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Sample records for absorption tpa properties

  1. Cooperative enhancement of TPA in cruciform double-chain DSB derivation: a femtosecond transient absorption spectra study

    NASA Astrophysics Data System (ADS)

    He, X.; Wang, Y.; Yang, Z.; Ma, Y.; Yang, Y.

    2010-09-01

    Femtosecond time-resolved transient absorption (TA) spectra study was adopted to study the mechanism of the cooperative enhancement of two-photon absorption (TPA) cross section from the linear structure 1,4-di(4'-N,N-diphenylaminostyryl)benzene (DPA-DSB) to its cruciform double-chain dimer DPA-TSB. The results suggested that a non-emissive intramolecular charge-transfer (ICT) state, ICT’, was present upon excitation in the dimer, which was absent in the monomer. The existence of this non-emissive state, indicating the enhancement of the intramolecular charge-transfer of the dimer, should be the reason for the cooperative enhancement of the TPA cross section of the dimer compared to the monomer.

  2. Quantum molecular dynamics simulations of the thermophysical properties of shocked liquid ammonia for pressures up to 1.3 TPa.

    PubMed

    Li, Dafang; Zhang, Ping; Yan, Jun

    2013-10-07

    We investigate via quantum molecular-dynamics simulations the thermophysical properties of shocked liquid ammonia up to the pressure 1.3 TPa and temperature 120,000 K. The principal Hugoniot is predicted from the wide-range equation of state, which agrees well with the available experimental measurements up to 64 GPa. Our systematic study of the structural properties demonstrates that the liquid ammonia undergoes a gradual phase transition along the Hugoniot. At about 4800 K, the system transforms into a metallic, complex mixture state consisting of NH3, N2, H2, N, and H. Furthermore, we discuss the implications for the interiors of Uranus and Neptune.

  3. Two-photon absorption properties of Dehydrobenzo[12]annulenes and hexakis(phenylethynyl)benzenes: effect of edge-linkage.

    PubMed

    Kamada, Kenji; Antonov, Liudmil; Yamada, Satoru; Ohta, Koji; Yoshimura, Takashi; Tahara, Kazukuni; Inaba, Akiko; Sonoda, Motohiro; Tobe, Yoshito

    2007-12-21

    Two-photon absorption (TPA) properties of two trefoil-shaped compounds with different edge linkages--tris(hexadehydrotribenzo[12]annulene) and tris(tetradehydrotribenzo[12]annulene)--and three asterisk-shaped compounds having no edge-linkage--hexakis(phenylethynyl)benzenes--are investigated experimentally by the open-aperture Z-scan and TPA-induced fluorescence methods with wavelength tuneable femtosecond pulses. The compound with ethynylene edge-linkage exhibits the most intense TPA (the maximal TPA cross section is 1300+/-170 GM at 572 nm where 1 GM=10(-50) cm(4) s molecule(-1) photon(-1)). The TPA activity of the compounds is primarily explained in terms of the planarity of the molecules in relation with the type of edge-linkage.

  4. Theoretical investigation of one-photon and two-photon absorption properties for multiply N-confused porphyrins.

    PubMed

    Yang, Zhao-Di; Feng, Ji-Kang; Ren, Ai-Min; Sun, Chia-Chung

    2006-12-28

    We have theoretically investigated a series of multiply N-confused porphyrins and their Zn or Cu complexes for the first time by using DFT(B3LYP/6-31G*) and ZINDO/SOS methods. The electronic structure, one-photon absorption (OPA), and two-photon absorption (TPA) properties have been studied in detail. The calculated results indicate that the OPA spectra of multiply N-confused porphyrins are red-shifted and the OPA intensities decrease compared to normal porphyrin. The maximum two photon absorption wavelengths lambda(max) are blue-shifted and the TPA cross sections delta(max) are increased 22.7-112.1 GM when the N atoms one by one are inverted from core to beta position to form multiply N-confused porphyrins. Especially delta(max) of N3CP get to 164.7 GM. The electron donors -C6F5s at meso-position can make the TPA cross section delta(max) increase. After forming metal complexes with Cu or Zn, the TPA properties of multiply N-confused porphyrins are further increased except for N3CP, N4CP. Our theoretical findings demonstrate that the multiply N-confused prophyrins as well as their metal complexes and derivatives are promising molecules that can be assembled series of materials with large TPA cross section, and are sure to be the subject of further investigation.

  5. Fluorescence upconversion properties of a class of improved pyridinium dyes induced by two-photon absorption

    NASA Astrophysics Data System (ADS)

    Xu, Guibao; Hu, Dawei; Zhao, Xian; Shao, Zongshu; Liu, Huijun; Tian, Yupeng

    2007-06-01

    We report the fluorescence upconversion properties of a class of improved pyridinium toluene- p-sulfonates having donor- π-acceptor (D- π-A) structure under two-photon excitation at 1064 nm. The experimental results show that both the two-photon excited (TPE) fluorescence lifetime and the two-photon pumped (TPP) energy upconversion efficiency were increased with the enhancement of electron-donating capability of the donor in the molecule. It is also indicated that an overlong alkyl group tends to result in a weakened molecular conjugation, leading to a decreased two-photon absorption (TPA) cross section. By choosing the donor, we can obtain a longest fluorescence lifetime of 837 ps, a highest energy upconversion efficiency of ˜6.1%, and a maximum TPA cross-section of 8.74×10 -48 cm 4 s/photon in these dyes.

  6. A comparative study of one- and two-photon absorption properties of pyrene and perylene diimide derivatives.

    PubMed

    Liu, Xiao-Ting; Zhao, Yang; Ren, Ai-Min; Feng, Ji-Kang

    2011-06-01

    Two important classes of organic molecules, perylene diimide (PDI) and pyrene derivatives have been found to possess relatively excellent photophysical and photochemical properties and especially high two-photon absorption cross sections (δ(T)(max)). Herein, one-photon absorption (OPA) and two-photon absorption (TPA) properties of some novel PDI and pyrene derivatives were comparatively investigated by the density functional theory (DFT) and Zerner's intermediate neglect of differential overlap (ZINDO) methods. The calculated results indicate that with respect to PDI derivatives, the maximum TPA cross-sections for pyrene compounds increase obviously, the maximum peaks of OPA and TPA spectra are blue-shifted, the ΔE(H-L) (energy gaps between the highest occupied orbital and the lowest unoccupied orbital) increase. The different π-conjugated bridges (fluorene and pyrene) and terminal groups have slight effect on the OPA properties. Nevertheless, the molecules bearing 1,6-disubstituted pyrene as the π-conjugated bridge display the largest δ(T)(max) in both series of compounds 3 and 4. Moreover, the δ(T)(max) values of molecules with benzothiazole-substituted terminal groups are larger than those of the molecules with diphenylamine, which is attributed to benzothiazole groups stabilizing the planarity of the branch parts, extending the conjugated length and increasing the π-electron delocalized extent. Furthermore, the molecular size has marked effect on OPA and TPA properties. It is worthy to mention that cruciform 8 displays the largest δ(T)(max) among all the studied molecules in the range of 600-1100 nm. This research could provide a better understanding for the origin of the linear and nonlinear optical properties, and it would be helpful to gain more information about designing two-photon absorption materials with large δ(T)(max).

  7. Two-photon absorption properties of proquinoidal D-A-D and A-D-A quadrupolar chromophores.

    PubMed

    Susumu, Kimihiro; Fisher, Jonathan A N; Zheng, Jieru; Beratan, David N; Yodh, Arjun G; Therien, Michael J

    2011-06-09

    We report the synthesis, one- and two-photon absorption spectroscopy, fluorescence, and electrochemical properties of a series of quadrupolar molecules that feature proquinoidal π-aromatic acceptors. These quadrupolar molecules possess either donor-acceptor-donor (D-A-D) or acceptor-donor-acceptor (A-D-A) electronic motifs, and feature 4-N,N-dihexylaminophenyl, 4-dodecyloxyphenyl, 4-(N,N-dihexylamino)benzo[c][1,2,5]thiadiazolyl or 2,5-dioctyloxyphenyl electron donor moieties and benzo[c][1,2,5]thiadiazole (BTD) or 6,7-bis(3',7'-dimethyloctyl)[1,2,5]thiadiazolo[3,4-g]quinoxaline (TDQ) electron acceptor units. These conjugated structures are highly emissive in nonpolar solvents and exhibit large spectral red-shifts of their respective lowest energy absorption bands relative to analogous reference compounds that incorporate phenylene components in place of BTD and TDQ moieties. BTD-based D-A-D and A-D-A chromophores exhibit increasing fluorescence emission red-shifts, and a concomitant decrease of the fluorescence quantum yield (Φ(f)) with increasing solvent polarity; these data indicate that electronic excitation augments benzothiadiazole electron density via an internal charge transfer mechanism. The BTD- and TDQ-containing structures exhibit blue-shifted two-photon absorption (TPA) spectra relative to their corresponding one-photon absorption (OPA) spectra, and display high TPA cross sections (>100 GM) within these spectral windows. D-A-D and A-D-A structures that feature more extensive conjugation within this series of compounds exhibit larger TPA cross sections consistent with computational simulation. Factors governing TPA properties of these quadrupolar chromophores are discussed within the context of a three-state model.

  8. Two-Photon Absorption Properties of Proquinoidal D-A-D and A-D-A Quadrupolar Chromophores

    PubMed Central

    Susumu, Kimihiro; Fisher, Jonathan A. N.; Zheng, Jieru

    2011-01-01

    We report the synthesis, one- and two-photon absorption spectroscopy, fluorescence, and electrochemical properties of a series of quadrupolar molecules that feature proquinoidal π-aromatic acceptors. These quadrupolar molecules possess either donor-acceptor-donor (D–A–D) or acceptor-donor-acceptor (A–D–A) electronic motifs, and feature 4-N,N-dihexylaminophenyl, 4-dodecyloxyphenyl, 4-(N,N-dihexylamino)benzo[c][1,2,5]thiadiazolyl or 2,5-dioctyloxyphenyl electron donor moieties and benzo[c][1,2,5]thiadiazole (BTD) or 6,7-bis(3’,7’-dimethyloctyl)[1,2,5]thiadiazolo[3,4-g]quinoxaline (TDQ) electron acceptor units. These conjugated structures are highly emissive in nonpolar solvents and exhibit large spectral red-shifts of their respective lowest energy absorption bands relative to analogous reference compounds that incorporate phenylene components in place of BTD and TDQ moieties. BTD-based D-A-D and A-D-A chromophores exhibit increasing fluorescence emission red-shifts, and a concomitant decrease of the fluorescence quantum yield (Φf) with increasing solvent polarity; these data indicate that electronic excitation augments benzothiadiazole electron density via an internal charge transfer mechanism. The BTD- and TDQ-containing structures exhibit blue-shifted two-photon absorption (TPA) spectra relative to their corresponding one-photon absorption (OPA) spectra, and display high TPA cross-sections (>100 GM) within these spectral windows. D-A-D and A-D-A structures that feature more extensive conjugation within this series of compounds exhibit larger TPA cross-sections consistent with computational simulation. Factors governing TPA properties of these quadrupolar chromophores are discussed within the context of a three-state model. PMID:21568299

  9. Dye-doped sol-gel materials for two-photon absorption induced fluorescence

    NASA Astrophysics Data System (ADS)

    Canva, Michael; Roger, Gisèle; Cassagne, Florence; Lévy, Yves; Brun, Alain; Chaput, Frédéric; Boilot, Jean-Pierre; Rapaport, Alexandra; Heerdt, Céline; Bass, Michael

    2002-01-01

    Two-photon absorption (TPA) and subsequent fluorescence properties of laser dyes are retained when doped into solid state sol-gel materials. These properties were demonstrated to be applicable in true 3D displays.

  10. Two-photon absorption properties of a new series of 2CTσ chromophores

    NASA Astrophysics Data System (ADS)

    Zhou, Yu-fang; Meng, Fan-qing; Zhao, Xian; Xu, Dong; Jiang, Min-hu

    2000-10-01

    We have designed and synthesized a new series of two-photon ASPT-like charge transfer moieties linked by σ-bond spacers to N-position of pyridine cycle. Both theoretical and experimental results show there is no linear absorption in 600-1300 nm, so two-photon properties can be expected in this range. Two-photon absorption (TPA) cross-sections were calculated by using INDO/CI and SOS methods. The results show that those compounds possess large cross-sections as well as appropriate absorption wavelengths. Also the magnitude of the cross-section changes regularly with the number of the σ-bond spacers. These imply that they are good candidates for two-photon devices.

  11. Investigation of two-photon absorption behavior in symmetrical acceptor-pi-acceptor derivatives with dimesitylboryl end-groups. Evidence of new engineering routes for TPA/transparency trade-off optimization.

    PubMed

    Chariot, Marina; Porrès, Laurent; Entwistle, Christopher D; Beeby, Andrew; Marder, Todd B; Blanchard-Desce, Mireille

    2005-02-21

    Investigations of the non-linear optical properties of a novel series of A-pi-A quadrupoles, based on dimesitylboron end-groups, reveal the promising potential of elongated vinylboranes derivatives for combined enhanced two-photon absorption cross-section and improved transparency in the visible region. In addition, the excited state lifetime can be significantly enhanced in A-pi-A'-pi-A derivatives. This opens a new route towards optimized molecules for optical power limiting.

  12. TPA - A COMPUTER PROGRAM TO BALANCE MAPPED TURBOPUMP ASSEMBLIES

    NASA Technical Reports Server (NTRS)

    Walton, J. T.

    1994-01-01

    Accurate simulation of nuclear thermal propulsion systems using computational methods will permit reductions in testing and, thus, the time and cost of achieving a flight ready status for systems utilizing this advanced technology. An accurate simulation must maintain a "balance-of-plant" where the required pump work equals the supplied turbine work. This turbopump assembly balancing must be integrated into the overall system analysis models. TPA was developed to balance turbine and pump work using performance maps. It requires the inlet properties, performance maps, and shaft speed. TPA then computes the exit conditions and work terms. The work terms can then be balanced by varying the input shaft speed. The objective of the pump analysis is to determine the propellant state properties at the pump exit and the pump work. The pump analysis algorithm for liquid flow assumes that the shaft speed, the propellant state properties at the pump entrance, the propellant flow rate, the pump entrance and exit areas, as well as performance curves, are all known. The analysis of both the pump pressure rise and pump efficiency curves is required. The objective of the turbine analysis is to determine the propellant state properties at the turbine exit and the turbine work. The turbine analysis algorithm assumes that the shaft speed, the propellant state properties at the turbine entrance, the propellant flow rate, the turbine root mean square blade diameter, the turbine entrance and exit areas, as well as performance curves, are all known. The analysis also requires the turbine flow parameter curve and the turbine total efficiency curve. TPA is written in FORTRAN 77 to be machine independent. The TPA package includes the NBS+_PH2 code, which is also available separately (LEW-15505). TPA has been successfully implemented on a DEC VAX series computer running VMS, a Sun4 series computer running SunOS, and an IBM PC compatible computer running MS-DOS. Lahey F77L3 EM/32 v. 5.01 or

  13. Polypyrrole layered SPEES/TPA proton exchange membrane for direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Neelakandan, S.; Kanagaraj, P.; Sabarathinam, R. M.; Nagendran, A.

    2015-12-01

    Hybrid membranes based on sulfonated poly(1,4-phenylene ether ether sulfone) (SPEES)/tungstophosphoric acid (TPA) were prepared. SPEES/TPA membrane surfaces were modified with polypyrrole (Ppy) by in situ polymerization method to reduce the TPA leaching. The morphology and electrochemical property of the surface coated membranes were studied by SEM, AFM, water uptake, ion exchange capacity, proton conductivity, methanol permeability and tensile strength. The water uptake and the swelling ratio of the surface coated membranes decreased with increasing the Ppy layer. The surface roughness of the hybrid membrane was decreased with an increase in Ppy layer on the membrane surface. The methanol permeability of SPEES/TPA-Ppy4 hybrid membrane was significantly suppressed and found to be 2.1 × 10-7 cm2 s-1, which is 1.9 times lower than pristine SPEES membrane. The SPEES/TPA-Ppy4 membrane exhibits highest relative selectivity (2.86 × 104 S cm-3 s) than the other membrane with low TPA leaching. The tensile strength of hybrid membranes was improved with the introduction of Ppy layer. Combining their lower swelling ratio, high thermal stability and selectivity, SPEES/TPA-Ppy4 membranes could be a promising material as PEM for DMFC applications.

  14. Excellent microwave absorption property of Graphene-coated Fe nanocomposites

    PubMed Central

    Zhao, Xingchen; Zhang, Zhengming; Wang, Liaoyu; Xi, Kai; Cao, Qingqi; Wang, Dunhui; Yang, Yi; Du, Youwei

    2013-01-01

    Graphene has evoked extensive interests for its abundant physical properties and potential applications. It is reported that the interfacial electronic interaction between metal and graphene would give rise to charge transfer and change the electronic properties of graphene, leading to some novel electrical and magnetic properties in metal-graphene heterostructure. In addition, large specific surface area, low density and high chemical stability make graphene act as an ideal coating material. Taking full advantage of the aforementioned features of graphene, we synthesized graphene-coated Fe nanocomposites for the first time and investigated their microwave absorption properties. Due to the charge transfer at Fe-graphene interface in Fe/G, the nanocomposites show distinct dielectric properties, which result in excellent microwave absorption performance in a wide frequency range. This work provides a novel approach for exploring high-performance microwave absorption material as well as expands the application field of graphene-based materials. PMID:24305606

  15. The saturable absorption and reverse saturable absorption properties of Cu doped zinc oxide thin films

    NASA Astrophysics Data System (ADS)

    Yao, Cheng-Bao; Wen, Xin; Li, Qiang-Hua; Yan, Xiao-Yan; Li, Jin; Zhang, Ke-Xin; Sun, Wen-Jun; Bai, Li-Na; Yang, Shou-Bin

    2017-03-01

    We present the structure and nonlinear absorption (NLA) properties of Cu-doped ZnO (CZO) films prepared by magnetron sputtering. The films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that the CZO films can maintain a wurtzite structure. Furthermore, the open-aperture (OA) Z-scan measurements of the film were carried out by nanosecond laser pulse. A transition from saturable absorption (SA) to reverse saturable absorption (RSA) was observed as the excitation intensity increasing. With good excellent nonlinear optical coefficient, the samples were expected to be the potential applications in optical devices.

  16. Microwave absorption properties of pyrolytic carbon nanofilm

    PubMed Central

    2013-01-01

    We analyzed the electromagnetic (EM) shielding effectiveness in the Ka band (26 to 37 GHz) of highly amorphous nanometrically thin pyrolytic carbon (PyC) films with lateral dimensions of 7.2 × 3.4 mm2, which consists of randomly oriented and intertwined graphene flakes with a typical size of a few nanometers. We discovered that the manufactured PyC films, whose thickness is thousand times less than the skin depth of conventional metals, provide a reasonably high EM attenuation. The latter is caused by absorption losses that can be as high as 38% to 20% in the microwave frequency range. Being semi-transparent in visible and infrared spectral ranges and highly conductive at room temperature, PyC films emerge as a promising material for manufacturing ultrathin microwave (e.g., Ka band) filters and shields. PMID:23388194

  17. Properties of MgO to 1.2 TPa from high-precision experiments on Sandia's Z machine and first-principles simulations using QMC and DFT

    NASA Astrophysics Data System (ADS)

    Shulenburger, Luke

    2015-11-01

    MgO is a major constituent of Earth's mantle, the rocky cores of gas giants and is a likely component of the interiors of many exoplanets. The high pressure - high temperature behavior of MgO directly affects equation of state models for planetary structure and formation. In this work, we examine MgO under extreme conditions using experimental and theoretical methods to determine the phase diagram and transport properties. Using plate impact experiments on Sandia's Z facility a low entropy solid-solid phase transition from B1 to B2 is clearly determined. The melting transition, on the other hand, is subtle, involving little to no signal in us-up space. Theoretical work utilizing density functional theory (DFT) provides a complementary picture of the phase diagram. The solid-solid phase transition is identified through a series of quasi-harmonic phonon calculations and thermodynamic integration, while the melt boundary is found using phase coexistence calculations. The calculation of reflectivity along the Hugoniot and the influence of the ionic structure on the transport properties requires particular care because of the underestimation of the band gap and attendant overestimation of transport properties due to the use of semi-local density functional theory. We will explore the impact of this theoretical challenge and its potential solutions in this talk. Finally, understanding the behavior of MgO as the pressure releases from the Hugoniot state is a key ingredient to modeling giant impact events. We explore this regime both through additional DFT calculations and by observing the release state of the MgO into lower impedance materials. The integrated use of DFT simulations and high-accuracy shock experiments together provide a comprehensive understanding of MgO under extreme conditions. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U

  18. Thermal properties of carbon black aqueous nanofluids for solar absorption

    NASA Astrophysics Data System (ADS)

    Han, Dongxiao; Meng, Zhaoguo; Wu, Daxiong; Zhang, Canying; Zhu, Haitao

    2011-07-01

    In this article, carbon black nanofluids were prepared by dispersing the pretreated carbon black powder into distilled water. The size and morphology of the nanoparticles were explored. The photothermal properties, optical properties, rheological behaviors, and thermal conductivities of the nanofluids were also investigated. The results showed that the nanofluids of high-volume fraction had better photothermal properties. Both carbon black powder and nanofluids had good absorption in the whole wavelength ranging from 200 to 2,500 nm. The nanofluids exhibited a shear thinning behavior. The shear viscosity increased with the increasing volume fraction and decreased with the increasing temperature at the same shear rate. The thermal conductivity of carbon black nanofluids increased with the increase of volume fraction and temperature. Carbon black nanofluids had good absorption ability of solar energy and can effectively enhance the solar absorption efficiency.

  19. Thermal properties of carbon black aqueous nanofluids for solar absorption

    PubMed Central

    2011-01-01

    In this article, carbon black nanofluids were prepared by dispersing the pretreated carbon black powder into distilled water. The size and morphology of the nanoparticles were explored. The photothermal properties, optical properties, rheological behaviors, and thermal conductivities of the nanofluids were also investigated. The results showed that the nanofluids of high-volume fraction had better photothermal properties. Both carbon black powder and nanofluids had good absorption in the whole wavelength ranging from 200 to 2,500 nm. The nanofluids exhibited a shear thinning behavior. The shear viscosity increased with the increasing volume fraction and decreased with the increasing temperature at the same shear rate. The thermal conductivity of carbon black nanofluids increased with the increase of volume fraction and temperature. Carbon black nanofluids had good absorption ability of solar energy and can effectively enhance the solar absorption efficiency. PMID:21767359

  20. Thermal properties of carbon black aqueous nanofluids for solar absorption.

    PubMed

    Han, Dongxiao; Meng, Zhaoguo; Wu, Daxiong; Zhang, Canying; Zhu, Haitao

    2011-07-18

    In this article, carbon black nanofluids were prepared by dispersing the pretreated carbon black powder into distilled water. The size and morphology of the nanoparticles were explored. The photothermal properties, optical properties, rheological behaviors, and thermal conductivities of the nanofluids were also investigated. The results showed that the nanofluids of high-volume fraction had better photothermal properties. Both carbon black powder and nanofluids had good absorption in the whole wavelength ranging from 200 to 2,500 nm. The nanofluids exhibited a shear thinning behavior. The shear viscosity increased with the increasing volume fraction and decreased with the increasing temperature at the same shear rate. The thermal conductivity of carbon black nanofluids increased with the increase of volume fraction and temperature. Carbon black nanofluids had good absorption ability of solar energy and can effectively enhance the solar absorption efficiency.

  1. Two-photon absorption in conjugated energetic molecule

    SciTech Connect

    Bjorgaard, Josiah August; Sifain, Andrew; Nelson, Tammie Renee; Myers, Thomas Winfield; Veauthier, Jacqueline Marie; Chavez, David E.; Scharff, Robert Jason; Tretiak, Sergei

    2016-06-03

    Time-dependent density functional theory (TD-DFT) is used to investigate the relationship between molecular structure and one- and two-photon absorption (OPA and TPA, respectively) properties in novel and recently synthesized conjugated energetic molecules (CEMs). The molecular structure of CEMs can be strategically altered to influence the heat of formation and oxygen balance, two factors that can contribute to the sensitivity and strength of an explosive material. OPA and TPA are sensitive to changes in molecular structure as well, influencing optical range of excitation. We find calculated vertical excitation energies in good agreement with experiment for most molecules. Peak TPA intensities are significant and on the order of 102 GM. Natural transition orbitals for essential electronic states defining TPA peaks of relatively large intensity to examine the character of relevant transitions. Minor modification of molecular substituents, such as additional oxygen and other functional groups, produces significant changes in electronic structure, OPA, TPA, and improves the oxygen balance. Results show that select molecules are apt to nonlinear absorption, opening the possibility for controlled, direct optical initiation of CEMs through photochemical pathways.

  2. Two-Photon Absorption in Conjugated Energetic Molecules.

    PubMed

    Bjorgaard, Josiah A; Sifain, Andrew E; Nelson, Tammie; Myers, Thomas W; Veauthier, Jacqueline M; Chavez, David E; Scharff, R Jason; Tretiak, Sergei

    2016-07-07

    Time-dependent density functional theory (TD-DFT) was used to investigate the relationship between molecular structure and the one- and two-photon absorption (OPA and TPA, respectively) properties of novel and recently synthesized conjugated energetic molecules (CEMs). The molecular structures of CEMs can be strategically altered to influence the heat of formation and oxygen balance, two factors that can contribute to the sensitivity and strength of an explosive material. OPA and TPA are sensitive to changes in molecular structure as well, influencing the optical range of excitation. We found calculated vertical excitation energies to be in good agreement with experiment for most molecules. Peak TPA intensities were found to be significant and on the order of 10(2) GM. Natural transition orbitals for essential electronic states defining TPA peaks of relatively large intensity were used to examine the character of relevant transitions. Modification of molecular substituents, such as additional oxygen or other functional groups, produces significant changes in electronic structure, OPA, and TPA and improves oxygen balance. The results show that certain molecules are apt to undergo nonlinear absorption, opening the possibility for controlled, direct optical initiation of CEMs through photochemical pathways.

  3. Two-photon absorption in conjugated energetic molecule

    DOE PAGES

    Bjorgaard, Josiah August; Sifain, Andrew; Nelson, Tammie Renee; ...

    2016-06-03

    Time-dependent density functional theory (TD-DFT) is used to investigate the relationship between molecular structure and one- and two-photon absorption (OPA and TPA, respectively) properties in novel and recently synthesized conjugated energetic molecules (CEMs). The molecular structure of CEMs can be strategically altered to influence the heat of formation and oxygen balance, two factors that can contribute to the sensitivity and strength of an explosive material. OPA and TPA are sensitive to changes in molecular structure as well, influencing optical range of excitation. We find calculated vertical excitation energies in good agreement with experiment for most molecules. Peak TPA intensities aremore » significant and on the order of 102 GM. Natural transition orbitals for essential electronic states defining TPA peaks of relatively large intensity to examine the character of relevant transitions. Minor modification of molecular substituents, such as additional oxygen and other functional groups, produces significant changes in electronic structure, OPA, TPA, and improves the oxygen balance. Results show that select molecules are apt to nonlinear absorption, opening the possibility for controlled, direct optical initiation of CEMs through photochemical pathways.« less

  4. Solvent effects on static polarizability, static first hyperpolarizability and one- and two-photon absorption properties of functionalized triply twisted Möbius annulenes: a DFT study.

    PubMed

    Alam, Md Mehboob; Kundi, Varun; Thankachan, Pompozhi Protasis

    2016-08-21

    The present work aims to study solvent effects on the polarizability (α), static first hyperpolarizability (β) and one- and two-photon absorption (OPA and TPA) properties of a new class of molecules viz. triply twisted Möbius annulenes, recently studied by us in vacuum phase [Kundi et al., Phys. Chem. Chem. Phys., 2015, 17, 6827]. We have employed linear and quadratic response theories within the framework of time-dependent density functional theory with the CAM-B3LYP functional and a cc-pVDZ basis set to calculate different parameters. The microscopic details of the said properties have been studied using a two-state model (2SM) approach, which performs very well in the case of β and TPA of the first excited state of all the systems. However for the second excited state, the 2SM results are far from those of response theory. In fact, in comparison to response theory, 2SM predicts an opposite trend for the TP activity of some of the model systems, indicating a significant contribution from the other higher excited states. The anomaly between the 2SM approach and response theory has been resolved by incorporating three states in the calculations.

  5. Absorption and emission properties of photonic crystals and metamaterials

    SciTech Connect

    Peng, Lili

    2007-01-01

    We study the emission and absorption properties of photonic crystals and metamaterials using Comsol Multiphysics and Ansoft HFSS as simulation tools. We calculate the emission properties of metallic designs using drude model and the results illustrate that an appropriate termination of the surface of the metallic structure can significantly increase the absorption and therefore the thermal emissivity. We investigate the spontaneous emission rate modifications that occur for emitters inside two-dimensional photonic crystals and find the isotropic and directional emissions with respect to different frequencies as we have expected.

  6. Microwave absorption properties of Ni/(C, silicides) nanocapsules

    PubMed Central

    2012-01-01

    The microwave absorption properties of Ni/(C, silicides) nanocapsules prepared by an arc discharge method have been studied. The composition and the microstructure of the Ni/(C, silicides) nanocapsules were determined by means of X-ray diffraction, X-ray photoelectric spectroscopy, and transmission electron microscope observations. Silicides, in the forms of SiOx and SiC, mainly exist in the shells of the nanocapsules and result in a large amount of defects at the ‘core/shell’ interfaces as well as in the shells. The complex permittivity and microwave absorption properties of the Ni/(C, silicides) nanocapsules are improved by the doped silicides. Compared with those of Ni/C nanocapsules, the positions of maximum absorption peaks of the Ni/(C, silicides) nanocapsules exhibit large red shifts. An electric dipole model is proposed to explain this red shift phenomenon. PMID:22548846

  7. Benzothiazoles with tunable electron-withdrawing strength and reverse polarity: a route to triphenylamine-based chromophores with enhanced two-photon absorption.

    PubMed

    Hrobárik, Peter; Hrobáriková, Veronika; Sigmundová, Ivica; Zahradník, Pavol; Fakis, Mihalis; Polyzos, Ioannis; Persephonis, Peter

    2011-11-04

    A series of dipolar and octupolar triphenylamine-derived dyes containing a benzothiazole positioned in the matched or mismatched fashion have been designed and synthesized via palladium-catalyzed Sonogashira cross-coupling reactions. Linear and nonlinear optical properties of the designed molecules were tuned by an additional electron-withdrawing group (EWG) and by changing the relative positions of the donor and acceptor substituents on the heterocyclic ring. This allowed us to examine the effect of positional isomerism and extend the structure-property relationships useful in the engineering of novel heteroaromatic-based systems with enhanced two-photon absorption (TPA). The TPA cross-sections (δ(TPA)) in the target compounds dramatically increased with the branching of the triphenylamine core and with the strength of the auxiliary acceptor. In addition, a change from the commonly used polarity in push-pull benzothiazoles to a reverse one has been revealed as a particularly useful strategy (regioisomeric control) for enhancing TPA cross-sections and shifting the absorption and emission maxima to longer wavelengths. The maximum TPA cross-sections of the star-shaped three-branched triphenylamines are ∼500-2300 GM in the near-infrared region (740-810 nm); thereby the molecular weight normalized δ(TPA)/MW values of the best performing dyes within the series (2.0-2.4 GM·g(-1)·mol) are comparable to those of the most efficient TPA chromophores reported to date. The large TPA cross-sections combined with high emission quantum yields and large Stokes shifts make these compounds excellent candidates for various TPA applications, including two-photon fluorescence microscopy.

  8. High-resolution three-dimensional imaging of a depleted CMOS sensor using an edge Transient Current Technique based on the Two Photon Absorption process (TPA-eTCT)

    NASA Astrophysics Data System (ADS)

    García, Marcos Fernández; Sánchez, Javier González; Echeverría, Richard Jaramillo; Moll, Michael; Santos, Raúl Montero; Moya, David; Pinto, Rogelio Palomo; Vila, Iván

    2017-02-01

    For the first time, the deep n-well (DNW) depletion space of a High Voltage CMOS sensor has been characterized using a Transient Current Technique based on the simultaneous absorption of two photons. This novel approach has allowed to resolve the DNW implant boundaries and therefore to accurately determine the real depleted volume and the effective doping concentration of the substrate. The unprecedented spatial resolution of this new method comes from the fact that measurable free carrier generation in two photon mode only occurs in a micrometric scale voxel around the focus of the beam. Real three-dimensional spatial resolution is achieved by scanning the beam focus within the sample.

  9. The Consequences of edTPA

    ERIC Educational Resources Information Center

    Greenblatt, Deborah

    2016-01-01

    States and teacher preparation programs across the country are increasingly using a teacher candidate assessment called edTPA. The purpose? To make sure that teacher candidates are ready and able to teach before they begin their careers. The teacher performance assessment requires candidates to compile a portfolio that consists of lesson plans,…

  10. Light absorption properties of brown carbon in the high Himalayas

    NASA Astrophysics Data System (ADS)

    Kirillova, Elena N.; Marinoni, Angela; Bonasoni, Paolo; Vuillermoz, Elisa; Facchini, Maria Cristina; Fuzzi, Sandro; Decesari, Stefano

    2016-08-01

    The light-absorbing properties of water-soluble brown carbon (WS-BrC) and methanol-soluble brown carbon (MeS-BrC) were studied in PM10 aerosols collected at the "Nepal Climate Observatory-Pyramid" (NCO-P) station (5079 m above sea level) during the period 2013-2014. The light absorption coefficients of WS-BrC and MeS-BrC were the highest during the premonsoon season and the lowest during monsoon. MeS-BrC absorbs about 2 times higher at 365 nm and about 3 times more at 550 nm compared to WS-BrC. The mass absorption cross section (MAC) of WS-BrC measured at 365 nm is similar to that observed previously at South Asian low-altitude sites. Fractional solar radiation absorption by BrC compared to BC considering the full solar spectrum showed that WS-BrC absorbs 4 ± 1% and MeS-BrC absorbs 9 ± 2% compared to BC at NCO-P. Such ratios become 8 ± 1% (for WS-BrC respect to BC) and 17 ± 5% (for MeS-BrC respect to BC) when accounting for correction factors proposed by previous studies to convert absorption coefficients in bulk solutions into light absorption by accumulation mode aerosol particles. These results confirm the importance of BrC in contributing to light-absorbing aerosols in this region of the world. However, the BrC absorption at 550 nm appears small compared to that of BC (1-5%, or 3-9% with conversion factors), and it is lower compared to global model estimates constrained by Aerosol Robotic Network observations. Finally, our study provides no clear evidence of a change in the fractional contribution of BrC with respect to BC to light absorption in the middle troposphere respect to the Indo-Gangetic plain boundary layer.

  11. Improvement of photovoltaic performance by substituent effect of donor and acceptor structure of TPA-based dye-sensitized solar cells.

    PubMed

    Inostroza, Natalia; Mendizabal, Fernando; Arratia-Pérez, Ramiro; Orellana, Carlos; Linares-Flores, Cristian

    2016-01-01

    We report a computational study of a series of organic dyes built with triphenylamine (TPA) as an electron donor group. We designed a set of six dyes called (TPA-n, where n = 0-5). In order to enhance the electron-injection process, the electron-donor effect of some specific substituent was studied. Thus, we gave insights into the rational design of organic TPA-based chromophores for use in dye-sensitized solar cells (DSSCs). In addition, we report the HOMO, LUMO, the calculated excited state oxidized potential E(dye*)(eV) and the free energy change for electron-injection ΔGinject(eV), and the UV-visible absorption bands for TPA-n dyes by a time-dependent density functional theory (TDDFT) procedure at the B3LYP and CAM-B3LYP levels with solvent effect. The results demonstrate that the introduction of the electron-acceptor groups produces an intramolecular charge transfer showing a shift of the absorption wavelengths of TPA-n under studies. Graphical Abstract Several organic dyes TPA-n with different donors and acceptors are modeled. A strong conjugation acrros the donor and anchoring groips (TPA-n) bas been studied. Candidate TPA-3 shows a promising results.

  12. Two-Photon Absorption and Fluorescence with Quadrupolar and Branched CHROMOPHORES—EFFECT of Structure and Branching

    NASA Astrophysics Data System (ADS)

    Porrès, Laurent; Mongin, Olivier; Katan, Claudine; Charlot, Marina; Bhatthula, Bharath Kumar Goud; Jouikov, Viatcheslav; Pons, Thomas; Mertz, Jerome; Blanchard-Desce, Mireille

    The photophysical and two-photon absorption (TPA) properties of three homologous quadrupolar and one related three-branched chromophores were investigated. Design of the quadrupoles is based on the symmetrical functionalization of a biphenyl core. Modulation of the nonlinear absorptivity/transparency/photostability trade-off can be achieved by playing with the twist angle of the core and on the spacers (phenylene-vinylene versus phenylene-ethynylene). The quadrupolar chromophores combine high TPA cross-sections, high fluorescence quantum yield and solvent sensitive photoluminescence properties. The branched structure exhibits spectrally broadened TPA in the NIR region (up to 3660 GM at 740 nm measured in the femtosecond regime) but reduced sensitivity to the environment.

  13. Two-photon absorption properties of fluorescent proteins

    PubMed Central

    Drobizhev, Mikhail; Makarov, Nikolay S.; Tillo, Shane E.; Hughes, Thomas E.; Rebane, Aleksander

    2016-01-01

    Two-photon excitation of fluorescent proteins is an attractive approach for imaging living systems. Today researchers are eager to know which proteins are the brightest, and what the best excitation wavelengths are. Here we review the two-photon absorption properties of a wide variety of fluorescent proteins, including new far-red variants, to produce a comprehensive guide to choosing the right FP and excitation wavelength for two-photon applications. PMID:21527931

  14. Spatial variability of absorption properties in Lake Balaton, Hungary

    NASA Astrophysics Data System (ADS)

    Riddick, C. A.; Hunter, P. D.; Tyler, A. N.; Vicente, V. M.; Groom, S.; Horváth, H.; Kovacs, A.; Preston, T.; Presing, M.

    2013-12-01

    In order to improve robustness of current remote sensing algorithms for lake monitoring, it is vital to understand the variability of inherent optical properties (IOPs) within a lake. In this study, absorption coefficients were measured in situ at 38 stations in Lake Balaton, Hungary, using a WET Labs AC-S and AC-9 and compared to concurrent absorption measurements by dual beam spectrophotometry in the laboratory. The spatial variability of bulk and chlorophyll-specific absorption coefficients was examined across 5 basins, demonstrating a gradient in total absorption corresponding to the trophic gradient. Our data suggests that sampling conditions had an impact on particulate absorption, affecting the proportion attributed to non-algal particles (aNAP), phytoplankton (aph) or color dissolved organic matter (aCDOM). The specific absorption of phytoplankton (a*ph) spectra showed a distinct peak in the UV portion of the spectra in Basins 3 and 4 (east), which may be due to the presence of phytoplankton photoprotective pigments to compensate for lower CDOM levels in these basins. In contrast to oceans, particulate attenuation (cp) had a weaker relationship to chlorophyll-a (R2=0.15) than to total suspended matter (R2=0.84), particularly the inorganic fraction. Additionally, the relative contribution of particulate scattering (bp) to attenuation was significantly higher in Lake Balaton (up to 85-99%) than that found in previous lacustrine studies. bp also demonstrated a gradient across the lake, where values increased as the water progressed from phytoplankton-dominated to mineral-dominated. These results provide knowledge of the heterogeneity of the IOPs within Lake Balaton, which is to be considered for the future improvement of bio-optical algorithms for constituent retrieval in inland waters.

  15. Mechanical properties and energy absorption characteristics of a polyurethane foam

    SciTech Connect

    Goods, S.H.; Neuschwanger, C.L.; Henderson, C.; Skala, D.M.

    1997-03-01

    Tension, compression and impact properties of a polyurethane encapsulant foam have been measured as a function of foam density. Significant differences in the behavior of the foam were observed depending on the mode of testing. Over the range of densities examined, both the modulus and the elastic collapse stress of the foam exhibited power-law dependencies with respect to density. The power-law relationship for the modulus was the same for both tension and compression testing and is explained in terms of the elastic compliance of the cellular structure of the foam using a simple geometric model. Euler buckling is used to rationalize the density dependence of the collapse stress. Neither tension nor compression testing yielded realistic measurements of energy absorption (toughness). In the former case, the energy absorption characteristics of the foam were severely limited due to the inherent lack of tensile ductility. In the latter case, the absence of a failure mechanism led to arbitrary measures of energy absorption that were not indicative of true material properties. Only impact testing revealed an intrinsic limitation in the toughness characteristics of the material with respect to foam density. The results suggest that dynamic testing should be used when assessing the shock mitigating qualities of a foam.

  16. Scattering and Absorption Properties of Biomaterials for Dental Restorative Applications

    NASA Astrophysics Data System (ADS)

    Fernandez-Oliveras, A.; Rubiño, M.; Pérez, M. M.

    2013-08-01

    The physical understanding of the optical properties of dental biomaterials is mandatory for their final success in restorative applications.Light propagation in biological media is characterized by the absorption coefficient, the scattering coefficient, the scattering phase function,the refractive index, and the surface conditions (roughness). We have employed the inverse adding-doubling (IAD) method to combine transmittance and reflectance measurements performed using an integrating-sphere setup with the results of the previous scattering-anisotropygoniometric measurements. This has led to the determination of the absorption and the scattering coefficients. The aim was to optically characterize two different dental-resin composites (nanocomposite and hybrid) and one type of zirconia ceramic, and comparatively study them. The experimental procedure was conducted under repeatability conditions of measurement in order to determine the uncertainty associated to the optical properties of the biomaterials. Spectral variations of the refraction index and the scattering anisotropy factor were also considered. The whole experimental procedure fulfilled all the necessary requirements to provide optical-property values with lower associated uncertainties. The effective transport coefficient presented a similar spectral behavior for the two composites but completely different for the zirconia ceramic. The results demonstrated that the scattering anisotropy exerted a clearly distinct impact on the optical properties of the zirconia ceramic compared with those of the dental-resin composites.

  17. Dynamics of absorption properties along a latitudinal gradient: sources of absorption in Australian inland waters

    NASA Astrophysics Data System (ADS)

    Hestir, E. L.; Campbell, G.; Malthus, T. J.; Dekker, A.; Botha, E.

    2013-12-01

    Australian inland waters are optically complex and vary spatially and temporally. Inversion of optical remote sensing data for the retrieval of optically active water quality constituents (chlorophyll, colored dissolved organic matter and total suspended solids) is impeded by the scarcity of inherent optical property (IOP) data sets. In 2012 a major measurement program commenced to improve understanding of IOPs in Australia. Seven large lakes were sampled along a latitudinal gradient in Eastern Australia; in situ observations were made of the absorption properties of the water quality during two epochs (wet and dry season). This study documents the seasonal, inter & intra lake variability of the absorption budget of Australian lakes. These data reveal the sources of biogeochemical constituents determining the light climate of lakes. Optically active water quality constituents (total suspended solids, chlorophyll-a, and colored dissolved organic matter) varied significantly between wet and dry season and between lakes. The primary contribution to the absorption budget was from non-algal particulate matter (NAP; 10-60%), followed by colored dissolved organic matter (CDOM; 20-80%). Absorption from phytoplankton contributed only 0-30% of the total budget. This indicates that these lakes are primarily light limited, though the limitation comes from multiple sources. The contribution of NAP to the total absorption budget showed the greatest amount of variance between wet and dry seasons. Examination of the organic matter and estimated phytoplankton biomass contributions to TSS reveal that chlorophyll is not the primary source of organic matter in Australian lakes: allochthonous inputs are the primary trophic driver. Finally, there is strong regional and seasonal variation in the IOPs of the lakes, with the exception of the slope of CDOM. The slope of CDOM was not significantly different between seasons (p=0.94). Non-parametric stepwise multiple comparisons showed the

  18. Selective Two-Photon-Absorption-Induced Reactions of Anthracene-2-Carboxylic Acid on Tunable Plasmonic Substrate with Incoherent Light Source.

    PubMed

    Pincella, Francesca; Isozaki, Katsuhiro; Taguchi, Tomoya; Song, Yeji; Miki, Kazushi

    2015-02-01

    In this research, we report the development, characterization and application of various plasmonic substrates (with localized surface plasmon resonance wavelength tunable by gold nanoparticle size) for two-photon absorption (TPA)-induced photodimerization of an anthracene derivative, anthracene carboxylic acid, in both surface and solution phase under incoherent visible light irradiation. Despite the efficient photoreaction property of anthracene derivatives and the huge number of publications about them, there has never been a report of a multiphoton photoreaction involving an anthracene derivative with the exception of a reverse photoconversion of anthracene photodimer to monomer with three-photon absorption. We examined the progress of the TPA-induced photoreaction by means of surface-enhanced Raman scattering, taking advantage of the ability of our plasmonic substrate to enhance and localize both incident light for photoreaction and Raman scattering signal for analysis of photoreaction products. The TPA-induced photoreaction in the case of anthracene carboxylic acid coated 2D array of gold nanoparticles gave different results according to the properties of the plasmonic substrate, such as the size of the gold nanoparticle and also its resultant optical properties. In particular, a stringent requirement to achieve TPA-induced photodimerization was found to be the matching between irradiation wavelength, localized surface plasmon resonance of the 2D array, and twice the wavelength of the molecular excitation of the target material (in this case, anthracene carboxylic acid). These results will be useful for the future development of efficient plasmonic substrates for TPA-induced photoreactions with various materials.

  19. Light absorption properties of laboratory generated tar ball particles

    NASA Astrophysics Data System (ADS)

    Hoffer, A.; Tóth, A.; Nyirő-Kósa, I.; Pósfai, M.; Gelencsér, A.

    2015-06-01

    Tar balls (TBs) are a specific particle type which is abundant in the global troposphere, in particular in biomass smoke plumes. These particles belong to the family of atmospheric brown carbon (BrC) which can absorb light in the visible range of the solar spectrum. Albeit TBs are typically present as individual particles in biomass smoke plumes, their absorption properties have been only indirectly inferred from field observations or calculations based on their electron energy-loss spectra. This is because in biomass smoke TBs coexist with various other particle types (e.g. organic particles with inorganic inclusions and soot, the latter is emitted mainly during flaming conditions) from which they cannot be physically separated; thus, a direct experimental determination of their absorption properties is not feasible. Very recently we have demonstrated that TBs can be generated in the laboratory from droplets of wood tar that resemble atmospheric TBs in all of their observed properties. As a follow-up study we have installed on-line instruments to our laboratory set-up generating pure TB particles to measure the absorption and scattering, as well as size distribution of the particles. In addition, samples were collected for transmission electron microscopy (TEM) and total carbon (TC) analysis. The effects of experimental parameters were also studied. The mass absorption coefficients of the laboratory generated TBs were found to be in the range of 0.8-3.0 m2 g-1 at 550 nm, with absorption Ångström exponents (AAE) between 2.7 and 3.4 (average 2.9) in the wavelength range 467-652 nm. The refractive index of TBs as derived from Mie calculations was about 1.84-0.21i at 550 nm. In the brown carbon continuum these values fall closer to those of soot than to other light-absorbing species such as humic-like substances (HULIS). Considering the abundance of TBs in biomass smoke and the global magnitude of biomass burning emissions, these findings may have substantial

  20. Light absorption properties of laboratory-generated tar ball particles

    NASA Astrophysics Data System (ADS)

    Hoffer, A.; Tóth, A.; Nyirő-Kósa, I.; Pósfai, M.; Gelencsér, A.

    2016-01-01

    Tar balls (TBs) are a specific particle type that is abundant in the global troposphere, in particular in biomass smoke plumes. These particles belong to the family of atmospheric brown carbon (BrC), which can absorb light in the visible range of the solar spectrum. Albeit TBs are typically present as individual particles in biomass smoke plumes, their absorption properties have been only indirectly inferred from field observations or calculations based on their electron energy-loss spectra. This is because in biomass smoke TBs coexist with various other particle types (e.g., organic particles with inorganic inclusions and soot, the latter emitted mainly during flaming conditions) from which they cannot be physically separated; thus, a direct experimental determination of their absorption properties is not feasible. Very recently we have demonstrated that TBs can be generated in the laboratory from droplets of wood tar that resemble atmospheric TBs in all of their observed properties. As a follow-up study, we have installed on-line instruments to our laboratory set-up, which generate pure TB particles to measure the absorption and scattering, as well as the size distribution of the particles. In addition, samples were collected for transmission electron microscopy (TEM) and total carbon (TC) analysis. The effects of experimental parameters were also studied. The mass absorption coefficients of the laboratory-generated TBs were found to be in the range of 0.8-3.0 m2 g-1 at 550 nm, with absorption Ångström exponents (AAE) between 2.7 and 3.4 (average 2.9) in the wavelength range 467-652 nm. The refractive index of TBs as derived from Mie calculations was about 1.84 - 0.21i at 550 nm. In the brown carbon continuum, these values fall closer to those of soot than to other light-absorbing species such as humic-like substances (HULIS). Considering the abundance of TBs in biomass smoke and the global magnitude of biomass burning emissions, these findings may have

  1. Size Dependence of Two-Photon Absorption in Semiconductor Quantum Dots

    SciTech Connect

    Dakovski, Georgi L.; Shan, Jie

    2013-01-01

    Quantum confinement plays an important role in the optical properties of semiconductor quantum dots (QDs). In this work, we combine experiment and modeling to systematically investigate the size dependence of the degenerate two-photon absorption (TPA) of below-band-gap radiation in CdSe QDs. The TPA coefficient β at 800 nm of CdSe QDs of varying radii was measured using femtosecond white-light transient absorption spectroscopy by probing the pump-induced bleaching at the first exciton transition energy. β was also calculated using a model based on the multiband effective-mass approximation. Satisfactory agreement between experiment and theory was obtained. Our findings show the evolution of the TPA in the QDs from that of atom-like to bulk-like with increasing the radius R. The TPA coefficient (or the volume normalized TPA cross-section) increases with radius approximately linearly in the strong confinement regime due to the rapid increase of the joint density of states for the two-photon allowed transitions, and saturates for R > 5 nm (the exciton Bohr radius), approaching that of bulk CdSe.

  2. Electromagnetic absorption properties of graphene/Fe nanocomposites

    SciTech Connect

    Chen, Yujin; Lei, Zhenyu; Wu, Hongyu; Zhu, Chunling; Gao, Peng; Ouyang, Qiuyun; Qi, Li-Hong; Qin, Wei

    2013-09-01

    Graphical abstract: - Highlights: • Graphene/Fe nanocomposites were prepared by a facile and green method. • 10 nm Fe nanoparticles were uniformly dispersed over the surface of the graphene sheets. • The nanocomposites exhibited strong electromagnetic wave absorption properties. - Abstract: Graphene (G)/Fe nanocomposites with ferromagnetic properties at room temperature were fabricated by a facile and green method. Transmission electron microscope (TEM) and atomic force microscopy (AFM) amylases reveal that the α-Fe nanoparticles with a diameter of only about 10 nm were uniformly dispersed over the surface of the graphene sheets. Compared with other magnetic materials and the graphene, the nanocomposites exhibited significantly enhanced electromagnetic absorption properties. The maximum reflection loss to electromagnetic wave was up to −31.5 dB at a frequency of 14.2 GHz for G/Fe nanocomposites with a thickness of 2.5 mm. Importantly, the addition of the nanocomposites is only about 20 wt.% in the matrix. The enhanced mechanism is discussed and it is related to high surface areas of G/Fe nanocomposites, interfacial polarizations between graphene and iron, synergetic effect and efficient dispersity of magnetic NPs.

  3. Microwave absorption properties of graphite flakes-phenolic resin composite

    NASA Astrophysics Data System (ADS)

    Gogoi, Jyoti P.; Gogoi, Pragyan J.; Bhattacharyya, Nidhi S.

    2013-01-01

    In the present investigation, microwave absorption properties of a conductor back single layer designed on graphite flakes (GF)-novolac phenolic resin (NPR) composites is studied. The complex permittivity of the developed composite enhance for higher GF percentages. The reflection loss(RL) measured using E8362C VNA shows a maximum RL values -25 dB at 9.8 GHz for 7 wt. % composition with -10 dB bandwidth of 0.3 GHz. The developed composites are being light weight and cost effective shows potential to be used as dielectric absorber.

  4. Relationship of the optical absorption and scattering properties with mechanical and structural properties of apple tissue

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optical absorption and scattering properties of fruit change with the physiological and biochemical activities in the tissue during ripening and postharvest storage. But it has not been well understood on how these changes are related to the structural and mechanical properties of fruit. This resear...

  5. Electromagnetic absorption properties of spacecraft and space debris

    NASA Astrophysics Data System (ADS)

    Micheli, D.; Santoni, F.; Giusti, A.; Delfini, A.; Pastore, R.; Vricella, A.; Albano, M.; Arena, L.; Piergentili, F.; Marchetti, M.

    2017-04-01

    Aim of the work is to present a method to evaluate the electromagnetic absorption properties of spacecraft and space debris. For these objects, the radar detection ability depends mainly on volume, shape, materials type and other electromagnetic reflecting behaviour of spacecraft surface components, such as antennas or thermal blankets, and of metallic components in space debris. The higher the electromagnetic reflection coefficient of such parts, the greater the radar detection possibility. In this research an electromagnetic reverberation chamber is used to measure the absorption cross section (ACS) of four objects which may represent space structure operating components as well as examples of space debris: a small satellite, a composite antenna dish, a Thermal Protection System (TPS) tile and a carbon-based composite missile shell. The ACS mainly depends on geometrical characteristics like apertures, face numbers and bulk porosity, as well as on the type of the material itself. The ACS, which is an electromagnetic measurement, is expressed in squared meters and thus can be compared with the objects geometrical cross section. A small ACS means a quite electromagnetic reflective tendency, which is beneficial for radar observations; on the contrary, high values of ACS indicate a strong absorption of the electromagnetic field, which in turn can result a critical hindering of radar tracking.

  6. Tuning nonlinear optical absorption properties of WS2 nanosheets

    NASA Astrophysics Data System (ADS)

    Long, Hui; Tao, Lili; Tang, Chun Yin; Zhou, Bo; Zhao, Yuda; Zeng, Longhui; Yu, Siu Fung; Lau, Shu Ping; Chai, Yang; Tsang, Yuen Hong

    2015-10-01

    To control the optical properties of two-dimensional (2D) materials is a long-standing goal, being of both fundamental and technological significance. Tuning nonlinear optical absorption (NOA) properties of 2D transition metal dichalcogenides in a cost effective way has emerged as an important research topic because of its possibility to custom design NOA properties, implying enormous applications including optical computers, communications, bioimaging, and so on. In this study, WS2 with different size and thickness distributions was fabricated. The results demonstrate that both NOA onset threshold, FON, and optical limiting threshold, FOL, of WS2 under the excitation of a nanosecond pulsed laser can be tuned over a wide range by controlling its size and thickness. The FON and FOL show a rapid decline with the decrease of size and thickness. Due to the edge and quantum confinement effect, WS2 quantum dots (2.35 nm) exhibit the lowest FON (0.01 J cm-2) and FOL (0.062 J cm-2) among all the samples, which are comparable to the lowest threshold achieved in graphene based materials, showing great potential as NOA materials with tunable properties.To control the optical properties of two-dimensional (2D) materials is a long-standing goal, being of both fundamental and technological significance. Tuning nonlinear optical absorption (NOA) properties of 2D transition metal dichalcogenides in a cost effective way has emerged as an important research topic because of its possibility to custom design NOA properties, implying enormous applications including optical computers, communications, bioimaging, and so on. In this study, WS2 with different size and thickness distributions was fabricated. The results demonstrate that both NOA onset threshold, FON, and optical limiting threshold, FOL, of WS2 under the excitation of a nanosecond pulsed laser can be tuned over a wide range by controlling its size and thickness. The FON and FOL show a rapid decline with the decrease of size

  7. Impact of Foliage Surface Properties on Vegetation Reflection and Absorption

    NASA Astrophysics Data System (ADS)

    Yang, B.; Knyazikhin, Y.; Yan, L.; Zhao, Y.; Jiao, J.

    2013-12-01

    Optical properties of phytoelements and their distribution in the canopy space (i.e., canopy structure) are among key factors that determine light environment in vegetation canopies, which in turn drives various physiological and physical processes required for the functioning of plants. Canopy radiative response is the source of information about ecosystem properties from remote sensing. Understanding of how radiation interacts with foliage and traverses in the 3D vegetation canopy is essential to both modeling and remote sensing communities. Radiation scattered by a leaf includes information from two dissimilar sources - the leaf surface and leaf interior. The first component of scattered radiation emanates from light reflected at the air-cuticle interface. This portion of reflected radiation does not interact with biochemical constituents inside the leaf and depends on the properties of the leaf surface. The leaf cuticle acts as a "barrier" for photons to enter the mesophyll and be absorbed; thus, tending to increase the leaf scattering. The second component mainly results from radiation interactions within the leaf-interior. The canopy radiation regime is sensitive to canopy structure, leaf surface properties and leaf biochemical constituents. Impact of leaf surface properties on canopy reflection and absorption is poorly understood. Radiation scattered at the surface of leaves is partly polarized. Fresnel reflection is the principal cause of light polarization. Polarization measurements provide a means to assess the impact of leaf surface properties on canopy radiation regime. We measured Bidirectional Reflectance Factor (BRF) in the principal plane and its polarized portion of needles and shoots of two coniferous species in the 400 to 1000 nm spectral interval. The needle and shoot BRF spectra were decomposed into polarized (PBRF) and diffuse (DBRF) components: BRF=PBRF+DBRF. Our analyses indicate: 1) PBRF in forward directions can account for up to 70% of

  8. Absorption properties of metal-semiconductor hybrid nanoparticles.

    PubMed

    Shaviv, Ehud; Schubert, Olaf; Alves-Santos, Marcelo; Goldoni, Guido; Di Felice, Rosa; Vallée, Fabrice; Del Fatti, Natalia; Banin, Uri; Sönnichsen, Carsten

    2011-06-28

    The optical response of hybrid metal-semiconductor nanoparticles exhibits different behaviors due to the proximity between the disparate materials. For some hybrid systems, such as CdS-Au matchstick-shaped hybrids, the particles essentially retain the optical properties of their original components, with minor changes. Other systems, such as CdSe-Au dumbbell-shaped nanoparticles, exhibit significant change in the optical properties due to strong coupling between the two materials. Here, we study the absorption of these hybrids by comparing experimental results with simulations using the discrete dipole approximation method (DDA) employing dielectric functions of the bare components as inputs. For CdS-Au nanoparticles, the DDA simulation provides insights on the gold tip shape and its interface with the semiconductor, information that is difficult to acquire by experimental means alone. Furthermore, the qualitative agreement between DDA simulations and experimental data for CdS-Au implies that most effects influencing the absorption of this hybrid system are well described by local dielectric functions obtained separately for bare gold and CdS nanoparticles. For dumbbell shaped CdSe-Au, we find a shortcoming of the electrodynamic model, as it does not predict the "washing out" of the optical features of the semiconductor and the metal observed experimentally. The difference between experiment and theory is ascribed to strong interaction of the metal and semiconductor excitations, which spectrally overlap in the CdSe case. The present study exemplifies the employment of theoretical approaches used to describe the optical properties of semiconductors and metal nanoparticles, to achieve better understanding of the behavior of metal-semiconductor hybrid nanoparticles.

  9. HAB detection based on absorption and backscattering properties of phytoplankton

    NASA Astrophysics Data System (ADS)

    Lei, Hui; Pan, Delu; Bai, Yan; Chen, Xiaoyan; Zhou, Yan; Zhu, Qiankun

    2011-11-01

    The coastal area of East China Sea (ECS) suffers from the harmful algal blooms (HAB) frequently every year in the warm season. The most common causative phytoplankton algal species of HAB in the ECS in recent years are Prorocentrum donghaiense (dinoflagellates), Karenia mikimotoi (dinoflagellates which could produce hemolytic and ichthyotoxins) and Skeletonema costatum (diatom). The discrimination between the dinoflagellates and diatom HAB through ocean color remote sensing approach can add the knowledge of HAB events in ECS and help to the precaution. A series of in-situ measurement consisted of absorption coefficient, total scattering and particulate backscattering coefficient was conducted in the southern coast of Zhejiang Province in May 2009, and the estuary of Changjiang River in August 2009 and December 2010, which encountered two HAB events and a moderate bloom. The Inherent Optical Properties (IOPs) of the bloom waters have significant difference between phytoplankton species in absorption and backscattering properties. The chlorophyll a specific absorption coefficient (a*phy(λ)) for the bloom patches (chlorophyll a concentration >6mg m-3) differ greatly from the adjacent normal seawater, with the a*phy(λ) of bloom water lower than 0.03 m2 mg-1 while the a*phy(λ) of the adjacent normal seawater is much higher (even up to 0.06 m2 mg-1). Meanwhile, the backscattering coefficients at 6 wavebands (420, 442, 470, 510, 590 and 700nm) are also remarkably lower for bloom waters (<0.01 m-1) than the normal seawater (> 0.02 m-1). The backscattering coefficient ratio (Rbp(λ)) is much lower for diatom bloom waters than for dinoflagellates types (0.01079 vs. 0.01227). A discrimination model based on IOPs is established, and several typical dinoflagellates and diatom bloom events including Prorocentrum donghaiense, Karenia mikimotoi and Skeletonema costatum in the ECS are picked out for testing with the MODIS-L2 and L3 ocean color remote sensing products from NASA

  10. Tissue Plasminogen Activator (tPA) Mediates Neurotoxin-Induced Cell Death and Microglial Activation

    DTIC Science & Technology

    2001-07-01

    Alzheimer’s disease and stroke. Tissue plasminogen activator (tPA), a protease converting plasminogen to plasmin, is necessary for neurodegeneration. In mice lacking tPA (tPA-/1), neurons are resistant to neurotoxic death. Delivery of tPA into tpA-/- mice restores susceptibility to neuronal death, indicating that tPA is neurotoxic in the context of excitotoxic injury. Although tPA is synthesized by neurons, the increase in tPA upon injury derives primarily from activated microglia, the immune cells of the brain. Microglia in tPA-/- mice demonstrate reduced activation.

  11. Nanofluid optical property characterization: towards efficient direct absorption solar collectors.

    PubMed

    Taylor, Robert A; Phelan, Patrick E; Otanicar, Todd P; Adrian, Ronald; Prasher, Ravi

    2011-03-15

    Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase.

  12. Nanofluid optical property characterization: towards efficient direct absorption solar collectors

    PubMed Central

    2011-01-01

    Suspensions of nanoparticles (i.e., particles with diameters < 100 nm) in liquids, termed nanofluids, show remarkable thermal and optical property changes from the base liquid at low particle loadings. Recent studies also indicate that selected nanofluids may improve the efficiency of direct absorption solar thermal collectors. To determine the effectiveness of nanofluids in solar applications, their ability to convert light energy to thermal energy must be known. That is, their absorption of the solar spectrum must be established. Accordingly, this study compares model predictions to spectroscopic measurements of extinction coefficients over wavelengths that are important for solar energy (0.25 to 2.5 μm). A simple addition of the base fluid and nanoparticle extinction coefficients is applied as an approximation of the effective nanofluid extinction coefficient. Comparisons with measured extinction coefficients reveal that the approximation works well with water-based nanofluids containing graphite nanoparticles but less well with metallic nanoparticles and/or oil-based fluids. For the materials used in this study, over 95% of incoming sunlight can be absorbed (in a nanofluid thickness ≥10 cm) with extremely low nanoparticle volume fractions - less than 1 × 10-5, or 10 parts per million. Thus, nanofluids could be used to absorb sunlight with a negligible amount of viscosity and/or density (read: pumping power) increase. PMID:21711750

  13. Hydrogen absorption-desorption properties of U 2Ti

    NASA Astrophysics Data System (ADS)

    Takuya, Yamamoto; Satoru, Tanaka; Michio, Yamawaki

    1990-02-01

    Hydrogen absorption-desorption properties of U 2Ti intermetallic compound was examined over the temperature range of 298 to 973 K and at hydrogen pressures below 10 5 Pa. It absorbs hydrogen up to 7.6 atoms per F.U. (formula unit) by two step reactions and hence each desorption isotherm is separated into two plateau regions. In the first plateau, a newly-found ternary hydride is formed, where the hydrogen concentration, cH, reaches 2.4 H atoms/F.U. In the second plateau, UH 3 is formed and cH reaches 7.6 H atoms/F.U. The specimen is disintegrated into fine powder in the second plateau, while in the first plateau the ternary hydride which was identified to be UTi 2H x, ( x = 4.8 to 6.2) showed high durability against powdering. It is predicted that UTi 2 can be suitable material for tritium storage.

  14. Beginning Teachers' Perceptions of the California Teaching Performance Assessment (TPA)

    ERIC Educational Resources Information Center

    Campbell, Conni; Ayala, Carlos Cuauhtémoc; Railsback, Gary; Freking, Frederick W.; McKenna, Corey; Lausch, David

    2016-01-01

    The teaching performance assessment (TPA) seeks to measure the knowledge, skills, and competencies of teachers during the credential phase of their training. The TPA was introduced in California in 2004 with programs piloting it and then became mandatory for candidates enrolling in preliminary programs in 2008. Although California has multiple…

  15. Prediction of two-photon absorption enhancement in red fluorescent protein chromophores made from non-canonical amino acids.

    PubMed

    Salem, M Alaraby; Twelves, Isaac; Brown, Alex

    2016-09-21

    Two-photon spectroscopy of fluorescent proteins is a powerful bio-imaging tool known for deep tissue penetration and little cellular damage. Being less sensitive than the one-photon microscopy alternatives, a protein with a large two-photon absorption (TPA) cross-section is needed. Here, we use time-dependent density functional theory (TD-DFT) at the B3LYP and CAM-B3LYP/6-31+G(d,p) levels of theory to screen twenty-two possible chromophores that can be formed upon replacing the amino-acid Tyr66 that forms the red fluorescent protein (RFP) chromophore with a non-canonical amino acid. The two-level model for TPA was used to assess the properties (i.e., transition dipole moment, permanent dipole moment difference, and the angle between them) leading to the TPA cross-sections determined via response theory. Computing TPA cross-sections with B3LYP and CAM-B3LYP yields similar overall trends. Results using both functionals agree that the RFP-derived model of the Gold Fluorescent Protein chromophore (Model 20) has the largest intrinsic TPA cross-section at the optimized geometry. TPA was further computed for selected chromophores following conformational changes: variation of both the dihedral angle of the acylimine moiety and the tilt and twist angles between the rings of the chromophore. The TPA cross-section assumed an oscillatory trend with the rotation of the acylimine dihedral, and the TPA is maximized in the planar conformation for almost all models. Model 21 (a hydroxyquinoline derivative) is shown to be comparable to Model 20 in terms of TPA cross-section. The conformational study on Model 21 shows that the acylimine angle has a much stronger effect on the TPA than its tilt and twist angles. Having an intrinsic TPA ability that is more than 7 times that of the native RFP chromophore, Models 20 and 21 appear to be very promising for future experimental investigation.

  16. Mg/Ti multilayers: Structural and hydrogen absorption properties

    NASA Astrophysics Data System (ADS)

    Baldi, A.; Pálsson, G. K.; Gonzalez-Silveira, M.; Schreuders, H.; Slaman, M.; Rector, J. H.; Krishnan, G.; Kooi, B. J.; Walker, G. S.; Fay, M. W.; Hjörvarsson, B.; Wijngaarden, R. J.; Dam, B.; Griessen, R.

    2010-06-01

    Mg-Ti alloys have uncommon optical and hydrogen absorbing properties, originating from a “spinodal-like” microstructure with a small degree of chemical short-range order in the atomic distribution. In the present study we artificially engineer short-range order by depositing Pd-capped Mg/Ti multilayers with different periodicities. Notwithstanding the large lattice mismatch between Mg and Ti, the as-deposited metallic multilayers show good structural coherence. On exposure to H2 gas a two-step hydrogenation process occurs with the Ti layers forming the hydride before Mg. From in situ measurements of the bilayer thickness Λ at different hydrogen pressures, we observe large out-of-plane expansions of Mg and Ti layers on hydrogenation, indicating strong plastic deformations in the films and a consequent shortening of the coherence length. On unloading at room temperature in air, hydrogen atoms remain trapped in the Ti layers due to kinetic constraints. Such loading/unloading sequence can be explained in terms of the different thermodynamic properties of hydrogen in Mg and Ti, as shown by diffusion calculations on a model multilayered systems. Absorption isotherms measured by hydrogenography can be interpreted as a result of the elastic clamping arising from strongly bonded Mg/Pd and broken Mg/Ti interfaces.

  17. Labeling of human clots in vitro with an active-site mutant of t-PA

    SciTech Connect

    Fry, E.T.; Mack, D.L.; Monge, J.C.; Billadello, J.J.; Sobel, B.E. )

    1990-02-01

    Prompt detection of acute thrombosis and its response to treatment with thrombolytic agents generally require angiography. Scintigraphic approaches with labeled antibodies to or components of the coagulation and fibrinolytic systems have been disappointing because of prolonged circulating half-lives of tracers and relatively slow or limited binding to thrombi. Accordingly, we developed and characterized a thrombolytically inactive, active-site mutant (Ser-478----Thr) of tissue-type plasminogen activator (t-PA) designed to detect thrombi in vivo. Binding of iodine-125-({sup 125}I) labeled Ser----Thr t-PA to thrombi in vitro was time- and concentration-dependent, and specific judging from inhibition by pre-incubation with anti-t-PA IgG. Clearance of 125I-labeled mutant t-PA in rabbits was rapid and biexponential (alpha t1/2 = 1.9 +/- 0.4 min, beta t1/2 = 39.8 +/- 11.2 min). Thus, the amidolytically inactive mutant of t-PA designed binds rapidly and specifically to human thrombi in vitro and is cleared rapidly from the circulation in vivo--properties rendering it attractive as a potentially useful clot imaging agent.

  18. Substituent Effects on the Absorption and Fluorescence Properties of Anthracene.

    PubMed

    Abou-Hatab, Salsabil; Spata, Vincent A; Matsika, Spiridoula

    2017-02-16

    Substitution can be used to efficiently tune the photophysical properties of chromophores. In this study, we examine the effect of substituents on the absorption and fluorescence properties of anthracene. The effects of mono-, di-, and tetrasubstitution of electron-donating and -withdrawing functional groups were explored. In addition, the influence of a donor-acceptor substituent pair and the position of substitution were investigated. Eleven functional groups were varied on positions 1, 2, and 9 of anthracene, and on position 6 of 2-methoxyanthracene and 2-carboxyanthracene. Moreover, the donor-acceptor pair NH2/CO2H was added on different positions of anthracene for additional studies of doubly substituted anthracenes. Finally, we looked into quadruple substitutions on positions 1,4,5,8 and 2,3,6,7. Vertical excitation energies and oscillator strengths were computed using density functional theory with the hybrid CAM-B3LYP functional and 6-311G(d) basis set. Correlations between the excitation energies or oscillator strengths of the low-lying bright La state and the Hammett sigma parameter, σp(+), of the substituents were examined. The energy is red-shifted for all cases of substitution. Oscillator strengths increase when substituents are placed along the direction of the transition dipole moment of the bright La excited state. Substitution of long chain conjugated groups significantly increases the oscillator strength in comparison to the cases for other substituents. In addition, the results of quadruply substituted geometries reveal symmetric substitution at the 1,4,5,8 positions significantly increases the oscillator strength and can lower the band gap compared to that of the unsubstituted anthracene molecule by up to 0.5 eV.

  19. Water absorption properties of ultrasonic treated brown rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To understand the effect of ultrasonic treated on brown rice, it is important to research the water absorption processing of brown rice before and after ultrasonic treatment. The objective of this study was investigate and modeling water absorption characteristics of brown rice using Peleg’s equatio...

  20. Connecting the Silicate Dust and Gas Properties of Distant Galaxies Using Quasar Absorption Systems

    NASA Astrophysics Data System (ADS)

    Aller, Monique C.; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam; Lackey, Kyle; Dwek, Eli; Beiranvand, Nassim; Morrison, Sean

    2016-01-01

    We present recent results from our program investigating the silicate dust properties in distant galaxies using quasar absorption systems. The dust and gas properties of distant galaxies can be characterized by studying the absorption features produced by them along the sightlines to luminous background quasars. Based on our prior finding that silicate dust absorption in z<1.5 quasar absorption systems exhibits a range of optical depths and absorption feature substructures, suggestive of silicate grain property variations, we are investigating silicate dust absorption in quasar absorption systems toward quasars with archival Spitzer Space Telescope Infrared Spectrograph (IRS) spectra. We present our measurements of the 10 and/or 18 micron silicate dust absorption feature(s) in these systems, and discuss constraints on the grain properties, such as composition and crystallinity, based on the shape and substructure present in these features. We also investigate the correlations between the silicate dust properties and the reddening. Connections between the silicate dust and gas phase metal absorption properties can also be probed for some of our targets with archival ground-based spectra. These relationships will yield valuable insights into the star formation history and evolution of metals and dust. This work is supported by NASA through ADAP grant NNX14AG74G and by an award issued by JPL/Caltech, and from US-NSF grant AST-1108830 to the University of South Carolina.

  1. UV absorption and scattering properties of inorganic-based sunscreens.

    PubMed

    Egerton, Terry A; Tooley, Ian R

    2012-04-01

    This article first introduces the concepts that underlie the calculations of scattering and absorption of light by small particles. Results of Mie theory calculations of light scattering and light absorption by 20, 50 and 100 nm TiO₂ and ZnO particles are then presented. As the attenuation, or extinction, by these particles is the sum of the scattering and absorption, the attenuation can then be calculated for wavelengths over the UVA and UVB region. These theoretical results are then shown to be in reasonable agreement with experimental results for alkyl benzoate dispersions of three different types of TiO₂ particle whose mean sizes range from 35 to 145 nm. Finally, the link between these measurements and the absorption curves of formulated dispersions of sunscreens are demonstrated and related to in vitro SPF and UVAPF measurements.

  2. Polymorphism in the spin-crossover ferric complexes [(TPA)Fe(III)(TCC)]PF6.

    PubMed

    Collet, Eric; Boillot, Marie Laure; Hebert, Johan; Moisan, Nicolas; Servol, Marina; Lorenc, Maciej; Toupet, Loïc; Buron-Le Cointe, Marylise; Tissot, Antoine; Sainton, Joelle

    2009-08-01

    We have identified two polymorphs of the molecular complex [(TPA)Fe((III))(TCC)]PF(6) [TPA = tris(2-pyridylmethyl)amine and TCC = 3,4,5,6-tetrachlorocatecholate dianion]: one is monoclinic and the other is orthorhombic. By lowering the temperature both undergo a thermal spin-crossover between a high-spin (S = 5/2) and a low-spin (S = 1/2) state, which we detected by magnetic, optical and X-ray diffraction measurements. The thermal crossover is only slightly shifted between the polymorphs. Their crystalline structures consist of similar cation layers alternating with PF(6) anion layers, packed differently in the two polymorphs. The magnetic and optical properties of the polymorphs are presented.

  3. Photovoltaic Small Molecules of TPA(FxBT-T-Cz)3: Tuning Open-Circuit Voltage over 1.0 V for Their Organic Solar Cells by Increasing Fluorine Substitution.

    PubMed

    Wang, Qiong; Duan, Linrui; Tao, Qiang; Peng, Wenhong; Chen, Jianhua; Tan, Hua; Yang, Renqiang; Zhu, Weiguo

    2016-11-09

    To simultaneously improve both open-circuit voltage (Voc) and short-circuit current density (Jsc) for organic solar cells, a novel D(A-π-Ar)3 type of photovoltaic small molecules of TPA(FxBT-T-3Cz)3 was designed and synthesized, which contain central triphenylamine (TPA), terminal carbazole (Cz), armed fluorine-substituted benzothiadiazole (FxBT, where x = 1 or 2), and bridged thiophene (T) units. A narrowed ultraviolet-visible absorption and a decreasing highest occupied molecular orbital energy level were observed from TPA(F1BT-T-3Cz)3 to TPA(F2BT-T-3Cz)3 with increasing fluorine substitution. However, the TPA(F2BT-T-3Cz)3/PC71BM-based solar devices showed a rising Voc of 1.01 V and an enhanced Jsc of 10.84 mA cm(-2) as well as a comparable power conversion efficiency of 4.81% in comparison to the TPA(F1BT-T-3Cz)3/PC71BM-based devices. Furthermore, in comparison to the parent TPA(BT-T-3Cz)3 molecule without fluorine substitution, the fluorine-substituted TPA(FxBT-T-3Cz)3 molecules exhibited significantly incremental Voc and Jsc values in their bulk heterojunction organic solar cells, owing to fluorine incorporation in the electron-deficient benzothiadiazole unit.

  4. Two-photon absorption of Zn(II) octupolar molecules.

    PubMed

    Mazzucato, Simone; Fortunati, Ilaria; Scolaro, Sara; Zerbetto, Michele; Ferrante, Camilla; Signorini, Raffaella; Pedron, Danilo; Bozio, Renato; Locatelli, Danika; Righetto, Stefania; Roberto, Dominique; Ugo, Renato; Abbotto, Alessandro; Archetti, Graziano; Beverina, Luca; Ghezzi, Sergio

    2007-06-21

    In this work we present an investigation of the non-linear optical (NLO) properties of two octupolar chromophores: [Zn(4,4'-bis(dibutylaminostyryl)-[2,2']-bipyridine)(3)](2+) and [Zn(4,4'-bis((E)-2-(N-(TEG)pyrrol-2-yl)vinyl)-[2,2']-bipyridine)(3)](2+) with Zn(ii) as the coordination center, using two-photon emission technique (TPE) in fs-pulse temporal regime. Compared to the free ligands, our results do not show a net increase in the two-photon absorption (TPA) cross-section for the octupolar complexes, once normalized to the ligand unit. This is in partial disagreement with a previous theoretical study investigating the first molecule where a significant increase of the TPA cross-section was predicted (X. J. Liu, et al., J. Chem. Phys., 2004, 120, 11 493).

  5. Radiative properties of the background aerosol: absorption component of extinction.

    PubMed

    Clarke, A D; Charlson, R J

    1985-07-19

    The light-scattering and light-absorption coefficients of the global background aerosol define its single-scatter albedo. Continuous, simultaneous measurements of these optical coefficients were made on a daily basis for the remote marine mid-troposphere; such measurements are essential for assessment of the effects of aerosol on atmospheric radiative transfer. Measurements of light-absorption coefficients made at the Mauna Loa Observatory in Hawaii were higher than expected, and the single-scatter albedo was lower than the value often used in radiative transfer models. Soot appears to be the most likely primary absorber, and hemispheric dispersal of this combustion-derived material is suggested.

  6. Nonlinear absorption properties and excited state dynamics of ferrocene.

    PubMed

    Scuppa, Stefano; Orian, Laura; Dini, Danilo; Santi, Saverio; Meneghetti, Moreno

    2009-08-20

    We report on the first observation of reverse saturable absorption by ferrocene (Fc) in toluene using nanosecond pulses at 532 nm. Pump and probe experiments in the visible spectral region show the existence of an excited triplet state with an intersystem crossing quantum yield S1 --> T1 of 0.085 and a molar extinction coefficient epsilon(Fc)(T) of 5650 L mol(-1) cm(-1) at 700 nm. The full understanding of the nonlinear optical behavior of Fc cannot be obtained, however, with a model that includes only the one-photon absorption from T1, but it is mandatory to consider also a simultaneous two-photon absorption from an excited singlet state of Fc (two-photon absorption cross section: 2.4 x 10(-41) cm4 s ph(-1) mol(-1)). The optical spectrum of the ground and triplet state of Fc are calculated within a TD-DFT approach considering several functionals (PBE, BLYP, LDA, OPBE) for the optimization of molecular geometry.

  7. Ripeness of 'Sun Bright' tomato using the optical absorption and scattering properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Maturity is one of the most important factors in determining the processing and eating quality of tomato. The objective of this research was to test the suitability of optical absorption and scattering properties for evaluating the maturity of tomatoes. Optical absorption and reduced scattering coef...

  8. Giant Two-photon Absorption in Circular Graphene Quantum Dots in Infrared Region

    PubMed Central

    Feng, Xiaobo; Li, Zhisong; Li, Xin; Liu, Yingkai

    2016-01-01

    We investigate theoretically the two-photon absorption (TPA) for circular graphene quantum dots (GQDs) with the edge of armchair and zigzag on the basis of electronic energy states obtained by solving the Dirac-Weyl equation numerically under finite difference method. The expressions for TPA cross section are derived and the transition selection rules are obtained. Results reveal that the TPA is significantly greater in GQDs than conventional semiconductor QDs in infrared spectrum (2–6 um) with a resonant TPA cross section of up to 1011 GM. The TPA peaks are tuned by the GQDs’ size, edge and electron relaxation rate. PMID:27629800

  9. Metal-free carbon nanotubes: synthesis, and enhanced intrinsic microwave absorption properties

    PubMed Central

    Qi, Xiaosi; Xu, Jianle; Hu, Qi; Deng, Yu; Xie, Ren; Jiang, Yang; Zhong, Wei; Du, Youwei

    2016-01-01

    In order to clearly understand the intrinsic microwave absorption properties of carbon nanomaterials, we proposed an efficient strategy to synthesize high purity metal-free carbon nanotubes (CNTs) over water-soluble K2CO3 particles through chemical vapor decomposition and water-washing process. The comparison results indicated the leftover catalyst caused negative effects in intrinsic microwave absorption properties of CNTs, while an enhanced microwave absorption performance could be observed over the metal-free CNT sample. Moreover, the results indicated that the microwave absorption properties could be tuned by the CNT content. Therefore, we provided a simple route to investigate the intrinsic properties of CNTs and a possible enhanced microwave absorbing mechanism. PMID:27324290

  10. Metal-free carbon nanotubes: synthesis, and enhanced intrinsic microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Qi, Xiaosi; Xu, Jianle; Hu, Qi; Deng, Yu; Xie, Ren; Jiang, Yang; Zhong, Wei; Du, Youwei

    2016-06-01

    In order to clearly understand the intrinsic microwave absorption properties of carbon nanomaterials, we proposed an efficient strategy to synthesize high purity metal-free carbon nanotubes (CNTs) over water-soluble K2CO3 particles through chemical vapor decomposition and water-washing process. The comparison results indicated the leftover catalyst caused negative effects in intrinsic microwave absorption properties of CNTs, while an enhanced microwave absorption performance could be observed over the metal-free CNT sample. Moreover, the results indicated that the microwave absorption properties could be tuned by the CNT content. Therefore, we provided a simple route to investigate the intrinsic properties of CNTs and a possible enhanced microwave absorbing mechanism.

  11. The tunable electronic structure and optic absorption properties of phosphorene by a normally applied electric field

    NASA Astrophysics Data System (ADS)

    Yang, Mou; Duan, Hou-Jian; Wang, Rui-Qiang

    2016-10-01

    We studied the electronic structure and optical absorption properties of phosphorene (a monolayer black phosphorus) under a normally applied electric field. The electric field enlarges the energy gap, weakens the effective mass anisotropy, and increases the effective mass component along the armchair direction (x-direction) for both conduction and valence bands but provides little change to the component along the zigzag direction (y-direction). The band edge optical absorption is completely polarized in the x-direction, and decreases when increasing the electric field. If the exciting frequency is beyond the energy gap, the absorption for the y-polarized light becomes nonzero, but the absorption is still highly polarized.

  12. Absorption measurement of thin films by using photothermal techniques: The influence of thermal properties

    SciTech Connect

    Wu, Z.L.; Kuo, P.K.; Thomas, R.L.; Fan, Z.X.

    1995-12-31

    Photothermal techniques are widely used for measuring optical absorption of thin film coatings. In these applications the calibration of photothermal signal is typically based on the assumption that the thermal properties of the thin film make very little contribution. In this paper we take mirage technique as an example and present a detailed analysis of the influence of thin film thermal properties on absorption measurements. The results show that the traditional calibration method is not valid on surprisingly many situations.

  13. Nonlinear absorption and transmission properties of Ge, Te and InAs using tuneable IR FEL

    SciTech Connect

    Amirmadhi, F.; Becker, K.; Brau, C.A.

    1995-12-31

    Nonlinear absorption properties of Ge, Te and InAs are being investigated using the transmission of FEL optical pulses through these semiconductors (z-scan method). Wavelength, intensity and macropulse dependence are used to differentiate between two-photon and free-carrier absorption properties of these materials. Macropulse dependence is resolved by using a Pockles Cell to chop the 4-{mu}s macropulse down to 100 ns. Results of these experiments will be presented and discussed.

  14. Cesium Absorption Spectrum Perturbed by Argon: Observation of Non-Lorentzian Wing Properties

    DTIC Science & Technology

    2012-03-01

    CESIUM ABSORPTION SPECTRUM PERTURBED BY ARGON : OBSERVATION OF NON-LORENTZIAN WING PROPERTIES THESIS Gordon E. Lott, Second Lieutenant, USAF AFIT...PERTURBED BY ARGON : OBSERVATION OF NON-LORENTZIAN WING PROPERTIES THESIS Presented to the Faculty Department of Engineering Physics Graduate School of...PUBLIC RELEASE; DISTRIBUTION UNLIMITED. AFIT / APPLPHY / ENP / 12-MOS CESIUM ABSORPTION SPECTRUM PERTURBED BY ARGON : OBSERVATION OF NON-LORENTZIAN

  15. Lymphatic fat absorption varies among rats administered dairy products differing in physiochemical properties.

    PubMed

    Fruekilde, Maj-Britt; Høy, Carl-Erik

    2004-05-01

    We examined in rats the intestinal absorption of fat from dairy products differing in physiochemical properties. Five dairy products (cream cheese, cream, sour cream, butter, and mixed butter) with minor differences in fatty acid composition were administered by gavage to rats, and lymphatic fat absorption was examined. Absorption was followed for 8 h after administration of 300 mg fat from the dairy products. Administration of cream and sour cream resulted in faster lymphatic fat absorption than cream cheese, butter, and mixed butter, and at 8 h the accumulated absorption of fat was significantly higher. The lymphatic absorption of fat after cream cheese administration was similar to the absorption after butter and mixed butter administration up to the 4-h time point; then it increased to a level between that of rats administered cream or sour cream and butter or mixed butter. Overall, these results demonstrated different lymphatic absorption patterns of fat from dairy products differing in physiochemical properties. Because the fatty acid composition of the dairy products differed only slightly, other factors such as viscosity, type of emulsion, particle size, and likely also protein content may have contributed to the differences in absorption.

  16. Spectral properties of molecular iodine in absorption cells filled to specified saturation pressure.

    PubMed

    Hrabina, Jan; Šarbort, Martin; Acef, Ouali; Burck, Frédéric Du; Chiodo, Nicola; Holá, Miroslava; Číp, Ondřej; Lazar, Josef

    2014-11-01

    We present the results of measurement and evaluation of spectral properties of iodine absorption cells filled at certain saturation pressure. A set of cells made of borosilicate glass instead of common fused silica was tested for their spectral properties in greater detail with special care for the long-term development of the absorption media purity. The results were compared with standard fused silica cells and the high quality of iodine was verified. A measurement method based on an approach relying on measurement of linewidth of the hyperfine transitions is proposed as a novel technique for iodine cell absorption media purity evaluation. A potential application in laser metrology of length is also discussed.

  17. Calculations of One- and Two-Photon Absorption Spectra for Molecular Metal Chalcogenide Clusters with Electron-Acceptor Ligands.

    PubMed

    Nguyen, Kiet A; Pachter, Ruth; Day, Paul N

    2017-03-02

    We present calculated one- and two-photon absorption (OPA, TPA) spectra for molecular neutral, cation, and anion cadmium chalcogenide nonstoichiometric clusters [CdnE'm'(ER)m, E = S and Se, R = hydrogen, methyl, phenyl, para-nitrophenyl, para-cyanophenyl], ranging from less than 1 nm to more than 2 nm in size with well-defined structures. A systematic treatment of the clusters is carried out to assess the effects of size and ligand on their linear and nonlinear optical properties. Ligands and cluster size were found to have a large influence on the color and intensity of the electronic absorption spectra. TPA cross sections were found to increase linearly with cluster size. Electron-accepting ligands were also found to induce linear enhancement in TPA cross sections. Blue shifts of TPA maxima were observed for the first band with reduced molecular size. The effects of phenyl, para-nitrophenyl, and para-cyanophenyl substitutions, as well as changes in the chalcogenide atom, have been analyzed in detail.

  18. Retrieval of Aerosol Absorption Properties from Satellite Observations

    NASA Technical Reports Server (NTRS)

    Torres, Omar; Bhartia, Pawan K.; Jethva, H.; Ahn, Chang-Woo

    2012-01-01

    The Angstrom Absorption Exponent (AAE) is a parameter commonly used to characterize the wavelength-dependence of aerosol absorption optical depth (AAOD). It is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses multi-spectral measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measurement can be explained, using an approximations of Beer's Law (BL), as the upwelling reflectance at the cloud top attenuated by the absorption effects of the overlying aerosol layer. The upwelling reflectance at the cloud-top in an aerosol-free atmospheric column is mainly a function of cloud optical depth (COD). In the proposed method of AAE derivation, the first step is determining COD which is retrieved using a previously developed color-ratio based approach. In the second step, corrections for molecular scattering effects are applied to both the observed ad the calculated cloud reflectance terms, and the spectral AAOD is then derived by an inversion of the BL approximation. The proposed technique will be discussed in detail and application results making use of OMI multi-spectral measurements in the UV-Vis. will be presented.

  19. Characterization of Spectral Absorption Properties of Aerosols Using Satellite Observations

    NASA Technical Reports Server (NTRS)

    Torres, O.; Jethva, H.; Bhartia, P. K.; Ahn, C.

    2012-01-01

    The wavelength-dependence of aerosol absorption optical depth (AAOD) is generally represented in terms of the Angstrom Absorption Exponent (AAE), a parameter that describes the dependence of AAOD with wavelength. The AAE parameter is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses high spectral resolution measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measured reflectance (rho lambda) is approximately given by Beer's law rho lambda = rho (sub 0 lambda) e (exp -mtau (sub abs lambda)) where rho(sub 0 lambda) is the cloud reflectance, m is the geometric slant path and tau (sub abs lambda) is the spectral AAOD. The rho (sub 0 lambda) term is determined by means of radiative transfer calculations using as input the cloud optical depth derived as described in Torres et al. [JAS, 2012] that accounts for the effects of aerosol absorption. In the second step, corrections for molecular and aerosol scattering effects are applied to the cloud reflectance term, and the spectral AAOD is then derived by inverting the equation above. The proposed technique will be discussed in detail and application results will be presented. The technique can be easily applied to hyper-spectral satellite measurements that include UV such as OMI, GOME and SCIAMACHY, or to multi-spectral visible measurements by other sensors provided that the aerosol-above-cloud events are easily identified.

  20. Transient Infrared Measurement of Laser Absorption Properties of Porous Materials

    NASA Astrophysics Data System (ADS)

    Marynowicz, Andrzej

    2016-06-01

    The infrared thermography measurements of porous building materials have become more frequent in recent years. Many accompanying techniques for the thermal field generation have been developed, including one based on laser radiation. This work presents a simple optimization technique for estimation of the laser beam absorption for selected porous building materials, namely clinker brick and cement mortar. The transient temperature measurements were performed with the use of infrared camera during laser-induced heating-up of the samples' surfaces. As the results, the absorbed fractions of the incident laser beam together with its shape parameter are reported.

  1. PACAP Interacts with PAC1 Receptors to Induce Tissue Plasminogen Activator (tPA) Expression and Activity in Schwann Cell-Like Cultures

    PubMed Central

    Castorina, Alessandro; Waschek, James A.; Marzagalli, Rubina; Cardile, Venera; Drago, Filippo

    2015-01-01

    Regeneration of peripheral nerves depends on the abilities of rejuvenating axons to migrate at the injury site through cellular debris and altered extracellular matrix, and then grow along the residual distal nerve sheath conduit and reinnervate synaptic targets. Considerable evidence suggest that glial cells participate in this process, although the mechanisms remain to be clarified. In cell culture, regenerating neurites secrete PACAP, a peptide shown to induce the expression of the protease tissue plasminogen activator (tPA) in neural cell types. In the present studies, we tested the hypothesis that PACAP can stimulate peripheral glial cells to produce tPA. More specifically, we addressed whether or not PACAP promoted the expression and activity of tPA in the Schwann cell line RT4-D6P2T, which shares biochemical and physical properties with Schwann cells. We found that PACAP dose- and time-dependently stimulated tPA expression both at the mRNA and protein level. Such effect was mimicked by maxadilan, a potent PAC1 receptor agonist, but not by the PACAP-related homolog VIP, suggesting a PAC1-mediated function. These actions appeared to be mediated at least in part by the Akt/CREB signaling cascade because wortmannin, a PI3K inhibitor, prevented peptide-driven CREB phosphorylation and tPA increase. Interestingly, treatment with BDNF mimicked PACAP actions on tPA, but acted through both the Akt and MAPK signaling pathways, while causing a robust increase in PACAP and PAC1 expression. PACAP6-38 totally blocked PACAP-driven tPA expression and in part hampered BDNF-mediated effects. We conclude that PACAP, acting through PAC1 receptors, stimulates tPA expression and activity in a Akt/CREB-dependent manner to promote proteolytic activity in Schwann-cell like cultures. PMID:25658447

  2. Enhanced Microwave Absorption Properties of Carbon Black/Silicone Rubber Coating by Frequency-Selective Surface

    NASA Astrophysics Data System (ADS)

    Yang, Zhaoning; Luo, Fa; Gao, Lu; Qing, Yuchang; Zhou, Wancheng; Zhu, Dongmei

    2016-10-01

    A square frequency-selective surface (FSS) design has been employed to improve the microwave absorption properties of carbon black/silicone rubber (CBSR) composite coating. The FSS is placed on the surface of the CBSR coating. The effects of FSS design parameters on the microwave absorption properties of the CBSR coating have been investigated, including the size and period of the FSS design, and the thickness and permittivity of the coating. Simulation results indicate that the absorption peak for the CBSR coating alone is related to its thickness and electromagnetic parameters, while the combination of the CBSR coating with a FSS can exhibit a new absorption peak in the reflection curve; the frequency of the new absorption peak is determined by the resonance of the square FSS design and tightly depends on the size of the squares, with larger squares in the FSS design leading to a lower frequency of the new absorption peak. The enhancement of the absorption performance depends on achievement of a new absorption peak using a suitable size and period of the FSS design. In addition, the FSS design has a stable frequency response for both transverse electromagnetic (TE) and transverse magnetic (TM) polarizations as the incident angle varies from 0° to 40°. The optimized results indicate that the bandwidth with reflection loss below -5 dB can encompass the whole frequency range from 8 GHz to 18 GHz for thickness of the CBSR coating of only 1.8 mm. The simulation results are confirmed by experiments.

  3. Enhancing absorption properties of composite nanosphere and nanowire arrays by localized surface plasmon resonance shift

    NASA Astrophysics Data System (ADS)

    Tang, Xiaobing; Zhou, Leping; Du, Xiaoze; Yang, Yongping

    Nanoparticles with nonmetallic core and metallic shell can improve the spectral solar absorption efficiency for traditional working fluids, due to the localized surface plasmon resonance (LSPR) effect exists at the surfaces of these core-shell composite nanoparticles. In this work, the effect of geometry and material, and hence the LSPR effect, on the optical absorption properties of core-shell nanostructures was numerically demonstrated by the finite difference time domain method. The nanostructures were formed by varying the inner and outer radii of the composite nanospheres and nanowires and by changing the particle spacing for their arrays. The result indicates that varying the inner radius itself can tune the absorption efficiency factors of the nanostructures monotonously, while an optimal outer radius may exist for maximizing the absorption efficiency factors. It also shows that varying the inner radius itself can widen the absorption spectrums for the arrays, but the absorptance tends to increase with decreasing inner radius or particle spacing. Meanwhile, the second absorption peaks may be observed for nanowires or nanosphere/nanowire arrays, which can be tuned by the resonance shifts induced by the change of either inner or outer radius and hence the LSPR effect. The coupled LSPR effect under studied can be efficiently utilized for tuning the optical absorption properties of nanoparticles used in many applications including photothermal conversion, and perspective also exists for many other applications including surface-enhanced Raman spectroscopy (SERS) enhancement.

  4. Effect of water absorption on the mechanical properties of poly(3-hydroxybutyrate)/vegetable fiber composites

    NASA Astrophysics Data System (ADS)

    Marinho, Vithória A. D.; Carvalho, Laura H.; Canedo, Eduardo L.

    2015-05-01

    The present work studies the effect of water absorption on the performance of composites of poly(3-hydroxybutyrate) (PHB) - a fully biodegradable semi-crystalline thermoplastic obtained from renewable resources through low-impact biotechnological process, biocompatible and non-toxic - and vegetable fiber from the fruit (coconut) of babassu palm tree.Water resistance is an important characteristic of structural composites, that may exposed to rain and humid environments. Both water absorption capacity (water solubility in the material) and the rate of water absorption (controlled by the diffusivity of water in the material) are important parameters. However, water absorption per se may not be the most important characteristic, insofar as the performance and applications of the compounds. It is the effect of the water content on the ultimate properties that determine the suitability of the material for applications that involve prolonged exposure to water.PHB/babassu composites with 0-20% load were prepared in an internal mixer. Two different types of babassu fibers having two different article size ranges were compounded with PHB and test specimens molded by compression. The water absorption capacity and the kinetic constant of water absorption were measured in triplicate. Mechanical properties under tension were measured for dry and moist specimens with different amounts of absorbed water.Results indicate that the performance of the composites is comparable to that of the pure matrix. Water absorption capacity increases from 0.7% (pure PHB) to 4% (PHB/20% babassu), but the water diffusivity (4.10□8 cm2/s) was found to be virtually independent of the water absorption level. Water absorption results in moderate drop in elastic modulus (10-30% at saturation, according to fiber content) but has little effect on tensile strength and elongation at break. Fiber type and initial particle size do not have a significant effect on water absorption or mechanical properties.

  5. Relationships between absorption efficiency of elements in mammals and chemical properties.

    PubMed

    Le, T T Yen; Hendriks, A Jan

    2013-10-01

    Oral absorption efficiency is an important factor to consider in human risk assessment and varies widely between elements. Linking absorption efficiency to chemical properties facilitates the understanding of underlying processes and enables extrapolation across elements. In our study, oral absorption efficiency in humans was predicted for a number of elements based on their ionization energy and electronegativity. Data on oral absorption efficiency in humans were retrieved via a literature survey. A model was developed based on the assumption that ionic species readily react with biotic ligands. Accordingly, ionization energy was presumed to represent the reactivity and absorption of atoms in the gastrointestinal tract. The coefficients of the model were parameterized by fitting the quantitative relationship between absorption efficiency and ionization energy to data collected from well-standardized studies. Generally, absorption efficiency was strongly related to ionization energy, explaining 94% of the variability in absorption efficiency between elements reported by the International Commission on Radiological Protection (ICRP). In addition, the absorption efficiencies predicted based on ionization energy were within a factor of two of those given by the ICRP (ME = -0.05; RMSE = 0.31). However, the model is not applicable to alkaline metals and molybdenum because of the uniquely high solubility of their compounds or the flexible electron configuration of these elements. Approximately 56% of the variability in absorption efficiency between elements could be explained by electronegativity. These strong relationships between absorption efficiency and ionization energy and, to a lesser extent, electronegativity indicate potential for extrapolation across elements using atomic properties.

  6. Large two-photon absorptivity of hemoglobin in the infrared range of 780-880 nm.

    PubMed

    Clay, G Omar; Schaffer, Chris B; Kleinfeld, David

    2007-01-14

    Porphyrin molecules have a highly conjugated cyclic structure and are theorized to have unusually large two-photon absorptivities (sigmaTPA), i.e., sigmaTPA approximately 10(2) GM. The authors tested this claim. Ultrafast two-photon absorption (TPA) spectroscopy was performed on solutions of hemoglobin, which contains a naturally occurring metaloporphyrin. They used a pump-probe technique to directly detect the change in transmission induced by TPA over the wavelength range of lambda0=780-880 nm. As controls, they measured the TPA of the dyes rhodamine 6G and B; their measurements both verify and extend previously reported values. In new results, hemoglobin was found to have a peak two-photon absorptivity of sigmaTPA approximately 150 GM at lambda0=825 nm, near a resonance of the Soret band. This value supports theoretical expectations. They also found a significant difference in the TPA of carboxyhemoglobin versus oxyhemoglobin, e.g., sigmaTPA=61 GM versus sigmaTPA=18 GM, respectively, at lambda0=850 nm, which shows that the ligand affects the electronic states involved in TPA.

  7. Perceived Influence of Cooperating Teachers on edTPA Performance

    ERIC Educational Resources Information Center

    Behney, Jennifer

    2016-01-01

    The Education Teaching Performance Assessment (edTPA) is a performance assessment of teacher effectiveness that is increasingly used to make decisions about licensure for teacher candidates, including candidates seeking certification in world languages. Because of the high-stakes nature of this assessment, it is important to isolate and better…

  8. Candidate Success and edTPA: Looking at the Data

    ERIC Educational Resources Information Center

    Evans, Lesley A.; Kelly, Mary K.; Baldwin, Joni L.; Arnold, Jackie M.

    2016-01-01

    This descriptive study looks at the correlations between Teacher Performance Assessment (edTPA) data and numerous program data points, including GPA, major GPA, and benchmark assignment scores, gathered in an Early Childhood Education (ECE) program. Previous studies have looked to correlate grade point average (GPA) with pre-service teacher…

  9. Teaching Elementary School Social Studies Methods under edTPA

    ERIC Educational Resources Information Center

    An, Sohyun

    2016-01-01

    This article reports a self-study that analyzes my experience as a teacher educator navigating a turbulent educational landscape with the advent of edTPA. The data consist of my journal entries, the syllabi, handouts, work submitted by my students, and course evaluations. Data were analyzed by using an inductive process to describe how the edTPA…

  10. Three Ways edTPA Prepared Me for the Classroom

    ERIC Educational Resources Information Center

    Butler, Matthew

    2015-01-01

    edTPA, a capstone assessment designed to assess whether new teachers are ready for the job by evaluating their teaching and their analysis of their teaching, helped prepare the author for the classroom in three ways. First, he became accountable to his students. Second, he learned to analyze his teaching. Third, he discovered how to relate…

  11. Loss mechanism and microwave absorption properties of hierarchical NiCo2O4 nanomaterial

    NASA Astrophysics Data System (ADS)

    Zhou, Min; Lu, Fei; Lv, Tianyi; Yang, Xing; Xia, Weiwei; Shen, Xiaoshuang; He, Hui; Zeng, Xianghua

    2015-06-01

    Understanding the loss mechanism of microwave absorption is of great significance for the design and fabrication of low-cost, high-efficient and light-weight microwave absorbing materials. In this study, the microwave absorption of a hierarchical NiCo2O4 nanomaterial synthesized via a hydrothermal method and a subsequent annealing process was investigated in detail. The effects of the annealing temperature on the phase evaluation and microwave absorption properties were also investigated to reveal the microwave loss mechanism of NiCo2O4 nanostructures. The results show that the Debye relaxation and superior electric conductivity of NiCo2O4 are beneficial to its excellent microwave absorption performance. This study will be useful for the fundamental understanding of microwave absorption in NiCo2O4 nanomaterial, and for the design of a novel microwave absorbent.

  12. Optical absorption properties of dispersed gold and silver alloy nanoparticles.

    PubMed

    Wilcoxon, Jess

    2009-03-05

    The oldest topic in nanoscience is the size-dependent optical properties of gold and silver colloids or nanoparticles, first investigated scientifically by Michael Faraday in 1857. In the modern era, advances in both synthesis and characterization have resulted in new insights into the size-dependent absorbance of Au and Ag nanoparticles with sizes below the classical limit for Mie theory. In this paper we discuss the synthesis and properties of core/shell and nanoalloy particles of Au and Ag, compare them to particles of pure gold and silver, and discuss how alloying affects nanoparticle chemical stability. We show that composition, size, and nanostructure (e.g., core/shell vs quasi-random nanoalloy) can all be employed to adjust the optical absorbance properties. The type of nanostructure--core/shell vs alloy--is reflected in their optical absorbance features.

  13. Synthesis and microwave absorption properties of graphene/nickel composite materials

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoxia; Yu, Mingxun; Zhang, Wei; Zhang, Baoqin; Dong, Lifeng

    2015-03-01

    Graphene/nickel composite materials were successfully prepared via a one-step in situ reduction from nickel chloride, graphene oxide, and hydrazine at 80 °C for 3 h. Face-centered cubic Ni nanostructures with uniform size and high dispersion assembled on graphene sheets. Through the measurement of complex relative permittivity and permeability, their microwave absorption properties were evaluated. In comparison with pure Ni nanoparticles and graphene, the composite materials demonstrated much better characteristics of microwave absorption. The lowest reflection loss value of the composites with a thickness of 3 mm can reach -23.3 dB at 7.5 GHz. Our research reveals that graphene/Ni composites are promising microwave absorption materials with desirable absorption properties and reduced material weight.

  14. Cheminformatics Modeling of Amine Solutions for Assessing their CO2 Absorption Properties.

    PubMed

    Kuenemann, Melaine A; Fourches, Denis

    2017-03-07

    As stricter regulations on CO2 emissions are adopted worldwide, identifying efficient chemical processes to capture and recycle CO2 is of critical importance for industry. The most common process known as amine scrubbing suffers from the lack of available amine solutions capable of capturing CO2 efficiently. Tertiary amines characterized by low heats of reaction are considered good candidates but their absorption properties can significantly differ from one analogue to another despite high structural similarity. Herein, after collecting and curating experimental data from the literature, we have built a modeling set of 41 amine structures with their absorption properties. Then we analyzed their chemical composition using molecular descriptors and non-supervised clustering. Furthermore, we developed a series of quantitative structure-property relationships (QSPR) to assess amines' CO2 absorption properties from their structural characteristics. These models afforded reasonable prediction performances (e. g., Q(2)LOO =0.63 for CO2 absorption amount) even though they are solely based on 2D chemical descriptors and individual machine learning techniques (random forest and neural network). Overall, we believe the chemical analysis and the series of QSPR models presented in this proof-of-concept study represent new knowledge and innovative tools that could be very useful for screening and prioritizing hypothetical amines to be synthesized and tested experimentally for their CO2 absorption properties.

  15. Role of non-Condon vibronic coupling and conformation change on two-photon absorption spectra of green fluorescent protein

    NASA Astrophysics Data System (ADS)

    Ai, Yuejie; Tian, Guangjun; Luo, Yi

    2013-07-01

    Two-photon absorption spectra of green fluorescent proteins (GFPs) often show a blue-shift band compared to their conventional one-photon absorption spectra, which is an intriguing feature that has not been well understood. We present here a systematic study on one- and two-photon spectra of GFP chromophore by means of the density functional response theory and complete active space self-consistent field (CASSCF) methods. It shows that the popular density functional fails to provide correct vibrational progression for the spectra. The non-Condon vibronic coupling, through the localised intrinsic vibrational modes of the chromophore, is responsible for the blue-shift in the TPA spectra. The cis to trans isomerisation can be identified in high-resolution TPA spectra. Our calculations demonstrate that the high level ab initio multiconfigurational CASSCF method, rather than the conventional density functional theory is required for investigating the essential excited-state properties of the GFP chromophore.

  16. Microwave absorption properties of double-layer absorber based on carbonyl iron/barium hexaferrite composites

    NASA Astrophysics Data System (ADS)

    Ren, Xiaohu; Fan, Huiqing; Cheng, Yankui

    2016-05-01

    The microwave absorption properties of BaCo0.4Zn1.6Fe16O27 ferrite and carbonyl iron powder with single-layer and double-layer composite absorbers were investigated based on the electromagnetic transmission line theory in the frequency range from 1 to 14 GHz. XRD was used to characterize the structure of prepared absorbing particles. SEM was used to examine the micromorphology of the particles and composites. The complex permittivity and permeability of composites were measured by using a vector network analyzer. The reflection loss of the single-layer and double-layer absorbers with different thicknesses and orders was investigated. The results show that double-layer absorbers have better microwave absorption properties than single-layer absorbers. The microwave absorption properties of the double-layer structure are influenced by the coupling interactions between the matching and absorption layers. As the pure ferrite used as matching layer and the composite of BF-5CI used as absorption, the minimum RL of absorber can achieve to -55.4 dB and the bandwidth of RL <-10 dB ranged from 5.6 to 10.8 GHz when the thicknesses of matching layer and absorption layer were 0.9 and 1.4 mm, respectively.

  17. Profiling biopharmaceutical deciding properties of absorption of lansoprazole enteric-coated tablets using gastrointestinal simulation technology.

    PubMed

    Wu, Chunnuan; Sun, Le; Sun, Jin; Yang, Yajun; Ren, Congcong; Ai, Xiaoyu; Lian, He; He, Zhonggui

    2013-09-10

    The aim of the present study was to correlate in vitro properties of drug formulation to its in vivo performance, and to elucidate the deciding properties of oral absorption. Gastrointestinal simulation technology (GST) was used to simulate the in vivo plasma concentration-time curve and was implemented by GastroPlus™ software. Lansoprazole, a typical BCS class II drug, was chosen as a model drug. Firstly, physicochemical and pharmacokinetic parameters of lansoprazole were determined or collected from literature to construct the model. Validation of the developed model was performed by comparison of the predicted and the experimental plasma concentration data. We found that the predicted curve was in a good agreement with the experimental data. Then, parameter sensitivity analysis (PSA) was performed to find the key parameters of oral absorption. The absorption was particularly sensitive to dose, solubility and particle size for lansoprazole enteric-coated tablets. With a single dose of 30 mg and the solubility of 0.04 mg/ml, the absorption was complete. A good absorption could be achieved with lansoprazole particle radius down to about 25 μm. In summary, GST is a useful tool for profiling biopharmaceutical deciding properties of absorption of lansoprazole enteric-coated tablets and guiding the formulation optimization.

  18. A role for Saccharomyces cerevisiae Tpa1 protein in direct alkylation repair.

    PubMed

    Shivange, Gururaj; Kodipelli, Naveena; Monisha, Mohan; Anindya, Roy

    2014-12-26

    Alkylating agents induce cytotoxic DNA base adducts. In this work, we provide evidence to suggest, for the first time, that Saccharomyces cerevisiae Tpa1 protein is involved in DNA alkylation repair. Little is known about Tpa1 as a repair protein beyond the initial observation from a high-throughput analysis indicating that deletion of TPA1 causes methyl methane sulfonate sensitivity in S. cerevisiae. Using purified Tpa1, we demonstrate that Tpa1 repairs both single- and double-stranded methylated DNA. Tpa1 is a member of the Fe(II) and 2-oxoglutarate-dependent dioxygenase family, and we show that mutation of the amino acid residues involved in cofactor binding abolishes the Tpa1 DNA repair activity. Deletion of TPA1 along with the base excision repair pathway DNA glycosylase MAG1 renders the tpa1Δmag1Δ double mutant highly susceptible to methylation-induced toxicity. We further demonstrate that the trans-lesion synthesis DNA polymerase Polζ (REV3) plays a key role in tolerating DNA methyl-base lesions and that tpa1Δmag1revΔ3 triple mutant is extremely susceptible to methylation-induced toxicity. Our results indicate a synergism between the base excision repair pathway and direct alkylation repair by Tpa1 in S. cerevisiae. We conclude that Tpa1 is a hitherto unidentified DNA repair protein in yeast and that it plays a crucial role in reverting alkylated DNA base lesions and cytotoxicity.

  19. Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1987-01-01

    Laboratory measurements were conducted to evaluate properties of atmospheric gases under simulated conditions for the outer planets. A significant addition to this effort was the capability to make such measurements at millimeter wavelengths. Measurements should soon be completed on the millimeter wave absorption from ammonia under Jovian conditions. Also studied will be the feasibility of measuring the microwave and millimeter wave properties of phosphine (PH3) under simulated Jovian conditions. Further analysis and application of the laboratory results to microwave and millimeter wave absorption data for the outer planet, such as Voyager Radio Occultation experiments, will be pursued.

  20. Flower-like carbonyl iron powder modified by nanoflakes: Preparation and microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Yu, Miao; Yang, Pingan; Fu, Jie; Liu, Shuzhi

    2015-04-01

    In this paper, flower-like carbonyl iron powder (CIP) is prepared under normal temperature and pressure by a simple method of chemical reduction. This flower-like morphology is conducive to forming discontinuous network, enhancing diffuse scattering of the incident microwave and polarizing more interface charges. Those are all in favor of electromagnetic wave penetration and absorption. The test results show that compared with the unmodified CIP, the electromagnetic wave absorbing property of flower-like CIP is significantly improved in X-band. It is concluded that this research paves a way to enhance the microwave absorption properties of spherical metal particles.

  1. Impact absorption properties of carbon fiber reinforced bucky sponges.

    PubMed

    Thevamaran, Ramathasan; Saini, Deepika; Karakaya, Mehmet; Zhu, Jingyi; Podila, Ramakrishna; Rao, Apparao; Daraio, Chiara

    2017-03-24

    We describe the super compressible and highly recoverable response of bucky sponges as they are struck by a heavy flat-punch striker. The bucky sponges studied here are structurally stable, self-assembled mixtures of multiwalled carbon nanotubes (MWCNTs) and carbon fibers (CFs). We engineered the microstructure of the sponges by controlling their porosity using different CF contents. Their mechanical properties and energy dissipation characteristics during impact loading are presented as a function of their composition. The inclusion of CFs improves the impact force damping by up to 50% and the specific damping capacity by up to 7% compared to bucky sponges without CFs. The sponges also exhibit significantly better stress mitigation characteristics compared to vertically aligned carbon nanotube foams of similar densities. We show that delamination on the MWCNT-CF interfaces occurs during unloading, and arises from the heterogeneous fibrous microstructure of the bucky sponges.

  2. Effect of Moisture Absorption on the Mechanical Properties of Ceramic Filled Jute/Epoxy Hybrid Composites

    NASA Astrophysics Data System (ADS)

    Tapas Ranjan Swain, Priyadarshi; Biswas, Sandhyarani

    2017-02-01

    The present work emphasizes on the mechanical properties such as micro-hardness, flexural and impact strength of jute fiber and Al2O3 filler based polymer composites at dry and wet conditions. Composite samples reinforced with different wt.% of fibers and filler were prepared by hand lay-up technique. To improve the mechanical properties, jute fiber was hybridized with Al2O3 filler. The maximum flexural strength of 72.94 MPa and impact strength of 1.902 J is obtained for composites with 30 wt.% fiber content and 10 wt.% of filler content. The hardness of composite increases with increase in fiber and filler loading i.e 40 wt.% fiber content and 10 wt.% of filler content. The maximum hardness value is obtained 29.9 Hv. The effect of water absorption on mechanical properties of jute reinforced hybrid polymer composites is also investigated. To determine the influence of water absorption on the mechanical properties, specimens were immersed in distilled water for 10 days before testing. For reference purpose, dry specimens were tested. It is observed that the rate of water absorption depends on the fiber content as well as filler content. All the mechanical properties of composites are decreased after water absorption. Scanning electron microscopy (SEM) is used to characterise the microstructure and failure mechanisms of dry and wet jute fiber reinforced polymer composites.

  3. Microstructure and microwave absorption properties of MWCNTs reinforced magnesium matrix composites fabriccated by FSP

    NASA Astrophysics Data System (ADS)

    Chen, Yu-hua; Mao, Yu-qing; Xie, Ji-lin; Zhan, Zi-lin; Yu, Liang

    2017-01-01

    Multiwall carbon nanotubes (MWCNTs) reinforced magnesium matrix (MWCNTs/Mg) composites were successfully fabricated by friction stir processing (FSP). Microstructure and microwave-absorption properties of WCNTs/Mg composites are studied. The results show that with increasing the MWCNTs content to 7.1% in volume fraction, the agglomeration of MWCNTs is found in the WCNTs/Mg composites. The addition of MWCNTs has little effect on microwave-absorption properties. With increasing the frequency from 2 GHz to 18 GHz, the microwave absorption of the composites decreases. Compared with the absorption loss of the MWCNTs, the reflection loss of base material takes the most part of the loss of the microwave, and the increase of the reflection loss can promote electromagnetic shielding properties of the composites. Moreover, the electromagnetic shielding properties of the composites are less than -85 dB in the lower frequency range from 0.1 MHz to 3 GHz. With increasing the content of MWCNTs, the electrical conductivity of the composites is decreased, and the electromagnetic shielding properties is slightly enhanced.

  4. Preparation of SnO2-coated Ni microsphere composites with controlled microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Zhao, Biao; Shao, Gang; Fan, Bingbing; Guo, Wenhui; Chen, Yongqiang; Zhang, Rui

    2015-03-01

    In this work, the core-shell structured Ni/SnO2 composites have been successfully synthesized by a hydrothermal deposition method (HDM). The crystal structure, morphology and electromagnetic (EM) properties of Ni/SnO2 composites were investigated. The effects of SnO32- and urea contents on the morphologies of final Ni/SnO2 samples were also considered. The microwave absorption properties of Ni microspheres are remarkably enhanced after coating whit SnO2 nanaoshells. Moreover, the microwave absorption properties of core-shell structured Ni/SnO2 composites can be tailored by tuning SnO2 contents. The results show that the Ni/SnO2 composites prepared at 0.017 M SnO32- exhibit outstanding microwave absorption properties with a minimum reflection loss of -42.8 dB at 9.8 GHz with the corresponding thickness of 3.0 mm. The reflection loss below -10 dB can be obtained in a wide range of 5.8-18.0 GHz by adjusting the absorber thicknesses from 1.5 mm to 4.5 mm. The excellent microwave absorption properties are attributed to high magnetic loss, dielectric loss, multi-resonance and interfacial polarization of the core-shelled Ni/SnO2 composites.

  5. Investigation on optical absorption properties of ion irradiated single walled carbon nanotubes

    SciTech Connect

    Vishalli, Dharamvir, Keya; Kaur, Ramneek; Raina, K. K.; Avasthi, D. K.; Jeet, Kiran

    2015-08-28

    In the present study change in the optical absorption properties of single walled carbon nanotubes (SWCNTs) under nickel ion (60 MeV) irradiation at various fluences has been investigated. Langmuir Blodgett technique is used to deposit SWCNT thin film of uniform thickness. AFM analysis shows a network of interconnected bundles of nanotubes. UV-Vis-NIR absorption spectra indicate that the sample mainly contain SWCNTs of semiconducting nature. It has been found in absorption spectra that there is decrease in the intensity of the characteristic SWCNT peaks with increase in fluence. At fluence value 1×10{sup 14} ions/cm{sup 2} there is almost complete suppression of the characteristic SWCNTs peaks.The decrease in the optical absorption with increase in fluence is due to the increase in the disorder in the system which leads to the decrease in optically active states.

  6. Microwave absorption properties and mechanism for hollow Fe3 O4 nanosphere composites

    NASA Astrophysics Data System (ADS)

    Li, Z. W.; Yang, Z. H.

    2015-08-01

    Hollow Fe3 O4 nanospheres with the diameter of 450 nm and the wall thickness of 80 nm are prepared using the Ostwald ripening process. The composites filled with the hollow nanospheres of 60 wt% have good high-frequency and absorption properties. In RL-f curves, two absorption frequencies are found, which have their origins in quarter-wavelength resonator and magnetic resonance, respectively. Based on the quarter-wavelength resonator model, the calculated fA1 and RLA1 are in a good agreement with the observed values. Due to the overlap of the two absorptions, the frequency band is expanded. The composite with light weight of the density of 2.71 g/cm3 has bandwidth WP of 65% with return loss RL ≤ - 10 dB at thickness of 0.3 cm for EM absorption or attenuation applications.

  7. Absorption properties of GaAsBi based p-i-n heterojunction diodes

    NASA Astrophysics Data System (ADS)

    Zhou, Zhize; Mendes, Danuta F.; Richards, Robert D.; Bastiman, Faebian; David, John PR

    2015-09-01

    The absorption properties of GaAsBi have been investigated using GaAsBi based p-i-n diodes with different bismuth compositions (˜2.1 and ˜3.4%). The absorption behaviour of GaAsBi as a function of incident photon energy above the band gap follows that of a direct band gap material. With increasing bismuth content, the absorption of photons with energy lower than the band gap in GaAsBi is enhanced, probably due to localized states caused by Bi-related defects. A simplified analysis has been undertaken on the behaviour of absorption as a function of bias voltage. By undertaking photoresponsivity measurements as a function of reverse bias, the background doping type and the minority carriers diffusion lengths in GaAsBi have been determined.

  8. Synthesis, multi-nonlinear dielectric resonance and electromagnetic absorption properties of hcp-cobalt particles

    NASA Astrophysics Data System (ADS)

    Wen, Shulai; Liu, Ying; Zhao, Xiuchen; Cheng, Jingwei; Li, Hong

    2014-03-01

    Hcp-cobalt particles were successfully prepared by a liquid phase reduction method, and the microstructure, static magnetic properties, electromagnetic and microwave absorption properties of the cobalt particles with irregular shape were investigated in detail. The measured results indicate that the saturation magnetization was less than that of hcp-Co single crystals, and the coercivity was larger than that of bulk cobalt crystal. The permittivity presents multi-nonlinear dielectric resonance, which may result from the irregular shape containing parts of cutting angle of dodecahedron of cobalt particles. The real part of permeability decreases with the frequency, and the imaginary part has a wide resonant peak. The paraffin-based composite containing 70 wt% cobalt particles possessed strong absorption characteristics with a minimum RL of -38.97 dB at 10.81 GHz and an absorption band with RL under -10 dB from 8.72 to 13.26 GHz when the thickness is 1.8 mm, which exhibits excellent microwave absorption in middle and high frequency. The architectural design of material morphologies is important for improving microwave absorption properties toward future application.

  9. Polycyclic aromatic hydrocarbons obtained by lateral core extension of mesogenic perylenes: absorption and optoelectronic properties.

    PubMed

    Vollbrecht, Joachim; Bock, Harald; Wiebeler, Christian; Schumacher, Stefan; Kitzerow, Heinz

    2014-09-15

    Bilaterally extended perylenes were synthesized, characterized, and used to create organic light-emitting devices. A detailed investigation of the electronic and optical properties, and a comparison of perylene derivatives and compounds with unilaterally and bilaterally extended aromatic cores, reveal unexpected changes of the absorption spectrum, which are in agreement with simulations based on DFT.

  10. Optical properties of black carbon aggregates with non-absorptive coating

    NASA Astrophysics Data System (ADS)

    Liu, Chao; Li, Ji; Yin, Yan; Zhu, Bin; Feng, Qian

    2017-01-01

    This study develops an idealized model to account for the effects of non-absorptive coating on the optical properties of black carbon (BC) aggregates. The classic fractal aggregate is applied to represent realistic BC particles, and the coating is assumed to be spherical. To accelerate the single-scattering simulation, BC monomers that were overlapped with coating sphere (not those completely inside the coating) are slightly moved to avoid overlapping. The multiple-sphere T-matrix method (MSTM) becomes applicable to calculate the optical properties of inhomogeneous particles with any coating amount, and is generally two orders of magnitude faster than the discrete-dipole approximation for particles we considered. Furthermore, the simple spherical coating is found to have similar effects on the optical properties to those based on more complicated coating structure. With the simple particle model and the efficient MSTM, it becomes possible to consider the influence of coating with much more details. The non-absorptive coating of BC aggregates can significantly enhance BC extinction and absorption, which is consistent with previous studies. The absorption of coated aggregates can be over two times stronger than that of BC particles without coating. Besides the coating volume, the relative position between the mass centers of BC aggregate and coating also plays an important role on the optical properties, and should obviously be considered in further studies.

  11. TPS/PCL composite reinforced with treated sisal fibers: property, biodegradation and water-absorption

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sisal fibers bleached with sodium-hydroxide followed by hydrogen peroxide treatment were incorporated in a thermoplastic starch;-polycaprolactone (TPS/PCL) blend via extrusion processing and examined for their property, biodegradability and water-absorption. Scanning electron microscopy revealed wel...

  12. Assessing multiple quality attributes of peaches using spectral absorption and scattering properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research was to measure the spectral absorption and reduced scattering coefficients of peaches, using a hyperspectral imaging-based spatially-resolved method, for maturity/quality assessment. A newly developed optical property measuring instrument was used for acquiring hypersp...

  13. Water absorption characteristics and structural properties of rice for sake brewing.

    PubMed

    Mizuma, Tomochika; Kiyokawa, Yoshifumi; Wakai, Yoshinori

    2008-09-01

    This study investigated the water absorption curve characteristics and structural properties of rice used for sake brewing. The parameter values in the water absorption rate equation were calculated using experimental data. Differences between sample parameters for rice used for sake brewing and typical rice were confirmed. The water absorption curve for rice suitable for sake brewing showed a quantitatively sharper turn in the S-shaped water absorption curve than that of typical rice. Structural characteristics, including specific volume, grain density, and powdered density of polished rice, were measured by a liquid substitution method using a Gay-Lussac pycnometer. In addition, we calculated internal porosity from whole grain and powdered grain densities. These results showed that a decrease in internal porosity resulted from invasion of water into the rice grain, and that a decrease in the grain density affected expansion during the water absorption process. A characteristic S-shape water absorption curve for rice suitable for sake brewing was related to the existence of an invisible Shinpaku-like structure.

  14. Nonlinear optical properties of tetrapyrazinoporphyrazinato indium chloride complexes due to excited-state absorption processes.

    PubMed

    Dini, Danilo; Hanack, Michael; Meneghetti, Moreno

    2005-07-07

    The multiphoton absorption properties of the axially substituted tetrapyrazinotetraazaporphyrinato complex Pyz(4)TAPInCl (1) are reported and interpreted. In particular, the nonlinear optical transmission of the complex and the excited states involved in the nonlinear absorption have been determined at the frequency of the second harmonic generation of a Nd:YAG laser in the nanosecond time regime. Pyz(4)TAPInCl has an excited-state absorption cross section larger than its ground state in the 460-540 nm spectral region, and it shows an optical limiting (OL) behavior at 532 nm, which derives from a sequential two-photon absorption with a larger absorption cross section of the excited triplet state with respect to the ground state. It results that the absorption cross section of 1 in the excited triplet state is 7.8 x 10(-18) cm(2) vs 0.9 x 10(-18) cm(2) of the ground state at the wavelength of OL analysis.

  15. Effects of insoles and additional shock absorption foam on the cushioning properties of sport shoes.

    PubMed

    Chiu, Hung-Ta; Shiang, Tzyy-Yuang

    2007-05-01

    The purpose of this study was to investigate the effects of insoles and additional shock absorption foam on the cushioning properties of various sport shoes with an impact testing method. Three commercial sport shoes were used in this study, and shock absorption foam (TPE5020; Vers Tech Science Co. Ltd., Taiwan) with 2-mm thickness was placed below the insole in the heel region for each shoe. Eight total impacts with potential energy ranged from 1.82 to 6.08 J were performed onto the heel region of the shoe. The order of testing conditions was first without insole, then with insole, and finally interposing the shock absorption foam for each shoe. Peak deceleration of the striker was measured with an accelerometer attached to the striker during impact. The results of this study seemed to show that the insole or additional shock absorption foam could perform its shock absorption effect well for the shoes with limited midsole cushioning. Further, our findings showed that insoles absorbed more, even up to 24-32% of impact energy under low impact energy. It seemed to indicate that insoles play a more important role in cushioning properties of sport shoes under a low impact energy condition.

  16. Identifying Aerosol Type/Mixture from Aerosol Absorption Properties Using AERONET

    NASA Technical Reports Server (NTRS)

    Giles, D. M.; Holben, B. N.; Eck, T. F.; Sinyuk, A.; Dickerson, R. R.; Thompson, A. M.; Slutsker, I.; Li, Z.; Tripathi, S. N.; Singh, R. P.; Zibordi, G.

    2010-01-01

    Aerosols are generated in the atmosphere through anthropogenic and natural mechanisms. These sources have signatures in the aerosol optical and microphysical properties that can be used to identify the aerosol type/mixture. Spectral aerosol absorption information (absorption Angstrom exponent; AAE) used in conjunction with the particle size parameterization (extinction Angstrom exponent; EAE) can only identify the dominant absorbing aerosol type in the sample volume (e.g., black carbon vs. iron oxides in dust). This AAE/EAE relationship can be expanded to also identify non-absorbing aerosol types/mixtures by applying an absorption weighting. This new relationship provides improved aerosol type distinction when the magnitude of absorption is not equal (e.g, black carbon vs. sulfates). The Aerosol Robotic Network (AERONET) data provide spectral aerosol optical depth and single scattering albedo - key parameters used to determine EAE and AAE. The proposed aerosol type/mixture relationship is demonstrated using the long-term data archive acquired at AERONET sites within various source regions. The preliminary analysis has found that dust, sulfate, organic carbon, and black carbon aerosol types/mixtures can be determined from this AAE/EAE relationship when applying the absorption weighting for each available wavelength (Le., 440, 675, 870nm). Large, non-spherical dust particles absorb in the shorter wavelengths and the application of 440nm wavelength absorption weighting produced the best particle type definition. Sulfate particles scatter light efficiently and organic carbon particles are small near the source and aggregate over time to form larger less absorbing particles. Both sulfates and organic carbon showed generally better definition using the 870nm wavelength absorption weighting. Black carbon generation results from varying combustion rates from a number of sources including industrial processes and biomass burning. Cases with primarily black carbon showed

  17. Microwave absorption properties of FeCo-coated carbon fibers with varying morphologies

    NASA Astrophysics Data System (ADS)

    Wan, Yizao; Xiao, Jian; Li, Chunzhi; Xiong, Guangyao; Guo, Ruisong; Li, Lili; Han, Ming; Luo, Honglin

    2016-02-01

    Hybridizing carbon materials with magnetic metals and oxides has attracted much attention for enhanced microwave absorption. In this study, a magnetic Fe-Co alloy was coated on the surface of carbon fibers (FeCo@CFs) by electrodeposition. For the first time, different Fe-Co coating morphologies (thin plate, irregular particle, and pyramid) were obtained by adjusting the plating temperature. The morphology, structure, magnetic properties, and complex permittivity and permeability of the FeCo@CFs were determined as a function of plating temperature. Results show that the FeCo@CFs with different coating morphologies exhibit different magnetic properties and complex permittivity. The FeCo@CFs with plate-like morphology demonstrate the best absorption performance. It has been shown that the absorption of FeCo@CFs can be controlled by adjusting the morphology of Fe-Co coating, which provides a new and effective way to endow Fe-Co-coated carbon fibers with good microwave absorption properties.

  18. CoxFey@C Composites with Tunable Atomic Ratios for Excellent Electromagnetic Absorption Properties

    PubMed Central

    Lv, Hualiang; Ji, Guangbin; Zhang, Haiqian; Li, Meng; Zuo, Zhongzheng; Zhao, Yue; Zhang, Baoshan; Tang, Dongming; Du, Youwei

    2015-01-01

    The shell on the nano-magnetic absorber can prevent oxidation, which is very important for its practical utilization. Generally, the nonmagnetic shell will decrease the integral magnetic loss and thus weaken the electromagnetic absorption. However, maintaining the original absorption properties of the magnetic core is a major challenge. Here, we designed novel and facile CoxFey@C composites by reducing CoxFe3−xO4@phenolic resin (x = 1, 0.5 and 0.25). High saturation magnetization value (Ms) of CoxFey particle, as a core, shows the interesting magnetic loss ability. Meanwhile, the carbon shell may increase the integral dielectric loss. The resulting composite shows excellent electromagnetic absorption properties. For example, at a coating thickness of 2 mm, the RLmin value can reach to −23 dB with an effective frequency range of 7 GHz (11–18 GHz). The mechanisms of the improved microwave absorption properties are discussed. PMID:26659124

  19. Transient thermal effect, nonlinear refraction and nonlinear absorption properties of graphene oxide sheets in dispersion.

    PubMed

    Zhang, Xiao-Liang; Liu, Zhi-Bo; Li, Xiao-Chun; Ma, Qiang; Chen, Xu-Dong; Tian, Jian-Guo; Xu, Yan-Fei; Chen, Yong-Sheng

    2013-03-25

    The nonlinear refraction (NLR) properties of graphene oxide (GO) in N, N-Dimethylformamide (DMF) was studied in nanosecond, picosecond and femtosecond time regimes by Z-scan technique. Results show that the dispersion of GO in DMF exhibits negative NLR properties in nanosecond time regime, which is mainly attributed to transient thermal effect in the dispersion. The dispersion also exhibits negative NLR in picosecond and femtosecond time regimes, which are arising from sp(2)- hybridized carbon domains and sp(3)- hybridized matrix in GO sheets. To illustrate the relations between NLR and nonlinear absorption (NLA), NLA properties of the dispersion were also studied in nanosecond, picosecond and femtosecond time regimes.

  20. Microwave absorption properties and mechanism of cagelike ZnO /SiO2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Cao, Mao-Sheng; Shi, Xiao-Ling; Fang, Xiao-Yong; Jin, Hai-Bo; Hou, Zhi-Ling; Zhou, Wei; Chen, Yu-Jin

    2007-11-01

    In this paper, cagelike ZnO /SiO2 nanocomposites were prepared and their microwave absorption properties were investigated in detail. Dielectric constants and losses of the pure cagelike ZnO nanostructures were measured in a frequency range of 8.2-12.4GHz. The measured results indicate that the cagelike ZnO nanostructures are low-loss material for microwave absorption in X band. However, the cagelike ZnO /SiO2 nanocomposites exhibit a relatively strong attenuation to microwave in X band. Such strong absorption is related to the unique geometrical morphology of the cagelike ZnO nanostructures in the composites. The microcurrent network can be produced in the cagelike ZnO nanostructures, which contributes to the conductive loss.

  1. Optical properties of Mg-doped VO{sub 2}: Absorption measurements and hybrid functional calculations

    SciTech Connect

    Hu Shuanglin; Li, S.-Y.; Granqvist, C. G.; Niklasson, G. A.; Ahuja, R.; Scheicher, R. H.; Hermansson, K.

    2012-11-12

    Mg-doped VO{sub 2} thin films with thermochromic properties were made by reactive DC magnetron co-sputtering onto heated substrates, and spectral absorption was recorded at room temperature in the 0.5 < h{omega} < 3.5 eV energy range. Clear evidence was found for a widening of the main band gap from 1.67 to 2.32 eV as the Mg/(V + Mg) atomic ratio went from zero to 0.19, thereby significantly lowering the luminous absorption. This technologically important effect could be reconciled with spin-polarized density functional theory calculations using the Heyd-Scuseria-Ernzerhof [Heyd et al., J. Chem. Phys. 118, 8207 (2003); ibid. 124, 219906 (2006)] hybrid functional. Specifically, the calculated luminous absorptance decreased when the Mg/(V + Mg) ratio was increased from 0.125 to 0.250.

  2. Tuning optical and three photon absorption properties in graphene oxide-polyvinyl alcohol free standing films

    NASA Astrophysics Data System (ADS)

    Karthikeyan, B.; Udayabhaskar, R.; Hariharan, S.

    2016-07-01

    We report the optical and nonlinear optical properties of graphene oxide (GO)-polyvinyl alcohol (PVA) free standing films. The composite polymer films were prepared in ex-situ method. The variation in optical absorption spectra and optical constants with the amount of GO loading was noteworthy from the optical absorption spectroscopic studies. Nonlinear optical studies done at 532 nm using 5 ns laser pulses show three photon absorption like behaviour. Both steady state and time resolved fluorescence studies reveal that the GO was functioning as a pathway for the decay of fluorescence from PVA. This is attributed to the energy level modifications of GO through hydroxyl groups with PVA. Raman spectroscopy also supports the interaction between GO and PVA ions through OH radicals.

  3. Enhancing the absorption properties of acoustic porous plates by periodically embedding Helmholtz resonators.

    PubMed

    Groby, J-P; Lagarrigue, C; Brouard, B; Dazel, O; Tournat, V; Nennig, B

    2015-01-01

    This paper studies the acoustical properties of hard-backed porous layers with periodically embedded air filled Helmholtz resonators. It is demonstrated that some enhancements in the acoustic absorption coefficient can be achieved in the viscous and inertial regimes at wavelengths much larger than the layer thickness. This enhancement is attributed to the excitation of two specific modes: Helmholtz resonance in the viscous regime and a trapped mode in the inertial regime. The enhancement in the absorption that is attributed to the Helmholtz resonance can be further improved when a small amount of porous material is removed from the resonator necks. In this way the frequency range in which these porous materials exhibit high values of the absorption coefficient can be extended by using Helmholtz resonators with a range of carefully tuned neck lengths.

  4. Tensile properties and water absorption of zein sheets plasticized with oleic and linoleic acids.

    PubMed

    Budi Santosa, F X; Padua, G W

    1999-05-01

    Corn zein has been investigated for fabrication of biodegradable packaging materials. Our objective was to investigate the effect of added plasticizers, oleic and linoleic acids, on tensile properties and water absorption of zein sheets. Moldable resins were precipitated from aqueous ethanol dispersions of zein and fatty acids and rolled into sheets of approximately 0.5 mm in thickness. To increase plasticization effects, zein-oleic acid sheets were replasticized by heating them in fatty acid baths. Plasticization resulted in flexible sheets of high clarity, low modulus, and high elongation and toughness, although low tensile strength. Water absorption of zein sheets was lowered by plasticization, attributed in part to reduced mass fraction of zein. Polymerization of linoleic acid may have sealed off pores on sheet surfaces, thus slowing water absorption.

  5. Light absorption properties and radiative effects of primary organic aerosol emissions.

    PubMed

    Lu, Zifeng; Streets, David G; Winijkul, Ekbordin; Yan, Fang; Chen, Yanju; Bond, Tami C; Feng, Yan; Dubey, Manvendra K; Liu, Shang; Pinto, Joseph P; Carmichael, Gregory R

    2015-04-21

    Organic aerosols (OAs) in the atmosphere affect Earth's energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called "brown carbon" (BrC) component. However, the absorptivities of OAs are not represented or are poorly represented in current climate and chemical transport models. In this study, we provide a method to constrain the BrC absorptivity at the emission inventory level using recent laboratory and field observations. We review available measurements of the light-absorbing primary OA (POA), and quantify the wavelength-dependent imaginary refractive indices (kOA, the fundamental optical parameter determining the particle's absorptivity) and their uncertainties for the bulk POA emitted from biomass/biofuel, lignite, propane, and oil combustion sources. In particular, we parametrize the kOA of biomass/biofuel combustion sources as a function of the black carbon (BC)-to-OA ratio, indicating that the absorptive properties of POA depend strongly on burning conditions. The derived fuel-type-based kOA profiles are incorporated into a global carbonaceous aerosol emission inventory, and the integrated kOA values of sectoral and total POA emissions are presented. Results of a simple radiative transfer model show that the POA absorptivity warms the atmosphere significantly and leads to ∼27% reduction in the amount of the net global average POA cooling compared to results from the nonabsorbing assumption.

  6. [Phytoplankton Light Absorption Properties During the Blooms in Adjacent Waters of the Changjiang Estuary].

    PubMed

    Liu, Yang-yang; Shen, Fang; Li, Xiu-zhen

    2015-06-01

    Phytoplankton dominant species and their light absorption properties during the blooms occurred in August 2013 in adjacent waters of the Changjiang Estuary were analyzed. The results showed that phytoplankton blooms broke out in 10 out of 34 investigation stations, among which diatom blooms occurred in 6 stations while 3 stations were predominated by dinoflagellate. Phytoplankton absorption coefficients of both bloom and non-bloom waters exhibited large variations, with respective ranges of 0.199-0.832 m(-1) and 0.012-0.109 m(-1), while phytoplankton specific absorption coefficients spanned much narrower range, with the average values of bloom and non-bloom waters being 0.023 and 0.035 m2 x mg(-1), respectively. When transitioned from bloom to non-bloom waters, the proportion of phytoplankton with larger cell size lowered while that of smaller phytoplankton elevated, causing a less extent of package effect and thus higher specific absorption coefficients. Distinctive absorption spectra were observed between different types of bloom (such as diatom and dinoflagellate blooms) with similar phytoplankton cell size, mostly attributed to distinctive accessory pigment composition. The ratios of diadinoxanthin and chlorophyll-c2 concentrations to chlorophyll-a concentration in dinoflagellate blooms were higher than those in diatom blooms, which largely contributed to the shoulder peaks at 465 nm in dinoflagellate blooms.

  7. Facile synthesis of Ni/ZnO composite: Morphology control and microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Zhao, Biao; Shao, Gang; Fan, Bingbing; Guo, Wenhui; Xie, Yajun; Zhang, Rui

    2015-05-01

    In this work, Ni/ZnO composites with varying morphologies were synthesized by a facile hydrothermal method. X-ray diffraction (XRD) and Scanning electron microscopy (SEM) were performed to characterize Ni/ZnO composites. SEM images reveal that NH3·H2O concentration play a vital role on morphology of Ni/ZnO composite. The complex permittivity and permeability of three different morphologies of Ni/ZnO were measured in the frequency range of 1-18 GHz and their microwave absorption properties were investigated. The core-shell structured Ni/ZnO (ZnO polyhedron coating) composite prepared for 1.0 mL NH3·H2O shows excellent microwave absorption properties. A minimum reflection loss is -48.6 dB at 13.4 GHz and the corresponding thickness is 2.0 mm. The effective absorption (below -10 dB) can be tuned between 9.0 GHz and 18.0 GHz by adjusting thickness in 1.5-2.5 mm, and the frequency for RL exceeding -20 dB is located at 11.1-16.2 GHz with thickness of 1.8-2.2 mm. It is demonstrated that the polyhedron ZnO-coated Ni composite is a promising microwave absorbent with small thickness, strong absorption, and broad bandwidth.

  8. Heteronanostructured Co@carbon nanotubes-graphene ternary hybrids: synthesis, electromagnetic and excellent microwave absorption properties

    PubMed Central

    Qi, Xiaosi; Hu, Qi; Cai, Hongbo; Xie, Ren; Bai, Zhongchen; Jiang, Yang; Qin, Shuijie; Zhong, Wei; Du, Youwei

    2016-01-01

    In order to explore high efficiency microwave absorption materials, heteronanostructured Co@carbon nanotubes-graphene (Co@CNTs-G) ternary hybrids were designed and produced through catalytic decomposition of acetylene at the designed temperature (400, 450, 500 and 550 °C) over Co3O4/reduced graphene oxide (Co3O4/RGO). By regulating the reaction temperatures, different CNT contents of Co@CNTs-G ternary hybrids could be synthesized. The investigations indicated that the as-prepared heteronanostructured Co@CNTs-G ternary hybrids exhibited excellent microwave absorption properties, and their electromagnetic and microwave absorption properties could be tuned by the CNT content. The minimum reflection loss (RL) value reached approximately −65.6, −58.1, −41.1 and −47.5 dB for the ternary hybrids synthesized at 400, 450, 500 and 550 °C, respectively. And RL values below −20 dB (99% of electromagnetic wave attenuation) could be obtained over the as-prepared Co@CNTs-G ternary hybrids in the large frequency range. Moreover, based on the obtained results, the possible enhanced microwave absorption mechanisms were discussed in details. Therefore, a simple approach was proposed to explore the high performance microwave absorbing materials as well as to expand the application field of graphene-based materials. PMID:27892515

  9. Heteronanostructured Co@carbon nanotubes-graphene ternary hybrids: synthesis, electromagnetic and excellent microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Qi, Xiaosi; Hu, Qi; Cai, Hongbo; Xie, Ren; Bai, Zhongchen; Jiang, Yang; Qin, Shuijie; Zhong, Wei; Du, Youwei

    2016-11-01

    In order to explore high efficiency microwave absorption materials, heteronanostructured Co@carbon nanotubes-graphene (Co@CNTs-G) ternary hybrids were designed and produced through catalytic decomposition of acetylene at the designed temperature (400, 450, 500 and 550 °C) over Co3O4/reduced graphene oxide (Co3O4/RGO). By regulating the reaction temperatures, different CNT contents of Co@CNTs-G ternary hybrids could be synthesized. The investigations indicated that the as-prepared heteronanostructured Co@CNTs-G ternary hybrids exhibited excellent microwave absorption properties, and their electromagnetic and microwave absorption properties could be tuned by the CNT content. The minimum reflection loss (RL) value reached approximately ‑65.6, ‑58.1, ‑41.1 and ‑47.5 dB for the ternary hybrids synthesized at 400, 450, 500 and 550 °C, respectively. And RL values below ‑20 dB (99% of electromagnetic wave attenuation) could be obtained over the as-prepared Co@CNTs-G ternary hybrids in the large frequency range. Moreover, based on the obtained results, the possible enhanced microwave absorption mechanisms were discussed in details. Therefore, a simple approach was proposed to explore the high performance microwave absorbing materials as well as to expand the application field of graphene-based materials.

  10. Absorption and scattering properties of carbon nanohorn-based nanofluids for direct sunlight absorbers

    PubMed Central

    2011-01-01

    In the present work, we investigated the scattering and spectrally resolved absorption properties of nanofluids consisting in aqueous and glycol suspensions of single-wall carbon nanohorns. The characteristics of these nanofluids were evaluated in view of their use as sunlight absorber fluids in a solar device. The observed nanoparticle-induced differences in optical properties appeared promising, leading to a considerably higher sunlight absorption with respect to the pure base fluids. Scattered light was found to be not more than about 5% with respect to the total attenuation of light. Both these effects, together with the possible chemical functionalization of carbon nanohorns, make this new kind of nanofluids very interesting for increasing the overall efficiency of the sunlight exploiting device. PACS 78.40.Ri, 78.35.+c, 78.67.Bf, 88.40.fh, 88.40.fr, 81.05.U. PMID:21711795

  11. Impact of silica-coating on the microwave absorption properties of carbonyl iron powder

    NASA Astrophysics Data System (ADS)

    Li, J.; Feng, W. J.; Wang, J. S.; Zhao, X.; Zheng, W. Q.; Yang, H.

    2015-11-01

    Microwave absorption properties, especially the band width and depth of reflection loss are highlighted as key measurement in studies of microwave absorber. In order to improve the band width and depth of reflection loss of carbonyl iron powder (CIP), we prepared SiO2 layers on the surface of CIP by using tetraethyl orthosilicate (TEOS) as a SiO2 source and 3-aminopropyl triethoxysilane (APTES) as a surface modifier. SiO2 layer was formed by the hydrolysis of TEOS. The results show that after treatment the CIP is covered by a 5-10 nm coating layer. Contrast to uncoated samples, coated samples show improved absorption properties. The minimum of reflection loss is -38.8 dB at 11 GHz and the band width of reflection loss exceeding -10 dB is from 8 GHz to 14 GHz.

  12. The Effects of Fluid Absorption on the Mechanical Properties of Joint Prostheses Components

    NASA Astrophysics Data System (ADS)

    Yarbrough, David; Viano, Ann

    2010-02-01

    Ultra-high-molecular-weight polyethylene (UHMWPE) is the material playing the role of cartilage in human prosthetic joints. Wear debris from UHMWPE is a common reason for joint arthroplasty failure, and the exact mechanism responsible for wear remains an area of investigation. In this study, the microstructure of UHMWPE was examined as a function of fluid absorption. Samples with varying exposure to e-beam radiation (as part of the manufacturing process) were soaked for forty days in saline or artificial synovial fluid, under zero or 100 lbs load. Samples were then tensile-tested according to ASTM D-3895. The post-stressed material was then examined by transmission electron microscopy to evaluate the molecular response to stress, which correlates with macroscopic mechanical properties. Three parameters of the crystalline lamellae were measured: thickness, stacking ratio, and alignment to stress direction. Results indicate that fluid absorption does affect the mechanical properties of UHMWPE at both the microscopic and microscopic levels. )

  13. Effects of irradiation on protein electrophoretic properties, water absorption and cooking quality of lentils.

    PubMed

    Celik, Süeda; Yalçin, Erkan; Başman, Arzu; Köksel, Hamit

    2004-12-01

    Effects of gamma irradiation at doses of 1 kGy, 5 kGy, and 10 kGy on water absorption properties, cooking quality and electrophoretic patterns of insoluble proteins of red and green lentil samples were investigated. The densitometric analysis indicated that the effects of irradiation on sodium dodecyl sulfate-polycrylamide gel electrophoresis patterns of red and green lentil proteins were not significant. Generally, a 1 kGy irradiation dose did not significantly affect the water absorption properties of the lentil samples while significant increases were observed at the 5 kGy level. The dry and wet cooking times were found to be significantly decreased, as the irradiation level increased in all red and green lentil samples.

  14. Absorption, luminescent and lasing properties of laser dyes in silica gel matrices and thin gel films

    SciTech Connect

    Shaposhnikov, A A; Kuznetsova, Rimma T; Kopylova, T N; Maier, G V; Tel'minov, E N; Pavich, T A; Arabei, S M

    2004-08-31

    The absorption and emission properties of eight organic compounds in silica gel matrices of different chemical compositions and different types (bulk samples and thin films) are studied upon excitation by a XeCl laser and the second harmonic of a Nd:YAG laser. The mechanisms of the laser-induced changes in the spectral parameters of molecules in silica gel matrices are discussed and the photostability of the laser dyes in silica gel films is estimated. (active media)

  15. Ultrafast recovery time and broadband saturable absorption properties of black phosphorus suspension

    SciTech Connect

    Wang, Yingwei; Huang, Guanghui; Chen, Jiazhang; Xiao, Si He, Jun; Mu, Haoran; Bao, Qiaoliang; Lin, Shenghuang

    2015-08-31

    As a new type of two-dimensional crystal material, black phosphorus (BP) exhibits excellent electronics and optical performance. Herein, we focus on carrier relaxation dynamics and nonlinear optical properties of BP suspension. Atomic force microscopy, transmission electron microscopy, and optical transmission spectrum are employed to characterize the structure and linear optical properties of the BP. Additionally, pump-probe experiments at wavelength of 1550 nm were carried out to study the carrier dynamics in BP suspension, and ultrafast recovery time was observed (τ{sub s} = 24 ± 2 fs). Furthermore, we demonstrate the saturable absorption signals by open aperture Z-scan experiments at wavelengths of 1550 nm, 532 nm, and 680 nm. The results indicate that BP has broadband saturable absorption properties and the nonlinear absorption coefficients were determined to be β{sub 2} = −0.20 ± 0.08 × 10{sup −3 }cm/GW (532 nm), β{sub 2} = −0.12 ± 0.05 × 10{sup −3 }cm/GW (680 nm), and β{sub 2} = −0.15 ± 0.09 × 10{sup −3 }cm/GW (1550 nm)

  16. Mammalian gastrointestinal tract parameters modulating the integrity, surface properties, and absorption of food-relevant nanomaterials.

    PubMed

    Bellmann, Susann; Carlander, David; Fasano, Alessio; Momcilovic, Dragan; Scimeca, Joseph A; Waldman, W James; Gombau, Lourdes; Tsytsikova, Lyubov; Canady, Richard; Pereira, Dora I A; Lefebvre, David E

    2015-01-01

    Many natural chemicals in food are in the nanometer size range, and the selective uptake of nutrients with nanoscale dimensions by the gastrointestinal (GI) tract is a normal physiological process. Novel engineered nanomaterials (NMs) can bring various benefits to food, e.g., enhancing nutrition. Assessing potential risks requires an understanding of the stability of these entities in the GI lumen, and an understanding of whether or not they can be absorbed and thus become systemically available. Data are emerging on the mammalian in vivo absorption of engineered NMs composed of chemicals with a range of properties, including metal, mineral, biochemical macromolecules, and lipid-based entities. In vitro and in silico fluid incubation data has also provided some evidence of changes in particle stability, aggregation, and surface properties following interaction with luminal factors present in the GI tract. The variables include physical forces, osmotic concentration, pH, digestive enzymes, other food, and endogenous biochemicals, and commensal microbes. Further research is required to fill remaining data gaps on the effects of these parameters on NM integrity, physicochemical properties, and GI absorption. Knowledge of the most influential luminal parameters will be essential when developing models of the GI tract to quantify the percent absorption of food-relevant engineered NMs for risk assessment.

  17. Spin canting effect and microwave absorption properties of Sm-Mn substituted nanosized material

    NASA Astrophysics Data System (ADS)

    Sadiq, Imran; Naseem, Shahzad; Naeem Ashiq, Muhammad; Asif Iqbal, M.; Ali, Irshad; Khan, M. A.; Niaz, Shanawar; Rana, M. U.

    2015-12-01

    In order to understand the substitutional effect of rare earth element Sm3+ and divalent Mn2+ on structural, magnetic and microwave absorption properties of hexagonal ferrites, a series of Sr2-x Smx Ni2 Fe28-yMnyO46 X-type hexagonal ferrites with concentration (x=0.00, 0.02, 0.04, 0.06, 0.08, 0.10 and y=0, 0.1, 0.2, 0.3, 0.4, 0.5) was synthesized by the sol-gel method. The XRD analysis shows that the material crystallized into single X-type hexagonal phase. The absorption bands at low wave number in FTIR curves are the characteristics of the X-type hexagonal ferrites. Decreasing trend in the magnetic properties with the substitution of Sm-Mn contents was also observed, which may be attributed to the oxidation of Mn2+ ions into Mn3+ ions and spin canting effect of rare earth element Sm3+. The reflection loss peak shifted towards the low frequency and microwave absorption properties of the material enhanced with the substitution of Sm-Mn contents which reflects its applications in super high frequency (SHF) devices. The attenuation constant curves are in good agreement with the reflection loss peak.

  18. Controlling light absorption and photoelectric properties of coumarin-triphenylaminedye by different acceptor functional groups.

    PubMed

    Sun, Chaofan; Bai, Yanpeng; Li, Yuanzuo; Liu, Dejiang; Xu, Beibei; Wang, Qungui

    2016-11-01

    The ground state and excited state properties of three coumarin dyes, ZCJ1, ZCJ2 and ZCJ3, including ground state structures, energy levels, absorption spectra and driving forces of electron injection, were investigated via density functional theory (DFT) and time-dependent density functional theory (TD-DFT). In addition, five new molecules ZCJ3-1, ZCJ3-2, ZCJ3-3, ZCJ3-4 and ZCJ3-5 were designed through the introduction of a -CN group into molecule ZCJ3. The ground state and excited state properties of the five designed molecules were also calculated and compared with that of the original molecule, aiming to investigate the effect of different position of -CN groups on the optical and electrical properties of dye molecules. Moreover, the external electric field was taken into account. The results indicated that all three original molecules have better absorption within the visible-light range, and the molecule with a thiophene-thiophene conjugated bridge enables a red shift of the absorption spectrum. The molecule with a thiophene-benzene ring conjugated bridge enables the increase of driving force of electron injection. The energy levels, spectra and driving force of electron injection for the designed molecules are discussed in terms of studying their potential utility in dye-sensitized solar cells.

  19. Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, P. G.

    1985-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and Earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or laboratory measurements of such properties under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often lead to significant misinterpretation of available opacity data. Steffes and Eshleman showed that under environmental conditions corresponding to the middle atmosphere of Venus, the microwave absorption due to atmospheric SO2 was 50 percent greater than that calculated from Van Vleck-Weiskopff theory. Similarly, the opacity from gaseous H2SO4 was found to be a factor of 7 greater than theoretically predicted for conditions of the Venus middle atmosphere. The recognition of the need to make such measurements over a range of temperatures and pressures which correspond to the periapsis altitudes of radio occultation experiments, and over a range of frequencies which correspond to both radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements.

  20. Intravenous tPA Therapy Does Not Worsen Acute Intracerebral Hemorrhage in Mice

    PubMed Central

    Foerch, Christian; Rosidi, Nathanael L.; Schlunk, Frieder; Lauer, Arne; Cianchetti, Flor A.; Mandeville, Emiri; Arai, Ken; Yigitkanli, Kazim; Fan, Xiang; Wang, Xiaoying; van Leyen, Klaus; Steinmetz, Helmuth; Schaffer, Chris B.; Lo, Eng H.

    2013-01-01

    Tissue plasminogen activator (tPA) is the only FDA-approved treatment for reperfusing ischemic strokes. But widespread use of tPA is still limited by fears of inadvertently administering tPA in patients with intracerebral hemorrhage (ICH). Surprisingly, however, the assumption that tPA will worsen ICH has never been biologically tested. Here, we assessed the effects of tPA in two models of ICH. In a mouse model of collagenase-induced ICH, hemorrhage volumes and neurological deficits after 24 hrs were similar in saline controls and tPA-treated mice, whereas heparin-treated mice had 3-fold larger hematomas. In a model of laser-induced vessel rupture, tPA also did not worsen hemorrhage volumes, while heparin did. tPA is known to worsen neurovascular injury by amplifying matrix metalloproteinases during cerebral ischemia. In contrast, tPA did not upregulate matrix metalloproteinases in our mouse ICH models. In summary, our experimental data do not support the assumption that intravenous tPA has a deleterious effect in acute ICH. However, due to potential species differences and the inability of models to fully capture the dynamics of human ICH, caution is warranted when considering the implications of these findings for human therapy. PMID:23408937

  1. Intravenous tPA therapy does not worsen acute intracerebral hemorrhage in mice.

    PubMed

    Foerch, Christian; Rosidi, Nathanael L; Schlunk, Frieder; Lauer, Arne; Cianchetti, Flor A; Mandeville, Emiri; Arai, Ken; Yigitkanli, Kazim; Fan, Xiang; Wang, Xiaoying; van Leyen, Klaus; Steinmetz, Helmuth; Schaffer, Chris B; Lo, Eng H

    2013-01-01

    Tissue plasminogen activator (tPA) is the only FDA-approved treatment for reperfusing ischemic strokes. But widespread use of tPA is still limited by fears of inadvertently administering tPA in patients with intracerebral hemorrhage (ICH). Surprisingly, however, the assumption that tPA will worsen ICH has never been biologically tested. Here, we assessed the effects of tPA in two models of ICH. In a mouse model of collagenase-induced ICH, hemorrhage volumes and neurological deficits after 24 hrs were similar in saline controls and tPA-treated mice, whereas heparin-treated mice had 3-fold larger hematomas. In a model of laser-induced vessel rupture, tPA also did not worsen hemorrhage volumes, while heparin did. tPA is known to worsen neurovascular injury by amplifying matrix metalloproteinases during cerebral ischemia. In contrast, tPA did not upregulate matrix metalloproteinases in our mouse ICH models. In summary, our experimental data do not support the assumption that intravenous tPA has a deleterious effect in acute ICH. However, due to potential species differences and the inability of models to fully capture the dynamics of human ICH, caution is warranted when considering the implications of these findings for human therapy.

  2. Modification of fish skin collagen film and absorption property of tannic acid.

    PubMed

    Liu, Haiying; Zhao, Lu; Guo, Shidong; Xia, Yu; Zhou, Peng

    2014-06-01

    Fish collagen is a biomacromolecule material and is usually used as a clarifying agent. However, fish collagen is not recyclable, and sedimentation usually occurs in the clarification process using fish collagen so that the filtration process is inevitable. This work aimed to provide a recyclable modified fish skin collagen film (MFCF) for adsorption of tannic acids. The collagen from channel catfish skin was extracted and used for preparation of the fish skin collagen film (FCF) and MFCF. The result indicated that the mechanical properties of MFCF were improved by addition of 2 ml/L glycerol, 6 ml/L polyvinyl alcohol (PVA) and 2 ml/L glutaraldehyde in 15 g/L collagen solution. As the most important property of adsorption material, the hydroscopicity of MFCF was only 54%, significantly lower than that of FCF (295%). Therefore, MFCF would not collapse in water. The infrared and thermal properties of MFCF were also investigated in this work. Results indicated that, in comparison to FCF, the physical and chemical properties of MFCF had been improved significantly. MFCF had higher shrink temperature (79.3 °C) and it did not collapse in distilled water at normal temperature. Furthermore, absorption and desorption properties of tannic acid were studied. MFCF showed good capability of absorption and desorption of tannic acid, which leaded to the suggestion that MFCF could have potential applications in adsorption material.

  3. Nonlinear optical properties of laser synthesized Pt nanoparticles: saturable and reverse saturable absorption

    NASA Astrophysics Data System (ADS)

    Chehrghani, A.; Torkamany, M. J.

    2014-01-01

    In this paper, the spectral and nonlinear optical properties of a colloidal solution of platinum nanoparticles (Pt NPs) in water are presented. The Pt NPs were prepared by laser ablation of a Pt metallic target in distilled water using a 1064 nm high frequency Nd:YAG laser. The intensity-dependent nonlinear optical absorption and nonlinear refraction behaviors of the sample exposed to the 532 nm nanosecond laser pulses were investigated by applying the Z-scan technique. The saturated nonlinear absorption coefficient 5.4 × 10-7 cm W-1 was obtained in a saturation intensity of 1.8 × 107 W cm-2. The saturable absorption response of the Pt NPs was switched to the reverse saturable absorption in the higher laser intensities. The nonlinear refractive index that has a negative value was increased from -3.5 × 10-13 cm2 W-1 up to -15 × 10-13 cm2 W-1 by increasing the laser intensity.

  4. Screening micro-organisms for cadmium absorption from aqueous solution and cadmium absorption properties of Arthrobacter nicotianae.

    PubMed

    Tsuruta, Takehiko; Umenai, Daishi; Hatano, Tomonobu; Hirajima, Tsuyoshi; Sasaki, Keiko

    2014-01-01

    To obtain basic information on how microbial cells absorb cadmium from aqueous solution, we examined cadmium absorption in various micro-organisms. Of 51 micro-organism strains tested, we found that some Gram-positive bacteria, such as, Arthrobacter nicotianae and Bacillus subtilis, and some actinomycetes, such as, Streptomyces flavoviridis and S. levoris were highly capable of absorbing cadmium from an aqueous solution. A. nicotianae absorbed the largest amount of cadmium, over 800 μmol cadmium per gram of dry wt. cells. However, cadmium absorption by A. nicotianae was affected by the solution pH, cadmium concentration, and cell density. The absorption of cadmium was very rapid. Some factors that affected cadmium absorption by A. nicotianae cells were also discussed.

  5. Correlation of electrical conductivity, dielectric properties, microwave absorption, and matrix properties of composites filled with graphene nanoplatelets and carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Khurram, A. A.; Rakha, Sobia A.; Zhou, Peiheng; Shafi, M.; Munir, Arshad

    2015-07-01

    The DC electrical conductivity, percolation threshold, and dielectric properties of Graphene Nanoplatelets (GNPs) filled epoxy composites are studied and correlated with microwave absorption. The properties of GNPs filled composites are also compared with multiwalled carbon nanotubes (MWCNTs) composites, and GNPs are observed to have superior conductivity than MWCNTs. In all batches, the nanofillers have 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 wt. %. All composites irrespective of the type of nanofiller and viscosity of the matrix have shown electrical percolation threshold at 3.0 wt. %. The dielectric properties, i.e., complex permittivity, tan loss, and AC conductivity, are studied in 100 Hz-5.5 MHz. The DC and AC electrical conductivities (at and below the percolation) measured in 100 Hz-5.5 MHz are correlated to the GNPs and MWCNTs epoxy composites in the microwave frequency range (11-17 GHz). The maximum return loss of -12 dB and -6 dB was determined for MWCNTs and GNPs, respectively. The effects of nanofiller shape and the viscosity of the matrix on the dispersion and interparticle spacing of the conductive fillers within the polymer matrix have been discussed based on the results of conductivity, dielectric, and absorption properties.

  6. The Sm-Ni-Fe System: Isothermal Section and Microwave Absorption Properties

    NASA Astrophysics Data System (ADS)

    Yao, Qingrong; Shen, Yihao; Yang, Pengcheng; Rao, Guanghui; Zhou, Huiying; Deng, Jianqiu; Wang, Zhongmin

    2017-04-01

    The Sm-Ni-Fe ternary system has been investigated at 773 K by means of powder x-ray diffraction, metallography and scanning electron microscopy equipped with energy dispersive x-ray spectroscopy. The isothermal section consists of 16 single-phase regions, 29 two-phase regions and 14 three-phase regions. The influence of Fe-doping on the structure and the microwave absorption properties of the SmNi5 compound has been systematically studied. The homogeneity range in Sm16.67Ni83.33- x Fe x was determined as x = 16.67. The lattice parameters were found to gradually increase and the particle size become much finer with the increase of Fe concentration. All the samples exhibited good microwave absorption properties in the X-band (8-12 GHz). The highest reflection loss of the Sm16.67Ni83.33- x Fe x ( x = 0.0, 5.0, 10.0,15.0, 16.67) alloys are -10.12 dB, -10.39 dB, -16.44 dB, -20.69 dB, and -43.05 dB at 6.96 GHz, 7.92 GHz, 8.56 GHz, 10.04 GHz, and 11.08 GHz, respectively. The absorption peak shifted towards the higher frequency region with the increasing amount of Fe substitution.

  7. Optical Absorption and Photo-Thermal Conversion Properties of CuO/H2O Nanofluids.

    PubMed

    Wang, Liangang; Wu, Mingyan; Wu, Daxiong; Zhang, Canying; Zhu, Qunzhi; Zhu, Haitao

    2015-04-01

    Stable CuO/H2O nanofluids were synthesized in a wet chemical method. Optical absorption property of CuO/H2O nanofluids was investigated with hemispheric transmission spectrum in the wavelength range from 200 nm to 2500 nm. Photo-thermal conversion property of the CuO/H2O nanofluids was studied with an evaluation system equipped with an AUT-FSL semiconductor/solid state laser. The results indicate that CuO/H2O nanofluids have strong absorption in visible light region where water has little absorption. Under the irradiation of laser beam with a wavelength of 635 nm and a power of 0.015 W, the temperature of CuO/H2O nanofluids with 1.0% mass fraction increased by 5.6 °C within 40 seconds. Furthermore, the temperature elevation of CuO/H2O nanofluids was proved to increase with increasing mass fractions. On the contrast, water showed little temperature elevation under the identical conditions. The present work shows that the CuO/H2O nanofluids have high potential in the application as working fluids for solar utilization purpose.

  8. Electrical and absorption properties of fresh cassava tubers and cassava starch

    NASA Astrophysics Data System (ADS)

    Harnsoongnoen, S.; Siritaratiwat, A.

    2015-09-01

    The objective of this study was to analyze the electrical and absorption properties of fresh cassava tubers and cassava starch at various frequencies using electric impedance spectroscopy and near-infrared spectroscopy, as well as determine the classification of the electrical parameters of both materials using the principle component analysis (PCA) method. All samples were measured at room temperature. The electrical and absorption parameters consisted of dielectric constant, dissipation factor, parallel capacitance, resistance, reactance, impedance and absorbance. It was found that the electrical and absorption properties of fresh cassava tubers and cassava starch were a function of frequency, and there were significant differences between the materials. The dielectric constant, parallel capacitance, resistance and impedance of fresh cassava tubers and cassava starch had similar dramatic decreases with increasing frequency. However, the reactance of both materials increased with an increasing frequency. The electrical parameters of both materials could be classified into two groups. Moreover, the dissipation factor and phase of impedance were the parameters that could be used in the separation of both materials. According to the absorbance patterns of the fresh cassava tubers and cassava starch, there were significant differences.

  9. Enhanced two-photon absorption property of silver nanoparticle aggregates induced by a thioether derivative

    NASA Astrophysics Data System (ADS)

    Liu, Yun; Wang, Xiao-lan; Wei, Meng-qing; Wang, Hui; Tian, Yu-peng; Li, Sheng-li; Xue, Zhao-ming; Yang, Jia-xiang; Kong, Lin

    2016-12-01

    A novel thioether derivative with two-photon absorption activity, 4,4'-((4-(dimethylamino)phenyl)methylene)bis (sulfanediyl)dianiline (abbreviated as L), was designed and synthesized, which was used to couple with Ag nanoparticles (Ag NPs, ∼6 nm) to construct L-Ag hybrid particles with L uniformly dispersed on the surface of Ag NPs. The newly-formed hybrid particles self-assembled through L-L interactions between L molecules in one hybrid particle and adjacent particle to from Ag NPs aggregates (100 nm in diameter). By Raman and XPS analysis, the interfacial interaction 'hot spot' was determined, which was between thioether group and primary amino group of L molecule and Ag+ ion on the surface of pure Ag NPs. The interfacial interactions between the two components brought about changeable linear optical properties and enhanced nonlinear optical properties, two-photon absorption cross section and two-photon absorption coefficient included. Furthermore, the optical power limiting application of Ag NPs aggregates was also optimized by this means.

  10. Synthesis, Characterization, and Microwave Absorption Properties of Reduced Graphene Oxide/Strontium Ferrite/Polyaniline Nanocomposites.

    PubMed

    Luo, Juhua; Shen, Pan; Yao, Wei; Jiang, Cuifeng; Xu, Jianguang

    2016-12-01

    Strontium ferrite nanoparticles were prepared by a coprecipitation method, and reduced graphene oxide/strontium ferrite/polyaniline (R-GO/SF/PANI) ternary nanocomposites were prepared by in situ polymerization method. The morphology, structure, and magnetic properties of the ternary nanocomposites were investigated by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), TEM, Raman, and VSM. The microwave-absorbing properties of the composites were measured by a vector network analyzer. The XRD patterns show the single phase of strontium hexaferrite without other intermediate phases. TEM photographs reveal that strontium ferrite nanoparticles are uniformly dispersed on the surfaces of R-GO sheets. The R-GO/SF/PANI nanocomposite exhibited the best absorption property with the optimum matching thickness of 1.5 mm in the frequency of 2-18 GHz. The value of the maximum RL was -45.00 dB at 16.08 GHz with the 5.48-GHz bandwidth. The excellent absorption properties of R-GO/SF/PANI nanocomposites indicated their great potential as microwave-absorbing materials.

  11. Synthesis, Characterization, and Microwave Absorption Properties of Reduced Graphene Oxide/Strontium Ferrite/Polyaniline Nanocomposites

    NASA Astrophysics Data System (ADS)

    Luo, Juhua; Shen, Pan; Yao, Wei; Jiang, Cuifeng; Xu, Jianguang

    2016-03-01

    Strontium ferrite nanoparticles were prepared by a coprecipitation method, and reduced graphene oxide/strontium ferrite/polyaniline (R-GO/SF/PANI) ternary nanocomposites were prepared by in situ polymerization method. The morphology, structure, and magnetic properties of the ternary nanocomposites were investigated by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), TEM, Raman, and VSM. The microwave-absorbing properties of the composites were measured by a vector network analyzer. The XRD patterns show the single phase of strontium hexaferrite without other intermediate phases. TEM photographs reveal that strontium ferrite nanoparticles are uniformly dispersed on the surfaces of R-GO sheets. The R-GO/SF/PANI nanocomposite exhibited the best absorption property with the optimum matching thickness of 1.5 mm in the frequency of 2-18 GHz. The value of the maximum RL was -45.00 dB at 16.08 GHz with the 5.48-GHz bandwidth. The excellent absorption properties of R-GO/SF/PANI nanocomposites indicated their great potential as microwave-absorbing materials.

  12. In vivo endoscopic tissue diagnostics based on spectroscopic absorption, scattering, and phase function properties.

    PubMed

    Thueler, Philippe; Charvet, Igor; Bevilacqua, Frederic; St Ghislain, M; Ory, G; Marquet, Pierre; Meda, Paolo; Vermeulen, Ben; Depeursinge, Christian

    2003-07-01

    A fast spectroscopic system for superficial and local determination of the absorption and scattering properties of tissue (480 to 950 nm) is described. The probe can be used in the working channel of an endoscope. The scattering properties include the reduced scattering coefficient and a parameter of the phase function called gamma, which depends on its first two moments. The inverse problem algorithm is based on the fit of absolute reflectance measurements to cubic B-spline functions derived from the interpolation of a set of Monte Carlo simulations. The algorithm's robustness was tested with simulations altered with various amounts of noise. The method was also assessed on tissue phantoms of known optical properties. Finally, clinical measurements performed endoscopically in vivo in the stomach of human subjects are presented. The absorption and scattering properties were found to be significantly different in the antrum and in the fundus and are correlated with histopathologic observations. The method and the instrument show promise for noninvasive tissue diagnostics of various epithelia.

  13. High sensitivity of Indian summer monsoon to Middle East dust absorptive properties.

    PubMed

    Jin, Qinjian; Yang, Zong-Liang; Wei, Jiangfeng

    2016-07-28

    The absorptive properties of dust aerosols largely determine the magnitude of their radiative impacts on the climate system. Currently, climate models use globally constant values of dust imaginary refractive index (IRI), a parameter describing the dust absorption efficiency of solar radiation, although it is highly variable. Here we show with model experiments that the dust-induced Indian summer monsoon (ISM) rainfall differences (with dust minus without dust) change from -9% to 23% of long-term climatology as the dust IRI is changed from zero to the highest values used in the current literature. A comparison of the model results with surface observations, satellite retrievals, and reanalysis data sets indicates that the dust IRI values used in most current climate models are too low, tending to significantly underestimate dust radiative impacts on the ISM system. This study highlights the necessity for developing a parameterization of dust IRI for climate studies.

  14. Absorption and fluorescence properties of aryl substituted porphyrins in different media

    NASA Astrophysics Data System (ADS)

    Bozkurt, Serap Seyhan; Merdivan, Melek; Ayata, Sevda

    2010-02-01

    Absorption and fluorescence properties of aryl substituted porphyrins, 5,10,15,20-tetra-4-oxy(aceticacid)phenylporphyrin (TAPP), 5,10,15,20-tetra-(4-phenoxyphenyl) porphyrin (TPPP), 5,10,15,20-tetra-(3-bromo-4-hydroxyphenyl) porphyrin (TBHPP), and 5,10,15,20-tetra-p-chloromethylphenyl porphyrin (CMPP) were investigated. The UV/vis absorption, fluorescence and excited spectra as the fluorescence quantum yields and fluorescence lifetimes for the compounds were measured in organic solvents (chloroform (CHCl 3), tetrahydrofuran (THF)) and immobilized media (PVC film, sol-gel matrix). The fluorescence quantum yields of TAPP and TPPP were higher than the others. The fluorescence lifetimes of all studied porphyrin derivates were found to be fifty percent lower and their fluorescence intensities were increased fifty percent more in both of immobilized mediums, as compared to organic solvents.

  15. High sensitivity of Indian summer monsoon to Middle East dust absorptive properties

    PubMed Central

    Jin, Qinjian; Yang, Zong-Liang; Wei, Jiangfeng

    2016-01-01

    The absorptive properties of dust aerosols largely determine the magnitude of their radiative impacts on the climate system. Currently, climate models use globally constant values of dust imaginary refractive index (IRI), a parameter describing the dust absorption efficiency of solar radiation, although it is highly variable. Here we show with model experiments that the dust-induced Indian summer monsoon (ISM) rainfall differences (with dust minus without dust) change from −9% to 23% of long-term climatology as the dust IRI is changed from zero to the highest values used in the current literature. A comparison of the model results with surface observations, satellite retrievals, and reanalysis data sets indicates that the dust IRI values used in most current climate models are too low, tending to significantly underestimate dust radiative impacts on the ISM system. This study highlights the necessity for developing a parameterization of dust IRI for climate studies. PMID:27465689

  16. 12-O-Tetradecanoylphorbol-13-acetate (TPA) is anti-tumorigenic in liver cancer cells via inhibiting YAP through AMOT

    PubMed Central

    Zhu, Guoqing; Chen, Yan; Zhang, Xiao; Wu, Qi; Zhao, Yinghui; Chen, Yuxin; Sun, Fenyong; Qiao, Yongxia; Wang, Jiayi

    2017-01-01

    TPA stimulates carcinogenesis in various types of cancers. However, we found that TPA inhibits transformative phenotypes in liver cancer cells via the translocation of YAP from the nucleus, where it functions as a transcriptional co-factor, to the cytoplasm. Such effects led to a separation of YAP from its dependent transcription factors. The inhibitory effects of TPA on YAP were AMOT dependent. Without AMOT, TPA was unable to alter YAP activity. Importantly, the depletion of YAP and AMOT blocked the TPA-reduced transformative phenotypes. In sum, TPA has been established as an anti-tumorigenic drug in liver cancer cells via YAP and AMOT. PMID:28322318

  17. Effect of phytoplankton community composition and cell size on absorption properties in eutrophic shallow lakes: field and experimental evidence.

    PubMed

    Zhang, Yunlin; Yin, Yan; Wang, Mingzhu; Liu, Xiaohan

    2012-05-21

    We investigated phytoplankton absorption properties of Lake Taihu, in the spring and summer of 2005 and 2006, and for 17 days studied laboratory cultures of Scenedesmus obliquus (chlorophyta) and Microcystis aeruginosa (cyanophyta) to determine the effect of phytoplankton community composition and cell size on the absorption properties. There were significant seasonal differences in phytoplankton community composition and absorption coefficients. In spring, the phytoplankton community was dominated by chlorophyta with large cells, whereas in summer was dominated by cyanophyta with small cells. Phytoplankton absorption coefficients increased significantly from spring to summer, with the increase in chlorophyll a (Chla) concentration. In addition, Chla-specific absorption coefficients increased with the phytoplankton community succession from chlorophyta to cyanophyta. In culture, the cells density of S. obliquus was generally lower than that of M. aeruginosa, and Chla concentrations of S. obliquus were significantly higher than those of M. aeruginosa. Correspondingly, the Chla-specific absorption coefficients of S. obliquus were significantly lower than those of M. aeruginosa. Significant exponential correlations were found between absorption and Chla-specific absorption coefficients and Chla concentration for S. obliquus and M. aeruginosa. In addition, we developed a model to predict absorption and Chla-specific absorption coefficients using Chla concentration and cell size when data from two species was grouped together. Field and experimental results both showed that the Chla-specific absorption coefficients of cyanophyta were significantly higher than those of chlorophyta. The variability in specific absorption can attributed to phytoplankton community composition, cell size and pigment composition. As phytoplankton community composition changed significantly with season in the lake, and as variation in the cell sizes and accessory pigments of the phytoplankton

  18. Using edTPA to Compare Online and Face to Face Teacher Preparation Programs

    ERIC Educational Resources Information Center

    Heafner, Tina; Petty, Teresa

    2016-01-01

    Central to determining the effectiveness of technology to support learning and the value of technology-mediated instruction is the quality of programs. edTPA is a widely accepted, national measure of teacher readiness and preparation. Using edTPA score reports for teacher candidates completing a teacher education program, this study provides data…

  19. Unstandardized Responses to a "Standardized" Test: The edTPA as Gatekeeper and Curriculum Change Agent

    ERIC Educational Resources Information Center

    Ledwell, Katherine; Oyler, Celia

    2016-01-01

    We examine edTPA (a teacher performance assessment) implementation at one private university during the first year that our state required this exam for initial teaching certification. Using data from semi-structured interviews with 19 teacher educators from 12 programs as well as public information on edTPA pass rates, we explore whether the…

  20. "What about Bilingualism?" A Critical Reflection on the edTPA with Teachers of Emergent Bilinguals

    ERIC Educational Resources Information Center

    Kleyn, Tatyana; López, Dina; Makar, Carmina

    2015-01-01

    Amidst the debates surrounding teacher quality and preparation programs, the edTPA (education Teaching Performance Assessment) has emerged to assess future teachers through a portfolio-based certification process. This study offers the perspective of three faculty members who participated in an experimental configuration of edTPA implementation…

  1. Synthesis, characterization and microwave absorption properties of polyaniline/Sm-doped strontium ferrite nanocomposite

    NASA Astrophysics Data System (ADS)

    Luo, Juhua; Xu, Yang; Gao, Duoduo

    2014-11-01

    Sm-doped strontium ferrite nanopowders (SrSm0.3Fe11.7O19) and their composites of polyaniline (PANI)/SrSm0.3Fe11.7O19 with 10 wt% and 20 wt% ferrite were prepared by a sol-gel method and an in-situ polymerization process, respectively. The structure, magnetic properties and microwave absorption properties of the samples were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and vector network analyzer, respectively. The particle size of SrSm0.3Fe11.7O19 was about 35 nm by using XRD. The ferrite successfully packed by PANI. PANI/SrSm0.3Fe11.7O19 possessed the best absorption property with the optimum matching thickness of 3 mm in the frequency of 2-18 GHz. The value of the maximum reflection loss (RL) were -26.0 dB at 14.2 GHz with the 6.5 GHz bandwidth and -24.0 dB at 13.8 GHz with the 7.9 GHz bandwidth for the samples with 10 wt% and 20 wt% ferrite, respectively.

  2. Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1992-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically derived microwave absorption properties for such atmospheric constituents, or using laboratory measurements of such properties under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. The goal of this investigation was to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

  3. Laboratory Evaluation and Application of Microwave Absorption Properties Under Simulated Conditions for Planetary Atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1997-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or using laboratory measurements of such properties under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. Laboratory measurements completed under this grant (NAGW-533), have shown that the opacity from, SO2 under simulated Venus conditions is best described by a different lineshape than was previously used in theoretical predictions. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

  4. Parameterization of the scattering and absorption properties of individual ice crystals

    SciTech Connect

    Yang, Ping; Liou, K. N.; Wyser, Klaus; Mitchell, David

    2000-02-27

    We present parameterizations of the single-scattering properties for individual ice crystals of various habits based on the results computed from the accurate light scattering calculations. The projected area, volume, and single-scattering properties of ice crystals with various shapes and sizes are computed for 56 narrow spectral bands covering 0.2-5 {mu}m. The ice crystal habits considered in this study are hexagonal plates, solid and hollow columns, planar and spatial bullet rosette, and aggregates that are commonly observed in cirrus clouds. Using the observational relationships between the aspect ratios and the sizes of ice crystals, we can define the three-dimensional structure of these ice crystal habits with respect to their maximum dimensions for light scattering calculations. The volume and projected area of ice crystals, expressed in terms of the diameters of the corresponding equivalent spheres, are first parameterized by employing the ice crystal maximum dimensions. Further, various analytical expressions as functions of the effective dimensions of ice crystals have been developed to parameterize the extinction and absorption efficiencies, asymmetry factor, and the truncation of the forward peak energy in the phase function. The present parameterization scheme provides an efficient approach to obtain the basic scattering and absorption properties of nonspherical ice crystals. (c) 2000 American Geophysical Union.

  5. Synthesis and significantly enhanced microwave absorption properties of hematite dendrites/polyaniline nanocomposite

    NASA Astrophysics Data System (ADS)

    Wu, Hao; Wang, Liuding; Wu, Hongjing; Lian, Qian

    2014-06-01

    Hematite dendrites/polyaniline (HDs/PANI) nanocomposite, i.e. coating HDs with conductive PANI, has been successfully synthesized through a two-step polymerization of aniline monomers on the surface of pre-synthesized HDs for the first time. It is discovered that a lower concentration of HCl (0.02 mol L-1) has only a slight adverse effect on the dendritic structures of the coated HDs, while a higher concentration of HCl (0.04 mol L-1) results in severe damage to the sub-branches of the HDs. The morphology, composition, structure, static magnetic, and spectral properties of the as-prepared pristine HDs and HDs/PANI composites were thoroughly characterized by various physicochemical techniques. Moreover, the electromagnetic and microwave absorbing properties of the HDs and HDs/PANI wax composites were compared in detail. It was found that the frequency of absorption obeys a quarter-wavelength model for both of them, and the HDs/PANI wax composite exhibits far superior microwave absorption properties. This phenomenon can be attributed to the improved dielectric loss abilities and the complementary behaviors resulting from the PANI coatings and fractal-structured HDs.

  6. Laboratory Evaluation and Application of Microwave Absorption Properties Under Simulated Conditions for Planetary Atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1998-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments, entry probe radio signal absorption measurements, and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or using laboratory measurements of such properties taken under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. For example, laboratory measurements completed recently by Kolodner and Steffes (ICARUS 132, pp. 151-169, March 1998, attached as Appendix A) under this grant (NAGS-4190), have shown that the opacity from gaseous H2SO4 under simulated Venus conditions is best described by a different formalism than was previously used. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both spacecraft entry probe and orbiter radio occultation experiments and by radio astronomical observations, and over a range of frequencies which correspond to those used in such experiments, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

  7. Laboratory Evaluation and Application of Microwave Absorption Properties under Simulated Conditions for Planetary Atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    2002-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments, entry probe radio signal absorption measurements, and earth-based or spacecraft-based radio astronomical (emission) observations can be used to infer abundances of microwave absorbing constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or the use of laboratory measurements of such properties taken under environmental conditions that are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. Laboratory measurements have shown that the centimeter-wavelength opacity from gaseous phosphine (PH3) under simulated conditions for the outer planets far exceeds that predicted from theory over a wide range of temperatures and pressures. This fundamentally changed the resulting interpretation of Voyager radio occultation data at Saturn and Neptune. It also directly impacts planning and scientific goals for study of Saturn's atmosphere with the Cassini Radio Science Experiment and the Rossini RADAR instrument. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both spacecraft entry probe and orbiter (or flyby) radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations

  8. Analysis and parameterization of absorption properties of northern Norwegian coastal water

    NASA Astrophysics Data System (ADS)

    Nima, Ciren; Frette, Øyvind; Hamre, Børge; Erga, Svein Rune; Chen, Yi-Chun; Zhao, Lu; Sørensen, Kai; Norli, Marit; Stamnes, Knut; Muyimbwa, Dennis; Ssenyonga, Taddeo; Ssebiyonga, Nicolausi; Stamnes, Jakob J.

    2017-02-01

    Coastal water bodies are generally classified as Case 2 water, in which non-algal particles (NAP) and colored dissolved organic matter (CDOM) contribute significantly to the optical properties in addition to phytoplankton. These three constituents vary independently in Case 2 water and tend to be highly variable in space and time. We present data from measurements and analyses of the spectral absorption due to CDOM, total suspended matter (TSM), phytoplankton, and NAP in high-latitude northern Norwegian coastal water based on samples taken in spring, summer, and autumn.

  9. Comparison of absorption properties of colored dissolved organic matter in six different case 2 water bodies

    NASA Astrophysics Data System (ADS)

    Nima, Ciren; Frette, Øyvind; Hamre, Børge; Erga, Svein Rune; Chen, Yi-Chun; Zhao, Lu; Muyimbwa, Dennis; Ssenyonga, Taddeo; Ssebiyonga, Nicolausi; Okullo, Willy; Stamnes, Knut; Stamnes, Jakob J.

    2017-02-01

    Colored Dissolved Organic Matter (CDOM) is one of the main factors controlling the penetration of solar radiation in Case 2 water and affecting satellite-based estimation of ocean color. We present absorption properties of CDOM sampled in 6 water bodies including three in Norway (Røst coastal water, Samnangerfjord, Lysefjord), two in China (Bohai Sea, Lake Namtso), and one in Africa (Lake Victoria). These locations, which range from near the equator to subarctic regions, include water types from oligotrophic to eutrophic, and altitudes from sea level to 4,700 m above sea level.

  10. Structural modifications induced by TPA (12-O-tetradecanoyl phorbol-13-acetate) in sea urchin eggs.

    PubMed

    Ciapa, B; Crossley, I; De Renzis, G

    1988-07-01

    We investigated the effect of the phorbol ester TPA (12-O-tetradecanoyl phorbol 13-acetate) on the egg morphology of the sea urchin Arbacia lixula. Our study indicates that TPA alters the cortical region of the egg: the pigment granules migrate toward the surface, while cortical granules detach from the plasma membrane. Cortical granule exocytosis did not occur but the endocytosis process was turned on. Prolonged treatment of the eggs by TPA partially inhibits the cortical granule exocytosis normally triggered by fertilization. We discuss the effects of TPA in terms of its interaction with the Ca2+ pool and cytoskeletal structures. In order to discern the respective roles of pHi and protein kinase C activity in endocytosis process activation, we compared the ultrastructural effects of TPA and ammonia. Finally, the role of pigment vesicles in egg metabolism activation is discussed.

  11. Two-photon absorption of ligand-protected Ag15 nanoclusters. Towards a new class of nonlinear optics nanomaterials.

    PubMed

    Sanader, Željka; Krstić, Marjan; Russier-Antoine, Isabelle; Bertorelle, Franck; Dugourd, Philippe; Brevet, Pierre-François; Antoine, Rodolphe; Bonačić-Koutecký, Vlasta

    2016-05-14

    We report theoretical and experimental results on two-photon absorption (TPA) cross section of thiolated small silver cluster Ag15L11 exhibiting extraordinary large TPA in red. Our findings provide the responsible mechanism and allow proposing new classes of nanoclusters with large TPAs which are promising for biological and medical applications.

  12. Two photon absorption in high power broad area laser diodes

    NASA Astrophysics Data System (ADS)

    Dogan, Mehmet; Michael, Christopher P.; Zheng, Yan; Zhu, Lin; Jacob, Jonah H.

    2014-03-01

    Recent advances in thermal management and improvements in fabrication and facet passivation enabled extracting unprecedented optical powers from laser diodes (LDs). However, even in the absence of thermal roll-over or catastrophic optical damage (COD), the maximum achievable power is limited by optical non-linear effects. Due to its non-linear nature, two-photon absorption (TPA) becomes one of the dominant factors that limit efficient extraction of laser power from LDs. In this paper, theoretical and experimental analysis of TPA in high-power broad area laser diodes (BALD) is presented. A phenomenological optical extraction model that incorporates TPA explains the reduction in optical extraction efficiency at high intensities in BALD bars with 100μm-wide emitters. The model includes two contributions associated with TPA: the straightforward absorption of laser photons and the subsequent single photon absorption by the holes and electrons generated by the TPA process. TPA is a fundamental limitation since it is inherent to the LD semiconductor material. Therefore scaling the LDs to high power requires designs that reduce the optical intensity by increasing the mode size.

  13. Effects of TPA on short-circuit current across frog skin

    SciTech Connect

    Mauro, T.; O'Brien, T.G.; Civan, M.M.

    1987-02-01

    TPA (12-O-tetradecanoylphorbol-13-acetate) is an effective tumor promoter that affects a variety of ion transport processes. To examine the relationship between effects on transport and growth and differentiation, the authors have been studying the actions of TPA on frog skin, a particularly well-characterized epithelium. They have reported that high concentrations of TPA stimulate base-line short-circuit current (I/sub SC/) and inhibit the subsequent natriferic action of vasopressin. The current study of 89 preparations extends those findings. The K/sub m/ of the stimulatory effect of TPA is approx. 3 nM; this high affinity indicates that the transport phenomenon does not simply reflect a nonspecific interaction of phorbol ester with the plasma membranes. TPA acts largely or entirely at the mucosal surface of both split and whole skins; thus the sidedness of the effect does not arise from adsorption onto the underlying connective tissue when TPA is applied to the serosal surface of whole skin. Amiloride, an inhibitor of apical Na entry, abolishes I/sub SC/ across frog skins pretreated with TPA. The phorbol ester also increases I/sub SC/ across split skins, preparations which do not produce net Cl transport. The present results indicate that frog skin is highly responsive to TPA at concentrations known to activate protein kinase C in broken-cell preparations. The actions on I/sub SC/ appear to reflect changes in transepithelial Na transport modulated at the apical membranes. The full biochemical events triggered by TPA remain to be clarified; in part, TPA's actions may be mediated by leukotrienes produced by activation of the lipoxygenase pathway of arachidonic acid metabolism.

  14. Seasonal variability in the light absorption properties of western Arctic waters: Parameterization of the individual components of absorption for ocean color applications

    NASA Astrophysics Data System (ADS)

    Matsuoka, Atsushi; Hill, Victoria; Huot, Yannick; Babin, Marcel; Bricaud, Annick

    2011-02-01

    The light absorption properties of particulate and dissolved materials strongly influence the propagation of visible light in oceanic waters and therefore the accuracy of ocean color algorithms. While the general absorption properties of these materials have been reported for Arctic waters, their seasonal variability remains unknown. We investigated the light absorption coefficients of phytoplankton [aϕ(λ)], nonalgal particles [aNAP(λ)], and colored dissolved organic matter [aCDOM(λ)] in both coastal and oceanic waters of the western Arctic Ocean from spring to autumn. Values for the chlorophyll a-specific absorption coefficient of phytoplankton [a*ϕ(440)] declined significantly from the ice melt period in the early spring to the summer. Using high-performance liquid chromatography, we show that the decrease in a*ϕ(440) was due to a strong package effect that overwhelmed the influence of the pigment composition. A decrease in the aNAP(λ) values from spring and summer to autumn likely originated from a decrease in the concentration of phytoplanktonic detritus. The aCDOM(λ) near the surface decreased by 34% from spring to summer as a result of photobleaching by solar radiation. The colored dissolved organic matter (CDOM) absorption values then increased significantly during autumn, resulting from the cumulative injection of Alaskan Coastal Waters into the Arctic as well as CDOM generated in situ. Our results suggest that all of the absorption components are tightly linked to biogeochemical processes, and thus the seasonal variability in aϕ(λ), aNAP(λ), and aCDOM(λ) should be taken into account in bio-optical models.

  15. Measurements of scattering and absorption properties of surface aerosols at a semi-arid site, Anantapur

    NASA Astrophysics Data System (ADS)

    Rama Gopal, K.; Balakrishnaiah, G.; Arafath, S. Md.; Raja Obul Reddy, K.; Siva Kumar Reddy, N.; Pavan Kumari, S.; Raghavendra Kumar, K.; Chakradhar Rao, T.; Lokeswara Reddy, T.; Reddy, R. R.; Nazeer Hussain, S.; Vasudeva Reddy, M.; Suresh Babu, S.; Mallikarjuna Reddy, P.

    2017-01-01

    Aerosol optical properties are continuously measured at a semi-arid station, Anantapur from June 2012 to May 2013 which describes the impact of surface aerosols on climate change over the region. Scattering coefficient (σsct) and absorption coefficient (σabs) are obtained from integrating Nephelometer and Aethalometer, respectively. Also, the single scattering albedo (ω0), Scattering/absorption Ångström exponents were examined during the period of study. Diurnal variations of σsct and σabs show a bi-peak pattern with two maxima and one minimum in a day. The largest values of σsct and σabs are obtained in winter while the lowest values are measured in monsoon. From the measurements σsct550 and σabs550 are found to be 110 ± 12.23 Mm- 1 and 33 ± 5.2 Mm- 1, respectively during the study period. An analysis of the ω0 suggests that there is a more absorbing fraction in the particle composition over the measurement site. The ω0 obtained in the surface boundary layer of Anantapur is below the critical value of 0.86 that determines the shift from cooling to warming. A relationship between scattering/absorption coefficients and scattering/absorption Ångström exponent and single scattering albedo is further examined. In order to understand the origins of the air masses in the study region, we performed seven-day back trajectory analyses based on the NOAA HYSPLIT model. These trajectories were computed at several altitudes (3000 m, 1500 m, and 500 m) for June 2012 and May 2013. These results put in evidence the need of efforts to reduce absorbing particles (black carbon) emissions to avoid the possible warming that would result from the reductions of the cooling aerosol only.

  16. Effect of heat treatment on microwave absorption properties of Ni-Zn-Mg-La ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Wei, Shicheng; Xu, Binshi; Wang, Yujiang; Tian, Haoliang; Tong, Hui

    2014-01-01

    Spinel structure Ni-Zn-Mg-La ferrites have been prepared by the sol-gel route and investigated as a radar absorbing material (RAM) in a frequency range of 1-18 GHz. The structure and morphological studies on the nanoparticles of the ferrites have been carried out using X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The complex permeability and complex permittivity are measured by a network analyzer. The electromagnetic wave loss and microwave absorbing property are studied as a function of frequency, annealing temperature and thickness of the absorber. The results indicate that electromagnetic wave loss of the ferrite only annealed at 850 °C shows two peaks. The reflection loss varies with the change of the annealing temperature. The absorber annealed at 850 °C exhibits the best microwave absorbing properties, which is suitable for microwave absorption materials.

  17. Non-degenerate two-photon absorption in silicon waveguides. Analytical and experimental study

    DOE PAGES

    Zhang, Yanbing; Husko, Chad; Lefrancois, Simon; ...

    2015-06-22

    We theoretically and experimentally investigate the nonlinear evolution of two optical pulses in a silicon waveguide. We provide an analytic solution for the weak probe wave undergoing non-degenerate two-photon absorption (TPA) from the strong pump. At larger pump intensities, we employ a numerical solution to study the interplay between TPA and photo-generated free carriers. We develop a simple and powerful approach to extract and separate out the distinct loss contributions of TPA and free-carrier absorption from readily available experimental data. Our analysis accounts accurately for experimental results in silicon photonic crystal waveguides.

  18. Absorption spectrum, mass spectrometric properties, and electronic structure of 1,2-benzoquinone.

    PubMed

    Albarran, Guadalupe; Boggess, William; Rassolov, Vitaly; Schuler, Robert H

    2010-07-22

    Absorption spectrophotometric and mass spectrometric properties of 1,2-benzoquinone, prepared in aqueous solution by the hexachloroiridate(IV) oxidation of catechol and isolated by HPLC, are reported. Its absorption spectrum has a broad moderately intense band in the near UV with an extinction coefficient of 1370 M(-1)cm(-1) at its 389 nm maximum. The oscillator strength of this band contrasts with those of the order-of-magnitude stronger approximately 250 nm bands of most 1,4-benzoquinones. Gaussian analysis of its absorption spectrum indicates that it also has modestly intense higher energy bands in the 250-320 nm region. In atmospheric pressure mass spectrometric studies 1,2-benzoquinone exhibits very strong positive and negative mass 109 signals that result from the addition of protons and hydride ions in APCI and ESI ion sources. It is suggested that the hydride adduct is formed as the result of the highly polar character of ortho-quinone. On energetic collision the hydride adduct loses an H atom to produce the 1,2-benzosemiquinone radical anion. The present studies also show that atmospheric pressure mass spectral patterns observed for catechol are dominated by signals of 1,2-benzoquinone resulting from oxidation of catechol in the ion sources. Computational studies of the electronic structures of 1,2-benzoquinone, its proton and hydride ion adducts, and 1,2-benzosemiquinone radical anion are reported. These computational studies show that the structures of the proton and hydride adducts are similar and indicate that the hydride adduct is the proton adduct of a doubly negatively charged 1,2-benzoquinone. The contrast between the properties of 1,2- and 1,4-benzoquinone provides the basis for considerations on the effects of conjugation in aromatic systems.

  19. Temperature dependent magnetic and microwave absorption properties of doubly substituted nanosized material

    NASA Astrophysics Data System (ADS)

    Sadiq, Imran; Naseem, Shahzad; Rana, M. U.; Ashiq, Muhammad Naeem; Ali, Irshad

    2015-07-01

    The sol gel method has been adopted to synthesize a series of X-type hexagonal ferrites with concentration Sr2-x Gdx Ni2 Fe28-yCdyO46 (x=0.00, 0.02, 0.04, 0.06, 0.08, 0.10 and y=0, 0.1, 0.2, 0.3, 0.4, 0.5). The XRD analysis reveals the single phase of the prepared material and the lattice constants a (Å) and c (Å) varies with additives. The crystallite size of the present investigated ferrite is found in the range of 20-30 nm measured from TEM image. The enhancement in the magnetic properties (saturation magnetization, remanance magnetization and coercivity) can be observed with the increase of dopping concentration and the coercivity lies in the range of (484.22-887.47) G. The saturation and remanance magnetization decreases monotonically with the temperature which is the characteristic of the hexagonal ferrites. The Gd-Cd substituted sample possesses low values of complex relative permittivity and permeability than the pure samples. The material exhibits maximum microwave absorption -23 dB at 11.87 GHz and attenuation peak is in good agreement with the reflection loss value. The microwave absorption properties reflect the applications of this material in super high frequency devices (SHF).

  20. Magnetic and microwave absorption properties of La-Nd-Fe alloys

    NASA Astrophysics Data System (ADS)

    Qiao, Ziqiang; Pan, Shunkang; Xiong, Jilei; Cheng, Lichun; Yao, Qingrong; Lin, Peihao

    2017-02-01

    Through arc smelting and high energy ball milling method to synthesized the powders of LaxNd2-xFe17 (x=0.0, 0.2, 0.4, 0.6). By x-ray diffraction (XRD), scanning electron microscopy (SEM) and laser particle analyzer (LPS) to study the structural, morphology, particle size distribution of the powders, respectively. The electromagnetic parameters and saturation magnetization of the powers were measured by a vector network analyzer (VNA) and vibrating sample magnetometer (VSM), respectively. The saturation magnetization decreases with the La increasing. The minimum absorption peak frequency shifts towards a lower frequency region with an increase of La concentration. The microwave absorbing properties of the composite with different ratios of La0.2Nd1.8Fe17/Ni were studied. The microwave absorbing peaks of the composite shift to higher frequencies, and the microwave absorbing properties improved with the Ni content increase to 20%. The minimum reflection loss is -32.5 dB at 9.8 GHz and the bandwidth less than -10 dB (Microwave absorption rate 90%) reaches 3 GHz with a thickness of 1.8 mm.

  1. One- and two-photon absorption properties of two metalloporphyrin complexes

    NASA Astrophysics Data System (ADS)

    Sun, Yuan-Hong; Wang, Chuan-Kui

    2011-10-01

    The linear and nonlinear optical properties of two metalloporphyrin complexes formed by the complementary coordination of central zinc or magnesium ions to the ligand 5, 10, 15-tri-(p-tolyl)-20-phenylethynylporphyrin are theoretically investigated by using the analytic response theory at the density functional theory level. The results indicate that the studied complexes present more symmetric geometry structures than the ligand. The charge-transfer states of the two complexes in the lower energy region are all almost degenerate but those of the ligand are well separated. The ratio of the two-photon absorption cross sections of the ligand, zinc-porphyrin and magnesium-porphyrin complexes is 1.0:1.5:1.8, demonstrating that the two-photon absorption capability can be greatly increased when the ligand is coordinated with a metal ion. Moreover, several physical micro-mechanisms including electron transitions and intramolecular charge-transfer processes are discussed to explore the differences in optical property between the ligand and two complexes.

  2. Investigation of Properties of Infrared Absorption of α-HELIX Protein Molecules

    NASA Astrophysics Data System (ADS)

    Pang, Xiao-Feng; Zhang, Huai-Wu

    2006-05-01

    The mechanism and properties of infrared absorption of α-helix protein molecules are studied by a theory of bio-energy transport established on the basis of molecular structure. From the vibrational energy-spectra of molecules obtained from this theory we know that the infrared lights with wavelengths of 2 µm -7 µm can be absorbed by α-helix protein molecules. This is basically consistent with experimental data of infrared absorption of collagen and hemoglobin and bivine serum albumen (BSA) proteins with α-helix structure. From these results we account further for the mechanism and properties of biological effect of infrared lights absorbed by the living systems, i.e., the energy of infrared lights is directly absorbed by the amide-Is in amino acid residues in the protein molecules, which results in vibration of amide-1 and change of conformation of proteins and transport of bio-energy from one place to other along the protein molecular chains in human beings and animals. This is a kind of non-thermally biological effect.

  3. Facile Synthesis of Fe3O4/GCs Composites and Their Enhanced Microwave Absorption Properties.

    PubMed

    Jian, Xian; Wu, Biao; Wei, Yufeng; Dou, Shi Xue; Wang, Xiaolin; He, Weidong; Mahmood, Nasir

    2016-03-09

    Graphene has good stability and adjustable dielectric properties along with tunable morphologies, and hence can be used to design novel and high-performance functional materials. Here, we have reported a facile synthesis method of nanoscale Fe3O4/graphene capsules (GCs) composites using the combination of catalytic chemical vapor deposition (CCVD) and hydrothermal process. The resulting composite has the advantage of unique morphology that offers better synergism among the Fe3O4 particles as well as particles and GCs. The microwave-absorbing characteristics of developed composites were investigated through experimentally measured electromagnetic properties and simulation studies based on the transmission line theory, explained on the basis of eddy current, natural and exchange resonance, as well as dielectric relaxation processes. The composites bear minimum RL value of -32 dB at 8.76 GHz along with the absorption bandwidth range from 5.4 to 17 GHz for RL lower than -10 dB. The better performance of the composite based on the reasonable impedance characteristic, existence of interfaces around the composites, and the polarization of free carriers in 3D GCs that make the as-prepared composites capable of absorbing microwave more effectively. These results offer an effective way to design high-performance functional materials to facilitate the research in electromagnetic shielding and microwave absorption.

  4. Electromagnetic wave absorption properties of composites with ultrafine hollow magnetic fibers

    NASA Astrophysics Data System (ADS)

    Yi, Jin Woo; Lee, Sang Bok; Kim, Jin Bong; Lee, Sang Kwan; Park, O. Ok

    2014-06-01

    Ultrafine hollow magnetic fibers were prepared by electroless plating using hydrolyzed polyester fiber as a sacrificial substrate. These hollow fibers can be served for lightweight and efficient electromagnetic (EM) absorbing materials. As observed from SEM and EDS analysis, hollow structures consisting of Ni inner layer and Fe or Fe-Co outer layer were obtained. By introducing Co onto Fe, oxidation of the Fe layer was successfully prevented making it possible to enhance the complex permeability compared to a case in which only Fe was used. Polymeric composites containing the hollow fibers with different weight fractions and fiber lengths were prepared by a simple mixing process. The electromagnetic wave properties of the composites were measured by a vector network analyzer and it was found that the hollow magnetic fibers show a clear resonance peak of the complex permittivity around the X-band range (8-12 GHz) and the resonance frequency strongly depends on the fiber concentration and length. A possible explanation for the unique resonance is that the hollow fibers possess relatively low electrical conductivity and a long mean free path due to their oxidized phase and hollow structure. The calculated EM wave absorption with the measured EM wave properties showed that the composite containing 30 wt% hollow Ni/Fe-Co (7:3) fibers in length of 180 μm exhibited multiple absorbance peaks resulting in a broad absorption bandwidth of 4.2 GHz. It is obvious that this multiple absorbance is attributed to the resonance characteristic of the composite.

  5. Dual-band microwave absorption properties of metamaterial absorber composed of split ring resonator on carbonyl iron powder composites

    NASA Astrophysics Data System (ADS)

    Lim, Jun-Hee; Ryu, Yo-Han; Kim, Sung-Soo

    2015-05-01

    This study investigated the dual-band absorption properties of metamaterial absorbers composed of a split ring resonator (SRR) on a grounded magnetic substrate. Polymer composites of carbonyl iron powders (CIP) of high permeability and magnetic loss were used as the substrate material. Computational tools were used to model the interaction between electromagnetic waves and materials with the SRR structure. For perpendicular polarization with an electric field (E) perpendicular to the SRR gap, dualband absorption peaks are predicted in the simulation result of reflection loss. Magnetic resonance resulting from antiparallel currents between the SRR and the ground plane is observed at the frequencies of two absorption peaks. The first strong absorption peak at the lower frequency (3.3 GHz) is due to magnetic resonance at the wire part of the SRR. The second absorption peak at the higher frequency (7.2 GHz) is due to magnetic resonance at the SRR split gap. The decreased capacitance with increased gap spacing moves the second absorption frequency to higher frequencies, while the first absorption peak is invariant with gap spacing. In the case of dual gaps at the opposite sides of the SRR, a single absorption peak is predicted due to the elimination of low-frequency resonance. For parallel polarization with the E-field parallel to the SRR gap, a single absorption peak is predicted, corresponding to magnetic resonance at the SRR wire.[Figure not available: see fulltext.

  6. Remote sensing of ocean color and aerosol properties: resolving the issue of aerosol absorption.

    PubMed

    Gordon, H R; Du, T; Zhang, T

    1997-11-20

    Current atmospheric correction and aerosol retrieval algorithms for ocean color sensors use measurements of the top-of-the-atmosphere reflectance in the near infrared, where the contribution from the ocean is known for case 1 waters, to assess the aerosol optical properties. Such measurements are incapable of distinguishing between weakly and strongly absorbing aerosols, and the atmospheric correction and aerosol retrieval algorithms fail if the incorrect absorption properties of the aerosol are assumed. We present an algorithm that appears promising for the retrieval of in-water biophysical properties and aerosol optical properties in atmospheres containing both weakly and strongly absorbing aerosols. By using the entire spectrum available to most ocean color instruments (412-865 nm), we simultaneously recover the ocean's bio-optical properties and a set of aerosol models that best describes the aerosol optical properties. The algorithm is applied to simulated situations that are likely to occur off the U.S. East Coast in summer when the aerosols could be of the locally generated weakly absorbing Maritime type or of the pollution-generated strongly absorbing urban-type transported over the ocean by the winds. The simulations show that the algorithm behaves well in an atmosphere with either weakly or strongly absorbing aerosol. The algorithm successfully identifies absorbing aerosols and provides close values for the aerosol optical thickness. It also provides excellent retrievals of the ocean bio-optical properties. The algorithm uses a bio-optical model of case 1 waters and a set of aerosol models for its operation. The relevant parameters of both the ocean and atmosphere are systematically varied to find the best (in a rms sense) fit to the measured top-of-the-atmosphere spectral reflectance. Examples are provided that show the algorithm's performance in the presence of errors, e.g., error in the contribution from whitecaps and error in radiometric calibration.

  7. Impacts of tissue-type plasminogen activator (tPA) on neuronal survival

    PubMed Central

    Chevilley, Arnaud; Lesept, Flavie; Lenoir, Sophie; Ali, Carine; Parcq, Jérôme; Vivien, Denis

    2015-01-01

    Tissue-type plasminogen activator (tPA) a serine protease is constituted of five functional domains through which it interacts with different substrates, binding proteins, and receptors. In the last years, great interest has been given to the clinical relevance of targeting tPA in different diseases of the central nervous system, in particular stroke. Among its reported functions in the central nervous system, tPA displays both neurotrophic and neurotoxic effects. How can the protease mediate such opposite functions remain unclear but several hypotheses have been proposed. These include an influence of the degree of maturity and/or the type of neurons, of the level of tPA, of its origin (endogenous or exogenous) or of its form (single chain tPA versus two chain tPA). In this review, we will provide a synthetic snapshot of our current knowledge regarding the natural history of tPA and discuss how it sustains its pleiotropic functions with focus on excitotoxic/ischemic neuronal death and neuronal survival. PMID:26528141

  8. Construction of CuS Nanoflakes Vertically Aligned on Magnetically Decorated Graphene and Their Enhanced Microwave Absorption Properties.

    PubMed

    Liu, Panbo; Huang, Ying; Yan, Jing; Yang, Yiwen; Zhao, Yang

    2016-03-02

    Hybrid nanocomposites with enhanced microwave absorption properties have been designed by growing CuS nanoflakes on magnetically decorated graphene, and the effect of special nanostructures on microwave absorption properties has been investigated. The structure of the nanocomposites was characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), N2 adsorption-desorption, and vibrating sample magnetometer (VSM). The influence of cetyltrimethylammonium bromide (CTAB) on the morphology of CuS nanoflakes was also investigated. A possible formation process of the nanocomposites and the mechanism of microwave absorption were explained in detail. As an absorber, the nanocomposites with a filler loading of 20 wt % exhibited enhanced microwave absorption properties due to the special nanostructures, extra void space, and synergistic effect. The maximum reflection loss can reach -54.5 dB at 11.4 GHz, and the absorption bandwidths exceeding -10 dB are 4.5 GHz with a thickness of 2.5 mm, which can be adjusted by the thickness. The results indicate that the hybrid nanocomposites with enhanced microwave absorption properties and lightweight have a promising future in decreasing electromagnetic wave irradiation.

  9. Three-dimensional printed optical phantoms with customized absorption and scattering properties.

    PubMed

    Diep, Phuong; Pannem, Sanjana; Sweer, Jordan; Lo, Justine; Snyder, Michael; Stueber, Gabriella; Zhao, Yanyu; Tabassum, Syeda; Istfan, Raeef; Wu, Junjie; Erramilli, Shyamsunder; Roblyer, Darren

    2015-11-01

    Three-dimensional (3D) printing offers the promise of fabricating optical phantoms with arbitrary geometry, but commercially available thermoplastics provide only a small range of physiologically relevant absorption (µa) and reduced scattering (µs`) values. Here we demonstrate customizable acrylonitrile butadiene styrene (ABS) filaments for dual extrusion 3D printing of tissue mimicking optical phantoms. µa and µs` values were adjusted by incorporating nigrosin and titanium dioxide (TiO2) in the filament extrusion process. A wide range of physiologically relevant optical properties was demonstrated with an average repeatability within 11.5% for µa and 7.71% for µs`. Additionally, a mouse-simulating phantom, which mimicked both the geometry and optical properties of a hairless mouse with an implanted xenograft tumor, was printed using dual extrusion methods. 3D printed tumor optical properties matched the live tumor with less than 3% error at a wavelength of 659 nm. 3D printing with user defined optical properties may provide a viable method for durable optically diffusive phantoms for instrument characterization and calibration.

  10. Microwave absorption property of the diatomite coated by Fe-CoNiP films

    NASA Astrophysics Data System (ADS)

    Yan, Zhenqiang; Cai, Jun; Xu, Yonggang; Zhang, Deyuan

    2015-08-01

    A bio-absorbent of Fe-CoNiP coated on the diatomite was fabricated by way of electroless plating of CoNiP and subsequent chemical vapor deposition of Fe. The surface morphology and composition of the above-mentioned diatomite particles at different stage were characterized with the scanning electron microscopy and the energy spectrum analysis respectively, and the results showed that the diatomite was successfully coated with CoNoP and Fe (carbony iron). The complex permittivity and permeability of composites filled with the bio-absorbent and paraffin was measured in frequency range of 2-18 GHz, and then the microwave reflection loss (RL) and the shielding effectiveness (SE) were calculated. The results showed that the permittivity and the permeability were both enlarged as Fe films were coated onto the CoNiP-coated diatomite, which was attributed to the excellent electromagnetic property of carbonyl irons. The composites made with the Fe-CoNiP diatomite had a better absorbing property (minimum RL -11.0 dB) as well as the shielding property (maximum SE 5.6 dB) at thickness 2 mm. It indicated the absorption property was mainly due to the attenuation on the microwave, and the Fe-CoNiP diatomite could be an effective absorbent with low-density.

  11. Three-dimensional printed optical phantoms with customized absorption and scattering properties

    PubMed Central

    Diep, Phuong; Pannem, Sanjana; Sweer, Jordan; Lo, Justine; Snyder, Michael; Stueber, Gabriella; Zhao, Yanyu; Tabassum, Syeda; Istfan, Raeef; Wu, Junjie; Erramilli, Shyamsunder; Roblyer, Darren

    2015-01-01

    Three-dimensional (3D) printing offers the promise of fabricating optical phantoms with arbitrary geometry, but commercially available thermoplastics provide only a small range of physiologically relevant absorption (µa) and reduced scattering (µs`) values. Here we demonstrate customizable acrylonitrile butadiene styrene (ABS) filaments for dual extrusion 3D printing of tissue mimicking optical phantoms. µa and µs` values were adjusted by incorporating nigrosin and titanium dioxide (TiO2) in the filament extrusion process. A wide range of physiologically relevant optical properties was demonstrated with an average repeatability within 11.5% for µa and 7.71% for µs`. Additionally, a mouse-simulating phantom, which mimicked both the geometry and optical properties of a hairless mouse with an implanted xenograft tumor, was printed using dual extrusion methods. 3D printed tumor optical properties matched the live tumor with less than 3% error at a wavelength of 659 nm. 3D printing with user defined optical properties may provide a viable method for durable optically diffusive phantoms for instrument characterization and calibration. PMID:26600987

  12. Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1992-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or using laboratory measurements of such properties under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. For example, laboratory measurements performed by Fahd and Steffes have shown that the opacity from gaseous SO2 under simulated Venus conditions can be well described by the Van Vleck-Weisskopf lineshape at wavelengths shortward of 2 cm, but that the opacity of wavelengths greater than 2 cm is best described by a different lineshape that was previously used in theoretical predictions. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

  13. Absorption Spectroscopy Study of Acid-Base and Metal-Binding Properties of Flavanones

    NASA Astrophysics Data System (ADS)

    Shubina, V. S.; Shatalina, Yu. V.

    2013-11-01

    We have used absorption spectroscopy to study the acid-base and metal-binding properties of two structurally similar flavanones: taxifolin and naringenin. We have determined the acid dissociation constants for taxifolin (pKa1 = 7.10 ± 0.05, pKa2 = 8.60 ± 0.09, pKa3 = 8.59 ± 0.19, pKa4 = 11.82 ± 0.36) and naringenin (pKa1 = 7.05 ± 0.05, pKa2 = 8.85 ± 0.09, pKa3 = 12.01 ± 0.38). The appearance of new absorption bands in the visible wavelength region let us determine the stoichiometric composition of the iron (II) complexes of the flavanones. We show that at pH 5, in solution there is a mixture of complexes between taxifolin and iron (II) ions in stoichiometric ratio 2:1 and 1:2, while at pH 7.4 and pH 9, we detect a 1:1 taxifolin:Fe(II) complex. We established that at these pH values, naringenin forms a 2:1 complex with iron (II) ions. We propose structures for the complexes formed. Comprehensive study of the acid-base properties and the metal-binding capability of the two structurally similar flavanones let us determine the structure-properties relation and the conditions under which antioxidant activity of the polyphenols appears, via chelation of variable-valence metal ions.

  14. Influence of particle size on water absorption capacity and mechanical properties of polyethylene-wood flour composites

    NASA Astrophysics Data System (ADS)

    Zykova, A. K.; Pantyukhov, P. V.; Kolesnikova, N. N.; Popov, A. A.; Olkhov, A. A.

    2015-10-01

    Biocomposites based on low density polyethylene (LDPE) and birch wood flour (WF) were investigated. The mechanical properties and water absorption capacity were examined depending on the particle size of a filler in biocomposites. The aim of the paper is the investigation of composite properties depending on the filler particle size. The filler particle sizes were 0-80 µm, 80-140 µm, 140-200 µm, and 0-200 µm. The tensile strength of composite samples varied within the range 5.7-8.2 MPa. Elongation at break of composites varied within the range 5.1-7.5%. Highest mechanical properties were found in composites with the lowest filler fraction. Highest water absorption was observed in composition with a complex fraction of the filler. The influence of the filler particle size on composite properties was shown. It was found that an increase of the filler particle size decreases mechanical parameters and increases water absorption.

  15. Mesenchymal Stromal Cells Promote Axonal Outgrowth Alone and Synergistically with Astrocytes via tPA

    PubMed Central

    Qian, Jian-Yong; Chopp, Michael

    2016-01-01

    We reported that mesenchymal stromal cells (MSCs) enhance neurological recovery from experimental stroke and increase tissue plasminogen activator (tPA) expression in astrocytes. Here, we investigate mechanisms by which tPA mediates MSC enhanced axonal outgrowth. Primary murine neurons and astrocytes were isolated from wild-type (WT) and tPA-knockout (KO) cortices of embryos. Mouse MSCs (WT) were purchased from Cognate Inc. Neurons (WT or KO) were seeded in soma side of Xona microfluidic chambers, and astrocytes (WT or KO) and/or MSCs in axon side. The chambers were cultured as usual (normoxia) or subjected to oxygen deprivation. Primary neurons (seeded in plates) were co-cultured with astrocytes and/or MSCs (in inserts) for Western blot. In chambers, WT axons grew significantly longer than KO axons and exogenous tPA enhanced axonal outgrowth. MSCs increased WT axonal outgrowth alone and synergistically with WT astrocytes at both normoxia and oxygen deprivation conditions. The synergistic effect was inhibited by U0126, an ERK inhibitor, and receptor associated protein (RAP), a low density lipoprotein receptor related protein 1 (LRP1) ligand antagonist. However, MSCs exerted neither individual nor synergistic effects on KO axonal outgrowth. Western blot showed that MSCs promoted astrocytic tPA expression and increased neuronal tPA alone and synergistically with astrocytes. Also, MSCs activated neuronal ERK alone and synergistically with astrocytes, which was inhibited by RAP. We conclude: (1) MSCs promote axonal outgrowth via neuronal tPA and synergistically with astrocytic tPA; (2) neuronal tPA is critical to observe the synergistic effect of MSC and astrocytes on axonal outgrowth; and (3) tPA mediates MSC treatment-induced axonal outgrowth through the LRP1 receptor and ERK. PMID:27959956

  16. tPA Prescription and Administration Errors within a Regional Stroke System

    PubMed Central

    Chung, Lee S; Tkach, Aleksander; Lingenfelter, Erin M; Dehoney, Sarah; Rollo, Jeannie; de Havenon, Adam; DeWitt, Lucy Dana; Grantz, Matthew Ryan; Wang, Haimei; Wold, Jana J; Hannon, Peter M; Weathered, Natalie R; Majersik, Jennifer J

    2015-01-01

    Background IV tPA utilization in acute ischemic stroke (AIS) requires weight-based dosing and a standardized infusion rate. In our regional network, we have tried to minimize tPA dosing errors. We describe the frequency and types of tPA administration errors made in our comprehensive stroke center (CSC) and at community hospitals (CHs) prior to transfer. Methods Using our stroke quality database, we extracted clinical and pharmacy information on all patients who received IV tPA from 2010–11 at the CSC or CH prior to transfer. All records were analyzed for the presence of inclusion/exclusion criteria deviations or tPA errors in prescription, reconstitution, dispensing, or administration, and analyzed for association with outcomes. Results We identified 131 AIS cases treated with IV tPA: 51% female; mean age 68; 32% treated at CSC, 68% at CH (including 26% by telestroke) from 22 CHs. tPA prescription and administration errors were present in 64% of all patients (41% CSC, 75% CH, p<0.001), the most common being incorrect dosage for body weight (19% CSC, 55% CH, p<0.001). Of the 27 overdoses, there were 3 deaths due to systemic hemorrhage or ICH. Nonetheless, outcomes (parenchymal hematoma, mortality, mRS) did not differ between CSC and CH patients nor between those with and without errors. Conclusion Despite focus on minimization of tPA administration errors in AIS patients, such errors were very common in our regional stroke system. Although an association between tPA errors and stroke outcomes was not demonstrated, quality assurance mechanisms are still necessary to reduce potentially dangerous, avoidable errors. PMID:26698642

  17. Kenaf/recycled Jute Natural Fibers Unsaturated Polyester Composites: Water Absorption/dimensional Stability and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Osman, Ekhlas A.; Vakhguelt, Anatoli; Sbarski, Igor; Mutasher, Saad A.

    2012-03-01

    Effects of water absorption on the flexural properties of kenaf-unsaturated polyester composites and kenaf/recycled jute-unsaturated polyester composites were investigated. In the hybrid composites, the total fiber content was fixed to 20 wt%. In this 20 wt%, the addition of jute fiber varied from 0 to 75%, with increment of 25%. The result demonstrates the water absorption and the thickness swelling increased with increase in immersion time. Effects of water absorption on flexural properties of kenaf fiber composites can be reduced significantly with incorporation of recycled jute in composites formulation. The process of absorption of water was found to approach Fickian diffusion behavior for both kenaf composites and hybrid composites.

  18. Influence of mixed alkalies on absorption and emission properties of Sm 3+ ions in borate glasses

    NASA Astrophysics Data System (ADS)

    Ratnakaram, Y. C.; Thirupathi Naidu, D.; Vijaya Kumar, A.; Gopal, N. O.

    2005-04-01

    The present work aims to study the variation of Judd-Ofelt intensity parameters, radiative transition probabilities, absorption and emission cross sections with alkali content in three different Sm 3+-doped mixed alkali borate glasses. Mixed alkali borate glasses in the composition 67H 3BO 3· xLi 2CO 3(32- x)Na 2CO 3·1Sm 2O 3, 67H 3BO 3· xLi 2CO 3(32- x)K 2CO 3·1Sm 2O 3 and 67H 3BO 3· xNa 2CO 3(32- x)K 2CO 3·1Sm 2O 3 with x=8, 12, 16, 20 and 24 mol% were prepared by quenching melts consisting of the above chemicals (850-950 °C, 1-2 h) between two brass plates. Judd-Ofelt theory is used to study the spectral properties and to calculate the radiative transition probabilities and branching ratios. The predicted radiative transition probabilities ( Aed), branching ratios ( β) and integrated absorption cross-sections ( Σ) for certain transitions are reported. From the emission spectra, emission cross-sections ( σ) are obtained for the four transitions, 4G 5/2→ 6H 5/2, 4G 5/2→ 6H 7/2, 4G 5/2→ 6H 9/2 and 4G 5/2→ 6H 11/2 of Sm 3+ ion in these mixed alkali borate glasses. Optical band gaps ( Eopt) and absorption edges are reported for the three Sm 3+-doped mixed alkali borate glasses.

  19. Characterization of bottom ice algal and detrital spectral absorption properties in first-year sea ice of an Arctic polynya

    NASA Astrophysics Data System (ADS)

    Mundy, C.; Gosselin, M.; Nozais, C.; Simard, M.

    2009-12-01

    Little information exists on the spectral absorption properties of algal and detrital matter in sea ice. During the International North Water polynya study, we collected a large dataset on ice algal spectral absorption characteristics within the bottom 2 to 4 cm of first-year sea ice from April to June 1998. The data compared surprisingly well with select phytoplankton models, given that the models were extrapolated well beyond their limits to ice algal chlorophyll a (Chl a) concentrations that ranged up to 2000 mg m-3. However, a strong packaging effect was apparent at Chl a concentrations >500 mg m-3, which tended to decrease the Chl a specific algal absorption coefficient relative to model predictions. Diatoms dominated the ice algae community for most of the period and subsequently, controlled absorption characteristics. Although not conclusive, an outlier dominated by nanoflagellates did show an increase in the Chl a specific algal absorption coefficient, demonstrating the decrease in packaging effect associated with the smaller cell size. Seasonal progression in ice algal spectral absorption revealed a change in pigment composition from strong absorption >500 nm, indicative of photosynthetic accessory pigments, to strong absorption between 450 nm to 500 nm, indicative of photoprotective pigments. Furthermore, the ratio of phytoplankton absorption at 490:470 nm regressed significantly with time (positive) and ice thickness (negative) throughout the study period, suggesting a continual photoacclimation of the ice algal community to increasing transmitted irradiance. The results of our study show that measurements of ice algal spectral absorption properties will not only improve their parameterization in sea ice bio-optical models, but can provide information on both taxonomic composition and physiological state.

  20. Structure of Molybdenum Under Dynamic Compression to 1 TPa

    NASA Astrophysics Data System (ADS)

    Duffy, Thomas; Wang, Jue; Coppari, Federica; Smith, Raymond; Eggert, Jon; Lazicki, Amy; Fratanduono, Dayne; Rygg, Ryan; Boehly, Thomas; Collins, Gilbert

    2015-06-01

    Molybdenum (Mo) is a refractory 4d transition metal that is widely used as a standard in static and dynamic high-pressure experiments. However, there are significant unanswered questions and unresolved discrepancies about the melting curve and high-pressure phase stability of this fundamental material. Similar questions surround the melting curve and phase stabilities of other transition metals including Ta and Fe, and so a better understanding of Mo has broad implications for high-pressure science and geophysics. Here we use x-ray diffraction to determine the crystal structure of molybdenum under both shock and ramp compression to pressures as high as 1 TPa. Under shock loading, we find that Mo remains in body centered cubic (BCC) structure until melting begins at near 390 GPa. Our results are in good agreement with recent theoretical calculations and recent re-measurement of sound speeds along the Hugoniot. We also carried out x-ray diffraction measurements of ramp-loaded molybdenum up to 1050 GPa. Our x-ray diffraction patterns are consistent with the persistence of the BCC phase up to the highest pressure achieved. The measured densities under ramp loading are intermediate between those achieved under shock compression and those expected from extrapolation of room-temperature data. We do not observe evidence for the theoretically predicted transition to face centered cubic or double hexagonal close packed phases above 600 GPa.

  1. [Effect of silver/zinc selenide core-shell structure spheres on the infrared absorption properties of sodium nitrate].

    PubMed

    Guo, Qiang; Li, Chun; Jia, Zhi-Jun; Yuan, Guang

    2013-10-01

    Silver/zinc selenide (Ag/ZnSe) core-shell structure spheres were made through the method of silver mirror reaction on zinc selenide micro spheres. Surface morphology of the spheres was depicted by scanning electron microscopy, X-ray diffraction and Fourier infrared absorption spectrum. This paper studies the effect of Ag/ZnSe core-shell structure spheres on the infrared absorption properties of sodium nitrate solution. The results show that, the anti-symmetric vibration absorption peaks of nitrate are blue-shifted, and the intensity are improved obviously by the effect of core-shell structure spheres.

  2. THE JHU-SDSS METAL ABSORPTION LINE CATALOG: REDSHIFT EVOLUTION AND PROPERTIES OF Mg II ABSORBERS

    SciTech Connect

    Zhu Guangtun; Menard, Brice

    2013-06-20

    We present a generic and fully automatic method aimed at detecting absorption lines in the spectra of astronomical objects. The algorithm estimates the source continuum flux using a dimensionality reduction technique and nonnegative matrix factorization, and then detects and identifies metal absorption lines. We apply it to a sample of {approx}10{sup 5} quasar spectra from the Sloan Digital Sky Survey and compile a sample of {approx}40,000 Mg II- and Fe II-absorber systems, spanning the redshift range 0.4 < z < 2.3. The corresponding catalog is publicly available. We study the statistical properties of these absorber systems and find that the rest equivalent width distribution of strong Mg II absorbers follows an exponential distribution at all redshifts, confirming previous studies. Combining our results with recent near-infrared observations of Mg II absorbers, we introduce a new parameterization that fully describes the incidence rate of these systems up to z {approx} 5. We find the redshift evolution of strong Mg II absorbers to be remarkably similar to the cosmic star formation history over 0.4 < z < 5.5 (the entire redshift range covered by observations), suggesting a physical link between these two quantities.

  3. Asymptotic Solutions for Optical Properties of Large Particles with Strong Absorption

    NASA Technical Reports Server (NTRS)

    Yang, Ping; Gao, Bo-Cai; Baum, Bryan A.; Hu, Yong X.; Wiscombe, Warren J.; Mishchenko, Michael I.; Winker, Dave M.; Nasiri, Shaima L.

    2001-01-01

    The transverse wave condition is not applicable to the refracted electromagnetic wave within the context of geometrical optics when absorption is involved. Either the transverse magnetic (TM) or the transverse electric (TE) wave condition can be assumed for the wave to locally satisfy the electromagnetic boundary condition in a ray-tracing calculation. The assumed wave mode affects both the reflection and the refraction coefficients. As a result, nonunique solutions for these coefficients are inevitable. In this study the appropriate solutions for the Fresnel reflection-refraction coefficients are identified in light-scattering calculations based on the ray-tracing technique. In particular, a 3x2 refraction or transmission matrix is derived to account for the inhomogeneity of the refracted wave in an absorbing medium. An asymptotic solution that completely includes the effect of medium absorption on Fresnel coefficients is obtained for the scattering properties of a general polyhedral particle. Numerical results are presented for hexagonal plates and columns with both preferred and random orientations.

  4. Enhanced microwave absorption properties of CTAB assisted Pr-Cu substituted nanomaterial

    NASA Astrophysics Data System (ADS)

    Sadiq, Imran; Naseem, Shahzad; Riaz, Saira; Khan, Hasan M.; Ashiq, Muhammad Naeem; Hussain, S. Sajjad; Rana, Mazhar

    2016-09-01

    In this study, the rare earth Pr3+and divalent Cu2+ elements substituted Sr1-xPrxMn2Fe16-yCuyO27 (x=0, 0.02, 0.06, 0.1 and y=0, 0.1, 0.3, 0.5) W-type hexagonal ferrites were prepared by Sol-Gel method. TGA and DSC analysis of as prepared material was carried out to confirm the temperature at which required phase can be obtained. The XRD patterns exhibit the single phase for all the samples and the lattice parameters were changed with the additives. The absorption bands at wave number 636 and 554 cm-1 in FTIR spectrum indicate the stretching vibration of metal-oxygen ions which also ratifies the single phase for the prepared material. Microstructural analysis confirms the agglomeration of nanograins which leads to formation of platelet like structure which cause in the enhancement of the microwave absorption properties of material. The minimum reflection loss of -59.8 dB at 9.34 GHz frequency was observed makes the prepared material good candidate to be used in super high frequency application. The attenuation constant and reflectivity results are also in good agreement with minimum reflection losses results.

  5. Spectral absorption properties of colored dissolved organic matter (CDOM) and total suspended matter (TSM) of inland waters

    NASA Astrophysics Data System (ADS)

    Song, Kaishan; Liu, Dianwei; Li, Lin; Wang, Zongming; Wang, Yuandong; Jiang, Guangjia

    2010-08-01

    Spectral absorption properties of total suspended matter (TSM) and colored dissolved organic matter (CDOM) are important for the use of the bio-optical model to estimate water quality parameters. This study aims to investigate the variation in the absorption coefficients of TSM and CDOM of inland waters. A total of 92 water samples were collected from Shitoukoumen Reservoir and Songhua Lake in Northeast China, analyzed for TSM and Chl-a, and measured for the absorption coefficient of TSM, CDOM and total pigments using a laboratory spectrophotometer. The absorption coefficient of TSM has been decomposed for phytoplankton and inorganic sediments. The results show that for Shitoukoumen Reservoir, CDOM has strong absorptions with shallow absorption slopes (i.e., the coefficient S in a(λ)=a(λ0)exp[-S(λ- λ0)]) and large absorption at 355 nm; and for Songhua Lake, CDOM follows similar spectral absorption curves but less variation in the S value. The results also show TSM has the average absorption coefficient 5.7 m-1 at 440 nm and 0.93 m-1 at 675 nm, and their concentration is well correlated to TSM with R2 larger than 0.85 at 440 nm over both Songhu Lake and Shitoukoumen Reservoir. In summer, CDOM was mainly terrigenous and had a high proportion of humic acid derived from the decomposition of phytoplankton and there were no obvious difference of S value. The results indicate that inorganic sediments contributed much more absorption than phytoplankton pigments in Shitoukoumen Reservoir than that in Songhua Lake, and there is strong association of TSM concentration to absorption coefficient at 440 nm.

  6. Development of hybrid cotton/hydrogel yarns with improved absorption properties for biomedical applications.

    PubMed

    Pollini, Mauro; Paladini, Federica; Sannino, Alessandro; Maffezzoli, Alfonso

    2016-06-01

    Hyperhidrosis, or excessive sweating, is an overlooked and potentially disabling symptom, which is often seen in social anxiety disorder. In this work an innovative advanced textile material was developed for application in the management of excessive sweating, preparing a drying yarn providing improved comfort. Hybrid cotton/hydrogel yarns were obtained by combining cotton with superabsorbent hydrogels through an optimization study focused on the achievement of the most promising product in terms of absorption properties and resistance to washings. Swelling and washing tests were performed using different hydrogels, and the effect of an additional crosslinking on the materials was also evaluated by testing different solutions containing Al(3+) and Ca(2+) ions. Scanning electron microscopy and infrared spectroscopy analyses were adopted to characterize morphology and chemical structure of the hydrogels undergoing different production processes. The biocompatibility of the hybrid fabrics was demonstrated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide colorimetric assay (MTT) through the extract method.

  7. Controlled growth of Cu-Ni nanowires and nanospheres for enhanced microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoxia; Dong, Lifeng; Zhang, Baoqin; Yu, Mingxun; Liu, Jingquan

    2016-03-01

    Copper is a good dielectric loss material but has low stability, whereas nickel is a good magnetic loss material and is corrosion resistant but with low conductivity, therefore Cu-Ni hybrid nanostructures have synergistic advantages as microwave absorption (MA) materials. Different Cu/Ni molar ratios of bimetallic nanowires (Cu13@Ni7, Cu5@Ni5 and Cu7@Ni13) and nanospheres (Cu13@Ni7, Cu5@Ni5 and Cu1@Ni3) have been successfully synthesized via facile reduction of hydrazine under similar reaction conditions, and the morphology can be easily tuned by varying the feed ratio or the complexing agent. Apart from the concentrations of Cu2+ and Ni2+, the reduction parameters are similar for all samples to confirm the effects of the Cu/Ni molar ratio and morphology on MA properties. Ni is incorporated into the Cu-Ni nanomaterials as a shell over the Cu core at low temperature, as proved by XRD, SEM, TEM and XPS. Through the complex relative permittivity and permeability, reflection loss was evaluated, which revealed that the MA capacity greatly depended on the Cu/Ni molar ratio and morphology. For Cu@Ni nanowires, as the molar ratio of Ni shell increased the MA properties decreased accordingly. However, for Cu@Ni nanospheres, the opposite trend was found, that is, as the molar ratio of the Ni shell increased the MA properties increased.

  8. Synthesis, Characterization and Microwave Absorption Properties of Polyaniline/Er-Doped Strontium Ferrite Nanocomposite.

    PubMed

    Luo, Juhua; Wang, Eryong; Xu, Yang

    2016-06-01

    Er-doped strontium ferrite nanopowders (SrEr0.3Fe11.7O19) were prepared by the sol-gel method, and then their composites of PANI/SrEr0.3Fe11.7O19 with 10 wt% and 20 wt% ferrite were prepared by an in-situ polymerization process. The characterization of obtained samples was accomplished by XRD, FT-IR, TEM, VSM, and vector network analyzer techniques. A successful conjugation of ferrite nanoparticles with polyaniline could be indicated by XRD and FT-IR analysis. TEM confirmed the formation of polyaniline packed on strontium ferrite surface. Magnetization measurements showed the substituted Er3+ of Fe3+ on basis site enhanced the magnetic property notably and the content of polyaniline also influenced the magnetic property prominently. PANI/SrEr0.3Fe11.7O19 possessed the best absorption property with the optimum matching thickness of 3 mm in the frequency of 2-18 GHz. The value of the maximum RL was -42.0 dB at 12.0 GHz with the 5.5 GHz bandwidth.

  9. UV absorption and fluorescence properties of gas-phase p-difluorobenzene

    NASA Astrophysics Data System (ADS)

    Benzler, Thorsten; Dreier, Thomas; Schulz, Christof

    2017-01-01

    1,4-Difluorobenzene ( p-DFB) is a promising aromatic tracer for determining concentration, temperature, and O2 partial pressure in mixing gas flows based on laser-induced fluorescence (LIF). Signal quantification requires the knowledge of absorption and fluorescence properties as a function of environmental conditions. We report absorption and fluorescence spectra as well as fluorescence lifetimes of p-DFB in the temperature, pressure, and oxygen partial pressure range that is relevant for many applications including internal combustion engines. The UV absorption cross section, investigated between 296 and 675 K, has a peak value close to 266 nm and decreases with temperature, while still exceeding other single-ring aromatics. Time-resolved fluorescence spectra were recorded after picosecond laser excitation at 266 nm as a function of temperature (296-1180 K), pressure (1-10 bar), and O2 partial pressure (0-210 mbar) using a streak camera (temporal resolution 50 ps) coupled to a spectrometer. The fluorescence spectra red-shift ( 2 nm/100 K) and broaden (increase in full width at half maximum by 58% in the investigated temperature range) with temperature. In N2 as bath gas (1 bar), the fluorescence lifetime τ eff decreases with temperature by a factor of about 20 (from 7 ns at 298 K down to 0.32 ns at 1180 K), while at 8 bar the shortest lifetime at 975 K is 0.4 ns. A noticeable pressure dependence (i.e., reduced τ eff) is only visible at 675 K and above. Quenching of p-DFB LIF by O2 (for partial pressures up to 210 mbar) shortens the fluorescence lifetime significantly at room temperature (by a factor of 8), but much less at higher temperatures (by a factor of 1.8 at 970 K). For fixed O2 partial pressures (52 mbar and above), τ eff shows a plateau region with temperature which shifts toward higher temperatures at the higher O2 partial pressures. O2 quenching is less prominent for p-DFB compared to other aromatic compounds investigated so far. The temperature

  10. Influence of two-photon absorption on the dynamic behaviors of microring resonators.

    PubMed

    Li, Qiliang; Chen, Haowen; Xu, Jie; Hu, Miao; Zeng, Ran; Zhou, Xuefang; Li, Shuqin

    2017-04-01

    In this paper, we have investigated the influence of two-photon absorption (TPA) on the dynamic behaviors of all-pass and add-drop microring resonators by using two iterative methods along with the linear stability analysis method. While the incident field is above a certain value, the TPA coefficient has greater influence on the steady state for all-pass and add-drop microring resonators. We use the linear stability analysis method to analyze the stability of the steady state solutions and obtain stability conditions. Results obtained have shown that the change of TPA coefficient will lead to different dynamic behaviors; in addition, while the TPA coefficient is small and its change is slight, the dynamic behaviors of the microring resonators will not change much for most regions. At last, we observe the period windows and route from chaotic to period-N in some original chaotic regions due to the fluctuation of the TPA coefficient.

  11. Organic Aerosols from SÃO Paulo and its Relationship with Aerosol Absorption and Scattering Properties

    NASA Astrophysics Data System (ADS)

    Artaxo, P.; Brito, J. F.; Rizzo, L. V.

    2012-12-01

    The megacity of São Paulo with its 19 million people and 7 million cars is a challenge from the point of view of air pollution. High levels of organic aerosols, PM10, black carbon and ozone and the peculiar situation of the large scale use of ethanol fuel makes it a special case. Little is known about the impact of ethanol on air quality and human health and the increase of ethanol as vehicle fuel is rising worldwide An experiment was designed to physico-chemical properties of aerosols in São Paulo, as well as their optical properties. Aerosol size distribution in the size range of 1nm to 10 micrometers is being measured with a Helsinki University SMPS (Scanning Mobility Particle Sizer), an NAIS (Neutral ion Spectrometer) and a GRIMM OPC (Optical Particle Counter). Optical properties are being measured with a TSI Nephelometer and a Thermo MAAP (Multi Angle Absorption Photometer). A CIMEL sunphotometer from the AERONET network measure the aerosol optical depth. Furthermore, a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) and an Aerosol Chemical Speciation Monitor (ACSM) are used to real-time VOC analysis and aerosol composition, respectively. The ACSM was operated for 3 months continuosly during teh wintertime of 2012. The measured total particle concentration typically varies between 10,000 and 30,000 cm-3 being the lowest late in the night and highest around noon and frequently exceeding 50,000 cm-3. Clear diurnal patterns in aerosol optical properties were observed. Scattering and absorption coefficients typically range between 20 and 100 Mm-1 at 450 nm, and between 10 to 40 Mm-1 at 637 nm, respectively, both of them peaking at 7:00 local time, the morning rush hour. The corresponding single scattering albedo varies between 0.50 and 0.85, indicating a significant contribution of primary absorbing particles to the aerosol population. During the first month a total of seven new particle formation events were observed with growth rates ranging from 9 to 25

  12. X-ray diffraction of solid tin to 1.2 TPa

    DOE PAGES

    Lazicki, A.; Rygg, J. R.; Coppari, F.; ...

    2015-08-12

    In this study, we report direct in situ measurements of the crystal structure of tin between 0.12 and 1.2 TPa, the highest stress at which a crystal structure has ever been observed. Using angle-dispersive powder x-ray diffraction, we find that dynamically compressed Sn transforms to the body-centered-cubic (bcc) structure previously identified by ambient-temperature quasistatic-compression studies and by zero-kelvin density-functional theory predictions between 0.06 and 0.16 TPa. However, we observe no evidence for the hexagonal close-packed (hcp) phase found by those studies to be stable above 0.16 TPa. Instead, our results are consistent with bcc up to 1.2 TPa. We conjecturemore » that at high temperature bcc is stabilized relative to hcp due to differences in vibrational free energy.« less

  13. X-ray diffraction of solid tin to 1.2 TPa

    SciTech Connect

    Lazicki, A.; Rygg, J. R.; Coppari, F.; Smith, R.; Fratanduono, D.; Kraus, R. G.; Collins, G. W.; Briggs, R.; Braun, D. G.; Swift, D. C.; Eggert, J. H.

    2015-08-12

    In this study, we report direct in situ measurements of the crystal structure of tin between 0.12 and 1.2 TPa, the highest stress at which a crystal structure has ever been observed. Using angle-dispersive powder x-ray diffraction, we find that dynamically compressed Sn transforms to the body-centered-cubic (bcc) structure previously identified by ambient-temperature quasistatic-compression studies and by zero-kelvin density-functional theory predictions between 0.06 and 0.16 TPa. However, we observe no evidence for the hexagonal close-packed (hcp) phase found by those studies to be stable above 0.16 TPa. Instead, our results are consistent with bcc up to 1.2 TPa. We conjecture that at high temperature bcc is stabilized relative to hcp due to differences in vibrational free energy.

  14. X-Ray Diffraction of Solid Tin to 1.2 TPa.

    PubMed

    Lazicki, A; Rygg, J R; Coppari, F; Smith, R; Fratanduono, D; Kraus, R G; Collins, G W; Briggs, R; Braun, D G; Swift, D C; Eggert, J H

    2015-08-14

    We report direct in situ measurements of the crystal structure of tin between 0.12 and 1.2 TPa, the highest stress at which a crystal structure has ever been observed. Using angle-dispersive powder x-ray diffraction, we find that dynamically compressed Sn transforms to the body-centered-cubic (bcc) structure previously identified by ambient-temperature quasistatic-compression studies and by zero-kelvin density-functional theory predictions between 0.06 and 0.16 TPa. However, we observe no evidence for the hexagonal close-packed (hcp) phase found by those studies to be stable above 0.16 TPa. Instead, our results are consistent with bcc up to 1.2 TPa. We conjecture that at high temperature bcc is stabilized relative to hcp due to differences in vibrational free energy.

  15. Modulation by glycyrrhetinic acid derivatives of TPA-induced mouse ear oedema.

    PubMed Central

    Inoue, H.; Mori, T.; Shibata, S.; Koshihara, Y.

    1989-01-01

    1. The anti-inflammatory effects of glycyrrhetinic acid and its derivatives on TPA (12-O-tetradecanoylphorbol-13-acetate)-induced mouse ear oedema were studied. The mechanisms of TPA-induced ear oedema were first investigated with respect to the chemical mediators. 2. The formation of ear oedema reached a maximum 5 h after TPA application (2 micrograms per ear) and the prostaglandin E2 (PGE2) production of mouse ear increased with the oedema formation. 3. TPA-induced ear oedema was prevented by actinomycin D and cycloheximide (0.1 mg per ear, respectively) when applied during 60 min after TPA treatment. 4. Of glycyrrhetinic acid derivatives examined, dihemiphthalate derivatives (IIe, IIe', IIIa, IIIa', IVa, IVa') most strongly inhibited ear oedema on both topical (ID50, 1.6 mg per ear for IIe, 2.0 mg per ear for IIIa and 1.6 mg per ear for IVa) and oral (ID50, 88 mg kg-1 for IIe', 130 mg kg-1 for IIIa' and 92 mg kg-1 for IVa') administration. 5. Glycyrrhetinic acid (Ia) and its derivatives applied 30 min before TPA treatment were much more effective in inhibiting oedema than when applied 30 min after TPA. A dihemiphthalate of triterpenoid compound IVa completely inhibited oedema, even when applied 3 h before TPA treatment. 6. Glycyrrhetinic acid (Ia) and deoxoglycyrrhetol (IIa), the parent compounds, produced little inhibition by oral administration at less than 200 mg kg-1. 7. These results suggest that the dihemiphthalate derivatives of triterpenes derived from glycyrrhetinic acid by chemical modification are useful for the treatment of skin inflammation by both topical and oral application. PMID:2924072

  16. Effects of Solution Physical Properties on Copper and Chromium Signals in Flame Atomic Absorption Spectrometry

    NASA Astrophysics Data System (ADS)

    Rocha, Fàbio R. P.; Nòbrega, Joaquim A.

    1996-10-01

    Instrumental techniques, such as flame atomic absorption spectrometry (FAAS), are frequently used in chemical analysis. Independently of the technique used, the chemical principles must be considered to assure that the analytical results are correct. In FAAS, the most critical step is the sample introduction, since solutions need to be converted in an aerosol (nebulization process) that should contain drops with suitable size to attain the flame. Solution physical properties, such as viscosity and surface tension, can severely affect the analytical signals. Solutions with high viscosity are less easily aspirated and the analyte mass that reach the flame is reduced. The surface tension of the solution affects the size of the drops generated by the nebulization process and can modify the quantity of analyte that attain the flame. This work describes an experiment that allow demonstrating the effects of viscosity and surface tension on analytical signals, using a set of copper solutions prepared in different concentrations of ethanol and chromium solutions prepared in surfactant (tetrapropylammonium bromide) medium. The experiment can be carried out in a 4 h laboratory class and is useful to demonstrate to undergraduate students the effects of samples physical properties on the analytical signals in FAAS.

  17. Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1991-01-01

    Laboratory measurements of microwave and millimeter wave properties of the simulated atmosphere of the outer planets and their satellites has continued. One of the focuses is on the development of a radiative transfer model of the Jovian atmosphere at wavelengths from 1 mm to 10 cm. This modeling effort led to laboratory measurements of the millimeter wave opacity of hydrogen sulfide (H2S) under simulated Jovian conditions. Descriptions of the modeling effort, the Laboratory experiment, and the observations are presented. Correlative studies of measurements with Pioneer-Venus radio occultation measurements with longer wavelength emission measurements have provided new ways for characterizing temporal and spatial variations in the abundance of both gases H2SO4 and SO2, and for modeling their roles in the subcloud atmosphere. Laboratory measurements were conducted on 1.35 cm (and 13 cm) opacity of gaseous SO2 and absorptivity of gaseous SO2 at the 3.2 mm wavelength under simulated Venus conditions. Laboratory measurements were completed on millimeter wave dielectric properties of liquid H2SO4, in order to model the effects of the opacity of the clouds of Venus onto millimeter wave emission spectrum.

  18. Microwave absorption properties of FeSi flaky particles prepared via a ball-milling process

    NASA Astrophysics Data System (ADS)

    Liu, Chao; Yuan, Yong; Jiang, Jian-tang; Gong, Yuan-xun; Zhen, Liang

    2015-12-01

    Flaky FeSi alloy particles with different aspect ratio were produced via ball-milling and a subsequent annealing. The microstructure and the morphology of the particles were examined by XRD and SEM. The dc resistivity, the static magnetization properties and electromagnetic properties were measured. Particles with high aspect ratio were found possess high permittivity and permeability. On the other hand, the variation of grain size and defects density was found influence the permittivity and permeability. High specific area was believed contribute to the intense dielectric loss and the high shape magnetic anisotropy lead to high permeability in the target band. Increased electromagnetic parameters compel the absorption peak's shift to lower frequency. Coating using flaky FeSi particles milled for 12 h as fillers presented a reflection loss of -10 dB at 2 GHz and a matching thickness of 1.88 mm. The flaky FeSi alloy particles prepared through ball-milling and annealing can be promising candidates for EMA application at 1-4 GHz band.

  19. Properties of aqueous nitrate and nitrite from x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Smith, Jacob W.; Lam, Royce K.; Shih, Orion; Rizzuto, Anthony M.; Prendergast, David; Saykally, Richard J.

    2015-08-01

    Nitrate and nitrite ions are of considerable interest, both for their widespread use in commercial and research contexts and because of their central role in the global nitrogen cycle. The chemistry of atmospheric aerosols, wherein nitrate is abundant, has been found to depend on the interfacial behavior of ionic species. The interfacial behavior of ions is determined largely by their hydration properties; consequently, the study of the hydration and interfacial behavior of nitrate and nitrite comprises a significant field of study. In this work, we describe the study of aqueous solutions of sodium nitrate and nitrite via X-ray absorption spectroscopy (XAS), interpreted in light of first-principles density functional theory electronic structure calculations. Experimental and calculated spectra of the nitrogen K-edge XA spectra of bulk solutions exhibit a large 3.7 eV shift between the XA spectra of nitrate and nitrite resulting from greater stabilization of the nitrogen 1s energy level in nitrate. A similar shift is not observed in the oxygen K-edge XA spectra of NO3- and NO2-. The hydration properties of nitrate and nitrite are found to be similar, with both anions exhibiting a similar propensity towards ion pairing.

  20. Physical-mechanical, moisture absorption and bioadhesive properties of hydroxypropylcellulose hot-melt extruded films.

    PubMed

    Repka, M A; McGinity, J W

    2000-07-01

    The objective of this study was to investigate the moisture absorption, physical-mechanical and bioadhesive properties of hot-melt extruded hydroxypropylcellulose (HPC) films containing polymer additives. These additives included polyethylene glycol (PEG) 5%, polycarbophil 5%, carbomer 5%, Eudragit E-100 5%, and sodium starch glycolate (SSG) 5%. Relative humidity (RH) and temperature parameters of the films studied included 25 degree C at 0, 50, 80 and 100% RH, and 40 degrees C at 0 and 100% RH, stored for 2 weeks. Tensile strength and percent elongation were determined on an Instron according to the ASTM standards. The bioadhesive properties of the HPC/PEG 3350 5% film and the polycarbophil 5% containing films, with and without PEG, were investigated in vivo on the human epidermis. Although all films studied exhibited an increase in percent water content as the percent RH increased, the SSG containing film exhibited an almost three-fold increase in percent water content compared to that of the HPC/PEG film. The temperature storage condition of 40 degrees C/100% RH (versus 25 degrees C/100% RH) increased the percent water content of the SSG containing film. Percent elongation was highest for films containing polycarbophil 5% (without PEG). In addition, the HPC film containing polycarbophil 5% exhibited a greater force of adhesion and elongation at adhesive failure in vivo, and a lower modulus of adhesion when compared to the HPC/PEG film. A novel approach to determine bioadhesion of films to the human epidermis is presented.

  1. Effect of Ce Doping on Microwave Absorption Properties of Pr2Fe17 Alloy

    NASA Astrophysics Data System (ADS)

    Cheng, Lichun; Xiong, Jilei; Zhou, Huaiying; Pan, Shunkang; Huang, Hehua

    2016-02-01

    Ce x Pr2- x Fe17 ( x = 0.0, 0.1, 0.2, 0.3, 0.4) alloy powders were successfully synthesized by arc smelting and a high energy ball milling method. The structure, morphology, magnetic properties and electromagnetic parameters of the powders were studied by x-ray diffraction (XRD), scanning electron microscopy (SEM), a vibrating sample magnetometer (VSM) and a vector network analyzer (VNA), respectively. The results show that the saturation magnetization decreases with an increase of Ce concentration. The minimum absorption peak frequency shifts towards a higher frequency region firstly and then towards a lower frequency region based upon the Ce concentration. The Ce x Pr2- x Fe17 alloys exhibit good microwave absorbing properties. The minimum reflection loss of Ce0.1Pr1.9Fe17 powder is about -13.67 dB at 6.40 GHz, and the frequency bandwidth of RL < -8 dB reaches about 2.24 GHz with a thickness of 1.8 mm.

  2. Magnetic nanoparticles for power absorption: Optimizing size, shape and magnetic properties

    SciTech Connect

    Gonzalez-Fernandez, M.A.; Torres, T.E.; Andres-Verges, M.; Costo, R.; Presa, P. de la; Serna, C.J.; Morales, M.P.; Marquina, C.; Ibarra, M.R.; Goya, G.F.

    2009-10-15

    We present a study on the magnetic properties of naked and silica-coated Fe{sub 3}O{sub 4} nanoparticles with sizes between 5 and 110 nm. Their efficiency as heating agents was assessed through specific power absorption (SPA) measurements as a function of particle size and shape. The results show a strong dependence of the SPA with the particle size, with a maximum around 30 nm, as expected for a Neel relaxation mechanism in single-domain particles. The SiO{sub 2} shell thickness was found to play an important role in the SPA mechanism by hindering the heat outflow, thus decreasing the heating efficiency. It is concluded that a compromise between good heating efficiency and surface functionality for biomedical purposes can be attained by making the SiO{sub 2} functional coating as thin as possible. - Graphical Abstract: The magnetic properties of Fe{sub 3}O{sub 4} nanoparticles from 5 to 110 nm are presented, and their efficiency as heating agents discussed as a function of particle size, shape and surface functionalization.

  3. Properties of aqueous nitrate and nitrite from x-ray absorption spectroscopy

    SciTech Connect

    Smith, Jacob W.; Lam, Royce K.; Saykally, Richard J.; Shih, Orion; Rizzuto, Anthony M.; Prendergast, David

    2015-08-28

    Nitrate and nitrite ions are of considerable interest, both for their widespread use in commercial and research contexts and because of their central role in the global nitrogen cycle. The chemistry of atmospheric aerosols, wherein nitrate is abundant, has been found to depend on the interfacial behavior of ionic species. The interfacial behavior of ions is determined largely by their hydration properties; consequently, the study of the hydration and interfacial behavior of nitrate and nitrite comprises a significant field of study. In this work, we describe the study of aqueous solutions of sodium nitrate and nitrite via X-ray absorption spectroscopy (XAS), interpreted in light of first-principles density functional theory electronic structure calculations. Experimental and calculated spectra of the nitrogen K-edge XA spectra of bulk solutions exhibit a large 3.7 eV shift between the XA spectra of nitrate and nitrite resulting from greater stabilization of the nitrogen 1s energy level in nitrate. A similar shift is not observed in the oxygen K-edge XA spectra of NO{sub 3}{sup −} and NO{sub 2}{sup −}. The hydration properties of nitrate and nitrite are found to be similar, with both anions exhibiting a similar propensity towards ion pairing.

  4. One- and two-photon absorption of highly conjugated multiporphyrin systems in the two-photon Soret transition region

    NASA Astrophysics Data System (ADS)

    Fisher, Jonathan A. N.; Susumu, Kimihiro; Therien, Michael J.; Yodh, Arjun G.

    2009-04-01

    This study presents a detailed investigation of near-infrared one- and two-photon absorption (TPA) in a series of highly conjugated (porphinato)zinc(II) compounds. The chromophores interrogated include meso-to-meso ethyne-bridged (porphinato)zinc(II) oligomers (PZnn species), (porphinato)zinc(II)-spacer-(porphinato)zinc(II) (PZn-Sp-PZn) complexes, PZnn structures featuring terminal electron-releasing and -withdrawing substituents, related conjugated arrays in which electron-rich and -poor PZn units alternate, and benchmark PZn monomers. Broadband TPA cross-section measurements were performed ratiometrically using fluorescein as a reference. Superficially, the measurements indicate very large TPA cross-sections (up to ˜104GM; 1GM =1×10-50cm4sphoton-1) in the two-photon Soret (or B-band) resonance region. However, a more careful analysis of fluorescence as a function of incident photon flux suggests that significant one-photon absorption is present in the same spectral region for all compounds in the series. TPA cross-sections are extracted for the first time for some of these compounds using a model that includes both one-photon absorption and TPA contributions. Resultant TPA cross-sections are ˜10GM. The findings suggest that large TPA cross-sections reported in the Soret resonance region of similar compounds might contain significant contributions from one-photon absorption processes.

  5. Frequency-domain method for measuring spectral properties in multiple-scattering media: methemoglobin absorption spectrum in a tissuelike phantom

    NASA Astrophysics Data System (ADS)

    Fishkin, Joshua B.; So, Peter T. C.; Cerussi, Albert E.; Gratton, Enrico; Fantini, Sergio; Franceschini, Maria Angela

    1995-03-01

    We have measured the optical absorption and scattering coefficient spectra of a multiple-scattering medium (i.e., a biological tissue-simulating phantom comprising a lipid colloid) containing methemoglobin by using frequency-domain techniques. The methemoglobin absorption spectrum determined in the multiple-scattering medium is in excellent agreement with a corrected methemoglobin absorption spectrum obtained from a steady-state spectrophotometer measurement of the optical density of a minimally scattering medium. The determination of the corrected methemoglobin absorption spectrum takes into account the scattering from impurities in the methemoglobin solution containing no lipid colloid. Frequency-domain techniques allow for the separation of the absorbing from the scattering properties of multiple-scattering media, and these techniques thus provide an absolute

  6. Mechanical, Dielectric, and Microwave-Absorption Properties of Alumina Ceramic Containing Dispersed Ti3SiC2

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Luo, Fa; Su, Jinbu; Zhou, Wancheng; Zhu, Dongmei

    2015-03-01

    Dense Al2O3 ceramics containing dispersed Ti3SiC2 were fabricated by hot-pressed sintering. Effects of Ti3SiC2 content on the mechanical, dielectric, and microwave-absorption properties of the ceramics were investigated. The bulk density, flexural strength, and dielectric constant were enhanced by increasing the Ti3SiC2 content. The complex permittivity increased dramatically when the Ti3SiC2 content was above the percolation threshold. The dielectric performance of the ceramics at high temperatures was also studied. The results revealed increases in both the real and imaginary parts with increasing temperature. Ceramic 2.2 mm thick containing 10% ( w/ w) Ti3SiC2 had the optimum microwave-absorption properties. The absorption bandwidth below -5 dB was in the range 8.2-12.4 GHz with a minimum value of -20 dB at 9.56 GHz. Although the reflection loss increased with the increasing temperature, the ceramic still had favorable microwave-absorption properties throughout the X-band. This study contributes to the development of the microwave absorption materials for high-temperature application.

  7. Effect of graphene modification on thermo-mechanical and microwave absorption properties of polystyrene/graphene nanocomposites.

    PubMed

    Hatui, Goutam; Das, Chapal Kumar

    2012-10-01

    In the present study the effect of graphene percentage and graphene modification on the microwave absorption properties of the polystyrene/graphene nanocomposites was studied in detail. Acid modified graphene was prepared by the mixed acid route. Polystyrene/graphene nanocomposites with various percentages of graphene and modified graphene were prepared by solution mixing process. The dispersion of graphene sheets in the polystyrene matrix was analyzed by TEM and SEM and found to be uniform for the 1%, 2 wt% of graphene and 1 wt% of modified graphene loading. Microwave absorption of modified graphene containing nanocomposite was found to be superior among the nanocomposites. Incorporation of 1 wt% of ferrite particles enhanced the microwave absorption of the nanocomposite above all the nanocomposites, in the whole range of X-band, due to the effective cancellation of both electrical and magnetic components of the microwave. Incorporation of graphene enhanced the thermal and mechanical properties of the nanocomposites.

  8. Influence of external magnetic field on the microwave absorption properties of carbonyl iron and polychloroprene composites film

    NASA Astrophysics Data System (ADS)

    Wang, Haiyan; Li, Mingjie; Li, Xueai

    2016-12-01

    The carbonyl iron particles were dispersed in a polychloroprene rubber (CR) matrix under a magnetic field for a practical application as microwave absorption composites film. In comparison with the carbonyl iron particles (CIP)/CR composites film prepared by general route, such films made with external magnetic field exhibit excellent microwave absorption properties, strongly depending on the increment of anisotropy and rearrangement of magnetic particles. The film made under external magnetic field with a thickness of only 0.54 mm shows least reflection loss of -15.98 dB and the reflection loss value less than -10.0 dB over the frequency range of 11.4˜14.8 GHz. The results indicated the composite film made under external magnetic field have excellent microwave absorption properties, which suggest that the composites thin film could be used as a thinner and lighter microwave absorber.

  9. Protective effect of fermented soybean dried extracts against TPA-induced oxidative stress in hairless mice skin.

    PubMed

    Georgetti, Sandra R; Casagrande, Rúbia; Vicentini, Fabiana T M C; Baracat, Marcela M; Verri, Waldiceu A; Fonseca, Maria J V

    2013-01-01

    This study evaluated the chemical properties (polyphenol and genistein contents) of soybean extracts obtained by biotransformation and dried by spray dryer at different conditions and their in vivo ability to inhibit 12-O-tetradecanoylphorbol-13-acetate- (TPA-) induced biochemical alterations in the skin of hairless mice. By comparing the obtained data with that of the well-known active soybean extract Isoflavin beta, we evaluated the influence of the fermentation and drying process in the extracts efficacy. The results demonstrated that inlet gas temperature and adjuvant concentration for the extract drying process have significantly affected the total polyphenol contents and, to a minor degree, the genistein contents. However, the effect of topical stimulus with TPA, an oxidative stress inducer, which caused significant depletion of reduced glutathione (GSH) and catalase, with increased levels of H2O2 and lipid peroxidation (MDA) in the skin of hairless mice, was significantly prevented by the soybean extracts treatment. These results indicate that the spray drying processing resulted in a product capable of limiting the oxidative stress with possible therapeutic applicability as an antioxidant in pharmaceutical forms.

  10. Protective Effect of Fermented Soybean Dried Extracts against TPA-Induced Oxidative Stress in Hairless Mice Skin

    PubMed Central

    Georgetti, Sandra R.; Casagrande, Rúbia; Vicentini, Fabiana T. M. C.; Baracat, Marcela M.; Verri, Waldiceu A.; Fonseca, Maria J. V.

    2013-01-01

    This study evaluated the chemical properties (polyphenol and genistein contents) of soybean extracts obtained by biotransformation and dried by spray dryer at different conditions and their in vivo ability to inhibit 12-O-tetradecanoylphorbol-13-acetate- (TPA-) induced biochemical alterations in the skin of hairless mice. By comparing the obtained data with that of the well-known active soybean extract Isoflavin beta, we evaluated the influence of the fermentation and drying process in the extracts efficacy. The results demonstrated that inlet gas temperature and adjuvant concentration for the extract drying process have significantly affected the total polyphenol contents and, to a minor degree, the genistein contents. However, the effect of topical stimulus with TPA, an oxidative stress inducer, which caused significant depletion of reduced glutathione (GSH) and catalase, with increased levels of H2O2 and lipid peroxidation (MDA) in the skin of hairless mice, was significantly prevented by the soybean extracts treatment. These results indicate that the spray drying processing resulted in a product capable of limiting the oxidative stress with possible therapeutic applicability as an antioxidant in pharmaceutical forms. PMID:24073399

  11. Toxicological review and oral risk assessment of terephthalic acid (TPA) and its esters: A category approach.

    PubMed

    Ball, Gwendolyn L; McLellan, Clifton J; Bhat, Virunya S

    2012-01-01

    Polyethylene terephthalate, a copolymer of terephthalic acid (TPA) or dimethyl terephthalate (DMT) with ethylene glycol, has food, beverage, and drinking water contact applications. Di-2-ethylhexyl terephthalate (DEHT) is a plasticizer in food and drinking water contact materials. Oral reference doses (RfDs) and total allowable concentrations (TACs) in drinking water were derived for TPA, DMT, and DEHT. Category RfD and TAC levels were also established for nine C(1)-C(8) terephthalate esters. The mode of action of TPA, and of DMT, which is metabolized to TPA, involves urinary acidosis, altered electrolyte elimination and hypercalciuria, urinary supersaturation with calcium terephthalate or calcium hydrogen terephthalate, and crystallization into bladder calculi. Weanling rats were more sensitive to calculus formation than dams. Calculi-induced irritation led to bladder hyperplasia and tumors in rats fed 1000 mg/kg-day TPA. The lack of effects at 142 mg/kg-day supports a threshold for urine saturation with calcium terephthalate, a key event for calculus formation. Chronic dietary DMT exposure in rodents caused kidney inflammation, but not calculi. Chronic dietary DEHT exposure caused general toxicity unrelated to calculi, although urine pH was reduced suggesting the TPA metabolite was biologically-active, but of insufficient concentration to induce calculi. Respective oral reference doses of 0.5, 0.5, and 0.2 mg/kg-day and total allowable drinking water concentrations of 3, 3, and 1 mg/L were derived for TPA, DMT, and DEHT. An oral RfD of 0.2 mg/kg-day for the terephthalate category chemicals corresponded to a drinking water TAC of 1 mg/L.

  12. Multiobjective adaptive feedback control of two-photon absorption coupled with propagation through a dispersive medium

    SciTech Connect

    Laforge, Francois O.; Roslund, Jonathan; Shir, Ofer M.; Rabitz, Herschel

    2011-07-15

    This work uses shaped femtosecond laser pulses to control the two-photon absorption (TPA) of coumarin 153 in a dispersive toluene medium. The dispersive medium reshapes the pulse along the optical path, and management of this effect is used to achieve spatial localization of TPA. Other control objectives were successfully implemented, including dual localization and high resolution local optimization of TPA. The solutions to these objectives were explored by means of evolutionary single- and multi-objective algorithms within a laboratory feedback loop.

  13. Preparation and characterization of novel glass-ceramic tile with microwave absorption properties from iron ore tailings

    NASA Astrophysics Data System (ADS)

    Yao, Rui; Liao, SongYi; Dai, ChangLu; Liu, YuChen; Chen, XiaoYu; Zheng, Feng

    2015-03-01

    A novel glass-ceramic tile consisting of one glass-ceramic layer (GC) attaining microwave absorption properties atop ceramic substrate was prepared through quench-heat treatment route derived from iron ore tailings (IOTs) and commercial raw materials (purity range 73-99%). X-ray diffraction (XRD), SEM, Energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), Physical property measurement system (PPMS) and Vector network analyzer (VNA) measurements were carried out to investigate phase, microstructure, magnetic and microwave absorption aspects of the glass-ceramic layer. Roughly 80.6±1.7 wt% borosilicate glass and 19.4±1.7 wt% spinel ferrite with chemical formula of (Zn2+0.17Fe3+0.83)[Fe3+1.17Fe2+0.06Ni2+0.77]O4 were found among the tested samples. Absorption of Electromagnetic wave by 3 mm thick glass-ceramic layer at frequency of 2-18 GHz reached peak reflection loss (RL) of -17.61 dB (98.27% microwave absorption) at 10.31 GHz. Altering the thickness of the glass-ceramic layer can meet the requirements of different level of microwave absorption.

  14. Measurement of the absorption properties of acoustic materials used in the fabrication of cowlings

    NASA Astrophysics Data System (ADS)

    Corlay, B.; Delalot, G.

    1981-07-01

    A wide selection of sound absorbing materials was tested, using the stationary wave tube method, and absorption factors were determined. Results are used to compile a catalog of industrial acoustically absorbant materials which can be employed as interior linings on cowlings for mobile or fixed noisy equipment. Theory that explains the absorptivity of these materials when used alone or in combinations is also presented. Results for low and middle frequency absorption are stressed.

  15. Broadband optical limiting and nonlinear optical absorption properties of a novel hyperbranched conjugated polymer

    NASA Astrophysics Data System (ADS)

    Li, Chao; Liu, Chunling; Li, Quanshui; Gong, Qihuang

    2004-12-01

    The nonlinear transmittance of a novel hyperbranched conjugated polymer named DMA-HPV has been measured in CHCl 3 solution using a nanosecond optical parametric oscillator. DMA-HPV shows excellent optical limiting performance in the visible region from 490 to 610 nm. An explanation based on the combination of two-photon absorption and reverse saturable absorption was proposed for its huge and broadband nonlinear optical absorption.

  16. Structure and microwave absorption properties of (Pr,Dy)Ni4Fe alloy

    NASA Astrophysics Data System (ADS)

    Xiong, Jilei; Pan, Shunkang; Qiao, Ziqiang

    2017-03-01

    The DyxPr1-xNi4Fe (x=0.0, 0.1, 0.2, 0.3, 0.4) alloys were synthesized by arc-smelting and high energy ball milling method. The structure, morphology, particle size and electromagnetic parameters of the powder were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser diffraction-based particle size analyzer and vector network analyzer (VNA), respectively. The results reveal that the DyxPr1-xNi4Fe compounds are crystallized in PrNi4Fe structure. The minimum absorption peak frequency of DyxPr1-xNi4Fe shifts towards higher frequency region upon the Fe content. The minimum reflection loss of the DyxPr1-xNi4Fe alloys increases first and then decreases with increasing Dy substitution. The Dy0.3Pr0.7Ni4Fe alloy possess the best absorbing properties: the minimum reflection loss is -31.65 dB at 15.28 GHz with the best matching thickness d =1.0 mm and the reflection loss with the thickness ranging of 1.0-4.0 mm could reach -10 dB.

  17. Enhanced microwave absorption properties in cobalt-zinc ferrite based nanocomposites

    NASA Astrophysics Data System (ADS)

    Poorbafrani, A.; Kiani, E.

    2016-10-01

    In an attempt to find a solution to the problem of the traditional spinel ferrite used as the microwave absorber, the Co0.6Zn0.4Fe2O4-Paraffin nanocomposites were investigated. Cobalt-zinc ferrite powders, synthesized through PVA sol-gel method, were combined with differing concentrations of Paraffin wax. The nanocomposite samples were characterized employing various experimental techniques including X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Alternating Gradient Force Magnetometer (AGFM), and Vector Network Analyzer (VNA). The saturation magnetization and coercivity were enhanced utilizing appropriate stoichiometry, coordinate agent, and sintering temperature required for the preparation of cobalt-zinc ferrite. The complex permittivity and permeability spectra, and Reflection Loss (RL) of Co0.6Zn0.4Fe2O4-Paraffin nanocomposites were measured in the frequency range of 1-18 GHz. The microwave absorption properties of nanocomposites indicated that the absorbing composite containing 20 wt% of paraffin manifests the strongest microwave attenuation ability. The composite exhibited the reflection loss less than -10 dB in the whole C-band and 30% of the X-band frequencies.

  18. Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1988-01-01

    In the first half of this grant year, laboratory measurements were conducted on the millimeter-wave properties of atmospheric gases under simulated conditions for the outer planet. Significant improvements in the current system have made it possible to accurately characterize the opacity from gaseous NH3 at longer millimeter wavelengths (7 to 10 mm) under simulated Jovian conditions. In the second half of the grant year, it is hoped to extend such measurements to even shorter millimeter-wavelengths. Further analysis and application of the laboratory results to microwave and millimeter-wave absorption data for the outer planets, such as results from Voyager Radio Occultation experiments and earth-based radio astronomical observations will be continued. The analysis of available multispectral microwave opacity data from Venus, including data from the most recent radio astronomical ovservations in the 1.3 to 3.6 cm wavelength range and newly obtained Pioneer-Venus Radio Occulatation measurements at 13 cm, using the laboratory measurements as an interpretative tool will be pursued.

  19. Optical absorption and fluorescence properties of Er3+/Yb3+ codoped lead bismuth alumina borate glasses

    NASA Astrophysics Data System (ADS)

    Goud, K. Krishna Murthy; Reddy, M. Chandra Shekhar; Rao, B. Appa

    2014-04-01

    Lead bismuth alumina borate glasses codoped with Er3+/Yb3+ were prepared by melt quenching technique. Optical absorption, FTIR and photoluminescence spectra of these glasses have been studied. Judd-Ofelt theory has been applied to to the f ↔ f transitions for evaluating Ω2, Ω4 and Ω6 parameters. Radiative properties like branching ratio βr and the radiative life time τR have been determined on the basis of Judd-Ofelt theory. Upconversion emissions have been observed under 980nm laser excitation at room temperature. Green and red up-conversion emissions are centered at 530, 550 and 656 nm corresponding to 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+ respectively. The results obtained are discussed quantitatively based on the energy transfer between Yb3+ and Er3+.

  20. The X-shooter sample of GRB afterglow spectra: Properties of the absorption features

    NASA Astrophysics Data System (ADS)

    de Ugarte Postigo, Antonio

    2015-08-01

    Since its commissioning at ESO's Very Large Telescope in 2009, the X-shooter spectrograph has become the reference instrument in gamma-ray burst (GRB) afterglow spectroscopy. During this time our collaboration has collected more than 70 spectra of GRB afterglows, with redshifts ranging from 0.06 to 6.3. Thanks to their extreme luminosity and simple intrinsic shape, GRB spectra are optimal tools for the study of galactic environments at basically any redshift. Being produced by the death of short-lived massive stars, they are also tracers of star formation.I will present the sample of absorption spectral features identified in X-shooter's GRB spectra describing observation and analysis techniques. The different features are compared with the characteristics of the explosion (duration, spectral shape, energetics, etc.) and with the properties of the host galaxy (mass, age, etc.) to improve our understanding of the nature of the explosions and how they interact with their environments. Using the large redshift range of the spectra collection we perform studies of the evolution of GRB environments across the history of the Universe and their relation with the evolution of star formation.

  1. Structure and microwave absorption properties of Pr-Fe-Ni alloys

    NASA Astrophysics Data System (ADS)

    Xiong, Jilei; Pan, Shunkang; Cheng, Lichun; Liu, Xing; Lin, Peihao

    2015-06-01

    The Pr2Fe17-xNix (X=0.0, 0.2, 0.6, 1.0) alloy powders were obtained by arc smelting and high energy ball milling method. The phase structure, morphology and particle size of the powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser diffraction-based particle size analyzer, respectively. The saturation magnetization and electromagnetic parameters were determined by vibrating sample magnetometer (VSM) and vector network analyzer (VNA), respectively. The results indicate that the lattice parameter and the saturation magnetization of Pr2Fe17-xNix alloys decrease with increasing Ni content. And the minimum absorption peak frequency shifts towards the higher region with increasing Ni content. Compared to the powders without heat treatment, the powders tempered at 100 °C for 2 h have better absorbing properties. The minimum reflectivity peak value of Pr2Fe16Ni alloy reaches about -23.6 dB at 2.72 GHz with the matching thickness of 3.5 mm.

  2. Synthesis and microwave absorption properties of graphene-oxide(GO)/polyaniline nanocomposite with gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Fu, Chen; He, Da-Wei; Wang, Yong-Sheng; Fu, Ming; Geng, Xin; Zhuo, Zu-Liang

    2015-08-01

    A composite of graphene/PANI/GAunano is synthesized using the co-blend method. The morphologies and microstructures of samples are examined by transition electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). Moreover, the microwave absorption properties of both graphene/PANI and GO/PANI/ GAunano composites are investigated in a microwave frequency band from 1 GHz to 18 GHz. The maximum reflection loss (RL) of GO/PANI/GAunano with a thickness of 2 mm is up to -24.61 dB at 15.45 GHz, and the bandwidth corresponding to RL at -10 dB can reach 4.08 GHz (from 13.92 GHz to 18.00 GHz) for a 2-mm-thick layer. The electromagnetic data demonstrate that GO/PANI/GAunano can be used as an attractive candidate for microwave absorbers. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB932700 and 2011CB932703), the National Natural Science Foundation of China (Grant Nos. 61335006, 61378073, and 61077044), and the Beijing Natural Science Fund (Grant No. 4132031).

  3. Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1989-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. Work performed has shown that laboratory measurements of the millimeter-wave opacity of ammonia between 7.5 mm and 9.3 mm and also at the 3.2 mm wavelength require a different lineshape to be used in the theoretical prediction for millimeter-wave ammonia opacity than was previously used. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

  4. Microwave absorption properties of double-layer composites using CoZn/NiZn/MnZn-ferrite and titanium dioxide

    NASA Astrophysics Data System (ADS)

    Das, Sukanta; Nayak, G. C.; Sahu, S. K.; Routray, P. C.; Roy, A. K.; Baskey, H.

    2015-03-01

    Zinc substituted ferrite powders Me0.5Zn0.5Fe2O4 (Me=Co, Mn and Ni) were prepared by the sol-gel auto-combustion method. The present study highlights development of Single layer and double layer composite microwave absorbing materials using Ferrites, Titanium dioxide and Epoxy matrix. Moreover microwave absorption property, i.e. reflection loss evaluated at X-band frequency. XRD analysis of the filler particles were carried out to evaluate crystal structure, average crystallite diameter. Morphology of the filler particles were studied with FESEM. Hysteresis behavior of the ferrites samples were studied with Vibrating Sample Magnetometer. The most important parameter governing the absorption properties of microwave absorbers i.e. permittivity and permeability studied in a vector network analyzer. Measured reflection loss value of single-layer NiZn-ferrite based microwave absorber reaches -11.2 dB at 12.05 GHz. Whereas, reflection loss value of double-layer CoZn-ferrite/ TiO2 based microwave absorber reaches -24.3 dB at 12.02 GHz. The result shows that microwave absorption property and bandwidth of absorption of double-layer microwave absorber was found to improve comparison to single layer.

  5. Asymptotic Solutions for Optical Properties of Large Particles with Strong Absorption

    NASA Technical Reports Server (NTRS)

    Yang, Ping; Gao, Bo-Cai; Baum, Bryan A.; Hu, Yong X.; Wiscombe, Warren J.; Mishchenko, Michael I.; Winker, Dave M.; Nasiri, Shaima L.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    For scattering calculations involving nonspherical particles such as ice crystals, we show that the transverse wave condition is not applicable to the refracted electromagnetic wave in the context of geometric optics when absorption is involved. Either the TM wave condition (i.e., where the magnetic field of the refracted wave is transverse with respect to the wave direction) or the TE wave condition (i.e., where the electric field is transverse with respect to the propagating direction of the wave) may be assumed for the refracted wave in an absorbing medium to locally satisfy the electromagnetic boundary condition in the ray tracing calculation. The wave mode assumed for the refracted wave affects both the reflection and refraction coefficients. As a result, a nonunique solution for these coefficients is derived from the electromagnetic boundary condition. In this study we have identified the appropriate solution for the Fresnel reflection/refraction coefficients in light scattering calculation based on the ray tracing technique. We present the 3 x 2 refraction or transmission matrix that completely accounts for the inhomogeneity of the refracted wave in an absorbing medium. Using the Fresnel coefficients for an absorbing medium, we derive an asymptotic solution in an analytical format for the scattering properties of a general polyhedral particle. Numerical results are presented for hexagonal plates and columns with both preferred and random orientations. The asymptotic theory can produce reasonable accuracy in the phase function calculations in the infrared window region (wavelengths near 10 micron) if the particle size (in diameter) is on the order of 40 micron or larger. However, since strong absorption is assumed in the computation of the single-scattering albedo in the asymptotic theory, the single scattering albedo does not change with variation of the particle size. As a result, the asymptotic theory can lead to substantial errors in the computation of

  6. Suppression of endothelial t-PA expression by prolonged high laminar shear stress

    SciTech Connect

    Ulfhammer, Erik; Carlstroem, Maria; Bergh, Niklas; Larsson, Pia; Karlsson, Lena; Jern, Sverker

    2009-02-06

    Primary hypertension is associated with an impaired capacity for acute release of endothelial tissue-type plasminogen activator (t-PA), which is an important local protective response to prevent thrombus extension. As hypertensive vascular remodeling potentially results in increased vascular wall shear stress, we investigated the impact of shear on regulation of t-PA. Cultured human endothelial cells were exposed to low ({<=}1.5 dyn/cm{sup 2}) or high (25 dyn/cm{sup 2}) laminar shear stress for up to 48 h in two different experimental models. Using real-time RT-PCR and ELISA, shear stress was observed to time and magnitude-dependently suppress t-PA transcript and protein secretion to approximately 30% of basal levels. Mechanistic experiments revealed reduced nuclear protein binding to the t-PA specific CRE element (EMSA) and an almost completely abrogated shear response with pharmacologic JNK inhibition. We conclude that prolonged high laminar shear stress suppresses endothelial t-PA expression and may therefore contribute to the enhanced risk of arterial thrombosis in hypertensive disease.

  7. Adenylate cyclase regulation in the spermatogenic cell plasma membrane: Modulating effects of TPA and TCDD

    SciTech Connect

    Beebe, L.E.

    1989-01-01

    This research was designed to compare the effects of TPA, a phorbol ester, and TCDD in a spermatogenic cell population, a target of TCDD toxicity. Membrane-bound adenylate cyclase activity was used an index of membrane function, and was quantified by the amount of {sup 32}P-cAMP formed from {sup 32}P-ATP following chromatographic separation. Exposure to male germ cells in-vitro to TPA and TCDD followed by direct measurement of enzyme activity was used to investigate the potential of each agent to perturb membrane function. TPA and TCDD consistently inhibited adenylate cyclase activity at the levels of G{sub s}-catalytic unit coupling and hormone-receptor activation, as measured by the stimulation of enzyme activity by concomitant addition of forskolin and GTP and FSH and GTP, respectively. The effect on coupling required at least 60 minutes of exposure to TPA or TCDD. Concentration-response curves demonstrated a progressive desensitization with increasing TPA concentration, while TCDD exhibited consistent inhibition over the same concentration range.

  8. Enhanced two-photon absorption and fluorescence upconversion in Thioflavin T micelle-type aggregates in glycerol/water solution

    NASA Astrophysics Data System (ADS)

    Donnelly, Julie; Vesga, Yuly; Hernandez, Florencio E.

    2016-09-01

    In this article, we report the systematic characterization of the two-photon absorption of ThT in different mixtures of glycerol/water solution. The relationships of TPA peak position and amplitude revealed a dependence on particle size suggesting that the curious trend observed in TPA with changing glycerol content can be attributed to the presence of micelle-type aggregates. Consequently, the relatively strong TPA cross-section (δTPA = 300 GM) obtained in 8.75% glycerol/water solutions could be attributed to the immobilization of dye molecules and the strong coupling of the molecular transition dipoles in micelle-type aggregates. This enhancement of TPA, in addition to the already reported significant fluorescence quantum yield of ThT attached to brain tissue, is expected to boost the application of this compound for in vitro and perhaps in vivo high resolution multiphoton bioimaging of amyloids in brain tissue.

  9. [Effect of silver/silcon dioxide film on the infrared absorption properties of sodium nitrate].

    PubMed

    Jia, Zhi-Jun; Kong, Xiang-Fei; Guo, Qiang; Yuan, Guang

    2012-12-01

    Silver/silicon dioxide (Ag/SiO2) film, which was used for surface enhanced infrared absorption spectroscopy, was made by mixing ammonia solution and SiO2 solution. Surface morphology of thin films was depicted by scanning electron microscopy, X-ray diffraction and ultraviolet-visible absorption spectrum. The present paper studies the spectroscopy of Ag/SiO2 film during the evaporation of water. Research results show that the anti-symmetric vibration absorption peak of nitrate is the function of solution concentration and the distances. Influence of surface enhanced infrared absorption spectroscopy in nitrate absorption peak is via the electromagnetic mechanism and increasing the effective surface area.

  10. NO-dependent attenuation of TPA-induced immunoinflammatory skin changes in Balb/c mice by pindolol, heptaminol or ATRA, but not by verapamil

    PubMed Central

    Chung, Jinhyuk F.; Yoon, Calvin J.; Cheon, Seon Ah; Seo, Eun Seok; Park, Sung Ho; Yang, Jae Seung; Kim, Bumju; Joo, Min Young; Park, Tae Jung; Kim, Ki Hean; Sood, Anil K.; Lee, Sang Joon

    2016-01-01

    Recently a mouse skin carcinogenesis study reported that a β-blocker carvedilol displayed antitumor-properties via antihyperplastic effects. However, the antihyperplastic mechanism is unclear as the β-blocker is characterized with multiple pleiotropic effects including stimulation of endothelial NO release and verapamil-like calcium channel blocking activity. To investigate the nature and the origin of the antihyperplastic effects, we tested topical pretreatment with pindolol, heptaminol, ATRA or verapamil against Balb/c mouse ear skin hyperplasia that was induced by TPA. We found that pindolol, heptaminol or ATRA, but not verapamil, inhibited the TPA-induced immunoinflammatory skin changes in an NO-dependent manner, which included epidermal hyperplasia, skin edema and fibrosis. Furthermore, we also observed NO-dependent alleviation of the TPA-induced NK cell depletion in the ear tissues by heptaminol pretreatment. Together our results suggest that stimulation of NO generation from constitutive synthases may be primarily responsible for the reported antihyperplastic and NK cell-preserving effects of the β-blockers, and that similar effects may be observed in other immunity normalizing compounds that also promote endothelial NO synthesis. PMID:27374093

  11. Effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) on phosphatidylethanolamine metabolism in HeLa cells

    SciTech Connect

    Mueller, H.W.; Vance, D.E.

    1986-05-01

    The potent tumor promoter, TPA, exerts its earliest effects at the plasma membrane. Recent findings have shown that TPA stimulates a phospholipase C-mediated turnover of phosphatidyl-choline in several different cell types. The present study was undertaken to investigate whether TPA elicits a similar effect on the phosphatidylethanolamine (PE) pool of HeLa cells. Three different series of experiments were performed. First, in HeLa cells pulse-labeled with (/sup 3/H)ethanolamine, TPA stimulated a 5-fold release of aqueous radiolabeled products into the extra-cellular medium after a 1-hour incubation. Second, when (/sup 3/H)ethanolamine and TPA were added simultaneously to the cells, TPA stimulated a 2-fold incorporation of radiolabel into the cellular PE pool. In both the release and incorporation of (/sup 3/H)ethanolamine, TPA had no significant effect on PE mass. Finally, when HeLa cells were incubated with exogenous 1-radyl-2-acyl-sn-glycero-3-phospho-(/sup 3/H)ethanolamine, TPA stimulated the formation of an aqueous radiolabeled product in the medium, which was identified as phosphoethanolamine. These results provide evidence that TPA stimulates a phospholipase C-mediated turnover of PE.

  12. Study of optical properties and effective three-photon absorption in Bi-doped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Karthikeyan, B.; Sandeep, C. S. Suchand; Philip, Reji; Baesso, M. L.

    2009-12-01

    In this paper we report the linear and nonlinear optical properties of Bi-doped ZnO nanoparticles. Bi-doped ZnO nanoparticles were prepared through the wet chemical method at room temperature. Optical absorption measurements show that the exciton peaks are situated at 272 and 368 nm, which are attributed to the n=2 and n=1 exciton states, respectively. Transmission electron microscopy measurements reveal the size and shape of the particles and energy dispersive X-ray measurements confirm the doping of Bi in ZnO. Steady state photoluminescence measurements show that the emission is composed of five peaks. Open aperture z-scan measurements done at 532 nm using 5 ns, 300 μJ laser pulses reveal nonlinear absorption which arises from an effective three-photon absorption process.

  13. Theoretical modeling of the spectroscopic absorption properties of luciferin and oxyluciferin: A critical comparison with recent experimental studies

    NASA Astrophysics Data System (ADS)

    Anselmi, Massimiliano; Marocchi, Simone; Aschi, Massimiliano; Amadei, Andrea

    2012-01-01

    Firefly luciferin and its oxidated form, oxyluciferin, are two heterocyclic compounds involved in the enzymatic reaction, catalyzed by redox proteins called luciferases, which provides the bioluminescence in a wide group of arthropods. Whereas the electronic absorption spectra of D-luciferin in water at different pHs are known since 1960s, only recently reliable experimental electronic spectra of oxyluciferin have become available. In addition oxyluciferin is involved in a triple chemical equilibria (deprotonation of the two hydroxyl groups and keto-enol tautomerism of the 4-hydroxythiazole ring), that obligates to select during an experiment a predominant species, tuning pH or solvent polarity besides introducing chemical modifications. In this study we report the absorption spectra of luciferin and oxyluciferin in each principal chemical form, calculated by means of perturbed matrix method (PMM), which allowed us to successfully introduce the effect of the solvent on the spectroscopic absorption properties, and compare the result with available experimental data.

  14. Low frequency absorption properties of a thin metamaterial absorber with cross-array on the surface of a magnetic substrate

    NASA Astrophysics Data System (ADS)

    Chen, Qian; Bie, Shaowei; Yuan, Wei; Xu, Yongshun; Xu, Haibing; Jiang, Jianjun

    2016-10-01

    The design, fabrication, and measurement of a metamaterial with broadband microwave absorption properties in the low frequency range are presented in this paper. The metamaterial has a layered structure with a thickness of 2.2 mm, and consists of a conventional printed circuit board (PCB) process fabricated cross array on the surface of a flake-shaped carbonyl iron (CI) powder-filled silicon rubber composite magnetic substrate backed by a metal plane. The measurement results indicate that the absorption bandwidth (defined as the frequency range with reflection coefficient below  -10 dB) of the proposed structure is 2.55 GHz-5.68 GHz. The power loss mechanism was outlined according to the current distribution on and off the resonance frequency. Moreover, the absorption performance of the proposed structure for incident angles ranging from 0° to 60° for both transverse electric (TE) wave and transverse magnetic (TM) waves were exhibited.

  15. Microwave absorption properties of multiwalled carbon nanotube/FeNi nanopowders as light-weight microwave absorbers

    NASA Astrophysics Data System (ADS)

    Wen, Fusheng; Zhang, Fang; Xiang, Jianyong; Hu, Wentao; Yuan, Shijun; Liu, Zhongyuan

    2013-10-01

    Multiwalled carbon nanotubes (MWCNTs) and FeNi nanopowders have been facilely synthesized by a simple chemical method. Excellent microwave absorption properties have been obtained due to a proper combination of complex permittivity and permeability which result from the high resistivity of the sintered composite of MWCNTs and the magnetic FeNi nanopowders. The minimum reflection loss (RL) is less than -20 dB at 2.72-18.0 GHz with a thickness between 1.21 and 6.00 mm for 40 wt% MWCNT/FeNi composites, and a minimum RL value of -47.6 dB is observed at 12.09 GHz on a specimen with a matching thickness of 1.79 mm. The frequency of microwave absorption complies with the quarter-wavelength (λ/4) matching model. The MWCNT/FeNi nanopowders are a promising candidate for lightweight microwave absorption materials.

  16. Simultaneous control of emission localization and two-photon absorption efficiency in dissymmetrical chromophores

    SciTech Connect

    Tretiak, Sergei

    2009-01-01

    The aim of the present work is to demonstrate that combined spectral tuning of fluorescence and two-photon absorption (TPA) properties of multipolar chromophores can be achieved by introduction of slight electronic chemical dissymmetry. In that perspective, two novel series of structurally related chromophores have been designed and studied: a first series based on rod-like quadrupolar chromophores bearing different electron-donating (D) end groups and a second series based on three-branched octupolar chromophores built from a trigonal donating moiety and bearing various acceptor (A) peripheral groups. The influence of the electronic dissymmetry is investigated by combined experimental and theoretical studies of the linear and nonlinear optical properties of dissymmetric chromophores compared to their symmetrical counterparts. In both types of systems (i.e. quadrupoles and octupoles) experiments and theory reveal that excitation is essentially delocalized and that excitation involves synchronized charge redistribution between the different D and A moieties within the multipolar structure (i.e. concerted intramolecular charge transfer). In contrast, the emission stems only from a particular dipolar subunit bearing the strongest D or A moieties due to fast excitation localization after excitation prior to emission. Hence control of emission characteristics (polarization and emission spectrum) in addition to localization can be achieved by controlled introduction of electronic dissymmetry (i.e. replacement of one of the D or A end-groups by a slightly stronger D{prime} or A{prime} units). Interestingly dissymmetrical functionalization of both quadrupolar and octupolar compounds does not lead to significant loss in TPA responses and can even be beneficial due to the spectral broadening and peak position tuning that it allows. This study thus reveals an original molecular engineering route strategy allowing major TPA enhancement in multipolar structures due to concerted

  17. [Study on the absorption spectrum properties of flexible black silicon doped with sulfur and fluorine based on first-principles].

    PubMed

    Wei, Wei; Zhu, Yong; Lin, Cheng; Tian, Li; Xu, Zu-Wen; Nong, Jin-Peng

    2014-04-01

    It is quite urgent to need a flexible photodetector in the ultraviolet-visible-near infrared region for building a miniaturization broadband spectrometer. In the present paper, one kind of flexible black silicon doped with sulfur and fluorine was proposed and the optical absorption spectrum was investigated in broadband region. Firstly, the electronic structure, band structure and the optical absorption properties of the flexible black silicon doped with sulfur and fluoride were calculated using the first-principles pseudo potential calculations based on density-functional theory. Then, the absorption spectrum model of the flexible black silicon was built based on both the first-principles and finite domain time difference method. The results show that the cut-off wavelength has a red shift as the band gap of doped material becomes narrower. The higher the doping concentration is, the higher the optical absorption coefficient is obtained. The absorption coefficient of flexible black silicon doped with 50% sulfur is 8.3 times higher than that of 1.5% sulfur doping sample at the wavelength of 1 500 nm while the ratio turns to be 3 times when doped with 50% and 1.5% fluoride. The black silicon with small-size surface microstructure has the highest absorptance in the near-infrared region at the same doping concentration of 50%. Finally, a sample of flexible black silicon was fabricated by the femtosecond laser auto scanning system. The test results indicate that the absorptance of the sample is higher than 95% both in the ultraviolet and visible region and is fluctuated from 70% to 80% in the near-infrared region. It shows that as a novel light-absorbing material in broadband region the flexible black silicon doped with Sulfur and Fluorine has an potential application in exploring miniaturization broadband spectroscopy.

  18. Low molecular weight quaternised chitosan (11): in vitro assessment of absorption enhancing properties.

    PubMed

    Jonker-Venter, C; Snyman, D; Janse van Rensburg, C; Jordaan, E; Schultz, C; Steenekamp, J H; Hamman, J H; Kotzé, A F

    2006-04-01

    N-Trimethyl chitosan chloride (TMC; high molecular weight) and N-trimethyl chitosan oligosaccharide (TMO; low molecular weight) with different degrees of quaternisation were synthesised and evaluated for their absorption enhancing properties across mucosal epithelia. These quaternised chitosan derivatives (0.0625% w/v-0.5% w/v) showed a significant decrease in the transepithelial electrical resistance (TEER) of cultured rabbit tracheal epithelial cell monolayers as compared to the control. The degree of quaternisation and concentration of the compounds influenced the extent of the reduction in TEER. Higher degrees of quaternisation and an increase in the concentration of the compound were associated with a more pronounced reduction in the TEER. The TMO derivatives seemed to be more effective in lowering the TEER of tracheal cell monolayers as compared to the TMC polymers. Ciliary beat frequency (CBF) is the main defence mechanism of the respiratory tract and is therefore a useful parameter in evaluating the toxicity of nasally administered drugs and additives. The effect of the synthesised chitosan derivatives on the CBF of human nasal epithelial cells at pH 7.4 was determined by a method based on an analogue contrast enhancement technique. The TMO oligomers exhibited lower inhibition of the CBF of human nasal epithelial cells compared to that of the TMC polymers. It was proposed that this reduced effect on the CBF is due to the lower viscosity and molecular weight of TMO. However, no acute toxicity was found with any of the synthesised chitosan derivatives by means of the CBF tests conducted in this study.

  19. Enhanced Dielectric Properties and High-Temperature Microwave Absorption Performance of Zn-Doped Al2O3 Ceramic

    NASA Astrophysics Data System (ADS)

    Wang, Yuan; Luo, Fa; Wei, Ping; Zhou, Wancheng; Zhu, Dongmei

    2015-07-01

    To improve the dielectric and microwave absorption properties of Al2O3 ceramic, Zn-doped Al2O3 ceramic was prepared by conventional ceramic processing. X-ray diffraction analysis confirmed that Zn atoms successfully entered the Al2O3 ceramic lattice and occupied Al sites. The complex permittivity increased with increasing Zn concentration, which is mainly attributed to the increase in charged vacancy defects and densification of the Al2O3 ceramic. In addition, the temperature-dependent complex permittivity of 3% Zn-doped Al2O3 ceramic was determined in the temperature range from 298 K to 873 K. Both the real and imaginary parts of the complex permittivity increased monotonically with increasing temperature, which can be ascribed to the shortened relaxation time and increasing electrical conductivity. The increased complex permittivity leads to a great improvement in microwave absorption. In particular, when the temperature is up to 873 K, the 3% Zn-doped Al2O3 ceramic exhibited the best absorption performance with a maximum peak (-12.1 dB) and broad effective absorption bandwidth (reflection loss less than -10 dB from 9.3 GHz to 12.3 GHz). These results reveal that Zn-doped Al2O3 ceramic is a promising candidate for use as a kind of high-temperature microwave absorption material.

  20. Study of nonlinear optical absorption properties of V2O5 nanoparticles in the femtosecond excitation regime

    NASA Astrophysics Data System (ADS)

    Molli, Muralikrishna; Bhat Kademane, Abhijit; Pradhan, Prabin; Sai Muthukumar, V.

    2016-08-01

    In this work, we report for the first time, the nonlinear optical absorption properties of vanadium pentoxide (V2O5) nanoparticles in the femtosecond excitation regime. V2O5 nanoparticles were synthesized through solution combustion technique. The as-synthesized samples were further characterized using XRD, FESEM, EDAX, TEM and UV-visible spectroscopy. X-ray diffraction results revealed the crystalline nature of the nanoparticles. Electron microscopy studies showed the size of the nanoparticles to be ~200 nm. Open-aperture z-scan technique was employed to study the nonlinear optical absorption behavior of the synthesized samples using a 100-fs laser pulses at 800 nm from a regeneratively amplified Ti: sapphire laser. The mechanism of nonlinear absorption was found to be a three-photon absorption process which was explained using the density of states of V2O5 obtained using density functional theory. These nanoparticles exhibit strong intensity-dependent nonlinear optical absorption and hence could be considered for optical-power-limiting applications.

  1. Optical absorption properties of electron bubbles and experiments on monitoring individual electron bubbles in liquid helium

    NASA Astrophysics Data System (ADS)

    Guo, Wei

    When a free electron is injected into liquid helium, it forms a microscopic bubble essentially free of helium atoms, which is referred to as an electron bubble. It represents a fine example of a quantum-mechanical particle confined in a potential well. In this dissertation, we describe our studies on bubble properties, especially the optical absorption properties of ground state electron bubbles and experiments on imaging individual electron bubbles in liquid helium. We studied the effect of zero-point and thermal fluctuations on the shape of ground state electron bubbles in liquid helium. The results are used to determine the line shape for the 1S to 1P optical transition. The calculated line shape is in very good agreement with the experimental measurements of Grimes and Adams. For 1S to 2P transition, the obtained transition line width agrees well with the measured data of Zipfel over a range of pressure up to 15 bars. Fluctuations in the bubble shape also make other "unallowed" transitions possible. The transition cross-sections from the 1S state to the 1D and 2D states are calculated with magnitude approximately two orders smaller than that of the 1S to 1P and 2P transitions. In our electron bubble imaging experiments, a planar ultrasonic transducer was used to generate strong sound wave pulse in liquid helium. The sound pulse passed through the liquid so as to produce a transient negative pressure over a large volume (˜ 1 cm3). An electron bubble that was passed by the sound pulse exploded for a fraction of a microsecond and grew to have a radius of around 10 microns. While the bubble had this large size it was illuminated with a flash lamp and its position was recorded. In this way, we can determine its position. Through the application of a series of sound pulses, we can then take images along the track of individual electrons. The motion of individual electron bubbles has been successfully monitored. Interesting bubble tracks that may relate to electrons

  2. Analysis and calculation of electronic properties and light absorption of defective sulfur-doped silicon and theoretical photoelectric conversion efficiency.

    PubMed

    Jiang, He; Chen, Changshui

    2015-04-23

    Most material properties can be traced to electronic structures. Black silicon produced from SF6 or sulfur powder via irradiation with femtosecond laser pulses displays decreased infrared absorption after annealing, with almost no corresponding change in visible light absorption. The high-intensity laser pulses destroy the original crystal structure, and the doping element changes the material performance. In this work, the structural and electronic properties of several sulfur-doped silicon systems are investigated using first principle calculations. Depending on the sulfur concentration (level of doping) and the behavior of the sulfur atoms in the silicon lattice, different states or an absence of states are exhibited, compared with the undoped system. Moreover, the visible-infrared light absorption intensities are structure specific. The results of our theoretical calculations show that the conversion efficiency of sulfur-doped silicon solar cells depends on the sulfur concentrations. Additionally, two types of defect configurations exhibit light absorption characteristics that differ from the other configurations. These two structures produce a rapid increase in the theoretical photoelectric conversion efficiency in the range of the specific chemical potential studied. By controlling the positions of the atomic sulfur and the sulfur concentration in the preparation process, an efficient photovoltaic (PV) material may be obtainable.

  3. [Study on absorption spectra and optical limiting properties of soluble polymer/multi-walled carbon nanotube composites].

    PubMed

    Qiu, Xue-Qiong; Wu, Hui-Xia; Tong, Rui; Qian, Shi-Xiong; Lin, Yang-Hui; Cai, Rui-Fang

    2008-07-01

    Three kinds of soluble polymer grafted multi-walled carbon nanotubes (MWNTs), including poly(N-vinylcarbazole)-MWNTs (MWNTs-PVK), polystyrene-MWNTs (MWNTs-PSt) and poly(methyl methacrylate)-MWNTs (MWNTs-PMMA) were synthesized. The TEM images of these samples show that polymers are coated outside the carbon nanotubes. The UV-Vis absorption spectra of the samples in CHCl3 were taken on a HP8452 spectrophotometer at room temperature. Compared with that of MWNTs suspension, there is a characteristic absorption peak in the ultraviolet region, which can be attributed to the polymers linked covalently with MWNTs. Their nonlinear optical properties and optical limiting (OL) performances were investigated by Z-scan method with 527 nm nanosecond laser pulses. These MWNTs dissolved in chloroform possess similar optical limiting properties, which are better than that of raw MWNT suspension and C60 in toluene solution. Nonlinear refraction, nonlinear absorption and nonlinear scattering mechanism were taken into consideration for explaining the observed results. The analysis of the experimental results shows that nonlinear absorption is the dominant mechanism behind the OL performance of these samples.

  4. TPA-inducible proteins may account for sensitivity to promotion of transformation

    SciTech Connect

    Hirano, K.; Smith, B.; Colburn, N.H.

    1986-05-01

    The preneoplastic JB6 mouse epidermal cell system includes cell lines sensitive (P/sup +/) or resistant (P/sup -/) to tumor promoter induced neoplastic transformation. The authors investigated whether a difference in TPA-inducible proteins may explain this differential sensitivity. The synthesis of a 39 Kd cytoplasmic protein (Major Excreted Protein) was TPA-inducible, but to a similar extent in both P/sup +/ and P/sup -/ cells. TPA stimulated phosphorylation but not synthesis of the previously described stress protein pp80 in both P/sup +/ and P/sup -/ cells from 1 to 5 hr after treatment. Pulse labelling of P/sup +/ and P/sup -/ cells with /sup 35/S-methionine revealed a TPA dependent P/sup +/ specific transient increase in the synthesis of 58Kd protein. Induction was observed at 1 hr, and returned to basal levels by 4 hr and 20 hr, in nuclear and cytoplasmic fractions, respectively. This protein is not phosphorylated in response to TPA treatment. P/sup +/ cells differ from P/sup -/ cells in one or more genes that specify sensitivity to promotion of transformation, designated pro genes. Antibodies to three peptides representing the pro-1 open reading frame were used in immunoprecipitation and Western blotting to isolate the pro-1 gene product. A 43 Kd protein was immunologically responsive to the pro-1 peptide antibodies, and showed an increased signal 40 min after TPA treatment. Since the predicted molecular weight of a pro-1 gene product is only 7 Kd, the possibility of a modification of the protein by poly(ADP-ribosylation) or glycosylation is being investigated.

  5. CpG and TpA frequencies in the plant system.

    PubMed Central

    Boudraa, M; Perrin, P

    1987-01-01

    Higher plant nuclear sequences reveal avoidance of CpG and TpA doublets. Chloroplast sequences avoid the TpA doublet in all codon positions. The chloroplast genome is not methylated but codon positions II-III and untranslated regions avoid CpG. The mitochondrial genome, also unmethylated, avoids CpG in all codon positions. We therefore deduce that methylation is not sufficient to explain CpG avoidance in the higher plant systems. Other factors must be taken into account such as amino acid composition, codon choices and perhaps stability of the DNA helix. PMID:3497385

  6. The Ablation Properties of CO2 Laser Irradiating to Absorption Media: An In Vitro Study

    PubMed Central

    Sattayut, Sajee; Hortong, Kittiwut; Kitichaiwan, Chorpaka

    2012-01-01

    This study aimed to compare histological affected zone of tissue samples irradiated by defocused CO2 laser at 1, 2, and 3W continuous wave with and without absorption media. The in vitro experiment was conducted in 70 tissue blocks. The samples were randomly allocated into 7 groups: 10 samples each group, namely, the groups irradiated with 1, 2, and 3W, defocused CO2 laser for 5 seconds, the groups irradiated with 1, 2, and 3W, defocused CO2 laser to the absorption media, and the media alone group as a control. Then the samples were stained with Masson's trichrome and measured the affected borders under light microscope at 10 × 10 magnification. There was no histological alteration in the groups irradiated with the defocused CO2 laser to the absorption media while the groups without using the absorption media showed the tissue alteration by photoablation. PMID:23227050

  7. Nonlinear absorption properties of DKDP crystal at 263 nm and 351 nm

    NASA Astrophysics Data System (ADS)

    Chai, Xiangxu; Zhu, Qihua; Feng, Bin; Li, Fuquan; Feng, Xi; Wang, Fang; Han, Wei; Wang, Liquan

    2017-02-01

    At the wavelength of 263 nm and 351 nm, the nonlinear absorption curves of 66% deuterated DKDP crystal were measured in the geometries of beam polarizing along the optics axis (E∥Z) and perpendicular to it (E⊥Z). The results indicate that the nonlinear absorption in the E⊥Z geometry is stronger than that in the E∥Z geometry. The nonlinear absorptions at 263 nm and 351 nm are identified to two- and three-photon absorption, respectively. The theoretical fits to the experimental data yields the two-photon absorption coefficients of 0.32 ± 0.03 cm/GW (E⊥Z geometry) and 0.17 ± 0.02 cm/GW (E∥Z geometry) at 263 nm, and the three-photon absorption coefficients of (8.1 ± 1.1) × 10-4 cm3/GW2 (E⊥Z geometry) and (2.2 ± 0.5) × 10-4 cm3/GW2 (E∥Z geometry) at 351 nm.

  8. Carbon dioxide absorption and release properties of pyrolysis products of dolomite calcined in vacuum atmosphere.

    PubMed

    Wang, Fei; Kuzuya, Toshihiro; Hirai, Shinji; Li, Jihua; Li, Te

    2014-01-01

    The decomposition of dolomite into CaO and MgO was performed at 1073 K in vacuum and at 1273 K in an Ar atmosphere. The dolomite calcined in vacuum was found to have a higher specific surface area and a higher micropore volume when compared to the dolomite calcined in the Ar atmosphere. These pyrolysis products of dolomite were reacted with CO2 at 673 K for 21.6 ks. On the absorption of CO2, the formation of CaCO3 was observed. The degree of absorption of the dolomite calcined in vacuum was determined to be above 50%, which was higher than the degree of absorption of the dolomite calcined in the Ar atmosphere. The CO2 absorption and release procedures were repeated three times for the dolomite calcined in vacuum. The specific surface area and micropore volume of calcined dolomite decreased with successive repetitions of the CO2 absorption and release cycles leading to a decrease in the degree of absorption of CO2.

  9. Nanostructure of tetrafunctional epoxy resins and composites: Correlation to moisture absorption properties

    NASA Astrophysics Data System (ADS)

    Bolan, Brett Andrew

    The effect that changes in network topology, while maintaining a constant network polarity (i.e. thermodynamic driving force was kept constant), had upon the moisture absorption properties of an aerospace grade tetrafunctional epoxy (TGMDA) cured with multifunctional amines were investigated. Utilizing Positron Annihilation Lifetime Spectroscopy (PALS) to characterize the nanoscale structure of these epoxies, it was found that as the "static" hole volume (a measurement of packing defects at 0K) increased so did the equilibrium uptake. PALS studies of one of these resins cured to varying extents, found that this static amount increased with degree of cure indicating that the network becomes more open as a direct consequence of crosslinking. Polar groups, which are the attractive force for diffusion, are in the vicinity of these crosslinks, therefore it is believed that the increase in static hole volume results in exposing more polar groups for absorption. The diffusion coefficient, which is representative of the kinetic aspect of diffusion, was also investigated. It was discovered that the amount of nanohole volume in the polymer; whether the total, the static, or dynamic (i.e. thermally activated) does not correlate to the diffusion coefficient in anyway. Furthermore, at an isotherm the diffusion coefficients for all these materials were relatively constant. From this it is hypothesized that it is the similar sub-Tsb{g} motions of these resins which is the rate limiting step in diffusion. This was bolstered by the fact that the activation energy for diffusion and for the sub-Tsb{g} motions for these epoxies are of the same order of magnitude. The nanostructure of fiber reinforced epoxy composites (i.e. a boron/epoxy and a graphite/epoxy) were probed with the bulk PALS technique as well. It was observed that for the graphite/epoxy composite and its flash (i.e. no fibers present) cured under identical conditions, that the nanoholes in the composite were larger than

  10. Absorption properties of high-latitude Norwegian coastal water: The impact of CDOM and particulate matter

    NASA Astrophysics Data System (ADS)

    Nima, Ciren; Frette, Øyvind; Hamre, Børge; Erga, Svein Rune; Chen, Yi-Chun; Zhao, Lu; Sørensen, Kai; Norli, Marit; Stamnes, Knut; Stamnes, Jakob J.

    2016-09-01

    We present data from measurements and analyses of the spectral absorption due to colored dissolved organic matter (CDOM), total suspended matter (TSM), phytoplankton, and non-algal particles (NAP) in high-latitude northern Norwegian coastal water based on samples taken in spring, summer, and autumn. The Chlorophyll-a (Chl-a) concentration was found to vary significantly with season, whereas regardless of season CDOM was found to be the dominant absorber for wavelengths shorter than 600 nm. The absorption spectral slope S350-500 for CDOM varied between 0.011 and 0.022 nm-1 with mean value and standard deviation given by (0.015 ± 0.002) nm-1. The absorption spectral slope was found to be strongly dependent on the wavelength interval used for fitting. On average, S280-500 was found to be 43% higher than S350-500. A linear relationship was found between the base 10 logarithm of the absorption coefficient at 440 nm [log(ag(440))] and S350-500. Regardless of season, phytoplankton were the dominant component of the TSM absorption indicating little influence from land drainage. The mean values of the Chl-a specific absorption coefficient of phytoplankton aph*(λ) at 440 nm and 676 nm were 0.052 m2 mg-1 and 0.023 m2 mg-1, respectively, and aph*(λ) was found to vary with season, being higher in summer and autumn than in spring. The absorption spectral slope SNAP, which is the spectral slope of absorption spectrum for non-algal particles, was lower than that for European coastal water in general. It varied between 0.0048 and 0.022 nm-1 with mean value and standard deviation given by (0.0083-1 ± 0.003) nm-1. Comparisons of absorption coefficients measured in situ using an ac-9 instrument with those measured in the laboratory from water samples show a good agreement.

  11. Magnetic and microwave absorption properties of ZnCo-substituted W-type strontium hexaferrite

    NASA Astrophysics Data System (ADS)

    Farhadizadeh, A. R.; Seyyed Ebrahimi, S. A.; Masoudpanah, S. M.

    2015-05-01

    Single phase ZnCo-substituted W-type strontium hexaferrite (SrZn2-xCoxFe16O27 with x=0-2.0) were prepared by ceramic conventional method. With the Co substitution, the saturation magnetization increases up to a maximum of 72.8 emu/g for SrZnCoFe16O27, and then decreases, while the coercivity decreases from 1000 Oe for x=0 to 430 Oe for x=1 and then increases up to 700 Oe for x=2. The microwave absorption measurements in the microwave frequency range of 8-12 GHz (X-band) exhibited the maximum absorption of -28 dB at 10.3 GHz with an absorption bandwidth of more than 2.1 GHz for x=1.

  12. Study of nonlinear optical absorption properties of Sb2Se3 nanoparticles in the nanosecond and femtosecond excitation regime

    NASA Astrophysics Data System (ADS)

    Molli, Muralikrishna; Pradhan, Prabin; Dutta, Devarun; Jayaraman, Aditya; Bhat Kademane, Abhijit; Muthukumar, V. Sai; Kamisetti, Venkataramaniah; Philip, Reji

    2016-05-01

    In this work, we report for the first time, the nonlinear optical absorption properties of antimony selenide (Sb2Se3) nanoparticles synthesized through solvothermal route. X-ray diffraction results revealed the crystalline nature of the nanoparticles. Electron microscopy studies revealed that the nanoparticles are in the range of 10-40 nm. Elemental analysis was performed using EDAX. The nanosecond optical limiting effect was characterized by using fluence-dependent transmittance measurements with 15-ns laser pulses at 532 and 1064 nm excitation wavelengths. Mechanistically, effective two-photon (2PA) absorption and nonlinear scattering processes were the dominant nonlinear processes at both the wavelengths. At 800 nm excitation in the femtosecond regime (100 fs), the nonlinear optical absorption was found to be a three-photon (3PA) process. Both 2PA and 3PA processes were explained using the band structure and density of states of Sb2Se3 obtained using density functional theory. These nanoparticles exhibit strong intensity-dependent nonlinear optical absorption and hence could be considered to have optical power-limiting applications in the visible range.

  13. Synthesis, spectral and third-order nonlinear optical properties of terpyridine Zn(II) complexes based on carbazole derivative with polyether group

    NASA Astrophysics Data System (ADS)

    Kong, Ming; Liu, Yanqiu; Wang, Hui; Luo, Junshan; Li, Dandan; Zhang, Shengyi; Li, Shengli; Wu, Jieying; Tian, Yupeng

    2015-01-01

    Four novel Zn(II) terpyridine complexes (ZnLCl2, ZnLBr2, ZnLI2, ZnL(SCN)2) based on carbazole derivative group were designed, synthesized and fully characterized. Their photophysical properties including absorption and one-photon excited fluorescence, two-photon absorption (TPA) and optical power limiting (OPL) were further investigated systematically and interpreted on the basis of theoretical calculations (TD-DFT). The influences of different solvents on the absorption and One-Photon Excited Fluorescence (OPEF) spectral behavior, quantum yields and the lifetime of the chromophores have been investigated in detail. The third-order nonlinear optical (NLO) properties were investigated by open/closed aperture Z-scan measurements using femtosecond pulse laser in the range from 680 to 1080 nm. These results revealed that ZnLCl2 and ZnLBr2 exhibited strong two-photon absorption and ZnLCl2 showed superior optical power limiting property.

  14. Where Practicum Meets Test Preparation: Supporting Teacher Candidates through EdTPA

    ERIC Educational Resources Information Center

    Clark-Gareca, Beth

    2015-01-01

    A strong focus on teacher performance is resurfacing in teacher-preparation programs across the US. EdTPA, a teacher-performance assessment designed to determine K-12 teacher candidates' readiness for the classroom, has become central in teacher-preparation programs in several states and promises to be implemented in more states in the coming…

  15. Breakers, Benders, and Obeyers: Inquiring into Teacher Educators' Mediation of edTPA

    ERIC Educational Resources Information Center

    Ratner, Andrew R.; Kolman, Joni S.

    2016-01-01

    This article reflects a qualitative exploratory inquiry into the lived experiences of faculty members working within a system of urban schools of education as they supported diverse teacher candidates in completing the Educative Teacher Performance Assessment (edTPA) during its first semesters of high-stakes implementation. Drawing upon…

  16. Next Generation Science Standards and edTPA: Evidence of Science and Engineering Practices

    ERIC Educational Resources Information Center

    Brownstein, Erica M.; Horvath, Larry

    2016-01-01

    Science teacher educators in the United States are currently preparing future science teachers to effectively implement the "Next Generation Science Standards" (NGSS) and, in thirteen states, to successfully pass a content-specific high stakes teacher performance assessment, the edTPA. Science education and teacher performance assessment…

  17. Developing a Culture of Learning around the edTPA: One University's Journey

    ERIC Educational Resources Information Center

    Miller, Matthew; Carroll, David; Jancic, Mitchell; Markworth, Kimberly

    2015-01-01

    In this article, we discuss how an interdisciplinary faculty team at a midsized public university created supports for the Teacher Performance Assessment (edTPA), a high-stakes performance assessment for preservice candidates being adopted by many states. We provide a general description of our work in contending with the challenge of developing a…

  18. Serum tissue polypeptide antigen (TPA) and prostatic acid phosphatase (PAP) in patients with prostatic cancer.

    PubMed

    Marczyńska, A; Kulpa, J; Leńko, J; Augustyn, M

    1988-01-01

    Concurrent measurements of serum TPA and PAP concentrations by double antibody radioimmunoassays were done in 49 patients with prostatic cancer in different clinical stages. The reference group comprised patients suffering from BPH. Positive TPA was found in 32.7% of cancer patients, the lowest percentage in stage A (11.1%) and the highest in stage D (55.6%). The additional value as a diagnostic aid of the TPA test was revealed on the basis of examination of the selected group of patients with not increased PAP. Positive TPA was found in 16.7% of patients: none in stage A, 22.2% in stage B, and 33.3% in stage D. Prostatic cancer remains the most common malignancy of the genitourinary tract. The improvement in the results of treatment involves not only a modernization of treatment modalities but also the introduction of laboratory tests which give the most ample information on the stage of tumour development and improve possibilities to control tumour therapy. Besides the refinement of the determination procedures of specific prostatic markers, prostatic acid phosphatase (PAP), through radio- and enzyme-immunological methods, there is a search for additional markers which might be helpful in diagnosis and follow-up of treatment.

  19. Buyer Beware: Lessons Learned from EdTPA Implementation in New York State

    ERIC Educational Resources Information Center

    Greenblatt, Deborah; O'Hara, Kate E.

    2015-01-01

    As states across the country continue their implementation of the Teacher Performance Assessment Portfolio (edTPA), a complex and high-stakes certification requirement for teacher certification, there are important lessons for educators and education advocates to learn from New York State's implementation. As Linda Darling-Hammond, developer and…

  20. Racist Ordering, Settler Colonialism, and EdTPA: A Participatory Policy Analysis

    ERIC Educational Resources Information Center

    Tuck, Eve; Gorlewski, Julie

    2016-01-01

    This article tells the story of an intervention by a collective of teacher educators on New York State's adoption of edTPA. Too often in education policy analysis, issues of race are discussed briefly, if at all. This article argues that attending to constructions of race specific to settler colonialism is an important approach to education policy…

  1. Draft Genome Sequence of an Anicemycin Producer, Streptomyces sp. TP-A0648

    PubMed Central

    Hosoyama, Akira; Kimura, Akane; Ichikawa, Natsuko; Igarashi, Yasuhiro

    2017-01-01

    ABSTRACT We report the draft genome sequence of Streptomyces sp. TP-A0648 isolated from a leaf of Aucuba japonica. This strain produces a new tumor cell growth inhibitor designated anicemycin. The genome harbors at least 12 biosynthetic gene clusters for polyketides and nonribosomal peptides, suggesting the potential to produce diverse secondary metabolites. PMID:28082502

  2. Parameterization of the light absorption properties of chromophoric dissolved organic matter in the Baltic Sea and Pomeranian lakes

    NASA Astrophysics Data System (ADS)

    Meler, Justyna; Kowalczuk, Piotr; Ostrowska, Mirosława; Ficek, Dariusz; Zabłocka, Monika; Zdun, Agnieszka

    2016-08-01

    This study presents three alternative models for estimating the absorption properties of chromophoric dissolved organic matter aCDOM(λ). For this analysis we used a database containing 556 absorption spectra measured in 2006-2009 in different regions of the Baltic Sea (open and coastal waters, the Gulf of Gdańsk and the Pomeranian Bay), at river mouths, in the Szczecin Lagoon and also in three lakes in Pomerania (Poland) - Obłęskie, Łebsko and Chotkowskie. The variability range of the chromophoric dissolved organic matter (CDOM) absorption coefficient at 400 nm, aCDOM(400), lay within 0.15-8.85 m-1. The variability in aCDOM(λ) was parameterized with respect to the variability over 3 orders of magnitude in the chlorophyll a concentration Chl a (0.7-119 mg m-3). The chlorophyll a concentration and aCDOM(400) were correlated, and a statistically significant, nonlinear empirical relationship between these parameters was derived (R2 = 0.83). On the basis of the covariance between these parameters, we derived two empirical mathematical models that enabled us to design the CDOM absorption coefficient dynamics in natural waters and reconstruct the complete CDOM absorption spectrum in the UV and visible spectral domains. The input variable in the first model was the chlorophyll a concentration, and in the second one it was aCDOM(400). Both models were fitted to a power function, and a second-order polynomial function was used as the exponent. Regression coefficients for these formulas were determined for wavelengths from 240 to 700 nm at 5 nm intervals. Both approximations reflected the real shape of the absorption spectra with a low level of uncertainty. Comparison of these approximations with other models of light absorption by CDOM demonstrated that our parameterizations were superior (bias from -1.45 to 62 %, RSME from 22 to 220 %) for estimating CDOM absorption in the optically complex waters of the Baltic Sea and Pomeranian lakes.

  3. Light Absorption Properties of Brown Carbon from Fresh and Aged Biomass Burning Aerosols Characterized in a Smog Chamber

    NASA Astrophysics Data System (ADS)

    Saleh, R.; Chuang, W.; Hennigan, C.; McMeeking, G. R.; Coe, H.; Donahue, N. M.; Robinson, A. L.

    2011-12-01

    Black carbon is an important particulate phase light absorber in the atmosphere. Recent studies have shown that some organic matter also absorb visible light, especially at short wavelengths. These organic compounds are referred to as "brown carbon". Biomass burning is a major contributor to brown carbon in atmospheric particulate matter; however, its optical properties are poorly characterized. We have conducted smog chamber experiments to investigate light absorption properties of brown carbon in primary and aged biomass burning emissions, namely the imaginary refractive index. The aging was performed in a smog chamber, where dilute emissions were exposed to UV lights to initiate photo-oxidation, which often produced substantial secondary organic aerosol. The experiments took place at Carnegie Mellon University (CMU) and at the US Fire Science Laboratory in Missoula, MT as part of the Fire Lab at Missoula field campaign (FLAME 2009). The CMU experiments simulated household wood burning (oak), and the FLAME experiments simulated wildland fires with fuels including gallberry, lodgepole pine, black spruce and ponderosa pine. Absorption coefficients were measured using an Aethalometer (Magee Scientific) at 7 different wavelengths ranging between 370 nm and 950 nm. The black carbon size distributions were measured using a Single Particle Soot Photometer (SP2, DMT), and total aerosol size distributions were measured using a Scanning Mobility Particle Sizer (SMPS, TSI). The absorption coefficients of both the fresh and aged aerosol were significantly larger, and had stronger wavelength dependence than what would be expected for black carbon alone, and for a black carbon core with a non-absorbing shell. This indicates that biomass burning organic aerosol should be classified as brown carbon. A (black carbon) core - (brown carbon) shell absorption model based on Mie theory was optimized to determine the shell imaginary refractive index which produces model outputs that

  4. Microhydration effects on geometric properties and electronic absorption spectra of ortho-aminobenzoic acid.

    PubMed

    Olivier, Danilo da Silva; Ito, Amando Siuiti; Galembeck, Sergio Emanuel

    2015-08-05

    TD-DFT and a combination of polarized continuum model (PCM) and microhydration methods helped to simulate the optical electronic absorption spectrum of ortho-aminobenzoic acid (o-Abz). The microhydration method involved the use of different numbers, from 1 to 5, of first solvation layer water molecules. We examined how implicit and explicit water affected the energies of the HOMO-LUMO transition in the o-Abz/water systems. Adding until five water molecules, the theoretical spectrum becomes closer to the experimental data. Microhydration combined with the PCM method leads to agreement between the theoretical result for five water molecules and the experimentally measured absorption bands.

  5. The mechanism and properties of bio-photon emission and absorption in protein molecules in living systems

    NASA Astrophysics Data System (ADS)

    Pang, Xiao-feng

    2012-05-01

    The mechanism and properties of bio-photon emission and absorption in bio-tissues were studied using Pang's theory of bio-energy transport, in which the energy spectra of protein molecules are obtained from the discrete dynamic equation. From the energy spectra, it was determined that the protein molecules could both radiate and absorb bio-photons with wavelengths of <3 μm and 5-7 μm, consistent with the energy level transitions of the excitons. These results were consistent with the experimental data; this consisted of infrared absorption data from collagen, bovine serum albumin, the protein-like molecule acetanilide, plasma, and a person's finger, and the laser-Raman spectra of acidity I-type collagen in the lungs of a mouse, and metabolically active Escherichia coli. We further elucidated the mechanism responsible for the non-thermal biological effects produced by the infrared light absorbed by the bio-tissues, using the above results. No temperature rise was observed; instead, the absorbed infrared light promoted the vibrations of amides as well the transport of the bio-energy from one place to other in the protein molecules, which changed their conformations. These experimental results, therefore, not only confirmed the validity of the mechanism of bio-photon emission, and the newly developed theory of bio-energy transport mentioned above, but also explained the mechanism and properties of the non-thermal biological effects produced by the absorption of infrared light by the living systems.

  6. Tailoring Microwave-Absorption Properties of Co x Ni y Alloy/RGO Nanocomposites with Tunable Atomic Ratios

    NASA Astrophysics Data System (ADS)

    Guo, Xiaoqin; Bai, Zhongyi; Zhao, Biao; Zhang, Rui; Chen, Jingbo

    2017-04-01

    Co x Ni y nanoparticles anchored on reduced graphene oxide (rGO) composites with different Co(0)/Ni(0) ratios were successfully prepared by a simple hydrothermal method. The morphology, structure, and magnetic and microwave electromagnetic properties of Co x Ni y /rGO composites were characterized by the x-ray diffraction, Fourier transform infrared spectrometry, scanning electron microscopy, Raman spectroscopy and a vector network analyzer. The Co x Ni y /rGO composites exhibited enhanced microwave absorption properties, which are attributed to the effective complementarities between dielectric loss and magnetic loss. For the Co3Ni1/rGO composite, the minimum reflection loss (RLmin) is -44.89 dB at 12.22 GHz with absorber thickness of 2.5 mm, and the effective absorption bandwidth of the reflection loss (RL) <-10 dB (indicating 90% attenuation) could achieve 5.61 GHz. It is believed that the Co3Ni1/rGO composite may be a promising candidate as a microwave absorber with the features of low density, strong absorption, wide band and low thickness.

  7. Tailoring Microwave-Absorption Properties of Co x Ni y Alloy/RGO Nanocomposites with Tunable Atomic Ratios

    NASA Astrophysics Data System (ADS)

    Guo, Xiaoqin; Bai, Zhongyi; Zhao, Biao; Zhang, Rui; Chen, Jingbo

    2016-11-01

    Co x Ni y nanoparticles anchored on reduced graphene oxide (rGO) composites with different Co(0)/Ni(0) ratios were successfully prepared by a simple hydrothermal method. The morphology, structure, and magnetic and microwave electromagnetic properties of Co x Ni y /rGO composites were characterized by the x-ray diffraction, Fourier transform infrared spectrometry, scanning electron microscopy, Raman spectroscopy and a vector network analyzer. The Co x Ni y /rGO composites exhibited enhanced microwave absorption properties, which are attributed to the effective complementarities between dielectric loss and magnetic loss. For the Co3Ni1/rGO composite, the minimum reflection loss (RLmin) is -44.89 dB at 12.22 GHz with absorber thickness of 2.5 mm, and the effective absorption bandwidth of the reflection loss (RL) <-10 dB (indicating 90% attenuation) could achieve 5.61 GHz. It is believed that the Co3Ni1/rGO composite may be a promising candidate as a microwave absorber with the features of low density, strong absorption, wide band and low thickness.

  8. Analysis of aerosol absorption properties and transport over North Africa and the Middle East using AERONET data

    NASA Astrophysics Data System (ADS)

    Farahat, Ashraf; El-Askary, Hesham; Adetokunbo, Peter; Fuad, Abu-Tharr

    2016-11-01

    In this paper particle categorization and absorption properties were discussed to understand transport mechanisms at different geographic locations and possible radiative impacts on climate. The long-term Aerosol Robotic Network (AERONET) data set (1999-2015) is used to estimate aerosol optical depth (AOD), single scattering albedo (SSA), and the absorption Ångström exponent (αabs) at eight locations in North Africa and the Middle East. Average variation in SSA is calculated at four wavelengths (440, 675, 870, and 1020 nm), and the relationship between aerosol absorption and physical properties is used to infer dominant aerosol types at different locations. It was found that seasonality and geographic location play a major role in identifying dominant aerosol types at each location. Analyzing aerosol characteristics among different sites using AERONET Version 2, Level 2.0 data retrievals and the Hybrid Single Particle Lagrangian Integrated Trajectory model (HYSPLIT) backward trajectories shows possible aerosol particle transport among different locations indicating the importance of understanding transport mechanisms in identifying aerosol sources.

  9. Light absorption properties of CDOM in the Changjiang (Yangtze) estuarine and coastal waters: An alternative approach for DOC estimation

    NASA Astrophysics Data System (ADS)

    Yu, Xiaolong; Shen, Fang; Liu, Yangyang

    2016-11-01

    Field measurements of CDOM absorption properties and DOC concentrations were collected in the Changjiang estuarine and coastal waters from 2011 to 2013. CDOM absorption coefficient at 355 nm (ag (355)) was found to be inversely correlated with salinity, with Pearson's coefficients r of -0.901 and -0.826 for summer and winter observations, respectively. Analysis results of the relationships between salinity and CDOM optical properties (i.e., absorption coefficient and spectral slope) suggested that terrigenous inputs dominated CDOM sources in the Changjiang estuary, but the proportion of terrigenous CDOM declined with increasing salinity. The level of CDOM in the Changjiang estuary was lower compared to some of the major estuaries in the world, which could be attributed to several controlling factors such as vegetation cover in the drainage basin, the origin of recharged streams and high sediment load in the Changjiang estuary. We further evaluated the relationships between CDOM and DOC and their mixing behavior among world's major estuaries. An empirical model was finally developed to estimate DOC concentration from ag (355) and spectral slope S275-295 using a non-linear regression. This empirical relationship was calibrated using the Cal dataset, and was validated with the Val dataset, resulting in an acceptable error with the R2 of 0.746, the RMSE of 20.99 μmol/L and the rMAD of 14.46%.

  10. Microwave absorption properties of polyaniline-Fe3O4/ZnO-polyester nanocomposite: Preparation and optimization

    NASA Astrophysics Data System (ADS)

    Dorraji, M. S. Seyed; Rasoulifard, M. H.; Khodabandeloo, M. H.; Rastgouy-Houjaghan, M.; Zarajabad, H. Karimi

    2016-03-01

    New nanocomposites have been successfully prepared based on polyester resin, including various metal oxides (ZnO nanorod bundles, Fe3O4 nanoparticles, and nano Fe3O4/ZnO) and Polyaniline (PANI) synthesized with different dopants. The microwave absorption properties of nanocomposites were investigated in X-band range. The Taguchi experimental design was used to study the effects of the type of metal oxide and that of PANI (doped with various acids) and the weight percent of metal oxide in PANI and that of filler (metal oxide and PANI) in polyester matrix on the microwave absorption properties with the absorber thickness of only 2 mm. The weight percent of metal oxide in PANI was found to be the most significant parameter, accounting for 45.611% of the total contribution of the four selected parameters. Fe3O4/ZnO as inorganic oxide, PTSA as dopant of PANI, 25 wt.% for inorganic oxide in PANI, and filler in the polyester matrix were selected as optimum conditions by Taguchi method. The sample prepared in optimal conditions had reflection loss of less than -10 dB (absorption >90%) and covering a frequency range of 8.4-11.6 GHz.

  11. Nonlinear absorption properties of AlGaAs/GaAs multiple quantum wells grown by metalorganic chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Lee, Hsing-Chung; Kost, A.; Kawase, M.; Hariz, A.; Dapkus, P. Daniel

    1988-01-01

    The nonlinear absorption properties of the excitonic resonances associated with multiple quantum wells (MQWs) in AlGaAs/GaAs grown by metalorganic chemical vapor deposition are reported. The dependence of the saturation properties on growth parameters, especially growth temperature, and the well width are described. The minimum measured saturation intensity for these materials is 250 W/sq cm, the lowest reported value to date. The low saturation intensities are the result of excellent minority carrier properties. A systematic study of minority carrier lifetimes in quantum wells are reported. Lifetimes range from 50-350 ns depending on growth temperature and well width. When corrected for lateral diffusion effects and the measured minority carrier lifetime, the saturation data suggest that saturation intensities as low as 2.3 W/sq cm can be achieved in this system. The first measurements of the dependence of the exciton area and the magnitude of the excitonic absorption on well width are prsented. The growth of MQW structures on transparent GaP substrates is demonstrated and the electroabsorption properties of these structures are reviewed.

  12. Light Absorption Properties and Radiative Effects of Primary Organic Aerosol Emissions

    EPA Science Inventory

    Organic aerosols (OA) in the atmosphere affect Earth’s energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called “brown carbon” (BrC) component. However, the absorptivities of OA are not or poorly represented in current climate m...

  13. NOTE: Visible absorption properties of radiation exposed XR type-T radiochromic film

    NASA Astrophysics Data System (ADS)

    Butson, Martin J.; Cheung, Tsang; Yu, Peter K. N.

    2004-10-01

    The visible absorption spectra of Gafchromic XR type-T radiochromic film have been investigated to analyse the dosimetry characteristics of the film with visible light densitometers. Common densitometers can use photo-spectrometry, fluorescent light (broad-band visible), helium neon (632 nm), light emitting diode (LED) or other specific bandwidth spectra. The visible absorption spectra of this film when exposed to photon radiation show peaks at 676 nm and 618 nm at 2 Gy absorbed doses which shift to slightly lower wavelengths (662 nm and 612 nm at 8 Gy absorbed dose) at higher doses. This is similar to previous models of Gafchromic film such as MD-55-2 and HS but XR type-T also includes a large absorption at lower visible wavelengths due to 'yellow' dyes placed within the film to aid with visible recognition of the film exposure level. The yellow dye band pass is produced at approximately 520 nm to 550 nm and absorbs wavelengths lower than this value within the visible spectrum. This accounts for the colour change from yellow to brown through the added absorption in the red wavelengths with radiation exposure. The film produces a relatively high dose sensitivity with up to 0.25 OD units per Gy change at 672 nm at 100 kVp x-ray energy. Variations in dose sensitivity can be achieved by varying wavelength analysis.

  14. A multivariant study of the absorption properties of poly(glutaric-acid-glycerol) films

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The solvent absorption into the matrix of poly(glutaric acid-glycerol) films made with or without either iminodiacetic acid, sugarcane bagasse, pectin, corn fiber gum or microcrystalline cellulose have been evaluated. The films were incubated in various solvent systems for 24h. The amounts of solve...

  15. An Analysis of AERONET Aerosol Absorption Properties and Classifications Representative of Aerosol Source Regions

    NASA Technical Reports Server (NTRS)

    Giles, David M.; Holben, Brent N.; Eck, Thomas F.; Sinyuk, Aliaksandr; Smirnov, Alexander; Slutsker, Ilya; Dickerson, R. R.; Thompson, A. M.; Schafer, J. S.

    2012-01-01

    Partitioning of mineral dust, pollution, smoke, and mixtures using remote sensing techniques can help improve accuracy of satellite retrievals and assessments of the aerosol radiative impact on climate. Spectral aerosol optical depth (tau) and single scattering albedo (omega (sub 0) ) from Aerosol Robotic Network (AERONET) measurements are used to form absorption [i.e., omega (sub 0) and absorption Angstrom exponent (alpha(sub abs))] and size [i.e., extinction Angstrom exponent (alpha(sub ext)) and fine mode fraction of tau] relationships to infer dominant aerosol types. Using the long-term AERONET data set (1999-2010), 19 sites are grouped by aerosol type based on known source regions to: (1) determine the average omega (sub 0) and alpha(sub abs) at each site (expanding upon previous work); (2) perform a sensitivity study on alpha(sub abs) by varying the spectral omega (sub 0); and (3) test the ability of each absorption and size relationship to distinguish aerosol types. The spectral omega (sub 0) averages indicate slightly more aerosol absorption (i.e., a 0.0 < delta omega (sub 0) <= 0.02 decrease) than in previous work and optical mixtures of pollution and smoke with dust show stronger absorption than dust alone. Frequency distributions of alpha(sub abs) show significant overlap among aerosol type categories and at least 10% of the alpha(sub abs) retrievals in each category are below 1.0. Perturbing the spectral omega (sub 0) by +/- 0.03 induces significant alpha(sub abs) changes from the unperturbed value by at least approx. +/- 0.6 for Dust, approx. +/-0.2 for Mixed, and approx. +/-0.1 for Urban/Industrial and Biomass Burning. The omega (sub 0)440nm and alpha(sub ext) 440-870nm relationship shows the best separation among aerosol type clusters, providing a simple technique for determining aerosol type from surface- and future space-based instrumentation.

  16. Third-Order Nonlinear Optic and Optical Limiting Properties of a Mn(iii) Transition Metal Complex

    NASA Astrophysics Data System (ADS)

    Karakas, Asli; Elmali, Ayhan; Yahsi, Yasemin; Kara, Hulya

    N,N‧-bis(5-bromosalicylidene)propane-1,2-diamine-O,O‧,N,N‧)-manganese(III) chloride transition metal complex has been synthesized and characterized by elemental analysis and UV-vis spectroscopy. Its crystal structure has been determined using X-ray diffraction analysis. To provide an insight into the optical limiting (OL) behavior of the title compound, the third-order nonlinear optical (NLO) properties, one-photon absorption (OPA) and two-photon absorption (TPA) characterizations have been theoretically investigated by means of the time-dependent Hartree-Fock (TDHF), AM1 and configuration interaction (CI) methods, respectively. According to ab initio calculation results, the examined molecule exhibits second hyperpolarizabilities (γ) with non-zero values at the positions of TPA peaks, implying microscopic third-order optical nonlinearity. The maximum OPA wavelengths recorded by linear optical experiment and quantum mechanical computations are estimated in the UV region to be shorter than 400 nm, showing good optical transparency to the visible light. The TPA cross-sections (δ(ω)) at λ max(2) values indicate that the synthesized compound might possess OL phenomena, which are in accord with the experimental observations on the manganese complexes in the literature.

  17. Flaky FeSiAl alloy-carbon nanotube composite with tunable electromagnetic properties for microwave absorption

    PubMed Central

    Huang, Lina; Liu, Xiaofang; Chuai, Dan; Chen, Yaxin; Yu, Ronghai

    2016-01-01

    Flaky FeSiAl alloy/multi-wall carbon nanotube (FeSiAl/MWCNT) composite was fabricated by facile and scalable ball milling method. The morphology and electromagnetic properties of the FeSiAl alloy can be well tuned by controlling the milling time. It is found that the magnetic loss of the FeSiAl alloy is improved by optimizing the milling time due to the increased anisotropy field. Meanwhile the addition of MWCNTs enhances the dielectric loss of the composite by increasing the interfacial polarizations, dipolar polarizations and conductive paths. Relative to conventional FeSiAl absorbers, the FeSiAl/MWCNT composite exhibits greatly improved microwave absorption performance with advantages of strong absorption and small thickness. The minimum reflection loss of the composite reaches −42.8 dB at 12.3 GHz at a very thin thickness of 1.9 mm. PMID:27762327

  18. Flaky FeSiAl alloy-carbon nanotube composite with tunable electromagnetic properties for microwave absorption.

    PubMed

    Huang, Lina; Liu, Xiaofang; Chuai, Dan; Chen, Yaxin; Yu, Ronghai

    2016-10-20

    Flaky FeSiAl alloy/multi-wall carbon nanotube (FeSiAl/MWCNT) composite was fabricated by facile and scalable ball milling method. The morphology and electromagnetic properties of the FeSiAl alloy can be well tuned by controlling the milling time. It is found that the magnetic loss of the FeSiAl alloy is improved by optimizing the milling time due to the increased anisotropy field. Meanwhile the addition of MWCNTs enhances the dielectric loss of the composite by increasing the interfacial polarizations, dipolar polarizations and conductive paths. Relative to conventional FeSiAl absorbers, the FeSiAl/MWCNT composite exhibits greatly improved microwave absorption performance with advantages of strong absorption and small thickness. The minimum reflection loss of the composite reaches -42.8 dB at 12.3 GHz at a very thin thickness of 1.9 mm.

  19. Flaky FeSiAl alloy-carbon nanotube composite with tunable electromagnetic properties for microwave absorption

    NASA Astrophysics Data System (ADS)

    Huang, Lina; Liu, Xiaofang; Chuai, Dan; Chen, Yaxin; Yu, Ronghai

    2016-10-01

    Flaky FeSiAl alloy/multi-wall carbon nanotube (FeSiAl/MWCNT) composite was fabricated by facile and scalable ball milling method. The morphology and electromagnetic properties of the FeSiAl alloy can be well tuned by controlling the milling time. It is found that the magnetic loss of the FeSiAl alloy is improved by optimizing the milling time due to the increased anisotropy field. Meanwhile the addition of MWCNTs enhances the dielectric loss of the composite by increasing the interfacial polarizations, dipolar polarizations and conductive paths. Relative to conventional FeSiAl absorbers, the FeSiAl/MWCNT composite exhibits greatly improved microwave absorption performance with advantages of strong absorption and small thickness. The minimum reflection loss of the composite reaches ‑42.8 dB at 12.3 GHz at a very thin thickness of 1.9 mm.

  20. Dependence of microwave absorption properties on ferrite volume fraction in MnZn ferrite/rubber radar absorbing materials

    NASA Astrophysics Data System (ADS)

    Gama, Adriana M.; Rezende, Mirabel C.; Dantas, Christine C.

    2011-11-01

    We report the analysis of measurements of the complex magnetic permeability ( μr) and dielectric permittivity ( ɛr) spectra of a rubber radar absorbing material (RAM) with various MnZn ferrite volume fractions. The transmission/reflection measurements were carried out in a vector network analyzer. Optimum conditions for the maximum microwave absorption were determined by substituting the complex permeability and permittivity in the impedance matching equation. Both the MnZn ferrite content and the RAM thickness effects on the microwave absorption properties, in the frequency range of 2-18 GHz, were evaluated. The results show that the complex permeability and permittivity spectra of the RAM increase directly with the ferrite volume fraction. Reflection loss calculations by the impedance matching degree (reflection coefficient) show the dependence of this parameter on both thickness and composition of RAM.

  1. Two-dimensional nanosheets of MoS2: a promising material with high dielectric properties and microwave absorption performance

    NASA Astrophysics Data System (ADS)

    Ning, Ming-Qiang; Lu, Ming-Ming; Li, Jing-Bo; Chen, Zhuo; Dou, Yan-Kun; Wang, Cheng-Zhi; Rehman, Fida; Cao, Mao-Sheng; Jin, Hai-Bo

    2015-09-01

    In this study, few-layered MoS2 nanosheets (MoS2-NS) were obtained via the top-down exfoliation method from bulk MoS2 (MoS2-Bulk), and the dielectric properties and microwave absorption performance of MoS2-NS were first reported. The dimension-dependent dielectric properties and microwave absorption performance of MoS2 were investigated by presenting a comparative study between MoS2-NS and MoS2-Bulk. Our results show that the imaginary permittivity (ε'') of MoS2-NS/wax is twice as large as that of MoS2-Bulk/wax. The minimum reflection loss (RL) value of MoS2-NS/wax with 60 wt% loading is -38.42 dB at a thickness of 2.4 mm, which is almost 4 times higher than that of MoS2-Bulk/wax, and the corresponding bandwidth with effective attenuation (<-10 dB) of MoS2-NS/wax is up to 4.1 GHz (9.6-13.76 GHz). The microwave absorption performance of MoS2-NS is comparable to those reported in carbon-related nanomaterials. The enhanced microwave absorption performance of MoS2-NS is attributed to the defect dipole polarization arising from Mo and S vacancies and its higher specific surface area. These results suggest that MoS2-NS is a promising candidate material not only in fundamental studies but also in practical microwave applications.In this study, few-layered MoS2 nanosheets (MoS2-NS) were obtained via the top-down exfoliation method from bulk MoS2 (MoS2-Bulk), and the dielectric properties and microwave absorption performance of MoS2-NS were first reported. The dimension-dependent dielectric properties and microwave absorption performance of MoS2 were investigated by presenting a comparative study between MoS2-NS and MoS2-Bulk. Our results show that the imaginary permittivity (ε'') of MoS2-NS/wax is twice as large as that of MoS2-Bulk/wax. The minimum reflection loss (RL) value of MoS2-NS/wax with 60 wt% loading is -38.42 dB at a thickness of 2.4 mm, which is almost 4 times higher than that of MoS2-Bulk/wax, and the corresponding bandwidth with effective attenuation (<-10

  2. Adding silanes to MMA: the effects on the water absorption, adhesive strength and mechanical properties of acrylic denture base resins.

    PubMed

    Kanie, T; Fujii, K; Arikawa, H; Inoue, K

    2000-12-01

    The adhesive strength of porcelain artificial teeth and polymethylmethacrylates (PMMAs), which contained silanes with various number of vinyl or ethoxy groups, and the mechanical and physical properties of the PMMAs were measured. Four types of PMMAs with silanes showed high adhesive shear strength and caused fractures in the porcelain. Water absorption of the PMMAs increased with the addition of silane, but that of one type with silane was almost the same as the PMMA only type. The flexural strengths of the PMMAs with silane, except for one type, showed no significant differences compared with that of PMMA (p < 0.05). The Tg levels of all PMMAs with silane fell less than that of PMMA. From these results, it was found that PMMA with silane from three vinyl groups and one ethoxy group showed excellent chemical bonding to porcelain and low water absorption.

  3. Electric field modulation of magnetic anisotropy and microwave absorption properties in Fe50Ni50/Teflon composite films

    NASA Astrophysics Data System (ADS)

    Xia, Zhenjun; He, Jun; Ou, Xiulong; Wang, Yu; He, Shuli; Zhao, Dongliang; Yu, Guanghua

    2016-05-01

    Fe50Ni50 nanoparticle films with the size about 6 nm were deposited by a high energetic cluster deposition source. An electric field of about 0 - 40 kV was applied on the sample platform when the films were prepared. The field assisted deposition technique can dramatically induce in-plane magnetic anisotropy. To probe the microwave absorption properties, the Fe50Ni50 nanoparticles were deliberately deposited on the dielectric Teflon sheet. Then the laminated Fe50Ni50/Teflon composites were used to do reflection loss scan. The results prove that the application of electric field is an effective avenue to improve the GHz microwave absorption performance of our magnetic nanoparticles films expressed by the movement of reflection loss peak to high GHz region for the composites.

  4. The dependence of C IV broad absorption line properties on accompanying Si IV and Al III absorption: relating quasar-wind ionization levels, kinematics, and column densities

    SciTech Connect

    Filiz Ak, N.; Brandt, W. N.; Schneider, D. P.; Trump, J. R.; Hall, P. B.; Anderson, S. F.; Hamann, F.; Myers, Adam D.; Pâris, I.; Petitjean, P.; Ross, Nicholas P.; Shen, Yue; York, Don

    2014-08-20

    We consider how the profile and multi-year variability properties of a large sample of C IV Broad Absorption Line (BAL) troughs change when BALs from Si IV and/or Al III are present at corresponding velocities, indicating that the line of sight intercepts at least some lower ionization gas. We derive a number of observational results for C IV BALs separated according to the presence or absence of accompanying lower ionization transitions, including measurements of composite profile shapes, equivalent width (EW), characteristic velocities, composite variation profiles, and EW variability. We also measure the correlations between EW and fractional-EW variability for C IV, Si IV, and Al III. Our measurements reveal the basic correlated changes between ionization level, kinematics, and column density expected in accretion-disk wind models; e.g., lines of sight including lower ionization material generally show deeper and broader C IV troughs that have smaller minimum velocities and that are less variable. Many C IV BALs with no accompanying Si IV or Al III BALs may have only mild or no saturation.

  5. Porous Three-Dimensional Flower-like Co/CoO and Its Excellent Electromagnetic Absorption Properties.

    PubMed

    Lv, Hualiang; Liang, Xiaohui; Ji, Guangbin; Zhang, Haiqian; Du, Youwei

    2015-05-13

    The porous three-dimensional (3-D) flower structures assembled by numerous ultrathin flakes were favor for strengthen electromagnetic absorption capability. However, it still remains a big challenge to fabricate such kind of materials. In this study, an easy and flexible two-step method consisting of hydrothermal and subsequent annealing process have been developed to synthesize the porous 3-D flower-like Co/CoO. Interestingly, we found that the suitable heat treatment temperature played a vital role on the flower-like structure, composition, and electromagnetic absorption properties. In detail, only in the composite treated with 400 °C can we gain the porous 3-D flower structure. If the annealing temperature were heated to 300 °C, the Co element was unable to generate. Moreover, when the annealing temperature increased from 400 to 500 °C, these flower-like structures were unable to be kept because the enlarged porous diameter would wreck the flower frame. Moreover, these 3-D porous flower-like structures presented outstanding electromagnetic absorption properties. For example, such special structure enabled an optimal reflection loss value of -50 dB with the frequency bandwidth ranged from 13.8 to 18 GHz. The excellent microwave absorption performance may attribute to the high impedance matching behavior and novel dielectric loss ability. Additionally, it can be supposed that this micrometer-size flower structure was more beneficial to scatter the incident electromagnetic wave. Meanwhile, the rough surface of the ultrathin flake is apt to increase the electromagnetic scattering among the leaves of the flower due to their large spacing and porous features.

  6. Passive element enriched photoacoustic computed tomography (PER PACT) for simultaneous imaging of acoustic propagation properties and light absorption.

    PubMed

    Jose, Jithin; Willemink, Rene G H; Resink, Steffen; Piras, Daniele; van Hespen, J C G; Slump, Cornelis H; Steenbergen, Wiendelt; van Leeuwen, Ton G; Manohar, Srirang

    2011-01-31

    We present a 'hybrid' imaging approach which can image both light absorption properties and acoustic transmission properties of an object in a two-dimensional slice using a computed tomography (CT) photoacoustic imager. The ultrasound transmission measurement method uses a strong optical absorber of small cross-section placed in the path of the light illuminating the sample. This absorber, which we call a passive element acts as a source of ultrasound. The interaction of ultrasound with the sample can be measured in transmission, using the same ultrasound detector used for photoacoustics. Such measurements are made at various angles around the sample in a CT approach. Images of the ultrasound propagation parameters, attenuation and speed of sound, can be reconstructed by inversion of a measurement model. We validate the method on specially designed phantoms and biological specimens. The obtained images are quantitative in terms of the shape, size, location, and acoustic properties of the examined heterogeneities.

  7. Experiences of t-PA use in moderate-to-severe hepatic veno-occlusive disease after hematopoietic SCT: is it still reasonable to use t-PA?

    PubMed

    Yoon, J-H; Min, W-S; Kim, H-Je; Kim, J-H; Shin, S-H; Yahng, S-A; Lee, S-E; Cho, B-S; Eom, K-S; Kim, Y-J; Lee, S; Min, C-K; Cho, S-G; Kim, D-W; Lee, J-W; Park, C-W

    2013-11-01

    Hepatic veno-occlusive disease (VOD) remains one of the most severe complications of hematopoietic SCT (HSCT). Anticoagulation and thrombolytic therapies using tissue-plasminogen activator (t-PA) have been used, but are reported to be ineffective and are associated with significant bleeding complications. We analyzed 56 moderate-to-severe post HSCT hepatic VOD cases treated with t-PA. We analyzed clinical outcomes according to the maximal daily dose of t-PA (t-PAmax) and the severity of VOD. Patients were stratified by t-PAmax10 mg (n=37) vs t-PAmax>10 mg (n=19). A higher t-PAmax was associated with increased mortality. Bleeding complications were more likely at higher t-PAmax in both moderate and severe VOD (P=0.036, 0.063), especially if patients had concomitant use of anticoagulants (36.4% vs 13.3%). In moderate VOD, the response rate was 86.4% for t-PAmax10 mg/day and 80% for t-PAmax>10 mg compared with 33.3% and 7.1%, respectively, for severe VOD (P=0.106). The 5-year OS in moderate and severe VOD was 49% and 7%, respectively, and it was 32% for t-PAmax10 mg and 18% for t-PAmax>10 mg. Our data demonstrate that lower bleeding complications and bleeding-related deaths may result from strict limitations on the t-PAmax without concomitant use of anticoagulation therapy. However, the overall response and survival outcomes should be re-evaluated by a well-validated study in the future.

  8. Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, P. G.

    1986-01-01

    After long arduous work with the simulator, measurements of the refractivity and absorptivity of nitrogen under conditions similar to those for Titan were completed. The most significant measurements, however, were those of the microwave absorption from gaseous ammonia under simulated conditions for the Jovian atmospheres over wavelengths from 1.3 to 22 cm. The results of these measurements are critical in that they confirm the theoretical calculation of the ammonia opacity using the Ben-Reuven lineshape. The application of both these results, and results obtained previously, to planetary observations at microwave frequencies were especially rewarding. Applications of the results for ammonia to radio astronomical observations of Jupiter in the 1.3 to 20 cm wavelength range and the application of results for gaseous H2SO4 under simulated Venus conditions are discussed.

  9. Microwave heating behavior and microwave absorption properties of barium titanate at high temperatures

    NASA Astrophysics Data System (ADS)

    Kashimura, K.; Sugawara, H.; Hayashi, M.; Mitani, T.; Shinohara, N.

    2016-06-01

    The temperature dependence of the microwave absorption behavior of BaTiO3 particles was investigated over various frequencies and temperatures of 25-1000 ∘C. First, using both the coaxial transmission line method and the cavity perturbation method by a network analyzer, the real and imaginary parts of the relative permittivity of BaTiO3 ( ɛr ' and ɛr ″ , respectively) were measured, in order to improve the reliability of the data obtained at 2.45 GHz. The imaginary parts of the relative permittivity as measured by the two methods were explored by their heating behaviors. Furthermore, the temperature dependence of the microwave absorption behavior of BaTiO3 particles was investigated for frequencies of 2.0-13.5 GHz and temperatures of 25-1000 ∘C using the coaxial transmission line method.

  10. Visible light absorption and photo-sensitizing properties of spinach leaves and beetroot extracted natural dyes.

    PubMed

    Sengupta, D; Mondal, B; Mukherjee, K

    2015-09-05

    Herein, chlorophyll and betalain dyes are extracted from fresh spinach leaves and beetroots. Fourier transform infrared spectra are used to identify the characteristic peaks of the extracted dyes. UV-vis light absorption characteristics of the dyes and their mixed counterpart are investigated by varying their pH and temperature. These dyes are used as photo sensitizer for fabrication of zinc oxide photo-anode based dye sensitized solar cells (DSSCs). The photo-voltaic characteristics of the developed DSSCs are measured under simulated solar light (power of incident light 100 mW cm(-2) from Air Mass 1.5G). The solar to electric conversion efficiencies for the chlorophyll, betalain and mixed dye based solar cells are estimated as 0.148%, 0.197% and 0.294% respectively. The highest conversion efficiency for mixed dye based solar cell is attributed due to the absorption of wider range of solar spectrum.

  11. Visible light absorption and photo-sensitizing properties of spinach leaves and beetroot extracted natural dyes

    NASA Astrophysics Data System (ADS)

    Sengupta, D.; Mondal, B.; Mukherjee, K.

    2015-09-01

    Herein, chlorophyll and betalain dyes are extracted from fresh spinach leaves and beetroots. Fourier transform infrared spectra are used to identify the characteristic peaks of the extracted dyes. UV-vis light absorption characteristics of the dyes and their mixed counterpart are investigated by varying their pH and temperature. These dyes are used as photo sensitizer for fabrication of zinc oxide photo-anode based dye sensitized solar cells (DSSCs). The photo-voltaic characteristics of the developed DSSCs are measured under simulated solar light (power of incident light 100 mW cm-2 from Air Mass 1.5G). The solar to electric conversion efficiencies for the chlorophyll, betalain and mixed dye based solar cells are estimated as 0.148%, 0.197% and 0.294% respectively. The highest conversion efficiency for mixed dye based solar cell is attributed due to the absorption of wider range of solar spectrum.

  12. What Do We Really Know about the EdTPA? Research, PACT, and Packaging a Local Teacher Performance Assessment for National Use

    ERIC Educational Resources Information Center

    Hébert, Cristyne

    2017-01-01

    This article calls attention to the overreliance on research about the Performance Assessment for California Teachers (PACT)--often labeled edTPA's predecessor--as justification for the edTPA. The article argues that the distinctions between the assessments are too vast to rely on PACT data to support the edTPA, given the localized nature of PACT…

  13. Preservice Teachers' Adaptations to Tensions Associated with the edTPA during Its Early Implementation in New York and Washington States

    ERIC Educational Resources Information Center

    Meuwissen, Kevin W.; Choppin, Jeffrey M.

    2015-01-01

    The edTPA is a teaching performance assessment (TPA) that the states of New York and Washington implemented as a licensure requirement in 2013. While TPAs are not new modes of assessment, New York and Washington are the first states to use the edTPA specifically as a compulsory, high-stakes policy lever in an effort to strengthen the quality and…

  14. Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, P. G.

    1985-01-01

    Radio absorptivity data for the Venus middle atmosphere (1 to 6 atm, temperatures from 500 to 575K) obtained from spacecraft radio occultation experiments (at 3.6 to 13.4 cm wavelengths) and earth-based radio astronomical observations (1 to 3 cm wavelength range) are compared to laboratory observations at the latter wavelength range under simulated Venus conditions to infer abundances of microwave-absorbing atmospheric constituents, i.e. H2SO4 in a CO2 atmosphere.

  15. Aerosol Scattering and Absorption Properties Over the Central Himalayan Location Nainital: Results from Gvax

    NASA Astrophysics Data System (ADS)

    Gogoi, M. M.; Babu, S.; Nair, V. S.; Satheesh, S.; Naja, M.; Kotamarthi, V. R.

    2012-12-01

    Extensive characterization of aerosols over a central Himalayan location, Nainital (29.4° N, 79.5° E, 1958 m amsl) were carried out during June 2011 to March 2012 under the Ganges Valley Aerosol Experiment (GVAX). Owing to the highly turbid, persistent and increasing aerosol concentration over the Ganges Valley in northern India, their influence on surface dimming, mid-tropospheric warming and monsoon circulations, the experimental site Nainital is best suited for studying the regional distribution of complex aerosol sources, their transport and direct and indirect radiative forcing mechanisms. During the study period, aerosol scattering (absorption) coefficients showed values as high as > 500 Mm-1 (> 50 Mm-1) in local noon time during the onset of winter and early spring and as low as < 300 Mm-1 (< 40 Mm-1) during the summer months. Consequently, aerosol single scattering albedo (SSA) decreased in winter (< 0.9, for 45% of occurrences) with large day-to-day modulations and higher values (> 0.9, for 81% of occurrences) during summer. Based on the spectral distribution of scattering coefficients, fine mode aerosols dominate the summer compared to winter season. The strong absorption during the winter and early spring is associated with the prevalence of biomass burning aerosols and/or dust as reveal by the steep spectral dependence of absorption coefficients (αabs >2.0). These observed seasonal variations are attributed to the dynamics of the atmospheric boundary layer as well as the influence of long range transport over the Himalayan location.

  16. Flexible and Thermostable Graphene/SiC Nanowire Foam Composites with Tunable Electromagnetic Wave Absorption Properties.

    PubMed

    Han, Meikang; Yin, Xiaowei; Hou, Zexin; Song, Changqing; Li, Xinliang; Zhang, Litong; Cheng, Laifei

    2017-04-05

    Three-dimensional (3D) flexible foams consisting of reduced graphene oxides (rGO) and in situ grown SiC nanowires (NWs) were prepared using freeze-drying and carbothermal reduction processes. By means of incorporating SiC nanowires into rGO foams, both the thermostability and electromagnetic absorption of the composites were improved. It was demonstrated that rGO/SiC NW foams were thermostable beyond ∼630 °C (90% weight retention in air atmosphere). As expected, rGO/SiC NW foams in the poly(dimethylsiloxane) matrix achieved effective absorption in the entire X-band (8.2-12.4 GHz) with a thinner thickness (3 mm) in comparison with those of the pure rGO foams. It is revealed that SiC nanowires with abundant stacking faults, twinning interfaces, and bridged junctions play an important role in the enhanced electromagnetic absorption performance, in addition to the contribution of interconnected graphene networks. Hierarchical rGO/SiC NW foams not only are efficient absorbers in the critical environments but also can be applied in photocatalytic and thermal-management fields.

  17. The effects of pH and surfactants on the absorption and fluorescence properties of ochratoxin A and zearalenone.

    PubMed

    Li, Taihua; Kim, Bo Bae; Ha, Tae Hwan; Shin, Yong-Beom; Kim, Min-Gon

    2015-11-01

    The pH and surfactant dependencies of the absorption and fluorescence properties of ochratoxin A (OTA) and zearalenone (ZEN), the main mycotoxins found as contaminants in foods and feeds, were evaluated. Three surfactants with different ionic properties were investigated, namely sodium dodecyl sulfate (SDS, anionic), Tween 20 (nonionic) and hexadecyltrimethylammonium bromide (CTAB, cationic). The results show that the effects of pH on the absorption wavelength maxima and fluorescence efficiencies of the mycotoxins, which are a consequence of the presence of acidic phenol and/or carboxyl containing fluorophores, are dependent on the ionic nature of the added surfactants. Specifically, the fluorescence responses to pH changes of OTA and ZEN are similar in the presence or absence of Tween 20 and SDS. By contrast, the pH-dependent fluorescence properties of these mycotoxins are altered when CTAB is present in the solutions. Moreover, unlike OTA, ZEN in aqueous solution displays almost no fluorescence. However, fluorescence enhancement takes place when surfactants are present in aqueous solutions of this mycotoxin. The results of this study demonstrate that the different microenvironments, present in the organized micellar systems created by the individual surfactants, can be potentially employed to modulate the sensitivities and selectivities of the fluorescence detection of OTA or ZEN.

  18. Observation of confinement effects through liner and nonlinear absorption spectroscopy in cuprous oxide

    NASA Astrophysics Data System (ADS)

    Sekhar, H.; Rakesh Kumar, Y.; Narayana Rao, D.

    2015-02-01

    Cuprous oxide nano clusters, micro cubes and micro particles were successfully synthesized by reducing copper (II) salt with ascorbic acid in the presence of sodium hydroxide via a co-precipitation method. The X-ray diffraction studies revealed the formation of pure single phase cubic. Raman spectrum shows the inevitable presence of CuO on the surface of the Cu2O powders which may have an impact on the stability of the phase. Transmission electron microscopy (TEM) data revealed that the morphology evolves from nanoclusters to micro cubes and micro particles by increasing the concentration of NaOH. Linear optical measurements show that the absorption peak maximum shifts towards red with changing morphology from nano clusters to micro cubes and micro particles. The nonlinear optical properties were studied using open aperture Z-scan technique with 532 nm, 6 ns laser pulses. Samples exhibited saturable as well as reverse saturable absorption. The results show that the transition from SA to RSA is ascribed to excited-state absorption (ESA) induced by two-photon absorption (TPA) process. Due to confinement effects (enhanced band gap) we observed enhanced nonlinear absorption coefficient (βeff) in the case of nano-clusters compared to their micro-cubes and micro-particles.

  19. Enhanced nonlinear optical absorption and optical limiting properties of superparamagnetic spinel zinc ferrite decorated reduced graphene oxide nanostructures

    NASA Astrophysics Data System (ADS)

    Saravanan, M.; T. C., Sabari Girisun

    2017-01-01

    Nonlinear absorption and optical limiting properties of ZnFe2O4-rGO magnetic nanostructures was investigated by the Z-scan technique using Q-switched Nd:YAG laser (5 ns, 532 nm, 10 Hz) as an excitation source. Excited state absorption was the dominant process responsible for the observed nonlinearity in ZnFe2O4 decorated rGO which arises due to photo-generated charge carriers in the conduction band of zinc ferrite and increases in defects at the surface of rGO due to the incorporation of ZnFe2O4. The magnitude of the nonlinear absorption co-efficient was found to be in the order of 10-10 m/W. A noteworthy enhancement in the third-order NLO properties in ZnFe2O4-(15 wt%) rGO with those of individual counter parts and well known graphene composites was reported. Role of induced defects states (sp3) arising from the functionalization of rGO in the enhancement of NLO response was explained through Raman studies. Earlier incorporation and distribution of ZnFe2O4 upon GO through one-step hydrothermal method was analyzed by XRD and FTIR. Formation of (nanospheres/nanospindles) ZnFe2O4 along with reduction of graphene oxide was confirmed through TEM analysis. VSM studies showed zinc ferrite decorated rGO posseses superparamagnetic behavior. The tuning of nonlinear optical and magnetic behavior with variation in the content of spinel ferrites upon reduced graphene oxide provides an easy way to attain tunable properties which are exceedingly required in both optoelectronics and photothermal therapy applications.

  20. Effect of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) upon membrane ionic exchanges in sea urchin eggs

    SciTech Connect

    Ciapa, B.; Payan, P. ); Allemand, D. )

    1989-12-01

    The effect of TPA (12-O-tetradecanoylphorbol-13-acetate) upon ionic exchanges was investigated in eggs of the sea urchin Arbacia lixula. Ouabain-sensitive {sup 86}Rb uptake and amiloride-sensitive {sup 24}Na influx were dramatically stimulated after TPA addition, indicating an enhancement of total ionic permeabilities. Stimulation by TPA of both Na{sup +}/H{sup +} and Na{sup +}/K{sup +} exchanges was canceled by amiloride, suggesting that activation of protein kinase C elicits, via Na{sup +}/H{sup +} activity, stimulation of the sodium pump. However, TPA did not stimulate sodium pump activity and Na{sup +}/H{sup +} exchange at the same rate as fertilization, probably because of an absence of calcium-dependent events. Further fertilization of TPA pretreated eggs triggered an enhancement of sodium pump activity when the TPA treatment duration did not exceed 10 minutes. It is suggested that TPA activates preexisting transporting mechanisms in plasma membranes of unfertilized eggs (Na{sup +} stat, pH stat).

  1. An analysis of AERONET aerosol absorption properties and classifications representative of aerosol source regions

    NASA Astrophysics Data System (ADS)

    Giles, D. M.; Holben, B. N.; Eck, T. F.; Sinyuk, A.; Smirnov, A.; Slutsker, I.; Dickerson, R. R.; Thompson, A. M.; Schafer, J. S.

    2012-09-01

    Partitioning of mineral dust, pollution, smoke, and mixtures using remote sensing techniques can help improve accuracy of satellite retrievals and assessments of the aerosol radiative impact on climate. Spectral aerosol optical depth (τ) and single scattering albedo (ωo) from Aerosol Robotic Network (AERONET) measurements are used to form absorption (i.e., ωo and absorption Ångström exponent (αabs)) and size (i.e., extinction Ångström exponent (αext) and fine mode fraction of τ) relationships to infer dominant aerosol types. Using the long-term AERONET data set (1999-2010), 19 sites are grouped by aerosol type based on known source regions to (1) determine the averageωo and αabs at each site (expanding upon previous work), (2) perform a sensitivity study on αabs by varying the spectral ωo, and (3) test the ability of each absorption and size relationship to distinguish aerosol types. The spectral ωo averages indicate slightly more aerosol absorption (i.e., a 0.0 < δωo ≤ 0.02 decrease) than in previous work, and optical mixtures of pollution and smoke with dust show stronger absorption than dust alone. Frequency distributions of αabs show significant overlap among aerosol type categories, and at least 10% of the αabs retrievals in each category are below 1.0. Perturbing the spectral ωo by ±0.03 induces significant αabs changes from the unperturbed value by at least ˜±0.6 for Dust, ˜±0.2 for Mixed, and ˜±0.1 for Urban/Industrial and Biomass Burning. The ωo440nm and αext440-870nmrelationship shows the best separation among aerosol type clusters, providing a simple technique for determining aerosol type from surface- and future space-based instrumentation.

  2. Effects of gamma-ray irradiation on mechanical properties, osteoconductivity, and absorption of porous hydroxyapatite/collagen.

    PubMed

    Kawasaki, Yuichi; Sotome, Shinichi; Yoshii, Toshitaka; Torigoe, Ichiro; Maehara, Hidetsugu; Sugata, Yumi; Hirano, Masahiro; Mochizuki, Naomi; Shinomiya, Kenichi; Okawa, Atsushi

    2010-01-01

    In this study, the effects of gamma-ray irradiation on the mechanical properties, absorbability, and osteoconductivity of porous hydroxyapatite/collagen (HAp/Col) were investigated. Porous HAp/Col was exposed to 16, 25, 35, or 50 kGy of gamma-ray irradiation. The compressive elastic modulus showed irradiation dose-dependence, with a particularly pronounced decrease in the 50-kGy treatment group. An in vitro enzymatic digestion test showed that gamma-ray irradiation of porous HAp/Col resulted in accelerated degradation by collagenase. For in vivo studies, porous HAp/Col was transplanted into the back muscles or bone defects in the femoral condyle of rats. Specimens were obtained at 2, 4, and 8 weeks postoperatively. Absorption of the implants in the muscle was time- and irradiation dose-dependent, with notable absorption for the 35- and 50-kGy groups at 2 weeks. At the skeletal sites, porous HAp/Col demonstrated high osteoconductivity in all irradiation treatment groups. Interestingly, not only implant absorption but also bone formation was irradiation dose-dependent at early time points.

  3. Self-assembly of large-scale aggregates of porphyrin from its dimers and their absorption and luminescence properties

    NASA Astrophysics Data System (ADS)

    Udal'tsov, A. V.; Kazarin, L. A.; Sweshnikov, A. A.

    2001-05-01

    Properties of aggregates of protonated meso-tetraphenylporphine (TPP) dimers have been investigated by absorption and luminescence spectroscopies and scanning electron microscopy. It was found that the absorption and fluorescence spectra obtained at a low and several times higher concentration of porphyrin differ considerably. The changes in absorption spectra of TPP in the water-THF-glycerol (84:6:10, v/v) mixture in the presence of 0.4 N HCl with time and the appearance of a green precipitate after several days indicate aggregation of the porphyrin. The near IR emission at 1000 nm, which is assigned to the fluorescence of donor-acceptor water-porphyrin dimeric complex, is revealed in the fluorescence spectra of TPP in aqueous solution of THF in the presence of 0.4 N HCl at the low concentration of porphyrin on excitation at 465 nm. In contrast, the near IR emission is not observed in the solution with several times higher concentration of porphyrin, but a shoulder at ca 800 nm is appreciable in the corresponding spectrum. The large-scale aggregates of TPP with sizes approximately from 1 μm to several micrometers are found in thin films of the protonated porphyrin. It is proposed that the aggregates are formed as a result of self-assembly from different protonated porphyrin dimers and have an ordered structure.

  4. Optical absorption measurements and quantum-chemical simulations of optical properties of novel fluoro derivatives of pyrazoloquinoline

    NASA Astrophysics Data System (ADS)

    Brik, M. G.; Kuznik, W.; Gondek, E.; Kityk, I. V.; Uchacz, T.; Szlachcic, P.; Jarosz, B.; Plucinski, K. J.

    2010-05-01

    The results of experimental research and quantum-chemical simulations of the absorption spectra of 1-(4-fluorophenyl)-3,4-diphenyl, 3-(4-fluorophenyl)-1,4-diphenyl, and 4-(4-fluorophenyl)-1,3-diphenyl-pyrazolo[3,4- b] quinoline are presented. Although the fluorine atom is located on different phenyl rings in these molecules, the absorption spectra do not differ significantly. Semi-empirical AM1, PM3 and RM1 methods, as well as ab initio ADF code-based calculations were used to optimize geometry, calculate the infrared and visible spectra of the afore mentioned compounds and analyze the molecular orbitals schemes. The results of calculations are in good agreement with the experimental data. It was also demonstrated that the positions of the fluorescence maxima depend significantly on the solvent (contrary to the absorption spectra), in which the molecules are embedded, which allows for manipulating with fluorescence properties of the synthesized molecules by changing the solvent.

  5. Effect of the bio-absorbent on the microwave absorption property of the flaky CIPs/rubber absorbers

    NASA Astrophysics Data System (ADS)

    Cheng, Yang; Xu, Yonggang; Cai, Jun; Yuan, Liming; Zhang, Deyuan

    2015-09-01

    Microwave absorbing composites filled with flaky carbonyl iron particles (CIPs) and the bio-absorbent were prepared by using a two-roll mixer and a vulcanizing machine. The electromagnetic (EM) parameters were measured by a vector network analyzer and the reflection loss (RL) was measured by the arch method in the frequency range of 1-4 GHz. The uniform dispersion of the absorbents was verified by comparing the calculated RL with the measured one. The results confirm that as the bio-absorbent was added, the permittivity was increased due to the volume content of absorbents, and the permeability was enlarged owing to the volume content of CIPs and interactions between the two absorbents. The composite filled with bio-absorbents achieved an excellent absorption property at a thickness of 1 mm (minimum RL reaches -7.8 dB), and as the RL was less than -10 dB the absorption band was widest (2.1-3.8 GHz) at a thickness of 2 mm. Therefore, the bio-absorbent is a promising additive candidate on fabricating microwave absorbing composites with a thinner thickness and wider absorption band.

  6. The influence of recycled expanded polystyrene (EPS) on concrete properties: Influence on flexural strength, water absorption and shrinkage

    NASA Astrophysics Data System (ADS)

    Elsalah, Jamaleddin; Al-Sahli, Yosra; Akish, Ahmed; Saad, Omar; Hakemi, Abdurrahman

    2013-12-01

    Expanded polystyrene waste in a granular form was used as a lightweight aggregate in order to produce lightweight concretë Lightweight EPS concrete composites were produced by replacing the coarse aggregate, either partially or fully with equal volume of EPS aggregates. The coarse aggregate replacements levels used were 25, 50, 75, and 100%, which corresponded to (9.20, 18.40, 27.60, and 36.8%) from total volume. The investigation is directed towards the development and performance evaluation of the concrete composites containing EPS aggregates, without addition of either bonding additives, or super-plasticizers on some concrete properties such as flexure strength, water absorption and change in length (or shrinkage). Experimental results showed that a density reduction of 12% caused flexure strength to decrease by 25.3% at a replacement level of 25% EPS. However, the reduction percentage strongly depends upon the replacement level of EPS granules. Moreover, the lower strength concretes showed a higher water absorption values compared to higher strength concrete, i.e., increasing the volume percentage of EPS increases the water absorption as well as the negative strain (shrinkage). The negative strain was higher at concretes of lower density (containing a high amount of EPS aggregate). The water to cement ratio of EPS aggregate concrete is found to be slightly lower than that of conventional concrete.

  7. Optical absorption and scattering properties of bulk porcine muscle phantoms from interstitial radiance measurements in 650-900 nm range

    NASA Astrophysics Data System (ADS)

    Grabtchak, Serge; Montgomery, Logan G.; Whelan, William M.

    2014-05-01

    We demonstrated the application of relative radiance-based continuous wave (cw) measurements for recovering absorption and scattering properties (the effective attenuation coefficient, the diffusion coefficient, the absorption coefficient and the reduced scattering coefficient) of bulk porcine muscle phantoms in the 650-900 nm spectral range. Both the side-firing fiber (the detector) and the fiber with a spherical diffuser at the end (the source) were inserted interstitially at predetermined locations in the phantom. The porcine phantoms were prostate-shaped with ˜4 cm in diameter and ˜3 cm thickness and made from porcine loin or tenderloin muscles. The described method was previously validated using the diffusion approximation on simulated and experimental radiance data obtained for homogenous Intralipid-1% liquid phantom. The approach required performing measurements in two locations in the tissue with different distances to the source. Measurements were performed on 21 porcine phantoms. Spectral dependences of the effective attenuation and absorption coefficients for the loin phantom deviated from corresponding dependences for the tenderloin phantom for wavelengths <750 nm. The diffusion constant and the reduced scattering coefficient were very close for both phantom types. To quantify chromophore presence, the plot for the absorption coefficient was matched with a synthetic absorption spectrum constructed from deoxyhemoglobin, oxyhemoglobin and water. The closest match for the porcine loin spectrum was obtained with the following concentrations: 15.5 µM (±30% s.d.) Hb, 21 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The tenderloin absorption spectrum was best described by 30 µM Hb (±30% s.d), 19 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The higher concentration of Hb in tenderloin was consistent with a dark-red appearance of the tenderloin phantom. The method can be applied to a number of biological

  8. The Hubble Space Telescope quasar absorption line key project. 6: Properties of the metal-rich systems

    NASA Technical Reports Server (NTRS)

    Bergeron, Jacqueline; Petitjean, Patrick; Sargent, W. L. W.; Bahcall, John N.; Boksenberg, Alec; Hartig, George F.; Jannuzi, Buell T.; Kirhakos, Sofia; Savage, Blair D.; Schneider, Donald P.

    1994-01-01

    We present an analysis of the properties of a sample of 18 metal-rich, low-redshift z(sub abs) much less than z(sub em) absorbers seen in low- and medium-resolution spectra obtained for the Quasar Absorption Line Key Project with the Hubble Space Telescope Faint Object Spectrograph (HST/FOS). For most of the C IV and Lyman-limit systems, observations in the optical wavelength range of the expected associated Mg II absorption are available. As at high redshift (z approximately 2), there are two subclasses of absorbers which are characterized by the presence or absence of MG II absorption. However, some low-redshift Mg II and Fe absorptions originate from regions optically thin to UV ionizing photons and thus, at low redshift, the low-ionization systems do not always trace high opacities, as is the case at high redshift. This implies that the mean ionization state of metal-rich, optically thin absorbing clouds falls with decreasing redshift, which is consistent with the hypothesis that the gas is photoionized by the metagalactic UV background radiation field. Two main constraints are derived from the analysis of the Lyman-limit sample, assuming photoionization models are valid. First, a low opacity to ionizing photons (tau(sub LL) approximately less than 1), as observed for several Mg II-Fe II systems at z approximately 0.5, sets limits on the ionization level of hydrogen, thus on the total hydrogen column density and the heavy element abundances, (Z/H) approximately -0.5 to -0.3. Second, the dimensions of individual Mg II clouds are smaller than at high redshift by a factor 3-10. At z approximately greater than 0.6, the O VI absorption doublet is detected in four of the five z(sub abs) much less than z(sub em) systems for which the O VI wavelength range has been observed, whereas the associated N V doublet is detected in only two cases. This suggests that the presence of a high-ionization O VI phase is a general property of z approximately 0.6-1 absorption systems

  9. 'Diamondlike' carbon films - Optical absorption, dielectric properties, and hardness dependence on deposition parameters

    NASA Technical Reports Server (NTRS)

    Natarajan, V.; Lamb, J. D.; Woollam, J. A.; Liu, D. C.; Gulino, D. A.

    1985-01-01

    An RF plasma deposition system was used to prepare amorphous 'diamondlike' carbon films. The source gases for the RF system include methane, ethylene, propane, and propylene, and the parameters varied were power, dc substrate bias, and postdeposition anneal temperature. Films were deposited on various substrates. The main diagnostics were optical absorption in the visible and in the infrared, admittance as a function of frequency, hardness, and Auger and ESCA spectroscopy. Band gap is found to depend strongly on RF power level and band gaps up to 2.7 eV and hardness up to 7 Mohs were found. There appears to be an inverse relationship between hardness and optical band gap.

  10. Change in soft magnetic properties of Fe-based metallic glasses during hydrogen absorption and desorption

    SciTech Connect

    Novak, L.; Lovas, A.; Kiss, L.F.

    2005-08-15

    The stress level can be altered in soft magnetic amorphous alloys by hydrogen absorption. The resulting changes in the soft magnetic parameters are reversible or irreversible, depending on the chemical composition. Some of these effects are demonstrated in Fe-B, Fe-W-B, and Fe-V-B glassy ribbons, in which various magnetic parameters are measured mainly during hydrogen desorption. The rate of hydrogen desorption is also monitored by measuring the pressure change in a hermetically closed bomb. The observed phenomena are interpreted on the basis of induced stresses and chemical interactions between the solute metal and hydrogen.

  11. Investigation of optical limiting properties of Aluminium nanoparticles prepared by pulsed laser ablation in different carrier media

    SciTech Connect

    Kuladeep, Rajamudili; Jyothi, L.; Narayana Rao, D.; Prakash, P.; Mayank Shekhar, S.; Durga Prasad, M.

    2013-12-28

    In this communication, we carried out the systematic investigation of nonlinear absorption and scattering properties of Aluminium nanoparticles (Al NPs) in various polar and non-polar solvents. Al NPs were synthesized with pulsed Nd:YAG laser operated at 1064 nm by ablating Al target in polar and non-polar liquid environment like chloroform, chlorobenzene, toluene, benzene, and carbon tetrachloride. Synthesized Al NPs colloids of various solvents differ in appearance and UV-Vis extinction spectra exhibit absorption in the UV region. The characterization of Al NPs performed by Transmission electron microscopy (TEM) studies reveal that NPs are made up of a well crystallized Al inner part (bright zone) embedded with an amorphous metal Al shell (dark region). Growth, aggregation, and precipitation mechanisms which influence the optical properties and stability of NPs are found to be related to the dipole moment of the surrounding liquid environment. The nonlinear absorption and scattering studies are performed by open aperture Z-scan technique with 532 nm under nanosecond pulse excitation. The Z-scan measurements are fitted theoretically to estimate both two-photon absorption (TPA) and nonlinear scattering (NLS) coefficients. In polar solvents like chlorobenzene, chloroform synthesized Al NPs exhibited higher TPA, NLS coefficient values, and lower optical limiting threshold values in comparison with partially polar solvent like toluene and non-polar solvents like benzene and carbontetrachloride. These results indicate the potential use of Al NPs as a versatile optical limiting material.

  12. Investigation of optical limiting properties of Aluminium nanoparticles prepared by pulsed laser ablation in different carrier media

    NASA Astrophysics Data System (ADS)

    Kuladeep, Rajamudili; Jyothi, L.; Prakash, P.; Mayank Shekhar, S.; Durga Prasad, M.; Narayana Rao, D.

    2013-12-01

    In this communication, we carried out the systematic investigation of nonlinear absorption and scattering properties of Aluminium nanoparticles (Al NPs) in various polar and non-polar solvents. Al NPs were synthesized with pulsed Nd:YAG laser operated at 1064 nm by ablating Al target in polar and non-polar liquid environment like chloroform, chlorobenzene, toluene, benzene, and carbon tetrachloride. Synthesized Al NPs colloids of various solvents differ in appearance and UV-Vis extinction spectra exhibit absorption in the UV region. The characterization of Al NPs performed by Transmission electron microscopy (TEM) studies reveal that NPs are made up of a well crystallized Al inner part (bright zone) embedded with an amorphous metal Al shell (dark region). Growth, aggregation, and precipitation mechanisms which influence the optical properties and stability of NPs are found to be related to the dipole moment of the surrounding liquid environment. The nonlinear absorption and scattering studies are performed by open aperture Z-scan technique with 532 nm under nanosecond pulse excitation. The Z-scan measurements are fitted theoretically to estimate both two-photon absorption (TPA) and nonlinear scattering (NLS) coefficients. In polar solvents like chlorobenzene, chloroform synthesized Al NPs exhibited higher TPA, NLS coefficient values, and lower optical limiting threshold values in comparison with partially polar solvent like toluene and non-polar solvents like benzene and carbontetrachloride. These results indicate the potential use of Al NPs as a versatile optical limiting material.

  13. Electromagnetic and microwave absorption properties of (Co2+-Si4+) substituted barium hexaferrites and its polymer composite

    NASA Astrophysics Data System (ADS)

    Abbas, S. M.; Chatterjee, R.; Dixit, A. K.; Kumar, A. V. R.; Goel, T. C.

    2007-04-01

    The electromagnetic (EM) and microwave absorption properties of (Co2+-Si4+) substituted barium hexaferrite compositions BaCox2+Fey+2Six+y4+Fe12-2x-2y+3O19 (x =0.9 and y =0.0, 0.05, and 0.2) and its polymer composites prepared from hexaferrite, polyaniline, and carbon powders dispersed in polyurethane matrix have been investigated at the microwave frequency range of the X band (8.2-12.4GHz). The hexaferrite compositions were synthesized by solid-state reaction technique, whereas polyaniline, by chemical route. The permeabilities of a ferrite are drastically reduced at higher gigahertz frequencies. The permittivities, however, can be enhanced by appropriate choice of composition and processing temperature. In the present ferrite composition, silicon content is taken in excess so as to convert some of the Fe3+ ions to Fe2+ ions. This conversion has been shown to enhance EM and absorption properties. Mössbauer spectroscopy on the samples establishes that addition of excess Si4+ converts some of the Fe3+ to Fe2+. The sintered ferrites have shown resonance phenomena, but the composites do not. The EM parameters ɛ', ɛ″, μ', and μ″ were measured using a vector network analyzer (Agilent, model PNA E8364B). These measured EM parameters were used to determine the absorption spectra at different sample thicknesses based on a model of a single layered plane wave absorber backed by a perfect conductor. The sintered ferrite composition (x =0.9 and y =0.05) showed the best absorption properties [a minimum reflection loss of -17.7to-14.3dB over the whole frequency range of the X band (8.2-12.4) for a sample thickness of just 0.8mm], and it is used in the composite absorbers in powder form along with other constituents. The optimized composite absorber has shown dielectric constant ɛ'˜11.5, dielectric loss ɛ″˜2.3, and a minimum reflection loss of -29dB at 10.97GHz with the -20dB bandwidth over the frequency range of 9.7-12.2GHz for a sample thickness of 2.0mm. The

  14. Influence of the Changjiang River on the light absorption properties of phytoplankton from the East China Sea

    NASA Astrophysics Data System (ADS)

    Wang, S. Q.; Ishizaka, J.; Yamaguchi, H.; Tripathy, S. C.; Hayashi, M.; Xu, Y. J.; Mino, Y.; Matsuno, T.; Watanabe, Y.; Yoo, S. J.

    2014-04-01

    Phytoplankton light absorption properties were investigated at the surface and subsurface chlorophyll a maximum (SCM) layer in the East China Sea (ECS), a marginal sea which is strongly influenced by the Changjiang discharge in summer. Results from ECS were compared with those from the Tsushima Strait (TS) where the influence of Changjiang discharge is less. The probable controlling factors, packaging effect (cell size) and pigment composition of total chlorophyll a (Tchl a)-specific absorption coefficient (aph*(λ)) were examined by the corresponding measurements of pigments identified by high-performance liquid chromatography. We observed distinct phytoplankton size structure and thereby absorption properties between ECS and TS. At the surface, mixed populations of micro-, nano- and pico-phytoplankton were recorded in ECS while pico-phytoplankton dominated in TS, generating a lower average aph*(λ) in ECS than in TS. Within SCM, average aph*(λ) was higher in ECS than in TS because of the dominance of nano- and micro-phytoplankton in ECS and TS, respectively. By pooling surface and SCM samples, we found regular trends in phytoplankton size-fraction versus Tchl a; and correlations between aph*(λ) and Tchl a consistent with previous observations for the global ocean in TS but not in ECS. In ECS phytoplankton size-fraction was not correlated with Tchl a, which consequently caused poor relationships between aph*(λ) and Tchl a. The abnormal values mainly originated from the surface low-salinity waters and SCM waters beneath them. At high Tchl a, aph*(λ) of these samples was substantially higher compared to the values in TS and from the global regressions, which was attributable to the lower micro-phytoplankton fraction, and higher nano- and/or pico-phytoplankton fractions in ECS. These observations indicated that the distinct light absorption properties of phytoplankton in ECS were possibly influenced by the Changjiang discharge. Our

  15. Study on EM-parameters and EM-wave absorption properties of materials with bio-flaky particles added

    NASA Astrophysics Data System (ADS)

    Zhang, Wenqiang; Zhang, Deyuan; Xu, Yonggang; McNaughton, Ryan

    2016-01-01

    Bio-flaky particles, fabricated through deposition of carbonyl iron on the surface of disk shaped diatomite, demonstrated beneficial performance on electromagnetic parameters. This paper will detail the improvements to the electromagnetic parameters and absorbing properties of traditional absorbing material generated by the addition of bio-flaky particles. Composites' electromagnetic parameters were measured using the transmission method. Calculated test results confirmed with bio-flaky particles were added, composites' permittivity increased due to the high permeability of bio-flaky particles. Secondly, the permeability of composites increased as a result of the increased volume content of iron particles. Composites with bio-flaky particles added exhibited superlative absorption properties at 0.5 mm thickness, with a maximum reflection loss of approximately -5.1 dB at 14.4 GHz.

  16. Shock wave equation of state experiments at multi-TPa pressures on NIF

    NASA Astrophysics Data System (ADS)

    Celliers, P. M.; Fratanduono, D. E.; Peterson, J. L.; Meezan, N. B.; MacKinnon, A. J.; Braun, D. G.; Millot, M.; Fry, J.; Boehm, K. J.; Collins, G. W.; Nikroo, A.; Fitzsimmons, P.

    2015-06-01

    The National Ignition Facility provides an unprecedented capability to generate steady, planar, ultra-high pressure shock waves (around 10 TPa) in solid samples. Building on successful laser shock equation of state experiments performed on a variety of other laser facilities, we have designed and fielded experiments to perform impedance match experiments on samples of C, Be, quartz and CH, in the range of 3 to 7 TPa. The experiments use a line-imaging VISAR as the primary diagnostic to measure the shock velocity in an Al reference standard and in an array of the four samples. Initial tests with the line-imaging VISAR show that the NIF is capable of driving shocks that are steady for several ns, with smooth planar breakout patterns over a 2 mm diameter spot. Initial results will be discussed. Prepared by LLNL under Contract DE-AC52-07NA27344.

  17. Synthesis of Absorption-Dominant Small Gold Nanorods and Their Plasmonic Properties.

    PubMed

    Jia, Henglei; Fang, Caihong; Zhu, Xiao-Ming; Ruan, Qifeng; Wang, Yi-Xiang J; Wang, Jianfang

    2015-07-07

    Absorption-dominant small Au nanorods with diameters of less than 10 nm are prepared using a facile seed-mediated growth method. The diameters of the small gold nanorods range from 6 to 9 nm, and their lengths vary from 16 to 45 nm. Their aspect ratios can be tailored from 2.7 to 4.7. As a result, the longitudinal plasmon resonance wavelengths are readily tunable from ∼720 nm to ∼830 nm by changing the seed-to-Au(III) molar ratio in the growth solution. The fractions of the scattering in the total extinction of the small Au nanorods are found to be in the range of 0.005 to 0.025 with finite-difference time-domain simulations, confirming that the extinction values of these small Au nanorods are dominantly contributed to by the light absorption. Moreover, the small Au nanorod sample is coated with a dense silica layer for photothermal therapy with three cell lines. It shows improved photothermal therapy performance compared to a large Au nanorod sample for the same cellular Au contents. Our study suggests that small Au nanorods are promising light absorbers and photothermal therapy agents.

  18. Water absorption and moisture permeation properties of chitosan/poly(acrylamide-co-itaconic acid) IPC films.

    PubMed

    Bajpai, M; Bajpai, S K; Jyotishi, Pooja

    2016-03-01

    In this work, aqueous solutions of chitosan (Ch) and [poly(acrylamide(AAm)-co-itaconicacid(IA)] have been mixed to yield Ch/poly(AAm-co-IA) Inter-polyelectrolyte complex (IPC) films. The films were characterized by FTIR, X-ray diffraction (XRD) and thermo gravimetric analysis (TGA). There was remarkable increase in the crystalline nature of IPC films. The films were investigated for their water absorption capacity in the physiological fluid (PF) of pH 7.4 at 37 °C. The amount of IA present in the film forming solutions affected the water absorption behavior of the resulting films. The dynamic water uptake data were interpreted by various kinetic models. The effect of pH on the swelling ratio (SR) indicated that the films showed highest swelling in lower as well as higher pH media. The water vapor transmission rates (WVTR) were obtained in the range of 6000-6645 g/m(2)/day.

  19. Preparation and radar absorptive properties of BaFe12O19 -coated glass fiber

    NASA Astrophysics Data System (ADS)

    Jia, F.; Xu, M.; Bao, H. Q.; Cui, K.; Zhang, F.

    2016-07-01

    Traditional passive jamming materials such as chaff and foil showed some limitations in use because they can only reflect the electromagnetic wave. Therefore, to develop a kind of absorptive passive jamming material to make up for deficiencies of traditional passive jamming materials and improve the jamming efficiency is of great significance. In this paper, the BaFe12O19-coated glass fiber, used as a kind of radar absorptive chaff, was prepared by sol-gel dip-coating method. The effects of heat treatment temperature, heat treatment time and coating times on film quality, tensile strength and attenuation efficiency of the samples were discussed. The study shows that an increase of the heat treatment temperature and an extension of the heat treatment time is conducive to the growth of barium ferrite grain, while they would introduce the loss of chaff strength at the same time. In addition, multi-coating process can improve the film quality and attenuation efficiency of the sample. Data show that the 10 times coated samples have a best reflectivity of (15GHz, -6.65dB) and the bandwidth of reflectivity lower than -5dB is11.8 GHz. According to the test results, the prepared material has certain attenuation efficiency in the range of 2GHz-18GHz, having a high practical value.

  20. Study on preparation and microwave absorption property of the core-nanoshell composite materials doped with La.

    PubMed

    Wei, Liqiu; Che, Ruxin; Jiang, Yijun; Yu, Bing

    2013-12-01

    Microwave absorbing material plays a great role in electromagnetic pollution controlling, electromagnetic interference shielding and stealth technology, etc. The core-nanoshell composite materials doped with La were prepared by a solid-state reaction method, which is applied to the electromagnetic wave absorption. The core is magnetic fly-ash hollow cenosphere, and the shell is the nanosized ferrite doped with La. The thermal decomposition process of the sample was investigated by thermogravimetry and differential thermal analysis. The morphology and components of the composite materials were investigated by the X-ray diffraction analysis, the microstructure was observed by scanning electron microscope and transmission electron microscope. The results of vibrating sample magnetometer analysis indicated that the exchange-coupling interaction happens between ferrite of magnetic fly-ash hollow cenosphere and nanosized ferrite coating, which caused outstanding magnetic properties. The microwave absorbing property of the sample was measured by reflectivity far field radar cross section of radar microwave absorbing material with vector network analyzer. The results indicated that the exchange-coupling interaction enhanced magnetic loss of composite materials. Therefore, in the frequency of 5 GHz, the reflection coefficient can achieve -24 dB. It is better than single material and is consistent with requirements of the microwave absorbing material at the low-frequency absorption.

  1. Enhancing and broadening absorption properties of frequency selective surfaces absorbers using FeCoB-based thin film

    NASA Astrophysics Data System (ADS)

    Ren, Wenyi; Nie, Yan; Xiong, Xuan; Zhang, Cui; Zhou, Yan; Gong, Rongzhou

    2012-04-01

    In this paper, the influence of FeCoB-based magnetic film on the absorption properties of traditional frequency selective surface (FSS) was investigated experimentally. A single-layer Minkowski fractal planar frequency selective surface was chosen, and the laser etching technique was proposed to fabricate aluminum-based FSS (AFSS) samples. Magnetic films were prepared by radio frequency magnetron sputtering, with the targets of Fe40Co40B20 and SiO2. It is found that after the magnetic film is incorporated, the bandwidth under -10 dB increases by 33.3% from 5.08 to 6.78 GHz and the peak value of reflectivity decreases from -12.46 to -38.41 dB. The 3.1-mm-thick radar absorber is relatively light and could obtain the reflectivity of -38.41 with -20 dB bandwidth of 1.85 GHz. As a consequence, under the circumstance that the total thickness of the sample maintains relatively constant, the magnetic thin film can effectively improve the absorption properties of the sample.

  2. Luminescence and optical absorption properties of Nd(3+) ions in K-Mg-Al phosphate and fluorophosphate glasses.

    PubMed

    Surendra Babu, S; Babu, P; Jayasankar, C K; Joshi, A S; Speghini, A; Bettinelli, M

    2006-04-26

    Absorption and emission properties and fluorescence lifetimes for the [Formula: see text] transition of Nd(3+) ions embedded in P(2)O(5)-K(2)O-MgO-Al(2)O(3) (PKMA)-based glasses modified with AlF(3) and BaF(2) are reported at room temperature. The observed energy levels of Nd(3+) ions in these glasses have been analysed through a semi-empirical free-ion Hamiltonian model. The spin-orbit interaction and net electrostatic interaction experienced by the Nd(3+) ions follow the trend as PKMA>PKMA+AlF(3)> PKMA+BaF(2) glasses. Judd-Ofelt analysis has been carried out on the absorption spectra of 1.0 mol% Nd(3+)-doped glasses to predict the radiative properties for the fluorescent levels of the Nd(3+) ion. Branching ratios and stimulated emission cross-sections show that the [Formula: see text] transition of the glasses under investigation has the potential for laser applications. The Inokuti-Hirayama model has been applied to investigate the non-radiative relaxation of the Nd(3+) ion emitting state, (4)F(3/2). Based on the decay curve analysis, concentration quenching of the (4)F(3/2) emission has been attributed to a cross-relaxation process between the Nd(3+) ions.

  3. Spectrally Consistent Scattering, Absorption, and Polarization Properties of Atmospheric Ice Crystals at Wavelengths from 0.2 to 100 um

    NASA Technical Reports Server (NTRS)

    Yang, Ping; Bi, Lei; Baum, Bryan A.; Liou, Kuo-Nan; Kattawar, George W.; Mishchenko, Michael I.; Cole, Benjamin

    2013-01-01

    A data library is developed containing the scattering, absorption, and polarization properties of ice particles in the spectral range from 0.2 to 100 microns. The properties are computed based on a combination of the Amsterdam discrete dipole approximation (ADDA), the T-matrix method, and the improved geometric optics method (IGOM). The electromagnetic edge effect is incorporated into the extinction and absorption efficiencies computed from the IGOM. A full set of single-scattering properties is provided by considering three-dimensional random orientations for 11 ice crystal habits: droxtals, prolate spheroids, oblate spheroids, solid and hollow columns, compact aggregates composed of eight solid columns, hexagonal plates, small spatial aggregates composed of 5 plates, large spatial aggregates composed of 10 plates, and solid and hollow bullet rosettes. The maximum dimension of each habit ranges from 2 to 10,000 microns in 189 discrete sizes. For each ice crystal habit, three surface roughness conditions (i.e., smooth, moderately roughened, and severely roughened) are considered to account for the surface texture of large particles in the IGOM applicable domain. The data library contains the extinction efficiency, single-scattering albedo, asymmetry parameter, six independent nonzero elements of the phase matrix (P11, P12, P22, P33, P43, and P44), particle projected area, and particle volume to provide the basic single-scattering properties for remote sensing applications and radiative transfer simulations involving ice clouds. Furthermore, a comparison of satellite observations and theoretical simulations for the polarization characteristics of ice clouds demonstrates that ice cloud optical models assuming severely roughened ice crystals significantly outperform their counterparts assuming smooth ice crystals.

  4. Overexpression of connexin26 in the basal keratinocytes reduces sensitivity to tumor promoter TPA.

    PubMed

    Wang, Xiao; Ramirez, Angel; Budunova, Irina

    2010-07-01

    Connexin 26 is important in keratinocyte proliferation, differentiation and skin pathologies. Cx26 is barely expressed in normal adult epidermis, but its expression is induced during wound healing, psoriasis, and skin hyperplasia stimulated by tumor promoters. In hyperplastic proliferating epidermis, Cx26 is co-expressed with Cx43 typical for basal and suprabasal keratinocytes. As Cx26 and Cx43 can not form permeable gap junctions, their co-expression may alter the gap junctional communication between keratinocytes and induce proliferation. To test the effect of persistent co-expression of Cx26 and Cx43 in epidermis, we generated transgenic mice using keratin5 promoter to target Cx26 to basal Cx43-positive keratinocytes. We evaluated the effect of ectopic Cx26 on keratinocyte proliferation and differentiation in normal and 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-treated skin. The ectopic Cx26 expression in epidermis did not significantly affect skin development, keratinocyte differentiation and proliferation in newborn and adult skin. Unexpectedly, the proliferative effect of tumor promoter TPA was strongly decreased in epidermis of K5.Cx26 transgenics. This correlated with significant down-regulation of TPA-induced activity of protein kinase C (PKC) in K5.Cx26 mice.

  5. Scattering and Absorption Properties of Polydisperse Wavelength-sized Particles Covered with Much Smaller Grains

    NASA Technical Reports Server (NTRS)

    Dlugach, Jana M.; Mishchenko, Michael I.; Mackowski, Daniel W.

    2012-01-01

    Using the results of direct, numerically exact computer solutions of the Maxwell equations, we analyze scattering and absorption characteristics of polydisperse compound particles in the form of wavelength-sized spheres covered with a large number of much smaller spherical grains.The results pertain to the complex refractive indices1.55 + i0.0003,1.55 + i0.3, and 3 + i0.1. We show that the optical effects of dusting wavelength-sized hosts by microscopic grains can vary depending on the number and size of the grains as well as on the complex refractive index. Our computations also demonstrate the high efficiency of the new superposition T-matrix code developed for use on distributed memory computer clusters.

  6. Synthesis of one-dimensional potassium tungsten bronze with excellent near-infrared absorption property.

    PubMed

    Guo, Chongshen; Yin, Shu; Huang, Lijun; Sato, Tsugio

    2011-07-01

    Potassium tungsten oxide nanofibers were successfully synthesized via a facile hydrothermal reaction route in the presence of sulfate. After reduction under a reductive atmosphere of H(2)(5 vol %)/N(2), the potassium tungsten oxide transformed to potassium tungsten bronze. Because of the lack of free electrons, the potassium tungsten oxide (K(x)WO(3+x/2)) showed no NIR shielding performance; however, the potassium tungsten bronze (K(x)WO(3)) showed promising optical characteristics such as high transmittance for visible light, as well as high shielding performance for near-infrared lights, indicating its potential application as a solar filter. Meanwhile, the potassium tungsten bronze (K(x)WO(3)) showed strong absorption of near-infrared light and instantaneous conversion of photoenergy to heat.

  7. Scattering and absorption properties of polydisperse wavelength-sized particles covered with much smaller grains

    NASA Astrophysics Data System (ADS)

    Dlugach, Janna M.; Mishchenko, Michael I.; Mackowski, Daniel W.

    2012-12-01

    Using the results of direct, numerically exact computer solutions of the Maxwell equations, we analyze scattering and absorption characteristics of polydisperse compound particles in the form of wavelength-sized spheres covered with a large number of much smaller spherical grains. The results pertain to the complex refractive indices 1.55+i0.0003, 1.55+i0.3, and 3+i0.1. We show that the optical effects of “dusting” wavelength-sized hosts by microscopic grains can vary depending on the number and size of the grains as well as on the complex refractive index. Our computations also demonstrate the high efficiency of the new superposition T-matrix code developed for use on distributed memory computer clusters.

  8. Optical absorption and photoluminescence properties of Er3+ doped mixed alkali borate glasses.

    PubMed

    Ratnakaram, Y C; Kumar, A Vijaya; Naidu, D Tirupathi; Rao, J L

    2005-07-01

    An investigations of the optical absorption and fluorescence spectra of 0.2 mol% Er2O3 in mixed alkali borate glasses of the type 67.8B2O3 x xLi2O(32-x)Na2O, 67.8B2O3 x xLi2O(32-x)K2O and 67.8B2O3 x xNa2O(32-x)K2O (where x = 8, 12, 16, 20 and 24) are presented. The glasses were obtained by quenching melts consisting of H3BO3, Li2CO3, Na2CO3, K2CO3 and Er2O3 (950-1100 degrees C, 1.5-2 h) between two brass plates. Spectroscopic parameters like Racah (E1, E2 and E3), spin-orbit (xi(4f)) and configuration interaction (alpha) parameters are deduced as function of x. Using Judd-Ofelt theory, Judd-Ofelt intensity parameters (omega2, omega4 and omega6) are obtained. Radiative and non-radiative transition rates (A(T) and W(MPR)), radiative lifetimes (tauR), branching ratios (beta) and integrated absorption cross-sections (sigma) have been computed for certain excited states of Er3+ in these mixed alkali borate glasses. Emission spectra have been studied for all the three Er3+ doped mixed alkali borate glasses. The present paper throws light on the trends observed in the intensity parameters, radiative lifetimes, branching ratios and emission cross-sections as a function of x in these borate glasses, keeping in view the effect of mixed alkalies in borate glasses.

  9. THE INTRINSIC FRACTIONS AND RADIO PROPERTIES OF LOW-IONIZATION BROAD ABSORPTION LINE QUASARS

    SciTech Connect

    Dai Xinyu; Shankar, Francesco; Sivakoff, Gregory R.

    2012-10-01

    Low-ionization (Mg II, Fe II, and Fe III) broad absorption line quasars (LoBALs) probe a relatively obscured quasar population and could be at an early evolutionary stage for quasars. We study the intrinsic fractions of LoBALs using the Sloan Digital Sky Survey (SDSS), Two Micron All Sky Survey, and Faint Images of the Radio Sky at Twenty cm survey. We find that the LoBAL fractions of the near-infrared (NIR) and radio samples are approximately 5-7 times higher than those measured in the optical sample. This suggests that the fractions measured in the NIR and radio bands are closer to the intrinsic fractions of the populations, and that the optical fractions are significantly biased due to obscuration effects, similar to high-ionization broad absorption line quasars (HiBALs). Considering a population of obscured quasars that do not enter the SDSS, which could have a much higher LoBAL fraction, we expect that the intrinsic fraction of LoBALs could be even higher. We also find that the LoBAL fractions decrease with increasing radio luminosities, again, similarly to HiBALs. In addition, we find evidence for increasing fractions of LoBALs toward higher NIR luminosities, especially for FeLoBALs with a fraction of {approx}18% at M{sub K{sub s}}< -31 mag. This population of NIR-luminous LoBALs may be at an early evolutionary stage of quasar evolution. To interpret the data, we use a luminosity-dependent model for LoBALs that yields significantly better fits than those from a pure geometric model.

  10. Introducing [Mn(CO)3(tpa-κ(3)N)](+) as a novel photoactivatable CO-releasing molecule with well-defined iCORM intermediates - synthesis, spectroscopy, and antibacterial activity.

    PubMed

    Nagel, Christoph; McLean, Samantha; Poole, Robert K; Braunschweig, Holger; Kramer, Thomas; Schatzschneider, Ulrich

    2014-07-14

    [Mn(CO)3(tpa-κ(3)N)]Br was prepared as a novel photoactivatable CO-releasing molecule (PhotoCORM) from [MnBr(CO)5] and tris(2-pyridylmethyl)amine (tpa) for the delivery of carbon monoxide to biological systems, with the κ(3)N binding mode of the tetradentate tpa ligand demonstrated by X-ray crystallography. The title compound is a CORM prodrug stable in solution in the dark for up to 16 h. However, photoactivation at 365 nm leads to CO release from the metal coordination sphere and transfer to haem proteins, as demonstrated by the standard myoglobin assay. Different iCORM intermediates could be detected with solution IR spectroscopy and assigned using DFT vibrational calculations. The antibacterial activity of the complex was studied on Escherichia coli. No effects were observed when the cultures were either kept in the dark in the presence of PhotoCORM or illuminated in the absence of metal complex. However, photoactivation of [Mn(CO)3(tpa-κ(3)N)]Br at 365 nm led to the appearance of the spectral signatures of CO-coordinated haems in the terminal oxidases of the bacterial electron transport chain in whole-cell UV/Vis absorption spectra. Significant internalization of the PhotoCORM was demonstrated by ICP-MS measurement of the intracellular manganese concentration. In particular when using medium with succinate as the sole carbon source, a very pronounced and concentration-dependent decrease in the E. coli growth rate could be observed upon illumination in the presence of metal complex, which is attributed to the constrained energy metabolism under these conditions and a strong indicator of terminal oxidase inhibition by carbon monoxide delivered from the PhotoCORM.

  11. Pro-Oxidant Role of Silibinin in DMBA/TPA Induced Skin Cancer: 1H NMR Metabolomic and Biochemical Study

    PubMed Central

    Sati, Jasmine; Mohanty, Biraja Prasad; Garg, Mohan Lal; Koul, Ashwani

    2016-01-01

    Silibinin, a major bioactive flavonolignan in Silybum marianum, has received considerable attention in view of its anticarcinogenic activity. The present study examines its anticancer potential against 7, 12-dimethylbenz(a)anthracene (DMBA) and 12-O-tetradecanoylphorbol-13-acetate (TPA) induced skin cancer. Male LACA mice were randomly segregated into 4 groups: Control, DMBA/TPA, Silibinin and Silibinin+DMBA/TPA. Tumors in DMBA/TPA and Silibinin+DMBA/TPA groups were histologically graded as squamous cell carcinoma. In the Silibinin+DMBA/TPA group, significant reduction in tumor incidence (23%), tumor volume (64.4%), and tumor burden (84.8%) was observed when compared to the DMBA/TPA group. The underlying protective mechanism of Silibinin action was studied at pre-initiation (2 weeks), post-initiation (10 weeks) and promotion (22 weeks) stages of the skin carcinogenesis. The antioxidant nature of Silibinin was evident at the end of 2 weeks of its treatment. However, towards the end of 10 and 22 weeks, elevated lipid peroxidation (LPO) levels indicate the pro-oxidative nature of Silibinin in the cancerous tissue. TUNEL assay revealed enhanced apoptosis in the Silibinin+DMBA/TPA group with respect to the DMBA/TPA group. Therefore, it may be suggested that raised LPO could be responsible for triggering apoptosis in the Silibinin+DMBA/TPA group. 1H Nuclear Magnetic Resonance (NMR) spectroscopy was used to determine the metabolic profile of the skin /skin tumors. Dimethylamine (DMA), glycerophosphocholine (GPC), glucose, lactic acid, taurine and guanine were identified as the major contributors for separation between the groups from the Principal Component Analysis (PCA) of the metabolite data. Enhanced DMA levels with no alteration in GPC, glucose and lactate levels reflect altered choline metabolism with no marked Warburg effect in skin tumors. However, elevated guanine levels with potent suppression of taurine and glucose levels in the Silibinin+DMBA/TPA group are

  12. Arachidonic acid enhances TPA-induced differentiation in human leukemia HL-60 cells via reactive oxygen species-dependent ERK activation.

    PubMed

    Chien, Chih-Chiang; Wu, Ming-Shun; Shen, Shing-Chuan; Yang, Liang-Yo; Wu, Wen-Shin; Chen, Yen-Chou

    2013-04-01

    The phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), is a potent stimulator of differentiation in human leukemia cells; however, the effects of arachidonic acid (AA) on TPA-induced differentiation are still unclear. In the present study, we investigated the contribution of AA to TPA-induced differentiation of human leukemia HL-60 cells. We found that treatment of HL-60 cells with TPA resulted in increases in cell attachment and nitroblue tetrazolium (NBT)-positive cells, which were significantly enhanced by the addition of AA. Stimulation of TPA-induced intracellular reactive oxygen species (ROS) production by AA was detected in HL-60 cells via a DCHF-DA analysis, and the addition of the antioxidant, N-acetyl-cysteine (NAC), was able to reduce TPA+AA-induced differentiation in accordance with suppression of intracellular peroxide elevation by TPA+AA. Furthermore, activation of extracellular-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) by TPA+AA was identified in HL-60 cells, and the ERK inhibitor, PD98059, but not the JNK inhibitor, SP600125, inhibited TPA+AA-induced NBT-positive cells. Suppression of TPA+AA-induced ERK protein phosphorylation by PD98059 and NAC was detected, and AA enhanced ERK protein phosphorylation by TPA was in HL-60 cells. AA clearly increased TPA-induced HL-60 cell differentiation, as evidenced by a marked increase in CD11b expression, which was inhibited by NAC and PD98059 addition. Eicosapentaenoic acid (EPA) as well as AA showed increased intracellular peroxide production and differentiation of HL-60 cells elicited by TPA. Evidence of AA potentiation of differentiation by TPA in human leukemia cells HL-60 via activation of ROS-dependent ERK protein phosphorylation was first demonstrated herein.

  13. Sensitive measurement of nonlinear absorption and optical limiting in undoped and Fe-doped ZnO quantum dots using pulsed laser

    NASA Astrophysics Data System (ADS)

    Sharma, D.; Malik, B. P.; Gaur, A.

    2016-11-01

    Zinc oxide quantum dots (QDs) with Fe-doping at different concentrations were prepared by chemical co-precipitation method. The prepared QDs were characterized by UV-Vis spectroscopy, X-ray diffraction and Z-scan technique. The sizes of QDs were found to be within 4.6-6.6 nm range. The nonlinear parameters viz. two-photon absorption coefficient (βTPA) and two-photon absorption cross-section (σTPA) were extracted with the help of open aperture Z-scan technique using nanosecond Nd:YAG laser operating at wavelength 532 nm. Higher values of βTPA and σTPA for Fe doped ZnO implied that they were potential materials for development of photonics devices and sensor protection applications. Fe doped sample (3 % by wt) was found to be the best optical limiter with limiting threshold intensity of 0.64 TW/cm2.

  14. Polarization and Thickness Dependent Absorption Properties of Black Phosphorus: New Saturable Absorber for Ultrafast Pulse Generation

    PubMed Central

    Li, Diao; Jussila, Henri; Karvonen, Lasse; Ye, Guojun; Lipsanen, Harri; Chen, Xianhui; Sun, Zhipei

    2015-01-01

    Black phosphorus (BP) has recently been rediscovered as a new and interesting two-dimensional material due to its unique electronic and optical properties. Here, we study the linear and nonlinear optical properties of BP flakes. We observe that both the linear and nonlinear optical properties are anisotropic and can be tuned by the film thickness in BP, completely different from other typical two-dimensional layered materials (e.g., graphene and the most studied transition metal dichalcogenides). We then use the nonlinear optical properties of BP for ultrafast (pulse duration down to ~786 fs in mode-locking) and large-energy (pulse energy up to >18 nJ in Q-switching) pulse generation in fiber lasers at the near-infrared telecommunication band ~1.5 μm. We observe that the output of our BP based pulsed lasers is linearly polarized (with a degree-of-polarization ~98% in mode-locking, >99% in Q-switching, respectively) due to the anisotropic optical property of BP. Our results underscore the relatively large optical nonlinearity of BP with unique polarization and thickness dependence, and its potential for polarized optical pulse generation, paving the way to BP based nonlinear and ultrafast photonic applications (e.g., ultrafast all-optical polarization switches/modulators, frequency converters etc.). PMID:26514090

  15. In vivo multispectral imaging of the absorption and scattering properties of exposed brain using a digital red-green-blue camera

    NASA Astrophysics Data System (ADS)

    Yoshida, Keiichiro; Ishizuka, Tomohiro; Mizushima, Chiharu; Nishidate, Izumi; Kawauchi, Satoko; Sato, Shunichi; Sato, Manabu

    2015-04-01

    To evaluate multi-spectral images of the absorption and scattering properties in the cerebral cortex of rat brain, we investigated spectral reflectance images estimated by the Wiener estimation method using a digital red-green-blue camera. A Monte Carlo simulation-based multiple regression analysis for the corresponding spectral absorbance images at nine wavelengths (500, 520, 540, 560, 570, 580, 600, 730, and 760 nm) was then used to specify the absorption and scattering parameters. The spectral images of absorption and reduced scattering coefficients were reconstructed from the absorption and scattering parameters. We performed in vivo experiments on exposed rat brain to confirm the feasibility of this method. The estimated images of the absorption coefficients were dominated by hemoglobin spectra. The estimated images of the reduced scattering coefficients had a broad scattering spectrum, exhibiting a larger magnitude at shorter wavelengths, corresponding to the typical spectrum of brain tissue published in the literature.

  16. Tuning the magnetic property of vacancy-defected graphyne by transition metal absorption

    SciTech Connect

    Bhattacharya, Barnali; Singh, Ngangbam Bedamani; Sarkar, Utpal

    2015-06-24

    In this work, we demonstrate a novel and simple approach to tune the electronic properties as well as magnetic properties of transition metal absorbed in vacancy-defected graphyne (VGY). A double vacancy has been introduced in the graphyne unit and TM atoms (V-Cu) are systematically doped in the vacant site. We find that combination of these two give rise to some interesting spintronics properties such as half-metalicity, and spin-select half-semiconductivity. Furthermore, the magnetic moments of TM absorbed vacancy-defected graphyne are found to be higher compare to TM absorbed graphyne. Although Ni absorbed graphyne is nonmagnetic in nature, we find that the Ni absorbed VGY behaves as half metal with a net magnetic moment of 2 µ{sub B} and can be used as spin filter. Thus, the TM absorbed vacancy-defected graphyne are more suitable candidate for magneto-optics and spintronics.

  17. Absorption Properties of Mediterranean Aerosols Obtained from Multi-year Ground-based and Satellite Remote Sensing Observations

    NASA Technical Reports Server (NTRS)

    Mallet, M.; Dubovik, O.; Nabat, P.; Dulac, F.; Kahn, R.; Sciare, J.; Paronis, D.; Leon, J. F.

    2013-01-01

    Aerosol absorption properties are of high importance to assess aerosol impact on regional climate. This study presents an analysis of aerosol absorption products obtained over the Mediterranean Basin or land stations in the region from multi-year ground-based AERONET and satellite observations with a focus on the Absorbing Aerosol Optical Depth (AAOD), Single Scattering Albedo (SSA) and their spectral dependence. The AAOD and Absorption Angstrom Exponent (AAE) data set is composed of daily averaged AERONET level 2 data from a total of 22 Mediterranean stations having long time series, mainly under the influence of urban-industrial aerosols and/or soil dust. This data set covers the 17 yr period 1996-2012 with most data being from 2003-2011 (approximately 89 percent of level-2 AAOD data). Since AERONET level-2 absorption products require a high aerosol load (AOD at 440 nm greater than 0.4), which is most often related to the presence of desert dust, we also consider level-1.5 SSA data, despite their higher uncertainty, and filter out data with an Angstrom exponent less than 1.0 in order to study absorption by carbonaceous aerosols. The SSA data set includes both AERONET level-2 and satellite level-3 products. Satellite-derived SSA data considered are monthly level 3 products mapped at the regional scale for the spring and summer seasons that exhibit the largest aerosol loads. The satellite SSA dataset includes the following products: (i) Multi-angle Imaging SpectroRadiometer (MISR) over 2000-2011, (ii) Ozone Monitoring Instrument (OMI) near-UV algorithm over 2004-2010, and (iii) MODerate resolution Imaging Spectroradiometer (MODIS) Deep-Blue algorithm over 2005-2011, derived only over land in dusty conditions. Sun-photometer observations show that values of AAOD at 440 nm vary between 0.024 +/- 0.01 (resp. 0.040 +/- 0.01) and 0.050 +/- 0.01 (0.055 +/- 0.01) for urban (dusty) sites. Analysis shows that the Mediterranean urban-industrial aerosols appear "moderately

  18. Carbonyl-functionalized quaterthiophenes: a study of the vibrational Raman and electronic absorption/emission properties guided by theoretical calculations.

    PubMed

    Aragó, Juan; Ponce Ortiz, Rocío; Nieto-Ortega, Belén; Hernández, Víctor; Casado, Juan; Facchetti, Antonio; Marks, Tobin J; Viruela, Pedro M; Ortí, Enrique; López Navarrete, Juan T

    2012-01-16

    This work investigates the evolution of the molecular, vibrational, and optical properties within a family of carbonyl-functionalized quaterthiophenes: 5,5'''-diheptanoyl-2,2':5',2'':5'',2'''-quaterthiophene (1), 5,5'''-diperfluorohexylcarbonyl-2,2':5',2'':5'',2'''-quaterthiophene (2), and 2,7-[bis(5-perfluorohexylcarbonylthien-2-yl)]-4H-cyclopenta[2,1-b:3,4-b']-dithiophene-4-one (3). The analysis is performed by Raman and UV/Vis absorption/excitation/fluorescence spectroscopy in combination with density functional calculations. Theoretical calculations show that substitution with carbonyl groups and perfluorohexyl chains induces progressive quinoidization of the π-conjugated backbone in comparison to the carbonyl-free compound 5,5'''-dimethyl-2,2':5',2'':5'',2'''-quaterthiophene (DM-4T) used as reference. Raman spectra are dominated by a strong Raman line which mainly corresponds to a combination of C-C/C=C stretching vibrations spreading over the whole thiophene core. This band undergoes a remarkable downshift as a consequence of the structural changes induced by the electron-withdrawing groups on the π-conjugated backbone. The band splitting on incorporation of a central carbonyl bridge evidences the formation of two structural domains in the molecule. The excitation and fluorescence spectra recorded at low temperature show well-resolved vibronic structures associated with the most intense collective C-C/C=C stretching mode. Optical absorption and fluorescence bands exhibit remarkable bathochromic dispersion on carbonyl functionalization, indicative of extension of π conjugation. TDDFT calculations enable a detailed description of the trends observed in the absorption spectra. Resonance Raman spectra reflect the structural changes predicted for the S(0)→S(1) electronic transition and evidence the cross-conjugated character that the central carbonyl group confers on 3.

  19. Difluorenyl carbo-Benzenes: Synthesis, Electronic Structure, and Two-Photon Absorption Properties of Hydrocarbon Quadrupolar Chromophores.

    PubMed

    Baglai, Iaroslav; de Anda-Villa, Manuel; Barba-Barba, Rodrigo M; Poidevin, Corentin; Ramos-Ortíz, Gabriel; Maraval, Valérie; Lepetit, Christine; Saffon-Merceron, Nathalie; Maldonado, José-Luis; Chauvin, Remi

    2015-09-28

    The synthesis, crystal and electronic structures, and one- and two-photon absorption properties of two quadrupolar fluorenyl-substituted tetraphenyl carbo-benzenes are described. These all-hydrocarbon chromophores, differing in the nature of the linkers between the fluorenyl substituents and the carbo-benzene core (C-C bonds for 3 a, C-C=C-C expanders for 3 b), exhibit quasi-superimposable one-photon absorption (1PA) spectra but different two-photon absorption (2PA) cross-sections σ2PA. Z-scan measurements (under NIR femtosecond excitation) indeed showed that the C≡C expansion results in an approximately twofold increase in the σ2PA value, from 336 to 656 GM (1 GM = 10(-50) cm(4) s molecule(-1) photon(-1)) at λ = 800 nm. The first excited states of Au and Ag symmetry accounting for 1PA and 2PA, respectively, were calculated at the TDDFT level of theory and used for sum-over-state estimations of σ2PA(λi), in which λi = 2 hc/Ei, h is Planck's constant, c is the speed of light, and Ei is the energy of the 2PA-allowed transition. The calculated σ2PA values of 227 GM at 687 nm for 3 a and 349 GM at 708 nm for 3 b are in agreement with the Z-scan results.

  20. Effect of heat treatment on absorption and fluorescence properties of PbS-doped silica optical fibre

    NASA Astrophysics Data System (ADS)

    Qin, Fu; Dong, Yanhua; Wen, Jianxiang; Pang, Fufei; Luo, Yanhua; Peng, Gang-Ding; Chen, Zhenyi; Wang, Tingyun

    2017-02-01

    The effect of heat treatment on the optical properties of a PbS-doped silica optical fibre was investigated. The experimental results showed that the absorption peak of the fibre red shifted from 1032 to 1133 nm when the heat treatment temperatures were carried out at 900, 950, 1000, and 1100 °C for 1 h, respectively. At the same time, when the heat treatment at 900 °C was carried out for 2, 5, 10, 20, and 40 h, the absorption spectra of the fibre showed a red shift from 1074 to 1143 nm. In addition, the intensity of the absorption peak increased from 0.258 to 1.384 dB/m and the full width at half maximum (FWHM) became narrower (from 130 to 50 nm) as the heat treatment proceeded. Moreover, the photoluminescence (PL) intensity in the wavelength range of 1100-1500 nm decreased with an increase in the heat treatment temperature. The theoretical analysis, using an effective mass method, showed that the effective band gap energy and average size of the lead sulphide (PbS) quantum dots (QDs) in the silica fibre core varied from 1.199 to 1.083 eV and from 4.28 to 4.81 nm, respectively. The results indicate that the size of the PbS QDs present in the silica fibre core could be controlled by a proper heat treatment, which is of great interest in optical fibre amplifiers and other fibre optic devices.

  1. Multi-mode interference revealed by two photon absorption in silicon rich SiO{sub 2} waveguides

    SciTech Connect

    Manna, S. E-mail: mattia.mancinelli@unitn.it; Ramiro-Manzano, F.; Mancinelli, M. E-mail: mattia.mancinelli@unitn.it; Turri, F.; Pavesi, L.; Ghulinyan, M.; Pucker, G.

    2015-02-16

    Photoluminescence (PL) from Si nanocrystals (NCs) excited by two-photon absorption (TPA) has been observed in Si nanocrystal-based waveguides fabricated by plasma enhanced chemical vapor deposition. The TPA excited photoluminescence emission resembles the one-photon excited photoluminescence arising from inter-band transitions in the quantum confined Si nanocrystals. By measuring the non-linear transmission of waveguides, a large TPA coefficient of β up to 10{sup −8 }cm/W has been measured at 1550 nm. These values of β depend on the Si NCs size and are two orders of magnitude larger than the bulk silicon value. Here, we propose to use the TPA excited visible PL emission as a tool to map the spatial intensity profile of the 1550 nm propagating optical modes in multimode waveguides. In this way, multimode interference has been revealed experimentally and confirmed through a finite element simulation.

  2. Influence of Helium Atoms Absorption on the Emission Properties of Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Umaev, S. M.; Levchenko, A. A.; Kolesnikov, N. N.; Filatov, S. V.

    2017-04-01

    We investigated the emission properties of charge sources based on carbon nanotubes prepared by arc discharge deposition of nanotubes onto a flat copper substrate (Borisenko et al. in Instrum Exp Tech 57(6):755, 2014; Low Temp Phys 41(7):567, 2015). The charge sources were submerged into superfluid helium at temperature T=1.3 K. The collector fixed above the charge source at a distance of 0.3 mm was connected to an electrometer. The current of charges was measured by the electrometer when a high voltage was applied to the charge source. In the originally prepared source, the emission of charges (electrons) on the level of 10^{-10}A is observed at a negative voltage above U=80 V and increases with increasing voltage. If the source of charge was kept in liquid helium for 15 h, the current-voltage characteristic changed significantly. The current of charges on the same level of 10^{-10} A was registered at a voltage of U=150 V. Extraction of gases from the source placed in a vacuum chamber at room temperature for 48 h leads to the complete recovery of the emission properties. One can assume that the degradation of the emission properties of the sources is associated with the adsorption of helium atoms by carbon nanotubes at low temperatures. We did not observe any degradation of the emission properties of the charge sources in the case of positive charges injection into superfluid helium.

  3. Morphology, absorptivity and viscoelastic properties of mineralized PVP-CMC hydrogel

    NASA Astrophysics Data System (ADS)

    Saha, Nabanita; Shah, Rushita; Vyroubal, Radek; Kitano, Takeshi; Saha, Petr

    2013-04-01

    A simple liquid diffusion mineralization technique was applied for the incorporation of calcium carbonate (CaCO3) in PVP-CMC hydrogel. The hydrogel was prepared 6.5 mm thick to achieve around 1 mm thick sample after mineralization of hydrogel matrix with calcite. The calcite crystals were round shaped and organized as building blocks inside the porous three dimensional cross linked structure of the PVP-CMC hydrogel. The present study was designed to evaluate the properties of mineralized (calcite) hydrogel with respect to freshly prepared hydrogel and those swelled in water (H2O) after drying. The viscoelastic properties of swelled and mineralized samples were reported though the dry PVP-CMC hydrogel were swelled and mineralized with calcite until 150 min. It is observed that there is not much difference in elastic property of fresh and 60 min mineralized hydrogels but the values of elastic property are decreased in the case of swelled hydrogels. It is interesting that in case of swelled samples the values of complex viscosity (η*) are increased with the increase of swelling time after 90 min but in case of calcite hydrogel the values (η*) are gradually decreased with the increase of time.

  4. Development And Optical Absorption Properties Of A Laser Induced Plasma During CO2-Laser Processing

    NASA Astrophysics Data System (ADS)

    Beyer, E.; Bakowsky, L.; Loosen, P.; Poprawe, R.; Herziger, G.

    1984-03-01

    Laser material processing is accompanied by a laser induced plasma in front of the target surface as soon as the laser radiation exceeds a certain critical intensity. For cw CO2-laser machining of metal targets the threshold for plasma onset is about 106 W/cm2. Critical condition for plasma generation at this intensity level is to reach evaporation temperature at the target's surface. At intensity levels exceeding 106 W/cm2 the laser light is interacting with the laser induced plasma and then the plasma in turn interacts with the target. The absorptivity is no longer constant, but increases with increasing intensity of the incident radiation, so that the total amount of power coupled to the target is increasing. This holds up to intensity levels of 2'10 Wicm2. Then the plasma begins to withdraw from the target surface, thus interrupting plasma-target interaction so that the laser power is no longer coupled into the target completely. The results of laser welding (welding depth) in the intensity level of 106 W/cm2 are governed by the product of incident intensity times focus radius, so that welding results are a measure to determine focus radius and laser intensity.

  5. Optical absorption and near infrared emission properties of Nd 3+ ions in alkali lead tellurofluoroborate glasses

    NASA Astrophysics Data System (ADS)

    Saleem, S. A.; Jamalaiah, B. C.; Kumar, J. Suresh; Babu, A. Mohan; Moorthy, L. Rama; Jayasimhadri, M.; Jang, Kiwan; Lee, Ho Sueb; Yi, Soung Soo; Jeong, Jung Hyun

    2009-12-01

    Nd 3+ doped H 3BO 3-PbO-TeO 2-RF (R = Li, Na and K) glasses were prepared through melt quenching technique. Optical absorption and near infrared (NIR) fluorescence spectra were recorded at room temperature. The spectral intensities were analyzed in terms of the Judd-Ofelt (J-O) parameters ( Ω λ = 2, 4, 6). The covalency effect of Nd-O bond on the J-O parameters was estimated from the relative absorbance ratio (R) between 4I 9/2 → 4F 7/2 and 4I 9/2 → 4S 3/2 transitions. The effect of Nd-O covalency on the Ω4 and Ω6 intensity parameters as well as on the spontaneous emission probabilities ( AR) was discussed. Lomheim and Shazer hybrid method was applied to determine the fluorescence branching ratios ( βR) of each emission transition from the 4F 3/2 metastable level to its lower lying levels. The evaluated total radiative transition probabilities ( AT), stimulated emission cross-sections ( σe) and gain bandwidth parameters ( σe × Δ λP) were compared with the earlier reports.

  6. Optoelectronic properties of Mg{sub 2}Si semiconducting layers with high absorption coefficients

    SciTech Connect

    Kato, Takashi; Sago, Yuichiro; Fujiwara, Hiroyuki

    2011-09-15

    In an attempt to develop a low-cost material for solar cell devices, polycrystalline magnesium silicide (poly-Mg{sub 2}Si) semiconducting layers have been prepared by applying rf magnetron sputtering using a Mg{sub 2}Si target. The optimum substrate temperature for the poly-Mg{sub 2}Si growth was found to be T{sub s} = 200 deg. C; the film deposition at higher temperatures leads to desorption of Mg atoms from the growing surface, while the amorphous phase formation occurs at room temperature. The poly-Mg{sub 2}Si layer deposited at T{sub s} = 200 deg. C shows the (111) preferential orientation with a uniform grain size of {approx}50 nm. The dielectric function of the poly-Mg{sub 2}Si layer has been determined accurately by spectroscopic ellipsometry. From the analysis, quite high absorption coefficients and an indirect gap of 0.77 eV in the poly-Mg{sub 2}Si layer have been confirmed. The above poly-Mg{sub 2}Si layer shows clear photoconductivity and can be applied as a narrow-gap bottom layer in multi-junction solar cell devices.

  7. Influence of barrier absorption properties on laser patterning thin organic films

    NASA Astrophysics Data System (ADS)

    Naithani, Sanjeev; Mandamparambil, Rajesh; van Assche, Ferdie; Schaubroeck, David; Fledderus, Henri; Prenen, An; Van Steenberge, Geert; Vanfleteren, Jan

    2012-06-01

    This paper presents a study of selective ablation of thin organic films (LEP- Light Emitting Polymer, PEDOT:PSS- Poly 3,4-ethylenedioxythiophene: polystyrene sulfonate) by using 248 nm Excimer laser, on various kinds of multilayered SiN barrier foils for the development of Organic Light Emitting Diodes (OLED). Different Silicon Nitride (SiN) barrier foils with dedicated absorption spectra are taken into account for this purpose. The drive for looking into different types of SiN originates from the fact that the laser selective removal of a polymer without damage to the barrier layer underneath is challenging in the dynamic laser processing of thin films. The barrier is solely responsible for the proper encapsulation of the OLED stack. The main limitation of current OLED design is its shorter life span, which is directly related to the moisture or water permeation into the stack, leading to black spots. An optimization of laser parameters like fluence and number of shots has been carried out for the various types of SiN barrier foils. We are able to obtain a wider working process window for the selective removal of LEP and PEDOT:PSS from SiN barrier, by variation of the different types of SiN.

  8. Structural, magnetic and microwave absorption properties of Ce-doped barium hexaferrite

    NASA Astrophysics Data System (ADS)

    Mosleh, Z.; Kameli, P.; Poorbaferani, A.; Ranjbar, M.; Salamati, H.

    2016-01-01

    Ba1-xCexFe12O19 (x=0.0, 0.05, 0.1, 0.15, and 0.2) polycrystalline samples were synthesized by the sol-gel method and characterized by thermogravimetric analysis (TG), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM) and vector network analyzer. All the synthesized samples showed nearly single magnetoplumbite phase and an average particle size of the undoped sample of about 500 nm decreasing with Ce doping content. The magnetization first increased and then decreased with the increase in Ce; on the other hand, coercivity showed no regular behavior with Ce content. Maximum values of magnetization (53 emu/g) and coercivity (5088 Oe) were obtained for x=0.1. Microwave absorption measured within the 2-18 microwave frequency range indicated maximum reflection losses of -16.74 dB at 10.3 GHz and of -20.47 dB at 16.22 GHz for x=0.15 and x=0.2 samples, respectively. The present investigation suggests Ce substituted barium hexaferrite as a promising candidate for microwave absorbing materials.

  9. Properties of solid dispersions of selected magnesium salts and the absorption process of Mg2+ ions in vitro

    NASA Astrophysics Data System (ADS)

    Marcoin, Waclawa; Duda, Henryk; Chrobak, Dariusz

    2011-01-01

    The paper presents an application of phosphatidylcholine 45% (PC 45) and polyvinylpyrrolidone (PVP) in formulations of magnesium salts such as Mg(VitB6) and Mg(VitB6Arg) prepared by solid dispersion (SD) techniques. The evaluation of influence of the selected carriers on some physicochemical properties of solid dispersions and on the absorption process of Mg +2 ions in vitro were made. An infrared (IR) spectra study suggested creation of a hydrogen bond between the carriers and the examined magnesium salts. The results of the following thermal analysis: differential thermal analysis (DTA), thermogravimetry (TG), and differential scanning calorimetry (DSC) showed that application of PVP into SD lower the temperature of the decomposition process. However, in the case of PC 45 into SD the characteristic thermal effects of higher temperatures were observed. Moreover, values of the enthalpy SD of decomposition process were decreased. The results of these studies on absorption process of Mg2+ ions in vitro showed the positive influence of the applied carriers on the partition coefficient values (log P) in the examined formulation.

  10. Degradation in Mechanical and Thermal Properties of Partially Aligned CNT/Epoxy Composites due to Seawater Absorption

    NASA Astrophysics Data System (ADS)

    Saha, Sunirmal; Bal, Smrutisikha

    2017-02-01

    This literature gives an overview of the effect of water uptake on the mechanical and thermal performances of partially aligned carbon nanotube (CNT)/ epoxy (having CNTs wt.%: 0.5, 0.75 and 1) along with pure epoxy composites. Weight change behaviour of all the composites immersed in seawater for a period of six months has been recorded. The state of CNT/matrix interface is believed to be influenced due to water absorption. Reduction in flexural modulus, strength, hardness and glass transition temperature (Tg ) of the specimens have been evaluated as compared to their unexposed counterparts due to adverse effect of water absorption. Results demonstrated 35-46% reduction in flexural modulus, 43-56% decrement in flexural strength, 4-7 MPa reduction in hardness and minor deterioration in Tg values for all the composites. However, the specimen having 0.75 wt.% CNT loading, exhibited minimum reduction in properties in all aspects compared to others. Scanning electron microscopy (SEM) has been employed to study the failure mechanism of the specimens after performing the mechanical tests.

  11. Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

    SciTech Connect

    Lee, Geon Joon Sim, Geon Bo; Choi, Eun Ha; Kim, Jun Young; Jang, Siun; Kim, Seong Hwan

    2015-01-14

    To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.

  12. Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Geon Joon; Sim, Geon Bo; Choi, Eun Ha; Kwon, Young-Wan; Kim, Jun Young; Jang, Siun; Kim, Seong Hwan

    2015-01-01

    To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.

  13. Absorption-improving effects of chitosan oligomers based on their mucoadhesive properties: a comparative study on the oral and pulmonary delivery of calcitonin.

    PubMed

    Zhang, Hailong; Huang, Xiaoyan; Sun, Ya; Xing, Jianfeng; Yamamoto, Akira; Gao, Yang

    2016-09-01

    Effects of chitosan oligomers with different types and varying concentrations on the intestinal and pulmonary absorptions of calcitonin were investigated in rats by an in situ closed loop method and an in vivo pulmonary absorption experiment, respectively. Various chitosan oligomers demonstrated different efficiencies in improving the intestinal and pulmonary absorptions of calcitonin, and chitosan hexamer with the optimal concentration of 0.5% (w/v) showed the greatest absorption enhancing effect. Moreover, pharmacodynamic parameters of calcitonin after its coadministration intrapulmonarily with various chitosan oligomers were consistently larger than that in the intestinal delivery, indicating the superior potential of pulmonary administration for systemic delivery of calcitonin. Furthermore, various chitosan oligomers neither obviously increased release amounts of protein nor activities of lactate dehydrogenase (LDH) in bronchoalveolar lavage fluid (BALF), revealing the safety of these chitosan oligomers to lung tissue. In addition, bioadhesions of various chitosan oligomers were well consistent with their absorption enhancing effects in the absorption experiment, suggesting the contribution of mucoadhesive properties of chitosan oligomers to their absorption improving effects. Taken together, chitosan oligomers, especially chitosan hexamer, can effectively improve the intestinal and pulmonary absorptions of calcitonin partly due to the mucoadhesion between positive chitosan oligomers and negative mucus in the membrane.

  14. Simulation model of absorption and scattering properties of laser light applied to urban aerosols over the city of Popayan, Colombia

    NASA Astrophysics Data System (ADS)

    Bastidas, Alvaro E.; Rodriguez, Edith; Jaramillo, Mauricio; Solarte, Efrain

    2004-11-01

    Aerosols are among the most spatially variable components of the atmosphere, and thus their study requires their monitoring over a broad geographic range. The backscattering of light from suspended solid and liquid particles in the atmosphere obeys Mie scattering theory. Light attenuation in the spectral region from 300 to 4000 nm due to Mie scattering exceeds that due to molecular (Rayleigh) scattering and ozone absorption combined. This occurs despite the fact that aerosol particle concentrations in the atmosphere are many orders of magnitude smaller than molecular concentrations. Starting from the characteristics of urban aerosols measured over the city of Popayan, Colombia), 2° 27" N; 76° 37' W, with a PM10 particle selector, we present the results of a study of light attenuation properties generated using Matlab computer code, to simulate and predict measurements with a Lidar system operating at 514.5 nm.

  15. Reversible modulation of electric transport properties by oxygen absorption and releasing on Nb:SrTiO{sub 3} surface

    SciTech Connect

    Lu, H. X.; Liu, Y. B.; Chen, Y. S. Wang, J.; Shen, B. G.; Sun, J. R.

    2014-11-07

    Pt Schottky contacts on (001)-orientated Nb-doped SrTiO{sub 3} (NSTO) in both ambient air and vacuum were investigated by the conductive atomic force microscope. The co-existed TiO{sub 2} and SrO termination layers were identified on the terrace-structured NSTO surface, where the former possessed a higher forward current than the latter. In ambient air, the barrier height of Pt/NSTO Schottky junction exhibited periodical variation with cyclic terrace plane and step sites, whereas it became homogeneous in ambient vacuum. We suggested that the oxygen absorption and releasing of surface dangling bonds were the origin for reversible changes in transport properties, which indicates a feasible approach for the surface modulation and band structure tailoring of NSTO based heterojunctions.

  16. Effects of cerium on the hydrogen absorption-desorption properties of rare earth-Mg-Ni hydrogen-absorbing alloys

    NASA Astrophysics Data System (ADS)

    Yasuoka, Shigekazu; Ishida, Jun; Kishida, Kyosuke; Inui, Haruyuki

    2017-04-01

    The influence of Ce addition on the phase constitution, microstructure, hydrogen absorption/desorption properties and battery performances of newly developed rare earth (RE)-Mg-Ni hydrogen-absorbing superlattice alloys for negative electrode materials in Ni-metal hydride (MH) batteries were investigated. The partial substitution of RE (La and Nd) with Ce results in a higher discharge performance and a lower cycle life in the battery. The Ce addition greatly affects the phase constitution, which is mainly characterized by increased formation of the AB2 phase (A = RE or Mg and B = Ni or Al). The existence of the AB2 phase is found to accelerate alloy pulverization and oxidation when the alloys are used as negative electrode materials in Ni-MH model cells. The accelerated pulverization and oxidation are considered to be responsible for the observed higher discharge performance and lower cycle life in the batteries, respectively.

  17. Effect of sand and moisture on molten salt properties for open direct absorption solar receiver/storage system

    NASA Astrophysics Data System (ADS)

    AlQaydi, M. S.; Delclos, T.; AlMheiri, S.; McKrell, T.; Calvet, N.

    2016-05-01

    Solar Salt (60 wt. % sodium nitrate, 40 wt. % potassium nitrate) is one candidate salt mixture for the CSPonD Demo project (Concentrated Solar Power On Demand Demonstration), ongoing collaboration between Masdar Institute and MIT. One prototype is under preparation at the Masdar Institute Solar Platform in Abu Dhabi. In this new concept, the salt will be used as an open direct absorption solar receiver integrated with a storage system so that the effects of dust/sand and moisture on the thermophysical properties have to be investigated. Thermal Gravimetric Analysis (TGA) was used to study the thermal stability and mass loss, while a Differential Scanning Calorimeter (DSC) was used to study the thermal properties and heat capacity of the salt mixture with and without sand. Considering the worst case scenario, the maximum mass loss rate at 550 °C, and in a fully open configuration, was measured to be 0.29 % per hour, around 2.34 per day of use (8 h of operation). The effect of sand was the same under nitrogen gas environment and air with moisture, which resulted in decreasing the melting temperature of the salts mixture and increasing its freezing temperature. The thermal properties remained stable even after 3 temperature cycles with impurities. Finally, the salt heat capacity increased due to the addition of 2 wt. % of sand.

  18. Selaginella tamariscina extract suppresses TPA-induced invasion and metastasis through inhibition of MMP-9 in human nasopharyngeal carcinoma HONE-1 cells

    PubMed Central

    2013-01-01

    Background Nasopharyngeal carcinoma (NPC) is known for its high incidence of neck lymph node metastasis, which represents poor prognosis. The present study aimed to examine the anti-metastatic properties of Selaginella tamariscina extract (STE) in human nasopharyngeal carcinoma HONE-1 cells in vitro. Methods Cell viability was examined by MTT assay, whereas cell motility was measured by invasive, migration and would healing assays. Real-time PCR, and promoter assays confirmed the inhibitory effects of STE on matrix metalloproteinase-9 (MMP-9) mRNA level in HONE-1 cells. Results The STE inhibits 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced HONE-1 cell migration and invasion in a concentration-dependent manner. By zymographic and Western blot analyses, STE was shown to inhibit the activities and expression of MMP-9. Treatment of STE on TPA-induced HONE-1 cells inhibited MMP-9 expression and ERK1/2 phosphorylation without affecting JNK and p38 phosphorylation. Conclusions STE inhibits MMP-9 expression and HONE-1 cell metastasis. Its inhibitory effects may involve the Src/FAK/ERK 1/2 pathway. STE may have the potential of being an anti-metastatic agent against NPC. PMID:24053256

  19. Electromagnetic wave absorption properties of Fe73Si16B7Nb3Cu1-based composites mixed with fine charcoal powder

    NASA Astrophysics Data System (ADS)

    Kim, Sun-I.; Kim, Mi Rae; Sohn, Keun Yong; Park, Won-Wook

    2010-05-01

    Fe73Si16B7Nb3Cu1 soft magnetic powder was crystallized to obtain a nano grain structure and mixed with a fine charcoal powder. The mixtures were tape-cast with polymer-based organic binders to form a sheet-type electromagnetic (EM) wave absorption composite. The EM wave absorption properties of the sheets were investigated using a network analyzer. The results showed that addition of charcoal powder improved the EM-absorbing properties of the composite. The power loss of the EM wave was directly related to the imaginary part of the permeability and permittivity, and it was reviewed in detail. Excellent absorption properties were achieved by adding 5 wt % charcoal powder (-500 mesh) to the Fe-based sheets.

  20. Electromagnetic properties and microwave absorption properties of BaTiO 3-carbonyl iron composite in S and C bands

    NASA Astrophysics Data System (ADS)

    Rui-gang, Yang

    2011-07-01

    BaTiO3 powders are prepared by sol-gel method. The carbonyl iron powder is prepared via thermal decomposition of iron pentacarbonyl. Then BaTiO3-carbonyl iron composite with different mixture ratios was prepared using the as-prepared material. The structure, morphology, and properties of the composites are characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, scanning electron microscopy (SEM), and a network analyzer. The complex permittivity and reflection loss of the composites have been measured at different microwave frequencies in S- and C-bands employing vector network analyzer model PNA 3629D vector. The effect of the mass ratio of BaTiO3/carbonyl iron on the microwave loss properties of the composites is investigated. A possible microwave absorbing mechanism of BaTiO3-carbonyl iron composite has been proposed. The BaTiO3-carbonyl iron composite can find applications in suppression of electromagnetic interference, and reduction of radar signature.

  1. Absorption and scattering properties of the Martian dust in the solar wavelengths.

    PubMed

    Ockert-Bell, M E; Bell JF 3rd; Pollack, J B; McKay, C P; Forget, F

    1997-04-25

    A new wavelength-dependent model of the single-scattering properties of the Martian dust is presented. The model encompasses the solar wavelengths (0.3 to 4.3 micrometers at 0.02 micrometer resolution) and does not assume a particular mineralogical composition of the particles. We use the particle size distribution, shape, and single-scattering properties at Viking Lander wavelengths presented by Pollack et al. [1995]. We expand the wavelength range of the aerosol model by assuming that the atmospheric dust complex index of refraction is the same as that of dust particles in the bright surface geologic units. The new wavelength-dependent model is compared to observations taken by the Viking Orbiter Infrared Thermal Mapper solar channel instrument during two dust storms. The model accurately matches afternoon observations and some morning observations. Some of the early morning observations are much brighter than the model results. The increased reflectance can be ascribed to the formation of a water ice shell around the dust particles, thus creating the water ice clouds which Colburn et al. [1989], among others, have predicted.

  2. Modulation of ADPase and t-PA release by radiographic contrast media in bovine aortic endothelium.

    PubMed

    Caprino, L; Togna, A R; Zappacosta, B; Giardina, B; Togna, G

    1997-05-01

    Vascular endothelial injuries induced by intravascular administration of radiographic contrast agents may be clinically relevant to the development of thrombosis and platelet activation. In this connection, we investigated the in vitro effects induced by iodamide, iopamidol, and ioxaglate on vascular endothelial ADPase activity and tissue plasminogen activator (t-PA) release in bovine aortic endothelium, in order to extend knowledge required to evaluate endothelial compatibility of radiographic contrast media. Undiluted and Tris-diluted contrast agent formulations were employed, and mannitol and sucrose hyperosmolar solutions were used as comparison. Results demonstrated that the high-osmolar ionic contrast agent iodamide, and to a lesser extent, the low-osmolar nonionic agent iopamidol, stimulated endothelial ADPase activity of the aortic endothelium; the low-osmolar ionic agent ioxaglate left endothelial ADPase activity unchanged. Furthermore, the diluted formulations of iodamide and iopamidol, as well as high-osmolar mannitol and sucrose solutions, were devoid of activity in ADPase. This suggests that the endothelial ADPase stimulation induced by both radiographic contrast media was a hyperosmolar-independent pharmacodynamic activity. Iopamidol and ioxaglate reduced endogenous t-PA release from bovine aortic endothelium only in undiluted formulation, while iodamide showed this inhibiting action in both diluted and undiluted formulations. No effect was observed when using mannitol solutions at different osmolarity values. Our in vitro findings agree with published data on the different thrombotic tendency attributed to the contrast agents used, suggesting endothelial enzymatic activities (ADPase and t-PA release) as suitable tools for evaluating endothelial vessel wall compatibility with radiographic contrast media.

  3. A Synthesis of Light Absorption Properties of the Arctic Ocean: Application to Semi-analytical Estimates of Dissolved Organic Carbon Concentrations from Space

    NASA Technical Reports Server (NTRS)

    Matsuoka, A.; Babin, M.; Doxaran, D.; Hooker, S. B.; Mitchell, B. G.; Belanger, S.; Bricaud, A.

    2014-01-01

    The light absorption coefficients of particulate and dissolved materials are the main factors determining the light propagation of the visible part of the spectrum and are, thus, important for developing ocean color algorithms. While these absorption properties have recently been documented by a few studies for the Arctic Ocean [e.g., Matsuoka et al., 2007, 2011; Ben Mustapha et al., 2012], the datasets used in the literature were sparse and individually insufficient to draw a general view of the basin-wide spatial and temporal variations in absorption. To achieve such a task, we built a large absorption database at the pan-Arctic scale by pooling the majority of published datasets and merging new datasets. Our results showed that the total non-water absorption coefficients measured in the Eastern Arctic Ocean (EAO; Siberian side) are significantly higher 74 than in the Western Arctic Ocean (WAO; North American side). This higher absorption is explained 75 by higher concentration of colored dissolved organic matter (CDOM) in watersheds on the Siberian 76 side, which contains a large amount of dissolved organic carbon (DOC) compared to waters off 77 North America. In contrast, the relationship between the phytoplankton absorption (a()) and chlorophyll a (chl a) concentration in the EAO was not significantly different from that in the WAO. Because our semi-analytical CDOM absorption algorithm is based on chl a-specific a() values [Matsuoka et al., 2013], this result indirectly suggests that CDOM absorption can be appropriately erived not only for the WAO but also for the EAO using ocean color data. Derived CDOM absorption values were reasonable compared to in situ measurements. By combining this algorithm with empirical DOC versus CDOM relationships, a semi-analytical algorithm for estimating DOC concentrations for coastal waters at the Pan-Arctic scale is presented and applied to satellite ocean color data.

  4. Controlled Synthesis and Microwave Absorption Property of Chain-Like Co Flower

    PubMed Central

    Wang, Chao; Hu, Surong; Han, Xijiang; Huang, Wen; Tian, Lunfu

    2013-01-01

    Chain-like Co flower is synthesized by simply modulating the reaction conditions via a facile liquid-phase reduction method. The morphology evolution process and transformation mechanism from particle to flower and finally to chain-like flower have been systematically investigated. [001] is the preferred growth orientation due to the existence of easy magnetic axis. The microwave loss mechanism can be attributed to the synergistic effect of magnetic loss and dielectric loss, while magnetic loss is the main loss mechanism. In addition, the special microstructure of chain-like Co flower may further enhance microwave attenuation. The architectural design of functional material morphology is critical for improving its property toward future application. PMID:23437073

  5. Microwave absorption property of plasma spray W-type hexagonal ferrite coating

    NASA Astrophysics Data System (ADS)

    Wei, Shicheng; Liu, Yi; Tian, Haoliang; Tong, Hui; Liu, Yuxin; Xu, Binshi

    2015-03-01

    In order to enhance the adhesion strength of microwave absorbing materials, W-type hexagonal ferrite coating is fabricated by plasma spray. The feedstock of ferrite powders is synthesized by solid-state reaction and spray dried process. Microstructures of the coating are analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectra (EDS). Hexagonal ferrite coating is successfully deposited on the substrate with adhesion strength of 28 MPa. The magnetic property of ferrite samples is measured using vibrating sample magnetometer (VSM). Saturation magnetization of the ferrite coating is lower than ferrite powder. Reflection loss of the hexagonal ferrite coating is measured in frequency of 2-18 GHz. The result shows that the coating is suitable for electromagnetic wave absorbers in Ku-band.

  6. Inhibitory Effects of Lysine Analogues on t-PA Induced Whole Blood Clot Lysis

    DTIC Science & Technology

    1994-01-01

    Tween - 80 , pH 7.4 at 4 0C for 2 min in a 12x75 mm glass tube precoated with 10 pg iodogen. The specific activity of t-PA was 3.6x10’ cpm/mg and...plasminogen (0.6-15 nM) in phosphate buffered saline with 0.01% Tween - 80 , pH 7.4 was incubated with the fibrin-coated wells for 1 hr at 37 0C. The

  7. Enhanced Microwave Absorption Properties by Tuning Cation Deficiency of Perovskite Oxides of Two-Dimensional LaFeO3/C Composite in X-Band.

    PubMed

    Liu, Xiang; Wang, Lai-Sen; Ma, Yating; Zheng, Hongfei; Lin, Liang; Zhang, Qinfu; Chen, Yuanzhi; Qiu, Yulong; Peng, Dong-Liang

    2017-03-01

    Development of microwave absorption materials with tunable thickness and bandwidth is particularly urgent for practical applications but remains a great challenge. Here, two-dimensional nanocomposites consisting of perovskite oxides (LaFeO3) and amorphous carbon were successfully obtained through a one pot with heating treatment using sodium chloride as a hard template. The tunable absorption properties were realized by introducing A-site cation deficiency in LaFeO3 perovskite. Among the A-site cation-deficient perovskites, La0.62FeO3/C (L0.62FOC) has the best microwave absorption properties in which the maximum absorption is -26.6 dB at 9.8 GHz with a thickness of 2.94 mm and the bandwidth range almost covers all X-band. The main reason affecting the microwave absorption performance was derived from the A-site cation deficiency which induced more dipoles polarization loss. This work proposes a promising method to tune the microwave absorption performance via introducing deficiency in a crystal lattice.

  8. Photon absorption and emission properties of 7 Å SiC nanoclusters: Electronic gap, surface state, and quantum size effect

    NASA Astrophysics Data System (ADS)

    Guo, Xiaoxiao; Chen, Xifang; Fan, Baolu; Zhang, Yumeng; Fan, Jiyang

    2016-07-01

    People know little experimentally about the physical properties of the SiC nanoclusters with sizes of a couple of angstroms. Herein, we study the electronic structure and light absorption/emission properties of the SiC nanoclusters with an average diameter of 7 Å that are fabricated by diminishing the sizes of the SiC microcrystals under high pressure and high temperature. The results reveal that the SiC nanoclusters have an indirect energy gap of 5.1 eV. Unlike the case of larger SiC nanocrystals, the luminescence of the SiC nanoclusters is dominated by two types of oxygen-related surface defects, and the maximum of their photoluminescence/photoluminescence excitation spectrum lies at 4.1/3.3 and 3.8/3.0 eV, respectively. The energy gap of the SiC nanoparticles with reference to bulk value is found to be inversely proportional to the diameter to the power 0.97, which shows slower increase of energy gap with decreasing size than what is predicted by using the first-principles calculations.

  9. Excellent improvement in the static and dynamic magnetic properties of carbon coated iron nanoparticles for microwave absorption

    NASA Astrophysics Data System (ADS)

    Khani, Omid; Shoushtari, Morteza Zargar; Farbod, Mansoor

    2015-11-01

    Carbon coated iron nanoparticles were synthesized, using a simple arc-discharge method. The morphology and the internal structure of the core/shell nanoparticles were studied, using field emission scanning electron microscopy and transmission electron microscopy. X-ray diffraction analysis showed that both magnetic α-Fe and nonmagnetic γ-Fe phases existed in the as-prepared particles. In order to improve the static and dynamic magnetic properties of the core/shell nanoparticles, the produced nanocapsules were annealed in argon atmosphere at two different temperatures. Hysteresis loops revealed that the value of the saturation magnetization (MS) increased more than 4.1 times of its original value by annealing and this led to 70% increase in the imaginary part of the permeability. Phase analysis showed that heat treatment eliminated the nonmagnetic γ-Fe phase completely. The reflection loss plots were studied for composite layers containing 20 vol% of the annealed and not annealed nanocapsules. One of the absorber layers which contained annealed nanocapsules showed at least -10 dB loss in the whole G, C, X and Ku frequency bands and the optimal absorption exceeded -37 dB at 5.8 GHz for the as-prepared sample with a thickness of 3.2 mm. The results revealed that the magnetic properties of the arc-made Fe/C core/shell nanoparticle can be improved significantly by annealing in argon.

  10. Influence of matching thickness on the absorption properties of doped barium ferrites at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Ghasemi, A.; Saatchi, A.; Salehi, M.; Hossienpour, A.; Morisako, A.; Liu, X.

    2006-02-01

    The development and characterization of hexagonal ferrite powders of BaFe9Mn1.5Ti1.5O19, BaFe9Mn1.5Co1.5O19, and BaFe9Ti1.5Co1.5O19 as the microwave absorbers have been investigated. The ferrites were fabricated by conventional ceramic technology. The developed ferrite powders 80% by weight were mixed with polyvinylchloride plasticizer and fired to form rubber-ferrite with the thickness of 1.5 mm, 2 mm and 2.5 mm. XRD was used to identify structures of the samples. The magnetoplumbite structures for all the samples have been formed. Vibrating sample magnetometer was used to determine the hysteresis loops of barium ferrite and BaFe9Mn1.5Ti1.5O19 at room temperature. The vector network analyzers in the frequency range of 12 to 20 GHz have measured the reflection loss properties of rubber-ferrite. It was concluded that BaFe9Mn1.5Ti1.5O19 with thickness of 2 mm could be designed as a wide-band microwave absorber. By SEM, the size and morphology of grains in BaFe9Mn1.5Ti1.5O19 ferrite were examined. The results showed that ferrite with grain size of 5 μm do not have any impurities.

  11. Tunable electronic and magnetic properties in stanene by 3d transition metal atoms absorption

    NASA Astrophysics Data System (ADS)

    Xing, Dan-Xu; Ren, Ceng-Ceng; Zhang, Shu-Feng; Feng, Yong; Chen, Xin-Lian; Zhang, Chang-Wen; Wang, Pei-Ji

    2017-03-01

    The electronic and magnetic properties of transition metal (TM) atoms (V, Cr, Mn, Fe, Co, Ni) adsorption on stanene are investigated by first-principles calculations. The results indicate that the TM atoms prefer to be relaxed on a H site on stanene except V atom which lies on the valley site. Fe-absorbed stanene is a spin gapless semiconductor with up-spin electron and down-spin hole carriers allowing the coexistence of charge current and the pure spin current. Co-absorbed stanene lies in the half metal phase. The V-, Cr-, Mn-, and Cu-absorbed stanene turn the stanene into metal, while Ni- and Zn-absorbed stanene open a narrow band gap. For V-, Cr-, Mn-, Fe-, and Co-absorbed stanene, the magnetic moment of the TM will survive while the Ni-, Cu-, and Zn-absorbed stanene will be non-magnetic material. These findings may have great potential in the design of new electrically controllable spintronic devices.

  12. Multi-photon absorption limits to heralded single photon sources

    NASA Astrophysics Data System (ADS)

    Husko, Chad A.; Clark, Alex S.; Collins, Matthew J.; de Rossi, Alfredo; Combrié, Sylvain; Lehoucq, Gaëlle; Rey, Isabella H.; Krauss, Thomas F.; Xiong, Chunle; Eggleton, Benjamin J.

    2013-11-01

    Single photons are of paramount importance to future quantum technologies, including quantum communication and computation. Nonlinear photonic devices using parametric processes offer a straightforward route to generating photons, however additional nonlinear processes may come into play and interfere with these sources. Here we analyse spontaneous four-wave mixing (SFWM) sources in the presence of multi-photon processes. We conduct experiments in silicon and gallium indium phosphide photonic crystal waveguides which display inherently different nonlinear absorption processes, namely two-photon (TPA) and three-photon absorption (ThPA), respectively. We develop a novel model capturing these diverse effects which is in excellent quantitative agreement with measurements of brightness, coincidence-to-accidental ratio (CAR) and second-order correlation function g(2)(0), showing that TPA imposes an intrinsic limit on heralded single photon sources. We build on these observations to devise a new metric, the quantum utility (QMU), enabling further optimisation of single photon sources.

  13. Multi-photon absorption limits to heralded single photon sources

    PubMed Central

    Husko, Chad A.; Clark, Alex S.; Collins, Matthew J.; De Rossi, Alfredo; Combrié, Sylvain; Lehoucq, Gaëlle; Rey, Isabella H.; Krauss, Thomas F.; Xiong, Chunle; Eggleton, Benjamin J.

    2013-01-01

    Single photons are of paramount importance to future quantum technologies, including quantum communication and computation. Nonlinear photonic devices using parametric processes offer a straightforward route to generating photons, however additional nonlinear processes may come into play and interfere with these sources. Here we analyse spontaneous four-wave mixing (SFWM) sources in the presence of multi-photon processes. We conduct experiments in silicon and gallium indium phosphide photonic crystal waveguides which display inherently different nonlinear absorption processes, namely two-photon (TPA) and three-photon absorption (ThPA), respectively. We develop a novel model capturing these diverse effects which is in excellent quantitative agreement with measurements of brightness, coincidence-to-accidental ratio (CAR) and second-order correlation function g(2)(0), showing that TPA imposes an intrinsic limit on heralded single photon sources. We build on these observations to devise a new metric, the quantum utility (QMU), enabling further optimisation of single photon sources. PMID:24186400

  14. Catheter-directed Thrombolysis with Argatroban and tPA for Massive Iliac and Femoropopliteal Vein Thrombosis

    SciTech Connect

    Sharifi, Mohsen; Bay, Curt; Nowroozi, Sasan; Bentz, Suzanne; Valeros, Gayle; Memari, Sara

    2013-12-15

    Purpose: Catheter-directed thrombolysis (CDT) is a highly effective approach in the treatment of deep venous thrombosis (DVT). There are no data on the primary use of CDT with argatroban and tissue plasminogen activator (tPA) in patients without heparin-induced thrombocytopenia (HIT). The aim of this study was to evaluate the efficacy and safety of the combined administration of argatroban and tPA during CDT for massive DVT in patients without HIT. Methods: Thirty-three patients with massive symptomatic iliac and femoropopliteal DVT underwent CDT with tPA and argatroban within 28 {+-} 6 h of presentation. The dose of tPA was 0.75-1 mg/h through the infusion port and that of argatroban at 0.3-1 {mu}g/kg/min through the side port of the sheath. The patients were evaluated for the efficacy and safety of CDT and recurrent symptomatic venous thromboembolism (VTE) at a mean follow-up of 22 months. Results: There was no bleeding or iatrogenic pulmonary embolism with the CDT regimen we used. Grade III lysis (complete resolution of thrombus on venography) was achieved in 30 patients (91 %). In 3 patients with additional inferior vena cava filter thrombosis, further thrombectomy of the filter was required. No patient developed recurrent VTE. Conclusion: Concomitant administration of argatroban and tPA is a highly safe and effective regimen for CDT for massive DVT.

  15. Electronic properties of superconductors studied using photo induced activation of microwave absorption (PIAMA)

    SciTech Connect

    Feenstra, B.J.; Schooveld, W.A.; Bos, C.

    1995-12-31

    Electronic properties of superconductors are contemporarily being studied using many different experimental techniques, among which infrared spectrometry, photoelectron spectroscopy and microwave cavity techniques play an important role. The data analysis, however, is complicated by the fact that in these materials the phonon-frequency range overlaps with the one in which the energy gap is expected. This problem can be circumvented by making use of two different sources, one to induce the excitations (the Free Electron Laser in Nieuwegein, The Netherlands, FELIX), and one to study the behavior of these excitations (i.e. quasiparticles). In our case the latter source is monochromatic microwave radiation, transmitted through a thin superconducting film. We measured both a conventional superconductor (NbN, T{sub c} = 17 K) and a high T{sub c} superconductor (SmBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, T{sub c} = 92 K). For NbN we observed a positive change in transmission, followed by a relaxation to a transmission smaller than the original value, after which the starting situation was restored within {approximately} 100 {mu}s. In case of SmBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, the changes persisted above T{sub c}. At very low temperatures we observed slow oscillations ({approximately} 4kHz) in the induced signal, which were absent in NbN. The long time scales can possibly be explained by the so-called bottleneck, i.e. quasiparticles excited with a lot of excess energy lose part of their energy by exciting other quasiparticles. In this case the quasiparticle lifetime is enhanced considerably. The oscillations point towards an intrinsic difference of the low energy excitations, i.e. the symmetry of the pairing.

  16. Nonlinear optical absorption and switching properties of gold nanoparticle doped SiO2-TiO2 sol-gel films.

    PubMed

    Venkatram, N; Kumar, R Sai Santosh; Rao, D Narayana; Medda, S K; De, Sucheta; De, Goutam

    2006-07-01

    The nonlinear optical absorption and switching properties of sol-gel derived of Au nanoparticle doped SiO2-TiO2 sol-gel films having different Au-surface plasmon absorption positions are reported in this paper. The Au nanoparticles are embedded in SiO2 and SiO2-TiO2 mixed glassy film matrices with different refractive index values. To study the nonlinear absorption properties, lasers with three different wavelengths are used. The optical switching behavior is studied by using the pump-probe technique with 532 nm as the excitation wavelength. Ground state conduction band, surface plasmon band, and the free carrier band are taken as three level model to explain theoretically the obtained RSA and SA behaviors.

  17. Shock wave equation of state experiments at multi-TPa pressures on NIF

    NASA Astrophysics Data System (ADS)

    Celliers, P. M.; Fratanduono, D. E.; Peterson, J. L.; Meezan, N. B.; MacKinnon, A. J.; Braun, D. G.; Millot, M.; Fry, J.; Boehm, K. J.; Sterne, P. A.; Collins, G. W.; Nikroo, A.; Fitzsimmons, P.

    2015-11-01

    The National Ignition Facility provides an unprecedented capability to generate steady, planar, ultra-high pressure shock waves (up to 10 TPa or more) in solid samples. Building on successful laser shock equation of state experiments performed on a variety of other laser facilities, we have designed and fielded experiments to perform impedance match experiments on samples of C, Be, SiO2 and CH, in the range of 3 to 7 TPa. The experiments use a line-imaging VISAR as the primary diagnostic to measure the shock velocity in an Al reference standard and in an array of the four samples. Initial tests with the line-imaging VISAR show that the NIF is capable of driving shocks that are steady to better than 2% in velocity for several ns, with smooth planar breakout patterns over a 2 mm diameter spot. Hugoniot data points will be compared to current equation-of-state models for the various materials under study. This work was performed under the auspices of the U.S. Department of Energy by LLNL under contract DE-AC52-07NA27344.

  18. Comparison of key absorption and optical properties between pure and transported anthropogenic dust over East and Central Asia

    NASA Astrophysics Data System (ADS)

    Bi, Jianrong; Huang, Jianping; Holben, Brent; Zhang, Guolong

    2016-12-01

    Asian dust particulate is one of the primary aerosol constituents in the Earth-atmosphere system that exerts profound influences on environmental quality, human health, the marine biogeochemical cycle, and Earth's climate. To date, the absorptive capacity of dust aerosol generated from the Asian desert region is still an open question. In this article, we compile columnar key absorption and optical properties of mineral dust over East and Central Asian areas by utilizing the multiyear quality-assured datasets observed at 13 sites of the Aerosol Robotic Network (AERONET). We identify two types of Asian dust according to threshold criteria from previously published literature. (1) The particles with high aerosol optical depth at 440 nm (AOD440 ≥ 0.4) and a low Ångström wavelength exponent at 440-870 nm (α < 0.2) are defined as Pure Dust (PDU), which decreases disturbance of other non-dust aerosols and keeps high accuracy of pure Asian dust. (2) The particles with AOD440 ≥ 0.4 and 0.2 < α < 0.6 are designated as Transported Anthropogenic Dust (TDU), which is mainly dominated by dust aerosol and might mix with other anthropogenic aerosol types. Our results reveal that the primary components of high AOD days are predominantly dust over East and Central Asian regions, even if their variations rely on different sources, distance from the source, emission mechanisms, and meteorological characteristics. The overall mean and standard deviation of single-scattering albedo, asymmetry factor, real part and imaginary part of complex refractive index at 550 nm for Asian PDU are 0.935 ± 0.014, 0.742 ± 0.008, 1.526 ± 0.029, and 0.00226 ± 0.00056, respectively, while corresponding values are 0.921 ± 0.021, 0.723 ± 0.009, 1.521 ± 0.025, and 0.00364 ± 0.0014 for Asian TDU. Aerosol shortwave direct radiative effects at the top of the atmosphere (TOA), at the surface (SFC), and in the atmospheric layer (ATM) for Asian PDU (α < 0.2) and TDU (0.2 < α < 0.6) computed in

  19. A CHANDRA SURVEY OF THE X-RAY PROPERTIES OF BROAD ABSORPTION LINE RADIO-LOUD QUASARS

    SciTech Connect

    Miller, B. P.; Brandt, W. N.; Garmire, G. P.; Gibson, R. R.; Shemmer, O. E-mail: niel@astro.psu.edu E-mail: rgibson@astro.washington.edu

    2009-09-10

    This work presents the results of a Chandra study of 21 broad absorption line (BAL) radio-loud quasars (RLQs). We conducted a Chandra snapshot survey of 12 bright BAL RLQs selected from Sloan Digital Sky Survey Data/Faint Images of the Radio Sky data and possessing a wide range of radio and C IV absorption properties. Optical spectra were obtained nearly contemporaneously with the Hobby-Eberly Telescope; no strong flux or BAL variability was seen between epochs. In addition to the snapshot targets, we include in our sample nine additional BAL RLQs possessing archival Chandra coverage. We compare the properties of (predominantly high-ionization) BAL RLQs to those of non-BAL RLQs as well as to BAL radio-quiet quasars (RQQs) and non-BAL RQQs for context. All 12 snapshots and 8/9 archival BAL RLQs are detected, with observed X-ray luminosities less than those of non-BAL RLQs having comparable optical/UV luminosities by typical factors of 4.1-8.5. (BAL RLQs are also X-ray weak by typical factors of 2.0-4.5 relative to non-BAL RLQs having both comparable optical/UV and radio luminosities.) However, BAL RLQs are not as X-ray weak relative to non-BAL RLQs as are BAL RQQs relative to non-BAL RQQs. While some BAL RLQs have harder X-ray spectra than typical non-BAL RLQs, some have hardness ratios consistent with those of non-BAL RLQs, and there does not appear to be a correlation between X-ray weakness and spectral hardness, in contrast to the situation for BAL RQQs. RLQs are expected to have X-ray continuum contributions from both accretion-disk corona and small-scale jet emission. While the entire X-ray continuum in BAL RLQs cannot be obscured to the same degree as in BAL RQQs, we calculate that the jet is likely partially covered in many BAL RLQs. We comment briefly on implications for geometries and source ages in BAL RLQs.

  20. A model predicting the evolution of ice particle size spectra and radiative properties of cirrus clouds. Part 2: Dependence of absorption and extinction on ice crystal morphology

    NASA Technical Reports Server (NTRS)

    Mitchell, David L.; Arnott, W. Patrick

    1994-01-01

    This study builds upon the microphysical modeling described in Part 1 by deriving formulations for the extinction and absorption coefficients in terms of the size distribution parameters predicted from the micro-physical model. The optical depth and single scatter albedo of a cirrus cloud can then be determined, which, along with the asymmetry parameter, are the input parameters needed by cloud radiation models. Through the use of anomalous diffraction theory, analytical expressions were developed describing the absorption and extinction coefficients and the single scatter albedo as functions of size distribution parameters, ice crystal shapes (or habits), wavelength, and refractive index. The extinction coefficient was formulated in terms of the projected area of the size distribution, while the absorption coefficient was formulated in terms of both the projected area and mass of the size distribution. These properties were formulated as explicit functions of ice crystal geometry and were not based on an 'effective radius.' Based on simulations of the second cirrus case study described in Part 1, absorption coefficients predicted in the near infrared for hexagonal columns and rosettes were up to 47% and 71% lower, respectively, than absorption coefficients predicted by using equivalent area spheres. This resulted in single scatter albedos in the near-infrared that were considerably greater than those predicted by the equivalent area sphere method. Reflectances in this region should therefore be underestimated using the equivalent area sphere approach. Cloud optical depth was found to depend on ice crystal habit. When the simulated cirrus cloud contained only bullet rosettes, the optical depth was 142% greater than when the cloud contained only hexagonal columns. This increase produced a doubling in cloud albedo. In the near-infrared (IR), the single scatter albedo also exhibited a significant dependence on ice crystal habit. More research is needed on the

  1. Two-photon absorption and nonlinear polariton effects in organic crystals

    SciTech Connect

    Johnson, C.K.

    1981-01-01

    Two-photon excitation (TPE) and second harmonic generation (SHG) have been studied in phenanthrene crystals at low temperatures (2 to 6K) in order to investigate mechanisms of two-photon absorption (TPA), the relationship between TPE and SHG, and polariton effects. The transition studied is of special interest because it is both one- and two-photon allowed in the dipole approximation. Consequently, polariton states and SHG play a role in the two-photon process. In the polariton model, both TPA and SHG are understood as resulting from the process of polariton fusion.

  2. Stability of protein-encapsulating DRV liposomes after freeze-drying: A study with BSA and t-PA.

    PubMed

    Ntimenou, Vassiliki; Mourtas, Spyridon; Christodoulakis, Emmanouil V; Tsilimbaris, Miltiadis; Antimisiaris, Sophia G

    2006-01-01

    Stability of protein-encapsulating DRV (dried-rehydrated vesicle) liposomes is evaluated after freeze-drying vesicles in presence (or not) of trehalose. Two proteins, bovine serum albumin (BSA) and tissue-type plasminogen activator (t-PA), are used, and protein-encapsulating liposomes with different lipid compositions are prepared by DRV technique. Encapsulation efficiencies are calculated, after measuring BSA with a fluorescence technique and t-PA's amidolytic activity toward a chromogenic substrate. Experimental results show that encapsulation of BSA in vesicles ranges between 35 and 53% of the protein and is only slightly affected by lipid composition. For t-PA, entrapment efficiencies are lower, ranging between 2 and 16%, while lipid composition has substantial effect on entrapment (cholesterol inclusion is very important). After freeze-drying, some lipid compositions remain stable, retaining most of initially entrapped proteins, while others do not, but they may be stabilized by trehalose. In the case of BSA, liposome behavior cannot be explained based on lipid membrane rigidity (more rigid = more stable). This may be connected with previously demonstrated interactions of BSA with membranes. Oppositely, t-PA behavior is more predictable, meaning that the lipid composition selected for the specific therapeutic application determines the need for cryoprotectant addition before freeze-drying t-PA containing DRV liposomes, perhaps due to the fact that under conditions applying minimum or no interactions between t-PA and lipid membranes occur.Thereby, interactions between proteins and membranes determine not only the encapsulation efficiency but also the need for cryopreservation of liposomal protein formulations.

  3. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Enhanced nonlinear optical absorption of Au/SiO2 nano-composite thin films

    NASA Astrophysics Data System (ADS)

    Zhao, Cui-Hua; Zhang, Bo-Ping; Shang, Peng-Peng

    2009-12-01

    Nano metal-particle dispersed glasses are the attractive candidates for nonlinear optical material applications. Au/SiO2 nano-composite thin films with 3 vol% to 65 vol% Au are prepared by inductively coupled plasma sputtering. Au particles as perfect spheres with diameters between 10 nm and 30 nm are uniformly dispersed in the SiO2 matrix. Optical absorption peaks due to the surface plasmon resonance of Au particles are observed. The absorption property is enhanced with the increase of Au content, showing a maximum value in the films with 37 vol% Au. The absorption curves of the Au/SiO2 thin films with 3 vol% to 37 vol% Au accord well with the theoretical optical absorption spectra obtained from Mie resonance theory. Increasing Au content over 37 vol% results in the partial connection of Au particles, whereby the intensity of the absorption peak is weakened and ultimately replaced by the optical absorption of the bulk. The band gap decreases with Au content increasing from 3 vol% to 37 vol% but increases as Au content further increases.

  4. Optical absorption and fluorescence properties of Er{sup 3+}/Yb{sup 3+} codoped lead bismuth alumina borate glasses

    SciTech Connect

    Goud, K. Krishna Murthy Reddy, M. Chandra Shekhar Rao, B. Appa

    2014-04-24

    Lead bismuth alumina borate glasses codoped with Er{sup 3+}/Yb{sup 3+} were prepared by melt quenching technique. Optical absorption, FTIR and photoluminescence spectra of these glasses have been studied. Judd-Ofelt theory has been applied to to the f ↔ f transitions for evaluating Ω{sub 2}, Ω{sub 4} and Ω{sub 6} parameters. Radiative properties like branching ratio β{sub r} and the radiative life time τ{sub R} have been determined on the basis of Judd-Ofelt theory. Upconversion emissions have been observed under 980nm laser excitation at room temperature. Green and red up-conversion emissions are centered at 530, 550 and 656 nm corresponding to {sup 2}H{sub 11/2}→{sup 4}I{sub 15/2}, {sup 4}S{sub 3/2}→{sup 4}I{sub 15/2} and {sup 4}F{sub 9/2}→{sup 4}I{sub 15/2} transitions of Er{sup 3+} respectively. The results obtained are discussed quantitatively based on the energy transfer between Yb{sup 3+} and Er{sup 3+}.

  5. Microwave-assisted synthesis of graphene-Ni composites with enhanced microwave absorption properties in Ku-band

    NASA Astrophysics Data System (ADS)

    Zhu, Zetao; Sun, Xin; Li, Guoxian; Xue, Hairong; Guo, Hu; Fan, Xiaoli; Pan, Xuchen; He, Jianping

    2015-03-01

    Recently, graphene has been applied as a new microwave absorber because of its high dielectric loss and low density. Nevertheless, the high dielectric constant of pristine graphene has caused unbalanced electromagnetic parameters and results in a bad impedance matching characteristic. In this study, we report a facile microwave-assisted heating approach to produce reduced graphene oxide-nickel (RGO-Ni) composites. The phase and morphology of as-synthesized RGO-Ni composites are characterized by XRD, Raman, FESEM and TEM. The results show that Ni nanoparticles with a diameter around 20 nm are grown densely and uniformly on the RGO sheets. In addition, enhanced microwave absorption properties in Ku-band of RGO-Ni composites is mainly due to the synergistic effect of dielectric loss and magnetic loss and the dramatically electron polarizations caused by the formation of large conductive network. The minimum reflection loss of RGO-Ni-2 composite with the thickness of 2 mm can reaches -42 dB at 17.6 GHz. The RGO-Ni composite is an attractive candidate for the new type of high performance microwave absorbing material.

  6. Electromagnetic wave absorption properties of NiCoP alloy nanoparticles decorated on reduced graphene oxide nanosheets

    NASA Astrophysics Data System (ADS)

    Ye, Weichun; Fu, Jiajia; Wang, Qin; Wang, Chunming; Xue, Desheng

    2015-12-01

    NiCoP alloy nanoparticles supported on reduced graphene oxide (NiCoP/RGO) are synthesized by in situ co-reduction of Ni2+, Co2+ and graphene oxide (GO) with sodium hypophosphite in a one-pot reaction. This synthesis route is simple and can be used for industrial preparation. The different molar ratios of Ni/Co can be obtained by changing the molar ratio of their salts in the reaction bath. The effect of annealing temperature on the crystal structure of NiCoP alloys has been further investigated. After 500 °C annealing, NiCoP alloys exhibit good crystallinity. The as-prepared NiCoP/RGO composites demonstrate high dielectric constant and magnetic loss in the frequency range of 2-18 GHz due to the conductive and ferromagnetic behavior. Also, their coercivity and magnetization strength are decreased from magnetic measurement with the increase of Ni content. As the molar ratio of Ni/Co is 3:1, the maximum value of the reflection loss reaches to -17.84 dB. Furthermore, the NiCoP/RGO composites have better corrosion resistance than traditional iron series magnetic nanoparticles. It is expected that the composites with the thin, light-weighted and broadband absorbing and good anti-corrosion properties will have a great potential for electromagnetic wave absorption applications.

  7. Structural, magnetic and microwave absorption properties of doped Ba-hexaferrite nanoparticles synthesized by co-precipitation method

    NASA Astrophysics Data System (ADS)

    Alam, Reza Shams; Moradi, Mahmood; Rostami, Mohammad; Nikmanesh, Hossein; Moayedi, Razieh; Bai, Yang

    2015-05-01

    The structural, magnetic and microwave absorption properties of the barium hexaferrite doped by Zn, Co and Zr cations have been investigated. BaZnxCoxZr2xFe12-4xO19 (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5) nanoparticles were synthesized by the co-precipitation method in the presence of polyvinyl alcohol (PVA). X-ray diffraction (XRD), thermal analysis (TGA-DTA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and vector network analyzer are employed to investigate the desired properties of the prepared samples. From the XRD evaluation it can be seen that the magnetoplumbite structure for all of the samples have been formed and the average crystallite size of nanoparticles lies in the range of 44 ±3 nm. The TGA-DTA curves of the undoped sample (x=0.0) indicate that the formation of barium hexaferrite can be obtained at a relatively low temperature of 709 °C. The results of VSM analysis show that the saturation magnetization and coercivity are decreased by increasing the percentage of the dopants. The reflection loss results indicate that the ferrite with the composition of BaZn0.5Co0.5 ZrFe10O19 has appropriate reflection loss (RL<-10 dB) and bandwidth in order to be used as a potential single layer absorber in the frequency range of 8-12 GHz.

  8. Near-infrared absorption properties of oxygen-rich stardust analogs. The influence of coloring metal ions

    NASA Astrophysics Data System (ADS)

    Zeidler, Simon; Posch, Thomas; Mutschke, Harald; Richter, Hannes; Wehrhan, Ortrud

    2011-02-01

    Context. Several astrophysically relevant solid oxides and silicates have extremely small opacities in the visual and near-infrared in their pure forms. Datasets for the opacities and for the imaginary part k of their complex indices of refraction are hardly available in these wavelength ranges. Aims: We aimed at determining k for spinel, rutile, anatase, and olivine, especially in the near-infrared region. Our measurements were made with impurity-containing, natural, and synthetic stardust analogs. Methods: Two experimental methods were used: preparing small sections of natural minerals and synthesizing melt droplets under the electric arc furnace. In both cases, the aborption properties of the samples were measured by transmission spectroscopy. Results: For spinel (MgAl2O4), anatase, rutile (both TiO2), and olivine ((Mg,Fe)2SiO4), the optical constants have been extended to the visual and near-infrared. We highlight that the individual values of k(λ) and the absorption cross section Qabs(λ) depend strongly on the content in transition metals like iron. Based on our measurements, we infer that k values below 10-5 are very rare in natural minerals including stardust grains, if they occur at all. Conclusions: Data for k and Qabs(λ) are important for various physical properties of stardust grains such as temperature and radiation pressure. With increasing Qabs(λ) due to impurities, the equilibrium temperature of small grains in circumstellar shells increases as well. We discuss why and to what extent this is the case.

  9. Synthesis, fine structure of 19F NMR and fluorescence of novel amorphous TPA derivatives having perfluorinated cyclopentenyl and benzo[b]thiophene unit

    NASA Astrophysics Data System (ADS)

    Wu, Bian-Peng; Pang, Mei-Li; Tan, Ting-Feng; Meng, Ji-ben

    2013-04-01

    Three novel triphenylamine (TPA) derivatives having perfluorinated cyclopentenyl and benzo[b]thiophene unit are obtained from 4-bromo-N,N-diphenyl-2-methylbenzo[b]thiophen-5-amine. The new compounds are expected to find their use in thin film devices as charge transport materials and host organic light-emitting materials. It is found that the new compounds show relatively strong fluorescence either in solution or in solid state, and are amorphous due to a special conformation which is elucidated by the fine structure of 19F NMR. Molecular structure and properties of these compounds is characterized by 1H NMR, 13C NMR (broadband decoupled), ESI-HRMS, elemental analysis and thermal analysis (DSC). Fluorescent quantum yield in solution is measured using 9,10-diphenylanthrancene (DPA) as standard fluorescent substance.

  10. Multispectral imaging of absorption and scattering properties of in vivo exposed rat brain using a digital red-green-blue camera

    NASA Astrophysics Data System (ADS)

    Yoshida, Keiichiro; Nishidate, Izumi; Ishizuka, Tomohiro; Kawauchi, Satoko; Sato, Shunichi; Sato, Manabu

    2015-05-01

    In order to estimate multispectral images of the absorption and scattering properties in the cerebral cortex of in vivo rat brain, we investigated spectral reflectance images estimated by the Wiener estimation method using a digital RGB camera. A Monte Carlo simulation-based multiple regression analysis for the corresponding spectral absorbance images at nine wavelengths (500, 520, 540, 560, 570, 580, 600, 730, and 760 nm) was then used to specify the absorption and scattering parameters of brain tissue. In this analysis, the concentrations of oxygenated hemoglobin and that of deoxygenated hemoglobin were estimated as the absorption parameters, whereas the coefficient a and the exponent b of the reduced scattering coefficient spectrum approximated by a power law function were estimated as the scattering parameters. The spectra of absorption and reduced scattering coefficients were reconstructed from the absorption and scattering parameters, and the spectral images of absorption and reduced scattering coefficients were then estimated. In order to confirm the feasibility of this method, we performed in vivo experiments on exposed rat brain. The estimated images of the absorption coefficients were dominated by the spectral characteristics of hemoglobin. The estimated spectral images of the reduced scattering coefficients had a broad scattering spectrum, exhibiting a larger magnitude at shorter wavelengths, corresponding to the typical spectrum of brain tissue published in the literature. The changes in the estimated absorption and scattering parameters during normoxia, hyperoxia, and anoxia indicate the potential applicability of the method by which to evaluate the pathophysiological conditions of in vivo brain due to the loss of tissue viability.

  11. Multispectral imaging of absorption and scattering properties of in vivo exposed rat brain using a digital red-green-blue camera.

    PubMed

    Yoshida, Keiichiro; Nishidate, Izumi; Ishizuka, Tomohiro; Kawauchi, Satoko; Sato, Shunichi; Sato, Manabu

    2015-05-01

    In order to estimate multispectral images of the absorption and scattering properties in the cerebral cortex of in vivo rat brain, we investigated spectral reflectance images estimated by the Wiener estimation method using a digital RGB camera. A Monte Carlo simulation-based multiple regression analysis for the corresponding spectral absorbance images at nine wavelengths (500, 520, 540, 560, 570, 580, 600, 730, and 760 nm) was then used to specify the absorption and scattering parameters of brain tissue. In this analysis, the concentrations of oxygenated hemoglobin and that of deoxygenated hemoglobin were estimated as the absorption parameters, whereas the coefficient a and the exponent b of the reduced scattering coefficient spectrum approximated by a power law function were estimated as the scattering parameters. The spectra of absorption and reduced scattering coefficients were reconstructed from the absorption and scattering parameters, and the spectral images of absorption and reduced scattering coefficients were then estimated. In order to confirm the feasibility of this method, we performed in vivo experiments on exposed rat brain. The estimated images of the absorption coefficients were dominated by the spectral characteristics of hemoglobin. The estimated spectral images of the reduced scattering coefficients had a broad scattering spectrum, exhibiting a larger magnitude at shorter wavelengths, corresponding to the typical spectrum of brain tissue published in the literature. The changes in the estimated absorption and scattering parameters during normoxia, hyperoxia, and anoxia indicate the potential applicability of the method by which to evaluate the pathophysiological conditions of in vivo brain due to the loss of tissue viability.

  12. Two-photon absorption of Tl1-xIn1-xSnxSe2 nanocrystallites

    NASA Astrophysics Data System (ADS)

    Myronchuk, Galyna; Parasyuk, Oleg; Piskach, Ludmila; Alzayed, Nasser Saleh; Prokhorenko, Serhii; Piasecki, Michal; Kityk, Iwan

    2016-12-01

    Novel materials for the infrared two-photon absorption — Tl1-xIn1-xSnxSe2 single crystals (x = 0.1,0.2) were grown. Two-photon absorption (TPA) was studied at CO2 laser wave-length 9.4μm with pulse duration 1μs. The studies were performed at different temperatures and for the nanocrystallite sizes varying within the 7-200 nm. The studies have shown that the TPA may be enhanced during the decrease of the nanocrystallite sizes below 50-60 nm. There exists also some critical x value at which the TPA value begin substantially to increase. The studied nanocrystallites are relatively stable to the infrared laser treatment and are not hygroscopic which allow to use them in different IR optoelectronic devices.

  13. Excellent electromagnetic absorption properties of poly(3,4-ethylenedioxythiophene)-reduced graphene oxide-Co3O4 composites prepared by a hydrothermal method.

    PubMed

    Liu, Pan-Bo; Huang, Ying; Sun, Xu

    2013-12-11

    The ternary composites of poly(3,4-ethylenedioxythiophene)-reduced graphene oxide-Co3O4 (PEDOT-RGO-Co3O4) were synthesized and the electromagnetic absorption property of the composites was investigated. The structure of the composites was characterized with Fourier-transform infrared spectra, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscope. The electromagnetic parameters indicate the enhanced electromagnetic absorption property of the composites was attributed to the better impedance matching. On the basis of the above characterization, an electromagnetic complementary theory was proposed to explain the impedance matching. It can be found that the maximum reflection loss of PEDOT-RGO-Co3O4 can reach -51.1 dB at 10.7 GHz, and the bandwidth exceeding -10 dB is 3.1 GHz with absorber thickness of 2.0 mm. Therefore, the PEDOT-RGO-Co3O4 composites, with such excellent electromagnetic absorption properties and wide absorption bandwidth, can be used as a new kind of candidate for microwave absorbing materials.

  14. Light absorption, optical and microphysical properties of trajectory-clustered aerosols at two AERONET sites in West Africa

    NASA Astrophysics Data System (ADS)

    Fawole, O. G.; Cai, X.; MacKenzie, A. R.

    2015-12-01

    Aerosol remote sensing techniques and back-trajectory modeling can be combined to identify aerosol types. We have clustered 7 years of AERONET aerosol signals using trajectory analysis to identify dominant aerosol sources at two AERONET sites in West Africa: Ilorin (4.34 oE, 8.32 oN) and Djougou (1.60 oE, 9.76 oN). Of particular interest are air masses that have passed through the gas flaring region in the Niger Delta area, of Nigeria, en-route the AERONET sites. 7-day back trajectories were calculated using the UK UGAMP trajectory model driven by ECMWF wind analyses data. Dominant sources identified, using literature classifications, are desert dust (DD), Biomass burning (BB) and Urban-Industrial (UI). Below, we use a combination of synoptic trajectories and aerosol optical properties to distinguish a fourth source: that due to gas flaring. Gas flaring, (GF) the disposal of gas through stack in an open-air flame, is believed to be a prominent source of black carbon (BC) and greenhouse gases. For these different aerosol source signatures, single scattering albedo (SSA), refractive index , extinction Angstrom exponent (EEA) and absorption Angstrom exponent (AAE) were used to classify the light absorption characteristics of the aerosols for λ = 440, 675, 870 and1020 nm. A total of 1625 daily averages of aerosol data were collected for the two sites. Of which 245 make up the GF cluster for both sites. For GF cluster, the range of fine-mode fraction is 0.4 - 0.7. Average values SSA(λ), for the total and GF clusters are 0.90(440), 0.93(675), 0.95(870) and 0.96(1020), and 0.93(440), 0.92(675), 0.9(870) and 0.9(1020), respectively. Values of for the GF clusters for both sites are 0.62 - 1.11, compared to 1.28 - 1.66 for the remainder of the clusters, which strongly indicates the dominance of carbonaceous particles (BC), typical of a highly industrial area. An average value of 1.58 for the real part of the refractive index at low SSA for aerosol in the GF cluster is also

  15. Improved microwave absorption and electromagnetic properties of BaFe12O19-poly(vinylidene fluoride) composites by incorporating reduced graphene oxides

    NASA Astrophysics Data System (ADS)

    He, Hongcai; Luo, Feifei; Qian, Neng; Wang, Ning

    2015-02-01

    Three-phase composites of poly(vinylidene fluoride)-BaFe12O19-reduced graphene oxide (PVDF-BFO-RGO) were synthesized by a facile wet chemical method and hot-pressing approach. The phase structure, topography of the hybrid materials were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectra. Influence of RGO on their electromagnetic properties was investigated. Especially, improved microwave absorption and electromagnetic properties of BaFe12O19-PVDF composites by incorporating RGO were obtained and studied. The PVDF/BFO/RGO sample with m(RGO):m(BFO) = 5:100 shows the best microwave absorption properties with a minimum RL = -32 dB at 11 GHz and with the bandwidth less than -20 dB from 9.6 to 12.8 GHz. The composites were believed to have potential applications as the microwave absorber.

  16. Microwave-assisted synthesis of water-soluble, fluorescent gold nanoclusters capped with small organic molecules and a revealing fluorescence and X-ray absorption study

    NASA Astrophysics Data System (ADS)

    Helmbrecht, C.; Lützenkirchen-Hecht, D.; Frank, W.

    2015-03-01

    Colourless solutions of blue light-emitting, water-soluble gold nanoclusters (AuNC) were synthesized from gold colloids under microwave irradiation using small organic molecules as ligands. Stabilized by 1,3,5-triaza-7-phosphaadamantane (TPA) or l-glutamine (GLU), fluorescence quantum yields up to 5% were obtained. AuNC are considered to be very promising for biological labelling, optoelectronic devices and light-emitting materials but the structure-property relationships have still not been fully clarified. To expand the knowledge about the AuNC apart from their fluorescent properties they were studied by X-ray absorption spectroscopy elucidating the oxidation state of the nanoclusters' gold atoms. Based on curve fitting of the XANES spectra in comparison to several gold references, optically transparent fluorescent AuNC are predicted to be ligand-stabilized Au5+ species. Additionally, their near edge structure compared with analogous results of polynuclear clusters known from the literature discloses an increasing intensity of the feature close to the absorption edge with decreasing cluster size. As a result, a linear relationship between the cluster size and the X-ray absorption coefficient can be established for the first time.Colourless solutions of blue light-emitting, water-soluble gold nanoclusters (AuNC) were synthesized from gold colloids under microwave irradiation using small organic molecules as ligands. Stabilized by 1,3,5-triaza-7-phosphaadamantane (TPA) or l-glutamine (GLU), fluorescence quantum yields up to 5% were obtained. AuNC are considered to be very promising for biological labelling, optoelectronic devices and light-emitting materials but the structure-property relationships have still not been fully clarified. To expand the knowledge about the AuNC apart from their fluorescent properties they were studied by X-ray absorption spectroscopy elucidating the oxidation state of the nanoclusters' gold atoms. Based on curve fitting of the XANES

  17. Stability of iron crystal structures at 0.3-1.5 TPa

    NASA Astrophysics Data System (ADS)

    Godwal, B. K.; González-Cataldo, F.; Verma, A. K.; Stixrude, Lars; Jeanloz, Raymond

    2015-01-01

    Ab initio molecular dynamics simulations carried out for tetragonal and orthorhombic distortions of iron closely follow the results of static-lattice electronic-structure calculations in revealing that the body-centered cubic (bcc) phase of Fe is mechanically unstable at pressures of 0.3-1.5 TPa and temperatures up to 7000 K. Crystal-structural instabilities originate in the static lattice for the bcc configuration, and are consistent with recent results from both static and dynamic high-pressure experiments. Both theory and experiment thus show that the close-packed (hexagonal, hcp and face-centered cubic, fcc) crystal structures of iron are those relevant to the cores of Earth-like planets.

  18. The quest for TPa Hugoniot data: using the DEMG in high velocity pulsed power experiments

    SciTech Connect

    Peterson, Jeff H; Rousculp, Christopher L; Holtkamp, David B; Oro, David M; Griego, Jeffrey R; Atchison, Walter L; Reinovsky, Robert E

    2010-12-20

    ALT-3 is an experiment being designed in collaboration between Russian VNIIEF scientists and LANL that aims to conduct high velocity material experiments to measure shock velocities at pressures near 1 TPa. The DEMG (Disk Explosive Magnetic Generator) is used to drive >60MA currents to accelerate an aluminum liner to speeds in excess of 20 km/s. The 1-D model of the DEMG has been refined from a given current profile to a time-varying inductance. Various techniques are used to model the FOS (Foil Opening Switch) on the DEMG and a refined DEMG model is then used to drive a liner into various targets to determine the optimum design for the experiment and analyze the possible conditions and complications.

  19. Increasing tPA Activity in Astrocytes Induced by Multipotent Mesenchymal Stromal Cells Facilitate Neurite Outgrowth after Stroke in the Mouse

    PubMed Central

    Xin, Hongqi; Li, Yi; Shen, Li Hong; Liu, Xianshuang; Wang, Xinli; Zhang, Jing; Pourabdollah-Nejad D, Siamak; Zhang, Chunling; Zhang, Li; Jiang, Hao; Zhang, Zheng Gang; Chopp, Michael

    2010-01-01

    We demonstrate that tissue plasminogen activator (tPA) and its inhibitors contribute to neurite outgrowth in the central nervous system (CNS) after treatment of stroke with multipotent mesenchymal stromal cells (MSCs). In vivo, administration of MSCs to mice subjected to middle cerebral artery occlusion (MCAo) significantly increased activation of tPA and downregulated PAI-1 levels in the ischemic boundary zone (IBZ) compared with control PBS treated mice, concurrently with increases of myelinated axons and synaptophysin. In vitro, MSCs significantly increased tPA levels and concomitantly reduced plasminogen activator inhibitor 1 (PAI-1) expression in astrocytes under normal and oxygen and glucose deprivation (OGD) conditions. ELISA analysis of conditioned medium revealed that MSCs stimulated astrocytes to secrete tPA. When primary cortical neurons were cultured in the conditioned medium from MSC co-cultured astrocytes, these neurons exhibited a significant increase in neurite outgrowth compared to conditioned medium from astrocytes alone. Blockage of tPA with a neutralizing antibody or knock-down of tPA with siRNA significantly attenuated the effect of the conditioned medium on neurite outgrowth. Addition of recombinant human tPA into cortical neuronal cultures also substantially enhanced neurite outgrowth. Collectively, these in vivo and in vitro data suggest that the MSC mediated increased activation of tPA in astrocytes promotes neurite outgrowth after stroke. PMID:20140248

  20. Regulation of ectodermal differentiation in Xenopus laevis animal caps treated with TPA and ammonium chloride.

    PubMed

    Sotgia, C; Fascio, U; Pennati, R; De Bernardi, F

    1998-02-01

    Animal caps isolated from Xenopus laevis embryos at the blastula stage were treated sequentially with NH4Cl, a known cement gland inducer, and with 12-O-tetradecanoyl phorbol-13-acetate (TPA), a known neural inducer. The two artificial inducers were also used in reverse order to see if they can mimic the natural inducers acting during the progressive determination of the ectodermal organ. Immunofluorescence and whole-mount in situ hybridization were used to study the expression of tubulin, taken to indicate an early step on the pathway of cell elongation, and neural cell adhesion molecule (N-CAM) taken to indicate an early step in the determination of the nervous system. The expression of XCG-1, a marker of early specification of the cement gland, was also studied. The results showed that the two artificial inducers can mimic the effects of the natural inducers in animal cap explants. The TPA behaves like a neural inducer, reducing the number and the extension of the cement gland when added to the medium in addition to NH4Cl, before or after NH4Cl treatment. In the process of cement gland/neural induction, it is possible to redirect the ectoderm already specified as cement gland to neural tissue, but it does not seem possible to respecify the neural tissue as cement gland. Moreover, the animal caps were also cut into dorsal and ventral parts and the two halves were treated separately. The results were similar to those obtained with treatment of the entire animal cap, suggesting that a dorsal-ventral pattern is not yet established before the gastrula stage, and that in normal embryos there are boundaries between the effects of different inducers.

  1. A comparative study of optical absorption and photocatalytic properties of nanocrystalline single-phase anatase and rutile TiO{sub 2} doped with transition metal cations

    SciTech Connect

    Kernazhitsky, L.; Shymanovska, V.; Gavrilko, T.; Naumov, V.; Kshnyakin, V.; Khalyavka, T.

    2013-02-15

    The effect of nanocrystalline TiO{sub 2} doping with transition metal cations (Cu{sup 2+}, Fe{sup 3+}, Co{sup 2+}, Cr{sup 3+}) on their optical absorption and photocatalytic properties was investigated. The obtained metal-doped TiO{sub 2} samples were characterized by X-ray diffraction, scanning electron microscopy, and UV-vis absorption spectroscopy. It is shown that doping effect on anatase (A) and rutile (R) properties is quite different, being much stronger and complicated on A than on R. Contrary to doped R, doped A revealed a significant red shift of the absorption edge along with the band gap narrowing. Photocatalytic activity of anatase increases upon doping in the order: AR/Co>R/Cu>R/Fe>R/Cr, indicating the inhibitory effect of impurity cations. This fact correlates with the decrease in the UV absorption of the doped rutile in the region of the Hg-lamp irradiation at 4.88 eV. - Graphical abstract: A red shift of the absorption edge of nanocrystalline single-phase anatase after doping with transition metal cations. Highlights: Black-Right-Pointing-Pointer Single-phase anatase and rutile powders surface-doped with transition metal cations. Black-Right-Pointing-Pointer Absorption edge and band gap of rutile do not change with surface doping. Black-Right-Pointing-Pointer Band gap of surface-doped anatase reduces being the lowest for A/Fe. Black-Right-Pointing-Pointer The surface-doping improves photocatalytic activity of anatase. Black-Right-Pointing-Pointer The surface-doping inhibits photocatalytic activity of rutile.

  2. Theory of direct and indirect effect of two-photon absorption on nonlinear optical losses in high power semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Avrutin, E. A.; Ryvkin, B. S.

    2017-01-01

    The effect of the transverse laser structure on two-photon absorption (TPA) related effects in high-power diode lasers is analysed theoretically. The direct effect of TPA is found to depend significantly on the transverse waveguide structure, and predicted to be weaker in broad and asymmetric waveguide designs. The indirect effect of TPA, via carrier generation in the waveguide and free-carrier absorption, is analysed for the case of a symmetric laser waveguide and shown to be strongly dependent on the active layer position. With the active layer near the mode peak, the indirect effect is weaker than the direct effect due to the population of TPA-created carriers being efficiently depleted by their diffusion and capture into the active layer, whereas for the active layer position strongly shifted towards the p-cladding, the indirect effect can become the dominant power limitation at very high currents. It is shown that for optimizing a laser design for pulsed high power operation, both TPA related effects and the inhomogeneous carrier accumulation in the waveguide caused by diffusive current need to be taken into account.

  3. Titania hollow spheres modified with tungstophosphoric acid with enhanced visible light absorption for the photodegradation of 4-chlorophenol.

    PubMed

    Orellana, M Á; Osiglio, L; Arnal, P M; Pizzio, L R

    2017-01-18

    Titania hollow spheres were synthesized using silica nanospheres as the template. The core was removed using NaOH solution. They were subsequently impregnated with tungstophosphoric acid (TPA) solutions and annealed at two different temperatures (100 and 500 °C). These materials were characterized by several physicochemical techniques (XRD, BET, SEM, DRS, FT-IR, FT-Raman and (31)P MAS-NMR). The (31)P MAS-NMR and FT-IR characterization showed that the main species present in the samples was the [PW12O40](3-) anion, which was partially transformed into the [P2W21O71](6-) anion during the synthesis and drying step. (31)P MAS-NMR, and FT-Raman characterization revealed the evidence of a strong interaction between the Keggin anion of TPA and TiO2 surfaces, possibly due to the formation of surface heteropolyacid-TiO2 complexes. The DRS results showed that the absorption threshold onset continuously shifted to the visible region with increased TPA concentration and calcination at 500 °C. The enhanced visible light absorption could be related to the formation of a surface complex TPA Keggin anion-TiO2. The catalytic activity of the materials in the photodegradation of 4-chlorophenol under UV and visible light irradiation increased when the TPA content and the calcination temperature of the samples were raised.

  4. In vivo estimation of light scattering and absorption properties of rat brain using single reflectance fiber probe during anoxic depolarization

    NASA Astrophysics Data System (ADS)

    Nishidate, Izumi; Yoshida, Keiichiro; Kawauchi, Satoko; Sato, Shunichi; Sato, Manabu

    2015-03-01

    Diffuse reflectance spectroscopy using fiber optic probe is one of most promising technique for evaluating optical properties of biological tissue. We present a method determining the reduced scattering coefficients μs', the absorption coefficients μ a, and tissue oxygen saturation StO2 of in vivo brain tissue using single reflectance fiber probe with two source-collector geometries. In the present study, we performed in vivo recordings of diffuse reflectance spectra and the electrophysiological signals for exposed brain of rats during normoxia, hyperoxia, hypoxia, and anoxia. The time courses of μa in the range from 500 to 584 nm and StO2 indicated the hemodynamic change in cerebral cortex. Time courses of μs' are well correlated with those of μa in the range from 530 to 570 nm, which also reflect the scattering by red blood cells. On the other hand, a fast decrease in μs' at 800 nm were observed after the respiratory arrest and it synchronized with the negative deflection of the extracellular DC potential. It is said that the DC shift coincident with a rise in extracellular potassium and can evoke cell deformation generated by water movement between intracellular and extracellular compartments, and hence the light scattering by tissue. Therefore, the decrease in μs' at 800 after the respiratory arrest is indicative of changes in light scattering by tissue. The results in this study indicate potential of the method to evaluate the pathophysiological and loss of tissue viability in brain tissue.

  5. Application of light scattering in studies of transport, thermodynamics, light absorption, and electric properties of single droplets

    NASA Astrophysics Data System (ADS)

    Tu, Haohua

    2001-12-01

    A variety of subjects related to an isolated microdroplet, including precise optical measurement, fundamental light scattering theory, in situ droplet spectroscopy, transport mechanism, solution thermodynamics, and electrical stability, have been studied. A technique based on optical resonance alignment is developed to automate the measurement of the optical parameters for a single component droplet. The technique is able to determine the size and refractive index of the droplet with an accuracy of 1 part in 10000, and is also applicable to multicomponent droplets undergoing various physical changes with tolerable degradation of accuracy or automation. By examining the finest details of optical resonances, Mie's light scattering theory is proved to be valid except for a constant background broadening deviation. The effect of eccentricity on light scattering of a layered droplet is first observed. By preparing a concentrically layered droplet, rigorous experimental verification is presented for Aden-Kerker light scattering theory of a concentric sphere. Novel computational technique is developed to identify optical resonances and locate their positions for a concentric sphere of specific properties. A unique technique based on accurate measurement of the imaginary refractive index of a droplet is developed for in situ determination of the concentrations of absorptive chemical species inside the droplet. The effects of Stefan flow, non-isothermal effect, unsteady state behavior, unstationary mechanism, and internal transport on the function of droplet size versus time of a relatively nonvolatile droplet have been proved unimportant. Remarkable accuracy of the asymptotic model based on Maxwell's diffusion controlled theory is justified both theoretically and experimentally. Particular evaporation characteristics are observed for several layered droplets. Explicit as well as implicit methods based on resonance alignment have been developed to determine the activity

  6. An Examination of the EeTPA Portfolio Assessment and Other Measures of Teacher Preparation and Readiness

    ERIC Educational Resources Information Center

    Russell, Victoria; Davidson Devall, Kelly F.

    2016-01-01

    The authors examined the outcomes on several measures of world language teacher preparedness, including university- and state-mandated summative evaluations and the edTPA portfolio assessment, for seven world language teacher candidates during their final semester of clinical practice. The candidates were enrolled in an initial certification…

  7. Effect of Critical Plasma Spray Parameters on Microstructure and Microwave Absorption Property of Ti3SiC2/Cordierite Coatings

    NASA Astrophysics Data System (ADS)

    Su, Jinbu; Zhou, Wancheng; Wang, Hongyu; Liu, Yi; Qing, Yuchang; Luo, Fa; Zhu, Dongmei; Zhou, Liang

    2016-04-01

    Ti3SiC2/cordierite coatings with different critical plasma spray parameters (CPSP) were fabricated via atmospheric plasma spraying method. The microstructure and phase constitution of the as-sprayed Ti3SiC2/cordierite coatings were characterized. The effects of CPSP conditions on the electromagnetic shielding, and dielectric and microwave absorption properties of coatings in the frequency of 8.2-12.4 GHz were also measured and investigated. The results showed that both real and imaginary part of the complex permittivity decrease with increasing CPSP values, which can be ascribed to the decomposition of some Ti3SiC2 into TiC. The calculated reflection loss of the as-sprayed Ti3SiC2/cordierite coatings with different CPSP conditions and thicknesses indicates that coatings with CPSP 0.3, 0.35, and 0.425 exhibit excellent microwave absorption property in the thickness of 1.5 mm. In order to broaden the bandwidth of the coatings, a double-layer coating system was designed. The calculated reflection loss results show that when the thickness of matching layer is 0.3 mm and the thickness of absorbing layer is 1.5 mm, the double-layer coating system shows a proper microwave absorption property with a minimum absorption value of -17.37 dB at 9.67 GHz and a absorption bandwidth (RL less than -5 dB) of 4.16 GHz in the investigated frequency.

  8. The dust, nebular emission, and dependence on QSO radio properties of the associated Mg II absorption line systems

    SciTech Connect

    Khare, Pushpa; Daniel, Vanden Berk; Rahmani, Hadi; York, Donald G.

    2014-10-10

    We studied dust reddening and [O II] emission in 1730 Mg II associated absorption systems (AAS; relative velocity with respect to QSOs, ≤3000 km s{sup –1}; in units of velocity of light, β, ≤0.01) with 0.4 ≤z {sub abs} ≤ 2 in the Sloan Digital Sky Survey DR7, focusing on their dependence on the radio and other QSO properties. We used control samples, several with matching radio properties, to show that (1) AAS in radio-detected (RD) QSOs cause 2.6 ± 0.2 times higher dust extinction than those in radio-undetected (RUD) ones, which in turn cause 2.9 ± 0.7 times the dust extinction in the intervening systems; (2) AAS in core-dominated QSOs cause 2.0 ± 0.1 times higher dust extinction than those in lobe-dominated QSOs; (3) the occurrence of AAS is 2.1 ± 0.2 times more likely in RD QSOs than in RUD QSOs and 1.8 ± 0.1 time more likely in QSOs having black holes with masses larger than 1.23 × 10{sup 9} M {sub ☉} than in those with lower-mass black holes; and (4) there is excess flux in [O II]λ3727 emission in the composite spectra of the AAS samples compared with those of the control samples, which is at the emission redshift. The presence of AAS enhances the O II emission from the active galactic nucleus and/or the host galaxy. This excess is similar for both RD and RUD samples and is 2.5 ± 0.4 times higher in lobe-dominated samples than in core-dominated samples. The excess depends on the black hole mass and Eddington ratio. All these point to the intrinsic nature of the AAS except for the systems with z {sub abs} > z {sub em}, which could be infalling galaxies.

  9. Contribution of the transition moments, form of the absorption band, exciton, and the correlation effects in the linear and nonlinear optical properties of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Díaz-Ponce, Javier Alejandro

    2017-04-01

    This work compares the linear and nonlinear optical properties of polyenes and polyenynes. The simulation was made for finite and infinite conjugation of conjugated polymers, such as polyacetylene, β-carotene, bis (p-toluene sulfonate) (PTS) polyenyne, and a short conjugated polyenyne poly-2,6-decadyin-1,6-ylene azelate (PHDAz). The resonance energy and degree of conjugation are determined by fitting the linear absorption spectra. These parameters are then used for calculating the two photon and third-order nonlinear optical properties. The contribution of the transition moment, the form of the absorption band, the exciton, and phonons in the optical properties are determined. The difference of the experimental values is assigned to correlation effects. We found that the exciton, the correlation effects, and the conduction band are more important in the optical properties of polyenynes than of polyenes. In this way, the dependence of the optical properties of polyenynes on the conduction band makes it possible to increase their nonlinear optical properties by interaction with photons (θ ≈ 0). The dependence of the optical properties on the conduction band also produces that the finiteness of the conjugation strongly decreases the optical properties of polyenynes in relation to polyenes with similar conjugation. On the other hand, the phonons are more important in the optical properties of polyenes than of polyenynes. Consequently, the band is indirect for the studied polyenes and direct for the polyenynes. Therefore, the nonlinear optical properties in the resonance frequency of polyenyne PTS are higher than those for polyacetylene. We also found that asymmetric oscillations of χ(3) in the Brillouin zone increases the χ(3) final value in polyenynes. In addition, we found a change of sign of the wave function coefficients by the Peierls distortion of polyenes to become polyenynes, but this change of sign does not affect the optical properties. As a corollary

  10. A comparative study of optical absorption and photocatalytic properties of nanocrystalline single-phase anatase and rutile TiO2 doped with transition metal cations

    NASA Astrophysics Data System (ADS)

    Kernazhitsky, L.; Shymanovska, V.; Gavrilko, T.; Naumov, V.; Kshnyakin, V.; Khalyavka, T.

    2013-02-01

    The effect of nanocrystalline TiO2 doping with transition metal cations (Cu2+, Fe3+, Co2+, Cr3+) on their optical absorption and photocatalytic properties was investigated. The obtained metal-doped TiO2 samples were characterized by X-ray diffraction, scanning electron microscopy, and UV-vis absorption spectroscopy. It is shown that doping effect on anatase (A) and rutile (R) properties is quite different, being much stronger and complicated on A than on R. Contrary to doped R, doped A revealed a significant red shift of the absorption edge along with the band gap narrowing. Photocatalytic activity of anatase increases upon doping in the order: AR/Co>R/Cu>R/Fe>R/Cr, indicating the inhibitory effect of impurity cations. This fact correlates with the decrease in the UV absorption of the doped rutile in the region of the Hg-lamp irradiation at 4.88 eV.

  11. Synthesis and luminescent properties of complexes of Eu(III) with 2-thienyltrifluoroacetonate, terephthalic acid and phenanthroline

    NASA Astrophysics Data System (ADS)

    Zhao, X. H.; Huang, K. L.; Jiao, F. P.; Liu, S. Q.; Liu, Z. G.; Hu, S. Q.

    2007-09-01

    This work reports the synthesis and luminescent properties of complexes of europium(III) with 2-thienyltrifluoroacetonate (HTTA), terephthalic acid (TPA) and phenanthroline (Phen), in the solid state. The new complexes were characterized by elemental analysis, infrared (IR) spectroscopy, scanning electronic microscopy (SEM) and thermal stability analysis. Both binuclear complex Eu2(TPA)(TTA)4Phen2 and polynuclear complex Eu(TPA)(TTA)Phen present better thermal stability than the mononuclear complex Eu(TTA)3Phen does. The formation of the binuclear/polynuclear structure of the complexes appears to be responsible for the enhancement of the thermal stability. The emission spectra show narrow emission bands that arise from the 5D0→7FJ (J=0 4) transition of the Eu3+ ion. The spectral data of the complexes Eu(TPA)(TTA)Phen and Eu2(TPA)(TTA)4Phen2 present only one sharp peak in the region of the 5D0→7F0 transition indicating that only one Eu3+ ion species is present in each sample. In addition, the luminescence decay curves of the complexes Eu(TPA)(TTA)Phen and Eu2(TPA)(TTA)4Phen2 fit a single-exponential decay law. The values of quantum efficiencies of the emitting 5D0 level for the complexes Eu(TPA)(TTA)Phen and Eu2(TPA)(TTA)4Phen2 are 29% and 28%, respectively.

  12. Absorption properties of type-II InAs/InAsSb superlattices measured by spectroscopic ellipsometry

    SciTech Connect

    Webster, P. T.; Riordan, N. A.; Liu, S.; Zhang, Y.-H.; Johnson, S. R.; Steenbergen, E. H.

    2015-02-09

    Strain-balanced InAs/InAsSb superlattices offer access to the mid- to long-wavelength infrared region with what is essentially a ternary material system at the GaSb lattice constant. The absorption coefficients of InAs/InAsSb superlattices grown by molecular beam epitaxy on (100)-oriented GaSb substrates are measured at room temperature over the 30 to 800 meV photon energy range using spectroscopic ellipsometry, and the miniband structure of each superlattice is calculated using a Kronig-Penney model. The InAs/InAsSb conduction band offset is used as a fitting parameter to align the calculated superlattice ground state transition energy to the measured absorption onset at room temperature and to the photoluminescence peak energy at low temperature. It is observed that the ground state absorption coefficient and transition strength are proportional to the square of the wavefunction overlap and the ground state absorption coefficient approaches a maximum value of around 5780 cm{sup −1} as the wavefunction overlap approaches 100%. The absorption analysis of these samples indicates that the optical joint density of states is weakly dependent on the period thickness and Sb content of the superlattice, and that wavefunction overlap is the principal design parameter in terms of obtaining strong absorption in these structures.

  13. Two-Photon-Absorption Scheme for Optical Beam Tracking

    NASA Technical Reports Server (NTRS)

    Ortiz, Gerardo G.; Farr, William H.

    2011-01-01

    A new optical beam tracking approach for free-space optical communication links using two-photon absorption (TPA) in a high-bandgap detector material was demonstrated. This tracking scheme is part of the canonical architecture described in the preceding article. TPA is used to track a long-wavelength transmit laser while direct absorption on the same sensor simultaneously tracks a shorter-wavelength beacon. The TPA responsivity was measured for silicon using a PIN photodiode at a laser beacon wavelength of 1,550 nm. As expected, the responsivity shows a linear dependence with incident power level. The responsivity slope is 4.5 x 10(exp -7) A/W2. Also, optical beam spots from the 1,550-nm laser beacon were characterized on commercial charge coupled device (CCD) and complementary metal-oxide semiconductor (CMOS) imagers with as little as 13.7 microWatts of optical power (see figure). This new tracker technology offers an innovative solution to reduce system complexity, improve transmit/receive isolation, improve optical efficiency, improve signal-to-noise ratio (SNR), and reduce cost for free-space optical communications transceivers.

  14. Temperature dependence of the two photon absorption in indium arsenide

    SciTech Connect

    Berryman, K.W.; Rella, C.W.

    1995-12-31

    Nonlinear optical processes in semiconductors have long been a source of interesting physics. Two photon absorption (TPA) is one such process, in which two photons provide the energy for the creation of an electron-hole pair. Researchers at other FEL centers have studied room temperature TPA in InSb, InAs, and HgCdTe. Working at the Stanford Picosecond FEL Center, we have extended and refined this work by measuring the temperature dependence of the TPA coefficient in InAs over the range from 80 to 350 K at four wavelengths: 4.5, 5.06, 6.01, and 6.3 microns. The measurements validate the functional dependence of recent band structure calculations with enough precision to discriminate parabolic from non-parabolic models, and to begin to observe smaller effects, such as contributions due to the split-off band. These experiments therefore serve as a strong independent test of the Kane band theory, as well as providing a starting point for detailed observations of other nonlinear absorption mechanisms.

  15. Light absorption and morphological properties of soot-containing aerosols observed at an East Asian outflow site, Noto Peninsula, Japan

    NASA Astrophysics Data System (ADS)

    Ueda, Sayako; Nakayama, Tomoki; Taketani, Fumikazu; Adachi, Kouji; Matsuki, Atsushi; Iwamoto, Yoko; Sadanaga, Yasuhiro; Matsumi, Yutaka

    2016-03-01

    The coating of black carbon (BC) with inorganic salts and organic compounds can enhance the magnitude of light absorption by BC. To elucidate the enhancement of light absorption of aged BC particles and its relation to the mixing state and morphology of individual particles, we conducted observations of particles at an Asian outflow site in Noto Peninsula, Japan, in the spring of 2013. Absorption and scattering coefficients at 405, 532, and 781 nm and mass concentrations/mixing states of refractory BC in PM2.5 were measured using a three-wavelength photoacoustic soot spectrometer and a single-particle soot photometer (SP2), respectively, after passage through a thermodenuder (TD) maintained at 300 or 400 °C or a bypass line maintained at room temperature (25 °C). The average enhancement factor of BC light absorption due to coating was estimated by comparing absorption coefficients at 781 nm for particles that with and without passing through the TD at 300 °C and was found to be 1.22. The largest enhancements (> 1.30) were observed under high absorption coefficient periods when the air mass was long-range transported from urban areas in China. Aerosol samples were also analyzed using a transmission electron microscope (TEM) equipped with an energy dispersive X-ray analyzer. The morphological features and mixing states of soot-containing particles of four samples collected during the high absorption events were analyzed by comparing microphotographs before and after the evaporation of beam-sensitive materials by irradiation with a high-density electron beam. The majority of the soot in all samples was found as mixed particles with sulfate-containing spherules or as clusters of such spherules. For samples showing high enhancement (> 1.30) of BC light absorption, the TEM showed that the internally mixed soot-containing particles tended to have a more spherical shape and to be thickly coated. The SP2 measurements also suggested that the proportion of thickly coated

  16. Synergistic effect of Fe-doping and stacking faults on the dielectric permittivity and microwave absorption properties of SiC whiskers

    NASA Astrophysics Data System (ADS)

    Kuang, Jianlei; Jiang, Peng; Liu, Wenxiu; Cao, Wenbin

    2015-05-01

    Previously, we have found that the stacking faults density in SiC whisker (SiCw) significantly affects its dielectric permittivity mainly through the enhanced dipolar loss mechanism. Doping has been considered as another effective way to increase the dielectric permittivity of granular SiC. In order to further investigate the possible synergistic effect of Fe-doping and stacking faults on permittivity, permeability, and microwave absorption properties, Fe-doped SiCw with various stacking faults densities were prepared. Experimental results indicate that the Fe-doped SiCw with internal stacking faults shows a higher dielectric permittivity than that of undoped SiCw with only stacking faults. Both dielectric permittivity and microwave absorption properties of Fe-doped SiCw increased significantly with the increase in dopant concentration. First-principle calculation reveals that Fe-doping tunes SiC to be half-metallic, and thus, its electric conductivity as well as conduction loss is enhanced. So, both the dielectric permittivity and microwave absorption properties of Fe-doped SiCw were significantly improved due to the synergistic effect of the enhanced conduction loss caused by Fe-doping and the dipolar loss induced by stacking faults. And, the measured weak magnetic loss contributes to that as well.

  17. The role of scattering and absorption on the optical properties of birefringent polycrystalline ceramics: Modeling and experiments on ruby (Cr:Al2O3)

    NASA Astrophysics Data System (ADS)

    Penilla, E. H.; Hardin, C. L.; Kodera, Y.; Basun, S. A.; Evans, D. R.; Garay, J. E.

    2016-01-01

    Light scattering due to birefringence has prevented the use of polycrystalline ceramics with anisotropic optical properties in applications such as laser gain media. However, continued development of processing technology has allowed for very low porosity and fine grains, significantly improving transparency and is paving the way for polycrystalline ceramics to be used in demanding optical applications. We present a method for producing highly transparent Cr3+ doped Al2O3 (ruby) using current activated pressure assisted densification. The one-step doping/densification process produces fine grained ceramics with well integrated (doped) Cr, resulting in good absorption and emission. In order to explain the light transmission properties, we extend the analytical model based on the Rayleigh-Gans-Debye approximation that has been previously used for undoped alumina to include absorption. The model presented captures reflection, scattering, and absorption phenomena in the ceramics. Comparison with measured transmission confirms that the model adequately describes the properties of polycrystalline ruby. In addition the measured emission spectra and emission lifetime are found to be similar to single crystals, confirming the high optical quality of the ceramics.

  18. Theoretical studies on electronic structures and photophysical properties of anthracene derivatives as hole-transporting materials for OLEDs.

    PubMed

    Chitpakdee, Chirawat; Namuangruk, Supawadee; Khongpracha, Pipat; Jungsuttiwong, Siriporn; Tarsang, Ruangchai; Sudyoadsuk, Taweesak; Promarak, Vinich

    2014-05-05

    The electronic structures and photophysical properties of anthracene derivatives as hole-transporting materials (HTM) in OLEDs have been studied by DFT and TD-DFT methods. Thiophene and triphenylamine (TPA) moieties are used as substituents in anthracene based HTMs providing FATn and FAPn compounds (n=1-2), respectively. The calculated electronic levels by B3LYP show proper energy matching of FAPn and hole-injecting layer (HIL), indicating that the hole-transports of the FAPn compounds are better than the FATn compounds. The photophysical properties calculated by TD-B3LYP elucidate that TPA in FAPn compounds acts as electron donating group and induces charge transfer character in the absorptions. Furthermore, the calculated ionization potential (IP), electron affinity (EA) and reorganization energies also revealed that the extended FAP2 compound has the highest charge-transporting ability among the studied compounds. The calculated results are consistent to our experimental observations showing that FAP2 exhibits bright fluorescence with highest quantum yield in electroluminescent devices. Understanding of these properties is useful for further design of new HTMs of desired properties, such as high efficiency and stability.

  19. Evaluation of an oral carrier system in rats: bioavailability and gastrointestinal absorption properties of curcumin encapsulated PBCA nanoparticles

    NASA Astrophysics Data System (ADS)

    Sun, Min; Zhao, Lixia; Guo, Chenyu; Cao, Fengliang; Chen, Huanlei; Zhao, Liyan; Tan, Qi; Zhu, Xiuqing; Zhu, Fanping; Ding, Tingting; Zhai, Yingjie; Zhai, Guangxi

    2012-02-01

    A new oral delivery system, polybutylcyanoacrylate nanoparticles (PBCNs), was introduced to improve the oral bioavailability of curcumin (CUR), a poorly soluble drug. The formulation was optimized by orthogonal design and the optimal PBCNs loading CUR exhibited a spherical shape under transmission electron microscopy with a range of 40-400 nm. Physicochemical state of CUR in PBCN was investigated by X-ray diffraction and the possible structure changes occurring in CUR after conjugating with polybutylcyanoacrylate were studied with FTIR. The results indicated that CUR in PBCN was in a non-crystalline state and CUR was encapsulated in PBCN without chemical reaction. The oral pharmacokinetic study was conducted in rats and the relative bioavailability of CUR encapsulated PBCNs to the crude CUR was more than 800%. The in situ absorption experiment in rat intestine indicated the absorption was first order with passive diffusion mechanism. The absorption results in various segments of intestine showed that the main absorption sites were ileum and colon. It can be concluded that PBCNs as an oral carrier can significantly improve the oral absorption of a poorly soluble drug.

  20. Sp1 involvement in the 4beta-phorbol 12-myristate 13-acetate (TPA)-mediated increase in resistance to methotrexate in Chinese hamster ovary cells.

    PubMed

    Noé, V; Alemany, C; Nicolás, M; Ciudad, C J

    2001-06-01

    4beta-Phorbol 12-myristate 13-acetate (TPA) increases the number of colonies resistant to methotrexate (MTX), mainly by amplification of the dihydrofolate reductase (dhfr) locus. We showed previously that inhibition of protein kinase C (PKC) prevents this resistance. Here, we studied the molecular changes involved in the development of TPA-mediated MTX resistance in Chinese hamster ovary (CHO) cells. TPA incubation increased the expression and activity of DHFR. Because Sp1 controls the dhfr promoter, we determined the effect of TPA on the expression of Sp1 and its binding to DNA. TPA incubation increased Sp1 binding and the levels of Sp1 protein. The latter effect was due to an increase in Sp1 mRNA. Dephosphorylation of nuclear extracts from control or TPA-treated cells reduced the binding of Sp1. Stable transfectants of PKCalpha showed increased Sp1 binding, and when treated with MTX, developed a greater number of resistant colonies than control cells. Seventy-five percent of the isolated colonies showed increased copy number for the dhfr gene. Transient expression of PKCalpha increased DHFR activity. Over-expression of Sp1 increased resistance to MTX, and inhibition of Sp1 binding by mithramycin decreased this resistance. We conclude that one mechanism by which TPA enhances MTX resistance, mainly by gene amplification, is through an increase in Sp1 expression which leads to DHFR activation.

  1. Influence of transannular interaction over absorption and fluorescent properties of [2.2] paracyclophane and its phenyl derivatives

    NASA Astrophysics Data System (ADS)

    Nurmukhametov, R. N.; Shapovalov, A. V.; Antonov, D. Yu.

    2016-12-01

    A significant bathochromic shift of the fluorescent and long-wavelength absorption bands of [2.2] paracyclophane comparing to corresponding bands of alkyl-benzenes is due to a strong transannular interaction, resulting in formation of a principally new excited state of lower energy. It is concluded that the fluorescent levels for alkylbenzene excimers and for the macrocycle are of the same nature. Analysis of [2.2] paracyclophane mono- and diphenylderivatives spectra shows that their intensive absorption bands (230-310 nm) are originated from electron transitions of biphenyl groups and weak long wavelength absorption (310-340 nm) and fluorescent bands are governed by the same electron transitions between ground and excimer-like excited states as in the case of non-substituted macrocycle.

  2. Theoretical and experimental study on the electronic structure and optical absorption properties of P-doped TiO 2

    NASA Astrophysics Data System (ADS)

    Xu, Ling; Tang, Chao-Qun; Qian, Jun; Huang, Zong-Bin

    2010-02-01

    Phosphorus-doped nanosized TiO 2 powders were prepared by a sol-gel technology. The optical absorption studies revealed that the spectral responses of phosphorus-doped (P-doped) TiO 2 powders shift to the visible light region. The optimum phosphorus (P) content in our experiments is 16.7% (mol), and the corresponding absorption edge shifts to 450 nm. Furthermore, our ab initio calculations support the conclusion that the doping of phosphorus can reduce the band gap by mixing the P 3p states with O 2p states. The theoretical lattice parameters and optimum phosphorus content are in agreement with the experimental results.

  3. Synthesis of nanostructured MnO2, SnO2, and Co3O4: graphene composites with enhanced microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoxia; Yu, Jianhua; Dong, Hongzhou; Yu, Mingxun; Zhang, Baoqin; Wang, Wen; Dong, Lifeng

    2015-06-01

    In this work, metal oxide (MnO2, SnO2 and Co3O4)-graphene composite materials were successfully prepared via different synthesis methods. Uniform metal oxide nanoparticles were well dispersed on graphene sheets, and transmission electron microscopy characterizations showed that the average sizes of MnO2, SnO2, and Co3O4 particles were about 60, 5, and 10 nm, respectively. Reflection losses of graphene composites and pure graphene were systematically evaluated between 2 and 18 GHz, which revealed that all composites exhibited enhanced microwave absorption properties compared to pure graphene. The minimum reflection losses of MnO2-graphene, SnO2-graphene, and Co3O4-graphene composites with a thickness of 2.0 mm were -20.9, -15.28, and -7.3 dB at the frequency of 14.8, 15.94, and 9.6 GHz, respectively, whereas -4.5 dB for pure graphene. The enhanced absorption ability probably originated from the combined advantage of metal oxide particles and graphene, which proved beneficial to improve the impedance matching of permittivity and permeability. Besides, the intrinsic characteristics of MnO2, SnO2, and Co3O4 nanoparticles, the interface between nanostructured metal oxides and graphene sheets, and the multi-dielectric relaxation processes are all influence factors to improve the properties of microwave absorption.

  4. Chemopreventive activity of sesquiterpene lactones (SLs) from yacon against TPA-induced Raji cells deformation.

    PubMed

    Siriwan, D; Miyawaki, C; Miyamoto, T; Naruse, T; Okazaki, K; Tamura, H

    2011-05-15

    Yacon is a medicinal plant used as a traditional medicine by the natives in South America. In Japan, it becomes popular as a health food. Sesquiterpene Lactones (SLs) from yacon leaves were investigated and the active SLs such as enhydrin, uvedalin and sonchifolin, bearing alpha-methylene-gamma-lactone and epoxides as the active functional groups, were identified by 1H-6000 MHz-NMR. Chemopreventive and cytotoxic activities were determined using different primary screening methods. In this study, all tested SLs strongly inhibited TPA-induced deformed of Raji cells. The IC50 values of yacon SLs from anti-deforming assay were 0.04-0.4 microM. Interestingly, yacon SLs showed more potential of chemo preventive activity than both curcumin and parthenolide. However, the cytotoxicity on Raji cells was observed at high concentration of yacon SLs. The degree of anti-deformation was ranked in order: enhydrin >uvedalin >sonchifolin >parthenolide >curcumin. As according to structure-activity relationship, the high activities of enhydrin, uvedalin and sonchifolin may be due to the 2-methyl-2-butenoate and its epoxide moiety.

  5. Russian Nesting Doll Complexes of Molecular Baskets and Zinc Containing TPA Ligands.

    PubMed

    Zhiquan, Lei; Polen, Shane; Hadad, Christopher M; RajanBabu, T V; Badjić, Jovica D

    2016-07-06

    In this study, we examined the structural and electronic complementarities of convex 1-Zn(II), comprising functionalized tris(2-pyridylmethyl)amine (TPA) ligand, and concave baskets 2 and 3, having glycine and (S)-alanine amino acids at the rim. With the assistance of (1)H NMR spectroscopy and mass spectrometry, we found that basket 2 would entrap 1-Zn(II) in water to give equimolar 1-Zn⊂2in complex (K = (2.0 ± 0.2) × 10(3) M(-1)) resembling Russian nesting dolls. Moreover, C3 symmetric and enantiopure basket 3, containing (S)-alanine groups at the rim, was found to transfer its static chirality to entrapped 1-Zn(II) and, via intermolecular ionic contacts, twist the ligand's pyridine rings into a left-handed (M) propeller (circular dichroism spectroscopy). With molecular baskets embodying the second coordination sphere about metal-containing TPAs, the here described findings should be useful for extending the catalytic function and chiral discrimination capability of TPAs.

  6. The impact of metal line reflections on through-wafer TPA SEE testing

    SciTech Connect

    Khachatrian, Ani; Roche, Nicolas J-H.; Dodds, Nathaniel A.; McMorrow, Dale; Warner, Jeffrey H.; Buchner, Stephen P.; Reed, Robert A.

    2015-12-17

    Charge-collection experiments and simulations designed to quantify the effects of reflections from metallization during through-wafer TPA testing are presented. The results reveal a strong dependence on metal line width and metal line position inside the SiO2 overlayer. The charge-collection enhancement is largest for the widest metal lines and the metal lines closest to the Si/SiO2 interface. The charge-collection enhancement is also dependent on incident laser pulse energy, an effect that is a consequence of higher-order optical nonlinearities induced by the ultrashort optical pulses. However, for the lines further away from the Si/SiO2 interface, variations in laser pulse energies affect the charge-collection enhancement to a lesser degree. Z-scan measurements reveal that the peak charge collection occurs when the axial position of the laser focal point is inside the Si substrate. There is a downward trend in peak collected-charge enhancement with the increase in laser pulse energies for the metal lines further away from the Si/SiO2 interface. Metallization enhances the collected charge by same amount regardless of the applied bias voltage. In conclusion, for thinner metal lines and laser pulse energies lower than 1 nJ, the collected charge enhancement due to metallization is negligible.

  7. The impact of metal line reflections on through-wafer TPA SEE testing

    DOE PAGES

    Khachatrian, Ani; Roche, Nicolas J-H.; Dodds, Nathaniel A.; ...

    2015-12-17

    Charge-collection experiments and simulations designed to quantify the effects of reflections from metallization during through-wafer TPA testing are presented. The results reveal a strong dependence on metal line width and metal line position inside the SiO2 overlayer. The charge-collection enhancement is largest for the widest metal lines and the metal lines closest to the Si/SiO2 interface. The charge-collection enhancement is also dependent on incident laser pulse energy, an effect that is a consequence of higher-order optical nonlinearities induced by the ultrashort optical pulses. However, for the lines further away from the Si/SiO2 interface, variations in laser pulse energies affect themore » charge-collection enhancement to a lesser degree. Z-scan measurements reveal that the peak charge collection occurs when the axial position of the laser focal point is inside the Si substrate. There is a downward trend in peak collected-charge enhancement with the increase in laser pulse energies for the metal lines further away from the Si/SiO2 interface. Metallization enhances the collected charge by same amount regardless of the applied bias voltage. In conclusion, for thinner metal lines and laser pulse energies lower than 1 nJ, the collected charge enhancement due to metallization is negligible.« less

  8. Absorption and photocurrent properties of low-temperature laser deposited thin-film GaAs on glass

    NASA Astrophysics Data System (ADS)

    Erlacher, A.; Ambrico, M.; Perna, G.; Schiavulli, L.; Ligonzo, T.; Jaeger, H.; Ullrich, B.

    2005-06-01

    The absorption edge of thin-film GaAs on glass has been investigated with the standard constant photocurrent method (s-CPM) method and photocurrent analysis. The films have been formed by pulsed-laser deposition (PLD) employing the 532 nm emission of a YAG:Nd laser (6 ns, 10 Hz). Notably, the films have been deposited without heating the substrate. Fitting the measured absorption data with the crystalline density of states and the Urbach tail a very good agreement has been found. X-ray analysis showed that the films are predominately oriented towards the (111) plane. The function used to fit the absorption data describes the photocurrent data at different biases as well. Annealing of the samples up to 400 K did not cause notable changes in the absorption edge and overall photocurrent spectra. The presented results reveal that "cold" PLD, i.e., without substrate heating, forms high-quality oriented photosensitive thin-film GaAs on glass, which hardly alters its optoelectronic features under thermal treatment. Under this prospect and due to the relative ease to form the films, PLD GaAs might be of interest for applications in optoelectronics and photovoltaics.

  9. Ultra-violet absorption induced modifications in bulk and nanoscale electrical transport properties of Al-doped ZnO thin films

    NASA Astrophysics Data System (ADS)

    Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata

    2015-08-01

    Using conductive atomic force microscopy and Kelvin probe force microscopy, we study local electrical transport properties in aluminum-doped zinc oxide (ZnO:Al or AZO) thin films. Current mapping shows a spatial variation in conductivity which corroborates well with the local mapping of donor concentration (˜1020 cm-3). In addition, a strong enhancement in the local current at grains is observed after exposing the film to ultra-violet (UV) light which is attributed to persistent photocurrent. Further, it is shown that UV absorption gives a smooth conduction in AZO film which in turn gives rise to an improvement in the bulk photoresponsivity of an n-AZO/p-Si heterojunction diode. This finding is in contrast to the belief that UV absorption in an AZO layer leads to an optical loss for the underneath absorbing layer of a heterojunction solar cell.

  10. Spectroscopic properties of Bi2ZnOB2O6 single crystals doped with Pr3+ ions: Absorption and luminescence investigations

    NASA Astrophysics Data System (ADS)

    Kasprowicz, D.; Brik, M. G.; Jaroszewski, K.; Pedzinski, T.; Bursa, B.; Głuchowski, P.; Majchrowski, A.; Michalski, E.

    2015-09-01

    Nonlinear optical Bi2ZnOB2O6 single crystals doped with Pr3+ ions were grown using the Kyropoulos method. The absorption and luminescence properties of these new systems were investigated for the first time. The crystals are characterized by the large values of nonlinear optical coefficients. Effective luminescence of the Pr3+ ions makes this system an excellent candidate for the near-infrared (NIR) and/or ultraviolet (UV) to visible (VIS) laser converters. Based on the obtained experimental spectroscopic data, detailed analysis of the absorption and luminescence spectra was performed using the conventional Judd-Ofelt theory. Those transitions, which can be potentially used for laser applications of the Pr3+ ion, have been identified. In addition to the intensity parameters Ω2, Ω4, Ω6 the branching ratios and radiative lifetimes were estimated for all possible transitions in the studied spectral region.

  11. Preparation and Absorption Spectral Property of a Multifunctional Water-Soluble Azo Compound with D-π-A Structure, 4-(4- Hydroxy-1-Naphthylazo)Benzoic Acid

    NASA Astrophysics Data System (ADS)

    Hu, L.; Lv, H.; Xie, C. G.; Chang, W. G.; Yan, Z. Q.

    2015-07-01

    A multifunctional water-soluble azo dye with the D-π-A conjugated structure, 4-(4-hydroxy-1-naphthylazo) benzoic acid ( HNBA), was designed and synthesized using 1-naphanol as the electron donator, benzoic acid as the electron acceptor, and -N=N- as the bridging group. After its structure was characterized by FTIR, 1H NMR, and element analysis, the UV-Vis absorption spectral performance of the target dye was studied in detail. The results showed that the dye, combining hydroxyl group, azo group, and carboxyl group, possessed excellent absorption spectral properties (ɛ = 1.2·104 l·mol-1·cm-1) changing with pH and solvents. In particular, in polar and protonic water, it had excellent optical response to some metal ions, i.e., Fe3+ and Pb2+, which might make it a latent colorimetric sensor for detecting heavy metal ions.

  12. Ultra-violet absorption induced modifications in bulk and nanoscale electrical transport properties of Al-doped ZnO thin films

    SciTech Connect

    Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata

    2015-08-07

    Using conductive atomic force microscopy and Kelvin probe force microscopy, we study local electrical transport properties in aluminum-doped zinc oxide (ZnO:Al or AZO) thin films. Current mapping shows a spatial variation in conductivity which corroborates well with the local mapping of donor concentration (∼10{sup 20 }cm{sup −3}). In addition, a strong enhancement in the local current at grains is observed after exposing the film to ultra-violet (UV) light which is attributed to persistent photocurrent. Further, it is shown that UV absorption gives a smooth conduction in AZO film which in turn gives rise to an improvement in the bulk photoresponsivity of an n-AZO/p-Si heterojunction diode. This finding is in contrast to the belief that UV absorption in an AZO layer leads to an optical loss for the underneath absorbing layer of a heterojunction solar cell.

  13. Microwave absorption properties of polypyrrole-SrFe12O19-TiO2-epoxy resin nanocomposites: Optimization using response surface methodology

    NASA Astrophysics Data System (ADS)

    Seyed Dorraji, M. S.; Rasoulifard, M. H.; Amani-Ghadim, A. R.; Khodabandeloo, M. H.; Felekari, M.; Khoshrou, M. R.; hajimiri, I.

    2016-10-01

    At a few works are discussed about formation of heterogeneous composites with different distribution of particle shape and size that are used for electromagnetic absorption purposes. In this study a novel heterogeneous nanocpmposites is investigated. The nanocomposite has been successfully prepared based on epoxy resin including various nano-metal oxides (TiO2, SrFe12O19) and polypyrrole (PPy) by sol-gel and the solution chemistry method, respectively. The performance of prepared nanocomposite in absorption of microwave in X-band range was investigated and transmission line method by X-band waveguide straight was used to measure EM parameters of nanocomposites. The Response surface methodology (RSM) with central composite design (CCD) was utilized to study the effects of the wt.% TiO2 in SrFe12O19, wt.% Tio2-SrFe12O19 in PPy and wt.% TiO2-SrFe12O19-PPy in epoxy resin, on the microwave absorption properties with the absorber thickness of only 2 mm. The proposed quadratic model was in accordance with the experimental results with correlation coefficient of 96.5%. The optimum condition for maximum microwave absorption efficiency were wt.% TiO2 in SrFe12O19 of 70, wt.% TiO2-SrFe12O19 in PPy of 10 and wt.% TiO2-SrFe12O19-PPy in epoxy of 25. The sample prepared in optimal conditions indicated reflection loss of -15 dB corresponding to 97% absorption, at the range of 9.2-10.8 GHz.

  14. Photophysical properties of an asymmetrical 2,5-diarylidene-cyclopentanone dye possessing electron donor and acceptor substituents

    NASA Astrophysics Data System (ADS)

    Zoto, Christopher A.; Connors, Robert E.

    2010-10-01

    Spectroscopic and photophysical properties have been measured in a variety of solvents for (2E,5E)-2-(p-cyanobenzylidene)-5-(p-dimethylaminobenzylidene)-cyclopentanone ( I), an asymmetrically substituted 2,5-diarylidene-cyclopentanone known to have potential for applications utilizing two-photon absorption (TPA). Compound I was synthesized by a simple procedure utilizing DIMCARB catalyst. Absorption and fluorescence maxima have been correlated with the ET(30) solvent polarity scale. Theoretical TD-DFT calculations and Lippert-Mataga analysis demonstrate the internal charge transfer (ICT) nature of the S0 → S1 excitation. Radiative and nonradiative decay constants have been determined from fluorescence quantum yields and lifetimes. Substantial variation with solvent in the rate of nonradiative decay is interpreted in terms of a competition between internal conversion and intersystem crossing.

  15. Facile synthesis of ZnFe{sub 2}O{sub 4}/reduced graphene oxide nanohybrids for enhanced microwave absorption properties

    SciTech Connect

    Yang, Zhiwei; Wan, Yizao; Xiong, Guangyao; Li, Deying; Li, Qiuping; Ma, Chunying; Guo, Ruisong; Luo, Honglin

    2015-01-15

    Highlights: • ZnFe{sub 2}O{sub 4} nanoparticles with a small diameter are uniformly anchored on RGO surface. • A strong interfacial bonding was formed between ZnFe{sub 2}O{sub 4} nanoparticles and RGO. • The minimum RL of ZnFe{sub 2}O{sub 4}/RGO nanohybrids is −29.3 dB at 16.7 GHz and 1.6 mm. • ZnFe{sub 2}O{sub 4}/RGO nanohybrids show great promise as a microwave absorption material. - Abstract: The nanohybrids composed of ZnFe{sub 2}O{sub 4} and reduced graphene oxide (RGO) have been synthesized by a facile one-step hydrothermal strategy. The morphology and structure of ZnFe{sub 2}O{sub 4}/RGO nanohybrids were characterized by transmission electron microscopy, X-ray diffraction and Raman spectra. RGO content was also determined by thermogravimetric analysis. The results confirm the formation of nanohybrids with a content of 20.4 wt% RGO and extensive interfaces between small-diameter ZnFe{sub 2}O{sub 4} nanoparticles and RGO sheets. The magnetic properties and electromagnetic parameters of ZnFe{sub 2}O{sub 4}/RGO nanohybrids were measured and the microwave absorption properties were investigated. ZnFe{sub 2}O{sub 4}/RGO nanohybrids exhibit the advantages of thin matching thickness and strong absorption at high frequency bands. It is demonstrated that ZnFe{sub 2}O{sub 4}/RGO nanohybrids can be a powerful candidate in the field of microwave absorption.

  16. Light absorption properties of water soluble organic aerosol from Residential Wood Burning in Fresno, CA: Results from 2013 NASA DISCOVER-AQ Campaign

    NASA Astrophysics Data System (ADS)

    Kim, H.; Zhang, Q.; Young, D. E.; Parworth, C.

    2015-12-01

    Light absorption properties of water soluble organic aerosol were investigated at Fresno, CA from 13 January to 11 February, 2013 as part of the NASA DISCOVER-AQ campaign. The light absorption spectra of water soluble organic aerosol in PM2.5 was measured using a UV/vis diode array detector (DAD) coupled with a particle into liquid sampler (PILS) that sampled downstream of a PM2.5 cyclone (URG). The PILS was also coupled with two ion chromatographs (IC) to measure inorganic and organic ionic species in PM2.5. In addition, an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was deployed at the same site to measure size-resolved chemical composition of submicrometer aerosol (PM1) in real time during this study. Light absorption at 365 nm (Abs365), which is typically used as a proxy of water-soluble brown carbon (BrC), showed strong enhancement during night time and appeared to correlate well (r = 0.71) with biomass burning organic aerosol (BBOA) from residential wood burning for heating in the Fresno area. The tight correlations between Abs365 and biomass burning relevant tracers such as acetonitrile (r = 0.69), AMS-signature ions for phenolic compounds (r = 0.52-0.71), PAH (r = 0.74), and potassium (r = 0.67) further confirm that biomass burning contributed significantly to water soluble brown carbon during this study. The absorption angstrom exponent (Åa) values fitted between 300 and 700 nm wavelength were 3.3 ± 1.1, 2.0 ± 0.9 and 4.0 ± 0.8, respectively, in the morning, afternoon and nighttime, indicating that BrC is prevalent at night in Fresno during wintertime. However, there are also indications that small amount of BrC existed during the daytime as well, likely due to daytime wood burning and other sources such as the formation of light-absorbing secondary organic aerosol (SOA). Finally, light absorption at 300 nm, 330 nm, and 390 nm were found to correlate tightly with BBOA, which indicate that biomass burning also emits

  17. Early recovery of microvascular perfusion induced by t-PA in combination with abciximab or eptifibatide during postischemic reperfusion

    PubMed Central

    Bertuglia, Silva; Giusti, Andrea

    2002-01-01

    Background GPIIb/IIIa inhibitors abciximab and eptifibatide have been shown to inhibit platelet aggregation in ischemic heart disease. Our aim was to test the efficacy of abiciximab (Reo Pro) or eptifibatide (Integrilin) alone or in combination with plasminogen activator (t-PA) in an experimental model of ischemia reperfusion (I/R) in hamster cheek pouch microcirculation visualized by fluorescence microscopy. Hamsters were treated with saline, or abiciximab or eptifibatide or these drugs combined with t-PA infused intravenously 10 minutes before ischemia and through reperfusion. We measured the microvessel diameter changes, the arteriolar red blood cell (RBC) velocity, the increase in permeability, the perfused capillary length (PCL), and the platelet and leukocyte adhesion on microvessels. Results I/R elicited large increases in the platelet and leukocyte adhesion and a decrease in microvascular perfusion. These responses were significantly attenuated by abiciximab or eptifibatide (PCL:70 and 65% at 5–10 mins of reperfusion and 85 and 87% at 30 mins of reperfusion, respectively, p < 0.001) while t-PA combined with abiciximab or eptifibatide, was more effective and microvascular perfusion recovered immediately after postischemic reperfusion. Conclusions Platelets are crucial in I/R injury, as shown by the treatment with abicixmab or eptifibatide, which decreased platelet aggregation in microvessels, and also decreased leukocyte adhesion in venules. Arterial vasoconstriction, decreased arterial RBC velocity and alterations in the endothelial barrier with increased permeability delayed the complete restoration of blood flow, while t-PA combined with inhibition of platelet aggregation speeded up the capillary perfusion after reperfusion. PMID:12086588

  18. Anti-inflammatory activity of flavonol glycosides from Erythrospermum monticolum depending on single or repeated local TPA administration.

    PubMed

    del Carmen Recio, M; Giner, R M; Máñez, S; Talens, A; Cubells, L; Gueho, J; Julien, H R; Hostettmann, K; Rios, J L

    1995-12-01

    Two anti-inflammatory principles were isolated from the methanol extract of the leaves of Erythrospermum monticolum (Flacourtiaceae). The isolation was based on a guided bioassay of the inhibitory activity on TPA-induced ear edema in mice. These compounds were identified as quercetin 3-O-xylosyl(1-->2) rhamnoside and quercetin 3-O-rhamnoside. In addition, their effects on a chronic topic inflammation model were evaluated.

  19. Human T cell activation. III. Induction of an early activation antigen, EA 1 by TPA, mitogens and antigens

    SciTech Connect

    Hara, T.; Jung, L.K.L.; FU, S.M.

    1986-03-01

    With human T cells activated for 12 hours by 12-o-tetradecanoyl phorbol-13-acetate (TPA) as immunogen, an IgG/sub 2a/ monoclonal antibody, mAb Ea 1, has been generated to a 60KD phosphorylated protein with 32KD and 28KD subunits. The antigen, Ea 1, is readily detected on 60% of isolated thymocytes by indirect immunofluorescence. A low level of Ea 1 expression is detectable on 2-6% of blood lymphocytes. Isolated T cells have been induced to express Ea 1 by TPA, mitogens and anitgens. TPA activated T cells express Ea 1 as early as 1 hour after activation. By 4 hours, greater than 95% of the T cells stain with mAb Ea 1. About 50% of the PHA or Con A activated T cells express Ea 1 with a similar kinetics. Ea 1 expression proceeds that of IL-2 receptor in these activation processes. T cells activated by soluble antigens (tetanus toxoid and PPD) and alloantigens in MLR also express Ea 1 after a long incubation. About 20% of the T cells stain for Ea 1 at day 6. Ea 1 expression is not limited to activated T cells. B cells activated by TPA or anti-IgM Ab plus B cell growth factor express Ea 1. The kinetics of Ea 1 expression is slower and the staining is less intense. Repeated attempts to detect Ea 1 on resting and activated monocytes and granulocytes have not been successful. Ea 1 expression is due to de novo synthesis for its induction is blocked by cycloheximide and actinomycin D. Ea 1 is the earliest activation antigen detectable to-date.

  20. Reduced Graphene Oxide-Cu0.5Ni0.5Fe2O4-Polyaniline Nanocomposite: Preparation, Characterization and Microwave Absorption Properties

    NASA Astrophysics Data System (ADS)

    Dat, Tran Quang; Ha, Nguyen Tran; Hung, Do Quoc

    2017-02-01

    Reduced graphene oxide-Cu0.5Ni0.5Fe2O4-polyaniline nanocomposite (RGO-CNF-PANI) was synthesized by a three-step method. The morphology, structure and magnetic properties of composite samples were characterized by scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy (RAMAN) and vibrating sample magnetometer. It was found that reduced graphene oxide was exfoliated and decorated homogeneously with ferrite nanoparticles having diameters between 11 nm and 21 nm. The polyaniline was coated by an in situ chemical oxidation polymerization. The measurement of magnetic properties found the remanence (Mr) and coercive field (Hc) were near zero, indicating that the obtained material was superparamagnetic. The microwave measurements found that the nanocomposite exhibited a good absorption property with the optimum matching thickness of 3 mm in the frequency of 8-12 GHz. The value of the maximum RL was -40.7 dB at 9.8 GHz.

  1. Benchmarking two-photon absorption cross sections: performance of CC2 and CAM-B3LYP.

    PubMed

    Beerepoot, Maarten T P; Friese, Daniel H; List, Nanna H; Kongsted, Jacob; Ruud, Kenneth

    2015-07-15

    We investigate the performance of CC2 and TDDFT/CAM-B3LYP for the calculation of two-photon absorption (TPA) strengths and cross sections and contrast our results to a recent coupled cluster equation-of-motion (EOM-EE-CCSD) benchmark study [K. D. Nanda and A. I. Krylov, J. Chem. Phys., 2015, 142, 064118]. In particular, we investigate whether CC2 TPA strengths are significantly overestimated compared to higher-level coupled-cluster calculations for fluorescent protein chromophores. Our conclusion is that CC2 TPA strengths are only slightly overestimated compared to the reference EOM-EE-CCSD results and that previously published overestimated cross sections are a result of inconsistencies in the conversion of the TPA strengths to macroscopic units. TDDFT/CAM-B3LYP TPA strengths, on the other hand, are found to be 1.5 to 3 times smaller than the coupled-cluster reference for the molecular systems considered. The unsatisfactory performance of TDDFT/CAM-B3LYP can be linked to an underestimation of excited-state dipole moments predicted by TDDFT/CAM-B3LYP.

  2. Intravitreal tPA Injection and Pneumatic Displacement for Submacular Hemorrhage in a 10-Year-Old Child

    PubMed Central

    Hirose, Hiroshi; Hattori, Tomohiro

    2016-01-01

    Background. Submacular hemorrhage can occur after blunt trauma to the eye. Intravitreal tissue plasminogen activator (tPA) and gas injection are often used for treatment and are effective for submacular hemorrhage caused by age-related macular degeneration. This report describes the clinical outcome in a child with submacular hemorrhage caused by traumatic choroidal rupture who underwent successful intravitreal tPA injection and pneumatic displacement. Case Presentation. A 10-year-old boy developed sudden decrease of vision and a central scotoma in his right eye after trauma. Submacular hemorrhage was found in the eye. Visual acuity was 20/70 OD. Tissue plasminogen activator (12.5 μg in 0.05 mL) and 0.3 mL of pure sulfur hexafluoride were injected into the vitreous cavity under general anesthesia. After surgery, the patient was instructed to maintain a prone position. Displacement of the submacular hemorrhage from the fovea revealed a choroidal rupture, presumed to be the cause of the hemorrhage. After 4 months of follow-up, visual acuity was restored and final visual acuity is 20/16. Conclusion. Intravitreal tPA and gas injection can be an effective treatment for children with submacular hemorrhage. PMID:27722001

  3. Local versus global electronic properties of chalcopyrite alloys: X-ray absorption spectroscopy and ab initio calculations

    SciTech Connect

    Sarmiento-Pérez, Rafael; Botti, Silvana; Schnohr, Claudia S.; Lauermann, Iver; Rubio, Angel; Johnson, Benjamin

    2014-09-07

    Element-specific unoccupied electronic states of Cu(In, Ga)S{sub 2} were studied as a function of the In/Ga ratio by combining X-ray absorption spectroscopy with density functional theory calculations. The S absorption edge shifts with changing In/Ga ratio as expected from the variation of the band gap. In contrast, the cation edge positions are largely independent of composition despite the changing band gap. This unexpected behavior is well reproduced by our calculations and originates from the dependence of the electronic states on the local atomic environment. The changing band gap arises from a changing spatial average of these localized states with changing alloy composition.

  4. A review and analysis on growth and optical absorption properties of silicon nanowire array for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Sharma, Ritu; Dusad, Lalit Kumar

    2015-11-01

    In this paper, optical absorptions in silicon nanowires (SiNWs) arrays obtained from theoretical studies and experimental approaches have been reviewed. A brief description on the different growth techniques for SiNW arrays reported so far is presented. Comparative analysis based on major research findings has been done and the advantages of SiNW-based solar cells over thin film solar cells are presented. Furthermore, future aspects of the use of SiNWs for photovoltaic applications are discussed.

  5. Improved microwave absorption and electromagnetic properties of BaFe{sub 12}O{sub 19}-poly(vinylidene fluoride) composites by incorporating reduced graphene oxides

    SciTech Connect

    He, Hongcai; Luo, Feifei; Qian, Neng; Wang, Ning

    2015-02-28

    Three-phase composites of poly(vinylidene fluoride)-BaFe{sub 12}O{sub 19}-reduced graphene oxide (PVDF–BFO-RGO) were synthesized by a facile wet chemical method and hot-pressing approach. The phase structure, topography of the hybrid materials were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectra. Influence of RGO on their electromagnetic properties was investigated. Especially, improved microwave absorption and electromagnetic properties of BaFe{sub 12}O{sub 19}–PVDF composites by incorporating RGO were obtained and studied. The PVDF/BFO/RGO sample with m(RGO):m(BFO) = 5:100 shows the best microwave absorption properties with a minimum RL = −32 dB at 11 GHz and with the bandwidth less than −20 dB from 9.6 to 12.8 GHz. The composites were believed to have potential applications as the microwave absorber.

  6. Characterization of the nonlinear optical properties of the new 2-amino-4,6-difenilnicotinonitrilo by UV-Vis spectroscopy absorption and Z-Scan

    NASA Astrophysics Data System (ADS)

    Cueto, C.; Pérez, A.; Racedo, F.

    2017-01-01

    The study of the nonlinear optical properties of new organic molecules in solution was performed. Z-Scan technique was used to investigate the nonlinear optical properties of 2-amino-4,6-diphenylnicotinenitrile depending on the solution concentration and the laser power; This compound was diluted in ethyl acetate at fixed concentration of 0.024M. Through this technique, nonlinear parameters such as the nonlinear refractive index (η2), the nonlinear absorption coefficient (β) and the third-order electric susceptibility (χ3) were determined. For these measurements, a laser Nd: YAG emitting at 532nm, a lens 10 cm focus, an iris of 1mm and a cell with a thickness of 1mm were used. The study was performed with laser powers of 55mW, 100mW, 145mW and 195mW; All measurements were made by transmission in closed and open configurations. Finally the sample was characterized by absorption spectroscopy UV-Vis. This study allows us to relate the molecular design with the optical properties.

  7. Understanding the electronic structures and absorption properties of porphyrin sensitizers YD2 and YD2-o-C8 for dye-sensitized solar cells.

    PubMed

    Han, Li-Heng; Zhang, Cai-Rong; Zhe, Jian-Wu; Jin, Neng-Zhi; Shen, Yu-Lin; Wang, Wei; Gong, Ji-Jun; Chen, Yu-Hong; Liu, Zi-Jiang

    2013-10-10

    The electronic structures and excitation properties of dye sensitizers determine the photon-to-current conversion efficiency of dye sensitized solar cells (DSSCs). In order to understand the different performance of porphyrin dye sensitizers YD2 and YD2-o-C8 in DSSC, their geometries and electronic structures have been studied using density functional theory (DFT), and the electronic absorption properties have been investigated via time-dependent DFT (TDDFT) with polarizable continuum model for solvent effects. The geometrical parameters indicate that YD2 and YD2-o-C8 have similar conjugate length and charge transfer (CT) distance. According to the experimental spectra, the HSE06 functional in TDDFT is the most suitable functional for describing the Q and B absorption bands of porphyrins. The transition configurations and molecular orbital analysis suggest that the diarylamino groups are major chromophores for effective CT excitations (ECTE), and therefore act as electron donor in photon-induced electron injection in DSSCs. The analysis of excited states properties and the free energy changes for electron injection support that the better performance of YD2-o-C8 in DSSCs result from the more excited states with ECTE character and the larger absolute value of free energy change for electron injection.

  8. One-Pot Synthesis of (NiFe2O4)x-(SrFe12O19)1-x Nanocomposites and Their Microwave Absorption Properties.

    PubMed

    Hazra, Subhenjit; Ghosh, Barun Kumar; Patra, Manoj Kumar; Jani, Raj Kumar; Vadera, Sampat Raj; Ghosh, Narendra Nath

    2015-09-01

    In this paper, we report a simple but novel aqueous solution based 'one-pot' method for preparation of (NiFe2O4)x-(SrFe12O19)1-x nanocomposites consist of hard ferrite-soft ferrite phases. A physical mixing method has also been employed to prepare nanocomposites having same compositions. The effects of synthetic methodologies on the microstructures of the nanocomposites as well as their magnetic and microwave absorption properties have been evaluated. Crystal structures and microstructures of these composites have been investigated by using X-ray diffraction, transmission electron microscope and scanning electron microscope. In the nanocomposites, prepared by both methods, presence of nanocrystalline NiFe2O4 and SrFe12O19 phases was detected. However, nanocomposites, prepared by one-pot method, possessed better homogeneous distribution of hard and soft ferrite phases than the nanocomposites, prepared by physical mixing method. Nanocomposites, prepared by one-pot method, demonstrated significant spring exchange coupling interaction between hard and soft ferrite phases and exhibited magnetically single phase behaviour. The spring exchange coupling interaction enhanced the magnetic properties (high saturation magnetization and coercivity) and microwave absorption properties of the nanocomposites, prepared by one-pot method, in comparison with the nanocomposites prepared by physical mixing method as well as pure NiFe2O4 and SrFe12O19 nanoparticles. Minimum reflection loss of the composite was ~ -17 dB (i.e., 98% absorption) at 8.2 GHz for an absorber thickness of 3.2 mm.

  9. Fructus ligustri lucidi ethanol extract improves bone mineral density and properties through modulating calcium absorption-related gene expression in kidney and duodenum of growing rats.

    PubMed

    Feng, Xin; Lyu, Ying; Wu, Zhenghao; Fang, Yuehui; Xu, Hao; Zhao, Pengling; Xu, Yajun; Feng, Haotian

    2014-04-01

    Optimizing peak bone mass in early life is one of key preventive strategies against osteoporosis. Fructus ligustri lucidi (FLL), the fruit of Ligustrum lucidum Ait., is a commonly prescribed herb in many kidney-tonifying traditional Chinese medicinal formulas to alleviate osteoporosis. Previously, FLL extracts have been shown to have osteoprotective effect in aged or ovariectomized rats. In the present study, we investigated the effects of FLL ethanol extract on bone mineral density (BMD) and mechanical properties in growing male rats and explored the underlying mechanisms. Male weaning Sprague-Dawley rats were randomized into four groups and orally administrated for 4 months an AIN-93G formula-based diet supplementing with different doses of FLL ethanol extract (0.40, 0.65, and 0.90 %) or vehicle control, respectively. Then calcium balance, serum level of Ca, P, 25(OH)2D3, 1,25(OH)2D3, osteocalcin (OCN), C-terminal telopeptide of type I collagen (CTX-I), and parathyroid hormone, bone microarchitecture, and calcium absorption-related genes expression in duodenum and kidney were analyzed. The results demonstrated that FLL ethanol extract increased BMD of growing rats and improved their bone microarchitecture and mechanical properties. FLL ethanol extract altered bone turnover, as evidenced by increasing a bone formation maker, OCN, and decreasing a bone resorption maker, CTX-I. Intriguingly, both Ca absorption and Ca retention rate were elevated by FLL ethanol extract treatment, possibly through the mechanisms of up-regulating the transcriptions of calcitropic genes in kidney (1α-hydroxylase) and duodenum (vitamin D receptor, calcium transporter calbindin-D9k, and transient receptor potential vanilloid 6). In conclusion, FLL ethanol extract increased bone mass gain and improved bone properties via modulating bone turnover and up-regulating calcium absorption-related gene expression in kidney and duodenum, which could then activate 1,25(OH)2D3-dependent calcium

  10. Bioassay-guided chemical study of the anti-inflammatory effect of Senna villosa (Miller) H.S. Irwin & Barneby (Leguminosae) in TPA-induced ear edema.

    PubMed

    Susunaga-Notario, Ana del Carmen; Pérez-Gutiérrez, Salud; Zavala-Sánchez, Miguel Angel; Almanza-Pérez, Julio Cesar; Gutiérrez-Carrillo, Atilano; Arrieta-Báez, Daniel; López-López, Ana Laura; Román-Ramos, Rubén; Flores-Sáenz, José Luis Eduardo; Alarcón-Aguilar, Francisco Javier

    2014-07-15

    Senna villosa (Miller) is a plant that grows in México. In traditional Mexican medicine, it is used topically to treat skin infections, pustules and eruptions and to heal wounds by scar formation. However, studies of its potential anti-inflammatory effects have not been performed. The aim of the present study was to determine the anti-inflammatory effect of extracts from the leaves of Senna villosa and to perform a bioassay-guided chemical study of the extract with major activity in a model of ear edema induced by 12-O-tetradecanoylphorbol 13-acetate (TPA). The results reveal that the chloroform extract from Senna villosa leaves has anti-inflammatory and anti-proliferative properties. Nine fractions were obtained from the bioassay-guided chemical study, including a white precipitate from fractions 2 and 3. Although none of the nine fractions presented anti-inflammatory activity, the white precipitate exhibited pharmacological activity. It was chemically characterized using mass spectrometry and infrared and nuclear magnetic resonance spectroscopy, resulting in a mixture of three aliphatic esters, which were identified as the principal constituents: hexyl tetradecanoate (C20H40O2), heptyl tetradecanoate (C21H42O2) and octyl tetradecanoate (C22H44O2). This research provides, for the first time, evidence of the anti-inflammatory and anti-proliferative properties of compounds isolated from Senna villosa.

  11. DFT/TDDFT investigation on the chemical reactivities, aromatic properties, and UV-Vis absorption spectra of 1-butoxy-4-methoxybenzenepillar[5]arene constitutional isomers.

    PubMed

    Zhang, Jian; Ren, Shuqing

    2016-09-01

    We investigate the chemical reactivities, aromatic properties, and UV-Vis absorption spectra of four constitutional isomers of 1-butoxy-4-methoxybenzenepillar[5]arene with the DFT and TDDFT methods. These characteristics in the gas and solvent phases are discussed on the basis of electronic energy, the highest occupied molecular orbital energy, electrophilicity, global hardness, chemical potential, and nucleus-independent chemical shift. The out-of-plane component of the NICS values reveals that there is a great contrast between aromatic rings of the isomer and benzene. The most intense wavelengths of BMpillar[5]arenes are all made up of delocalized-delocalized π → π* transition.

  12. Chemical and light absorption properties of humic-like substances from biomass burning emissions under controlled combustion experiments

    NASA Astrophysics Data System (ADS)

    Park, Seung Shik; Yu, Jaemyeong

    2016-07-01

    PM2.5 samples from biomass burning (BB) emissions of three types - rice straw (RS), pine needles (PN), and sesame stems (SS) - were collected through laboratory-controlled combustion experiments and analyzed for the mass, organic and elemental carbon (OC and EC), water-soluble organic carbon (WSOC), humic-like substances (HULIS), and water soluble inorganic species (Na+, NH4+, K+, Ca2+, Mg2+, Cl-, NO3-, SO42-, and oxalate). The combustion experiments were carried out at smoldering conditions. Water-soluble HULIS in BB samples was isolated using a one-step solid phase extraction method, followed by quantification with a total organic carbon analyzer. This study aims to explore chemical and light absorption characteristics of HULIS from BB emissions. The contributions of HULIS (=1.94 × HULIS-C) to PM2.5 emissions were observed to be 29.5 ± 2.0, 15.3 ± 3.1, and 25.8 ± 4.0%, respectively, for RS, PN, and SS smoke samples. Contributions of HULIS-C to OC and WSOC for the RS, PN, and SS burning emissions were 0.26 ± 0.03 and 0.63 ± 0.05, 0.15 ± 0.04 and 0.36 ± 0.08, and 0.29 ± 0.08 and 0.51 ± 0.08, respectively. Light absorption by the water extracts from BB aerosols exhibited strong wavelength dependence, which is characteristic of brown carbon spectra with a sharply increasing absorption as wavelength decreases. The average absorption Ångström exponents (AAE) of the water extracts (WSOC) fitted between wavelengths of 300-400 nm were 8.3 (7.4-9.0), 7.4 (6.2-8.5), and 8.0 (7.1-9.3) for the RS, PN, and SS burning samples, which are comparable to the AAE values of BB samples reported in previous publications (e.g., field and laboratory chamber studies). The average mass absorption efficiencies of WSOC measured at 365 nm (MAE365) were 1.37 ± 0.23, 0.86 ± 0.09, and 1.38 ± 0.21 m2/gṡC for RS, PN, and SS burning aerosols, respectively. Correlations of total WSOC, hydrophilic WSOC (= total WSOC-HULIS-C), and HULIS-C concentrations in solution with the light

  13. Ultraviolet stimulated melanogenesis by human melanocytes is augmented by di-acyl glycerol but not TPA

    SciTech Connect

    Friedmann, P.S.; Wren, F.E.; Matthews, J.N. )

    1990-02-01

    Epidermal melanocytes (MC) synthesize melanin in response to ultraviolet radiation (UVR). The mechanisms mediating the UV-induced activation of melanogenesis are unknown but since UVR induces turnover of membrane phospholipids generating prostaglandins (PGs) and other products, it is possible that one of these might provide the activating signal. We have examined the effects of prostaglandins (PGs) E1, E2, D2, F2 alpha, and di-acyl glycerol upon the UV-induced responses of cultured human MC and the Cloudman S91 melanoma cell line. The PGs had little effect on unirradiated cells and did not alter the response to UVR in either human MC or S91 melanoma cells. However, a synthetic analogue of di-acyl glycerol, 1-oleyl 2-acetyl glycerol (OAG), caused a significant (P less than 0.0001), dose-related augmentation of melanin content both in human MC (seven-fold) and S91 cells (three-fold). UVR caused a significant augmentation of the OAG-induced melanogenesis of both human MC and S91 cells. Since OAG is known to activate protein kinase C, it was possible that the observed modulation of the UVR signal could be via that pathway. Di-octanoyl glycerol, another di-acyl glycerol, which activates kinase C, caused a small (70%) increase in melanogenesis in MC which was not altered by UVR. However, 12-0 tetradecanoyl phorbol 13-acetate (TPA), a potent activator of protein kinase C, had no significant effect on either basal or UV-induced melanin synthesis in either cell type. These data suggest that the UV-induced signal activating melanogenesis could be mediated by di-acyl glycerol. Furthermore, they imply that the signal is transduced via an alternative, pathway that might be independent of protein kinase C.

  14. Exogenous t-PA Administration Increases Hippocampal Mature BDNF Levels. Plasmin- or NMDA-Dependent Mechanism?

    PubMed Central

    Rodier, Marion; Prigent-Tessier, Anne; Béjot, Yannick; Jacquin, Agnès; Mossiat, Claude; Marie, Christine; Garnier, Philippe

    2014-01-01

    Brain-derived neurotrophic factor (BDNF) through TrkB activation is central for brain functioning. Since the demonstration that plasmin is able to process pro-BDNF to mature BDNF and that these two forms have opposite effects on neuronal survival and plasticity, a particular attention has been paid to the link between tissue plasminogen activator (tPA)/plasmin system and BDNF metabolism. However, t-PA via its action on different N-methyl-D-aspartate (NMDA) receptor subunits is also considered as a neuromodulator of glutamatergic transmission. In this context, the aim of our study was to investigate the effect of recombinant (r)t-PA administration on brain BDNF metabolism in rats. In the hippocampus, we found that rt-PA (10 mg/kg) administration induced a progressive increase in mature BDNF levels associated with TrkB activation. In order to delineate the mechanistic involved, plasmin activity was assessed and its inhibition was attempted using tranexamic acid (30 or 300 mg/kg, i.v.) while NMDA receptors were antagonized with MK801 (0.3 or 3 mg/kg, i.p.) in combination with rt-PA treatment. Our results showed that despite a rise in rt-PA activity, rt-PA administration failed to increase hippocampal plasmin activity suggesting that the plasminogen/plasmin system is not involved whereas MK801 abrogated the augmentation in mature BDNF levels observed after rt-PA administration. All together, our results show that rt-PA administration induces increase in hippocampal mature BDNF expression and suggests that rt-PA contributes to the control of brain BDNF synthesis through a plasmin-independent potentiation of NMDA receptors signaling. PMID:24670989

  15. Exogenous t-PA administration increases hippocampal mature BDNF levels. plasmin- or NMDA-dependent mechanism?

    PubMed

    Rodier, Marion; Prigent-Tessier, Anne; Béjot, Yannick; Jacquin, Agnès; Mossiat, Claude; Marie, Christine; Garnier, Philippe

    2014-01-01

    Brain-derived neurotrophic factor (BDNF) through TrkB activation is central for brain functioning. Since the demonstration that plasmin is able to process pro-BDNF to mature BDNF and that these two forms have opposite effects on neuronal survival and plasticity, a particular attention has been paid to the link between tissue plasminogen activator (tPA)/plasmin system and BDNF metabolism. However, t-PA via its action on different N-methyl-D-aspartate (NMDA) receptor subunits is also considered as a neuromodulator of glutamatergic transmission. In this context, the aim of our study was to investigate the effect of recombinant (r)t-PA administration on brain BDNF metabolism in rats. In the hippocampus, we found that rt-PA (10 mg/kg) administration induced a progressive increase in mature BDNF levels associated with TrkB activation. In order to delineate the mechanistic involved, plasmin activity was assessed and its inhibition was attempted using tranexamic acid (30 or 300 mg/kg, i.v.) while NMDA receptors were antagonized with MK801 (0.3 or 3 mg/kg, i.p.) in combination with rt-PA treatment. Our results showed that despite a rise in rt-PA activity, rt-PA administration failed to increase hippocampal plasmin activity suggesting that the plasminogen/plasmin system is not involved whereas MK801 abrogated the augmentation in mature BDNF levels observed after rt-PA administration. All together, our results show that rt-PA administration induces increase in hippocampal mature BDNF expression and suggests that rt-PA contributes to the control of brain BDNF synthesis through a plasmin-independent potentiation of NMDA receptors signaling.

  16. RBC-coupled tPA prevents cerebrovasodilatory impairment and tissue injury in pediatric cerebral hypoxia/ischemia through inhibition of ERK MAPK unregulation

    SciTech Connect

    Ganguly, Kumkum; Armstead, William M; Kiessling, J W; Chen, Xiao - Han; Smith, Douglas H; Higazi, Abd Ar; Cines, Douglas B; Bdeir, Khalil; Zaitsev, Sergei; Muzykantov, Vladimir R

    2008-01-01

    Babies experience hypoxia (H) and ischemia (I) from stroke. The only approved treatment for stroke is fibrinolytic therapy with tissue-type plasminogen activator (tPA). However, tPA potentiates H/I-induced impairment of responses to cerebrovasodilators such as hypercapnia and hypotension, and blockade of tPA-mediated vasoactivity prevents this deleterious effect. Coupling tPA to RBCs reduces its CNS toxicity through spatially confining the drug to the vasculature. Mitogen activated protein kinase (MAPK), a family of at least 3 kinases, is upregulated after H/I. In this study we determined if RBC-tPA given before or after cerebral H/I would preserve responses to cerebrovasodilators and prevent neuronal injury mediated through the ERK MAPK pathway. Animals given RBC-tPA maintained responses to cerebrovasodilators at levels equivalent to pre-H/I values. CSF and brain parenchymal ERK MAPK was elevated by H/I and this upregulation was potentiated by tPA, but blunted by RBC-tPA. U 0126, an ERK MAPK antagonist, also maintained cerebrovasodilation post H/I. Neuronal degeneration in CA1 hippocampus and parietal cortex after H/I was exacerbated by tPA, but ameliorated by RBC-tPA and U 0126. These data suggest that coupling tPA to RBCs may offer a novel approach towards increasing the benefit/risk ratio of thrombolytic therapy for CNS disorders associated with H/I.

  17. Optical absorption and scattering properties of bulk porcine muscle phantoms from interstitial radiance measurements in 650-900 nm range.

    PubMed

    Grabtchak, Serge; Montgomery, Logan G; Whelan, William M

    2014-05-21

    We demonstrated the application of relative radiance-based continuous wave (cw) measurements for recovering absorption and scattering properties (the effective attenuation coefficient, the diffusion coefficient, the absorption coefficient and the reduced scattering coefficient) of bulk porcine muscle phantoms in the 650-900 nm spectral range. Both the side-firing fiber (the detector) and the fiber with a spherical diffuser at the end (the source) were inserted interstitially at predetermined locations in the phantom. The porcine phantoms were prostate-shaped with ∼4 cm in diameter and ∼3 cm thickness and made from porcine loin or tenderloin muscles. The described method was previously validated using the diffusion approximation on simulated and experimental radiance data obtained for homogenous Intralipid-1% liquid phantom. The approach required performing measurements in two locations in the tissue with different distances to the source. Measurements were performed on 21 porcine phantoms. Spectral dependences of the effective attenuation and absorption coefficients for the loin phantom deviated from corresponding dependences for the tenderloin phantom for wavelengths <750 nm. The diffusion constant and the reduced scattering coefficient were very close for both phantom types. To quantify chromophore presence, the plot for the absorption coefficient was matched with a synthetic absorption spectrum constructed from deoxyhemoglobin, oxyhemoglobin and water. The closest match for the porcine loin spectrum was obtained with the following concentrations: 15.5 µM (±30% s.d.) Hb, 21 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The tenderloin absorption spectrum was best described by 30 µM Hb (±30% s.d), 19 µM (±30% s.d.) HbO2 and 0.3 (±30% s.d.) fractional volume of water. The higher concentration of Hb in tenderloin was consistent with a dark-red appearance of the tenderloin phantom. The method can be applied to a number of

  18. Optical Absorption Spectra and Electronic Properties of Symmetric and Asymmetric Squaraine Dyes for Use in DSSC Solar Cells: DFT and TD-DFT Studies

    PubMed Central

    El-Shishtawy, Reda M.; Elroby, Shaaban A.; Asiri, Abdullah M.; Müllen, Klaus

    2016-01-01

    The electronic absorption spectra, ground-state geometries and electronic structures of symmetric and asymmetric squaraine dyes (SQD1–SQD4) were investigated using density functional theory (DFT) and time-dependent (TD-DFT) density functional theory at the B3LYP/6-311++G** level. The calculated ground-state geometries reveal pronounced conjugation in these dyes. Long-range corrected time dependent density functionals Perdew, Burke and Ernzerhof (PBE, PBE1PBE (PBE0)), and the exchange functional of Tao, Perdew, Staroverov, and Scuseria (TPSSh) with 6-311++G** basis set were employed to examine optical absorption properties. In an extensive comparison between the optical data and DFT benchmark calculations, the BEP functional with 6-311++G** basis set was found to be the most appropriate in describing the electronic absorption spectra. The calculated energy values of lowest unoccupied molecular orbitals (LUMO) were 3.41, 3.19, 3.38 and 3.23 eV for SQD1, SQD2, SQD3, and SQD4, respectively. These values lie above the LUMO energy (−4.26 eV) of the conduction band of TiO2 nanoparticles indicating possible electron injection from the excited dyes to the conduction band of the TiO2 in dye-sensitized solar cells (DSSCs). Also, aromaticity computation for these dyes are in good agreement with the data obtained optically and geometrically with SQD4 as the highest aromatic structure. Based on the optimized molecular geometries, relative positions of the frontier orbitals, and the absorption maxima, we propose that these dyes are suitable components of photovoltaic DSSC devices. PMID:27043556

  19. Shortwave Radiative Fluxes, Solar-Beam Transmissions, and Aerosol Properties: TARFOX and ACE-2 Find More Absorption from Flux Radiometry than from Other Measurements

    NASA Technical Reports Server (NTRS)

    Russell, Philip B.; Redemann, J.; Schmid, B.; Livingston, J. M.; Bergstrom, R. W.; Ramirez, S. A.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the Second Aerosol Characterization Experiment (ACE-2) made simultaneous measurements of shortwave radiative fluxes, solar-beam transmissions, and the aerosols affecting those fluxes and transmissions. Besides the measured fluxes and transmissions, other obtained properties include aerosol scattering and absorption measured in situ at the surface and aloft; aerosol single scattering albedo retrieved from skylight radiances; and aerosol complex refractive index derived by combining profiles of backscatter, extinction, and size distribution. These measurements of North Atlantic boundary layer aerosols impacted by anthropogenic pollution revealed the following characteristic results: (1) Better agreement among different types of remote measurements of aerosols (e.g., optical depth, extinction, and backscattering from sunphotometers, satellites, and lidars) than between remote and in situ measurements; 2) More extinction derived from transmission measurements than from in situ measurements; (3) Larger aerosol absorption inferred from flux radiometry than from other measurements. When the measured relationships between downwelling flux and optical depth (or beam transmission) are used to derive best-fit single scattering albedos for the polluted boundary layer aerosol, both TARFOX and ACE-2 yield midvisible values of 0.90 +/- 0.04. The other techniques give larger single scattering albedos (i.e. less absorption) for the polluted boundary layer, with a typical result of 0.95 +/- 0.04. Although the flux-based results have the virtue of describing the column aerosol unperturbed by sampling, they are subject to questions about representativeness and other uncertainties (e.g., unknown gas absorption). Current uncertainties in aerosol single scattering albedo are large in terms of climate effects. They also have an important influence on aerosol optical depths retrieved from satellite radiances

  20. Optical Absorption Spectra and Electronic Properties of Symmetric and Asymmetric Squaraine Dyes for Use in DSSC Solar Cells: DFT and TD-DFT Studies.

    PubMed

    El-Shishtawy, Reda M; Elroby, Shaaban A; Asiri, Abdullah M; Müllen, Klaus

    2016-04-01

    The electronic absorption spectra, ground-state geometries and electronic structures of symmetric and asymmetric squaraine dyes (SQD1-SQD4) were investigated using density functional theory (DFT) and time-dependent (TD-DFT) density functional theory at the B3LYP/6-311++G** level. The calculated ground-state geometries reveal pronounced conjugation in these dyes. Long-range corrected time dependent density functionals Perdew, Burke and Ernzerhof (PBE, PBE1PBE (PBE0)), and the exchange functional of Tao, Perdew, Staroverov, and Scuseria (TPSSh) with 6-311++G** basis set were employed to examine optical absorption properties. In an extensive comparison between the optical data and DFT benchmark calculations, the BEP functional with 6-311++G** basis set was found to be the most appropriate in describing the electronic absorption spectra. The calculated energy values of lowest unoccupied molecular orbitals (LUMO) were 3.41, 3.19, 3.38 and 3.23 eV for SQD1, SQD2, SQD3, and SQD4, respectively. These values lie above the LUMO energy (-4.26 eV) of the conduction band of TiO₂ nanoparticles indicating possible electron injection from the excited dyes to the conduction band of the TiO₂ in dye-sensitized solar cells (DSSCs). Also, aromaticity computation for these dyes are in good agreement with the data obtained optically and geometrically with SQD4 as the highest aromatic structure. Based on the optimized molecular geometries, relative positions of the frontier orbitals, and the absorption maxima, we propose that these dyes are suitable components of photovoltaic DSSC devices.

  1. An experimental study of the electronic absorption and fluorescence spectral properties of new p-substituted-N-phenylpyrroles and their electrosynthesized polymers.

    PubMed

    Diaw, A K D; Gningue-Sall, D; Yassar, A; Brochon, J-C; Henry, E; Aaron, J-J

    2015-01-25

    Electronic absorption and fluorescence spectral properties of new p-substituted-N-phenylpyrroles (N-PhPys), including HOPhPy, MeOPhPy, ThPhPy, PhDPy, DPhDPy, PyPhThThPhPy, and their available, electrosynthesized polymers were investigated. Electronic absorption spectra, fluorescence excitation and emission spectra, fluorescence quantum yields (ΦF) and lifetimes (τF), and other photophysical parameters of these N-PhPy derivatives and their polymers were measured in DMF, DMSO diluted solutions and/or solid state at room temperature. The electronic absorption spectra of N-PhPy derivatives and their polymers included one to several bands, located in the 270-395 nm region, according to the p-phenyl substituent electron-donating effect and conjugated heteroaromatic system length. The fluorescence excitation spectra were characterized by one broad main peak, with, in most cases, one (or more) poorly resolved shoulder (s), appearing in the 270-405 nm region, and their emission spectra were generally constituted of several bands located in the 330-480 nm region. No significant shift of the absorption, fluorescence excitation and emission spectra wavelengths was found upon going from the monomers to the corresponding polymers. ΦF values were high, varying between 0.11 and 0.63, according to the nature of substituents(s) and to the conjugated system extension. Fluorescence decays were mono-exponential for the monomers and poly-exponential for PyPhThThPhPy and for polymers. τF values were relatively short (0.35-5.17 ns), and markedly decreased with the electron-donor character of the phenyl group p-substituent and the conjugated system extension.

  2. Weaning induces both transient and long-lasting modifications of absorptive, secretory, and barrier properties of piglet intestine.

    PubMed

    Boudry, Gaëlle; Péron, Vincent; Le Huërou-Luron, Isabelle; Lallès, Jean Paul; Sève, Bernard

    2004-09-01

    This study investigated intestinal physiology of piglets at weaning. Piglets (n = 60) weaned at 21 d were food deprived for 2 d and then tube-fed using 2 different diets (a conventional diet vs. a wheat-enriched diet). They were slaughtered at d 0, 2, 5, 8, or 15 postweaning. Jejunum, ileum, and colon were mounted in Ussing chambers. In addition, segments of the proximal jejunum of 4 growing pigs were studied 35 d after weaning. Secretory function was assessed by basal short-circuit current (Isc) and secretagogue-stimulated Isc. Glucose absorption was measured by the increase in Isc after the addition of glucose. Epithelial barrier function was measured by transmucosal resistance (R) and horseradish peroxidase (HRP) fluxes across the epithelium. There were no significant differences between the pigs fed the 2 diets for any of the parameters studied. As already reported, a transient villous atrophy was observed. At the same time, we observed an increased basal Isc in jejunum and colon, increased glucose absorption and a dramatic drop of R in jejunum. These parameters had returned to preweaning values by d 5. Weaning was also followed by long-lasting modifications. In jejunum, responses to the secretagogues and glucose absorption were decreased at wk 2 after weaning and were not different between d 15 and 35. Ileal transmucosal resistance increased on d 5 and was stable thereafter. HRP flux in jejunum declined on d 2 and stayed at this low level throughout the experiment. We conclude that weaning induces transient dramatic changes in intestinal physiology but is also a period of maturation of the intestine.

  3. Intranasal absorption of oxymorphone.

    PubMed

    Hussain, M A; Aungst, B J

    1997-08-01

    The nasal bioavailability of oxymorphone HCI was determined. Rats were surgically prepared to isolate the nasal cavity, into which a solution of oxymorphone was administered. A reference group of rats was administered oxymorphone HCl intravenously. Plasma oxymorphone concentrations were determined by HPLC. Nasal absorption was rapid, nasal bioavailability was 43%, and the iv and nasal elimination profiles were similar. Oxymorphone HCI appears to have the solubility, potency, and absorption properties required for efficient nasal delivery, which is an alternative to injections.

  4. Ultrasonication assisted preparation of carbonaceous nanoparticles modified polyurethane foam with good conductivity and high oil absorption properties

    NASA Astrophysics Data System (ADS)

    Shi, Hengchong; Shi, Dean; Yin, Ligang; Yang, Zhihua; Luan, Shifang; Gao, Jiefeng; Zha, Junwei; Yin, Jinghua; Li, Robert K. Y.

    2014-10-01

    In this work, we report a facile, low cost and time-saving method for the fabrication of compressible, electrically conductive, oil absorptive, cost-effective and flexible polyurethane (PU) foam through ultrasonication induced carbonaceous nanoparticles (CNP) onto flexible PU foam (CNP-PU foam). SEM images showed that the CNP could be firmly anchored onto the PU foam, and made the PU foam surface much rougher. Zero-dimensional carbonaceous nanoparticles were easier to anchor onto the PU foam surface than one-dimensional nanoparticles (e.g., carbon nanotube) or two-dimensional nanoparticles (e.g., graphene oxide). The CNP-PU foam exhibited excellent elasticity and high mechanical durability even when it was subjected to 500 cyclic compression. The CNP-PU foam had excellent absorption of organic solvents up to 121 times the weight of the initial PU foam. In addition, the electrical conductivity of PU foams was considerably increased with the anchoring of CNP onto the matrix. In addition, compression experiments confirmed that the electrical conductivity of CNP-PU foams changed with their compression ratios, thus exhibiting excellent pressure sensitivity. The as-prepared materials have significant potential as oil absorbents, elastic conductors, flexible electrodes, pressure sensors, etc.In this work, we report a facile, low cost and time-saving method for the fabrication of compressible, electrically conductive, oil absorptive, cost-effective and flexible polyurethane (PU) foam through ultrasonication induced carbonaceous nanoparticles (CNP) onto flexible PU foam (CNP-PU foam). SEM images showed that the CNP could be firmly anchored onto the PU foam, and made the PU foam surface much rougher. Zero-dimensional carbonaceous nanoparticles were easier to anchor onto the PU foam surface than one-dimensional nanoparticles (e.g., carbon nanotube) or two-dimensional nanoparticles (e.g., graphene oxide). The CNP-PU foam exhibited excellent elasticity and high mechanical

  5. Electronic properties and absorption spectra of ZnSnP{sub 2} using mBJ potential

    SciTech Connect

    Joshi, Ritu Ahuja, B. L.

    2015-06-24

    We present the energy bands and density of states of ZnSnP{sub 2} using full potential linearized augmented plane wave method with modified Becke Johnson potential. It is found that this compound has a direct band gap of about 2.01 eV at Γ point, which originates from the energy difference between P-3p and Sn-5s states. In addition, we have also calculated absorption spectra in the solar energy range and compared it with that of bulk Si to explore the applicability of ZnSnP{sub 2} in photovoltaic and optoelectronic devices.

  6. Ligand-assisted fabrication of hollow CdSe nanospheres viaOstwald ripening and their microwave absorption properties

    NASA Astrophysics Data System (ADS)

    Cao, Minhua; Lian, Huiqin; Hu, Changwen

    2010-12-01

    Hollow CdSe nanospheres were successfully synthesized by a ligand-assisted solvothermal method based on an Ostwald ripening mechanism. The hollow CdSe nanospheres were synthesized in benzyl alcohol under solvothermal conditions using Cd(Ac)2 and Se as the precursors, and tryptophan as a ligand. The resulting hollow structures consisted of small nanocrystallite building blocks. More importantly, the hollow CdSe nanospheres could be used as an excellent microwave absorber for cm- and mm-wave absorption, depending on the thickness of the absorber.

  7. Effect of zeolite properties on ground-state and triplet-triplet absorption, prompt and oxygen induced delayed fluorescence of tetraphenylporphyrin at gas/solid interface

    NASA Astrophysics Data System (ADS)

    Levin, P. P.; Costa, Silvia M. B.; Lopes, J. M.; Serralha, F. N.; Ribeiro, F. Ramôa

    2000-08-01

    The ground-state and transient absorption, prompt and delayed fluorescence of tetraphenylporphyrin (TPP) adsorbed onto the external surface of different zeolites was monitored using diffuse-reflectance steady-state and laser flash photolysis. The delayed fluorescence (DF) of TPP detected in the presence of O 2 is attributed to the energy transfer from 3TPP to 3O 2 to form 1O 2 and subsequent energy transfer from 1O 2 to some other 3TPP within the organised molecular ensembles on the zeolite surface. The spectroscopic and kinetic parameters, namely the yield of DF (2-20% relative to prompt fluorescence), depend on the zeolite properties: the observed differences were correlated with the acid-base properties of the two zeolite series studied in this work (KA, NaA, CaA) and (NaA, NaX, NaY).

  8. Flavonoid interactions during digestion, absorption, distribution and metabolism: a sequential structure-activity/property relationship-based approach in the study of bioavailability and bioactivity.

    PubMed

    Gonzales, Gerard Bryan; Smagghe, Guy; Grootaert, Charlotte; Zotti, Moises; Raes, Katleen; Van Camp, John

    2015-05-01

    Flavonoids are a group of polyphenols that provide health-promoting benefits upon consumption. However, poor bioavailability has been a major hurdle in their use as drugs or nutraceuticals. Low bioavailability has been associated with flavonoid interactions at various stages of the digestion, absorption and distribution process, which is strongly affected by their molecular structure. In this review, we use structure-activity/property relationship to discuss various flavonoid interactions with food matrices, digestive enzymes, intestinal transporters and blood proteins. This approach reveals specific bioactive properties of flavonoids in the gastrointestinal tract as well as various barriers for their bioavailability. In the last part of this review, we use these insights to determine the effect of different structural characteristics on the overall bioavailability of flavonoids. Such information is crucial when flavonoid or flavonoid derivatives are used as active ingredients in foods or drugs.

  9. Role of incoherent pumping field on absorption-dispersion properties of probe pulse in a graphene nanostructure under external magnetic field

    NASA Astrophysics Data System (ADS)

    Asadpour, Seyyed Hossein; Hamedi, H. R.; Soleimani, H. Rahimpour

    2015-07-01

    The optical properties of weak probe light based on quantum coherence and interference in Landau-quantized graphene nanostructure driven by two coherent fields and incoherent pumping field is investigated. The linear dynamical properties of the graphene by means of density matrix method and perturbation theory are discussed. It is found that under certain condition and for appropriate choosing the parameters of the medium, the absorption, dispersion, group index of the weak probe light can be controlled. Moreover, it is shown that by means of incoherent pumping field the superluminal light propagation in the system is accompanied by amplification to make sure that the probe field is amplified as it passes through the system. Moreover, it is observed that the probe amplification can be obtained in the presence or absence of population inversion by properly choosing of system's parameters. We hope that these results may have useful in the future quantum communicational system and networks.

  10. Controlled synthesis and microwave absorption properties of Ni0.6Zn0.4Fe2O4/PANI composite via an in-situ polymerization process

    NASA Astrophysics Data System (ADS)

    Wang, Min; Ji, Guangbin; Zhang, Baoshan; Tang, Dongming; Yang, Yi; Du, Youwei

    2015-03-01

    The binary composites of conducting polyaniline (PANI) and nickle zinc ferrite were synthesized by an in-situ polymerization process, and the electromagnetic absorption properties of the composites were also investigated. The FT-IR spectra present the peaks of PANI (1562, 1481, 1301, 1109, and 799 cm-1) and the bonds of NiZn ferrite (579 and 390 cm-1), indicating the existence of both NiZn ferrite particles and PANI in the composites. With the increasing ratio of nickle zinc ferrite, the composites distributes in irregular compared with pure PANI and Ni0.6Zn0.4Fe2O4. The TG curves of the pure PANI and PANI/Ni0.6Zn0.4Fe2O4 composites with different molar ratios clearly show the increase percentage of the ferrite in the composites. Furthermore, we found that the excellent electromagnetic absorption properties and wide absorption bandwidth can be achieved by adjusting proper molar ratios Ni0.6Zn0.4Fe2O4 to PANI. The maximum reflection loss of Ni0.6Zn0.4Fe2O4/PANI can reach to -41 dB at 12.8 GHz and the bandwidth exceeding -10 dB can reach to 5 GHz with the absorber thickness of 2.6 mm at the molar ratio of 1:2. This can be attributed to the enhancing magnetic loss and the better impedance matching. Therefore, Ni0.6Zn0.4Fe2O4/PANI ferrite composites can become a new kind of candidate in the field of the microwave absorbing.

  11. Enhanced Microwave Absorption Properties of Flexible Polymer Composite Based on Hexagonal NiCo2O4 Microplates and PVDF

    NASA Astrophysics Data System (ADS)

    Luo, Hui; Wang, Xian; Song, Kai; Yang, Jing; Gong, Rongzhou

    2016-08-01

    Hexagonal NiCo2O4 microplates were synthesized via a facile one-pot hydrothermal method and followed by a subsequent annealing process. The complex permittivity and permeability of a NiCo2O4 and polyvinylidene fluoride (PVDF) composite were investigated over 2-18 GHz. The experiment indicated that the good microwave absorption performance of NiCo2O4@PVDF depends on dielectric loss and quarter-wavelength cancellation. Our results show that the absorption frequency bandwidth of reflection loss (RL) less than -20 dB for the NiCo2O4@PVDF composite can be measured over the frequency range of 3-15.5 GHz with an absorbing thickness that varies in the range of 1.25-5 mm. Furthermore, an optimal RL of -44.8 dB was observed at 10.7 GHz with a thickness of 1.75 mm. The loss mechanism is also discussed.

  12. Absorption and photoluminescence properties of Er-doped and Er/Yb codoped soda-silicate laser glasses

    SciTech Connect

    Li, S.F.; Zhang, Q.Y.; Lee, Y.P.

    2004-11-01

    Er-doped and Er/Yb codoped soda-silicate laser glasses with various concentrations of Er and Yb were fabricated. The absorption and the photoluminescence (PL) spectra were measured and analyzed. For the Er- doped soda-slilicate glasses, the optimum Er concentration for the PL intensity at 1536 nm turns out to be 0.5 at. %, and the full width at half maximum (FWHM) of PL spectrum increases from 18 to 26 nm, with the increase of the concentration from 0.1 to 0.8 at. %. The PL intensity of Er/Yb codoped soda-silicate glasses with an Er concentration of 0.5 at. % is enhanced approximately by four times, and the optimum Yb concentration for the PL intensity at 1536 nm is analyzed to be 3.0 at. %. The PL spectrum becomes broader with increasing the Yb concentration, up to a FWHM of 80 nm at 6.0 at. %. Yb. The relation between the absorption and PL spectra, together with the mechanism of PL broadening, has also been addressed.

  13. Physical Properties of the Interstellar Medium Using High-resolution Chandra Spectra: O K-edge Absorption

    NASA Astrophysics Data System (ADS)

    Gatuzz, E.; García, J.; Mendoza, C.; Kallman, T. R.; Bautista, M. A.; Gorczyca, T. W.

    2014-08-01

    Chandra high-resolution spectra toward eight low-mass Galactic binaries have been analyzed with a photoionization model that is capable of determining the physical state of the interstellar medium. Particular attention is given to the accuracy of the atomic data. Hydrogen column densities are derived with a broadband fit that takes into account pileup effects, and in general are in good agreement with previous results. The dominant features in the oxygen-edge region are O I and O II Kα absorption lines whose simultaneous fits lead to average values of the ionization parameter of log ξ = -2.90 and oxygen abundance of A O = 0.70. The latter is given relative to the standard by Grevesse & Sauval, but rescaling with the revision by Asplund et al. would lead to an average abundance value fairly close to solar. The low average oxygen column density (N O = 9.2 × 1017 cm-2) suggests a correlation with the low ionization parameters, the latter also being in evidence in the column density ratios N(O II)/N(O I) and N(O III)/N(O I) that are estimated to be less than 0.1. We do not find conclusive evidence for absorption by any other compound but atomic oxygen in our oxygen-edge region analysis.

  14. Physical properties of the interstellar medium using high-resolution Chandra spectra: O K-edge absorption

    SciTech Connect

    Gatuzz, E.; Mendoza, C.; García, J.; Kallman, T. R.; Bautista, M. A.; Gorczyca, T. W. E-mail: claudio@ivic.gob.ve E-mail: manuel.bautista@wmich.edu E-mail: timothy.r.kallman@nasa.gov

    2014-08-01

    Chandra high-resolution spectra toward eight low-mass Galactic binaries have been analyzed with a photoionization model that is capable of determining the physical state of the interstellar medium. Particular attention is given to the accuracy of the atomic data. Hydrogen column densities are derived with a broadband fit that takes into account pileup effects, and in general are in good agreement with previous results. The dominant features in the oxygen-edge region are O I and O II Kα absorption lines whose simultaneous fits lead to average values of the ionization parameter of log ξ = –2.90 and oxygen abundance of A{sub O} = 0.70. The latter is given relative to the standard by Grevesse and Sauval, but rescaling with the revision by Asplund et al. would lead to an average abundance value fairly close to solar. The low average oxygen column density (N{sub O} = 9.2 × 10{sup 17} cm{sup –2}) suggests a correlation with the low ionization parameters, the latter also being in evidence in the column density ratios N(O II)/N(O I) and N(O III)/N(O I) that are estimated to be less than 0.1. We do not find conclusive evidence for absorption by any other compound but atomic oxygen in our oxygen-edge region analysis.

  15. Ultrasonication assisted preparation of carbonaceous nanoparticles modified polyurethane foam with good conductivity and high oil absorption properties.

    PubMed

    Shi, Hengchong; Shi, Dean; Yin, Ligang; Yang, Zhihua; Luan, Shifang; Gao, Jiefeng; Zha, Junwei; Yin, Jinghua; Li, Robert K Y

    2014-11-21

    In this work, we report a facile, low cost and time-saving method for the fabrication of compressible, electrically conductive, oil absorptive, cost-effective and flexible polyurethane (PU) foam through ultrasonication induced carbonaceous nanoparticles (CNP) onto flexible PU foam (CNP-PU foam). SEM images showed that the CNP could be firmly anchored onto the PU foam, and made the PU foam surface much rougher. Zero-dimensional carbonaceous nanoparticles were easier to anchor onto the PU foam surface than one-dimensional nanoparticles (e.g., carbon nanotube) or two-dimensional nanoparticles (e.g., graphene oxide). The CNP-PU foam exhibited excellent elasticity and high mechanical durability even when it was subjected to 500 cyclic compression. The CNP-PU foam had excellent absorption of organic solvents up to 121 times the weight of the initial PU foam. In addition, the electrical conductivity of PU foams was considerably increased with the anchoring of CNP onto the matrix. In addition, compression experiments confirmed that the electrical conductivity of CNP-PU foams changed with their compression ratios, thus exhibiting excellent pressure sensitivity. The as-prepared materials have significant potential as oil absorbents, elastic conductors, flexible electrodes, pressure sensors, etc.

  16. Influence of resin system on the energy absorption capability and morphological properties of plain woven kenaf composites

    NASA Astrophysics Data System (ADS)

    Salman, S. D.; Leman, Z.; Sultan, M. T. H.; Ishak, M. R.; Cardona, F.

    2015-12-01

    Due to both environmental and technical advantages, natural fibers are being used as reinforcement of polymeric composite in many industries. The flexibility of the most natural fibers is one of the important technical characteristic which allows them to resist impact forces. An investigation was carried out to compare the energy absorption capability of kenaf/PVB film and kenaf/epoxy composites. The hot and cold press techniques were used to fabricate the specimens with 35% kenaf fibre weight fraction. The charpy impact test was performed on forty notched specimens using a pendulum impact tester with different hammer energy. The results showed that the kenaf/PVB film composite has the highest energy absorption, strength and toughness compared with the epoxy composite. At high energy levels, the impact strength and toughness of the kenaf/PVB film was six times of kenaf/epoxy composite. In addition, the scanning electron microscopy was assessed to demonstrate the different failure in fracture surfaces. It was found that the kenaf/PVB film composite failed by fibre fracture while kenaf/epoxy composite failed by a combination of fibre pull-out and fibre fracture as well as crack propagations through the matrix.