show that the film surface was relatively smooth with RMS surface roughness in the range of 1.7-3.8 nm. XRD analysis has revealed that all diffraction lines belong to a cubic Y2O3 structure. The films consisted of small nanocrystals. Their average grain size increases from 1.6 nm to 22 nm, with substrate temperature rising from 323 K to 673 K. Optical examinations of transmittance and reflectance were performed in the spectral range of 0.2-2.5 μm. Optical constants and their dispersion curves were determined. Values of the refractive index of the films were in the range of n = 1.79-1.90 (at 0.55 μm) for substrate temperature during film deposition of 323-673 K. The changes in the refractive index upon substrate temperature correspond very well with the increase in the nanocrystals grain diameter and with film porosity.

Anisotropy of Seebeck coefficient in Si/Ge composite quantum dots

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

Hsin, Cheng-Lun, E-mail: clhsin@ee.ncu.edu.tw; Tsai, Yue-Yun; Lee, Sheng-Wei

2016-08-22

In this report, Si{sub 5}Ge{sub 5} alloy and Si/Ge composite quantum dots (CQDs) layers were grown on Si substrates. Seebeck coefficient (S) of Si and Ge wafers, as well as these two samples, were patterned and measured from 60 to 180 °C in [110] and [010] directions. For Si, Ge, and Si{sub 5}Ge{sub 5}, the S of each is a constant in this temperature range. However, the S of the CQDs at 60–80 °C is anomalous and much higher than the others. The behavior of the voltage difference is linear to the temperature difference even as large as 50 °C, except for CQDsmore » at 60–80 °C. This result indicates that a narrow distribution of carriers energy with a sharp change in density of state near Fermi-level and selective carrier scattering in the miniband at Si/Ge interface make the discrepancy of charge transport enhanced. The CQDs can be a good candidate for temperature sensing and thermoelectric applications due to their high S and low thermal conductivity near room temperature.« less

The N-terminus of glycogen phosphorylase b is not required for activation by adenosine 5'-monophosphate.

PubMed

Bigley, Andrew N; Reinhart, Gregory D

2010-06-15

The, so far unsuccessful, search for selective effective inhibitors of glycogen phosphorylase for the treatment of type II diabetes has made phosphorylase an active target of research for the past 20 years. Many crystallographic structures of phosphorylase are currently available to aid in this research. However, those structures have been interpreted, at least in part, on the basis of work conducted with a proteolytically derived form of phosphorylase that lacked the N-terminus (phosphorylase b'). It has been reported that phosphorylase b' shows no allostery, neither homotropic nor heterotropic. The original report on phosphorylase b' examined the allosteric characteristics over very narrow ranges of effector and substrate concentrations and reported the presence of proteolytic cleavages in addition to the removal of the N-terminus. We have applied molecular biological techniques to generate a truncate lacking the N-terminus with known primary structure, and we have established conditions for fully quantifying the allosteric effect of AMP on glycogen phosphorylase b. We report here for the first time the full thermodynamic effect of AMP on phosphorylase b. Our findings with a truncate lacking the N-terminus show that the effect of AMP binding does not depend on the N-terminus.

Reconstruction of perfect ZnO nanowires facets with high optical quality

NASA Astrophysics Data System (ADS)

Zehani, E.; Hassani, S.; Lusson, A.; Vigneron, J.; Etcheberry, A.; Galtier, P.; Sallet, V.

2017-07-01

ZnO nanowires were grown on sapphire substrates using metalorganic chemical vapor deposition. The samples were subsequently annealed under zinc pressure in a vacuum-sealed ampoule, at temperature ranging from 500 to 800 °C. The originality and the main motivation to provide a zinc-rich atmosphere were to prevent the out-diffusion of zinc from the nanowires. In doing so, the perfect structural properties and the morphology of the nanowires are kept. Interestingly, photoluminescence experiments performed on nanowires annealed in a narrow window of temperature [580-620 °C] show a spectacular improvement of the optical quality, as transitions commonly observable in high quality bulk samples are found. In addition, the intensity of the so-called "surface excitons" (SX) is strongly decreased. To accurately investigate the chemical modifications of the surface, XPS experiments were carried out and show that zinc hydroxide species and/or Zn(OH)2 sublayer were partially removed from the surface. These results suggest that the annealing process in zinc vapor helps to properly reconstruct the surface of ZnO nanowires, and improves the optical quality of their core. Such a thermal treatment at moderate temperature should be beneficial to nanodevices involving surface reaction, e.g. gas sensors.

Synthesis and electronic properties of Ruddlesden-Popper strontium iridate epitaxial thin films stabilized by control of growth kinetics

NASA Astrophysics Data System (ADS)

Liu, Xiaoran; Cao, Yanwei; Pal, B.; Middey, S.; Kareev, M.; Choi, Y.; Shafer, P.; Haskel, D.; Arenholz, E.; Chakhalian, J.

2017-12-01

We report on the selective fabrication of high-quality Sr2IrO4 and SrIrO3 epitaxial thin films from a single polycrystalline Sr2IrO4 target by pulsed laser deposition. Using a combination of x-ray diffraction and photoemission spectroscopy characterizations, we discover that within a relatively narrow range of substrate temperature, the oxygen partial pressure plays a critical role in the cation stoichiometric ratio of the films, and triggers the stabilization of different Ruddlesden-Popper (RP) phases. Resonant x-ray absorption spectroscopy measurements taken at the Ir L edge and the O K edge demonstrate the presence of strong spin-orbit coupling, and reveal the electronic and orbital structures of both compounds. These results suggest that in addition to the conventional thermodynamics consideration, higher members of the Srn +1IrnO3 n +1 series can possibly be achieved by kinetic control away from the thermodynamic limit. These findings offer an approach to the synthesis of ultrathin films of the RP series of iridates and can be extended to other complex oxides with layered structure.

Synthesis and electronic properties of Ruddlesden-Popper strontium iridate epitaxial thin films stabilized by control of growth kinetics

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

Liu, Xiaoran; Cao, Yanwei; Pal, B.

2017-12-01

We report on the selective fabrication of high-quality Sr2IrO4 and SrIrO3 epitaxial thin films from a single polycrystalline Sr2IrO4 target by pulsed laser deposition. Using a combination of x-ray diffraction and photoemission spectroscopy characterizations, we discover that within a relatively narrow range of substrate temperature, the oxygen partial pressure plays a critical role in the cation stoichiometric ratio of the films, and triggers the stabilization of different Ruddlesden-Popper (RP) phases. Resonant x-ray absorption spectroscopy measurements taken at the Ir L edge and the O K edge demonstrate the presence of strong spin-orbit coupling, and reveal the electronic and orbital structuresmore » of both compounds. These results suggest that in addition to the conventional thermodynamics consideration, higher members of the Srn+1IrnO3n+1 series can possibly be achieved by kinetic control away from the thermodynamic limit. These findings offer an approach to the synthesis of ultrathin films of the RP series of iridates and can be extended to other complex oxides with layered structure.« less

Periodic domain boundary ordering in a dense molecular adlayer: Sub-saturation carbon monoxide on Pd(111)

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

Xu, Pan; Liu, Shizhong; Hong, Sung -Young

Here, we describe a previously unreported ordered phase of carbon monoxide adsorbed on the (111) facet of single crystal palladium at near-saturation coverage. The adlayer superstructure is identified from low energy electron diffraction to be c(16×2) with respect to the underlying Pd(111) surface net. The ideal coverage is determined to be 0.6875 ML, approximately 92% of the 0.75–ML saturation coverage. Density functional theory calculations support a model for the molecular packing characterized by strips of locally-saturated (2×2) regions, with the CO bound near high-symmetry surface sites, separated by antiphase domain boundaries. The structure exists in a narrow coverage range andmore » is prepared by heating the saturated adlayer to desorb a small fraction of the CO. Comparison of the c(16×2) domain-boundary structure with structural motifs at lower coverages suggests that between 0.6 and 0.6875 ML the adlayer order may be more strongly influenced by interadsorbate repulsion than by adsorption-site-specific interactions. The system is an example of the structural complexity that results from the compromise between adsorbate–substrate and adsorbate–adsorbate interactions.« less

Periodic domain boundary ordering in a dense molecular adlayer: Sub-saturation carbon monoxide on Pd(111)

DOE PAGES

Xu, Pan; Liu, Shizhong; Hong, Sung -Young; ...

2016-12-31

Here, we describe a previously unreported ordered phase of carbon monoxide adsorbed on the (111) facet of single crystal palladium at near-saturation coverage. The adlayer superstructure is identified from low energy electron diffraction to be c(16×2) with respect to the underlying Pd(111) surface net. The ideal coverage is determined to be 0.6875 ML, approximately 92% of the 0.75–ML saturation coverage. Density functional theory calculations support a model for the molecular packing characterized by strips of locally-saturated (2×2) regions, with the CO bound near high-symmetry surface sites, separated by antiphase domain boundaries. The structure exists in a narrow coverage range andmore » is prepared by heating the saturated adlayer to desorb a small fraction of the CO. Comparison of the c(16×2) domain-boundary structure with structural motifs at lower coverages suggests that between 0.6 and 0.6875 ML the adlayer order may be more strongly influenced by interadsorbate repulsion than by adsorption-site-specific interactions. The system is an example of the structural complexity that results from the compromise between adsorbate–substrate and adsorbate–adsorbate interactions.« less

Ceramic membrane by tape casting and sol-gel coating for microfiltration and ultrafiltration application

NASA Astrophysics Data System (ADS)

Das, Nandini; Maiti, H. S.

2009-11-01

Alumina membrane filters in the form of thin (0.3-0.8 mm) discs of 25-30 mm diameter suitable for microfiltration application have been fabricated by tape-casting technique. Further using this microfiltration membrane as substrate, boehmite sol coating was applied on it and ultrafiltration membrane with very small thickness was formed. The pore size of the microfiltration membrane could be varied in the range of 0.1-0.7 μm through optimisation of experimental parameter. In addition, each membrane shows a very narrow pore size distribution. The most important factor, which determines the pore size of the membrane, is the initial particle size and its distribution of the ceramic powder. The top thin ultrafiltration, boehmite layer was prepared by sol-gel method, with a thickness of 0.5 μm. Particle size of the sol was approximately 30-40 nm. The structure and formation of the layer was analysed through TEM. At 550 °C formation of the top layer was completed. The pore size of the ultrafiltration membrane measured from TEM micrograph was almost 10 nm. Results of microbial (Escherichia coli—smallest-sized water-borne bacteria) test confirm the possibility of separation through this membrane

Habitat associations of three crayfish endemic to the Ouachita Mountain Ecoregion

USGS Publications Warehouse

Dyer, Joseph J.; Brewer, Shannon K.

2018-01-01

Many crayfish are of conservation concern because of their use of unique habitats and often narrow ranges. In this study, we determined fine-scale habitat use by 3 crayfishes that are endemic to the Ouachita Mountains, in Oklahoma and Arkansas. We sampled Faxonius menae (Mena Crayfish), F. leptogonopodus (Little River Creek Crayfish), and Fallicambarus tenuis (Ouachita Mountain Crayfish) from wet and dry erosional channel units of 29 reaches within the Little River catchment. We compared channel-unit and microhabitat selection for each species. Crayfish of all species and life stages selected erosional channel units more often than depositional units, even though these sites were often dry. Accordingly, crayfish at all life stages typically selected the shallowest available microhabitats. Adult crayfish of all species and juvenile Little River Creek Crayfish selected patches of coarse substrate, and all crayfish tended to use the lowest amount of bedrock available. In general, we showed that these endemic crayfish used erosional channel units of streams, even when the channel units were dry. Conservation efforts that protect erosional channel units and mitigate actions that cause channel downcutting to bedrock would benefit these crayfish, particularly during harsh, summer drying periods.

Simultaneous high-resolution measurement of mitochondrial respiration and hydrogen peroxide production.

PubMed

Krumschnabel, Gerhard; Fontana-Ayoub, Mona; Sumbalova, Zuzana; Heidler, Juliana; Gauper, Kathrin; Fasching, Mario; Gnaiger, Erich

2015-01-01

Mitochondrial respiration is associated with the formation of reactive oxygen species, primarily in the form of superoxide (O2 (•-)) and particularly hydrogen peroxide (H2O2). Since H2O2 plays important roles in physiology and pathology, measurement of hydrogen peroxide has received considerable attention over many years. Here we describe how the well-established Amplex Red assay can be used to detect H2O2 production in combination with the simultaneous assessment of mitochondrial bioenergetics by high-resolution respirometry. Fundamental instrumental and methodological parameters were optimized for analysis of the effects of various substrate, uncoupler, and inhibitor titrations (SUIT) on respiration versus H2O2 production. The sensitivity of the H2O2 assay was strongly influenced by compounds contained in different mitochondrial respiration media, which also exerted significant effects on chemical background fluorescence changes. Near linearity of the fluorescence signal was restricted to narrow ranges of accumulating resorufin concentrations independent of the nature of mitochondrial respiration media. Finally, we show an application example using isolated mouse brain mitochondria as an experimental model for the simultaneous measurement of mitochondrial respiration and H2O2 production in SUIT protocols.

Kleptothermy: an additional category of thermoregulation, and a possible example in sea kraits (Laticauda laticaudata, Serpentes).

PubMed

Brischoux, François; Bonnet, Xavier; Shine, Richard

2009-12-23

Lacking the capacity for thermogenesis, most ectotherms inhabiting thermally heterogeneous environments rely instead upon exploiting that ambient heterogeneity. In many cases they maintain body temperatures within a narrow range despite massive spatial and temporal variation in ambient conditions. Reliance on diverse thermal opportunities is reflected in specific terms for organisms that bask in sunlight to regulate their temperature (heliotherms), or that press their bodies against warm substrates to facilitate heat flow (thigmotherms), or that rely on large body mass to maintain thermal constancy (gigantothermy). We propose an additional category of thermoregulators: kleptotherms, which regulate their own temperature by 'stealing' heat from other organisms. This concept involves two major conditions: the thermal heterogeneity created by the presence of a warm organism in a cool environment and the selective use of that heterogeneity by another animal to maintain body temperatures at higher (and more stable) levels than would be possible elsewhere in the local area. Kleptothermy occurs in endotherms also, but is usually reciprocal (rather than unilateral as in ectotherms). Thermal monitoring on a small tropical island documents a possible example of kleptothermy, based on high stable temperatures of a sea snake (Laticauda laticaudata) inside a burrow occupied by seabirds.

Variation in capture efficiency of a beach seine for small fishes

USGS Publications Warehouse

Parsley, M.J.; Palmer, D.E.; Burkhardt, R.W.

1989-01-01

We determined the capture efficiency of a beach seine as a means of improving abundance estimates of small fishes in littoral areas. Capture efficiency for 14 taxa (individual species or species groups) was determined by seining within an enclosure at night over fine and coarse substrates in the John Day Reservoir, Oregon–Washington. Mean efficiency ranged from 12% for prickly sculpin Cottus asper captured over coarse substrates to 96% for peamouth Mylocheilus caurinus captured over fine substrates. Mean capture efficiency for a taxon (genus or species) was generally higher over fine substrates than over coarse substrates, although mean capture efficiencies over fine substrates were significantly greater for only 3 of 10 taxa. Capture efficiency generally was not influenced by fish density or by water temperature (range, 8–26°C). Conclusions about the relative abundance of taxa captured by seining can change substantially after capture efficiencies are taken into account.

Preparation of CuIn{sub x}Ga{sub 1{minus}x}Se{sub 2} thin films on Si substrates

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

Yamamoto, Yukio; Yamaguchi, Toshiyuki; Suzuki, Masayoshi

For fabricating efficient tandem solar cells, CuIn{sub x}Ga{sub 1{minus}x}Se{sub 2} thin films have been prepared on Si(100), Si(110) and Si(111) substrates in the temperature range (R.T.{approximately}400 C) by rf sputtering. From EPMA analysis, these sputtered thin films are found to be nearly stoichiometric over the whole substrate temperature range, irrespective of the azimuth plane of the Si substrate. XPS studies showed that the compositional depth profile in these thin films is uniform. X-ray diffraction analysis indicated that all the thin films had a chalcopyrite structure. CuIn{sub x}Ga{sub 1{minus}x}Se{sub 2} thin films were strongly oriented along the (112) plane with increasingmore » the substrate temperature, independent of the azimuth plane of the Si substrate, suggesting the larger grain growth.« less

Phase behavior of mixtures of DPPC and POPG.

PubMed

Wiedmann, T; Salmon, A; Wong, V

1993-04-07

The phase relation of dipalmitoylphosphatidylcholine (DPPC) and 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG) has been determined by measurement of the endothermic transitions of mixtures of DPPC and POPG in 100 mM NaCl, 50 mM PIPES (pH 7.0). With the use of differential scanning calorimetry, the gel-liquid crystalline phase transitions of pure POPG and DPPC were estimated to be 274 K and 315.8 K, respectively. With mixtures, there was considerable broadening of the endotherms, but there was no evidence of immiscibility. At high and low mole fractions of DPPC, the observed transition regions are not different from that calculated assuming ideal behavior. However in the central region of the phase diagram, there were deviations from both the ideal liquidus and solidus curves. The chemical shift anisotropy of the 13C-labelled carbonyl carbon of pure DPPC was determined as a function of temperature. At 298 K, a broad peak characteristic of axially symmetric motional averaging of the shielding tensor was observed. At a temperature of 300 K, a narrow peak at 173 ppm was superimposed upon the broad peak. The magnitude of the narrow resonance increased with temperature over the range of 300 to 315 K with the spectrum obtained at the latter point almost completely devoid of any broad features. Spectra obtained with a 9:1 mole ratio of DPPC/POPG was very similar to that obtained with pure DPPC. However, with increasing amounts of POPG, both the temperature at which the narrow resonance appeared and the temperature at which only a narrow resonance was observed were reduced. Over the range of 0 to 50 mol % POPG, there was no major change in the width or shape of the spectra which contained only a broad or narrow resonance. Also for mol % of POPG of 20% and less, there was agreement between the temperature at which only the narrow component was observed and the completion of the main phase transition based on the DSC scans. However, at the two higher mol % of 33 and 50%, the temperature at which only the narrow component was observed was lower than the temperature established for the completion of the main phase transition.

Black holes, disks, and jets following binary mergers and stellar collapse: The narrow range of electromagnetic luminosities and accretion rates.

PubMed

Shapiro, Stuart L

2017-05-15

We have performed magnetohydrodynamic simulations in general relativity of binary neutron star and binary black hole-neutron star mergers, as well as the magnetorotational collapse of supermassive stars. In many cases the outcome is a spinnng black hole (BH) immersed in a magnetized disk, with a jet emanating from the poles of the BH. While their formation scenarios differ and their BH masses, as well as their disk masses, densities, and magnetic field strengths, vary by orders of magnitude, these features conspire to generate jet Poynting luminosities that all lie in the same, narrow range of ~10 52±1 erg s -1 . A similar result applies to their BH accretion rates upon jet launch, which is ~0.1-10 M ⊙ s -1 . We provide a simple model that explains these unanticipated findings. Interestingly, these luminosities reside in the same narrow range characterizing the observed luminosity distributions of over 400 short and long GRBs with distances inferred from spectroscopic redshifts or host galaxies. This result, together with the GRB lifetimes predicted by the model, supports the belief that a compact binary merger is the progenitor of an SGRB, while a massive, stellar magnetorotational collapse is the progenitor of an LGRB.

Black holes, disks, and jets following binary mergers and stellar collapse: The narrow range of electromagnetic luminosities and accretion rates

PubMed Central

Shapiro, Stuart L.

2018-01-01

We have performed magnetohydrodynamic simulations in general relativity of binary neutron star and binary black hole-neutron star mergers, as well as the magnetorotational collapse of supermassive stars. In many cases the outcome is a spinnng black hole (BH) immersed in a magnetized disk, with a jet emanating from the poles of the BH. While their formation scenarios differ and their BH masses, as well as their disk masses, densities, and magnetic field strengths, vary by orders of magnitude, these features conspire to generate jet Poynting luminosities that all lie in the same, narrow range of ~1052±1 erg s−1. A similar result applies to their BH accretion rates upon jet launch, which is ~0.1–10 M⊙ s−1. We provide a simple model that explains these unanticipated findings. Interestingly, these luminosities reside in the same narrow range characterizing the observed luminosity distributions of over 400 short and long GRBs with distances inferred from spectroscopic redshifts or host galaxies. This result, together with the GRB lifetimes predicted by the model, supports the belief that a compact binary merger is the progenitor of an SGRB, while a massive, stellar magnetorotational collapse is the progenitor of an LGRB. PMID:29881790

Bio-inspired in situ growth of monolayer silver nanoparticles on graphene oxide paper as multifunctional substrate

NASA Astrophysics Data System (ADS)

Li, Shi-Kuo; Yan, You-Xian; Wang, Jin-Long; Yu, Shu-Hong

2013-11-01

In this study, we report a facile bio-inspired method for large-scale preparation of highly dispersed Ag nanoparticles (NPs) on the surface of flexible reduced graphene oxide (rGO) paper with using dopamine (DA) both as a reductant and a surface modifier. Through the self-polymerization of dopamine, free-standing GO paper can be simultaneously reduced and modified with following in situ growth of monolayer Ag NPs on such a substrate. The spherical Ag NPs with an average diameter of 80 nm have a narrow size distribution and tunable cover density. Such a flexible rGO/Ag hybrid paper presents enhanced antibacterial activity against E. coli and a high active and sensitive SERS response toward Rhodamine 6G (R6G) molecules. The detection signals can be obtained while the R6G concentration is as low as to 10-8 M. This work provides a simple strategy for large-scale fabrication of monolayer Ag NPs on flexible rGO paper as a portable antibacterial substrate and a potential SERS substrate for molecular detection applications.In this study, we report a facile bio-inspired method for large-scale preparation of highly dispersed Ag nanoparticles (NPs) on the surface of flexible reduced graphene oxide (rGO) paper with using dopamine (DA) both as a reductant and a surface modifier. Through the self-polymerization of dopamine, free-standing GO paper can be simultaneously reduced and modified with following in situ growth of monolayer Ag NPs on such a substrate. The spherical Ag NPs with an average diameter of 80 nm have a narrow size distribution and tunable cover density. Such a flexible rGO/Ag hybrid paper presents enhanced antibacterial activity against E. coli and a high active and sensitive SERS response toward Rhodamine 6G (R6G) molecules. The detection signals can be obtained while the R6G concentration is as low as to 10-8 M. This work provides a simple strategy for large-scale fabrication of monolayer Ag NPs on flexible rGO paper as a portable antibacterial substrate and a potential SERS substrate for molecular detection applications. Electronic supplementary information (ESI) available: Preparation of GO aqueous colloid solution; XPS spectra of GO paper and PDA modified rGO paper; SEM images of rGO/Ag hybrid paper after immersed in mercaptoethanol solution or in high alkaline solution; photograph and SEM image of pure rGO paper after reaction with AgNO3 solution. SEM image and TEM graph of the pre-synthesized Ag NPs and their SEM images incubated with PDA modified rGO paper; SERS spectra of R6G (1.0 × 10-4 M) molecules before and after cleaning with concentrated hydrochloric acid liquid taken on rGO/Ag hybrid paper obtained by a reaction with 1.0 M AgNO3 solution; SERS spectra of R6G (1.0 × 10-4 M) molecules with different reusable cycles taken on rGO/Ag hybrid paper obtained by a reaction with 1.0 M AgNO3 solution; comparison between different kinds of substrates with the detection limit toward R6G. See DOI: 10.1039/c3nr03857b

Improved pulse laser ranging algorithm based on high speed sampling

NASA Astrophysics Data System (ADS)

Gao, Xuan-yi; Qian, Rui-hai; Zhang, Yan-mei; Li, Huan; Guo, Hai-chao; He, Shi-jie; Guo, Xiao-kang

2016-10-01

Narrow pulse laser ranging achieves long-range target detection using laser pulse with low divergent beams. Pulse laser ranging is widely used in military, industrial, civil, engineering and transportation field. In this paper, an improved narrow pulse laser ranging algorithm is studied based on the high speed sampling. Firstly, theoretical simulation models have been built and analyzed including the laser emission and pulse laser ranging algorithm. An improved pulse ranging algorithm is developed. This new algorithm combines the matched filter algorithm and the constant fraction discrimination (CFD) algorithm. After the algorithm simulation, a laser ranging hardware system is set up to implement the improved algorithm. The laser ranging hardware system includes a laser diode, a laser detector and a high sample rate data logging circuit. Subsequently, using Verilog HDL language, the improved algorithm is implemented in the FPGA chip based on fusion of the matched filter algorithm and the CFD algorithm. Finally, the laser ranging experiment is carried out to test the improved algorithm ranging performance comparing to the matched filter algorithm and the CFD algorithm using the laser ranging hardware system. The test analysis result demonstrates that the laser ranging hardware system realized the high speed processing and high speed sampling data transmission. The algorithm analysis result presents that the improved algorithm achieves 0.3m distance ranging precision. The improved algorithm analysis result meets the expected effect, which is consistent with the theoretical simulation.

Detection of electromagnetic radiation using nonlinear materials

DOEpatents

Hwang, Harold Y.; Liu, Mengkun; Averitt, Richard D.; Nelson, Keith A.; Sternbach, Aaron; Fan, Kebin

2016-06-14

An apparatus for detecting electromagnetic radiation within a target frequency range is provided. The apparatus includes a substrate and one or more resonator structures disposed on the substrate. The substrate can be a dielectric or semiconductor material. Each of the one or more resonator structures has at least one dimension that is less than the wavelength of target electromagnetic radiation within the target frequency range, and each of the resonator structures includes at least two conductive structures separated by a spacing. Charge carriers are induced in the substrate near the spacing when the resonator structures are exposed to the target electromagnetic radiation. A measure of the change in conductivity of the substrate due to the induced charge carriers provides an indication of the presence of the target electromagnetic radiation.

Effect of ferromagnetic exchange field on band gap and spin polarisation of graphene on a TMD substrate

NASA Astrophysics Data System (ADS)

Goswami, Partha

2018-03-01

We calculate the electronic band dispersion of graphene monolayer on a two-dimensional transition metal dichalcogenide substrate (GrTMD) around K and K^' } points by taking into account the interplay of the ferromagnetic impurities and the substrate-induced interactions. The latter are (strongly enhanced) intrinsic spin-orbit interaction (SOI), the extrinsic Rashba spin-orbit interaction (RSOI) and the one related to the transfer of the electronic charge from graphene to substrate. We introduce exchange field ( M) in the Hamiltonian to take into account the deposition of magnetic impurities on the graphene surface. The cavalcade of the perturbations yield particle-hole symmetric band dispersion with an effective Zeeman field due to the interplay of the substrate-induced interactions with RSOI as the prime player. Our graphical analysis with extremely low-lying states strongly suggests the following: The GrTMDs, such as graphene on WY2, exhibit (direct) band-gap narrowing / widening (Moss-Burstein (MB) gap shift) including the increase in spin polarisation ( P) at low temperature due to the increase in the exchange field ( M) at the Dirac points. The polarisation is found to be electric field tunable as well. Finally, there is anticrossing of non-parabolic bands with opposite spins, the gap closing with same spins, etc. around the Dirac points. A direct electric field control of magnetism at the nanoscale is needed here. The magnetic multiferroics, like BiFeO3 (BFO), are useful for this purpose due to the coupling between the magnetic and electric order parameters.

Nutritive quality and protein production from grain legumes in a boreal climate.

PubMed

Lizarazo, Clara I; Lampi, Anna-Maija; Liu, Jingwei; Sontag-Strohm, Tuula; Piironen, Vieno; Stoddard, Frederick L

2015-08-15

Boreal cropping systems are heavily focused on the production of small-grain cereals; to improve their resilience to climate change and to achieve food and feed security, diversification is needed. This study investigated the potential of faba bean, narrow-leafed lupin and lentil as protein crops in southern Finland, where faba bean is traditional but the other two are novel. Early cultivars of narrow-leafed lupin and lentil matured adequately. Protein concentration in faba bean was, at 32%, higher than the world average of 29%, while those of narrow-leafed lupin and lentil were close to their world averages. Protein yields decreased in the order faba bean > narrow-leafed lupin > lentil. Lipid content of faba bean and lentil was about 1.2% and that of narrow-leafed lupin about 5.5%, and fatty acid composition was largely oleic and linoleic in all three species. Both lentil and narrow-leafed lupin can be added to the range of feed and food crops produced at high latitudes in Europe. While faba bean produces the greatest protein yield and lysine concentration, the higher sulfur amino acid concentration in lupin, its oil content and its adaptation to acid, sandy soils not suitable for faba bean make it an attractive alternative. © 2014 Society of Chemical Industry.

Reducing uncertainty in species sensitivity distributions with interspecies toxicity estimation models

EPA Science Inventory

Determining harmful levels of contaminants for a wide range of species is limited by available toxicological data. Ecological risk assessments typically depend on empirical data from only a few species that represent a narrow range of the life history spectrum. Extrapolation mo...

Application of Methods of Numerical Analysis to Physical and Engineering Data.

DTIC Science & Technology

1980-10-15

directed algorithm would seem to be called for. However, 1(0) is itself a random process, making its gradient too unreliable for such a sensitive algorithm...radiation energy on the detector . Active laser systems, on the other hand, have created now the possibility for extremely narrow path band systems...emitted by the earth and its atmosphere. The broad spectral range was selected so that the field of view of the detector could be narrowed to obtain

Scopolin-hydrolyzing beta-glucosidases in roots of Arabidopsis.

PubMed

Ahn, Young Ock; Shimizu, Bun-ichi; Sakata, Kanzo; Gantulga, Dashzeveg; Zhou, Changhe; Zhou, Zhanghe; Bevan, David R; Esen, Asim

2010-01-01

Three beta-glucosidases (At1g66270-BGLU21, At1g66280-BGLU22, and At3g09260-BGLU23) were purified from the roots of Arabidopsis and their cDNAs were expressed in insect cells. In addition, two beta-glucosidase binding protein cDNAs (At3g16420; PBPI and At3g16430; PBPII) were expressed in Escherichia coli and their protein products purified. These binding proteins interact with beta-glucosidases and activate them. BGLU21, 22 and 23 hydrolyzed the natural substrate scopolin specifically and also hydrolyzed to some extent substrates whose aglycone moiety is similar to scopolin (e.g. esculin and 4-MU-glucoside). In contrast, they hydrolyzed poorly DIMBOA-glucoside and did not hydrolyze pNP- and oNP-glucosides. We determined the physicochemical properties of native and recombinant BGLUs, and found no differences between them. They were stable in a narrow pH range (5-7.5) and had temperature and pH optima for activity at 35 degrees C and pH 5.5, respectively. As for thermostability, >95% of their activity was retained at 40 degrees C but dramatically decreased at >50 degrees C. The apparent K(m) of native and recombinant enzymes for scopolin was 0.73 and 0.81 mM, respectively, and it was 5.8 and 9.7 mM, respectively, for esculin. Western blot analysis showed that all three enzymes were exclusively expressed in roots of seedlings but not in any other plant part or organ under normal conditions. Furthermore, spatial expression patterns of all eight genes belonging to subfamily 3 were investigated at the transcription level by RT-PCR.

A NEW MODEL OF PODIAL DEPOSIT FEEDING IN THE SAND DOLLAR, MELLITA QUINQUJESPERFORATA (LESKE): THE SIEVE HYPOTHESIS CHALLENGED.

PubMed

Telford, Malcolm; Mooi, Rich; Ellers, Olaf

1985-10-01

The feeding mechanism of Mellita quinquiesperforata (Leske) has been examined in detail. This sand dollar is a deposit feeder, ingesting particles mostly in the range of 100-250 µm. The particles are picked out of the substrate individually by specialized long barrel-tipped podia, which form a narrow palisade surrounding the geniculate spine fields on the oral surface. Selected food items are passed to short barrel-tipped podia, thence from podium to podium until they reach the food grooves where they are finally aggregated into mucus cords. The cords are passed to the mouth by the activity of food groove podia. At the peristome, the cord is passed between the circumoral spines by large food groove podia and steered into the mouth by five pairs of buccal podia. The lantern is powerfully muscled and has hardened teeth which crush diatoms and fracture many sand grains. For this reason, there is an apparent accumulation of fine particles (<50 µm) in the gut. Analysis of size frequencies of the material in the mucus cords and substrate indicates that no selection of fine particles occurs and, in fact, that they are virtually absent from the native sediment. An account of spine and podial morphology and distribution is included with descriptions and measurements of surface ciliary currents. It is shown that the formerly accepted sieve hypothesis of feeding cannot be entirely rejected on theoretical grounds. However, during feeding there was no evidence of the operation of any of the elements of the supposed sieve mechanism. Furthermore, the ciliary currents are not fast enough to account for the movement of most ingested material. Patterns of ciliary flow on the oral surface are not simply centripetal, but are much more complex than previously supposed.

Customized broadband sloan-filters for the JST/T250 and JAST/T80 telescopes: summary of results

NASA Astrophysics Data System (ADS)

Brauneck, U.; Sprengard, R.; Bourquin, S.; Marín-Franch, A.

2017-09-01

The Centro de Estudios de Fisica del Cosmos de Aragon (CEFCA) will conduct a photometric sky survey with 2 new telescopes recently setup on the Javalambre mountain in Spain: the JST/T250 is a 2.55m telescope with a plate scale of 22.67"/mm and a 3° diameter field of view (FoV) and the auxiliary telescope JAST/T80 with a 82cm primary mirror and a FoV of 2 deg diameter. A multiple CCD (9k-by-9k array size, 10μm pixel size) mosaic camera is used in combination with filter trays or filter wheels, each containing a multitude of filters in dimensions of 101.7x96.5mm or 106.8x106.8mm. For this project, SCHOTT manufactured 56 specially designed narrow band steep edged bandpass interference filters and 5 broadband sloan-filters which were completed only recently. We report here on the results of the broadband sloanfilters with transmission bands of 324-400nm (sloan-u), 400-550nm (sloan-g), 550-700nm (sloan-r), 695-850nm (sloan-i) and 830-1200nm (sloan-z). The filters are composed of SCHOTT filterglasses and clearglass substrates coated with interference filters and represent an improvement of broadband sloan filters commonly used in astronomy. Inspite of the absorptive elements, the filters show maximum possible transmissions achieved by magnetron sputtered filter coatings. In addition the blocking of the filters is better than OD5 in the range 250-1050nm. A high image quality required a low transmitted wavefront error (<λ/8 locally, respectively <λ/2 globally) which was achieved by combining up to 2 substrates. We report on the spectral and interferometric results measured on the filters.

ASSESSMENT OF LOW-FREQUENCY HEARING WITH NARROW-BAND CHIRP EVOKED 40-HZ SINUSOIDAL AUDITORY STEADY STATE RESPONSE

PubMed Central

Wilson, Uzma S.; Kaf, Wafaa A.; Danesh, Ali A.; Lichtenhan, Jeffery T.

2016-01-01

Objective To determine the clinical utility of narrow-band chirp evoked 40-Hz sinusoidal auditory steady state responses (s-ASSR) in the assessment of low-frequency hearing in noisy participants. Design Tone bursts and narrow-band chirps were used to respectively evoke auditory brainstem responses (tb-ABR) and 40-Hz s-ASSR thresholds with the Kalman-weighted filtering technique and were compared to behavioral thresholds at 500, 2000, and 4000 Hz. A repeated measure ANOVA and post-hoc t-tests, and simple regression analyses were performed for each of the three stimulus frequencies. Study Sample Thirty young adults aged 18–25 with normal hearing participated in this study. Results When 4000 equivalent responses averages were used, the range of mean s-ASSR thresholds from 500, 2000, and 4000 Hz were 17–22 dB lower (better) than when 2000 averages were used. The range of mean tb-ABR thresholds were lower by 11–15 dB for 2000 and 4000 Hz when twice as many equivalent response averages were used, while mean tb-ABR thresholds for 500 Hz were indistinguishable regardless of additional response averaging Conclusion Narrow band chirp evoked 40-Hz s-ASSR requires a ~15 dB smaller correction factor than tb-ABR for estimating low-frequency auditory threshold in noisy participants when adequate response averaging is used. PMID:26795555

Band gap narrowing in BaTiO{sub 3} nanoparticles facilitated by multiple mechanisms

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

Ramakanth, S.; James Raju, K. C., E-mail: kcjrsp@uohyd.ernet.in; School of Physics, University of Hyderabad, Hyderabad 500046

2014-05-07

In the present work, BaTiO{sub 3} nanoparticles of four different size ranges were prepared by sol-gel method. The optical band gap of these particles at some size ranges has come down to 2.53 eV from 3.2 eV, resulting in substantial increase in optical absorption by these ferroelectric nanoparticles making them potential candidates for light energy harvesting. XRD results show the presence of higher compressive strain in 23 nm and 54 nm size particles, they exhibit a higher band gap narrowing, whereas tensile strain is observed in 31 nm and 34 nm particles, and they do not show the marginal band gap narrowing. The 23 nm and 54 nmmore » particles also show a coupling of free carriers to phonons by increasing the intensity of LO phonon mode at 715 cm{sup −1}. The higher surface charge density is expected in case of enhanced surface optical Raman modes (638 cm{sup −1}) contained in 31 and 34 nm size particles. In addition to this, the red shift in an LO mode Raman spectral line at 305 cm{sup −1} with decrease in particle size depicts the presence of phonon confinement in it. The enhanced optical absorption in 23 nm and 54 nm size particles with a narrowed band gap of 3 eV and 2.53 eV is due to exchange correlation interactions between the carriers present in these particles. In 31 nm and 34 nm range particles, the absorption got bleached exhibiting increased band gaps of 3.08 eV and 3.2 eV, respectively. It is due to filling up of conduction band resulting from weakening of exchange correlation interactions between the charge carriers. Hence, it is concluded that the band gap narrowing in the nanoparticles of average size 23 nm/54 nm is a consequence of multiple effects like strain, electron-phonon interaction, and exchange correlation interactions between the carriers which is subdued in some other size ranges like 31 nm/34 nm.« less

Generation and oxidation of aerosol deposited PdAg nanoparticles

NASA Astrophysics Data System (ADS)

Blomberg, S.; Gustafson, J.; Martin, N. M.; Messing, M. E.; Deppert, K.; Liu, Z.; Chang, R.; Fernandes, V. R.; Borg, A.; Grönbeck, H.; Lundgren, E.

2013-10-01

PdAg nanoparticles with a diameter of 10 nm have been generated by an aerosol particle method, and supported on a silica substrate. By using a combination of X-ray Energy Dispersive Spectroscopy and X-ray Photoelectron Spectroscopy it is shown that the size distribution of the particles is narrow and that the two metals form an alloy with a mixture of 75% Pd and 25% Ag. Under oxidizing conditions, Pd is found to segregate to the surface and a thin PdO like oxide is formed similar to the surface oxide previously reported on extended PdAg and pure Pd surfaces.

Field effect transistor and method of construction thereof

NASA Technical Reports Server (NTRS)

Fletner, W. R. (Inventor)

1978-01-01

A field effect transistor is constructed by placing a semi-conductor layer on an insulating substrate so that the gate region is separated from source and drain regions. The gate electrode and gate region of the layer are of generally reduced length, the gate region being of greatest length on its surface closest to the gate electrode. This is accomplished by initially creating a relatively large gate region of one polarity, and then reversing the polarity of a central portion of this gate region by ion bombardment, thus achieving a narrower final gate region of the stated configuration.

Controlling the width of self-assembled dysprosium silicide nanowires on the Si(001) surface.

PubMed

Cui, Y; Chung, J; Nogami, J

2012-02-01

We present STM data that show that it is possible to use a metal induced 2 × 7 reconstruction of Si(001) to narrow the width distribution of Dy silicide nanowires. This behavior is distinct from the effect of the 7 × 7 reconstruction on the Si(111) surface, where the 7 × 7 serves as a static template and the deposited metal avoids the unit cell boundaries on the substrate. In this case, the 2 × 7 is a dynamic template, and the nanowires nucleate at anti-phase boundaries between 2 × 7 reconstruction domains.

Plant Productivity and Characterization of Zeoponic Substrates after Three Successive Crops of Radish (Raphanus sativus L.)

NASA Technical Reports Server (NTRS)

Gruener, J. E.; Ming, Douglas W.; Galindo, C., Jr.; Henderson, K. E.; Golden, D. C.

2007-01-01

The National Aeronautics and Space Administration (NASA) has developed a zeolite-based synthetic substrate, termed zeoponics. The zeoponic substrate (consisting of NH4(-) and K-exchanged clinoptilolite, synthetic apatite, and dolomite) provides all of the plant-essential nutrients through mineral dissolution and ion exchange, with only the addition of water. Previous studies have shown high productivity of wheat in zeoponic substrates; however, no experiments have been conducted on other crops. The objective of this study was to determine the productivity and nutrient uptake of radish (Raphanus sativus L.) grown in zeoponic substrates with three successive crops in the same substrate. Radish was chosen because of its sensitivities to NH4(+). Average fresh weights of edible roots were similar for radish grown in zeoponic substrates watered with deionized H2O (10.97 g/plant) and in potting mix control substrate irrigated with nutrient solution (10.92 g/plant). Average fresh weight production of edible roots for radish grown in same zeoponic substrate increased in yield over time with the lowest yield in the first crop (7.10 g/plant) and highest in the third crop (13.90 g/plant). The Ca plant tissue levels in radishes (1.8-2.9 wt. %) grown in zeoponic substrates are lower than the suggested sufficient range of 3.0-4.5 wt. % Ca; however, the Ca level is highest (2.9 wt. %) in radishes grown in the third crop in the same zeoponic substrates. The higher radish yield in the third crop was attributed to a reduction in an NH4(-) induced Ca deficiency that has been previously described for wheat grown in zeoponic substrates. The P levels in plant tissues of radish grown in the zeoponic substrates ranged from 0.94-1.15 wt. %; which is slightly higher than the sufficient levels of 0.3-0.7 wt. %. With the exception of Ca and P, other macronutrient and micronutrient levels in radish grown in zeoponic substrates were well within the recommended sufficient ranges. After three successive crops of radish growth, the zeoponic substrates had 52% of the original NH4(-)N and 78% of the original K remaining on zeolite exchange sites. Zeoponic substrates are capable of long-term productivity of radishes for space.

Clinical and electrophysiological characteristics of patients with paroxysmal intra-His block with narrow QRS complexes.

PubMed

Ragupathi, Loheetha; Johnson, Drew; Greenspon, Arnold; Frisch, Daniel; Ho, Reginald T; Pavri, Behzad B

2018-04-18

Atrioventricular (AV) block is usually due to infranodal disease and associated with a wide QRS complex; such patients often progress to complete AV block and pacemaker dependency. Uncommonly, infranodal AV block can occur within the His bundle with a narrow QRS complex. The aims of this study were to define clinical/echocardiographic characteristics of patients with AV block within the His bundle and report progression to pacemaker dependency. We retrospectively identified patients with narrow QRS complexes and documented intra-His delay or block at electrophysiology study (group A) or with electrocardiogram-documented Mobitz II AV block/paroxysmal AV block (group B). Clinical, electrophysiological, and echocardiographic variables at presentation and pacemaker parameters at the last follow-up visit were evaluated. Twenty-seven patients (19 women) were identified (mean age 64 ± 13 years; range, 38-85 years). Four patients who had <1 month of follow-up were excluded. There were 12 patients in group A and 11 in group B; 21 of 23 presented with syncope/presyncope. All patients received pacemakers: 8 single chamber and 15 dual chamber. After a median follow-up of 6.4 years, the median percentage of ventricular pacing was 1% (interquartile range 0%-4.66%). One patient developed true pacemaker dependency. Aortic and/or mitral annular calcification was present in 13 of 22 patients with available echocardiograms. Patients who present with syncope and narrow QRS complexes with intra-His delay or Mobitz II paroxysmal AV block with narrow QRS complexes rarely progress to pacemaker dependency and require infrequent pacing. This entity is more common in women, with a higher prevalence of aortic and/or mitral annular calcification. If confirmed by additional studies, single-chamber pacemaker may be sufficient. Copyright © 2018 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Genomes: At the edge of chaos with maximum information capacity

NASA Astrophysics Data System (ADS)

Kong, Sing-Guan; Chen, Hong-Da; Torda, Andrew; Lee, H. C.

2016-12-01

We propose an order index, ϕ, which quantifies the notion of “life at the edge of chaos” when applied to genome sequences. It maps genomes to a number from 0 (random and of infinite length) to 1 (fully ordered) and applies regardless of sequence length and base composition. The 786 complete genomic sequences in GenBank were found to have ϕ values in a very narrow range, 0.037 ± 0.027. We show this implies that genomes are halfway towards being completely random, namely, at the edge of chaos. We argue that this narrow range represents the neighborhood of a fixed-point in the space of sequences, and genomes are driven there by the dynamics of a robust, predominantly neutral evolution process.

Injection-seeded tunable mid-infrared pulses generated by difference frequency mixing

NASA Astrophysics Data System (ADS)

Miyamoto, Yuki; Hara, Hideaki; Masuda, Takahiko; Hiraki, Takahiro; Sasao, Noboru; Uetake, Satoshi

2017-03-01

We report on the generation of nanosecond mid-infrared pulses having frequency tunability, a narrow linewidth, and a high pulse energy. These pulses are obtained by frequency mixing between injection-seeded near-infrared pulses in potassium titanyl arsenate crystals. A continuous-wave external cavity laser diode or a Ti:sapphire ring laser is used as a tunable seeding source for the near-infrared pulses. The typical energy of the generated mid-infrared pulses is in the range of 0.4-1 mJ/pulse. The tuning wavelength ranges from 3142 to 4806 nm. A narrow linewidth of 1.4 GHz and good frequency reproducibility of the mid-infrared pulses are confirmed by observing a rovibrational absorption line of gaseous carbon monoxide at 4587 nm.

Degeneracy allows for both apparent homogeneity and diversification in populations

PubMed Central

Whitacre, James M.; Atamas, Sergei P.

2013-01-01

Trait diversity – the substrate for natural selection – is necessary for adaptation through selection, particularly in populations faced with environmental changes that diminish population fitness. In habitats that remain unchanged for many generations, stabilizing selection maximizes exploitation of resources by reducing trait diversity to a narrow optimal range. One might expect that such ostensibly homogeneous populations would have a reduced potential for heritable adaptive responses when faced with fitness-reducing environmental changes. However, field studies have documented populations that, even after long periods of evolutionary stasis, can still rapidly evolve in response to changed environmental conditions. We argue that degeneracy, the ability of diverse population elements to function similarly, can satisfy both the current need to maximize fitness and the future need for diversity. Degenerate ensembles appear functionally redundant in certain environmental contexts and functionally diverse in others. We propose that genetic variation not contributing to the observed range of phenotypes in a current population, also known as cryptic genetic variation (CGV), is a specific case of degeneracy. We argue that CGV, which gradually accumulates in static populations in stable environments, reveals hidden trait differences when environments change. By allowing CGV accumulation, static populations prepare themselves for future rapid adaptations to environmental novelty. A greater appreciation of degeneracy’s role in resolving the inherent tension between current stabilizing selection and future directional selection has implications in conservation biology and may be applied in social and technological systems to maximize current performance while strengthening the potential for future changes. PMID:22910487

Method and apparatus for laser scribing glass sheet substrate coatings

DOEpatents

Borgeson, Frank A.; Hanak, Joseph J.; Harju, Ricky S.; Helman, Norman L.; Hecht, Kenneth R.

2003-05-06

A method and apparatus (42) for laser scribing coatings on glass sheet substrates by conveying the substrate adjacent a laser source (83) that provides a pulsed laser beam (84) with a wavelength at a near-infrared fundamental frequency and having a frequency in the range of 50 to 100 kilohertz and a pulse duration in the range of 8 to 70 nanoseconds, and by reflecting the beam by an XYZ galvanometer controlled mirror system (90) toward an uncoated surface of the substrate for passage therethrough to the coating on the other surface to provide overlapping ablations through the coating and scribing at a speed of at least 1000 millimeters per second.

Method and apparatus for laser scribing glass sheet substrate coatings

DOEpatents

Borgeson, Frank A.; Hanak, Joseph J.; Harju, Ricky S.; Harju, Karen M.; Helman, Norman L.; Hecht, Kenneth R.

2005-07-19

A method and apparatus (42) for laser scribing coatings on glass sheet substrates by conveying the substrate adjacent a laser source (83) that provides a pulsed laser beam (84) with a wavelength at a near-infrared fundamental frequency and having a frequency in the range of 50 to 100 kilohertz and a pulse duration in the range of 8 to 70 nanoseconds, and by reflecting the beam by an XYZ galvanometer controlled mirror system (90) toward an uncoated surface of the substrate for passage therethrough to the coating on the other surface to provide overlapping ablations through the coating and scribing at a speed of at least 1000 millimeters per second.

Control of nanoparticle size and amount by using the mesh grid and applying DC-bias to the substrate in silane ICP-CVD process

NASA Astrophysics Data System (ADS)

Yoo, Seung-Wan; Hwang, Nong-Moon; You, Shin-Jae; Kim, Jung-Hyung; Seong, Dae-Jin

2017-11-01

The effect of applying a bias to the substrate on the size and amount of charged crystalline silicon nanoparticles deposited on the substrate was investigated in the inductively coupled plasma chemical vapor deposition process. By inserting the grounded grid with meshes above the substrate, the region just above the substrate was separated from the plasma. Thereby, crystalline Si nanoparticles formed by the gas-phase reaction in the plasma could be deposited directly on the substrate, successfully avoiding the formation of a film. Moreover, the size and the amount of deposited nanoparticles could be changed by applying direct current bias to the substrate. When the grid of 1 × 1-mm-sized mesh was used, the nanoparticle flux was increased as the negative substrate bias increased from 0 to - 50 V. On the other hand, when a positive bias was applied to the substrate, Si nanoparticles were not deposited at all. Regardless of substrate bias voltages, the most frequently observed nanoparticles synthesized with the grid of 1 × 1-mm-sized mesh had the size range of 10-12 nm in common. When the square mesh grid of 2-mm size was used, as the substrate bias was increased from - 50 to 50 V, the size of the nanoparticles observed most frequently increased from the range of 8-10 to 40-45 nm but the amount that was deposited on the substrate decreased.

Polaron theory of high- Tc superconductors

NASA Astrophysics Data System (ADS)

Alexandrov, A. S.

1989-05-01

It is shown that the ordinary electron-phonon interaction can produce a high Tc as a result of the polaron narrowing of the band, which is not considered by the traditional theory of strong-coupling superconductors based on Migdal-Eliashberg equations, which are violated even in the range of moderate values λ ⪖1. Numerous experimental data are discussed which seem to favour a phonon-mediated attraction, polaron mass enhancement, narrow band and nonadiabatic motion of carriers and charged Bose-like excitations in high Tc metallic oxides.

Transient enhancement and spectral narrowing of the photothermal effect of plasmonic nanoparticles under pulsed excitation.

PubMed

Lukianova-Hleb, Ekaterina Y; Volkov, Alexey N; Wu, Xiangwei; Lapotko, Dmitri O

2013-02-06

The transient 100-fold enhancement and spectral narrowing to 2 nm of the photothermal conversion by solid gold nanospheres under near-infrared excitation with a short laser pulse is reported. This non-stationary effect was observed for a wide range of optical fluences starting from 10 mJ cm(-2) for single nanospheres, their ensembles and aggregated clusters in water, in vitro and in vivo. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Developing upconversion nanoparticle-based smart substrates for remote temperature sensing

NASA Astrophysics Data System (ADS)

Coker, Zachary; Marble, Kassie; Alkahtani, Masfer; Hemmer, Philip; Yakovlev, Vladislav V.

2018-02-01

Recent developments in understanding of nanomaterial behaviors and synthesis have led to their application across a wide range of commercial and scientific applications. Recent investigations span from applications in nanomedicine and the development of novel drug delivery systems to nanoelectronics and biosensors. In this study, we propose the application of a newly engineered temperature sensitive water-based bio-compatible core/shell up-conversion nanoparticle (UCNP) in the development of a smart substrate for remote temperature sensing. We developed this smart substrate by dispersing functionalized nanoparticles into a polymer solution and then spin-coating the solution onto one side of a microscope slide to form a thin film substrate layer of evenly dispersed nanoparticles. By using spin-coating to deposit the particle solution we both create a uniform surface for the substrate while simultaneously avoid undesired particle agglomeration. Through this investigation, we have determined the sensitivity and capabilities of this smart substrate and conclude that further development can lead to a greater range of applications for this type smart substrate and use in remote temperature sensing in conjunction with other microscopy and spectroscopy investigations.

Status of backthinned AlGaN based focal plane arrays for deep-UV imaging

NASA Astrophysics Data System (ADS)

Reverchon, J.-L.; Lehoucq, G.; Truffer, J.-P.; Costard, E.; Frayssinet, E.; Semond, F.; Duboz, J.-Y.; Giuliani, A.; Réfrégiers, M.; Idir, M.

2017-11-01

The achievement of deep ultraviolet (UV) focal plane arrays (FPA) is required for both solar physics [1] and micro electronics industry. The success of solar mission (SOHO, STEREO [2], SDO [3]…), has shown the accuracy of imaging at wavelengths from 10 nm to 140 nm to reveal effects occurring in the sun corona. Deep UV steppers at 13 nm are another demanding imaging technology for the microelectronic industry in terms of uniformity and stability. A third application concerns beam shaping of Synchrotron lines [4]. Consequently, such wavelengths are of prime importance whereas the vacuum UV wavelengths are very difficult to detect due to the dramatic interaction of light with materials. The fast development of nitrides has given the opportunity to investigate AlGaN as a material for UV detection. Camera based on AlGaN present an intrinsic spectral selectivity and an extremely low dark current at room temperature. We have previously presented several FPA dedicated to deep UV based on 320 x 256 pixels of Schottky photodiodes with a pitch of 30 μm [4, 5]. AlGaN is grown on a silicon substrate instead of sapphire substrate only transparent down to 200 nm. After a flip-chip hybridization, silicon substrate and AlGaN basal layer was removed by dry etching. Then, the spectral responsivity of the FPA presented a quantum efficiency (QE) from 5% to 20% from 50 nm to 290 nm when removing the highly doped contact layer via a selective wet etching. This FPA suffered from a low uniformity incompatible with imaging, and a long time response due to variations of conductivity in the honeycomb. We also observed a low rejection of visible. It is probably due to the same honeycomb conductivity enhancement for wavelength shorter than 360 nm, i.e., the band gap of GaN. We will show hereafter an improved uniformity due to the use of a precisely ICP (Inductively Coupled Plasma) controlled process. The final membrane thickness is limited to the desertion layer. Neither access resistance limitation nor long response time are observed. QE varies from 5% at 50 nm to 15% at 6 nm (85% more when taking into account the filling factor). Consequently, we can propose prototypes concerning not only "solar blind" camera optimized for narrow band in the near UV range (between 280 nm and 260 nm), but also devices with spectral range extended in the deep UV (290 nm to 10 nm). Both detectors are available for an optical budget evaluation.

Sexual dimorphism in the attachment ability of the ladybird beetle Coccinella septempunctata on soft substrates

NASA Astrophysics Data System (ADS)

Heepe, Lars; Petersen, Dennis S.; Tölle, Lisa; Wolff, Jonas O.; Gorb, Stanislav N.

2017-01-01

Many insects possess adhesive foot pads, which enable reliable attachment to diverse and unpredictable substrates. The function of these adhesive organs was shown to be affected by environmental conditions such as substrate roughness, chemistry, and ambient humidity. So far, the attachment ability of insects and also that of spiders and geckos has been tested on rigid substrates only. However, the natural habitats of climbing animals may provide a variety of substrate stiffness ranging from rigid rock surfaces to soft, biofilm covered substrates. In order to test the effect of different substrate stiffness on the attachment ability of insects, we have performed friction experiments with female and male ladybird beetles Coccinella septempunctata on smooth silicone elastomer substrates of different stiffness, using a centrifugal force tester. Whereas in females, the attachment ability was not affected by the substrate stiffness within the range of tested stiffness, males showed decreasing attachment ability with decreasing substrate stiffness. This sexual dimorphism in attachment ability is explained by the presence of a specialized, discoidal seta type in males, which is not present in females. It is argued that discoidal setae, when softer if compared to the substrate, may show an advantageous peak-free interfacial stress distribution when being pulled off the substrate. For such setae being stiffer if compared the substrate, they potentially show increased edge stress concentration. In this case, lower pull-off forces are expected, in agreement with the experimentally obtained results. With the present study, we demonstrate for the first time that the substrate stiffness may have an effect on the attachment ability of climbing animals, which may also be of relevance for technical and medical applications involving adhesion to soft substrates.

Ultrathin diamond-like carbon film coated silver nanoparticles-based substrates for surface-enhanced Raman spectroscopy.

PubMed

Liu, Fanxin; Cao, Zhishen; Tang, Chaojun; Chen, Ling; Wang, Zhenlin

2010-05-25

We have demonstrated that by coating with a thin dielectric layer of tetrahedral amorphous carbon (ta-C), a biocompatible and optical transparent material in the visible range, the Ag nanoparticle-based substrate becomes extremely suitable for surface-enhanced Raman spectroscopy (SERS). Our measurements show that a 10 A or thicker ta-C layer becomes efficient to protect the oxygen-free Ag in air and prevent Ag ionizing in aqueous solutions. Furthermore, the Ag nanoparticles substrate coated with a 10 A ta-C film shows a higher enhancement of Raman signals than the uncoated substrate. These observations are further supported by our numerical simulations. We suggest that biomolecule detections in analytic assays could be easily realized using ta-C-coated Ag-based substrate for SERS especially in the visible range. The coated substrate also has higher mechanical stability, chemical inertness, and technological compliance, and may be useful, for example, to enhance TiO(2) photocatalysis and solar-cell efficiency by the surface plasmons.

Elevated gold ellipse nanoantenna dimers as sensitive and tunable surface enhanced Raman spectroscopy substrates

DOE PAGES

Jubb, A. M.; Jiao, Y.; Eres, Gyula; ...

2016-02-15

Here we demonstrate large area arrays of elevated gold ellipse dimers with precisely controlled gaps for use as sensitive and highly controllable surface enhanced Raman scattering (SERS) substrates. The significantly enhanced Raman signal observed with SERS arises from both localized and long range plasmonic effects. By controlling the geometry of a SERS substrate, in this case the size and aspect ratio of individual ellipses, the plasmon resonance can be tuned in a broad wavelength range, providing a method for designing the response of SERS substrates at different excitation wavelengths. Plasmon effects exhibited by the elevated gold ellipse dimer substrates aremore » also demonstrated and confirmed through finite difference time domain (FDTD) simulations. A plasmon resonance red shift with an increase of the ellipse aspect ratio is observed, allowing systematic control of the resulting SERS signal intensity. Optimized elevated ellipse dimer substrates with 10±2 nm gaps exhibit uniform SERS enhancement factors on the order of 10 9 for adsorbed p-mercaptoaniline molecules.« less

Watt-level tunable 1.5  μm narrow linewidth fiber ring laser based on a temperature tuning π-phase-shifted fiber Bragg grating.

PubMed

Sun, Junjie; Wang, Zefeng; Wang, Meng; Zhou, Zhiyue; Tang, Ni; Chen, Jinbao; Gu, Xijia

2017-11-10

A watt-level tunable 1.5 μm narrow linewidth fiber ring laser using a temperature tuning π-phase-shifted fiber Bragg grating (π-PSFBG) is demonstrated here, to the best of our knowledge, for the first time. The π-PSFBG is employed as both a narrow band filter and a wavelength tuning component, and its central wavelength is thermally tuned by a thermo-electric cooler. The maximum laser power is about 1.1 W with a linewidth of ∼318  MHz (∼2.57  pm) and a power fluctuation of less than 3%. The wavelength tuning range of the laser is about 1.29 nm with a sensitivity of ∼14.33  pm/°C, and the wavelength fluctuation is about 0.2 pm. This work provides important reference for tunable fiber lasers with both high power and narrow linewidth.

Temperature-modulated annealing of c-plane sapphire for long-range-ordered atomic steps

NASA Astrophysics Data System (ADS)

Yatsui, Takashi; Kuribara, Kazunori; Sekitani, Tsuyoshi; Someya, Takao; Yoshimoto, Mamoru

2016-03-01

High-quality single-crystalline sapphire is used to prepare various semiconductors because of its thermal stability. Here, we applied the tempering technique, which is well known in the production of chocolate, to prepare a sapphire substrate. Surprisingly, we successfully realised millimetre-range ordering of the atomic step of the sapphire substrate. We also obtained a sapphire atomic step with nanometre-scale uniformity in the terrace width and atomic-step height. Such sapphire substrates will find applications in the preparation of various semiconductors and devices.

Fear, Worry, and Ritualistic Behaviour in Childhood: Developmental Trends and Interrelations

ERIC Educational Resources Information Center

Laing, Sarah V.; Fernyhough, Charles; Turner, Michelle; Freeston, Mark H.

2009-01-01

Previous studies of childhood fear, worry, and ritualistic behaviour have been limited by restricted age ranges, narrow ranges of anxiety phenomena, non-comparable methodologies, and assessment of typical behaviour within a pathological context. Content and intensity of fear, worry, and ritualistic behaviour, and associations among these…

Flexible organic transistors and circuits with extreme bending stability

NASA Astrophysics Data System (ADS)

Sekitani, Tsuyoshi; Zschieschang, Ute; Klauk, Hagen; Someya, Takao

2010-12-01

Flexible electronic circuits are an essential prerequisite for the development of rollable displays, conformable sensors, biodegradable electronics and other applications with unconventional form factors. The smallest radius into which a circuit can be bent is typically several millimetres, limited by strain-induced damage to the active circuit elements. Bending-induced damage can be avoided by placing the circuit elements on rigid islands connected by stretchable wires, but the presence of rigid areas within the substrate plane limits the bending radius. Here we demonstrate organic transistors and complementary circuits that continue to operate without degradation while being folded into a radius of 100μm. This enormous flexibility and bending stability is enabled by a very thin plastic substrate (12.5μm), an atomically smooth planarization coating and a hybrid encapsulation stack that places the transistors in the neutral strain position. We demonstrate a potential application as a catheter with a sheet of transistors and sensors wrapped around it that enables the spatially resolved measurement of physical or chemical properties inside long, narrow tubes.

Front-Side Microstrip Line Feeding a Raised Antenna Patch

NASA Technical Reports Server (NTRS)

Hodges, Richard; Hoppe, Daniel

2005-01-01

An improved design concept for a printed-circuit patch antenna and the transmission line that feeds the patch calls for (1) a microstrip transmission line on the front (radiative) side of a printed-circuit board based on a thin, high-permittivity dielectric substrate; (2) using the conductor covering the back side of the circuit board as a common ground plane for both the microstrip line and the antenna patch; (3) supporting the antenna patch in front of the circuit board on a much thicker, lower-permittivity dielectric spacer layer; and (4) connecting the microstrip transmission line to the patch by use of a thin wire or narrow ribbon that extends through the thickness of the spacer and is oriented perpendicularly to the circuit-board plane. The thickness of the substrate is typically chosen so that a microstrip transmission line of practical width has an impedance between 50 and 100 ohms. The advantages of this design concept are best understood in the context of the disadvantages of prior design concepts, as explained

Sodium-coupled neutral amino acid (System N/A) transporters of the SLC38 gene family.

PubMed

Mackenzie, Bryan; Erickson, Jeffrey D

2004-02-01

The sodium-coupled neutral amino acid transporters (SNAT) of the SLC38 gene family resemble the classically-described System A and System N transport activities in terms of their functional properties and patterns of regulation. Transport of small, aliphatic amino acids by System A subtypes (SNAT1, SNAT2, and SNAT4) is rheogenic and pH sensitive. The System N subtypes SNAT3 and SNAT5 also countertransport H(+), which may be key to their operation in reverse, and have narrower substrate profiles than do the System A subtypes. Glutamine emerges as a favored substrate throughout the family, except for SNAT4. The SLC38 transporters undoubtedly play many physiological roles including the transfer of glutamine from astrocyte to neuron in the CNS, ammonia detoxification and gluconeogenesis in the liver, and the renal response to acidosis. Probing their regulation has revealed additional roles, and recent work has considered SLC38 transporters as therapeutic targets in neoplasia.

Sensitive SERS detection at the single-particle level based on nanometer-separated mushroom-shaped plasmonic dimers

NASA Astrophysics Data System (ADS)

Xiang, Quan; Li, Zhiqin; Zheng, Mengjie; Liu, Qing; Chen, Yiqin; Yang, Lan; Jiang, Tian; Duan, Huigao

2018-03-01

Elevated metallic nanostructures with nanogaps (<10 nm) possess advantages for surface enhanced Raman scattering (SERS) via the synergic effects of nanogaps and efficient decoupling from the substrate through an elevated three-dimensional (3D) design. In this work, we demonstrate a pattern-transfer-free process to reliably define elevated nanometer-separated mushroom-shaped dimers directly from 3D resist patterns based on the gap-narrowing effect during the metallic film deposition. By controlling the initial size of nanogaps in resist structures and the following deposited film thickness, metallic nanogaps could be tuned at the sub-10 nm scale with single-digit nanometer precision. Both experimental and simulated results revealed that gold dimer on mushroom-shaped pillars have the capability to achieve higher SERS enhancement factor comparing to those plasmonic dimers on cylindrical pillars or on a common SiO2/Si substrate, implying that the nanometer-gapped elevated dimer is an ideal platform to achieve the highest possible field enhancement for various plasmonic applications.

Structure of a Type-1 Secretion System ABC Transporter.

PubMed

Morgan, Jacob L W; Acheson, Justin F; Zimmer, Jochen

2017-03-07

Type-1 secretion systems (T1SSs) represent a widespread mode of protein secretion across the cell envelope in Gram-negative bacteria. The T1SS is composed of an inner-membrane ABC transporter, a periplasmic membrane-fusion protein, and an outer-membrane porin. These three components assemble into a complex spanning both membranes and providing a conduit for the translocation of unfolded polypeptides. We show that ATP hydrolysis and assembly of the entire T1SS complex is necessary for protein secretion. Furthermore, we present a 3.15-Å crystal structure of AaPrtD, the ABC transporter found in the Aquifex aeolicus T1SS. The structure suggests a substrate entry window just above the transporter's nucleotide binding domains. In addition, highly kinked transmembrane helices, which frame a narrow channel not observed in canonical peptide transporters, are likely involved in substrate translocation. Overall, the AaPrtD structure supports a polypeptide transport mechanism distinct from alternating access. Copyright © 2017 Elsevier Ltd. All rights reserved.

Analysis of epitaxial drift field N on P silicon solar cells

NASA Technical Reports Server (NTRS)

Baraona, C. R.; Brandhorst, H. W., Jr.

1976-01-01

The performance of epitaxial drift field silicon solar cell structures having a variety of impurity profiles was calculated. These structures consist of a uniformly doped P-type substrate layer, and a P-type epitaxial drift field layer with a variety of field strengths. Several N-layer structures were modeled. A four layer solar cell model was used to calculate efficiency, open circuit voltage and short circuit current. The effect on performance of layer thickness, doping level, and diffusion length was determined. The results show that peak initial efficiency of 18.1% occurs for a drift field thickness of about 30 micron with the doping rising from 10 to the 17th power atoms/cu cm at the edge of the depletion region to 10 to the 18th power atoms/cu cm in the substrate. Stronger drift fields (narrow field regions) allowed very high performance (17% efficiency) even after irradiation to 3x10 to the 14th power 1 MeV electrons/sq cm.

Highly oriented Bi-based thin films with zero resistance at 106 K

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

Kula, W.; Sobolewski, R.; Gorecka, J.

1991-03-01

This paper reports on fabrication and characterization of nearly single-phase superconducting Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} thin films. The films were dc magnetron sputtered from heavily Pb-doped (Pb/Bi molar ratios up to 1.25), sintered targets on unheated MgO, SrTiO{sub 3}, CaNdAlO{sub 4}, and SrLaAlO{sub 4} single crystals. For the films grown on the (100) oriented MgO substrate, less than 1 hour of annealing in air at 870{degrees} C was sufficient to obtain more than 90% of the 110-K-phase material, with highly c-axis oriented crystalline structure and zero resistivity at 106 K. The films fabricated on the other substrates alsomore » exhibited a narrow superconducting transition and were fully superconducting above 100 K, but they consisted of a mixed-phase material with a large percentage of the 80 K phase.« less

Low resistance thin film organic solar cell electrodes

DOEpatents

Forrest, Stephen [Princeton, NJ; Xue, Jiangeng [Piscataway, NJ

2008-01-01

A method which lower the series resistance of photosensitive devices includes providing a transparent film of a first electrically conductive material arranged on a transparent substrate; depositing and patterning a mask over the first electrically conductive material, such that openings in the mask have sloping sides which narrow approaching the substrate; depositing a second electrically conductive material directly onto the first electrically conductive material exposed in the openings of the mask, at least partially filling the openings; stripping the mask, leaving behind reentrant structures of the second electrically conductive material which were formed by the deposits in the openings of the mask; after stripping the mask, depositing a first organic material onto the first electrically conductive material in between the reentrant structures; and directionally depositing a third electrically conductive material over the first organic material deposited in between the reentrant structures, edges of the reentrant structures aligning deposition so that the third electrically conductive material does not directly contact the first electrically conductive material, and does not directly contact the second electrically conductive material.

Encapsulation of Polymer Colloids in a Sol-Gel Matrix. Direct-Writing of Coassembling Organic-Inorganic Hybrid Photonic Crystals.

PubMed

Mikosch, Annabel; Kuehne, Alexander J C

2016-03-22

The spontaneous self-assembly of polymer colloids into ordered arrangements provides a facile strategy for the creation of photonic crystals. However, these structures often suffer from defects and insufficient cohesion, which result in flaking and delamination from the substrate. A coassembly process has been developed for convective assembly, resulting in large-area encapsulated colloidal crystals. However, to generate patterns or discrete deposits in designated places, convective assembly is not suitable. Here we experimentally develop conditions for direct-writing of coassembling monodisperse dye-doped polystyrene particles with a sol-gel precursor to form solid encapsulated photonic crystals. In a simple procedure the colloids are formulated in a sol-gel precursor solution, drop-cast on a flat substrate, and dried. We here establish the optimal parameters to form reproducible highly ordered photonic crystals with good optical performance. The obtained photonic crystals interact with light in the visible spectrum with a narrow optical stop-gap.

High aspect ratio nano-fabrication of photonic crystal structures on glass wafers using chrome as hard mask.

PubMed

Hossain, Md Nazmul; Justice, John; Lovera, Pierre; McCarthy, Brendan; O'Riordan, Alan; Corbett, Brian

2014-09-05

Wafer-scale nano-fabrication of silicon nitride (Si x N y ) photonic crystal (PhC) structures on glass (quartz) substrates is demonstrated using a thin (30 nm) chromium (Cr) layer as the hard mask for transferring the electron beam lithography (EBL) defined resist patterns. The use of the thin Cr layer not only solves the charging effect during the EBL on the insulating substrate, but also facilitates high aspect ratio PhCs by acting as a hard mask while deep etching into the Si x N y . A very high aspect ratio of 10:1 on a 60 nm wide grating structure has been achieved while preserving the quality of the flat top of the narrow lines. The presented nano-fabrication method provides PhC structures necessary for a high quality optical response. Finally, we fabricated a refractive index based PhC sensor which shows a sensitivity of 185 nm per RIU.

Photodetectors based on single-walled carbon nanotubes and thiamonomethinecyanine J-aggregates on flexible substrates

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

Fedorov, I. V., E-mail: i-v-fedorov@mail.ru; Emel’yanov, A. V.; Romashkin, A. V.

2015-09-15

The present paper is devoted to observations of the photoresistive effect in multilayer structures with a sensitive layer of J-aggregates of thiamonomethinecyanine polymethine dye and a transparent electrode of a conductive carbon-nanotube network on a flexible polyethylenenaphtalate substrate. The effect of narrow-band emission with a wavelength of 465 nm on a change in the conductivity of the fabricated structures is studied. The prepared samples are studied by atomic-force microscopy, Raman spectroscopy, and spectrophotometry methods. It is shown that these structures are photosensitive to the indicated spectral region, and the dye layer is a film of dye J-aggregates. The change inmore » the sample conductivity upon exposure to light one hundred times exceeds the dark conductivity. In general, the principal possibility of developing a photoresistive detector based on J-aggregates of cyanine dyes on flexible supports on account of the use of transparent and conductive carbon-nanotube layers is shown.« less

Extended Versus Narrow-spectrum Antibiotics in the Management of Uncomplicated Appendicitis in Children: A Propensity-matched Comparative Effectiveness Study.

PubMed

Cameron, Danielle B; Melvin, Patrice; Graham, Dionne A; Glass, Charity C; Serres, Stephanie K; Kronman, Matthew P; Saito, Jacqueline M; Rangel, Shawn J

2018-07-01

The aim of this study was to compare the effectiveness of extended versus narrow spectrum antibiotics in preventing surgical site infections (SSIs) and hospital revisits in children with uncomplicated appendicitis. There is a paucity of high-quality evidence in the pediatric literature comparing the effectiveness of extended versus narrow-spectrum antibiotics in the prevention of SSIs associated with uncomplicated appendicitis. Clinical data from the ACS NSQIP-Pediatric Appendectomy Pilot Project were merged with antibiotic utilization data from the Pediatric Health Information System database for patients undergoing appendectomy for uncomplicated appendicitis at 17 hospitals from January 1, 2013 to June 30, 2015. Patients who received piperacillin/tazobactam (extended spectrum) were compared with those who received either cefoxitin or ceftriaxone with metronidazole (narrow spectrum) after propensity matching on demographic and severity characteristics. Study outcomes were 30-day SSI and hospital revisit rates. Of the 1389 patients included, 39.1% received piperacillin/tazobactam (range by hospital: 0% to 100%), and the remainder received narrow-spectrum agents. No differences in demographics or severity characteristics were found between groups following matching. In the matched analysis, the rates of SSI were similar between groups [extended spectrum: 2.4% vs narrow spectrum 1.8% (odds ratio, OR: 1.05, 95% confidence interval, 95% CI 0.34-3.26)], as was the rate of revisits [extended spectrum: 7.9% vs narrow spectrum 5.1% (OR: 1.46, 95% CI 0.75-2.87)]. Use of extended-spectrum antibiotics was not associated with lower rates of SSI or hospital revisits when compared with narrow-spectrum antibiotics in children with uncomplicated appendicitis. Our results challenge the routine use of extended-spectrum antibiotics observed at many hospitals, particularly given the increasing incidence of antibiotic-resistant organisms.

Narrow bandgap semiconducting silicides: Intrinsic infrared detectors on a silicon chip

NASA Technical Reports Server (NTRS)

Mahan, John E.

1989-01-01

Polycrystalline thin films of CrSi2, LaSi2, and ReSi2 were grown on silicon substrates. Normal incidence optical transmittance and reflectance measurements were made as a function of wavelength. It was demonstrated that LaSi2 is a metallic conductor, but that CrSi2 and ReSi2 are, in fact, narrow bandgap semiconductors. For CrSi2, the complex index of refraction was determined by computer analysis of the optical data. From the imaginary part, the optical absorption coefficient was determined as a function of photon energy. It was shown that CrSi2 possesses an indirect forbidden energy gap of slightly less than 0.31 eV, and yet it is a very strong absorber of light above the absorption edge. On the other hand, the ReSi2 films exhibit an absorption edge in the vicinity of 0.2 eV. Measurements of the thermal activation energy of resistivity for ReSi2 indicate a bandgap of 0.18 eV. It is concluded that the semiconducting silicides merit further investigation for development as new silicon-compatible infrared detector materials.

Nonlinear dynamic range transformation in visual communication channels.

PubMed

Alter-Gartenberg, R

1996-01-01

The article evaluates nonlinear dynamic range transformation in the context of the end-to-end continuous-input/discrete processing/continuous-display imaging process. Dynamic range transformation is required when we have the following: (i) the wide dynamic range encountered in nature is compressed into the relatively narrow dynamic range of the display, particularly for spatially varying irradiance (e.g., shadow); (ii) coarse quantization is expanded to the wider dynamic range of the display; and (iii) nonlinear tone scale transformation compensates for the correction in the camera amplifier.

Automated preparation method for colloidal crystal arrays of monodisperse and binary colloid mixtures by contact printing with a pintool plotter.

PubMed

Burkert, Klaus; Neumann, Thomas; Wang, Jianjun; Jonas, Ulrich; Knoll, Wolfgang; Ottleben, Holger

2007-03-13

Photonic crystals and photonic band gap materials with periodic variation of the dielectric constant in the submicrometer range exhibit unique optical properties such as opalescence, optical stop bands, and photonic band gaps. As such, they represent attractive materials for the active elements in sensor arrays. Colloidal crystals, which are 3D gratings leading to Bragg diffraction, are one potential precursor of such optical materials. They have gained particular interest in many technological areas as a result of their specific properties and ease of fabrication. Although basic techniques for the preparation of regular patterns of colloidal crystals on structured substrates by self-assembly of mesoscopic particles are known, the efficient fabrication of colloidal crystal arrays by simple contact printing has not yet been reported. In this article, we present a spotting technique used to produce a microarray comprising up to 9600 single addressable sensor fields of colloidal crystal structures with dimensions down to 100 mum on a microfabricated substrate in different formats. Both monodisperse colloidal crystals and binary colloidal crystal systems were prepared by contact printing of polystyrene particles in aqueous suspension. The array morphology was characterized by optical light microscopy and scanning electron microscopy, which revealed regularly ordered crystalline structures for both systems. In the case of binary crystals, the influence of the concentration ratio of the large and small particles in the printing suspension on the obtained crystal structure was investigated. The optical properties of the colloidal crystal arrays were characterized by reflection spectroscopy. To examine the stop bands of the colloidal crystal arrays in a high-throughput fashion, an optical setup based on a CCD camera was realized that allowed the simultaneous readout of all of the reflection spectra of several thousand sensor fields per array in parallel. In agreement with Bragg's relation, the investigated arrays exhibited strong opalescence and stop bands in the expected wavelength range, confirming the successful formation of highly ordered colloidal crystals. Furthermore, a narrow distribution of wavelength-dependent stop bands across the sensor array was achieved, demonstrating the capability of producing highly reproducible crystal spots by the contact printing method with a pintool plotter.

Interplay of catalysis, fidelity, threading, and processivity in the exo- and endonucleolytic reactions of human exonuclease I

PubMed Central

Shi, Yuqian; Hellinga, Homme W.; Beese, Lorena S.

2017-01-01

Human exonuclease 1 (hExo1) is a member of the RAD2/XPG structure-specific 5′-nuclease superfamily. Its dominant, processive 5′–3′ exonuclease and secondary 5′-flap endonuclease activities participate in various DNA repair, recombination, and replication processes. A single active site processes both recessed ends and 5′-flap substrates. By initiating enzyme reactions in crystals, we have trapped hExo1 reaction intermediates that reveal structures of these substrates before and after their exo- and endonucleolytic cleavage, as well as structures of uncleaved, unthreaded, and partially threaded 5′ flaps. Their distinctive 5′ ends are accommodated by a small, mobile arch in the active site that binds recessed ends at its base and threads 5′ flaps through a narrow aperture within its interior. A sequence of successive, interlocking conformational changes guides the two substrate types into a shared reaction mechanism that catalyzes their cleavage by an elaborated variant of the two-metal, in-line hydrolysis mechanism. Coupling of substrate-dependent arch motions to transition-state stabilization suppresses inappropriate or premature cleavage, enhancing processing fidelity. The striking reduction in flap conformational entropy is catalyzed, in part, by arch motions and transient binding interactions between the flap and unprocessed DNA strand. At the end of the observed reaction sequence, hExo1 resets without relinquishing DNA binding, suggesting a structural basis for its processivity. PMID:28533382

Interactions between Soil Habitat and Geographic Range Location Affect Plant Fitness

PubMed Central

Stanton-Geddes, John; Shaw, Ruth G.; Tiffin, Peter

2012-01-01

Populations are often found on different habitats at different geographic locations. This habitat shift may be due to biased dispersal, physiological tolerances or biotic interactions. To explore how fitness of the native plant Chamaecrista fasciculata depends on habitat within, at and beyond its range edge, we planted seeds from five populations in two soil substrates at these geographic locations. We found that with reduced competition, lifetime fitness was always greater or equivalent in one habitat type, loam soils, though early-season survival was greater on sand soils. At the range edge, natural populations are typically found on sand soil habitats, which are also less competitive environments. Early-season survival and fitness differed among source populations, and when transplanted beyond the range edge, range edge populations had greater fitness than interior populations. Our results indicate that even when the optimal soil substrate for a species does not change with geographic range location, the realized niche of a species may be restricted to sub-optimal habitats at the range edge because of the combined effects of differences in abiotic and biotic effects (e.g. competitors) between substrates. PMID:22615745

Laccase versus Laccase-Like Multi-Copper Oxidase: A Comparative Study of Similar Enzymes with Diverse Substrate Spectra

PubMed Central

Reiss, Renate; Ihssen, Julian; Richter, Michael; Eichhorn, Eric; Schilling, Boris; Thöny-Meyer, Linda

2013-01-01

Laccases (EC 1.10.3.2) are multi-copper oxidases that catalyse the one-electron oxidation of a broad range of compounds including substituted phenols, arylamines and aromatic thiols to the corresponding radicals. Owing to their broad substrate range, copper-containing laccases are versatile biocatalysts, capable of oxidizing numerous natural and non-natural industry-relevant compounds, with water as the sole by-product. In the present study, 10 of the 11 multi-copper oxidases, hitherto considered to be laccases, from fungi, plant and bacterial origin were compared. A substrate screen of 91 natural and non-natural compounds was recorded and revealed a fairly broad but distinctive substrate spectrum amongst the enzymes. Even though the enzymes share conserved active site residues we found that the substrate ranges of the individual enzymes varied considerably. The EC classification is based on the type of chemical reaction performed and the actual name of the enzyme often refers to the physiological substrate. However, for the enzymes studied in this work such classification is not feasible, even more so as their prime substrates or natural functions are mainly unknown. The classification of multi-copper oxidases assigned as laccases remains a challenge. For the sake of simplicity we propose to introduce the term “laccase-like multi-copper oxidase” (LMCO) in addition to the term laccase that we use exclusively for the enzyme originally identified from the sap of the lacquer tree Rhus vernicifera. PMID:23755261

Accessing the dynamics of end-grafted flexible polymer chains by atomic force-electrochemical microscopy. Theoretical modeling of the approach curves by the elastic bounded diffusion model and Monte Carlo simulations. Evidence for compression-induced lateral chain escape.

PubMed

Abbou, Jeremy; Anne, Agnès; Demaille, Christophe

2006-11-16

The dynamics of a molecular layer of linear poly(ethylene glycol) (PEG) chains of molecular weight 3400, bearing at one end a ferrocene (Fc) label and thiol end-grafted at a low surface coverage onto a gold substrate, is probed using combined atomic force-electrochemical microscopy (AFM-SECM), at the scale of approximately 100 molecules. Force and current approach curves are simultaneously recorded as a force-sensing microelectrode (tip) is inserted within the approximately 10 nm thick, redox labeled, PEG chain layer. Whereas the force approach curve gives access to the structure of the compressed PEG layer, the tip-current, resulting from tip-to-substrate redox cycling of the Fc head of the chain, is controlled by chain dynamics. The elastic bounded diffusion model, which considers the motion of the Fc head as diffusion in a conformational field, complemented by Monte Carlo (MC) simulations, from which the chain conformation can be derived for any degree of confinement, allows the theoretical tip-current approach curve to be calculated. The experimental current approach curve can then be very satisfyingly reproduced by theory, down to a tip-substrate separation of approximately 2 nm, using only one adjustable parameter characterizing the chain dynamics: the effective diffusion coefficient of the chain head. At closer tip-substrate separations, an unpredicted peak is observed in the experimental current approach curve, which is shown to find its origin in a compression-induced escape of the chain from within the narrowing tip-substrate gap. MC simulations provide quantitative support for lateral chain elongation as the escape mechanism.

Wet-chemical passivation of atomically flat and structured silicon substrates for solar cell application

NASA Astrophysics Data System (ADS)

Angermann, H.; Rappich, J.; Korte, L.; Sieber, I.; Conrad, E.; Schmidt, M.; Hübener, K.; Polte, J.; Hauschild, J.

2008-04-01

Special sequences of wet-chemical oxidation and etching steps were optimised with respect to the etching behaviour of differently oriented silicon to prepare very smooth silicon interfaces with excellent electronic properties on mono- and poly-crystalline substrates. Surface photovoltage (SPV) and photoluminescence (PL) measurements, atomic force microscopy (AFM) and scanning electron microscopy (SEM) investigations were utilised to develop wet-chemical smoothing procedures for atomically flat and structured surfaces, respectively. Hydrogen-termination as well as passivation by wet-chemical oxides were used to inhibit surface contamination and native oxidation during the technological processing. Compared to conventional pre-treatments, significantly lower micro-roughness and densities of surface states were achieved on mono-crystalline Si(100), on evenly distributed atomic steps, such as on vicinal Si(111), on silicon wafers with randomly distributed upside pyramids, and on poly-crystalline EFG ( Edge-defined Film-fed- Growth) silicon substrates. The recombination loss at a-Si:H/c-Si interfaces prepared on c-Si substrates with randomly distributed upside pyramids was markedly reduced by an optimised wet-chemical smoothing procedure, as determined by PL measurements. For amorphous-crystalline hetero-junction solar cells (ZnO/a-Si:H(n)/c-Si(p)/Al) with textured c-Si substrates the smoothening procedure results in a significant increase of short circuit current Isc, fill factor and efficiency η. The scatter in the cell parameters for measurements on different cells is much narrower, as compared to conventional pre-treatments, indicating more well-defined and reproducible surface conditions prior to a-Si:H emitter deposition and/or a higher stability of the c-Si surface against variations in the a-Si:H deposition conditions.

LETTER TO THE EDITOR: Green emission and bandgap narrowing due to two-photon excitation in thin film CdS formed by spray pyrolysis

NASA Astrophysics Data System (ADS)

Ullrich, B.; Schroeder, R.

2001-08-01

Thin (10 µm) film CdS on Pyrex® formed by spray pyrolysis is excited below the gap at 804 nm with 200 fs laser pulses at room temperature. Excitation intensities up to 250 GW cm-2 evoke green bandgap emission due to two-photon transitions. This two-photon photoluminescence does not show a red emission contribution in contrast to the single-photon excited emission, which is dominated by broad emission in the red spectral range. It is demonstrated that two-photon excitation causes photo-induced bandgap narrowing due to Debye screening. At 250 GW cm-2 bandgap narrowing of 47 meV is observed, which corresponds to an excited electron density of 1.6×1018 cm-3.

Derivative Analysis of AVIRIS Data for Crop Stress Detection

NASA Technical Reports Server (NTRS)

Estep, Lee; Carter, Gregory A.; Berglund, Judith

2003-01-01

Low-altitude Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) hyperspectral imagery of a cornfield in Nebraska was used to determine whether derivative analysis methods provided enhanced plant stress detection compared with narrow-band ratios. The field was divided into 20 plots representing 4 replicates each of 5 nitrogen (N) fertilization treatments that ranged from 0 to 200 kg N/ha in 50 kg/ha increments. The imagery yielded a 3 m ground pixel size for 224 spectral bands. Derivative analysis provided no advantage in stress detection compared with the performance of narrow-band indices derived from the literature. This result was attributed to a high leaf area index at the time of overflight (LAI approx. equal to 5 to 6t) and the high signal-to-noise character of the narrow AVIRIS bands.

Fracture strength and probability of survival of narrow and extra-narrow dental implants after fatigue testing: In vitro and in silico analysis.

PubMed

Bordin, Dimorvan; Bergamo, Edmara T P; Fardin, Vinicius P; Coelho, Paulo G; Bonfante, Estevam A

2017-07-01

To assess the probability of survival (reliability) and failure modes of narrow implants with different diameters. For fatigue testing, 42 implants with the same macrogeometry and internal conical connection were divided, according to diameter, as follows: narrow (Ø3.3×10mm) and extra-narrow (Ø2.9×10mm) (21 per group). Identical abutments were torqued to the implants and standardized maxillary incisor crowns were cemented and subjected to step-stress accelerated life testing (SSALT) in water. The use-level probability Weibull curves, and reliability for a mission of 50,000 and 100,000 cycles at 50N, 100, 150 and 180N were calculated. For the finite element analysis (FEA), two virtual models, simulating the samples tested in fatigue, were constructed. Loading at 50N and 100N were applied 30° off-axis at the crown. The von-Mises stress was calculated for implant and abutment. The beta (β) values were: 0.67 for narrow and 1.32 for extra-narrow implants, indicating that failure rates did not increase with fatigue in the former, but more likely were associated with damage accumulation and wear-out failures in the latter. Both groups showed high reliability (up to 97.5%) at 50 and 100N. A decreased reliability was observed for both groups at 150 and 180N (ranging from 0 to 82.3%), but no significant difference was observed between groups. Failure predominantly involved abutment fracture for both groups. FEA at 50N-load, Ø3.3mm showed higher von-Mises stress for abutment (7.75%) and implant (2%) when compared to the Ø2.9mm. There was no significant difference between narrow and extra-narrow implants regarding probability of survival. The failure mode was similar for both groups, restricted to abutment fracture. Copyright © 2017 Elsevier Ltd. All rights reserved.

Detection of trace explosives on relevant substrates using a mobile platform for photothermal infrared imaging spectroscopy (PT-IRIS)

NASA Astrophysics Data System (ADS)

Kendziora, Christopher A.; Furstenberg, Robert; Papantonakis, Michael; Nguyen, Viet; Byers, Jeff; McGill, R. Andrew

2015-05-01

This manuscript describes the results of recent tests regarding standoff detection of trace explosives on relevant substrates using a mobile platform. We are developing a technology for detection based on photo-thermal infrared (IR) imaging spectroscopy (PT-IRIS). This approach leverages one or more microfabricated IR quantum cascade lasers, tuned to strong absorption bands in the analytes and directed to illuminate an area on a surface of interest. An IR focal plane array is used to image the surface thermal emission upon laser illumination. The PT-IRIS signal is processed as a hyperspectral image cube comprised of spatial, spectral and temporal dimensions as vectors within a detection algorithm. Increased sensitivity to explosives and selectivity between different analyte types is achieved by narrow bandpass IR filters in the collection path. We have previously demonstrated the technique at several meters of stand-off distance indoors and in field tests, while operating the lasers below the infrared eye-safe intensity limit (100 mW/cm2). Sensitivity to explosive traces as small as a single 10 μm diameter particle (~1 ng) has been demonstrated. Analytes tested here include RDX, TNT, ammonium nitrate and sucrose. The substrates tested in this current work include metal, plastics, glass and painted car panels.

Direct spontaneous growth and interfacial structural properties of inclined GaN nanopillars on r-plane sapphire

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

Adikimenakis, A.; Aretouli, K. E.; Tsagaraki, K.

2015-06-28

The spontaneous growth of GaN nanopillars (NPs) by direct plasma-assisted molecular beam epitaxy on nitridated r-plane sapphire substrates has been studied. The emanation of metal-polarity NPs from inside an a-plane nonpolar GaN film was found to depend on both the substrate nitridation and the growth conditions. The density of NPs increased with increasing the duration of the nitridation process and the power applied on the radio-frequency plasma source, as well as the III/V flux ratio, while variation of the first two parameters enhanced the roughness of the substrate's surface. Transmission electron microscopy (TEM) techniques were employed to reveal the structuralmore » characteristics of the NPs and their nucleation mechanism from steps on the sapphire surface and/or interfacial semipolar GaN nanocrystals. Lattice strain measurements showed a possible Al enrichment of the first 5–6 monolayers of the NPs. By combining cross-sectional and plan-view TEM observations, the three-dimensional model of the NPs was constructed. The orientation relationship and interfacial accommodation between the NPs and the nonpolar a-plane GaN film were also elucidated. The NPs exhibited strong and narrow excitonic emission, suggesting an excellent structural quality.« less

Optical cross-talk and surface characterization of SERS nanoimaging bundle substrates

NASA Astrophysics Data System (ADS)

Kiser, John B.; Cullum, Brian M.

2010-04-01

Due to the narrow vibrational bandwidths and unique molecular fingerprints, Raman spectroscopy can be an information rich transduction technique for chemical imaging. Dynamic systems are often difficult to measure using spontaneous Raman due to the relatively weak scattering cross-sections. Using a Raman enhancement mechanism such as surface enhanced Raman scattering (SERS), exposure times can be reduced to a reasonable level for dynamic imaging, due to the increased Raman signal intensity. This paper will discuss the development of a novel SERS substrate, fabricated on the tips of fiber-optic imaging bundles, which can be integrated into a multispectral imaging system for non-scanning chemical imaging. These substrates are fabricated by mechanically tapering a polished fiber optic imaging bundle consisting of 30,000 individual elements; producing 100-nm or smaller diameter core elements on the distal tip. Chemical etching with hydrofluoric acid creates uniform cladding spikes onto which a SERS active metal is vacuum deposited, forming the SERS active surface. By varying the size of the silver islands deposited on the cladding peaks active, surface plasmons can be tuned to various excitation frequencies. The surface of these tapered fiber optic probes will be evaluated by analysis of the SERS signal, location and shape of the active surface plasmons. The cross talk between the fiber elements will also be evaluated.

III/V nano ridge structures for optical applications on patterned 300 mm silicon substrate

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

Kunert, B.; Guo, W.; Mols, Y.

We report on an integration approach of III/V nano ridges on patterned silicon (Si) wafers by metal organic vapor phase epitaxy (MOVPE). Trenches of different widths (≤500 nm) were processed in a silicon oxide (SiO{sub 2}) layer on top of a 300 mm (001) Si substrate. The MOVPE growth conditions were chosen in a way to guarantee an efficient defect trapping within narrow trenches and to form a box shaped ridge with increased III/V volume when growing out of the trench. Compressively strained InGaAs/GaAs multi-quantum wells with 19% indium were deposited on top of the fully relaxed GaAs ridges as an activemore » material for optical applications. Transmission electron microcopy investigation shows that very flat quantum well (QW) interfaces were realized. A clear defect trapping inside the trenches is observed whereas the ridge material is free of threading dislocations with only a very low density of planar defects. Pronounced QW photoluminescence (PL) is detected from different ridge sizes at room temperature. The potential of these III/V nano ridges for laser integration on Si substrates is emphasized by the achieved ridge volume which could enable wave guidance and by the high crystal quality in line with the distinct PL.« less

Mapping Strain Gradients in the FIB-Structured InGaN/GaN Multilayered Films with 3D X-ray Microbeam

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

Barabash, Rozaliya; Gao, Yanfei; Ice, Gene E

2010-01-01

This research presents a combined experimental-modeling study of lattice rotations and deviatoric strain gradients induced by focused-ion beam (FIB) milling in nitride heterostructures. 3D X-ray polychromatic microdiffraction (PXM) is used to map the local lattice orientation distribution in FIB-structured areas. Results are discussed in connection with microphotoluminescence ({mu}-PL), fluorescent analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) data. It is demonstrated that FIB-milling causes both direct and indirect damage to the InGaN/GaN layers. In films subjected to direct ion beam impact, a narrow amorphidized top layer is formed. Near the milling area, FIB-induced stress relaxation and formation ofmore » complicated 3D strain fields are observed. The resulting lattice orientation changes are found to correlate with a decrease and/or loss of PL intensity, and agree well with finite element simulations of the three-dimensional strain fields near the relaxed trenches. Experimentally, it is found that the lattice surface normal has an in-plane rotation, which only appears in simulations when the GaN-substrate lattice mismatch annihilates the InGaN-substrate mismatch. This behavior further supports the notion that the film/substrate interface is incoherent.« less

Mapping strain gradients in the FIB-structured InGaN/GaN multilayered films with 3D x-ray microbeam.

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

Barabash, R. I.; Gao, Y. F.; Ice, G. E.

2010-11-25

This research presents a combined experimental-modeling study of lattice rotations and deviatoric strain gradients induced by focused-ion beam (FIB) milling in nitride heterostructures. 3D X-ray polychromatic microdiffraction (PXM) is used to map the local lattice orientation distribution in FIB-structured areas. Results are discussed in connection with microphotoluminescence ({mu}-PL), fluorescent analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) data. It is demonstrated that FIB-milling causes both direct and indirect damage to the InGaN/GaN layers. In films subjected to direct ion beam impact, a narrow amorphidized top layer is formed. Near the milling area, FIB-induced stress relaxation and formation ofmore » complicated 3D strain fields are observed. The resulting lattice orientation changes are found to correlate with a decrease and/or loss of PL intensity, and agree well with finite element simulations of the three-dimensional strain fields near the relaxed trenches. Experimentally, it is found that the lattice surface normal has an in-plane rotation, which only appears in simulations when the GaN-substrate lattice mismatch annihilates the InGaN-substrate mismatch. This behavior further supports the notion that the film/substrate interface is incoherent.« less

Effect of Sophora flavescens on the pharmacokinetics of carbamazepine in rats.

PubMed

Shi, Lei; Dang, Xue-Liang; Liu, Xin-You; Wei, Hua-Mei; Yang, Meng-Meng; Zhang, Yan

2014-12-01

Carbamazepine (CBZ), an antiepileptic with narrow therapeutic window, is a substrate of CYP 3A4 which metabolizes CBZ to carbamazepine-10,11-epoxide (CBZE). CBZE is an active and toxicity metabolite, and it is a substrate of MRP-2. Using CBZ for a long time can cause hepatic injury. Sophora flavescens (SF) is a medicinal herb used for the protected hepatic injury. This study investigated the acute and chronic effects of SF on the pharmacokinetics of CBZ in rats. The concentrations of CBZ and CBZE in plasma and tissues were determined by HPLC method. The results showed that SF which significantly decreased the AUC0-t of CBZ, increased CBZE conversely. Tissue analysis showed that the concentrations of CBZ and CBZE in brain and liver were decreased by SF. In addition, the distribution of CBZE in kidney was reduced significantly, which influenced the CBZE excretion and increased the drug toxic potentially. Results in the current study suggest that patients using CBZ might be cautioned in the use of SF extract or Sophora-derived products. Meanwhile, patients receiving drugs which are substrates of CYP 3A4 and/or MRP-2 should be advised of the potential herb-drug interaction to reduce the risk of therapeutic failure or increased toxicity of conventional drug therapy.

Laser Cladding of Ultra-Thin Nickel-Based Superalloy Sheets.

PubMed

Gabriel, Tobias; Rommel, Daniel; Scherm, Florian; Gorywoda, Marek; Glatzel, Uwe

2017-03-10

Laser cladding is a well-established process to apply coatings on metals. However, on substrates considerably thinner than 1 mm it is only rarely described in the literature. In this work 200 µm thin sheets of nickel-based superalloy 718 are coated with a powder of a cobalt-based alloy, Co-28Cr-9W-1.5Si, by laser cladding. The process window is very narrow, therefore, a precisely controlled Yb fiber laser was used. To minimize the input of energy into the substrate, lines were deposited by setting single overlapping points. In a design of experiments (DoE) study, the process parameters of laser power, laser spot area, step size, exposure time, and solidification time were varied and optimized by examining the clad width, weld penetration, and alloying depth. The microstructure of the samples was investigated by optical microscope (OM) and scanning electron microscopy (SEM), combined with electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDX). Similarly to laser cladding of thicker substrates, the laser power shows the highest influence on the resulting clad. With a higher laser power, the clad width and alloying depth increase, and with a larger laser spot area the weld penetration decreases. If the process parameters are controlled precisely, laser cladding of such thin sheets is manageable.

Laser Cladding of Ultra-Thin Nickel-Based Superalloy Sheets

PubMed Central

Gabriel, Tobias; Rommel, Daniel; Scherm, Florian; Gorywoda, Marek; Glatzel, Uwe

2017-01-01

Laser cladding is a well-established process to apply coatings on metals. However, on substrates considerably thinner than 1 mm it is only rarely described in the literature. In this work 200 µm thin sheets of nickel-based superalloy 718 are coated with a powder of a cobalt-based alloy, Co–28Cr–9W–1.5Si, by laser cladding. The process window is very narrow, therefore, a precisely controlled Yb fiber laser was used. To minimize the input of energy into the substrate, lines were deposited by setting single overlapping points. In a design of experiments (DoE) study, the process parameters of laser power, laser spot area, step size, exposure time, and solidification time were varied and optimized by examining the clad width, weld penetration, and alloying depth. The microstructure of the samples was investigated by optical microscope (OM) and scanning electron microscopy (SEM), combined with electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDX). Similarly to laser cladding of thicker substrates, the laser power shows the highest influence on the resulting clad. With a higher laser power, the clad width and alloying depth increase, and with a larger laser spot area the weld penetration decreases. If the process parameters are controlled precisely, laser cladding of such thin sheets is manageable. PMID:28772639

Evaluation of aqueous and ethanol extract of bioactive medicinal plant, Cassia didymobotrya (Fresenius) Irwin & Barneby against immature stages of filarial vector, Culex quinquefasciatus Say (Diptera: Culicidae).

PubMed

Nagappan, Raja

2012-09-01

To evaluate aqueous and ethanol extract of Cassia didymobotrya leaves against immature stages of Culex quinquefasciatus. The mortality rate of immature mosquitoes was tested in wide and narrow range concentration of the plant extract based on WHO standard protocol. The wide range concentration tested in the present study was 10 000, 1 000, 100, 10 and 1 mg/L and narrow range concentration was 50, 100, 150, 200 and 250 mg/L. 2nd instar larvae exposed to 100 mg/L and above concentration of ethanol extract showed 100% mortality. Remaining stages such as 3rd, 4th and pupa, 100% mortality was observed at 1 000 mg/L and above concentration after 24 h exposure period. In aqueous extract all the stages 100% mortality was recorded at 1 000 mg/L and above concentration. In narrow range concentration 2nd instar larvae 100% mortality was observed at 150 mg/L and above concentration of ethanol extract. The remaining stages 100% mortality was recorded at 250 mg/L. In aqueous extract all the tested immature stages 100% mortality was observed at 250 mg/L concentration after 24 h exposure period. The results clearly indicate that the rate of mortality was based dose of the plant extract and stage of the mosquitoes. From this study it is confirmed and concluded that Cassia didymobotrya is having active principle which is responsible for controlling Culex quinquefasciatus. The isolation of bioactive molecules and development of simple formulation technique is important for large scale implementation.

Optimization of Cold Spray Deposition of High-Density Polyethylene Powders

NASA Astrophysics Data System (ADS)

Bush, Trenton B.; Khalkhali, Zahra; Champagne, Victor; Schmidt, David P.; Rothstein, Jonathan P.

2017-10-01

When a solid, ductile particle impacts a substrate at sufficient velocity, the resulting heat, pressure and plastic deformation can produce bonding between the particle and the substrate. The use of a cool supersonic gas flow to accelerate these solid particles is known as cold spray deposition. The cold spray process has been commercialized for some metallic materials, but further research is required to unlock the exciting potential material properties possible with polymeric particles. In this work, a combined computational and experimental study was employed to study the cold spray deposition of high-density polyethylene powders over a wide range of particle temperatures and impact velocities. Cold spray deposition of polyethylene powders was demonstrated across a range broad range of substrate materials including several different polymer substrates with different moduli, glass and aluminum. A material-dependent window of successful deposition was determined for each substrate as a function of particle temperature and impact velocity. Additionally, a study of deposition efficiency revealed the optimal process parameters for high-density polyethylene powder deposition which yielded a deposition efficiency close to 10% and provided insights into the physical mechanics responsible for bonding while highlighting paths toward future process improvements.

Time-dependent areal mass density for disc-shaped substrates in a corona-activated flow stream at atmospheric pressure for argon/acetylene admixture

NASA Astrophysics Data System (ADS)

Xie, Shuzheng; Islam, Rokibul; Hussein, Bashir; Englund, Karl; Pedrow, Patrick

2015-09-01

In this research we use a 40-needle array energized with 60 Hz AC voltage in the range 5 to 15 kV RMS. Plasma processing takes place downstream from a grounded planar screen (the opposing electrode). The needle-to-screen gap is in the range 4 to 10 cm and its E-field generates weakly ionized plasma via streamers and back corona. Deposited material is plasma-polymerized acetylene. Substrates are potassium bromide, mica, wood, paper, and gold-covered solids. Substrate chemical species influence the efficiency with which the disc amasses plasma-polymerized material, at least until the substrate is fully covered with film. Early plasma-polymerization is accompanied by nucleation-site-dominated nodules but longer term deposition results in a film that fully covers the substrate. We will report on time-dependent areal mass density associated with run times in the range 5-60 minutes. Film thickness will be measured using instruments that include visible light microscopy, TEM, and SEM. Others in our research group are studying areal mass density for early times (1-5 minutes) when nodule growth (at nucleation sites) dominates the deposition process.

Strategic Estimate: India

DTIC Science & Technology

1992-04-16

the two major ranges is the narrow valley of the ...although lower, is also prominent and rises south of the Northern Plains to form the Aravalli Range in the west and the jungle- covered Chota Nagpur... The global components of the United States’ national security are defined by its national interests. These are delineated in the

Re-Os Isotope Systematics in Lunar Soils and Breccias

NASA Technical Reports Server (NTRS)

Chen, J. H.; Papanastassiou, D. A; Wasserburg, G. J.

2002-01-01

Lunar soil and breccia samples show a narrow range in 187Os/188Os, in the range for H-chondrites and unfractionated irons. All samples show enrichments in 187Re/188Os, possibly reflecting loss of Os, associated with the terminal lunar cataclysm. Additional information is contained in the original extended abstract.

RL10 ignition limits test for Shuttle Centaur

NASA Technical Reports Server (NTRS)

1987-01-01

During routine development testing of the RL10A-3-3B engine a potential no-ignition condition was encountered when operating at certain propellant inlet conditions within the Shuttle Centaur G operating region. The conditions, the resulting investigative program, and methods to correct the potential problem are discussed. The Shuttle Centaur program was cancelled prior to completion of this effort. Although the RL10 engine in the Atlas Centaur vehicle is required by specification to operate over a wide range of propellant inlet conditions. The vehicle actually operates over a narrow range of conditions. This factor, combined with configuration differences between Atlas Centaur (or Titan Centaur) and the Shuttle Centaur RL10 engines, indicates the ignition problem does not exist for these vehicles. As a precautionary measure the vehicle manufacturer was requested to coordinate with Pratt and Whitney any anticipated changes in propellant inlet conditions from the current narrow range. An engineering change will be proposed for future RL10 deliveries to provide more consistent propellant flow to the igniter. This will permit operation of the engine throughout the wide range specification inlet conditions if desired.

Influence of solidification on the impact of supercooled water drops onto cold surfaces

NASA Astrophysics Data System (ADS)

Li, Hai; Roisman, Ilia V.; Tropea, Cameron

2015-06-01

This study presents an experimental investigation of the impact of a supercooled drop onto hydrophilic and superhydrophobic substrates. The aim is to better understand the process of airframe icing caused by supercooled large droplets, which has been recently identified as a severe hazard in aviation. The Weber number and Reynolds number of the impinging drop ranged from 200 to 300 and from 2600 to 5800, respectively. Drop impact, spreading, and rebound were observed using a high-speed video system. The maximum spreading diameter of an impacting drop on hydrophilic surfaces was measured. The temperature effect on this parameter was only minor for a wide range of the drop and substrate temperatures. However, ice/water mixtures emerged when both the drop and substrate temperatures were below 0 °C. Similarly, drop rebound on superhydrophobic substrates was significantly hindered by solidification when supercooled drop impacted onto substrates below the freezing point. The minimum receding diameter and the speed of ice accretion on the substrate were measured for various wall temperatures. Both parameters increased almost linearly with decreasing wall temperature, but eventually leveled off beyond a certain substrate temperature. The rate of ice formation on the substrate was significantly higher than the growth rate of free ice dendrites, implying that multiple nucleation sites were present.

A novel continuous two-phase partitioning bioreactor operated with polymeric tubing: Performance validation for enhanced biological removal of toxic substrates.

PubMed

Tomei, M Concetta; Mosca Angelucci, Domenica; Daugulis, Andrew J

2017-02-01

A continuous two-phase partitioning bioreactor (C-TPPB), operated with coiled tubing made of the DuPont polymer Hytrel 8206, was tested for the bioremediation of 4-chlorophenol, as a model toxic compound. The tubing was immersed in the aqueous phase, with the contaminated water flowing tube-side, and an adapted microbial culture suspended in the bioreactor itself, with the metabolic demand of the cells creating a concentration gradient to cause the substrate to diffuse into the bioreactor for biodegradation. The system was operated over a range of loadings (tubing influent concentration 750-1500 mg L -1 ), with near-complete substrate removal in all cases. Distribution of the contaminant at the end of the tests (96 h) highlighted biological removal in the range of 87-95%, while the amount retained in the polymer ranged from ∼1 to 8%. Mass transfer of the substrate across the tubing wall was not limiting, and the polymer demonstrated the capacity to buffer the substrate loadings and to adapt to microbial metabolism. The impact of C-TPPB operation on biomass activity was also investigated by a kinetic characterization of the microbial culture, which showed better resistance to substrate inhibition after C-TPPB operation, thereby confirming the beneficial effect of sub-inhibitory controlled conditions, characteristic of TPPB systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

Numerical modeling of the destruction of steel plates with a gradient substrate

NASA Astrophysics Data System (ADS)

Orlov, M. Yu.; Glazyrin, V. P.; Orlov, Yu. N.

2017-10-01

The paper presents the results of numerical simulation of the shock loading process of steel barriers with a gradient substrate. In an elastic plastic axisymmetric statement, a shock is simulated along the normal in the range of initial velocities up to 300 m / s. A range of initial velocities was revealed, in which the presence of a substrate "saved" the obstacle from spallation. New tasks were announced to deepen scientific knowledge about the behavior of unidirectional gradient barriers at impact. The results of calculations are obtained in the form of graphs, calculated configurations of the "impact - barrier" and tables.

Spectrophotometric determination of substrate-borne polyacrylamide.

PubMed

Lu, Jianhang; Wu, Laosheng

2002-08-28

Polyacrylamides (PAMs) have wide application in many industries and in agriculture. Scientific research and industrial applications manifested a need for a method that can quantify substrate-borne PAM. The N-bromination method (a PAM analytical technique based on N-bromination of amide groups and spectrophotometric determination of the formed starch-triiodide complex), which was originally developed for determining PAM in aqueous solutions, was modified to quantify substrate-borne PAM. In the modified method, the quantity of substrate-borne PAM was converted to a concentration of starch-triiodide complex in aqueous solution that was then measured by spectrophotometry. The method sensitivity varied with substrates due to sorption of reagents and reaction intermediates on the substrates. Therefore, separate calibration for each substrate was required. Results from PAM samples in sand, cellulose, organic matter burnt soils, and clay minerals showed that this method had good accuracy and reproducibility. The PAM recoveries ranged from 95.8% to 103.7%, and the relative standard deviations (n = 4) were <7.5% in all cases. The optimum range of PAM in each sample is 10-80 microg. The technique can serve as an effective tool in improving PAM application and facilitating PAM-related research.

Polarization of cells and soft objects driven by mechanical interactions: consequences for migration and chemotaxis.

PubMed

Leoni, M; Sens, P

2015-02-01

We study a generic model for the polarization and motility of self-propelled soft objects, biological cells, or biomimetic systems, interacting with a viscous substrate. The active forces generated by the cell on the substrate are modeled by means of oscillating force multipoles at the cell-substrate interface. Symmetry breaking and cell polarization for a range of cell sizes naturally "emerge" from long range mechanical interactions between oscillating units, mediated both by the intracellular medium and the substrate. However, the harnessing of cell polarization for motility requires substrate-mediated interactions. Motility can be optimized by adapting the oscillation frequency to the relaxation time of the system or when the substrate and cell viscosities match. Cellular noise can destroy mechanical coordination between force-generating elements within the cell, resulting in sudden changes of polarization. The persistence of the cell's motion is found to depend on the cell size and the substrate viscosity. Within such a model, chemotactic guidance of cell motion is obtained by directionally modulating the persistence of motion, rather than by modulating the instantaneous cell velocity, in a way that resembles the run and tumble chemotaxis of bacteria.

Overshoot and Non-Overshoot Pathways to 1.5oC and Above: The Temperature Tunnel

NASA Astrophysics Data System (ADS)

Feijoo, F.; Edmonds, J.; Wise, M. A.; Mignone, B.; Kheshgi, H. S.

2017-12-01

We create 3000 temperature pathways that lead to a wide range of outcomes in 2100 from below 1.5oC to over 3oC. We use the Global Change Assessment Model (GCAM), which includes the HECTOR physical Earth system model, to generate emission, climate forcing and global temperature trajectories driven by a wide range of assumed carbon price trajectories. While no probability is estimated for the generated trajectories, we report the central estimate of temperature response to emissions from HECTOR. We find that despite the wide range of generated carbon emission trajectories, temperature pathways were constrained to a narrow range until shortly before mid-century. This "temperature tunnel" was the result of two phenomena: first, a narrow range of radiative forcing for 10-15 years created by the concurrent reduction of carbon and aerosol emissions; and second, the thermal lag of the climate response to radiative forcing change of roughly 10-15 years. Scenarios consistent with 1.5oC showed higher short-term temperatures than scenarios consistent with higher temperature outcomes. No scenarios were found that peak below approximately 1.9oC.

Evidence for proton tunneling and a transient covalent flavin-substrate adduct in choline oxidase S101A.

PubMed

Uluisik, Rizvan; Romero, Elvira; Gadda, Giovanni

2017-11-01

The effect of temperature on the reaction of alcohol oxidation catalyzed by choline oxidase was investigated with the S101A variant of choline oxidase. Anaerobic enzyme reduction in a stopped-flow spectrophotometer was biphasic using either choline or 1,2-[ 2 H 4 ]-choline as a substrate. The limiting rate constants k lim1 and k lim2 at saturating substrate were well separated (k lim1 /k lim2 >9), and were >15-fold slower than for wild-type choline oxidase. Solvent deuterium kinetic isotope effects (KIEs) ~4 established that k lim1 probes the proton transfer from the substrate hydroxyl to a catalytic base. Primary substrate deuterium KIEs ≥7 demonstrated that k lim2 reports on hydride transfer from the choline alkoxide to the flavin. Between 15°C and 39°C the k lim1 and k lim2 values increased with increasing temperature, allowing for the analyses of H + and H - transfers using Eyring and Arrhenius formalisms. Temperature-independent KIE on the k lim1 value ( H2O k lim1 / D2O k lim1 ) suggests that proton transfer occurs within a highly reorganized tunneling-ready-state with a narrow distribution of donor-acceptor distances. Eyring analysis of the k lim2 value gave lines with the slope (choline) >slope (D-choline) , suggesting kinetic complexity. Spectral evidence for the transient occurrence of a covalent flavin-substrate adduct during the first phase of the anaerobic reaction of S101A CHO with choline is presented, supporting the notion that an important role of amino acid residues in the active site of flavin-dependent enzymes is to eliminate alternative reactions of the versatile enzyme-bound flavin for the reaction that needs to be catalyzed. Copyright © 2017 Elsevier B.V. All rights reserved.

Effects of ion and nanosecond-pulsed laser co-irradiation on the surface nanostructure of Au thin films on SiO{sub 2} glass substrates

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

Yu, Ruixuan; Meng, Xuan; Takayanagi, Shinya

2014-04-14

Ion irradiation and short-pulsed laser irradiation can be used to form nanostructures on the surfaces of substrates. This work investigates the synergistic effects of ion and nanosecond-pulsed laser co-irradiation on surface nanostructuring of Au thin films deposited under vacuum on SiO{sub 2} glass substrates. Gold nanoparticles are randomly formed on the surface of the substrate after nanosecond-pulsed laser irradiation under vacuum at a wavelength of 532 nm with a repetition rate of 10 Hz and laser energy density of 0.124 kJ/m{sup 2}. Gold nanoparticles are also randomly formed on the substrate after 100-keV Ar{sup +} ion irradiation at doses of upmore » to 3.8 × 10{sup 15} ions/cm{sup 2}, and nearly all of these nanoparticles are fully embedded in the substrate. With increasing ion irradiation dose (number of incident laser pulses), the mean diameter of the Au nanoparticles decreases (increases). However, Au nanoparticles are only formed in a periodic surface arrangement after co-irradiation with 6000 laser pulses and 3.8 × 10{sup 15} ions/cm{sup 2}. The periodic distance is ∼540 nm, which is close to the wavelength of the nanosecond-pulsed laser, and the mean diameter of the Au nanoparticles remains at ∼20 nm with a relatively narrow distribution. The photoabsorption peaks of the ion- or nanosecond-pulsed laser-irradiated samples clearly correspond to the mean diameter of Au nanoparticles. Conversely, the photoabsorption peaks for the co-irradiated samples do not depend on the mean nanoparticle diameter. This lack of dependence is likely caused by the periodic nanostructure formed on the surface by the synergistic effects of co-irradiation.« less

Phylogenetic and Functional Substrate Specificity for Endolithic Microbial Communities in Hyper-Arid Environments

PubMed Central

Crits-Christoph, Alexander; Robinson, Courtney K.; Ma, Bing; Ravel, Jacques; Wierzchos, Jacek; Ascaso, Carmen; Artieda, Octavio; Souza-Egipsy, Virginia; Casero, M. Cristina; DiRuggiero, Jocelyne

2016-01-01

Under extreme water deficit, endolithic (inside rock) microbial ecosystems are considered environmental refuges for life in cold and hot deserts, yet their diversity and functional adaptations remain vastly unexplored. The metagenomic analyses of the communities from two rock substrates, calcite and ignimbrite, revealed that they were dominated by Cyanobacteria, Actinobacteria, and Chloroflexi. The relative distribution of major phyla was significantly different between the two substrates and biodiversity estimates, from 16S rRNA gene sequences and from the metagenomic data, all pointed to a higher taxonomic diversity in the calcite community. While both endolithic communities showed adaptations to extreme aridity and to the rock habitat, their functional capabilities revealed significant differences. ABC transporters and pathways for osmoregulation were more diverse in the calcite chasmoendolithic community. In contrast, the ignimbrite cryptoendolithic community was enriched in pathways for secondary metabolites, such as non-ribosomal peptides (NRP) and polyketides (PK). Assemblies of the metagenome data produced population genomes for the major phyla found in both communities and revealed a greater diversity of Cyanobacteria population genomes for the calcite substrate. Draft genomes of the dominant Cyanobacteria in each community were constructed with more than 93% estimated completeness. The two annotated proteomes shared 64% amino acid identity and a significantly higher number of genes involved in iron update, and NRPS gene clusters, were found in the draft genomes from the ignimbrite. Both the community-wide and genome-specific differences may be related to higher water availability and the colonization of large fissures and cracks in the calcite in contrast to a harsh competition for colonization space and nutrient resources in the narrow pores of the ignimbrite. Together, these results indicated that the habitable architecture of both lithic substrates- chasmoendolithic versus cryptoendolithic – might be an essential element in determining the colonization and the diversity of the microbial communities in endolithic substrates at the dry limit for life. PMID:27014224

Rational design of Raman-labeled nanoparticles for a dual-modality, light scattering immunoassay on a polystyrene substrate.

PubMed

Israelsen, Nathan D; Wooley, Donald; Hanson, Cynthia; Vargis, Elizabeth

2016-01-01

Surface-enhanced Raman scattering (SERS) is a powerful light scattering technique that can be used for sensitive immunoassay development and cell labeling. A major obstacle to using SERS is the complexity of fabricating SERS probes since they require nanoscale characterization and optical uniformity. The light scattering response of SERS probes may also be modulated by the substrate used for SERS analysis. A typical SERS substrate such as quartz can be expensive. Polystyrene is a cheaper substrate option but can decrease the SERS response due to interfering Raman emission peaks and high background fluorescence. The goal of this research is to develop an optimized process for fabricating Raman-labeled nanoparticles for a SERS-based immunoassay on a polystyrene substrate. We have developed a method for fabricating SERS nanoparticle probes for use in a light scattering immunoassay on a polystyrene substrate. The light scattering profile of both spherical gold nanoparticle and gold nanorod SERS probes were characterized using Raman spectroscopy and optical absorbance spectroscopy. The effects of substrate interference and autofluorescence were reduced by selecting a Raman reporter with a strong light scattering response in a spectral region where interfering substrate emission peaks are minimized. Both spherical gold nanoparticles and gold nanorods SERS probes used in the immunoassay were detected at labeling concentrations in the low pM range. This analytical sensitivity falls within the typical dynamic range for direct labeling of cell-surface biomarkers using SERS probes. SERS nanoparticle probes were fabricated to produce a strong light scattering signal despite substrate interference. The optical extinction and inelastic light scattering of these probes was detected by optical absorbance spectroscopy and Raman spectroscopy, respectively. This immunoassay demonstrates the feasibility of analyzing strongly enhanced Raman signals on polystyrene, which is an inexpensive yet non-ideal Raman substrate. The assay sensitivity, which is in the low pM range, suggests that these SERS probe particles could be used for Raman labeling of cell or tissue samples in a polystyrene tissue culture plate. With continued development, this approach could be used for direct labeling of multiple cell surface biomarkers on strongly interfering substrate platforms.

Narrow-band double-pass superluminescent diodes emitting at 1060 nm

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

Lobintsov, A A; Perevozchikov, M V; Shramenko, M V

2009-09-30

Experimental data are presented which show that double-pass superluminescent diodes (SLDs) with fibre Bragg grating (FBG) based spectrally selective external reflectors offer emission linewidths in the range 0.1-1.0 nm, i.e., one to two orders of magnitude narrower in comparison with conventional SLDs and considerably broader in comparison with single-frequency semiconductor lasers. Their optical power at the single-mode fibre output reaches 5.0-8.0 mW, and can be raised to 50 mW using a semiconductor optical amplifier. (lasers)

Observation of coherently enhanced tunable narrow-band terahertz transition radiation from a relativistic sub-picosecond electron bunch train

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

Piot, P.; Sun, Y. -E; Maxwell, T. J.

2011-06-27

We experimentally demonstrate the production of narrow-band (δf/f ~ =20% at f ~ = 0.5 THz) THz transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. In addition, we show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.

Partially Filled Aperture Interferometric Telescopes: Achieving Large Aperture and Coronagraphic Performance

NASA Astrophysics Data System (ADS)

Moretto, G.; Kuhn, J.; Langlois, M.; Berdugyna, S.; Tallon, M.

2017-09-01

Telescopes larger than currently planned 30-m class instruments must break the mass-aperture scaling relationship of the Keck-generation of multi-segmented telescopes. Partially filled aperture, but highly redundant baseline interferometric instruments may achieve both large aperture and high dynamic range. The PLANETS FOUNDATION group has explored hybrid telescope-interferometer concepts for narrow-field optical systems that exhibit coronagraphic performance over narrow fields-of-view. This paper describes how the Colossus and Exo-Life Finder telescope designs achieve 10x lower moving masses than current Extremely Large Telescopes.

Rifting the continental lithosphere: case studies of the lithosphere-asthenosphere system in rifted settings across the western U.S. and in the southern East African Rift

NASA Astrophysics Data System (ADS)

Hopper, E.; Gaherty, J. B.; Shillington, D. J.

2016-12-01

Continental extension comes in many guises, often described in terms of two endmembers. Narrow rifting is typified by a rift valley narrower than lithospheric thickness (50-100 km), presumed to result in steep lateral changes in crustal and lithospheric topography; wide rifting by a broad zone (<1000 km) of normal faulting associated with much smaller topographic gradients. A type example for the former is the East African Rift Valley; for the latter, the Basin and Range in the western U.S.A. An important control on rift development is the state of the lithosphere: for example, its strength and thickness. We analyse common conversion point stacked Sp converted wave images of the lithosphere beneath rift systems in the contiguous U.S., both the wide Basin and Range, and narrow rift systems such as the Rio Grande Rift and Salton Trough. We use Sp waves recorded by EarthScope's Transportable Array and other available permanent and temporary broadband stations. Beneath the Basin and Range, we observe a very strong, shallow velocity decrease (the lithosphere-asthenosphere boundary, or LAB) that is relatively uniform over 100s of km. The strength of this feature indicates melt has ponded at this transition. We have not observed a clear relationship between lithospheric thickness beneath the Basin and Range, and total degree of extension, current extension rate, or age since surface volcanism. Beneath narrow rifts in the western U.S., however, more localised thinning of the lithosphere has been observed. We also compare these observations with seismic images of the Malawi Rift, at the southern end of the Western Branch of the East African Rift System, using broadband data acquired as part of the Study of Extension and MaGmatism in Malawi aNd Tanzania (SEGMeNT) experiment. The Malawi Rift is extending slowly in a magma-poor region of relatively strong lithosphere. We constrain the pattern of plate-scale extension by observations of crustal thinning, and image complex variations in deeper lithospheric structure.

Rifting the continental lithosphere: case studies of the lithosphere-asthenosphere system in rifted settings across the western U.S. and in the southern East African Rift

NASA Astrophysics Data System (ADS)

Hopper, E.; Gaherty, J. B.; Shillington, D. J.

2017-12-01

Continental extension comes in many guises, often described in terms of two endmembers. Narrow rifting is typified by a rift valley narrower than lithospheric thickness (50-100 km), presumed to result in steep lateral changes in crustal and lithospheric topography; wide rifting by a broad zone (<1000 km) of normal faulting associated with much smaller topographic gradients. A type example for the former is the East African Rift Valley; for the latter, the Basin and Range in the western U.S.A. An important control on rift development is the state of the lithosphere: for example, its strength and thickness. We analyse common conversion point stacked Sp converted wave images of the lithosphere beneath rift systems in the contiguous U.S., both the wide Basin and Range, and narrow rift systems such as the Rio Grande Rift and Salton Trough. We use Sp waves recorded by EarthScope's Transportable Array and other available permanent and temporary broadband stations. Beneath the Basin and Range, we observe a very strong, shallow velocity decrease (the lithosphere-asthenosphere boundary, or LAB) that is relatively uniform over 100s of km. The strength of this feature indicates melt has ponded at this transition. We have not observed a clear relationship between lithospheric thickness beneath the Basin and Range, and total degree of extension, current extension rate, or age since surface volcanism. Beneath narrow rifts in the western U.S., however, more localised thinning of the lithosphere has been observed. We also compare these observations with seismic images of the Malawi Rift, at the southern end of the Western Branch of the East African Rift System, using broadband data acquired as part of the Study of Extension and MaGmatism in Malawi aNd Tanzania (SEGMeNT) experiment. The Malawi Rift is extending slowly in a magma-poor region of relatively strong lithosphere. We constrain the pattern of plate-scale extension by observations of crustal thinning, and image complex variations in deeper lithospheric structure.

Millimeter-wave/infrared rectenna development at Georgia Tech

NASA Technical Reports Server (NTRS)

Gouker, Mark A.

1989-01-01

The key design issues of the Millimeter Wave/Infrared (MMW/IR) monolithic rectenna have been resolved. The work at Georgia Tech in the last year has focused on increasing the power received by the physically small MMW rectennas in order to increase the rectification efficiency. The solution to this problem is to place a focusing element on the back side of the substrate. The size of the focusing element can be adjusted to help maintain the optimum input power density not only for different power densities called for in various mission scenarios, but also for the nonuniform power density profile of a narrow EM-beam.

Low cost microminiature refrigerators for large unit volume applications

NASA Technical Reports Server (NTRS)

Duboc, R. M., Jr.

1983-01-01

Photolithographic techniques were employed to fabricate small Joule-Thomson refrigerators in laminated substrates. The gas passages of a J-T refrigerator are formed by etching channels as narrow as 50 microns and as shallow as 5 microns in glass plates which are laminated together. Circular refrigerators on the order of 1.5 centimeters in diameter and .75 millimeters thick were produced which cool down to cryogenic temperatures in a few seconds, using Argon or Nitrogen, with no vacuum or radiation insulation. Smaller refrigerators are developed for both faster cooldown and low refrigeration capacity applications. By using this technology, custom refrigerators can be designed to meet specific application requirements.

Terraced-heterostructure large-optical-cavity AlGaAs diode laser - A new type of high-power CW single-mode device

NASA Technical Reports Server (NTRS)

Botez, D.; Connolly, J. C.

1982-01-01

A new terraced lateral wave confining structure is obtained by liquid phase epitaxy over channeled substrates misoriented perpendicular to the channels' direction. Single spatial and longitudinal mode CW operation is achieved to 50 mW from one facet, in large spot sizes (2 x 7.5 micron, 1/e squared points in intensity) and narrow beams (6 deg x 23 deg), full width half-power). At 70 C ambient temperature CW lasing is obtained to 15 mW from one facet. Weak mode confinement in an asymmetric lateral waveguides provides discrimination against high-order mode oscillation.

Plasmon-Induced Transparency Based on Triple Arc-Ring Resonators.

PubMed

Dong, Guang-Xi; Xie, Qin; Zhang, Qi; Wang, Ben-Xin; Huang, Wei-Qing

2018-06-06

This paper presents a plasmon-induced transparency (PIT) using an easy-fabricating metamaterial composed of three pieces of metallic arc-rings on top of a dielectric substrate. The transmission of the transparent peak of 1.32 THz reaches approximately 93%. The utilization of the coupled Lorentzian oscillator model and the distribution of electromagnetic fields together explain the cause of the transparent peak. The simulation results further demonstrate that the bandwidth of the transmission peak can be narrowed by changing the sizes of the arc-rings. Moreover, an on/off effect based on the transparent peak is discussed by introducing photosensitive silicon into the air gaps of the suggested metamaterial structure.

Coexistence of non-volatile bi-polar resistive switching and tunneling magnetoresistance in spatially confined La0.3Pr0.4Ca0.3MnO3 films

NASA Astrophysics Data System (ADS)

Jeon, J.; Jung, J.; Chow, K. H.

2017-12-01

We report the coexistence of non-volatile bi-polar resistive switching (RS) and tunneling magnetoresistance (TMR) in spatially confined La0.3Pr0.4Ca0.3MnO3 films grown on LaAlO3 substrates. At certain temperatures, the arrangement of electronic phase domains in these narrow systems mimics those found in heterostructured metal-insulator-metal devices. The relative spin orientations between adjacent ferromagnetic metallic phase domains enable the TMR effect, while the creation/annihilation of conduction filaments between the metallic phase domains produces the RS effect.

Quantum dots for GaAs-based surface emitting lasers at 1300 nm

NASA Astrophysics Data System (ADS)

Grundmann, M.; Ledentsov, N. N.; Hopfer, F.; Heinrichsdorff, F.; Guffarth, F.; Bimberg, D.; Ustinov, V. M.; Zhukov, A. E.; Kovsh, A. R.; Maximov, M. V.; Musikhin, Yu. G.; Alferov, Zh. I.; Lott, J. A.; Zhakharov, N. D.; Werner, P.

InGaAs quantum dots (QD's) on GaAs substrate have been fabricated using metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) for the use in vertical cavity surface emitting laser diodes. Similar recombination spectra are obtained by employing the two different approaches of seeding and overgrowth with a quantum well. Despite the shift to larger wavelengths a large separation (=80 meV) between excited states is maintained. The introduction of such QD's into a vertical cavity leads to strong narrowing of the emission spectrum. Lasing from a 1300 nm InGaAs quantum dot VCSEL is reported.

Vapor bridges between solid substrates in the presence of the contact line pinning effect: Stability and capillary force

NASA Astrophysics Data System (ADS)

Liu, Yawei; Zhang, Xianren

2016-12-01

In this work, we focus on investigating how nanobubbles mediate long-range interaction between neighboring solid substrates in the presence of the contact line pinning effect caused by surface heterogeneities. Using the constrained lattice density functional theory (LDFT), we prove that the nanobubbles, which take the form of vapor bridges here, are stabilized by the pinning effect if the separation between two substrates is less than a critical distance. The critical distance strongly depends on the chemical potential (i.e., the degree of saturation) and could become extremely long at a special chemical potential. Moreover, under the pinning effect, the substrate chemistry only determines the stability of the vapor bridges and the range of the capillary force, but has less influences on the magnitude of the capillary force, indicating that the substrate chemistry or the apparent contact angle for droplets or bubbles on the substrates is no longer a direct parameter to determine the magnitude of capillary force. A qualitative analysis for the two dimensional vapor bridges by considering the feedback mechanism can explain the results from the LDFT calculations.

Voltage-impulse-induced dual-range nonvolatile magnetization modulation in metglas/PZT heterostructure

NASA Astrophysics Data System (ADS)

Tang, Xiaoli; Su, Hua; Zhang, Huaiwu; Sun, Nian X.

2016-11-01

Dual-range, nonvolatile magnetization modulation induced by voltage impulses was investigated in the metglas/lead zirconate titanate (PZT) heterostructure at room temperature. The heterostructure was obtained by bonding a square metglas ribbon on the top electrode of the PZT substrate, which contained defect dipoles resulting from acceptor doping. The PZT substrate achieved two strain hysteretic loops with the application of specific voltage impulse excitation modes. Through strain-mediated magnetoelectric coupling between the metglas ribbon and the PZT substrate, two strain hysteretic loops led to a dual-range nonvolatile magnetization modulation in the heterostructure. Reversible and stable voltage-impulse-induced nonvolatile modulation in the ferromagnetic resonance field and magnetic hysteresis characteristics were also realized. This method provides a promising approach in reducing energy consumption in magnetization modulation and other related devices.

Substrate for thin silicon solar cells

DOEpatents

Ciszek, Theodore F.

1995-01-01

A photovoltaic device for converting solar energy into electrical signals comprises a substrate, a layer of photoconductive semiconductor material grown on said substrate, wherein the substrate comprises an alloy of boron and silicon, the boron being present in a range of from 0.1 to 1.3 atomic percent, the alloy having a lattice constant substantially matched to that of the photoconductive semiconductor material and a resistivity of less than 1.times.10.sup.-3 ohm-cm.

DESIGN NOTE: On the frustration of back-surface reflection from transparent substrates in ellipsometry

NASA Astrophysics Data System (ADS)

Hayton, D. J.; Jenkins, T. E.

2004-02-01

The effects of back-surface reflection from transparent substrates on ellipsometric measurements are discussed and it is shown that their effects can be minimized by placing the substrate on a commercially available product, Blu-tack. The ellipsometric properties of Blu-tack in the range 250 850 nm are presented and the frustration of the back-surface reflection is discussed in terms of index matching between substrate and Blu-tack.

Spectroscopic studies of the reaction between bovine serum amine oxidase (copper-containing) and some hydrazides and hydrazines.

PubMed Central

Morpurgo, L; Befani, O; Sabatini, S; Mondovì, B; Artico, M; Corelli, F; Massa, S; Stefancich, G; Avigliano, L

1988-01-01

The carbonyl cofactor of bovine serum amine oxidase, recently identified as pyrroloquinoline quinone [Ameyama, Hayashi, Matsushita, Shinagawa & Adachi (1984) Agric. Biol. Chem. 48, 561-565; Lobenstein-Verbeek, Jongejan, Frank & Duine (1984) FEBS Lett. 170, 305-309], reacts stoichiometrically and irreversibly with hydrazides of phenylacetic acid and of benzoic acid. With the phenylacetic hydrazides a reversible intermediate step was detected by competition with substrate, carbonylic reagents or phenylhydrazine, a typical inhibitor of the enzyme. All hydrazides form an intense broad band with maximum absorbance in a narrow wavelength range (350-360 nm), irrespective of the acyl group, suggesting that the transition is located on the organic cofactor. A different situation is found with some phenylhydrazines, where extended conjugation can occur between the cofactor and the phenyl pi-electron system via the azo group, as shown by the lower energy and higher intensity of the transition. In this case the transition is sensitive to substituents in the phenyl ring. The c.d. spectrum of the adducts is influenced by the type of hydrazide (derived from phenylacetic acid or benzoic acid), by pH and by NN-diethyldithiocarbamate binding to copper, probably as a result of shifts of equilibria between hydrazone-azo tautomers. PMID:3146976

Architecture and migration of an epithelium on a cylindrical wire.

PubMed

Yevick, Hannah G; Duclos, Guillaume; Bonnet, Isabelle; Silberzan, Pascal

2015-05-12

In a wide range of epithelial tissues such as kidney tubules or breast acini, cells organize into bidimensional monolayers experiencing an out-of-plane curvature. Cancer cells can also migrate collectively from epithelial tumors by wrapping around vessels or muscle fibers. However, in vitro experiments dealing with epithelia are mostly performed on flat substrates, neglecting this out-of-plane component. In this paper, we study the development and migration of epithelial tissues on glass wires of well-defined radii varying from less than 1 µm up to 85 µm. To uncouple the effect of out-of-plane curvature from the lateral confinement experienced by the cells in these geometries, we compare our results to experiments performed on narrow adhesive tracks. Because of lateral confinement, the velocity of collective migration increases for radii smaller than typically 20 µm. The monolayer dynamics is then controlled by front-edge protrusions. Conversely, high curvature is identified as the inducer of frequent cell detachments at the front edge, a phenotype reminiscent of the Epithelial-Mesenchymal Transition. High curvature also induces a circumferential alignment of the actin cytoskeleton, stabilized by multiple focal adhesions. This organization of the cytoskeleton is reminiscent of in vivo situations such as the development of the trachea of the Drosophila embryo. Finally, submicron radii halt the monolayer, which then reconfigures into hollow cysts.

Label-free biodetection using a smartphone.

PubMed

Gallegos, Dustin; Long, Kenneth D; Yu, Hojeong; Clark, Peter P; Lin, Yixiao; George, Sherine; Nath, Pabitra; Cunningham, Brian T

2013-06-07

Utilizing its integrated camera as a spectrometer, we demonstrate the use of a smartphone as the detection instrument for a label-free photonic crystal biosensor. A custom-designed cradle holds the smartphone in fixed alignment with optical components, allowing for accurate and repeatable measurements of shifts in the resonant wavelength of the sensor. Externally provided broadband light incident upon an entrance pinhole is subsequently collimated and linearly polarized before passing through the biosensor, which resonantly reflects only a narrow band of wavelengths. A diffraction grating spreads the remaining wavelengths over the camera's pixels to display a high resolution transmission spectrum. The photonic crystal biosensor is fabricated on a plastic substrate and attached to a standard glass microscope slide that can easily be removed and replaced within the optical path. A custom software app was developed to convert the camera images into the photonic crystal transmission spectrum in the visible wavelength range, including curve-fitting analysis that computes the photonic crystal resonant wavelength with 0.009 nm accuracy. We demonstrate the functionality of the system through detection of an immobilized protein monolayer, and selective detection of concentration-dependent antibody binding to a functionalized photonic crystal. We envision the capability for an inexpensive, handheld biosensor instrument with web connectivity to enable point-of-care sensing in environments that have not been practical previously.

Gas-Sensing Devices Based on Zn-Doped NiO Two-Dimensional Grainy Films with Fast Response and Recovery for Ammonia Molecule Detection

NASA Astrophysics Data System (ADS)

Wang, Jian; Wei, Xiaowei; Wangyang, Peihua

2015-12-01

Zn-doped NiO two-dimensional grainy films on glass substrates are shown to be an ammonia-sensing material with excellent comprehensive performance, which could real-time detect and monitor ammonia (NH3) in the surrounding environment. The morphology and structure analysis indicated that the as-fabricated semiconductor films were composed of particles with diameters ranging from 80 to 160 nm, and each particle was composed of small crystalline grain with a narrow size about 20 nm, which was the face-centered cubic single crystal structure. X-ray diffraction peaks shifted toward lower angle, and the size of the lattice increased compared with undoped NiO, which demonstrated that zinc ions have been successfully doped into the NiO host structure. Simultaneously, we systematically investigated the gas-sensing properties of the Zn-doped NiO sensors for NH3 detection at room temperature. The sensor based on doped NiO sensing films gave four to nine times faster response and four to six times faster recovery speeds than those of sensor with undoped NiO films, which is important for the NiO sensor practical applications. Moreover, we found that the doped NiO sensors owned outstanding selectivity toward ammonia.

Kleptothermy: an additional category of thermoregulation, and a possible example in sea kraits (Laticauda laticaudata, Serpentes)

PubMed Central

Brischoux, François; Bonnet, Xavier; Shine, Richard

2009-01-01

Lacking the capacity for thermogenesis, most ectotherms inhabiting thermally heterogeneous environments rely instead upon exploiting that ambient heterogeneity. In many cases they maintain body temperatures within a narrow range despite massive spatial and temporal variation in ambient conditions. Reliance on diverse thermal opportunities is reflected in specific terms for organisms that bask in sunlight to regulate their temperature (heliotherms), or that press their bodies against warm substrates to facilitate heat flow (thigmotherms), or that rely on large body mass to maintain thermal constancy (gigantothermy). We propose an additional category of thermoregulators: kleptotherms, which regulate their own temperature by ‘stealing’ heat from other organisms. This concept involves two major conditions: the thermal heterogeneity created by the presence of a warm organism in a cool environment and the selective use of that heterogeneity by another animal to maintain body temperatures at higher (and more stable) levels than would be possible elsewhere in the local area. Kleptothermy occurs in endotherms also, but is usually reciprocal (rather than unilateral as in ectotherms). Thermal monitoring on a small tropical island documents a possible example of kleptothermy, based on high stable temperatures of a sea snake (Laticauda laticaudata) inside a burrow occupied by seabirds. PMID:19656862

High brightness diode lasers controlled by volume Bragg gratings

NASA Astrophysics Data System (ADS)

Glebov, Leonid

2017-02-01

Volume Bragg gratings (VBGs) recorded in photo-thermo-refractive (PTR) glass are holographic optical elements that are effective spectral and angular filters withstanding high power laser radiation. Reflecting VBGs are narrow-band spectral filters while transmitting VBGs are narrow-band angular filters. The use of these optical elements in external resonators of semiconductor lasers enables extremely resonant feedback that provides dramatic spectral and angular narrowing of laser diodes radiation without significant power and efficiency penalty. Spectral narrowing of laser diodes by reflecting VBGs demonstrated in wide spectral region from near UV to 3 μm. Commercially available VBGs have spectral width ranged from few nanometers to few tens of picometers. Efficient spectral locking was demonstrated for edge emitters (single diodes, bars, modules, and stacks), vertical cavity surface emitting lasers (VCSELs), grating coupled surface emitting lasers (GCSELs), and interband cascade lasers (ICLs). The use of multiplexed VBGs provides multiwavelength emission from a single emitter. Spectrally locked semiconductor lasers demonstrated CW power from milliwatts to a kilowatt. Angular narrowing by transmitting VBGs enables single transverse mode emission from wide aperture diode lasers having resonators with great Fresnel numbers. This feature provides close to diffraction limit divergence along a slow axis of wide stripe edge emitters. Radiation exchange between lasers by means of spatially profiled or multiplexed VBGs enables coherent combining of diode lasers. Sequence of VBGs or multiplexed VBGs enable spectral combining of spectrally narrowed diode lasers or laser modules. Thus the use of VBGs for diode lasers beam control provides dramatic increase of brightness.

Value of intracochlear electrically evoked auditory brainstem response after cochlear implantation in patients with narrow internal auditory canal.

PubMed

Song, Mee Hyun; Bae, Mi Ran; Kim, Hee Nam; Lee, Won-Sang; Yang, Won Sun; Choi, Jae Young

2010-08-01

Cochlear implantation in patients with narrow internal auditory canal (IAC) can result in variable outcomes; however, preoperative evaluations have limitations in accurately predicting outcomes. In this study, we analyzed the outcomes of cochlear implantation in patients with narrow IAC and correlated the intracochlear electrically evoked auditory brainstem response (EABR) findings to postoperative performance to determine the prognostic significance of intracochlear EABR. Retrospective case series at a tertiary hospital. Thirteen profoundly deaf patients with narrow IAC who received cochlear implantation from 2002 to 2008 were included in this study. Postoperative performance was evaluated after at least 12 months of follow-up, and postoperative intracochlear EABR was measured to determine its correlation with outcome. The clinical significance of electrically evoked compound action potential (ECAP) was also analyzed. Patients with narrow IAC showed postoperative auditory performances ranging from CAP 0 to 4 after cochlear implantation. Intracochlear EABR measured postoperatively demonstrated prognostic value in the prediction of long-term outcomes, whereas ECAP measurements failed to show a significant correlation with outcome. Consistent with the advantages of intracochlear EABR over extracochlear EABR, this study demonstrates that intracochlear EABR has prognostic significance in predicting long-term outcomes in patients with narrow IAC. Intracochlear EABR measured either intraoperatively or in the early postoperative period may play an important role in deciding whether to continue with auditory rehabilitation using a cochlear implant or to switch to an auditory brainstem implant so as not to miss the optimal timing for language development.

Ultra-narrow-linewidth Brillouin/erbium fiber laser

NASA Astrophysics Data System (ADS)

Chen, Mo; Wang, Chenyu; Wang, Jianfei; Luo, Hong; Meng, Zhou

2018-02-01

Ultra-narrow-linewidth lasers are of great interest in many applications, such as precise spectroscopy, optical communications, and sensors. Stimulated Brillouin scattering (SBS), as one of the main nonlinear effects in fibers, is capable of generating narrow-linewidth light emission. We establish a compact Brillouin/erbium fiber laser (BEFL) utilizing 4-m erbium-doped fiber as both the Brillouin gain and linear media. A 360-kHz-linewidth laser diode is injected into the cavity as the Brillouin pump (BP) light and generates Brillouin Stokes lasing light. Both of the phase noise of the BP and BEFL output are measured by a high-accuracy unbalanced Michelson interferometer. It is demonstrated that 53- dB phase noise reduction is achieved after the BP is transferred into Brillouin Stokes emission. The linewidth of the BEFL is indicated at Hz-range by both calculation and experiment.

Spectral properties of rf emission from high Tc films

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

Jung, G.; Konopka, J.; Vitale, S.

1990-09-15

Spectral properties of rf radiation from intrinsic Josephson junctions in high {Tc} Y-Ba-Cu-O thin film have been measured in the frequency range up to 1.5 GHz. Narrow emission lines with the 3 dB bandwidth of the order of 20 MHz were detected indicating that Josephson clusters radiate coherently. Synchronization conditions are determined by dc current and external magnetic field bias. Frequency locking of radiation to external resonant circuit was also observed. Spectral line narrowing due to resonant lock was distinguished from the coherence-induced narrowing by different tuning properties of the emission line. Noncoherent Josephson radiation manifests itself as a broadbandmore » background noise increase. A pronounced 1/{ital f}-like tail sensitive to dc bias and magnetic field was observed in a low frequency part of the spectrum.« less

Intensity Variations of Narrow Bands of Solar UV Radiation during Descending Phases of SACs 21-23

NASA Astrophysics Data System (ADS)

Gigolashvili, M.; Kapanadze, N.

2014-12-01

The study of variations of four narrow bands of solar spectral irradiance (SSI) in the ultraviolet (UV) range for period 1981-2008 is presented. Observational data obtained by space-flight missions SORCE, UARS, SME and daily meanings of international sunspot number (ISN) have been used. The investigated data cover the decreasing phases of the solar activity cycles (SACs) 21, 22 and 23. We have revealed a peculiar behavior of intensity variability of some solar ultraviolet spectral lines originated in the solar chromospheres for period corresponding to the declining phase of the solar cycle 23. It is found that variability of emission of different solar spectral narrow bands (289.5 nm, 300.5 nm) does not agree equally well with ISN variability during decreasing phase of the solar activity cycle 23. The negative correlations between total solar irradiance and the solar spectral narrow bands of UV emission (298.5 nm, 300.5 nm) had been revealed. The existence of the negative correlation can be explained by the sensitivity of SSI of some emission lines to the solar global magnetic field.

Reduction of timing jitter and intensity noise in normal-dispersion passively mode-locked fiber lasers by narrow band-pass filtering.

PubMed

Qin, Peng; Song, Youjian; Kim, Hyoji; Shin, Junho; Kwon, Dohyeon; Hu, Minglie; Wang, Chingyue; Kim, Jungwon

2014-11-17

Fiber lasers mode-locked with normal cavity dispersion have recently attracted great attention due to large output pulse energy and femtosecond pulse duration. Here we accurately characterized the timing jitter of normal-dispersion fiber lasers using a balanced cross-correlation method. The timing jitter characterization experiments show that the timing jitter of normal-dispersion mode-locked fiber lasers can be significantly reduced by using narrow band-pass filtering (e.g., 7-nm bandwidth filtering in this work). We further identify that the timing jitter of the fiber laser is confined in a limited range, which is almost independent of cavity dispersion map due to the amplifier-similariton formation by insertion of the narrow bandpass filter. The lowest observed timing jitter reaches 0.57 fs (rms) integrated from 10 kHz to 10 MHz Fourier frequency. The rms relative intensity noise (RIN) is also reduced from 0.37% to 0.02% (integrated from 1 kHz to 5 MHz Fourier frequency) by the insertion of narrow band-pass filter.

Biodegradation of Oil Slicks on the Marine Environment.

DTIC Science & Technology

1976-11-01

Ransenula, Candida, Rho4o~torula and Penicillium . The substrate range of these organisms wasevaluated on 11 aliphatic , alicyclic and aromatic...and aromatic compounds (TR 1, ],97C). On the basis of the above substrate range tests and growth, characteristic., a Flavobacteri um sp . and a...incubation. ~ -Paraff Ins served as the bestsubstrates for both organisms, but Plavobacteriua sp . exhibited higher rates of mineralization. Branching

Alkaline pH sensor molecules.

PubMed

Murayama, Takashi; Maruyama, Ichiro N

2015-11-01

Animals can survive only within a narrow pH range. This requires continual monitoring of environmental and body-fluid pH. Although a variety of acidic pH sensor molecules have been reported, alkaline pH sensor function is not well understood. This Review describes neuronal alkaline pH sensors, grouped according to whether they monitor extracellular or intracellular alkaline pH. Extracellular sensors include the receptor-type guanylyl cyclase, the insulin receptor-related receptor, ligand-gated Cl- channels, connexin hemichannels, two-pore-domain K+ channels, and transient receptor potential (TRP) channels. Intracellular sensors include TRP channels and gap junction channels. Identification of molecular mechanisms underlying alkaline pH sensing is crucial for understanding how animals respond to environmental alkaline pH and how body-fluid pH is maintained within a narrow range. © 2015 Wiley Periodicals, Inc.

Spectral data of specular reflectance, narrow-angle transmittance and angle-resolved surface scattering of materials for solar concentrators.

PubMed

Good, Philipp; Cooper, Thomas; Querci, Marco; Wiik, Nicolay; Ambrosetti, Gianluca; Steinfeld, Aldo

2016-03-01

The spectral specular reflectance of conventional and novel reflective materials for solar concentrators is measured with an acceptance angle of 17.5 mrad over the wavelength range 300-2500 nm at incidence angles 15-60° using a spectroscopic goniometry system. The same experimental setup is used to determine the spectral narrow-angle transmittance of semi-transparent materials for solar collector covers at incidence angles 0-60°. In addition, the angle-resolved surface scattering of reflective materials is recorded by an area-scan CCD detector over the spectral range 350-1050 nm. A comprehensive summary, discussion, and interpretation of the results are included in the associated research article "Spectral reflectance, transmittance, and angular scattering of materials for solar concentrators" in Solar Energy Materials and Solar Cells.

Fixation of virgin lunar surface soil

NASA Technical Reports Server (NTRS)

Conley, J. M.; Frazer, R.; Cannon, W. A.

1972-01-01

Two systems are shown to be suitable for fixing loose particulate soils with a polymer film, without visually detectable disturbance of the soil particle spatial relationships. A two-component system is described, which uses a gas monomer condensible at the soil temperature and a gas phase catalyst acting to polymerize the monomer. A one-component system using a monomer which polymerizes spontaneously on and within the top few millimeters of the soil is also considered. The two-component system employs a simpler apparatus, but it operates over a narrower temperature range (approximately -40 to -10 C). Other two-component systems were identified which may operate at soil temperatures as high as +100 C, at relatively narrow temperature ranges of approximately 30 C. The one-component system was demonstrated to operate successfully with initial soil temperatures from -70 C or lower to +150 C.

Acoustic-assisted fluidic hourglasses

NASA Astrophysics Data System (ADS)

Guimaraes, Tamara; Marin, Alvaro; Kaehler, Christian J.; Barnkob, Rune

2017-11-01

Microfluidic devices are prone to get clogged when suspensions are forced through narrow passages. Such clogging events occur when particles form arches that block the channel. In this work we study the clogging probabilities in a microfluidic hourglass when subject to ultrasound. We measure the clogging probabilities for certain ranges of sound amplitudes and particle-to-neck size ratios in which clogging events are more likely to occur. The ultrasound induces acoustic radiation forces on the suspended particles, leading to particle migration perpendicular to the channel flow direction. The transverse particle rearrangement can significantly reduce the clogging probability by decreasing the chances of arching in the narrowing of the passage. We show that by choosing proper sound actuation conditions, the method is reliable, non-intrusive, preventive, and allows to increase the life of fluidic devices (microfluidic or larger) with particles in a wide range of sizes.

Quantum-Well Thermophotovoltaic Cells

NASA Technical Reports Server (NTRS)

Freudlich, Alex; Ignatiev, Alex

2009-01-01

Thermophotovoltaic cells containing multiple quantum wells have been invented as improved means of conversion of thermal to electrical energy. The semiconductor bandgaps of the quantum wells can be tailored to be narrower than those of prior thermophotovoltaic cells, thereby enabling the cells to convert energy from longer-wavelength photons that dominate the infrared-rich spectra of typical thermal sources with which these cells would be used. Moreover, in comparison with a conventional single-junction thermophotovoltaic cell, a cell containing multiple narrow-bandgap quantum wells according to the invention can convert energy from a wider range of wavelengths. Hence, the invention increases the achievable thermal-to-electrical energy-conversion efficiency. These thermophotovoltaic cells are expected to be especially useful for extracting electrical energy from combustion, waste-heat, and nuclear sources having temperatures in the approximate range from 1,000 to 1,500 C.

Improved wavelength coded optical time domain reflectometry based on the optical switch.

PubMed

Zhu, Ninghua; Tong, Youwan; Chen, Wei; Wang, Sunlong; Sun, Wenhui; Liu, Jianguo

2014-06-16

This paper presents an improved wavelength coded time-domain reflectometry based on the 2 × 1 optical switch. In this scheme, in order to improve the signal-noise-ratio (SNR) of the beat signal, the improved system used an optical switch to obtain wavelength-stable, low-noise and narrow optical pulses for probe and reference. Experiments were set up to demonstrate a spatial resolution of 2.5m within a range of 70km and obtain the beat signal with line width narrower than 15 MHz within a range of 50 km in fiber break detection. A system for wavelength-division-multiplexing passive optical network (WDM-PON) monitoring was also constructed to detect the fiber break of different channels by tuning the current applied on the gating section of the distributed Bragg reflector (DBR) laser.

Computational model for behavior shaping as an adaptive health intervention strategy.

PubMed

Berardi, Vincent; Carretero-González, Ricardo; Klepeis, Neil E; Ghanipoor Machiani, Sahar; Jahangiri, Arash; Bellettiere, John; Hovell, Melbourne

2018-03-01

Adaptive behavioral interventions that automatically adjust in real-time to participants' changing behavior, environmental contexts, and individual history are becoming more feasible as the use of real-time sensing technology expands. This development is expected to improve shortcomings associated with traditional behavioral interventions, such as the reliance on imprecise intervention procedures and limited/short-lived effects. JITAI adaptation strategies often lack a theoretical foundation. Increasing the theoretical fidelity of a trial has been shown to increase effectiveness. This research explores the use of shaping, a well-known process from behavioral theory for engendering or maintaining a target behavior, as a JITAI adaptation strategy. A computational model of behavior dynamics and operant conditioning was modified to incorporate the construct of behavior shaping by adding the ability to vary, over time, the range of behaviors that were reinforced when emitted. Digital experiments were performed with this updated model for a range of parameters in order to identify the behavior shaping features that optimally generated target behavior. Narrowing the range of reinforced behaviors continuously in time led to better outcomes compared with a discrete narrowing of the reinforcement window. Rapid narrowing followed by more moderate decreases in window size was more effective in generating target behavior than the inverse scenario. The computational shaping model represents an effective tool for investigating JITAI adaptation strategies. Model parameters must now be translated from the digital domain to real-world experiments so that model findings can be validated.

Deformation across the Pacific-North America plate boundary near San Francisco, California

USGS Publications Warehouse

Prescott, W.H.; Savage, J.C.; Svarc, J.L.; Manaker, D.

2001-01-01

We have detected a narrow zone of compression between the Coast Ranges and the Great Valley, and we have estimated slip rates for the San Andreas, Rodgers Creek, and Green Valley faults just north of San Francisco. These results are based on an analysis of campaign and continuous Global Positioning System (GPS) data collected between 1992 and 2000 in central California. The zone of compression between the Coast Ranges and the Great Valley is 25 km wide. The observations clearly show 3.8??1.5 mm yr-1 of shortening over this narrow zone. The strike slip components are best fit by a model with 20.8??1.9 mm yr-1 slip on the San Andreas fault, 10.3??2.6 mm yr-1 on the Rodgers Creek fault, and 8.1??2.1 mm yr-1 on the Green Valley fault. The Pacific-Sierra Nevada-Great Valley motion totals 39.2??3.8 mm yr-1 across a zone that is 120 km wide (at the latitude of San Francisco). Standard deviations are one ??. The geodetic results suggest a higher than geologic rate for the Green Valley fault. The geodetic results also suggest an inconsistency between geologic estimates of the San Andreas rate and seismologic estimates of the depth of locking on the San Andreas fault. The only convergence observed is in the narrow zone along the border between the Great Valley and the Coast Ranges.

Granular bamboo-derived activated carbon for high CO(2) adsorption: the dominant role of narrow micropores.

PubMed

Wei, Haoran; Deng, Shubo; Hu, Bingyin; Chen, Zhenhe; Wang, Bin; Huang, Jun; Yu, Gang

2012-12-01

Cost-effective biomass-derived activated carbons with a high CO(2) adsorption capacity are attractive for carbon capture. Bamboo was found to be a suitable precursor for activated carbon preparation through KOH activation. The bamboo size in the range of 10-200 mesh had little effect on CO(2) adsorption, whereas the KOH/C mass ratio and activation temperature had a significant impact on CO(2) adsorption. The bamboo-derived activated carbon had a high adsorption capacity and excellent selectivity for CO(2) , and also the adsorption process was highly reversible. The adsorbed amount of CO(2) on the granular activated carbon was up to 7.0 mmol g(-1) at 273 K and 1 bar, which was higher than almost all carbon materials. The pore characteristics of activated carbons responsible for high CO(2) adsorption were fully investigated. Based on the analysis of narrow micropore size distribution of several activated carbons prepared under different conditions, a more accurate micropore range contributing to CO(2) adsorption was proposed. The volume of micropores in the range of 0.33-0.82 nm had a good linear relationship with CO(2) adsorption at 273 K and 1 bar, and the narrow micropores of about 0.55 nm produced the major contribution, which could be used to evaluate CO(2) adsorption on activated carbons. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.