Graphene-oxide-supported CuAl and CoAl layered double hydroxides as enhanced catalysts for carbon-carbon coupling via Ullmann reaction

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

Ahmed, Nesreen S.; Surface Chemistry and Catalytic Studies Group, King Abdulaziz University; Menzel, Robert

Two efficient catalyst based on CuAl and CoAl layered double hydroxides (LDHs) supported on graphene oxide (GO) for the carbon-carbon coupling (Classic Ullmann Homocoupling Reaction) are reported. The pure and hybrid materials were synthesised by direct precipitation of the LDH nanoparticles onto GO, followed by a chemical, structural and physical characterisation by electron microscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), surface area measurements and X-ray photoelectron spectroscopy (XPS). The GO-supported and unsupported CuAl-LDH and CoAl-LDH hybrids were tested over the Classic Ullman Homocoupling Reaction of iodobenzene. In the current study CuAl- and CoAl-LDHs have shown excellent yields (91% and 98%,more » respectively) at very short reaction times (25 min). GO provides a light-weight, charge complementary and two-dimensional material that interacts effectively with the 2D LDHs, in turn enhancing the stability of LDH. After 5 re-use cycles, the catalytic activity of the LDH/GO hybrid is up to 2 times higher than for the unsupported LDH. - Graphical abstract: CuAl- and CoAl-LDHs have shown excellent yields (91% and 98%, respectively) at very short reaction times (25 min). GO provides a light-weight, charge complementary, two-dimensional material that interacts effectively with the 2D LDHs, in turn enhancing the stability of LDH. - Highlights: • CuAl LDH/GO and CoAl LDH/GO hybrid materials with different LDH compositions were prepared. • Hybrids were fully characterised and their catalytic efficiency over the Classic Ullman Reaction was studied. • CuAl- and CoAl-LDHs have shown excellent yields (91% and 98%, respectively) in 25 min reaction times. • GO provides a light-weight, charge complementary, two-dimensional material that interacts effectively with the 2D LDHs. • After 5 re-use cycles, the catalytic activity of the LDH/GO hybrid is up to 2 times higher than for the unsupported LDH.« less

Absolute dimensions and masses of eclipsing binaries. V. IQ Persei

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

Lacy, C.H.; Frueh, M.L.

1985-08-01

New photometric and spectroscopic observations of the 1.7 day eclipsing binary IQ Persei (B8 + A6) have been analyzed to yield very accurate fundamental properties of the system. Reticon spectroscopic observations obtained at McDonald Observatory were used to determine accurate radial velocities of both stars in this slightly eccentric large light-ratio binary. A new set of VR light curves obtained at McDonald Observatory were analyzed by synthesis techniques, and previously published UBV light curves were reanalyzed to yield accurate photometric orbits. Orbital parameters derived from both sets of photometric observations are in excellent agreement. The absolute dimensions, masses, luminosities, andmore » apsidal motion period (140 yr) derived from these observations agree well with the predictions of theoretical stellar evolution models. The A6 secondary is still very close to the zero-age main sequence. The B8 primary is about one-third of the way through its main-sequence evolution. 27 references.« less

Photochemical preparation of pyrimidin-2(1H)-ones by rhenium(I) complexes with visible light.

PubMed

Liu, Qiang; Li, Ya-Nan; Zhang, Hui-Hui; Chen, Bin; Tung, Chen-Ho; Wu, Li-Zhu

2011-03-04

With visible light irradiation (λ > 400 nm) of rhenium(I) complexes (P1-P4), a photochemical conversion from 3,4-dihydropyrimidin-2(1H)-ones to pyrimidin-2(1H)-ones at room temperature has been achieved with good to excellent yields in CH(3)CN-H(2)O solution containing CCl(4) and K(2)CO(3). Luminescence quenching study and product analysis reveal that photoinduced electron transfer between rhenium(I) complex P and 3,4-dihydropyrimidin-2(1H)-ones plays an important role in the initial event.

Scintillator tiles read out with silicon photomultipliers

NASA Astrophysics Data System (ADS)

Pooth, O.; Radermacher, T.; Weingarten, S.; Weinstock, L.

2015-10-01

A detector prototype based on a fast plastic scintillator read out with silicon photomultipliers is presented. All studies have been done with cosmic muons and focus on parameter optimization such as coupling the SiPM to the scintillator or wrapping the scintillator with reflective material. The prototype shows excellent results regarding the light-yield and offers a detection efficiency of 99.5% with a signal purity of 99.9% for cosmic muons.

A Brown Mesoporous TiO2-x /MCF Composite with an Extremely High Quantum Yield of Solar Energy Photocatalysis for H2 Evolution.

PubMed

Xing, Mingyang; Zhang, Jinlong; Qiu, Bocheng; Tian, Baozhu; Anpo, Masakazu; Che, Michel

2015-04-24

A brown mesoporous TiO2-x /MCF composite with a high fluorine dopant concentration (8.01 at%) is synthesized by a vacuum activation method. It exhibits an excellent solar absorption and a record-breaking quantum yield (Φ = 46%) and a high photon-hydrogen energy conversion efficiency (η = 34%,) for solar photocatalytic H2 production, which are all higher than that of the black hydrogen-doped TiO2 (Φ = 35%, η = 24%). The MCFs serve to improve the adsorption of F atoms onto the TiO2 /MCF composite surface, which after the formation of oxygen vacancies by vacuum activation, facilitate the abundant substitution of these vacancies with F atoms. The decrease of recombination sites induced by high-concentration F doping and the synergistic effect between lattice Ti(3+)-F and surface Ti(3+)-F are responsible for the enhanced lifetime of electrons, the observed excellent absorption of solar light, and the photocatalytic production of H2 for these catalysts. The as-prepared F-doped composite is an ideal solar light-driven photocatalyst with great potential for applications ranging from the remediation of environmental pollution to the harnessing of solar energy for H2 production. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Two-dimensional assembly structure of graphene and TiO2 nanosheets from titanic acid with enhanced visible-light photocatalytic performance

NASA Astrophysics Data System (ADS)

Hao, Rong; Guo, Shien; Wang, Xiuwen; Feng, Tong; Feng, Qingmao; Li, Mingxia; Jiang, Baojiang

2016-06-01

The titanic acid sheets were prepared by one-step hydrazine hydrate-assisted hydrothermal process. Then the reduced graphite oxide (rGO)@TiO2 nanosheet composites were finally obtained through ultrasonic exfoliation and following calcination treatment process. rGO@TiO2 nanosheet composites show excellent hydrogen production performance under AM1.5 light source. The highest hydrogen evolution yield (923.23 μmol) is nearly two times higher than that of pure TiO2, mainly due to the special electron structure and more active sites for TiO2 nanosheet. The introduction of graphene could improve the TiO2 nanosheet stability and extend visible-light absorption range.

Facile synthesis of highly active reduced graphene oxide-CuI catalyst through a simple combustion method for photocatalytic reduction of CO2 to methanol

NASA Astrophysics Data System (ADS)

Zhang, Wenjun; Li, Yingjie; Zhang, Xiaoxiong; Li, Cuiluo

2017-09-01

We report a facile combustion method synthesis of reduced graphene oxide/CuI composites as a photocatalyst, in which CuI nanoparticles were homogeneously distributed on the surface of reduced graphene oxide (rGO), showing a good visible light response. The rGO-supported and unsupported CuI hybrids were tested over the photocatalytic reduction of CO2 for methanol evolution in visible light. In the current study rGO-CuI composites have shown excellent yields (19.91 μmol g-cat-1). rGO provides a light-weight, charge complementary and two-dimensional material that interacts effectively with the CuI nanoparticles.

Highly Efficient Carbon Dots with Reversibly Switchable Green-Red Emissions for Trichromatic White Light-Emitting Diodes.

PubMed

Yuan, Biao; Guan, Shanyue; Sun, Xingming; Li, Xiaoming; Zeng, Haibo; Xie, Zheng; Chen, Ping; Zhou, Shuyun

2018-05-09

Carbon dots (CDs) have potentials to be utilized in optoelectronic devices, bioimaging, and photocatalysis. The majority of the current CDs with high quantum yield to date were limited in the blue light emission region. Herein, on the basis of surface electron-state engineering, we report a kind of CDs with reversible switching ability between green and red photoluminescence with a quantum yield (QY) of both up to 80%. Highly efficient green and red solid-state luminescence is realized by doping CDs into a highly transparent matrix of methyltriethoxysilane and 3-triethoxysilylpropylamine to form CDs/gel glasses composites with QYs of 80 and 78%. The CDs/gel glasses show better transmittance in visible light bands and excellent thermal stability. A blue-pumped CDs/gel glasses phosphor-based trichromatic white light-emitting diode (WLED) is realized, whose color rendering index is 92.9. The WLED gets the highest luminous efficiency of 71.75 lm W -1 in CDs-based trichromatic WLEDs. This work opens a door for developing highly efficient green- and red-emissive switching CDs which were used as phosphors for WLEDs and have the tendency for applications in other fields, such as sensing, bioimaging, and photocatalysis.

Bismuth germanate coupled to near ultraviolet silicon photomultipliers for time-of-flight PET

PubMed Central

Kwon, Sun Il; Gola, Alberto; Ferri, Alessandro; Piemonte, Claudio; Cherry, Simon R.

2016-01-01

Bismuth germanate (BGO) was a very attractive scintillator in early-generation positron emission tomography (PET) scanners. However, the major disadvantages of BGO are lower light yield and longer rise and decay time compared to currently popular scintillators such as LSO and LYSO. This results in poorer coincidence timing resolution and it has generally been assumed that BGO is not a suitable scintillator for time-of-flight (TOF) PET applications. However, when a 511-keV photon interacts in a scintillator, a number of Cerenkov photons are produced promptly by energetic electrons released by photoelectric or Compton interactions. If these prompt photons can be captured, they could provide a better timing trigger for PET. Since BGO has a high refractive index (increasing the Cerenkov light yield) and excellent optical transparency down to 320 nm (Cerenkov light yield is higher at shorter wavelengths), we hypothesized that the coincidence timing resolution of BGO can be significantly improved by efficient detection of the Cerenkov photons. However, since the number of Cerenkov photons is far less than the number of scintillation photons, and they are more abundant in the UV and blue part of the spectrum, photosensors need to have high UV/blue sensitivity, fast temporal response, and very low noise in order to trigger on the faint Cerenkov signal. In this respect, NUV-HD silicon photomultipliers (SiPMs) (FBK, Trento, Italy) are an excellent fit for our approach. In this study, coincidence events were measured using BGO crystals coupled with NUV-HD SiPMs. The existence and influence of Cerenkov photons on the timing measurements were studied using different configurations to exploit the directionality of the Cerenkov emissions. Coincidence resolving time values (FWHM) of ~270 ps from 2 × 3 × 2 mm3 BGO crystals and ~560 ps from 3 × 3 × 20 mm3 BGO crystals were obtained. To our knowledge, these are the best coincidence resolving time values reported for BGO to date. With these values, BGO can be considered as a relevant scintillator for TOF PET scanners, especially if photodetectors with even better near UV/blue response can be developed to further improve the efficiency of Cerenkov light detection. PMID:27589153

Stable CdS QDs with intense broadband photoluminescence and high quantum yields

NASA Astrophysics Data System (ADS)

Mandal, Abhijit; Saha, Jony; De, Goutam

2011-11-01

Aqueous synthesis of CdS quantum dots (QDs) using thiolactic acid (TLA) as a capping agent was reported. These QDs exhibited excellent colloidal and photostability over a span of 2 years and showed intense broadband and almost white photoluminescence suitable for solid state lighting devices. The photoluminescence (PL) property of the aqueous CdS QDs is optimized by adjusting various processing parameters. The highest quantum yield (QY) achieved for TLA capped CdS QDs of average size 3.5 nm was ˜50%. Luminescence lifetime measurements of CdS-TLA QDs indicated longer lifetimes and a larger contribution of the surface-related emission, indicating removal of quenching defects.

Recombinant Cyanobacteria for the Asymmetric Reduction of C=C Bonds Fueled by the Biocatalytic Oxidation of Water.

PubMed

Köninger, Katharina; Gómez Baraibar, Álvaro; Mügge, Carolin; Paul, Caroline E; Hollmann, Frank; Nowaczyk, Marc M; Kourist, Robert

2016-04-25

A recombinant enoate reductase was expressed in cyanobacteria and used for the light-catalyzed, enantioselective reduction of C=C bonds. The coupling of oxidoreductases to natural photosynthesis allows asymmetric syntheses fueled by the oxidation of water. Bypassing the addition of sacrificial cosubstrates as electron donors significantly improves the atom efficiency and avoids the formation of undesired side products. Crucial factors for product formation are the availability of NADPH and the amount of active enzyme in the cells. The efficiency of the reaction is comparable to typical whole-cell biotransformations in E. coli. Under optimized conditions, a solution of 100 mg prochiral 2-methylmaleimide was reduced to optically pure 2-methylsuccinimide (99 % ee, 80 % yield of isolated product). High product yields and excellent optical purities demonstrate the synthetic usefulness of light-catalyzed whole-cell biotransformations using recombinant cyanobacteria. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Capillary-scale direct measurement of hemoglobin concentration of erythrocytes using photothermal angular light scattering.

PubMed

Kim, Uihan; Song, Jaewoo; Lee, Donghak; Ryu, Suho; Kim, Soocheol; Hwang, Jaehyun; Joo, Chulmin

2015-12-15

We present a direct, rapid and chemical-free detection method for hemoglobin concentration ([Hb]), based on photothermal angular light scattering. The iron oxides contained in hemoglobin molecules exhibit high absorption of 532-nm light and generate heat under the illumination of 532-nm light, which subsequently alters the refractive index of blood. We measured this photothermal change in refractive index by employing angular light scattering spectroscopy with the goal of quantifying [Hb] in blood samples. Highly sensitive [Hb] measurement of blood samples was performed by monitoring the shifts in angularly dispersed scattering patterns from the blood-loaded microcapillary tubes. Our system measured [Hb] over the range of 0.35-17.9 g/dL with a detection limit of ~0.12 g/dL. Our sensor was characterized by excellent correlation with a reference hematology analyzer (r>0.96), and yielded a precision of 0.63 g/dL for a blood sample of 9.0 g/dL. Copyright © 2015 Elsevier B.V. All rights reserved.

Greenhouse intelligent control system based on microcontroller

NASA Astrophysics Data System (ADS)

Zhang, Congwei

2018-04-01

As one of the hallmarks of agricultural modernization, intelligent greenhouse has the advantages of high yield, excellent quality, no pollution and continuous planting. Taking AT89S52 microcontroller as the main controller, the greenhouse intelligent control system uses soil moisture sensor, temperature and humidity sensors, light intensity sensor and CO2 concentration sensor to collect measurements and display them on the 12864 LCD screen real-time. Meantime, climate parameter values can be manually set online. The collected measured values are compared with the set standard values, and then the lighting, ventilation fans, warming lamps, water pumps and other facilities automatically start to adjust the climate such as light intensity, CO2 concentration, temperature, air humidity and soil moisture of the greenhouse parameter. So, the state of the environment in the greenhouse Stabilizes and the crop grows in a suitable environment.

A fluorimetric study of the thorium-morin system

USGS Publications Warehouse

Milkey, Robert G.; Fletcher, Mary H.

1956-01-01

Thorium reacts with morin to yield a yellow complex that fluoresces when irradiated with ultraviolet light. The effect on the fluorescence of such variable as concentration of acid, alcohol, thorium, morin, and complex; time, temperature, and wavelength of exciting light are studied to determine experimental conditions yielding maximum fluorescence. The effects of Zr4+, Al3+, Fe3+, Ca2+, and La3+ are discussed. The fundamental relationships between light absorption and fluorescence are expressed in a general equation which applied to a three-component system when the fluorescence is measured in a transmission-type fluorimeter. This general equation is used to obtain an expression for the fluorescence of the thorium-morin system. Equations, derived from experimental data, related both the fraction of thorium reacted to form complex and the fraction of unquenched fluorescence to the concentration of uncombined morin. These functions, when combined with the general equation, give an expression which relates the total net fluorescence to the amount of uncombined morin in the solution. This last equation can be used to determine the one region for the concentration of uncombined morin that gives maximum sensitivity for the system. Calculated standard curves are in excellent agreement with experimental curves.

Spectroscopic ellipsometer based on direct measurement of polarization ellipticity.

PubMed

Watkins, Lionel R

2011-06-20

A polarizer-sample-Wollaston prism analyzer ellipsometer is described in which the ellipsometric angles ψ and Δ are determined by direct measurement of the elliptically polarized light reflected from the sample. With the Wollaston prism initially set to transmit p- and s-polarized light, the azimuthal angle P of the polarizer is adjusted until the two beams have equal intensity. This condition yields ψ=±P and ensures that the reflected elliptically polarized light has an azimuthal angle of ±45° and maximum ellipticity. Rotating the Wollaston prism through 45° and adjusting the analyzer azimuth until the two beams again have equal intensity yields the ellipticity that allows Δ to be determined via a simple linear relationship. The errors produced by nonideal components are analyzed. We show that the polarizer dominates these errors but that for most practical purposes, the error in ψ is negligible and the error in Δ may be corrected exactly. A native oxide layer on a silicon substrate was measured at a single wavelength and multiple angles of incidence and spectroscopically at a single angle of incidence. The best fit film thicknesses obtained were in excellent agreement with those determined using a traditional null ellipsometer.

Diboron compound-based organic light-emitting diodes with high efficiency and reduced efficiency roll-off

NASA Astrophysics Data System (ADS)

Wu, Tien-Lin; Huang, Min-Jie; Lin, Chih-Chun; Huang, Pei-Yun; Chou, Tsu-Yu; Chen-Cheng, Ren-Wu; Lin, Hao-Wu; Liu, Rai-Shung; Cheng, Chien-Hong

2018-04-01

Organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) materials are promising for the realization of highly efficient light emitters. However, such devices have so far suffered from efficiency roll-off at high luminance. Here, we report the design and synthesis of two diboron-based molecules, CzDBA and tBuCzDBA, which show excellent TADF properties and yield efficient OLEDs with very low efficiency roll-off. These donor-acceptor-donor (D-A-D) type and rod-like compounds concurrently generate TADF with a photoluminescence quantum yield of 100% and an 84% horizontal dipole ratio in the thin film. A green OLED based on CzDBA exhibits a high external quantum efficiency of 37.8 ± 0.6%, a current efficiency of 139.6 ± 2.8 cd A-1 and a power efficiency of 121.6 ± 3.1 lm W-1 with an efficiency roll-off of only 0.3% at 1,000 cd m-2. The device has a peak emission wavelength of 528 nm and colour coordinates of the Commission International de ĺEclairage (CIE) of (0.31, 0.61), making it attractive for colour-display applications.

The low-temperature scintillation properties of bismuth germanate and its application to high-energy gamma radiation imaging devices.

PubMed

Piltingsrud, H V

1979-12-01

Bismuth germanate is a scintillation material with very high z, and high density (7.13 g/cm3). It is a rugged, nonhygroscopic, crystalline material with room-temperature scintillation properties described by previous investigators as having a light yield approximately 8% of that of NaI(Tl), emission peak at approximately 480 nm, decay constant of 0.3 microsec, and energy resolution congruent to 15% (FWHM) for Cs-137 gamma radiations. These properties make it an excellent candidate for applications involving the detection of high-energy gamma photons and positron annihilation radiation, particularly when good spatial resolution is desired. At room temperature, however, the application of this material is somewhat limited by low light output and poor energy resolution. This paper presents new data on the scintillation properties of bismuth germanate as a function of temperature from -- 196 degrees C to j0 degrees C. Low-temperature use of the material is shown to greatly improve its light yield and energy resolution. The implications of this work to the design of imaging devices for high-energy radiation in health physics and nuclear medicine are discussed.

Effect of Nitrogen Doping Level on the Performance of N-Doped Carbon Quantum Dot/TiO2 Composites for Photocatalytic Hydrogen Evolution.

PubMed

Shi, Run; Li, Zi; Yu, Huijun; Shang, Lu; Zhou, Chao; Waterhouse, Geoffrey I N; Wu, Li-Zhu; Zhang, Tierui

2017-11-23

Carbon quantum dots (CQDs) have attracted widespread interest for photocatalytic applications, owing to their low cost and excellent electron donor/acceptor properties. However, their advancement as visible-light photosensitizers in CQDs/semiconductor nanocomposites is currently impaired by their poor quantum yields (QYs). Herein, we describe the successful fabrication of a series of nitrogen-doped CQDs (NCDs) with N/C atomic ratios ranging from 0.14-0.30. NCDs with the highest N-doping level afforded a remarkable external QY of 66.8 % at 360 nm, and outstanding electron transfer properties and photosensitization efficiencies when physically adsorbed on P25 TiO 2 . A NCDs/P25-TiO 2 hybrid demonstrated excellent performance for hydrogen evolution in aqueous methanol under both UV and visible-light illumination relative to pristine P25 TiO 2 . Controlled nitrogen doping of CQDs therefore represents a very effective strategy for optimizing the performance of CQDs/semiconductor hybrid photocatalysts. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spontaneous light emission by atomic hydrogen: Fermi's golden rule without cheating

NASA Astrophysics Data System (ADS)

Debierre, V.; Durt, T.; Nicolet, A.; Zolla, F.

2015-10-01

Focusing on the 2 p- 1 s transition in atomic hydrogen, we investigate through first order perturbation theory the time evolution of the survival probability of an electron initially taken to be in the excited (2 p) state. We examine both the results yielded by the standard dipole approximation for the coupling between the atom and the electromagnetic field - for which we propose a cutoff-independent regularisation - and those yielded by the exact coupling function. In both cases, Fermi's golden rule is shown to be an excellent approximation for the system at hand: we found its maximal deviation from the exact behaviour of the system to be of order 10-8 /10-7. Our treatment also yields a rigorous prescription for the choice of the optimal cutoff frequency in the dipole approximation. With our cutoff, the predictions of the dipole approximation are almost indistinguishable at all times from the exact dynamics of the system.

A Systematic Approach to Achieving High Performance Hybrid Lighting Phosphors with Excellent Thermal- and Photostability

DOE PAGES

Fang, Yang; Liu, Wei; Teat, Simon J.; ...

2016-12-07

We have designed and synthesized a family of high-performance inorganic-organic hybrid phosphor materials composed of extended and robust networks of one-, two- and three-dimensions. Following a bottom-up solution-based synthetic approach, these structures are constructed by connecting highly emissive Cu 4I 4 cubic clusters via carefully selected ligands that form strong Cu-N bonds. They emit intensive yellow-orange light with high luminescence quantum efficiency, coupled with large Stokes shift which greatly reduces self-absorption. They also demonstrate exceptionally high framework- and photo-stability, comparable to those of commercial phosphors. The high stabilities are the result of significantly enhanced Cu-N bonds, as confirmed by themore » DFT binding energy and electron density calculations. Possible emission mechanisms are analyzed based on the results of theoretical calculations and optical experiments. Two-component white phosphors obtained by blending blue and yellow emitters reach an internal quantum yield (IQY) as high as 82% and correlated color temperature (CCT) as low as 2534 K. The performance level of this sub-family exceeds all other types of Cu-I based hybrid systems. The combined advantages make them excellent candidates as alternative rare-earth element (REE) free phosphors for possible use in energy-efficient lighting devices.« less

High-nitrogen-based pyrotechnics: longer- and brighter-burning, perchlorate-free, red-light illuminants for military and civilian applications.

PubMed

Sabatini, Jesse J; Nagori, Amita V; Chen, Gary; Chu, Phillip; Damavarapu, Reddy; Klapötke, Thomas M

2012-01-09

The full-up prototype testing of perchlorate-free, hand-held, signal illuminants for the US Army's M126A1 red star parachute hand-held signal is described. Compared to the perchlorate-containing control, the disclosed illuminants yielded excellent stabilities toward various ignition stimuli while offering superior pyrotechnic performance. Militarily, the illuminants provided further evidence that development of smaller hand-held signal items in an environmentally conscious way is a realistic and obtainable goal. The results are also important from the perspective of civilian fireworks, as the development of brighter, longer-burning, and environmentally compatible red-light-emitting pyrotechnics is now possible. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bismuth germanate coupled to near ultraviolet silicon photomultipliers for time-of-flight PET.

PubMed

Kwon, Sun Il; Gola, Alberto; Ferri, Alessandro; Piemonte, Claudio; Cherry, Simon R

2016-09-21

Bismuth germanate (BGO) was a very attractive scintillator in early-generation positron emission tomography (PET) scanners. However, the major disadvantages of BGO are lower light yield and longer rise and decay time compared to currently popular scintillators such as LSO and LYSO. This results in poorer coincidence timing resolution and it has generally been assumed that BGO is not a suitable scintillator for time-of-flight (TOF) PET applications. However, when a 511 keV photon interacts in a scintillator, a number of Cerenkov photons are produced promptly by energetic electrons released by photoelectric or Compton interactions. If these prompt photons can be captured, they could provide a better timing trigger for PET. Since BGO has a high refractive index (increasing the Cerenkov light yield) and excellent optical transparency down to 320 nm (Cerenkov light yield is higher at shorter wavelengths), we hypothesized that the coincidence timing resolution of BGO can be significantly improved by efficient detection of the Cerenkov photons. However, since the number of Cerenkov photons is far less than the number of scintillation photons, and they are more abundant in the UV and blue part of the spectrum, photosensors need to have high UV/blue sensitivity, fast temporal response, and very low noise in order to trigger on the faint Cerenkov signal. In this respect, NUV-HD silicon photomultipliers (SiPMs) (FBK, Trento, Italy) are an excellent fit for our approach. In this study, coincidence events were measured using BGO crystals coupled with NUV-HD SiPMs. The existence and influence of Cerenkov photons on the timing measurements were studied using different configurations to exploit the directionality of the Cerenkov emissions. Coincidence resolving time values (FWHM) of ~270 ps from 2  ×  3  ×  2 mm 3 BGO crystals and ~560 ps from 3  ×  3  ×  20 mm 3 BGO crystals were obtained. To our knowledge, these are the best coincidence resolving time values reported for BGO to date. With these values, BGO can be considered as a relevant scintillator for TOF PET scanners, especially if photodetectors with even better near UV/blue response can be developed to further improve the efficiency of Cerenkov light detection.

High-Performance Doped Strontium Iodide Crystal Growth Using a Modified Bridgman Method

NASA Astrophysics Data System (ADS)

Rowe, Emmanuel

The importance of gamma-ray spectroscopy---the science of determining the distribution of energy in a gamma field---can rarely be overstated. High performance scintillators for gamma-ray spectroscopy in Nuclear Nonproliferation applications and homeland security require excellent energy resolution to distinguish neighboring element and isotope lines while minimizing the time and exposure to do so. Semiconductor detectors operate by converting incident photons directly into electrical pulses, but often have problems of high costs due to constituent segregation and surface states as is the case for Cadmium Zinc Telluride. The ideal scintillator material for gamma spectrometer will therefore requires high light yield, excellent proportionality between light yield and gamma photon energy, and material uniformity. A scintillator should possess the following properties; it should convert the kinetic energy of the generated charged particles (typically K-shell electrons) into detectable visible light. This conversion should be linear-the light yield should be proportional to deposited energy over as wide a range as possible. For good light collection, the medium should be transparent to the wavelength of its own emission. The decay time of the induced luminescence should be short so that fast signal pulses can be generated. The medium should be of good optical quality and subject to manufacture in sizes large enough to be of interest as a practical detector. Its index of refraction should be near that of glass (~1.5) to permit efficient coupling of scintillation light to a photomultiplier tube or other photo-sensor. In the past decade, inorganic scintillator research has focused less on improving the characteristics of known scintillators, but rather on the search for new hosts capable of fast response and high energy resolution. Extensive searches have been made for hosts doped with lanthanide activators utilizing the allowed 5d-4f transition. These 5d-4f transitions are dipole-allowed and thus are about 106 times stronger than the more frequently observed 4f-4f transition in the trivalent rare earth ions. Ce3+, Nd3+ and Pr3+ have been investigated for fast response applications while Ce3+, Eu 2+, and Yb2+ stand out as the most promising activators offering high light yield, and high energy resolution. Using a modified Bridgman growth technique we have grown crystals with a low energy resolution of 2.6% at 662 keV, which is lower than the previous 2.8% reported for SrI2:Eu 2+. The modified technique (called so for its vertical crystal growth orientation) is necessary due to the anisotropic thermal expansion coefficient of Strontium Iodide. The problem plaguing the growth of the crystal is spontaneous cracking, which usually appear during cooling in the bulk. With the use of a zone separating shield, one can achieve more control of the temperature gradient between the two zones without compromising the actual temperature of the two zones. Additionally the use of codopants, in particular divalent magnesium improved the crystalline quality by acting as a gathering for iodine ions, which led to reduction of defect density.

Vertical pillar-superlattice array and graphene hybrid light emitting diodes.

PubMed

Lee, Jung Min; Choung, Jae Woong; Yi, Jaeseok; Lee, Dong Hyun; Samal, Monica; Yi, Dong Kee; Lee, Chul-Ho; Yi, Gyu-Chul; Paik, Ungyu; Rogers, John A; Park, Won Il

2010-08-11

We report a type of device that combines vertical arrays of one-dimensional (1D) pillar-superlattice (PSL) structures with 2D graphene sheets to yield a class of light emitting diode (LED) with interesting mechanical, optical, and electrical characteristics. In this application, graphene sheets coated with very thin metal layers exhibit good mechanical and electrical properties and an ability to mount, in a freely suspended configuration, on the PSL arrays as a top window electrode. Optical characterization demonstrates that graphene exhibits excellent optical transparency even after deposition of the thin metal films. Thermal annealing of the graphene/metal (Gr/M) contact to the GaAs decreases the contact resistance, to provide enhanced carrier injection. The resulting PSL-Gr/M LEDs exhibit bright light emission over large areas. The result suggests the utility of graphene-based materials as electrodes in devices with unusual, nonplanar 3D architectures.

History and current status of strontium iodide scintillators

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

Cherepy, Nerine J.; Beck, Patrick R.; Payne, Stephen A.

Eu-doped strontium iodide single crystal growth has reached maturity and prototype SrI 2(Eu)-based gamma ray spectrometers provide detection performance advantages over standard detectors. SrI 2(Eu) offers a high, proportional light yield of >80,000 photons/MeV. Energy resolution of <3% at 662 keV with 1.5” x 1.5” SrI2(Eu) crystals is routinely achieved, by employing either a small taper at the top of the crystal or a digital readout technique. These methods overcome light-trapping, in which scintillation light is re-absorbed and re-emitted in Eu 2+-doped crystals. As a result, its excellent energy resolution, lack of intrinsic radioactivity or toxicity, and commercial availability makemore » SrI 2(Eu) the ideal scintillator for use in handheld radioisotope identification devices. A 6-lb SrI 2(Eu) radioisotope identifier is described.« less

History and current status of strontium iodide scintillators

DOE PAGES

Cherepy, Nerine J.; Beck, Patrick R.; Payne, Stephen A.; ...

2017-09-15

Eu-doped strontium iodide single crystal growth has reached maturity and prototype SrI 2(Eu)-based gamma ray spectrometers provide detection performance advantages over standard detectors. SrI 2(Eu) offers a high, proportional light yield of >80,000 photons/MeV. Energy resolution of <3% at 662 keV with 1.5” x 1.5” SrI2(Eu) crystals is routinely achieved, by employing either a small taper at the top of the crystal or a digital readout technique. These methods overcome light-trapping, in which scintillation light is re-absorbed and re-emitted in Eu 2+-doped crystals. As a result, its excellent energy resolution, lack of intrinsic radioactivity or toxicity, and commercial availability makemore » SrI 2(Eu) the ideal scintillator for use in handheld radioisotope identification devices. A 6-lb SrI 2(Eu) radioisotope identifier is described.« less

Crystal growth and scintillation properties of strontium iodide scintillators

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

van Loef, Edgar; Wilson, Cody; Cherepy, Nerine

2009-06-01

Single crystals of SrI{sub 2}:Eu and SrI{sub 2}:Ce/Na were grown from anhydrous iodides by the vertical Bridgman technique in evacuated silica ampoules. Growth rates were of the order of 5-30 mm/day. Radioluminescence spectra of SrI{sub 2}:Eu and SrI{sub 2}:Ce/Na exhibit a broad band due to Eu{sup 2+} and Ce{sup 3+} emission, respectively. The maximum in the luminescence spectrum of SrI{sub 2}:Eu is found at 435 nm. The spectrum of SrI{sub 2}:Ce/Na exhibits a doublet peaking at 404 and 435 nm attributed to Ce{sup 3+} emission, while additional impurity - or defected - related emission is present at approximately 525 nm.more » The strontium iodide scintillators show very high light yields of up to 120,000 photons/MeV, have energy resolutions down to 3% at 662 keV (Full Width Half Maximum) and exhibit excellent light yield proportionality with a standard deviation of less than 5% between 6 and 460 keV.« less

Doping Lanthanide into Perovskite Nanocrystals: Highly Improved and Expanded Optical Properties.

PubMed

Pan, Gencai; Bai, Xue; Yang, Dongwen; Chen, Xu; Jing, Pengtao; Qu, Songnan; Zhang, Lijun; Zhou, Donglei; Zhu, Jinyang; Xu, Wen; Dong, Biao; Song, Hongwei

2017-12-13

Cesium lead halide (CsPbX 3 ) perovskite nanocrystals (NCs) have demonstrated extremely excellent optical properties and great application potentials in various optoelectronic devices. However, because of the anion exchange, it is difficult to achieve white-light and multicolor emission for practical applications. Herein, we present the successful doping of various lanthanide ions (Ce 3+ , Sm 3+ , Eu 3+ , Tb 3+ , Dy 3+ , Er 3+ , and Yb 3+ ) into the lattices of CsPbCl 3 perovskite NCs through a modified hot-injection method. For the lanthanide ions doped perovskite NCs, high photoluminescence quantum yield (QY) and stable and widely tunable multicolor emissions spanning from visible to near-infrared (NIR) regions are successfully obtained. This work indicates that the doped perovskite NCs will inherit most of the unique optical properties of lanthanide ions and deliver them to the perovskite NC host, thus endowing the family of perovskite materials with excellent optical, electric, or magnetic properties.

Single-mode light source fabrication based on colloidal quantum dots

NASA Astrophysics Data System (ADS)

Xu, Jianfeng; Chen, Bing; Baig, Sarfaraz; Wang, Michael R.

2009-02-01

There are huge market demands for innovative, cheap and efficient light sources, including light emitting devices, such as LEDs and lasers. However, the light source development in the visible spectral range encounters significant difficulties these years. The available visible wavelength LEDs or lasers are few, large and expensive. The main challenge lies at the lack of efficient light media. Semiconductor nanocrystal quantum dots (QDs) have recently commanded considerable attention. As a result of quantum confinement effect, the emission color of these QDs covers the whole visible spectral range and can be modified dramatically by simply changing their size. Such spectral tunability, together with large photoluminescence quantum yield and photostability, make QDs attractive for potential applications in a variety of light emitting technologies. However, there are still several technical problems that hinder their application as light sources. One main issue is how to fabricate these QDs into a solid state device while still retaining their original optical emission properties. A vacuum assisted micro-fluidic fabrication of guided wave devices has demonstrated low waveguide propagation loss, lower crosstalk, and improved waveguide structures. We report herein the combination of the excellent emission properties of QDs and novel vacuum assisted micro-fluidic photonic structure fabrication technique to realize single-mode efficient light sources.

Mild and Low-Pressure fac-Ir(ppy)3 -Mediated Radical Aminocarbonylation of Unactivated Alkyl Iodides through Visible-Light Photoredox Catalysis.

PubMed

Chow, Shiao Y; Stevens, Marc Y; Åkerbladh, Linda; Bergman, Sara; Odell, Luke R

2016-06-27

A novel, mild and facile preparation of alkyl amides from unactivated alkyl iodides employing a fac-Ir(ppy)3 -catalyzed radical aminocarbonylation protocol has been developed. Using a two-chambered system, alkyl iodides, fac-Ir(ppy)3 , amines, reductants, and CO gas (released ex situ from Mo(CO)6 ), were combined and subjected to an initial radical reductive dehalogenation generating alkyl radicals, and a subsequent aminocarbonylation with amines affording a wide range of alkyl amides in moderate to excellent yields. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Low-energy antikaon-nuclei interactions studies by AMADEUS: from QCD with strangeness to neutron stars

NASA Astrophysics Data System (ADS)

Piscicchia, K.; Curceanu, C.; Cargnelli, M.; Del Grande, R.; Fabbietti, L.; Marton, J.; Scordo, A.; Sirghi, D.; Tucakovic, I.; Vazquez Doce, O.; Wycech, S.; Zmeskal, J.; Mandaglio, G.; Martini, M.; Moskal, P.

2018-01-01

The AMADEUS collaboration aims to provide unique quality results from K- hadronic interactions in light nuclear targets, in order to solve fundamental open questions in the non-perturbative strangeness QCD sector, like the controversial nature of the Λ(1405) state, the yield of hyperon formation below threshold, the yield and shape of multi-nucleon K- absorption, processes which are intimately connected to the possible existence of exotic antikaon multi-nucleon clusters and to the role of strangeness in neutron stars. AMADEUS takes advantage of the DAΦNE collider, which provides a unique source of monochromatic low-momentum kaons and exploits the KLOE detector as an active target, in order to obtain excellent acceptance and resolution data for K- nuclear capture on H, 4He, 9Be and 12C, both at-rest and in-flight.

Morphology-controlled cactus-like branched anatase TiO2 arrays with high light-harvesting efficiency for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Wu, Wu-Qiang; Rao, Hua-Shang; Feng, Hao-Lin; Guo, Xin-Dong; Su, Cheng-Yong; Kuang, Dai-Bin

2014-08-01

The present work establishes a facile process for one-step hydrothermal growth of vertically aligned anatase cactus-like branched TiO2 (CBT) arrays on a transparent conducting oxide (TCO) substrate. Various CBT morphologies are obtained by adjusting the potassium titanium oxide oxalate (PTO) reactant concentration (from 0.05 M to 0.15 M) and this yields a morphologically-controllable branched TiO2 arrays geometry. The CBT arrays consist of a vertically oriented nanowire (NW) or nanosheet (NS) stem and a host of short nanorod (NR) branches. The hierarchical CBT arrays demonstrate their excellent candidatures as photoanodes, which are capable of exhibiting high light-harvesting efficiency in dye-sensitized solar cells (DSSCs). Consequently, DSSCs based on 7 μm long optimized CBT arrays (0.05 M PTO), which are assembled with high density and high aspect-ratio NR branches, exhibit an impressive power conversion efficiency of 6.43% under AM 1.5G one sun illumination. The high performance can be attributed to the prominent light-harvesting efficiency, resulting from larger surface area and superior light-scattering capability.

Carbon Quantum Dot Implanted Graphite Carbon Nitride Nanotubes: Excellent Charge Separation and Enhanced Photocatalytic Hydrogen Evolution.

PubMed

Wang, Yang; Liu, Xueqin; Liu, Jia; Han, Bo; Hu, Xiaoqin; Yang, Fan; Xu, Zuwei; Li, Yinchang; Jia, Songru; Li, Zhen; Zhao, Yanli

2018-05-14

Graphite carbon nitride (g-C 3 N 4 ) is a promising candidate for photocatalytic hydrogen production, but only shows moderate activity owing to sluggish photocarrier transfer and insufficient light absorption. Herein, carbon quantum dots (CQDs) implanted in the surface plane of g-C 3 N 4 nanotubes were synthesized by thermal polymerization of freeze-dried urea and CQDs precursor. The CQD-implanted g-C 3 N 4 nanotubes (CCTs) could simultaneously facilitate photoelectron transport and suppress charge recombination through their specially coupled heterogeneous interface. The electronic structure and morphology were optimized in the CCTs, contributing to greater visible light absorption and a weakened barrier of the photocarrier transfer. As a result, the CCTs exhibited efficient photocatalytic performance under light irradiation with a high H 2 production rate of 3538.3 μmol g -1  h -1 and a notable quantum yield of 10.94 % at 420 nm. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Centers of excellence in healthcare institutions: what they are and how to assemble them.

PubMed

Elrod, James K; Fortenberry, John L

2017-07-11

Centers of excellence-specialized programs within healthcare institutions which supply exceptionally high concentrations of expertise and related resources centered on particular medical areas and delivered in a comprehensive, interdisciplinary fashion-afford many advantages for healthcare providers and the populations they serve. To achieve full value from centers of excellence, proper assembly is an absolute necessity, but guidance is somewhat limited. This effectively forces healthcare providers to pursue establishment largely via trial-and-error, diminishing opportunities for success. Successful development of a center of excellence first requires the acquisition of a detailed understanding of the delivery model and its benefits. Then, concerted actions must be taken on a particular series of administrative and clinical fronts, treating them in prescribed manners to afford synergies which yield an exceptionally high level of care. To reduce hardships associated with acquiring this rather elusive knowledge, remedy shortcomings in the literature, and potentially bolster community health broadly, this article presents information and insights gleaned from Willis-Knighton Health System's extensive experience assembling and operating centers of excellence. This work is intended to educate and enlighten, but most importantly, supply guidance which will permit healthcare establishments to replicate noted processes to realize their own centers of excellence. Centers of excellence have the ability to dramatically enhance the depth and breadth of healthcare services available in communities. Given the numerous mutual benefits afforded by this delivery model, it is hoped that the light shed by this article will help healthcare providers better understand centers of excellence and be more capable and confident in associated development initiatives, affording greater opportunities for themselves and their patient populations.

Perovskite Quantum Dots with Near Unity Solution and Neat-Film Photoluminescent Quantum Yield by Novel Spray Synthesis.

PubMed

Dai, Shu-Wen; Hsu, Bo-Wei; Chen, Chien-Yu; Lee, Chia-An; Liu, Hsiao-Yun; Wang, Hsiao-Fang; Huang, Yu-Ching; Wu, Tien-Lin; Manikandan, Arumugam; Ho, Rong-Ming; Tsao, Cheng-Si; Cheng, Chien-Hong; Chueh, Yu-Lun; Lin, Hao-Wu

2018-02-01

In this study, a novel perovskite quantum dot (QD) spray-synthesis method is developed by combining traditional perovskite QD synthesis with the technique of spray pyrolysis. By utilizing this new technique, the synthesis of cubic-shaped perovskite QDs with a homogeneous size of 14 nm is demonstrated, which shows an unprecedented stable absolute photoluminescence quantum yield ≈100% in the solution and even in the solid-state neat film. The highly emissive thin films are integrated with light emission devices (LEDs) and organic light emission displays (OLEDs). The color conversion type QD-LED (ccQD-LED) hybrid devices exhibit an extremely saturated green emission, excellent external quantum efficiency of 28.1%, power efficiency of 121 lm W -1 , and extraordinary forward-direction luminescence of 8 500 000 cd m -2 . The conceptual ccQD-OLED hybrid display also successfully demonstrates high-definition still images and moving pictures with a 119% National Television System Committee 1931 color gamut and 123% Digital Cinema Initiatives-P3 color gamut. These very-stable, ultra-bright perovskite QDs have the properties necessary for a variety of useful applications in optoelectronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthetic Engineering of Spider Silk Fiber as Implantable Optical Waveguides for Low-Loss Light Guiding.

PubMed

Qiao, Xin; Qian, Zhigang; Li, Junjie; Sun, Hongji; Han, Yao; Xia, Xiaoxia; Zhou, Jin; Wang, Chunlan; Wang, Yan; Wang, Changyong

2017-05-03

A variety of devices used for biomedical engineering have been fabricated using protein polymer because of their excellent properties, such as strength, toughness, biocompatibility, and biodegradability. In this study, we fabricated an optical waveguide using genetically engineered spider silk protein. This method has two significant advantages: (1) recombinant spider silk optical waveguide exhibits excellent optical and biological properties and (2) biosynthesis of spider silk protein can overcome the limitation to the research on spider silk optical waveguide due to the low yield of natural spider silk. In detail, two kinds of protein-based optical waveguides made from recombinant spider silk protein and regenerative silkworm silk protein were successfully prepared. Results suggested that the recombinant spider silk optical waveguide showed a smoother surface and a higher refractive index when compared with regenerative silkworm silk protein. The optical loss of recombinant spider silk optical waveguide was 0.8 ± 0.1 dB/cm in air and 1.9 ± 0.3 dB/cm in mouse muscles, which were significantly lower than those of regenerative silkworm silk optical waveguide. Moreover, recombinant spider silk optical waveguide can meet the demand to guide and efficiently deliver light through biological tissue. In addition, recombinant spider silk optical waveguide showed low toxicity to cells in vitro and low-level inflammatory reaction with surrounding tissue in vivo. Therefore, recombinant spider silk optical waveguide is a promising implantable device to guide and deliver light with low loss.

Recent advances in light outcoupling from white organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Gather, Malte C.; Reineke, Sebastian

2015-01-01

Organic light-emitting diodes (OLEDs) have been successfully introduced to the smartphone display market and have geared up to become contenders for applications in general illumination where they promise to combine efficient generation of white light with excellent color quality, glare-free illumination, and highly attractive designs. Device efficiency is the key requirement for such white OLEDs, not only from a sustainability perspective, but also because at the high brightness required for general illumination, losses lead to heating and may, thus, cause rapid device degradation. The efficiency of white OLEDs increased tremendously over the past two decades, and internal charge-to-photon conversion can now be achieved at ˜100% yield. However, the extraction of photons remains rather inefficient (typically <30%). Here, we provide an introduction to the underlying physics of outcoupling in white OLEDs and review recent progress toward making light extraction more efficient. We describe how structures that scatter, refract, or diffract light can be attached to the outside of white OLEDs (external outcoupling) or can be integrated close to the active layers of the device (internal outcoupling). Moreover, the prospects of using top-emitting metal-metal microcavity designs for white OLEDs and of tuning the average orientation of the emissive molecules within the OLED are discussed.

Nanostructured organosilicon luminophores as a new concept of nanomaterials for highly efficient down-conversion of light

NASA Astrophysics Data System (ADS)

Ponomarenko, Sergey A.; Surin, Nikolay M.; Borshchev, Oleg V.; Skorotetcky, Maxim S.; Muzafarov, Aziz M.

2015-10-01

Nanostructured organosilicon luminophores (NOLs) are branched molecular structures having two types of covalently bonded via silicon atoms organic luminophores with efficient Förster energy transfer between them. They combine the best properties of organic luminophores and inorganic quantum dots: high absorption cross-section, excellent photoluminescence quantum yield, fast luminescence decay time, good processability and low toxicity. A smart choice of organic luminophores allowed us to design and synthesize a library of NOLs, absorbing from VUV to visible region and emitting at the desired wavelengths from 390 to 650 nm. They can be used as unique wavelength shifters in plastic scintillators and other applications.

Triphenylphosphonium cation: a valuable functional group for antimicrobial photodynamic therapy.

PubMed

Bresolí-Obach, Roger; Gispert, Ignacio; García Peña, Diego; Boga, Sonia; Gulias, Óscar; Agut, Montserrat; Vázquez, M Eugenio; Nonell, Santi

2018-06-08

Light-mediated killing of pathogens by cationic photosensitisers is a promising antimicrobial approach that avoids the development of resistance inherent to the use of antimicrobials. In this study, we demonstrate that modification of different photosensitisers with the triphenylphosphonium cation yields derivatives with excellent photoantimicrobial activity against Gram-positive bacteria (i.e., S. aureus and E. faecalis). Thus, the triphenylphosphonium functional group should be considered for the development of photoantimicrobials for the selective killing of Gram-positive bacteria in the presence of Gram-negative species. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Ferrocene Derived Bifunctional Phosphine-Catalyzed Asymmetric Oxa-[4+2] Cycloaddition of α-Substituted Allenones with Enones.

PubMed

Wang, Huamin; Lu, Weike; Zhang, Junliang

2017-10-04

An efficient ferrocene-derived bifunctional phosphine-catalyzed enantioselective oxa-[4+2] cycloaddition of α-substituted allenones with a broad range of enones is investigated for the preparation of stereodefined dihydropyrans in good to excellent yields (up to 99 %) and excellent enantioselectivity (up to 99 % ee). Furthermore, a series of valuable chiral polyheterocyclic frameworks can be efficiently achieved in good yields with excellent enantioselectivities. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultralow-Power Near Infrared Lamp Light Operable Targeted Organic Nanoparticle Photodynamic Therapy.

PubMed

Huang, Ling; Li, Zhanjun; Zhao, Yang; Zhang, Yuanwei; Wu, Shuang; Zhao, Jianzhang; Han, Gang

2016-11-09

Tissue penetration depth is a major challenge in practical photodynamic therapy (PDT). A biocompatible and highly effective near infrared (NIR)-light-absorbing carbazole-substituted BODIPY (Car-BDP) molecule is reported as a class of imaging-guidable deep-tissue activatable photosensitizers for PDT. Car-BDP possesses an intense, broad NIR absorption band (600-800 nm) with a remarkably high singlet oxygen quantum yield (Φ Δ = 67%). After being encapsulated with biodegradable PLA-PEG-FA polymers, Car-BDP can form uniform and small organic nanoparticles that are water-soluble and tumor-targetable. Rather than using laser light, such nanoparticles offer an unprecedented deep-tissue, tumor targeting photodynamic therapeutic effect by using an exceptionally low-power-density and cost-effective lamp light (12 mW cm -2 ). In addition, these nanoparticles can be simultaneously traced in vivo due to their excellent NIR fluorescence. This study signals a major step forward in photodynamic therapy by developing a new class of NIR-absorbing biocompatible organic nanoparticles for effective targeting and treatment of deep-tissue tumors. This work also provides a potential new platform for precise tumor-targeting theranostics and novel opportunities for future affordable clinical cancer treatment.

Photoreversible Covalent Hydrogels for Soft-Matter Additive Manufacturing.

PubMed

Kabb, Christopher P; O'Bryan, Christopher S; Deng, Christopher C; Angelini, Thomas E; Sumerlin, Brent S

2018-05-16

Reversible covalent chemistry provides access to robust materials with the ability to be degraded and reformed upon exposure to an appropriate stimulus. Photoresponsive units are attractive for this purpose, as the spatial and temporal application of light is easily controlled. Coumarin derivatives undergo a [2 + 2] cycloaddition upon exposure to long-wave UV irradiation (365 nm), and this process can be reversed using short-wave UV light (254 nm). Therefore, polymers cross-linked by coumarin groups are excellent candidates as reversible covalent gels. In this work, copolymerization of coumarin-containing monomers with the hydrophilic comonomer N, N-dimethylacrylamide yielded water-soluble, linear polymers that could be cured with long-wave UV light into free-standing hydrogels, even in the absence of a photoinitiator. Importantly, the gels were reverted back to soluble copolymers upon short-wave UV irradiation. This process could be cycled, allowing for recycling and remolding of the hydrogel into additional shapes. Further, this hydrogel can be imprinted with patterns through a mask-based, post-gelation photoetching method. Traditional limitations of this technique, such as the requirement for uniform etching in one direction, have been overcome by combining these materials with a soft-matter additive manufacturing methodology. In a representative application of this approach, we printed solid structures in which the interior coumarin-cross-linked gel is surrounded by a nondegradable gel. Upon exposure to short-wave UV irradiation, the coumarin-cross-linked gel was reverted to soluble prepolymers that were washed away to yield hollow hydrogel objects.

Solar photochemical oxidation of alcohols using catalytic hydroquinone and copper nanoparticles under oxygen: oxidative cleavage of lignin models.

PubMed

Mitchell, Lorna J; Moody, Christopher J

2014-11-21

Alcohols are converted into to their corresponding carbonyl compounds using catalytic amounts of 1,4-hydroquinone with a copper nanoparticle electron transfer mediator with oxygen as the terminal oxidant in acetone as solvent under visible light irradiation. These conditions employing biorenewable hydroquinone as reagent were developed from initial experiments using stoichiometric amounts of 1,4-benzoquinone as oxidant. A range of benzylic and aliphatic primary and secondary alcohols are oxidized, affording the corresponding aldehydes or ketones in moderate to excellent yields. The methodology is also applicable to the oxidative degradation of lignin model compounds that undergo C-C bond cleavage to give simple aromatic compounds.

Modulation of the photoluminescence in carbon dots through surface modification: from mechanism to white light-emitting diodes.

PubMed

Zhu, Jinyang; Shao, He; Bai, Xue; Zhai, Yue; Zhu, Yongsheng; Chen, Xu; Pan, Gencai; Dong, Biao; Xu, Lin; Zhang, Hanzhuang; Song, Hongwei

2018-06-15

Carbon dots (CDs) have emerged as a new type of fluorescent material because of their unique optical advantages, such as high photoluminescence quantum yields (QYs), excellent photo-stability, excitation-dependent emissions, and low toxicity. However, the photoluminescence mechanism for CDs remains unclear, which limits their further practical application. Here, CDs were synthesized via a solvothermal route from citric acid and urea. Through the oxidation and reduction treatment of pristine CDs, the origin of the photoluminescence and the involved mechanism were revealed. We found that the blue/green/red emissions originated from three diverse emitting states, i.e. the intrinsic state, and C=O- and C=N-related surface states, respectively. Based on the as-prepared CDs, a pH sensor depending on the radiometric luminescence detection was developed. Furthermore, we constructed CD/PVP (PVP, polyvinylpyrrolidone) composite films, which exhibited white light emission with photoluminescence QYs of 15.3%. The white light emission with different correlated color temperatures (CCTs), from 4807 K to 3319 K, was obtained by simply changing the amount of PVP solution. Benefiting from the white light-emitting solid-state films, single-component white light-emitting diodes were fabricated with an average color rendering index value (Ra) of 80.0, luminous efficiency of 10.2 lm W -1 , and good working stability, thus indicating a promising potential for practical lighting applications.

Modulation of the photoluminescence in carbon dots through surface modification: from mechanism to white light-emitting diodes

NASA Astrophysics Data System (ADS)

Zhu, Jinyang; Shao, He; Bai, Xue; Zhai, Yue; Zhu, Yongsheng; Chen, Xu; Pan, Gencai; Dong, Biao; Xu, Lin; Zhang, Hanzhuang; Song, Hongwei

2018-06-01

Carbon dots (CDs) have emerged as a new type of fluorescent material because of their unique optical advantages, such as high photoluminescence quantum yields (QYs), excellent photo-stability, excitation-dependent emissions, and low toxicity. However, the photoluminescence mechanism for CDs remains unclear, which limits their further practical application. Here, CDs were synthesized via a solvothermal route from citric acid and urea. Through the oxidation and reduction treatment of pristine CDs, the origin of the photoluminescence and the involved mechanism were revealed. We found that the blue/green/red emissions originated from three diverse emitting states, i.e. the intrinsic state, and C=O- and C=N-related surface states, respectively. Based on the as-prepared CDs, a pH sensor depending on the radiometric luminescence detection was developed. Furthermore, we constructed CD/PVP (PVP, polyvinylpyrrolidone) composite films, which exhibited white light emission with photoluminescence QYs of 15.3%. The white light emission with different correlated color temperatures (CCTs), from 4807 K to 3319 K, was obtained by simply changing the amount of PVP solution. Benefiting from the white light-emitting solid-state films, single-component white light-emitting diodes were fabricated with an average color rendering index value (Ra) of 80.0, luminous efficiency of 10.2 lm W‑1, and good working stability, thus indicating a promising potential for practical lighting applications.

A Novel Real-Time Data Acquisition Using an Excel Spreadsheet in Pendulum Experiment Tool with Light-Based Timer

ERIC Educational Resources Information Center

Adhitama, Egy; Fauzi, Ahmad

2018-01-01

In this study, a pendulum experimental tool with a light-based timer has been developed to measure the period of a simple pendulum. The obtained data was automatically recorded in an Excel spreadsheet. The intensity of monochromatic light, sensed by a 3DU5C phototransistor, dynamically changes as the pendulum swings. The changed intensity varies…

Effect of low electric fields on alpha scintillation light yield in liquid argon

NASA Astrophysics Data System (ADS)

Agnes, P.; Albuquerque, I. F. M.; Alexander, T.; Alton, A. K.; Asner, D. M.; Back, H. O.; Baldin, B.; Biery, K.; Bocci, V.; Bonfini, G.; Bonivento, W.; Bossa, M.; Bottino, B.; Brigatti, A.; Brodsky, J.; Budano, F.; Bussino, S.; Cadeddu, M.; Cadoni, M.; Calaprice, F.; Canci, N.; Candela, A.; Caravati, M.; Cariello, M.; Carlini, M.; Catalanotti, S.; Cavalcante, P.; Chepurnov, A.; Cicalò, C.; Cocco, A. G.; Covone, G.; D'Angelo, D.; D'Incecco, M.; Davini, S.; De Cecco, S.; De Deo, M.; De Vincenzi, M.; Derbin, A.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Dionisi, C.; Edkins, E.; Empl, A.; Fan, A.; Fiorillo, G.; Fomenko, K.; Forster, G.; Franco, D.; Gabriele, F.; Galbiati, C.; Giagu, S.; Giganti, C.; Giovanetti, G. K.; Goretti, A. M.; Granato, F.; Gromov, M.; Guan, M.; Guardincerri, Y.; Hackett, B. R.; Herner, K.; Hughes, D.; Humble, P.; Hungerford, E. V.; Ianni, A.; James, I.; Johnson, T. N.; Jollet, C.; Keeter, K.; Kendziora, C. L.; Koh, G.; Korablev, D.; Korga, G.; Kubankin, A.; Li, X.; Lissia, M.; Loer, B.; Lombardi, P.; Longo, G.; Ma, Y.; Machulin, I. N.; Mandarano, A.; Mari, S. M.; Maricic, J.; Marini, L.; Martoff, C. J.; Meregaglia, A.; Meyers, P. D.; Milincic, R.; Miller, J. D.; Montanari, D.; Monte, A.; Mount, B. J.; Muratova, V. N.; Musico, P.; Napolitano, J.; Navrer Agasson, A.; Odrowski, S.; Oleinik, A.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, M.; Pantic, E.; Parmeggiano, S.; Pelczar, K.; Pelliccia, N.; Pocar, A.; Pordes, S.; Pugachev, D. A.; Qian, H.; Randle, K.; Ranucci, G.; Razeti, M.; Razeto, A.; Reinhold, B.; Renshaw, A. L.; Rescigno, M.; Riffard, Q.; Romani, A.; Rossi, B.; Rossi, N.; Rountree, D.; Sablone, D.; Saggese, P.; Sands, W.; Savarese, C.; Schlitzer, B.; Segreto, E.; Semenov, D. A.; Shields, E.; Singh, P. N.; Skorokhvatov, M. D.; Smirnov, O.; Sotnikov, A.; Stanford, C.; Suvorov, Y.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Tonazzo, A.; Trinchese, P.; Unzhakov, E. V.; Verducci, M.; Vishneva, A.; Vogelaar, B.; Wada, M.; Walker, S.; Wang, H.; Wang, Y.; Watson, A. W.; Westerdale, S.; Wilhelmi, J.; Wojcik, M. M.; Xiang, X.; Xiao, X.; Xu, J.; Yang, C.; Zhong, W.; Zhu, C.; Zuzel, G.

2017-01-01

Measurements were made of scintillation light yield of alpha particles from the 222Rn decay chain within the DarkSide-50 liquid argon time projection chamber. The light yield was found to increase as the applied electric field increased, with alphas in a 200 V/cm electric field exhibiting a ~2% increase in light yield compared to alphas in no field.

Synthesis and optical properties of metal (M) atom-doped polycarbosilane (PCS) with extended conjugation (M = Al, Dy, Er and Eu)

NASA Astrophysics Data System (ADS)

Yao, Rongqian; Zhao, Haoran; Feng, Zude; Chen, Lifu; Zhang, Ying

2013-10-01

Optical properties of metal atom-doped polycarbosilane (PCS) which originated from σ-conjugation effect were studied. Al, Dy, Er and Eu were introduced into PCS by one-pot method to yield polyaluminocarbosilane (PACS), polydysprosiumcarbosilane (PDCS), polyerbiumcarbosilane (PErCS) and polyeuropiumcarbosilane (PECS), respectively. Effects of oxidation curing and ultraviolet (UV) radiation on the photoluminescence (PL) properties of the samples were investigated. PL spectra show strong blue light-emissions and the intensity of PCS is enhanced by adding metal atoms. PACS with extended σ-conjugation exhibits an obvious PL red-shift, high intensity, high quantum yield and excellent oxidation resistance as compared with those of others. As treated under UV lamp for 3 h in air, PACS retains good UV resistance performance, owing to the AlOx (x = 4, 5, or 6) groups which effectively extend the σ-conjugation. The obtained results are expected to have important applications in active sources for electroluminescence (EL) devices, especially suitable for blue emission.

Synthesis, Amphiphilic Property and Thermal Stability of Novel Main-chain Poly(o-carborane-benzoxazines)

NASA Astrophysics Data System (ADS)

Yang, Xiaoxue; Han, Guo; Yang, Zhen; Zhang, Xiaoa; Jiang, Shengling; Lyu, Yafei

2017-10-01

Five poly(o-carborane-benzoxazines) were synthesized via Mannich reaction of o-carborane bisphenol, paraformaldehyde, and diamine, and their structures were well characterized. Light transmission and 1H NMR in D2O confirmed that poly(o-carborane-benzoxazines) with PEG segments showed excellent water solubility and amphiphilic property. TGA analyses were conducted under nitrogen and air, and the results showed that the polymers own high initial decomposition temperatures owing to the shielding effect of carborane moiety on its adjacent aromatic structures. Besides, poly(o-carborane-benzoxazines) own high char yield at elevated temperatures, for the boron atom could combine with oxygen from the polymer structure or/and the air and be oxidized to form boron oxide, and thus the polymer weight is retained to a large extent. PEG segments had an adverse effect on the initial decomposition and char yield, and thus their concentration should be adjusted to control the polymer’s thermal stability.

Preparation of grape-like Bi{sub 2}O{sub 3}/Ti photoanode and its visible light activity

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

Li, Guoting; Department of Biology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR; Yip, H.Y.

2011-02-15

Graphical abstract: Compact and grape-like bismuth oxide (Bi{sub 2}O{sub 3}) coated titania (Ti) anode was prepared by oxalic acid (H{sub 2}C{sub 2}O{sub 4}) etching, electrodeposition and calcination in order to explore its photoelectrocatalytic activities. The Bi{sub 2}O{sub 3} coating was demonstrated to be full of pores, and a good combination between Bi{sub 2}O{sub 3} layer and honeycomb-like Ti substrate was observed by scanning electron microscopy. A synergy was found between electrolysis and photocatalysis using the prepared Bi{sub 2}O{sub 3}/Ti anode for photoelectrocatalytic oxidation of azo dye Acid Orange 7 under visible light irradiation (420 nm). Research highlights: {yields} Bi{sub 2}O{submore » 3}/Ti anode was prepared by H{sub 2}C{sub 2}O{sub 4} etching, electrodeposition and calcination. {yields} A compact and grape-like Bi{sub 2}O{sub 3} coated Ti anode was obtained. {yields} Bi{sub 2}O{sub 3} coating was full of pores, and have a good combination with Ti substrate. {yields} A synergy was observed in photoelectrocatalytic oxidation under visible light. -- Abstract: Compact and grape-like bismuth oxide (Bi{sub 2}O{sub 3}) coated titania (Ti) anode was prepared by oxalic acid (H{sub 2}C{sub 2}O{sub 4}) etching, electrodeposition and calcination in order to explore its photoelectrocatalytic activities. The Bi{sub 2}O{sub 3} coating was demonstrated to be full of pores, and a good combination between Bi{sub 2}O{sub 3} layer and honeycomb-like Ti substrate was observed by scanning electron microscopy. The characteristic morphology of Bi{sub 2}O{sub 3} coating indicated that the electrode is stable during degradation. The Bi{sub 2}O{sub 3}/Ti electrode was used in oxidative degradation of Acid Orange 7 by electrolysis, photocatalytic oxidation and photoelectrocatalytic oxidation processes. The pseudo-first order kinetics parameter (K{sub app}) of photoelectrocatalytic process was 1.15 times of the sum of electrolysis and photocatalytic oxidation under visible light irradiation at 420 nm. The results indicated that the synergy of electrolysis and photocatalysis lead to an excellent photoelectrocatalytic property of the Bi{sub 2}O{sub 3}/Ti electrode.« less

Isomerization of 7-oxabenzonorbornadienes into naphthols catalyzed by [RuCl(2)(CO)(3)](2).

PubMed

Ballantine, Melissa; Menard, Michelle L; Tam, William

2009-10-02

Ruthenium-catalyzed isomerization of 7-oxanorbornadienes into naphthols was investigated. Among the various ruthenium catalysts tested, [RuCl(2)(CO)(3)](2) gave the highest yields in the isomerization, and various substituted naphthols were synthesized in moderate to excellent yields. Both symmetrical and unsymmetrical 7-oxanorbornadienes were employed in the study, and moderate to excellent regioselectivities were observed.

Light response of sunflower and canola as affected by plant density, plant genotype and N fertilization.

PubMed

Soleymani, A

2017-08-01

Crop response to light is an important parameter determining crop growth. Three field (split plots) experiments were conducted to investigate the effects of plant density, plant genotype and N fertilization on the light absorption and light extinction of sunflower (Helianthus annuus L.) and canola (Brassica napus L.). A detailed set of plant growth, light absorption and crop yield and oil related parameters were determined. Light was measured at noon during the sunny days with clear sky. In experiment I, although the plant density (PD) of 14 resulted in the highest rate of sunflower light absorption (31.37%) and light extinction (0.756), the highest rate of grain yield and grain oil yield was resulted at PD12 at 3639 and 1457.9kg/ha, respectively; as well as by genotype SUP.A. In experiment II (canola), PD80 resulted in the highest rate of light absorption (13.13%), light extinction (0.63), grain yield (2189.4kg/ha) and grain oil yield (556.54kg/ha). This was also the case for Genotype H. In experiment III (canola), although N150 resulted in the highest rate of light absorption (10.74%) and light extinction (0.48), the highest rate of grain yield (3413.6kg/ha) and grain oil yield (891.86kg/ha) was resulted at N100 as well as by Genotype H401. Results indicate how light properties, crop growth and yield of sunflower and canola can be affected by plant and environmental parameters, which are also of practical use by farmers. Copyright © 2017 Elsevier B.V. All rights reserved.

Space-resolved diffusing wave spectroscopy measurements of the macroscopic deformation and the microscopic dynamics in tensile strain tests

NASA Astrophysics Data System (ADS)

Nagazi, Med-Yassine; Brambilla, Giovanni; Meunier, Gérard; Marguerès, Philippe; Périé, Jean-Noël; Cipelletti, Luca

2017-01-01

We couple a laser-based, space-resolved dynamic light scattering apparatus to a universal traction machine for mechanical extensional tests. We perform simultaneous optical and mechanical measurements on polyether ether ketone, a semi-crystalline polymer widely used in the industry. Due to the high turbidity of the sample, light is multiply scattered by the sample and the diffusing wave spectroscopy (DWS) formalism is used to interpret the data. Space-resolved DWS yields spatial maps of the sample strain and of the microscopic dynamics. An excellent agreement is found between the strain maps thus obtained and those measured by a conventional stereo-digital image correlation technique. The microscopic dynamics reveals both affine motion and plastic rearrangements. Thanks to the extreme sensitivity of DWS to displacements as small as 1 nm, plastic activity and its spatial localization can be detected at an early stage of the sample strain, making the technique presented here a valuable complement to existing material characterization methods.

Effect of low electric fields on alpha scintillation light yield in liquid argon

DOE PAGES

Agnes, P.; Albuquerque, I. F. M.; Alexander, T.; ...

2017-01-24

Measurements were made of scintillation light yield of alpha particles from themore » $$^{222}$$Rn decay chain within the DarkSide-50 liquid argon time projection chamber. Furthermore, the light yield was found to increase as the applied electric field increased, with alphas in a 200 V/cm electric field exhibiting a 2% increase in light yield compared to alphas in no field.« less

A Review on Organic-Inorganic Halide Perovskite Photodetectors: Device Engineering and Fundamental Physics.

PubMed

Ahmadi, Mahshid; Wu, Ting; Hu, Bin

2017-11-01

The last eight years (2009-2017) have seen an explosive growth of interest in organic-inorganic halide perovskites in the research communities of photovoltaics and light-emitting diodes. In addition, recent advancements have demonstrated that this type of perovskite has a great potential in the technology of light-signal detection with a comparable performance to commercially available crystalline Si and III-V photodetectors. The contemporary growth of state-of-the-art multifunctional perovskites in the field of light-signal detection has benefited from its outstanding intrinsic optoelectronic properties, including photoinduced polarization, high drift mobilities, and effective charge collection, which are excellent for this application. Photoactive perovskite semiconductors combine effective light absorption, allowing detection of a wide range of electromagnetic waves from ultraviolet and visible, to the near-infrared region, with low-cost solution processability and good photon yield. This class of semiconductor might empower breakthrough photodetector technology in the field of imaging, optical communications, and biomedical sensing. Therefore, here, the focus is specifically on the critical understanding of materials synthesis, design, and engineering for the next-stage development of perovskite photodetectors and highlighting the current challenges in the field, which need to be further studied in the future. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The unbearable lightness of "light" cigarettes: a comparison of smoke yields in six varieties of Canadian "light" cigarettes.

PubMed

Gendreau, Paul L; Vitaro, Frank

2005-01-01

Labelling cigarettes as "light" or "mild" is claimed to be one of the biggest marketing scams in Canadian history. Arguably, such labelling implies that these varieties of cigarettes are less harmful than "regular" cigarettes. In Canada, a food product can be labelled "light" if there is a 25% reduction from the "reference food" and if the constituent being reduced is clearly identified (e.g., light in fat). Cigarette labelling does not comply with these regulations, however. To examine whether or not some tobacco constituents meet the 25% reduction criterion, we compared yields of 41 toxic and/or carcinogenic smoke constituents in six varieties of "light" cigarettes to the yields of "regular" cigarettes. We selected cigarettes from the two most popular Canadian brands, Du Maurier and Players. Using a set of data provided by Imperial Tobacco Canada and made available to the public by the Government of British Columbia, we compared yields measured under a laboratory protocol (modified ISO) that was designed to provide a more rigorous evaluation of the differences between varieties of cigarettes and a more accurate assessment of smokers' potential smoke intake than the traditional protocol (standard ISO). For all six varieties of "light" cigarettes, the yields of nicotine were higher by an average of 5% (range: 1% to 13%). The 25% reduction criterion was not met for any variety of "light" cigarettes concerning yields of tar. For all cigarettes tested, yields of tar were reduced on average by only 16% (range: 5% to 22%). For carbon monoxide (CO), only Player's Smooth Light had an over 25% reduction (30%) compared with Player's Regular. Conversely, yield of CO was 24% higher for Du Maurier Lights compared with Du Maurier Regular. As for the other smoke constituents, the majority (75%) were not reduced by 25% or more in "light" cigarettes, and a sizeable proportion of yields (e.g., acrylonitrile, benzene, chromium, m+p cresol, mercury, nickel, toluene) were larger in these varieties of cigarettes. Only yields of formaldehyde, crotonaldehyde, 1-aminonaphtalene, and proprionaldehyde were systematically reduced in all varieties of "light" cigarettes. The six varieties of "light" cigarettes examined in this study do not differ substantially from "regular" cigarettes in terms of smoke yields. We argue that the modified ISO protocol should be implemented for a more valid comparison of potential smoke yields in all varieties of cigarettes and that labelling based on this protocol should be promoted.

Synthesis of N-doped TiO2 Using Guanidine Nitrate: An Excellent Visible Light Photocatalyst

EPA Science Inventory

An excellent visible light active nitrogen-rich TiO2 photocatalyst have been synthesized by using guanidine nitrate as the doping material. The catalytic efficiency of the catalyst has been demonstrated by the decomposition of the dye, methyl orange (MO), and the pollutant, 2,4 d...

The Application of Fluorescent Quantum Dots to Confocal, Multiphoton, and Electron Microscopic Imaging

PubMed Central

Deerinck, Thomas J.

2009-01-01

Fluorescent quantum dots are emerging as an important tool for imaging cells and tissues, and their unique optical and physical properties have captured the attention of the research community. The most common types of commercially available quantum dots consist of a nanocrystalline semiconductor core composed of cadmium selenide with a zinc sulfide capping layer and an outer polymer layer to facilitate conjugation to targeting biomolecules such as immunoglobulins. They exhibit high fluorescent quantum yields and have large absorption cross-sections, possess excellent photostability, and can be synthesized so that their narrow-band fluorescence emission can occur in a wide spectrum of colors. These properties make them excellent candidates for serving as multiplexing molecular beacons using a variety of imaging modalities including highly correlated microscopies. Whereas much attention has been focused on quantum-dot applications for live-cell imaging, we have sought to characterize and exploit their utility for enabling simultaneous multiprotein immunolabeling in fixed cells and tissues. Considerations for their application to immunolabeling for correlated light and electron microscopic analysis are discussed. PMID:18337229

A LYSO crystal array readout by silicon photomultipliers as compact detector for space applications

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

Kryemadhi, A.; Barner, L.; Grove, A.

Precise measurements of GeV range gamma rays help narrow down among var- ious gamma emission models and increase sensitivity for dark matter searches. Construction of precise as well as compact instruments requires detectors with high efficiency, high stopping power, excellent energy resolution, and excellent angular resolution. Fast and bright crystal scintillators coupled with small foot- print photo-detectors are suitable candidates. We prototyped a detector array consisting of four LYSO crystals where each crystal is read out by a 2x2 SensL ArrayJ60035 silicon photomultipliers. The LYSO crystals were chosen because of their good light yield, fast decay time, demonstrated radiation hardness,more » and small radiation length. Here, we used the silicon photomultiplier arrays as photo- detectors because of their small size, simple readout, low voltage operation, and immunity to magnetic elds. We also studied the detector performance in the energy range of interest by exposing it to 2-16 GeV particles produced at the Test Beam Facility of Fermi National Accelerator Laboratory.« less

A LYSO crystal array readout by silicon photomultipliers as compact detector for space applications

DOE PAGES

Kryemadhi, A.; Barner, L.; Grove, A.; ...

2017-10-31

Precise measurements of GeV range gamma rays help narrow down among var- ious gamma emission models and increase sensitivity for dark matter searches. Construction of precise as well as compact instruments requires detectors with high efficiency, high stopping power, excellent energy resolution, and excellent angular resolution. Fast and bright crystal scintillators coupled with small foot- print photo-detectors are suitable candidates. We prototyped a detector array consisting of four LYSO crystals where each crystal is read out by a 2x2 SensL ArrayJ60035 silicon photomultipliers. The LYSO crystals were chosen because of their good light yield, fast decay time, demonstrated radiation hardness,more » and small radiation length. Here, we used the silicon photomultiplier arrays as photo- detectors because of their small size, simple readout, low voltage operation, and immunity to magnetic elds. We also studied the detector performance in the energy range of interest by exposing it to 2-16 GeV particles produced at the Test Beam Facility of Fermi National Accelerator Laboratory.« less

One-Pot Amide Bond Formation from Aldehydes and Amines via a Photoorganocatalytic Activation of Aldehydes.

PubMed

Papadopoulos, Giorgos N; Kokotos, Christoforos G

2016-08-19

A mild, one-pot, and environmentally friendly synthesis of amides from aldehydes and amines is described. Initially, a photoorganocatalytic reaction of aldehydes with di-isopropyl azodicarboxylate leads to an intermediate carbonyl imide, which can react with a variety of amines to afford the desired amides. The initial visible light-mediated activation of a variety of monosubstituted or disubstituted aldehydes is usually fast, occurring in a few hours. Following the photocatalytic reaction, addition of the primary amine at room temperature or the secondary amine at elevated temperatures leads to the corresponding amide from moderate to excellent yields without epimerization. This methodology was applied in the synthesis of Moclobemide, a drug against depression and social anxiety.

Exploring growth conditions and Eu2+ concentration effects for KSr2I5:Eu scintillator crystals II: Ø 25 mm crystals

NASA Astrophysics Data System (ADS)

Stand, L.; Zhuravleva, M.; Johnson, J.; Koschan, M.; Wu, Y.; Donnald, S.; Vaigneur, K.; Lukosi, E.; Melcher, C. L.

2018-02-01

Europium doped potassium strontium iodide is a very promising scintillator for national security applications due to its ease of growth and excellent scintillation properties. For this work the fast crystal growth and scintillation properties of 1-inch diameter single crystals of KSr2I5:Eu2+ (KSI:Eu) were investigated. We focused our efforts on optimizing the growth parameters required to produce one-inch diameter crystals without decreasing the previously reported fast pulling rate of 5 mm/h. Cracking was minimized by replacing the quartz ampoules with carbon coated quartz ampoules; thus, several crack free single crystals of KSI with varying Eu2+ concentrations were grown, including a Ø 1″ by 6″ long boule with 2.5% Eu. The maximum achievable performance of each crystal was measured using small 0.012 cm3 specimens. The volumetric dependencies of the light yield, energy resolution and decay time were evaluated using KSI:Eu 2% specimens with volumes ranging from 0.012 cm3 to 18 cm3. For large volumes (≥ 9 cm3), the performance was comparable to other high performing scintillators, with light yields up to 78,200 ph/MeV and energy resolutions as good as 3.2% at 662 keV. The initial version of a hermetic package has been developed, and the stability of the sealed crystal is promising.

New high performing scintillators: RbSr2Br5:Eu and RbSr2I5:Eu

NASA Astrophysics Data System (ADS)

Stand, L.; Zhuravleva, M.; Johnson, J.; Koschan, M.; Lukosi, E.; Melcher, C. L.

2017-11-01

We report the crystal growth and scintillation properties of two new ternary metal halide scintillators, RbSr2Br5 and RbSr2I5, activated with divalent europium. Transparent 7 mm diameter single crystals with 2.5% Eu2+ were grown in evacuated quartz ampoules via the Bridgman technique. RbSr2Br5 and RbSr2I5 have monoclinic crystal structures with densities of 4.18 g/cm3 and 4.55 g/cm3 respectively. These materials are hygroscopic and have some intrinsic radioactivity due to the presence of 87Rb. Luminescence properties typical of the 5d-4f radiative transition in Eu2+ were observed. The X-ray excited emissions consisted of singular peaks centered at 429 nm for RbSr2Br5:Eu 2.5% and 445 nm for RbSr2I4:Eu 2.5%. RbSr2Br5:Eu 2.5% had a light yield of 64,700 photons/MeV, with an energy resolution of 4.0%, and RbSr2I5:Eu 2.5% had a light yield of 90,400 ph/MeV with an energy resolution of 3.0% at 662 keV. Both crystals have an excellent proportional response over a wide range of gamma-ray energies.

A Tutorial on the Use of Excel 2010 and Excel for Mac 2011 for Conducting Delay-Discounting Analyses

ERIC Educational Resources Information Center

Reed, Derek D.; Kaplan, Brent A.; Brewer, Adam T.

2012-01-01

In recent years, researchers and practitioners in the behavioral sciences have profited from a growing literature on delay discounting. The purpose of this article is to provide readers with a brief tutorial on how to use Microsoft Office Excel 2010 and Excel for Mac 2011 to analyze discounting data to yield parameters for both the hyperbolic…

OP-Yield Version 1.00 user's guide

Treesearch

Martin W. Ritchie; Jianwei Zhang

2018-01-01

OP-Yield is a Microsoft Excel™ spreadsheet with 14 specified user inputs to derive custom yield estimates using the original Oliver and Powers (1978) functions as the foundation. It presents yields for ponderosa pine (Pinus ponderosa Lawson & C. Lawson) plantations in northern California. The basic model forms for dominantand...

Rhodium(II)-catalyzed enantioselective synthesis of troponoids.

PubMed

Murarka, Sandip; Jia, Zhi-Jun; Merten, Christian; Daniliuc, Constantin-G; Antonchick, Andrey P; Waldmann, Herbert

2015-06-22

We report a rhodium(II)-catalyzed highly enantioselective 1,3-dipolar cycloaddition reaction between the carbonyl moiety of tropone and carbonyl ylides to afford troponoids in good to high yields with excellent enantioselectivity. We demonstrate that α-diazoketone-derived carbonyl ylides, in contrast to carbonyl ylides derived from diazodiketoesters, undergo [6+3] cycloaddition reactions with tropone to yield the corresponding bridged heterocycles with excellent stereoselectivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of hierarchical ZnV2O6 nanosheets with enhanced activity and stability for visible light driven CO2 reduction to solar fuels

NASA Astrophysics Data System (ADS)

Bafaqeer, Abdullah; Tahir, Muhammad; Amin, Nor Aishah Saidina

2018-03-01

Hierarchical nanostructures have lately garnered enormous attention because of their remarkable performances in energy storage and catalysis applications. In this study, novel hierarchical ZnV2O6 nanosheets, formulated by one-step solvothermal method, for enhanced photocatalytic CO2 reduction with H2O to solar fuels has been investigated. The structure and properties of the catalysts were characterized by XRD, FESEM, TEM, BET, UV-vis, Raman and PL spectroscopy. The hierarchical ZnV2O6 nanosheets show excellent performance towards photoreduction of CO2 with H2O to CH3OH, CH3COOH and HCOOH under visible light. The main product yield, CH3OH of 3253.84 μmol g-cat-1 was obtained over ZnV2O6, 3.4 times the amount of CH3OH produced over the ZnO/V2O5 composite (945.28 μmol g-cat-1). In addition, CH3OH selectivity of 39.96% achieved over ZnO/V2O5, increased to 48.78% in ZnV2O6 nanosheets. This significant improvement in photo-activity over ZnV2O6 structure was due to hierarchical structure with enhanced charge separation by V2O5. The obtained ZnV2O6 hierarchical nanosheets exhibited excellent photocatalytic stability for selective CH3OH production.

Facile preparation of a new BINAP-based building block, 5,5'-diiodoBINAP, and its synthetic application.

PubMed

Shimada, Toyoshi; Suda, Masahiko; Nagano, Toyohiro; Kakiuchi, Kiyomi

2005-11-25

[reaction: see text] Bis(pyridine)iodonium tetrafluoroborate was successfully used for regioselective iodination of BINAP dioxide to give 5,5'-diiodoBINAP dioxide in an excellent yield of 92%, with no observed formation of 4,4'-diiodoBINAP dioxide. A Sonogashira cross-coupling reaction with 5,5'-diiodoBINAP dioxide gave the desired bis(trimethylsilylethynyl) product in 86% yield. The resulting 5,5'-disubstituted BINAP dioxides were reduced to the corresponding phosphines, which were used as chiral ligands for rhodium-catalyzed asymmetric 1,4-addition of phenylboronic acid to 2-cyclohexenone to give 3-phenylcyclohexanone in excellent yield with high enantioselectivity.

Scale-up of a Luminescent Solar Concentrator-Based Photomicroreactor via Numbering-up.

PubMed

Zhao, Fang; Cambié, Dario; Janse, Jeroen; Wieland, Eric W; Kuijpers, Koen P L; Hessel, Volker; Debije, Michael G; Noël, Timothy

2018-01-02

The use of solar energy to power chemical reactions is a long-standing dream of the chemical community. Recently, visible-light-mediated photoredox catalysis has been recognized as the ideal catalytic transformation to convert solar energy into chemical bonds. However, scaling photochemical transformations has been extremely challenging due to Bouguer-Lambert-Beer law. Recently, we have pioneered the development of luminescent solar concentrator photomicroreactors (LSC-PMs), which display an excellent energy efficiency. These devices harvest solar energy, convert the broad solar energy spectrum to a narrow-wavelength region, and subsequently waveguide the re-emitted photons to the reaction channels. Herein, we report on the scalability of such LSC-PMs via a numbering-up strategy. Paramount in our work was the use of molds that were fabricated via 3D printing. This allowed us to rapidly produce many different prototypes and to optimize experimentally key design aspects in a time-efficient fashion. Reactors up to 32 parallel channels have been fabricated that display an excellent flow distribution using a bifurcated flow distributor (standard deviations below 10%). This excellent flow distribution was crucial to scale up a model reaction efficiently, displaying yields comparable to those obtained in a single-channel device. We also found that interchannel spacing is an important and unique design parameter for numbered-up LSC-PMs, which influences greatly the photon flux experienced within the reaction channels.

Scale-up of a Luminescent Solar Concentrator-Based Photomicroreactor via Numbering-up

PubMed Central

2017-01-01

The use of solar energy to power chemical reactions is a long-standing dream of the chemical community. Recently, visible-light-mediated photoredox catalysis has been recognized as the ideal catalytic transformation to convert solar energy into chemical bonds. However, scaling photochemical transformations has been extremely challenging due to Bouguer–Lambert–Beer law. Recently, we have pioneered the development of luminescent solar concentrator photomicroreactors (LSC-PMs), which display an excellent energy efficiency. These devices harvest solar energy, convert the broad solar energy spectrum to a narrow-wavelength region, and subsequently waveguide the re-emitted photons to the reaction channels. Herein, we report on the scalability of such LSC-PMs via a numbering-up strategy. Paramount in our work was the use of molds that were fabricated via 3D printing. This allowed us to rapidly produce many different prototypes and to optimize experimentally key design aspects in a time-efficient fashion. Reactors up to 32 parallel channels have been fabricated that display an excellent flow distribution using a bifurcated flow distributor (standard deviations below 10%). This excellent flow distribution was crucial to scale up a model reaction efficiently, displaying yields comparable to those obtained in a single-channel device. We also found that interchannel spacing is an important and unique design parameter for numbered-up LSC-PMs, which influences greatly the photon flux experienced within the reaction channels. PMID:29333350

Highly luminescent colloidal nanoplates of perovskite cesium lead halide and their oriented assemblies

DOE PAGES

Bekenstein, Yehonadav; Koscher, Brent A.; Eaton, Samuel W.; ...

2015-12-15

Anisotropic colloidal quasi-two-dimensional nanoplates (NPLs) hold great promise as functional materials due to their combination of low dimensional optoelectronic properties and versatility through colloidal synthesis. Recently, lead-halide perovskites have emerged as important optoelectronic materials with excellent efficiencies in photovoltaic and light-emitting applications. Here we report the synthesis of quantum confined all inorganic cesium lead halide nanoplates in the perovskite crystal structure that are also highly luminescent (PLQY 84%). The controllable self-assembly of nanoplates either into stacked columnar phases or crystallographic-oriented thin-sheet structures is demonstrated. Furthermore, the broad accessible emission range, high native quantum yields, and ease of self-assembly make perovskitemore » NPLs an ideal platform for fundamental optoelectronic studies and the investigation of future devices.« less

[Dynamics of Amomum villosum growth and its fruit yield cultivated under tropical forests].

PubMed

Zheng, Zheng; Gan, Jianmin; Feng, Zhili; Meng, Ying

2004-01-01

Investigations on the dynamics of Amomum villosum growth and its fruit yield cultivated under tropical ravine rainforest and secondary forest at different elevations in Xishuangbanna showed that the yield of A. villosum was influenced by the site age, sun light level of understorey, and water stress in dry season. The fruit yield and mature plant density decreased with increasing age of the A. villosum site. The fruit yield increased with sun light level when the light level in understorey was under 35% of full sun light (P < 0.05). The fruit yield at the lower site by stream was significantly higher than that at upper site (P < 0.05). The yield difference between ravine rainforest and secondary forest was not significant. Planned cultivation of A. villosum in the secondary forest of the shifting cultivation land by ravine from 800-1000 m elevation instead of customary cultivation in the ravine rainforest, could not only resolve the problem of the effect of light deficiency in understorey and water stress in the dry season on A. villosum fruit yield, but also be useful to protect the tropical ravine rain forest.

Nighttime Supplemental LED Inter-lighting Improves Growth and Yield of Single-Truss Tomatoes by Enhancing Photosynthesis in Both Winter and Summer.

PubMed

Tewolde, Fasil T; Lu, Na; Shiina, Kouta; Maruo, Toru; Takagaki, Michiko; Kozai, Toyoki; Yamori, Wataru

2016-01-01

Greenhouses with sophisticated environmental control systems, or so-called plant factories with solar light, enable growers to achieve high yields of produce with desirable qualities. In a greenhouse crop with high planting density, low photosynthetic photon flux density (PPFD) at the lower leaves tends to limit plant growth, especially in the winter when the solar altitude and PPFD at the canopy are low and day length is shorter than in summer. Therefore, providing supplemental lighting to the lower canopy can increase year-round productivity. However, supplemental lighting can be expensive. In some places, the cost of electricity is lower at night, but the effect of using supplemental light at night has not yet been examined. In this study, we examined the effects of supplemental LED inter-lighting (LED inter-lighting hereafter) during the daytime or nighttime on photosynthesis, growth, and yield of single-truss tomato plants both in winter and summer. We used LED inter-lighting modules with combined red and blue light to illuminate lower leaves right after the first anthesis. The PPFD of this light was 165 μmol m(-2) s(-1) measured at 10 cm from the LED module. LED inter-lighting was provided from 4:00 am to 4:00 pm for the daytime treatments and from 10:00 pm to 10:00 am for the nighttime treatments. Plants exposed only to solar light were used as controls. Daytime LED inter-lighting increased the photosynthetic capacity of middle and lower canopy leaves, which significantly increased yield by 27% in winter; however, photosynthetic capacity and yield were not significantly increased during summer. Nighttime LED inter-lighting increased photosynthetic capacity in both winter and summer, and yield increased by 24% in winter and 12% in summer. In addition, nighttime LED inter-lighting in winter significantly increased the total soluble solids and ascorbic acid content of the tomato fruits, by 20 and 25%, respectively. Use of nighttime LED inter-lighting was also more cost-effective than daytime inter-lighting. Thus, nighttime LED inter-lighting can effectively improve tomato plant growth and yield with lower energy cost compared with daytime both in summer and winter.

Nighttime Supplemental LED Inter-lighting Improves Growth and Yield of Single-Truss Tomatoes by Enhancing Photosynthesis in Both Winter and Summer

PubMed Central

Tewolde, Fasil T.; Lu, Na; Shiina, Kouta; Maruo, Toru; Takagaki, Michiko; Kozai, Toyoki; Yamori, Wataru

2016-01-01

Greenhouses with sophisticated environmental control systems, or so-called plant factories with solar light, enable growers to achieve high yields of produce with desirable qualities. In a greenhouse crop with high planting density, low photosynthetic photon flux density (PPFD) at the lower leaves tends to limit plant growth, especially in the winter when the solar altitude and PPFD at the canopy are low and day length is shorter than in summer. Therefore, providing supplemental lighting to the lower canopy can increase year-round productivity. However, supplemental lighting can be expensive. In some places, the cost of electricity is lower at night, but the effect of using supplemental light at night has not yet been examined. In this study, we examined the effects of supplemental LED inter-lighting (LED inter-lighting hereafter) during the daytime or nighttime on photosynthesis, growth, and yield of single-truss tomato plants both in winter and summer. We used LED inter-lighting modules with combined red and blue light to illuminate lower leaves right after the first anthesis. The PPFD of this light was 165 μmol m-2 s-1 measured at 10 cm from the LED module. LED inter-lighting was provided from 4:00 am to 4:00 pm for the daytime treatments and from 10:00 pm to 10:00 am for the nighttime treatments. Plants exposed only to solar light were used as controls. Daytime LED inter-lighting increased the photosynthetic capacity of middle and lower canopy leaves, which significantly increased yield by 27% in winter; however, photosynthetic capacity and yield were not significantly increased during summer. Nighttime LED inter-lighting increased photosynthetic capacity in both winter and summer, and yield increased by 24% in winter and 12% in summer. In addition, nighttime LED inter-lighting in winter significantly increased the total soluble solids and ascorbic acid content of the tomato fruits, by 20 and 25%, respectively. Use of nighttime LED inter-lighting was also more cost-effective than daytime inter-lighting. Thus, nighttime LED inter-lighting can effectively improve tomato plant growth and yield with lower energy cost compared with daytime both in summer and winter. PMID:27092163

Red light and carbon dioxide differentially affect growth, lipid production, and quality in the microalga, Ettlia oleoabundans.

PubMed

Yang, Ying; Weathers, Pamela

2015-01-01

Ettlia oleoabundans, a freshwater unicellular green microalga, was grown under different light qualities ± carbon dioxide-enriched air to determine the combined effects on growth and lipid production of this oleaginous species. Keeping total light intensity constant, when a portion of the cool white was replaced by red, volumetric lipid yield increased 2.8-fold mainly due to the greater yield of oleic acid, a desirable biodiesel precursor. Only 30 min of red light treatment was sufficient to increase lipid yield and quality to the same level as cultures provided red light for >14 days, indicating the potential role of red light in stimulating lipid production of this species. Carbon dioxide enrichment via air sparging enhanced exponential growth, carbon conversion efficiency, and nutrient consumption. Together, these results showed that light quality plays an important role in microalgal lipid production. Adjustment in light quality and gas delivery efficiency with carbon dioxide enrichment improved lipid yield and quality in this and possibly other oleaginous algal species.

Imaging of Jurassic fossils from the Talbragar Fish Bed using fluorescence, photoluminescence, and elemental and mineralogical mapping.

PubMed

Frese, Michael; Gloy, Gerda; Oberprieler, Rolf G; Gore, Damian B

2017-01-01

The Talbragar Fish Bed is one of Australia's most important Jurassic deposits for freshwater fishes, land plants and aquatic and terrestrial insects. The site has yielded many well preserved fossils, which has led to the formal description of numerous new species and higher taxa. The excellent preservation of many fossils has allowed detailed anatomical studies, e.g. of the early teleost fish Cavenderichthys talbragarensis (Woodward, 1895). Here we report on the fluorescent characteristics and mineral composition of a range of Talbragar fossils. Most specimens fluoresce under ultraviolet, blue and green light. Elemental and mineralogical analyses revealed that the Talbragar fossils consist predominantly of quartz (SiO2), a mineral that is likely to account for the observed fluorescence, with trace kaolinite (Al2Si2O5(OH)4) in some of the fish fossils. Rock matrices are predominantly composed of quartz and goethite (FeO(OH)). Closer inspection of a plant leaf (Pentoxylon australicum White, 1981) establishes fluorescence as a useful tool for the visualisation of anatomical details that are difficult to see under normal light conditions.

Imaging of Jurassic fossils from the Talbragar Fish Bed using fluorescence, photoluminescence, and elemental and mineralogical mapping

PubMed Central

Gloy, Gerda; Oberprieler, Rolf G.; Gore, Damian B.

2017-01-01

The Talbragar Fish Bed is one of Australia’s most important Jurassic deposits for freshwater fishes, land plants and aquatic and terrestrial insects. The site has yielded many well preserved fossils, which has led to the formal description of numerous new species and higher taxa. The excellent preservation of many fossils has allowed detailed anatomical studies, e.g. of the early teleost fish Cavenderichthys talbragarensis (Woodward, 1895). Here we report on the fluorescent characteristics and mineral composition of a range of Talbragar fossils. Most specimens fluoresce under ultraviolet, blue and green light. Elemental and mineralogical analyses revealed that the Talbragar fossils consist predominantly of quartz (SiO2), a mineral that is likely to account for the observed fluorescence, with trace kaolinite (Al2Si2O5(OH)4) in some of the fish fossils. Rock matrices are predominantly composed of quartz and goethite (FeO(OH)). Closer inspection of a plant leaf (Pentoxylon australicum White, 1981) establishes fluorescence as a useful tool for the visualisation of anatomical details that are difficult to see under normal light conditions. PMID:28582427

Enhanced scintillation of Ba3In(B3O6)3 based on nitrogen doping

NASA Astrophysics Data System (ADS)

Wang, Z. X.; Pei, H.; Tao, X. M.; Cai, G. M.; Mao, R. H.; Jin, Z. P.

2018-02-01

Scintillating materials, as a class of luminescent materials, are highly demanded for practical use in the high-energy detection. However, the applications are often hampered by their low light yield (LY) or long decay time for many traditional scintillators. In this work, upon nitrogen anion doping, scintillation performance in layered borate Ba3In(B3O6)3 (BIB) has been excellently enhanced with high XEL intensity of ～3 times as large as that of commercial Bi4Ge3O12 (BGO) and ultra-fast fluorescent decay time of ～1.25 ns. To shed light on origins of the intrinsic violet-blue emission, we measured the in-situ vacuum ultraviolet excited (VUV) emission spectra of N-BIB ceramic. Combined with experiments and first principles calculations, the band-gap reduction and donor-acceptor density increasing by nitrogen (N) doping is responsible for the enhancement of scintillation performance for N-doped Ba3In(B3O6)3. Moreover, nitrogen anion doping rather than conventional cation doping is found to be also applicable to other intrinsic luminescent materials for enhancing performance.

Reflected Light from Giant Planets in Habitable Zones: Tapping into the Power of the Cross-Correlation Function

NASA Astrophysics Data System (ADS)

Martins, J. H. C.; Santos, N. C.; Figueira, P.; Melo, C.

2016-11-01

The direct detection of reflected light from exoplanets is an excellent probe for the characterization of their atmospheres. The greatest challenge for this task is the low planet-to-star flux ratio, which even in the most favourable case is of the order of 10-4 in the optical. This ratio decreases even more for planets in their host's habitable zone, typically lower than 10-7. To reach the signal-to-noise level required for such detections, we propose to unleash the power of the Cross Correlation Function in combination with the collecting power of next generation observing facilities. The technique we propose has already yielded positive results by detecting the reflected spectral signature of 51 Pegasi b (see Martins et al. 2015). In this work, we attempted to infer the number of hours required for the detection of several planets in their host's habitable zone using the aforementioned technique from theoretical EELT observations. Our results show that for 5 of the selected planets it should be possible to directly recover their reflected spectral signature.

Light aircraft lift, drag, and moment prediction: A review and analysis

NASA Technical Reports Server (NTRS)

Smetana, F. O.; Summey, D. C.; Smith, N. S.; Carden, R. K.

1975-01-01

The historical development of analytical methods for predicting the lift, drag, and pitching moment of complete light aircraft configurations in cruising flight is reviewed. Theoretical methods, based in part on techniques described in the literature and in part on original work, are developed. These methods form the basis for understanding the computer programs given to: (1) compute the lift, drag, and moment of conventional airfoils, (2) extend these two-dimensional characteristics to three dimensions for moderate-to-high aspect ratio unswept wings, (3) plot complete configurations, (4) convert the fuselage geometric data to the correct input format, (5) compute the fuselage lift and drag, (6) compute the lift and moment of symmetrical airfoils to M = 1.0 by a simplified semi-empirical procedure, and (7) compute, in closed form, the pressure distribution over a prolate spheroid at alpha = 0. Comparisons of the predictions with experiment indicate excellent lift and drag agreement for conventional airfoils and wings. Limited comparisons of body-alone drag characteristics yield reasonable agreement. Also included are discussions for interference effects and techniques for summing the results above to obtain predictions for complete configurations.

Reflected Light from Giant Planets in Habitable Zones: Tapping into the Power of the Cross-Correlation Function.

PubMed

Martins, J H C; Santos, N C; Figueira, P; Melo, C

2016-11-01

The direct detection of reflected light from exoplanets is an excellent probe for the characterization of their atmospheres. The greatest challenge for this task is the low planet-to-star flux ratio, which even in the most favourable case is of the order of 10 -4 in the optical. This ratio decreases even more for planets in their host's habitable zone, typically lower than 10 -7 . To reach the signal-to-noise level required for such detections, we propose to unleash the power of the Cross Correlation Function in combination with the collecting power of next generation observing facilities. The technique we propose has already yielded positive results by detecting the reflected spectral signature of 51 Pegasi b (see Martins et al. 2015). In this work, we attempted to infer the number of hours required for the detection of several planets in their host's habitable zone using the aforementioned technique from theoretical EELT observations. Our results show that for 5 of the selected planets it should be possible to directly recover their reflected spectral signature.

A novel real-time data acquisition using an Excel spreadsheet in pendulum experiment tool with light-based timer

NASA Astrophysics Data System (ADS)

Adhitama, Egy; Fauzi, Ahmad

2018-05-01

In this study, a pendulum experimental tool with a light-based timer has been developed to measure the period of a simple pendulum. The obtained data was automatically recorded in an Excel spreadsheet. The intensity of monochromatic light, sensed by a 3DU5C phototransistor, dynamically changes as the pendulum swings. The changed intensity varies the resistance value and was processed by the microcontroller, ATMega328, to obtain a signal period as a function of time and brightness when the pendulum crosses the light. Through the experiment, using calculated average periods, the gravitational acceleration value has been accurately and precisely determined.

A Highly Efficient and Photostable Photosensitizer with Near-Infrared Aggregation-Induced Emission for Image-Guided Photodynamic Anticancer Therapy.

PubMed

Wu, Wenbo; Mao, Duo; Hu, Fang; Xu, Shidang; Chen, Chao; Zhang, Chong-Jing; Cheng, Xiamin; Yuan, Youyong; Ding, Dan; Kong, Deling; Liu, Bin

2017-09-01

Photodynamic therapy (PDT), which relies on photosensitizers (PS) and light to generate reactive oxygen species to kill cancer cells or bacteria, has attracted much attention in recent years. PSs with both bright emission and efficient singlet oxygen generation have also been used for image-guided PDT. However, simultaneously achieving effective 1 O 2 generation, long wavelength absorption, and stable near-infrared (NIR) emission with low dark toxicity in a single PS remains challenging. In addition, it is well known that when traditional PSs are made into nanoparticles, they encounter quenched fluorescence and reduced 1 O 2 production. In this contribution, these challenging issues have been successfully addressed through designing the first photostable photosensitizer with aggregation-induced NIR emission and very effective 1 O 2 generation in aggregate state. The yielded nanoparticles show very effective 1 O 2 generation, bright NIR fluorescence centered at 820 nm, excellent photostability, good biocompatibility, and negligible dark in vivo toxicity. Both in vitro and in vivo experiments prove that the nanoparticles are excellent candidates for image-guided photodynamic anticancer therapy. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Scintillation properties of Eu 2+-doped KBa 2I 5 and K 2BaI 4

DOE PAGES

Stand, L.; Zhuravleva, M.; Chakoumakos, Bryan C.; ...

2015-09-25

We report two new ternary metal halide scintillators, KBa 2I 5 and K 2BaI 4, activated with divalent europium. Single crystal X-ray diffraction measurements confirmed that KBa 2I 5 has a monoclinic structure (P2 1/c) and that K 2BaI 4 has a rhombohedral structure (R3c). Differential scanning calorimetry showed singular melting and crystallization points, making these compounds viable candidates for melt growth. We grew 13 mm diameter single crystals of KBa 2I 5:Eu 2+ and K 2BaI 4:Eu2+ in evacuated quartz ampoules via the vertical Bridgman technique. The optimal Eu 2+ concentration was 4% for KBa 2I 5 and 7%more » for K 2BaI 4. The X-ray excited emissions at 444 nm for KBa 2I 5:Eu 4% and 448 nm for K 2BaI 4:Eu 7% arise from the 5d-4f radiative transition in Eu 2+. KBa 2I 5:Eu 4% has a light yield of 90,000 photons/MeV, with an energy resolution of 2.4% and K 2BaI 4:Eu 7% has a light yield of 63,000 ph/MeV, with an energy resolution of 2.9% at 662 keV. Both crystals have an excellent proportional response to a wide range of gamma-ray energies.« less

LED Lighting – Modification of Growth, Metabolism, Yield and Flour Composition in Wheat by Spectral Quality and Intensity

PubMed Central

Monostori, István; Heilmann, Márk; Kocsy, Gábor; Rakszegi, Marianna; Ahres, Mohamed; Altenbach, Susan B.; Szalai, Gabriella; Pál, Magda; Toldi, Dávid; Simon-Sarkadi, Livia; Harnos, Noémi; Galiba, Gábor; Darko, Éva

2018-01-01

The use of light-emitting diode (LED) technology for plant cultivation under controlled environmental conditions can result in significant reductions in energy consumption. However, there is still a lack of detailed information on the lighting conditions required for optimal growth of different plant species and the effects of light intensity and spectral composition on plant metabolism and nutritional quality. In the present study, wheat plants were grown under six regimens designed to compare the effects of LED and conventional fluorescent lights on growth and development, leaf photosynthesis, thiol and amino acid metabolism as well as grain yield and flour quality of wheat. Benefits of LED light sources over fluorescent lighting were manifested in both yield and quality of wheat. Elevated light intensities made possible with LEDs increased photosynthetic activity, the number of tillers, biomass and yield. At lower light intensities, blue, green and far-red light operated antagonistically during the stem elongation period. High photosynthetic activity was achieved when at least 50% of red light was applied during cultivation. A high proportion of blue light prolonged the juvenile phase, while the shortest flowering time was achieved when the blue to red ratio was around one. Blue and far-red light affected the glutathione- and proline-dependent redox environment in leaves. LEDs, especially in Blue, Pink and Red Low Light (RedLL) regimens improved flour quality by modifying starch and protein content, dough strength and extensibility as demonstrated by the ratios of high to low molecular weight glutenins, ratios of glutenins to gliadins and gluten spread values. These results clearly show that LEDs are efficient for experimental wheat cultivation, and make it possible to optimize the growth conditions and to manipulate metabolism, yield and quality through modification of light quality and quantity. PMID:29780400

LED Lighting - Modification of Growth, Metabolism, Yield and Flour Composition in Wheat by Spectral Quality and Intensity.

PubMed

Monostori, István; Heilmann, Márk; Kocsy, Gábor; Rakszegi, Marianna; Ahres, Mohamed; Altenbach, Susan B; Szalai, Gabriella; Pál, Magda; Toldi, Dávid; Simon-Sarkadi, Livia; Harnos, Noémi; Galiba, Gábor; Darko, Éva

2018-01-01

The use of light-emitting diode (LED) technology for plant cultivation under controlled environmental conditions can result in significant reductions in energy consumption. However, there is still a lack of detailed information on the lighting conditions required for optimal growth of different plant species and the effects of light intensity and spectral composition on plant metabolism and nutritional quality. In the present study, wheat plants were grown under six regimens designed to compare the effects of LED and conventional fluorescent lights on growth and development, leaf photosynthesis, thiol and amino acid metabolism as well as grain yield and flour quality of wheat. Benefits of LED light sources over fluorescent lighting were manifested in both yield and quality of wheat. Elevated light intensities made possible with LEDs increased photosynthetic activity, the number of tillers, biomass and yield. At lower light intensities, blue, green and far-red light operated antagonistically during the stem elongation period. High photosynthetic activity was achieved when at least 50% of red light was applied during cultivation. A high proportion of blue light prolonged the juvenile phase, while the shortest flowering time was achieved when the blue to red ratio was around one. Blue and far-red light affected the glutathione- and proline-dependent redox environment in leaves. LEDs, especially in Blue, Pink and Red Low Light (RedLL) regimens improved flour quality by modifying starch and protein content, dough strength and extensibility as demonstrated by the ratios of high to low molecular weight glutenins, ratios of glutenins to gliadins and gluten spread values. These results clearly show that LEDs are efficient for experimental wheat cultivation, and make it possible to optimize the growth conditions and to manipulate metabolism, yield and quality through modification of light quality and quantity.

Epigenetic and Posttranslational Modifications in Light Signal Transduction and the Circadian Clock in Neurospora crassa

PubMed Central

Proietto, Marco; Bianchi, Michele Maria; Ballario, Paola; Brenna, Andrea

2015-01-01

Blue light, a key abiotic signal, regulates a wide variety of physiological processes in many organisms. One of these phenomena is the circadian rhythm presents in organisms sensitive to the phase-setting effects of blue light and under control of the daily alternation of light and dark. Circadian clocks consist of autoregulatory alternating negative and positive feedback loops intimately connected with the cellular metabolism and biochemical processes. Neurospora crassa provides an excellent model for studying the molecular mechanisms involved in these phenomena. The White Collar Complex (WCC), a blue-light receptor and transcription factor of the circadian oscillator, and Frequency (FRQ), the circadian clock pacemaker, are at the core of the Neurospora circadian system. The eukaryotic circadian clock relies on transcriptional/translational feedback loops: some proteins rhythmically repress their own synthesis by inhibiting the activity of their transcriptional factors, generating self-sustained oscillations over a period of about 24 h. One of the basic mechanisms that perpetuate self-sustained oscillations is post translation modification (PTM). The acronym PTM generically indicates the addition of acetyl, methyl, sumoyl, or phosphoric groups to various types of proteins. The protein can be regulatory or enzymatic or a component of the chromatin. PTMs influence protein stability, interaction, localization, activity, and chromatin packaging. Chromatin modification and PTMs have been implicated in regulating circadian clock function in Neurospora. Research into the epigenetic control of transcription factors such as WCC has yielded new insights into the temporal modulation of light-dependent gene transcription. Here we report on epigenetic and protein PTMs in the regulation of the Neurospora crassa circadian clock. We also present a model that illustrates the molecular mechanisms at the basis of the blue light control of the circadian clock. PMID:26198228

Transparent, Flexible, Conformal Capacitive Pressure Sensors with Nanoparticles.

PubMed

Kim, Hyeohn; Kim, Gwangmook; Kim, Taehoon; Lee, Sangwoo; Kang, Donyoung; Hwang, Min-Soo; Chae, Youngcheol; Kang, Shinill; Lee, Hyungsuk; Park, Hong-Gyu; Shim, Wooyoung

2018-02-01

The fundamental challenge in designing transparent pressure sensors is the ideal combination of high optical transparency and high pressure sensitivity. Satisfying these competing demands is commonly achieved by a compromise between the transparency and usage of a patterned dielectric surface, which increases pressure sensitivity, but decreases transparency. Herein, a design strategy for fabricating high-transparency and high-sensitivity capacitive pressure sensors is proposed, which relies on the multiple states of nanoparticle dispersity resulting in enhanced surface roughness and light transmittance. We utilize two nanoparticle dispersion states on a surface: (i) homogeneous dispersion, where each nanoparticle (≈500 nm) with a size comparable to the visible light wavelength has low light scattering; and (ii) heterogeneous dispersion, where aggregated nanoparticles form a micrometer-sized feature, increasing pressure sensitivity. This approach is experimentally verified using a nanoparticle-dispersed polymer composite, which has high pressure sensitivity (1.0 kPa -1 ), and demonstrates excellent transparency (>95%). We demonstrate that the integration of nanoparticle-dispersed capacitor elements into an array readily yields a real-time pressure monitoring application and a fully functional touch device capable of acting as a pressure sensor-based input device, thereby opening up new avenues to establish processing techniques that are effective on the nanoscale yet applicable to macroscopic processing. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High reliable and chromaticity-tunable flip-chip w-LEDs with Ce:YAG glass-ceramics phosphor for long-lifetime automotive headlights applications

NASA Astrophysics Data System (ADS)

Ma, Chaoyang; Cao, Yongge; Shen, Xiaofei; Wen, Zicheng; Ma, Ran; Long, Jiaqi; Yuan, Xuanyi

2017-07-01

Nowadays, major commercial w-LEDs fabricated by the traditionally gold-wire-welding packaging technology have undergone considerable development as indoor/outdoor lighting sources due to its high-energy utilization efficiency, long service life, environmental friendliness, and excellent chromatic stability. While, new generation applications in projections, automotive lighting, street lighting, plaza lighting, and high-end general lighting need further improvements in power handling and light extraction. Herein, transparent Ce:YAG glass-ceramics (GCs) phosphor was prepared by low-temperature co-sintering polycrystalline Ce:YAG phosphor powder and home-made PbO-B2O3-ZnO-SiO2 glass powder. Thereafter, the flip-chip (FC) w-LEDs were fabricated with the GCs phosphor plates and FC blue chips. The GCs-based FC w-LEDs show not only excellent heat- and humidity-resistance characteristics, but also superior optical performances with an LE of 112.8 lm/W, a CRI of 71.2, a CCT of 6103 K as well as a chromaticity coordinate of (0.3202, 0.3298), under a high operation current of 400 mA. The technology route will open a practically commercial feasible approach to achieve excellent performances for advanced high-power FC w-LEDs.

o-Naphthoquinone-Catalyzed Aerobic Oxidation of Amines to (Ket)imines: A Modular Catalyst Approach.

PubMed

Goriya, Yogesh; Kim, Hun Young; Oh, Kyungsoo

2016-10-07

A modular aerobic oxidation of amines to imines has been achieved using an ortho-naphthoquinone (o-NQ) catalyst. The cooperative catalyst system of o-NQ and Cu(OAc) 2 enabled the formation of homocoupled imines from benzylamines, while the presence of TFA helped the formation of cross-coupled imines in excellent yields. The current mild aerobic oxidation protocol could also be applied to the oxidation of secondary amines to imines or ketimines with the help of cocatalyst, Ag 2 CO 3 , with excellent yields.

One-pot synthesis of β-acetamido ketones using boric acid at room temperature.

PubMed

Karimi-Jaberi, Zahed; Mohammadi, Korosh

2012-01-01

β-acetamido ketones were synthesized in excellent yields through one-pot condensation reaction of aldehydes, acetophenones, acetyl chloride, and acetonitrile in the presence of boric acid as a solid heterogeneous catalyst at room temperature. It is the first successful report of boric acid that has been used as solid acid catalyst for the preparation of β-acetamido ketones. The remarkable advantages offered by this method are green catalyst, mild reaction conditions, simple procedure, short reaction times, and good-to-excellent yields of products.

One-Pot Synthesis of β-Acetamido Ketones Using Boric Acid at Room Temperature

PubMed Central

Karimi-Jaberi, Zahed; Mohammadi, Korosh

2012-01-01

β-acetamido ketones were synthesized in excellent yields through one-pot condensation reaction of aldehydes, acetophenones, acetyl chloride, and acetonitrile in the presence of boric acid as a solid heterogeneous catalyst at room temperature. It is the first successful report of boric acid that has been used as solid acid catalyst for the preparation of β-acetamido ketones. The remarkable advantages offered by this method are green catalyst, mild reaction conditions, simple procedure, short reaction times, and good-to-excellent yields of products. PMID:22666168

Synthesis of crystalline Ce-activated garnet phosphor powders and technique to characterize their scintillation light yield

NASA Astrophysics Data System (ADS)

Gordienko, E.; Fedorov, A.; Radiuk, E.; Mechinsky, V.; Dosovitskiy, G.; Vashchenkova, E.; Kuznetsova, D.; Retivov, V.; Dosovitskiy, A.; Korjik, M.; Sandu, R.

2018-04-01

This work reports on a process of preparation of garnet phosphor powders and a technique for light yield evaluation of strongly light scattering samples. Powders of scintillation compounds could be used as individual materials or as samples for express tests of scintillation properties. However, estimation of their light yield (LY) is complicated by strong light scattering of this kind of materials. Ce3+-activated yttrium-aluminum and gallium-gadolinium-aluminum garnet phosphor powders, Y3Al5O12 (YAG:Ce) and Gd3Ga3Al2O12 (GGAG:Ce), were obtained using a modified coprecipitation technique. Ga tends to residue in mother liquor in ammonia media, but the modification allows to avoid the loss of components. We propose an approach for sample preparation and LY measurement setup with alpha particles excitation, allowing to decrease light scattering influence and to estimate a light yield of powder samples. This approach is used to evaluate the obtained powders.

In vivo 808 nm image-guided photodynamic therapy based on an upconversion theranostic nanoplatform

NASA Astrophysics Data System (ADS)

Liu, Xiaomin; Que, Ivo; Kong, Xianggui; Zhang, Youlin; Tu, Langping; Chang, Yulei; Wang, Tong Tong; Chan, Alan; Löwik, Clemens W. G. M.; Zhang, Hong

2015-09-01

A new strategy for efficient in vivo image-guided photodynamic therapy (PDT) has been demonstrated utilizing a ligand-exchange constructed upconversion-C60 nanophotosensitizer. This theranostic platform is superior to the currently reported nanophotosensitizers in (i) directly bonding photosensitizer C60 to the surface of upconversion nanoparticles (UCNPs) by a smart ligand-exchange strategy, which greatly shortened the energy transfer distance and enhanced the 1O2 production, resulting in the improvement of the therapeutic effect; (ii) realizing in vivo NIR 808 nm image-guided PDT with both excitation (980 nm) and emission (808 nm) light falling in the biological window of tissues, which minimized auto-fluorescence, reduced light scatting and improved the imaging contrast and depth, and thus guaranteed noninvasive diagnostic accuracy. In vivo and ex vivo tests demonstrated its favorable bio-distribution, tumor-selectivity and high therapeutic efficacy. Owing to the effective ligand exchange strategy and the excellent intrinsic photophysical properties of C60, 1O2 production yield was improved, suggesting that a low 980 nm irradiation dosage (351 J cm-2) and a short treatment time (15 min) were sufficient to perform NIR (980 nm) to NIR (808 nm) image-guided PDT. Our work enriches the understanding of UCNP-based PDT nanophotosensitizers and highlights their potential use in future NIR image-guided noninvasive deep cancer therapy.A new strategy for efficient in vivo image-guided photodynamic therapy (PDT) has been demonstrated utilizing a ligand-exchange constructed upconversion-C60 nanophotosensitizer. This theranostic platform is superior to the currently reported nanophotosensitizers in (i) directly bonding photosensitizer C60 to the surface of upconversion nanoparticles (UCNPs) by a smart ligand-exchange strategy, which greatly shortened the energy transfer distance and enhanced the 1O2 production, resulting in the improvement of the therapeutic effect; (ii) realizing in vivo NIR 808 nm image-guided PDT with both excitation (980 nm) and emission (808 nm) light falling in the biological window of tissues, which minimized auto-fluorescence, reduced light scatting and improved the imaging contrast and depth, and thus guaranteed noninvasive diagnostic accuracy. In vivo and ex vivo tests demonstrated its favorable bio-distribution, tumor-selectivity and high therapeutic efficacy. Owing to the effective ligand exchange strategy and the excellent intrinsic photophysical properties of C60, 1O2 production yield was improved, suggesting that a low 980 nm irradiation dosage (351 J cm-2) and a short treatment time (15 min) were sufficient to perform NIR (980 nm) to NIR (808 nm) image-guided PDT. Our work enriches the understanding of UCNP-based PDT nanophotosensitizers and highlights their potential use in future NIR image-guided noninvasive deep cancer therapy. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03690a

Synthesis of 3-iodoindoles by the Pd/Cu-catalyzed coupling of N,N-dialkyl-2-iodoanilines and terminal acetylenes, followed by electrophilic cyclization.

PubMed

Yue, Dawei; Yao, Tuanli; Larock, Richard C

2006-01-06

[reaction: see text] 3-Iodoindoles have been prepared in excellent yields by coupling terminal acetylenes with N,N-dialkyl-o-iodoanilines in the presence of a Pd/Cu catalyst, followed by an electrophilic cyclization of the resulting N,N-dialkyl-o-(1-alkynyl)anilines using I2 in CH2Cl2. Aryl-, vinylic-, alkyl-, and silyl-substituted terminal acetylenes undergo this process to produce excellent yields of 3-iodoindoles. The reactivity of the carbon-nitrogen bond cleavage during cyclization follows the following order: Me > n-Bu, Me > Ph, and cyclohexyl > Me. Subsequent palladium-catalyzed Sonogashira, Suzuki, and Heck reactions of the resulting 3-iodoindoles proceed smoothly in good yields.

Advanced Thermally Stable Coal-Based Jet Fuels

DTIC Science & Technology

2008-02-01

of hydrotreated refined chemical oil derived jet fuels in the pyrolytic regime. Preprints of Papers-American Chemical Society Division of Fuel...hydrogenation of a mixture of light cycle oil and refined chemical oil met or exceeded all but four JP-8 specifications. The fuel has excellent low-temperature...mixture of light cycle oil and refined chemical oil met or exceeded all but four JP-8 specifications. The fuel has excellent low-temperature viscosity

Motorist actions at a crosswalk with an in-pavement flashing light system.

PubMed

Karkee, Ganesh J; Nambisan, Shashi S; Pulugurtha, Srinivas S

2010-12-01

An in-pavement flashing light system is used at crosswalks to alert motorists and pedestrians of possible conflicts and to influence their behavior to enhance safety. The relative behaviors of the drivers and the pedestrians affect safety. An evaluation of motorist behavior at a pedestrian crosswalk with an in-pavement flashing light system is presented in this manuscript. Field observations provide the basis to evaluate motorist behavior at a crosswalk with an in-pavement flashing light system. Outcomes of pedestrian and motorists actions were observed to quantify measures of effectiveness (MOEs) such as yielding behavior of motorists, vehicle speeds, and yielding distance from the crosswalk. A before-and-after study design was used. The before condition was prior to the activation of the in-pavement flashing light system and the after condition was after the activation of the in-pavement flashing light system. The study was conducted on a relatively low-volume roadway located in the Henderson, Nevada. The significance of the differences in the MOEs between the 2 study periods was evaluated using statistical analysis tools such as a one-tailed test for proportions and the Welch-Satterthwaite t-test. The results show that the installation of the in-pavement flashing light system increased the yielding behavior of motorists significantly (P < 0.001). The vehicular speeds decreased when pedestrians were waiting at the curb to cross and when they were crossing (P < 0.001). Motorists yielded to pedestrians on an average about 3 m (∼10 feet) upstream from the yield markings and the yielding distances were consistent in both directions. The in-pavement flashing light system is seen to be effective to improve motorists' yielding behavior and the speeds of vehicles were also observed to decrease in the presence of pedestrians.

Light yield in DarkSide-10: A prototype two-phase argon TPC for dark matter searches

NASA Astrophysics Data System (ADS)

Alexander, T.; Alton, D.; Arisaka, K.; Back, H. O.; Beltrame, P.; Benziger, J.; Bonfini, G.; Brigatti, A.; Brodsky, J.; Cadonati, L.; Calaprice, F.; Candela, A.; Cao, H.; Cavalcante, P.; Chavarria, A.; Chepurnov, A.; Cline, D.; Cocco, A. G.; Condon, C.; D'Angelo, D.; Davini, S.; De Haas, E.; Derbin, A.; Di Pietro, G.; Dratchnev, I.; Durben, D.; Empl, A.; Etenko, A.; Fan, A.; Fiorillo, G.; Fomenko, K.; Gabriele, F.; Galbiati, C.; Gazzana, S.; Ghag, C.; Ghiano, C.; Goretti, A.; Grandi, L.; Gromov, M.; Guan, M.; Guo, C.; Guray, G.; Hungerford, E. V.; Ianni, Al.; Ianni, An.; Kayunov, A.; Keeter, K.; Kendziora, C.; Kidner, S.; Kobychev, V.; Koh, G.; Korablev, D.; Korga, G.; Shields, E.; Li, P.; Loer, B.; Lombardi, P.; Love, C.; Ludhova, L.; Lukyanchenko, L.; Lund, A.; Lung, K.; Ma, Y.; Machulin, I.; Maricic, J.; Martoff, C. J.; Meng, Y.; Meroni, E.; Meyers, P. D.; Mohayai, T.; Montanari, D.; Montuschi, M.; Mosteiro, P.; Mount, B.; Muratova, V.; Nelson, A.; Nemtzow, A.; Nurakhov, N.; Orsini, M.; Ortica, F.; Pallavicini, M.; Pantic, E.; Parmeggiano, S.; Parsells, R.; Pelliccia, N.; Perasso, L.; Perfetto, F.; Pinsky, L.; Pocar, A.; Pordes, S.; Ranucci, G.; Razeto, A.; Romani, A.; Rossi, N.; Saggese, P.; Saldanha, R.; Salvo, C.; Sands, W.; Seigar, M.; Semenov, D.; Skorokhvatov, M.; Smirnov, O.; Sotnikov, A.; Sukhotin, S.; Suvorov, Y.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Teymourian, A.; Thompson, J.; Unzhakov, E.; Vogelaar, R. B.; Wang, H.; Westerdale, S.; Wojcik, M.; Wright, A.; Xu, J.; Yang, C.; Zavatarelli, S.; Zehfus, M.; Zhong, W.; Zuzel, G.

2013-09-01

As part of the DarkSide program of direct dark matter searches using two-phase argon TPCs, a prototype detector with an active volume containing 10 kg of liquid argon, DarkSide-10, was built and operated underground in the Gran Sasso National Laboratory in Italy. A critically important parameter for such devices is the scintillation light yield, as photon statistics limits the rejection of electron-recoil backgrounds by pulse shape discrimination. We have measured the light yield of DarkSide-10 using the readily-identifiable full-absorption peaks from gamma ray sources combined with single-photoelectron calibrations using low-occupancy laser pulses. For gamma lines of energies in the range 122-1275 keV, we get light yields averaging 8.887±0.003(stat)±0.444(sys) p.e./keVee. With additional purification, the light yield measured at 511 keV increased to 9.142±0.006(stat) p.e./keVee.

All-solution processed transparent organic light emitting diodes

NASA Astrophysics Data System (ADS)

Zhang, Min; Höfle, Stefan; Czolk, Jens; Mertens, Adrian; Colsmann, Alexander

2015-11-01

In this work, we report on indium tin oxide-free, all-solution processed transparent organic light emitting diodes (OLEDs) with inverted device architecture. Conductive polymer layers are employed as both transparent cathodes and transparent anodes, with the top anodes having enhanced conductivities from a supporting stochastic silver nanowire mesh. Both electrodes exhibit transmittances of 80-90% in the visible spectral regime. Upon the incorporation of either yellow- or blue-light emitting fluorescent polymers, the OLEDs show low onset voltages, demonstrating excellent charge carrier injection from the polymer electrodes into the emission layers. Overall luminances and current efficiencies equal the performance of opaque reference OLEDs with indium tin oxide and aluminium electrodes, proving excellent charge carrier-to-light conversion within the device.

Layered Crystal Structure, Color-Tunable Photoluminescence, and Excellent Thermal Stability of MgIn2P4O14 Phosphate-Based Phosphors.

PubMed

Zhang, Jing; Cai, Ge-Mei; Yang, Lv-Wei; Ma, Zhi-Yuan; Jin, Zhan-Peng

2017-11-06

Single-component white phosphors stand a good chance to serve in the next-generation high-power white light-emitting diodes. Because of low thermal stability and containing lanthanide ions with reduced valence state, most of reported phosphors usually suffer unstable color of lighting for practical packaging and comparably complex synthetic processes. In this work, we present a type of novel color-tunable blue-white-yellow-emitting MgIn 2 P 4 O 14 :Tm 3+ /Dy 3+ phosphor with high thermal stability, which can be easily fabricated in air. Under UV excitation, the MgIn 2 P 4 O 14 :Tm 0.02 Dy 0.03 white phosphor exhibits negligible thermal-quenching behavior, with a 99.5% intensity retention at 150 °C, relative to its initial value at room temperature. The phosphor host MgIn 2 P 4 O 14 was synthesized and reported for the first time. MgIn 2 P 4 O 14 crystallizes in the space group of C2/c (No. 15) with a novel layered structure built of alternate anionic and cationic layers. Its disordering structure, with Mg and In atoms co-occupying the same site, is believed to facilitate the energy transfer between rare-earth ions and benefit by sustaining the luminescence with increasing temperature. The measured absolute quantum yields of MgIn 2 P 4 O 14 :Dy 0.04 , MgIn 2 P 4 O 14 :Tm 0.01 Dy 0.04 , and MgIn 2 P 4 O 14 :Tm 0.02 Dy 0.03 phosphors under the excitation of 351 nm ultraviolet radiation are 70.50%, 53.24%, and 52.31%, respectively. Present work indicates that the novel layered MgIn 2 P 4 O 14 is a promising candidate as a single-component white phosphor host with an excellent thermal stability for near-UV-excited white-light-emitting diodes (wLEDs).

Photomorphogenesis, photosynthesis, and seed yield of wheat plants grown under red light-emitting diodes (LEDs) with and without supplemental blue lighting

NASA Technical Reports Server (NTRS)

Goins, G. D.; Yorio, N. C.; Sanwo, M. M.; Brown, C. S.; Sager, J. C. (Principal Investigator)

1997-01-01

Red light-emitting diodes (LEDs) are a potential light source for growing plants in spaceflight systems because of their safety, small mass and volume, wavelength specificity, and longevity. Despite these attractive features, red LEDs must satisfy requirements for plant photosynthesis and photomorphogenesis for successful growth and seed yield. To determine the influence of gallium aluminium arsenide (GaAlAs) red LEDs on wheat photomorphogenesis, photosynthesis, and seed yield, wheat (Triticum aestivum L., cv. 'USU-Super Dwarf') plants were grown under red LEDs and compared to plants grown under daylight fluorescent (white) lamps and red LEDs supplemented with either 1% or 10% blue light from blue fluorescent (BF) lamps. Compared to white light-grown plants, wheat grown under red LEDs alone demonstrated less main culm development during vegetative growth through preanthesis, while showing a longer flag leaf at 40 DAP and greater main culm length at final harvest (70 DAP). As supplemental BF light was increased with red LEDs, shoot dry matter and net leaf photosynthesis rate increased. At final harvest, wheat grown under red LEDs alone displayed fewer subtillers and a lower seed yield compared to plants grown under white light. Wheat grown under red LEDs+10% BF light had comparable shoot dry matter accumulation and seed yield relative to wheat grown under white light. These results indicate that wheat can complete its life cycle under red LEDs alone, but larger plants and greater amounts of seed are produced in the presence of red LEDs supplemented with a quantity of blue light.

Kinoform design with an optimal-rotation-angle method.

PubMed

Bengtsson, J

1994-10-10

Kinoforms (i.e., computer-generated phase holograms) are designed with a new algorithm, the optimalrotation- angle method, in the paraxial domain. This is a direct Fourier method (i.e., no inverse transform is performed) in which the height of the kinoform relief in each discrete point is chosen so that the diffraction efficiency is increased. The optimal-rotation-angle algorithm has a straightforward geometrical interpretation. It yields excellent results close to, or better than, those obtained with other state-of-the-art methods. The optimal-rotation-angle algorithm can easily be modified to take different restraints into account; as an example, phase-swing-restricted kinoforms, which distribute the light into a number of equally bright spots (so called fan-outs), were designed. The phase-swing restriction lowers the efficiency, but the uniformity can still be made almost perfect.

Laser deposition of resonant silicon nanoparticles on perovskite for photoluminescence enhancement

NASA Astrophysics Data System (ADS)

Tiguntseva, E. Y.; Zalogina, A. S.; Milichko, V. A.; Zuev, D. A.; Omelyanovich, M. M.; Ishteev, A.; Cerdan Pasaran, A.; Haroldson, R.; Makarov, S. V.; Zakhidov, A. A.

2017-11-01

Hybrid lead halide perovskite based optoelectronics is a promising area of modern technologies yielding excellent characteristics of light emitting diodes and lasers as well as high efficiencies of photovoltaic devices. However, the efficiency of perovskite based devices hold a potential of further improvement. Here we demonstrate high photoluminescence efficiency of perovskites thin films via deposition of resonant silicon nanoparticles on their surface. The deposited nanoparticles have a number of advances over their plasmonic counterparts, which were applied in previous studies. We show experimentally the increase of photoluminescence of perovskite film with the silicon nanoparticles by 150 % as compared to the film without the nanoparticles. The results are supported by numerical calculations. Our results pave the way to high throughput implementation of low loss resonant nanoparticles in order to create highly effective perovskite based optoelectronic devices.

Crystal structure and thermal expansion of CsCaI3:Eu and CsSrBr3:Eu scintillators

NASA Astrophysics Data System (ADS)

Loyd, Matthew; Lindsey, Adam; Patel, Maulik; Koschan, Merry; Melcher, Charles L.; Zhuravleva, Mariya

2018-01-01

The distorted-perovskite scintillator materials CsCaI3:Eu and CsSrBr3:Eu prepared as single crystals have shown promising potential for use in radiation detection applications requiring a high light yield and excellent energy resolution. We present a study using high temperature powder X-ray diffraction experiments to examine a deleterious high temperature phase transition. High temperature phases were identified through sequential diffraction pattern Rietveld refinement in GSAS II. We report the linear coefficients of thermal expansion for both high and low temperature phases of each compound. Thermal expansion for both compositions is greatest in the [0 0 1] direction. As a result, Bridgman growth utilizing a seed oriented with the [0 0 1] along the growth direction should be used to mitigate thermal stress.

Noninvasive 3D Visualization of Defects and Crack Propagation in Layered Foam Structures by Phase Contrast Microimaging

NASA Technical Reports Server (NTRS)

Hu, Z. W.; DeCarlo, F.

2006-01-01

Applications of polymeric foams in our modern society continue to grow because of their light weight, high strength, excellent thermal and mechanical insulation, and the ease of engineering. Among others, closed-cell foam has been structurally used for thermally insulating the shuttle external tank. However, internal defects of the foams were difficult to observe non-invasively due to limited sensitivity to the low-density structures possessed by traditional imaging tools such as computed X-ray tomography By combining phase contrast X-ray imaging with pressure loading, we succeeded in precisely mapping intact cellular structure and defects inside the bulk of layered foam and visualizing its subsequent response to the pressure in three-dimensional space. The work demonstrated a powerfir1 approach for yielding insight into underlying problems in lightweight cellular materials otherwise unobtainable.

Photoluminescent carbon quantum dots as a directly film-forming phosphor towards white LEDs.

PubMed

Zhang, Feng; Feng, Xiaoting; Zhang, Yi; Yan, Lingpeng; Yang, Yongzhen; Liu, Xuguang

2016-04-28

Photoluminescent organosilane-functionalized carbon quantum dots (CQDs), 3.0-3.5 nm in diameter, were synthesized via a facile hydrothermal method using citric acid monohydrate as a precursor and N-(3-(trimethoxysilyl) propyl) ethylenediamine as a coordinating and passivation agent. The optical properties of the as-obtained CQDs were investigated in detail. The CQD aqueous solution emits bright blue-white light under ultraviolet (UV) illumination with a quantum yield of 57.3% and high red-green-blue (RGB) spectral composition of 60.1%, and in particular the CQDs exhibit excitation-independent photoluminescence. The CQDs have a narrow size distribution around 3.1 nm and good film-forming ability through simple heat-treatment. By virtue of these excellent optical characteristics and good film-forming ability, a white light-emitting device (LED) was fabricated by combining a UV-LED chip with a single CQD phosphor film, which exhibited cool white light with a CIE coordinate of (0.31, 0.36), a color rendering index of 84 and a correlated color temperature of 6282 K. In addition, the white LED exhibits good optical stability under various working currents and for different working time intervals. Moreover, the interaction between the carbogenic core and surface groups was discussed using the DMol(3) program based on density functional theory. This research suggests the great potential of CQDs for solid-state lighting systems and reveals the effect of the surface state on the photoluminescent mechanism of CQDs.

Powder, paper and foam of few-layer graphene prepared in high yield by electrochemical intercalation exfoliation of expanded graphite.

PubMed

Wu, Liqiong; Li, Weiwei; Li, Peng; Liao, Shutian; Qiu, Shengqiang; Chen, Mingliang; Guo, Yufen; Li, Qi; Zhu, Chao; Liu, Liwei

2014-04-09

A facile and high-yield approach to the preparation of few-layer graphene (FLG) by electrochemical intercalation exfoliation (EIE) of expanded graphite in sulfuric acid electrolyte is reported. Stage-1 H2SO4-graphite intercalation compound is used as a key intermediate in EIE to realize the efficient exfoliation. The yield of the FLG sheets (<7 layers) with large lateral sizes (tens of microns) is more than 75% relative to the total amount of starting expanded graphite. A low degree of oxygen functionalization existing in the prepared FLG flakes enables them to disperse effectively, which contributes to the film-forming characteristics of the FLG flakes. These electrochemically exfoliated FLG flakes are integrated into several kinds of macroscopic graphene structures. Flexible and freestanding graphene papers made of the FLG flakes retain excellent conductivity (≈24,500 S m(-1)). Three-dimensional (3D) graphene foams with light weight are fabricated from the FLG flakes by the use of Ni foams as self-sacrifice templates. Furthermore, 3D graphene/Ni foams without any binders, which are used as supercapacitor electrodes in aqueous electrolyte, provide the specific capacitance of 113.2 F g(-1) at a current density of 0.5 A g(-1), retaining 90% capacitance after 1000 cycles. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photoresponse in La0.9Hf0.1MnO3/0.05wt%Nb-doped SrTiO3 heteroepitaxial junctions

NASA Astrophysics Data System (ADS)

Qi, Yaping; Ni, Hao; Zheng, Ming; Zeng, Jiali; Jiang, Yucheng; Gao, Ju

2018-05-01

Excellent photo detectors need to have the rapid response and good repeatability from the requirement of industrial applications. In this paper, transport behavior and opto-response of heterostructures made with La0.9Hf0.1MnO3 and 0.05wt%Nb-doped SrTiO3 were investigated. The heterojunctions exhibited an excellent rectifying feature with very low leakage in a broad temperature region (from 40 to 300 K). These thin films presented persistent and stable photovoltages upon light illumination. Rapid shift between small and large voltages corresponding to "light OFF" and "light ON" states, respectively, was observed, demonstrating reliable photo detection behavior. A semiconductor laser with a wavelength of 650 nm was used as the light source. It is also noted that the observed photovoltages are strongly determined by light intensity. The injection of photoexcited charge carriers (electrons) could be responsible for the appearance of the observed opto-response. Such manipulative features by light irradiation exhibit great potential for light detectors for visible light.

The influence of day/night cycles on biomass yield and composition of Neochloris oleoabundans.

PubMed

de Winter, Lenneke; Cabanelas, Iago Teles Dominguez; Martens, Dirk E; Wijffels, René H; Barbosa, Maria J

2017-01-01

Day/night cycles regulate the circadian clock of organisms to program daily activities. Many species of microalgae have a synchronized cell division when grown under a day/night cycle, and synchronization might influence biomass yield and composition. Therefore, the aim of this study was to study the influence of day/night cycle on biomass yield and composition of the green microalgae Neochloris oleoabundans . Hence, we compared continuous turbidostat cultures grown under continuous light with cultures grown under simulated day/night cycles. Under day/night cycles, cultures were synchronized as cell division was scheduled in the night, whereas under continuous light cell division occurred randomly synchronized cultures were able to use the light 10-15% more efficiently than non-synchronized cultures. Our results indicate that the efficiency of light use varies over the cell cycle and that synchronized cell division provides a fitness benefit to microalgae. Biomass composition under day/night cycles was similar to continuous light, with the exception of starch content. The starch content was higher in cultures under continuous light, most likely because the cells never had to respire starch to cover for maintenance during dark periods. Day/night cycles were provided in a 'block' (continuous light intensity during the light period) and in a 'sine' (using a sine function to simulate light intensities from sunrise to sunset). There were no differences in biomass yield or composition between these two ways of providing light (in a 'block' or in a 'sine'). The biomass yield and composition of N. oleoabundans were influenced by day/night cycles. These results are important to better understand the relations between research done under continuous light conditions and with day/night cycle conditions. Our findings also imply that more research should be done under day/night cycles.

Maximizing and stabilizing luminescence from halide perovskites with potassium passivation.

PubMed

Abdi-Jalebi, Mojtaba; Andaji-Garmaroudi, Zahra; Cacovich, Stefania; Stavrakas, Camille; Philippe, Bertrand; Richter, Johannes M; Alsari, Mejd; Booker, Edward P; Hutter, Eline M; Pearson, Andrew J; Lilliu, Samuele; Savenije, Tom J; Rensmo, Håkan; Divitini, Giorgio; Ducati, Caterina; Friend, Richard H; Stranks, Samuel D

2018-03-21

Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield-a quantity that must be maximized to obtain high efficiency-remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications.

The Thermoluminescence Response of Ge-Doped Flat Fibers to Gamma Radiation

PubMed Central

Mat Nawi, Siti Nurasiah Binti; Wahib, Nor Fadira Binti; Zulkepely, Nurul Najua Binti; Amin, Yusoff Bin Mohd; Min, Ung Ngie; Bradley, David Andrew; Md Nor, Roslan Bin; Maah, Mohd Jamil

2015-01-01

Study has been undertaken of the thermoluminescence (TL) yield of various tailor-made flat cross-section 6 mol% Ge-doped silica fibers, differing only in respect of external dimensions. Key TL dosimetric characteristics have been investigated, including glow curves, dose response, sensitivity, fading and reproducibility. Using a 60Co source, the samples were irradiated to doses within the range 1 to 10 Gy. Prior to irradiation, the flat fibers were sectioned into 6 mm lengths, weighed, and annealed at 400 °C for 1 h. TL readout was by means of a Harshaw Model 3500 TLD reader, with TLD-100 chips (LiF:Mg, Ti) used as a reference dosimeter to allow the relative response of the fibers to be evaluated. The fibers have been found to provide highly linear dose response and excellent reproducibility over the range of doses investigated, demonstrating high potential as TL-mode detectors in radiation medicine applications. Mass for mass, the results show the greatest TL yield to be provided by fibers of the smallest cross-section, analysis indicating this to be due to minimal light loss in transport of the TL through the bulk of the silica medium. PMID:26307987

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

Shen, Yu, E-mail: shenyuqing0322@gmail.com; Key Laboratory of Industrial Ecology and Environmental Engineering and State Key Laboratory of Fine Chemical, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024; Wu, Yanbo

Graphical abstract: - Highlights: • Spinel CuFe{sub 2}O{sub 4} nanospheres were successfully synthesized via a facile method. • CuFe{sub 2}O{sub 4} nanospheres showed high photocatalytic activity toward benzene. • Ethyl acetate, carboxylic acid and aldehyde were the intermediate products. - Abstract: Spinel copper ferrite nanospheres with diameters of about 116 nm were synthesized in high yield via a facile solvothermal route. The prepared nanospheres had cubic spinel structure and exhibited good size uniformity and regularity. The band-gap energy of CuFe{sub 2}O{sub 4} nanospheres was calculated to be about 1.69 eV, indicating their potential visible-light-induced photocatalytic activity. The dramatically enhanced photocatalyticmore » activity of the CuFe{sub 2}O{sub 4} nanospheres was evaluated via the photocatalytic conversion of benzene under Xe lamp irradiation. By using the in situ FTIR technique, ethyl acetate, carboxylic acid and aldehyde could be regarded as the intermediate products, and CO{sub 2} was produced as the final product during the reaction process. This study provided new insight into the design and preparation of functional nanomaterials with sphere structure in high yield, and the as-grown architectures demonstrated an excellent ability to remove organic pollutants in the atmosphere.« less

X-ray Scintillation in Lead Halide Perovskite Crystals

PubMed Central

Birowosuto, M. D.; Cortecchia, D.; Drozdowski, W.; Brylew, K.; Lachmanski, W.; Bruno, A.; Soci, C.

2016-01-01

Current technologies for X-ray detection rely on scintillation from expensive inorganic crystals grown at high-temperature, which so far has hindered the development of large-area scintillator arrays. Thanks to the presence of heavy atoms, solution-grown hybrid lead halide perovskite single crystals exhibit short X-ray absorption length and excellent detection efficiency. Here we compare X-ray scintillator characteristics of three-dimensional (3D) MAPbI3 and MAPbBr3 and two-dimensional (2D) (EDBE)PbCl4 hybrid perovskite crystals. X-ray excited thermoluminescence measurements indicate the absence of deep traps and a very small density of shallow trap states, which lessens after-glow effects. All perovskite single crystals exhibit high X-ray excited luminescence yields of >120,000 photons/MeV at low temperature. Although thermal quenching is significant at room temperature, the large exciton binding energy of 2D (EDBE)PbCl4 significantly reduces thermal effects compared to 3D perovskites, and moderate light yield of 9,000 photons/MeV can be achieved even at room temperature. This highlights the potential of 2D metal halide perovskites for large-area and low-cost scintillator devices for medical, security and scientific applications. PMID:27849019

No. 1 and No. 2 Common red oak yields: similar part sizes when gang-ripping is used to process boards with crook

Treesearch

Charles J. Gatchell; Charles J. Gatchell

1990-01-01

Computer simulation was used to gang rip No. 1 and No. 2 Common red oak boards before and after removal of crook. While No. 1 Common produced slightly more total yield, the part yields were very similar. No. 1 Common was superior only in yielding 75-inch-long pieces. Either grade is an excellent choice for the furniture and cabinet industries.

Iron-catalyzed cross-coupling of imidoyl chlorides with Grignard reagents.

PubMed

Ottesen, Lars K; Ek, Fredrik; Olsson, Roger

2006-04-27

[reaction: see text] A general, high yielding rapid iron-catalyzed cross-coupling reaction between Grignard reagents and imidoyl chlorides is described. These reactions are typically completed within 5 min, resulting in high yields of 71-96% using 5% iron catalyst in a THF-NMP solvent mixture. Functionalized imidoyl chlorides (e.g., R = CO(2)Me) gave excellent yields (89%).

Co-production of bio-ethanol, xylonic acid and slow-release nitrogen fertilizer from low-cost straw pulping solid residue.

PubMed

Huang, Chen; Ragauskas, Arthur J; Wu, Xinxing; Huang, Yang; Zhou, Xuelian; He, Juan; Huang, Caoxing; Lai, Chenhuan; Li, Xin; Yong, Qiang

2018-02-01

A novel bio-refinery sequence yielding varieties of co-products was developed using straw pulping solid residue. This process utilizes neutral sulfite pretreatment which under optimal conditions (160 °C and 3% (w/v) sulfite charge) provides 64.3% delignification while retaining 90% of cellulose and 67.3% of xylan. The pretreated solids exhibited excellent enzymatic digestibility, with saccharification yields of 86.9% and 81.1% for cellulose and xylan, respectively. After pretreatment, the process of semi-simultaneous saccharification and fermentation (S-SSF) and bio-catalysis was investigated. The results revealed that decreased ethanol yields were achieved when solid loading increased from 5% to 30%. An acceptable ethanol yield of 76.8% was obtained at 20% solid loading. After fermentation, bio-catalysis of xylose remaining in fermentation broth resulted in near 100% xylonic acid (XA) yield at varied solid loadings. To complete the co-product portfolio, oxidation ammoniation of the dissolved lignin successfully transformed it into biodegradable slow-release nitrogen fertilizer with excellent agricultural properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fabrication of p-n heterostructure ZnO/Si moth-eye structures: Antireflection, enhanced charge separation and photocatalytic properties

NASA Astrophysics Data System (ADS)

Zeng, Yu; Chen, XiFang; Yi, Zao; Yi, Yougen; Xu, Xibin

2018-05-01

The pyramidal silicon substrate is formed by wet etching, then ZnO nanorods are grown on the surface of the pyramidal microstructure by a hydrothermal method to form a moth-eye composite heterostructure. The composite heterostructure of this material determines its excellent anti-reflection properties and ability to absorb light from all angles. In addition, due to the effective heterojunction binding area, the composite micro/nano structure has excellent photoelectric conversion performance. Its surface structure and the large specific surface area gives the material super hydrophilicity, excellent gas sensing characteristic, and photocatalytic properties. Based on the above characteristics, the micro/nano heterostructure can be used in solar cells, sensors, light-emitting devices, and photocatalytic fields.

Identified hadron production in pp collisions measured with ALICE.

NASA Astrophysics Data System (ADS)

Corrales Morales, Yasser; ALICE Collaboration

2017-07-01

The production of identified hadrons in proton-proton collisions is frequently studied as a reference for the investigation of the strongly-interacting medium created in heavy-ion collisions. In addition, at LHC energies measurements in pp and p-Pb collisions as a function of the event multiplicity have shown some features reminiscent of those related to collective effects in Pb-Pb collisions. Thanks to its excellent PID capabilities and p Τ coverage, the ALICE detector offers a unique opportunity for the measurement of p Τ spectra, integrated yields (dN/dy) and mean transverse momenta (

) of identified light-flavour hadrons at midrapidity over a wide p Τ range. In this contribution, results on π, K, p, {{{K}}}{{S}}0, Λ, Ξ, Ω and K*0 as a function of multiplicity in pp collisions at \\sqrt{s}=7 {TeV} are presented. The results are compared with those measured in p-Pb and Pb-Pb collisions. A similar evolution of the spectral shape, the p Τ-differential particle ratios and the integrated yield ratios with the charged particle multiplicity in both small and large systems is observed. The production rates of strange hadrons in pp collisions increase more than those of non-strange particles, showing an enhancement pattern with multiplicity which is remarkably similar to the one measured in p-Pb collisions. In addition, results on the production of light flavour hadrons in pp collisions at \\sqrt{s}=13 {TeV}, the highest centre-of-mass energy reached so far in the laboratory, are also presented and the behaviour observed as a function of \\sqrt{s} are discussed.

Quantum dot agglomerates in biological media and their characterization by asymmetrical flow field-flow fractionation.

PubMed

Moquin, Alexandre; Neibert, Kevin D; Maysinger, Dusica; Winnik, Françoise M

2015-01-01

The molecular composition of the biological environment of nanoparticles influences their physical properties and changes their pristine physicochemical identity. In order to understand, or predict, the interactions of cells with specific nanoparticles, it is critical to know their size, shape, and agglomeration state not only in their nascent state but also in biological media. Here, we use asymmetrical flow field-flow fractionation (AF4) with on-line multiangle light scattering (MALS), dynamic light scattering (DLS) and UV-Visible absorption detections to determine the relative concentration of isolated nanoparticles and agglomerates in the case of three types of semi-conductor quantum dots (QDs) dispersed in Dulbecco's Modified Eagle Media (DMEM) containing 10% of fetal bovine serum (DMEM-FBS). AF4 analysis also yielded the size and size distribution of the agglomerates as a function of the time of QDs incubation in DMEM-FBS. The preferred modes of internalization of the QDs are assessed for three cell-types, N9 microglia, human hepatocellular carcinoma cells (HepG2) and human embryonic kidney cells (Hek293), by confocal fluorescence imaging of live cells, quantitative determination of the intracellular QD concentration, and flow cytometry. There is an excellent correlation between the agglomeration status of the three types of QDs in DMEM-FBS determined by AF4 analysis and their preferred mode of uptake by the three cell lines, which suggests that AF4 yields an accurate description of the nanoparticles as they encounter cells and advocates its use as a means to characterize particles under evaluation. Copyright © 2014 Elsevier B.V. All rights reserved.

Development of antibacterial and high light transmittance bulk materials: Incorporation and sustained release of hydrophobic or hydrophilic antibiotics.

PubMed

Wang, Bailiang; Liu, Huihua; Zhang, Binjun; Han, Yuemei; Shen, Chenghui; Lin, Quankui; Chen, Hao

2016-05-01

Infection associated with medical devices is one of the most frequent complications of modern medical biomaterials. Bacteria have a strong ability to attach on solid surfaces, forming colonies and subsequently biofilms. In this work, a novel antibacterial bulk material was prepared through combining poly(dimethyl siloxane) (PDMS) with either hydrophobic or hydrophilic antibiotics (0.1-0.2 wt%). Scanning electron microscopy, water contact angle and UV-vis spectrophotometer were used to measure the changes of surface topography, wettability and optical transmission. For both gentamicin sulfate (GS) and triclosan (TCA), the optical transmission of the PDMS-GS and PDMS-TCA blend films was higher than 90%. Drug release studies showed initial rapid release and later sustained release of GS or TCA under aqueous physiological conditions. The blend films demonstrated excellent bactericidal and sufficient biofilm inhibition functions against Gram-positive bacteria (Staphylococcus aureus, S. aureus) measured by LIVE/DEAD bacterial viability kit staining method. Kirby-Bauer method showed that there was obvious zone of inhibition (7.5-12.5mm). Cytocompatibility assessment against human lens epithelial cells (HLECs) revealed that the PDMS-GS blend films had good cytocompatibility. However, the PDMS-TCA blend films showed certain cytotoxicity against HLECs. The PDMS-0.2 wt% GS blend films were compared to native PDMS in the rabbit subcutaneous S. aureus infection model. The blend films yielded a significantly lower degree of infection than native PDMS at day 7. The achievement of the PDMS-drug bulk materials with high light transmittance, excellent bactericidal function and good cytocompatibility can potentially be widely used as bio-optical materials. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

Non-Doped Sky-Blue OLEDs Based on Simple Structured AIE Emitters with High Efficiencies at Low Driven Voltages.

PubMed

Islam, Amjad; Zhang, Dongdong; Peng, Ruixiang; Yang, Rongjuan; Hong, Ling; Song, Wei; Wei, Qiang; Duan, Lian; Ge, Ziyi

2017-09-05

Blue organic light-emitting diodes (OLEDs) are necessary for flat-panel display technologies and lighting applications. To make more energy-saving, low-cost and long-lasting OLEDs, efficient materials as well as simple structured devices are in high demand. However, a very limited number of blue OLEDs achieving high stability and color purity have been reported. Herein, three new sky-blue emitters, 1,4,5-triphenyl-2-(4-(1,2,2-triphenylvinyl)phenyl)-1H-imidazole (TPEI), 1-(4-methoxyphenyl)-4,5-diphenyl-2-(4-(1,2,2-triphenylvinyl)phenyl)-1H-imidazole (TPEMeOPhI) and 1-phenyl-2,4,5-tris(4-(1,2,2-triphenylvinyl)phenyl)-1H-imidazole (3TPEI), with a combination of imidazole and tetraphenylethene groups, have been developed. High photoluminescence quantum yields are obtained for these materials. All derivatives have demonstrated aggregation-induced emission (AIE) behavior, excellent thermal stability with high decomposition and glass transition temperatures. Non-doped sky-blue OLEDs with simple structure have been fabricated employing these materials as emitters and realized high efficiencies of 2.41 % (4.92 cd A -1 , 2.70 lm W -1 ), 2.16 (4.33 cd A -1 , 2.59 lm W -1 ) and 3.13 % (6.97 cd A -1 , 4.74 lm W -1 ) for TPEI, TPEMeOPhI and 3TPEI, with small efficiency roll-off. These are among excellent results for molecules constructed from the combination of imidazole and TPE reported so far. The high performance of a 3TPEI-based device shows the promising potential of the combination of imidazole and AIEgen for synthesizing efficient electroluminescent materials for OLED devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

An efficient copper-catalyzed synthesis of anilines by employing aqueous ammonia.

PubMed

Zeng, Xin; Huang, Wenming; Qiu, Yatao; Jiang, Sheng

2011-12-21

Under the catalysis of CuI/2-carboxylic acid-quinoline-N-oxide, the cross coupling reactions between aryl iodides or bromides and aqueous ammonia proceed very well to afford N-unprotected aniline derivatives in excellent yields. This inexpensive catalytic system shows great functional group tolerance and excellent reaction selectivity.

A tutorial on the use of Excel 2010 and Excel for Mac 2011 for conducting delay-discounting analyses.

PubMed

Reed, Derek D; Kaplan, Brent A; Brewer, Adam T

2012-01-01

In recent years, researchers and practitioners in the behavioral sciences have profited from a growing literature on delay discounting. The purpose of this article is to provide readers with a brief tutorial on how to use Microsoft Office Excel 2010 and Excel for Mac 2011 to analyze discounting data to yield parameters for both the hyperbolic discounting model and area under the curve. This tutorial is intended to encourage the quantitative analysis of behavior in both research and applied settings by readers with relatively little formal training in nonlinear regression.

A TUTORIAL ON THE USE OF EXCEL 2010 AND EXCEL FOR MAC 2011 FOR CONDUCTING DELAY-DISCOUNTING ANALYSES

PubMed Central

Reed, Derek D; Kaplan, Brent A; Brewer, Adam T

2012-01-01

In recent years, researchers and practitioners in the behavioral sciences have profited from a growing literature on delay discounting. The purpose of this article is to provide readers with a brief tutorial on how to use Microsoft Office Excel 2010 and Excel for Mac 2011 to analyze discounting data to yield parameters for both the hyperbolic discounting model and area under the curve. This tutorial is intended to encourage the quantitative analysis of behavior in both research and applied settings by readers with relatively little formal training in nonlinear regression. PMID:22844143

New higher-order Godunov code for modelling performance of two-stage light gas guns

NASA Technical Reports Server (NTRS)

Bogdanoff, D. W.; Miller, R. J.

1995-01-01

A new quasi-one-dimensional Godunov code for modeling two-stage light gas guns is described. The code is third-order accurate in space and second-order accurate in time. A very accurate Riemann solver is used. Friction and heat transfer to the tube wall for gases and dense media are modeled and a simple nonequilibrium turbulence model is used for gas flows. The code also models gunpowder burn in the first-stage breech. Realistic equations of state (EOS) are used for all media. The code was validated against exact solutions of Riemann's shock-tube problem, impact of dense media slabs at velocities up to 20 km/sec, flow through a supersonic convergent-divergent nozzle and burning of gunpowder in a closed bomb. Excellent validation results were obtained. The code was then used to predict the performance of two light gas guns (1.5 in. and 0.28 in.) in service at the Ames Research Center. The code predictions were compared with measured pressure histories in the powder chamber and pump tube and with measured piston and projectile velocities. Very good agreement between computational fluid dynamics (CFD) predictions and measurements was obtained. Actual powder-burn rates in the gun were found to be considerably higher (60-90 percent) than predicted by the manufacturer and the behavior of the piston upon yielding appears to differ greatly from that suggested by low-strain rate tests.

Quark-novae Occurring in Massive Binaries : A Universal Energy Source in Superluminous Supernovae with Double-peaked Light Curves

NASA Astrophysics Data System (ADS)

Ouyed, Rachid; Leahy, Denis; Koning, Nico

2016-02-01

A quark-nova (QN; the sudden transition from a neutron star into a quark star), which occurs in the second common envelope (CE) phase of a massive binary, gives excellent fits to superluminous, hydrogen-poor, supernovae (SLSNe) with double-peaked light curves, including DES13S2cmm, SN 2006oz, and LSQ14bdq (http://www.quarknova.ca/LCGallery.html). In our model, the H envelope of the less massive companion is ejected during the first CE phase, while the QN occurs deep inside the second, He-rich, CE phase after the CE has expanded in size to a radius of a few tens to a few thousands of solar radii; this yields the first peak in our model. The ensuing merging of the quark star with the CO core leads to black hole formation and accretion, explaining the second long-lasting peak. We study a sample of eight SLSNe Ic with double-humped light curves. Our model provides good fits to all of these, with a universal explosive energy of 2 × 1052 erg (which is the kinetic energy of the QN ejecta) for the first hump. The late-time emissions seen in iPTF13ehe and LSQ14bdq are fit with a shock interaction between the outgoing He-rich (I.e., second) CE and the previously ejected H-rich (I.e., first) CE.

Nanostructured organosilicon luminophores and their application in highly efficient plastic scintillators

NASA Astrophysics Data System (ADS)

Ponomarenko, Sergei A.; Surin, Nikolay M.; Borshchev, Oleg V.; Luponosov, Yuriy N.; Akimov, Dmitry Y.; Alexandrov, Ivan S.; Burenkov, Alexander A.; Kovalenko, Alexey G.; Stekhanov, Viktor N.; Kleymyuk, Elena A.; Gritsenko, Oleg T.; Cherkaev, Georgiy V.; Kechek'yan, Alexander S.; Serenko, Olga A.; Muzafarov, Aziz M.

2014-10-01

Organic luminophores are widely used in various optoelectronic devices, which serve for photonics, nuclear and particle physics, quantum electronics, medical diagnostics and many other fields of science and technology. Improving their spectral-luminescent characteristics for particular technical requirements of the devices is a challenging task. Here we show a new concept to universal solution of this problem by creation of nanostructured organosilicon luminophores (NOLs), which are a particular type of dendritic molecular antennas. They combine the best properties of organic luminophores and inorganic quantum dots: high absorption cross-section, excellent photoluminescence quantum yield, fast luminescence decay time and good processability. A NOL consists of two types of covalently bonded via silicon atoms organic luminophores with efficient Förster energy transfer between them. Using NOLs in plastic scintillators, widely utilized for radiation detection and in elementary particles discoveries, led to a breakthrough in their efficiency, which combines both high light output and fast decay time. Moreover, for the first time plastic scintillators, which emit light in the desired wavelength region ranging from 370 to 700 nm, have been created. We anticipate further applications of NOLs as working elements of pulsed dye lasers in photonics, optoelectronics and as fluorescent labels in biology and medical diagnostics.

Synthesis and Characterization of Photoactivatable Doxycycline Analogues Bearing Two-Photon-Sensitive Photoremovable Groups Suitable for Light-Induced Gene Expression.

PubMed

Goegan, Bastien; Terzi, Firat; Bolze, Frédéric; Cambridge, Sidney; Specht, Alexandre

2018-06-18

We report the synthesis and photolytic properties of caged 9-aminodoxycycline derivatives modified with 2-{4'-bis-[2-(2methoxyethoxy)ethyl]-4-nitrobiphenyl-3-yl}prop-1-oxy (EANBP) and PEG7-ylated (7-diethylamino-2-oxo-2H-chromen-4-yl)methyl (PEG7-DEACM) groups. 9-Aminodoxycycline is a tetracycline analogue capable of activating transcription through the inducible TetOn transgene expression system and can be regioselectively coupled to two-photon-sensitive photo-removable protecting groups by carbamoylation. The EANBP-based caged 9-aminodoxycycline showed complex photochemical reactions but did release 10 % of 9-aminodoxycycline. However, 9-(PEG7-DEACMamino)doxycycline exhibited excellent photolysis efficiency at 405 nm with quantitative release of 9-aminodoxycycline and a 0.21 uncaging quantum yield. Thanks to the good two-photon sensitivity of the DEACM chromophore, 9-aminodoxycycline release by two-photon photolysis is possible, with calculated action cross-sections of up to 4.0 GM at 740 nm. Therefore, 9-(PEG7-DEACMamino)doxycycline represents a very attractive tool for the development of a light-induced gene expression method in living cells. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A fully synthetic human Fab antibody library based on fixed VH/VL framework pairings with favorable biophysical properties

PubMed Central

Tiller, Thomas; Schuster, Ingrid; Deppe, Dorothée; Siegers, Katja; Strohner, Ralf; Herrmann, Tanja; Berenguer, Marion; Poujol, Dominique; Stehle, Jennifer; Stark, Yvonne; Heßling, Martin; Daubert, Daniela; Felderer, Karin; Kaden, Stefan; Kölln, Johanna; Enzelberger, Markus; Urlinger, Stefanie

2013-01-01

This report describes the design, generation and testing of Ylanthia, a fully synthetic human Fab antibody library with 1.3E+11 clones. Ylanthia comprises 36 fixed immunoglobulin (Ig) variable heavy (VH)/variable light (VL) chain pairs, which cover a broad range of canonical complementarity-determining region (CDR) structures. The variable Ig heavy and Ig light (VH/VL) chain pairs were selected for biophysical characteristics favorable to manufacturing and development. The selection process included multiple parameters, e.g., assessment of protein expression yield, thermal stability and aggregation propensity in fragment antigen binding (Fab) and IgG1 formats, and relative Fab display rate on phage. The framework regions are fixed and the diversified CDRs were designed based on a systematic analysis of a large set of rearranged human antibody sequences. Care was taken to minimize the occurrence of potential posttranslational modification sites within the CDRs. Phage selection was performed against various antigens and unique antibodies with excellent biophysical properties were isolated. Our results confirm that quality can be built into an antibody library by prudent selection of unmodified, fully human VH/VL pairs as scaffolds. PMID:23571156

Hybrid silicon honeycomb/organic solar cells with enhanced efficiency using surface etching.

PubMed

Liu, Ruiyuan; Sun, Teng; Liu, Jiawei; Wu, Shan; Sun, Baoquan

2016-06-24

Silicon (Si) nanostructure-based photovoltaic devices are attractive for their excellent optical and electrical performance, but show lower efficiency than their planar counterparts due to the increased surface recombination associated with the high surface area and roughness. Here, we demonstrate an efficiency enhancement for hybrid nanostructured Si/polymer solar cells based on a novel Si honeycomb (SiHC) structure using a simple etching method. SiHC structures are fabricated using a combination of nanosphere lithography and plasma treatment followed by a wet chemical post-etching. SiHC has shown superior light-trapping ability in comparison with the other Si nanostructures, along with a robust structure. Anisotropic tetramethylammonium hydroxide etching not only tunes the final surface morphologies of the nanostructures, but also reduces the surface roughness leading to a lower recombination rate in the hybrid solar cells. The suppressed recombination loss, benefiting from the reduced surface-to-volume ratio and roughness, has resulted in a high open-circuit voltage of 600 mV, a short-circuit current of 31.46 mA cm(-2) due to the light-trapping ability of the SiHCs, and yields a power conversion efficiency of 12.79% without any other device structure optimization.

Protective Effect of Fucoxanthin Isolated from Laminaria japonica against Visible Light-Induced Retinal Damage Both in Vitro and in Vivo.

PubMed

Liu, Yixiang; Liu, Meng; Zhang, Xichun; Chen, Qingchou; Chen, Haixiu; Sun, Lechang; Liu, Guangming

2016-01-20

With increasingly serious eye exposure to light stresses, such as light-emitting diodes, computers, and widescreen mobile phones, efficient natural compounds for preventing visible light-induced retinal damages are becoming compelling needs in the modern society. Fucoxanthin, as the main light absorption system in marine algae, may possess an outstanding bioactivity in vision protection because of its filtration of blue light and excellent antioxidative activity. In this work, both in vitro and in vivo simulated visible light-induced retinal damage models were employed. The in vitro results revealed that fucoxanthin exhibited better bioactivities than lutein, zeaxanthin, and blueberry anthocyanins in inhibiting overexpression of vascular endothelial growth factor, resisting senescence, improving phagocytic function, and clearing intracellular reactive oxygen species in retinal pigment epithelium cells. The in vivo experiment also confirmed the superiority of fucoxanthin than lutein in protecting retina against photoinduced damage. This excellent bioactivity may be attributed to its unique structural features, including allenic, epoxide, and acetyl groups. Fucoxanthin is expected to be an important ocular nutrient in the future.

Growth, yield and compositional characteristics of Jerusalem artichoke as it relates to biomass production

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

Stauffer, M.D.; Chubey, B.B.; Dorrell, D.G.

1980-01-01

Jerusalem artichoke (Helianthus tuberosus L.) has shown excellent potential as a carbohydrate-rich crop. Initial investigations determined inulin and tuber yields; however, when additional studies showed that good quality pulp remained after inulin extraction and high forage yields per hectare were obtainable, the scope of investigation was broadened to assess utilization of the total plant. Plant growth, yield and compositional characteristics of Jerusalem artichoke as they relate to biomass production will be reported.

A Facile Methodology for Engineering the Morphology of CsPbX3 Perovskite Nanocrystals under Ambient Condition

NASA Astrophysics Data System (ADS)

Seth, Sudipta; Samanta, Anunay

2016-11-01

A facile and highly reproducible room temperature, open atmosphere synthesis of cesium lead halide perovskite nanocrystals of six different morphologies is reported just by varying the solvent, ligand and reaction time. Sequential evolution of the quantum dots, nanoplates and nanobars in one medium and nanocubes, nanorods and nanowires in another medium is demonstrated. These perovskite nanoparticles are shown to be of excellent crystalline quality with high fluorescence quantum yield. A mechanism of the formation of nanoparticles of different shapes and sizes is proposed. Considering the key role of morphology in nanotechnology, this simple method of fabrication of a wide range of high quality nanocrystals of different shapes and sizes of all-inorganic lead halide perovskites, whose potential is already demonstrated in light emitting and photovoltaic applications, is likely to help widening the scope and utility of these materials in optoelectronic devices.

Unlocking the Potential of Phenacyl Protecting Groups: CO2-Based Formation and Photocatalytic Release of Caged Amines.

PubMed

Speckmeier, Elisabeth; Klimkait, Michael; Zeitler, Kirsten

2018-04-06

Orthogonal protection and deprotection of amines remain important tools in synthetic design as well as in chemical biology and material research applications. A robust, highly efficient, and sustainable method for the formation of phenacyl-based carbamate esters was developed using CO 2 for the in situ preparation of the intermediate carbamates. Our mild and broadly applicable protocol allows for the formation of phenacyl urethanes of anilines, primary amines, including amino acids, and secondary amines in high to excellent yields. Moreover, we demonstrate the utility by a mild and convenient photocatalytic deprotection protocol using visible light. A key feature of the [Ru(bpy) 3 ](PF 6 ) 2 -catalyzed method is the use of ascorbic acid as reductive quencher in a neutral, buffered, two-phase acetonitrile/water mixture, granting fast and highly selective deprotection for all presented examples.

MiX: a position sensitive dual-phase liquid xenon detector

NASA Astrophysics Data System (ADS)

Stephenson, S.; Haefner, J.; Lin, Q.; Ni, K.; Pushkin, K.; Raymond, R.; Schubnell, M.; Shutty, N.; Tarlé, G.; Weaverdyck, C.; Lorenzon, W.

2015-10-01

The need for precise characterization of dual-phase xenon detectors has grown as the technology has matured into a state of high efficacy for rare event searches. The Michigan Xenon detector was constructed to study the microphysics of particle interactions in liquid xenon across a large energy range in an effort to probe aspects of radiation detection in liquid xenon. We report the design and performance of a small 3D position sensitive dual-phase liquid xenon time projection chamber with high light yield (Ly122=15.2 pe/keV at zero field), long electron lifetime (τ > 200 μs), and excellent energy resolution (σ/E = 1% for 1,333 keV gamma rays in a drift field of 200 V/cm). Liquid xenon time projection chambers with such high energy resolution may find applications not only in dark matter direct detection searches, but also in neutrinoless double beta decay experiments and other applications.

Columnar aerosol properties over oceans by combining surface and aircraft measurements: sensitivity analysis.

PubMed

Zhang, T; Gordon, H R

1997-04-20

We report a sensitivity analysis for the algorithm presented by Gordon and Zhang [Appl. Opt. 34, 5552 (1995)] for inverting the radiance exiting the top and bottom of the atmosphere to yield the aerosol-scattering phase function [P(?)] and single-scattering albedo (omega(0)). The study of the algorithm's sensitivity to radiometric calibration errors, mean-zero instrument noise, sea-surface roughness, the curvature of the Earth's atmosphere, the polarization of the light field, and incorrect assumptions regarding the vertical structure of the atmosphere, indicates that the retrieved omega(0) has excellent stability even for very large values (~2) of the aerosol optical thickness; however, the error in the retrieved P(?) strongly depends on the measurement error and on the assumptions made in the retrieval algorithm. The retrieved phase functions in the blue are usually poor compared with those in the near infrared.

The water soluble axially disubstituted silicon phthalocyanines: photophysicochemical properties and in vitro studies.

PubMed

Göksel, Meltem; Biyiklioglu, Zekeriya; Durmuş, Mahmut

2017-08-01

Two novel silicon(IV) phthalocyanines bearing 1,3-bis[3(dimethylamino)phenoxy]propan-2-ol or 1,3-bis[3(diethylamino)phenoxy]propan-2-ol groups at their axial positions were synthesized. These phthalocyanines were converted into their water soluble derivatives by the quaternization reaction with methyl iodide. The quaternized phthalocyanines show excellent solubility aqueous solutions without any aggregation which makes them potential photosensitizers for use in photodynamic therapy (PDT). For this reason, the photophysical and photochemical properties such as fluorescence quantum yields, lifetimes, singlet oxygen generation and photodegradation of both non-ionic (3 and 5) and quaternized cationic silicon(IV) phthalocyanines were investigated. Furthermore, the cytotoxicity of PDT was determined by colorimetric proliferation assay against to hepatocellular carcinoma (HuH-7) cancer cells. In this study, the cells were incubated with a novel water soluble silicon(IV) phthalocyanine derivatives and thereafter the cells were illuminated using broad-band incoherent light source.

Solute-solvent interactions and dynamics probed by THz light

NASA Astrophysics Data System (ADS)

Schwaab, Gerhard; Böhm, Fabian; Ma, Chun-Yu; Havenith, Martina

The THz range (1-12 THz, 30-400 cm-1) is especially suited to probe changes in the solvent dynamics induced by solutes of different character (hydrophobic, hydrophilic, charged, neutral). In recent years we have investigated a large variety of such solutes and found characteristic spectral fingerprints for ions, but also for uncharged solutes, such as alcohols. We will present a status report on our current understanding of the observed spectral changes and how they relate to physico-chemical parameters like hydration shell size or the lifetime of an excited intermolecular oscillation. In addition, we will show, that in some cases the spectral changes are closely related to the partition function yielding access to a microscopic understanding of macroscopic thermodynamic functions. The authors gratefully acknowledge financial support from the Cluster of Excellence RESOLV (Ruhr-Universität, EXC1069) funded by the Deutsche Forschungsgemeinschaft.

Asymmetric Catalysis with Organic Azides and Diazo Compounds Initiated by Photoinduced Electron Transfer.

PubMed

Huang, Xiaoqiang; Webster, Richard D; Harms, Klaus; Meggers, Eric

2016-09-28

Electron-acceptor-substituted aryl azides and α-diazo carboxylic esters are used as substrates for visible-light-activated asymmetric α-amination and α-alkylation, respectively, of 2-acyl imidazoles catalyzed by a chiral-at-metal rhodium-based Lewis acid in combination with a photoredox sensitizer. This novel proton- and redox-neutral method provides yields of up to 99% and excellent enantioselectivities of up to >99% ee with broad functional group compatibility. Mechanistic investigations suggest that an intermediate rhodium enolate complex acts as a reductive quencher to initiate a radical process with the aryl azides and α-diazo carboxylic esters serving as precursors for nitrogen and carbon-centered radicals, respectively. This is the first report on using aryl azides and α-diazo carboxylic esters as substrates for asymmetric catalysis under photoredox conditions. These reagents have the advantage that molecular nitrogen is the leaving group and sole byproduct in this reaction.

Facile Preparation of Porous WO3 Film for Photoelectrochemical Splitting of Natural Seawater

NASA Astrophysics Data System (ADS)

Shi, Yonghong; Li, Yuangang; Wei, Xiaoliang; Feng, Juan; Li, Huajing; Zhou, Wanyi

2017-12-01

Sunlight-driven natural seawater splitting provides a promising way for large-scale conversion and storage of solar energy. Here, we develop a facile and low-cost method via a deposition-annealing technique to fabricate porous WO3 film and demonstrate its application as a photoanode for natural seawater splitting. The WO3 film yields a photocurrent density of 1.95 mA cm-2 and possesses excellent stability at 1.23 V (versus RHE), under the illumination of 100 mW cm-2 (AM 1.5G). The photoelectrochemical performance is ascribed to the large surface area and good permeation of the electrolyte into the porous film. Furthermore, the photocurrent density remains almost the same during 3 h continuous light irradiation. The evolution of chlorine gas from seawater splitting was determined with qualitative and quantitative analyses, with a Faradic efficiency of about 56%.

Highly efficient water-mediated approach to access benzazoles: metal catalyst and base-free synthesis of 2-substituted benzimidazoles, benzoxazoles, and benzothiazoles.

PubMed

Bala, Manju; Verma, Praveen Kumar; Sharma, Deepika; Kumar, Neeraj; Singh, Bikram

2015-05-01

An efficient water-catalyzed method has been developed for the synthesis of 2-substituted benzimidazoles, benzoxazoles, and benzothiazoles in one step. The present method excludes the usage of toxic metal catalysts and bases to produce benzazoles in good to excellent yields. An efficient and versatile water-mediated method has been established for the synthesis of various 2-arylbenzazoles. The present protocol excludes the usage of any catalyst and additive provided excellent selectivities and yields with high functional group tolerance for the synthesis of 2-arylated benzimidazoles, benzoxazoles, and benzothiazoles. Benzazolones were also synthesized using similar reaction protocol.

Model-assisted forest yield estimation with light detection and ranging

Treesearch

Jacob L. Strunk; Stephen E. Reutebuch; Hans-Erik Andersen; Peter J. Gould; Robert J. McGaughey

2012-01-01

Previous studies have demonstrated that light detection and ranging (LiDAR)-derived variables can be used to model forest yield variables, such as biomass, volume, and number of stems. However, the next step is underrepresented in the literature: estimation of forest yield with appropriate confidence intervals. It is of great importance that the procedures required for...

Predawn and high intensity application of supplemental blue light decreases the quantum yield of PSII and enhances the amount of phenolic acids, flavonoids, and pigments in Lactuca sativa

PubMed Central

Ouzounis, Theoharis; Razi Parjikolaei, Behnaz; Fretté, Xavier; Rosenqvist, Eva; Ottosen, Carl-Otto

2015-01-01

To evaluate the effect of blue light intensity and timing, two cultivars of lettuce [Lactuca sativa cv. “Batavia” (green) and cv. “Lollo Rossa” (red)] were grown in a greenhouse compartment in late winter under natural light and supplemental high pressure sodium (SON-T) lamps yielding 90 (±10) μmol m−2 s−1 for up to 20 h, but never between 17:00 and 21:00. The temperature in the greenhouse compartments was 22/11°C day/night, respectively. The five light-emitting diode (LED) light treatments were Control (no blue addition), 1B 06-08 (Blue light at 45 μmol m−2 s−1 from 06:00 to 08:00), 1B 21-08 (Blue light at 45 μmol m−2 s−1 from 21:00 to 08:00), 2B 17-19 (Blue at 80 μmol m−2 s−1 from 17:00 to 19:00), and 1B 17-19 (Blue at 45 μmol m−2 s−1 from 17:00 to 19:00). Total fresh and dry weight was not affected with additional blue light; however, plants treated with additional blue light were more compact. The stomatal conductance in the green lettuce cultivar was higher for all treatments with blue light compared to the Control. Photosynthetic yields measured with chlorophyll fluorescence showed different response between the cultivars; in red lettuce, the quantum yield of PSII decreased and the yield of non-photochemical quenching increased with increasing blue light, whereas in green lettuce no difference was observed. Quantification of secondary metabolites showed that all four treatments with additional blue light had higher amount of pigments, phenolic acids, and flavonoids compared to the Control. The effect was more prominent in red lettuce, highlighting that the results vary among treatments and compounds. Our results indicate that not only high light level triggers photoprotective heat dissipation in the plant, but also the specific spectral composition of the light itself at low intensities. However, these plant responses to light are cultivar dependent. PMID:25767473

Photoperiod shift effects on yield characteristics of rice

NASA Technical Reports Server (NTRS)

Volk, G. M.; Mitchell, C. A.

1995-01-01

Edible yield must be maximized for each crop species selected for inclusion in the Controlled Ecological Life-Support System (CELSS) proposed by NASA to support long-term manned space missions. In a greenhouse study aimed at increasing biomass partitioning to rice (Oryza sativa L.) grain, plants of the high yielding semi-dwarf rice cultivar Ai-Nan-Tsao were started in pots under 8-h photoperiods at a density of 212 plants m-2. After different periods of time under 8-h photoperiods, pots were switched to continuous light for the remainder of the cropping cycle. Continuous light did not delay time to first panicle emergence (60 d) or time to harvest (83 d). There was a positive correlation between the length of continuous light treatments and nongrain biomass. Grain yield (1.6 +/- 0.2 g plant-1) did not increase in continuous light. Yield-efficiency rate (grain weight per length of cropping cycle, canopy volume, and weight of nongrain shoot biomass) was used to compare treatments. Small Ai-Nan-Tsao rice canopies grown under 8-h photoperiods were more efficient producers of grain than canopies grown under continuous light for a portion of the rice cropping cycle.

Light propagation and fluorescence quantum yields in liquid scintillators

NASA Astrophysics Data System (ADS)

Buck, C.; Gramlich, B.; Wagner, S.

2015-09-01

For the simulation of the scintillation and Cherenkov light propagation in large liquid scintillator detectors a detailed knowledge about the absorption and emission spectra of the scintillator molecules is mandatory. Furthermore reemission probabilities and quantum yields of the scintillator components influence the light propagation inside the liquid. Absorption and emission properties are presented for liquid scintillators using 2,5-Diphenyloxazole (PPO) and 4-bis-(2-Methylstyryl)benzene (bis-MSB) as primary and secondary wavelength shifter. New measurements of the quantum yields for various aromatic molecules are shown.

Recapitalization and Acquisition of Light Tactical Wheeled Vehicles (REDACTED)

DTIC Science & Technology

2010-01-29

representative from Red River Army Depot in Texarkana , Texas,18 stated that recapitalizing current HMMWVs to the XM1166 model was an excellent proposition...Red River Army Depot in Texarkana , Texas, stated that recapitalizing current HMMWVs to the XM1166 model was an excellent proposition. The Deputy...Army Depot in Texarkana , Texas, stated that recapitalizing current HMMWVs to the XM1166 model was an excellent proposition because the U.S

Copper(II)-catalyzed electrophilic amination of quinoline N-oxides with O-benzoyl hydroxylamines.

PubMed

Li, Gang; Jia, Chunqi; Sun, Kai; Lv, Yunhe; Zhao, Feng; Zhou, Kexiao; Wu, Hankui

2015-03-21

Copper acetate-catalyzed C-H bond functionalization amination of quinoline N-oxides was achieved using O-benzoyl hydroxylamine as an electrophilic amination reagent, thereby affording the desired products in moderate to excellent yields. Electrophilic amination can also be performed in good yield on a gram scale.

Effects of light intensity on components and topographical structures of extracellular polysaccharides from the cyanobacteria Nostoc sp.

PubMed

Ge, Hongmei; Xia, Ling; Zhou, Xuping; Zhang, Delu; Hu, Chunxiang

2014-02-01

A study on the effects of light intensity (40 and 80 μE/m(2)/sec) on the components and topographical structures of extracellular polysaccharides (EPS) was carried out in cyanobacteria Nostoc sp.. EPS yield increased with light intensity. However, light intensity did not significantly affect the EPS fractions and monosaccharide composition. Higher light intensity generally resulted in higher protein content of EPS in similar fractions. The topographical structure of EPS, investigated by atomic force microscopy, appeared as spherical lumps, chains and networks. The long chains were observed at higher light intensity. Thus, light intensity affected the yield and nature of EPS.

Optimizing concentration of shifter additive for plastic scintillators of different size

NASA Astrophysics Data System (ADS)

Adadurov, A. F.; Zhmurin, P. N.; Lebedev, V. N.; Titskaya, V. D.

2009-02-01

This paper concerns the influence of wavelength shifting (secondary) luminescent additive (LA 2) on the light yield of polystyrene-based plastic scintillator (PS) taking self-absorption into account. Calculations of light yield dependence on concentration of 1.4-bis(2-(5-phenyloxazolyl)-benzene (POPOP) as LA 2 were made for various path lengths of photons in PS. It is shown that there is an optimal POPOP concentration ( Copt), which provides a maximum light yield for a given path length. This optimal concentration is determined by the competition of luminescence and self-reflection processes. Copt values were calculated for PS of different dimensions. For small PS, Copt≈0.02%, which agree with a common (standard) value of POPOP concentration. For higher PS dimensions, the optimal POPOP concentration is decreased (to Copt≈0.006% for 320×30×2 cm sample), reducing the light yield from PS by almost 35%.

Enhancing the Performance of CdSe/CdS Dot-in-Rod Light-Emitting Diodes via Surface Ligand Modification.

PubMed

Rastogi, Prachi; Palazon, Francisco; Prato, Mirko; Di Stasio, Francesco; Krahne, Roman

2018-02-14

The surface ligands on colloidal nanocrystals (NCs) play an important role in the performance of NC-based optoelectronic devices such as photovoltaic cells, photodetectors, and light-emitting diodes (LEDs). On one hand, the NC emission depends critically on the passivation of the surface to minimize trap states that can provide nonradiative recombination channels. On the other hand, the electrical properties of NC films are dominated by the ligands that constitute the barriers for charge transport from one NC to its neighbor. Therefore, surface modifications via ligand exchange have been employed to improve the conductance of NC films. However, in LEDs, such surface modifications are more critical because of their possible detrimental effects on the emission properties. In this work, we study the role of surface ligand modifications on the optical and electrical properties of CdSe/CdS dot-in-rods (DiRs) in films and investigate their performance in all-solution-processed LEDs. The DiR films maintain high photoluminescence quantum yield, around 40-50%, and their electroluminescence in the LED preserves the excellent color purity of the photoluminescence. In the LEDs, the ligand exchange boosted the luminance, reaching a fourfold increase from 2200 cd/m 2 for native surfactants to 8500 cd/m 2 for the exchanged aminoethanethiol (AET) ligands. Moreover, the efficiency roll-off, operational stability, and shelf life are significantly improved, and the external quantum efficiency is modestly increased from 5.1 to 5.4%. We relate these improvements to the increased conductivity of the emissive layer and to the better charge balance of the electrically injected carriers. In this respect, we performed ultraviolet photoelectron spectroscopy (UPS) to obtain a deeper insight into the band alignment of the LED structure. The UPS data confirm similar flat-band offsets of the emitting layer to the electron- and hole-transport layers in the case of AET ligands, which translates to more symmetric barriers for charge injection of electrons and holes. Furthermore, the change in solubility of the NCs induced by the ligand exchange allows for a layer-by-layer deposition process of the DiR films, which yields excellent homogeneity and good thickness control and enables the fabrication of all the LED layers (except for cathode and anode) by spin-coating.

Evaluation of the Nutraceutical and Cosmeceutical Potential of Two Cultivars of Rubus fruticosus L. under Different Cultivation Conditions.

PubMed

Papaioanou, Maria; Chronopoulou, Evangelia G; Ciobotari, Gheorghii; Efrose, Rodica C; Sfichi-Duke, Liliana; Chatzikonstantinou, Marianna; Pappa, Evangelia; Ganopoulos, Ioannis; Madesis, Panagiotis; Nianiou-Obeidat, Irini; Zeng, Taofen; Labrou, Nikolaos E

2017-01-01

The starting point for the development of new, functional products derived from Rubus fruticosus L. is to determine the optimal cultivation conditions that produce maximal yield of fruits containing desirable bioactive properties. Towards that goal, the effect of soil, soil/peat mixture and light intensity on the nutraceutical and cosmeceutical potential of two cultivars ('Thornfree' and 'Loch Ness') of Rubus fruticosus L. were evaluated. The assessment was carried out employing a range of methods for evaluating fruit properties associated with promoting good health such as total antioxidant capacity, secondary metabolites content (vitamin C, polyphenols, flavonoids and anthocyanins) and inhibition analysis of skin-regulating enzymes. 'Thornfree' cultivar produced fruits in all light conditions, while 'Loch Ness' did not produce fruits in low light conditions. The results showed that in Rubus fruticosus L. fruit, the chemical composition and bioactivity are strongly affected by both genetics factors and growing conditions. Extract from 'Thornfree' fruits obtained under low light and soil/peat conditions displayed superior properties such as high antioxidant capacity, high concentrations of phenolics, flavonoids and anthocyanins and high inhibitory potency towards the enzymes tyrosinase and elastase. This extract was used for the development of a topical skin care cream with excellent compatibility and stability. Our findings conclude that Rubus fruticosus L. cultivation may be efficiently and effectively manipulated through conventional cultivation techniques to produce promising bioactive ingredients with potential use in commercial cosmetics and pharmaceuticals. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

A Fiber-Optic Current Sensor for Lightning Measurement Applications

NASA Technical Reports Server (NTRS)

Nguyen, Truong X.; Ely, Jay J.; Szatkowski, George N.

2015-01-01

An optical-fiber sensor based on Faraday Effect is developed for measuring total lightning electric current. It has many unique capabilities not possible with traditional current sensors. Designed for aircraft installation, the sensor is lightweight, non-conducting, structure-conforming, and is immune to electromagnetic interference, hysteresis and saturation. It can also be used on windmills, lightning towers, and can help validate lightning detection network measurements. Faraday Effect causes light polarization to rotate when the fiber is exposed to a magnetic field in the direction of light propagation. Thus, the magnetic field strength can be determined from the light polarization change. By forming closed fiber loops and applying Ampere's law, measuring the total light rotation yields the total current enclosed. The broadband, dual-detector, reflective polarimetric scheme allows measurement of both DC component and AC waveforms with about 60 dB dynamic range. Three sensor systems were built with different sensitivities from different laser wavelengths. Operating at 850nm, the first system uses twisted single-mode fiber and has a 150 A - 150 KA range. The second system operates at 1550nm, uses spun polarization maintaining fiber, and can measure 400 A - 400 KA. Both systems were validated with rocket-triggered lightning measurements and achieved excellent results when compared to a resistive shunt. The third system operates at 1310nm, uses spun polarization maintaining fiber, and can measure approximately 300 A - 300 KA. High current measurements up to 200 KA were demonstrated at a commercial lightning test facility. The system was recently installed on an aircraft and flown near icing weather conditions.

A fiber-optic current sensor for lightning measurement applications

NASA Astrophysics Data System (ADS)

Nguyen, Truong X.; Ely, Jay J.; Szatkowski, George N.

2015-05-01

An optical-fiber sensor based on Faraday Effect is developed for measuring total lightning electric current. It has many unique capabilities not possible with traditional current sensors. Designed for aircraft installation, the sensor is lightweight, non-conducting, structure-conforming, and is immune to electromagnetic interference, hysteresis and saturation. It can also be used on windmills, lightning towers, and can help validate lightning detection network measurements. Faraday Effect causes light polarization to rotate when the fiber is exposed to a magnetic field in the direction of light propagation. Thus, the magnetic field strength can be determined from the light polarization change. By forming closed fiber loops and applying Ampere's law, measuring the total light rotation yields the total current enclosed. The broadband, dual-detector, reflective polarimetric scheme allows measurement of both DC component and AC waveforms with about 60 dB dynamic range. Three sensor systems were built with different sensitivities from different laser wavelengths. Operating at 850nm, the first system uses twisted single-mode fiber and has a 150 A - 150 KA range. The second system operates at 1550nm, uses spun polarization maintaining fiber, and can measure 400 A - 400 KA. Both systems were validated with rocket-triggered lightning measurements and achieved excellent results when compared to a resistive shunt. The third system operates at 1310nm, uses spun polarization maintaining fiber, and can measure approximately 300 A - 300 KA. High current measurements up to 200 KA were demonstrated at a commercial lightning test facility. The system was recently installed on an aircraft and flown near icing weather conditions.

Wafer-Scale Integration of Inverted Nanopyramid Arrays for Advanced Light Trapping in Crystalline Silicon Thin Film Solar Cells.

PubMed

Zhou, Suqiong; Yang, Zhenhai; Gao, Pingqi; Li, Xiaofeng; Yang, Xi; Wang, Dan; He, Jian; Ying, Zhiqin; Ye, Jichun

2016-12-01

Crystalline silicon thin film (c-Si TF) solar cells with an active layer thickness of a few micrometers may provide a viable pathway for further sustainable development of photovoltaic technology, because of its potentials in cost reduction and high efficiency. However, the performance of such cells is largely constrained by the deteriorated light absorption of the ultrathin photoactive material. Here, we report an efficient light-trapping strategy in c-Si TFs (~20 μm in thickness) that utilizes two-dimensional (2D) arrays of inverted nanopyramid (INP) as surface texturing. Three types of INP arrays with typical periodicities of 300, 670, and 1400 nm, either on front, rear, or both surfaces of the c-Si TFs, are fabricated by scalable colloidal lithography and anisotropic wet etch technique. With the extra aid of antireflection coating, the sufficient optical absorption of 20-μm-thick c-Si with a double-sided 1400-nm INP arrays yields a photocurrent density of 39.86 mA/cm(2), which is about 76 % higher than the flat counterpart (22.63 mA/cm(2)) and is only 3 % lower than the value of Lambertian limit (41.10 mA/cm(2)). The novel surface texturing scheme with 2D INP arrays has the advantages of excellent antireflection and light-trapping capabilities, an inherent low parasitic surface area, a negligible surface damage, and a good compatibility for subsequent process steps, making it a good alternative for high-performance c-Si TF solar cells.

Red-light-controllable liquid-crystal soft actuators via low-power excited upconversion based on triplet-triplet annihilation.

PubMed

Jiang, Zhen; Xu, Ming; Li, Fuyou; Yu, Yanlei

2013-11-06

A red-light-controllable soft actuator has been achieved, driven by low-power excited triplet-triplet annihilation-based upconversion luminescence (TTA-UCL). First, a red-to-blue TTA-based upconversion system with a high absolute quantum yield of 9.3 ± 0.5% was prepared by utilizing platinum(II) tetraphenyltetrabenzoporphyrin (PtTPBP) as the sensitizer and 9,10-bis(diphenylphosphoryl)anthracene (BDPPA) as the annihilator. In order to be employed as a highly effective phototrigger of photodeformable cross-linked liquid-crystal polymers (CLCPs), the PtTPBP&BDPPA system was incorporated into a rubbery polyurethane film and then assembled with an azotolane-containing CLCP film. The generating assembly film bent toward the light source when irradiated with a 635 nm laser at low power density of 200 mW cm(-2) because the TTA-UCL was effectively utilized by the azotolane moieties in the CLCP film, inducing their trans-cis photoisomerization and an alignment change of the mesogens via an emission-reabsorption process. It is the first example of a soft actuator in which the TTA-UCL is trapped and utilized to create photomechanical effect. Such advantages of using this novel red-light-controllable soft actuator in potential biological applications have also been demonstrated as negligible thermal effect and its excellent penetration ability into tissues. This work not only provides a novel photomanipulated soft actuation material system based on the TTA-UCL technology but also introduces a new technological application of the TTA-based upconversion system in photonic devices.

Light-enhanced acid catalysis over a metal-organic framework.

PubMed

Xu, Caiyun; Sun, Keju; Zhou, Yu-Xiao; Ma, Xiao; Jiang, Hai-Long

2018-03-06

A Brønsted acid-functionalized metal-organic framework (MOF), MIL-101-SO 3 H, was prepared for acid-engaged esterification reactions. Strikingly, for the first time, the MOF exhibits significantly light-enhanced activity and possesses excellent activity and recyclability, with even higher activity than H 2 SO 4 under light irradiation.

Effect of light with different wavelengths on Nostoc flagelliforme cells in liquid culture.

PubMed

Dai, Yu-Jie; Li, Jing; Wei, Shu-Mei; Chen, Nan; Xiao, Yu-Peng; Tan, Zhi-Lei; Jia, Shi-Ru; Yuan, Nan-Nan; Tan, Ning; Song, Yi-Jie

2013-04-01

The effects of lights with different wavelengths on the growth and the yield of extracellular polysaccharides of Nostoc flagelliforme cells were investigated in a liquid cultivation. N. flagelliforme cells were cultured for 16 days in 500 ml conical flasks containing BG11 culture medium under 27 micromol·m-2·s-1 of light intensity and 25 degrees C on a rotary shaker (140 rpm). The chlorophyll a, phycocyanin, allophycocyanin, and phycoerythrin contents in N. flagelliforme cells under the lights of different wavelengths were also measured. It was found that the cell biomass and the yield of polysaccharide changed with different wavelengths of light. The biomass and the yield of extracellular polysaccharides under the red or violet light were higher than those under other light colors. Chlorophyll a, phycocyanin, and allophycocyanin are the main pigments in N. flagelliforme cells. The results showed that N. flagelliforme, like other cyanobacteria, has the ability of adjusting the contents and relative ratio of its pigments with the light quality. As a conclusion, N. flagelliforme cells favor red and violet lights and perform the complementary chromatic adaptation ability to acclimate to the changes of the light quality in the environment.

Many light Higgs bosons in the next-to-minimal supersymmetric model

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

Dermisek, Radovan; Gunion, John F.

2009-03-01

The next-to-minimal supersymmetric model with a light doubletlike CP-odd Higgs boson and small tan{beta} can satisfy all experimental limits on Higgs bosons even with light superpartners. In these scenarios, the two lightest CP-even Higgs bosons, h{sub 1} and h{sub 2}, and the charged Higgs boson, h{sup +}, can all be light enough to be produced at CERN LEP and yet have decays that have not been looked for or are poorly constrained by existing collider experiments. The channel h{sub 1}{yields}a{sub 1}a{sub 1} with a{sub 1}{yields}{tau}{sup +}{tau}{sup -} or 2j is still awaiting LEP constraints for m{sub h{sub 1}}>86 or 82more » GeV, respectively. LEP data may also contain e{sup +}e{sup -}{yields}h{sub 2}a{sub 1} events where h{sub 2}{yields}Za{sub 1} is the dominant decay, a channel that was never examined. Decays of the charged Higgs bosons are often dominated by H{sup {+-}}{yields}W{sup {+-}}{sup (}*{sup )}a{sub 1} with a{sub 1}{yields}gg, cc, and {tau}{sup +}{tau}{sup -}. This is a channel that has so far been ignored in the search for t{yields}h{sup +}b decays at the Tevatron. A specialized analysis might reveal a signal. The light a{sub 1} might be within the reach of B factories via {upsilon}{yields}{gamma}a{sub 1} decays. We study typical mass ranges and branching ratios of Higgs bosons in this scenario and compare these scenarios where the a{sub 1} has a large doublet component to the more general scenarios with arbitrary singlet component for the a{sub 1}.« less

Trends in leaf photosynthesis in historical rice varieties developed in the Philippines since 1966.

PubMed

Hubbart, S; Peng, S; Horton, P; Chen, Y; Murchie, E H

2007-01-01

Crop improvement in terms of yield is rarely linked to leaf photosynthesis. However, in certain crop plants such as rice, it is predicted that an increase in photosynthetic rate will be required to support future grain yield potential. In order to understand the relationships between yield improvement and leaf photosynthesis, controlled environment conditions were used to grow 10 varieties which were released from the International Rice Research Institute (IRRI) between 1966 and 1995 and one newly developed line. Two growth light intensities were used: high light (1500 micromol m(-2) s(-1)) and low light (300 micromol m(-2) s(-1)). Gas exchange, leaf protein, chlorophyll, and leaf morphology were measured in the ninth leaf on the main stem. A high level of variation was observed among high light-grown plants for light-saturated photosynthetic rate per unit leaf area (P(max)), stomatal conductance (g), content of ribulose bisphosphate carboxylase-oxygenase (Rubisco), and total leaf protein content. Notably, between 1966 and 1980 there was a decline in P(max), g, leaf protein, chlorophyll, and Rubisco content. Values recovered in those varieties released after 1980. This striking trend coincides with a previous published observation that grain yield in IRRI varieties released prior to 1980 correlated with harvest index whereas that for those released after 1980 correlated with biomass. P(max) showed significant correlations with both g and Rubisco content. Large differences were observed between high light- and low light-grown plants (photoacclimation). The photoacclimation 'range' for P(max) correlated with P(max) in high light-grown plants. It is concluded that (i) leaf photosynthesis may be systematically affected by breeding strategy; (ii) P(max) is a useful target for yield improvements where yield is limited by biomass production rather than partitioning; and (iii) the capacity for photoacclimation is related to high P(max) values.

Polymer dots grafted TiO2 nanohybrids as high performance visible light photocatalysts.

PubMed

Li, Gen; Wang, Feng; Liu, Peng; Chen, Zheming; Lei, Ping; Xu, Zhongshan; Li, Zengxi; Ding, Yanfen; Zhang, Shimin; Yang, Mingshu

2018-04-01

As a new member of carbon dots (CDs), Polymer dots (PDs) prepared by hydrothermal treatment of polymers, usually consist of the carbon core and the connected partially degraded polymer chains. This type of CDs might possess aqueous solubility, non-toxicity, excellent stability against photo-bleaching and high visible light activity. In this research, PDs were prepared by a moderate hydrothermal treatment of polyvinyl alcohol, and PDs grafted TiO 2 (PDs-TiO 2 ) nanohybrids with TiOC bonds were prepared by a facile in-situ hydrothermal treatment of PDs and Ti (SO 4 ) 2 . Under visible light irradiation, the PDs-TiO 2 demonstrate excellent photocatalytic activity for methyl orange degradation, and the photocatalytic rate constant of PDs-TiO 2 is 3.6 and 9.5 times higher than that of pure TiO 2 and commercial P25, respectively. In addition, the PDs-TiO 2 exhibit good recycle stability under UV-Vis light irradiation. The interfacial TiOC bonds and the π-conjugated structures in PDs-TiO 2 can act as the pathways to quickly transfer the excited electrons between PDs and TiO 2 , therefore contribute to the excellent photocatalytic activity. Copyright © 2018 Elsevier Ltd. All rights reserved.

High-efficiency organic glass scintillators

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

Feng, Patrick L.; Carlson, Joseph S.

A new family of neutron/gamma discriminating scintillators is disclosed that comprises stable organic glasses that may be melt-cast into transparent monoliths. These materials have been shown to provide light yields greater than solution-grown trans-stilbene crystals and efficient PSD capabilities when combined with 0.01 to 0.05% by weight of the total composition of a wavelength-shifting fluorophore. Photoluminescence measurements reveal fluorescence quantum yields that are 2 to 5 times greater than conventional plastic or liquid scintillator matrices, which accounts for the superior light yield of these glasses. The unique combination of high scintillation light-yields, efficient neutron/gamma PSD, and straightforward scale-up via melt-castingmore » distinguishes the developed organic glasses from existing scintillators.« less

FeF(3) catalyzed cascade C-C and C-N bond formation: synthesis of differentially substituted triheterocyclic benzothiazole functionalities under solvent-free condition.

PubMed

Atar, Amol B; Jeong, Yeon Tae

2014-05-01

A series of diverse polyfunctionalized triheterocyclic benzothiazoles were easily prepared in excellent yields via the Biginelli reaction of 2-aminobenzothiazole with substituted benzaldehydes and α-methylene ketones using FeF(3) as an expeditious catalyst under solvent-free conditions. The protocol provides a practical and straightforward approach toward highly functionalized triheterocyclic benzothiazole derivatives in excellent yields. The reaction was conveniently promoted by FeF(3) and the catalyst could be recovered easily after the reaction and reused without any loss of its catalytic activity. The advantageous features of this methodology are high atom economy, operational simplicity, shorter reaction time, convergence, and facile automation.

The conversion of biomass to light olefins on Fe-modified ZSM-5 catalyst: Effect of pyrolysis parameters.

PubMed

Zhang, Shihong; Yang, Mingfa; Shao, Jingai; Yang, Haiping; Zeng, Kuo; Chen, Yingquan; Luo, Jun; Agblevor, Foster A; Chen, Hanping

2018-07-01

Light olefins are the key building blocks for the petrochemical industry. In this study, the effects of in-situ and ex-situ process, temperature, Fe loading, catalyst to feed ratio and gas flow rate on the olefins carbon yield and selectivity were explored. The results showed that Fe-modified ZSM-5 catalyst increased the olefins yield significantly, and the ex-situ process was much better than in-situ. With the increasing of temperature, Fe-loading amount, catalyst to feed ratio, and gas flow rate, the carbon yields of light olefins were firstly increased and further decreased. The maximum carbon yield of light olefins (6.98% C-mol) was obtained at the pyrolysis temperature of 600°C, catalyst to feed ratio of 2, gas flow rate of 100ml/min, and 3wt% Fe/ZSM-5 for cellulose. The selectivity of C 2 H 4 was more than 60% for all feedstock, and the total light olefins followed the decreasing order of cellulose, corn stalk, hemicelluloses and lignin. Copyright © 2018 Elsevier B.V. All rights reserved.

High energy resolution with transparent ceramic garnet scintillators

NASA Astrophysics Data System (ADS)

Cherepy, N. J.; Seeley, Z. M.; Payne, S. A.; Beck, P. R.; Swanberg, E. L.; Hunter, S.; Ahle, L.; Fisher, S. E.; Melcher, C.; Wei, H.; Stefanik, T.; Chung, Y.-S.; Kindem, J.

2014-09-01

Breakthrough energy resolution, R(662keV) < 4%, has been achieved with an oxide scintillator, Cerium-doped Gadolinium Yttrium Gallium Aluminum Garnet, or GYGAG(Ce). Transparent ceramic GYGAG(Ce), has a peak emission wavelength of 550 nm that is better matched to Silicon photodetectors than to standard PMTs. We are therefore developing a spectrometer based on pixelated GYGAG(Ce) on a Silicon photodiode array that can provide R(662 keV) = 3.6%. In comparison, with large 1-2 in3 size GYGAG(Ce) ceramics we obtain R(662 keV) = 4.6% with PMT readout. We find that ceramic GYGAG(Ce) of a given stoichiometric chemical composition can exhibit very different scintillation properties, depending on sintering conditions and post-anneal treatments. Among the characteristics of transparent ceramic garnet scintillators that can be controlled by fabrication conditions are: scintillation decay components and their amplitudes, intensity and duration of afterglow, thermoluminescence glow curve peak positions and amplitudes, integrated light yield, light yield non-proportionality - as measured in the Scintillator Light Yield Non-Proportionality Characterization Instrument (SLYNCI), and energy resolution for gamma spectroscopy. Garnet samples exhibiting a significant fraction of Cerium dopant in the tetravalent valence also exhibit: faster overall scintillation decay, very low afterglow, high light yield, but poor light yield proportionality and degraded energy resolution.

Scintillation properties of the silver doped lithium iodide single crystals at room and low temperature

NASA Astrophysics Data System (ADS)

Khan, Sajid; Kim, H. J.; Lee, M. H.

2016-06-01

This study presents luminescence and scintillation properties of Silver doped LiI crystals. Single crystals of LiI: x% Ag (x=0.02, 0.05, 0.1 and 0.5) were grown by using the Bridgman technique. X-ray induced luminescence spectra show emission bands spanning from 275 nm to 675 nm, dominated by Ag+ band having a peak at 300 nm. Under UV-luminescence, a similar emission band was observed with the peak excitation wavelength of 265 nm. Energy resolution, light yield and decay time profiles of the samples were measured under a 137Cs γ-ray irradiation. The LiI(0.1%Ag) showed the highest light yield and the best energy resolution among the samples. The light yield of LiI(0.1%Ag) is higher than commercially available LiI(Eu) crystal (15,000±1500 ph/MeV). The LiI(Ag) samples exhibit three exponential decay time components except the LiI(0.02%Ag), where the fitting found two decay time components. Temperature dependences of emission spectra, light yield and decay time were studied from 300 K to 10 K. The LiI(0.1%Ag) crystal showed an increase in the light yield and a shortening of decay time with a decrease in temperature..

What Remains of History? Historical Epistemology and Historical Understanding in Scotland's "Curriculum for Excellence"

ERIC Educational Resources Information Center

Smith, Joseph

2016-01-01

This paper critically examines the framing of historical knowledge in the primary and "broad general education" phases (ages 4-14) of Scotland's "Curriculum for Excellence". The paper focuses on curriculum documentation, particularly the curriculum's aims and "Experiences and Outcomes" and evaluates these in light of…

UV-Enhanced Ethanol Sensing Properties of RF Magnetron-Sputtered ZnO Film.

PubMed

Huang, Jinyu; Du, Yu; Wang, Quan; Zhang, Hao; Geng, Youfu; Li, Xuejin; Tian, Xiaoqing

2017-12-26

ZnO film was deposited by the magnetron sputtering method. The thickness of ZnO film is approximately 2 μm. The influence of UV light illumination on C₂H₅OH sensing properties of ZnO film was investigated. Gas sensing results revealed that the UV-illuminated ZnO film displays excellent C₂H₅OH characteristics in terms of high sensitivity, excellent selectivity, rapid response/recovery, and low detection limit down to 0.1 ppm. The excellent sensing performance of the sensor with UV activation could be attributed to the photocatalytic oxidation of ethanol on the surface of the ZnO film, the planar film structure with high utilizing efficiency of UV light, high electron mobility, and a good surface/volume ratio of of ZnO film with a relatively rough and porous surface.

Lamoka, a variety with excellent chip color out of cold storage and resistance to the golden potato cyst nematode

USDA-ARS?s Scientific Manuscript database

Lamoka is a white-skinned, white-fleshed potato cultivar variety notable for excellent chip color from cold storage, good yield, and resistance to both common scab and race Ro1 of the golden potato cyst nematode (Globodera rostochiensis). It was selected from a cross made at Cornell University in 1...

Dispersion of borax in plastic is excellent fire-retardant heat insulator

NASA Technical Reports Server (NTRS)

Evans, H.; Hughes, J.; Schmitz, F.

1967-01-01

A mix of borax powder and a chlorinated anhydrous polyester resin yields a plastic composition that is fire-retardant, yields a minimum of toxic gases when heated, and exhibits high thermal insulating properties. This composition can be used as a coating or can be converted into laminated or cast shapes.

Comparative timber-yields

Treesearch

I. T. Haig

1932-01-01

During the last decade the U. S. Forest Service and several of the forest schools have completed rather comprehensive studies of the growth and yield of a number of commercially important native conifers. As the majority of these studies show the volumes obtainable in fully-stocked stands to very similar standards of utilization, they furnish an excellent opportunity...

Efficient synthesis of methylene exo-glycals: another use of glycosylthiomethyl chlorides.

PubMed

Zhu, Xiangming; Jin, Ying; Wickham, John

2007-03-30

A new approach to the synthesis of methylene exo-glycals is described. Oxidation of glycosylthiolmethyl chloride (GTM-Cl) with mCPBA afforded the corresponding glycosylchloromethyl sulfone in almost quantitative yield, which underwent KOtBu-induced Ramberg-Bäcklund rearrangement to furnish the desired methylene exo-glycal in excellent yield.

Factors determining yield and quality of illicit indoor cannabis (Cannabis spp.) production.

PubMed

Vanhove, Wouter; Van Damme, Patrick; Meert, Natalie

2011-10-10

Judiciary currently faces difficulties in adequately estimating the yield of illicit indoor cannabis plantations. The latter data is required in penalization which is based on the profits gained. A full factorial experiment in which two overhead light intensities, two plant densities and four varieties were combined in the indoor cultivation of cannabis (Cannabis spp.) was used to reveal cannabis drug yield and quality under each of the factor combinations. Highest yield was found for the Super Skunk and Big Bud varieties which also exhibited the highest concentrations of Δ(9)-tetrahydrocannabinol (THC). Results show that plant density and light intensity are additive factors whereas the variety factor significantly interacts with both plant density and light intensity factors. Adequate estimations of yield of illicit, indoor cannabis plantations can only be made if upon seizure all factors considered in this study are accounted for. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Historical gains in soybean (Glycine max Merr.) seed yield are driven by linear increases in light interception, energy conversion, and partitioning efficiencies

PubMed Central

Koester, Robert P.; Skoneczka, Jeffrey A.; Cary, Troy R.; Diers, Brian W.; Ainsworth, Elizabeth A.

2014-01-01

Soybean (Glycine max Merr.) is the world’s most widely grown leguminous crop and an important source of protein and oil for food and feed. Soybean yields have increased substantially throughout the past century, with yield gains widely attributed to genetic advances and improved cultivars as well as advances in farming technology and practice. Yet, the physiological mechanisms underlying the historical improvements in soybean yield have not been studied rigorously. In this 2-year experiment, 24 soybean cultivars released between 1923 and 2007 were grown in field trials. Physiological improvements in the efficiencies by which soybean canopies intercepted light (εi), converted light energy into biomass (εc), and partitioned biomass into seed (εp) were examined. Seed yield increased by 26.5kg ha–1 year–1, and the increase in seed yield was driven by improvements in all three efficiencies. Although the time to canopy closure did not change in historical soybean cultivars, extended growing seasons and decreased lodging in more modern lines drove improvements in εi. Greater biomass production per unit of absorbed light resulted in improvements in εc. Over 84 years of breeding, soybean seed biomass increased at a rate greater than total aboveground biomass, resulting in an increase in εp. A better understanding of the physiological basis for yield gains will help to identify targets for soybean improvement in the future. PMID:24790116

Ab initio prediction of fast non-equilibrium transport of nascent polarons in SrI2: a key to high-performance scintillation

NASA Astrophysics Data System (ADS)

Zhou, Fei; Sadigh, Babak; Erhart, Paul; Åberg, Daniel

2016-08-01

The excellent light yield proportionality of europium-doped strontium iodide (SrI2:Eu) has resulted in state-of-the-art γ-ray detectors with remarkably high-energy resolution, far exceeding that of most halide compounds. In this class of materials, the formation of self-trapped hole polarons is very common. However, polaron formation is usually expected to limit carrier mobilities and has been associated with poor scintillator light-yield proportionality and resolution. Here using a recently developed first-principles method, we perform an unprecedented study of polaron transport in SrI2, both for equilibrium polarons, as well as nascent polarons immediately following a self-trapping event. We propose a rationale for the unexpected high-energy resolution of SrI2. We identify nine stable hole polaron configurations, which consist of dimerised iodine pairs with polaron-binding energies of up to 0.5 eV. They are connected by a complex potential energy landscape that comprises 66 unique nearest-neighbour migration paths. Ab initio molecular dynamics simulations reveal that a large fraction of polarons is born into configurations that migrate practically barrier free at room temperature. Consequently, carriers created during γ-irradiation can quickly diffuse away reducing the chance for non-linear recombination, the primary culprit for non-proportionality and resolution reduction. We conclude that the flat, albeit complex, landscape for polaron migration in SrI2 is a key for understanding its outstanding performance. This insight provides important guidance not only for the future development of high-performance scintillators but also of other materials, for which large polaron mobilities are crucial such as batteries and solid-state ionic conductors.

Ab initio prediction of fast non-equilibrium transport of nascent polarons in SrI 2: a key to high-performance scintillation [First-principles study of hole polaron formation and migration in strontium iodide

DOE PAGES

Zhou, Fei; Sadigh, Babak; Aberg, Daniel; ...

2016-08-12

The excellent light yield proportionality of europium-doped strontium iodide (SrI 2:Eu) has resulted in state-of-the-art γ-ray detectors with remarkably high-energy resolution, far exceeding that of most halide compounds. In this class of materials, the formation of self-trapped hole polarons is very common. However, polaron formation is usually expected to limit carrier mobilities and has been associated with poor scintillator light-yield proportionality and resolution. Here using a recently developed first-principles method, we perform an unprecedented study of polaron transport in SrI 2, both for equilibrium polarons, as well as nascent polarons immediately following a self-trapping event. We propose a rationale formore » the unexpected high-energy resolution of SrI 2. We identify nine stable hole polaron configurations, which consist of dimerised iodine pairs with polaron-binding energies of up to 0.5 eV. They are connected by a complex potential energy landscape that comprises 66 unique nearest-neighbour migration paths. Ab initio molecular dynamics simulations reveal that a large fraction of polarons is born into configurations that migrate practically barrier free at room temperature. Consequently, carriers created during γ-irradiation can quickly diffuse away reducing the chance for nonlinear recombination, the primary culprit for non-proportionality and resolution reduction. We conclude that the flat, albeit complex, landscape for polaron migration in SrI 2 is a key for understanding its outstanding performance. This insight provides important guidance not only for the future development of high-performance scintillators but also of other materials, for which large polaron mobilities are crucial such as batteries and solid-state ionic conductors.« less

Optical and scintillation properties of ce-doped (Gd2Y1)Ga2.7Al2.3O12 single crystal grown by Czochralski method

NASA Astrophysics Data System (ADS)

Wang, Chao; Wu, Yuntao; Ding, Dongzhou; Li, Huanying; Chen, Xiaofeng; Shi, Jian; Ren, Guohao

2016-06-01

Multicomponent garnets, due to their excellent light yield and energy resolution, become one of the most promising scintillators used for homeland security and nuclear non-proliferation applications. This work focuses on the optimization of Ce-doped (Gd,Y)3(Ga,Al)5O12 scintillators using a combination strategy of pre-screening and scale-up. Ce-doped GdxY1-xGayAl5-yO12 (x=1, 2 and y=2, 2.2, 2.5, 2.7, 3) polycrystalline powders were prepared by high-temperature solid state reaction method. The desired garnet phase in all the samples was confirmed using X-ray diffraction measurement. By comparing the radioluminescence intensity, the highest scintillation efficiency was achieved at a component of Gd2Y1Ga2.7Al2.3O12:Ce powders. A (Gd2Y1)Ga2.7Al2.3O12 doped with 1% Ce single crystal with dimensions of Ø35×40 mm was grown by Czochralski method using a <111> oriented seed. Luminescence and scintillation properties were measured. An optical transmittance of 84% was achieved in the concerned wavelength from 500 to 800 nm. Its 5d-4f emission of Ce3+ is at 530 nm. The light yield of a Ce1%: Gd2Y1Ga2.7Al2.3O12 single crystal slab at a size of 5×5×1 mm3 can reach about 65,000±3000 Ph/MeV along with two decay components of 94 and 615 ns under 137Cs source irradiation.

Maximizing and stabilizing luminescence from halide perovskites with potassium passivation

NASA Astrophysics Data System (ADS)

Abdi-Jalebi, Mojtaba; Andaji-Garmaroudi, Zahra; Cacovich, Stefania; Stavrakas, Camille; Philippe, Bertrand; Richter, Johannes M.; Alsari, Mejd; Booker, Edward P.; Hutter, Eline M.; Pearson, Andrew J.; Lilliu, Samuele; Savenije, Tom J.; Rensmo, Håkan; Divitini, Giorgio; Ducati, Caterina; Friend, Richard H.; Stranks, Samuel D.

2018-03-01

Metal halide perovskites are of great interest for various high-performance optoelectronic applications. The ability to tune the perovskite bandgap continuously by modifying the chemical composition opens up applications for perovskites as coloured emitters, in building-integrated photovoltaics, and as components of tandem photovoltaics to increase the power conversion efficiency. Nevertheless, performance is limited by non-radiative losses, with luminescence yields in state-of-the-art perovskite solar cells still far from 100 per cent under standard solar illumination conditions. Furthermore, in mixed halide perovskite systems designed for continuous bandgap tunability (bandgaps of approximately 1.7 to 1.9 electronvolts), photoinduced ion segregation leads to bandgap instabilities. Here we demonstrate substantial mitigation of both non-radiative losses and photoinduced ion migration in perovskite films and interfaces by decorating the surfaces and grain boundaries with passivating potassium halide layers. We demonstrate external photoluminescence quantum yields of 66 per cent, which translate to internal yields that exceed 95 per cent. The high luminescence yields are achieved while maintaining high mobilities of more than 40 square centimetres per volt per second, providing the elusive combination of both high luminescence and excellent charge transport. When interfaced with electrodes in a solar cell device stack, the external luminescence yield—a quantity that must be maximized to obtain high efficiency—remains as high as 15 per cent, indicating very clean interfaces. We also demonstrate the inhibition of transient photoinduced ion-migration processes across a wide range of mixed halide perovskite bandgaps in materials that exhibit bandgap instabilities when unpassivated. We validate these results in fully operating solar cells. Our work represents an important advance in the construction of tunable metal halide perovskite films and interfaces that can approach the efficiency limits in tandem solar cells, coloured-light-emitting diodes and other optoelectronic applications.

V-378A: A modified bismaleimide for advanced composites

NASA Technical Reports Server (NTRS)

Street, S. W.

1985-01-01

Addition polyimides cure with no evolution of gaseous by-products at relatively low temperatures and may be cured at low pressures to yield composites with excellent hot-wet strength retention. These properaties have made them excellent candidates as matrix resins for advanced composites. However, commercially available bismaleimides are solids and difficult to handle in preimpregnated form. V-378A is an addition polyimide composed of a mixture of bismaleimides and other reactive ingredients formulated to provide good prepreg properties and handling, facile cure and excellent composite mechanical properties. Several curing mechanisms are utilized to provide the characteristics exhibited by V-378A. Part of the mechanism is free radial and takes place at ambient temperature and above. Other mechanisms are principally Diels-Alder in nature. V-378A prepregs are tacky at ambient temperature, but do not have long tacky outlife similar to some epoxies. V-378A yields composites which exhibit hot-wet strength retention which is superior to that provided by epoxy resin systems.

Controllable synthesis of dual emissive Ag:InP/ZnS quantum dots with high fluorescence quantum yield

NASA Astrophysics Data System (ADS)

Yang, Wu; He, Guoxing; Mei, Shiliang; Zhu, Jiatao; Zhang, Wanlu; Chen, Qiuhang; Zhang, Guilin; Guo, Ruiqian

2017-11-01

Dual emissive Cd-free quantum dots (QDs) are in great demand for various applications. However, their synthesis has been faced with challenges. Here, we demonstrate the dual emissive Ag:InP/ZnS core/shell QDs with the excellent photoluminescence quantum yield (PL QY) up to 75% and their PL dependence on the reaction temperature, reaction time, the different ZnX2 (X = I, Cl, and Br) precursors, the ratio of In/Zn and the Ag dopant concentration. The as-prepared Ag:InP/ZnS QDs exhibit dual emission with one peak position of about 492 nm owing to the intrinsic emission, and the other peak position of about 575 nm resulting from Ag-doped emission. These dual emissive QDs are integrated with the commercial GaN-based blue LEDs, and the simulation results show that the Ag:InP/ZnS QDs-based white LEDs could realize bright natural white-lights with the luminous efficacy (LE) of 94.2-98.4 lm/W, the color rendering index (CRI) of 82-83 and the color quality scale (CQS) of 82-83 at different correlated color temperatures (CCT). This unique combination of the above properties makes this new class of dual emissive QDs attractive for white LED applications.

Chemometric investigation of light-shade effects on essential oil yield and morphology of Moroccan Myrtus communis L.

PubMed

Fadil, Mouhcine; Farah, Abdellah; Ihssane, Bouchaib; Haloui, Taoufik; Lebrazi, Sara; Zghari, Badreddine; Rachiq, Saâd

2016-01-01

To investigate the effect of environmental factors such as light and shade on essential oil yield and morphological traits of Moroccan Myrtus communis, a chemometric study was conducted on 20 individuals growing under two contrasting light environments. The study of individual's parameters by principal component analysis has shown that essential oil yield, altitude, and leaves thickness were positively correlated between them and negatively correlated with plants height, leaves length and leaves width. Principal component analysis and hierarchical cluster analysis have also shown that the individuals of each sampling site were grouped separately. The one-way ANOVA test has confirmed the effect of light and shade on essential oil yield and morphological parameters by showing a statistically significant difference between them from the shaded side to the sunny one. Finally, the multiple linear model containing main, interaction and quadratic terms was chosen for the modeling of essential oil yield in terms of morphological parameters. Sun plants have a small height, small leaves length and width, but they are thicker and richer in essential oil than shade plants which have shown almost the opposite. The highlighted multiple linear model can be used to predict essential oil yield in the studied area.

Creating single-subject design graphs in Microsoft Excel 2007.

PubMed

Dixon, Mark R; Jackson, James W; Small, Stacey L; Horner-King, Mollie J; Lik, Nicholas Mui Ker; Garcia, Yors; Rosales, Rocio

2009-01-01

Over 10 years have passed since the publication of Carr and Burkholder's (1998) technical article on how to construct single-subject graphs using Microsoft Excel. Over the course of the past decade, the Excel program has undergone a series of revisions that make the Carr and Burkholder paper somewhat difficult to follow with newer versions. The present article provides task analyses for constructing various types of commonly used single-subject design graphs in Microsoft Excel 2007. The task analyses were evaluated using a between-subjects design that compared the graphing skills of 22 behavior-analytic graduate students using Excel 2007 and either the Carr and Burkholder or newly developed task analyses. Results indicate that the new task analyses yielded more accurate and faster graph construction than the Carr and Burkholder instructions.

Enhancement of light yield and stability of radio-pure tetraphenyl-butadiene based coatings for VUV light detection in cryogenic environments

NASA Astrophysics Data System (ADS)

Baudis, L.; Benato, G.; Dressler, R.; Piastra, F.; Usoltsev, I.; Walter, M.

2015-09-01

The detection of VUV scintillation light in (liquid) argon (LAr) detectors commonly includes a reflector with a fluorescent coating, converting UV photons to visible light. The light yield of these detectors depends directly on the conversion efficiency. Several coating/reflector combinations were produced using VM2000, a specular reflecting multi-layer polymer, and Tetratex®, a diffuse reflecting PTFE fabric, as reflector foils. The light yield of these coatings was optimised and has been measured in a dedicated liquid argon setup built at the University of Zurich. It employs a small, 1.3 kg LAr cell viewed by a 3-inch, low radioactivity PMT of type R11065-10 from Hamamatsu. The cryogenic stability of these coatings was additionally studied. The optimum reflector/coating combination was found to be Tetratex® dip-coated with Tetraphenyl-butadiene with a thickness of 0.9 mg/cm2, resulting in a 3.6 times higher light yield compared to uncoated VM2000. Its performance was stable in long-term measurements, performed up to 100 days in liquid argon. This coated reflector was also investigated concerning radioactive impurities and found to be suitable for current and upcoming low-background experiments. Therefore it is used for the liquid argon veto in Phase II of the GERDA neutrinoless double beta decay experiment.

Effects of blue light on pigment biosynthesis of Monascus.

PubMed

Chen, Di; Xue, Chunmao; Chen, Mianhua; Wu, Shufen; Li, Zhenjing; Wang, Changlu

2016-04-01

The influence of different illumination levels of blue light on the growth and intracellular pigment yields of Monascus strain M9 was investigated. Compared with darkness, constant exposure to blue light of 100 lux reduced the yields of six pigments, namely, rubropunctatamine (RUM), monascorubramine (MOM), rubropunctatin (RUN), monascorubrin (MON), monascin (MS), and ankaflavin (AK). However, exposure to varying levels of blue light had different effects on pigment production. Exposure to 100 lux of blue light once for 30 min/day and to 100 lux of blue light once and twice for 15 min/day could enhance RUM, MOM, MS, and AK production and reduce RUN and MON compared with non-exposure. Exposure to 100 lux twice for 30 min/day and to 200 lux once for 45 min/day decreased the RUM, MOM, MS, and AK yields and increased the RUN and MON. Meanwhile, the expression levels of pigment biosynthetic genes were analyzed by real-time quantitative PCR. Results indicated that gene MpPKS5, mppR1, mppA, mppB, mmpC, mppD, MpFasA, MpFasB, and mppF were positively correlated with the yields of RUN and MON, whereas mppE and mppR2 were associated with RUM, MOM, MS, and AK production.

Lithographic process window optimization for mask aligner proximity lithography

NASA Astrophysics Data System (ADS)

Voelkel, Reinhard; Vogler, Uwe; Bramati, Arianna; Erdmann, Andreas; Ünal, Nezih; Hofmann, Ulrich; Hennemeyer, Marc; Zoberbier, Ralph; Nguyen, David; Brugger, Juergen

2014-03-01

We introduce a complete methodology for process window optimization in proximity mask aligner lithography. The commercially available lithography simulation software LAB from GenISys GmbH was used for simulation of light propagation and 3D resist development. The methodology was tested for the practical example of lines and spaces, 5 micron half-pitch, printed in a 1 micron thick layer of AZ® 1512HS1 positive photoresist on a silicon wafer. A SUSS MicroTec MA8 mask aligner, equipped with MO Exposure Optics® was used in simulation and experiment. MO Exposure Optics® is the latest generation of illumination systems for mask aligners. MO Exposure Optics® provides telecentric illumination and excellent light uniformity over the full mask field. MO Exposure Optics® allows the lithography engineer to freely shape the angular spectrum of the illumination light (customized illumination), which is a mandatory requirement for process window optimization. Three different illumination settings have been tested for 0 to 100 micron proximity gap. The results obtained prove, that the introduced process window methodology is a major step forward to obtain more robust processes in mask aligner lithography. The most remarkable outcome of the presented study is that a smaller exposure gap does not automatically lead to better print results in proximity lithography - what the "good instinct" of a lithographer would expect. With more than 5'000 mask aligners installed in research and industry worldwide, the proposed process window methodology might have significant impact on yield improvement and cost saving in industry.

Highly Efficient Red and White Organic Light-Emitting Diodes with External Quantum Efficiency beyond 20% by Employing Pyridylimidazole-Based Metallophosphors.

PubMed

Miao, Yanqin; Tao, Peng; Wang, Kexiang; Li, Hongxin; Zhao, Bo; Gao, Long; Wang, Hua; Xu, Bingshe; Zhao, Qiang

2017-11-01

Two highly efficient red neutral iridium(III) complexes, Ir1 and Ir2, were rationally designed and synthesized by selecting two pyridylimidazole derivatives as the ancillary ligands. Both Ir1 and Ir2 show nearly the same photoluminescence emission with the maximum peak at 595 nm (shoulder band at about 638 nm) and achieve high solution quantum yields of up to 0.47 for Ir1 and 0.57 for Ir2. Employing Ir1 and Ir2 as emitters, the fabricated red organic light-emitting diodes (OLEDs) show outstanding performance with the maximum external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE) of 20.98%, 33.04 cd/A, and 33.08 lm/W for the Ir1-based device and 22.15%, 36.89 cd/A, and 35.85 lm/W for the Ir2-based device, respectively. Furthermore, using Ir2 as red emitter, a trichromatic hybrid white OLED, showing good warm white emission with low correlated color temperature of <2200 K under the voltage of 4-6 V, was fabricated successfully. The white device also realizes excellent device efficiencies with the maximum EQE, CE, and PE reaching 22.74%, 44.77 cd/A, and 46.89 lm/W, respectively. Such high electroluminescence performance for red and white OLEDs indicates that Ir1 and Ir2 as efficient red phosphors have great potential for future OLED displays and lightings applications.

Emission spectra of electron irradiated metal foils

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

Emerson, L. C.; Arakawa, E. T.; Ritchie, R. H.

1963-08-09

Thesis submitted to Univ. of Tennessee by L. C. Emerson. An experimental investigation of the visible and ultraviolet light emitted when a charged particle moves across a boundary between two media with different dielectric properties was carried out. The spectral distributions of the light from evaporated foils of copper, germanium, silver, tin, and antimony bombarded by a 1.5-microamp beam of electrons were measured as a function of electron energy between 25 and 100 kev. The analysis was carried out with a Seya-Namioka vacuum ultraviolet spectrometer, Glan-Foucault prism polarizer, and a quartz- window photomultiplier. Calibration of the optical system with amore » NBS tungsten filament lamp enabled the intensity measurements to be carried out on an absolute basis. The experimental results for light polarized parallel to the plane containing the photon and the electron were compared with the calculated intensity of transftion radiation, and in general the agreement was found to be excellent. The component of the photon intensity polarized perpendicular to this plane was compared with the calculated intensity of the optical portion of the bremsstrahlung spectrum. The predicted dependence on electron energy, photon wavelength, and foil thickness was observed although the measured yield was higher than that predicted by theory. The possibility of contributions from Cherenkov radiation and plasma radiation is also considered, but it is shown that it would be unlikely for these radiations to be observed under the experimental conditions of this study.« less

Tricolor White-Light-Emitting Carbon Dots with Multiple-Cores@Shell Structure for WLED Application.

PubMed

Zhang, Tianyi; Zhao, Feifei; Li, Li; Qi, Bin; Zhu, Dongxia; Lü, Jianhua; Lü, Changli

2018-06-13

The past few years have witnessed the rapid development of carbon dots (CDs) due to their outstanding optical properties and a wide range of applications. However, the design and control of CDs with long-wavelength multicolor emission are still huge challenges to be addressed for their practical use in different fields. Here, novel nitrogen-doped multiple-core@shell-structured AC-CDs with tricolor emissions of red, green, and blue were constructed via one-pot hydrothermal method from 5-amino-1,10-phenanthroline and citric acid as reactants and the growth process of AC-CDs was monitored with the reaction time in the synthetic system. The origin of different fluorescence emissions was explored using the unique coordination ability of the surface groups of AC-CDs. An obvious concentration dependence of fluorescent properties was observed for the as-prepared AC-CDs, and a highly fluorescent quantum yield (QY) of 67% for red emission at 630 nm can be obtained by adjusting concentration of AC-CDs. The pure white-light emission (0.33, 0.33; Commission Internationale de l'Elcairage coordinate) was carried out from single carbon dot with QY of 29% through regulation of the excitation and concentration of multiple-core@shell-structured AC-CDs. In addition, because of their excellent photoluminescent properties, the white-emitting AC-CDs as emitting phosphor can be easily used in the fabrication of white-light-emitting diode with good anti-photobleaching and temperature stability.

Green and Efficient Processing of Cinnamomum cassia Bark by Using Ionic Liquids: Extraction of Essential Oil and Construction of UV-Resistant Composite Films from Residual Biomass.

PubMed

Mehta, Mohit J; Kumar, Arvind

2017-12-14

There is significant interest in the development of a sustainable and integrated process for the extraction of essential oils and separation of biopolymers by using novel and efficient solvent systems. Herein, cassia essential oil enriched in coumarin is extracted from Cinnamomum cassia bark by using a protic ionic liquid (IL), ethylammonium nitrate (EAN), through dissolution and the creation of a biphasic system with the help of diethyl ether. The process has been perfected, in terms of higher biomass dissolution ability and essential oil yield through the addition of aprotic ILs (based on the 1-butyl-3-methylimidazolium (C 4 mim) cation and chloride or acetate anions) to EAN. After extraction of oil, cellulose-rich material and free lignin were regenerated from biomass-IL solutions by using a 1:1 mixture of acetone-water. The purity of the extracted essential oil and biopolymers were ascertained by means of FTIR spectroscopy, NMR spectroscopy, and GC-MS techniques. Because lignin contains UV-blocking chromophores, the oil-free residual lignocellulosic material has been directly utilized to construct UV-light-resistant composite materials in conjunction with the biopolymer chitosan. Composite material thus obtained was processed to form biodegradable films, which were characterized for mechanical and optical properties. The films showed excellent UV-light resistance and mechanical properties, thereby making it a material suitable for packaging and light-sensitive applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantum yield measurements of light-induced H₂ generation in a photosystem I-[FeFe]-H₂ase nanoconstruct.

PubMed

Applegate, Amanda M; Lubner, Carolyn E; Knörzer, Philipp; Happe, Thomas; Golbeck, John H

2016-01-01

The quantum yield for light-induced H2 generation was measured for a previously optimized bio-hybrid cytochrome c 6-crosslinked PSI(C13G)-1,8-octanedithiol-[FeFe]-H2ase(C97G) (PSI-H2ase) nanoconstruct. The theoretical quantum yield for the PSI-H2ase nanoconstruct is 0.50 molecules of H2 per photon absorbed, which equates to a requirement of two photons per H2 generated. Illumination of the PSI-H2ase nanoconstruct with visible light between 400 and 700 nm resulted in an average quantum yield of 0.10-0.15 molecules of H2 per photon absorbed, which equates to a requirement of 6.7-10 photons per H2 generated. A possible reason for the difference between the theoretical and experimental quantum yield is the occurrence of non-productive PSI(C13G)-1,8-octanedithiol-PSIC13G (PSI-PSI) conjugates, which would absorb light without generating H2. Assuming the thiol-Fe coupling is equally efficient at producing PSI-PSI conjugates as well as in producing PSI-H2ase nanoconstructs, the theoretical quantum yield would decrease to 0.167 molecules of H2 per photon absorbed, which equates to 6 photons per H2 generated. This value is close to the range of measured values in the current study. A strategy that purifies the PSI-H2ase nanoconstructs from the unproductive PSI-PSI conjugates or that incorporates different chemistries on the PSI and [FeFe]-H2ase enzyme sites could potentially allow the PSI-H2ase nanoconstruct to approach the expected theoretical quantum yield for light-induced H2 generation.

Potential for Excellence: Interdisciplinary Learning Outdoors as a Moral Enterprise

ERIC Educational Resources Information Center

Allison, Pete; Carr, David; Meldrum, George

2012-01-01

This article is concerned with the place and status of outdoor learning within formal schooling. In light of recent British outdoor educational trends, it considers the general educational significance of outdoor learning in the context of the recent Scottish "Curriculum for Excellence". The article begins with an overview of some key…

Ground-water geology of Karnes County, Texas

USGS Publications Warehouse

Anders, Robert B.

1963-01-01

Most of the usable ground water in Karnes County is of substandard quality; whereas water from the San Antonio River, although hard, is of excellent quality. Wells tapping the Carrizo may yield as much as 1,000 gpm in the northwestern part of the county; wells in the shallower formations may yield as much as 600 gpm in the most favorable areas, but in some places may yield only a few gallons per minute of water suitable only for stock.

Oxygen quenching in a LAB based liquid scintillator and the nitrogen bubbling model

NASA Astrophysics Data System (ADS)

Xiao, Hua-Lin; Deng, Jing-Shan; Wang, Nai-Yan

2010-05-01

The oxygen quenching effect in a Linear Alkl Benzene (LAB) based liquid scintillator (LAB as the solvent, 3 g/L 2, 5 diphe-nyloxazole (PPO) as the fluor and 15 mg/L p-bis-(o-methylstyryl)-benzene (bis-MSB) as the λ-shifter) is studied by measuring the light yield as a function of the nitrogen bubbling time. It is shown that the light yield of the fully purged liquid scintillator is increased by 11% at room temperature and the room atmospheric pressure. A simple nitrogen bubbling model is proposed to describe the relationship between the relative light yield (oxygen quenching factor) and the bubbling time.

Classic Russet: A Potato Cultivar with Excellent Fresh Market Characteristics and High Yields of U.S. No. 1 Tubers Suitable for Early Harvest or Full-Season Production.

USDA-ARS?s Scientific Manuscript database

Classic Russet is a medium maturing potato cultivar with rapid tuber bulking making it suitable for early harvest, as well as full-season production. Classic Russet is notable for its attractive tubers with medium russet skin and excellent culinary characteristics. It resulted from a 1995 cross bet...

High-Speed 3D Printing of High-Performance Thermosetting Polymers via Two-Stage Curing.

PubMed

Kuang, Xiao; Zhao, Zeang; Chen, Kaijuan; Fang, Daining; Kang, Guozheng; Qi, Hang Jerry

2018-04-01

Design and direct fabrication of high-performance thermosets and composites via 3D printing are highly desirable in engineering applications. Most 3D printed thermosetting polymers to date suffer from poor mechanical properties and low printing speed. Here, a novel ink for high-speed 3D printing of high-performance epoxy thermosets via a two-stage curing approach is presented. The ink containing photocurable resin and thermally curable epoxy resin is used for the digital light processing (DLP) 3D printing. After printing, the part is thermally cured at elevated temperature to yield an interpenetrating polymer network epoxy composite, whose mechanical properties are comparable to engineering epoxy. The printing speed is accelerated by the continuous liquid interface production assisted DLP 3D printing method, achieving a printing speed as high as 216 mm h -1 . It is also demonstrated that 3D printing structural electronics can be achieved by combining the 3D printed epoxy composites with infilled silver ink in the hollow channels. The new 3D printing method via two-stage curing combines the attributes of outstanding printing speed, high resolution, low volume shrinkage, and excellent mechanical properties, and provides a new avenue to fabricate 3D thermosetting composites with excellent mechanical properties and high efficiency toward high-performance and functional applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

π-Expanded α,β-unsaturated ketones: synthesis, optical properties, and two-photon-induced polymerization.

PubMed

Nazir, Rashid; Bourquard, Florent; Balčiūnas, Evaldas; Smoleń, Sabina; Gray, David; Tkachenko, Nikolai V; Farsari, Maria; Gryko, Daniel T

2015-02-23

A library of π-expanded α,β-unsaturated ketones was designed and synthesized. They were prepared by a combination of Wittig reaction, Sonogashira reaction, and aldol condensation. It was further demonstrated that the double aldol condensation can be performed effectively for highly polarized styrene- and diphenylacetylene-derived aldehydes. The strategic placement of two dialkylamino groups at the periphery of D-π-A-π-D molecules resulted in dyes with excellent solubility. These ketones absorb light in the region 400-550 nm. Many of them display strong solvatochromism so that the emission ranges from 530-580 nm in toluene to the near-IR region in benzonitrile. Ketones based on cyclobutanone as central moieties display very high fluorescence quantum yields in nonpolar solvents, which decrease drastically in polar media. Photophysical studies of these new functional dyes revealed that they possess an enhanced two-photon absorption cross section when compared with simpler ketone derivatives. Due to strong polarization of the resulting dyes, values of two-photon absorption cross sections on the level of 200-300 GM at 800 nm were achieved, and thanks to that as well as the presence of the keto group, these new two-photon initiators display excellent performance so that the operating region is 5-75 mW in some cases. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Catalytic conversion of biomass-derived ethanol to liquid hydrocarbon blend-stock: Effect of light gas recirculation

DOE PAGES

Li, Zhenglong; Lepore, Andrew W.; Davison, Brian H.; ...

2016-01-01

Here, we describe a light gas recirculation (LGR) method to increase the liquid hydrocarbon yield with reduced aromatic content from catalytic conversion of ethanol to hydrocarbons. The previous liquid hydrocarbon yield is ~40% from one-pass ethanol conversion over V-ZSM-5 at 350 C and atmospheric pressure where the remaining ~60% yield is light gas hydrocarbons. In comparison, the liquid hydrocarbon yield increases to 80% when a simulated light gas hydrocarbon stream is co-fed at a rate of 0.053 mol g-1 h-1 with ethanol due to the conversion of most of the light olefins. The LGR also significantly improves the quality ofmore » the liquid hydrocarbon blend-stock by reducing aromatic content and overall benzene concentration. For 0.027 mol g-1 h-1 light gas mixture co-feeding, the average aromatic content in liquid hydrocarbons is 51.5% compared with 62.5% aromatic content in ethanol only experiment. Average benzene concentration decreases from 3.75% to 1.5% which is highly desirable since EPA limits benzene concentration in gasoline to 0.62%. As a result of low benzene concentration, the blend-wall for ethanol derived liquid hydrocarbons changes from ~18% to 43%. The remaining light paraffins and olefins can be further converted to valuable BTX products (94% BTX in the liquid) over Ga-ZSM-5 at 500 C. Thus, the LGR is an effective approach to convert ethanol to liquid hydrocarbons with higher liquid yield and low aromatic content, especially low benzene concentration, which could be blended with gasoline in a much higher ratio than ethanol or ethanol derived hydrocarbon blend-stock.« less

Catalytic conversion of biomass-derived ethanol to liquid hydrocarbon blend-stock: Effect of light gas recirculation

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

Li, Zhenglong; Lepore, Andrew W.; Davison, Brian H.

Here, we describe a light gas recirculation (LGR) method to increase the liquid hydrocarbon yield with reduced aromatic content from catalytic conversion of ethanol to hydrocarbons. The previous liquid hydrocarbon yield is ~40% from one-pass ethanol conversion over V-ZSM-5 at 350 C and atmospheric pressure where the remaining ~60% yield is light gas hydrocarbons. In comparison, the liquid hydrocarbon yield increases to 80% when a simulated light gas hydrocarbon stream is co-fed at a rate of 0.053 mol g-1 h-1 with ethanol due to the conversion of most of the light olefins. The LGR also significantly improves the quality ofmore » the liquid hydrocarbon blend-stock by reducing aromatic content and overall benzene concentration. For 0.027 mol g-1 h-1 light gas mixture co-feeding, the average aromatic content in liquid hydrocarbons is 51.5% compared with 62.5% aromatic content in ethanol only experiment. Average benzene concentration decreases from 3.75% to 1.5% which is highly desirable since EPA limits benzene concentration in gasoline to 0.62%. As a result of low benzene concentration, the blend-wall for ethanol derived liquid hydrocarbons changes from ~18% to 43%. The remaining light paraffins and olefins can be further converted to valuable BTX products (94% BTX in the liquid) over Ga-ZSM-5 at 500 C. Thus, the LGR is an effective approach to convert ethanol to liquid hydrocarbons with higher liquid yield and low aromatic content, especially low benzene concentration, which could be blended with gasoline in a much higher ratio than ethanol or ethanol derived hydrocarbon blend-stock.« less

Template synthesis of Ag/AgCl microrods and their efficient visible light-driven photocatalytic performance

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

Chen, Hua; Xiao, Liang; Huang, Jianhua, E-mail: jhhuang@zstu.edu.cn

2014-09-15

Highlights: • Preparation ofAg/AgCl microrods by reaction of Ag{sub 2}WO{sub 4} microrods with NaCl solution. • Generation of metallic Ag is induced by the ambient light in the synthesis process. • Ag/AgCl shows excellent visible light-driven photodegradation of organic dyes. - Abstract: Ag/AgCl microrods, aggregated by nanoparticles with a diameter ranging from 100 nm to 2 μm, were prepared by an ion-exchange reaction at 80 °C between Ag{sub 2}WO{sub 4} template and NaCl solution. The existence of metallic Ag species was confirmed by XRD, DRS and XPS measurements. Ag/AgCl microrods showed excellent photocatalytic activity for the degradation of rhodamine Bmore » and methylene blue under visible light irradiation. The degradation rate constants of rhodamine B and methylene blue are 0.176 and 0.114 min{sup −1}, respectively. The cycling photodegradation experiments suggest that Ag/AgCl microds could be employed as stable plasmonic photocatalysts for the degradation of organic dyes under visible light irradiation.« less

Virtual chromoendoscopy improves the diagnostic yield of small bowel capsule endoscopy in obscure gastrointestinal bleeding.

PubMed

Boal Carvalho, Pedro; Magalhães, Joana; Dias de Castro, Francisca; Gonçalves, Tiago Cúrdia; Rosa, Bruno; Moreira, Maria João; Cotter, José

2016-02-01

Small bowel capsule endoscopy represents the initial investigation for obscure gastrointestinal bleeding. Flexible spectral imaging colour enhancement (FICE) is a virtual chromoendoscopy technique designed to enhance mucosal lesions, available in different settings according to light wavelength-- FICE1, 2 and 3. To compare the diagnostic yield of FICE1 and white light during capsule endoscopy in patients with obscure gastrointestinal bleeding. Retrospective single-centre study including 60 consecutive patients referred for small bowel capsule endoscopy for obscure gastrointestinal bleeding. Endoscopies were independently reviewed in FICE1 and white light; findings were then reviewed by another researcher, establishing a gold standard. Diagnostic yield was defined as the presence of lesions with high bleeding potential (P2) angioectasias, ulcers or tumours. Diagnostic yield using FICE1 was significantly higher than white light (55% vs. 42%, p=0.021). A superior number of P2 lesions was detected with FICE1 (74 vs. 44, p=0.003), particularly angioectasias (54 vs. 26, p=0.002), but not ulcers or tumours. FICE1 was significantly superior to white light, resulting in a 13% improvement in diagnostic yield, and potentially bleeding lesions particularly angioectasias were more often observed. Our results support the use of FICE1 while reviewing small bowel capsule endoscopy for obscure gastrointestinal bleeding. Copyright © 2015 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

A Simple yet Accurate Method for Students to Determine Asteroid Rotation Periods from Fragmented Light Curve Data

ERIC Educational Resources Information Center

Beare, R. A.

2008-01-01

Professional astronomers use specialized software not normally available to students to determine the rotation periods of asteroids from fragmented light curve data. This paper describes a simple yet accurate method based on Microsoft Excel[R] that enables students to find periods in asteroid light curve and other discontinuous time series data of…

Fe(OTf)3-catalysed Friedel–Crafts reaction of benzenoid arenes with α,β-unsaturated carbonyl compounds: easy access to 1,1-diarylalkanes

PubMed Central

Bhattacharya, Aditya; Shukla, Pushpendra Mani

2017-01-01

A simple and efficient method for the synthesis of 1,1-diarylalkanes via the Friedel–Crafts-type alkylation reaction of electron-rich arenes with cinnamic acid ester derivatives or chalcones is reported. Iron triflate has been found to be the best catalyst for the Friedel–Crafts-type alkylation reaction with α,β-unsaturated carbonyl compounds. This reaction afforded β,β-diaryl carbonyl compounds in good yields (65–93%) and with excellent regioselectivities. Remarkably, this method is also compatible with a variety of indoles to provide 3-indolyl-aryl carbonyl compounds in excellent yields. Great efforts have been made to deduce a plausible reaction mechanism based on isotopic labelling experiments. PMID:29134078

Gold Redox Catalysis through Base-Initiated Diazonium Decomposition toward Alkene, Alkyne, and Allene Activation.

PubMed

Dong, Boliang; Peng, Haihui; Motika, Stephen E; Shi, Xiaodong

2017-08-16

The discovery of photoassisted diazonium activation toward gold(I) oxidation greatly extended the scope of gold redox catalysis by avoiding the use of a strong oxidant. Some practical issues that limit the application of this new type of chemistry are the relative low efficiency (long reaction time and low conversion) and the strict reaction condition control that is necessary (degassing and inert reaction environment). Herein, an alternative photofree condition has been developed through Lewis base induced diazonium activation. With this method, an unreactive Au I catalyst was used in combination with Na 2 CO 3 and diazonium salts to produce a Au III intermediate. The efficient activation of various substrates, including alkyne, alkene and allene was achieved, followed by rapid Au III reductive elimination, which yielded the C-C coupling products with good to excellent yields. Relative to the previously reported photoactivation method, our approach offered greater efficiency and versatility through faster reaction rates and broader reaction scope. Challenging substrates such as electron rich/neutral allenes, which could not be activated under the photoinitiation conditions (<5 % yield), could be activated to subsequently yield the desired coupling products in good to excellent yield. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanostructured organosilicon luminophores and their application in highly efficient plastic scintillators

PubMed Central

Ponomarenko, Sergei A.; Surin, Nikolay M.; Borshchev, Oleg V.; Luponosov, Yuriy N.; Akimov, Dmitry Y.; Alexandrov, Ivan S.; Burenkov, Alexander A.; Kovalenko, Alexey G.; Stekhanov, Viktor N.; Kleymyuk, Elena A.; Gritsenko, Oleg T.; Cherkaev, Georgiy V.; Kechek'yan, Alexander S.; Serenko, Olga A.; Muzafarov, Aziz M.

2014-01-01

Organic luminophores are widely used in various optoelectronic devices, which serve for photonics, nuclear and particle physics, quantum electronics, medical diagnostics and many other fields of science and technology. Improving their spectral-luminescent characteristics for particular technical requirements of the devices is a challenging task. Here we show a new concept to universal solution of this problem by creation of nanostructured organosilicon luminophores (NOLs), which are a particular type of dendritic molecular antennas. They combine the best properties of organic luminophores and inorganic quantum dots: high absorption cross-section, excellent photoluminescence quantum yield, fast luminescence decay time and good processability. A NOL consists of two types of covalently bonded via silicon atoms organic luminophores with efficient Förster energy transfer between them. Using NOLs in plastic scintillators, widely utilized for radiation detection and in elementary particles discoveries, led to a breakthrough in their efficiency, which combines both high light output and fast decay time. Moreover, for the first time plastic scintillators, which emit light in the desired wavelength region ranging from 370 to 700 nm, have been created. We anticipate further applications of NOLs as working elements of pulsed dye lasers in photonics, optoelectronics and as fluorescent labels in biology and medical diagnostics. PMID:25293808

Measurement of radiation damage of water-based liquid scintillator and liquid scintillator

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

Bignell, L. J.; Diwan, M. V.; Hans, S.

2015-10-19

Liquid scintillating phantoms have been proposed as a means to perform real-time 3D dosimetry for proton therapy treatment plan verification. We have studied what effect radiation damage to the scintillator will have upon this application. We have performed measurements of the degradation of the light yield and optical attenuation length of liquid scintillator and water-based liquid scintillator after irradiation by 201 MeV proton beams that deposited doses of approximately 52 Gy, 300 Gy, and 800 Gy in the scintillator. Liquid scintillator and water-based liquid scintillator (composed of 5% scintillating phase) exhibit light yield reductions of 1.74 ± 0.55 % andmore » 1.31 ± 0.59 % after ≈ 800 Gy of proton dose, respectively. Some increased optical attenuation was observed in the irradiated samples, the measured reduction to the light yield is also due to damage to the scintillation light production. Based on our results and conservative estimates of the expected dose in a clinical context, a scintillating phantom used for proton therapy treatment plan verification would exhibit a systematic light yield reduction of approximately 0.1% after a year of operation.« less

Historical gains in soybean (Glycine max Merr.) seed yield are driven by linear increases in light interception, energy conversion, and partitioning efficiencies.

PubMed

Koester, Robert P; Skoneczka, Jeffrey A; Cary, Troy R; Diers, Brian W; Ainsworth, Elizabeth A

2014-07-01

Soybean (Glycine max Merr.) is the world's most widely grown leguminous crop and an important source of protein and oil for food and feed. Soybean yields have increased substantially throughout the past century, with yield gains widely attributed to genetic advances and improved cultivars as well as advances in farming technology and practice. Yet, the physiological mechanisms underlying the historical improvements in soybean yield have not been studied rigorously. In this 2-year experiment, 24 soybean cultivars released between 1923 and 2007 were grown in field trials. Physiological improvements in the efficiencies by which soybean canopies intercepted light (εi), converted light energy into biomass (εc), and partitioned biomass into seed (εp) were examined. Seed yield increased by 26.5kg ha(-1) year(-1), and the increase in seed yield was driven by improvements in all three efficiencies. Although the time to canopy closure did not change in historical soybean cultivars, extended growing seasons and decreased lodging in more modern lines drove improvements in εi. Greater biomass production per unit of absorbed light resulted in improvements in εc. Over 84 years of breeding, soybean seed biomass increased at a rate greater than total aboveground biomass, resulting in an increase in εp. A better understanding of the physiological basis for yield gains will help to identify targets for soybean improvement in the future. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Photosynthesis, light use efficiency, and yield of reduced-chlorophyll soybean mutants in field conditions

USDA-ARS?s Scientific Manuscript database

Reducing chlorophyll (chl) content may improve the conversion efficiency of absorbed radiation into biomass (ec) and therefore yield in dense monoculture crops by improving light penetration and distribution within the canopy. Modeling suggests that reducing chl content may also reduce leaf temperat...

Arrays of Ultrathin CdS Nanoflakes with High-Energy Surface for Efficient Gas Detection.

PubMed

Liu, Xiao-Hua; Yin, Peng-Fei; Kulinich, Sergei A; Zhou, Yu-Zhu; Mao, Jing; Ling, Tao; Du, Xi-Wen

2017-01-11

It is fascinating and challenging to endow conventional materials with unprecedented properties. For instance, cadmium sulfide (CdS) is an important semiconductor with excellent light response; however, its potential in gas-sensing was underestimated owing to relatively low chemical activity and poor electrical conductivity. Herein, we demonstrate that an ideal architecture, ultrathin nanoflake arrays (NFAs), can improve significantly gas-sensing properties of CdS material. The CdS NFAs are grown directly on the interdigitated electrode to expose large surface area. Their thickness is reduced below the double Debye length of CdS, permitting to achieve a full depletion of carriers. Particularly, the prepared CdS nanoflakes are enclosed with high-energy {0001} facets exposed, which provides more active sites for gas adsorption. Moreover, the NFAs exhibit the light-trapping effect, which further enhances their gas sensitivity. As a result, the as-prepared CdS NFAs demonstrate excellent gas-sensing and light-response properties, thus being capable of dual gas and light detection.

Development of X-ray scanner using 450-kVp X-ray

NASA Astrophysics Data System (ADS)

Kwak, Sung-Woo; Kim, Kwang Hyun; Kim, Insu; Cho, Gyuseong

2003-12-01

The objective of this paper is to develop an X-ray scanner that consists of a 450-kVp X-ray generator, a linear detector array, an electric circuit for data acquisition, and image processing software. This work is composed of three main parts. First, Monte Carlo simulations and experiments have been performed to determine the scintillator geometry and its surface condition so that the light output from it can be maximized. According to the simulations and experiments, the CdWO/sub 4/ (CWO) of 1.7 mm/spl times/3.0 mm/spl times/10 mm with ground surface, which is treated with grinding material of 28-/spl mu/m grain size, gives the best light yield. Secondly, a PIN photodiode for this system is fabricated and its characteristic parameters are measured to compare with those of two commercial products, one from Detection Technology and the other from Hamamatsu. From experimental results, at zero bias where the system is operated, all three diodes have nearly identical leakage currents of a few pA, and junction capacitances of this study and DT are about 40 pF/mm/sup 2/ and that of Hamamatsu about 9 pF/mm/sup 2/. At 490 nm, the peak wavelength of the CWO light, the spectral responses of this work, DT, and Hamamatsu are 0.4, 0.3, and 0.2, respectively. It appears that the photodiode of this work gives excellent light sensitivity in the range of 400 to 900 nm. Thirdly, the spatial resolution of the system including our developed data acquisition system (DAS) shows 0.29 lp/mm at MTF of 10%, and this system satisfies the resolution of 4.75-mm objects that the U.S. Customs Service has suggested for cargo container inspection systems.

Seed-to-seed growth of superdwarf wheat and arabidopsis using red light-emitting diodes (LED's): A report on baseline tests conducted for NASA's proposed Plant Research Unit (PRU)

NASA Technical Reports Server (NTRS)

Goins, G. D.; Yorio, N. C.; Sanwo, M. M.; Brown, C. S.

1996-01-01

To determine the influence of narrow-spectrum red light-emitting diodes (LED's) on plant growth and seed production, wheat (Triticum aestivum L.cv Superdwarf) and Arabidopsis (Arabidopsis thaliana (L.) Heynh, race Columbia) plants were grown under red LED's (peak emission 660 nm) and compared to plants grown under daylight fluorescent (white) light and red LED's supplemented with either 1 percent or 10 percent blue fluorescent (BF) light. Wheat growth under red LED's alone appeared normal, whereas Arabidopsis under red LED's alone developed curled leaf margins and a spiraling growth pattern. Both wheat and Arabidopsis under red LED's alone or red LED's + 1 percent BF light had significantly lower seed yield than plants grown under white light. However, the addition of 10 percent BF light to red LED's partially alleviated the adverse effect of red LED's on yield. Irrespective of the light treatment, viable seeds were produced by wheat(75-92 percent germination rate) and Arabidopsis (85-100 percent germination rate). These results indicate that wheat, and to a lesser extent Arabidopsis, can be successfully grown under red LED's alone, but supplemental blue light is required with red LED's to sufficiently match the growth characteristics and seed yield associated with plants grown under white light.

Scientific Research in the Kingdom of Saudi Arabia: Potential for Excellence and Indicators of Underdevelopment

ERIC Educational Resources Information Center

Alshayea, Ali

2013-01-01

This study analyzes the status of scientific research and development efforts in the Kingdom of Saudi Arabia, and then sheds lights on the potential for excellence in this area in terms of organization and structure, financing and partnership, and human resources. Accordingly, the study reviews both achievements and indicators of underdevelopment…

The Urgent Need for New Approaches in School Evaluation to Enable Scotland's Curriculum for Excellence

ERIC Educational Resources Information Center

MacKinnon, Niall

2011-01-01

This paper presents observations on the nature of school audit methods in light of the implementation of Scotland's incoming Curriculum for Excellence and the major normative, technological, and cultural changes affecting schools. It points to a mismatch between the concepts and structures of the incoming curriculum and that of the universalistic…

Chemoenzymatic one-pot synthesis in an aqueous medium: combination of metal-catalysed allylic alcohol isomerisation-asymmetric bioamination.

PubMed

Ríos-Lombardía, Nicolás; Vidal, Cristian; Cocina, María; Morís, Francisco; García-Álvarez, Joaquín; González-Sabín, Javier

2015-07-11

The ruthenium-catalysed isomerisation of allylic alcohols was coupled, for the first time, with asymmetric bioamination in a one-pot process in an aqueous medium. In the cases involving prochiral ketones, the ω-TA exhibited excellent enantioselectivity, identical to that observed in the single step. As a result, amines were obtained from allylic alcohols with high overall yields and excellent enantiomeric excesses.

Mechanism of rapid suppression of cell expansion in cucumber hypocotyls after blue-light irradiation

NASA Technical Reports Server (NTRS)

Cosgrove, D. J.

1988-01-01

Rapid suppression of hypocotyl elongation by blue light in cucumber (Cucumis sativus L.) was studied to examine possible hydraulic and wall changes responsible for diminished growth. Cell-sap osmotic pressure, measured by vapor-pressure osmometry, was not decreased by blue light; turgor pressure, measured by the pressure-probe technique, remained constant during the growth inhibition; and stem hydraulic conductance, measured by dynamic and static methods, was likewise unaffected by blue light. Wall yielding properties were assessed by the pressure-block technique for in-vivo stress relaxation. Blue light reduced the initial rate of relaxation by 77%, but had little effect on the final amount of relaxation. The results demonstrate that blue irradiation acts to decrease the wall yielding coefficient, but not the yield threshold. Stress-strain (Instron) analysis showed that irradiation of the seedlings had little effect on the mechanical extensibilities of the isolated wall. The results indicate that blue light can reduce cell-wall loosening without affecting bulk viscoelastic properties, and indicate a chemorheological mechanism of cell-wall expansion.

LED power efficiency of biomass, fatty acid, and carotenoid production in Nannochloropsis microalgae.

PubMed

Ma, Ruijuan; Thomas-Hall, Skye R; Chua, Elvis T; Eltanahy, Eladl; Netzel, Michael E; Netzel, Gabriele; Lu, Yinghua; Schenk, Peer M

2018-03-01

The microalga Nannochloropsis produces high-value omega-3-rich fatty acids and carotenoids. In this study the effects of light intensity and wavelength on biomass, fatty acid, and carotenoid production with respect to light output efficiency were investigated. Similar biomass and fatty acid yields were obtained at high light intensity (150 μmol m -2  s -1 ) LEDs on day 7 and low light intensity (50 μmol m -2  s -1 ) LEDs on day 11 during cultivation, but the power efficiencies of biomass and fatty acid (specifically eicosapentaenoic acid) production were higher for low light intensity. Interestingly, low light intensity enhanced both, carotenoid power efficiency of carotenoid biosynthesis and yield. White LEDs were neither advantageous for biomass and fatty acid yields, nor the power efficiency of biomass, fatty acid, and carotenoid production. Noticeably, red LED resulted in the highest biomass and fatty acid power efficiency, suggesting that LEDs can be fine-tuned to grow Nannochloropsis algae more energy-efficiently. Copyright © 2017 Elsevier Ltd. All rights reserved.

ZnO-based microrockets with light-enhanced propulsion.

PubMed

Dong, Renfeng; Wang, Chun; Wang, Qinglong; Pei, Allen; She, Xueling; Zhang, Yuxian; Cai, Yuepeng

2017-10-12

Improving the propulsion of artificial micro-nanomotors represents an exciting nanotechnology challenge, especially considering their cargo delivery ability and fuel efficiency. In light of the excellent photocatalytic performance of zinc oxide (ZnO) and chemical catalytic properties of platinum (Pt), ZnO-Pt microrockets with light-enhanced propulsion have been developed by atomic layer deposition (ALD) technology. The velocity of such microrockets is dramatically doubled upon irradiation by 77 mW cm -2 ultraviolet (UV) light in 10% H 2 O 2 and is almost 3 times higher than the classic poly(3,4-ethylenedioxythiophene)-Pt microrockets (PEDOT-Pt microrockets) even in 6% H 2 O 2 under the same UV light. In addition, such micromotors not only retain the standard approach to improve propulsion by varying the fuel concentration, but also demonstrate a simple way to enhance the movement velocity by adjusting the UV light intensity. High reversibility and controllable "weak/strong" propulsion can be easily achieved by switching the UV irradiation on or off. Finally, light-enhanced propulsion has been investigated by electrochemical measurements which further confirm the enhanced photocatalytic properties of ZnO and Pt. The successful demonstration of ZnO-based microrockets with excellent light-enhanced propulsion is significant for developing highly efficient synthetic micro-nanomotors which have strong delivery ability and economic fuel requirements for future practical applications in the micro-nanoscale world.

Supplemental Upward Lighting from Underneath to Obtain Higher Marketable Lettuce (Lactuca sativa) Leaf Fresh Weight by Retarding Senescence of Outer Leaves.

PubMed

Zhang, Geng; Shen, Shanqi; Takagaki, Michiko; Kozai, Toyoki; Yamori, Wataru

2015-01-01

Recently, the so-called "plant factory with artificial lighting" (PFAL) approach has been developed to provide safe and steady food production. Although PFALs can produce high-yielding and high-quality plants, the high plant density in these systems accelerates leaf senescence in the bottom (or outer) leaves owing to shading by the upper (or inner) leaves and by neighboring plants. This decreases yield and increases labor costs for trimming. Thus, the establishment of cultivation methods to retard senescence of outer leaves is an important research goal to improve PFAL yield and profitability. In the present study, we developed an LED lighting apparatus that would optimize light conditions for PFAL cultivation of a leafy vegetable. Lettuce (Lactuca sativa L.) was hydroponically grown under white, red, or blue LEDs, with light provided from above (downward), with or without supplemental upward lighting from underneath the plant. White LEDs proved more appropriate for lettuce growth than red or blue LEDs, and the supplemental lighting retarded the senescence of outer leaves and decreased waste (i.e., dead or low-quality senescent leaves), leading to an improvement of the marketable leaf fresh weight.

Luminescence of water or ice as a new detection method for magnetic monopoles

NASA Astrophysics Data System (ADS)

Pollmann, Anna Obertacke

2017-12-01

Cosmic ray detectors use air as a radiator for luminescence. In water and ice, Cherenkov light is the dominant light producing mechanism when the particle's velocity exceeds the Cherenkov threshold, approximately three quarters of the speed of light in vacuum. Luminescence is produced by highly ionizing particles passing through matter due to the electronic excitation of the surrounding molecules. The observables of luminescence, such as the wavelength spectrum and decay times, are highly dependent on the properties of the medium, in particular, temperature and purity. The results for the light yield of luminescence of previous measurements vary by two orders of magnitude. It will be shown that even for the lowest measured light yield, luminescence is an important signature of highly ionizing particles below the Cherenkov threshold. These could be magnetic monopoles or other massive and highly ionizing exotic particles. With the highest observed efficiencies, luminescence may even contribute significantly to the light output of standard model particles such as the PeV IceCube neutrinos. We present analysis techniques to use luminescence in neutrino telescopes and discuss experimental setups to measure the light yield of luminescence for the particular conditions in neutrino detectors.

Chemoselective Deprotection of Triethylsilyl Ethers

PubMed Central

Chandra, Tilak; Broderick, William E.; Broderick, Joan B.

2009-01-01

An efficient and selective method was developed for the deprotection of triethylsilyl (TES) ethers using formic acid in methanol (5–10%) or in methylene chloride 2–5%) with excellent yields. TES ethers are selectively deprotected to the corresponding alcohols in high yields using formic acid in methanol under mild reaction conditions. Other hydroxyl protecting groups like t-butyldimethylsilyl (TBDMS) remain unaffected. PMID:20183570

Mountain Gem Russet: A medium to late season potato variety with high early and full season yield potential and excellent fresh market characteristics

USDA-ARS?s Scientific Manuscript database

Mountain Gem Russet is a medium to late maturing variety with both high early and full season yields of oblong-long, medium-russeted tubers having higher protein content than those of standard potato varieties. Mountain Gem Russet has greater resistance to tuber late blight, tuber malformations and ...

The light-yield response of a NE-213 liquid-scintillator detector measured using 2-6 MeV tagged neutrons

NASA Astrophysics Data System (ADS)

Scherzinger, J.; Al Jebali, R.; Annand, J. R. M.; Fissum, K. G.; Hall-Wilton, R.; Kanaki, K.; Lundin, M.; Nilsson, B.; Perrey, H.; Rosborg, A.; Svensson, H.

2016-12-01

The response of a NE-213 liquid-scintillator detector has been measured using tagged neutrons from 2 to 6 MeV originating from an Am/Be neutron source. The neutron energies were determined using the time-of-flight technique. Pulse-shape discrimination was employed to discern between gamma-rays and neutrons. The behavior of both the fast (35 ns) and the combined fast and slow (475 ns) components of the neutron scintillation-light pulses were studied. Three different prescriptions were used to relate the neutron maximum energy-transfer edges to the corresponding recoil-proton scintillation-light yields, and the results were compared to simulations. The overall normalizations of parametrizations which predict the fast or total light yield of the scintillation pulses were also tested. Our results agree with both existing data and existing parametrizations. We observe a clear sensitivity to the portion and length of the neutron scintillation-light pulse considered.

Acoustic vibrations of metal nano-objects: Time-domain investigations

NASA Astrophysics Data System (ADS)

Crut, Aurélien; Maioli, Paolo; Del Fatti, Natalia; Vallée, Fabrice

2015-01-01

Theoretical and time-domain experimental investigations of the vibrational acoustic response of nano-objects are described focusing on metallic ones. Acoustic vibrations are modeled using a macroscopic-like approach based on continuum mechanics with the proper boundary conditions, a model which yields results in excellent agreement with the experimental ones and those of atomistic calculations, down to the nanometric scale. Vibrational mode excitation and detection mechanisms and the associated mode selection in ultrafast pump-probe spectroscopy are discussed, and the measured time-dependent signals in single and ensemble of nanoparticles modeled. The launched modes, their period and their damping rate are compared to experimental results obtained on ensembles of nano-objects with different composition, morphology and environment, and with size ranging from one to hundreds of nanometers. Recent extension of time-domain spectroscopy to individual nano-objects has shed new light on the vibrational responses of isolated nanoparticles, in particular on their damping, but also raises questions on the origin of its large particle to particle dispersion.

Interface engineering of Cu(In,Ga)Se2 and atomic layer deposited Zn(O,S) heterojunctions

NASA Astrophysics Data System (ADS)

Schmidt, Sebastian S.; Merdes, Saoussen; Steigert, Alexander; Klenk, Reiner; Kaufmann, Christian A.; Simsek Sanli, Ekin; van Aken, Peter A.; Oertel, Mike; Schneikart, Anja; Dimmler, Bernhard; Schlatmann, Rutger

2017-08-01

Atomic layer deposition of Zn(O,S) is an attractive dry and Cd-free process for the preparation of buffer layers for chalcopyrite solar modules. As we previously reported, excellent cell and module efficiencies were achieved using absorbers from industrial pilot production. These absorbers were grown using a selenization/sulfurization process. In this contribution we report on the interface engineering required to adapt the process to sulfur-free multi source evaporated absorbers. Different approaches to a local sulfur enrichment at the heterojunction have been studied by using surface analysis (XPS) and scanning transmission electron microscopy. We correlate the microstructure and element distribution at the interface with device properties obtained by electronic characterization. The optimized completely dry process yields cell efficiencies >16% and 30 × 30 cm2 minimodule efficiencies of up to 13.9% on industrial substrates. Any degradation observed in the dry heat stress test is fully reversible after light soaking.

Scintillation characterization of the pure Tl2LiGdBr6 single crystal

NASA Astrophysics Data System (ADS)

Jang, Jonghun; Rooh, Gul; Kim, Sunghwan; Kim, HongJoo

2018-05-01

A pure Tl2LiGdBr6 (TLGB) single crystal was developed. This scintillator was grown by the two-zone vertical Bridgman technique. Owing to the improvement in the crystal quality of TLGB, excellent scintillation properties were observed. The characterization of this scintillation material was carried out under X- and γ-ray excitations. In the X-ray excitation emission spectrum, the Tl+ ion emission band was observed between 390 and 550 nm and peaked at 435 nm. Under 662 keV γ-ray excitation, the energy resolution and light yield of the grown sample were measured to be 7.2% (FWHM) and 27,000 ± 2,700 ph/MeV, respectively. In addition, under the same γ-ray excitation, scintillation decay time was also measured at room temperature. Three decay time components were found to be 56 ns (24%), 105 ns (53%), and 1.5 µs (23%). Further improvements in scintillation properties are expected with the good quality crystal of this compound.

Enhancement of Rydberg-mediated single-photon nonlinearities by electrically tuned Förster resonances

PubMed Central

Gorniaczyk, H.; Tresp, C.; Bienias, P.; Paris-Mandoki, A.; Li, W.; Mirgorodskiy, I.; Büchler, H. P.; Lesanovsky, I.; Hofferberth, S.

2016-01-01

Mapping the strong interaction between Rydberg atoms onto single photons via electromagnetically induced transparency enables manipulation of light at the single-photon level and few-photon devices such as all-optical switches and transistors operated by individual photons. Here we demonstrate experimentally that Stark-tuned Förster resonances can substantially increase this effective interaction between individual photons. This technique boosts the gain of a single-photon transistor to over 100, enhances the non-destructive detection of single Rydberg atoms to a fidelity beyond 0.8, and enables high-precision spectroscopy on Rydberg pair states. On top, we achieve a gain larger than 2 with gate photon read-out after the transistor operation. Theory models for Rydberg polariton propagation on Förster resonance and for the projection of the stored spin-wave yield excellent agreement to our data and successfully identify the main decoherence mechanism of the Rydberg transistor, paving the way towards photonic quantum gates. PMID:27515278

Status Report on the CEBAF IR and UV FELs

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

Leemann, Christoph; Bisognano, Joseph; Douglas, David

1993-07-01

The CEBAF five pass recirculating, superconducting linac, being developed as a high power electron source for nuclear physics, is also an ideal FEL driver.The 45 MeV front end linac is presently operational with a CW (low peak current) nuclear physics gun and has met all CEBAF performance specifications including low emittance and energy spread (< 1 * 10^-4). Progress will be reported in commissioning.This experience leads to predictions of excellent FEL performance.Initial designs reported last year have been advanced.Using the output of a high charge DC photoemission gun under development with a 6 cm period wiggler produces kilowatt output powersmore » in the 3.6 to 17 micrometer range in the fundamental.Third harmonic operation extends IR performance down to 1.2 micrometer.Beam at energies up to 400 MeV from the first full CEBAF linac will interact in a similar but longer wiggler to yield kilowatt UV light production at wavelengths as short as 0.15 micrometers.Full power FEL« less

Transition-Metal Chalcogenide/Graphene Ensembles for Light-Induced Energy Applications.

PubMed

Kagkoura, Antonia; Skaltsas, Theodosis; Tagmatarchis, Nikos

2017-09-21

Recently, nanomaterials that harvest solar energy and convert it to other forms of energy are of great interest. In this context, transition metal chalcogenides (TMCs) have recently been in the spotlight due to their optoelectronic properties that render them potential candidates mainly in energy conversion applications. Integration of TMCs onto a strong electron-accepting material, such as graphene, yielding novel TMC/graphene ensembles is of high significance, since photoinduced charge-transfer phenomena, leading to intra-ensemble charge separation, may occur. In this review, we highlight the utility of TMC/graphene ensembles, with a specific focus on latest trends in applications, while their synthetic routes are also discussed. In fact, TMC/graphene ensembles are photocatalytically active and superior as compared to intact TMCs analogues, when examined toward photocatalytic H 2 evolution, dye degradation and redox transformations of organic compounds. Moreover, TMC/graphene ensembles have shown excellent prospect when employed in photovoltaics and biosensing applications. Finally, the future prospects of such materials are outlined. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Boron-doped diamond semiconductor electrodes: Efficient photoelectrochemical CO2 reduction through surface modification

NASA Astrophysics Data System (ADS)

Roy, Nitish; Hirano, Yuiri; Kuriyama, Haruo; Sudhagar, Pitchaimuthu; Suzuki, Norihiro; Katsumata, Ken-Ichi; Nakata, Kazuya; Kondo, Takeshi; Yuasa, Makoto; Serizawa, Izumi; Takayama, Tomoaki; Kudo, Akihiko; Fujishima, Akira; Terashima, Chiaki

2016-11-01

Competitive hydrogen evolution and multiple proton-coupled electron transfer reactions limit photoelectrochemical CO2 reduction in aqueous electrolyte. Here, oxygen-terminated lightly boron-doped diamond (BDDL) thin films were synthesized as a semiconductor electron source to accelerate CO2 reduction. However, BDDL alone could not stabilize the intermediates of CO2 reduction, yielding a negligible amount of reduction products. Silver nanoparticles were then deposited on BDDL because of their selective electrochemical CO2 reduction ability. Excellent selectivity (estimated CO:H2 mass ratio of 318:1) and recyclability (stable for five cycles of 3 h each) for photoelectrochemical CO2 reduction were obtained for the optimum silver nanoparticle-modified BDDL electrode at -1.1 V vs. RHE under 222-nm irradiation. The high efficiency and stability of this catalyst are ascribed to the in situ photoactivation of the BDDL surface during the photoelectrochemical reaction. The present work reveals the potential of BDDL as a high-energy electron source for use with co-catalysts in photochemical conversion.

Room temperature decarboxylative cyanation of carboxylic acids using photoredox catalysis and cyanobenziodoxolones: a divergent mechanism compared to alkynylation† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc04907a Click here for additional data file.

PubMed Central

Le Vaillant, Franck; Wodrich, Matthew D.

2017-01-01

The one-step conversion of aliphatic carboxylic acids to the corresponding nitriles has been accomplished via the merger of visible light mediated photoredox and cyanobenziodoxolones (CBX) reagents. The reaction proceeded in high yields with natural and non-natural α-amino and α-oxy acids, affording a broad scope of nitriles with excellent tolerance of the substituents in the α position. The direct cyanation of dipeptides and drug precursors was also achieved. The mechanism of the decarboxylative cyanation was investigated both computationally and experimentally and compared with the previously developed alkynylation reaction. Alkynylation was found to favor direct radical addition, whereas further oxidation by CBX to a carbocation and cyanide addition appeared more favorable for cyanation. A concerted mechanism is proposed for the reaction of radicals with EBX reagents, in contrast to the usually assumed addition elimination process. PMID:28451301

500  Gb/s free-space optical transmission over strong atmospheric turbulence channels.

PubMed

Qu, Zhen; Djordjevic, Ivan B

2016-07-15

We experimentally demonstrate a high-spectral-efficiency, large-capacity, featured free-space-optical (FSO) transmission system by using low-density, parity-check (LDPC) coded quadrature phase shift keying (QPSK) combined with orbital angular momentum (OAM) multiplexing. The strong atmospheric turbulence channel is emulated by two spatial light modulators on which four randomly generated azimuthal phase patterns yielding the Andrews spectrum are recorded. The validity of such an approach is verified by reproducing the intensity distribution and irradiance correlation function (ICF) from the full-scale simulator. Excellent agreement of experimental, numerical, and analytical results is found. To reduce the phase distortion induced by the turbulence emulator, the inexpensive wavefront sensorless adaptive optics (AO) is used. To deal with remaining channel impairments, a large-girth LDPC code is used. To further improve the aggregate data rate, the OAM multiplexing is combined with WDM, and 500 Gb/s optical transmission over the strong atmospheric turbulence channels is demonstrated.

Preparation of Gd Loaded Liquid Scintillator for Daya Bay Neutrino Experiment

NASA Astrophysics Data System (ADS)

Ya-yun, Ding; Zhi-yong, Zhang

2010-05-01

Gadolinium loaded liquid scintillator (Gd-LS) is an excellent target material for reactor antineutrino experiments. Ideal Gd-LS should have long attenuation length, high light yield, long term stability, low toxicity, and should be compatible with the material used to build the detector. We have developed a new Gd-LS recipe in which carboxylic acid 3,5,5-trimethylhexanoic acid is used as the complexing ligand to gadolinium, 2,5-diphenyloxazole (PPO) and 1,4-bis[2-methylstyryl]benzene (bis-MSB) are used as primary fluor and wavelength shifter, respectively. The scintillator base is linear alkyl benzene (LAB). Eight hundred liters of Gd-LS has been synthesized and tested in a prototype detector. Results show that the Gd-LS has high quality and is suitable for underground experiments in large quantity. Large scale production facility has been built. A full batch production of 4 t Gd-LS has been produced and monitored for several months. The production of 180 t Gd-LS will be carried out in the near future.

Energy Transfer Highway in Nd3+-Sensitized Nanoparticles for Efficient near-Infrared Bioimaging.

PubMed

Cao, Cong; Xue, Meng; Zhu, Xingjun; Yang, Pengyuan; Feng, Wei; Li, Fuyou

2017-06-07

Despite the large absorption cross-section of Nd 3+ dopant as a sensitizer in lanthanide doped luminescence system, the strong cross-relaxation effect of it impedes the promotion of doping concentration and thus reduces the utilization of excitation light. In this work, we introduce a highly efficient acceptor, Yb 3+ ion, which can quickly receive energy from Nd 3+ ions, to construct an energy transfer highway for the enhancement of near-infrared emission. By using the energy transfer highway, the doping amount of Nd 3+ ions in our NaYF 4 :Yb,Nd@CaF 2 core/shell nanoparticles (CSNPs) can be markedly elevated to 60%. The quantum yield of CSNPs was determined to be 20.7%, which provides strong near-infrared luminescence for further bioimaging application. Remarkably, deep tissue penetration depth (∼10 mm) in in vitro imaging and high spatial resolution of blood vessel (∼0.19 mm) in in vivo imaging were detected clearly with weak autofluorescence, demonstrating that probes can be used as excellent NIR biosensors.

Prediction of apparent extinction for optical transmission through rain

NASA Astrophysics Data System (ADS)

Vasseur, H.; Gibbins, C. J.

1996-12-01

At optical wavelengths, geometrical optics holds that the extinction efficiency of raindrops is equal to two. This approximation yields a wavelength-independent extinction coefficient that, however, can hardly be used to predict accurately rain extinction measured in optical transmissions. Actually, in addition to the extinct direct incoming light, a significant part of the power scattered by the rain particles reaches the receiver. This leads to a reduced apparent extinction that depends on both rain characteristics and link parameters. A simple method is proposed to evaluate this apparent extinction. It accounts for the additional scattered power that enters the receiver when one considers the forward-scattering pattern of the raindrops as well as the multiple-scattering effects using, respectively, the Fraunhofer diffraction and Twersky theory. It results in a direct analytical formula that enables a quick and accurate estimation of the rain apparent extinction and highlights the influence of the link parameters. Predictions of apparent extinction through rain are found in excellent agreement with measurements in the visible and IR regions.

Transparent ceramic garnet scintillator optimization via composition and co-doping for high-energy resolution gamma spectrometers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Cherepy, Nerine J.; Payne, Stephen A.; Seeley, Zachary M.; Beck, Patrick R.; Swanberg, Erik L.; Hunter, Steven L.

2016-09-01

Breakthrough energy resolution, R(662keV) <4%, has been achieved with an oxide scintillator, Cerium-doped Gadolinium Yttrium Gallium Aluminum Garnet, or GYGAG(Ce), by optimizing fabrication conditions. Here we describe the dependence of scintillation light yield and energy resolution on several variables: (1) Stoichiometry, in particular Gd/Y and Ga/Al ratios which modify the bandgap energy, (2) Processing methods, including vacuum vs. oxygen sintering, and (3) Trace co-dopants that influence the formation of Ce4+ and modify the intra-bandgap trap distribution. To learn about how chemical composition influences the scintillation properties of transparent ceramic garnet scintillators, we have measured: scintillation decay component amplitudes; intensity and duration of afterglow; thermoluminescence glow curve peak positions and amplitudes; integrated light yield; light yield non-proportionality, as measured in the Scintillator Light Yield Non-Proportionality Characterization Instrument (SLYNCI); and energy resolution for gamma spectroscopy. Optimized GYGAG(Ce) provides R(662 keV) =3.0%, for 0.05 cm3 size ceramics with Silicon photodiode readout, and R(662 keV) =4.6%, at 2 in3 size with PMT readout.

Photosystem II Photochemistry and Phycobiliprotein of the Red Algae Kappaphycus alvarezii and Their Implications for Light Adaptation

PubMed Central

Wang, Jinfeng; Zhu, Jianyi; Yao, Chunyan; Liu, Jianguo; Qin, Song; Jiang, Peng

2013-01-01

Photosystem II photochemistry and phycobiliprotein (PBP) genes of red algae Kappaphycus alvarezii, raw material of κ-carrageenan used in food and pharmaceutical industries, were analyzed in this study. Minimum saturating irradiance (I k) of this algal species was less than 115 μmol m−2 s−1. Its actual PSII efficiency (yield II) increased when light intensity enhanced and decreased when light intensity reached 200 μmol m−2 s−1. Under dim light, yield II declined at first and then increased on the fourth day. Under high light, yield II retained a stable value. These results indicate that K. alvarezii is a low-light-adapted species but possesses regulative mechanisms in response to both excessive and deficient light. Based on the PBP gene sequences, K. alvarezii, together with other red algae, assembled faster and showed a closer relationship with LL-Prochlorococcus compared to HL-Prochlorococcus. Many amino acid loci in PBP sequences of K. alvarezii were conserved with those of LL-Prochlorococcus. However, loci conserved with HL-Prochlorococcus but divergent with LL-Prochlorococcus were also found. The diversities of PE and PC are proposed to have played some roles during the algal evolution and divergence of light adaption. PMID:24380080

Photosystem II photochemistry and phycobiliprotein of the red algae Kappaphycus alvarezii and their implications for light adaptation.

PubMed

Guan, Xiangyu; Wang, Jinfeng; Zhu, Jianyi; Yao, Chunyan; Liu, Jianguo; Qin, Song; Jiang, Peng

2013-01-01

Photosystem II photochemistry and phycobiliprotein (PBP) genes of red algae Kappaphycus alvarezii, raw material of κ -carrageenan used in food and pharmaceutical industries, were analyzed in this study. Minimum saturating irradiance (I k) of this algal species was less than 115 μmol m(-2) s(-1). Its actual PSII efficiency (yield II) increased when light intensity enhanced and decreased when light intensity reached 200 μmol m(-2) s(-1). Under dim light, yield II declined at first and then increased on the fourth day. Under high light, yield II retained a stable value. These results indicate that K. alvarezii is a low-light-adapted species but possesses regulative mechanisms in response to both excessive and deficient light. Based on the PBP gene sequences, K. alvarezii, together with other red algae, assembled faster and showed a closer relationship with LL-Prochlorococcus compared to HL-Prochlorococcus. Many amino acid loci in PBP sequences of K. alvarezii were conserved with those of LL-Prochlorococcus. However, loci conserved with HL-Prochlorococcus but divergent with LL-Prochlorococcus were also found. The diversities of PE and PC are proposed to have played some roles during the algal evolution and divergence of light adaption.

Amphibious fluorescent carbon dots: one-step green synthesis and application for light-emitting polymer nanocomposites.

PubMed

Zhou, Li; He, Benzhao; Huang, Jiachang

2013-09-21

A facile and green approach for the synthesis of amphibious fluorescent carbon dots (CDs) from natural polysaccharide is reported. Light-emitting polymer nanocomposites with excellent optical performance can be easily prepared by incorporation of the amphibious CDs into the polymer matrix.

High Brightness OLED Lighting

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

Spindler, Jeffrey; Kondakova, Marina; Boroson, Michael

2016-05-25

In this work we describe the technology developments behind our current and future generations of high brightness OLED lighting panels. We have developed white and amber OLEDs with excellent performance based on the stacking approach. Current products achieve 40-60 lm/W, while future developments focus on achieving 80 lm/W or higher.

A low-cost procedure for production of fresh autochthonous wine yeast.

PubMed

Maqueda, Matilde; Pérez-Nevado, Francisco; Regodón, José A; Zamora, Emiliano; Alvarez, María L; Rebollo, José E; Ramírez, Manuel

2011-03-01

A low-cost procedure was designed for easy and rapid response-on-demand production of fresh wine yeast for local wine-making. The pilot plant produced fresh yeast culture concentrate with good microbial quality and excellent oenological properties from four selected wine yeasts. The best production yields were obtained using 2% sugar beet molasses and a working culture volume of less than 60% of the fermenter capacity. The yeast yield using 2% sugar grape juice was low and had poor cell viability after freeze storage, although the resulting yeast would be directly available for use in the winery. The performance of these yeasts in commercial wineries was excellent; they dominated must fermentation and improved its kinetics, as well as improving the physicochemical parameters and the organoleptic quality of red and white wines.

Catalyst–Controlled C–O versus C–N Allylic Functionalization of Terminal Olefins

PubMed Central

Strambeanu, Iulia I.; White, M. Christina

2014-01-01

The divergent synthesis of syn-1, 2-aminoalcohol or syn-1,2-diamine precursors from a common terminal olefin has been accomplished using a combination of palladium(II) catalysis with Lewis acid co-catalysis. Palladium(II)/bis-sulfoxide catalysis with a silver triflate co-catalyst leads for the first time to anti-2-aminooxazolines (C—O) in good to excellent yields. Simple removal of the bis-sulfoxide ligand from this reaction results in a complete switch in reactivity to afford anti-imidazolidinone products (C—N) in good yields and excellent diastereoselectivities. Mechanistic studies suggest the divergent C—O versus C—N reactivity from a common ambident nucleophile arises due to a switch in mechanism from allylic C—H cleavage/functionalization to olefin isomerization/oxidative amination. PMID:23855956

Highly photoresponsive and wavelength-selective circularly-polarized-light detector based on metal-oxides hetero-chiral thin film.

PubMed

Lee, Seung Hee; Singh, Dhruv Pratap; Sung, Ji Ho; Jo, Moon-Ho; Kwon, Ki Chang; Kim, Soo Young; Jang, Ho Won; Kim, Jong Kyu

2016-01-22

A highly efficient circularly-polarized-light detector with excellent wavelength selectivity is demonstrated with an elegant and simple microelectronics-compatible way. The circularly-polarized-light detector based on a proper combination of the geometry-controlled TiO2-SnO2 hetero-chiral thin film as an effective chiroptical filter and the Si active layer shows excellent chiroptical response with external quantum efficiency as high as 30% and high helicity selectivity of ~15.8% in an intended wavelength range. Furthermore, we demonstrated the ability of manipulating both bandwidth and responsivity of the detector simultaneously in whole visible wavelength range by a precise control over the geometry and materials constituting hetero-chiral thin film. The high efficiency, wavelength selectivity and compatibility with conventional microelectronics processes enabled by the proposed device can result in remarkable developments in highly integrated photonic platforms utilizing chiroptical responses.

Highly photoresponsive and wavelength-selective circularly-polarized-light detector based on metal-oxides hetero-chiral thin film

PubMed Central

Lee, Seung Hee; Singh, Dhruv Pratap; Sung, Ji Ho; Jo, Moon-Ho; Kwon, Ki Chang; Kim, Soo Young; Jang, Ho Won; Kim, Jong Kyu

2016-01-01

A highly efficient circularly-polarized-light detector with excellent wavelength selectivity is demonstrated with an elegant and simple microelectronics-compatible way. The circularly-polarized-light detector based on a proper combination of the geometry-controlled TiO2-SnO2 hetero-chiral thin film as an effective chiroptical filter and the Si active layer shows excellent chiroptical response with external quantum efficiency as high as 30% and high helicity selectivity of ~15.8% in an intended wavelength range. Furthermore, we demonstrated the ability of manipulating both bandwidth and responsivity of the detector simultaneously in whole visible wavelength range by a precise control over the geometry and materials constituting hetero-chiral thin film. The high efficiency, wavelength selectivity and compatibility with conventional microelectronics processes enabled by the proposed device can result in remarkable developments in highly integrated photonic platforms utilizing chiroptical responses. PMID:26795601

Highly photoresponsive and wavelength-selective circularly-polarized-light detector based on metal-oxides hetero-chiral thin film

NASA Astrophysics Data System (ADS)

Lee, Seung Hee; Singh, Dhruv Pratap; Sung, Ji Ho; Jo, Moon-Ho; Kwon, Ki Chang; Kim, Soo Young; Jang, Ho Won; Kim, Jong Kyu

2016-01-01

A highly efficient circularly-polarized-light detector with excellent wavelength selectivity is demonstrated with an elegant and simple microelectronics-compatible way. The circularly-polarized-light detector based on a proper combination of the geometry-controlled TiO2-SnO2 hetero-chiral thin film as an effective chiroptical filter and the Si active layer shows excellent chiroptical response with external quantum efficiency as high as 30% and high helicity selectivity of ~15.8% in an intended wavelength range. Furthermore, we demonstrated the ability of manipulating both bandwidth and responsivity of the detector simultaneously in whole visible wavelength range by a precise control over the geometry and materials constituting hetero-chiral thin film. The high efficiency, wavelength selectivity and compatibility with conventional microelectronics processes enabled by the proposed device can result in remarkable developments in highly integrated photonic platforms utilizing chiroptical responses.

Universal Parameterization of Absorption Cross Sections

NASA Technical Reports Server (NTRS)

Tripathi, R. K.; Cucinotta, Francis A.; Wilson, John W.

1999-01-01

Our prior nuclear absorption cross sections model is extended for light systems (A less than or equal to 4) where either both projectile and target are light particles or one is a light particle and the other is a medium or heavy nucleus. The agreement with experiment is excellent for these cases as well. Present work in combination with our original model provides a comprehensive picture of absorption cross sections for light, medium, and heavy systems, a very valuable input for radiation protection studies.

Exploring the Concepts of Knowledge Adoption and Conceptual Impact: Implications for Educational Research Submissions to the Research Excellence Framework (2014)

ERIC Educational Resources Information Center

Brown, Chris

2011-01-01

This article examines how research(ers) can impact upon policy, a pertinent issue in light of England's 2014 Research Excellence Framework. It presents the findings of a literature review and interviews with educational researchers and policymakers in England and Wales. The projects' aims were (i) to understand the actions researchers should…

The dark side of marketing seemingly "Light" cigarettes: successful images and failed fact.

PubMed

Pollay, R W; Dewhirst, T

2002-03-01

To understand the development, intent, and consequences of US tobacco industry advertising for low machine yield cigarettes. Analysis of trade sources and internal US tobacco company documents now available on various web sites created by corporations, litigation, or public health bodies. When introducing low yield products, cigarette manufacturers were concerned about maintaining products with acceptable taste/flavour and feared consumers might become weaned from smoking. Several tactics were employed by cigarette manufacturers, leading consumers to perceive filtered and low machine yield brands as safer relative to other brands. Tactics include using cosmetic (that is, ineffective) filters, loosening filters over time, using medicinal menthol, using high tech imagery, using virtuous brand names and descriptors, adding a virtuous variant to a brand's product line, and generating misleading data on tar and nicotine yields. Advertisements of filtered and low tar cigarettes were intended to reassure smokers concerned about the health risks of smoking, and to present the respective products as an alternative to quitting. Promotional efforts were successful in getting smokers to adopt filtered and low yield cigarette brands. Corporate documents demonstrate that cigarette manufacturers recognised the inherent deceptiveness of cigarette brands described as "Light"or "Ultra-Light" because of low machine measured yields.

Rational design of 3D inverse opal heterogeneous composite microspheres as excellent visible-light-induced NO2 sensors at room temperature.

PubMed

Wang, Tianshuang; Yu, Qi; Zhang, Sufang; Kou, Xueying; Sun, Peng; Lu, Geyu

2018-03-08

The lower gas sensitivity, humidity dependence of the gas sensing properties, and long recovery times of room-temperature gas sensors severely limit their applications. Herein, to address these issues, a series of 3D inverse opal (IO) In 2 O 3 -ZnO heterogeneous composite microspheres (HCMs) are fabricated by ultrasonic spray pyrolysis (USP) employing self-assembled sulfonated polystyrene (S-PS) spheres as a sacrificial template. The 3D IO In 2 O 3 -ZnO HCMs possess highly ordered 3D inverse opal structures and bimodal (meso-scale and macro-scale) pores, which can provide large accessible surface areas and rapid mass transfer, resulting in enhanced gas sensing characteristics. Furthermore, the 3D IO architecture and n-n heterojunctions can extend the photoabsorption range to the visible light area, effectively prolonging the lifetimes of photo-generated charge carriers, and can increase separation of visible light-generated charges. As a result, the as-prepared 3D IO In 2 O 3 -ZnO HCMs deliver excellent NO 2 sensing performance under visible light irradiation at room temperature, such as high sensitivity (R gas /R air = 54.3 to 5 ppm NO 2 ), low detection limit (250 ppb), fast recovery time (188 s), excellent selectivity and humidity independence. These enhanced photo-electronic gas sensing properties are attributed to the combination of highly ordered 3D IO microspheres and In 2 O 3 -ZnO heterogeneous composites.

Synthesis of hierarchically meso-macroporous TiO2/CdS heterojunction photocatalysts with excellent visible-light photocatalytic activity.

PubMed

Zhao, Haixin; Cui, Shu; Yang, Lan; Li, Guodong; Li, Nan; Li, Xiaotian

2018-02-15

Photocatalysts with a hierarchically porous structure have attracted considerable attention owing to their wide pore size distribution and high surface area, which enhance the efficiency of transporting species to active sites. In this study, hierarchically meso-macroporous TiO 2 photocatalysts decorated with highly dispersed CdS nanoparticles were synthesized via hydrolysis, followed by a hydrothermal treatment. The textural mesopores and interconnected pore framework provided more accessible active sites and efficient mass transport for the photocatalytic process. The light collection efficiency was enhanced because of multiple scattering of incident light in the macropores. Moreover, the formation of a heterojunction between the CdS and TiO 2 nanoparticles extended the photoresponse of TiO 2 to the visible-light range and enhanced the charge separation efficiency. Therefore, the hierarchically meso-macroporous TiO 2 /CdS photocatalysts exhibited excellent photocatalytic activity for the degradation of rhodaming B under visible-light irradiation. Trapping experiments demonstrated that superoxide radicals (O 2 - ) and hydroxyl radicals (OH) were the main active species in photocatalysis. A reasonable photocatalytic mechanism of TiO 2 /CdS heterojunction photocatalysts was also presented. Copyright © 2017 Elsevier Inc. All rights reserved.

Cascade upgrading of γ-valerolactone to biofuels.

PubMed

Yan, Kai; Lafleur, Todd; Wu, Xu; Chai, Jiajue; Wu, Guosheng; Xie, Xianmei

2015-04-25

Cascade upgrading of γ-valerolactone (GVL), produced from renewable cellulosic biomass, with selective conversion to biofuels pentyl valerate (PV) and pentane in one pot using a bifunctional Pd/HY catalyst is described. Excellent catalytic performance (over 99% conversion of GVL, 60.6% yield of PV and 22.9% yield of pentane) was achieved in one step. These biofuels can be targeted for gasoline and jet fuel applications.

Organocatalytic sequential α-amination/Corey-Chaykovsky reaction of aldehydes: a high yield synthesis of 4-hydroxypyrazolidine derivatives.

PubMed

Kumar, B Senthil; Venkataramasubramanian, V; Sudalai, Arumugam

2012-05-18

A tandem reaction of in situ generated α-amino aldehydes with dimethyloxosulfonium methylide under Corey-Chaykovsky reaction conditions proceeds efficiently to give 4-hydroxypyrazolidine derivatives in high yields with excellent enantio- and diastereoselectivities. This organocatalytic sequential method provides for the efficient synthesis of anti-1,2-aminoalcohols, structural subunits present in several bioactive molecules as well.

Separation of photoactive conformers based on hindered diarylethenes: efficient modulation in photocyclization quantum yields.

PubMed

Li, Wenlong; Jiao, Changhong; Li, Xin; Xie, Yongshu; Nakatani, Keitaro; Tian, He; Zhu, Weihong

2014-04-25

Endowing both solvent independency and excellent thermal bistability, the benzobis(thiadiazole)-bridged diarylethene system provides an efficient approach to realize extremely high photocyclization quantum yields (Φo-c , up to 90.6 %) by both separating completely pure anti-parallel conformer and suppressing intramolecular charge transfer (ICT). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Effects of light intensity on growth and photosynthetic characteristics of Tulipa edulis].

PubMed

Xu, Hongjian; Zhu, Zaibiao; Guo, Qiaosheng; Wu, Zhengjun; Ma, Hongliang; Miao, Yuanyuan

2012-02-01

Present study was conducted to explore the growth and photosynthetic characteristics of Tulipa edulis under different light conditions (23%, 45%, 63%, 78%, 100% of full sunlight) and to determine the optimum light intensity for growth of T. edulis. The leaf area and biomass indicators as well as reproductive characteristics were measured. The photosynthetic basic parameters and light response curve were determined by a LI-6400XT portable photosynthesis system, and the light response curve characteristic parameters was determined. Additionally, chlorophyll fluorescence parameters were determined by assorted fluorescence leaf chamber of LI-6400XT. The lowest biomass yield was observed in the 23% and 100% of full sunlight treatments while the highest value was found under the 78% of full sunlight conditions. With the reduction of light availability, the success rate of sexual reproduction, light saturation point (LSP) and light compensation point (LCP) reduced, while apparent quantum yield (AQY) increased. 23% and 45% of full sunlight treatments led to lower photosynthesis rate (Pn) and higher apparent quantum yield (AQY) in comparison with other treatents. The highest photosynthesis rate was observed in the 78% and 100% of full sunlight treatments. In addition, 78% of full sunlight treatments led to highest Fv/Fm, Fv'/Fm', PhiPS II, ETR, and qP. T. edulis was able to adapt in a wide range of light intensity, and 78% of full sunlinght was the most suitable light condition for growth of T. edulis.

An Intrinsic Fiber-Optic Sensor for Structure Lightning Current Measurement

NASA Technical Reports Server (NTRS)

Nguyen, Truong X.; Ely, Jay J.; Szatkowski, George N.; Mata, Carlos T.; Mata, Angel. G.; Snyder, Gary P.

2014-01-01

An intrinsic optical-fiber sensor based on Faraday Effect is developed that is highly suitable for measuring lightning current on aircraft, towers and complex structures. Originally developed specifically for aircraft installations, it is light-weight, non-conducting, structure conforming, and is immune to electromagnetic interference, hysteresis and saturation. It can measure total current down to DC. When used on lightning towers, the sensor can help validate other sensors and lightning detection network measurements. Faraday Effect causes light polarization to rotate when the fiber is exposed to a magnetic field in the direction of light propagation. Thus, the magnetic field strength can be determined from the light polarization change. By forming closed fiber loops and applying Ampere's law, measuring the total light rotation yields the total current enclosed. A broadband, dual-detector, reflective polarimetric scheme allows measurement of both DC component and AC waveforms with a 60 dB dynamic range. Two systems were built that are similar in design but with slightly different sensitivities. The 1310nm laser system can measure 300 A - 300 kA, and has a 15m long sensing fiber. It was used in laboratory testing, including measuring current on an aluminum structure simulating an aircraft fuselage or a lightning tower. High current capabilities were demonstrated up to 200 kA at a lightning test facility. The 1550nm laser system can measure 400 A - 400 kA and has a 25m fiber length. Used in field measurements, excellent results were achieved in the summer of 2012 measuring rocket-triggered lightning at the International Center for Lightning Research and Testing (ICLRT), Camp Blanding, Florida. In both systems increased sensitivity can be achieved with multiple fiber loops. The fiber optic sensor provides many unique capabilities not currently possible with traditional sensors. It represents an important new tool for lightning current measurement where low weight, complex shapes, large structure dimension, large current, and low frequency capabilities are important considerations.

Effects of Controlled-Release Fertilizer on Leaf Area Index and Fruit Yield in High-Density Soilless Tomato Culture Using Low Node-Order Pinching

PubMed Central

Kinoshita, Takafumi; Yano, Takayoshi; Sugiura, Makoto; Nagasaki, Yuji

2014-01-01

To further development of a simplified fertigation system using controlled-release fertilizers (CRF), we investigated the effects of differing levels of fertilizers and plant density on leaf area index (LAI), fruit yields, and nutrient use in soilless tomato cultures with low node-order pinching and high plant density during spring-summer (SS), summer-fall (SF), and fall-winter (FW) seasons. Plants were treated with 1 of 3 levels of CRF in a closed system, or with liquid fertilizer (LF) with constant electrical conductivity (EC) in a drip-draining system. Two plant densities were examined for each fertilizer treatment. In CRF treatments, LAI at pinching increased linearly with increasing nutrient supply for all cropping seasons. In SS, both light interception by plant canopy at pinching and total marketable fruit yield increased linearly with increasing LAI up to 6 m2·m−2; the maximization point was not reached for any of the treatments. In FW, both light interception and yield were maximized at an LAI of approximately 4. These results suggest that maximizing the LAI in SS and FW to the saturation point for light interception is important for increasing yield. In SF, however, the yield maximized at an LAI of approximately 3, although the light interception linearly increased with increasing LAI, up to 4.5. According to our results, the optimal LAI at pinching may be 6 in SS, 3 in SF, and 4 in FW. In comparing LAI values with similar fruit yield, we found that nutrient supply was 32−46% lower with the CRF method than with LF. In conclusion, CRF application in a closed system enables growers to achieve a desirable LAI to maximize fruit yield with a regulated amount of nutrient supply per unit area. Further, the CRF method greatly reduced nutrient use without decreasing fruit yield at similar LAIs, as compared to the LF method. PMID:25402478

CREATING SINGLE-SUBJECT DESIGN GRAPHS IN MICROSOFT EXCELTM 2007

PubMed Central

Dixon, Mark R; Jackson, James W; Small, Stacey L; Horner-King, Mollie J; Lik, Nicholas Mui Ker; Garcia, Yors; Rosales, Rocio

2009-01-01

Over 10 years have passed since the publication of Carr and Burkholder's (1998) technical article on how to construct single-subject graphs using Microsoft Excel. Over the course of the past decade, the Excel program has undergone a series of revisions that make the Carr and Burkholder paper somewhat difficult to follow with newer versions. The present article provides task analyses for constructing various types of commonly used single-subject design graphs in Microsoft Excel 2007. The task analyses were evaluated using a between-subjects design that compared the graphing skills of 22 behavior-analytic graduate students using Excel 2007 and either the Carr and Burkholder or newly developed task analyses. Results indicate that the new task analyses yielded more accurate and faster graph construction than the Carr and Burkholder instructions. PMID:19949515

Nonlinear optical behavior of two tetrathiafulvalene derivatives in the picosecond regime

NASA Astrophysics Data System (ADS)

Marcovicz, Crislaine; Ferreira, Rudson C.; Santos, Arthur B. S.; Reyna, Albert S.; de Araújo, Cid B.; Malvestiti, Ivani; Falcão, Eduardo H. L.

2018-06-01

We report the microwave-assisted synthesis of two symmetrical tetrathiafulvalene (TTF) derivatives via trialkyl phosphite-promoted coupling of a DMIT precursor. The microwave irradiation led to an increase in the reaction yield and significantly reduced the reaction time, affording the 2,3,6,7-tetrakis(2‧-methylacetatethio)tetrathiafulvalene (4) in 74% isolated yield. Hydrolysis of 4 yielded the tetraacid 5 in excellent yield. The nonlinear optical properties of both TTF compounds at 532 nm were studied by using the Z-scan technique in the picosecond regime exhibiting large third-order refractive index and saturated nonlinear absorption with promising applications in optical limiting devices.

Formation of the imidazolides of dinucleotides under potentially prebiotic conditions

NASA Technical Reports Server (NTRS)

Sleeper, H. L.; Lohrmann, R.; Orgel, L. E.

1978-01-01

Imidazolides of dinucleotides such as ImpApA can be formed from the corresponding dinucleotides in a two-stage process, which gives up to 15% yields under potentially prebiotic conditions. First a solution of the dinucleotide and sodium trimetaphosphate is dried out at constant temperature and humidity. This produces polyphosphates such as p(n)ApA in excellent yield (greater than or equal to 80%). The products are dissolved in water, imidazole is added, and the solution is dried out again. This yields the 5'-phosphorimidazolides.

A green-yellow emitting oxyfluoride solid solution phosphor Sr[subscript 2]Ba(AlO[subscript 4]F)[subscript 1;#8722;x](SiO[subscript 5])x:Ce[superscript 3+] for thermally stable, high color rendition solid state white lighting

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

Denault, Kristin A.; George, Nathan C.; Paden, Sara R.

2012-10-23

A near-UV excited, oxyfluoride phosphor solid solution Sr{sub 1.975}Ce{sub 0.025}Ba(AlO{sub 4}F){sub 1-x}(SiO{sub 5}){sub x} has been developed for solid state white lighting applications. An examination of the host lattice, and the local structure around the Ce{sup 3+} activator ions through a combination of density functional theory, synchrotron X-ray and neutron powder diffraction and total scattering, and electron paramagnetic resonance, points to how chemical substitutions play a crucial role in tuning the optical properties of the phosphor. The maximum emission wavelength can be tuned from green ({lambda}{sub em} = 523 nm) to yellow ({lambda}{sub em} = 552 nm) by tuning themore » composition, x. Photoluminescent quantum yield is determined to be 70 {+-} 5% for some of the examples in the series. Excellent thermal properties were found for the x = 0.5 sample, with the photoluminescence intensity at 160 C only decreased to 82% of its room temperature value. Phosphor-converted LED devices fabricated using an InGaN LED ({lambda}{sub max} = 400 nm) exhibit high color rendering white light with R{sub a} = 70 and a correlated color temperature near 7000 K. The value of R{sub a} could be raised to 90 by the addition of a red component, and the correlated color temperature lowered to near 4000 K.« less

MMW/THz imaging using upconversion to visible, based on glow discharge detector array and CCD camera

NASA Astrophysics Data System (ADS)

Aharon, Avihai; Rozban, Daniel; Abramovich, Amir; Yitzhaky, Yitzhak; Kopeika, Natan S.

2017-10-01

An inexpensive upconverting MMW/THz imaging method is suggested here. The method is based on glow discharge detector (GDD) and silicon photodiode or simple CCD/CMOS camera. The GDD was previously found to be an excellent room-temperature MMW radiation detector by measuring its electrical current. The GDD is very inexpensive and it is advantageous due to its wide dynamic range, broad spectral range, room temperature operation, immunity to high power radiation, and more. An upconversion method is demonstrated here, which is based on measuring the visual light emitting from the GDD rather than its electrical current. The experimental setup simulates a setup that composed of a GDD array, MMW source, and a basic CCD/CMOS camera. The visual light emitting from the GDD array is directed to the CCD/CMOS camera and the change in the GDD light is measured using image processing algorithms. The combination of CMOS camera and GDD focal plane arrays can yield a faster, more sensitive, and very inexpensive MMW/THz camera, eliminating the complexity of the electronic circuits and the internal electronic noise of the GDD. Furthermore, three dimensional imaging systems based on scanning prohibited real time operation of such imaging systems. This is easily solved and is economically feasible using a GDD array. This array will enable us to acquire information on distance and magnitude from all the GDD pixels in the array simultaneously. The 3D image can be obtained using methods like frequency modulation continuous wave (FMCW) direct chirp modulation, and measuring the time of flight (TOF).

Supplemental Upward Lighting from Underneath to Obtain Higher Marketable Lettuce (Lactuca sativa) Leaf Fresh Weight by Retarding Senescence of Outer Leaves

PubMed Central

Zhang, Geng; Shen, Shanqi; Takagaki, Michiko; Kozai, Toyoki; Yamori, Wataru

2015-01-01

Recently, the so-called “plant factory with artificial lighting” (PFAL) approach has been developed to provide safe and steady food production. Although PFALs can produce high-yielding and high-quality plants, the high plant density in these systems accelerates leaf senescence in the bottom (or outer) leaves owing to shading by the upper (or inner) leaves and by neighboring plants. This decreases yield and increases labor costs for trimming. Thus, the establishment of cultivation methods to retard senescence of outer leaves is an important research goal to improve PFAL yield and profitability. In the present study, we developed an LED lighting apparatus that would optimize light conditions for PFAL cultivation of a leafy vegetable. Lettuce (Lactuca sativa L.) was hydroponically grown under white, red, or blue LEDs, with light provided from above (downward), with or without supplemental upward lighting from underneath the plant. White LEDs proved more appropriate for lettuce growth than red or blue LEDs, and the supplemental lighting retarded the senescence of outer leaves and decreased waste (i.e., dead or low-quality senescent leaves), leading to an improvement of the marketable leaf fresh weight. PMID:26697055

Preparation and characterization of ZnO-TiO{sub 2} nanocomposite for photocatalytic disinfection of bacteria and detoxification of cyanide under visible light

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

Karunakaran, C., E-mail: karunakaranc@rediffmail.com; Abiramasundari, G.; Gomathisankar, P.

2011-10-15

Highlights: {yields} ZnO-TiO{sub 2} nanocomposite, obtained by modified ammonia-evaporation-induced synthetic method, absorbs visible light. {yields} ZnO-TiO{sub 2} nanoparticles catalyze bacteria disinfection and cyanide detoxification under sunlight. {yields} ZnO-TiO{sub 2} nanocomposite is selective in photocatalysis. -- Abstract: ZnO-TiO{sub 2} nanocomposite was prepared by modified ammonia-evaporation-induced synthetic method. It was characterized by powder X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray, UV-visible diffuse reflectance, photoluminescence and electrochemical impedance spectroscopies. Incorporation of ZnO leads to visible light absorption, larger charge transfer resistance and lower capacitance. The nanocomposite effectively catalyzes the inactivation of E. coli under visible light. Further,more » the prepared nanocomposite displays selective photocatalysis. While its photocatalytic efficiency to detoxify cyanide with visible light is higher than that of TiO{sub 2} P25, its efficiency to degrade methylene blue, sunset yellow and rhodamine B dyes under UV-A light is less than that of TiO{sub 2} P25.« less

Neutron spectroscopy by thermalization light yield measurement in a composite heterogeneous scintillator

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

Shi, T.; Nattress, J.; Mayer, Michael F.

2016-12-11

An exothermic neutron capture reaction can be used to uniquely identify neutrons in particle detectors. With the use of a capture-gated coincidence technique, the sequence of scatter events that lead to neutron thermalization prior to the neutron capture can also be used to measure neutron energy. We report on the measurement of thermalization light yield via a time-of-flight technique in a polyvinyl toluene-based scintillator EJ-290 within a heterogeneous composite detector that also includes 6Li-doped glass scintillator. The thermalization light output exhibits a strong correlation with neutron energy because of the preference for near-complete energy deposition prior to the 6Li(n,t)4He neutronmore » capture reaction. The nonproportionality of the light yield from nuclear recoils contributes to the observed broadening of the distribution of thermalization light output. The nonproportional dependence of the scintillation light output in the EJ-290 scintillator as a function of proton recoil energy has been characterized in the range of 0.3–14.1 MeV via the Birks parametrization through a combination of time-of-flight measurement and previously conducted measurements with Monoenergetic neutron sources.« less

Dissipation of electronic excitation energy within a C60 [6:0]-hexaadduct carrying 12 pyropheophorbide a moieties.

PubMed

Helmreich, Matthias; Ermilov, Eugeny A; Meyer, Matthias; Jux, Norbert; Hirsch, Andreas; Röder, Beate

2005-06-15

The synthesis and photophysical studies of a fullerene [6:0]-hexaadduct that carries 12 pyropheophorbide a units are reported. The synthesis started with the malonate 1, which was coupled under template conditions to C(60)() to give the hexaadduct 2. After removal of the protecting group with acid the dodecakis amino-substituted precursor compound 3 was generated. 3 was not isolated but directly reacted with the N-succinimid ester 4 of pyropheophorbide a (5), which delivered the desired fullerene [6:0]-hexaadduct 6 in excellent yield. The photophysical properties of 6 were studied and compared with those of the fullerene [5:1]-hexaadduct 7 with six pyropheophorbide a groups and the bispyropheophorbide a-fullerene [5:1]-hexaadduct 8. The pyropheophorbide a units in 6 undergo after light absorption very efficient energy transfer as well as partly excitonic interaction. The last process results in formation of energy traps, which could be resolved experimentally. Compared to the reference compounds 7 and 8, 6 has a higher probability of trap formation due to a higher local concentration of dye molecules and shorter distances between them. As a consequence, the excitation energy is delivered rapidly (within 23 ps) to the traps, resulting in decreases of the fluorescence, intersystem crossing, and singlet oxygen quantum yields in comparison with the values of the reference compounds.

Solvent-Controlled Synthesis of Highly Luminescent Carbon Dots with a Wide Color Gamut and Narrowed Emission Peak Widths.

PubMed

Ding, Hui; Wei, Ji-Shi; Zhang, Peng; Zhou, Zi-Yuan; Gao, Qing-Yu; Xiong, Huan-Ming

2018-05-01

Carbon dots (CDs) have tremendous potential applications in bioimaging, biomedicine, and optoelectronics. By far, it is still difficult to produce photoluminescence (PL) tunable CDs with high quantum yield (QY) across the entire visible spectrum and narrow the emission peak widths of CDs close to those of typical quantum dots. In this work, a series of CDs with tunable emission from 443 to 745 nm, quantum yield within 13-54%, and narrowed full width at half maximum (FWHM) from 108 to 55 nm, are obtained by only adjusting the reaction solvents in a one-pot solvothermal route. The distinct optical features of these CDs are based on their differences in the particle size, and the content of graphitic nitrogen and oxygen-containing functional groups, which can be modulated by controlling the dehydration and carbonization processes during solvothermal reactions. Blue, green, yellow, red, and even pure white light emitting films (Commission Internationale de L'Eclairage (CIE)= 0.33, 0.33, QY = 39%) are prepared by dispersing one or three kinds of CDs into polyvinyl alcohol with appropriate ratios. The near-infrared emissive CDs are excellent fluorescent probes for both in vitro and in vivo bioimaging because of their high QY in water, long-term stability, and low cytotoxicity. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

UV-resonance Raman spectroscopy of amino acids

NASA Astrophysics Data System (ADS)

Höhl, Martin; Meinhardt-Wollweber, Merve; Schmitt, Heike; Lenarz, Thomas; Morgner, Uwe

2016-03-01

Resonant enhancement of Raman signals is a useful method to increase sensitivity in samples with low concentration such as biological tissue. The investigation of resonance profiles shows the optimal excitation wavelength and yields valuable information about the molecules themselves. However careful characterization and calibration of all experimental parameters affecting quantum yield is required in order to achieve comparability of the single spectra recorded. We present an experimental technique for measuring the resonance profiles of different amino acids. The absorption lines of these molecules are located in the ultraviolet (UV) wavelength range. One limitation for broadband measurement of resonance profiles is the limited availability of Raman filters in certain regions of the UV for blocking the Rayleigh scattered light. Here, a wavelength range from 244.8 nm to 266.0 nm was chosen. The profiles reveal the optimal wavelength for recording the Raman spectra of amino acids in aqueous solutions in this range. This study provides the basis for measurements on more complex molecules such as proteins in the human perilymph. The composition of this liquid in the inner ear is essential for hearing and cannot be analyzed non-invasively so far. The long term aim is to implement this technique as a fiber based endoscope for non-invasive measurements during surgeries (e. g. cochlear implants) making it available as a diagnostic tool for physicians. This project is embedded in the interdisciplinary cluster of excellence "Hearing for all" (H4A).

Highly Luminescent Phase-Stable CsPbI3 Perovskite Quantum Dots Achieving Near 100% Absolute Photoluminescence Quantum Yield.

PubMed

Liu, Feng; Zhang, Yaohong; Ding, Chao; Kobayashi, Syuusuke; Izuishi, Takuya; Nakazawa, Naoki; Toyoda, Taro; Ohta, Tsuyoshi; Hayase, Shuzi; Minemoto, Takashi; Yoshino, Kenji; Dai, Songyuan; Shen, Qing

2017-10-24

Perovskite quantum dots (QDs) as a new type of colloidal nanocrystals have gained significant attention for both fundamental research and commercial applications owing to their appealing optoelectronic properties and excellent chemical processability. For their wide range of potential applications, synthesizing colloidal QDs with high crystal quality is of crucial importance. However, like most common QD systems such as CdSe and PbS, those reported perovskite QDs still suffer from a certain density of trapping defects, giving rise to detrimental nonradiative recombination centers and thus quenching luminescence. In this paper, we show that a high room-temperature photoluminescence quantum yield of up to 100% can be obtained in CsPbI 3 perovskite QDs, signifying the achievement of almost complete elimination of the trapping defects. This is realized with our improved synthetic protocol that involves introducing organolead compound trioctylphosphine-PbI 2 (TOP-PbI 2 ) as the reactive precursor, which also leads to a significantly improved stability for the resulting CsPbI 3 QD solutions. Ultrafast kinetic analysis with time-resolved transient absorption spectroscopy evidence the negligible electron or hole-trapping pathways in our QDs, which explains such a high quantum efficiency. We expect the successful synthesis of the "ideal" perovskite QDs will exert profound influence on their applications to both QD-based light-harvesting and -emitting devices.

Iron oxide nanozyme catalyzed synthesis of fluorescent polydopamine for light-up Zn2+ detection

NASA Astrophysics Data System (ADS)

Liu, Biwu; Han, Xiao; Liu, Juewen

2016-07-01

Fluorescent polydopamine (FPD) is an interesting material with excellent biocompatibility. However, its preparation is currently a lengthy and potentially dangerous process. We herein employ magnetic iron oxide (Fe3O4) nanoparticles as a peroxidase-mimicking nanozyme to produce FPD under mild conditions. Different from previous protocols using multiple steps with up to 6% (~2 M) H2O2, this preparation takes place in a single step with just 5 mM H2O2 at room temperature. The oxidized product shows excitation-wavelength-dependent emission peaks, similar to previous reports. The reaction kinetics, pH, temperature, and ionic strength are individually optimized. Among a diverse range of other nanomaterials tested, including Fe2O3, CeO2, CoO, Co3O4, NiO, TiO2, gold nanoparticles, and graphene oxide, Fe2O3 and graphene oxide yielded relatively weak emission, while the rest of the materials failed to produce FPD. The Fe3O4 nanoparticles retained ~90% catalytic activity even after ten cycles of synthesis. Finally, Zn2+ can enhance the fluorescence of FPD under 360 nm excitation but not under 480 nm excitation, leading to a sensitive light-up sensor with a detection limit of 60 nM Zn2+. Therefore, this work has demonstrated not only a novel use of nanozymes, but also an interesting application of FPD.Fluorescent polydopamine (FPD) is an interesting material with excellent biocompatibility. However, its preparation is currently a lengthy and potentially dangerous process. We herein employ magnetic iron oxide (Fe3O4) nanoparticles as a peroxidase-mimicking nanozyme to produce FPD under mild conditions. Different from previous protocols using multiple steps with up to 6% (~2 M) H2O2, this preparation takes place in a single step with just 5 mM H2O2 at room temperature. The oxidized product shows excitation-wavelength-dependent emission peaks, similar to previous reports. The reaction kinetics, pH, temperature, and ionic strength are individually optimized. Among a diverse range of other nanomaterials tested, including Fe2O3, CeO2, CoO, Co3O4, NiO, TiO2, gold nanoparticles, and graphene oxide, Fe2O3 and graphene oxide yielded relatively weak emission, while the rest of the materials failed to produce FPD. The Fe3O4 nanoparticles retained ~90% catalytic activity even after ten cycles of synthesis. Finally, Zn2+ can enhance the fluorescence of FPD under 360 nm excitation but not under 480 nm excitation, leading to a sensitive light-up sensor with a detection limit of 60 nM Zn2+. Therefore, this work has demonstrated not only a novel use of nanozymes, but also an interesting application of FPD. Electronic supplementary information (ESI) available: Methods, TEM, ζ-potential, and original fluorescence spectra. See DOI: 10.1039/c6nr02584f

A stable Alq3@MOF composite for white-light emission.

PubMed

Xie, Wei; He, Wen-Wen; Du, Dong-Ying; Li, Shun-Li; Qin, Jun-Sheng; Su, Zhong-Min; Sun, Chun-Yi; Lan, Ya-Qian

2016-02-25

A stable mesoporous blue-emitting MOF NENU-521 was successfully constructed. NENU-521 can serve as a host for encapsulating Alq3 to obtain tunable and efficient white-light emission. The Alq3@NENU-521 composite possesses excellent stability and can be used as a promising white phosphor in WLEDs.

Fabrication of the replica templated from butterfly wing scales with complex light trapping structures

NASA Astrophysics Data System (ADS)

Han, Zhiwu; Li, Bo; Mu, Zhengzhi; Yang, Meng; Niu, Shichao; Zhang, Junqiu; Ren, Luquan

2015-11-01

The polydimethylsiloxane (PDMS) positive replica templated twice from the excellent light trapping surface of butterfly Trogonoptera brookiana wing scales was fabricated by a simple and promising route. The exact SiO2 negative replica was fabricated by using a synthesis method combining a sol-gel process and subsequent selective etching. Afterwards, a vacuum-aided process was introduced to make PDMS gel fill into the SiO2 negative replica, and the PDMS gel was solidified in an oven. Then, the SiO2 negative replica was used as secondary template and the structures in its surface was transcribed onto the surface of PDMS. At last, the PDMS positive replica was obtained. After comparing the PDMS positive replica and the original bio-template in terms of morphology, dimensions and reflectance spectra and so on, it is evident that the excellent light trapping structures of butterfly wing scales were inherited by the PDMS positive replica faithfully. This bio-inspired route could facilitate the preparation of complex light trapping nanostructure surfaces without any assistance from other power-wasting and expensive nanofabrication technologies.

Mechanical properties of low-nickel stainless steel

NASA Technical Reports Server (NTRS)

Montano, J. W.

1978-01-01

Demand for improved corrosion-resistant steels, coupled with increased emphasis on conserving strategic metals, has led to development of family of stainless steels in which manganese and nitrogen are substituted for portion of usual nickel content. Advantages are approximately-doubled yield strength in annealed condition, better resistance to stress-corrosion cracking, retention of low magnetic permeability even after severe cold working, excellent strength and ductility at cryogenic temperatures, superior resistance to wear and galling, and excellent high-temperature properties.

Tests of Scintillator+WLS Strips for Muon System at Future Colliders

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

Denisov, Dmitri; Evdokimov, Valery; Lukić, Strahinja

2015-10-11

Prototype scintilator+WLS strips with SiPM readout for muon system at future colliders were tested for light yield, time resolution and position resolution. Depending on the configuration, light yield of up to 36 photoelectrons per muon per SiPM has been achieved, as well as time resolution of 0.5 ns and position resolution of ~ 7 cm.

Generation of the neutron response function of an NE213 scintillator for fusion applications

NASA Astrophysics Data System (ADS)

Binda, F.; Eriksson, J.; Ericsson, G.; Hellesen, C.; Conroy, S.; Nocente, M.; Sundén, E. Andersson; JET Contributors

2017-09-01

In this work we present a method to evaluate the neutron response function of an NE213 liquid scintillator. This method is particularly useful when the proton light yield function of the detector has not been measured, since it is based on a proton light yield function taken from literature, MCNPX simulations, measurements of gamma-rays from a calibration source and measurements of neutrons from fusion experiments with ohmic plasmas. The inclusion of the latter improves the description of the proton light yield function in the energy range of interest (around 2.46 MeV). We apply this method to an NE213 detector installed at JET, inside the radiation shielding of the magnetic proton recoil (MPRu) spectrometer, and present the results from the calibration along with some examples of application of the response function to perform neutron emission spectroscopy (NES) of fusion plasmas. We also investigate how the choice of the proton light yield function affects the NES analysis, finding that the result does not change significantly. This points to the fact that the method for the evaluation of the neutron response function is robust and gives reliable results.

Characterization of hybrid lighting systems of the Electrical Engineering Building in the Industrial University of Santander

NASA Astrophysics Data System (ADS)

Galvis, D.; Exposito, C.; Osma, G.; Amado, L.; Ordóñez, G.

2016-07-01

This paper presents an analysis of hybrid lighting systems of Electrical Engineering Building in the Industrial University of Santander, which is a pilot of green building for warm- tropical conditions. Analysis of lighting performance of inner spaces is based on lighting curves obtained from characterization of daylighting systems of these spaces. A computation tool was made in Excel-Visual Basic to simulate the behaviour of artificial lighting system considering artificial control system, user behaviour and solar condition. Also, this tool allows to estimate the electrical energy consumption of the lighting system for a day, a month and a year.

Regioselective alkali metal reduction of dibenzocyclooctadiene lignan derivatives, demethoxylation followed by dehalogenation.

PubMed

Wang, Qing-Yao; Fang, Jia-Qi; Deng, Lu-Lu; Hao, Xiao-Jiang; Mu, Shu-Zhen

2017-12-27

The regioselective demethoxylation and dehalogenation of dihalogenated dibenzocyclooctadiene lignans derivatives were realized in a one-step reaction with excellent yields in the sodium and t-butanol reaction system.

Lanthanum tricyanide-catalyzed acyl silane-ketone benzoin additions.

PubMed

Tarr, James C; Johnson, Jeffrey S

2009-09-03

Lanthanum tricyanide efficiently catalyzes a benzoin-type coupling between acyl silanes and ketones. Yields range from moderate to excellent over a broad substrate scope encompassing aryl, alkyl, electron-rich, and sterically hindered ketones.

Observation of {chi}{sub cJ} Radiative Decays to Light Vector Mesons

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

Bennett, J. V.; Mitchell, R. E.; Shepherd, M. R.

2008-10-10

Using a total of 2.74x10{sup 7} decays of the {psi}(2S) collected with the CLEO-c detector, we present a study of {chi}{sub cJ}{yields}{gamma}V, where V={rho}{sup 0}, {omega}, {phi}. The transitions {chi}{sub c1}{yields}{gamma}{rho}{sup 0} and {chi}{sub c1}{yields}{gamma}{omega} are observed with B({chi}{sub c1}{yields}{gamma}{rho}{sup 0})=(2.43{+-}0.19{+-}0.22)x10{sup -4} and B({chi}{sub c1}{yields}{gamma}{omega})=(8.3{+-}1.5{+-}1.2)x10{sup -5}. In the {chi}{sub c1}{yields}{gamma}{rho}{sup 0} transition, the final state meson is dominantly longitudinally polarized. Upper limits on the branching fractions of other {chi}{sub cJ} states to light vector mesons are presented.

Improved photoluminescence quantum yield and stability of CdSe-TOP, CdSe-ODA-TOPO, CdSe/CdS and CdSe/EP nanocomposites

NASA Astrophysics Data System (ADS)

Wei, Shutian; Zhu, Zhilin; Wang, Zhixiao; Wei, Gugangfen; Wang, Pingjian; Li, Hai; Hua, Zhen; Lin, Zhonghai

2016-07-01

Size-controllable monodisperse CdSe nanocrystals with different organic capping were prepared based on the hot-injection method. The effective separation of nucleation and growth was achieved by rapidly mixing two highly reactive precursors. As a contrast, we prepared CdSe/CdS nanocrystals (NCs) successfully based on the selective ion layer adsorption and reaction (SILAR) technique. This inorganic capping obtained higher photoluminescence quantum yield (PLQY) of 59.3% compared with organic capping of 40.8%. Furthermore, the CdSe-epoxy resin (EP) composites were prepared by adopting a flexible ex situ method, and showed excellent stability in the ambient environment for one year. So the composites with both high PLQY of nanocrystals and excellent stability are very promising to device application.

How does spatial and temporal resolution of vegetation index impact crop yield estimation?

USDA-ARS?s Scientific Manuscript database

Timely and accurate estimation of crop yield before harvest is critical for food market and administrative planning. Remote sensing data have long been used in crop yield estimation for decades. The process-based approach uses light use efficiency model to estimate crop yield. Vegetation index (VI) ...

Light-curve solutions for S Cancri and TT Hydrae with rapid rotation

NASA Technical Reports Server (NTRS)

Van Hamme, W.; Wilson, R. E.

1993-01-01

Physical model light- and velocity-curve solutions for S Cancri and TT Hydrae are obtained, and analyses with incorporation of asynchronous rotation are carried out. A photometric rotation rate for the primary star of TT Hya is determined, and excellent agreement with results from spectral line profiles is found. Both separate light- and velocity-curve solutions and simultaneous light-velocity solutions are listed. The photometric rotation for S Cnc from existing light curves is indeterminate, but is compatible with line profile measures. Evidence for third light from the light curves of S Cnc is found. An explanation for the apparent conflict between the rotational states and mass-transfer activities of the two binaries is suggested.

Light Yield Measurements of Heavy Photon Search (HPS) Muon Scintillator Hodoscopes

NASA Astrophysics Data System (ADS)

Skolnik, Marianne; Stepanyan, Stepan

2013-10-01

The HPS is an experiment that will search for new heavy vector boson(s) in the mass range of 20 MeV/c2 to 1000 MeV/c2. One of the detectors used for this experiment is a muon hodoscope. We are interested in finding the light yield for the scintillator - wavelength-shifting fiber coupling that will be used in this muon hodoscope. The muon hodoscope will have background signals distorting the data. In order to reduce the background, a threshold cut will be made on the signal coming from the photo-detector. Precision of this cut depends on the average number of photoelectrons, Npe. Previous tests have shown that Npe with Wavelength Shifting (WLS) fibers placed through the holes that go lengthwise down the scintillator is ~12/MeV. In this new muon hodoscope the scintillators will have WLS fibers glued inside the holes. The optical epoxy allows more light, changing Npe. To find Npe, two scintillators with fibers will be used, one of which will have glued WLS fibers. Light will be readout out using photo multiplier tubes (PMTs). The system of two scintillator-fiber-PMTs and one trigger PMT with a scintillator are placed in a dark box. First, position of a single photoelectron peaks is found using an LED light, then using the signal from cosmic muons from trigger PMT light yield is measured. Data are analyzed using ROOT macros. Result of this measurement suggests that light yield form glued fibers is higher than from WLS fibers without glue by a factor of ~1.7, which is sufficient for operation of the HPS muon hodoscope.

Development of a New Class of Scintillating Fibres with Very Short Decay Time and High Light Yield

NASA Astrophysics Data System (ADS)

Borshchev, O.; Cavalcante, A. B. R.; Gavardi, L.; Gruber, L.; Joram, C.; Ponomarenko, S.; Shinji, O.; Surin, N.

2017-05-01

We present first studies of a new class of scintillating fibres which are characterised by very short decay times and high light yield. The fibres are based on a novel type of luminophores admixed to a polystyrene core matrix. These so-called Nanostructured Organosilicon Luminophores (NOL) have high photoluminescense quantum yield and decay times just above 1 ns. A blue and a green emitting prototype fibre with 250 μm diameter were produced and characterised in terms of attenuation length, ionisation light yield, decay time and tolerance to x-ray irradiation. The well-established Kuraray SCSF-78 and SCSF-3HF fibres were taken as references. Even though the two prototype fibres mark just an intermediate step in an ongoing development, their performance is already on a competitive level. In particular, their decay time constants are about a factor of two shorter than the fastest known fibres, which makes them promising candidates for time critical applications.

Measurement of light and charge yield of low-energy electronic recoils in liquid xenon

NASA Astrophysics Data System (ADS)

Goetzke, L. W.; Aprile, E.; Anthony, M.; Plante, G.; Weber, M.

2017-11-01

The dependence of the light and charge yield of liquid xenon on the applied electric field and recoil energy is important for dark matter detectors using liquid xenon time projections chambers. Few measurements have been made of this field dependence at recoil energies less than 10 keV. In this paper, we present results of such measurements using a specialized detector. Recoil energies are determined via the Compton coincidence technique at four drift fields relevant for liquid xenon dark matter detectors: 0.19, 0.48, 1.02, and 2.32 kV /cm . Mean recoil energies down to 1 keV were measured with unprecedented precision. We find that the charge and light yield are anticorrelated above ˜3 keV and that the field dependence becomes negligible below ˜6 keV . However, below 3 keV, we find a charge yield significantly higher than expectation and a reconstructed energy deviating from linearity.

Thulium-170-labeled microparticles for local radiotherapy: preliminary studies.

PubMed

Polyak, Andras; Das, Tapas; Chakraborty, Sudipta; Kiraly, Reka; Dabasi, Gabriella; Joba, Robert Peter; Jakab, Csaba; Thuroczy, Julianna; Postenyi, Zita; Haasz, Veronika; Janoki, Gergely; Janoki, Gyozo A; Pillai, Maroor R A; Balogh, Lajos

2014-10-01

The present article describes the preparation, characterization, and biological evaluation of Thulium-170 ((170)Tm) [T1/2 = 128.4 days; Eβmax = 968 keV; Eγ = 84 keV (3.26%)] labeled tin oxide microparticles for its possible use in radiation synovectomy (RSV) of medium-sized joints. (170)Tm was produced by irradiation of natural thulium oxide target. 170Tm-labeled microparticles were synthesized with high yield and radionuclidic purity (> 99%) along with excellent in vitro stability by following a simple process. Particle sizes and morphology of the radiolabeled particles were examined by light microscope, dynamic light scattering, and transmission electron microscope and found to be of stable spherical morphology within the range of 1.4-3.2 μm. The preparation was injected into the knee joints of healthy Beagle dogs intraarticularly for biological studies. Serial whole-body and regional images were taken by single-photon-emission computed tomography (SPECT) and SPECT-CT cameras up to 9 months postadministration, which showed very low leakage (< 8% of I.D.) of the instilled particles. The majority of leaked radiocolloid particles were found in inguinal lymph nodes during the 9 months of follow-up. All the animals tolerated the treatment well; the compound did not show any possible radiotoxicological effect. These preliminary studies showed that 170Tm-labeled microparticles could be a promising nontoxic and effective radiopharmaceutical for RSV applications or later local antitumor therapy.

Bioaggregate of photo-fermentative bacteria for enhancing continuous hydrogen production in a sequencing batch photobioreactor

NASA Astrophysics Data System (ADS)

Xie, Guo-Jun; Liu, Bing-Feng; Wang, Rui-Qing; Ding, Jie; Ren, Hong-Yu; Zhou, Xu; Ren, Nan-Qi

2015-11-01

Hydrogen recovery through solar-driven biomass conversion by photo-fermentative bacteria (PFB) has been regarded as a promising way for sustainable energy production. However, a considerable fraction of organic substrate was consumed for the growth of PFB as biocatalysts, furthermore, these PFB were continuously washed out from the photobioreactor in continuous operation because of their poor flocculation. In this work, PFB bioaggregate induced by L-cysteine was applied in a sequencing batch photobioreactor to enhance continuous hydrogen production and reduce biomass washout. The effects of the hydraulic retention time (HRT), influent concentration and light intensity on hydrogen production of the photobioreactor were investigated. The maximum hydrogen yield (3.35 mol H2/mol acetate) and production rate (1044 ml/l/d) were obtained at the HRT of 96 h, influent concentration of 3.84 g COD/l, and light intensity of 200 W/m2. With excellent settling ability, biomass accumulated in the photobioreactor and reached 2.15 g/l under the optimum conditions. Structural analysis of bioaggregate showed that bacterial cells were covered and tightly linked together by extracellular polymeric substances, and formed a stable structure. Therefore, PFB bioaggregate induced by L-cysteine is an efficient strategy to improve biomass retention capacity of the photobioreactor and enhance hydrogen recovery efficiency from organic wastes.

In vivo 808 nm image-guided photodynamic therapy based on an upconversion theranostic nanoplatform.

PubMed

Liu, Xiaomin; Que, Ivo; Kong, Xianggui; Zhang, Youlin; Tu, Langping; Chang, Yulei; Wang, Tong Tong; Chan, Alan; Löwik, Clemens W G M; Zhang, Hong

2015-09-28

A new strategy for efficient in vivo image-guided photodynamic therapy (PDT) has been demonstrated utilizing a ligand-exchange constructed upconversion-C60 nanophotosensitizer. This theranostic platform is superior to the currently reported nanophotosensitizers in (i) directly bonding photosensitizer C60 to the surface of upconversion nanoparticles (UCNPs) by a smart ligand-exchange strategy, which greatly shortened the energy transfer distance and enhanced the (1)O2 production, resulting in the improvement of the therapeutic effect; (ii) realizing in vivo NIR 808 nm image-guided PDT with both excitation (980 nm) and emission (808 nm) light falling in the biological window of tissues, which minimized auto-fluorescence, reduced light scatting and improved the imaging contrast and depth, and thus guaranteed noninvasive diagnostic accuracy. In vivo and ex vivo tests demonstrated its favorable bio-distribution, tumor-selectivity and high therapeutic efficacy. Owing to the effective ligand exchange strategy and the excellent intrinsic photophysical properties of C60, (1)O2 production yield was improved, suggesting that a low 980 nm irradiation dosage (351 J cm(-2)) and a short treatment time (15 min) were sufficient to perform NIR (980 nm) to NIR (808 nm) image-guided PDT. Our work enriches the understanding of UCNP-based PDT nanophotosensitizers and highlights their potential use in future NIR image-guided noninvasive deep cancer therapy.

Photo reduction of CO2 to CH4 on g-C3N4: The effect of concentrating light and pretreatment

NASA Astrophysics Data System (ADS)

Li, Dong; Fang, Xiaoxiang; Liu, Huayan; Lu, Hanfeng; Zhang, Zekai

2018-06-01

The behavior of CO2 photoreduction to CH4 on the g-C3N4 catalyst was studied in a concentrating light reactor. The g-C3N4 catalysts before and after pretreatment were characterized by FE-SEM, XRD and photoilluminance. It is found that concentrating light increases the CH4 yield on the g-C3N4 by heightening the incident light intensity, and light pretreatment has an excessive effect on the performance. Pretreated by suitable light intensity, air atmosphere and time, the CH4 yield on the g-C3N4 under concentrating light irradiation reached about 3.39 μmol.g-1.h-1, which is about 16 times of that g-C3N4 reacted at nature incident light without pretreatment. The mechanism of pretreatment is considered to be from the surface oxidation state change of the catalyst either from the oxidation of the catalyst surface or the activation of surface oxygen.

Photosynthetic limitation as a factor influencing yield in highbush blueberries (Vaccinium corymbosum) grown in a northern European environment.

PubMed

Petridis, Antonios; van der Kaay, Jeroen; Chrysanthou, Elina; McCallum, Susan; Graham, Julie; Hancock, Robert D

2018-05-25

Published evidence indicates that nearly 60% of blueberry-producing countries experience yield instability. Yield is a complex trait determined by genetic and environmental factors. Here, using physiological and biochemical approaches, we tested the hypothesis that yield instability results from year-to-year environmental variation that limits carbon assimilation, storage and partitioning. The data indicate that fruit development depends primarily on the daily production of non-structural carbohydrates by leaves, and there is no accumulation of a starch buffer to allow continuous ripening under conditions limiting for photosynthesis. Photosynthesis was saturated at moderate light irradiance and this was mainly due to stomatal and biochemical limitations. In a dynamic light environment, photosynthesis was further limited by slow stomatal response to increasing light. Finally, labelling with 13CO2 at specific stages of fruit development revealed a relatively even distribution of newly assimilated carbon between stems, roots and fruits, suggesting that the fruit is not a strong sink. We conclude that a significant component of yield variability results from limitations in photosynthetic efficiency that are compounded by an inability to accumulate starch reserves in blueberry storage tissues in a typical northern European environment. This work informs techniques for improving agronomic management and indicates key traits required for yield stability in such environments.

Photosynthetic limitation as a factor influencing yield in highbush blueberries (Vaccinium corymbosum) grown in a northern European environment

PubMed Central

van der Kaay, Jeroen; Chrysanthou, Elina; McCallum, Susan

2018-01-01

Abstract Published evidence indicates that nearly 60% of blueberry-producing countries experience yield instability. Yield is a complex trait determined by genetic and environmental factors. Here, using physiological and biochemical approaches, we tested the hypothesis that yield instability results from year-to-year environmental variation that limits carbon assimilation, storage and partitioning. The data indicate that fruit development depends primarily on the daily production of non-structural carbohydrates by leaves, and there is no accumulation of a starch buffer to allow continuous ripening under conditions limiting for photosynthesis. Photosynthesis was saturated at moderate light irradiance and this was mainly due to stomatal and biochemical limitations. In a dynamic light environment, photosynthesis was further limited by slow stomatal response to increasing light. Finally, labelling with 13CO2 at specific stages of fruit development revealed a relatively even distribution of newly assimilated carbon between stems, roots and fruits, suggesting that the fruit is not a strong sink. We conclude that a significant component of yield variability results from limitations in photosynthetic efficiency that are compounded by an inability to accumulate starch reserves in blueberry storage tissues in a typical northern European environment. This work informs techniques for improving agronomic management and indicates key traits required for yield stability in such environments. PMID:29590429

{lambda}{sub b}{yields}p, {lambda} transition form factors from QCD light-cone sum rules

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

Wang Yuming; Lue Caidian; Shen Yuelong

2009-10-01

Light-cone sum rules for the {lambda}{sub b}{yields}p, {lambda} transition form factors are derived from the correlation functions expanded by the twist of the distribution amplitudes of the {lambda}{sub b} baryon. In terms of the {lambda}{sub b} three-quark distribution amplitude models constrained by the QCD theory, we calculate the form factors at small momentum transfers and compare the results with those estimated in the conventional light-cone sum rules (LCSR) and perturbative QCD approaches. Our results indicate that the two different versions of sum rules can lead to the consistent numbers of form factors responsible for {lambda}{sub b}{yields}p transition. The {lambda}{sub b}{yields}{lambda}more » transition form factors from LCSR with the asymptotic {lambda} baryon distribution amplitudes are found to be almost 1 order larger than those obtained in the {lambda}{sub b}-baryon LCSR, implying that the preasymptotic corrections to the baryonic distribution amplitudes are of great importance. Moreover, the SU(3) symmetry breaking effects between the form factors f{sub 1}{sup {lambda}{sub b}}{sup {yields}}{sup p} and f{sub 1}{sup {lambda}{sub b}}{sup {yields}}{sup {lambda}} are computed as 28{sub -8}{sup +14}% in the framework of {lambda}{sub b}-baryon LCSR.« less

Effect of light intensity adjusted for species-specific spectral sensitivity on live performance and processing yield of male broiler chickens

USDA-ARS?s Scientific Manuscript database

Adoption of alternative lighting systems to replace traditional incandescent light sources offers the opportunity to tailor lighting systems according to spectral sensitivity needs of different species. Providing a lighting environment that accounts for poultry vision may improve bird welfare and p...

Excellent photocatalytic performance under visible-light irradiation of ZnS/rGO nanocomposites synthesized by a green method

NASA Astrophysics Data System (ADS)

Azimi, Hassan Rayat; Ghoranneviss, Mahmood; Elahi, Seyed Mohammad; Mahmoudian, Mohammad Reza; Jamali-Sheini, Farid; Yousefi, Ramin

2016-12-01

ZnS/graphene nanocomposites with different graphene concentrations (5, 10 and 15 wt.%) were synthesized using L-cysteine as surfactant and graphene oxide (GO) powders as graphene source. Excellent performance for nanocomposites to remove methylene blue (MB) dye and hexavalent chromium (Cr(VI)) under visible-light illumination was revealed. TEM images showed that ZnS NPs were decorated on GO sheets and the GO caused a significant decrease in the ZnS diameter size. XRD patterns, XPS and FTIR spectroscopy results indicated that GO sheets changed into reduced graphene oxide (rGO) during the synthesis process. Photocurrent measurements under a visiblelight source indicated a good chemical reaction between ZnS NPs and rGO sheets.

Interface-Located Photothermoelectric Effect of Organic Thermoelectric Materials in Enabling NIR Detection.

PubMed

Huang, Dazhen; Zou, Ye; Jiao, Fei; Zhang, Fengjiao; Zang, Yaping; Di, Chong-an; Xu, Wei; Zhu, Daoben

2015-05-06

Organic photothermoelectric (PTE) materials are promising candidates for various photodetection applications. Herein, we report on poly[Cux(Cu-ett)]:PVDF, which is an excellent polymeric thermoelectric composite, possesses unprecedented PTE properties. The NIR light irradiation on the poly[Cu(x)(Cu-ett)]:PVDF film could induce obvious enhancement in Seebeck coefficient from 52 ± 1.5 to 79 ± 5.0 μV/K. By taking advantage of prominent photothermoelectric effect of poly[Cu(x)(Cu-ett)]:PVDF, an unprecedented voltage of 12 mV was obtained. This excellent performance enables its promising applications in electricity generation from solar energy and NIR detection to a wide range of light intensities ranging from 1.7 mW/cm(2) to 17 W/cm(2).

[Optical and spectral parameters in Ce3+ -doped gadolinium gallium aluminum garnet glass-ceramics].

PubMed

Gong, Hua; Zhao, Xin; Yu, Xiao-bo; Setsuhisa, Tanabe; Lin, Hai

2010-01-01

The crystalline phases of Ce3+ -doped gadolinium gallium aluminum garnet (GGAG) glass-ceramics were investigated by X-ray diffraction, and the fluorescence spectra were recorded under the pumping of blue light-emitting diode (LED) using an integrating sphere of 10-inch in diameter, which connected to a CCD detector. The spectral power distribution of the glass-ceramics was obtained from the measured spectra first, and then the quantum yield was derived based on the photon distribution. The quantum yield of Ce3+ emission in GGAG glass-ceramics is 29.2%, meanwhile, the color coordinates and the correlated color temperature (CCT) of combined white light were proved to be x = 0.319, y = 0.349 and 6086 K, respectively. Although the quantum yield is a little smaller than the value in Ce3+ -doped YAG glass-ceramics, the CCT of the combined white light is much smaller than that in the latter. The optical behavior of GGAG glass-ceramics provides new vision for developing comfortable LED lighting devices.

[Effects of plastic film mulching and rain harvesting modes on chlorophyll fluorescence characteristics, yield and water use efficiency of dryland maize].

PubMed

Li, Shang-Zhong; Fan, Ting-Lu; Wang, Yong; Zhao, Gang; Wang, Lei; Tang, Xiao-Ming; Dang, Yi; Zhao, Hui

2014-02-01

The differences on chlorophyll fluorescence parameters, yield and water use efficiency of dryland maize were compared among full plastic film mulching on double ridges and planting in catchment furrows (FFDRF), half plastic film mulching on double ridges and planting in catchment furrows (HFDRF), plastic film mulching on ridge and planting in film-side (FS), and flat planting with no plastic film mulching (NM) under field conditions in dry highland of Loess Plateau in 2007-2012. The results showed that fluorescence yield (Fo), the maximum fluorescence yield (Fm), light-adapted fluorescence yield when PS II reaction centers were totally open (F), light-adapted fluorescence yield when PS II reaction centers closed (Fm'), the maximal photochemical efficiency of PS II (Fv/Fm), the actual photochemical efficiency of PS II in the light (Phi PS II), the relative electron transport rate (ETR), photochemical quenching (qP) and non-photochemical quenching (qN) in maize leaves of FFDRF were higher than that of control (NM), and the value of 1-qP was lower than that of control, at 13:00, chlorophyll fluorescence parameters values of FFDRF was significantly higher than control, which were increased by 5.3%, 56.8%, 10.7%, 36.3%, 23.6%, 56.7%, 64.4%, 45.5%, 23.6% and -55.6%, respectively, compared with the control. Yield and water use efficiency of FFDRF were the highest in every year no matter dry year, normal year, humid year and hail disaster year. Average yield and water use efficiency of FFDRF were 12,650 kg x hm(-2) and 40.4 kg x mm(-1) x hm(-2) during 2007-2012, increased by 57.8% and 61.6% compared with the control, respectively, and also significantly higher compared with HFDRF and PS. Therefore, it was concluded that FFDRF had significantly increased the efficiency of light energy conversion and improved the production capacity of dryland maize.

Light harvesting control in plants.

PubMed

Ruban, Alexander V

2018-05-23

In 1991, my colleagues and I published a hypothesis article that proposed a mechanism that controls light harvesting in plants and protects them against photodamage. The major light harvesting complex, LHCII, was suggested to undergo aggregation upon exposure of the plant to damaging levels of light. Aggregated LHCII was found to be much less efficient in light harvesting, as it promptly dissipated absorbed energy into heat, possessing a very low chlorophyll fluorescence yield. Non-photochemical quenching (NPQ) is a term coined to describe this reduction in chlorophyll fluorescence yield. This article is a story of how the hypothesis that LHCII aggregation is involved in NPQ is developed into a model that is now becoming broadly accepted by the research community. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Weight and volume yields from thinning two oak-hickory stands

Treesearch

E. Paul Craft; John E. Baumgras

1979-01-01

Two sample plots in oak-hickory stands of poletimber-small sawtimber were thinned to determine product yields from thinnings. One stand received a light thinning; the other was heavily thinned. Light thinning reduced basal area from 120 ft² to 84 ft² per acre and removed 22 tons of roundwopd per acre, including 2,543 board feet of sawed products and 7...

Optical Microfiber Technology for Current, Temperature, Acceleration, Acoustic, Humidity and Ultraviolet Light Sensing

PubMed Central

Lancaster, David G.; Monro, Tanya M.

2017-01-01

Optical microfibers possess excellent optical and mechanical properties that have been exploited for sensing. We highlight the authors’ recent work in the areas of current, temperature, acceleration, acoustic, humidity and ultraviolet-light sensing based on this exquisite technology, and the advantages and challenges of using optical microfibers are discussed. PMID:29283414

CALiPER Special Summary Report: Retail Replacement Lamp Testing

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

None

2011-04-01

CALiPER testing has evaluated many products for commercial lighting markets and found some excellent performers. However, many of these are not available on the retail market. This special testing was undertaken to identify and test solid-state lighting (SSL) replacement lamp products that are available to the general public through retail stores and websites.

Synthesis and visible light photoactivity of anatase Ag, and garlic loaded TiO2 nanocrystalline catalyst

EPA Science Inventory

An excellent visible light activated Ag and S doped TiO2 nanocatalyst was prepared by using AgNO3 and garlic (Allium sativum) as Ag+ and sulfur sources, respectively. The catalyst resisted the change from anatase to rutile phase even at calcination at 700 oC. The photocatalytic e...

Parasitic light scattered by complex optical coatings: modelization and metrology

NASA Astrophysics Data System (ADS)

Zerrad, Myriam; Lequime, Michel; Liukaityte, Simona; Amra, Claude

2017-12-01

Optical components realized for space applications have to be mastered in term of parasitic light. This paper present the last improvements performed at the Institute Fresnel to predict and measure scattering losses of optical components with a special care to complex optical coatings. Agreement between numerical models and metrology is now excellent. Some examples will be presented.

Lithium Alkaline Halides—Next Generation of Dual Mode Scintillators

NASA Astrophysics Data System (ADS)

Soundara-Pandian, L.; Hawrami, R.; Glodo, J.; Ariesanti, E.; van Loef, E. V.; Shah, K.

2016-04-01

We report on a new family of scintillators - Lithium alkaline halides, developed based on the alkaline halides by introducing lithium for dual mode gamma-neutron detection. Many different compositions were grown, among which LiSr2I5 (LSI), LiCa2I5 (LCI), LiSr2Br5 (LSB) activated with divalent Europium show good gamma and neutron detection properties. LSI shows the main emission at 497 nm under X-ray excitation. It also shows good proportionality, which in combination with the light yield as high as 60000 photons/MeV, results in an energy resolution of 3.5% at 662 keV. The electron or gamma equivalent energy (GEE) of the thermal neutron peak due to the 6Li neutron capture is 4.1 MeV, which amounts to a very high neutron light yield of 245000 photons. The decay times for neutrons are faster compared to that for gamma-rays, hence we achieved good pulse shape discrimination (PSD) between gamma and neutron events. Our initial studies on the effects of Eu concentration on the properties of LSI show that 3%-4% Eu concentration is optimal for the best performance in terms of gamma and neutron light yields and pulse shape discrimination. LCI shows the main emission at 475 nm under X-ray excitation and a very high gamma light yield of 90000 photons/MeV. The measured energy resolution is 6% at 662 keV. The electron equivalent energy for neutron detection has been measured to be around 3 MeV, which gives a neutron light yield of 270 000 photons. The measured decay times for neutrons are faster compared to gamma decays and the PSD between the gamma-rays and neutrons is not as good as LSI. LSB shows two emissions at 410 and 475 nm under X-ray excitation. The measured light yield is 32000 ph/MeV gamma-ray with an energy resolution of 6% at 662 keV. The electron equivalent energy of the 6Li capture peak was measured to be 3.3 MeV.

Direct catalytic asymmetric alpha-amination of aldehydes.

PubMed

List, Benjamin

2002-05-22

The first direct catalytic asymmetric alpha-amination of aldehydes is described herein. alpha-Unbranched aldehydes react in this novel proline-catalyzed reaction with dialkyl azodicarboxylates to give alpha-amino aldehydes in excellent yields and enantioselectivities.

Lanthanum Tricyanide-Catalyzed Acyl Silane-Ketone Benzoin Additions

PubMed Central

Tarr, James C.; Johnson, Jeffrey S.

2009-01-01

Lanthanum tricyanide efficiently catalyzes a benzoin-type coupling between acyl silanes and ketones. Yields range from moderate to excellent over a broad substrate scope encompassing aryl, alkyl, electron-rich, and sterically hindered ketones. PMID:19655731

N-Triflylthiophosphoramide Catalyzed Enantioselective Mukaiyama Aldol Reaction of Aldehydes with Silyl Enol Ethers of Ketones

PubMed Central

Cheon, Cheol Hong; Yamamoto, Hisashi

2010-01-01

The first Brønsted acid catalyzed asymmetric Mukaiyama aldol reaction of aldehydes using silyl enol ethers of ketones as nucleophiles has been reported. A variety of aldehydes and silyl enol ethers of ketones afforded the aldol products in excellent yields and good to excellent enantioselectivities. Mechanistic studies revealed that the actual catalyst may be changed from the silylated Brønsted acid to Brønsted acid itself depending on the reaction temperature. PMID:20465277

N-triflylthiophosphoramide catalyzed enantioselective Mukaiyama aldol reaction of aldehydes with silyl enol ethers of ketones.

PubMed

Cheon, Cheol Hong; Yamamoto, Hisashi

2010-06-04

The first Brønsted acid catalyzed asymmetric Mukaiyama aldol reaction of aldehydes using silyl enol ethers of ketones as nucleophiles has been reported. A variety of aldehydes and silyl enol ethers of ketones afforded the aldol products in excellent yields and good to excellent enantioselectivities. Mechanistic studies revealed that the actual catalyst may be changed from the silylated Brønsted acid to the Brønsted acid itself depending on the reaction temperature.

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

Yan, Minyan; Shen, Yi, E-mail: shenyiemail@163.com; Zhao, Li

Graphical abstract: The MoO{sub 3} powder, which exhibits highly dispersed floral aggregated-like structure built up by superimposed and staggered nanoflakes with a diameter of 1-1.5 {mu}m and a thickness of 0.1-0.2 {mu}m, has been successfully obtained when the molar ratio of EDTA/Mo{sup 6+} is 0.05:1. The EDTA inducer obviously enlarges the surface area and apparently enhances the reactivity of MoO{sub 3} powders, making it show greater absorptive capacity to the excitation light and better photochromic properties than the pure MoO{sub 3} powder. Highlights: {yields} EDTA as organic inducing agent. {yields} EDTA inducer at EDTA/Mo{sup 6+} molar ratio of 0.05:1 enablesmore » growth of flower-like microspheres. {yields} The formation of flower-like MoO{sub 3} makes its photochromic properties strongly enhanced. -- Abstract: In this study, the photochromic MoO{sub 3} powder with novel morphology has been synthesized via hydrothermal method, using ethylene diamine tetraacetice acid (EDTA) as organic inducing agent. The influence of EDTA on the morphology, structure and photochromic properties of MoO{sub 3} powder has been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), as well as ultraviolet and visible spectroscopy (UV-vis) and color difference meter. When the molar ratio of EDTA/Mo{sup 6+} is 0.05:1, the EDTA-induced MoO{sub 3} powder is found to have 3D flower-like morphologies and excellent photochromic properties. Furthermore, the possible growth mechanism of the flower-like structure and the photochromic mechanism of MoO{sub 3} powder are also discussed in detail.« less

Lunisolar tidal force and its relationship to chlorophyll fluorescence in Arabidopsis thaliana.

PubMed

Fisahn, Joachim; Klingelé, Emile; Barlow, Peter

2015-01-01

The yield of chlorophyll fluorescence Ft was measured in leaves of Arabidopsis thaliana over periods of several days under conditions of continuous illumination (LL) without the application of saturating light pulses. After linearization of the time series of the chlorophyll fluorescence yield (ΔFt), oscillations became apparent with periodicities in the circatidal range. Alignments of these linearized time series ΔFt with the lunisolar tidal acceleration revealed high degrees of synchrony and phase congruence. Similar congruence with the lunisolar tide was obtained with the linearized quantum yield of PSII (ΔФII), recorded after application of saturating light pulses. These findings strongly suggest that there is an exogenous timekeeper which is a stimulus for the oscillations detected in both the linearized yield of chlorophyll fluorescence (ΔFt) and the linearized quantum yield of PSII (ΔФII).

Lunisolar tidal force and its relationship to chlorophyll fluorescence in Arabidopsis thaliana

PubMed Central

Fisahn, Joachim; Klingelé, Emile; Barlow, Peter

2015-01-01

The yield of chlorophyll fluorescence Ft was measured in leaves of Arabidopsis thaliana over periods of several days under conditions of continuous illumination (LL) without the application of saturating light pulses. After linearization of the time series of the chlorophyll fluorescence yield (ΔFt), oscillations became apparent with periodicities in the circatidal range. Alignments of these linearized time series ΔFt with the lunisolar tidal acceleration revealed high degrees of synchrony and phase congruence. Similar congruence with the lunisolar tide was obtained with the linearized quantum yield of PSII (ΔФII), recorded after application of saturating light pulses. These findings strongly suggest that there is an exogenous timekeeper which is a stimulus for the oscillations detected in both the linearized yield of chlorophyll fluorescence (ΔFt) and the linearized quantum yield of PSII (ΔФII). PMID:26376108

To enhance light extraction of OLED devices by multi-optic layers including a micro lens array

NASA Astrophysics Data System (ADS)

Chiu, Chuang-Hung; Chien, Chao-Heng; Kuo, Yu-Xaong; Lee, Jen-Chi

2014-10-01

In recent years, OLED has advantages including that larger light area, thinner thickness, excellent light uniformity, and can be as a flexible light source. Many display panel and lighting have been started to use the OLED due to OLED without back light system, thus how to make and employ light extracting layer could be important issue to enhance OLED brightness. The purpose of this study is to enhance the light extraction efficiency and light emitting area of OLED, so the micro lens array and the prism reflection layer were provided to enhance the surface light extracting efficiency of OLD. Finally the prism layer and diffusing layer were used to increase the uniformity of emitting area of OLED, which the efficiency of 31% increasing to compare with the OLED without light extracting film.

Effect of light on growth, intracellular and extracellular pigment production by five pigment-producing filamentous fungi in synthetic medium.

PubMed

Velmurugan, Palanivel; Lee, Yong Hoon; Venil, Chidambaram Kulandaisamy; Lakshmanaperumalsamy, Perumalsamy; Chae, Jong-Chan; Oh, Byung-Taek

2010-04-01

The competence of the living creatures to sense and respond to light is well known. The effect of darkness and different color light quality on biomass, extracellular and intracellular pigment yield of five potent pigment producers Monascus purpureus, Isaria farinosa, Emericella nidulans, Fusarium verticillioides and Penicillium purpurogenum, with different color shades such as red, pink, reddish brown and yellow, were investigated. Incubation in total darkness increased the biomass, extracellular and intracellular pigment production in all the fungi. Extracellular red pigment produced by M. purpureus resulted maximum in darkness 36.75 + or - 2.1 OD and minimum in white unscreened light 5.90 + or - 1.1 OD. Similarly, intracellular red pigment produced by M. purpureus resulted maximum in darkness 18.27 + or - 0.9 OD/g and minimum in yellow light 8.03 + or - 0.6 OD/g of substrate. The maximum biomass production was also noticed in darkness 2.51 g/L and minimum in yellow light 0.5 g/L of dry weight. In contrast, growth of fungi in green and yellow wavelengths resulted in low biomass and pigment yield. It was found that darkness, (red 780-622 nm, blue 492-455 nm) and white light influenced pigment and biomass yield. Copyright 2009 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

The dark side of marketing seemingly "Light" cigarettes: successful images and failed fact

PubMed Central

Pollay, R; Dewhirst, T

2002-01-01

Methods: Analysis of trade sources and internal US tobacco company documents now available on various web sites created by corporations, litigation, or public health bodies. Results: When introducing low yield products, cigarette manufacturers were concerned about maintaining products with acceptable taste/flavour and feared consumers might become weaned from smoking. Several tactics were employed by cigarette manufacturers, leading consumers to perceive filtered and low machine yield brands as safer relative to other brands. Tactics include using cosmetic (that is, ineffective) filters, loosening filters over time, using medicinal menthol, using high tech imagery, using virtuous brand names and descriptors, adding a virtuous variant to a brand's product line, and generating misleading data on tar and nicotine yields. Conclusions: Advertisements of filtered and low tar cigarettes were intended to reassure smokers concerned about the health risks of smoking, and to present the respective products as an alternative to quitting. Promotional efforts were successful in getting smokers to adopt filtered and low yield cigarette brands. Corporate documents demonstrate that cigarette manufacturers recognised the inherent deceptiveness of cigarette brands described as "Light"or "Ultra-Light" because of low machine measured yields. PMID:11893811

Development of transgenic crops based on photo-biotechnology.

PubMed

Ganesan, Markkandan; Lee, Hyo-Yeon; Kim, Jeong-Il; Song, Pill-Soon

2017-11-01

The phenotypes associated with plant photomorphogenesis such as the suppressed shade avoidance response and de-etiolation offer the potential for significant enhancement of crop yields. Of many light signal transducers and transcription factors involved in the photomorphogenic responses of plants, this review focuses on the transgenic overexpression of the photoreceptor genes at the uppermost stream of the signalling events, particularly phytochromes, crytochromes and phototropins as the transgenes for the genetic engineering of crops with improved harvest yields. In promoting the harvest yields of crops, the photoreceptors mediate the light regulation of photosynthetically important genes, and the improved yields often come with the tolerance to abiotic stresses such as drought, salinity and heavy metal ions. As a genetic engineering approach, the term photo-biotechnology has been coined to convey the idea that the greater the photosynthetic efficiency that crop plants can be engineered to possess, the stronger the resistance to biotic and abiotic stresses. Development of GM crops based on photoreceptor transgenes (mainly phytochromes, crytochromes and phototropins) is reviewed with the proposal of photo-biotechnology that the photoreceptors mediate the light regulation of photosynthetically important genes, and the improved yields often come with the added benefits of crops' tolerance to environmental stresses. © 2016 John Wiley & Sons Ltd.

Sweetpotato vine management for confined food production in a space life-support system

NASA Astrophysics Data System (ADS)

Massa, Gioia D.; Mitchell, Cary A.

2012-01-01

Sweetpotato (Ipomea batatas L.) 'Whatley-Loretan' was developed for space life support by researchers at Tuskegee University for its highly productive, nutritious storage roots. This promising candidate space life-support crop has a sprawling habit and aggressive growth rate in favorable environments that demands substantial growing area. Shoot pruning is not a viable option for vine control because removal of the main shoot apex drastically inhibits storage-root initiation and development, and chemical growth retardants typically are not cleared for use with food crops. As part of a large effort by the NASA Specialized Center of Research and Training in Advanced Life Support to reduce equivalent system mass (ESM) for food production in space, the dilemma of vine management for sweetpotato was addressed in effort to conserve growth area without compromising root yield. Root yields from unbranched vines trained spirally around wire frames configured either in the shapes of cones or cylinders were similar to those from vines trained horizontally along the bench, but occupying only a small fraction of the bench area. This finding indicates that sweetpotato is highly adaptable to a variety of vine-training architectures. Planting a second plant in the growth container and training the two vines in opposite directions around frames enhanced root yield and number, but had little effect on average length of each vine or bench area occupied. Once again, root yields were similar for both configurations of wire support frames. The 3-4-month crop-production cycles for sweetpotato in the greenhouse spanned all seasons of multiple years during the course of the study, and although electric lighting was used for photoperiod control and to supplement photosynthetic light during low-light seasons, there still were differences in total light available across seasons. Light variations and other environmental differences among experiments in the greenhouse had more effects on vine length than on root yield. Average vine length correlated positively with total hours of daylight received across seasons, and responses for one plant per container were higher above a threshold duration of solar exposure, suggesting that the vines of two plants per container compete for available light. In addition to the adaptability of sweetpotato to various vine-training architectures and across seasons in terms of maintaining root productivity, the open, interior volumes of the support frames tested in this study will provide future opportunity to enhance sweetpotato root yield in space by adding novel interior lighting, such as from intracanopy arrays of light-emitting diodes. This work was sponsored by NASA grant NAG 5 1286.

Measurement of the Rate of Stellar Tidal Disruption Flares

NASA Astrophysics Data System (ADS)

van Velzen, Sjoert; Farrar, Glennys R.

2014-09-01

We report an observational estimate of the rate of stellar tidal disruption flares (TDFs) in inactive galaxies based on a successful search for these events among transients in galaxies using archival Sloan Digital Sky Survey (SDSS) multi-epoch imaging data (Stripe 82). This search yielded 186 nuclear flares in galaxies, 2 of which are excellent TDF candidates. Because of the systematic nature of the search, the very large number of galaxies, the long time of observation, and the fact that non-TDFs were excluded without resorting to assumptions about TDF characteristics, this study provides an unparalleled opportunity to measure the TDF rate. To compute the rate of optical stellar tidal disruption events, we simulate our entire pipeline to obtain the efficiency of detection. The rate depends on the light curves of TDFs, which are presently still poorly constrained. Using only the observed part of the SDSS light curves gives a model-independent upper limit to the optical TDF rate, \\dot{N}<2\\times 10^{-4}\\,yr^{-1}\\,galaxy^{-1} (90% CL), under the assumption that the SDSS TDFs are representative examples. We develop three empirical models of the light curves based on the two SDSS light curves and two more recent and better-sampled Pan-STARRS TDF light curves, leading to our best estimate of the rate: \\dot{N}_TDF = (1.5{--}2.0)_{-1.3}^{+2.7} \\times 10^{-5} \\,yr^{-1}\\, galaxy^{-1}. We explore the modeling uncertainties by considering two theoretically motivated light curve models, as well as two different relationships between black hole mass and galaxy luminosity, and two different treatments of the cutoff in the visibility of TDFs at large M BH. From this we conclude that these sources of uncertainty are not significantly larger than the statistical ones. Our results are applicable for galaxies hosting black holes with mass in the range of a few 106-108 M ⊙, and translates to a volumetric TDF rate of (4-8) × 10-8 ± 0.4 yr-1 Mpc-3, with the statistical uncertainty in the exponent.

Non-contact pumping of light emitters via non-radiative energy transfer

DOEpatents

Klimov, Victor I.; Achermann, Marc

2010-01-05

A light emitting device is disclosed including a primary light source having a defined emission photon energy output, and, a light emitting material situated near to said primary light source, said light emitting material having an absorption onset equal to or less in photon energy than the emission photon energy output of the primary light source whereby non-radiative energy transfer from said primary light source to said light emitting material can occur yielding light emission from said light emitting material.

Photoenhanced degradation of veratraldehyde upon the heterogeneous ozone reactions.

PubMed

Net, Sopheak; Gligorovski, Sasho; Pietri, Sylvia; Wortham, Henri

2010-07-21

Light-induced heterogeneous reactions between gas-phase ozone and veratraldehyde adsorbed on silica particles were performed. At an ozone mixing ratio of 250 ppb, the loss of veratraldehyde largely increased from 1.81 x 10(-6) s(-1) in the dark to 2.54 x 10(-5) s(-1) upon exposure to simulated sunlight (lambda > 300 nm). The observed rates of degradation exhibited linear dependence with the ozone in the dark ozonolysis experiments which change in the non-linear Langmuir-Hinshelwood dependence in the experiments with simultaneous ozone and light exposure of the coated particles. When the coated silica particles were exposed only to simulated sunlight in absence of ozone the loss of veratraldehyde was about three times higher i.e. 5.97 x 10(-6) s(-1) in comparison to the ozonolysis experiment under dark conditions at 250 ppb ozone mixing ratio, 1.81 x 10(-6) s(-1).These results clearly show that the most important loss of veratraldehyde occurs under simultaneous ozone and light exposure of the coated silica particles. The main identified product in the heterogeneous reactions between gaseous ozone and adsorbed veratraldehyde under dark conditions and in presence of light was veratric acid.Carbon yields of veratric acid were calculated and the obtained results indicated that at low ozone mixing ratio (250 ppb) the carbon yield obtained under dark conditions is 70% whereas the carbon yield obtained in the experiments with simultaneous ozone and light exposure of the coated particles is 40%. In both cases the carbon yield of veratric acid exponentially decayed leading to the plateau ( approximately 35% of carbon yield) at an ozone mixing ratio of 6 ppm. Two reaction products i.e. 3-hydroxy-4-methoxybenzoic acid and 4-hydroxy-3-methoxybenzoic acid were identified (confirmed with the standards) only in the experiments performed under simultaneous ozonolysis and light irradiation of the particles.

A Facile Preparation of Imidazolinium Chlorides

PubMed Central

Kuhn, Kevin M.; Grubbs, Robert H.

2009-01-01

A process for the preparation of symmetric and unsymmetric imidazolinium chlorides that involves reaction of a formamidine with dichloroethane and a base (a) is described. This method makes it possible to obtain numerous imidazolinium chlorides under solvent-free reaction conditions and in excellent yields with purification by simple filtration. Alternatively, symmetric imidazolinium chlorides can be prepared directly in moderate yields from substituted anilines by utilizing half of the formamidine intermediate as sacrificial base (b). PMID:18412354

Yielding and flow of colloidal glasses.

PubMed

Petekidis, Georgios; Vlassopoulos, Dimitris; Pusey, Peter N

2003-01-01

We investigate the yielding and flow of hard-sphere colloidal glasses by combining rheological measurements with the technique of light scattering echo. The polymethylmethacrylate particles used are sufficiently polydisperse that crystallization is suppressed. Creep and recovery measurements show that the glasses can tolerate surprisingly large strains, up to at least 15%, before yielding irreversibly. We attribute this behaviour to 'cage elasticity', the ability of a particle and its cage of neighbours to retain their identity under quite large distortion. Results from light scattering echo, which measures the extent of irreversible particle rearrangement under oscillatory shear, support the notion of cage elasticity. In the lower concentration glasses we find that particle trajectories are partly reversible under strains which significantly exceed the yield strain.

Nitromethane with IBX/TBAF as a nitrosating agent: synthesis of nitrosamines from secondary or tertiary amines under mild conditions.

PubMed

Potturi, Hima K; Gurung, Ras K; Hou, Yuqing

2012-01-06

Aliphatic or aromatic N,N-disubstituted nitrosamine was generated in fair to excellent yield from the reaction of a secondary or tertiary amine with o-iodoxybenzoic acid (IBX) or o-iodosylbenzoic acid (IBA)/R(4)NX (X = halide) and nitromethane. The product yield was strongly influenced by both the halide of R(4)NX and iodanes. IBX gave a higher yield than IBA, while the halides follow F(-) > Cl(-) > Br(-) ∼ I(-). Nitrous acid formed in situ from nitromethane and IBX (or IBA)/halides is likely responsible for the observed reaction.

Positive hysteresis of Ce-doped GAGG scintillator

NASA Astrophysics Data System (ADS)

Yanagida, Takayuki; Fujimoto, Yutaka; Koshimizu, Masanori; Watanabe, Kenichi; Sato, Hiroki; Yagi, Hideki; Yanagitani, Takagimi

2014-10-01

Positive hysteresis and radiation tolerance to high-dose radiation exposure were investigated for Ce 1% and 3% doped Gd3(Al, Ga)5O12 (Ce:GAGG) crystal scintillator on comparison with other garnet scintillators such Ce:YAG, Ce:LuAG, Pr:LuAG, and ceramic Ce:GAGG. When they were irradiated by several Gy 60Co γ-rays, Ce 1% doped GAGG crystal exhibited ∼20% light yield enhancement (positive hysteresis). This is the first time to observe positive hysteresis in Ce doped GAGG. On the other hand, other garnet materials did not show the positive hysteresis and their light yields were stable after 800 Gy irradiation except Pr:LuAG. The light yield of Pr:LuAG decreased largely. When irradiated Ce:GAGG which showed positive hysteresis was evaluated in Synchrotron facility (UVSOR), new excitation band was created around 60 nm.

Singlet oxygen production by combining erythrosine and halogen light for photodynamic inactivation of Streptococcus mutans.

PubMed

Fracalossi, Camila; Nagata, Juliana Yuri; Pellosi, Diogo Silva; Terada, Raquel Sano Suga; Hioka, Noboru; Baesso, Mauro Luciano; Sato, Francielle; Rosalen, Pedro Luiz; Caetano, Wilker; Fujimaki, Mitsue

2016-09-01

Photodynamic inactivation of microorganisms is based on a photosensitizing substance which, in the presence of light and molecular oxygen, produces singlet oxygen, a toxic agent to microorganisms and tumor cells. This study aimed to evaluate singlet oxygen quantum yield of erythrosine solutions illuminated with a halogen light source in comparison to a LED array (control), and the photodynamic effect of erythrosine dye in association with the halogen light source on Streptococcus mutans. Singlet oxygen quantum yield of erythrosine solutions was quantified using uric acid as a chemical-probe in an aqueous solution. The in vitro effect of the photodynamic antimicrobial activity of erythrosine in association with the halogen photopolimerizing light on Streptococcus mutans (UA 159) was assessed during one minute. Bacterial cultures treated with erythrosine alone served as negative control. Singlet oxygen with 24% and 2.8% degradation of uric acid in one minute and a quantum yield of 0.59 and 0.63 was obtained for the erythrosine samples illuminated with the halogen light and the LED array, respectively. The bacterial cultures with erythrosine illuminated with the halogen light presented a decreased number of CFU mL(-1) in comparison with the negative control, with minimal inhibitory concentrations between 0.312 and 0.156mgmL(-1). The photodynamic response of erythrosine induced by the halogen light was capable of killing S. mutans. Clinical trials should be conducted to better ascertain the use of erythrosine in association with halogen light source for the treatment of dental caries. Copyright © 2016 Elsevier B.V. All rights reserved.

Measuring the absolute deuterium-tritium neutron yield using the magnetic recoil spectrometer at OMEGA and the NIF.

PubMed

Casey, D T; Frenje, J A; Gatu Johnson, M; Séguin, F H; Li, C K; Petrasso, R D; Glebov, V Yu; Katz, J; Knauer, J P; Meyerhofer, D D; Sangster, T C; Bionta, R M; Bleuel, D L; Döppner, T; Glenzer, S; Hartouni, E; Hatchett, S P; Le Pape, S; Ma, T; MacKinnon, A; McKernan, M A; Moran, M; Moses, E; Park, H-S; Ralph, J; Remington, B A; Smalyuk, V; Yeamans, C B; Kline, J; Kyrala, G; Chandler, G A; Leeper, R J; Ruiz, C L; Cooper, G W; Nelson, A J; Fletcher, K; Kilkenny, J; Farrell, M; Jasion, D; Paguio, R

2012-10-01

A magnetic recoil spectrometer (MRS) has been installed and extensively used on OMEGA and the National Ignition Facility (NIF) for measurements of the absolute neutron spectrum from inertial confinement fusion implosions. From the neutron spectrum measured with the MRS, many critical implosion parameters are determined including the primary DT neutron yield, the ion temperature, and the down-scattered neutron yield. As the MRS detection efficiency is determined from first principles, the absolute DT neutron yield is obtained without cross-calibration to other techniques. The MRS primary DT neutron measurements at OMEGA and the NIF are shown to be in excellent agreement with previously established yield diagnostics on OMEGA, and with the newly commissioned nuclear activation diagnostics on the NIF.

High Performance OLED Panel and Luminaire

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

Spindler, Jeffrey

2017-02-20

In this project, OLEDWorks developed and demonstrated the technology required to produce OLED lighting panels with high energy efficiency and excellent light quality. OLED panels developed in this program produce high quality warm white light with CRI greater than 85 and efficacy up to 80 lumens per watt (LPW). An OLED luminaire employing 24 of the high performance panels produces practical levels of illumination for general lighting, with a flux of over 2200 lumens at 60 LPW. This is a significant advance in the state of the art for OLED solid-state lighting (SSL), which is expected to be a complementarymore » light source to the more advanced LED SSL technology that is rapidly replacing all other traditional forms of lighting.« less

Spectral emission measurement of igneous rocks using a spectroradiometer

NASA Technical Reports Server (NTRS)

Hunton, W. D.

1970-01-01

Spectroradiometer is used for either close or remote identification of rocks not heated to high temperatures. Instrument yields reproducible data spectra with excellent signal-to-noise ratios and readily identifiable spectral details, including differences in subclasses.

Microstructure and wear properties of laser clad Ti2Ni3Si/Ni3Ti multiphase intermetallic coatings

NASA Astrophysics Data System (ADS)

Wang, H. M.; Tang, H. B.; Cai, L. X.; Cao, F.; Zhang, L. Y.; Yu, R. L.

2005-05-01

Wear resistant Ti2Ni3Si/Ni3Ti multiphase intermetallic coatings with a microstructure consisting of Ti2Ni3Si primary dendrites and interdendritic Ti2Ni3Si/Ni3Ti eutectic were fabricated on a substrate of 0.2% C plain carbon steel by a laser cladding process with Ti-Ni-Si alloy powders. The Ti2Ni3Si/Ni3Ti coatings have excellent wear resistance and a low coefficient of friction under metallic dry sliding wear test conditions with hardened 0.45% C carbon steel as the silide-mating counterpart. The excellent tribological properties of the coating are attributed to the high hardness, strong covalent-dominant atomic bonds of the ternary metal silicide Ti2Ni3Si and to the high yield strength and strong yield anomaly of the intermetallic compound Ni3Ti.

Insights from Placing Photosynthetic Light Harvesting into Context.

PubMed

Demmig-Adams, Barbara; Stewart, Jared J; Burch, Tyson A; Adams, William W

2014-08-21

Solar-energy conversion through natural photosynthesis forms the base of virtually all food chains on Earth and provides fiber, materials, and fuels, as well as inspiration for the design of biomimetic energy-conversion systems. We summarize well-known as well as recently discovered feedback loops between natural light-harvesting systems and whole-organism function in natural settings. We propose that the low effective quantum yield of natural light-harvesting systems in high light is caused by downstream limitations rather than unavoidable intrinsic vulnerabilities. We evaluate potential avenues, and their costs and benefits, for increasing the maximal rate and photon yield of photosynthesis in high light in plants and photosynthetic microbes. By summarizing mechanisms observable only in complex systems (whole plants, algae, or, in some cases, intact leaves), we aim to stimulate future research efforts on reciprocal feedback loops between light harvesting and downstream processes in whole organisms and to provide additional arguments for the significance of research on photosynthetic light harvesting.

White light photothermal lens spectrophotometer for the determination of absorption in scattering samples.

PubMed

Marcano, Aristides; Alvarado, Salvador; Meng, Junwei; Caballero, Daniel; Moares, Ernesto Marín; Edziah, Raymond

2014-01-01

We developed a pump-probe photothermal lens spectrophotometer that uses a broadband arc-lamp and a set of interference filters to provide tunable, nearly monochromatic radiation between 370 and 730 nm as the pump light source. This light is focused onto an absorbing sample, generating a photothermal lens of millimeter dimensions. A highly collimated monochromatic probe light from a low-power He-Ne laser interrogates the generated lens, yielding a photothermal signal proportional to the absorption of light. We measure the absorption spectra of scattering dye solutions using the device. We show that the spectra are not affected by the presence of scattering, confirming that the method only measures the absorption of light that results in generation of heat. By comparing the photothermal spectra with the usual absorption spectra determined using commercial transmission spectrophotometers, we estimate the quantum yield of scattering of the sample. We discuss applications of the device for spectroscopic characterization of samples such as blood and gold nanoparticles that exhibit a complex behavior upon interaction with light.

Recent Results from the WASA-at-COSY Experiment

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

Kupsc, Andrzej

2011-10-24

Studies of light meson decays are the key experiments for the WASA detector at COSY-Juelich. One of the world largest data samples of the {eta} meson decays have been recently collected in the pd {yields}{sup 3}He{eta} and in the pp {yields} pp{eta} reactions. The status of the analysis of various decay channels and the further plans for the light meson decay program are presented.

Test beam studies of the light yield, time and coordinate resolutions of scintillator strips with WLS fibers and SiPM readout

DOE PAGES

Denisov, Dmitri; Evdokimov, Valery; Lukic, Strahinja; ...

2016-12-24

Prototype scintilator+WLS strips with SiPM readout for large muon detection systems were tested in the muon beam of the Fermilab Test Beam Facility. Furthermore, light yield of up to 137 photoelectrons per muon per strip has been observed, as well as time resolution of 330 ps and position resolution along the strip of 5.4 cm.

Exploring growth conditions and Eu2+ concentration effects for KSr2I5:Eu scintillator crystals

NASA Astrophysics Data System (ADS)

Stand, L.; Zhuravleva, M.; Camarda, G.; Lindsey, A.; Johnson, J.; Hobbs, C.; Melcher, C. L.

2016-04-01

Our current research is focused on understanding dopant optimization, growth rate, homogeneity and their impact on the overall performance of KSr2I5:Eu2+ single crystal scintillators. In this work we have investigated the effects of Eu2+ concentration in the potassium strontium iodide matrix, and we found that the concentration needed to maximize the light yield was 4 mol%. In order to assess the effects of the pulling rate, we grew single crystals at 12, 24 and 120 mm/day via the vertical Bridgman technique. For the sample sizes measured (5×5×5 mm3), we found that the crystal grown at the fastest rate of 120 mm/day showed a light yield within ~7% of the more slowly grown boules, and no significant change was observed in the energy resolution. Therefore, light yields from 88,000 to 96,000 ph/MeV and energy resolutions from 2.4 to 3.0% (at 662 keV) were measured for KSr2I5:Eu 4% over a relatively wide range of growth conditions. In order to assess the homogeneity of KSr2I5:Eu 4%, a newly developed micro-resolution X-ray technique was used to map the light yield as a function of excitation position. In the crystals that we studied, we did not observe any significant inhomogeneity other than a smooth gradient due to light collection and self absorption effects.

A New Chief of Staff, a Golden Opportunity: Building the Right Force over the Next Decade

DTIC Science & Technology

2013-01-01

acquire both light attack and light mobility aircraft that would further its efforts in building partnership capacity ( BPC ). In light of the...contributions to the department’s efforts in both BPC and IW. The document refers to this type of warfare as a struggle for legitimacy and influence...are designed to improve the Air Force’s capabilities in IW and BPC . The Gaps Sections of Headquarters Air Force have outlined excellent plans to

Interfacing a quantum dot with a spontaneous parametric down-conversion source

NASA Astrophysics Data System (ADS)

Huber, Tobias; Prilmüller, Maximilian; Sehner, Michael; Solomon, Glenn S.; Predojević, Ana; Weihs, Gregor

2017-09-01

Quantum networks require interfacing stationary and flying qubits. These flying qubits are usually nonclassical states of light. Here we consider two of the leading source technologies for nonclassical light, spontaneous parametric down-conversion and single semiconductor quantum dots. Down-conversion delivers high-grade entangled photon pairs, whereas quantum dots excel at producing single photons. We report on an experiment that joins these two technologies and investigates the conditions under which optimal interference between these dissimilar light sources may be achieved.

The Fresnel Zone Light Field Spectral Imager

DTIC Science & Technology

2017-03-23

Marciniak Member AFIT-ENP-MS-17-M-095 Abstract This thesis provides a computational model and the first experimental demonstration of a Fresnel zone...Fresnel propagation. It was validated experimentally and provides excellent demonstration of system capabilities. The experimentally demonstrated system...in the measured light fields, they did not degrade the system’s performance. Experimental demonstration also showed the capability to resolve between

Graphene oxide coated coordination polymer nanobelt composite material: a new type of visible light active and highly efficient photocatalyst for Cr(VI) reduction.

PubMed

Shi, Gui-Mei; Zhang, Bin; Xu, Xin-Xin; Fu, Yan-Hong

2015-06-28

A visible light active photocatalyst was synthesized successfully by coating graphene oxide (GO) on a coordination polymer nanobelt (CPNB) using a simple colloidal blending process. Compared with neat CPNB, the resulting graphene oxide coated coordination polymer nanobelt composite material (GO/CPNB) exhibits excellent photocatalytic efficiency in the reduction of K2Cr2O7 under visible light irradiation. In the composite material, GO performs two functions. Firstly, it cuts down the band gap (E(g)) of the photocatalyst and extends its photoresponse region from the ultraviolet to visible light region. Secondly, GO exhibits excellent electron transportation ability that impedes its recombination with holes, and this can enhance photocatalytic efficiency. For GO, on its surface, the number of functional groups has a great influence on the photocatalytic performance of the resulting GO/CPNB composite material and an ideal GO"coater" to obtain a highly efficient GO/CPNB photocatalyst has been obtained. As a photocatalyst that may be used in the treatment of Cr(VI) in wastewater, GO/CPNB exhibited outstanding stability during the reduction of this pollutant.

Mechanical Properties of Elastomeric Impression Materials: An In Vitro Comparison

PubMed Central

De Angelis, Francesco; Caputi, Sergio; D'Amario, Maurizio; D'Arcangelo, Camillo

2015-01-01

Purpose. Although new elastomeric impression materials have been introduced into the market, there are still insufficient data about their mechanical features. The tensile properties of 17 hydrophilic impression materials with different consistencies were compared. Materials and Methods. 12 vinylpolysiloxane, 2 polyether, and 3 hybrid vinylpolyether silicone-based impression materials were tested. For each material, 10 dumbbell-shaped specimens were fabricated (n = 10), according to the ISO 37:2005 specifications, and loaded in tension until failure. Mean values for tensile strength, yield strength, strain at break, and strain at yield point were calculated. Data were statistically analyzed using one-way ANOVA and Tukey's tests (α = 0.05). Results. Vinylpolysiloxanes consistently showed higher tensile strength values than polyethers. Heavy-body materials showed higher tensile strength than the light bodies from the same manufacturer. Among the light bodies, the highest yield strength was achieved by the hybrid vinylpolyether silicone (2.70 MPa). Polyethers showed the lowest tensile (1.44 MPa) and yield (0.94 MPa) strengths, regardless of the viscosity. Conclusion. The choice of an impression material should be based on the specific physical behavior of the elastomer. The light-body vinylpolyether silicone showed high tensile strength, yield strength, and adequate strain at yield/brake; those features might help to reduce tearing phenomena in the thin interproximal and crevicular areas. PMID:26693227

Nd:AlN polycrystalline ceramics: A candidate media for tunable, high energy, near IR lasers

NASA Astrophysics Data System (ADS)

Wieg, A. T.; Grossnickle, M. J.; Kodera, Y.; Gabor, N. M.; Garay, J. E.

2016-09-01

We present processing and characterization of Nd-doped aluminum nitride (Nd:AlN) polycrystalline ceramics. We compare ceramics with significant segregation of Nd to those exhibiting minimal segregation. Spatially resolved photoluminescence maps reveal a strong correlation between homogeneous Nd doping and spatially homogeneous light emission. The spectroscopically resolved light emission lines show excellent agreement with the expected Nd electronic transitions. Notably, the lines are significantly broadened, producing near IR emission (˜1077 nm) with a remarkable ˜100 nm bandwidth at room temperature. We attribute the broadened lines to a combination of effects: multiple Nd-sites, anisotropy of AlN and phonon broadening. These broadened, overlapping lines in a media with excellent thermal conductivity have potential for Nd-based, tunable lasers with high average power.

Visible-light-driven Efficient Photocatalytic Reduction of Organic Azides to Amines over CdS Sheet-rGO Nanocomposite.

PubMed

Singha, Krishnadipti; Mondal, Aniruddha; Ghosh, Subhash Chandra; Panda, Asit Baran

2018-02-02

CdS sheet-rGO nanocomposite as a heterogeneous photocatalyst enables visible-light-induced photocatalytic reduction of aromatic, heteroaromatic, aliphatic and sulfonyl azides to the corresponding amines using hydrazine hydrate as a reductant. The reaction shows excellent conversion and chemoselectivity towards the formation of the amine without self-photoactivated azo compounds. In the adopted strategy, CdS not only accelerates the formation of nitrene through photoactivation of azide but also enhances the decomposition of azide to a certain extent, which entirely suppressed formation of the azo compound. The developed CdS sheet-rGO nanocomposite catalyst is very active, providing excellent results under irradiation with a 40 W simple household CFL lamp. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Light-weight plastination.

PubMed

Steinke, Hanno; Rabi, Suganthy; Saito, Toshiyuki; Sawutti, Alimjan; Miyaki, Takayoshi; Itoh, Masahiro; Spanel-Borowski, Katharina

2008-11-20

Plastination is an excellent technique which helps to keep the anatomical specimens in a dry, odourless state. Since the invention of plastination technique by von Hagens, research has been done to improve the quality of plastinated specimens. In this paper, we have described a method of producing light-weight plastinated specimens using xylene along with silicone and in the final step, substitute xylene with air. The finished plastinated specimens were light-weight, dry, odourless and robust. This method requires less use of resin thus making the plastination technique more cost-effective. The light-weight specimens are easy to carry and can easily be used for teaching.

Stereoselective synthesis of novel highly substituted isochromanone and isoquinolinone-containing exocyclic tetrasubstituted alkenes.

PubMed

Arthuis, Martin; Pontikis, Renée; Florent, Jean-Claude

2009-03-06

An efficient synthetic route toward the synthesis of highly substituted arylethylidene-isoquinolinones/isochromanones is reported. The tandem carbopalladation/Suzuki-Miyaura coupling sequence stereoselectively provided various functionalized polycyclic compounds in moderate to excellent yields.

New odourless protocols for efficient Pauson-Khand annulations.

PubMed

Brown, Jack A; Irvine, Stephanie; Kerr, William J; Pearson, Colin M

2005-07-07

An inexpensive and commercially available odourless additive, dodecyl methyl sulfide, has been shown to be a highly effective promoter in the Pauson-Khand cyclisation of both intra- and intermolecular substrates, affording good to excellent yields of cyclopentenone products.

Limitations to photosynthesis under light and heat stress in three high-yielding wheat genotypes.

PubMed

Monneveux, Philippe; Pastenes, Claudio; Reynolds, Matthew P

2003-06-01

Three high-yielding wheat genotypes (T. aestivum L., c.v. Siete Cerros, Seri and Bacanora, released in 1966, 1982 and 1988, respectively) were grown under irrigation in two high radiation, low relative humidity environments (Tlaltizapan and Ciudad Obregon CIMMYT experimental stations, Mexico). Gas exchange and fluorescence parameters were assessed on the flag leaf during the day. Carbon isotope discrimination (delta) was analysed in flag leaf at anthesis and in grain at maturity. In both environments, gas exchange and fluorescence parameters varied markedly with irradiance and temperature. Analysis of their respective variation indicated the occurrence of photo-respiration and photo-inhibition, particularly in Tlaltizapan, the warmest environment, and in Siete Cerros. In Ciudad Obregon (high-yielding environment) lower Ci (internal CO2 concentration) and delta La (carbon isotope discrimination of the leaf) suggested a higher intrinsic photosynthetic capacity in the variety Bacanora. Higher yield of this genotype was also associated with higher Fv'/Fo' (ratio of photochemical and non photochemical rate constants in the light) and Fm'/Fm (ratio of the non photochemical rate constants in the dark and light adapted state).

A Global Analysis of Light and Charge Yields in Liquid Xenon

DOE PAGES

Lenardo, Brian; Kazkaz, Kareem; Manalaysay, Aaron; ...

2015-11-04

Here, we present an updated model of light and charge yields from nuclear recoils in liquid xenon with a simultaneously constrained parameter set. A global analysis is performed using measurements of electron and photon yields compiled from all available historical data, as well as measurements of the ratio of the two. These data sweep over energies from keV and external applied electric fields from V/cm. The model is constrained by constructing global cost functions and using a simulated annealing algorithm and a Markov Chain Monte Carlo approach to optimize and find confidence intervals on all free parameters in the model.more » This analysis contrasts with previous work in that we do not unnecessarily exclude datasets nor impose artificially conservative assumptions, do not use spline functions, and reduce the number of parameters used in NEST v 0.98. Here, we report our results and the calculated best-fit charge and light yields. These quantities are crucial to understanding the response of liquid xenon detectors in the energy regime important for rare event searches such as the direct detection of dark matter particles.« less

Iridium-catalyzed direct tetraborylation of perylene bisimides.

PubMed

Teraoka, Takuro; Hiroto, Satoru; Shinokubo, Hiroshi

2011-05-20

Treatment of perylene bisimides (PBIs) with bis(pinacolato)diboron in the presence of an iridium catalyst provides tetraborylated PBIs at 2,5,8,11-positions in good yields with perfect regioselectivity. The planar structure of the perylene core has been confirmed by X-ray diffraction analysis. Oxidation of tetraborylated PBI with hydroxylamine hydrochloride affords tetrahydroxy PBI in excellent yield, which exhibits a substantially blue-shifted absorption spectrum due to an intramolecular hydrogenbonding interaction between carbonyl and hydroxy groups.

A facile microwave-assisted Diels-Alder reaction of vinylboronates.

PubMed

Sarotti, Ariel M; Pisano, Pablo L; Pellegrinet, Silvina C

2010-11-21

The Diels-Alder reaction of vinylboronates can be easily performed using microwave irradiation giving excellent yields of the cycloadducts. Pinacol vinylboronate was the reagent of choice due to its stability towards hydrolysis, operational simplicity and yields of Diels-Alder products. To the best of our knowledge, this is the first example of microwave-assisted Diels-Alder reaction of boron-substituted dienophiles. Subsequent in situ oxidation of the cycloadducts with alkaline hydrogen peroxide afforded the alcohols efficiently.

Hydrogen Gas-Mediated Deoxydehydration/Hydrogenation of Sugar Acids: Catalytic Conversion of Glucarates to Adipates.

PubMed

Larson, Reed T; Samant, Andrew; Chen, Jianbin; Lee, Woojin; Bohn, Martin A; Ohlmann, Dominik M; Zuend, Stephan J; Toste, F Dean

2017-10-11

The development of a system for the operationally simple, scalable conversion of polyhydroxylated biomass into industrially relevant feedstock chemicals is described. This system includes a bimetallic Pd/Re catalyst in combination with hydrogen gas as a terminal reductant and enables the high-yielding reduction of sugar acids. This procedure has been applied to the synthesis of adipate esters, precursors for the production of Nylon-6,6, in excellent yield from biomass-derived sources.

Fabrication and characterization of poly (bisphenol A borate) with high thermal stability

NASA Astrophysics Data System (ADS)

Wang, Shujuan; Wang, Xiao; Jia, Beibei; Jing, Xinli

2017-01-01

In this work, poly (bisphenol A borate) (PBAB), which has excellent thermal resistance and a high char yield, was synthesized via a convenient A2 + B3 strategy by using bisphenol A (BPA) and boric acid (BA). The chemical reaction between BPA and BA and the chemical structure of PBAB were investigated. The results demonstrate that PBAB consists of aromatic, Ph-O-B and B-O-B structures, as well as a small number of boron hydroxyl groups and phenolic hydroxyl groups. The thermal properties of PBAB were studied by DMA and TGA. The results indicate that the glass transition temperature and char yield are gradually enhanced by increasing the boron content, where the char yield of PBAB at 800 °C in nitrogen (N2) reaches up to 71.3%. It is of particular importance that PBAB show excellent thermal resistance in N2 and air atmospheres. By analysing the pyrolysis of PBAB, the high char yield of PBAB can be attributed to the formation of boron oxide and boron carbide at high temperatures, which reduced the release of volatile carbon dioxide and improved the thermal stability of the carbonization products. This study provides a new perspective on the design of novel boron-containing polymers and possesses significant potential for the improvement of the comprehensive performance of thermosetting resins to broaden their applicability in the field of advanced composites.

Diastereo- and regioselective addition of thioamide dianions to imines and aziridines: synthesis of N-thioacyl-1,2-diamines and N-thioacyl-1,3-diamines.

PubMed

Shibahara, Fumitoshi; Kobayashi, Shun-ichiro; Maruyama, Toshifumi; Murai, Toshiaki

2013-01-02

Addition reactions of thioamide dianions that were derived from N-arylmethyl thioamides to imines and aziridines were carried out. The reactions of imines gave the addition products of N-thioacyl-1,2-diamines in a highly diastereoselective manner in good-to-excellent yields. The diastereomeric purity of these N-thioacyl-1,2-diamines could be enriched by simple recrystallization. The reduction of N-thioacyl-1,2-diamines with LiAlH(4) gave their corresponding 1,2-diamines in moderate-to-good yields with retention of their stereochemistry. The oxidative-desulfurization/cyclization of an N-thioacyl-1,2-diamine in CuCl(2)/O(2) and I(2)/pyridine systems gave the cyclized product in moderate yield and the trans isomer was obtained as the sole product. On the other hand, a similar cyclization reaction with antiformin (aq. NaClO) as an oxidant gave the cis isomer as the major product. The reactions of N-tosylaziridines gave the addition products of N-thioacyl-1,3-diamines with low diastereoselectivity but high regioselectivity and in good-to-excellent yields. The use of AlMe(3) as an additive improved the efficiency and regioselectivity of the reaction. The stereochemistry of the obtained products was determined by X-ray diffraction. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microkinetic modeling of H 2SO 4 formation on Pt based diesel oxidation catalysts

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

Sharma, Hom N.; Sun, Yunwei; Glascoe, Elizabeth A.

The presence of water vapor and sulfur oxides in diesel engine exhaust leads to the formation of sulfuric acid (H 2SO 4), which severely impacts the performance of Pt/Pd based emissions aftertreatment catalysts. In this study, a microkinetic model is developed to investigate the reaction pathways of H 2SO 4 formation on Pt based diesel oxidation catalysts (DOCs). The microkinetic model consists of 14 elementary step reactions (7 reversible pairs) and yields prediction in excellent agreement with data obtained from experiments at practically relevant sulfur oxides environment in engine exhaust. The model simulation utilizing a steady-state plug flow reactor demonstratesmore » that it matches experimental data in both kinetically and thermodynamically controlled regions. Results clearly show the negative impact of SO 3 on the SO 2 oxidation light-off temperature, consistent with experimental observations. A reaction pathway analysis shows that the primary pathway of sulfuric acid formation on Pt surface involves SO 2* oxidation to form SO 3* with the subsequent interaction of SO 3* with H 2O* to form H 2SO 4*.« less

Decarbonylative Phosphorylation of Amides by Palladium and Nickel Catalysis: The Hirao Cross-Coupling of Amide Derivatives.

PubMed

Liu, Chengwei; Szostak, Michal

2017-10-02

Considering the ubiquity of organophosphorus compounds in organic synthesis, pharmaceutical discovery agrochemical crop protection and materials chemistry, new methods for their construction hold particular significance. A conventional method for the synthesis of C-P bonds involves cross-coupling of aryl halides and dialkyl phosphites (the Hirao reaction). We report a catalytic deamidative phosphorylation of a wide range of amides using a palladium or nickel catalyst giving aryl phosphonates in good to excellent yields. The present method tolerates a wide range of functional groups. The reaction constitutes the first example of a transition-metal-catalyzed generation of C-P bonds from amides. This redox-neutral protocol can be combined with site-selective conventional cross-coupling for the regioselective synthesis of potential pharmacophores. Mechanistic studies suggest an oxidative addition/transmetallation pathway. In light of the importance of amides and phosphonates as synthetic intermediates, we envision that this Pd and Ni-catalyzed C-P bond forming method will find broad application. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Preparation of Gd Loaded Liquid Scintillator for Daya Bay Neutrino Experiment

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

Ding Yayun; Zhang Zhiyong

2010-05-12

Gadolinium loaded liquid scintillator (Gd-LS) is an excellent target material for reactor antineutrino experiments. Ideal Gd-LS should have long attenuation length, high light yield, long term stability, low toxicity, and should be compatible with the material used to build the detector. We have developed a new Gd-LS recipe in which carboxylic acid 3,5,5-trimethylhexanoic acid is used as the complexing ligand to gadolinium, 2,5-diphenyloxazole (PPO) and 1,4-bis[2-methylstyryl]benzene (bis-MSB) are used as primary fluor and wavelength shifter, respectively. The scintillator base is linear alkyl benzene (LAB). Eight hundred liters of Gd-LS has been synthesized and tested in a prototype detector. Results showmore » that the Gd-LS has high quality and is suitable for underground experiments in large quantity. Large scale production facility has been built. A full batch production of 4 t Gd-LS has been produced and monitored for several months. The production of 180 t Gd-LS will be carried out in the near future.« less

Four spot laser anemometer and optical access techniques for turbine applications

NASA Astrophysics Data System (ADS)

Wernet, Mark P.

A time-of-flight anemometer (TOFA) system utilizing a spatial lead-lag filter for bipolar pulse generation has been constructed and tested. This system, called a four-spot laser anemometer, was specifically designed for use in high-speed, turbulent flows in the presence of walls or surfaces. The TOFA system uses elliptical spots to increase the flow acceptance angle to be comparable with that of a fringe-type anemometer. The tightly focused spots used in the four spot yield excellent flare light rejection capabilities. Good results have been obtained to 75 microns normal to a surface, with an f/2.5 collection lens. This system is being evaluated for use in a warm turbine facility. Results from both a particle-lag velocity experiment and boundary layer profiles will be discussed. In addition, an analysis of the use of curved windows in a turbine casing will be presented. Curved windows, matching the inner radius of the turbine casing, preserve the flow conditions, but introduce astigmatic aberrations. A correction optic was designed that virtually eliminates these astigmatic aberrations throughout the intrablade survey region for normal incidence.

Four spot laser anemometer and optical access techniques for turbine applications

NASA Astrophysics Data System (ADS)

Wernet, Mark P.

A time-of-flight anemometer (TOFA) system, utilizing a spatial lead-lag filter for bipolar pulse generation was constructed and tested. This system, called a Four Spot Laser Anemometer, was specifically designed for use in high speed, turbulent flows in the presence of walls or surfaces. The TOFA system uses elliptical spots to increase the flow acceptance angle to be comparable with that of a fringe type anemometer. The tightly focused spots used in the Four Spot yield excellent flare light rejection capabilities. Good results were obtained to 75 microns normal to a surface, with a f/2.5 collecting lens. This system is being evaluated for use in a warm turbine facility. Results from both a particle lag velocity experiment and boundary layer profiles will be discussed. In addition, an analysis of the use of curved windows in a turbine casing will be presented. Curved windows, matching the inner radius of the turbine casing, preserve the flow conditions, but introduce astigmatic aberrations. A correction optic was designed that virtually eliminates these astigmatic aberrations throughout the intrablade survey region for normal incidence.

Microkinetic modeling of H 2SO 4 formation on Pt based diesel oxidation catalysts

DOE PAGES

Sharma, Hom N.; Sun, Yunwei; Glascoe, Elizabeth A.

2017-08-10

The presence of water vapor and sulfur oxides in diesel engine exhaust leads to the formation of sulfuric acid (H 2SO 4), which severely impacts the performance of Pt/Pd based emissions aftertreatment catalysts. In this study, a microkinetic model is developed to investigate the reaction pathways of H 2SO 4 formation on Pt based diesel oxidation catalysts (DOCs). The microkinetic model consists of 14 elementary step reactions (7 reversible pairs) and yields prediction in excellent agreement with data obtained from experiments at practically relevant sulfur oxides environment in engine exhaust. The model simulation utilizing a steady-state plug flow reactor demonstratesmore » that it matches experimental data in both kinetically and thermodynamically controlled regions. Results clearly show the negative impact of SO 3 on the SO 2 oxidation light-off temperature, consistent with experimental observations. A reaction pathway analysis shows that the primary pathway of sulfuric acid formation on Pt surface involves SO 2* oxidation to form SO 3* with the subsequent interaction of SO 3* with H 2O* to form H 2SO 4*.« less

Graphene-oxide-supported CuAl and CoAl layered double hydroxides as enhanced catalysts for carbon-carbon coupling via Ullmann reaction

NASA Astrophysics Data System (ADS)

Ahmed, Nesreen S.; Menzel, Robert; Wang, Yifan; Garcia-Gallastegui, Ainara; Bawaked, Salem M.; Obaid, Abdullah Y.; Basahel, Sulaiman N.; Mokhtar, Mohamed

2017-02-01

Two efficient catalyst based on CuAl and CoAl layered double hydroxides (LDHs) supported on graphene oxide (GO) for the carbon-carbon coupling (Classic Ullmann Homocoupling Reaction) are reported. The pure and hybrid materials were synthesised by direct precipitation of the LDH nanoparticles onto GO, followed by a chemical, structural and physical characterisation by electron microscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), surface area measurements and X-ray photoelectron spectroscopy (XPS). The GO-supported and unsupported CuAl-LDH and CoAl-LDH hybrids were tested over the Classic Ullman Homocoupling Reaction of iodobenzene. In the current study CuAl- and CoAl-LDHs have shown excellent yields (91% and 98%, respectively) at very short reaction times (25 min). GO provides a light-weight, charge complementary and two-dimensional material that interacts effectively with the 2D LDHs, in turn enhancing the stability of LDH. After 5 re-use cycles, the catalytic activity of the LDH/GO hybrid is up to 2 times higher than for the unsupported LDH.

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

Wang, Peng; State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012; Bai, Xue, E-mail: baix@jlu.edu.cn, E-mail: yuzhang@jlu.edu.cn

High quantum yield, narrow full width at half-maximum and tunable emission color of perovskite quantum dots (QDs) make this kind of material good prospects for light-emitting diodes (LEDs). However, the relatively poor stability under high temperature and air condition limits the device performance. To overcome this issue, the liquid-type packaging structure in combination with blue LED chip was employed to fabricate the fluorescent perovskite quantum dot-based LEDs. A variety of monochromatic LEDs with green, yellow, reddish-orange, and red emission were fabricated by utilizing the inorganic cesium lead halide perovskite quantum dots as the color-conversion layer, which exhibited the narrow fullmore » width at half-maximum (<35 nm), the relatively high luminous efficiency (reaching 75.5 lm/W), and the relatively high external quantum efficiency (14.6%), making it the best-performing perovskite LEDs so far. Compared to the solid state LED device, the liquid-type LED devices exhibited excellent color stability against the various working currents. Furthermore, we demonstrated the potential prospects of all-inorganic perovskite QDs for the liquid-type warm white LEDs.« less

Motor fuels and chemicals from coal via the Sasol Synthol route

NASA Astrophysics Data System (ADS)

Hoogendoorn, J. C.

1981-03-01

The production of synthetic motor fuels and chemicals from coal by the Sasol procedures is discussed. This process is based on the Fischer-Tropsch reaction by passing hydrogen and carbon monoxide in a specific ratio over iron catalysts at elevated temperatures and pressures. Two parallel reactor systems are discussed. The smaller system employs fixed-bed reactors, using a precipitated iron catalyst and produces predominantly heavy hydrocarbons of an aliphatic nature with carbon chains up to 100. These straight-chain hydrocarbons yield excellent waxes and high quality diesel oil. The larger system uses a powdered iron catalyst in a circulating fluid-bed reactor, a concept developed from American catalytic cracker technology. This system has the advantage of high production capacity and scale-up potential, and produces light olefins which can be used either as petrochemical feedstock or refined and added to the motor fuel pool, and ethylene which is augmented by ethane cracking. Analysis of product selectivities and values shows that co-production of chemicals and motor fuels from coal is profitable and efficient.

Four spot laser anemometer and optical access techniques for turbine applications

NASA Technical Reports Server (NTRS)

Wernet, Mark P.

1987-01-01

A time-of-flight anemometer (TOFA) system utilizing a spatial lead-lag filter for bipolar pulse generation has been constructed and tested. This system, called a four-spot laser anemometer, was specifically designed for use in high-speed, turbulent flows in the presence of walls or surfaces. The TOFA system uses elliptical spots to increase the flow acceptance angle to be comparable with that of a fringe-type anemometer. The tightly focused spots used in the four spot yield excellent flare light rejection capabilities. Good results have been obtained to 75 microns normal to a surface, with an f/2.5 collection lens. This system is being evaluated for use in a warm turbine facility. Results from both a particle-lag velocity experiment and boundary layer profiles will be discussed. In addition, an analysis of the use of curved windows in a turbine casing will be presented. Curved windows, matching the inner radius of the turbine casing, preserve the flow conditions, but introduce astigmatic aberrations. A correction optic was designed that virtually eliminates these astigmatic aberrations throughout the intrablade survey region for normal incidence.

Four spot laser anemometer and optical access techniques for turbine applications

NASA Technical Reports Server (NTRS)

Wernet, Mark P.

1987-01-01

A time-of-flight anemometer (TOFA) system, utilizing a spatial lead-lag filter for bipolar pulse generation was constructed and tested. This system, called a Four Spot Laser Anemometer, was specifically designed for use in high speed, turbulent flows in the presence of walls or surfaces. The TOFA system uses elliptical spots to increase the flow acceptance angle to be comparable with that of a fringe type anemometer. The tightly focused spots used in the Four Spot yield excellent flare light rejection capabilities. Good results were obtained to 75 microns normal to a surface, with a f/2.5 collecting lens. This system is being evaluated for use in a warm turbine facility. Results from both a particle lag velocity experiment and boundary layer profiles will be discussed. In addition, an analysis of the use of curved windows in a turbine casing will be presented. Curved windows, matching the inner radius of the turbine casing, preserve the flow conditions, but introduce astigmatic aberrations. A correction optic was designed that virtually eliminates these astigmatic aberrations throughout the intrablade survey region for normal incidence.

Time and position resolution of the scintillator strips for a muon system at future colliders

DOE PAGES

Denisov, Dmitri; Evdokimov, Valery; Lukic, Strahinja

2016-03-31

In this study, prototype scintilator+WLS strips with SiPM readout for a muon system at future colliders were tested for light yield, time resolution and position resolution. Depending on the configuration, light yield of up to 36 photoelectrons per muon per SiPM has been observed, as well as time resolution of 0.45 ns and position resolution along the strip of 7.7 cm.

Hydrodeoxygenation of the angelica lactone dimer, a cellulose-based feedstock: simple, high-yield synthesis of branched C7 -C10 gasoline-like hydrocarbons.

PubMed

Mascal, Mark; Dutta, Saikat; Gandarias, Inaki

2014-02-10

Dehydration of biomass-derived levulinic acid under solid acid catalysis and treatment of the resulting angelica lactone with catalytic K2 CO3 produces the angelica lactone dimer in excellent yield. This dimer serves as a novel feedstock for hydrodeoxygenation, which proceeds under relatively mild conditions with a combination of oxophilic metal and noble metal catalysts to yield branched C7 -C10 hydrocarbons in the gasoline volatility range. Considering that levulinic acid is available in >80 % conversion from raw biomass, a field-to-tank yield of drop-in, cellulosic gasoline of >60 % is possible. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Step edge sputtering yield at grazing incidence ion bombardment.

PubMed

Hansen, Henri; Polop, Celia; Michely, Thomas; Friedrich, Andreas; Urbassek, Herbert M

2004-06-18

The surface morphology of Pt(111) was investigated by scanning tunneling microscopy after 5 keV Ar+ ion bombardment at grazing incidence in dependence of the ion fluence and in the temperature range between 625 and 720 K. The average erosion rate was found to be strongly dependent on the ion fluence and the substrate temperature during bombardment. This dependence is traced back to the variation of step concentration with temperature and fluence. We develop a simple model allowing us to determine separately the constant sputtering yields for terraces and for impact area stripes in front of ascending steps. The experimentally determined yield of these stripes--the step-edge sputtering yield--is in excellent agreement with our molecular dynamics simulations performed for the experimental situation.

Can time-dependent density functional theory predict intersystem crossing in organic chromophores? A case study on benzo(bis)-X-diazole based donor-acceptor-donor type molecules.

PubMed

Tam, Teck Lip Dexter; Lin, Ting Ting; Chua, Ming Hui

2017-06-21

Here we utilized new diagnostic tools in time-dependent density functional theory to explain the trend of intersystem crossing in benzo(bis)-X-diazole based donor-acceptor-donor type molecules. These molecules display a wide range of fluorescence quantum yields and triplet yields, making them excellent candidates for testing the validity of these diagnostic tools. We believe that these tools are cost-effective and can be applied to structurally similar organic chromophores to predict/explain the trends of intersystem crossing, and thus fluorescence quantum yields and triplet yields without the use of complex and expensive multireference configuration interaction or multireference pertubation theory methods.

Improved Heat Dissipation of High-Power LED Lighting by a Lens Plate with Thermally-Conductive Plastics.

PubMed

Lee, Dong Kyu; Park, Hyun Jung; Cha, Yu-Jung; Kim, Hyeong Jin; Kwak, Joon Seop

2018-03-01

The junction temperature of high-power LED lighting was reduced effectively using a lens plate made from a thermally-conductive plastics (TCP). TCP has an excellent thermal conductivity, approximately 5 times that of polymethylmethacrylate (PMMA). Two sets of high-power LED lighting were designed using a multi array LED package with a lens plate for thermal simulation. The difference between two models was the materials of the lens plate. The lens plates of first and second models were fabricated by PMMA (PMMA lighting) and TCP (TCP lighting), respectively. At the lens plate, the simulated temperature of the TCP lighting was higher than that of the PMMA lighting. Near the LED package, the temperature of the TCP lighting was 2 °C lower than that of the PMMA lighting. This was well matched with the measured temperature of the fabricated lighting with TCP and PMMA.

Light, plants, and power for life support on Mars

NASA Technical Reports Server (NTRS)

Salisbury, F. B.; Dempster, W. F.; Allen, J. P.; Alling, A.; Bubenheim, D.; Nelson, M.; Silverstone, S.

2002-01-01

Regardless of how well other growing conditions are optimized, crop yields will be limited by the available light up to saturation irradiances. Considering the various factors of clouds on Earth, dust storms on Mars, thickness of atmosphere, and relative orbits, there is roughly 2/3 as much light averaged annually on Mars as on Earth. On Mars, however, crops must be grown under controlled conditions (greenhouse or growth rooms). Because there presently exists no material that can safely be pressurized, insulated, and resist hazards of puncture and deterioration to create life support systems on Mars while allowing for sufficient natural light penetration as well, artificial light will have to be supplied. If high irradiance is provided for long daily photoperiods, the growing area can be reduced by a factor of 3-4 relative to the most efficient irradiance for cereal crops such as wheat and rice, and perhaps for some other crops. Only a small penalty in required energy will be incurred by such optimization. To obtain maximum yields, crops must be chosen that can utilize high irradiances. Factors that increase ability to convert high light into increased productivity include canopy architecture, high-yield index (harvest index), and long-day or day-neutral flowering and tuberization responses. Prototype life support systems such as Bios-3 in Siberia or the Mars on Earth Project need to be undertaken to test and further refine systems and parameters.

Light, plants, and power for life support on Mars.

PubMed

Salisbury, F B; Dempster, W F; Allen, J P; Alling, A; Bubenheim, D; Nelson, M; Silverstone, S

2002-01-01

Regardless of how well other growing conditions are optimized, crop yields will be limited by the available light up to saturation irradiances. Considering the various factors of clouds on Earth, dust storms on Mars, thickness of atmosphere, and relative orbits, there is roughly 2/3 as much light averaged annually on Mars as on Earth. On Mars, however, crops must be grown under controlled conditions (greenhouse or growth rooms). Because there presently exists no material that can safely be pressurized, insulated, and resist hazards of puncture and deterioration to create life support systems on Mars while allowing for sufficient natural light penetration as well, artificial light will have to be supplied. If high irradiance is provided for long daily photoperiods, the growing area can be reduced by a factor of 3-4 relative to the most efficient irradiance for cereal crops such as wheat and rice, and perhaps for some other crops. Only a small penalty in required energy will be incurred by such optimization. To obtain maximum yields, crops must be chosen that can utilize high irradiances. Factors that increase ability to convert high light into increased productivity include canopy architecture, high-yield index (harvest index), and long-day or day-neutral flowering and tuberization responses. Prototype life support systems such as Bios-3 in Siberia or the Mars on Earth Project need to be undertaken to test and further refine systems and parameters.

Smart design to resolve spectral overlapping of phosphor-in-glass for high-powered remote-type white light-emitting devices.

PubMed

Lee, Jin Seok; Arunkumar, P; Kim, Sunghoon; Lee, In Jae; Lee, Hyungeui; Im, Won Bin

2014-02-15

The white light-emitting diode (WLED) is a state-of-the-art solid state technology, which has replaced conventional lighting systems due to its reduced energy consumption, its reliability, and long life. However, the WLED presents acute challenges in device engineering, due to its lack of color purity, efficacy, and thermal stability of the lighting devices. The prime cause for inadequacies in color purity and luminous efficiency is the spectral overlapping of red components with yellow/green emissions when generating white light by pumping a blue InGaN chip with yellow YAG:Ce³⁺ phosphor, where red phosphor is included, to compensate for deficiencies in the red region. An innovative strategy was formulated to resolve this spectral overlapping by alternatively arranging phosphor-in-glass (PiG) through cutting and reassembling the commercial red CaAlSiN₃:Eu²⁺ and green Lu₃Al₅O₁₂:Ce³⁺ PiG. PiGs were fabricated using glass frits with a low softening temperature of 600°C, which exhibited excellent thermal stability and high transparency, improving life time even at an operating temperature of 200°C. This strategy overcomes the spectral overlapping issue more efficiently than the randomly mixed and patented stacking design of multiple phosphors for a remote-type WLED. The protocol for the current design of PiG possesses excellent thermal and chemical stability with high luminous efficiency and color purity is an attempt to make smarter solid state lighting for high-powered remote-type white light-emitting devices.

Efficient production of antibody Fab fragment by transient gene expression in insect cells.

PubMed

Mori, Keita; Hamada, Hirotsugu; Ogawa, Takafumi; Ohmuro-Matsuyama, Yuki; Katsuda, Tomohisa; Yamaji, Hideki

2017-08-01

Transient gene expression allows a rapid production of diverse recombinant proteins in early-stage preclinical and clinical developments of biologics. Insect cells have proven to be an excellent platform for the production of functional recombinant proteins. In the present study, the production of an antibody Fab fragment by transient gene expression in lepidopteran insect cells was investigated. The DNA fragments encoding heavy-chain (Hc; Fd fragment) and light-chain (Lc) genes of an Fab fragment were individually cloned into the plasmid vector pIHAneo, which contained the Bombyx mori actin promoter downstream of the B. mori nucleopolyhedrovirus (BmNPV) IE-1 transactivator and the BmNPV HR3 enhancer for high-level expression. Trichoplusia ni BTI-TN-5B1-4 (High Five) cells were co-transfected with the resultant plasmid vectors using linear polyethyleneimine. When the transfection efficiency was evaluated, a plasmid vector encoding an enhanced green fluorescent protein (EGFP) gene was also co-transfected. Transfection and culture conditions were optimized based on both the flow cytometry of the EGFP expression in transfected cells and the yield of the secreted Fab fragments determined by enzyme-linked immunosorbent assay (ELISA). Under optimal conditions, a yield of approximately 120 mg/L of Fab fragments was achieved in 5 days in a shake-flask culture. Transient gene expression in insect cells may offer a promising approach to the high-throughput production of recombinant proteins. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

An Illuminating Reaction.

ERIC Educational Resources Information Center

Matthews, Catherine E.

1996-01-01

Describes the use of carbide lights as an excellent mechanism for introducing or reviewing many basic chemistry concepts including elements and compounds, endothermic and exothermic reactions, physical and chemical changes, and balancing chemical equations. (JRH)

Formation of the thioester, N,S-diacetylcysteine, from acetaldehyde and N,N'-diacetylcystine in aqueous solution with ultraviolet light

NASA Technical Reports Server (NTRS)

Weber, A. L.

1981-01-01

The thioester, N,S-diacetylcysteine, is formed during the illumination of phosphate buffered (pH 7.0) aqueous solutions of acetaldehyde and N,N'-diacetylcystine with ultraviolet light. The yield of N,S-diacetylcysteine relative to N-acetylcysteine and unidentified products progressively increases as ultraviolet light below 239 nm, 253 nm and 281 nm is cut off with optical filters. When ultraviolet light below 320 nm is removed with an optical filter, there is no detectable reaction. Illumination of 0.025 M N,N'-diacetylcystine with 0.5 M and 1.0 M acetaldehyde with filtered ultraviolet light gives, respectively, 20% and 80% yields of N,S-diacetylcysteine. In the reaction with 1.0 M acetaldehyde, N-acetylcysteine forms early in the reaction and later decreases with its conversion to N,S-diacetylcysteine. The prebiotic significance of these reactions is discussed.

The initiating radical yields and the efficiency of polymerization for various dental photoinitiators excited by different light curing units.

PubMed

Neumann, Miguel G; Schmitt, Carla C; Ferreira, Giovana C; Corrêa, Ivo C

2006-06-01

To evaluate the efficiency of the photopolymerization of dental resins it is necessary to know to what extent the light emitted by the light curing units is absorbed by the photoinitiators. On the other hand, the efficiency of the absorbed photons to produce species that launch the polymerization process is also of paramount importance. Therefore, the previously determined PAE (photon absorption efficiency) is used in conjunction with the polymerization quantum yields for the photoinitiators, in order to be able to compare the total process on an equivalent basis. This parameter can be used to identify the best performance for the photochemical process with specific photoinitiators. The efficiency of LED (Ultrablue IS) and QTH (Optilux 401) lamps were tested comparing their performances with the photoinitiators camphorquinone (CQ); phenylpropanedione (PPD); monoacylphosphine oxide (Lucirin TPO); and bisacylphosphine oxide (Irgacure 819). The extent of photopolymerization per absorbed photon was determined from the polymerization quantum yields obtained by using the photoinitiators to polymerize methyl methacrylate, and afterwards combined with the previously determined PAEs. Although CQ presents a rather low polymerization quantum yield, its photopolymerization efficiency is practically the highest when irradiated with the Ultrablue LED. On the other hand, Lucirin is much more efficient than the other photoinitiators when irradiated with a QTH lamp, due to its high quantum yield and the overlap between its absorption spectrum and the output of the visible lamp light. Difference in photopolymerization efficiencies arise when combinations of photoinitiators are used, and when LED sources are used in preference to QTH. Mechanistic understanding is essential to optimal initiator formulation.

Developing Investigation Skills in an Introductory Multistep Synthesis Using Fluorene Oxidation and Reduction

ERIC Educational Resources Information Center

Stocksdale, Mark G; Pointer, Roy D; Benson, Barret W.; Fletcher, Steven E. S.; Henry, Ian; Ogren, Paul J.; Berg, Michael A. G.

2004-01-01

A two-step oxidation-reduction sequence that incorporates several important aspects of synthesis into introductory organic chemistry laboratories is described. This experiment is an excellent vehicle for introducing elements of discovery and intermediate yield improvement strategies.

Microscopy and Image Analysis.

PubMed

McNamara, George; Difilippantonio, Michael; Ried, Thomas; Bieber, Frederick R

2017-07-11

This unit provides an overview of light microscopy, including objectives, light sources, filters, film, and color photography for fluorescence microscopy and fluorescence in situ hybridization (FISH). We believe there are excellent opportunities for cytogeneticists, pathologists, and other biomedical readers, to take advantage of specimen optical clearing techniques and expansion microscopy-we briefly point to these new opportunities. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

Intrinsic light yield and light loss coefficient of Bi4Ge3O12 single crystals

NASA Astrophysics Data System (ADS)

Yawai, Nattasuda; Chewpraditkul, Weerapong; Wanarak, Chalerm; Nikl, Martin; Ratanatongchai, Wichian

2014-10-01

In this paper we present the scintillation properties of polished Bi4Ge3O12 (BGO) crystals grown by the Bridgman method. The light yield (LY) and energy resolution were measured using XP5200B photomultiplier. At 662 keV γ-rays, high LY of 9680 photons/MeV and good energy resolution of 8.6% were obtained for a 5 × 5 × 1 mm3 BGO sample. The intrinsic LY and light loss coefficient were evaluated. The photofraction in pulse height spectrum of 662 keV γ-rays and the mass attenuation coefficient at 59.5 and 662 keV γ-rays were also determined and compared with the theoretical ones calculated using the WinXCom program.

Efficient solar-pumped Nd:YAG laser by a double-stage light-guide/V-groove cavity

NASA Astrophysics Data System (ADS)

Almeida, Joana; Liang, Dawei

2011-05-01

Since the first reported Nd:YAG solar laser, researchers have been exploiting parabolic mirrors and heliostats for enhancing laser output performance. We are now investigating the production of an efficient solar-pumped laser for the reduction of magnesium from magnesium oxide, which could be an alternative solution to fossil fuel. Therefore both high conversion efficiency and excellent beam quality are imperative. By using a single fused silica light guide of rectangular cross section, highly concentrated solar radiation at the focal spot of a stationary parabolic mirror is efficiently transferred to a water-flooded V-groove pump cavity. It allows for the double-pass absorption of pump light along a 4mm diameter, 30mm length, 1.1at% Nd:YAG rod. Optimum pumping parameters and solar laser output power are found through ZEMAXTM non-sequential ray-tracing and LASCADTM laser cavity analysis. 11.0 W of multimode laser output power with excellent beam profile is numerically calculated, corresponding to 6.1W/m2 collection efficiency. To validate the proposed pumping scheme, an experimental setup of the double-stage light-guide/V-groove cavity was built. 78% of highly concentrated solar radiation was efficiently transmitted by the fused silica light guide. The proposed pumping scheme can be an effective solution for enhancing solar laser performances when compared to other side-pump configurations.

Molecular Based Temperature and Strain Rate Dependent Yield Criterion for Anisotropic Elastomeric Thin Films

NASA Technical Reports Server (NTRS)

Bosi, F.; Pellegrino, S.

2017-01-01

A molecular formulation of the onset of plasticity is proposed to assess temperature and strain rate effects in anisotropic semi-crystalline rubbery films. The presented plane stress criterion is based on the strain rate-temperature superposition principle and the cooperative theory of yielding, where some parameters are assumed to be material constants, while others are considered to depend on specific modes of deformation. An orthotropic yield function is developed for a linear low density polyethylene thin film. Uniaxial and biaxial inflation experiments were carried out to determine the yield stress of the membrane via a strain recovery method. It is shown that the 3% offset method predicts the uniaxial elastoplastic transition with good accuracy. Both the tensile yield points along the two principal directions of the film and the biaxial yield stresses are found to obey the superposition principle. The proposed yield criterion is compared against experimental measurements, showing excellent agreement over a wide range of deformation rates and temperatures.

Silicon carbidonitride based phosphors and lighting devices using the same

DOEpatents

Li, Yuanqiang; Romanelli, Michael Dennis; Tian, Yongchi

2013-09-17

Disclosed herein are novel families of silicon carbidonitride phosphor compositions. In certain embodiments, optimal ranges of carbon content have been identified which provide excellent luminescence and thermal stability characteristics.

New Carrollton Federal Building Lighting Retrofit Captures Cool Savings

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

None

2017-01-01

Case study describes how the U.S. General Services Administration cut a $291,000 annual lighting electric bill to an estimated $53,500 by upgrading their fluorescent lighting to a new LED troffer lighting and controls system in the New Carrollton Federal Building in Lanham, Maryland. The lighting project yielded an 82% reduction in energy use and earned GSA two awards for exemplary performance from the Interior Lighting Campaign in 2016.

Photochemical cycloaddition reactions of cyanoacetylene and dicyanoacetylene

NASA Technical Reports Server (NTRS)

Ferris, J. P.; Guillemin, J. C.

1990-01-01

Photolysis of cyanoacetylene with 185- or 206-nm light yields 1,3,5-tricyanobenzene while 254-nm radiation yields a mixture of tetracyanocyclooctatetraenes, 1,2,4- and 1,3,5-tricyanobenzene. A polymer of cyanoacetylene is the major photoproduct. 1,3,5-Tricarbomethoxybenzene was the only photoproduct identified from the irradiation of methyl propiolate at 254 nm. Mono-, di-, and tricyanobenzenes are formed by irradiation of mixtures of acetylene and cyanoacetylene at 185, 206, and 254 nm along with trace amounts of cyclooctatetraenes. No photoadducts were detected on photolysis of mixtures of cyanoacetylene and CO or HCN. The tetracyanocyclooctatetraene structures were established by UV, MS, and NMR analyses. The 1H NMR of the product mixture exhibited a singlet at delta 7.028 consistent with either 1 or 2 and two singlets at delta 6.85 and 6.91 assigned to 3. Photolysis of mixtures of dicyanoacetylene and acetylene with either 185- or 206-nm light yielded 1,2-dicyanobenzene and (E,Z)-1-buten-3-yne-1,4-dicarbonitrile. These products were also obtained using 254-nm light along with a mixture of tetracyanocyclooctatetraenes. The same three singlets were observed in this product mixture as were observed in the tetracyanocyclooctatetraenes obtained from cyanoacetylene. From this observation it was concluded that the delta 7.02 signal is due to 2 and not 1. The photolysis of cyanoacetylene and dicyanoacetylene in the presence of ethylene with 185-nm light yields 1-cyanocylobutene and 1,2-dicyanocyclobutene, respectively. 2-Cyanobutadiene and 2,3-dicyanobutadiene are the photoproducts with 254-nm light. Reaction pathways are proposed to explain these findings.

Light yield and energy resolution studies for SoLid phase 1

NASA Astrophysics Data System (ADS)

Boursette, Delphine; SoLid Collaboration

2017-09-01

The SoLid experiment is searching for sterile neutrinos at a nuclear research reactor. It looks for inverse beta decays (producing a positron and a neutron in delayed coincidence) with a very segmented detector made of thousands of scintillating cubes. SoLid has a very innovative hybrid technology with two different scintillators which have different light emissions: polyvynil-toluene cubes (PVT) to detect the positrons and 6LiF:ZnS sheets on two faces of each PVT cube to detect the neutrons. It allows us to do an efficient pulse shape analysis to identify the signals from neutrons and positrons. The 288 kg detector prototype (SM1) took data in 2015. It demonstrated the detection principle and background rejection efficiency. The construction of SoLid phase I (˜ 1.5 t) has now started. To improve the energy resolution of SoLid phase I, we have tried to increase the light yield studying separately the two scintillators: PVT and ZnS. A test bench has been built to fully characterize and improve the neutron detection with the ZnS using an AmBe source. To study the positron light yield on the PVT, we have built another test bench with a 207Bi source. We have improved the design of the cubes, their wrapping or the type and the configuration of the fibers. We managed to increase the PVT light yield by about 66 % and improve the resolution of the positron energy on the test bench from 21 % to 16 % at 1 MeV.

Characterization of PbWO4 crystals for high-energy physics experiments

NASA Astrophysics Data System (ADS)

Kim, M. J.; Park, H.; Kim, H. J.

2016-09-01

High-energy physics (HEP) experiments have employed many new types of scintillators. Specifically, bismuth germanate, thallium-doped cesium iodide, and lead tungstate (PbWO4, PWO) have been used for the L3 experiment; CLEO II, Belle and BES-III; and CMS, respectively. PWO has particularly beneficial properties, such as high density, fast decay time, short radiation length and radiation hardness. In this study, we tested the PWO crystals at low temperatures to determine their applicability in future calorimeters. Various crystals from the Proton Antiproton Annihilations at Darmstadt (PANDA) experiment in Giessen, the Bogoroditsk Techno-Chemical Plant (BTCP) in Russia and by Shanghai Institute of Ceramics, Chinese Academy of Sciences (SICCAS) in China were investigated. We studied the scintillation properties of PWO crystals, such as their X-ray luminescence, relative light yields, absolute light yields, energy resolutions, decay times and longitudinal uniformities of their light yields. In addition, we measured the temperature dependences of the light yields and decay times by using a 137Cs γ-ray source. The emission spectra of the PWO crystals consisted of a broad band from 350 nm to 700 nm, and the peak emission wavelength in each spectrum was 420 nm. The emission spectra of the PWO crystals from SICCAS were slightly shifted to longer wavelengths compared with those of the crystals from the other institutions.

Studies On Particle-Accompanied Fission Of 252Cf(sf) And 235U(nth,f)

NASA Astrophysics Data System (ADS)

Kopatch, Yu N.; Tishchenko, V.; Speransky, M.; Mutterer, M.; Gönnenwein, F.; Jesinger, P.; Gagarski, A. M.; von Kalben, J.; Kojouharov, I.; Lubkiewics, E.; Mezentseva, Z.; Nezvishevsky, V.; Petrov, G. A.; Schaffner, H.; Scharma, H.; Trzaska, W. H.; Wollersheim, H.-J.

2005-11-01

In recent multi-parameter studies of spontaneous and thermal neutron induced fission, 252Cf(sf) and 235U(nth,f) respectively, the energies and emission angles of fission fragments and light charged particles were measured. Fragments were detected by an energy and angle sensitive twin ionization chamber while the light charged particles were identified by a series of ΔE-Erest telescopes. Up to Be the light particle isotopes could be disentangled. In addition, in the 252Cf(sf) experiment, gammas emitted by the fragments were analyzed by a pair of large-volume segmented clover Ge detectors. Here the main interest is to study the γ-decay and the anisotropy of gammas emitted by fragments and light particles. On the other hand, the high count rates achieved in the U-experiment performed at the high flux reactor of the ILL, Grenoble, should allow to explore fragment-particle correlations in very rare events like quaternary fission. At the present stage of data evaluation, yields and energy distributions of light particles are available. For the present contribution in particular the yields of Be-isotopes for the two reactions studied are compared and discussed. For 252Cf(sf) these isotopic yields were hitherto not known.

An Efficient, Optimized Synthesis of Fentanyl and Related Analogs

DOE PAGES

Valdez, Carlos A.; Leif, Roald N.; Mayer, Brian P.; ...

2014-09-18

The alternate and optimized syntheses of the parent opioid fentanyl and its analogs are described. The routes presented exhibit high-yielding transformations leading to these powerful analgesics after optimization studies were carried out for each synthetic step. The general three-step strategy produced a panel of four fentanyls in excellent yields (73–78%) along with their more commonly encountered hydrochloride and citric acid salts. In conclusion, the following strategy offers the opportunity for the gram-scale, efficient production of this interesting class of opioid alkaloids.

An Efficient, Optimized Synthesis of Fentanyl and Related Analogs

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

Valdez, Carlos A.; Leif, Roald N.; Mayer, Brian P.

The alternate and optimized syntheses of the parent opioid fentanyl and its analogs are described. The routes presented exhibit high-yielding transformations leading to these powerful analgesics after optimization studies were carried out for each synthetic step. The general three-step strategy produced a panel of four fentanyls in excellent yields (73–78%) along with their more commonly encountered hydrochloride and citric acid salts. In conclusion, the following strategy offers the opportunity for the gram-scale, efficient production of this interesting class of opioid alkaloids.

Eastern Kodak Company

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

Y.S. Tyan

2009-06-30

Lighting consumes more than 20% of electricity generated in the United States. Solid state lighting relies upon either inorganic or organic light-emitting diodes (OLEDs). OLED devices because of their thinness, fast response, excellent color, and efficiency could become the technology of choice for future lighting applications, provided progress is made to increase power efficiency and device lifetime and to develop cost-effective manufacturing processes. As a first step in this process, Eastman Kodak Company has demonstrated an OLED device architecture having an efficacy over 50 lm/W that exceeds the specifications of DOE Energy Star Program Requirements for Solid State Lighting. Themore » project included work designed to optimize an OLED device, based on a stacked-OLED structure, with performance parameters of: low voltage; improved light extraction efficiency; improved internal quantum efficiency; and acceptable lifetime. The stated goal for the end of the project was delivery of an OLED device architecture, suitable for development into successful commercial products, having over 50 lum/W power efficiency and 10,000 hours lifetime at 1000 cd/m{sup 2}. During the project, Kodak developed and tested a tandem hybrid IES device made with a fluorescent blue emitter, a phosphorescent yellow emitter, and a phosphorescent red emitter in a stacked structure. The challenge was to find low voltage materials that do not absorb excessive amounts of emitted light when the extraction enhancement structure is applied. Because an extraction enhancement structure forces the emitted light to travel several times through the OLED layers before it is emitted, it exacerbates the absorption loss. A variety of ETL and HTL materials was investigated for application in the low voltage SSL device structure. Several of the materials were found to successfully yield low operating device voltages without incurring excessive absorption loss when the extraction enhancement structure was applied. An internal extraction layer comprises two essential components: a light extraction element (LEE) that does the actual extraction of emitted light and a light coupling layer (LCL) that allows the emitted light to interact with the extraction element. Modeling results show that the optical index of the LCL needs to be high, preferably higher than that of the organic layers with an n value of {approx}1.8. In addition, since the OLED structure needs to be built on top of it the LCL needs to be physically and chemically benign. As the project concluded, our focus was on the tandem hybrid device, which proved to be the more efficient architecture. Cost-efficient device fabrication will provide the next challenges with this device architecture in order to allow this architecture to be commercialized.« less

Light-responsive smart surface with controllable wettability and excellent stability.

PubMed

Zhou, Yin-Ning; Li, Jin-Jin; Zhang, Qing; Luo, Zheng-Hong

2014-10-21

Novel fluorinated gradient copolymer was designed for smart surface with light-responsive controllable wettability and excellent stability. The switchable mechanism and physicochemical characteristics of the as-prepared surface decorated by designed polymeric material were investigated by ultraviolet-visible (UV-vis) spectrum, scanning electron microscope (SEM), atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS). Thanks to the functional film and surface roughening, etched silicon surface fabricated by copolymer involving spiropyran (Sp) moieties possesses a fairly large variation range of WCA (28.1°) and achieves the transformation between hydrophilicity (95.2° < 109.2°) and hydrophobicity (123.3° > 109.2°) relative to blank sample (109.2°). The synthetic strategy and developed smart surface offer a promising application in coating with controllable wettability, which bridge the gap between chemical structure and material properties.

Luminescence and light yield of (Gd2Y)(Ga3Al2)O12:Pr3+ single crystal scintillators

NASA Astrophysics Data System (ADS)

Lertloypanyachai, Prapon; Pathumrangsan, Nichakorn; Sreebunpeng, Krittiya; Pattanaboonmee, Nakarin; Chewpraditkul, Weerapong; Yoshikawa, Akira; Kamada, Kei; Nikl, Martin

2017-06-01

Praseodymium-doped (Gd2Y)(Ga3Al2)O12 (GYGAG: Pr) single crystals are grown by the micro-pulling down method with different Pr concentrations. The energy transfer process between Pr3+ and Gd3+ is investigated by photoluminescence excitation (PLE) and emission (PL) spectra measurements. Photoelectron yield measurements are carried out using photomultiplier. At 662 keV γ-rays, photoelectron yield of 2520 phe/MeV obtained for the GYGAG: Pr (0.01%) sample is larger than that of 1810 phe/MeV obtained for BGO crystal. Light yield degradation for the GYGAG: Pr scintillators is presumably due to the energy transfer from 5d state of Pr3+ to 4f state of Gd3+ together with the concentration quenching in the Gd3+-sublattice.

Interferometric apparatus and method for detection and characterization of particles using light scattered therefrom

DOEpatents

Johnston, Roger G.

1988-01-01

Interferometric apparatus and method for detection and characterization of particles using light scattered therefrom. Differential phase measurements on scattered light from particles are possible using the two-frequency Zeeman effect laser which emits two frequencies of radiation 250 kHz apart. Excellent discrimination and reproducibility for various pure pollen and bacterial samples in suspension have been observed with a single polarization element. Additionally, a 250 kHz beat frequency was recorded from an individual particle traversing the focused output from the laser in a flow cytometer.

Apparatus and method for detection and characterization of particles using light scattered therefrom

DOEpatents

Johnston, R.G.

1987-03-23

Apparatus and method for detection and characterization of particles using light scattered therefrom. Differential phase measurements on scattered light from particles are possible using the two-frequency Zeeman effect laser which emits two frequencies of radiation 250 kHz apart. Excellent discrimination and reproducibility for various pure pollen and bacterial samples in suspension have been observed with a single polarization element. Additionally, a 250 kHz beat frequency was recorded from an individual particle traversing the focused output from the laser in a flow cytometer. 13 figs.

Naturally formed graded junction for organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Shao, Yan; Yang, Yang

2003-09-01

In this letter, we report naturally-formed graded junctions (NFGJ) for organic light-emitting diodes (OLEDs). These junctions are fabricated using single thermal evaporation boat loaded with uniformly mixed charge transport and light-emitting materials. Upon heating, materials sublimate sequentially according to their vaporizing temperatures forming the graded junction. Two kinds of graded structures, sharp and shallow graded junctions, can be formed based on the thermal properties of the selected materials. The NFGJ OLEDs have shown excellent performance in both brightness and lifetime compared with heterojunction devices.

RCWA and FDTD modeling of light emission from internally structured OLEDs.

PubMed

Callens, Michiel Koen; Marsman, Herman; Penninck, Lieven; Peeters, Patrick; de Groot, Harry; ter Meulen, Jan Matthijs; Neyts, Kristiaan

2014-05-05

We report on the fabrication and simulation of a green OLED with an Internal Light Extraction (ILE) layer. The optical behavior of these devices is simulated using both Rigorous Coupled Wave Analysis (RCWA) and Finite Difference Time-Domain (FDTD) methods. Results obtained using these two different techniques show excellent agreement and predict the experimental results with good precision. By verifying the validity of both simulation methods on the internal light extraction structure we pave the way to optimization of ILE layers using either of these methods.

High resolution phoswich gamma-ray imager utilizing monolithic MPPC arrays with submillimeter pixelized crystals

NASA Astrophysics Data System (ADS)

Kato, T.; Kataoka, J.; Nakamori, T.; Kishimoto, A.; Yamamoto, S.; Sato, K.; Ishikawa, Y.; Yamamura, K.; Kawabata, N.; Ikeda, H.; Kamada, K.

2013-05-01

We report the development of a high spatial resolution tweezers-type coincidence gamma-ray camera for medical imaging. This application consists of large-area monolithic Multi-Pixel Photon Counters (MPPCs) and submillimeter pixelized scintillator matrices. The MPPC array has 4 × 4 channels with a three-side buttable, very compact package. For typical operational gain of 7.5 × 105 at + 20 °C, gain fluctuation over the entire MPPC device is only ± 5.6%, and dark count rates (as measured at the 1 p.e. level) amount to <= 400 kcps per channel. We selected Ce-doped (Lu,Y)2(SiO4)O (Ce:LYSO) and a brand-new scintillator, Ce-doped Gd3Al2Ga3O12 (Ce:GAGG) due to their high light yield and density. To improve the spatial resolution, these scintillators were fabricated into 15 × 15 matrices of 0.5 × 0.5 mm2 pixels. The Ce:LYSO and Ce:GAGG scintillator matrices were assembled into phosphor sandwich (phoswich) detectors, and then coupled to the MPPC array along with an acrylic light guide measuring 1 mm thick, and with summing operational amplifiers that compile the signals into four position-encoded analog outputs being used for signal readout. Spatial resolution of 1.1 mm was achieved with the coincidence imaging system using a 22Na point source. These results suggest that the gamma-ray imagers offer excellent potential for applications in high spatial medical imaging.

Advanced optical smoke meters for jet engine exhaust measurement

NASA Technical Reports Server (NTRS)

Pitz, R. W.

1986-01-01

Smoke meters with increased sensitivity, improved accuracy, and rapid response are needed to measure the smoke levels emitted by modern jet engines. The standard soiled tape meter in current use is based on filtering, which yields long term averages and is insensitive to low smoke levels. Two new optical smoke meter techniques that promise to overcome these difficulties have been experimentally evaluated: modulated transmission (MODTRAN) and photothermal deflection spectroscopy (PDS). Both techniques are based on light absorption by smoke, which is closely related to smoke density. They are variations on direct transmission measurements which produce a modulated signal that can be easily measured with phase sensitive detection. The MODTRAN and PDS techniques were tested on low levels of smoke and diluted samples of NO2 in nitrogen, simulating light adsorption due to smoke. The results are evaluated against a set of ideal smoke meter criteria that include a desired smoke measurement range of 0.1 to 12 mg cu.m. (smoke numbers of 1 to 50) and a frequency response of 1 per second. The MODTRAN instrument is found to be inaccurate for smoke levels below 3 mg/cu.m. and is able to make a only about once every 20 seconds because of its large sample cell. The PDS instrument meets nearly all the characteristics of an ideal smoke meter: it has excellent sensitivity over a range of smoke levels from 0.1 to 20 mg/cu.m. (smoke numbers of 1 to 60) and good frequency response (1 per second).

Measurement of D0 elliptic flow using the heavy flavor tracker detector in Au+Au collisions at √sNN = 200 GeV

NASA Astrophysics Data System (ADS)

Lipiec, Andrzej

2017-08-01

In heavy ion collisions at relativistic energies conducted at Relativistic Heavy Ion Collider (RHIC, Upton, USA) a new state of matter, Quark Gluon Plasma (QGP), is produced. QGP is a state of matter with partonic (i.e. gluons + quarks) degrees of freedom and is believed to be existing only during first moments after the Big Bang, and possibly inside of the heaviest neutron stars. One of the key QGP signatures is the elliptic flow (v2) - a coefficient that describes spatial assymetry of particle yield. It has been observed that v2 of particles composed of light quarks (i.e. up, down and strange) follow the same trends when scaled to the number of constituent quarks. Such observations implied that all light quarks gain the same flow in the heavy ion collision. On the other hand it was speculated that heavy quarks (charm and bottom) should have smaller v2 because of their in-medium energy losses. Due to their heavy mass, c quarks are produced mostly before QGP is formed, which makes them excellent probes to study this hot, dense and strongly interacting medium. The Solenoidal Tracker At RHIC (STAR) experiment took data with the newly installed Heavy Flavor Tracker (HFT) detector. Thanks to the state-of-the-art tracking resolution of the HFT it is possible to measure D0 mesons with unprecedented precision. This paper presents the STAR experiment measurement of D0 elliptic flow.

Towards cancer cell-specific phototoxic organometallic rhenium(I) complexes.

PubMed

Leonidova, Anna; Pierroz, Vanessa; Rubbiani, Riccardo; Heier, Jakob; Ferrari, Stefano; Gasser, Gilles

2014-03-21

Over the recent years, several Re(I) organometallic compounds have been shown to be toxic to various cancer cell lines. However, these compounds lacked sufficient selectivity towards cancer tissues to be used as novel chemotherapeutic agents. In this study, we probe the potential of two known N,N-bis(quinolinoyl) Re(I) tricarbonyl complex derivatives, namely Re(I) tricarbonyl [N,N-bis(quinolin-2-ylmethyl)amino]-4-butane-1-amine (Re-NH₂) and Re(I) tricarbonyl [N,N-bis(quinolin-2-ylmethyl)amino]-5-valeric acid (Re-COOH), as photodynamic therapy (PDT) photosensitizers. Re-NH₂ and Re-COOH proved to be excellent singlet oxygen generators in a lipophilic environment with quantum yields of about 75%. Furthermore, we envisaged to improve the selectivity of Re-COOH via conjugation to two types of peptides, namely a nuclear localization signal (NLS) and a derivative of the neuropeptide bombesin, to form Re-NLS and Re-Bombesin, respectively. Fluorescent microscopy on cervical cancer cells (HeLa) showed that the conjugation of Re-COOH to NLS significantly enhanced the compound's accumulation into the cell nucleus and more specifically into its nucleoli. Importantly, in view of PDT applications, the cytotoxicity of the Re complexes and their bioconjugates increased significantly upon light irradiation. In particular, Re-Bombesin was found to be at least 20-fold more toxic after light irradiation. DNA photo-cleavage studies demonstrated that all compounds damaged DNA via singlet oxygen and, to a minor extent, superoxide production.

Sweetie Pie Thornless Blackberry

USDA-ARS?s Scientific Manuscript database

‘Sweetie Pie’ is a new thornless blackberry (Rubus L. subg. Watson) cultivar developed and released by the USDA-ARS Thad Cochran Southern Horticultural Laboratory. ‘Sweetie Pie’ is a vigorous, semi-erect blackberry that produces moderate yields of sweet high quality fruit having excellent flavor, ...

Synthesis of disulfides and diselenides by copper-catalyzed coupling reactions in water.

PubMed

Li, Zhengkai; Ke, Fang; Deng, Hang; Xu, Hualong; Xiang, Haifeng; Zhou, Xiangge

2013-05-14

A simple and efficient protocol for copper-catalyzed coupling reactions between aryl halides and elemental sulfur or selenium has been developed. A variety of disulfides and diselenides can be obtained in moderate to excellent yields up to 96%.

Synthesis of aryl azides and vinyl azides via proline-promoted CuI-catalyzed coupling reactions.

PubMed

Zhu, Wei; Ma, Dawei

2004-04-07

The coupling reaction of aryl halides or vinyl iodide with sodium azide under catalysis of CuI/L-proline works at relatively low temperature to provide aryl azides or vinyl azides in good to excellent yields.

Enantioselective Michael Addition of Pyrroles with Nitroalkenes in Aqueous Media Catalyzed by a Water-soluble Catalyst.

PubMed

Gui, Yang; Li, Yanan; Sun, Jianan; Zha, Zhenggen; Wang, Zhiyong

2018-06-11

A new water-soluble catalytic system were developed and therefor used in an enantioselective Michael addition of pyrroles with nitroalkenes in water to afford the nitroethylpyrrole derivatives with both excellent yields and ee values.

[Light competition and productivity of agroforestry system in loess area of Weibei in Shaanxi].

PubMed

Peng, Xiao-bang; Cai, Jing; Jiang, Zai-min; Zhang, Yuan-ying; Zhang, Shuo-xin

2008-11-01

Agroforestry is the most effective way for the restoration of disturbed land on Loess Plateau and the development of poorly local economy. Taking the tree-based intercropping systems of walnut or plum with soybean or pepper in the loess area of Weibei as test objects, the photosynthesis, growth, and yield of soybean (Qindou 8) and pepper (Shanjiao 981) in the systems were studied. The results showed that the photosynthetic active radiation (PAR), net photosynthetic rate (Pn), growth, and yield of individual soybean or pepper plants were significantly decreased, with the effects increased with decreasing distance from tree rows. Leaf water potential was not significantly or poorly correlated with the Pn, growth, and yield of the two crops. However, there were significant positive correlations between the soil moisture content in 10-20 cm layer and the biomass and yield of soybean, and the above-ground biomass of pepper. PAR was highly correlated with the yield of both crops, which indicated that light competition was one of the key factors leading to the decrease of crop yield.

Effects and Mechanism of Blue Light on Monascus in Liquid Fermentation.

PubMed

Zhang, Xiaowei; Liu, Wenqing; Chen, Xiying; Cai, Junhui; Wang, Changlu; He, Weiwei

2017-03-01

The effect of light on Monascus and the underlying mechanism have received a great deal of interest for the industrial application of Monascus pigments. In this study, we have examined the effects of blue light on the culture morphology, mycelium growth, pigments, and citrinin yield of Monascus in liquid-state and oscillation fermentation, and explored the mechanism at a physiological level. It was found that blue light affected the colony morphology, the composition (chitin content), and permeability of the Monascus mycelium cell wall in static liquid culture, which indicates blue light benefits pigments secreting from aerial mycelium to culture medium. In liquid oscillation fermentation, the yields of Monascus pigments in fermentation broth (darkness 1741 U/g, blue light 2206 U/g) and mycelium (darkness 2442 U/g, blue light 1900 U/g) cultured under blue light and darkness are different. The total pigments produced per gram of Monascus mycelium under blue light was also higher (4663 U/g) than that in darkness (4352 U/g). However, the production of citrinin (88 μg/g) under blue light was evidently lower than that in darkness (150 μg/g). According to the degradation of citrinin caused by blue light and hydrogen peroxide, it can be concluded that blue light could degrade citrinin and inhibit the catalase activity of Monascus mycelium, subsequently suppressing the decomposition of hydrogen peroxide, which is the active species that degrades citrinin.

Crop yield and light/energy efficiency in a closed ecological system: Laboratory Biosphere experiments with wheat and sweet potato

NASA Astrophysics Data System (ADS)

Nelson, M.; Dempster, W. F.; Silverstone, S.; Alling, A.; Allen, J. P.; van Thillo, M.

Two crop growth experiments in the soil-based closed ecological facility, Laboratory Biosphere, were conducted from 2003 to 2004 with candidate space life support crops. Apogee wheat (Utah State University variety) was grown, planted at two densities, 400 and 800 seeds m -2. The lighting regime for the wheat crop was 16 h of light - 8 h dark at a total light intensity of around 840 μmol m -2 s -1 and 48.4 mol m -2 d -1 over 84 days. Average biomass was 1395 g m -2, 16.0 g m -2 d -1 and average seed production was 689 g m -2 and 7.9 g m -2 d -1. The less densely planted side was more productive than the denser planting, with 1634 g m -2 and 18.8 g m -2 d -1 of biomass vs. 1156 g m -2 and 13.3 g m -2 d -1; and a seed harvest of 812.3 g m -2 and 9.3 g m -2 d -1 vs. 566.5 g m -2 and 6.5 g m -2 d -1. Harvest index was 0.49 for the wheat crop. The experiment with sweet potato used TU-82-155 a compact variety developed at Tuskegee University. Light during the sweet potato experiment, on a 18 h on/6 h dark cycle, totaled 5568 total moles of light per square meter in 126 days for the sweet potatoes, or an average of 44.2 mol m -2 d -1. Temperature regime was 28 ± 3 °C day/22 ± 4 °C night. Sweet potato tuber yield was 39.7 kg wet weight, or an average of 7.4 kg m -2, and 7.7 kg dry weight of tubers since dry weight was about 18.6% wet weight. Average per day production was 58.7 g m -2 d -1 wet weight and 11.3 g m -2 d -1. For the wheat, average light efficiency was 0.34 g biomass per mole, and 0.17 g seed per mole. The best area of wheat had an efficiency of light utilization of 0.51 g biomass per mole and 0.22 g seed per mole. For the sweet potato crop, light efficiency per tuber wet weight was 1.33 g mol -1 and 0.34 g dry weight of tuber per mole of light. The best area of tuber production had 1.77 g mol -1 wet weight and 0.34 g mol -1 of light dry weight. The Laboratory Biosphere experiment's light efficiency was somewhat higher than the USU field results but somewhat below greenhouse trials at comparable light levels, and the best portion of the crop at 0.22 g mol -1 was in-between those values. Sweet potato production was overall close to 50% higher than trials using hydroponic methods with TU-82-155 at NASA JSC. Compared to projected yields for the Mars on Earth life support system, these wheat yields were about 15% higher, and the sweet potato yields averaged over 80% higher.

Crop yield and light / energy efficiency in a closed ecological system: two laboratory biosphere experiments

NASA Astrophysics Data System (ADS)

Nelson, M.; Dempster, W. F.; Silverstone, S.; Alling, A.; Allen, J. P.; van Thillo, M.

Two crop growth experiments in the soil-based closed ecological facity, Laboratory Biosphere, were conducted from 2003-2004 with candidate space life support crops. Apogee wheat (Utah State University variety) was grown, planted in 2 densities, 400 and 800 seeds m-2. The lighting regime for the wheat crop was 16 hours of light -- 8 hours dark at a total light intensity of around 840 mol m2 sec-1 and 48.4 mol m-2 d-1 over 84 days Average biomass was 1395 g m-2, 16.0 g m-2 day-1 and average seed production was 689 g m-2 and 7.9 g m2 day-1. The less densely planted side was more productive than the denser planting, with 1634 g m-2 and 18.8g m-2 day-1 of biomass vs. 1156 g m-2 and 13.3 g m-2 day-1; and a seed harvest of 812.3 g m-2 and 9.3 g m-2 day-1 vs. 566.5 g m-2 and 6.5 g m-2 day-1 Harvest index was 0.49 for the wheat crop. The experiment with sweet potato used TU-82-155, a compact variety developed at Tuskegee University. Light during the sweet potato experiment, on a 16 hour on/8 hours dark cycle, totalled 5568 total moles of light in 126 days for the sweet potatoes, or an average of 44.2 moles m-2 day-1. Temperature regime was 28 deg +/- 3 deg C day /22 deg +/- 4 deg C night. Sweet potato tuber yield was 39.7 kg wet weight, or an average of 7.4 kg m-2 and 7.7 kg dry weight of tubers since dry weight was about 18.6% wet weight.^Average per day production was 58.7 g m-2 day-1 wet weight and 11.3 g m-2 day-1. For the wheat, average light efficiency was 0.34 grams biomass per mole, and 0.17 grams seed per mole. The best area of wheat had an efficiency of light utilization of 0.51 g biomass per mole and 0.22 g seed per mole. For the sweet potato crop, light efficiency per tuber wet weight was 7.13 g/mole and 1.38 g dry weight of tuber per mole of light. The best area of tuber production had 9.49 g/mole wet weight and 1.85 g/mole of light dry weight. Production from the wheat was The Laboratory Biosphere experiment's light efficiency was somewhat higher than the USU field results but somewhat below greenhouse trials at comparable light levels, and the best portion of the crop at 0.22g/mole was inbetween those values. Sweet potato production was overall close to 50% higher than trials using hydroponic methods with TU-82-155 at NASA JSC. Compared to projected yields for the Mars on Earth life support system, these wheat yields were about 15% higher, and the sweet potato yields averaged over 80% higher

Identification and genetic characterization of maize cell wall variation for improved biorefinery feedstock characteristics

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

Pauly, Markus; Hake, Sarah

2013-10-31

The objectives of this program are to 1) characterize novel maize mutants with altered cell walls for enhanced biorefinery characteristics and 2) find quantitative trait loci (QTLs) related to biorefinery characteristics by taking advantage of the genetic diversity of maize. As a result a novel non-transgenic maize plant (cal1) has been identified, whose stover (leaves and stalk) contain more glucan in their walls leading to a higher saccharification yield, when subjected to a standard enzymatic digestion cocktail. Stacking this trait with altered lignin mutants yielded evene higher saccharification yields. Cal-1 mutants do not show a loss of kernel and ormore » biomass yield when grown in the field . Hence, cal1 biomass provides an excellent feedstock for the biofuel industry.« less

Enhancing photoluminescence yields in lead halide perovskites by photon recycling and light out-coupling

PubMed Central

Richter, Johannes M.; Abdi-Jalebi, Mojtaba; Sadhanala, Aditya; Tabachnyk, Maxim; Rivett, Jasmine P.H.; Pazos-Outón, Luis M.; Gödel, Karl C.; Price, Michael; Deschler, Felix; Friend, Richard H.

2016-01-01

In lead halide perovskite solar cells, there is at least one recycling event of electron–hole pair to photon to electron–hole pair at open circuit under solar illumination. This can lead to a significant reduction in the external photoluminescence yield from the internal yield. Here we show that, for an internal yield of 70%, we measure external yields as low as 15% in planar films, where light out-coupling is inefficient, but observe values as high as 57% in films on textured substrates that enhance out-coupling. We analyse in detail how externally measured rate constants and photoluminescence efficiencies relate to internal recombination processes under photon recycling. For this, we study the photo-excited carrier dynamics and use a rate equation to relate radiative and non-radiative recombination events to measured photoluminescence efficiencies. We conclude that the use of textured active layers has the ability to improve power conversion efficiencies for both LEDs and solar cells. PMID:28008917

Enhancing photoluminescence yields in lead halide perovskites by photon recycling and light out-coupling.

PubMed

Richter, Johannes M; Abdi-Jalebi, Mojtaba; Sadhanala, Aditya; Tabachnyk, Maxim; Rivett, Jasmine P H; Pazos-Outón, Luis M; Gödel, Karl C; Price, Michael; Deschler, Felix; Friend, Richard H

2016-12-23

In lead halide perovskite solar cells, there is at least one recycling event of electron-hole pair to photon to electron-hole pair at open circuit under solar illumination. This can lead to a significant reduction in the external photoluminescence yield from the internal yield. Here we show that, for an internal yield of 70%, we measure external yields as low as 15% in planar films, where light out-coupling is inefficient, but observe values as high as 57% in films on textured substrates that enhance out-coupling. We analyse in detail how externally measured rate constants and photoluminescence efficiencies relate to internal recombination processes under photon recycling. For this, we study the photo-excited carrier dynamics and use a rate equation to relate radiative and non-radiative recombination events to measured photoluminescence efficiencies. We conclude that the use of textured active layers has the ability to improve power conversion efficiencies for both LEDs and solar cells.

Green light drives leaf photosynthesis more efficiently than red light in strong white light: revisiting the enigmatic question of why leaves are green.

PubMed

Terashima, Ichiro; Fujita, Takashi; Inoue, Takeshi; Chow, Wah Soon; Oguchi, Riichi

2009-04-01

The literature and our present examinations indicate that the intra-leaf light absorption profile is in most cases steeper than the photosynthetic capacity profile. In strong white light, therefore, the quantum yield of photosynthesis would be lower in the upper chloroplasts, located near the illuminated surface, than that in the lower chloroplasts. Because green light can penetrate further into the leaf than red or blue light, in strong white light, any additional green light absorbed by the lower chloroplasts would increase leaf photosynthesis to a greater extent than would additional red or blue light. Based on the assessment of effects of the additional monochromatic light on leaf photosynthesis, we developed the differential quantum yield method that quantifies efficiency of any monochromatic light in white light. Application of this method to sunflower leaves clearly showed that, in moderate to strong white light, green light drove photosynthesis more effectively than red light. The green leaf should have a considerable volume of chloroplasts to accommodate the inefficient carboxylation enzyme, Rubisco, and deliver appropriate light to all the chloroplasts. By using chlorophylls that absorb green light weakly, modifying mesophyll structure and adjusting the Rubisco/chlorophyll ratio, the leaf appears to satisfy two somewhat conflicting requirements: to increase the absorptance of photosynthetically active radiation, and to drive photosynthesis efficiently in all the chloroplasts. We also discuss some serious problems that are caused by neglecting these intra-leaf profiles when estimating whole leaf electron transport rates and assessing photoinhibition by fluorescence techniques.

Convenient determination of luminescence quantum yield using a combined electronic absorption and emission spectrometer

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

Prakash, John; Mishra, Ashok Kumar

2016-01-15

It is possible to measure luminescence quantum yield in a facile way, by designing an optical spectrometer capable of obtaining electronic absorption as well as luminescence spectra, with a setup that uses the same light source and detector for both the spectral measurements. Employment of a single light source and single detector enables use of the same correction factor profile for spectral corrections. A suitable instrumental scaling factor is used for adjusting spectral losses.

Light-induced crosslinkable semiconducting polymer dots† †Electronic supplementary information (ESI) available: Synthesis and characterization of monomers and polymers, preparation and characterization of thin film and Pdots, optical property measurements and flow cytometry is available. See DOI: 10.1039/c4sc03959a Click here for additional data file.

PubMed Central

Zhang, Yue; Ye, Fangmao; Sun, Wei; Yu, Jiangbo; Wu, I-Che; Rong, Yu; Zhang, Yong

2015-01-01

This paper describes a synthetic approach for photocrosslinkable polyfluorene (pc-PFO) semiconducting polymer dots, and demonstrates their superior ability to crosslink and form 3-D intermolecular polymer networks. The crosslinked pc-PFO Pdots are equipped with excellent encapsulating ability of functional small molecules. Optimum conditions of light irradiation on pc-PFO Pdots were investigated and clarified by using polymer thin films as a model. By employing the optimal light irradiation conditions, we successfully crosslinked pc-PFO Pdots and studied their particle sizes, photophysical, and colloidal properties. Single-particle imaging and dynamic-light-scattering measurements were conducted to understand the behaviors of photocrosslinked Pdots. Our results indicate pc-PFO Pdots can be easily photocrosslinked and the crosslinked species have excellent colloidal stability, physical and chemical stability, fluorescence brightness, and specific binding properties for cellular labeling. Considering that optical stimulus can work remotely, cleanly, and non-invasively, this study should pave the way for a promising approach to further develop stimuli-responsive ultrabright and versatile Pdot probes for biomedical imaging. PMID:25709806

Preparation and characterization of Bi-doped TiO{sub 2} and its solar photocatalytic activity for the degradation of isoproturon herbicide

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

Reddy, Police Anil Kumar; Srinivas, Basavaraju; Kala, Pruthu

Highlights: {yields} Visible active Bi-TiO{sub 2} photocatalyst preparation and thorough charaterization. {yields} Bi-TiO{sub 2} shows high activity for isoproturon degradation under solar light irradiation. {yields} The spectral response of TiO{sub 2} shifts from UV to visible light region by Bi doping. {yields} Bi{sup 3+{delta}+} species are playing a vital role in minimizing e{sup -}/h{sup +} recombination. -- Abstract: Bi-doped TiO{sub 2} catalyst was prepared by sol-gel method and was characterized by thermo gravimetric analysis (TGA), X-ray diffraction spectra (XRD), X-ray photo electronic spectroscopy (XPS), UV-Vis diffused reflectance spectra (DRS), photoluminescence spectra (PLS), transmission electron microscopy (TEM), energy dispersive analysis ofmore » X-rays (EDAX) and BET surface area. The photocatalytic activity of the catalysts were evaluated for the degradation of isoproturon herbicide under solar light irradiation. The UV-Visible DRS of Bi-doped TiO{sub 2} showed red shift in optical absorption. The presence of Bi{sup 3+{delta}+} species are playing a vital role in minimizing the electron hole recombination resulting higher activity compared to bare TiO{sub 2}.« less

Light Charged and CP-odd Higgses in MSSM-like Models

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

Dermisek, Radovan

2008-11-23

We study the Higgs sector of supersymmetric models containing two Higgs doublets with a light MSSM-like CP odd Higgs, m{sub A} < or approx. 10 GeV, and tan{beta} < or approx. 2.5. In this scenario all Higgses resulting from two Higgs doublets: light and heavy CP even Higgses, h and H, the CP odd Higgs, A, and the charged Higgs, H{sup {+-}}, could have been produced at LEP or the Tevatron, but would have escaped detection because they decay in modes that have not been searched for or the experiments are not sensitive to. Especially H{yields}ZA and H{sup {+-}}{yields}W{sup {+-}}*Amore » with A{yields}cc-bar, {tau}{sup +}{tau}{sup -} present an opportunity to discover some of the Higgses at LEP, the Tevatron and also at B factories. In addition, the 2.8{sigma} excess of the branching ratio W{yields}{tau}v with respect to the other leptons measured at LEP correlates well with the existence of the charged Higgs with properties typical for this scenario. Dominant {tau}- and c-rich decay products of all Higgses require modified strategies for their discovery at the LHC.« less

DANSS Neutrino Spectrometer: Detector Calibration, Response Stability, and Light Yield

NASA Astrophysics Data System (ADS)

Alekseev, I. G.; Belov, V. V.; Danilov, M. V.; Zhitnikov, I. V.; Kobyakin, A. S.; Kuznetsov, A. S.; Machikhiliyan, I. V.; Medvedev, D. V.; Rusinov, V. Yu.; Svirida, D. N.; Skrobova, N. A.; Starostin, A. S.; Tarkovsky, E. I.; Fomina, M. V.; Shevchik, E. A.; Shirchenko, M. V.

2018-05-01

Apart from monitoring nuclear reactor parameters, the DANSS neutrino experiment is aimed at searching for sterile neutrinos through a detailed analysis of the ratio of reactor antineutrino spectra measured at different distances from the reactor core. The light collection system of the detector is dual, comprising both the vacuum photomultiplier tubes (PMTs) and silicon photomultipliers (SiPMs). In this paper, the techniques developed to calibrate the responses of these photodetectors are discussed in detail. The long-term stability of the key parameters of the detector and their dependences on the ambient temperature are investigated. The results of detector light yield measurements, performed independently with PMTs and SiPMs are reported.

Large-scale synthesis of water-soluble luminescent hydroxyapatite nanorods for security printing.

PubMed

Chen, Xiaohu; Jin, Xiaoying; Tan, Junjun; Li, Wei; Chen, Minfang; Yao, Lan; Yang, Haitao

2016-04-15

Luminescent hydroxyapatite nanoparticles, which have excellent biocompatibility, excellent photostability, and strong fluorescence, have received increasing attention as bioprobes in cell imaging. However, they are also excellent candidates for use in ink-jet security printing. Successful products for related applications usually require highly crystalline, mono-dispersible hydroxyapatite nanorods with good colloidal stability and high fluorescence in aqueous media. These requirements are hard to simultaneously satisfy using most synthetic methods. In this paper, we report a simple and versatile hydrothermal method that incorporates the use of sodium citrate to prepare water-dispersible Eu(3+)-doped hydroxyapatite nanorods. The hydroxyapatite nanorods obtained using this method are highly crystalline rod-shaped particles with an average length of 50-80 nm and an average diameter of 15-30 nm. Dispersions of these hydroxyapatite nanorods, which are transparent with a slightly milky color under natural light and a bright red color when excited with 241 nm UV light, display zeta potentials of -35 mV and hydrodynamic diameters of 120 nm. These dispersions remain colloidally stable for a few months. Dispersions with these properties could be easily applied to security printing for confidential information storage and anti-counterfeiting technologies. Copyright © 2016 Elsevier Inc. All rights reserved.

Cost-Effective Experiments on the Diffraction and Interference of Light.

ERIC Educational Resources Information Center

Sprigham, S. V.

2000-01-01

Presents an alternative experimental arrangement that results in a considerable cost savings by reducing the number of sensors and other apparati required while giving excellent quantitative results for comparison with theory. (Author/CCM)

A Breath of Fresh Air.

ERIC Educational Resources Information Center

Freeman, Laurie

1996-01-01

A new elementary school in New Hampshire uses innovative European ventilation technology to ensure excellent air quality. Combined with high-efficiency lighting, the system should reduce energy consumption by 10 to 20%, compared with a traditional facility. (MLF)

Variation in canopy duration in the perennial biofuel crop Miscanthus reveals complex associations with yield.

PubMed

Robson, Paul R H; Farrar, Kerrie; Gay, Alan P; Jensen, Elaine F; Clifton-Brown, John C; Donnison, Iain S

2013-05-01

Energy crops can provide a sustainable source of power and fuels, and mitigate the negative effects of CO2 emissions associated with fossil fuel use. Miscanthus is a perennial C4 energy crop capable of producing large biomass yields whilst requiring low levels of input. Miscanthus is largely unimproved and therefore there could be significant opportunities to increase yield. Further increases in yield will improve the economics, energy balance, and carbon mitigation of the crop, as well as reducing land-take. One strategy to increase yield in Miscanthus is to maximize the light captured through an extension of canopy duration. In this study, canopy duration was compared among a diverse collection of 244 Miscanthus genotypes. Canopy duration was determined by calculating the number of days between canopy establishment and senescence. Yield was positively correlated with canopy duration. Earlier establishment and later senescence were also both separately correlated with higher yield. However, although genotypes with short canopy durations were low yielding, not all genotypes with long canopy durations were high yielding. Differences of yield between genotypes with long canopy durations were associated with variation in stem and leaf traits. Different methodologies to assess canopy duration traits were investigated, including visual assessment, image analysis, light interception, and different trait thresholds. The highest correlation coefficients were associated with later assessments of traits and the use of quantum sensors for canopy establishment. A model for trait optimization to enable yield improvement in Miscanthus and other bioenergy crops is discussed.

Variation in canopy duration in the perennial biofuel crop Miscanthus reveals complex associations with yield

PubMed Central

Robson, Paul R.H.; Farrar, Kerrie; Gay, Alan P.; Jensen, Elaine F.; Clifton-Brown, John C.; Donnison, Iain S.

2013-01-01

Energy crops can provide a sustainable source of power and fuels, and mitigate the negative effects of CO2 emissions associated with fossil fuel use. Miscanthus is a perennial C4 energy crop capable of producing large biomass yields whilst requiring low levels of input. Miscanthus is largely unimproved and therefore there could be significant opportunities to increase yield. Further increases in yield will improve the economics, energy balance, and carbon mitigation of the crop, as well as reducing land-take. One strategy to increase yield in Miscanthus is to maximize the light captured through an extension of canopy duration. In this study, canopy duration was compared among a diverse collection of 244 Miscanthus genotypes. Canopy duration was determined by calculating the number of days between canopy establishment and senescence. Yield was positively correlated with canopy duration. Earlier establishment and later senescence were also both separately correlated with higher yield. However, although genotypes with short canopy durations were low yielding, not all genotypes with long canopy durations were high yielding. Differences of yield between genotypes with long canopy durations were associated with variation in stem and leaf traits. Different methodologies to assess canopy duration traits were investigated, including visual assessment, image analysis, light interception, and different trait thresholds. The highest correlation coefficients were associated with later assessments of traits and the use of quantum sensors for canopy establishment. A model for trait optimization to enable yield improvement in Miscanthus and other bioenergy crops is discussed. PMID:23599277

Winter cover crop effect on corn seedling pathogens

USDA-ARS?s Scientific Manuscript database

Cover crops are an excellent management tool to improve the sustainability of agriculture. Winter rye cover crops have been used successfully in Iowa corn-soybean rotations. Unfortunately, winter rye cover crops occasionally reduce yields of the following corn crop. We hypothesize that one potential...

Evaluation of switchgrass for improved biomass yield on marginal land

USDA-ARS?s Scientific Manuscript database

The national strategy is to produce bioenergy crops on marginal cropland where there will be no competition with food production. The characteristics of switchgrass (Panicum virgatum) make it an excellent candidate for sustainable biomass production on marginal land. However, few studies have evalu...

Saccharomyces boulardii fungaemia in an intensive care unit patient treated with caspofungin

PubMed Central

Lolis, Nikolaos; Veldekis, Dimitrios; Moraitou, Hellen; Kanavaki, Sofia; Velegraki, Aristea; Triandafyllidis, Charis; Tasioudis, Chronis; Pefanis, Angellos; Pneumatikos, Ioannis

2008-01-01

We describe a case of Saccharomyces boulardii fugaemia in a critically ill patient with septic shock treated with a probiotic agent containing this yeast. We attributed this fugaemia to gut translocation. Our use of caspofugin yielded excellent results. PMID:18423057

Methodology of Spread-Spectrum Image Steganography

DTIC Science & Technology

1998-06-01

the message was literally uncovered. Modern times have yielded more advanced techniques, such as the use of invisible inks, where certain chemical ...MILITARY ACADEMY MATH SCI CTR OF EXCELLENCE DEPT OF MATHEMATICAL SCI MDN A MAJ DON ENGEN THAYERHALL WEST POINT NY 10996-1786 1 DIRECTOR

Preparation of porphyrins and their metal complexes

DOEpatents

Ellis, Jr., Paul E.; Langdale, Wayne A.

1997-01-01

A hydroxyl-containing pyrrolic compound having a hydroxyl group or a hydroxyl-containing group in the 2-position, optionally substituted in the beta positions, is condensed in an acidified two immiscible phase solvent system to produce excellent yields of the corresponding porphyrin or metal porphyrin.

Preparation of porphyrins and their metal complexes

DOEpatents

Ellis, P.E. Jr.; Langdale, W.A.

1997-08-19

A hydroxyl-containing pyrrolic compound having a hydroxyl group or a hydroxyl-containing group in the 2-position, optionally substituted in the beta positions, is condensed in an acidified two immiscible phase solvent system to produce excellent yields of the corresponding porphyrin or metal porphyrin.

The Key Pieces of the Career Survival and Success Puzzle.

ERIC Educational Resources Information Center

Simonetti, Jack L.

1999-01-01

Analysis of career-success factors identified by 5,000 managers yielded 10 key pieces: excellent performance record, communication skills, interpersonal skills, personality, skill currency, significant work experiences, power, ability to withstand pressure, ability to make difficult decisions, and having a mentor. (SK)

Significant rate accelerated synthesis of glycosyl azides and glycosyl 1,2,3-triazole conjugates.

PubMed

Kumar, Rishi; Maulik, Prakas R; Misra, Anup Kumar

2008-10-01

An efficient and significantly rapid access of a series of glycosyl azides and glycosyl 1,2,3-triazole conjugates is reported using modified one-pot reaction conditions. In both cases yields were excellent and single diastereomers were obtained.

The application of a monolithic triphenylphosphine reagent for conducting Appel reactions in flow microreactors.

PubMed

Roper, Kimberley A; Lange, Heiko; Polyzos, Anastasios; Berry, Malcolm B; Baxendale, Ian R; Ley, Steven V

2011-01-01

Herein we describe the application of a monolithic triphenylphosphine reagent to the Appel reaction in flow-chemistry processing, to generate various brominated products with high purity and in excellent yields, and with no requirement for further off-line purification.

Magnetically separable nanoferrite-anchored glutathione: Aqueous homocoupling of arylboronic acids under microwave irradiation

EPA Science Inventory

A highly active, stable and magnetically separable glutathione based organocatalyst provided good to excellent yields to symmetric biaryls in the homocoupling of arylboronic acids under microwave irradiation. Symmetrical biaryl motifs are present in a wide range of natural p...

Comparisons of Photosynthetic Responses of Xanthium strumarium and Helianthus annuus to Chronic and Acute Water Stress in Sun and Shade 1

PubMed Central

Ben, Gui-Ying; Osmond, C. Barry; Sharkey, Thomas D.

1987-01-01

We have examined the effects of mild, chronic water stress and acute water stress on two water stress sensitive plants, Xanthium strumarium and Helianthus annuus. Using a combination of the leaf disc O2 electrode to measure the light responses of photosynthesis and 77 K fluorescence to monitor damage to the primary photochemistry, we have found the following: (a) The CO2 saturated rate of photosynthesis at high light is the most water stress sensitive parameter measured. (b) The apparent quantum yield (moles O2 per mole photons) was slightly, if at all, affected by mild water stress (>−1.5 megapascals). (c) Severe water stress (<−1.5 megapascals) reduced the quantum yield of photosynthesis regardless of whether the stress was applied in sun or shade. The light independent reduction of quantum yield was not associated with a reduction in 77 K fluorescence (Fv/Fm) indicating that the quantum yield reduction was not the result of damage to primary photochemistry. (d) The diel fluctuation in 77 K fluorescence seen in sun-exposed control leaves was greatly exaggerated in water stressed leaves because of enhanced decline in 77 K fluorescence in the morning. The rate of recovery was similar in both control and water stressed leaves. Shaded leaves showed no change in 77 K fluorescence regardless of whether water stress was imposed or not. (e) The water stress sensitive plants used in these experiments did not recover from acute water stress severe enough to reduce the quantum yield or chronic water stress which lasted long enough that light dependent damage to primary photochemistry occurred. PMID:16665465

Comparisons of Photosynthetic Responses of Xanthium strumarium and Helianthus annuus to Chronic and Acute Water Stress in Sun and Shade.

PubMed

Ben, G Y; Osmond, C B; Sharkey, T D

1987-06-01

We have examined the effects of mild, chronic water stress and acute water stress on two water stress sensitive plants, Xanthium strumarium and Helianthus annuus. Using a combination of the leaf disc O(2) electrode to measure the light responses of photosynthesis and 77 K fluorescence to monitor damage to the primary photochemistry, we have found the following: (a) The CO(2) saturated rate of photosynthesis at high light is the most water stress sensitive parameter measured. (b) The apparent quantum yield (moles O(2) per mole photons) was slightly, if at all, affected by mild water stress (>-1.5 megapascals). (c) Severe water stress (<-1.5 megapascals) reduced the quantum yield of photosynthesis regardless of whether the stress was applied in sun or shade. The light independent reduction of quantum yield was not associated with a reduction in 77 K fluorescence (F(v)/F(m)) indicating that the quantum yield reduction was not the result of damage to primary photochemistry. (d) The diel fluctuation in 77 K fluorescence seen in sun-exposed control leaves was greatly exaggerated in water stressed leaves because of enhanced decline in 77 K fluorescence in the morning. The rate of recovery was similar in both control and water stressed leaves. Shaded leaves showed no change in 77 K fluorescence regardless of whether water stress was imposed or not. (e) The water stress sensitive plants used in these experiments did not recover from acute water stress severe enough to reduce the quantum yield or chronic water stress which lasted long enough that light dependent damage to primary photochemistry occurred.

Multicolor white light-emitting diodes for illumination applications

NASA Astrophysics Data System (ADS)

Chi, Solomon W. S.; Chen, Tzer-Perng; Tu, Chuan-Cheng; Chang, Chih-Sung; Tsai, Tzong-Liang; Hsieh, Mario C. C.

2004-01-01

Semiconductor light emitting diode (LED) has become a promising device for general-purpose illumination applications. LED has the features of excellent durability, long operation life, low power consumption, no mercury containing and potentially high efficiency. Several white LED technologies appear capable of meeting the technical requirements of illumination. In this paper we present a new multi-color white (MCW) LED as a high luminous efficacy, high color rendering index and low cost white illuminator. The device consists of two LED chips, one is AlInGaN LED for emitting shorter visible spectra, another is AlInGaP LED for emitting longer visible spectra. At least one chip in the MCW-LED has two or more transition energy levels used for emitting two or more colored lights. The multiple colored lights generated from the MCW-LED can be mixed into a full-spectral white light. Besides, there is no phosphors conversion layer used in the MCW-LED structure. Therefore, its color rendering property and illumination efficiency are excellent. The Correlated Color Temperature (CCT) of the MCW-LED may range from 2,500 K to over 10,000 K. The theoretical General Color Rendering Index (Ra) could be as high as 94, which is close to the incandescent and halogen sources, while the Ra of binary complementary white (BCW) LED is about 30 ~ 45. Moreover, compared to the expensive ternary RGB (Red AlInGaP + Green AlInGaN + Blue AlInGaN) white LED sources, the MCW-LED uses only one AlInGaN chip in combination with one cheap AlInGaP chip, to form a low cost, high luminous performance white light source. The MCW-LED is an ideal light source for general-purpose illumination applications.

Facile and Promising Method for Michael Addition of Indole and Pyrrole to Electron-Deficient trans-β-Nitroolefins Catalyzed by a Hydrogen Bond Donor Catalyst Feist's Acid and Preliminary Study of Antimicrobial Activity

PubMed Central

Al Majid, Abdullah M. A.; Islam, Mohammad Shahidul; Barakat, Assem; Al-Agamy, Mohamed H. M.; Naushad, Mu.

2014-01-01

The importance of cooperative hydrogen-bonding effects has been demonstrated using novel 3-methylenecyclopropane-1,2-dicarboxylic acid (Feist's acid (FA)) as hydrogen bond donor catalysts for the addition of indole and pyrrole to trans-β-nitrostyrene derivatives. Because of the hydrogen bond donor (HBD) ability, Feist's acid (FA) has been introduced as a new class of hydrogen bond donor catalysts for the activation of nitroolefin towards nucleophilic substitution reaction. It has effectively catalyzed the Michael addition of indoles and pyrrole to β-nitroolefins under optimum reaction condition to furnish the corresponding Michael adducts in good to excellent yields (up to 98%). The method is general, atom-economical, convenient, and eco-friendly and could provide excellent yields and regioselectivities. Some newly synthesized compounds were for examined in vitro antimicrobial activity and their preliminary results are reported. PMID:24574906

Highly ordered nanowire arrays on plastic substrates for ultrasensitive flexible chemical sensors.

PubMed

McAlpine, Michael C; Ahmad, Habib; Wang, Dunwei; Heath, James R

2007-05-01

The development of a robust method for integrating high-performance semiconductors on flexible plastics could enable exciting avenues in fundamental research and novel applications. One area of vital relevance is chemical and biological sensing, which if implemented on biocompatible substrates, could yield breakthroughs in implantable or wearable monitoring systems. Semiconducting nanowires (and nanotubes) are particularly sensitive chemical sensors because of their high surface-to-volume ratios. Here, we present a scalable and parallel process for transferring hundreds of pre-aligned silicon nanowires onto plastic to yield highly ordered films for low-power sensor chips. The nanowires are excellent field-effect transistors, and, as sensors, exhibit parts-per-billion sensitivity to NO2, a hazardous pollutant. We also use SiO2 surface chemistries to construct a 'nano-electronic nose' library, which can distinguish acetone and hexane vapours via distributed responses. The excellent sensing performance coupled with bendable plastic could open up opportunities in portable, wearable or even implantable sensors.

Highly ordered nanowire arrays on plastic substrates for ultrasensitive flexible chemical sensors

NASA Astrophysics Data System (ADS)

McAlpine, Michael C.; Ahmad, Habib; Wang, Dunwei; Heath, James R.

2007-05-01

The development of a robust method for integrating high-performance semiconductors on flexible plastics could enable exciting avenues in fundamental research and novel applications. One area of vital relevance is chemical and biological sensing, which if implemented on biocompatible substrates, could yield breakthroughs in implantable or wearable monitoring systems. Semiconducting nanowires (and nanotubes) are particularly sensitive chemical sensors because of their high surface-to-volume ratios. Here, we present a scalable and parallel process for transferring hundreds of pre-aligned silicon nanowires onto plastic to yield highly ordered films for low-power sensor chips. The nanowires are excellent field-effect transistors, and, as sensors, exhibit parts-per-billion sensitivity to NO2, a hazardous pollutant. We also use SiO2 surface chemistries to construct a `nano-electronic nose' library, which can distinguish acetone and hexane vapours via distributed responses. The excellent sensing performance coupled with bendable plastic could open up opportunities in portable, wearable or even implantable sensors.

A highly efficient silole-containing dithienylethene with excellent thermal stability and fatigue resistance: a promising candidate for optical memory storage materials.

PubMed

Chan, Jacky Chi-Hung; Lam, Wai Han; Yam, Vivian Wing-Wah

2014-12-10

Diarylethene compounds are potential candidates for applications in optical memory storage systems and photoswitchable molecular devices; however, they usually show low photocycloreversion quantum yields, which result in ineffective erasure processes. Here, we present the first highly efficient photochromic silole-containing dithienylethene with excellent thermal stability and fatigue resistance. The photochemical quantum yields for photocyclization and photocycloreversion of the compound are found to be high and comparable to each other; the latter of which is rarely found in diarylethene compounds. These would give rise to highly efficient photoswitchable material with effective writing and erasure processes. Incorporation of the silole moiety as a photochromic dithienylethene backbone also was demonstrated to enhance the thermal stability of the closed form, in which the thermal backward reaction to the open form was found to be negligible even at 100 °C, which leads to a promising candidate for use as photoswitchable materials and optical memory storage.

Highly ordered nanowire arrays on plastic substrates for ultrasensitive flexible chemical sensors

PubMed Central

McAlpine, Michael C.; Ahmad, Habib; Wang, Dunwei; Heath, James R.

2013-01-01

The development of a robust method for integrating high-performance semiconductors on flexible plastics could enable exciting avenues in fundamental research and novel applications. One area of vital relevance is chemical and biological sensing, which if implemented on biocompatible substrates, could yield breakthroughs in implantable or wearable monitoring systems. Semiconducting nanowires (and nanotubes) are particularly sensitive chemical sensors because of their high surface-to-volume ratios. Here, we present a scalable and parallel process for transferring hundreds of pre-aligned silicon nanowires onto plastic to yield highly ordered films for low-power sensor chips. The nanowires are excellent field-effect transistors, and, as sensors, exhibit parts-per-billion sensitivity to NO2, a hazardous pollutant. We also use SiO2 surface chemistries to construct a ‘nano-electronic nose’ library, which can distinguish acetone and hexane vapours via distributed responses. The excellent sensing performance coupled with bendable plastic could open up opportunities in portable, wearable or even implantable sensors. PMID:17450146

Coumarin-Based Oxime Esters: Photobleachable and Versatile Unimolecular Initiators for Acrylate and Thiol-Based Click Photopolymerization under Visible Light-Emitting Diode Light Irradiation.

PubMed

Li, Zhiquan; Zou, Xiucheng; Zhu, Guigang; Liu, Xiaoya; Liu, Ren

2018-05-09

Developing efficient unimolecular visible light-emitting diode (LED) light photoinitiators (PIs) with photobleaching capability, which are essential for various biomedical applications and photopolymerization of thick materials, remains a great challenge. Herein, we demonstrate the synthesis of a series of novel PIs, containing coumarin moieties as chromophores and oxime ester groups as initiation functionalities and explore their structure-activity relationship. The investigated oxime esters can effectively induce acrylates and thiol-based click photopolymerization under 450 nm visible LED light irradiation. The initiator O-3 exhibited excellent photobleaching capability and enabled photopolymerization of thick materials (∼4.8 mm). The efficient unimolecular photobleachable initiators show great potential in dental materials and 3D printings.

Production of organic compounds in plasmas: A comparison among electric sparks, laser-induced plasmas and UV light

NASA Technical Reports Server (NTRS)

Scattergood, T. W.; Mckay, C. P.; Borucki, W. J.; Giver, L. P.; Vanghyseghem, H.; Parris, J. E.; Miller, S. L.

1991-01-01

In order to study the production of organic compounds in plasmas (and shocks), various mixtures of N2, CH4, and H2, modeling the atmosphere of Titan, were exposed to discrete sparks, laser-induced plasmas (LIP) and ultraviolet light. The yields of HCN and simple hydrocarbons were measured and compared to those calculated from a simple quenched thermodynamic equilibrium model. The agreement between experiment and theory was fair for HCN and C2H2. However, the yields of C2H6 and other hydrocarbons were much higher than those predicted by the model. Our experiments suggest that photolysis by ultraviolet light from the plasma is an important process in the synthesis. This was confirmed by the photolysis of gas samples exposed to the light, but not to the plasma or shock waves. The results of these experiments demonstrate that, in addition to the well-known efficient synthesis of organic compounds in plasmas, the yields of saturated species, e.g., ethane, may be higher than predicted by theory and that LIP provide a convenient and clean way of simulating planetary lightning and impact plasmas in the laboratory.

Increased phytochrome B alleviates density effects on tuber yield of field potato crops.

PubMed

Boccalandro, Hernán E; Ploschuk, Edmundo L; Yanovsky, Marcelo J; Sánchez, Rodolfo A; Gatz, Christiane; Casal, Jorge J

2003-12-01

The possibility that reduced photomorphogenic responses could increase field crop yield has been suggested often, but experimental support is still lacking. Here, we report that ectopic expression of the Arabidopsis PHYB (phytochrome B) gene, a photoreceptor involved in detecting red to far-red light ratio associated with plant density, can increase tuber yield in field-grown transgenic potato (Solanum tuberosum) crops. Surprisingly, this effect was larger at very high densities, despite the intense reduction in the red to far-red light ratios and the concomitant narrowed differences in active phytochrome B levels between wild type and transgenics at these densities. Increased PHYB expression not only altered the ability of plants to respond to light signals, but they also modified the light environment itself. This combination resulted in larger effects of enhanced PHYB expression on tuber number and crop photosynthesis at high planting densities. The PHYB transgenics showed higher maximum photosynthesis in leaves of all strata of the canopy, and this effect was largely due to increased leaf stomatal conductance. We propose that enhanced PHYB expression could be used in breeding programs to shift optimum planting densities to higher levels.

A metallic metal oxide (Ti5O9)-metal oxide (TiO2) nanocomposite as the heterojunction to enhance visible-light photocatalytic activity

NASA Astrophysics Data System (ADS)

Li, L. H.; Deng, Z. X.; Xiao, J. X.; Yang, G. W.

2015-06-01

Coupling titanium dioxide (TiO2) with other semiconductors is a popular method to extend the optical response range of TiO2 and improve its photon quantum efficiency, as coupled semiconductors can increase the separation rate of photoinduced charge carriers in photocatalysts. Differing from normal semiconductors, metallic oxides have no energy gap separating occupied and unoccupied levels, but they can excite electrons between bands to create a high carrier mobility to facilitate kinetic charge separation. Here, we propose the first metallic metal oxide-metal oxide (Ti5O9-TiO2) nanocomposite as a heterojunction for enhancing the visible-light photocatalytic activity of TiO2 nanoparticles and we demonstrate that this hybridized TiO2-Ti5O9 nanostructure possesses an excellent visible-light photocatalytic performance in the process of photodegrading dyes. The TiO2-Ti5O9 nanocomposites are synthesized in one step using laser ablation in liquid under ambient conditions. The as-synthesized nanocomposites show strong visible-light absorption in the range of 300-800 nm and high visible-light photocatalytic activity in the oxidation of rhodamine B. They also exhibit excellent cycling stability in the photodegrading process. A working mechanism for the metallic metal oxide-metal oxide nanocomposite in the visible-light photocatalytic process is proposed based on first-principle calculations of Ti5O9. This study suggests that metallic metal oxides can be regarded as partners for metal oxide photocatalysts in the construction of heterojunctions to improve photocatalytic activity.

A metallic metal oxide (Ti5O9)-metal oxide (TiO2) nanocomposite as the heterojunction to enhance visible-light photocatalytic activity.

PubMed

Li, L H; Deng, Z X; Xiao, J X; Yang, G W

2015-01-26

Coupling titanium dioxide (TiO2) with other semiconductors is a popular method to extend the optical response range of TiO2 and improve its photon quantum efficiency, as coupled semiconductors can increase the separation rate of photoinduced charge carriers in photocatalysts. Differing from normal semiconductors, metallic oxides have no energy gap separating occupied and unoccupied levels, but they can excite electrons between bands to create a high carrier mobility to facilitate kinetic charge separation. Here, we propose the first metallic metal oxide-metal oxide (Ti5O9-TiO2) nanocomposite as a heterojunction for enhancing the visible-light photocatalytic activity of TiO2 nanoparticles and we demonstrate that this hybridized TiO2-Ti5O9 nanostructure possesses an excellent visible-light photocatalytic performance in the process of photodegrading dyes. The TiO2-Ti5O9 nanocomposites are synthesized in one step using laser ablation in liquid under ambient conditions. The as-synthesized nanocomposites show strong visible-light absorption in the range of 300-800 nm and high visible-light photocatalytic activity in the oxidation of rhodamine B. They also exhibit excellent cycling stability in the photodegrading process. A working mechanism for the metallic metal oxide-metal oxide nanocomposite in the visible-light photocatalytic process is proposed based on first-principle calculations of Ti5O9. This study suggests that metallic metal oxides can be regarded as partners for metal oxide photocatalysts in the construction of heterojunctions to improve photocatalytic activity.

Photocatalytic Pre-Oxidation of Arsenic (III) in Groundwater by a Visible-Light-Driven System with Magnetic Separating Characteristic

NASA Astrophysics Data System (ADS)

Cui, Y.; Liu, Y.; Peng, L.; Qin, Y.

2017-12-01

Arsenic was a typical toxic metalloid element and its contamination in groundwater was widely recognized as a global health problem, especially in north China, where people depended on groundwater as water resource. Arsenic was existed as As(III) in underground water, and has low affinity to the surface of various minerals and more toxic and more difficultly to be removed compared with As(V), so a pre-oxidation technology by transforming As (III) to As (V) is highly desirable. Electrochemical and oxidizing agents were traditional technology, which usually causes secondary pollution. A novel methodology is presented here, using prepared magnetic visible-light-driven nanomaterials as recyclable media to investigate As(III) pre-oxidation processing. Ag@AgCl core-shell nanowires were first synthesized by oxidation of Ag nanowires with moderate FeCl3, and exhibited excellent photocatalytic activity to As(III) with visible-light. The ratio of chloridization was proved to act as key effect on photocatalytic oxidation efficiency. Testing with simulated groundwater condition proved that pH, ionic strength and concentration of humic acid have obvious effects on Ag@AgCl photocatalytic ability. h+ and ·O2- were confirmed to be the main active species during the visible-light driven photocatalytic oxidation process for As(III) by trapping experiments with radical scavengers. Then Fe0 was introduced to prepare Fe-Ag nanowire and chloridized into Fe-Ag@AgCl to provide magnetic characteristic. The magnetic recycling and re-chloride experiments validated this visible-light-driven material has excellent stable and high reused ability as photocatalyst under visible light irradiation.

Effect of Microstructure on the Radioluminescence and Transparency of Ce-Doped Strontium Hafnate Ceramics

PubMed Central

van Loef, Edgar V.; Wang, Yimin; Miller, Stuart R.; Brecher, Charles; Rhodes, William H.; Baldoni, Gary; Topping, Stephen; Lingertat, Helmut; Sarin, Vinod K.; Shah, Kanai S.

2011-01-01

In this paper we report on the fabrication and characterization of SrHfO3:Ce ceramics. Powders were prepared by solid-state synthesis using metal oxides and carbonates. X-ray diffraction measurements showed that phase-pure SrHfO3 is formed at 1200°C. Inductively coupled plasma spectroscopy confirmed the purity and composition of each batch. SrHfO3 exhibits several phase changes in the solid, but this does not appear to be detrimental to the ceramics. Microprobe experiments showed uniform elemental grain composition, whereas aluminum added as charge compensation for trivalent cerium congregated at grain boundaries and triple points. Radioluminescence spectra revealed that the light yield decreases when the concentration of excess Sr increases. The decrease in the light yield may be related to the change of Ce3+ into Ce4+ ions. For stoichiometric SrHfO3:Ce, the light yield is about four times that of bismuth germanate (BGO), the conventional benchmark, indicating great potential for many scintillator applications. PMID:21339835

Crystal growth and characterization of europium doped KCaI3, a high light yield scintillator

NASA Astrophysics Data System (ADS)

Lindsey, Adam C.; Zhuravleva, Mariya; Stand, Luis; Wu, Yuntao; Melcher, Charles L.

2015-10-01

The presented study reports on the spectroscopic characteristics of a new high performance scintillation material KCaI3:Eu. The growth of ∅ 17 mm boules using the Bridgman-Stockbarger method in fused silica ampoules is demonstrated to produce yellow tinted, yet transparent single crystals suitable for use in spectroscopic applications due to very promising performance. Scintillation light yield of 72,000 ± 3000 ph/MeV and energy resolution of 3% (FWHM) at 662 keV and 6.1% at 122 keV was obtained from small single crystals of approximately 15 mm3. For a much larger 3.8 cm3 detector, 4.4% and 7.3% for the same energy. Proportionality of the scintillation response to the energy of ionizing radiation is within 96% of the ideal response over an energy range of 14-662 keV. The high light yield and energy resolution of KCaI3:Eu make it suitable for potential use in domestic security applications requiring radionuclide identification.

Microcolumnar and polycrystalline growth of LaBr3:Ce scintillator

NASA Astrophysics Data System (ADS)

Nagarkar, V. V.; Miller, S.; Sia, R.; Gaysinskiy, V.

2011-05-01

While a wide variety of new scintillators are now available, cerium-doped lanthanide halide scintillators have shown a strong potential toward fulfilling the needs of highly demanding applications such as radioisotope identification at room temperature, homeland security, quantitative molecular imaging for medical diagnostics, and disease staging and research. Despite their extraordinary advantages in terms of light yield and response uniformity over a wide energy range, issues related to reliable, large volume manufacturing of these high-light-yield materials in a rapid and economic manner has not been resolved or purposefully addressed. Here we report on synthesizing LaBr3:Ce scintillator using a thermal evaporation technique, which offers the potential to synthesize large quantities of small-to-large volume, high-quality material in a time-efficient and cost-effective manner. To date we have successfully applied this method to form both microcolumnar films and thick polycrystalline slabs of LaBr3:Ce, and have characterized their light yield, response linearity, decay time and afterglow.

Estimating chlorophyll content and photochemical yield of photosystem II (ΦPSII) using solar-induced chlorophyll fluorescence measurements at different growing stages of attached leaves

PubMed Central

Tubuxin, Bayaer; Rahimzadeh-Bajgiran, Parinaz; Ginnan, Yusaku; Hosoi, Fumiki; Omasa, Kenji

2015-01-01

This paper illustrates the possibility of measuring chlorophyll (Chl) content and Chl fluorescence parameters by the solar-induced Chl fluorescence (SIF) method using the Fraunhofer line depth (FLD) principle, and compares the results with the standard measurement methods. A high-spectral resolution HR2000+ and an ordinary USB4000 spectrometer were used to measure leaf reflectance under solar and artificial light, respectively, to estimate Chl fluorescence. Using leaves of Capsicum annuum cv. ‘Sven’ (paprika), the relationships between the Chl content and the steady-state Chl fluorescence near oxygen absorption bands of O2B (686nm) and O2A (760nm), measured under artificial and solar light at different growing stages of leaves, were evaluated. The Chl fluorescence yields of ΦF 686nm/ΦF 760nm ratios obtained from both methods correlated well with the Chl content (steady-state solar light: R2 = 0.73; artificial light: R2 = 0.94). The SIF method was less accurate for Chl content estimation when Chl content was high. The steady-state solar-induced Chl fluorescence yield ratio correlated very well with the artificial-light-induced one (R2 = 0.84). A new methodology is then presented to estimate photochemical yield of photosystem II (ΦPSII) from the SIF measurements, which was verified against the standard Chl fluorescence measurement method (pulse-amplitude modulated method). The high coefficient of determination (R2 = 0.74) between the ΦPSII of the two methods shows that photosynthesis process parameters can be successfully estimated using the presented methodology. PMID:26071530

Cellulose nanofibers/reduced graphene oxide flexible transparent conductive paper.

PubMed

Gao, Kezheng; Shao, Ziqiang; Wu, Xue; Wang, Xi; Li, Jia; Zhang, Yunhua; Wang, Wenjun; Wang, Feijun

2013-08-14

The cellulose nanofibers (CNFs) paper exhibit high visible light transmittance, high mechanical strength, and excellent flexibility. Therefore, CNFs paper may be an excellent substrate material for flexible transparent electronic devices. In this paper, we endeavor to prepare CNFs-based flexible transparent conductive paper by layer-by-layer (LbL) assembly using divalent copper ions (Cu(2+)) as the crosslinking agent. The thickness of the reduced graphene oxide (RGO) active layer in the CNFs paper can be controlled by the cycle times of the LbL assembly. CNFs/[RGO]20 paper has the sheet resistances of ∼2.5 kΩ/□, and the transmittance of about 76% at a wavelength of 550 nm. Furthermore, CNFs/[RGO]20 paper inherits the excellent mechanical properties of CNFs paper, and the ultimate strength is about 136 MPa. CNFs-based flexible transparent conductive paper also exhibits excellent electrical stability and flexibility. Copyright © 2013. Published by Elsevier Ltd.

Effect of pulsed electric fields treatment and mash size on extraction and composition of apple juices.

PubMed

Turk, Mohammad F; Baron, Alain; Vorobiev, Eugene

2010-09-08

This study explored the effect of pulsed electric field (PEF) treatment (E=450 V/cm; tt=10 ms; E<3 kJ/kg) and apple mash size on juice yield, polyphenolic compounds, sugars, and malic acid. Juice yield increased significantly after PEF treatment of large mash (Y=71.4%) and remained higher than the juice yield obtained for a control small mash (45.6%). The acid sweet balance was not altered by PEF. A correlation was established between the decrease of light absorbance (control: 1.43; treated: 1.10) and the decline of native polyphenols yield due to PEF treatment (control: 9.6%; treated: 5.9% for small mash). An enhanced oxidation of phenolic compounds in cells due to electroporation of the inner cell membrane and the adsorption of the oxidized products on the mash may explain both the lower light absorbance and the lower native polyphenol concentration.

Aryl triolborates: novel reagent for copper-catalyzed N arylation of amines, anilines, and imidazoles.

PubMed

Yu, Xiao-Qiang; Yamamoto, Yasunori; Miyaura, Norio

2008-09-01

The N arylation of primary and secondary aliphatic amines, anilines, and imidazoles with novel potassium aryl triolborates was carried out in the presence of a reoxidant and a catalytic amount of Cu(OAc)(2) (10 mol %). Aryl triolborates were found to be better reagents than aryl boronic acids or potassium aryl trifluoroborates as the former achieved high yields under mild conditions. Coupling of primary and secondary aliphatic amines to give N-aryl amines in excellent yields was performed under oxygen atmosphere. The reactions of anilines and imidazoles to provide N-aryl anilines and N-aryl imidazoles in good yields proceeded smoothly when trimethylamine N-oxide was used as an oxidant.

Effects of periodic photoinhibitory light exposure on physiology and productivity of Arabidopsis plants grown under low light.

PubMed

Tian, Yonglan; Sacharz, Joanna; Ware, Maxwell A; Zhang, Huayong; Ruban, Alexander V

2017-07-10

This work examined the long-term effects of periodic high light stress on photosynthesis, morphology, and productivity of low-light-acclimated Arabidopsis plants. Significant photoinhibition of Arabidopsis seedlings grown under low light (100 μmol photons m-2 s-1) was observed at the beginning of the high light treatment (three times a day for 30 min at 1800 μmol photons m-2 s-1). However, after 2 weeks of treatment, similar photosynthesis yields (Fv/Fm) to those of control plants were attained. The daily levels of photochemical quenching measured in the dark (qPd) indicated that the plants recovered from photoinhibition within several hours once transferred back to low light conditions, with complete recovery being achieved overnight. Acclimation to high light stress resulted in the modification of the number, structure, and position of chloroplasts, and an increase in the average chlorophyll a/b ratio. During ontogenesis, high-light-exposed plants had lower total leaf areas but higher above-ground biomass. This was attributed to the consumption of starch for stem and seed production. Moreover, periodic high light exposure brought forward the reproductive phase and resulted in higher seed yields compared with control plants grown under low light. The responses to periodic high light exposure of mature Arabidopsis plants were similar to those of seedlings but had higher light tolerance. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Green Synthesis of Bifunctional Fluorescent Carbon Dots from Garlic for Cellular Imaging and Free Radical Scavenging.

PubMed

Zhao, Shaojing; Lan, Minhuan; Zhu, Xiaoyue; Xue, Hongtao; Ng, Tsz-Wai; Meng, Xiangmin; Lee, Chun-Sing; Wang, Pengfei; Zhang, Wenjun

2015-08-12

Nitrogen and sulfur codoped carbon dots (CDs) were prepared from garlic by a hydrothermal method. The as-prepared CDs possess good water dispersibility, strong blue fluorescence emission with a fluorescent quantum yield of 17.5%, and excellent photo and pH stabilities. It is also demonstrated that the fluorescence of CDs are resistant to the interference of metal ions, biomolecules, and high ionic strength environments. Combining with low cytotoxicity properties, CDs could be used as an excellent fluorescent probe for cellular multicolor imaging. Moreover, the CDs were also demonstrated to exhibit favorable radical scavenging activity.

Correlation of Non-proportionality and Scintillation Properties with Cerium Concentration in YAlO 3:Ce

DOE PAGES

Donnald, Samuel B.; Williams, Richard; Melcher, Charles L.; ...

2018-04-19

Cerium doped YAlO3 (YAP:Ce) is an interesting oxide scintillator in that it exhibits a wider range of light yield non-proportionality on a sample-to-sample basis than most other well-known oxide scintillators. In general, most oxide materials, such as BGO and LSO:Ce, are thought to have an intrinsic proportional response that is nearly constant between samples and independent of growth conditions. Since light yield nonproportionality is responsible for degrading the achievable energy resolution of all known scintillators, it is important to understand what contributes to the behavior. In this study, in an attempt to understand if the phenomenon can be affected bymore » growth parameters or by other means, seven samples of YAP:Ce were collected from various sources, and eight samples were grown inhouse using the Czochralski method. Based on optical and scintillation measurement as well as direct measurement of the cerium concentration, it was determined that the light yield proportionality in YAlO3:Ce is strongly related to the cerium concentration. Samples that were found to have a higher relative cerium concentration displayed a more proportional light yield response. In addition, it was determined that samples with a higher cerium concentration also exhibit a faster decay time and an enhanced energy resolution when compared to samples with less cerium. Finally, it was also determined that growth in a reducing atmosphere can effectively suppress a parasitic optical absorption band.« less

Correlation of Non-proportionality and Scintillation Properties with Cerium Concentration in YAlO 3:Ce

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

Donnald, Samuel B.; Williams, Richard; Melcher, Charles L.

Cerium doped YAlO3 (YAP:Ce) is an interesting oxide scintillator in that it exhibits a wider range of light yield non-proportionality on a sample-to-sample basis than most other well-known oxide scintillators. In general, most oxide materials, such as BGO and LSO:Ce, are thought to have an intrinsic proportional response that is nearly constant between samples and independent of growth conditions. Since light yield nonproportionality is responsible for degrading the achievable energy resolution of all known scintillators, it is important to understand what contributes to the behavior. In this study, in an attempt to understand if the phenomenon can be affected bymore » growth parameters or by other means, seven samples of YAP:Ce were collected from various sources, and eight samples were grown inhouse using the Czochralski method. Based on optical and scintillation measurement as well as direct measurement of the cerium concentration, it was determined that the light yield proportionality in YAlO3:Ce is strongly related to the cerium concentration. Samples that were found to have a higher relative cerium concentration displayed a more proportional light yield response. In addition, it was determined that samples with a higher cerium concentration also exhibit a faster decay time and an enhanced energy resolution when compared to samples with less cerium. Finally, it was also determined that growth in a reducing atmosphere can effectively suppress a parasitic optical absorption band.« less

Skeleton/skin structured (RGO/CNTs)@PANI composite fiber electrodes with excellent mechanical and electrochemical performance for all-solid-state symmetric supercapacitors.

PubMed

Liu, Dong; Du, Pengcheng; Wei, Wenli; Wang, Hongxing; Wang, Qi; Liu, Peng

2018-03-01

Polyaniline coated reduced graphene oxide/carbon nanotube composite fibers ((RGO/CNTs)@PANI, RCP) with skeleton/skin structure are designed as fiber-shaped electrodes for high performance all-solid-state symmetric supercapacitor. The one-dimensional reduced graphene oxide/carbon nanotube composite fibers (RGO/CNTs, RC) are prepared via a simple in-situ reduction of graphene oxide in presence of carbon nanotubes in quartz glass pipes, which exhibit excellent mechanical performance of >193.4 MPa of tensile strength. Then polyaniline is coated onto the RC fibers by electrodepositing technique. The electrochemical properties of the RCP fiber-shaped electrodes are optimized by adjusting the feeding ratio of carbon nanotubes. The optimized one exhibits good electrochemical characteristic such as highest volumetric specific capacitance of 193.1 F cm -3 at 1 A cm -3 , as well as excellent cyclic retention of 92.60% after 2000 cyclic voltammetry cycles. Furthermore, the all-solid-state symmetric supercapacitor, fabricated by using the final composite fiber as both positive and negative electrodes pre-coated with the poly(vinyl alcohol)/H 2 SO 4 gel polyelectrolyte, possesses volumetric capacitance of 36.7 F cm -3 at 0.2 A cm -3 and could light up a red light-emitting diode easily. The excellent mechanical and electrochemical performances make the designed supercapacitor as promising high performance wearable energy storage device. Copyright © 2017 Elsevier Inc. All rights reserved.

Treatment of hypertrophic scars and keloids using intense pulsed light (IPL).

PubMed

Erol, O Onur; Gurlek, Ali; Agaoglu, Galip; Topcuoglu, Ela; Oz, Hayat

2008-11-01

Keloids and hypertrophic scars are extremely disturbing to patients, both physically and psychologically. This study prospectively assessed the safety and efficacy of intense pulsed light (IPL) on scars originating from burns, trauma, surgery, and acne. Hypertrophic scars in 109 patients, originating from surgical incisions (n = 55), traumatic cuts (traffic accidents) (n = 24), acne scars (n = 6), keloids (n = 5), and burns (n = 19), were treated using an IPL Quantum device. Treatment was administered at 2-4-week intervals, and patients received an average of 8 treatments (range = 6-24). Using digital photographs, Changes in scar appearance were assessed by two physicians who were blinded to the study patients and treatments. The photographs were graded on a scale of 0 to 4 (none, minimal, moderate, good, excellent) for improvement in overall clinical appearance and reduction in height, erythema, and hardness. An overall clinical improvement in the appearance of scars and reductions in height, erythema, and hardness were seen in the majority of the patients (92.5%). Improvement was excellent in 31.2% of the patients, good in 25.7%, moderate in 34%, and minimal in 9.1%. Over half the patients had good or excellent improvement. In the preventive IPL treatment group, 65% had good to excellent improvement in clinical appearance. Patient satisfaction was very high. This study suggests that IPL is effective not only in improving the appearance of hypertrophic scars and keloids regardless of their origin, but also in reducing the height, redness, and hardness of scars.

CeO2 /Bi2 WO6 Heterostructured Microsphere with Excellent Visible-light-driven Photocatalytic Performance for Degradation of Tetracycline Hydrochloride.

PubMed

Zhang, Fengjun; Zou, Shuang; Wang, Tianye; Shi, Yuxi; Liu, Peng

2017-10-01

CeO 2 /Bi 2 WO 6 heterostructured microsphere with excellent and stable photocatalytic activity for degradation tetracyclines was successfully synthesized via a facile solvothermal route. The photocatalytic experiments indicated that CeO 2 /Bi 2 WO 6 heterostructured microspheres exhibited enhanced photocatalytic activity compared to pure Bi 2 WO 6 in both the degradation of tetracycline hydrochloride (TCH) and rhodamine B (RhB) under visible-light irradiation. The 1CeO 2 /2Bi 2 WO 6 exhibited the best photocatalytic activity for degradation of TCH, reaching 91% after 60 min reaction. The results suggested that the particular morphological conformation of the microspheres resulted in smaller size and more uniform morphology so as to increase the specific surface area. Meanwhile, the heterojunction was formed by coupling CeO 2 and Bi 2 WO 6 in the as-prepared microspheres, so that the separation efficiency of photogenerated electrons and holes was dramatically improved and the lifetimes of charge carriers were prolonged. Hence, introduction of CeO 2 could significantly enhance the photocatalytic activity of CeO 2 /Bi 2 WO 6 heterostructured microspheres and facilitate the degradation of TCH. This work provided not only a principle method to synthesize CeO 2 /Bi 2 WO 6 with the excellent photocatalytic performance for actual produce, but also a excellent property of the photocatalyst for potential application in photocatalytic treatment of tetracyclines wastewater from pharmaceutical factory. © 2017 The American Society of Photobiology.

LED lighting – modification of growth, metabolism, yield and flour composition in wheat by spectral quality and intensity

USDA-ARS?s Scientific Manuscript database

The use of light-emitting diode (LED) technology for plant cultivation under controlled environmental conditions can result in significant reductions in energy consumption. However, there is still a lack of detailed information on the lighting conditions required for optimal growth of different plan...

Biomass and pigments production in photosynthetic bacteria wastewater treatment: effects of light sources.

PubMed

Zhou, Qin; Zhang, Panyue; Zhang, Guangming

2015-03-01

This study is aimed at enhancing biomass and pigments production together with pollution removal in photosynthetic bacteria (PSB) wastewater treatment via different light sources. Red, yellow, blue, white LED and incandescent lamp were used. Results showed different light sources had great effects on the PSB. PSB had the highest biomass production, COD removal and biomass yield with red LED. The corresponding biomass, COD removal and biomass yield reached 2580 mg/L, 88.6% and 0.49 mg-biomass/mg-COD-removal, respectively. The hydraulic retention time of wastewater treatment could be shortened to 72 h with red LED. Mechanism analysis showed higher ATP was produced with red LED than others. Light sources could significantly affect the pigments production. The pigments productions were greatly higher with LED than incandescent lamp. Yellow LED had the highest pigments production while red LED produced the highest carotenoid/bacteriochlorophyll ratio. Considering both efficiency and energy cost, red LED was the optimal light source. Copyright © 2014 Elsevier Ltd. All rights reserved.

Estimating Texas motor vehicle operating costs.

DOT National Transportation Integrated Search

2009-10-01

A specific Vcost model was developed for Texas conditions based on a sophisticated fuel model for light : duty vehicles, several excellent sources of secondary vehicle cost data, and the ability to measure heavy truck fuel : consumption through both ...

Fabrication of a PANI/CPs composite material: a feasible method to enhance the photocatalytic activity of coordination polymers.

PubMed

Xu, Xin-Xin; Cui, Zhong-Ping; Qi, Ji; Liu, Xiao-Xia

2013-03-21

To improve the photocatalytic activity of a coordination polymer in the visible light region, polyaniline (PANI) was loaded onto its surface through a facile in situ chemical oxidation polymerization process. The resulting PANI loaded coordination polymer composite materials with excellent stability exhibit significantly higher photocatalytic activities than the pure coordination polymer photocatalyst on the degradation of methyl orange (MO) under visible light irradiation. This enhancement can be ascribed to the introduction of PANI on the surface of the coordination polymer, which leads to efficient separation of photogenerated electron-hole pairs as well as a significant expansion of the photoresponse region. Finally, we discussed the influence of acidity on the morphology and photocatalytic activity of the composite material. An optimal condition to obtain the PANI loaded coordination polymer composite material with excellent photocatalytic activity has been obtained.

Research on optical biosensor with up-converting phosphor marker

NASA Astrophysics Data System (ADS)

Zhao, Yongkai; Zhou, Lei; Wang, Jing; Huang, Lihua; Yan, Zhongqiang; Huang, Huijie; Yang, Ruifu; Liu, Lei; Ren, Bingqiang; Wang, Xiangzhao

2006-08-01

An optical biosensor with up-converting phosphor (UCP) marker is developed for the sensitive rapid immunoassay to the specific biomolecule. UCP can emit visible light when excited by infrared light. Through detecting and analyzing the content of UCP particles on the test strip after immunoreaction, the concentration of target analyte in the sample can be obtained. The detection sensitivity to plague IgG is better than 5 ng/ml; to plague FI-Ab is better than 100 pg/ml; to plague Yersinia pestis cell is better than 3*10^(4) CFU/ml. Good linear response characteristics and an excellent correlation (R2>=0.95) have been verified by quantitative detection results. In the practical application, detection results to 167 analytic samples have an excellent consistency with those obtained by reverse hemagglutination test. The up-converting phosphor technology (UPT) based biosensor has stable, reliable, and sensitive performances. It can meet the need of various bioassay applications.

Poly(vinylpyrrolidone) supported copper nanoclusters: glutathione enhanced blue photoluminescence for application in phosphor converted light emitting devices

NASA Astrophysics Data System (ADS)

Wang, Zhenguang; Susha, Andrei S.; Chen, Bingkun; Reckmeier, Claas; Tomanec, Ondrej; Zboril, Radek; Zhong, Haizheng; Rogach, Andrey L.

2016-03-01

Poly(vinylpyrrolidone) supported Cu nanoclusters were synthesized by reduction of Cu(ii) ions with ascorbic acid in water, and initially showed blue photoluminescence with a quantum yield of 8%. An enhancement of the emission quantum yield has been achieved by treatment of Cu clusters with different electron-rich ligands, with the most pronounced effect (photoluminescence quantum yield of 27%) achieved with glutathione. The bright blue emission of glutathione treated Cu NCs is fully preserved in the solid state powder, which has been combined with commercial green and red phosphors to fabricate down-conversion white light emitting diodes with a high colour rendering index of 92.Poly(vinylpyrrolidone) supported Cu nanoclusters were synthesized by reduction of Cu(ii) ions with ascorbic acid in water, and initially showed blue photoluminescence with a quantum yield of 8%. An enhancement of the emission quantum yield has been achieved by treatment of Cu clusters with different electron-rich ligands, with the most pronounced effect (photoluminescence quantum yield of 27%) achieved with glutathione. The bright blue emission of glutathione treated Cu NCs is fully preserved in the solid state powder, which has been combined with commercial green and red phosphors to fabricate down-conversion white light emitting diodes with a high colour rendering index of 92. Electronic supplementary information (ESI) available: The optical spectra of control experiments for Cu NC synthesis, optimization of the reaction conditions, and spectra for LEDs chips and blue LEDs. See DOI: 10.1039/c6nr00806b

Nanoparticle-supported and magnetically recoverable palladium (Pd) catalyst: a selective and sustainable oxidation protocol with high turnover number

EPA Science Inventory

A magnetic nanoparticle-supported ruthenium hydroxide catalyst was readily prepared from inexpensive starting materials and shown to catalyze hydration of nitriles with excellent yield in benign aqueous medium. Catalyst recovery using an external magnetic field, superior activity...

Release of OLe peanut

USDA-ARS?s Scientific Manuscript database

OLe is a high oleic Spanish-type peanut that has excellent yield and enhanced Sclerotinia blight and pod rot resistance when compared to other high oleic Spanish cultivars. The purpose for releasing OLe is to provide peanut producers with a true Spanish peanut that is high oleic and has enhanced yi...

Muon g -2 in an alternative quasi-Yukawa unification with a less fine-tuned seesaw mechanism

NASA Astrophysics Data System (ADS)

Altın, Zafer; Ã-zdal, Ã.-zer; Ün, Cem Salih

2018-03-01

We explore the low-scale implications of the Pati-Salam Model including the TeV scale right-handed neutrinos interacting and mixing with the MSSM fields through the inverse seesaw (IS) mechanism in light of the muon anomalous magnetic moment (muon g -2 ) resolution and highlight the solutions which are compatible with the quasi-Yukawa unification condition (QYU). We find that the presence of the right-handed neutrinos causes heavy smuons as mμ ˜≳800 GeV in order to avoid tachyonic staus at the low scale. On the other hand, the sneutrinos can be as light as about 100 GeV, and along with the light charginos of mass ≲400 GeV , they can yield such large contributions to muon g -2 that the discrepancy between the experiment and the theory can be resolved. These solutions also require mχ˜1 ±≲400 GeV and mχ˜10≲200 . We also discuss such light chargino and neutralino along with the light stau (mτ ˜≳200 GeV ) in the light of current LHC results. Besides, the gluino mass lies in a range ˜[2.5 - 3.5 ] TeV , which is tested in near future experiments. In addition, the model predicts relatively light Higgsinos (μ ≲700 GeV ); hence, the second chargino mass is also light enough (≲700 GeV ) to contribute to muon g -2 . Light Higgsinos also yield less fine-tuning at the electroweak scale, and the regions compatible with muon g -2 restrict ΔEW≲100 strictly, and this region also satisfies the QYU condition. In addition, the ratios among the Yukawa couplings should be 1.8 ≲yt/yb≲2.6 , yτ/yb˜1.3 to yield correct fermion masses. Even though the right-handed neutrino Yukawa coupling can be varied freely, the solutions bound its range to 0.8 ≲yν/yb≲1.7 .

Blackbody emission from light interacting with an effective moving dispersive medium.

PubMed

Petev, M; Westerberg, N; Moss, D; Rubino, E; Rimoldi, C; Cacciatori, S L; Belgiorno, F; Faccio, D

2013-07-26

Intense laser pulses excite a nonlinear polarization response that may create an effective flowing medium and, under appropriate conditions, a blocking horizon for light. Here, we analyze in detail the interaction of light with such laser-induced flowing media, fully accounting for the medium dispersion properties. An analytical model based on a first Born approximation is found to be in excellent agreement with numerical simulations based on Maxwell's equations and shows that when a blocking horizon is formed, the stimulated medium scatters light with a blackbody emission spectrum. Based on these results, diamond is proposed as a promising candidate medium for future studies of Hawking emission from artificial, dispersive horizons.

Even illumination in total internal reflection fluorescence microscopy using laser light.

PubMed

Fiolka, R; Belyaev, Y; Ewers, H; Stemmer, A

2008-01-01

In modern fluorescence microscopy, lasers are a widely used source of light, both for imaging in total internal reflection and epi-illumination modes. In wide-field imaging, scattering of highly coherent laser light due to imperfections in the light path typically leads to nonuniform illumination of the specimen, compromising image analysis. We report the design and construction of an objective-launch total internal reflection fluorescence microscopy system with excellent evenness of specimen illumination achieved by azimuthal rotation of the incoming illuminating laser beam. The system allows quick and precise changes of the incidence angle of the laser beam and thus can also be used in an epifluorescence mode. 2007 Wiley-Liss, Inc

Cesium alignment produced by pumping with unpolarized light★

NASA Astrophysics Data System (ADS)

Shi, Yongqi; Weis, Antoine

2018-04-01

We demonstrate optical pumping on the four hyperfine components of the Cs D 1 transition by unpolarized (UPL) resonant laser light. The evidence is based on the reduction of the absorption coefficients κ 0 with increasing light power P in an uncoated Cs vapor cell with isotropic spin relaxation. For comparison we perform the same quantitative κ 0( P) measurements with linearly-polarized light (LPL) and circularly-polarized light (CPL). We find that our previously published algebraic expressions give an excellent description of all experimentally recorded induced transparency signals. Based on this we can make reliable absolute predictions for the power dependence of the spin orientation and alignment produced by pumping with LPL, CPL and UPL.

Efficient formation of benzylic quaternary centers via palladium catalysis.

PubMed

Gottumukkala, Aditya L; Suljagic, Jasmin; Matcha, Kiran; de Vries, Johannes G; Minnaard, Adriaan J

2013-09-01

Four's a crowd: An efficient protocol for the formation of benzylic quaternary centers via arylation of enones using a catalyst made from Pd(O2 CCF3 )2 and 2,2'-bipyridine is developed. For cyclic substrates, catalyst loadings as low as 1 mol % Pd are enough to afford excellent yields (>90%) using a variety of arylboronic acids. In case of acyclic substrates, the addition of KSbF6 was found to improve conversions and yields. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Unidirectional flow over asymmetric and symmetric ripples

NASA Astrophysics Data System (ADS)

Wiberg, Patricia L.; Nelson, Jonathan M.

1992-08-01

An LDV-equipped flume has yielded detailed measurements of velocity and turbulence over fixed sets of two-dimensional symmetric and asymmetric ripples. The measured velocities over the ripples are compared with the Nelson and Smith (1989)results for flow over larger-scale dunes; the new results are larger in the outer region of the flow, and the velocity profiles exhibit no sharp inflection at the top of the lowest wake. A model for flow over bedforms which has yielded excellent agreement with dune measurements is presently modified to better represent the observed flow over ripples.

Asymmetric organocatalyzed Michael addition of nitromethane to a 2-oxoindoline-3-ylidene acetaldehyde and the three one-pot sequential synthesis of (-)-horsfiline and (-)-coerulescine.

PubMed

Mukaiyama, Takasuke; Ogata, Kento; Sato, Itaru; Hayashi, Yujiro

2014-10-13

(-)-Horsfiline and (-)-coerulescine were synthesized through three one-pot operations in 33 and 46% overall yield, respectively. Key to the success was the efficient use of a diarylprolinol silyl ether to catalyze the asymmetric Michael addition of nitromethane to a 2-oxoindoline-3-ylidene acetaldehyde. This allowed the all-carbon quaternary, spirocyclic carbon stereocenter to be constructed in good yield with excellent enantioselectivity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enantioselective organocatalytic one-pot amination/aza-Michael/aldol condensation reaction sequence: synthesis of 3-pyrrolines with a quaternary stereocenter.

PubMed

Desmarchelier, Alaric; Coeffard, Vincent; Moreau, Xavier; Greck, Christine

2012-10-08

Primary amine-catalyzed direct conversion of α,α-disubstituted aldehydes into 3-pyrrolines with a quaternary stereocenter is reported. The one-pot enantioselective sequence is based on a α-amination, an aza-Michael addition of hydrazine, an aldol condensation dehydratation and proceeds with good yields and excellent levels of enantioselectivity. Synthetically attractive applications including the formation of aziridinopyrrolidine or epoxypyrrolidine derivatives with good yields and selectivities are also described. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Rhodium-catalyzed Asymmetric Hydrogenation of α-Dehydroamino Ketones: A General Approach to Chiral α-amino Ketones.

PubMed

Gao, Wenchao; Wang, Qingli; Xie, Yun; Lv, Hui; Zhang, Xumu

2016-01-01

Rhodium/DuanPhos-catalyzed asymmetric hydrogenation of aliphatic α-dehydroamino ketones has been achieved and afforded chiral α-amino ketones in high yields and excellent enantioselectives (up to 99 % ee), which could be reduced further to chiral β-amino alcohols by LiAlH(tBuO)3 with good yields. This protocol provides a readily accessible route for the synthesis of chiral α-amino ketones and chiral β-amino alcohols. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stray Light Analysis

NASA Technical Reports Server (NTRS)

1997-01-01

Based on a Small Business Innovation Research contract from the Jet Propulsion Laboratory, TracePro is state-of-the-art interactive software created by Lambda Research Corporation to detect stray light in optical systems. An image can be ruined by incidental light in an optical system. To maintain image excellence from an optical system, stray light must be detected and eliminated. TracePro accounts for absorption, specular reflection and refraction, scattering and aperture diffraction of light. Output from the software consists of spatial irradiance plots and angular radiance plots. Results can be viewed as contour maps or as ray histories in tabular form. TracePro is adept at modeling solids such as lenses, baffles, light pipes, integrating spheres, non-imaging concentrators, and complete illumination systems. The firm's customer base includes Lockheed Martin, Samsung Electronics and other manufacturing, optical, aerospace, and educational companies worldwide.

Combination of carbon dot and polymer dot phosphors for white light-emitting diodes.

PubMed

Sun, Chun; Zhang, Yu; Sun, Kai; Reckmeier, Claas; Zhang, Tieqiang; Zhang, XiaoYu; Zhao, Jun; Wu, Changfeng; Yu, William W; Rogach, Andrey L

2015-07-28

We realized white light-emitting diodes with high color rendering index (85-96) and widely variable color temperatures (2805-7786 K) by combining three phosphors based on carbon dots and polymer dots, whose solid-state photoluminescence self-quenching was efficiently suppressed within a polyvinyl pyrrolidone matrix. All three phosphors exhibited dominant absorption in the UV spectral region, which ensured the weak reabsorption and no energy transfer crosstalk. The WLEDs showed excellent color stability against the increasing current because of the similar response of the tricolor phosphors to the UV light variation.

Synthesis of Ce doped ZnO nanoparticles coupled with graphene oxide as efficient photocatalyst for the degradation of dye under day light

NASA Astrophysics Data System (ADS)

Labhane, P. K.; Patle, L. B.; Huse, V. R.; Sonawane, G. H.

2018-05-01

Ce doped ZnO nanoparticles coupled with graphene oxide (Ce-ZnO/GO) photocatalyst was prepared by co-precipitation and wet impregnation method. The effect of Ce doping on ZnO and ZnO-GO composite has been evaluated by using XRD, Williamson-Hall Plot, FESEM and EDX data. Solar light photocatalytic activities of samples were evaluated spectrophotometrically by the degradation of methylene blue (MB). Ce doped ZnO coupled with GO shows excellent catalytic efficiency compared to other samples, degrading MB completely within 120 min under day light.

Combined production of fucoxanthin and EPA from two diatom strains Phaeodactylum tricornutum and Cylindrotheca fusiformis cultures.

PubMed

Wang, Hui; Zhang, Yan; Chen, Lin; Cheng, Wentao; Liu, Tianzhong

2018-04-04

Fucoxanthin and eicosapentaenoic acid (EPA) provide significant health benefits for human population. Diatom is a potential natural livestock for the combined production of EPA and fucoxanthin. In this study, first, the effects of three important parameters including light intensity, nitrogen concentration and salinity were evaluated for the production of EPA and fucoxanthin in two diatom strains Phaeodactylum tricornutum and Cylindrotheca fusiformis. And then, two steps method based on light intensity were applied to produce EPA and fucoxanthin in large scale. Higher light intensity was first adopted for the high growth rate and lipid content of diatom, and after a period of time, light intensity was lowered to enhance the accumulation of fucoxanthin and EPA. In final, the highest EPA yields were 62.55 and 27.32 mg L -1 for P. tricornutum and C. fusiformis, and the fucoxanthin yield reached 8.32 and 6.05 mg L -1 , respectively.

Characterizing Chain Processes in Visible Light Photoredox Catalysis

PubMed Central

Cismesia, Megan A.

2015-01-01

The recognition that Ru(bpy)32+ andsimilar visible light absorbing transition metal complexes can be photocatalysts for a variety of synthetically useful organic reactions has resulted in a recent resurgence of interest in photoredox catalysis. However, many of the critical mechanistic aspects of this class of reactions remain poorly understood. In particular, the degree to which visible light photoredox reactions involve radical chain processes has been a point of some disagreement that has not been subjected to systematic analysis. We have now performed quantum yield measurements to demonstrate that threerepresentative, mechanistically distinct photoredox processes involve product-forming chain reactions. Moreover, we show that the combination of quantum yield and luminescence quenching experiments provides a rapid method to estimate the length of these chains. Together, these measurements constitute a robust, operationally facile strategy for characterizing chain processes in a wide range of visible light photoredox reactions. PMID:26668708

[Photosynthetic fluorescence characteristics of floating-leaved and submersed macrophytes commonly found in Taihu Lake].

PubMed

Song, Yu-zhi; Cai, Wei; Qin, Bo-qiang

2009-03-01

Some aquatic macrophytes commonly found in Taihu Lake, including Trapa bispinosa, Nymphyoides peltatum, Vallisneria natans, and Hydrilla verticillata were collected, and their maximal quantum yield of photosystem II (Fv/Fm) as well as the rapid light curves (RLCs) under conditions of light adaptation and dark adaptation were measured in situ by using a submersible and pulse-amplitude modulated fluorometer (Diving-PAM). The results showed that floating-leaved plants T. bispinosa and N. peltatum had higher potential maximum photosynthetic capacity than submerged macrophytes V. natans and H. verticillata. The measured maximal quantum yield of T. bispinosa, N. peltatum, V. natans, and H. verticillata was 0.837, 0.831, 0.684, and 0.764, respectively. Both the maximal relative electron transport rate and the half saturation point of light intensity of T. bispinosa and N. peltatum were higher than those of V. natans and H. verticillata, especially under the condition of light adaptation.

A versatile method for the determination of photochemical quantum yields via online UV-Vis spectroscopy.

PubMed

Stadler, Eduard; Eibel, Anna; Fast, David; Freißmuth, Hilde; Holly, Christian; Wiech, Mathias; Moszner, Norbert; Gescheidt, Georg

2018-05-16

We have developed a simple method for determining the quantum yields of photo-induced reactions. Our setup features a fibre coupled UV-Vis spectrometer, LED irradiation sources, and a calibrated spectrophotometer for precise measurements of the LED photon flux. The initial slope in time-resolved absorbance profiles provides the quantum yield. We show the feasibility of our methodology for the kinetic analysis of photochemical reactions and quantum yield determination. The typical chemical actinometers, ferrioxalate and ortho-nitrobenzaldehyde, as well as riboflavin, a spiro-compound, phosphorus- and germanium-based photoinitiators for radical polymerizations and the frequently utilized photo-switch azobenzene serve as paradigms. The excellent agreement of our results with published data demonstrates the high potential of the proposed method as a convenient alternative to the time-consuming chemical actinometry.

Facile synthesis of nanorod-type graphitic carbon nitride/Fe{sub 2}O{sub 3} composite with enhanced photocatalytic performance

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

Wang, Jiangpeng; Li, Changqing; Cong, Jingkun

2016-06-15

Here we report a facile synthesis of nanorod-type graphitic carbon nitride/Fe{sub 2}O{sub 3} composite (Fe{sub 2}O{sub 3}-g-C{sub 3}N{sub 4}) by using Fe-melamine supramolecular framework as precursor. The chemical and optical properties of the nanocomposites are well-characterized. The Fe{sub 2}O{sub 3}-g-C{sub 3}N{sub 4} nanocomposite demonstrated excellent photocatalytic activities under visible light due to the efficient utilization of sunlight and the construction of Z-scheme electron transfer pathway. The results indicated that it could be a promising approach for the preparation of efficient g-C{sub 3}N{sub 4} nanocomposites photocatalysts by using metal-melamine supramolecular framework as precursors. - Graphical abstract: Nanorod-type graphitic carbon nitride/Fe{sub 2}O{submore » 3} composite (Fe{sub 2}O{sub 3}-g-C{sub 3}N{sub 4}) was synthesized by using Fe-melamine supramolecular framework as precursor. The Fe{sub 2}O{sub 3}-g-C{sub 3}N{sub 4} nanocomposite demonstrated excellent photocatalytic activities under visible light. Display Omitted - Highlights: • Nanorod-type graphitic carbon nitride/Fe{sub 2}O{sub 3} composite (Fe{sub 2}O{sub 3}-g-C{sub 3}N{sub 4}) was synthesized. • Fe{sub 2}O{sub 3}-g-C{sub 3}N{sub 4} showed strong optical absorption in the visible-light region. • The Fe{sub 2}O{sub 3}-g-C{sub 3}N{sub 4} nanocomposite demonstrated excellent photocatalytic activities.« less

Crop yield and light/energy efficiency in a closed ecological system: Laboratory Biosphere experiments with wheat and sweet potato.

PubMed

Nelson, M; Dempster, W F; Silverstone, S; Alling, A; Allen, J P; van Thillo, M

2005-01-01

Two crop growth experiments in the soil-based closed ecological facility, Laboratory Biosphere, were conducted from 2003 to 2004 with candidate space life support crops. Apogee wheat (Utah State University variety) was grown, planted at two densities, 400 and 800 seeds m-2. The lighting regime for the wheat crop was 16 h of light-8 h dark at a total light intensity of around 840 micromoles m-2 s-1 and 48.4 mol m-2 d-1 over 84 days. Average biomass was 1395 g m-2, 16.0 g m-2 d-1 and average seed production was 689 g m-2 and 7.9 g m-2 d-1. The less densely planted side was more productive than the denser planting, with 1634 g m-2 and 18.8 g m-2 d-1 of biomass vs. 1156 g m-2 and 13.3 g m-2 d-1; and a seed harvest of 812.3 g m-2 and 9.3 g m-2 d-1 vs. 566.5 g m-2 and 6.5 g m-2 d-1. Harvest index was 0.49 for the wheat crop. The experiment with sweet potato used TU-82-155 a compact variety developed at Tuskegee University. Light during the sweet potato experiment, on a 18 h on/6 h dark cycle, totaled 5568 total moles of light per square meter in 126 days for the sweet potatoes, or an average of 44.2 mol m-2 d-1. Temperature regime was 28 +/- 3 degrees C day/22 +/- 4 degrees C night. Sweet potato tuber yield was 39.7 kg wet weight, or an average of 7.4 kg m-2, and 7.7 kg dry weight of tubers since dry weight was about 18.6% wet weight. Average per day production was 58.7 g m-2 d-1 wet weight and 11.3 g m-2 d-1. For the wheat, average light efficiency was 0.34 g biomass per mole, and 0.17 g seed per mole. The best area of wheat had an efficiency of light utilization of 0.51 g biomass per mole and 0.22 g seed per mole. For the sweet potato crop, light efficiency per tuber wet weight was 1.33 g mol-1 and 0.34 g dry weight of tuber per mole of light. The best area of tuber production had 1.77 g mol-1 wet weight and 0.34 g mol-1 of light dry weight. The Laboratory Biosphere experiment's light efficiency was somewhat higher than the USU field results but somewhat below greenhouse trials at comparable light levels, and the best portion of the crop at 0.22 g mol-1 was in-between those values. Sweet potato production was overall close to 50% higher than trials using hydroponic methods with TU-82-155 at NASA JSC. Compared to projected yields for the Mars on Earth life support system, these wheat yields were about 15% higher, and the sweet potato yields averaged over 80% higher. c2005 Published by Elsevier Ltd on behalf of COSPAR.

Development of a Microsoft Excel tool for one-parameter Rasch model of continuous items: an application to a safety attitude survey.

PubMed

Chien, Tsair-Wei; Shao, Yang; Kuo, Shu-Chun

2017-01-10

Many continuous item responses (CIRs) are encountered in healthcare settings, but no one uses item response theory's (IRT) probabilistic modeling to present graphical presentations for interpreting CIR results. A computer module that is programmed to deal with CIRs is required. To present a computer module, validate it, and verify its usefulness in dealing with CIR data, and then to apply the model to real healthcare data in order to show how the CIR that can be applied to healthcare settings with an example regarding a safety attitude survey. Using Microsoft Excel VBA (Visual Basic for Applications), we designed a computer module that minimizes the residuals and calculates model's expected scores according to person responses across items. Rasch models based on a Wright map and on KIDMAP were demonstrated to interpret results of the safety attitude survey. The author-made CIR module yielded OUTFIT mean square (MNSQ) and person measures equivalent to those yielded by professional Rasch Winsteps software. The probabilistic modeling of the CIR module provides messages that are much more valuable to users and show the CIR advantage over classic test theory. Because of advances in computer technology, healthcare users who are familiar to MS Excel can easily apply the study CIR module to deal with continuous variables to benefit comparisons of data with a logistic distribution and model fit statistics.