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Sample records for doped small molecular

  1. Stable inverted small molecular organic solar cells using a p-doped optical spacer.

    PubMed

    Lee, Sang-Hoon; Seo, Ji-Won; Lee, Jung-Yong

    2015-01-07

    We report inverted small molecular organic solar cells using a doped window layer as an optical spacer. The optical spacer was used to shift the optical field distribution inside the active layers, generating more charge carriers from sunlight. In this report, N,N,N',N'-tetrakis(4-methoxyphenyl)-benzidine (MeO-TPD) was doped with 2,2-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6-TCNNQ), a p-type dopant material. P-doped MeO-TPD was adopted as an optical spacer because it has a large energy band gap, and its conductivity can be increased by several orders of magnitude through a doping process. As a result, a power conversion efficiency of 4.15% was achieved with the doped window layer of optimized thickness. Lastly, we present significantly improved stability of the inverted devices with the MeO-TPD layer.

  2. The Electric and Optical Properties of Doped Small Molecular Organic Light-Emitting Devices

    SciTech Connect

    Cheon, Kwang-Ohk

    2003-01-01

    Organic light-emitting devices (OLEDs) constitute a new and exciting emissive display technology. In general, the basic OLED structure consists of a stack of fluorescent organic layers sandwiched between a transparent conducting-anode and metallic cathode. When an appropriate bias is applied to the device, holes are injected from the anode and electrons from the cathode; some of the recombination events between the holes and electrons result in electroluminescence (EL). Until now, most of the efforts in developing OLEDs have focused on display applications, hence on devices within the visible range. However some organic devices have been developed for ultraviolet or infrared emission. Various aspects of the device physics of doped small molecular OLEDs were described and discussed. The doping layer thickness and concentration were varied systematically to study their effects on device performances, energy transfer, and turn-off dynamics. Low-energy-gap DCM2 guest molecules, in either α-NPD or DPVBi host layers, are optically efficient fluorophores but also generate deep carrier trap-sites. Since their traps reduce the carrier mobility, the current density decreases with increased doping concentration. At the same time, due to efficient energy transfer, the quantum efficiency of the devices is improved by light doping or thin doping thickness, in comparison with the undoped neat devices. However, heavy doping induces concentration quenching effects. Thus, the doping concentration and doping thickness may be optimized for best performance.

  3. Molecularly doped metals.

    PubMed

    Avnir, David

    2014-02-18

    The many millions of organic, inorganic, and bioorganic molecules represent a very rich library of chemical, biological, and physical properties that do not show up among the approximately 100 metals. The ability to imbue metals with any of these molecular properties would open up tremendous potential for the development of new materials. In addition to their traditional features and their traditional applications, metals would have new traits, which would merge their classical virtues such as conductivity and catalytic activity with the diverse properties of these molecules. In this Account, we describe a new materials methodology, which enables, for the first time, the incorporation and entrapment of small organic molecules, polymers, and biomolecules within metals. These new materials are denoted dopant@metal. The creation of dopant@metal yields new properties that are more than or different from the sum of the individual properties of the two components. So far we have developed methods for the doping of silver, copper, gold, iron, palladium, platinum, and some of their alloys, as well as Hg-Ag amalgams. We have successfully altered classical metal properties (such as conductivity), induced unorthodox properties (such as rendering a metal acidic or basic), used metals as heterogeneous matrices for homogeneous catalysts, and formed new metallic catalysts such as metals doped with organometallic complexes. In addition, we have created materials that straddle the border between polymers and metals, we have entrapped enzymes to form bioactive metals, we have induced chirality within metals, we have made corrosion-resistant iron, we formed efficient biocidal materials, and we demonstrated a new concept for batteries. We have developed a variety of methods for synthesizing dopant@metals including aqueous homogeneous and heterogeneous reductions of the metal cations, reductions in DMF, electrochemical entrapments, thermal decompositions of zerovalent metal carbonyls

  4. Method of making molecularly doped composite polymer material

    DOEpatents

    Affinito, John D [Tucson, AZ; Martin, Peter M [Kennewick, WA; Graff, Gordon L [West Richland, WA; Burrows, Paul E [Kennewick, WA; Gross, Mark E. , Sapochak, Linda S.

    2005-06-21

    A method of making a composite polymer of a molecularly doped polymer. The method includes mixing a liquid polymer precursor with molecular dopant forming a molecularly doped polymer precursor mixture. The molecularly doped polymer precursor mixture is flash evaporated forming a composite vapor. The composite vapor is cryocondensed on a cool substrate forming a composite molecularly doped polymer precursor layer, and the cryocondensed composite molecularly doped polymer precursor layer is cross linked thereby forming a layer of the composite polymer layer of the molecularly doped polymer.

  5. Enhanced short-circuit current density in poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 based organic solar cells by doping small molecular perylene

    NASA Astrophysics Data System (ADS)

    Lou, Yanhui; Wang, Zhaokui; Naka, Shigeki; Okada, Hiroyuki

    2011-07-01

    The authors investigate the effects of a small molecular dye, perylene, on the performance of organic solar cells based on poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) blends. The short-circuit current density is improved, and a maximum 27% enhancement in power conversion efficiency is achieved by doping suitable perylene into P3HT:PCBM blends. It is attributed to be the enhanced absorption of perylene doped P3HT:PCBM blends, which is also confirmed in single-carrier devices. Moreover, the barrier height at the anode/blend is largely lowered from 0.61 eV to 0.28 eV through evaluating temperature dependence of current-voltage characteristics.

  6. Electron transport in doped fullerene molecular junctions

    NASA Astrophysics Data System (ADS)

    Kaur, Milanpreet; Sawhney, Ravinder Singh; Engles, Derick

    The effect of doping on the electron transport of molecular junctions is analyzed in this paper. The doped fullerene molecules are stringed to two semi-infinite gold electrodes and analyzed at equilibrium and nonequilibrium conditions of these device configurations. The contemplation is done using nonequilibrium Green’s function (NEGF)-density functional theory (DFT) to evaluate its density of states (DOS), transmission coefficient, molecular orbitals, electron density, charge transfer, current, and conductance. We conclude from the elucidated results that Au-C16Li4-Au and Au-C16Ne4-Au devices behave as an ordinary p-n junction diode and a Zener diode, respectively. Moreover, these doped fullerene molecules do not lose their metallic nature when sandwiched between the pair of gold electrodes.

  7. Small Molecular as SIRT Modulators.

    PubMed

    Yao, Lei; Xu, Xiangming; Chen, Kai

    2016-06-19

    Sirtuins are class III histone deacetylases, they involve in many important biological functions. Small molecules that can modulate sirtuin activity have been shown to have potential for treating many human diseases. In the article, recent development of small molecular as SIRT modulators has been reviewed.

  8. Self-doped molecular composite battery electrolytes

    DOEpatents

    Harrup, Mason K.; Wertsching, Alan K.; Stewart, Frederick F.

    2003-04-08

    This invention is in solid polymer-based electrolytes for battery applications. It uses molecular composite technology, coupled with unique preparation techniques to render a self-doped, stabilized electrolyte material suitable for inclusion in both primary and secondary batteries. In particular, a salt is incorporated in a nano-composite material formed by the in situ catalyzed condensation of a ceramic precursor in the presence of a solvated polymer material, utilizing a condensation agent comprised of at least one cation amenable to SPE applications. As such, the counterion in the condensation agent used in the formation of the molecular composite is already present as the electrolyte matrix develops. This procedure effectively decouples the cation loading levels required for maximum ionic conductivity from electrolyte physical properties associated with condensation agent loading levels by utilizing the inverse relationship discovered between condensation agent loading and the time domain of the aging step.

  9. Efficient small molecular organic light emitting diode with graphene cathode covered by a Sm layer with nano-hollows and n-doped by Bphen:Cs2CO3 in the hollows

    NASA Astrophysics Data System (ADS)

    Yao, Li; Li, Lei; Qin, Laixiang; Ma, Yaoguang; Wang, Wei; Meng, Hu; Jin, Weifeng; Wang, Yilun; Xu, Wanjin; Ran, Guangzhao; You, Liping; Qin, Guogang

    2017-03-01

    Graphene is a favorable candidate for electrodes of organic light emitting diodes (OLEDs). Graphene has quite a high work function of ˜4.5 eV, and has been extensively studied when used as anodes of OLEDs. In order to use graphene as a cathode, the electron injection barrier between the graphene cathode and the electron transport layer has to be low enough. Using 4,7-diphenyl-1,10-phenanthroline (Bphen):Cs2CO3 to n-dope graphene is a very good method, but the electron injection barrier between the n-doped graphene and Bphen:Cs2CO3 is still too high to be ˜1.0 eV. In this work, in order to further reduce the electron injection barrier, a novel method is suggested. On the graphene cathode, a Sm layer with a lot of nano-hollows, and subsequently a layer of Bphen:Cs2CO3, are deposited. The Bphen:Cs2CO3 can n-dope graphene in the nano-hollows, and the Fermi level of the graphene rises. The nano Sm layer is very easily oxidized. Oxygen adsorbed on the surface of graphene may react with Sm to form an O--Sm+ dipole layer. On the areas of the Sm oxide dipole layer without nano-hollows, the electron injection barrier can be further lowered by the dipole layer. Electrons tend to mainly inject through the lower electron barrier where the dipole layer exists. Based on this idea, an effective inverted small molecular OLED with the structure of graphene/1 nm Sm layer with a lot of nano-hollows/Bphen:Cs2CO3/Alq3:C545T/NPB/MoO3/Al is presented. The maximum current efficiency and maximum power efficiency of the OLED with a 1 nm Sm layer are about two and three times of those of the reference OLED without any Sm layer, respectively.

  10. Efficient small molecular organic light emitting diode with graphene cathode covered by a Sm layer with nano-hollows and n-doped by Bphen:Cs2CO3 in the hollows.

    PubMed

    Yao, Li; Li, Lei; Qin, Laixiang; Ma, Yaoguang; Wang, Wei; Meng, Hu; Jin, Weifeng; Wang, Yilun; Xu, Wanjin; Ran, Guangzhao; You, Liping; Qin, Guogang

    2017-03-10

    Graphene is a favorable candidate for electrodes of organic light emitting diodes (OLEDs). Graphene has quite a high work function of ∼4.5 eV, and has been extensively studied when used as anodes of OLEDs. In order to use graphene as a cathode, the electron injection barrier between the graphene cathode and the electron transport layer has to be low enough. Using 4,7-diphenyl-1,10-phenanthroline (Bphen):Cs2CO3 to n-dope graphene is a very good method, but the electron injection barrier between the n-doped graphene and Bphen:Cs2CO3 is still too high to be ∼1.0 eV. In this work, in order to further reduce the electron injection barrier, a novel method is suggested. On the graphene cathode, a Sm layer with a lot of nano-hollows, and subsequently a layer of Bphen:Cs2CO3, are deposited. The Bphen:Cs2CO3 can n-dope graphene in the nano-hollows, and the Fermi level of the graphene rises. The nano Sm layer is very easily oxidized. Oxygen adsorbed on the surface of graphene may react with Sm to form an O(-)-Sm(+) dipole layer. On the areas of the Sm oxide dipole layer without nano-hollows, the electron injection barrier can be further lowered by the dipole layer. Electrons tend to mainly inject through the lower electron barrier where the dipole layer exists. Based on this idea, an effective inverted small molecular OLED with the structure of graphene/1 nm Sm layer with a lot of nano-hollows/Bphen:Cs2CO3/Alq3:C545T/NPB/MoO3/Al is presented. The maximum current efficiency and maximum power efficiency of the OLED with a 1 nm Sm layer are about two and three times of those of the reference OLED without any Sm layer, respectively.

  11. Effect of molecular electrical doping on polyfuran based photovoltaic cells

    SciTech Connect

    Yu, Shuwen; Opitz, Andreas; Salzmann, Ingo; Frisch, Johannes; Cohen, Erez; Bendikov, Michael; Koch, Norbert

    2015-05-18

    The electronic, optical, and morphological properties of molecularly p-doped polyfuran (PF) films were investigated over a wide range of doping ratio in order to explore the impact of doping in photovoltaic applications. We find evidence for integer-charge transfer between PF and the prototypical molecular p-dopant tetrafluoro-tetracyanoquinodimethane (F4TCNQ) and employed the doped polymer in bilayer organic solar cells using fullerene as acceptor. The conductivity increase in the PF films at dopant loadings ≤2% significantly enhances the short-circuit current of photovoltaic devices. For higher doping ratios, however, F4TCNQ is found to precipitate at the heterojunction between the doped donor polymer and the fullerene acceptor. Ultraviolet photoelectron spectroscopy reveals that its presence acts beneficial to the energy-level alignment by doubling the open-circuit voltage of solar cells from 0.2 V to ca. 0.4 V, as compared to pristine PF.

  12. Unraveling the mechanism of molecular doping in organic semiconductors.

    PubMed

    Mityashin, Alexander; Olivier, Yoann; Van Regemorter, Tanguy; Rolin, Cedric; Verlaak, Stijn; Martinelli, Nicolas G; Beljonne, David; Cornil, Jérôme; Genoe, Jan; Heremans, Paul

    2012-03-22

    The mechanism by which molecular dopants donate free charge carriers to the host organic semiconductor is investigated and is found to be quite different from the one in inorganic semiconductors. In organics, a strong correlation between the doping concentration and its charge donation efficiency is demonstrated. Moreover, there is a threshold doping level below which doping simply has no electrical effect. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. [Gene doping: gene transfer and possible molecular detection].

    PubMed

    Argüelles, Carlos Francisco; Hernández-Zamora, Edgar

    2007-01-01

    The use of illegal substances in sports to enhance athletic performance during competition has caused international sports organizations such as the COI and WADA to take anti doping measures. A new doping method know as gene doping is defined as "the non-therapeutic use of genes, genetic elements and/or cells that have the capacity to enhance athletic performance". However, gene doping in sports is not easily identified and can cause serious consequences. Molecular biology techniques are needed in order to distinguish the difference between a "normal" and an "altered" genome. Further, we need to develop new analytic methods and biological molecular techniques in anti-doping laboratories, and design programs that avoid the non therapeutic use of genes.

  14. Origin and structure of polar domains in doped molecular crystals

    PubMed Central

    Meirzadeh, E.; Azuri, I.; Qi, Y.; Ehre, D.; Rappe, A. M.; Lahav, M.; Kronik, L.; Lubomirsky, I.

    2016-01-01

    Doping is a primary tool for the modification of the properties of materials. Occlusion of guest molecules in crystals generally reduces their symmetry by the creation of polar domains, which engender polarization and pyroelectricity in the doped crystals. Here we describe a molecular-level determination of the structure of such polar domains, as created by low dopant concentrations (<0.5%). The approach comprises crystal engineering and pyroelectric measurements, together with dispersion-corrected density functional theory and classical molecular dynamics calculations of the doped crystals, using neutron diffraction data of the host at different temperatures. This approach is illustrated using centrosymmetric α-glycine crystals doped with minute amounts of different L-amino acids. The experimentally determined pyroelectric coefficients are explained by the structure and polarization calculations, thus providing strong support for the local and global understanding of how different dopants influence the properties of molecular crystals. PMID:27824050

  15. Reactions of small molecular systems

    SciTech Connect

    Wittig, C.

    1993-12-01

    This DOE program remains focused on small molecular systems relevant to combustion. Though a number of experimental approaches and machines are available for this research, the authors` activities are centered around the high-n Rydberg time-of-flight (HRTOF) apparatus in this laboratory. One student and one postdoc carry out experiments with this machine and also engage in small intra-group collaborations involving shared equipment. This past year was more productive than the previous two, due to the uninterrupted operation of the HRTOF apparatus. Results were obtained with CH{sub 3}OH, CH{sub 3}SH, Rg-HX complexes, HCOOH, and their deuterated analogs where appropriate. One paper is in print, three have been accepted for publication, and one is under review. Many preliminary results that augur well for the future were obtained with other systems such as HNO{sub 3}, HBr-HI complexes, toluene, etc. Highlights from the past year are presented below that display some of the features of this program.

  16. Molecular behavior in small spaces.

    PubMed

    Rebek, Julius

    2009-10-20

    The study of physical organic chemistry in solution is a mature science, over a century old, but over the last 10 years or so, reversible encapsulation has changed the way researchers view molecular interactions. It is now clear that the behavior of molecules in dilute solution is really quite different from their behavior in capsules. Molecules isolated from bulk media in spaces barely large enough to accommodate them and a few neighbors show new phenomena: their activities resemble those of molecules inside biochemical structures--pockets of enzymes, interiors of chaperones, or the inner space of the ribosome--rather than conventional behavior in solution. In this Account, we recount the behavior of molecules in these small spaces with emphasis on structures and reactivities that have not been, and perhaps cannot be, seen in conventional solution chemistry. The capsules self-assemble through a variety of forces, including hydrogen bonds, metal-ligand interactions, and hydrophobic effects. Their lifetimes range from milliseconds to hours, long enough for NMR spectroscopy to reveal what is going on inside. We describe one particular capsule, the elongated shape of which gives rise to many of the effects and unique phenomena. Molecular guests that are congruent to the space of the host can be tightly packed inside and show reduced mobilities such as rotation and translation within the capsule. These mobilities depend strongly on what else is encapsulated with them. We also relate how asymmetric spaces can be created inside the capsule by using a chiral guest. In contrast to the situation in dilute solution, where rapid exchange of solute partners and free molecular motion average out the steric and magnetic effects of chirality, the long lifetimes of the encounters in the capsules magnify the effects of an asymmetric environment. The capsule remains achiral, but the remaining space is chiral, and coencapsulated molecules respond in an amplified way. We probe the

  17. Small-polaron theory of doped antiferromagnets

    NASA Astrophysics Data System (ADS)

    Auerbach, Assa; Larson, Brond E.

    1991-04-01

    The spin-hole coherent-state path integral is used to generate a systematic large-spin expansion of the t-J model on the square lattice. The single hole's classical energy is minimized by small polarons with short-ranged interactions. Intersublattice hopping of polarons is forbidden by a tunneling selection rule. We derive the low-energy Lagrangian which reduces to the model of Wiegmann, Wen, Shankar, and Lee of Néel-gauge-field induced superconductivity.

  18. Stable doping of carbon nanotubes via molecular self assembly

    SciTech Connect

    Lee, B.; Chen, Y.; Podzorov, V.; Cook, A.; Zakhidov, A.

    2014-10-14

    We report a novel method for stable doping of carbon nanotubes (CNT) based on methods of molecular self assembly. A conformal growth of a self-assembled monolayer of fluoroalkyl trichloro-silane (FTS) at CNT surfaces results in a strong increase of the sheet conductivity of CNT electrodes by 60–300%, depending on the CNT chirality and composition. The charge carrier mobility of undoped partially aligned CNT films was independently estimated in a field-effect transistor geometry (~100 cm²V⁻¹s⁻¹). The hole density induced by the FTS monolayer in CNT sheets is estimated to be ~1.8 ×10¹⁴cm⁻². We also show that FTS doping of CNT anodes greatly improves the performance of organic solar cells. This large and stable doping effect, easily achieved in large-area samples, makes this approach very attractive for applications of CNTs in transparent and flexible electronics.

  19. Contact potential difference measurements of doped organic molecular thin films

    NASA Astrophysics Data System (ADS)

    Chan, Calvin; Gao, Weiying; Kahn, Antoine

    2004-07-01

    The possibility of nonequilibrium conditions in doped organic molecular thin films is investigated using a combination of ultraviolet photoemission spectroscopy (UPS) and contact potential difference measurements. Surface or interface photovoltage is of particular concern in materials with large band gap and appreciable band (or energy level) bending at interfaces. We investigate here zinc phthalocyanine (ZnPc) and N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'biphenyl-4,4'' diamine (α-NPD) p-doped with the acceptor molecule, tetrafluorotetracyanoquinodimethane (F4-TCNQ). In both cases, we observe an upward movement of the vacuum level away from the metal interface with respect to the Fermi level, consistent with the formation of a depletion region. We show that photovoltage is not a significant factor in these doped films, under ultraviolet illumination during UPS. We suggest that the carrier recombination rate in organic films is sufficiently fast to exclude any photovoltage effects at room temperature. .

  20. Charge transport in photochemically modified molecularly doped polymers

    NASA Astrophysics Data System (ADS)

    Stasiak, James W.; Storch, Teresa J.; Mao, Erji

    1995-08-01

    Hole mobilities in p-diethylaminobenzaldehyde diphenylhydrazone (DEH) doped polycarbonate films are determined using the time-of-flight transient photocurrent technique. Measurements of hole transport parameters are determined over a range of electric fields before and after the samples are deliberately irradiated with UV light. UV irradiation of the hole transport molecule DEH results in the creation of a photoproduct, 1-phenyl-3-(4- diethylamino-1-phenyl)-1, 3-indazole with moderately high efficiency. Once formed, this photoproduct has been shown to act as a barrier to hole conduction. We exploit this photochemical reaction to examine the hole transport properties in a molecularly doped polymer system containing DEH doped polycarbonate. We propose that the increase in concentration of the photoproduct modifies the intrinsic order of the system and provides a unique probe to distinguish between the disorder formalism of Baessler and coworkers and models which propose polaron formation.

  1. Small business development for molecular diagnostics.

    PubMed

    Anagostou, Anthanasia; Liotta, Lance A

    2012-01-01

    Molecular profiling, which is the application of molecular diagnostics technology to tissue and blood -specimens, is an integral element in the new era of molecular medicine and individualized therapy. Molecular diagnostics is a fertile ground for small business development because it can generate products that meet immediate demands in the health-care sector: (a) Detection of disease risk, or early-stage disease, with a higher specificity and sensitivity compared to previous testing methods, and (b) "Companion diagnostics" for stratifying patients to receive a treatment choice optimized to their individual disease. This chapter reviews the promise and challenges of business development in this field. Guidelines are provided for the creation of a business model and the generation of a marketing plan around a candidate molecular diagnostic product. Steps to commercialization are outlined using existing molecular diagnostics companies as learning examples.

  2. In vivo Noninvasive Small Animal Molecular Imaging

    PubMed Central

    Youn, Hyewon; Hong, Kee-Jong

    2012-01-01

    The remarkable efforts that are made on molecular imaging technologies demonstrate its potential importance and range of applications. The generation of disease-specific animal models, and the developments of target-specific probes and genetically encoded reporters are another important component. Continued improvements in the instrumentation, the identification of novel targets and genes, and the availability of improved imaging probes should be made. Multimodal imaging probes should provide easier transitions between laboratory studies, including small animal studies and clinical applications. Here, we reviewed basic strategies of noninvasive in vivo imaging methods in small animals to introducing the concept of molecular imaging. PMID:24159487

  3. Abnormal behavior of silica doped with small amounts of aluminum

    PubMed Central

    Liu, Jinling; Wang, Yiguang; An, Linan

    2016-01-01

    Silica is the most abundant mineral in the crust of the Earth. It has been demonstrated that the aluminum concentration in silica plays a key role in determining many properties of silica-based components. Although the alumina-silica system has been intensely studied, the effect of very small amounts of aluminum on the structure and properties of silica remains unclear. We report results of first principles calculations showing that small amounts of aluminum could be metastable when located in the center of Si-O rings without breaking the silica network. In contrast, higher aluminum contents will result in the destruction of the Si-O bonds, leading to the formation of triclusters and a 4-, 5-, and 6-fold Al-O coordination, as observed in previous studies. Based on the silica structure obtained through geometric optimization, the properties of silica doped with small amounts of aluminum were calculated. The results can account for many ‘abnormal’ phenomena experimentally observed. The results benefit most areas such as geosciences, microelectronics, glass industry, and ceramic materials. PMID:27752133

  4. Abnormal behavior of silica doped with small amounts of aluminum

    NASA Astrophysics Data System (ADS)

    Liu, Jinling; Wang, Yiguang; An, Linan

    2016-10-01

    Silica is the most abundant mineral in the crust of the Earth. It has been demonstrated that the aluminum concentration in silica plays a key role in determining many properties of silica-based components. Although the alumina-silica system has been intensely studied, the effect of very small amounts of aluminum on the structure and properties of silica remains unclear. We report results of first principles calculations showing that small amounts of aluminum could be metastable when located in the center of Si-O rings without breaking the silica network. In contrast, higher aluminum contents will result in the destruction of the Si-O bonds, leading to the formation of triclusters and a 4-, 5-, and 6-fold Al-O coordination, as observed in previous studies. Based on the silica structure obtained through geometric optimization, the properties of silica doped with small amounts of aluminum were calculated. The results can account for many ‘abnormal’ phenomena experimentally observed. The results benefit most areas such as geosciences, microelectronics, glass industry, and ceramic materials.

  5. Indium antimonide doped with manganese grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Partin, D. L.; Heremans, J.; Thrush, C. M.

    1997-05-01

    Indium antimonide is of interest for infrared detecting and emitting devices and for magnetic field sensors. In this study, indium antimonide doped with manganese and grown by molecular beam epitaxy was investigated. Secondary ion mass spectroscopy (SIMS) was used to show that the incorporation of managenese is near unity over a wide range of manganese concentrations. Manganese is observed to be an acceptor with a dopant efficiency which follows a power law in which the hole density is proportional to the manganese concentration raised to the power α. The power α depends on the growth temperature; at 300°C, α = 0.86 and at 360°C, α = 0.78. Lightly manganese doped samples have transport dominated by electrons at low temperatures due to hole freeze out, followed by holes at intermediate temperatures and finally by intrinsic electrons at high temperatures. Additional SIMS studies showed that manganese diffuses relatively slowly in indium antimonide.

  6. Controlled in situ boron doping of short silicon nanowires grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Das Kanungo, Pratyush; Zakharov, Nikolai; Bauer, Jan; Breitenstein, Otwin; Werner, Peter; Goesele, Ulrich

    2008-06-01

    Epitaxial silicon nanowires (NWs) of short heights (˜280nm) on Si ⟨111⟩ substrate were grown and doped in situ with boron on a concentration range of 1015-1019cm-3 by coevaporation of atomic Si and B by molecular beam epitaxy. Transmission electron microscopy revealed a single-crystalline structure of the NWs. Electrical measurements of the individual NWs confirmed the doping. However, the low doped (1015cm-3) and medium doped (3×1016 and 1×1017cm-3) NWs were heavily depleted by the surface states while the high doped (1018 and 1019cm-3) ones showed volume conductivities expected for the corresponding intended doping levels.

  7. Spectroscopic Evidence of Formation of Small Polarons in Doped Manganites

    NASA Astrophysics Data System (ADS)

    Moritomo, Yutaka; Machida, Akihiko; Nakamura, Arao

    1998-03-01

    Temperature dependence of absorption spectra for thin films of doped manganites R_0.6Sr_0.4MnO_3, where R is rare-earth atom, has been investigated systematically changing averaged ionic radius < rA > of perovskite A-site. We have observed a specific absorption band at ~1.5eV due to optical excitations from small polarons (SP)(Machida et al.), submitted.. Spectral weight of the SP band increases with decreasing temperature and eventually disappears at the insulator-metal (IM) transition, indicating that SP in the paramagnetic state (T >= T_C) changes into bare electrons (or large polarons) in the ferromagnetic state due to the enhanced one-electron bandwidth W. We further derived important physical quantities, i.e., W, on-site exchange interaction J and binding energy Ep of SP, and discuss material dependence of stability of SP. This work was supported by a Grant-In-Aid for Scientific Research from the Ministry of Education, Science, Sport and Culture and from PRESTO, Japan Scienece and Technology Corporation (JST), Japan.

  8. Molecular effects of supraphysiological doses of doping agents on health.

    PubMed

    Imperlini, Esther; Mancini, Annamaria; Alfieri, Andreina; Martone, Domenico; Caterino, Marianna; Orrù, Stefania; Buono, Pasqualina

    2015-06-01

    Performance-enhancing drugs (PEDs) gained wide popularity not only among sportsmen but also among specific subsets of population, such as adolescents. Apart from their claimed effects on athletic performance, they are very appealing due to the body shaping effect exerted on fat mass and fat-free mass. Besides the "underestimated" massive misuse of PEDs, the short- as well as long-term consequences of such habits remain largely unrecognized. They have been strictly associated with serious adverse effects, but molecular mechanisms are yet to be elucidated. Here, we analyze the current understanding of the molecular effects of supraphysiological doses of doping agents in healthy biological systems, at genomic and proteomic levels, in order to define the molecular sensors of organ/tissue impairment, determined by their misuse. The focus is put on the anabolic androgenic steroids (AASs), specifically testosterone (T) and its most potent derivative dihydrotestosterone (DHT), and on the peptide hormones, specifically the growth hormone (GH) and the insulin-like growth factor-1 (IGF-1). A map of molecular targets is defined and the risk incidence for human health is taken into account.

  9. Lutetium-doped EuO films grown by molecular-beam epitaxy

    SciTech Connect

    Melville, A.; Heeg, T.; Mairoser, T.; Schmehl, A.; Shai, D. E.; Monkman, E. J.; Harter, J. W.; Hollaender, B.; Schubert, J.; Shen, K. M.; Mannhart, J.; Schlom, D. G.

    2012-05-28

    The effect of lutetium doping on the structural, electronic, and magnetic properties of epitaxial EuO thin films grown by reactive molecular-beam epitaxy is experimentally investigated. The behavior of Lu-doped EuO is contrasted with doping by lanthanum and gadolinium. All three dopants are found to behave similarly despite differences in electronic configuration and ionic size. Andreev reflection measurements on Lu-doped EuO reveal a spin-polarization of 96% in the conduction band, despite non-magnetic carriers introduced by 5% lutetium doping.

  10. Perspective. Extremely fine tuning of doping enabled by combinatorial molecular-beam epitaxy

    DOE PAGES

    Wu, J.; Bozovic, I.

    2015-04-06

    Chemical doping provides an effective method to control the electric properties of complex oxides. However, the state-of-art accuracy in controlling doping is limited to about 1%. This hampers elucidation of the precise doping dependences of physical properties and phenomena of interest, such as quantum phase transitions. Using the combinatorial molecular beam epitaxy, we improve the accuracy in tuning the doping level by two orders of magnitude. We illustrate this novel method by two examples: a systematic investigation of the doping dependence of interface superconductivity, and a study of the competing ground states in the vicinity of the insulator-to-superconductor transition.

  11. Perspective: Extremely fine tuning of doping enabled by combinatorial molecular-beam epitaxy

    SciTech Connect

    Wu, J.; Božović, I.

    2015-06-01

    Chemical doping provides an effective method to control the electric properties of complex oxides. However, the state-of-art accuracy in controlling doping is limited to about 1%. This hampers elucidation of the precise doping dependences of physical properties and phenomena of interest, such as quantum phase transitions. Using the combinatorial molecular beam epitaxy, we improve the accuracy in tuning the doping level by two orders of magnitude. We illustrate this novel method by two examples: a systematic investigation of the doping dependence of interface superconductivity, and a study of the competing ground states in the vicinity of the insulator-to-superconductor transition.

  12. Molecular Interactions and Ordering in Electrically Doped Polymers: Blends of PBTTT and F4TCNQ

    SciTech Connect

    Cochran, Justin E; Junk, Matthias J. N.; Glaudell, Anne M.; Miller, P. L.; Cowart, John S.; Toney, Michael F.; Hawker, Craig J.; Chmelka, Bradley F.; Chabinyc, Michael L.

    2014-09-12

    Identifying how small molecular acceptors pack with polymer donors in thin and thick (bulk) films is critical to understanding the nature of electrical doping by charge transfer. In this study, the packing structure of the molecular acceptor tetrafluorotetracyanoquinodimethane (F4TCNQ) with the semiconducting polymer poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno-[3,2-b]thiophene) (PBTTT-C14) is examined. A combination of solid-state NMR, synchrotron X-ray scattering, and optical spectroscopy was used to determine the packing motif for blends of PBTTT-C14 and F4TCNQ in thin and bulk films. These results indicate that F4TCNQ and PBTTT-C14 order in a cofacial arrangement where charge transfer is near 100% efficient in the solid state. These results provide crucial insights into the structures and compositions of ordered domains in doped semiconducting polymers and suggest a model for the microstructure where the location of the molecular acceptors are correlated rather than randomly dispersed.

  13. Precise doping of metals by small gas flows

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.

    1968-01-01

    Simple method was developed for doping refractory metals with oxygen. The metal specimens are heated in a dynamic high-vacuum system. The system can be used for other oxygen absorption processes /such as low-pressure oxidation measurements/ and for gases other than oxygen.

  14. Analytical and numerical studies of photo-injected charge transport in molecularly-doped polymers

    NASA Astrophysics Data System (ADS)

    Roy Chowdhury, Amrita

    The mobility of photo-injected charge carriers in molecularly-doped polymers (MDPs) exhibits a commonly observed, and nearly universal Poole-Frenkel field dependence, mu exp√(beta0E), that has been shown to arise from the correlated Gaussian energy distribution of transport sites encountered by charges undergoing hopping transport through the material. Analytical and numerical studies of photo-injected charge transport in these materials are presented here with an attempt to understand how specific features of the various models developed to describe these systems depend on the microscopic parameters that define them. Specifically, previously published time-of-flight mobility data for the molecularly doped polymer 30% DEH:PC (polycarbonate doped with 30 wt.% aromatic hydrazone DEH) is compared with direct analytical and numerical predictions of five disorder-based models, the Gaussian disorder model (GDM) of Bassler, and four correlated disorder models introduced by Novikov, et al., and by Parris, et al. In these numerical studies, disorder parameters describing each model were varied from reasonable starting conditions, in order to give the best overall fit. The uncorrelated GDM describes the Poole-Frenkel field dependence of the mobility only at very high fields, but fails for fields lower than about 64 V/mum. The correlated disorder models with small amounts of geometrical disorder do a good over-all job of reproducing a robust Poole-Frenkel field dependence, with correlated disorder theories that employ polaron transition rates showing qualitatively better agreement with experiment than those that employ Miller-Abrahams rates. In a separate study, the heuristic treatment of spatial or geometric disorder incorporated in existing theories is critiqued, and a randomly-diluted lattice gas model is developed to describe the spatial disorder of the transport sites in a more realistic way.

  15. Quantitative Fermi level tuning in amorphous organic semiconductor by molecular doping: Toward full understanding of the doping mechanism

    SciTech Connect

    Yang, Jin-Peng E-mail: uenon@faculty.chiba-u.jp; Wang, Wen-Qing; Cheng, Li-Wen; Zeng, Xiang-Hua; Bussolotti, Fabio; Li, Yan-Qing; Tang, Jian-Xin; Kera, Satoshi; Ueno, Nobuo E-mail: uenon@faculty.chiba-u.jp

    2016-08-29

    The doping mechanism in organic-semiconductor films has been quantitatively studied via ultrahigh-sensitivity ultraviolet photoelectron spectroscopy of N,N-bis(1-naphthyl)-N,N-diphenyl-1,1-biphenyl-4,4-diamine (α-NPD) films doped with hexaazatriphenylene-hexacarbonitrile [HAT(CN){sub 6}]. We observed that HOMO of α-NPD shifts to the Fermi level (E{sub F}) in two different rates with the doping concentration of HAT(CN){sub 6}, but HOMO distributions of both pristine and doped amorphous α-NPD films are excellently approximated with a same Gaussian distribution without exponential tail states over ∼5 × 10{sup 18} cm{sup −3} eV{sup −1}. From the theoretical simulation of the HAT(CN){sub 6}-concentration dependence of the HOMO in doped films, we show that the passivation of Gaussian-distributed hole traps, which peak at 1.1 eV above the HOMO onset, occurs at ultralow doping [HAT(CN){sub 6} molecular ratio (MR) < 0.01], leading to a strong HOMO shift of ∼0.40 eV towards E{sub F}, and MR dependence of HOMO changes abruptly at MR ∼ 0.01 to a weaker dependence for MR > 0.01 due to future of the dopant acceptor level.

  16. Quantitative Fermi level tuning in amorphous organic semiconductor by molecular doping: Toward full understanding of the doping mechanism

    NASA Astrophysics Data System (ADS)

    Yang, Jin-Peng; Wang, Wen-Qing; Bussolotti, Fabio; Cheng, Li-Wen; Li, Yan-Qing; Kera, Satoshi; Tang, Jian-Xin; Zeng, Xiang-Hua; Ueno, Nobuo

    2016-08-01

    The doping mechanism in organic-semiconductor films has been quantitatively studied via ultrahigh-sensitivity ultraviolet photoelectron spectroscopy of N,N-bis(1-naphthyl)-N,N-diphenyl-1,1-biphenyl-4,4-diamine (α-NPD) films doped with hexaazatriphenylene-hexacarbonitrile [HAT(CN)6]. We observed that HOMO of α-NPD shifts to the Fermi level (EF) in two different rates with the doping concentration of HAT(CN)6, but HOMO distributions of both pristine and doped amorphous α-NPD films are excellently approximated with a same Gaussian distribution without exponential tail states over ˜5 × 1018 cm-3 eV-1. From the theoretical simulation of the HAT(CN)6-concentration dependence of the HOMO in doped films, we show that the passivation of Gaussian-distributed hole traps, which peak at 1.1 eV above the HOMO onset, occurs at ultralow doping [HAT(CN)6 molecular ratio (MR) < 0.01], leading to a strong HOMO shift of ˜0.40 eV towards EF, and MR dependence of HOMO changes abruptly at MR ˜ 0.01 to a weaker dependence for MR > 0.01 due to future of the dopant acceptor level.

  17. Controlled in situ boron doping of short silicon nanowires grown by molecular beam epitaxy

    SciTech Connect

    Das Kanungo, Pratyush; Zakharov, Nikolai; Bauer, Jan; Breitenstein, Otwin; Werner, Peter; Goesele, Ulrich

    2008-06-30

    Epitaxial silicon nanowires (NWs) of short heights ({approx}280 nm) on Si <111> substrate were grown and doped in situ with boron on a concentration range of 10{sup 15}-10{sup 19} cm{sup -3} by coevaporation of atomic Si and B by molecular beam epitaxy. Transmission electron microscopy revealed a single-crystalline structure of the NWs. Electrical measurements of the individual NWs confirmed the doping. However, the low doped (10{sup 15} cm{sup -3}) and medium doped (3x10{sup 16} and 1x10{sup 17} cm{sup -3}) NWs were heavily depleted by the surface states while the high doped (10{sup 18} and 10{sup 19} cm{sup -3}) ones showed volume conductivities expected for the corresponding intended doping levels.

  18. Molecular adsorption of hydrogen peroxide on N- and Fe-doped titania nanoclusters

    NASA Astrophysics Data System (ADS)

    Mohajeri, Afshan; Dashti, Nasimeh Lari

    2017-06-01

    Titanium dioxide (titania) nanoparticles have been extensively investigated for photocatalytic applications such as the decomposition and adsorption of pollutant and undesirable compound in air and waste water. In this context, the present article reports the molecular adsorption of hydrogen peroxide on the surface of doped titania clusters. Density functional theory calculations were performed to investigate the structures and electronic properties of two nanoscale (TiO2)n clusters (n = 5,6) modified by nitrogen and iron dopants. The relative stability of all possible N-doped and Fe-doped isomers has been compared with each other and with the parent cluster. It was found that the Fe-doped clusters are in general more stable than the N-doped counterparts. Moreover, after N/Fe doping an enhanced in the magnetization of the clusters is observed. In the second part, we have investigated different modes of H2O2 adsorption on the lowest-energy isomers of doped clusters. In almost all the cases, the adsorptions on the doped clusters are found to be less exothermic than on the corresponding undoped parent cluster. Our results highlight the essential role of charge transfer into the interaction between H2O2 and doped (TiO2)n clusters, especially for Fe-doped clusters.

  19. Electroless Functionalization of Silver Films by Its Molecular Doping.

    PubMed

    Naor, Hadas; Avnir, David

    2015-12-09

    We present a methodology which by far extends the potential applications of thin conductive silver films achieved by an electroless molecular doping process of the metal with any of the endless functional molecules that the large library of organic molecules offer. The resulting metallic films within which the molecule is entrapped--molecule@Ag--carry both the classical chemical and physical properties of silver films, as well as the function of the entrapped molecule. Raman measurements of the organic molecules from within the silver films provide the first spectroscopic observations from within silver, and clearly show that entrapment, a three-dimensional process, and adsorption, a two-dimensional process, on silver films are distinctly different processes. Three organic molecules, the cationic Neutral red, the anionic Congo red, and the antibacterial agent chlorhexidine digluconate (CH), were used to demonstrate the generality of this method for various types of molecules. We studied the sensitivity of the film conductivity to the type of the molecule entrapped within the film, to its concentration, and to temperature. Dual functionality was demonstrated with CH@Ag films, which are both conductive and have prolonged and high antibacterial activity, a combination of properties that has been unknown so far.

  20. Systems Pharmacology in Small Molecular Drug Discovery

    PubMed Central

    Zhou, Wei; Wang, Yonghua; Lu, Aiping; Zhang, Ge

    2016-01-01

    Drug discovery is a risky, costly and time-consuming process depending on multidisciplinary methods to create safe and effective medicines. Although considerable progress has been made by high-throughput screening methods in drug design, the cost of developing contemporary approved drugs did not match that in the past decade. The major reason is the late-stage clinical failures in Phases II and III because of the complicated interactions between drug-specific, human body and environmental aspects affecting the safety and efficacy of a drug. There is a growing hope that systems-level consideration may provide a new perspective to overcome such current difficulties of drug discovery and development. The systems pharmacology method emerged as a holistic approach and has attracted more and more attention recently. The applications of systems pharmacology not only provide the pharmacodynamic evaluation and target identification of drug molecules, but also give a systems-level of understanding the interaction mechanism between drugs and complex disease. Therefore, the present review is an attempt to introduce how holistic systems pharmacology that integrated in silico ADME/T (i.e., absorption, distribution, metabolism, excretion and toxicity), target fishing and network pharmacology facilitates the discovery of small molecular drugs at the system level. PMID:26901192

  1. Systems Pharmacology in Small Molecular Drug Discovery.

    PubMed

    Zhou, Wei; Wang, Yonghua; Lu, Aiping; Zhang, Ge

    2016-02-18

    Drug discovery is a risky, costly and time-consuming process depending on multidisciplinary methods to create safe and effective medicines. Although considerable progress has been made by high-throughput screening methods in drug design, the cost of developing contemporary approved drugs did not match that in the past decade. The major reason is the late-stage clinical failures in Phases II and III because of the complicated interactions between drug-specific, human body and environmental aspects affecting the safety and efficacy of a drug. There is a growing hope that systems-level consideration may provide a new perspective to overcome such current difficulties of drug discovery and development. The systems pharmacology method emerged as a holistic approach and has attracted more and more attention recently. The applications of systems pharmacology not only provide the pharmacodynamic evaluation and target identification of drug molecules, but also give a systems-level of understanding the interaction mechanism between drugs and complex disease. Therefore, the present review is an attempt to introduce how holistic systems pharmacology that integrated in silico ADME/T (i.e., absorption, distribution, metabolism, excretion and toxicity), target fishing and network pharmacology facilitates the discovery of small molecular drugs at the system level.

  2. High-density Two-Dimensional Small Polaron Gas in a Delta-Doped Mott Insulator

    PubMed Central

    Ouellette, Daniel G.; Moetakef, Pouya; Cain, Tyler A.; Zhang, Jack Y.; Stemmer, Susanne; Emin, David; Allen, S. James

    2013-01-01

    Heterointerfaces in complex oxide systems open new arenas in which to test models of strongly correlated material, explore the role of dimensionality in metal-insulator-transitions (MITs) and small polaron formation. Close to the quantum critical point Mott MITs depend on band filling controlled by random disordered substitutional doping. Delta-doped Mott insulators are potentially free of random disorder and introduce a new arena in which to explore the effect of electron correlations and dimensionality. Epitaxial films of the prototypical Mott insulator GdTiO3 are delta-doped by substituting a single (GdO)+1 plane with a monolayer of charge neutral SrO to produce a two-dimensional system with high planar doping density. Unlike metallic SrTiO3 quantum wells in GdTiO3 the single SrO delta-doped layer exhibits thermally activated DC and optical conductivity that agree in a quantitative manner with predictions of small polaron transport but with an extremely high two-dimensional density of polarons, ~7 × 1014 cm−2. PMID:24257578

  3. High-density two-dimensional small polaron gas in a delta-doped Mott insulator.

    PubMed

    Ouellette, Daniel G; Moetakef, Pouya; Cain, Tyler A; Zhang, Jack Y; Stemmer, Susanne; Emin, David; Allen, S James

    2013-11-21

    Heterointerfaces in complex oxide systems open new arenas in which to test models of strongly correlated material, explore the role of dimensionality in metal-insulator-transitions (MITs) and small polaron formation. Close to the quantum critical point Mott MITs depend on band filling controlled by random disordered substitutional doping. Delta-doped Mott insulators are potentially free of random disorder and introduce a new arena in which to explore the effect of electron correlations and dimensionality. Epitaxial films of the prototypical Mott insulator GdTiO3 are delta-doped by substituting a single (GdO)(+1) plane with a monolayer of charge neutral SrO to produce a two-dimensional system with high planar doping density. Unlike metallic SrTiO3 quantum wells in GdTiO3 the single SrO delta-doped layer exhibits thermally activated DC and optical conductivity that agree in a quantitative manner with predictions of small polaron transport but with an extremely high two-dimensional density of polarons, ~7 × 10(14) cm(-2).

  4. NH3 molecular doping of silicon nanowires grown along the [112], [110], [001], and [111] orientations

    PubMed Central

    2012-01-01

    The possibility that an adsorbed molecule could provide shallow electronic states that could be thermally excited has received less attention than substitutional impurities and could potentially have a high impact in the doping of silicon nanowires (SiNWs). We show that molecular-based ex-situ doping, where NH3 is adsorbed at the sidewall of the SiNW, can be an alternative path to n-type doping. By means of first-principle electronic structure calculations, we show that NH3 is a shallow donor regardless of the growth orientation of the SiNWs. Also, we discuss quantum confinement and its relation with the depth of the NH3 doping state, showing that the widening of the bandgap makes the molecular donor level deeper, thus more difficult to activate. PMID:22709657

  5. Molecular doping and gas sensing in Si nanowires: From charge injection to reduced dielectric mismatch

    NASA Astrophysics Data System (ADS)

    Amato, Giampiero; Cultrera, Alessandro; Boarino, Luca; Lamberti, Carlo; Bordiga, Silvia; Mercuri, Francesco; Cartoixà, Xavier; Rurali, Riccardo

    2013-11-01

    We report experimental and theoretical evidence of the different mechanisms that lead to doping of Si nanowires upon molecular adsorption of two paradigmatic Lewis bases. Pyridine genuinely dopes the nanowires by injecting charge carriers. Ethanol, on the other hand, simply modifies the dielectric screening conditions, allowing the reactivation of preexisting electrically passive impurities, and thus cannot control neither the nature (n- vs p-type) nor the concentration of the carriers.

  6. Antimony segregation in Ge and formation of n-type selectively doped Ge films in molecular beam epitaxy

    SciTech Connect

    Yurasov, D. V. Antonov, A. V.; Drozdov, M. N.; Schmagin, V. B.; Novikov, A. V.; Spirin, K. E.

    2015-10-14

    Antimony segregation in Ge(001) films grown by molecular beam epitaxy was studied. A quantitative dependence of the Sb segregation ratio in Ge on growth temperature was revealed experimentally and modeled theoretically taking into account both the terrace-mediated and step-edge-mediated segregation mechanisms. A nearly 5-orders-of-magnitude increase in the Sb segregation ratio in a relatively small temperature range of 180–350 °C was obtained, which allowed to form Ge:Sb doped layers with abrupt boundaries and high crystalline quality using the temperature switching method that was proposed earlier for Si-based structures. This technique was employed for fabrication of different kinds of n-type Ge structures which can be useful for practical applications like heavily doped n{sup +}-Ge films or δ-doped layers. Estimation of the doping profiles sharpness yielded the values of 2–5 nm per decade for the concentration gradient at the leading edge and 2–3 nm for the full-width-half-maximum of the Ge:Sb δ-layers. Electrical characterization of grown Ge:Sb structures revealed nearly full electrical activation of Sb atoms and the two-dimensional nature of charge carrier transport in δ-layers.

  7. Effects of manganese doping on the structure evolution of small-sized boron clusters.

    PubMed

    Zhao, Lingquan; Qu, Xin; Wang, Yanchao; Lv, Jian; Zhang, Lijun; Hu, Ziyu; Gu, Guangrui; Ma, Yanming

    2017-07-05

    Atomic doping of clusters is known as an effective approach to stabilize or modify the structures and properties of resulting doped clusters. We herein report the effect of manganese (Mn) doping on the structure evolution of small-sized boron (B) clusters. The global minimum structures of both neutral and charged Mn doped B cluster [Formula: see text] (n  =  10-20 and Q  =  0, ±1) have been proposed through extensive first-principles swarm-intelligence based structure searches. It is found that Mn doping has significantly modified the grow behaviors of B clusters, leading to two novel structural transitions from planar to tubular and then to cage-like B structures in both neutral and charged species. Half-sandwich-type structures are most favorable for small [Formula: see text] (n  ⩽  13) clusters and gradually transform to Mn-centered double-ring tubular structures at [Formula: see text] clusters with superior thermodynamic stabilities compared with their neighbors. Most strikingly, endohedral cages become the ground-state structures for larger [Formula: see text] (n  ⩾  19) clusters, among which [Formula: see text] adopts a highly symmetric structure with superior thermodynamic stability and a large HOMO-LUMO gap of 4.53 eV. The unique stability of the endohedral [Formula: see text] cage is attributed to the geometric fit and formation of 18-electron closed-shell configuration. The results significantly advance our understanding about the structure and bonding of B-based clusters and strongly suggest transition-metal doping as a viable route to synthesize intriguing B-based nanomaterials.

  8. Study of fluorescence quenching in aluminum-doped ceria nanoparticles: potential molecular probe for dissolved oxygen.

    PubMed

    Shehata, N; Meehan, K; Leber, D

    2013-05-01

    This work investigates a novel usage of aluminum-doped ceria nanoparticles (ADC-NPs), as the molecular probe in optical fluorescence quenching for sensing the dissolved oxygen (DO). Cerium oxide (ceria) nanoparticles can be considered one of the most unique nanomaterials that are being studied today due to the diffusion and reactivity of oxygen vacancies in ceria, which contributes to its high oxygen storage capability. Aluminum can be considered a promising dopant to increase the oxygen ionic conductivity in ceria nanoparticles which can improve the sensitivity of ceria nanoparticles to DO. The fluorescence intensity of ADC-NPs, synthesized via chemical precipitation, is found to have a strong inverse relationship with the DO concentration in aqueous solutions. Stern-Volmer constant of ADC-NPs at room temperature is determined to be 454.6 M(-1), which indicates that ADC-NPs have a promising sensitivity to dissolved oxygen, compared to many presently used fluorophores. In addition, Stern-Volmer constant is found to have a relatively small dependence on temperature between 25 °C to 50 °C, which shows excellent thermal stability of ADC-NPs sensitivity. Our work suggests that ADC-NPs, at 6 nm, are the smallest diameter DO molecular probes between the currently used optical DO sensors composed of different nanostructures. This investigation can improve the performance of fluorescence-quenching DO sensors for industrial and environmental applications.

  9. Adsorption of molecular oxygen on VIIIB transition metal-doped graphene: A DFT study

    NASA Astrophysics Data System (ADS)

    Nasehnia, F.; Seifi, M.

    2014-12-01

    Adsorption of molecular oxygen with a triplet ground state on Fe-, Co-, Ni-, Ru-, Rh-, Pd-, OS-, Ir- and Pt-doped graphene is studied using density functional theory (DFT) calculations. The calculations show that O2 molecule is chemisorbed on the doped graphene sheets with large adsorption energies ranging from -0.653 eV to -1.851 eV and the adsorption process is irreversible. Mulliken atomic charge analysis of the structure shows that charge transfer from doped graphene sheets to O2 molecule. The amounts of transferred charge are between 0.375e- to 0.650e-, indicating a considerable change in the structures conductance. These results imply that the effect of O2 adsorption on transition metal-doped graphene structures can alter the possibility of using these materials as a toxic-gas (carbon monoxide, hydrogen fluoride, etc.) sensor.

  10. Well-ordered monolayers of alkali-doped coronene and picene: Molecular arrangements and electronic structures

    SciTech Connect

    Yano, M.; Endo, M.; Hasegawa, Y.; Okada, R.; Yamada, Y. Sasaki, M.

    2014-07-21

    Adsorptions of alkali metals (such as K and Li) on monolayers of coronene and picene realize the formation of ordered phases, which serve as well-defined model systems for metal-intercalated aromatic superconductors. Upon alkali-doping of the monolayers of coronene and picene, scanning tunneling microscopy and X-ray absorption spectroscopy revealed the rearrangement of the entire molecular layer. The K-induced reconstruction of both monolayers resulted in the formation of a structure with a herringbone-like arrangement of molecules, suggesting the intercalation of alkali metals between molecular planes. Upon reconstruction, a shift in both the vacuum level and core levels of coronene was observed as a result of a charge transfer from alkali metals to coronene. In addition, a new density of states near the Fermi level was formed in both the doped coronene and the doped picene monolayers. This characteristic electronic feature of the ordered monolayer has been also reported in the multilayer picene films, ensuring that the present monolayer can model the properties of the metal-intercalated aromatic hydrocarbons. It is suggested that the electronic structure near the Fermi level is sensitive to the molecular arrangement, and that both the strict control and determinations of the molecular structure in the doped phase should be important for the determination of the electronic structure of these materials.

  11. Well-ordered monolayers of alkali-doped coronene and picene: molecular arrangements and electronic structures.

    PubMed

    Yano, M; Endo, M; Hasegawa, Y; Okada, R; Yamada, Y; Sasaki, M

    2014-07-21

    Adsorptions of alkali metals (such as K and Li) on monolayers of coronene and picene realize the formation of ordered phases, which serve as well-defined model systems for metal-intercalated aromatic superconductors. Upon alkali-doping of the monolayers of coronene and picene, scanning tunneling microscopy and X-ray absorption spectroscopy revealed the rearrangement of the entire molecular layer. The K-induced reconstruction of both monolayers resulted in the formation of a structure with a herringbone-like arrangement of molecules, suggesting the intercalation of alkali metals between molecular planes. Upon reconstruction, a shift in both the vacuum level and core levels of coronene was observed as a result of a charge transfer from alkali metals to coronene. In addition, a new density of states near the Fermi level was formed in both the doped coronene and the doped picene monolayers. This characteristic electronic feature of the ordered monolayer has been also reported in the multilayer picene films, ensuring that the present monolayer can model the properties of the metal-intercalated aromatic hydrocarbons. It is suggested that the electronic structure near the Fermi level is sensitive to the molecular arrangement, and that both the strict control and determinations of the molecular structure in the doped phase should be important for the determination of the electronic structure of these materials.

  12. Small organic molecular imprinted materials: their preparation and application.

    PubMed

    Jiang, Xiaoman; Jiang, Na; Zhang, Haixia; Liu, Mancang

    2007-09-01

    Molecular imprinting is a technique for preparing polymeric materials that are capable of recognizing and binding the desired molecular target with a high affinity and selectivity. The materials can be applied to a wide range of target molecules, even those for which no natural binder exists or whose antibodies are difficult to raise. The imprinting of small organic molecules (e.g., pharmaceuticals, pesticides, amino acids, steroids, and sugars) is now almost routine. In this review, we pay special attention to the synthesis and application of molecular imprinted polymer (MIPs) imprinted with small organic molecules, including herbicides, pesticides, and drugs. The advantages, applications, and recent developments in small organic molecular imprinted technology are highlighted.

  13. Usage of antimony segregation for selective doping of Si in molecular beam epitaxy

    SciTech Connect

    Yurasov, D. V.; Drozdov, M. N.; Murel, A. V.; Shaleev, M. V.; Novikov, A. V.; Zakharov, N. D.

    2011-06-01

    An original approach to selective doping of Si by antimony (Sb) in molecular beam epitaxy (MBE) is proposed and verified experimentally. This approach is based on controllable utilization of the effect of Sb segregation. In particular, the sharp dependence of Sb segregation on growth temperature in the range of 300-550 deg. C is exploited. The growth temperature variations between the kinetically limited and maximum segregation regimes are suggested to be utilized in order to obtain selectively doped structures with abrupt doping profiles. It is demonstrated that the proposed technique allows formation of selectively doped Si:Sb layers, including delta ({delta}-)doped layers in which Sb concentrations can be varied from 5 x 10{sup 15} to 10{sup 20} cm{sup -3}. The obtained doped structures are shown to have a high crystalline quality and the short-term growth interruptions, which are needed to change the substrate temperature, do not lead to any significant accumulation of background impurities in grown samples. Realization of the proposed approach requires neither too low (<300 deg. C), nor too high (>600 deg. C) growth temperatures or any special equipment for the MBE machines.

  14. Voltage-Dependent Luminescence Properties of Molecularly Doped Polymer System

    NASA Astrophysics Data System (ADS)

    Mingliang, Wang; Junxiang, Zhang; Juzheng, Liu; Chunxiang, Xu

    2001-05-01

    Single-layer light-emitting diodes (LEDs) are fabricated using a mixture of a blue-emitting polymer and green-emitting 9, 10-bis(phenylethynyl)anthracene as emitting layer. The blend device with these two components in the emitting layer exhibits voltage-induced evolution of the electroluminescence. But when polystyrene is also blended into the emitting layer, the EL spectra show emission bands from both ether-PPV and BPEA in proportion to concentrations of the two materials, and the spectra exhibit no change with applied voltage. This implies that doping inert polymer is helpful in suppressing voltage-induced evolution of electroluminescence in LED blends.

  15. Molecular pairing and fully gapped superconductivity in Yb-doped CeCoIn(5).

    PubMed

    Erten, Onur; Flint, Rebecca; Coleman, Piers

    2015-01-16

    The recent observation of fully gapped superconductivity in Yb doped CeCoIn_{5} poses a paradox, for the disappearance of nodes suggests that they are accidental, yet d-wave symmetry with protected nodes is well established by experiment. Here, we show that composite pairing provides a natural resolution: in this scenario, Yb doping drives a Lifshitz transition of the nodal Fermi surface, forming a fully gapped d-wave molecular superfluid of composite pairs. The T^{4} dependence of the penetration depth associated with the sound mode of this condensate is in accordance with observation.

  16. Molecular Pairing and Fully Gapped Superconductivity in Yb-doped CeCoIn5

    NASA Astrophysics Data System (ADS)

    Erten, Onur; Flint, Rebecca; Coleman, Piers

    2015-01-01

    The recent observation of fully gapped superconductivity in Yb doped CeCoIn5 poses a paradox, for the disappearance of nodes suggests that they are accidental, yet d -wave symmetry with protected nodes is well established by experiment. Here, we show that composite pairing provides a natural resolution: in this scenario, Yb doping drives a Lifshitz transition of the nodal Fermi surface, forming a fully gapped d -wave molecular superfluid of composite pairs. The T4 dependence of the penetration depth associated with the sound mode of this condensate is in accordance with observation.

  17. Optical properties of Si-doped and Be-doped InAlAs lattice-matched to InP grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Lumb, M. P.; Yakes, M. K.; González, M.; Tischler, J. G.; Walters, R. J.

    2013-09-01

    In this paper, we determine the optical constants and carrier mobilities of Si-doped and Be-doped InAlAs lattice matched to InP. The samples were grown using molecular beam epitaxy and characterized using Hall measurements, variable angle spectroscopic ellipsometry, and room temperature photoluminescence spectroscopy. A Moss-Burstein shift in the fundamental absorption edge was observed in both Si-doped and Be-doped materials. We fitted a multiple-oscillator, critical point model to the dielectric function of the materials extracted using the spectroscopic ellipsometry. The tabulated input parameters of this model allow for accurate calculations of the dielectric function of doped InAlAs to be made, which is useful information for simulating a variety of InP-based optoelectronic devices.

  18. Cu-doped AlN: A possible spinaligner at room-temperature grown by molecular beam epitaxy?

    SciTech Connect

    Ganz, P. R.; Schaadt, D. M.

    2011-12-23

    Cu-doped AlN was prepared by plasma assisted molecular beam epitaxy on C-plane sapphire substrates. The growth conditions were investigated for different Cu to Al flux ratios from 1.0% to 4.0%. The formation of Cu-Al alloys on the surface was observed for all doping level. In contrast to Cu-doped GaN, all samples showed diamagnetic behavior determined by SQUID measurements.

  19. Advances in simulation study on organic small molecular solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Xuan; Guo, Wenge; Li, Ming; Ma, Wentao; Meng, Sen

    2015-02-01

    Recently, more focuses have been put on organic semiconductors because of its advantages, such as its flexibility, ease of fabrication and potential low cost, etc. The reasons we pay highlight on small molecular photovoltaic material are its ease of purification, easy to adjust and determine structure, easy to assemble range units and get high carrier mobility, etc. Simulation study on organic small molecular solar cells before the experiment can help the researchers find relationship between the efficiency and structure parameters, properties of material, estimate the performance of the device, bring the optimization of guidance. Also, the applicability of the model used in simulation can be discussed by comparison with experimental data. This paper summaries principle, structure, progress of numerical simulation on organic small molecular solar cells.

  20. Ultrasonic spray coating polymer and small molecular organic film for organic light-emitting devices

    PubMed Central

    Liu, Shihao; Zhang, Xiang; Zhang, Letian; Xie, Wenfa

    2016-01-01

    Ultrasonic spray coating process (USCP) with high material -utilization, low manufacture costs and compatibility to streamline production has been attractive in researches on photoelectric devices. However, surface tension exists in the solvent is still a huge obstacle to realize smooth organic film for organic light emitting devices (OLEDs) by USCP. Here, high quality polymer anode buffer layer and small molecular emitting layer are successfully realized through USCP by introducing extra-low surface tension diluent and surface tension control method. The introduction of low surface tension methyl alcohol is beneficial to the formation of poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) films and brings obvious phase separation and improved conductivity to PEDOT:PSS film. Besides, a surface tension control method, in which new stable tension equilibrium is built at the border of wetting layer, is proposed to eliminate the effect of surface tension during the solvent evaporation stage of ultrasonic spray coating the film consists of 9,9-Spirobifluoren-2-yl-diphenyl-phosphine oxide doped with 10 wt% tris [2-(p -tolyl) pyridine] iridium (III). A smooth and homogenous small molecular emitting layer without wrinkles is successfully realized. The effectiveness of the ultrasonic spray coating polymer anode buffer layer and small molecular emitting layer are also proved by introducing them in OLEDs. PMID:27874030

  1. Ultrasonic spray coating polymer and small molecular organic film for organic light-emitting devices.

    PubMed

    Liu, Shihao; Zhang, Xiang; Zhang, Letian; Xie, Wenfa

    2016-11-22

    Ultrasonic spray coating process (USCP) with high material -utilization, low manufacture costs and compatibility to streamline production has been attractive in researches on photoelectric devices. However, surface tension exists in the solvent is still a huge obstacle to realize smooth organic film for organic light emitting devices (OLEDs) by USCP. Here, high quality polymer anode buffer layer and small molecular emitting layer are successfully realized through USCP by introducing extra-low surface tension diluent and surface tension control method. The introduction of low surface tension methyl alcohol is beneficial to the formation of poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) films and brings obvious phase separation and improved conductivity to PEDOT:PSS film. Besides, a surface tension control method, in which new stable tension equilibrium is built at the border of wetting layer, is proposed to eliminate the effect of surface tension during the solvent evaporation stage of ultrasonic spray coating the film consists of 9,9-Spirobifluoren-2-yl-diphenyl-phosphine oxide doped with 10 wt% tris [2-(p -tolyl) pyridine] iridium (III). A smooth and homogenous small molecular emitting layer without wrinkles is successfully realized. The effectiveness of the ultrasonic spray coating polymer anode buffer layer and small molecular emitting layer are also proved by introducing them in OLEDs.

  2. Ultrasonic spray coating polymer and small molecular organic film for organic light-emitting devices

    NASA Astrophysics Data System (ADS)

    Liu, Shihao; Zhang, Xiang; Zhang, Letian; Xie, Wenfa

    2016-11-01

    Ultrasonic spray coating process (USCP) with high material -utilization, low manufacture costs and compatibility to streamline production has been attractive in researches on photoelectric devices. However, surface tension exists in the solvent is still a huge obstacle to realize smooth organic film for organic light emitting devices (OLEDs) by USCP. Here, high quality polymer anode buffer layer and small molecular emitting layer are successfully realized through USCP by introducing extra-low surface tension diluent and surface tension control method. The introduction of low surface tension methyl alcohol is beneficial to the formation of poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) films and brings obvious phase separation and improved conductivity to PEDOT:PSS film. Besides, a surface tension control method, in which new stable tension equilibrium is built at the border of wetting layer, is proposed to eliminate the effect of surface tension during the solvent evaporation stage of ultrasonic spray coating the film consists of 9,9-Spirobifluoren-2-yl-diphenyl-phosphine oxide doped with 10 wt% tris [2-(p -tolyl) pyridine] iridium (III). A smooth and homogenous small molecular emitting layer without wrinkles is successfully realized. The effectiveness of the ultrasonic spray coating polymer anode buffer layer and small molecular emitting layer are also proved by introducing them in OLEDs.

  3. Effect of polymer matrices on hopping charge transport in molecularly doped polymers

    NASA Astrophysics Data System (ADS)

    Kanemitsu, Yoshihiko; Einami, Jiro

    1990-08-01

    We have studied the effect of polymer matrices on time-of-flight (TOF) photocurrent pulse shape and the drift mobility of holes in polymers doped with 2-(p-dipropylaminophenyl)-4-(p-dimethylaminophenyl)-5-(o-chlorophenyl)-1, 3-oxazole in order to understand the nature of hopping charge transport in molecularly doped polymers (MDPs). The TOF pulse shapes in oxazole-doped polymers are classed into two groups: near rectangular or dispersive shapes. The drift mobility of holes in MDPs exhibiting near-rectangular TOF shape is large compared with that exhibiting dispersive. Moreover, the drift mobility of holes depends on the dielectric constant and the glass transition temperature of polymers. These results show that the polarization and phonon mode of polymers play an important role in hopping charge transport in MDPs.

  4. Molecular Electrical Doping of Organic Semiconductors: Fundamental Mechanisms and Emerging Dopant Design Rules.

    PubMed

    Salzmann, Ingo; Heimel, Georg; Oehzelt, Martin; Winkler, Stefanie; Koch, Norbert

    2016-03-15

    Today's information society depends on our ability to controllably dope inorganic semiconductors, such as silicon, thereby tuning their electrical properties to application-specific demands. For optoelectronic devices, organic semiconductors, that is, conjugated polymers and molecules, have emerged as superior alternative owing to the ease of tuning their optical gap through chemical variability and their potential for low-cost, large-area processing on flexible substrates. There, the potential of molecular electrical doping for improving the performance of, for example, organic light-emitting devices or organic solar cells has only recently been established. The doping efficiency, however, remains conspicuously low, highlighting the fact that the underlying mechanisms of molecular doping in organic semiconductors are only little understood compared with their inorganic counterparts. Here, we review the broad range of phenomena observed upon molecularly doping organic semiconductors and identify two distinctly different scenarios: the pairwise formation of both organic semiconductor and dopant ions on one hand and the emergence of ground state charge transfer complexes between organic semiconductor and dopant through supramolecular hybridization of their respective frontier molecular orbitals on the other hand. Evidence for the occurrence of these two scenarios is subsequently discussed on the basis of the characteristic and strikingly different signatures of the individual species involved in the respective doping processes in a variety of spectroscopic techniques. The critical importance of a statistical view of doping, rather than a bimolecular picture, is then highlighted by employing numerical simulations, which reveal one of the main differences between inorganic and organic semiconductors to be their respective density of electronic states and the doping induced changes thereof. Engineering the density of states of doped organic semiconductors, the Fermi

  5. Molecular targets for small-molecule modulators of circadian clocks

    PubMed Central

    He, Baokun; Chen, Zheng

    2016-01-01

    Background Circadian clocks are endogenous timing systems that regulate various aspects of mammalian metabolism, physiology and behavior. Traditional chronotherapy refers to the administration of drugs in a defined circadian time window to achieve optimal pharmacokinetic and therapeutic efficacies. In recent years, substantial efforts have been dedicated to developing novel small-molecule modulators of circadian clocks. Methods Here, we review the recent progress in the identification of molecular targets of small-molecule clock modulators and their efficacies in clock-related disorders. Specifically, we examine the clock components and regulatory factors as possible molecular targets of small molecules, and we review several key clock-related disorders as promising venues for testing the preventive/therapeutic efficacies of these small molecules. Finally, we also discuss circadian regulation of drug metabolism. Results Small molecules can modulate the period, phase and/or amplitude of the circadian cycle. Core clock proteins, nuclear hormone receptors, and clock-related kinases and other epigenetic regulators are promising molecular targets for small molecules. Through these targets small molecules exert protective effects against clock-related disorders including the metabolic syndrome, immune disorders, sleep disorders and cancer. Small molecules can also modulate circadian drug metabolism and response to existing therapeutics. Conclusion Small-molecule clock modulators target clock components or diverse cellular pathways that functionally impinge upon the clock. Target identification of new small-molecule modulators will deepen our understanding of key regulatory nodes in the circadian network. Studies of clock modulators will facilitate their therapeutic applications, alone or in combination, for clock-related diseases. PMID:26750111

  6. Ultrasensitive molecular sensor using N-doped graphene through enhanced Raman scattering

    PubMed Central

    Feng, Simin; dos Santos, Maria Cristina; Carvalho, Bruno R.; Lv, Ruitao; Li, Qing; Fujisawa, Kazunori; Elías, Ana Laura; Lei, Yu; Perea-López, Nestor; Endo, Morinobu; Pan, Minghu; Pimenta, Marcos A.; Terrones, Mauricio

    2016-01-01

    As a novel and efficient surface analysis technique, graphene-enhanced Raman scattering (GERS) has attracted increasing research attention in recent years. In particular, chemically doped graphene exhibits improved GERS effects when compared with pristine graphene for certain dyes, and it can be used to efficiently detect trace amounts of molecules. However, the GERS mechanism remains an open question. We present a comprehensive study on the GERS effect of pristine graphene and nitrogen-doped graphene. By controlling nitrogen doping, the Fermi level (EF) of graphene shifts, and if this shift aligns with the lowest unoccupied molecular orbital (LUMO) of a molecule, charge transfer is enhanced, thus significantly amplifying the molecule’s vibrational Raman modes. We confirmed these findings using different organic fluorescent molecules: rhodamine B, crystal violet, and methylene blue. The Raman signals from these dye molecules can be detected even for concentrations as low as 10−11 M, thus providing outstanding molecular sensing capabilities. To explain our results, these nitrogen-doped graphene-molecule systems were modeled using dispersion-corrected density functional theory. Furthermore, we demonstrated that it is possible to determine the gaps between the highest occupied and the lowest unoccupied molecular orbitals (HOMO-LUMO) of different molecules when different laser excitations are used. Our simulated Raman spectra of the molecules also suggest that the measured Raman shifts come from the dyes that have an extra electron. This work demonstrates that nitrogen-doped graphene has enormous potential as a substrate when detecting low concentrations of molecules and could also allow for an effective identification of their HOMO-LUMO gaps. PMID:27532043

  7. Ultrasensitive molecular sensor using N-doped graphene through enhanced Raman scattering.

    PubMed

    Feng, Simin; Dos Santos, Maria Cristina; Carvalho, Bruno R; Lv, Ruitao; Li, Qing; Fujisawa, Kazunori; Elías, Ana Laura; Lei, Yu; Perea-López, Nestor; Endo, Morinobu; Pan, Minghu; Pimenta, Marcos A; Terrones, Mauricio

    2016-07-01

    As a novel and efficient surface analysis technique, graphene-enhanced Raman scattering (GERS) has attracted increasing research attention in recent years. In particular, chemically doped graphene exhibits improved GERS effects when compared with pristine graphene for certain dyes, and it can be used to efficiently detect trace amounts of molecules. However, the GERS mechanism remains an open question. We present a comprehensive study on the GERS effect of pristine graphene and nitrogen-doped graphene. By controlling nitrogen doping, the Fermi level (E F) of graphene shifts, and if this shift aligns with the lowest unoccupied molecular orbital (LUMO) of a molecule, charge transfer is enhanced, thus significantly amplifying the molecule's vibrational Raman modes. We confirmed these findings using different organic fluorescent molecules: rhodamine B, crystal violet, and methylene blue. The Raman signals from these dye molecules can be detected even for concentrations as low as 10(-11) M, thus providing outstanding molecular sensing capabilities. To explain our results, these nitrogen-doped graphene-molecule systems were modeled using dispersion-corrected density functional theory. Furthermore, we demonstrated that it is possible to determine the gaps between the highest occupied and the lowest unoccupied molecular orbitals (HOMO-LUMO) of different molecules when different laser excitations are used. Our simulated Raman spectra of the molecules also suggest that the measured Raman shifts come from the dyes that have an extra electron. This work demonstrates that nitrogen-doped graphene has enormous potential as a substrate when detecting low concentrations of molecules and could also allow for an effective identification of their HOMO-LUMO gaps.

  8. Doping Effect of Graphene Nanoplatelets on Electrical Insulation Properties of Polyethylene: From Macroscopic to Molecular Scale

    PubMed Central

    Jing, Ziang; Li, Changming; Zhao, Hong; Zhang, Guiling; Han, Baozhong

    2016-01-01

    The doping effect of graphene nanoplatelets (GNPs) on electrical insulation properties of polyethylene (PE) was studied by combining experimental and theoretical methods. The electric conduction properties and trap characteristics were tested for pure PE and PE/GNPs composites by using a direct measurement method and a thermal stimulated current (TSC) method. It was found that doping smaller GNPs is more beneficial to decrease the conductivity of PE/GNPs. The PE/GNPs composite with smaller size GNPs mainly introduces deep energy traps, while with increasing GNPs size, besides deep energy traps, shallow energy traps are also introduced. These results were also confirmed by density functional theory (DFT) and the non-equilibrium Green’s function (NEGF) method calculations. Therefore, doping small size GNPs is favorable for trapping charge carriers and enhancing insulation ability, which is suggested as an effective strategy in exploring powerful insulation materials. PMID:28773802

  9. Doping Effect of Graphene Nanoplatelets on Electrical Insulation Properties of Polyethylene: From Macroscopic to Molecular Scale.

    PubMed

    Jing, Ziang; Li, Changming; Zhao, Hong; Zhang, Guiling; Han, Baozhong

    2016-08-10

    The doping effect of graphene nanoplatelets (GNPs) on electrical insulation properties of polyethylene (PE) was studied by combining experimental and theoretical methods. The electric conduction properties and trap characteristics were tested for pure PE and PE/GNPs composites by using a direct measurement method and a thermal stimulated current (TSC) method. It was found that doping smaller GNPs is more beneficial to decrease the conductivity of PE/GNPs. The PE/GNPs composite with smaller size GNPs mainly introduces deep energy traps, while with increasing GNPs size, besides deep energy traps, shallow energy traps are also introduced. These results were also confirmed by density functional theory (DFT) and the non-equilibrium Green's function (NEGF) method calculations. Therefore, doping small size GNPs is favorable for trapping charge carriers and enhancing insulation ability, which is suggested as an effective strategy in exploring powerful insulation materials.

  10. About mobility thickness dependence in molecularly doped polymers

    NASA Astrophysics Data System (ADS)

    Tyutnev, A. P.; Weiss, D. S.; Saenko, V. S.; Pozhidaev, E. D.

    2017-09-01

    We have investigated the dependence of hole mobility on thickness in free-standing films of bisphenol-A-polycarbonate (PC) doped with 30 wt% p-diethylaminobenzaldehyde diphenylhydrazone (DEH). Carrier generation in a time-of-flight (TOF) experiment was achieved through direct ionization of dopant molecules by electron impact using an electron gun supplying pulses of monoenergetic electrons in the range of 2-50 keV. The position of dopant ionization depends upon the electron energy and three TOF variants have been recently developed and used in this study. We have found that the hole mobility generally decreased with increasing film thickness with concomitant acceleration of the post-flight current decay indicating that the transport process approaches the steady-state regime, this process happening slightly faster than our model predicts. Numerical calculations have been compared with experimental data. The results are discussed in detail. The way to reconcile ostensibly contradictory interpretations of our results and those commonly reported in literature relying on photo injection technique has been proposed.

  11. Molecular doping for control of gate bias stress in organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Hein, Moritz P.; Zakhidov, Alexander A.; Lüssem, Björn; Jankowski, Jens; Tietze, Max L.; Riede, Moritz K.; Leo, Karl

    2014-01-01

    The key active devices of future organic electronic circuits are organic thin film transistors (OTFTs). Reliability of OTFTs remains one of the most challenging obstacles to be overcome for broad commercial applications. In particular, bias stress was identified as the key instability under operation for numerous OTFT devices and interfaces. Despite a multitude of experimental observations, a comprehensive mechanism describing this behavior is still missing. Furthermore, controlled methods to overcome these instabilities are so far lacking. Here, we present the approach to control and significantly alleviate the bias stress effect by using molecular doping at low concentrations. For pentacene and silicon oxide as gate oxide, we are able to reduce the time constant of degradation by three orders of magnitude. The effect of molecular doping on the bias stress behavior is explained in terms of the shift of Fermi Level and, thus, exponentially reduced proton generation at the pentacene/oxide interface.

  12. Recent Advance of Biological Molecular Imaging Based on Lanthanide-Doped Upconversion-Luminescent Nanomaterials

    PubMed Central

    Min, Yuanzeng; Li, Jinming; Liu, Fang; Padmanabhan, Parasuraman; Yeow, Edwin K. L.; Xing, Bengang

    2014-01-01

    Lanthanide-doped upconversion-luminescent nanoparticles (UCNPs), which can be excited by near-infrared (NIR) laser irradiation to emit multiplex light, have been proven to be very useful for in vitro and in vivo molecular imaging studies. In comparison with the conventionally used down-conversion fluorescence imaging strategies, the NIR light excited luminescence of UCNPs displays high photostability, low cytotoxicity, little background auto-fluorescence, which allows for deep tissue penetration, making them attractive as contrast agents for biomedical imaging applications. In this review, we will mainly focus on the latest development of a new type of lanthanide-doped UCNP material and its main applications for in vitro and in vivo molecular imaging and we will also discuss the challenges and future perspectives.

  13. Poole-Frenkel mobility field dependence in molecularly doped polymers revisited

    NASA Astrophysics Data System (ADS)

    Tyutnev, A. P.; Saenko, V. S.

    2017-02-01

    We have examined the Poole-Frenkel mobility field dependence in a molecularly doped polymer (MDP) both experimentally and theoretically trying to separate two physically different contributions to this phenomenon, one constituting a real physical effect and the other arising from the fact that the charge carrier transport in MDP is not fully equilibrated. The former is ascribed to the influence of an electric field on the transport process itself affecting at least one of the model parameters. The latter should be associated with the mobility field effect under conditions when neither model parameter is field sensitive. Numerical calculations have been used to achieve their deconvolution. On the experimental front, we relied on the time of flight technique specifically modified to suit this task. Both approaches show that the contribution of the second (operational) field effect in the investigated MDP is quite appreciable. This result is compared with the traditional interpretation of the Poole-Frenkel effect in molecularly doped polymers.

  14. Couple molecular excitons to surface plasmon polaritons in an organic-dye-doped nanostructured cavity

    NASA Astrophysics Data System (ADS)

    Zhang, Kun; Shi, Wen-Bo; Wang, Di; Xu, Yue; Peng, Ru-Wen; Fan, Ren-Hao; Wang, Qian-Jin; Wang, Mu

    2016-05-01

    In this work, we demonstrate experimentally the hybrid coupling among molecular excitons, surface plasmon polaritons (SPPs), and Fabry-Perot (FP) mode in a nanostructured cavity, where a J-aggregates doped PVA (polyvinyl alcohol) layer is inserted between a silver grating and a thick silver film. By tuning the thickness of the doped PVA layer, the FP cavity mode efficiently couples with the molecular excitons, forming two nearly dispersion-free modes. The dispersive SPPs interact with these two modes while increasing the incident angle, leading to the formation of three hybrid polariton bands. By retrieving the mixing fractions of the polariton band components from the measured angular reflection spectra, we find all these three bands result from the strong coupling among SPPs, FP mode, and excitons. This work may inspire related studies on hybrid light-matter interactions, and achieve potential applications on multimode polariton lasers and optical spectroscopy.

  15. Thermodynamic and kinetic studies of laser thermal processing of heavily boron-doped amorphous silicon using molecular dynamics

    NASA Astrophysics Data System (ADS)

    Wang, Liguo; Clancy, Paulette; Thompson, Michael O.; Murthy, Cheruvu S.

    2002-09-01

    Laser thermal processing (LTP) has been proposed as a means to avoid unwanted transient enhanced diffusion and deactivation of dopants, especially boron and arsenic, during the formation of ultrashallow junctions. Although experimental studies have been carried out to determine the efficacy of LTP for pure Si and lightly B-doped junctions, the effects of high concentrations of dopants (above 2% B) on the thermodynamic and kinetic properties of the regrown film are unknown. In this study, a classical interatomic potential model [Stillinger-Weber (SW)] is used with a nonequilibrium molecular dynamics computer simulation technique to study the laser thermal processing of heavily B-doped Si in the range 2-10 at. % B. We observe only a small effect of boron concentration on the congruent melting temperature of the B:Si alloy, and thus the narrowing of the "process window" for LTP is predicted to be small. No significant tendency for boron to segregate was observed at either the regrowth front or the buried c-Si interface during fast regrowth. The B-doped region regrew as defect-free crystal with full activation of the boron atoms at low boron concentrations (2%), in good agreement with experiments. As the concentration of boron increased, the number of intrinsic Si defects and boron interstitials in the regrown materials increased, with a minor amount of boron atoms in clusters (<2%). An instability limit for crystal regrowth was observed at around 8%-10% boron atoms during fast regrowth; systems with 10% B showed partial amorphization during regrowth. Comparison with tight-binding quantum mechanical calculations showed that the SW model gives similar diffusivities in the liquid and tendency to cluster, but the lifetimes of the SW clusters are considerably too long (>150 ps, compared to 5 ps in tight binding). The importance of adequate system size is discussed.

  16. Arsenic {delta}-doped HgTe/HgCdTe superlattices grown by molecular beam epitaxy

    SciTech Connect

    Tsen, G. K. O.; Musca, C. A.; Dell, J. M.; Antoszewski, J.; Faraone, L.; Becker, C. R.

    2008-02-25

    Arsenic incorporation in HgTe/Hg{sub 0.05}Cd{sub 0.95}Te superlattices grown by molecular beam epitaxy (MBE) is reported. The incorporation was carried out by a {delta}-doping approach where arsenic was incorporated during MBE growth as acceptors. The superlattices were characterized via high resolution x-ray diffraction, Fourier transform infrared spectroscopy, secondary ion mass spectrometry, and magnetotransport Hall measurements coupled with the quantitative mobility spectrum analysis algorithm.

  17. Long-wavelength PtSi infrared detectors fabricated by incorporating a p(+) doping spike grown by molecular beam epitaxy

    NASA Technical Reports Server (NTRS)

    Lin, T. L.; Park, J. S.; George, T.; Jones, E. W.; Fathauer, R. W.; Maserjian, J.

    1993-01-01

    By incorporating a 1-nm-thick p(+) doping spike at the PtSi/Si interface, we have successfully demonstrated extended cutoff wavelengths of PtSi Schottky infrared detectors in the long wavelength infrared (LWIR) regime for the first time. The extended cutoff wavelengths resulted from the combined effects of an increased electric field near the silicide/Si interface due to the p(+) doping spike and the Schottky image force. The p(+) doping spikes were grown by molecular beam epitaxy at 450 C, using elemental boron as the dopant source, with doping concentrations ranging from 5 x 10 exp 19 to 2 x 10 exp 20/cu cm. Transmission electron microscopy indicated good crystalline quality of the doping spikes. The cutoff wavelengths were shown to increase with increasing doping concentrations of the p(+) spikes. Thermionic emission dark current characteristics were observed and photoresponses in the LWIR regime were demonstrated.

  18. Characterization of Si volume- and delta-doped InGaAs grown by molecular beam epitaxy

    SciTech Connect

    Fedoryshyn, Y.; Kaspar, P.; Jaeckel, H.; Beck, M.

    2010-05-15

    Bulk InGaAs layers were grown at 400 deg. C lattice-matched to InP semi-insulating substrates by molecular beam epitaxy. Si doping of the layers was performed by applying volume- and delta-doping techniques. The samples were characterized by capacitance-voltage, van der Pauw-Hall, secondary ion mass spectroscopy and photoluminescence measurements. Good agreement in terms of dependence of mobility and Burstein-Moss shift shift on doping concentration in samples doped by the two different techniques was obtained. Amphoteric behavior of Si was observed at doping concentrations higher than {approx}2.9x10{sup 19} cm{sup -3} in both delta- and volume-doped samples. Degradation of InGaAs crystalline quality occurred in samples with Si concentrations higher than {approx}4x10{sup 19} cm{sup -3}.

  19. Long-wavelength PtSi infrared detectors fabricated by incorporating a p(+) doping spike grown by molecular beam epitaxy

    NASA Technical Reports Server (NTRS)

    Lin, T. L.; Park, J. S.; George, T.; Jones, E. W.; Fathauer, R. W.; Maserjian, J.

    1993-01-01

    By incorporating a 1-nm-thick p(+) doping spike at the PtSi/Si interface, we have successfully demonstrated extended cutoff wavelengths of PtSi Schottky infrared detectors in the long wavelength infrared (LWIR) regime for the first time. The extended cutoff wavelengths resulted from the combined effects of an increased electric field near the silicide/Si interface due to the p(+) doping spike and the Schottky image force. The p(+) doping spikes were grown by molecular beam epitaxy at 450 C, using elemental boron as the dopant source, with doping concentrations ranging from 5 x 10 exp 19 to 2 x 10 exp 20/cu cm. Transmission electron microscopy indicated good crystalline quality of the doping spikes. The cutoff wavelengths were shown to increase with increasing doping concentrations of the p(+) spikes. Thermionic emission dark current characteristics were observed and photoresponses in the LWIR regime were demonstrated.

  20. Synthesis of doped graphene nanoribbons from molecular and polymeric precursors

    NASA Astrophysics Data System (ADS)

    Cloke, Ryan Randal

    As electronic devices continue to shrink and energy problems continue to grow, nanoscale materials are becoming increasingly important. Graphene is a material with exceptional promise to complement silicon in next-generation electronics because of its extraordinary charge carrier mobility, while also finding a role in cutting-edge energy solutions due to its high surface area and conductivity. Improving on this material even further by reducing the width of graphene to nanoscale dimensions with atomically-precise dopant patterns is the subject of this thesis. Nanometer-wide strips of graphene, known as graphene nanoribbons (GNRs), offer the advantages of semiconducting behavior, combined with more accessible surface area compared to bulk graphene (Chapter 1). Additionally, it is demonstrated that GNRs can be doped with atomic precision, allowing for intricate modulation of the electronic properties of this material, which was studied by STM, STS, and nc-AFM (Chapter 2). Controlled growth of GNRs on surfaces is still an outstanding challenge within the field, and to this end, a variety of porphyrin-GNR template materials were synthesized (Chapter 3). The GNRs obtained in this work were also synthesized in solution, and it was shown that these materials possess excellent properties for applications in hydrogen storage, carbon dioxide reduction, and Li-ion batteries (Chapter 4). A prerequisite for solution-synthesized GNRs, conjugated aromatic polymers are an important class of materials in their own right. Therefore, Ring-Opening Alkyne Metathesis Polymerization was developed using conjugated, strained diynes (Chapter 5). The resulting conjugated polymers were explored both for their own materials properties due to a remarkable self-assembly process that was discovered, and also as precursors to GNRs (Chapter 6). This work advances the fundamental understanding of carbon-based nanostructures, as well as the large-scale production of GNRs for next-generation energy

  1. Molecular adsorbates as probes of the local properties of doped graphene

    PubMed Central

    Pham, Van Dong; Joucken, Frédéric; Repain, Vincent; Chacon, Cyril; Bellec, Amandine; Girard, Yann; Rousset, Sylvie; Sporken, Robert; Santos, Maria Cristina dos; Lagoute, Jérôme

    2016-01-01

    Graphene-based sensors are among the most promising of graphene’s applications. The ability to signal the presence of molecular species adsorbed on this atomically thin substrate has been explored from electric measurements to light scattering. Here we show that the adsorbed molecules can be used to sense graphene properties. The interaction of porphyrin molecules with nitrogen-doped graphene has been investigated using scanning tunneling microscopy and ab initio calculations. Molecular manipulation was used to reveal the surface below the adsorbed molecules allowing to achieve an atomic-scale measure of the interaction of molecules with doped graphene. The adsorbate’s frontier electronic states are downshifted in energy as the molecule approaches the doping site, with largest effect when the molecule sits over the nitrogen dopant. Theoretical calculations showed that, due to graphene’s high polarizability, the adsorption of porphyrin induces a charge rearrangement on the substrate similar to the image charges on a metal. This charge polarization is enhanced around nitrogen site, leading to an increased interaction of molecules with their image charges on graphene. Consequently, the molecular states are stabilized and shift to lower energies. These findings reveal the local variation of polarizability induced by nitrogen dopant opening new routes towards the electronic tuning of graphene. PMID:27097555

  2. Molecular Doping the Topological Dirac Semimetal Na3Bi across the Charge Neutrality Point with F4-TCNQ.

    PubMed

    Edmonds, Mark T; Hellerstedt, Jack; O'Donnell, Kane M; Tadich, Anton; Fuhrer, Michael S

    2016-06-29

    We perform low-temperature transport and high-resolution photoelectron spectroscopy on 20 nm thin film topological Dirac semimetal Na3Bi grown by molecular beam epitaxy. We demonstrate efficient electron depletion ∼10(13) cm(-2) of Na3Bi via vacuum deposition of molecular F4-TCNQ without degrading the sample mobility. For samples with low as-grown n-type doping (1 × 10(12) cm(-2)), F4-TCNQ doping can achieve charge neutrality and even a net p-type doping. Photoelectron spectroscopy and density functional theory are utilized to investigate the behavior of F4-TCNQ on the Na3Bi surface.

  3. Self-doping of molecular quantum-dot cellular automata: mixed valence zwitterions.

    PubMed

    Lu, Yuhui; Lent, Craig

    2011-09-07

    Molecular quantum-dot cellular automata (QCA) is a promising paradigm for realizing molecular electronics. In molecular QCA, binary information is encoded in the distribution of intramolecular charge, and Coulomb interactions between neighboring molecules combine to create long-range correlations in charge distribution that can be exploited for signal transfer and computation. Appropriate mixed-valence species are promising candidates for single-molecule device operation. A complication arises because many mixed-valence compounds are ions and the associated counterions can potentially disrupt the correct flow of information through the circuit. We suggest a self-doping mechanism which incorporates the counterion covalently into the structure of a neutral molecular cell, thus producing a zwitterionic mixed-valence complex. The counterion is located at the geometrical center of the QCA molecule and bound to the working dots via covalent bonds, thus avoiding counterion effects that bias the system toward one binary information state or the other. We investigate the feasibility of using multiply charged anion (MCA) boron clusters, specifically closo-borate dianion, as building blocks. A first principle calculation shows that neutral, bistable, and switchable QCA molecules are possible. The self-doping mechanism is confirmed by molecular orbital analysis, which shows that MCA counterions can be stabilized by the electrostatic interaction between negatively charged counterions and positively charged working dots. This journal is © the Owner Societies 2011

  4. Theoretical design of a novel copper doped gold cluster supported on graphene utilizing ab initio molecular dynamics simulations

    SciTech Connect

    Koizumi, Kenichi; Nobusada, Katsuyuki; Boero, Mauro

    2015-12-31

    Ab initio molecular dynamics simulations have been used to inspect the adsorption of O{sub 2} to a small gold-copper alloy cluster supported on graphene. The exposed Cu atom in this cluster acts as a crucial attractive site for the approaching of O{sub 2} and consequently widens the reaction channel for the adsorption process. Conversely, a pure Au cluster on the same graphene support is inactive for the O{sub 2} adsorption because the corresponding reaction channel for the adsorption is very narrow. These results clearly indicate that doping a different metal to the Au cluster is a way to enhance the oxygen adsorption and to promote catalytic reactions.

  5. Carbon doping in molecular beam epitaxy of GaAs from a heated graphite filament

    NASA Technical Reports Server (NTRS)

    Malik, R. J.; Nottenberg, R. N.; Schubert, E. F.; Walker, J. F.; Ryan, R. W.

    1988-01-01

    Carbon doping of GaAs grown by molecular beam epitaxy has been obtained for the first time by use of a heated graphite filament. Controlled carbon acceptor concentrations over the range of 10 to the 17th-10 to the 20th/cu cm were achieved by resistively heating a graphite filament with a direct current power supply. Capacitance-voltage, p/n junction and secondary-ion mass spectrometry measurements indicate that there is negligible diffusion of carbon during growth and with postgrowth rapid thermal annealing. Carbon was used for p-type doping in the base of Npn AlGaAs/GaAs heterojunction bipolar transistors. Current gains greater than 100 and near-ideal emitter heterojunctions were obtained in transistors with a carbon base doping of 1 x 10 to the 19th/cu cm. These preliminary results indicate that carbon doping from a solid graphite source may be an attractive substitute for beryllium, which is known to have a relatively high diffusion coefficient in GaAs.

  6. Carbon doping in molecular beam epitaxy of GaAs from a heated graphite filament

    NASA Technical Reports Server (NTRS)

    Malik, R. J.; Nottenberg, R. N.; Schubert, E. F.; Walker, J. F.; Ryan, R. W.

    1988-01-01

    Carbon doping of GaAs grown by molecular beam epitaxy has been obtained for the first time by use of a heated graphite filament. Controlled carbon acceptor concentrations over the range of 10 to the 17th-10 to the 20th/cu cm were achieved by resistively heating a graphite filament with a direct current power supply. Capacitance-voltage, p/n junction and secondary-ion mass spectrometry measurements indicate that there is negligible diffusion of carbon during growth and with postgrowth rapid thermal annealing. Carbon was used for p-type doping in the base of Npn AlGaAs/GaAs heterojunction bipolar transistors. Current gains greater than 100 and near-ideal emitter heterojunctions were obtained in transistors with a carbon base doping of 1 x 10 to the 19th/cu cm. These preliminary results indicate that carbon doping from a solid graphite source may be an attractive substitute for beryllium, which is known to have a relatively high diffusion coefficient in GaAs.

  7. Molecular doping of single-walled carbon nanotube transistors: optoelectronic study

    NASA Astrophysics Data System (ADS)

    Zhang, Jiangbin; Emelianov, Aleksei V.; Bakulin, Artem A.; Bobrinetskiy, Ivan I.

    2016-09-01

    Single-walled carbon nanotubes (SWCNT) are a promising material for future optoelectronic applications, including flexible electrodes and field-effect transistors. Molecular doping of carbon nanotube surface can be an effective way to control the electronic structure and charge dynamics of these material systems. Herein, two organic semiconductors with different energy level alignment in respect to SWCNT are used to dope the channel of the SWCNT-based transistor. The effects of doping on the device performance are studied with a set of optoelectronic measurements. For the studied system, we observed an opposite change in photo-resistance, depending on the type (electron donor vs electron acceptor) of the dopants. We attribute this effect to interplay between two effects: (i) the change in the carrier concentration and (ii) the formation of trapping states at the SWCNT surface. We also observed a modest 4 pA photocurrent generation in the doped systems, which indicates that the studied system could be used as a platform for multi-pulse optoelectronic experiments with photocurrent detection.

  8. Switchable Multiple Spin States in the Kondo description of Doped Molecular Magnets

    PubMed Central

    Ray, Rajyavardhan; Kumar, Sanjeev

    2017-01-01

    We show that introducing electrons in magnetic clusters and molecular magnets lead to rich phase diagrams with a variety of low-spin and high-spin states allowing for multiple switchability. The analysis is carried out for a quantum spin-fermion model using the exact diagonalization, and the cluster mean-field approach. The model is relevant for a number of molecular magnets with triangular motifs consisting of transition metal ions such as Cr, Cu and V. Re-entrant spin-state behavior and chirality on-off transitions exist over a wide parameter regime. A subtle competition among geometrical frustration effects, electron itinerancy, and Kondo coupling at the molecular level is highlighted. Our results demonstrate that electron doping provides a viable mean to tame the magnetic properties of molecular magnets towards potential technological applications. PMID:28176869

  9. Switchable Multiple Spin States in the Kondo description of Doped Molecular Magnets.

    PubMed

    Ray, Rajyavardhan; Kumar, Sanjeev

    2017-02-08

    We show that introducing electrons in magnetic clusters and molecular magnets lead to rich phase diagrams with a variety of low-spin and high-spin states allowing for multiple switchability. The analysis is carried out for a quantum spin-fermion model using the exact diagonalization, and the cluster mean-field approach. The model is relevant for a number of molecular magnets with triangular motifs consisting of transition metal ions such as Cr, Cu and V. Re-entrant spin-state behavior and chirality on-off transitions exist over a wide parameter regime. A subtle competition among geometrical frustration effects, electron itinerancy, and Kondo coupling at the molecular level is highlighted. Our results demonstrate that electron doping provides a viable mean to tame the magnetic properties of molecular magnets towards potential technological applications.

  10. Switchable Multiple Spin States in the Kondo description of Doped Molecular Magnets

    NASA Astrophysics Data System (ADS)

    Ray, Rajyavardhan; Kumar, Sanjeev

    2017-02-01

    We show that introducing electrons in magnetic clusters and molecular magnets lead to rich phase diagrams with a variety of low-spin and high-spin states allowing for multiple switchability. The analysis is carried out for a quantum spin-fermion model using the exact diagonalization, and the cluster mean-field approach. The model is relevant for a number of molecular magnets with triangular motifs consisting of transition metal ions such as Cr, Cu and V. Re-entrant spin-state behavior and chirality on-off transitions exist over a wide parameter regime. A subtle competition among geometrical frustration effects, electron itinerancy, and Kondo coupling at the molecular level is highlighted. Our results demonstrate that electron doping provides a viable mean to tame the magnetic properties of molecular magnets towards potential technological applications.

  11. Molecular and cellular biology of small-bowel mucosa.

    PubMed

    Kitchen, Paul A.; Walters, Julian R.F.

    2001-03-01

    Study of the molecular and cellular biology of the small-intestinal mucosa is providing insights into the remarkable properties of this unique tissue. With its structured pattern of cell proliferation, differentiation, and apoptosis, and its ability to adapt following exposure to luminal nutrients or injury from surgery or pathogens, it functions in a regulated but responsive manner. We review recent publications on factors affecting development, gene expression, cell turnover, and adaptation.

  12. A full-configuration-interaction nuclear orbital approach and application for small doped He clusters

    SciTech Connect

    Lara-Castells, M. P. de Aguirre, N. F. Delgado-Barrio, G. Villarreal, P.; Mitrushchenkov, A. O.

    2015-01-22

    An efficient full-configuration-interaction 'nuclear orbital' treatment was developed as a benchmark quantum-chemistry-like method to calculate, ground and excited, fermionic 'solvent' wave-functions and applied to {sup 3}He{sub N} clusters with atomic or molecular impurities [J. Chem. Phys. (Communication) 125, 221101 (2006)]. The main difficulty in handling doped {sup 3}He{sub N} clusters lies in the Fermi-Dirac nuclear statistics, the wide amplitudes of the He-dopant and He-He motions, and the hard-core He-He interaction at short distances. This paper overviews the theoretical approach and its recent applications to energetic, structural and spectroscopic aspects of different dopant-{sup 3}He{sub N} clusters. Preliminary results by using the latest version of the FCI-NO computational implementation, to bosonic Cl{sub 2}(X)-({sup 4}He){sub N} clusters, are also shown.

  13. Molecular doping and band-gap opening of bilayer graphene.

    PubMed

    Samuels, Alexander J; Carey, J David

    2013-03-26

    The ability to induce an energy band gap in bilayer graphene is an important development in graphene science and opens up potential applications in electronics and photonics. Here we report the emergence of permanent electronic and optical band gaps in bilayer graphene upon adsorption of π electron containing molecules. Adsorption of n- or p-type dopant molecules on one layer results in an asymmetric charge distribution between the top and bottom layers and in the formation of an energy gap. The resultant band gap scales linearly with induced carrier density though a slight asymmetry is found between n-type dopants, where the band gap varies as 47 meV/10(13) cm(-2), and p-type dopants where it varies as 40 meV/10(13) cm(-2). Decamethylcobaltocene (DMC, n-type) and 3,6-difluoro-2,5,7,7,8,8-hexacyano-quinodimethane (F2-HCNQ, p-type) are found to be the best molecules at inducing the largest electronic band gaps up to 0.15 eV. Optical adsorption transitions in the 2.8-4 μm region of the spectrum can result between states that are not Pauli blocked. Comparison is made between the band gaps calculated from adsorbate-induced electric fields and from average displacement fields found in dual gate bilayer graphene devices. A key advantage of using molecular adsorption with π electron containing molecules is that the high binding energy can induce a permanent band gap and open up possible uses of bilayer graphene in mid-infrared photonic or electronic device applications.

  14. Vanadium-doped small silicon clusters: Photoelectron spectroscopy and density-functional calculations

    NASA Astrophysics Data System (ADS)

    Xu, Hong-Guang; Zhang, Zeng-Guang; Feng, Yuan; Yuan, Jinyun; Zhao, Yuchao; Zheng, Weijun

    2010-03-01

    Vanadium-doped small silicon clusters, VSin- and VSin- ( n = 3-6), have been studied by anion photoelectron spectroscopy. The vertical detachment energies (VDEs) and adiabatic detachment energies (ADEs) of these clusters were obtained from their photoelectron spectra. We have also conducted density-functional calculations of VSin- and VSin- clusters and determined their structures by comparison of theoretical calculations with experimental results. Our results show that two V atoms in VSin- clusters tend to form a strong V-V bond. VSi6- has D3d symmetry with the six Si atoms forming a chair like six-membered ring similar to the ring in cyclohexane and the two vanadium atoms are joined with a δ bond.

  15. Nitrogen doping and vacancy effects on the mechanical properties of graphene: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Mortazavi, Bohayra; Ahzi, Said; Toniazzo, Valérie; Rémond, Yves

    2012-02-01

    In this Letter, we used classical Molecular Dynamics (MD) simulations to investigate the tensile behavior of graphene. The validity of the proposed MD architecture is verified by comparing the simulation results with the available experimental results. By performing uniaxial tension simulations, we studied the effects of strain rate, chirality, nanoribbons width and number of atomic planes on the mechanical properties of graphene. We particularly investigated the effects of doped nitrogen atoms and point vacancies concentrations on the Young's modulus and tensile strength of graphene. By plotting the deformation process of graphene at various strain levels, the failure behavior is discussed.

  16. Sb surface segregation and doping in Si(100) grown at reduced temperature by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Hobart, K. D.; Godbey, D. J.; Thompson, P. E.; Simons, D. S.

    1993-09-01

    X-ray photoelectron spectroscopy, depth profiling with secondary ion mass spectrometry, and conductivity measurements have been performed on Sb-doped Si(100) films grown at low temperature (350 °C) by molecular beam epitaxy. The measurements reveal two important effects: (1) a significant increase in the surface segregation of Sb as the dopant concentration approaches 1×1020 cm-3, and (2) a decrease in surface segregation as the surface concentration of Sb reaches one monolayer. We believe that the presence of this monolayer of Sb is responsible for the surface segregation becoming self-limited and the associated bulk concentration exceeding 1×1020 cm-3.

  17. On the structure of biomedical silver-doped phosphate-based glasses from molecular dynamics simulations.

    PubMed

    Ainsworth, Richard I; Christie, Jamieson K; de Leeuw, Nora H

    2014-10-21

    First-principles and classical molecular dynamics simulations of undoped and silver-doped phosphate-based glasses with 50 mol% P2O5, 0-20 mol% Ag2O, and varying amounts of Na2O and CaO have been carried out. Ag occupies a distorted local coordination with a mean Ag-O bond length of 2.5 Å and an ill-defined first coordination shell. This environment is shown to be distorted octahedral/trigonal bipyramidal. Ag-O coordination numbers of 5.42 and 5.54-5.71 are calculated for first-principles and classical methodologies respectively. A disproportionation in the medium-range phosphorus Q(n) distribution is explicitly displayed upon silver-doping via CaO substitution, approximating 2Q(2)→Q(1) + Q(3), but not on silver-doping via Na2O substitution. An accompanying increase in FWHM of the phosphorus to bridging oxygen partial pair-correlation function is strong evidence for a bulk structural mechanism associated with decreased dissolution rates with increased silver content. Experimentally, Ag2O ↔ Na2O substitution is known to decrease dissolution and we show this to be a result of Ag's local bonding.

  18. Growth and magnetic property of antiperovskite manganese nitride films doped with Cu by molecular beam epitaxy

    SciTech Connect

    Yu, Fengmei; Ren, Lizhu; Meng, Meng; Wang, Yunjia; Yang, Mei; Wu, Shuxiang; Li, Shuwei

    2014-04-07

    Manganese nitrides thin films on MgO (100) substrates with and without Cu-doping have been fabricated by plasma assisted molecular beam epitaxy. Antiperovskite compounds Mn{sub 3.6}Cu{sub 0.4}N have been grown in the case of Cu-doping, and the pure Mn{sub 3}N{sub 2} single crystal has been obtained without Cu-doping. The Mn{sub 3.6}Cu{sub 0.4}N exhibits ferrimagnetism, and the magnetization of Mn{sub 3.6}Cu{sub 0.4}N increases upon the temperature decreasing from 300 K to 5 K, similar to Mn{sub 4}N. The exchange bias (EB) effects emerge in the Mn{sub 3.6}Cu{sub 0.4}N films. The EB behavior is originated from the interfaces between ferrimagnetic Mn{sub 3.6}Cu{sub 0.4}N and antiferromagnetic metal Mn, which is verified to be formed by the data of x-ray photoelectron spectroscopy. The present results not only provide a strategy for producing functional antiperovskite manganese nitrides, but also shed promising light on fabricating the exchange bias part of spintronic devices.

  19. Growth and characterization of Sc-doped EuO thin films

    SciTech Connect

    Altendorf, S. G.; Reisner, A.; Chang, C. F.; Hollmann, N.; Rata, A. D.; Tjeng, L. H.

    2014-02-03

    The preparation of 3d-transition metal-doped EuO thin films by molecular beam epitaxy is investigated using the example of Sc doping. The Sc-doped EuO samples display a good crystalline structure, despite the relatively small ionic radius of the dopant. The Sc doping leads to an enhancement of the Curie temperature to up to 125 K, remarkably similar to previous observations on lanthanide-doped EuO.

  20. Detection of small interfering RNA (siRNA) by mass spectrometry procedures in doping controls.

    PubMed

    Thomas, Andreas; Walpurgis, Katja; Delahaut, Philippe; Kohler, Maxie; Schänzer, Wilhelm; Thevis, Mario

    2013-01-01

    Uncovering manipulation of athletic performance via small interfering (si)RNA is an emerging field in sports drug testing. Due to the potential to principally knock down every target gene in the organism by means of the RNA interference pathway, this facet of gene doping has become a realistic scenario. In the present study, two distinct model siRNAs comprising 21 nucleotides were designed as double strands which were perfect counterparts to a sequence of the respective messenger RNA coding the muscle regulator myostatin of Rattus norvegicus. Several modified nucleotides were introduced in both the sense and the antisense strand comprising phosphothioates, 2'-O-methylation, 2'-fluoro-nucleotides, locked nucleic acids and a cholesterol tag at the 3'-end. The model siRNAs were applied to rats at 1 mg/kg (i.v.) and blood as well as urine samples were collected. After isolation of the RNA by means of a RNA purification kit, the target analytes were detected by liquid chromatography - high resolution/high accuracy mass spectrometry (LC-HRMS). Analytes were detected as modified nucleotides after alkaline hydrolysis, as intact oligonucleotide strands (top-down) and by means of denaturing SDS-PAGE analysis. The gel-separated siRNA was further subjected to in-gel hydrolysis with different RNases and subsequent identification of the fragments by untargeted LC-HRMS analysis (bottom-up, 'experimental RNomics'). Combining the results of all approaches, the identification of several 3'-truncated urinary metabolites was accomplished and target analytes were detected up to 24 h after a single administration. Simultaneously collected blood samples yielded no promising results. The methods were validated and found fit-for-purpose for doping controls.

  1. Glass beads and Ge-doped optical fibres as thermoluminescence dosimeters for small field photon dosimetry.

    PubMed

    Jafari, S M; Alalawi, A I; Hussein, M; Alsaleh, W; Najem, M A; Hugtenburg, R P; Bradley, D A; Spyrou, N M; Clark, C H; Nisbet, A

    2014-11-21

    An investigation has been made of glass beads and optical fibres as novel dosimeters for small-field photon radiation therapy dosimetry. Commercially available glass beads of largest dimension 1.5 mm and GeO2-doped SiO2 optical fibres of 5 mm length and 120 µm diameter were characterized as thermoluminescence dosimeters. Results were compared against Monte-Carlo simulations with BEAMnrc/DOSXYZnrc, EBT3 Gafchromic film, and a high-resolution 2D-array of liquid-filled ionization chambers. Measurements included relative output factors and dose profiles for square-field sizes of 1, 2, 3, 4, and 10 cm. A customized Solid-Water® phantom was employed, and the beads and fibres were placed at defined positions along the longitudinal axis to allow accurate beam profile measurement. Output factors and the beam profile parameters were compared against those calculated by BEAMnrc/DOSXYZnrc. The output factors and field width measurements were found to be in agreement with reference measurements to within better than 3.5% for all field sizes down to 2 cm2 for both dosimetric systems, with the beads showing a discrepancy of no more than 2.8% for all field sizes. The results confirm the potential of the beads and fibres as thermoluminescent dosimeters for use in small photon radiation field sizes.

  2. N-doped carbon networks: alternative materials tracing new routes for activating molecular hydrogen.

    PubMed

    Cortese, Remedios; Ferrante, Francesco; Roggan, Stefan; Duca, Dario

    2015-02-23

    The fragmentation of molecular hydrogen on N-doped carbon networks was investigated by using molecular (polyaromatic macrocycles) as well as truncated and periodic (carbon nanotubes) models. The computational study was focused on the ergonicity analysis of the reaction and on the properties of the transition states involved when constellations of three or four pyridinic nitrogen atom defects are present in the carbon network. Calculations show that whenever N-defects are embedded in species characterized by large conjugated π-systems, either in polyaromatic macrocycles or carbon nanotubes, the corresponding H2 bond cleavage is largely exergonic. The fragmentation Gibbs free energy is affected by the final arrangement of the hydrogen atoms on the defect and by the extension of the π-electron cloud, but it is not influenced by the curvature of the system.

  3. Exploiting molecular dynamics in Nested Sampling simulations of small peptides

    NASA Astrophysics Data System (ADS)

    Burkoff, Nikolas S.; Baldock, Robert J. N.; Várnai, Csilla; Wild, David L.; Csányi, Gábor

    2016-04-01

    Nested Sampling (NS) is a parameter space sampling algorithm which can be used for sampling the equilibrium thermodynamics of atomistic systems. NS has previously been used to explore the potential energy surface of a coarse-grained protein model and has significantly outperformed parallel tempering when calculating heat capacity curves of Lennard-Jones clusters. The original NS algorithm uses Monte Carlo (MC) moves; however, a variant, Galilean NS, has recently been introduced which allows NS to be incorporated into a molecular dynamics framework, so NS can be used for systems which lack efficient prescribed MC moves. In this work we demonstrate the applicability of Galilean NS to atomistic systems. We present an implementation of Galilean NS using the Amber molecular dynamics package and demonstrate its viability by sampling alanine dipeptide, both in vacuo and implicit solvent. Unlike previous studies of this system, we present the heat capacity curves of alanine dipeptide, whose calculation provides a stringent test for sampling algorithms. We also compare our results with those calculated using replica exchange molecular dynamics (REMD) and find good agreement. We show the computational effort required for accurate heat capacity estimation for small peptides. We also calculate the alanine dipeptide Ramachandran free energy surface for a range of temperatures and use it to compare the results using the latest Amber force field with previous theoretical and experimental results.

  4. Infrared spectra of small molecular ions trapped in solid neon

    SciTech Connect

    Jacox, Marilyn E.

    2015-01-22

    The infrared spectrum of a molecular ion provides a unique signature for that species, gives information on its structure, and is amenable to remote sensing. It also serves as a comparison standard for refining ab initio calculations. Experiments in this laboratory trap molecular ions in dilute solid solution in neon at 4.2 K in sufficient concentration for observation of their infrared spectra between 450 and 4000 cm{sup !1}. Discharge-excited neon atoms produce cations by photoionization and/or Penning ionization of the parent molecule. The resulting electrons are captured by other molecules, yielding anions which provide for overall charge neutrality of the deposit. Recent observations of ions produced from C{sub 2}H{sub 4} and BF{sub 3} will be discussed. Because of their relatively large possibility of having low-lying excited electronic states, small, symmetric molecular cations are especially vulnerable to breakdown of the Born-Oppenheimer approximation. Some phenomena which can result from this breakdown will be discussed. Ion-molecule reaction rates are sufficiently high that in some systems absorptions of dimer cations and anions are also observed. When H{sub 2} is introduced into the system, the initially-formed ion may react with it. Among the species resulting from such ion-molecule reactions that have recently been studied are O{sub 4}{sup +}, NH{sub 4}{sup +}, HOCO{sup +}, and HCO{sub 2}{sup !}.

  5. Molecular Design of Doped Polymers for Thermoelectric Systems-Final Technical Report

    SciTech Connect

    Chabinyc, Michael L.; Hawker, Craig J.

    2013-10-09

    The self-assembly of organic semiconducting molecules and polymers is critical for their electrical properties. This project addressed the design of organic semiconductors with novel synthetic building blocks for proton-dopable conducting materials and the molecular order and microstructure of high performance semiconducting polymers blended with charge transfer dopants. Novel azulene donor-acceptor materials were designed and synthesized with unique electronic effects upon protonation to generate charged species in solution. The microstructure and optical properties of these derivatives were examined to develop structure-property relationships. Studies of the microstructure of blends of charge transfer doped semiconducting polymers revealed highly ordered conductive phases in blends. The molecular packing of one blend was studied in detail using a combination of solid-state NMR and x-ray scattering revealing that dopant incorporation is unlikely to be random as assumed in transport models. Studies of the electrical properties of these highly ordered blends revealed a universal trend between the thermopower and electrical conductivity of semiconducting polymers that is independent of the doping mechanism.

  6. Photophysical processes of triplet states and radical ions in pure and molecularly doped polymers. Final report

    SciTech Connect

    Burkhart, R.D.

    1998-01-01

    Both the past and current objectives are to learn how to control the rate and direction of triplet exciton migration in both pure and molecularly doped polymer systems. Since triplet excimers are efficient traps for migrating excitons, a secondary objective has been to characterize these excimers with a view toward their use as rate modifiers or excited state quenchers. Further objectives included those stated above as past and current objectives but with an additional goal. The authors learned that fluid solutions of many of the nitrogen containing chromophores with which they work produce both radical cations and anions upon excimer laser excitation. They also learned that a phosphorus analogue behaves similarly. At this time the mechanism of charge generation in these systems is not well established but they do know that the electronically excited states and radical ions can potentially interconvert. They wanted to find out whether or not the pure or molecularly doped polymer systems could be used in a step-wise sequence involving light absorption followed by charge generation. All of their activities are oriented toward the potential end use of polymeric systems in the conversion of light energy to perform various types of useful work.

  7. Molecular Responses to Small Regulating Molecules against Huanglongbing Disease.

    PubMed

    Martinelli, Federico; Dolan, David; Fileccia, Veronica; Reagan, Russell L; Phu, My; Spann, Timothy M; McCollum, Thomas G; Dandekar, Abhaya M

    2016-01-01

    Huanglongbing (HLB; citrus greening) is the most devastating disease of citrus worldwide. No cure is yet available for this disease and infected trees generally decline after several months. Disease management depends on early detection of symptoms and chemical control of insect vectors. In this work, different combinations of organic compounds were tested for the ability to modulate citrus molecular responses to HLB disease beneficially. Three small-molecule regulating compounds were tested: 1) L-arginine, 2) 6-benzyl-adenine combined with gibberellins, and 3) sucrose combined with atrazine. Each treatment contained K-phite mineral solution and was tested at two different concentrations. Two trials were conducted: one in the greenhouse and the other in the orchard. In the greenhouse study, responses of 42 key genes involved in sugar and starch metabolism, hormone-related pathways, biotic stress responses, and secondary metabolism in treated and untreated mature leaves were analyzed. TGA5 was significantly induced by arginine. Benzyladenine and gibberellins enhanced two important genes involved in biotic stress responses: WRKY54 and WRKY59. Sucrose combined with atrazine mainly upregulated key genes involved in carbohydrate metabolism such as sucrose-phosphate synthase, sucrose synthase, starch synthase, and α-amylase. Atrazine also affected expression of some key genes involved in systemic acquired resistance such as EDS1, TGA6, WRKY33, and MYC2. Several treatments upregulated HSP82, which might help protect protein folding and integrity. A subset of key genes was chosen as biomarkers for molecular responses to treatments under field conditions. GPT2 was downregulated by all small-molecule treatments. Arginine-induced genes involved in systemic acquired resistance included PR1, WRKY70, and EDS1. These molecular data encourage long-term application of treatments that combine these regulating molecules in field trials.

  8. Molecular Responses to Small Regulating Molecules against Huanglongbing Disease

    PubMed Central

    Martinelli, Federico; Dolan, David; Fileccia, Veronica; Reagan, Russell L.; Phu, My; Spann, Timothy M.; McCollum, Thomas G.; Dandekar, Abhaya M.

    2016-01-01

    Huanglongbing (HLB; citrus greening) is the most devastating disease of citrus worldwide. No cure is yet available for this disease and infected trees generally decline after several months. Disease management depends on early detection of symptoms and chemical control of insect vectors. In this work, different combinations of organic compounds were tested for the ability to modulate citrus molecular responses to HLB disease beneficially. Three small-molecule regulating compounds were tested: 1) L-arginine, 2) 6-benzyl-adenine combined with gibberellins, and 3) sucrose combined with atrazine. Each treatment contained K-phite mineral solution and was tested at two different concentrations. Two trials were conducted: one in the greenhouse and the other in the orchard. In the greenhouse study, responses of 42 key genes involved in sugar and starch metabolism, hormone-related pathways, biotic stress responses, and secondary metabolism in treated and untreated mature leaves were analyzed. TGA5 was significantly induced by arginine. Benzyladenine and gibberellins enhanced two important genes involved in biotic stress responses: WRKY54 and WRKY59. Sucrose combined with atrazine mainly upregulated key genes involved in carbohydrate metabolism such as sucrose-phosphate synthase, sucrose synthase, starch synthase, and α-amylase. Atrazine also affected expression of some key genes involved in systemic acquired resistance such as EDS1, TGA6, WRKY33, and MYC2. Several treatments upregulated HSP82, which might help protect protein folding and integrity. A subset of key genes was chosen as biomarkers for molecular responses to treatments under field conditions. GPT2 was downregulated by all small-molecule treatments. Arginine-induced genes involved in systemic acquired resistance included PR1, WRKY70, and EDS1. These molecular data encourage long-term application of treatments that combine these regulating molecules in field trials. PMID:27459099

  9. A rhenium complex doped in a silica molecular sieve for molecular oxygen sensing: Construction and characterization

    NASA Astrophysics Data System (ADS)

    Yang, Xiaozhou; Li, Yanxiao

    2016-01-01

    This paper reported a diamine ligand and its Re(I) complex for potential application in oxygen sensing. The novelty of this diamine ligand localized at its increased conjugation chain which had a typical electron-withdrawing group of 1,3,4-oxadiazole. Electronic distribution of excited electrons and their lifetime were supposed to be increased, favoring oxygen sensing collision. This hypothesis was confirmed by single crystal analysis, theoretical calculation and photophysical measurement. It was found that this Re(I) complex had a long-lived emission peaking at 545 nm, favoring sensing application. By doping this complex into a silica matrix MCM-41, oxygen sensing performance and mechanism of the resulting composites were discussed in detail. Non-linear Stern-Volmer working curves were observed with maximum sensitivity of 5.54 and short response time of 6 s.

  10. A rhenium complex doped in a silica molecular sieve for molecular oxygen sensing: Construction and characterization.

    PubMed

    Yang, Xiaozhou; Li, Yanxiao

    2016-01-15

    This paper reported a diamine ligand and its Re(I) complex for potential application in oxygen sensing. The novelty of this diamine ligand localized at its increased conjugation chain which had a typical electron-withdrawing group of 1,3,4-oxadiazole. Electronic distribution of excited electrons and their lifetime were supposed to be increased, favoring oxygen sensing collision. This hypothesis was confirmed by single crystal analysis, theoretical calculation and photophysical measurement. It was found that this Re(I) complex had a long-lived emission peaking at 545 nm, favoring sensing application. By doping this complex into a silica matrix MCM-41, oxygen sensing performance and mechanism of the resulting composites were discussed in detail. Non-linear Stern-Volmer working curves were observed with maximum sensitivity of 5.54 and short response time of ~6 s. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Small-Molecule Hormones: Molecular Mechanisms of Action

    PubMed Central

    Budzińska, Monika

    2013-01-01

    Small-molecule hormones play crucial roles in the development and in the maintenance of an adult mammalian organism. On the molecular level, they regulate a plethora of biological pathways. Part of their actions depends on their transcription-regulating properties, exerted by highly specific nuclear receptors which are hormone-dependent transcription factors. Nuclear hormone receptors interact with coactivators, corepressors, basal transcription factors, and other transcription factors in order to modulate the activity of target genes in a manner that is dependent on tissue, age and developmental and pathophysiological states. The biological effect of this mechanism becomes apparent not earlier than 30–60 minutes after hormonal stimulus. In addition, small-molecule hormones modify the function of the cell by a number of nongenomic mechanisms, involving interaction with proteins localized in the plasma membrane, in the cytoplasm, as well as with proteins localized in other cellular membranes and in nonnuclear cellular compartments. The identity of such proteins is still under investigation; however, it seems that extranuclear fractions of nuclear hormone receptors commonly serve this function. A direct interaction of small-molecule hormones with membrane phospholipids and with mRNA is also postulated. In these mechanisms, the reaction to hormonal stimulus appears within seconds or minutes. PMID:23533406

  12. How does the isomerization rate affect the photoisomerization-induced transport properties of a doped molecular glass-former?

    NASA Astrophysics Data System (ADS)

    Accary, J.-B.; Teboul, V.

    2013-07-01

    We investigate the effect of the isomerization rate f on the microscopic mechanisms at the origin of the massive mass transport found in glass-formers doped with isomerizing azobenzene molecules that result in surface relief gratings formation. To this end we simulate the isomerization of dispersed probe molecules embedded into a molecular host glass-former. The host diffusion coefficient first increases linearly with f and then saturates. The saturated value of the diffusion coefficient and of the viscosity does not depend on f but increases with temperature while the linear response for these transport coefficients depends only slightly on the temperature. We interpret this saturation as arising from the appearance of increasingly soft regions around the probes for high isomerization rates, a result in qualitative agreement with experiments. These two different physical behaviors, linear response and saturation, are reminiscent of the two different unexplained mass transport mechanisms observed for small or large light intensities (for small intensities the molecules move towards the dark regions while for large intensities they move towards the illuminated regions).

  13. Prediction of low-energy boron doping profile for ultrashallow junction formation by hybrid molecular dynamics method

    NASA Astrophysics Data System (ADS)

    Yabuhara, Hidehiko; Miyamoto, Akira

    2016-01-01

    Our original hybrid method combining tight-binding quantum chemical and classical molecular dynamics was first applied to the low-energy doping process of boron into a silicon substrate, which has a depth of more than 10 nm that is needed to evaluate an ultrashallow junction position. Tight-binding quantum chemical molecular dynamics calculation was used for an injected boron atom and surrounding silicon atoms within a sphere with a radius of 0.5 nm centered at the boron atom. This method is advantageous in treating the many-body collision effect and electron-electron interaction, which are more important in low-energy doping, compared with the Monte Carlo method with binary collision approximation. A comparison with a plasma doping experiment was also carried out. The junction positions were 6.2 nm for boron doping at an initial kinetic energy of 200 eV in the simulation results and 6.4 nm for 200 eV in the experimental results. Good agreement between simulation and experimental results indicates that our hybrid molecular dynamics method is applicable to doping profile prediction in a silicon structure with a depth of more than 10 nm that is needed to evaluate ultrashallow junction formation.

  14. Doping ZnO with Water/Alcohol-Soluble Small Molecules as Electron Transport Layers for Inverted Polymer Solar Cells.

    PubMed

    Liu, Chang; Zhang, Lin; Xiao, Liangang; Peng, Xiaobin; Cao, Yong

    2016-10-03

    By doping ZnO with porphyrin small molecules (FNEZnP-OE and FNEZnP-T) as cathode electron transport layers (ETLs), the inverted polymer solar cells (i-PSC) with PTB7:PC71BM (PTB7: polythieno[3,4-b]-thiophene-co-benzodithiophene, PC71BM: [6, 6]-phenyl-C71-butyric acid methyl ester) as the active materials exhibit enhanced device performance. While the power conversion efficiency (PCE) of the PSCs with pure ZnO ETL is 7.52%, that of the devices with FNEZnP-T-doped ZnO ETL shows a slightly improved PCE of 8.09%, and that of the PSCs with FNEZnP-OE-doped ZnO ETL is further enhanced up to 9.24% with an over 20% improvement compared to that with pure ZnO ETL. The better performance is contributed by the better interfacial contact and reduced work function induced by 9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorenes and 3,4-bis-(2-(2-methoxy-ethoxy)-ethoxy)-phenyls in the porphyrin small molecules. More importantly, the PCE is still higher than 8% even when the thickness of FNEZnP-OE-doped ZnO ETL is up to 110 nm, which are important criteria for eventually making organic photovoltaic modules with roll-to-roll coat processing.

  15. A molecular dynamics study of thermal transport in nanoparticle doped Argon like solid

    SciTech Connect

    Shahadat, Muhammad Rubayat Bin Ahmed, Shafkat; Morshed, A. K. M. M.

    2016-07-12

    Interfacial phenomena such as mass and type of the interstitial atom, nano scale material defect influence heat transfer and the effect become very significant with the reduction of the material size. Non Equilibrium Molecular Dynamics (NEMD) simulation was carried out in this study to investigate the effect of the interfacial phenomena on solid. Argon like solid was considered in this study and LJ potential was used for atomic interaction. Nanoparticles of different masses and different molecular defects were inserted inside the solid. From the molecular simulation, it was observed that a large interfacial mismatch due to change in mass in the homogenous solid causes distortion of the phonon frequency causing increase in thermal resistance. Position of the doped nanoparticles have more profound effect on the thermal conductivity of the solid whereas influence of the mass ratio is not very significant. Interstitial atom positioned perpendicular to the heat flow causes sharp reduction in thermal conductivity. Structural defect caused by the molecular defect (void) also observed to significantly affect the thermal conductivity of the solid.

  16. Surface ionisation of molecular H2 and atomic H Rydberg states at doped silicon surfaces

    NASA Astrophysics Data System (ADS)

    Sashikesh, G.; So, E.; Ford, M. S.; Softley, T. P.

    2014-09-01

    The detection of ions or electrons from the surface ionisation of molecular H2 and atomic H Rydberg states incident at doped Si surfaces is investigated experimentally to analyse the effect of the dopant charge distribution on the surface-ionisation processes. In both experimental studies, the molecular H2 and atomic H Rydberg states are generated via two-colour vacuum ultraviolet--ultraviolet (VUV-UV) resonant excitation. For H2, various Stark states of the N+ = 2, n = 17 manifold are populated in the presence of an electric field. The variation of the observed surface-ionisation signal with surface dopant concentration and type, shows similar characteristics for all the Stark states. A comparison is made between these ion-detected surface-ionisation profiles and those obtained via electron detection. Different trends as a function of dopant concentration and type are observed for the two cases, explained by the greater effect of surface charges on the post-ionisation ion trajectory compared to the electron trajectory. For the atomic-H Rydberg states with principal quantum number ? populated in the absence of a Stark field, the observed behaviour is similar to the interaction of molecular H2 Rydberg states at the same surfaces, and these measurements confirm that the observed effects are attributable to the nature of the target surface rather than the specific atomic or molecular Rydberg species.

  17. Tyrosine kinase inhibitors - small molecular weight compounds inhibiting EGFR.

    PubMed

    Hegymegi-Barakonyi, Bálint; Eros, Dániel; Szántai-Kis, Csaba; Breza, Nóra; Bánhegyi, Péter; Szabó, Gábor Viktor; Várkondi, Edit; Peták, István; Orfi, László; Kéri, György

    2009-06-01

    Abnormally elevated EGFR kinase activity can lead to various pathological states, including proliferative diseases such as cancer. The development of selective protein kinase inhibitors has become an important area of drug discovery for the potential treatment of a variety of solid tumors such as breast, ovarian and colorectal cancers, NSCLC, and carcinoma of the head and neck. There are three small molecule EGFR kinase inhibitor drugs in clinical use (gefitinib, erlotinib and lapatinib), and several others are currently undergoing clinical development. This review summarizes the development of EGFR kinase inhibitors, and includes descriptions of the binding modes, the importance of a multiple-targets strategy, the effects of sensitizing and resistance mutations in the EGFR, and molecular diagnostic approaches. In addition, the use of target fishing for selectivity profiling, off-target identification and quantitative structure-activity relationship modeling for the prediction of EGFR inhibition is discussed.

  18. Packaging stiff polymers in small containers: A molecular dynamics study.

    PubMed

    Rapaport, D C

    2016-09-01

    The question of how stiff polymers are able to pack into small containers is particularly relevant to the study of DNA packaging in viruses. A reduced version of the problem based on coarse-grained representations of the main components of the system-the DNA polymer and the spherical viral capsid-has been studied by molecular dynamics simulation. The results, involving longer polymers than in earlier work, show that as polymers become more rigid there is an increasing tendency to self-organize as spools that wrap from the inside out, rather than the inverse direction seen previously. In the final state, a substantial part of the polymer is packed into one or more coaxial spools, concentrically layered with different orientations, a form of packaging achievable without twisting the polymer.

  19. Packaging stiff polymers in small containers: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Rapaport, D. C.

    2016-09-01

    The question of how stiff polymers are able to pack into small containers is particularly relevant to the study of DNA packaging in viruses. A reduced version of the problem based on coarse-grained representations of the main components of the system—the DNA polymer and the spherical viral capsid—has been studied by molecular dynamics simulation. The results, involving longer polymers than in earlier work, show that as polymers become more rigid there is an increasing tendency to self-organize as spools that wrap from the inside out, rather than the inverse direction seen previously. In the final state, a substantial part of the polymer is packed into one or more coaxial spools, concentrically layered with different orientations, a form of packaging achievable without twisting the polymer.

  20. Quantum-chemical investigations of small molecular anions

    NASA Astrophysics Data System (ADS)

    Botschwina, P.; Seeger, S.; Mladenović, M.; Schulz, B.; Horn, M.; Schmatz, S.; Flügge, J.; Oswald, R.

    Dedicated to Dr Gerhard Herzberg on the occasion of his 90th birthday Recent large-scale ab initio calculations for small negative molecular ions are reviewed. Accurate equilibrium geometries are established for several species like NH2-, HCC-, NO2-, CH2N- C5- and C6-. Predictions are made for various spectroscopic properties like vibrational frequencies, rotational constants and infrared intensities. The effects of a shallow energy minimum in the T-shaped configuration on the rovibrational term energies of HCC - are investigated. The calculated vibrational structures of the photoelectron spectra of SiH3- and CH2N - are in very good agreement with the experiment. The present calculations support the assignment of an absorption observed at 608 nm in a neon matrix to the

  1. Minority carrier lifetime in iodine-doped molecular beam epitaxy-grown HgCdTe

    SciTech Connect

    Madni, I.; Umana-Membreno, G. A.; Lei, W.; Gu, R.; Antoszewski, J.; Faraone, L.

    2015-11-02

    The minority carrier lifetime in molecular beam epitaxy grown layers of iodine-doped Hg{sub 1−x}Cd{sub x}Te (x ∼ 0.3) on CdZnTe substrates has been studied. The samples demonstrated extrinsic donor behavior for carrier concentrations in the range from 2 × 10{sup 16} cm{sup −3} to 6 × 10{sup 17} cm{sup −3} without any post-growth annealing. At a temperature of 77 K, the electron mobility was found to vary from 10{sup 4} cm{sup 2}/V s to 7 × 10{sup 3} cm{sup 2}/V s and minority carrier lifetime from 1.6 μs to 790 ns, respectively, as the carrier concentration was increased from 2 × 10{sup 16} cm{sup −3} to 6 × 10{sup 17} cm{sup −3}. The diffusion of iodine is much lower than that of indium and hence a better alternative in heterostructures such as nBn devices. The influence of carrier concentration and temperature on the minority carrier lifetime was studied in order to characterize the carrier recombination mechanisms. Measured lifetimes were also analyzed and compared with the theoretical models of the various recombination processes occurring in these materials, indicating that Auger-1 recombination was predominant at higher doping levels. An increase in deep-level generation-recombination centers was observed with increasing doping level, which suggests that the increase in deep-level trap density is associated with the incorporation of higher concentrations of iodine into the HgCdTe.

  2. Integrated molecular portrait of non-small cell lung cancers

    PubMed Central

    2013-01-01

    Background Non-small cell lung cancer (NSCLC), a leading cause of cancer deaths, represents a heterogeneous group of neoplasms, mostly comprising squamous cell carcinoma (SCC), adenocarcinoma (AC) and large-cell carcinoma (LCC). The objectives of this study were to utilize integrated genomic data including copy-number alteration, mRNA, microRNA expression and candidate-gene full sequencing data to characterize the molecular distinctions between AC and SCC. Methods Comparative genomic hybridization followed by mutational analysis, gene expression and miRNA microarray profiling were performed on 123 paired tumor and non-tumor tissue samples from patients with NSCLC. Results At DNA, mRNA and miRNA levels we could identify molecular markers that discriminated significantly between the various histopathological entities of NSCLC. We identified 34 genomic clusters using aCGH data; several genes exhibited a different profile of aberrations between AC and SCC, including PIK3CA, SOX2, THPO, TP63, PDGFB genes. Gene expression profiling analysis identified SPP1, CTHRC1and GREM1 as potential biomarkers for early diagnosis of the cancer, and SPINK1 and BMP7 to distinguish between AC and SCC in small biopsies or in blood samples. Using integrated genomics approach we found in recurrently altered regions a list of three potential driver genes, MRPS22, NDRG1 and RNF7, which were consistently over-expressed in amplified regions, had wide-spread correlation with an average of ~800 genes throughout the genome and highly associated with histological types. Using a network enrichment analysis, the targets of these potential drivers were seen to be involved in DNA replication, cell cycle, mismatch repair, p53 signalling pathway and other lung cancer related signalling pathways, and many immunological pathways. Furthermore, we also identified one potential driver miRNA hsa-miR-944. Conclusions Integrated molecular characterization of AC and SCC helped identify clinically relevant markers

  3. Integrated molecular portrait of non-small cell lung cancers.

    PubMed

    Lazar, Vladimir; Suo, Chen; Orear, Cedric; van den Oord, Joost; Balogh, Zsofia; Guegan, Justine; Job, Bastien; Meurice, Guillaume; Ripoche, Hugues; Calza, Stefano; Hasmats, Johanna; Lundeberg, Joakim; Lacroix, Ludovic; Vielh, Philippe; Dufour, Fabienne; Lehtiö, Janne; Napieralski, Rudolf; Eggermont, Alexander; Schmitt, Manfred; Cadranel, Jacques; Besse, Benjamin; Girard, Philippe; Blackhall, Fiona; Validire, Pierre; Soria, Jean-Charles; Dessen, Philippe; Hansson, Johan; Pawitan, Yudi

    2013-12-03

    Non-small cell lung cancer (NSCLC), a leading cause of cancer deaths, represents a heterogeneous group of neoplasms, mostly comprising squamous cell carcinoma (SCC), adenocarcinoma (AC) and large-cell carcinoma (LCC). The objectives of this study were to utilize integrated genomic data including copy-number alteration, mRNA, microRNA expression and candidate-gene full sequencing data to characterize the molecular distinctions between AC and SCC. Comparative genomic hybridization followed by mutational analysis, gene expression and miRNA microarray profiling were performed on 123 paired tumor and non-tumor tissue samples from patients with NSCLC. At DNA, mRNA and miRNA levels we could identify molecular markers that discriminated significantly between the various histopathological entities of NSCLC. We identified 34 genomic clusters using aCGH data; several genes exhibited a different profile of aberrations between AC and SCC, including PIK3CA, SOX2, THPO, TP63, PDGFB genes. Gene expression profiling analysis identified SPP1, CTHRC1 and GREM1 as potential biomarkers for early diagnosis of the cancer, and SPINK1 and BMP7 to distinguish between AC and SCC in small biopsies or in blood samples. Using integrated genomics approach we found in recurrently altered regions a list of three potential driver genes, MRPS22, NDRG1 and RNF7, which were consistently over-expressed in amplified regions, had wide-spread correlation with an average of ~800 genes throughout the genome and highly associated with histological types. Using a network enrichment analysis, the targets of these potential drivers were seen to be involved in DNA replication, cell cycle, mismatch repair, p53 signalling pathway and other lung cancer related signalling pathways, and many immunological pathways. Furthermore, we also identified one potential driver miRNA hsa-miR-944. Integrated molecular characterization of AC and SCC helped identify clinically relevant markers and potential drivers, which are

  4. Pitfall in quantum mechanical/molecular mechanical molecular dynamics simulation of small solutes in solution.

    PubMed

    Hu, Hao; Liu, Haiyan

    2013-05-30

    Developments in computing hardware and algorithms have made direct molecular dynamics simulation with the combined quantum mechanical/molecular mechanical methods affordable for small solute molecules in solution, in which much improved accuracy can be obtained via the quantum mechanical treatment of the solute molecule and even sometimes water molecules in the first solvation shell. However, unlike the conventional molecular mechanical simulations of large molecules, e.g., proteins, in solutions, special care must be taken in the technical details of the simulation, including the thermostat of the solute/solvent system, so that the conformational space of the solute molecules can be properly sampled. We show here that the common setup for classical molecular mechanical molecular dynamics simulations, such as the Berendsen or single Nose-Hoover thermostat, and/or rigid water models could lead to pathological sampling of the solutes' conformation. In the extreme example of a methanol molecule in aqueous solution, improper and sluggish setups could generate two peaks in the distribution of the O-H bond length. We discuss the factors responsible for this somewhat unexpected result and evoke a simple and ancient technical fix-up to resolve this problem.

  5. Absolute photoluminescence quantum yield of molecular organic thin films: effects of doping with strongly fluorescent rubrene

    NASA Astrophysics Data System (ADS)

    Mattoussi, Hedi M.; Murata, Hideyuki; Merritt, Charles D.; Kafafi, Zakya H.

    1998-12-01

    We present data on the absolute photoluminescence quantum yield (phi) PL, for a set of pure and molecularly doped organic solid films. The procedure uses an integrating sphere to provide accurate measure of the photoluminescence efficiency for solid, sub-micron thickness, films. Host materials include a common hole transport compounds, N,N- dipheny-N,N-bis(3-methylphenyl)-1,1-biphenyl-4,4-diamine, TPD, and two metal chelates used as electron transport and/or light emitting materials, tris (8- hydroxyquinolinolato) aluminum (III), Alq3, and one of its methyl derivatives, tris (8- trimethylhydroxyquinolinolator) aluminum (III), Almq3, Tetraphenylnapthacene, or rubrene, is used as the dopant. A substantial increase in (phi) PL is measured with respect to the pure host. For example, the measured (phi) PL increases from 0.25 and 0.40 for pure Alq3 and Almq3, respectively, to near unity upon doping with rubrene at approximately 1 mol percent. The data are discussed within the framework of Foerster energy transfer.

  6. Thermal grafting of fluorinated molecular monolayers on doped amorphous silicon surfaces

    SciTech Connect

    Sabbah, H.; Zebda, A.; Ababou-Girard, S.; Solal, F.; Godet, C.; Conde, J. P.; Chu, V.

    2009-03-15

    Thermally induced (160-300 deg. C) gas phase grafting of linear alkene molecules (perfluorodecene) was performed on hydrogenated amorphous silicon (a-Si:H) films, either nominally undoped or doped with different boron and phosphorus concentrations. Dense and smooth a-Si:H films were grown using plasma decomposition of silane. Quantitative analysis of in situ x-ray photoelectron spectroscopy indicates the grafting of a single layer of organic molecules. The hydrophobic properties of perfluorodecene-modified surfaces were studied as a function of surface coverage. Annealing experiments in ultrahigh vacuum show the covalent binding and the thermal stability of these immobilized layers up to 370 deg. C; this temperature corresponds to the Si-C bond cleavage temperature. In contrast with hydrogenated crystalline Si(111):H, no heavy wet chemistry surface preparation is required for thermal grafting of alkene molecules on a-Si:H films. A threshold grafting temperature is observed, with a strong dependence on the doping level which produces a large contrast in the molecular coverage for grafting performed at 230 deg. C.

  7. Transient space-charge-limited current pulse shapes in molecularly doped polymers

    NASA Astrophysics Data System (ADS)

    Goldie, D. M.

    1999-12-01

    The transient current response of molecularly doped polymers have been numerically modelled under space-charge-limited (SCL) conditions for the situation in which a step potential is applied to an ideal injecting contact. Under trap-free conditions, the transient SCL current pulse shape is found to be sensitive not only to the underlying field dependence of the injected carrier mobilities and diffusivities, but also to the magnitude of the applied step potential. A progressive reduction in the ratio of the peak current density jp to the final steady-state magnitude jss is obtained by increasing either the field strength of the mobility or the relative amount of diffusion. It is demonstrated, however, that for times preceding the location tp of the current peak, the rate of current increase displays a gradual transition from a super-linear to linear time dependence upon the introduction of diffusion. The diminishing observability of jp/jss is accompanied by a shift in the position of tp relative to the space-charge-free carrier transit time t0. The classical fixed-mobility value tp/t0 = 0.786 is modestly reduced as the field strength of the mobility or amount of carrier diffusion is enhanced. The numerical predictions are compared with experimental SCL current transients obtained from hydrazone doped polyester samples fitted with gold contacts.

  8. Terahertz Conductivity and Hindered Molecular Reorientation of Lithium Salt Doped Succinonitrile in its Plastic Crystal Phase

    NASA Astrophysics Data System (ADS)

    Nickel, Daniel V.; Bian, Hongtao; Zheng, Junrong; Mittleman, Daniel M.

    2014-09-01

    The terahertz complex permittivity of the molecular plastic crystal succinonitrile (SN) or 1,2 dicyanoethane (N≡C-CH2-CH2-C≡N), doped with the lithium salts LiBF4, LiPF6, LiTFSI, and LiClO4 to form solid-state plastic crystal electrolytes, is measured and compared using temperature-dependent terahertz time-domain spectroscopy (THz-TDS). In contrast to the trends at low frequency, SN's terahertz conductivity decreases slightly when doped with Li-salts. This indicates that at high frequencies the dielectric response is not dominated by ionic charge transport, but instead by relaxational processes which are hindered by the presence of the ionic dopants. Assuming a single Cole-Cole distribution of Debye-like processes dominates the measured spectra, the average relaxation times τ and Arrhenius activation energies E a are extracted for each electrolyte and are shown to increase significantly relative to undoped SN's τ and E a, indicating the relaxational processes are hindered by the presence of the ionic dopants.

  9. Optical investigations of Be doped ZnO films grown by molecular beam epitaxy

    SciTech Connect

    Chen, Mingming; Zhu, Yuan; Chen, Anqi; Shen, Zhen; Tang, Zikang

    2016-06-15

    Highlights: • The optical properties of Be doped ZnO films were investigated. • Low temperature photoluminescence spectrum was dominated by D°X and DAP emissions. • Shallow acceptor state with ionization energy of 116 meV was found in ZnO:Be films. • It is suggested that the incorporated Be atom might favor formation of Zn vacancies defects. • This work demonstrates that N doping BeZnO might be suitable for fabricating reliable p-type ZnO materials. - Abstract: In this article, the optical properties of ZnO:Be films grown by plasma-assisted molecular beam epitaxy were investigated by the excitation density-dependent and temperature-dependent photoluminescence measurements. The low temperature photoluminescence spectra showed a dominant excitons bound to neutral donors (D°X) emission centered at 3.3540 eV and strong donor-acceptor pair (DAP) transitions at 3.3000 eV. In addition, it showed that the intensity ratio of the DAP and D°X peaks changed with background electron concentration. Furthermore, a shallow acceptor state with ionization energy of 116 meV was found and attributed to Zn vacancy. The present study further suggests that Be and N codoping ZnO might be suitable for fabricating reliable p-type ZnO materials.

  10. Frequency Domain Fluorescent Molecular Tomography and Molecular Probes for Small Animal Imaging

    NASA Astrophysics Data System (ADS)

    Kujala, Naresh Gandhi

    Fluorescent molecular tomography (FMT) is a noninvasive biomedical optical imaging that enables 3-dimensional quantitative determination of fluorochromes distributed in biological tissues. There are three methods for imaging large volume tissues based on different light sources: (a) using a light source of constant intensity, through a continuous or constant wave, (b) using a light source that is intensity modulated with a radio frequency (RF), and (c) using ultrafast pulses in the femtosecond range. In this study, we have developed a frequency domain fluorescent molecular tomographic system based on the heterodyne technique, using a single source and detector pair that can be used for small animal imaging. In our system, the intensity of the laser source is modulated with a RF frequency to produce a diffuse photon density wave in the tissue. The phase of the diffuse photon density wave is measured by comparing the reference signal with the signal from the tissue using a phasemeter. The data acquisition was performed by using a Labview program. The results suggest that we can measure the phase change from the heterogeneous inside tissue. Combined with fiber optics and filter sets, the system can be used to sensitively image the targeted fluorescent molecular probes, allowing the detection of cancer at an early stage. We used the system to detect the tumor-targeting molecular probe Alexa Fluor 680 and Alexa Fluor 750 bombesin peptide conjugates in phantoms as well as mouse tissues. We also developed and evaluated fluorescent Bombesin (BBN) probes to target gastrin-releasing peptide (GRP) receptors for optical molecular imaging. GRP receptors are over-expressed in several types of human cancer cells, including breast, prostate, small cell lung, and pancreatic cancers. BBN is a 14 amino acid peptide that is an analogue to human gastrin-releasing peptide that binds specifically to GRPr receptors. BBN conjugates are significant in cancer detection and therapy. The

  11. Indium antimonide doped with lead telluride grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Partin, D. L.; Heremans, J.; Trush, C. M.

    1991-05-01

    A PbTe dopant source has been used to grow n-type InSb using the molecular beam epitaxy growth technique. From Auger electron spectroscopy studies, no surface segregation of tellurium or lead is observed up to ∽ 10 19 cm -3 doping levels. The correlation between the PbTe flux used during growth and the electron density in the grown films is very good, suggesting that the incorporation of tellurium is near unity. Six-probe Hall measurements of carrier transport gave room temperature mobilities as high as 51,300 cm 2 V -1 s -1 at an electron density of 2.9×10 16 cm -3 (54,300 at an electron density of 1.9×10 16 cm -3 at 110 K) for a film of 4.0 μm thickness on an InP substrate.

  12. Effect of ion structure on conductivity in lithium-doped ionic liquid electrolytes: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Liu, Hongjun; Maginn, Edward

    2013-09-01

    Molecular dynamics simulations were performed to examine the role cation and anion structure have on the performance of ionic liquid (IL) electrolytes for lithium conduction over the temperature range of 320-450 K. Two model ionic liquids were studied: 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([bmim][Tf2N]) and 1-butyl-4-methylpyridinium pyrrolide ([bmpyr][pyl]) doped with Li[Tf2N] and Li[pyl], respectively. The results have demonstrated that the Li+ doped IL containing the planar [bmpyr] cation paired with the planar [pyl] anion significantly outperformed the [bmim][Tf2N] IL. The different coordination of Li+ with the [Tf2N]- or [pyl]- anions produces a remarkable change in IL structure with a concomitant effect on the transport of all ions. For the doped [bmim][Tf2N], each Li+ is coordinated by four oxygen atoms from [Tf2N]- anions. Formation of a rigid structure between Li+ and [Tf2N]- induces a decrease in the mobility of all ions. In contrast, for the doped [bmpyr][pyl], each Li+ is coordinated by two nitrogen atoms from [pyl]- anions. The original alternating structure cation|anion|cation in the neat [bmpyr][pyl] is replaced by another alternating structure cation|anion|Li+|anion|cation in the doped [bmpyr][pyl]. Increases of Li+ mole fraction in doped [bmpyr][pyl] affects the dynamics to a much lesser extent compared with [bmim][Tf2N] and leads to reduced diffusivities of cations and anions, but little change in the dynamics of Li+. More importantly, the calculations predict that the Li+ ion conductivity of doped [bmpyr][pyl] is comparable to that observed in organic liquid electrolytes and is about an order of magnitude higher than that of doped [bmim][Tf2N]. Such Li+ conductivity improvement suggests that this and related ILs may be promising candidates for use as electrolytes in lithium ion batteries and capacitors.

  13. Pervasive small-scale structure in molecular clouds

    NASA Technical Reports Server (NTRS)

    Martin, B.; Lada, E.

    1986-01-01

    An unbiased CO survey of molecular cloud cores was completed, and the profiles were analyzed within the context of a model for emission from clumpy clouds. It was found that all sources observed contain a significant amount of structure that is not resolved with our 2.3-arcmin beam, and that the parameters which describe the degree of clumping span a remarkably narrow range of the possible values. We studied two separate samples of cloud cores: a large sample of warm cores from the Massachusetts-Stony Brook 12CO survey of the first galactic quadrant, and a sample of cool cores in the Taurus dark clouds chosen primarily on the basis of H2CO emission. We observed all sources in the 1-0 transition of 12CO and 13CO with the 5-m telescope of the Millimeter Wave Observatory. The 12CO/13CO ratios can be explained if there is unresolved structure giving rise to significant variations of opacity across the beam. Our model cloud consists of a large number of identical clumps distributed randomly in the beam. These clumps have velocity widths v small compared to the width of the observed profile, which is determined by the relative motion of the clumps. The entire cloud is isothermal and in local thermodynamic equilibrium. With these assumptions the intensity and linewidth ratios depend on three parameters: the abundance ratio; the peak 13CO opacity through a single clump, tau(0); and the average number of clumps on a line of sight N. Small tau(0) and large N correspond to the microturbulent limit, which is indistinguishable from a uniform gas distribution. In the other extreme, large tau(0) and snall N, at a given velocity at most one clump contributes to the profile on each line of sight. A figure is presented which shows the model parameters which reproduce the measured intensity and linewidth ratios for the sample of warm cores, assuming an abundance ratio of 75.

  14. Inhomogeneous Si-doping of gold-seeded InAs nanowires grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Rolland, Chloé; Caroff, Philippe; Coinon, Christophe; Wallart, Xavier; Leturcq, Renaud

    2013-06-01

    We have investigated in situ Si doping of InAs nanowires grown by molecular beam epitaxy from gold seeds. The effectiveness of n-type doping is confirmed by electrical measurements showing an increase of the electron density with the Si flux. We also observe an increase of the electron density along the nanowires from the tip to the base, attributed to the dopant incorporation on the nanowire facets whereas no detectable incorporation occurs through the seed. Furthermore, the Si incorporation strongly influences the lateral growth of the nanowires without giving rise to significant tapering, revealing the complex interplay between axial and lateral growth.

  15. Heavily boron-doped Si layers grown below 700 C by molecular beam epitaxy using a HBO2 source

    NASA Technical Reports Server (NTRS)

    Lin, T. L.; Fathauer, R. W.; Grunthaner, P. J.

    1989-01-01

    Boron doping in Si layers grown by molecular beam epitaxy (MBE) at 500-700 C using an HBO2 source has been studied. The maximum boron concentration without detectable oxygen incorporation for a given substrate temperature and Si growth rate has been determined using secondary-ion mass spectrometry analysis. Boron present in the Si MBE layers grown at 550-700 C was found to be electrically active, independent of the amount of oxygen incorporation. By reducing the Si growth rate, highly boron-doped layers have been grown at 600 C without detectable oxygen incorporation.

  16. Post-growth annealing of low temperature-grown Sb-doped Si molecular beam epitaxial films

    NASA Astrophysics Data System (ADS)

    Hobart, K. D.; Godbey, D. J.; Thompson, P. E.

    1992-07-01

    Sb-doped Si films have been grown on (100) Si substrates at low temperature (˜350 °C) by molecular beam epitaxy. Through coevaporation with Sb, very high doping efficiencies were achieved over a carrier concentration range of 1×1017 to 1×1020 cm-3. Through calibration of the beam flux we found that the incorporation of Sb was very near unity up to a concentration of ˜5×1019 cm-3. As-grown films are of good quality. However, furnace annealing was shown to improve the mobility and completely activate the Sb. Temperature dependent Hall measurements were used to further characterize the films.

  17. Heavily boron-doped Si layers grown below 700 C by molecular beam epitaxy using a HBO2 source

    NASA Technical Reports Server (NTRS)

    Lin, T. L.; Fathauer, R. W.; Grunthaner, P. J.

    1989-01-01

    Boron doping in Si layers grown by molecular beam epitaxy (MBE) at 500-700 C using an HBO2 source has been studied. The maximum boron concentration without detectable oxygen incorporation for a given substrate temperature and Si growth rate has been determined using secondary-ion mass spectrometry analysis. Boron present in the Si MBE layers grown at 550-700 C was found to be electrically active, independent of the amount of oxygen incorporation. By reducing the Si growth rate, highly boron-doped layers have been grown at 600 C without detectable oxygen incorporation.

  18. Graphene coated with controllable N-doped carbon layer by molecular layer deposition as electrode materials for supercapacitors

    NASA Astrophysics Data System (ADS)

    Chen, Yao; Gao, Zhe; Zhang, Bin; Zhao, Shichao; Qin, Yong

    2016-05-01

    In this work, graphene is coated with nitrogen-doped carbon layer, which is produced by a carbonization process of aromatic polyimide (PI) films deposited on the surfaces of graphene by molecular layer deposition (MLD). The utilization of MLD not only allows uniform coating of PI layers on the surfaces of pristine graphene without any surface treatment, but also enables homogenous dispersion of doped nitrogen atoms in the carbonized products. The as-prepared N-doped carbon layer coated graphene (NC-G) exhibited remarkable capacitance performance as electrode materials for supercapacitor, showing a high specific capacitance of 290.2 F g-1 at current density of 1 A g-1 in 6 M KOH aqueous electrolyte, meanwhile maintaining good rate performance and stable cycle capability. The NC-G synthesized by this way represents an alternative promising candidate as electrode material for supercapacitors.

  19. Effect of the orientation of doped nanoparticles on thermal transportation of a solid: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Shahadat, Muhammad Rubayat Bin; Masnoon, Ahmed Shafkat; Ahmed, Shafkat; Morshed, A. K. M. M.

    2017-06-01

    Interstitial phenomena like different types of atoms, doping and their orientation in nano scale influence the heat transfer and these effects become very significant with the reduction of material size. Non equilibrium Molecular Dynamics (NEMD) simulation was employed in this study to understand the effects of interfacial thermal resistance named kapitza resistance on solid. Argon like solid was considered in this study and LJ potential model was employed for the calculation of atomic interaction. Doping of nanoparticles at different orientation was inserted into the solid. From the simulation, it was observed that a large interfacial mismatch due to change in orientation in homogenous solid causes distortion of phonon frequency causing an increase in thermal resistance. The position of doped particles has a profound effect on thermal conductivity of solid. Interfacial atoms positioned perpendicular to heat flow direction causes sharp reduction in thermal conductivity. Phonon scattering at the material interface has been observed.

  20. Major Ampullate Spider Silk with Indistinguishable Spidroin Dope Conformations Leads to Different Fiber Molecular Structures.

    PubMed

    Dionne, Justine; Lefèvre, Thierry; Auger, Michèle

    2016-08-18

    To plentifully benefit from its properties (mechanical, optical, biological) and its potential to manufacture green materials, the structure of spider silk has to be known accurately. To this aim, the major ampullate (MA) silk of Araneus diadematus (AD) and Nephila clavipes (NC) has been compared quantitatively in the liquid and fiber states using Raman spectromicroscopy. The data show that the spidroin conformations of the two dopes are indistinguishable despite their specific amino acid composition. This result suggests that GlyGlyX and GlyProGlyXX amino acid motifs (X = Leu, Glu, Tyr, Ser, etc.) are conformationally equivalent due to the chain flexibility in the aqueous environment. Species-related sequence specificity is expressed more extensively in the fiber: the β-sheet content is lower and width of the orientation distribution of the carbonyl groups is broader for AD (29% and 58°, respectively) as compared to NC (37% and 51°, respectively). β-Sheet content values are close to the proportion of polyalanine segments, suggesting that β-sheet formation is mainly dictated by the spidroin sequence. The extent of molecular alignment seems to be related to the presence of proline (Pro) that may decrease conformational flexibility and inhibit chain extension and alignment upon drawing. It appears that besides the presence of Pro, secondary structure and molecular orientation contribute to the different mechanical properties of MA threads.

  1. Major Ampullate Spider Silk with Indistinguishable Spidroin Dope Conformations Leads to Different Fiber Molecular Structures

    PubMed Central

    Dionne, Justine; Lefèvre, Thierry; Auger, Michèle

    2016-01-01

    To plentifully benefit from its properties (mechanical, optical, biological) and its potential to manufacture green materials, the structure of spider silk has to be known accurately. To this aim, the major ampullate (MA) silk of Araneus diadematus (AD) and Nephila clavipes (NC) has been compared quantitatively in the liquid and fiber states using Raman spectromicroscopy. The data show that the spidroin conformations of the two dopes are indistinguishable despite their specific amino acid composition. This result suggests that GlyGlyX and GlyProGlyXX amino acid motifs (X = Leu, Glu, Tyr, Ser, etc.) are conformationally equivalent due to the chain flexibility in the aqueous environment. Species-related sequence specificity is expressed more extensively in the fiber: the β-sheet content is lower and width of the orientation distribution of the carbonyl groups is broader for AD (29% and 58°, respectively) as compared to NC (37% and 51°, respectively). β-Sheet content values are close to the proportion of polyalanine segments, suggesting that β-sheet formation is mainly dictated by the spidroin sequence. The extent of molecular alignment seems to be related to the presence of proline (Pro) that may decrease conformational flexibility and inhibit chain extension and alignment upon drawing. It appears that besides the presence of Pro, secondary structure and molecular orientation contribute to the different mechanical properties of MA threads. PMID:27548146

  2. Photoluminescence study on heavily donor and acceptor impurity doped GaAs layers grown by molecular-beam epitaxy

    SciTech Connect

    Islam, A. Z. M. Touhidul; Jung, D. W.; Noh, J. P.; Otsuka, N.

    2009-05-01

    Gallium arsenide layers doped with high concentrations of Be and Si by molecular-beam epitaxy are studied by photoluminescence (PL) spectroscopy. PL peaks from doped layers are observed at energies significantly lower than the band-gap of GaAs. The growth and doping conditions suggest that the origin of these peaks is different from that of low energy PL peaks, which were observed in earlier studies and attributed to impurity-vacancy complexes. The dependence of the peak energy on the temperature and the annealing is found to differ from that of the peaks attributed to impurity-vacancy complexes. On the basis of these observations, it is suggested that the low energy peaks are attributed to short range ordered arrangements of impurity ions. This possibility is examined by calculations of the PL spectra with models of pairs of acceptor and donor delta-doped layers and PL experiments of a superlattice of pairs of Be and Si delta-doped layers.

  3. Folding of Small Proteins Using Constrained Molecular Dynamics

    PubMed Central

    Balaraman, Gouthaman S.; Park, In-Hee; Jain, Abhinandan; Vaidehi, Nagarajan

    2011-01-01

    The focus of this paper is to examine whether conformational search using constrained molecular dynamics (MD) method is more enhanced and enriched towards “native-like” structures compared to all-atom MD for the protein folding as a model problem. Constrained MD methods provide an alternate MD tool for protein structure prediction and structure refinement. It is computationally expensive to perform all-atom simulations of protein folding because the processes occur on a timescale of microseconds. Compared to the all-atom MD simulation, constrained MD methods have the advantage that stable dynamics can be achieved for larger time steps and the number of degrees of freedom is an order of magnitude smaller, leading to a decrease in computational cost. We have developed a generalized constrained MD method that allows the user to “freeze and thaw” torsional degrees of freedom as fit for the problem studied. We have used this method to perform all-torsion constrained MD in implicit solvent coupled with the replica exchange method to study folding of small proteins with various secondary structural motifs such as, α-helix (polyalanine, WALP16), β-turn (1E0Q), and a mixed motif protein (Trp-cage). We demonstrate that constrained MD replica exchange method exhibits a wider conformational search than all-atom MD with increased enrichment of near native structures. “Hierarchical” constrained MD simulations, where the partially formed helical regions in the initial stretch of the all-torsion folding simulation trajectory of Trp-cage were frozen, showed a better sampling of near native structures than all-torsion constrained MD simulations. This is in agreement with the zipping-and-assembly folding model put forth by Dill and coworkers for folding proteins. The use of hierarchical “freeze and thaw” clustering schemes in constrained MD simulation can be used to sample conformations that contribute significantly to folding of proteins. PMID:21591767

  4. Growth of highly doped p-type ZnTe films by pulsed laser ablation in molecular nitrogen

    SciTech Connect

    Lowndes, D.H.; Rouleau, C.M.; Budai, J.D.; Poker, D.B.; Geohegan, D.B.; Zhu, Shen; McCamy, J.W.; Puretzky, A.

    1995-04-01

    Highly p-doped ZnTe films have been grown on semi-insulating GaAs (001) substrates by pulsed-laser ablation (PLA) of a stoichiometric ZnTe target in a high-purity N{sub 2} ambient without the use of any assisting (DC or AC) plasma source. Free hole concentrations in the mid-10{sup 19} cm{sup {minus}3} to > 10{sup 20} cm{sup {minus}3} range were obtained for a range of nitrogen pressures The maximum hole concentration equals the highest hole doping reported to date for any wide band gap II-VI compound. The highest hole mobilities were attained for nitrogen pressures of 50--100 mTorr ({approximately}6.5-13 Pa). Unlike recent experiments in which atomic nitrogen beams, extracted from RF and DC plasma sources, were used to produce p-type doping during molecular beam epitaxy deposition, spectroscopic measurements carried out during PLA of ZnTe in N{sub 2} do not reveal the presence of atomic nitrogen. This suggests that the high hole concentrations in laser ablated ZnTe are produced by a new and different mechanism, possibly energetic beam-induced reactions with excited molecular nitrogen adsorbed on the growing film surface, or transient formation of Zn-N complexes in the energetic ablation plume. This appears to be the first time that any wide band gap (Eg > 2 eV) II-VI compound (or other) semiconductor has been impurity-doped from the gas phase by laser ablation. In combination with the recent discovery that epitaxial ZnSe{sub l-x}S{sub x} films and heterostructures with continuously variable composition can be grown by ablation from a single target of fixed composition, these results appear to open the way to explore PLA growth and doping of compound semiconductors as a possible alternative to molecular beam epitaxy.

  5. Energy level alignment at planar organic heterojunctions: influence of contact doping and molecular orientation.

    PubMed

    Opitz, Andreas

    2017-04-05

    Planar organic heterojunctions are widely used in photovoltaic cells, light-emitting diodes, and bilayer field-effect transistors. The energy level alignment in the devices plays an important role in obtaining the aspired gap arrangement. Additionally, the π-orbital overlap between the involved molecules defines e.g. the charge-separation efficiency in solar cells due to charge-transfer effects. To account for both aspects, direct/inverse photoemission spectroscopy and near edge x-ray absorption fine structure spectroscopy were used to determine the energy level landscape and the molecular orientation at prototypical planar organic heterojunctions. The combined experimental approach results in a comprehensive model for the electronic and morphological characteristics of the interface between the two investigated molecular semiconductors. Following an introduction on heterojunctions used in devices and on energy levels of organic materials, the energy level alignment of planar organic heterojunctions will be discussed. The observed energy landscape is always determined by the individual arrangement between the energy levels of the molecules and the work function of the electrode. This might result in contact doping due to Fermi level pinning at the electrode for donor/acceptor heterojunctions, which also improves the solar cell efficiency. This pinning behaviour can be observed across an unpinned interlayer and results in charge accumulation at the donor/acceptor interface, depending on the transport levels of the respective organic semiconductors. Moreover, molecular orientation will affect the energy levels because of the anisotropy in ionisation energy and electron affinity and is influenced by the structural compatibility of the involved molecules at the heterojunction. High structural compatibility leads to π-orbital stacking between different molecules at a heterojunction, which is of additional interest for photovoltaic active interfaces and for ground

  6. Energy level alignment at planar organic heterojunctions: influence of contact doping and molecular orientation

    NASA Astrophysics Data System (ADS)

    Opitz, Andreas

    2017-04-01

    Planar organic heterojunctions are widely used in photovoltaic cells, light-emitting diodes, and bilayer field-effect transistors. The energy level alignment in the devices plays an important role in obtaining the aspired gap arrangement. Additionally, the π-orbital overlap between the involved molecules defines e.g. the charge-separation efficiency in solar cells due to charge-transfer effects. To account for both aspects, direct/inverse photoemission spectroscopy and near edge x-ray absorption fine structure spectroscopy were used to determine the energy level landscape and the molecular orientation at prototypical planar organic heterojunctions. The combined experimental approach results in a comprehensive model for the electronic and morphological characteristics of the interface between the two investigated molecular semiconductors. Following an introduction on heterojunctions used in devices and on energy levels of organic materials, the energy level alignment of planar organic heterojunctions will be discussed. The observed energy landscape is always determined by the individual arrangement between the energy levels of the molecules and the work function of the electrode. This might result in contact doping due to Fermi level pinning at the electrode for donor/acceptor heterojunctions, which also improves the solar cell efficiency. This pinning behaviour can be observed across an unpinned interlayer and results in charge accumulation at the donor/acceptor interface, depending on the transport levels of the respective organic semiconductors. Moreover, molecular orientation will affect the energy levels because of the anisotropy in ionisation energy and electron affinity and is influenced by the structural compatibility of the involved molecules at the heterojunction. High structural compatibility leads to π-orbital stacking between different molecules at a heterojunction, which is of additional interest for photovoltaic active interfaces and for ground

  7. Structural Distortion of Molybdenum-Doped Manganese Oxide Octahedral Molecular Sieves for Enhanced Catalytic Performance.

    PubMed

    Chen, Chun-Hu; Njagi, Eric C; Chen, Sheng-Yu; Horvath, Dayton T; Xu, Linping; Morey, Aimee; Mackin, Charles; Joesten, Raymond; Suib, Steven L

    2015-11-02

    Due to the excellent catalytic performance of manganese oxide (K-OMS-2) in a wide range of applications, incorporation of various dopants has been commonly applied for K-OMS-2 to acquire additional functionality or activities. However, the understanding of its substitution mechanism with respect to the catalytic performance of doped K-OMS-2 materials remains unclear. Here we present the structural distortion (from tetragonal to monoclinic cell) and morphological evolution in K-OMS-2 materials by doping hexavalent molybdenum. With a Mo-to-Mn ratio of 1:20 (R-1:20) in the preparation, the resultant monoclinic K-OMS-2 shows a small equidimensional particle size (∼15 nm), a high surface area of 213 m(2) g(-1), and greatly improved catalytic activity toward CO oxidation with lower onset temperatures (40 °C) than that of pristine K-OMS-2 (above 130 °C). HR-TEM analyses reveal direct evidence of structural distortion on the cross-section of 2 × 2 tunnels with the absence of 4-fold rotation symmetry expected for a tetragonal cell, which are indexed using a monoclinic cell. Our results suggest that substitution of Mo(6+) for Mn(3+) (rather than Mn(4+)) coupled with the vacancy generation results in a distorted structure and unique morphology. The weakened Mn-O bonds and Mn vacancies associated with the structural distortion may be mainly responsible for the enhanced catalytic activity of monoclinic K-OMS-2 instead of dopant species.

  8. Transient electroluminescence spikes in small molecular organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Liu, Rui; Gan, Zhengqing; Shinar, Ruth; Shinar, Joseph

    2011-06-01

    We present a comprehensive study of transient nanosecond electroluminescence (EL) spikes that exceed the dc level and microseconds-long EL tails following a bias pulse in guest-host small molecular organic light-emitting diodes (SMOLEDs), including relatively efficient devices, which elucidates carrier and exciton dynamics in such devices. The transient EL is strongly dependent, among other parameters, on device materials and structure. At low temperatures, all measured devices, with the exception of Pt octaethylporphyrin (PtOEP)-doped tris(8-hydroxyquinoline) Al (Alq3) SMOLEDs, exhibit the spikes at ˜70-300 ns. At room temperature (RT), however, only those with a hole injection barrier, carrier-trapping guest-host emitting layer, and no strong electron-transporting and hole-blocking layer [such as 4,7-diphenyl-1,10-phenanthroline (BPhen)] exhibit strong spikes. These narrow and appear earlier under postpulse reverse bias. To further elucidate the origin of the spikes, we monitored their dependence on the pulsed bias width and voltage, the doped layer thickness, and its location within the OLED structure. The characteristics of the microseconds-long tails were also evaluated through the effect of the postpulse voltage. A model based on the recombination of correlated charge pairs (CCPs) and on charge detrapping is presented; the model agrees well with the experimental data. The results suggest that reduced electric-field-induced dissociative quenching of singlet excitons is responsible for the spikes’ amplitude exceeding the on-pulse dc EL level. The long tails are attributed to recombination of charges detrapped from a distribution of shallow, mostly host, sites, reminiscent of the detrapping and recombination processes that yield the thermally stimulated luminescence of such materials. The comprehensive transient EL measurements in guest-host devices demonstrate the generality of the strong spike phenomenon in devices with charge trapping in the emitting guest

  9. High performance carbon molecular sieving membranes derived from pyrolysis of metal-organic framework ZIF-108 doped polyimide matrices.

    PubMed

    Jiao, Wenmei; Ban, Yujie; Shi, Zixing; Jiang, Xuesong; Li, Yanshuo; Yang, Weishen

    2016-12-11

    Carbon molecular sieve membranes (CMSMs) were fabricated by pyrolysis of MOF-doped polyimide mixed matrix membranes. ZIF-108 (Zn(2-nitroimidazolate)2) was used as a dopant to tailor the micropores of the as-prepared CMSMs into narrow ultramicropores, providing a remarkable combination of permeability and selectivity of membranes in CO2/CH4, O2/N2 and N2/CH4 separation.

  10. Small Ion Channel Linking Molecular Simulations and Electrophysiology

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrzej

    2017-01-01

    Ion channels are pore-forming protein assemblies that mediate the transport of small ions across cell membranes. Otherwise, membrane bilayers would be almost impermeable to ions incapable to traverse the low dielectric constant, hydrophobic membrane core. Ion channels are ubiquitous to all life forms. In humans and other higher organisms they play the central role in conducting nerve impulses, cardiac functions, muscle contraction and apoptosis. On the other extreme of biological complexity, viral ion channels (viroporins) influence many stages of the virus infection cycle either through regulating virus replication, such as entry, assembly and release or modulating the electrochemical balance in the subcellular compartments of host cells. Ion channels were crucial components of protocells. Their emergence facilitated adaptation of nascent life to different environmental conditions. The earliest ion channels must have been much simpler than most of their modern ancestors. Viral channels are among only a few naturally occurring models to study the structure, function and evolution of primordial channels. Experimental studies of these properties are difficult and often unreliable. In principle, computational methods, and molecular dynamics (MD) simulations in particular, can aid in providing information about both the structure and the function of ion channels. However, MD suffers from its own problems, such as inability to access sufficiently long time scales or limited accuracy of force fields. It is, therefore, essential to determine the reliability of MD simulations. We propose to do so on the basis of two criteria. One is channel stability on time scales that extend for several microseconds or longer. The other is the ability to reproduce the measured ionic conductance as a function of applied voltage. If both the stability and the calculated ionic conductance are satisfactory it will greatly increase our confidence that the structure and the function of a

  11. Molecular theory of phase separation in nematic liquid crystals doped with spherical nanoparticles.

    PubMed

    Osipov, Mikhail A; Gorkunov, Maxim V

    2014-05-19

    A molecular-statistical theory is developed, which enables one to describe the nematic-isotropic phase transition in liquid crystals doped with spherical nanoparticles taking into account the effects of phase separation. It has been shown that in the case of strong interaction between nanoparticles and mesogenic molecules the nematic nanocomposite possesses a number of unexpected properties. In particular, the nematic-isotropic co-existence region appears to be very broad, and the system either undergoes a direct transition from the isotropic phase into the phase-separated state, or undergoes the transition into the homogeneous nematic phase first and then phase-separates at a lower temperature. Phase separation does not occur at all if the concentration of the nanoparticles is sufficiently low, and in some cases it takes place only within a finite region of nanoparticle concentration. A number of temperature-concentration phase diagrams is presented and the molar fractions of nanoparticles in the co-existing isotropic and nematic phases are calculated numerically as functions of temperature. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Non-dispersive carrier transport in molecularly doped polymers and the convection-diffusion equation

    NASA Astrophysics Data System (ADS)

    Tyutnev, A. P.; Parris, P. E.; Saenko, V. S.

    2015-08-01

    We reinvestigate the applicability of the concept of trap-free carrier transport in molecularly doped polymers and the possibility of realistically describing time-of-flight (TOF) current transients in these materials using the classical convection-diffusion equation (CDE). The problem is treated as rigorously as possible using boundary conditions appropriate to conventional time of flight experiments. Two types of pulsed carrier generation are considered. In addition to the traditional case of surface excitation, we also consider the case where carrier generation is spatially uniform. In our analysis, the front electrode is treated as a reflecting boundary, while the counter electrode is assumed to act either as a neutral contact (not disturbing the current flow) or as an absorbing boundary at which the carrier concentration vanishes. As expected, at low fields transient currents exhibit unusual behavior, as diffusion currents overwhelm drift currents to such an extent that it becomes impossible to determine transit times (and hence, carrier mobilities). At high fields, computed transients are more like those typically observed, with well-defined plateaus and sharp transit times. Careful analysis, however, reveals that the non-dispersive picture, and predictions of the CDE contradict both experiment and existing disorder-based theories in important ways, and that the CDE should be applied rather cautiously, and even then only for engineering purposes.

  13. Dy 3 + -doped yttrium complex molecular crystals for two-color thermometry in heterogeneous materials

    NASA Astrophysics Data System (ADS)

    Anderson, Benjamin R.; Gunawidjaja, Ray; Eilers, Hergen

    2017-08-01

    We develop Dy$^{3+}$-doped yttrium complexes for use as two-color thermometry (TCT) phosphor molecular crystals in heterogeneous materials. These complexes include: Dy:Y(acac)$_3$(phen), Dy:Y(hfa)$_3$(DPEPO), Dy:Y(4-BBA)$_3$(TPPO), Dy:Y(acac)$_3$, and Dy:Y(acac)$_3$(DPEPO), where the Dy/Y ratio is 1:9. We characterize the materials' photoluminescence at different temperatures to determine the TCT calibration parameters and the degree to which thermal quenching influences the emission. From this data we observe a link between the excited state lifetime at room temperature and the degree to which the material is susceptible to thermal quenching (i.e. materials having long room temperature lifetimes are more resistant to thermal quenching than materials with short room temperature lifetimes). Of the five complexes tested we find that Dy:Y(acac)$_3$(DPEPO) has the best thermal performance, with the most likely source of improvement being DPEPO's compact rigid structure. This rigidity helps with energy transfer to the Dy$^{3+}$ ion, suppresses non-radiative loss modes, and reduces exciplex formation.

  14. Optically generated small electron and hole polarons in nominally undoped and Fe-doped KNbO3 investigated by transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Torbrügge, S.; Imlau, M.; Schoke, B.; Merschjann, C.; Schirmer, O. F.; Vernay, S.; Gross, A.; Wesemann, V.; Rytz, D.

    2008-09-01

    Transient light-induced absorption in nominally undoped and Fe-doped KNbO3 crystals is observed in the visible and infrared spectral ranges after single pulse illumination with λ=532nm . For nominally undoped KNbO3 the decay of the light-induced absorption in a single step can be explained by incoherent hopping transport of optically generated small bound O- hole and small free Nb4+ electron polarons and their mutual recombination. Iron doping causes an additional slow decay component and, remarkably, accelerates the initial decay process. A consistent model for the formation, hopping, and recombination paths of hole and electron polarons is deduced from the experimental data set for both nominally undoped and Fe-doped KNbO3 . The decrease in the polaron hopping-transport length in Fe-doped samples is attributed to the increased number densities of optically generated hole polarons by additional one-quantum excitations.

  15. Photoacoustic molecular imaging of small animals in vivo

    NASA Astrophysics Data System (ADS)

    Xie, Xueyi; Li, Meng-Lin; Oh, Jung-Taek; Ku, Geng; Wang, Wei; Li, Chun; Similache, Sergiu; Lungu, Gina F.; Stoica, George; Wang, Lihong V.

    2006-02-01

    Molecular imaging is a newly emerging field in which the modern tools of molecular and cell biology have been married to state-of-the-art technologies for noninvasive imaging. The study of molecular imaging will lead to better methods for understanding biological processes as well as diagnosing and managing disease. Here we present noninvasive in vivo spectroscopic photoacoustic tomography (PAT)-based molecular imaging of αvβ3 integrin in a nude mouse U87 brain tumor. PAT combines high optical absorption contrast and high ultrasonic resolution by employing short laser pulses to generate acoustic waves in biological tissues through thermoelastic expansion. Spectroscopic PAT-based molecular imaging offers the separation of the contributions from different absorbers based on the differences in optical absorption spectra among those absorbers. In our case, in the near infrared (NIR) range, oxy-heamoglobin (O2Hb), deoxy-heamoglobin (HHb) and the injected αvβ3-targeted peptide-ICG conjugated NIR fluorescent contrast agent are the three main absorbers. Therefore, with the excitation by multiple wavelength laser pulses, spectroscopic PAT-based molecular imaging not only provides the level of the contrast agent accumulation in the U87 glioblastoma tumor, which is related to the metabolism and angiogenesis of the tumor, but also offers the information on tumor angiogenesis and tumor hypoxia.

  16. Non-equilibrium Approach to Doping of Wide Bandgap materials by Molecular Beam Epitaxy. Final Report

    SciTech Connect

    Tamargo, M. C.; Neumark, G. F.

    2004-04-19

    It is well known that it has been difficult to obtain good bipolar doping in a wide bandgap semiconductors. Developed a new doping technique, involving use of a standard dopant, together with a ''co-dopant'' used to facilitate the introduction of the dopant, and have vastly alleviated this problem.

  17. Reduction of molecular aggregation and its application to the high-performance blue perylene-doped organic electroluminescent device

    NASA Astrophysics Data System (ADS)

    Mi, B. X.; Gao, Z. Q.; Lee, C. S.; Lee, S. T.; Kwong, H. L.; Wong, N. B.

    1999-12-01

    A nonplanar derivative of perylene, 2,5,8,11-tetra-tertbutylperylene (TBPe), was synthesized via the Friedel-Crafts alkylation reaction. Electroluminescent (EL) devices were made using TBPe or perylene as a dopant in bis(2-methyl-8-quinolinolato)(para-phenylphenolato)aluminum(III) and their EL performance was compared. Similar to the device doped with the parent perylene molecule, the device doped with TBPe also emitted strongly in the blue. As the concentration of TBPe increased from 1% to 5%, the color coordinates in CIE 1931 chromaticity of the TBPe-doped device changed only slightly from (0.168,0.273) to (0.175,0.273), whereas the perylene-doped device exhibited a much larger shift from (0.165,0.196) to (0.178,0.252). The constancy of EL color and efficiency with respect to TBPe dopant concentration is attributable to diminishing molecular aggregation in the nonplanar perylene derivative, TBPe, due to the steric hindrance of the tert-butyl groups.

  18. Behaviors of beryllium compensation doping in InGaAsP grown by gas source molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Ma, Y. J.; Zhang, Y. G.; Gu, Y.; Xi, S. P.; Chen, X. Y.; Liang, Baolai; Juang, Bor-Chau; Huffaker, Diana L.; Du, B.; Shao, X. M.; Fang, J. X.

    2017-07-01

    We report structural properties as well as electrical and optical behaviors of beryllium (Be)-doped InGaAsP lattice-matched to InP grown by gas source molecular beam epitaxy. P type layers present a high degree of compensation on the order of 1018 cm-3, and for Be densities below 9.5×1017 cm-3, they are found to be n type. Enhanced incorporation of oxygen during Be doping is observed by secondary ion mass spectroscopy. Be in forms of interstitial donors or donor-like Be-O complexes for cell temperatures below 800°C is proposed to account for such anomalous compensation behaviors. A constant photoluminescence energy of 0.98 eV without any Moss-Burstein shift for Be doping levels up to 1018 cm-3 along with increased emission intensity due to passivation effect of Be is also observed. An increasing number of minority carriers tend to relax via Be defect state-related Shockley-Read-Hall recombination with the increase of Be doping density.

  19. Highly p-doped regions in silicon solar cells quantitatively analyzed by small angle beveling and micro-Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Becker, M.; Gösele, U.; Hofmann, A.; Christiansen, S.

    2009-10-01

    Highly p-doped regions in multicrystalline silicon solar cells, such as the back surface field region, are analyzed by means of small angle beveling and micro-Raman spectroscopy. Small angle beveling and subsequent Secco etching are used to enhance the lateral resolution of the micro-Raman spectroscopic measurements and to investigate the microstructure of the back surface field region in detail. The position-dependent analysis of the free carrier concentrations within the back surface field region is based on the Raman specific Fano resonances. The Raman spectroscopic measurement results are compared to results obtained from electrochemical capacitance-voltage measurements, which allows a subsequent calibration of the Raman data for the quantitative analysis of the free carrier concentrations within the highly p-doped regions of silicon solar cells and other devices. Our investigations show that the free carrier as well as the dopant concentration profiles within the back surface field region exhibit a nearly step-functional shape instead of the extended gradient shape which the electrochemical capacitance-voltage measurements suggest. Moreover, we show that the shape of the back surface field is often influenced by grain boundaries and other defects that occur in multicrystalline silicon wafers.

  20. Modelling the interaction of molecular hydrogen with lithium-doped hydrogen storage materials

    NASA Astrophysics Data System (ADS)

    Kolmann, Stephen J.; Chan, Bun; Jordan, Meredith J. T.

    2008-12-01

    Density functional theory (DFT) and ab initio methods are used to investigate the interaction of one, two and three hydrogen molecules with Li +-doped benzene, a model for lithium-doped carbon-based and metal organic framework materials. M05-2X is found to be the best DFT method considered, reproducing MP2 and CCSD(T) H 2 binding energies to Li +-doped benzene. The M05-2X results also agree with H 2 binding energies previously obtained in an extended model of Li atom-doped MOF-5. These calculations suggest H 2 binding in Li-doped materials is, primarily, a local interaction, implying that model compounds can be used to describe these systems.

  1. The art of building small: from molecular switches to molecular motors.

    PubMed

    Feringa, Ben L

    2007-08-31

    Molecular switches and motors are essential components of artificial molecular machines. In this perspective, we discuss progress in our design, synthesis, and functioning of photochemical and electrochemical switches and chemical and light-driven molecular motors. Special emphasis is given to the control of a range of functions and properties, including luminescence, self-assembly, motion, color, conductance, transport, and chirality. We will also discuss our efforts to control mechanical movement at the molecular level, a feature that is at the heart of molecular motors and machines. The anchoring of molecular motors on surfaces and molecular motors at work are discussed.

  2. Low defect densities in molecular beam epitaxial GaAs achieved by isoelectronic In doping

    NASA Technical Reports Server (NTRS)

    Bhattacharya, P. K.; Dhar, S.; Berger, P.; Juang, F.-Y.

    1986-01-01

    A study has been made of the effects of adding small amounts of In (0.2-1.2 pct) to GaAs grown by molecular beam epitaxy. The density of four electron traps decreases in concentration by an order of magnitude, and the peak intensities of prominent emissions in the excitonic spectra are reduced with increase in In content. Based on the higher surface migration rate of In, compared to Ga, at the growth temperatures it is apparent that the traps and the excitonic transitions are related to point defects. This agrees with earlier observations by Briones and Collins (1982) and Skromme et al. (1985).

  3. Low defect densities in molecular beam epitaxial GaAs achieved by isoelectronic In doping

    NASA Technical Reports Server (NTRS)

    Bhattacharya, P. K.; Dhar, S.; Berger, P.; Juang, F.-Y.

    1986-01-01

    A study has been made of the effects of adding small amounts of In (0.2-1.2 pct) to GaAs grown by molecular beam epitaxy. The density of four electron traps decreases in concentration by an order of magnitude, and the peak intensities of prominent emissions in the excitonic spectra are reduced with increase in In content. Based on the higher surface migration rate of In, compared to Ga, at the growth temperatures it is apparent that the traps and the excitonic transitions are related to point defects. This agrees with earlier observations by Briones and Collins (1982) and Skromme et al. (1985).

  4. Molecular mechanism of monodisperse colloidal tin-doped indium oxide nanocrystals by a hot-injection approach

    PubMed Central

    2013-01-01

    Molecular mechanisms and precursor conversion pathways associated with the reactions that generate colloidal nanocrystals are crucial for the development of rational synthetic protocols. In this study, Fourier transform infrared spectroscopy technique was employed to explore the molecular mechanism associated with the formation of tin-doped indium oxide (ITO) nanocrystals. We found that the reaction pathways of the indium precursor were not consistent with simple ligand replacements proposed in the literature. The resulting understanding inspired us to design a hot-injection approach to separate the ligand replacements of indium acetate and the aminolysis processes, generating quality ITO nanocrystals with decent size distributions. The hot-injection approach was readily applied to the synthesis of ITO nanocrystals with a broad range of tin doping. Structural, chemical, and optical analyses revealed effective doping of Sn4+ ions into the host lattices, leading to characteristic and tunable near-infrared surface plasmon resonance peaks. The size control of ITO nanocrystals by multiple hot-injections of metal precursors was also demonstrated. PMID:23547801

  5. Organic solution-processible electroluminescent molecular glasses for non-doped standard red OLEDs with electrically stable chromaticity

    SciTech Connect

    Bi, Xiaoman; Zuo, Weiwei; Liu, Yingliang Zhang, Zhenru; Zeng, Cen; Xu, Shengang; Cao, Shaokui

    2015-10-15

    Highlights: • The D–A–D electroluminescent molecular glasses are synthesized. • Non-doped red electroluminescent film is fabricated by spin-coating. • Red OLED shows stable wavelength, luminous efficiency and chromaticity. • CIE1931 coordinate is in accord with standard red light in PAL system. - Abstract: Organic light-emitting molecular glasses (OEMGs) are synthesized through the introduction of nonplanar donor and branched aliphatic chain into electroluminescent emitters. The target OEMGs are characterized by {sup 1}H NMR, {sup 13}C NMR, IR, UV–vis and fluorescent spectra as well as elemental analysis, TG and DSC. The results indicated that the optical, electrochemical and electroluminescent properties of OEMGs are adjusted successfully by the replacement of electron-donating group. The non-doped OLED device with a standard red electroluminescent emission is achieved by spin-coating the THF solution of OEMG with a triphenylamine moiety. This non-doped red OLED device takes on an electrically stable electroluminescent performance, including the stable maximum electroluminescent wavelength of 640 nm, the stable luminous efficiency of 2.4 cd/A and the stable CIE1931 coordinate of (x, y) = (0.64, 0.35), which is basically in accord with the CIE1931 coordinate (x, y) = (0.64, 0.33) of standard red light in PAL system.

  6. Realization of Cu-Doped p-Type ZnO Thin Films by Molecular Beam Epitaxy.

    PubMed

    Suja, Mohammad; Bashar, Sunayna B; Morshed, Muhammad M; Liu, Jianlin

    2015-04-29

    Cu-doped p-type ZnO films are grown on c-sapphire substrates by plasma-assisted molecular beam epitaxy. Photoluminescence (PL) experiments reveal a shallow acceptor state at 0.15 eV above the valence band edge. Hall effect results indicate that a growth condition window is found for the formation of p-type ZnO thin films, and the best conductivity is achieved with a high hole concentration of 1.54 × 10(18) cm(-3), a low resistivity of 0.6 Ω cm, and a moderate mobility of 6.65 cm(2) V(-1) s(-1) at room temperature. Metal oxide semiconductor capacitor devices have been fabricated on the Cu-doped ZnO films, and the characteristics of capacitance-voltage measurements demonstrate that the Cu-doped ZnO thin films under proper growth conditions are p-type. Seebeck measurements on these Cu-doped ZnO samples lead to positive Seebeck coefficients and further confirm the p-type conductivity. Other measurements such as X-ray diffraction, X-ray photoelectron, Raman, and absorption spectroscopies are also performed to elucidate the structural and optical characteristics of the Cu-doped p-type ZnO films. The p-type conductivity is explained to originate from Cu substitution of Zn with a valency of +1 state. However, all p-type samples are converted to n-type over time, which is mostly due to the carrier compensation from extrinsic defects of ZnO.

  7. Ultra-low resistance ohmic contacts to GaN with high Si doping concentrations grown by molecular beam epitaxy

    SciTech Connect

    Afroz Faria, Faiza; Guo Jia; Zhao Pei; Li Guowang; Kumar Kandaswamy, Prem; Wistey, Mark; Xing Huili; Jena, Debdeep

    2012-07-16

    Ti/Al/Ni/Au ohmic contacts were formed on heavily doped n{sup +} metal-polar GaN samples with various Si doping concentrations grown by molecular beam epitaxy. The contact resistivity (R{sub C}) and sheet resistance (R{sub sh}) as a function of corresponding GaN free carrier concentration (n) were measured. Very low R{sub C} values (<0.09 {Omega} mm) were obtained, with a minimum R{sub C} of 0.035 {Omega} mm on a sample with a room temperature carrier concentration of {approx}5 Multiplication-Sign 10{sup 19} cm{sup -3}. Based on the systematic study, the role of R{sub C} and R{sub sh} is discussed in the context of regrown n{sup +} GaN ohmic contacts for GaN based high electron mobility transistors.

  8. Fabrication and characterizations of nitrogen-doped BaSi2 epitaxial films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Xu, Zhihao; Deng, Tianguo; Takabe, Ryota; Toko, Kaoru; Suemasu, Takashi

    2017-08-01

    Nitrogen doped BaSi2 layers are grown on high-resistivity n-Si (1 1 1) substrates by molecular beam epitaxy using a radio-frequency nitrogen plasma. The nitrogen concentration measured by secondary ion mass spectrometry is homogeneous throughout the grown layers. The carrier concentration is measured by Hall measurement using the van der Pauw method. Nitrogen-doped BaSi2 shows n- or p-type conductivity, depending on the intensity of nitrogen plasma. The hole concentration is of the order of 1016-1017 cm-3 at room temperature. The acceptor level is estimated to be approximately 64 meV from the temperature dependence of hole concentration. The temperature dependence of resistivity is explained by variable-range hopping conduction in p-BaSi2. First-principle calculation suggests that the nitrogen atoms are most likely to occupy the interstitial site in BaSi2.

  9. Anomalous doping of a molecular crystal monitored with confocal fluorescence microscopy: Terrylene in a p-terphenyl crystal.

    PubMed

    Białkowska, Magda; Deperasińska, Irena; Makarewicz, Artur; Kozankiewicz, Bolesław

    2017-09-21

    Highly terrylene doped single crystals of p-terphenyl, obtained by co-sublimation of both components, showed bright spots in the confocal fluorescence images. Polarization of the fluorescence excitation spectra, blinking and bleaching, and saturation behavior allowed us to attribute them to single molecules of terrylene anomalously embedded between two neighbor layers of the host crystal, in the (a,b) plane. Such an orientation of terrylene molecules results in much more efficient absorption and collection of the fluorescence photons than in the case of previously investigated molecules embedded in the substitution sites. The above conclusion was supported by quantum chemistry calculations. We postulate that the kind of doping considered in this work should be possible in other molecular crystals where the host molecules are organized in a herringbone pattern.

  10. Antimony segregation and n-type doping in Si/Si(111) films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Yurasov, D. V.; Drozdov, M. N.; Schmagin, V. B.; Yunin, P. A.; Novikov, A. V.

    2017-10-01

    The temperature dependence of antimony segregation in Si/Si(111) films grown by molecular-beam epitaxy was investigated experimentally. The obtained results were found to be qualitatively similar to the previously reported data for Si(001) case, but rather significant quantitative differences were observed. It was obtained that segregation ratio, which is defined as surface-to-bulk impurity concentration ratio, varies by nearly 5 orders of magnitude in the relatively narrow temperature interval of 500-675 °C for Si(111). This finding allowed to disseminate the previously proposed technique of selective doping of Si(001) to the Si(111) case. Using this technique selectively n-type doped Si films were fabricated which have abrupt boundaries of the antimony concentration profiles. A profile abruptness as low as 1.5 nm/decade was obtained.

  11. Photoluminescence study of Sb-doped p-type ZnO films by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Xiu, F. X.; Yang, Z.; Mandalapu, L. J.; Zhao, D. T.; Liu, J. L.

    2005-12-01

    We investigated photoluminescence (PL) from reliable and reproducible Sb-doped p-type ZnO films grown on n-Si (100) by molecular-beam epitaxy. Well-resolved PL spectra were obtained from completely dopant-activated samples with hole concentrations above 1.0×1018cm-3. From free electron to acceptor transitions, acceptor binding energy of 0.14 eV is determined, which is in good agreement with analytical results of the temperature-dependent PL measurements. Another broad peak at 3.050 eV, which shifts to lower energy at higher temperatures, indicates the formation of deep acceptor level bands related to Zn vacancies, which are created by Sb doping.

  12. Nanoclusters of CaSe in calcium-doped Bi2Se3 grown by molecular-beam epitaxy.

    PubMed

    Shang, Panju; Guo, Xin; Zhao, Bao; Dai, Xianqi; Bin, Li; Jia, Jinfeng; Li, Quan; Xie, Maohai

    2016-02-26

    In calcium (Ca) doped Bi2Se3 films grown by molecular beam epitaxy, nanoclusters of CaSe are revealed by high-angle annular dark field imaging and energy dispersive x-ray spectroscopy analysis using a scanning transmission electron microscope. As the interface between the ordinary insulator CaSe and topological insulator, Bi2Se3, can host topological nontrivial interface state, this represents an interesting material system for further studies. We show by first principles total energy calculations that aggregation of Ca atoms in Bi2Se3 is driven by energy minimization and a preferential intercalation of Ca in the van der Waals gap between quintuple layers of Bi2Se3 induces reordering of atomic stacking and causes an increasing amount of stacking faults in film. The above findings also provide an explanation of less-than-expected electrical carrier (hole) concentrations in Ca-doped samples.

  13. Molecular beam epitaxial growth of intermediate-band materials based on GaAs:N δ-doped superlattices

    NASA Astrophysics Data System (ADS)

    Suzuki, Tomoya; Osada, Kazuki; Yagi, Shuhei; Naitoh, Shunya; Shoji, Yasushi; Hijikata, Yasuto; Okada, Yoshitaka; Yaguchi, Hiroyuki

    2015-08-01

    We fabricated GaAs:N δ-doped superlattices (SLs) by molecular beam epitaxy and investigated their potential as an intermediate-band photoabsorber in high-efficiency solar cells. The N area concentration in a N δ-doped layer was well controlled by adjusting the fabrication conditions, and the SLs with the average N composition of up to 1.5% were obtained. The SL minibands related to the N-induced E+ and E- conduction subbands were formed with well-separated bottom energies of up to 0.4 eV, indicating the suitability of this material system for use in intermediate-band solar cells. A two-step photoabsorption process in a solar cell with the SL absorber was successfully demonstrated through external quantum efficiency measurements under additional infrared illumination at room temperature.

  14. Ge doping of β-Ga2O3 films grown by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Ahmadi, Elaheh; Koksaldi, Onur S.; Kaun, Stephen W.; Oshima, Yuichi; Short, Dane B.; Mishra, Umesh K.; Speck, James S.

    2017-04-01

    The Ge doping of β-Ga2O3(010) films was investigated using plasma-assisted molecular beam epitaxy as the growth method. The dependences of the amount of Ge incorporated on the substrate temperature, Ge-cell temperature, and growth regime were studied by secondary ion mass spectrometry. The electron concentration and mobility were investigated using Van der Pauw Hall patterns. Hall measurement confirmed that Ge acts as an n-dopant in β-Ga2O3(010) films. These results were compared with similar films doped by Sn. The Hall data showed an improved electron mobility for the same electron concentration when Ge is used instead of Sn as the dopant.

  15. Elemental boron-doped p(+)-SiGe layers grown by molecular beam epitaxy for infrared detector applications

    NASA Astrophysics Data System (ADS)

    Lin, T. L.; George, T.; Jones, E. W.; Ksendzov, A.; Huberman, M. L.

    1992-01-01

    SiGe/Si heterojunction internal photoemission (HIP) detectors have been fabricated utilizing molecular beam epitaxy of p(+)-SiGe layers on p(-)-Si substrates. Elemental boron from a high-temperature effusion cell was used as the dopant source during MBE growth, and high doping concentrations have been achieved. Strong infrared absorption, mainly by free-carrier absorption, was observed for the degenerately doped SiGe layers. The use of elemental boron as the dopant source allows a low MBE growth temperature, resulting in improved crystalline quality and smooth surface morphology of the Si(0.7)Ge(0.3) layers. Nearly ideal thermionic emission dark current characteristics have been obtained. Photoresponse of the HIP detectors in the long-wavelength infrared regime has been demonstrated.

  16. Elemental boron-doped p(+)-SiGe layers grown by molecular beam epitaxy for infrared detector applications

    NASA Technical Reports Server (NTRS)

    Lin, T. L.; George, T.; Jones, E. W.; Ksendzov, A.; Huberman, M. L.

    1992-01-01

    SiGe/Si heterojunction internal photoemission (HIP) detectors have been fabricated utilizing molecular beam epitaxy of p(+)-SiGe layers on p(-)-Si substrates. Elemental boron from a high-temperature effusion cell was used as the dopant source during MBE growth, and high doping concentrations have been achieved. Strong infrared absorption, mainly by free-carrier absorption, was observed for the degenerately doped SiGe layers. The use of elemental boron as the dopant source allows a low MBE growth temperature, resulting in improved crystalline quality and smooth surface morphology of the Si(0.7)Ge(0.3) layers. Nearly ideal thermionic emission dark current characteristics have been obtained. Photoresponse of the HIP detectors in the long-wavelength infrared regime has been demonstrated.

  17. Anomalous doping of a molecular crystal monitored with confocal fluorescence microscopy: Terrylene in a p-terphenyl crystal

    NASA Astrophysics Data System (ADS)

    Białkowska, Magda; Deperasińska, Irena; Makarewicz, Artur; Kozankiewicz, Bolesław

    2017-09-01

    Highly terrylene doped single crystals of p-terphenyl, obtained by co-sublimation of both components, showed bright spots in the confocal fluorescence images. Polarization of the fluorescence excitation spectra, blinking and bleaching, and saturation behavior allowed us to attribute them to single molecules of terrylene anomalously embedded between two neighbor layers of the host crystal, in the (a,b) plane. Such an orientation of terrylene molecules results in much more efficient absorption and collection of the fluorescence photons than in the case of previously investigated molecules embedded in the substitution sites. The above conclusion was supported by quantum chemistry calculations. We postulate that the kind of doping considered in this work should be possible in other molecular crystals where the host molecules are organized in a herringbone pattern.

  18. [Advances in the study of natural small molecular antibody].

    PubMed

    Zhu, Lei; Zhang, Da-peng

    2012-10-01

    Small molecule antibodies are naturally existed and well functioned but not structurally related to the conventional antibodies. They are only composed of heavy protein chains or light chains, much smaller than common antibody. The first small molecule antibody, called Nanobody was engineered from heavy-chain antibodies found in camelids. Cartilaginous fishes also have heavy-chain antibodies (IgNAR, "immunoglobulin new antigen receptor"), from which single-domain antibodies called Vnar fragments can be obtained. In addition, free light chain (FLC) antibodies in human bodies are being developed as therapeutic and diagnostic agents. Comparing to intact antibodies, common advantages of small molecule antibodies are with better solubility, tissue penetration, stability towards heat and enzymes, and comparatively low production costs. This article reviews the structural characteristics and mechanism of action of the Nanobody, IgNAR and FLC.

  19. Fast synthesis and bioconjugation of (68) Ga core-doped extremely small iron oxide nanoparticles for PET/MR imaging.

    PubMed

    Pellico, Juan; Ruiz-Cabello, Jesús; Saiz-Alía, Marina; Del Rosario, Gilberto; Caja, Sergio; Montoya, María; Fernández de Manuel, Laura; Morales, M Puerto; Gutiérrez, Lucia; Galiana, Beatriz; Enríquez, Jose A; Herranz, Fernando

    2016-05-01

    Combination of complementary imaging techniques, like hybrid PET/MRI, allows protocols to be developed that exploit the best features of both. In order to get the best of these combinations the use of dual probes is highly desirable. On this sense the combination of biocompatible iron oxide nanoparticles and 68Ga isotope is a powerful development for the new generation of hybrid systems and multimodality approaches. Our objective was the synthesis and application of a chelator-free 68Ga-iron oxide nanotracer with improved stability, radiolabeling yield and in vivo performance in dual PET/MRI. We carried out the core doping of iron oxide nanoparticles, without the use of any chelator, by a microwave-driven protocol. The synthesis allowed the production of extremely small (2.5 nm) 68Ga core-doped iron oxide nanoparticles. The microwave approach allowed an extremely fast synthesis with a 90% radiolabeling yield and T1 contrast in MRI. With the same microwave approach the nano-radiotracer was functionalized in a fast and efficient way. We finally evaluated these dual targeting nanoparticles in an angiogenesis murine model by PET/MR imaging. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  20. Influence of Cr doping on the stability and structure of small cobalt oxide clusters

    SciTech Connect

    Tung, Nguyen Thanh; Lievens, Peter; Janssens, Ewald; Tam, Nguyen Minh; Nguyen, Minh Tho

    2014-07-28

    The stability of mass-selected pure cobalt oxide and chromium doped cobalt oxide cluster cations, Co{sub n}O{sub m}{sup +} and Co{sub n−1}CrO{sub m}{sup +} (n = 2, 3; m = 2–6 and n = 4; m = 3–8), has been investigated using photodissociation mass spectrometry. Oxygen-rich Co{sub n}O{sub m}{sup +} clusters (m ⩾ n + 1 for n = 2, 4 and m ⩾ n + 2 for n = 3) prefer to photodissociate via the loss of an oxygen molecule, whereas oxygen poorer clusters favor the evaporation of oxygen atoms. Substituting a single Co atom by a single Cr atom alters the dissociation behavior. All investigated Co{sub n−1}CrO{sub m}{sup +} clusters, except CoCrO{sub 2}{sup +} and CoCrO{sub 3}{sup +}, prefer to decay by eliminating a neutral oxygen molecule. Co{sub 2}O{sub 2}{sup +}, Co{sub 4}O{sub 3}{sup +}, Co{sub 4}O{sub 4}{sup +}, and CoCrO{sub 2}{sup +} are found to be relatively difficult to dissociate and appear as fragmentation product of several larger clusters, suggesting that they are particularly stable. The geometric structures of pure and Cr doped cobalt oxide species are studied using density functional theory calculations. Dissociation energies for different evaporation channels are calculated and compared with the experimental observations. The influence of the dopant atom on the structure and the stability of the clusters is discussed.

  1. Solid-state tellurium doping of AlInP and its application to photovoltaic devices grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Dai, P.; Tan, M.; Wu, Y. Y.; Ji, L.; Bian, L. F.; Lu, S. L.; Yang, H.

    2015-03-01

    Solid-state tellurium (Te) is used as an n-type dopant of AlInP grown by molecular beam epitaxy (MBE). The carrier concentration proportionally increases with increasing Te beam equivalent pressure (BEP) up to a high doping density of 1×1019 cm-3. The incorporation of Te into AlInP results in a mirror-like surface at a moderate doping density due to its surfactant effect, while the surface roughness increased with a further rising of Te doping concentration. Furthermore, for the same In and Al flux ratio, the increase of the Te flux leads to a decreased In-content, but little effect on the alloy's disorder is observed. The highly Te-doped AlInP was used in a GaAs solar cell as a window layer. As compared with the solar cell with the Si-doped AlInP window layer, the device with the Te-doped AlInP window layer exhibits the higher efficiency and an extended increase under concentrated solar illumination, due to the benefits of the higher doping density in the Te-doped epilayer.

  2. Small interfering RNA-based molecular therapy of cancers

    PubMed Central

    Guo, Wei; Chen, Wangbing; Yu, Wendan; Huang, Wenlin; Deng, Wuguo

    2013-01-01

    RNA interference (RNAi) has become a gold standard for validating gene function in basic life science research and provides a promising therapeutic modality for cancer and other diseases. This mini-review focuses on the potential of small interfering RNAs (siRNAs) in anticancer treatment, including the establishment and screening of cancer-associated siRNA libraries and their applications in anticancer drug target discovery and cancer therapy. This article also describes the current delivery approaches of siRNAs using lipids, polymers, and, in particular, gold nanoparticles to induce significant gene silencing and tumor growth regression. PMID:23327796

  3. Conformational Changes of Doped Polyaniline as Characterized by Small-Angle Neutron Scattering (SANS)

    DTIC Science & Technology

    2007-11-02

    analyze the weight average molecular weight, Mw, radius of gyration, Rg, and the second virial coefficient , A2. The conformation of polyaniline was...an expanded conformation and allowed for an increase in the second virial coefficient .

  4. Influence of annealing conditions on impurity species in arsenic-doped HgCdTe grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Yue, Fang-Yu; Chen, Lu; Li, Ya-Wei; Hu, Zhi-Gao; Sun, Lin; Yang, Ping-Xiong; Chu, Jun-Hao

    2010-11-01

    Based on our previous work, the influence of annealing conditions on impurity species in in-situ arsenic (As)-doped Hg1-xCdxTe (x approx 0.3) grown by molecular beam epitaxy has been systematically investigated by modulated photoluminescence spectra. The results show that (i) the doped-As acting as undesirable shallow/deep levels in as-grown can be optimized under proper annealing conditions and the physical mechanism of the disadvantage of high activation temperature, commonly assumed to be more favourable for As activation, has been discussed as compared with the reports in the As-implanted HgCdTe epilayers (x approx 0.39), (ii) the density of VHg has an evident effect on the determination of bandgap (or composition) of epilayers and the excessive introduction of VHg will lead to a short-wavelength shift of epilayers, and (iii) the VHg prefers forming the VHg-AsHg complex when the inactivated-As (AsHg or related) coexists in a certain density, which makes it difficult to annihilate VHg in As-doped epilayers. As a result, the bandedge electronic structures of epilayers under different conditions have been drawn as a brief guideline for preparing extrinsic p-type epilayers or related devices.

  5. High-mobility Sb-doped p-type ZnO by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Xiu, F. X.; Yang, Z.; Mandalapu, L. J.; Zhao, D. T.; Liu, J. L.; Beyermann, W. P.

    2005-10-01

    Reproducible Sb-doped p-type ZnO films were grown on n-Si (100) by electron-cyclotron-resonance-assisted molecular-beam epitaxy. The existence of Sb in ZnO:Sb films was confirmed by low-temperature photoluminescence measurements. An acceptor-bound exciton (A °X) emission was observed at 3.358 eV at 8 K. The acceptor energy level of the Sb dopant is estimated to be 0.2 eV above the valence band. Temperature-dependent Hall measurements were performed on Sb-doped ZnO films. At room temperature, one Sb-doped ZnO sample exhibited a low resistivity of 0.2Ωcm, high hole concentration of 1.7×1018cm-3 and high mobility of 20.0cm2/Vs. This study suggests that Sb is an excellent dopant for reliable and reproducible p-type ZnO fabrication.

  6. Effects of excitation energy on the autodetachment lifetimes of small iodide-doped ROH clusters (R═H-, CH3-, CH3CH(2)-).

    PubMed

    Yandell, Margaret A; Young, Ryan M; King, Sarah B; Neumark, Daniel M

    2012-03-22

    The effect of excitation energy on the lifetimes of the charge-transfer-to-solvent (CTTS) states of small (4 ≤ n ≤ 10) iodide-doped water and alcohol clusters was explored using femtosecond time-resolved photoelectron imaging. Excitation of the CTTS state at wavelengths ranging from 272 to 238 nm leads to the formation of the I···(ROH)(n)(-) (R═H-, CH(3)-, and CH(3)CH(2)-) species, which can be thought of as a vibrationally excited bare solvent cluster anion perturbed by an iodine atom. Autodetachment lifetimes for alcohol-containing clusters range from 1 to 71 ps, while water clusters survive for hundreds of ps in this size range. Autodetachment lifetimes were observed to decrease significantly with increasing excitation energy for a particular number and type of solvent molecules. The application of Klots' model for thermionic emission from clusters to I(-)(H(2)O)(5) and I(-)(CH(3)OH)(7) qualitatively reproduces experimental trends and reveals a high sensitivity to energy parametrization while remaining relatively insensitive to the number of vibrational modes. Experimental and computational results therefore suggest that the rate of electron emission is primarily determined by the energetics of the cluster system rather than by details of molecular structure. © 2011 American Chemical Society

  7. First molecular detection and characterization of Akabane virus in small ruminants in Turkey.

    PubMed

    Oğuzoğlu, T Ç; Toplu, N; Koç, B T; Doğan, F; Epikmen, E T; İpek, E; Akkoç, A N

    2015-10-01

    Abortion outbreaks associated with congenital malformations in two distinct small-ruminant flocks were reported in Turkey in 2013-2014. This paper describes the first molecular characterization of Turkish Akabane virus strains in small-ruminant flocks using partial sequence analysis of the S segment and pathological findings.

  8. High-Energy Molecular Beam Source Using a Small Shock Tube: Evaluation of Convergent Type Design

    SciTech Connect

    Yoshimoto, Y.; Miyoshi, N.; Kinefuchi, I.; Takagi, S.; Matsumoto, Y.; Shimizu, K.

    2011-05-20

    Molecular beam source using a small shock tube has the potential to frequently generate high energy molecular beam in a range of 1-5 eV without any undesirable impurities. We measured shock Mach numbers in 2 and 4-mm-diameter straight tubes to know about the propagation of shock wave in a very small shock tube. In addition, we measured shock Mach numbers in convergent shock tubes of which diameters linearly decrease from 4 mm to 2 mm, which demonstrated the possibility of a convergent shock tube to generate higher energy molecular beam than straight one.

  9. Improved understanding and control of magnesium-doped gallium nitride by plasma assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Burnham, Shawn D.

    By an improved understanding of Mg-doped GaN through an exhaustive review of current limitations, increased control over the material was achieved by addressing several of these issues. To address the issues of the memory effect, low sticking coefficient and high vapor pressure of Mg, a new Mg dopant source was implemented, characterized and modeled for p-type doping of GaN. The device enhanced the sticking coefficient of Mg by energizing the outgoing Mg flux, and also allowed the first reported demonstration of an abrupt junction between two non-zero Mg concentrations and a graded Mg-doped GaN film. The significant compensation of Mg acceptors at high dopant concentrations was used advantageously to develop a new ex situ resistivity analysis technique using the energy distributions of SIMS to characterize doping of buried layers. The new technique was used to identify the barrier between conductive and resistive Mg doping for increased Mg concentration, which was then used to optimize Mg-doped GaN. Because Mg doping exhibits a dependence upon the growth regime, a new growth and regime characterization technique was developed using specific RHEED intensity responses to repeat growth conditions. During the development of this technique, a new surface kinetics growth model for III-nitrides was discovered based on DMS observations, which suggests preferential buildup of the metal bilayer before growth begins with an unfamiliar cation-anion exchange process initially upon metal shutter opening. Using the new RHEED growth and regime characterization technique, a new growth technique called metal modulated epitaxy (MME) was developed to increase repeatability, uniformity and smoothness. The MME technique was enhanced with a closed-loop control using real-time feedback from RHEED transients to control shutter transitions. This enhancement, called "smart shuttering," led to improved growth rate and further improvement of surface roughness and grain size, which were

  10. Upconversion fluorescence imaging of cells and small animals using lanthanide doped nanocrystals.

    PubMed

    Chatterjee, Dev K; Rufaihah, Abdul J; Zhang, Yong

    2008-03-01

    Upconversion fluorescence imaging technique with excitation in the near-infrared (NIR) region has been used for imaging of biological cells and tissues. This has several advantages, including absence of photo-damage to living organisms, very low auto-fluorescence, high detection sensitivity, and high light penetration depth in biological tissues. In this report we demonstrate the use of a new upconversion fluorophore, lanthanide doped nanocrystals, for imaging of cells and some deep tissues in animal. Polyethyleneimine (PEI) coated NaYF(4):Yb,Er nanoparticles were synthesized, which produce very strong upconversion fluorescence when excited at 980 nm by a NIR laser. The nanoparticles were shown to be stable in physiologic buffered saline (PBS), non-toxic to bone marrow stem cells, and resistant to photo-bleaching. The nanoparticles delivered into some cell lines or injected intradermally and intramuscularly into some tissues either near the body surface or deep in the body of rats showed visible fluorescence, when exposed to a 980 nm NIR laser. To the best of our knowledge, this represents the first demonstration of use of upconversion fluorophores for cellular and tissue imaging.

  11. Polar Side Chains Enhance Processability, Electrical Conductivity, and Thermal Stability of a Molecularly p-Doped Polythiophene.

    PubMed

    Kroon, Renee; Kiefer, David; Stegerer, Dominik; Yu, Liyang; Sommer, Michael; Müller, Christian

    2017-06-01

    Molecular doping of organic semiconductors is critical for optimizing a range of optoelectronic devices such as field-effect transistors, solar cells, and thermoelectric generators. However, many dopant:polymer pairs suffer from poor solubility in common organic solvents, which leads to a suboptimal solid-state nanostructure and hence low electrical conductivity. A further drawback is the poor thermal stability through sublimation of the dopant. The use of oligo ethylene glycol side chains is demonstrated to significantly improve the processability of the conjugated polymer p(g4 2T-T)-a polythiophene-in polar aprotic solvents, which facilitates coprocessing of dopant:polymer pairs from the same solution at room temperature. The use of common molecular dopants such as 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is explored. Doping of p(g4 2T-T) with F4TCNQ results in an electrical conductivity of up to 100 S cm(-1) . Moreover, the increased compatibility of the polar dopant F4TCNQ with the oligo ethylene glycol functionalized polythiophene results in a high degree of thermal stability at up to 150 °C. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Nitrogen-doped graphene: beyond single substitution and enhanced molecular sensing

    PubMed Central

    Lv, Ruitao; Li, Qing; Botello-Méndez, Andrés R.; Hayashi, Takuya; Wang, Bei; Berkdemir, Ayse; Hao, Qingzhen; Elías, Ana Laura; Cruz-Silva, Rodolfo; Gutiérrez, Humberto R.; Kim, Yoong Ahm; Muramatsu, Hiroyuki; Zhu, Jun; Endo, Morinobu; Terrones, Humberto; Charlier, Jean-Christophe; Pan, Minghu; Terrones, Mauricio

    2012-01-01

    Graphene is a two-dimensional network in which sp2-hybridized carbon atoms are arranged in two different triangular sub-lattices (A and B). By incorporating nitrogen atoms into graphene, its physico-chemical properties could be significantly altered depending on the doping configuration within the sub-lattices. Here, we describe the synthesis of large-area, highly-crystalline monolayer N-doped graphene (NG) sheets via atmospheric-pressure chemical vapor deposition, yielding a unique N-doping site composed of two quasi-adjacent substitutional nitrogen atoms within the same graphene sub-lattice (N2AA). Scanning tunneling microscopy and spectroscopy (STM and STS) of NG revealed the presence of localized states in the conduction band induced by N2AA-doping, which was confirmed by ab initio calculations. Furthermore, we demonstrated for the first time that NG could be used to efficiently probe organic molecules via a highly improved graphene enhanced Raman scattering. PMID:22905317

  13. Molecular doping of MoS2 transistors by self-assembled oleylamine networks

    NASA Astrophysics Data System (ADS)

    Lockhart de la Rosa, César J.; Phillipson, Roald; Teyssandier, Joan; Adisoejoso, Jinne; Balaji, Yashwanth; Huyghebaert, Cedric; Radu, Iuliana; Heyns, Marc; De Feyter, Steven; De Gendt, Stefan

    2016-12-01

    Thin MoS2 films continue to be of key interest for numerous applications; however, effective doping and high metal to MoS2 contact resistance are challenges for future applications. We report on the self-assembly of oleylamine on top of MoS2 thin-films and the effective doping of MoS2 thin-film field effect transistors by oleylamine. Atomic force microscopy revealed that oleylamine organizes in lamellae domains on MoS2 thin films with similar characteristics of those previously observed on highly ordered pyrolytic graphite. A carrier concentration increase from 7.1 × 1011 cm-2 up to 1.9 × 1013 cm-2 at 0 V gate voltage is achieved together with a reduction of the contact resistance by a factor of 5 when using gold as metal contact. Furthermore, this non-covalent doping proves to be removable and reproducible among different flakes and does not degrade the electron mobility. Thus, this work opens the path for future works on controlling the doping of MoS2 by proper selection of the self-assembled species.

  14. A density functional study of small sized silver-doped silicon clusters: Ag2Sin (n = 1-13)

    NASA Astrophysics Data System (ADS)

    Yang, Cai; Hao Jia, Song; Ma, Mao Fen; Zhang, Shuai; Lu, Cheng; Li, Gen Quan

    2015-11-01

    The structures and electronic properties for global minimum geometric structures of small-sized neutral Ag2Sin (n = 1-13) clusters have been investigated using the CALYPSO structure searching method coupled with density functional theory calculations. A great deal of low-energy geometric isomers are optimised at the B3LYP / GENECP theory level. The optimised structures suggest that the ground state Ag2Sin clusters are visibly distorted compared with the corresponding pure silicon clusters and favor a three-dimensional configuration. Starting with Ag2Si12, one Ag atom is fully encapsulated by the Si outer cages. Based on the averaged binding energy, fragmentation energy, second-order energy difference and HOMO-LUMO energy gap, it is seen that Ag2Si2 and Ag2Si5 are tested to be the most stable clusters, and the chemical stabilities of pure Sin+2 clusters can be reduced to some extent after doping two Ag atoms. Additionally, natural population and natural electronic configuration are discussed and the results reveal that charges transfer from the Ag atoms to the silicon frames and the spd hybridisations are present in all Ag2Sin clusters. Lastly, the results of natural bonds show that the Ag-Si bond in Ag2Sin clusters is dominated by small ionic character. Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2015-60404-1

  15. Molecular statistical theory of small bodies and their thermophysical and thermodynamic characteristics

    NASA Astrophysics Data System (ADS)

    Tovbin, Yu. K.

    2015-03-01

    The constraints of classical thermodynamics on analyzing nanosized objects are considered. It is shown that it is essential to separate the thermodynamic concepts of a cluster and a drop. Using the lattice gas model, a molecular statistical theory of small multicomponent mixtures is developed that considers inter-particle interactions in several coordination spheres and the effects of size equilibrium fluctuations. Kinetic equations describing the particle redistribution dynamics inside small bodies and the problems of allowing for size fluctuations in them are discussed. The principles of the molecular statistical theory are compared to results from applying molecular dynamics to modeling the states of small clusters and the surface states of metal atoms during their adsorption and diffusion on graphene.

  16. Correlated electron-hole mechanism for molecular doping in organic semiconductors

    NASA Astrophysics Data System (ADS)

    Li, Jing; D'Avino, Gabriele; Pershin, Anton; Jacquemin, Denis; Duchemin, Ivan; Beljonne, David; Blase, Xavier

    2017-07-01

    The electronic and optical properties of the paradigmatic F4TCNQ-doped pentacene in the low-doping limit are investigated by a combination of state-of-the-art many-body ab initio methods accounting for environmental screening effects, and a carefully parametrized model Hamiltonian. We demonstrate that while the acceptor level lies very deep in the gap, the inclusion of electron-hole interactions strongly stabilizes dopant-semiconductor charge transfer states and, together with spin statistics and structural relaxation effects, rationalize the possibility for room-temperature dopant ionization. Our findings reconcile available experimental data, shedding light on the partial vs. full charge transfer scenario discussed in the literature, and question the relevance of the standard classification in shallow or deep impurity levels prevailing for inorganic semiconductors.

  17. Density of states determination in organic donor-acceptor blend layers enabled by molecular doping

    NASA Astrophysics Data System (ADS)

    Fischer, Janine; Ray, Debdutta; Kleemann, Hans; Pahner, Paul; Schwarze, Martin; Koerner, Christian; Vandewal, Koen; Leo, Karl

    2015-06-01

    Charge carrier transport is a key parameter determining the efficiency of organic solar cells, and is closely related to the density of free and trapped states. For trap characterization, impedance spectroscopy is a suitable, non-invasive method, applicable to complete organic semiconductor devices. In order to contribute to the capacitive signal, the traps must be filled with charge carriers. Typically, trap filling is achieved by illuminating the device or by injecting charge carriers through application of a forward bias voltage. However, in both cases, the exact number of charge carriers in the device is not known and depends strongly on the measurement conditions. Here, hole trap states of the model blend layer ZnPc:C60 are filled by weak p-doping, enabling trap characterization in a blend layer at a controlled hole density. We evaluate impedance spectra at different temperatures in order to determine the density of occupied states (DOOS) directly from the capacitance-frequency spectra by assuming a simple energy diagram. The reconstructed DOOS distribution is analyzed at different doping concentrations and device thicknesses and compared to thermally stimulated current measurements performed on the same devices. In both methods, a pronounced Gaussian peak at about 0.4 eV below the transport level is found as well as deep, exponential tail states, providing a deeper insight into the density of states distribution of this donor-acceptor blend layer. Additionally, the effect of doping-induced trap filling on the solar cell characteristics is studied in these devices.

  18. Multisource Synergistic Electrocatalytic Oxidation Effect of Strongly Coupled PdM (M = Sn, Pb)/N-doped Graphene Nanocomposite on Small Organic Molecules

    PubMed Central

    Wu, Peng; Huang, Yiyin; Kang, Longtian; Wu, Maoxiang; Wang, Yaobing

    2015-01-01

    A series of palladium-based catalysts of metal alloying (Sn, Pb) and/or (N-doped) graphene support with regular enhanced electrocatalytic activity were investigated. The peak current density (118.05 mA cm−2) of PdSn/NG is higher than the sum current density (45.63 + 47.59 mA cm−2) of Pd/NG and PdSn/G. It reveals a synergistic electrocatalytic oxidation effect in PdSn/N-doped graphene Nanocomposite. Extend experiments show this multisource synergetic catalytic effect of metal alloying and N-doped graphene support in one catalyst on small organic molecule (methanol, ethanol and Ethylene glycol) oxidation is universal in PdM(M = Sn, Pb)/NG catalysts. Further, The high dispersion of small nanoparticles, the altered electron structure and Pd(0)/Pd(II) ratio of Pd in catalysts induced by strong coupled the metal alloying and N-doped graphene are responsible for the multisource synergistic catalytic effect in PdM(M = Sn, Pb) /NG catalysts. Finally, the catalytic durability and stability are also greatly improved. PMID:26434949

  19. Current and future molecular diagnostics in non-small-cell lung cancer.

    PubMed

    Li, Chun Man; Chu, Wing Ying; Wong, Di Lun; Tsang, Hin Fung; Tsui, Nancy Bo Yin; Chan, Charles Ming Lok; Xue, Vivian Wei Wen; Siu, Parco Ming Fai; Yung, Benjamin Yat Ming; Chan, Lawrence Wing Chi; Wong, Sze Chuen Cesar

    2015-01-01

    The molecular investigation of lung cancer has opened up an advanced area for the diagnosis and therapeutic management of lung cancer patients. Gene alterations in cancer initiation and progression provide not only information on molecular changes in lung cancer but also opportunities in advanced therapeutic regime by personalized targeted therapy. EGFR mutations and ALK rearrangement are important predictive biomarkers for the efficiency of tyrosine kinase inhibitor treatment in lung cancer patients. Moreover, epigenetic aberration and microRNA dysregulation are recent advances in the early detection and monitoring of lung cancer. Although a wide range of molecular tests are available, standardization and validation of assay protocols are essential for the quality of the test outcome. In this review, current and new advancements of molecular biomarkers for non-small-cell lung cancer will be discussed. Recommendations on future development of molecular diagnostic services will also be explored.

  20. Carrier Lifetimes of Iodine-Doped CdMgTe/CdSeTe Double Heterostructures Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Sohal, S.; Edirisooriya, M.; Ogedengbe, O. S.; Petersen, J. E.; Swartz, C. H.; LeBlanc, E. G.; Myers, T. H.; Li, J. V.; Holtz, M.

    2017-09-01

    Iodine-doped CdMgTe/CdSeTe double heterostructures (DHs) have been grown by molecular beam epitaxy and studied using time-resolved photoluminescence (PL), focusing on absorber layer thickness of 2 μm. The n-type free carrier concentration was varied to ˜7 × 1015 cm-3, 8.4 × 1016 cm-3, and 8.4 × 1017 cm-3 using iodine as dopant in DHs. Optical injection at 1 × 1010 photons/pulse/cm2 to 3 × 1011 photons/pulse/cm2, corresponding to initial injection of photocarriers up to ˜8 × 1015 cm-3, was applied to examine the effects of excess carrier concentration on the PL lifetimes. Iodine-doped DHs exhibited an initial rapid decay followed by a slower decay at free carrier concentration of 7 × 1015 cm-3 and 8.4 × 1016 cm-3. The optical injection dependence of the carrier lifetimes for DHs was interpreted based on the Shockley-Read-Hall model. The observed decrease in lifetime with increasing n is consistent with growing importance of radiative recombination.

  1. Ag/N-doped reduced graphene oxide incorporated with molecularly imprinted polymer: An advanced electrochemical sensing platform for salbutamol determination.

    PubMed

    Li, Junhua; Xu, Zhifeng; Liu, Mengqin; Deng, Peihong; Tang, Siping; Jiang, Jianbo; Feng, Haibo; Qian, Dong; He, Lingzhi

    2017-04-15

    In this work, the metallic silver and non-metallic nitrogen co-doped reduced graphene oxide (Ag-N-RGO) was first synthesized by a simple and cost-effective strategy, and then a molecularly imprinted polymer (MIP) was formed in situ at the surface of the prepared composite via electropolymerization of o-phenylenediamine in the presence of salbutamol as the template molecule. The electrochemical characterizations demonstrate that the bifunctional graphene-based composite shows improved catalytic performance than that of pristine graphene doped with one-component or none. The MIP sensor based on Ag-N-RGO owns high porous surface structure, resulting in the increased current response and enhanced recognition capacity than that of non-imprinted sensor. The outstanding performance of the developed sensor derives from the combined advantages of Ag-N-RGO with effective catalytic property and MIP with excellent selectivity. Under the optimal conditions, the electrochemical response of the developed sensor is linearly proportional to the concentration of salbutamol in the range of 0.03-20.00µmolL(-1) with a low detection limit of 7 nmol L(-1). The designed sensor has exhibited the multiple advantages such as low cost, simple manufacture, convenient use, excellent selectivity and good reproducibility. Finally, the proposed method has been extended for the determinations of salbutamol in human urine and pork samples, and the satisfactory recoveries between 98.9-105.3% are achieved. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. A urea electrochemical sensor based on molecularly imprinted chitosan film doping with CdS quantum dots.

    PubMed

    Lian, Hui-Ting; Liu, Bin; Chen, Yan-Ping; Sun, Xiang-Ying

    2012-07-01

    An improved imprinted film-based electrochemical sensor for urea recognition was developed using CdS quantum dots (QDs) doped chitosan as the functional matrix. The microstructure and composition of the imprinted films depicted by scanning electron microscopy (SEM), attenuated total reflection infrared (ATR-IR), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS) indicated the fabricated feasibility of the nanoparticle doped films via in situ electrodeposition. Differential pulse voltammetric responses under the optimal fabrication conditions showed that the sensitivity of CdS QDs-MIP (molecularly imprinted polymer) electrochemical sensor was enhanced from the favorable electron transfer and magnified surface area of CdS QDs with a short adsorption equilibrium time (7 min), wide linear range (5.0 × 10(-12) to 4.0 × 10(-10) M and 5.0 × 10(-10) to 7.0 × 10(-8) M), and low detection limit (1.0 × 10(-12) M). Meanwhile, the fabricated sensor showed excellent specific recognition to template molecule among the structural similarities and coexistence substances. Furthermore, the proposed sensor was applied to determine the urea in human blood serum samples based on its good reproducibility and stability, and the acceptable recovery implied its feasibility for practical application. Copyright © 2012 Elsevier Inc. All rights reserved.

  3. Amperometric detection of dopamine in human serum by electrochemical sensor based on gold nanoparticles doped molecularly imprinted polymers.

    PubMed

    Xue, Cheng; Han, Qing; Wang, Yang; Wu, Jinhua; Wen, Tingting; Wang, Ruoyu; Hong, Junli; Zhou, Xuemin; Jiang, Huijun

    2013-11-15

    In this work, a highly sensitive and selective biomimetic electrochemical sensor for the amperometric detection of trace dopamine (DA) in human serums was achieved by gold nanoparticles (AuNPs) doped molecularly imprinted polymers (MIPs). Functionalized AuNPs (F-AuNPs), a novel functional monomer bearing aniline moieties on the surface of the AuNPs, were prepared via a direct synthesis method and then used to fabricate the conductive MIPs film on the modified electrode by electropolymerization method in the presence of DA and p-aminobenzenethiol (p-ATP). The obtained electrochemical sensor based on the conductive film of AuNPs doped MIPs (AuNPs@MIPs) could effectively minimize the interferences caused by ascorbic acid (AA) and uric acid (UA). The linear range for amperometric detection of DA was from 0.02 μmol L(-1) to 0.54 μmol L(-1) with the detection limit of 7.8 nmol L(-1) (S/N=3). Furthermore, the AuNPs@MIPs modified electrode (AuNPs@MIES) was successfully employed to detect trace DA in different human serums.

  4. Atomic and Molecular Hydrogen Interaction with Ti-Doped Al (100): Hydrogen Dissociation and Surface Alane Formation

    NASA Astrophysics Data System (ADS)

    Muller, Erik; Sutter, Peter; Zahl, Percy; Chaudhuri, Santanu; Muckerman, James

    2006-03-01

    A comprehensive research effort on the atomistic mechanisms underlying hydrogen storage in Ti-doped NaAlH4 is aimed at deriving a knowledge base for the rational optimization of this and other related complex hydride materials. Our investigation focuses on the role of the Ti dopants in promoting reversible hydrogenation, a key requirement for any practical hydrogen storage material. The re-hydrogenation reaction proceeds from the crucial initial step of dissociative adsorption of molecular hydrogen on Al or NaH. A specific Al:Ti complex was recently predicted as an active site for H2 dissociation on extended Al(100) surfaces [1]. Combining high-resolution surface imaging experiments (scanning tunneling microscopy, low-energy electron microscopy) with density functional theory, we are investigating the dissociative adsorption of H2 on Ti-doped Al(100) prepared in ultrahigh vacuum. We will discuss our progress toward identifying catalytically active sites for H2 dissociation on this surface, as well as pathways toward the formation of mobile Al-species. [1] S. Chaudhuri and J.T. Muckerman, J. Phys. Chem. B 109, 6952 (2005).

  5. Importance of Molecular Features of Non–Small Cell Lung Cancer for Choice of Treatment

    PubMed Central

    Moran, Cesar

    2011-01-01

    Lung cancer is the leading cause of cancer-related deaths in the United States. Approximately 85% of lung cancer is categorized as non–small cell lung cancer, and traditionally, non–small cell lung cancer has been treated with surgery, radiation, and chemotherapy. Targeted agents that inhibit the epidermal growth factor receptor pathway have been developed and integrated into the treatment regimens in non–small cell lung cancer. Currently, approved epidermal growth factor receptor inhibitors include the tyrosine kinase inhibitors erlotinib and gefitinib. Molecular determinants, such as epidermal growth factor receptor–activating mutations, have been associated with response to epidermal growth factor receptor tyrosine kinase inhibitors and may be used to guide treatment choices in patients with non–small cell lung cancer. Thus, treatment choice for patients with non–small cell lung cancer depends on molecular features of tumors; however, improved techniques are required to increase the specificity and efficiency of molecular profiling so that these methods can be incorporated into routine clinical practice. This review provides an overview of how genetic analysis is currently used to direct treatment choices in non–small cell lung cancer. PMID:21514411

  6. Germanium doping of self-assembled GaN nanowires grown by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Schörmann, Jörg; Hille, Pascal; Schäfer, Markus; Müßener, Jan; Becker, Pascal; Klar, Peter J.; Hofmann, Detlev M.; Teubert, Jörg; Eickhoff, Martin; Kleine-Boymann, Matthias; Rohnke, Marcus; Mata, Maria de la; Arbiol, Jordi

    2013-09-14

    Germanium doping of GaN nanowires grown by plasma-assisted molecular beam epitaxy on Si(111) substrates is studied. Time of flight secondary ion mass spectrometry measurements reveal a constant Ge-concentration along the growth axis. A linear relationship between the applied Ge-flux and the resulting ensemble Ge-concentration with a maximum content of 3.3×10{sup 20} cm{sup −3} is extracted from energy dispersive X-ray spectroscopy measurements and confirmed by a systematic increase of the conductivity with Ge-concentration in single nanowire measurements. Photoluminescence analysis of nanowire ensembles and single nanowires reveals an exciton localization energy of 9.5 meV at the neutral Ge-donor. A Ge-related emission band at energies above 3.475 eV is found that is assigned to a Burstein-Moss shift of the excitonic emission.

  7. Germanium doping of self-assembled GaN nanowires grown by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Schörmann, Jörg; Hille, Pascal; Schäfer, Markus; Müßener, Jan; Becker, Pascal; Klar, Peter J.; Kleine-Boymann, Matthias; Rohnke, Marcus; de la Mata, Maria; Arbiol, Jordi; Hofmann, Detlev M.; Teubert, Jörg; Eickhoff, Martin

    2013-09-01

    Germanium doping of GaN nanowires grown by plasma-assisted molecular beam epitaxy on Si(111) substrates is studied. Time of flight secondary ion mass spectrometry measurements reveal a constant Ge-concentration along the growth axis. A linear relationship between the applied Ge-flux and the resulting ensemble Ge-concentration with a maximum content of 3.3×1020 cm-3 is extracted from energy dispersive X-ray spectroscopy measurements and confirmed by a systematic increase of the conductivity with Ge-concentration in single nanowire measurements. Photoluminescence analysis of nanowire ensembles and single nanowires reveals an exciton localization energy of 9.5 meV at the neutral Ge-donor. A Ge-related emission band at energies above 3.475 eV is found that is assigned to a Burstein-Moss shift of the excitonic emission.

  8. The Role of Super-Atom Molecular Orbitals in Doped Fullerenes in a Femtosecond Intense Laser Field

    DOE PAGES

    Xiong, Hui; Mignolet, Benoit; Fang, Li; ...

    2017-03-09

    The interaction of gas phase endohedral fullerene Ho3N@C80 with intense (0.1–5 × 1014 W/cm2), short (30 fs), 800 nm laser pulses was investigated. The power law dependence of Ho3N@C80 q+, q = 1–2, was found to be different from that of C60. Time-dependent density functional theory computations revealed different light-induced ionization mechanisms. Unlike in C60, in doped fullerenes, the breaking of the cage spherical symmetry makes super atomic molecular orbital (SAMO) states optically active. Theoretical calculations suggest that the fast ionization of the SAMO states in Ho3N@C80 is responsible for the n = 3 power law for singly charged parentmore » molecules at intensities lower than 1.2 × 1014 W/cm2.« less

  9. Polarity control and transport properties of Mg-doped (0001) InN by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Choi, Soojeong; Wu Feng; Bierwagen, Oliver; Speck, James S.

    2013-05-15

    The authors report on the plasma-assisted molecular beam epitaxy growth and carrier transport of Mg-doped In-face (0001) InN. The 1.2 {mu}m thick InN films were grown on GaN:Fe templates under metal rich conditions with Mg concentration from 1 Multiplication-Sign 10{sup 17}/cm{sup 3} to 3 Multiplication-Sign 10{sup 20}/cm{sup 3}. A morphological transition, associated with the formation of V-shape polarity inversion domains, was observed at Mg concentration over 7 Multiplication-Sign 10{sup 19}/cm{sup 3} by atomic force microscopy and transmission electron microscopy. Seebeck measurements indicated p-type conductivity for Mg-concentrations from 9 Multiplication-Sign 10{sup 17}/cm{sup 3} to 7 Multiplication-Sign 10{sup 19}/cm{sup 3}, i.e., as it exceeded the compensating (unintentional) donor concentration.

  10. Al- and Cu-doped BaSi2 films on Si(111) substrate by molecular beam epitaxy and evaluation of depth profiles of Al and Cu atoms

    NASA Astrophysics Data System (ADS)

    Ajmal Khan, M.; Takeishi, M.; Matsumoto, Y.; Saito, T.; Suemasu, T.

    The main objective of the present work is to evaluate and compare the depth profiles of Al and Cu atoms in in-situ doped BaSi2. Furthermore, it is also desired to investigate and compare the carrier concentration of Al-doped as well as Cu-doped BaSi2 films and qualify as a potential dopant-candidate for more efficient solar cells of BaSi2. During the experiment, reactive deposition epitaxy and molecular beam epitaxy were used to develop the samples. X-ray diffraction (XRD) measurements and secondary ion mass spectroscopy (SIMS), were used to determine the structure, depth profile and composition of the already grown films. The electrical properties were characterized by Hall measurement using the van der Pauw method. In case of Al-doped BaSi2 films, it was not encouraging result due to diffusion and segregation of Al in both the surface and BaSi2/ Si interface regions. On the other hand, those phenomena were not observed for Cu-doped BaS2 films. Heavily Cu-doped BaSi2 showed n+ conductivity, differently from our prediction.

  11. Tuning the charge carriers in epitaxial graphene on SiC(0001) from electron to hole via molecular doping with C60F48

    NASA Astrophysics Data System (ADS)

    Tadich, A.; Edmonds, M. T.; Ley, L.; Fromm, F.; Smets, Y.; Mazej, Z.; Riley, J.; Pakes, C. I.; Seyller, Th.; Wanke, M.

    2013-06-01

    We demonstrate that the intrinsic electron doping of monolayer epitaxial graphene on SiC(0001) can be tuned in a controlled fashion to holes via molecular doping with the fluorinated fullerene C60F48. In situ angle-resolved photoemission is used to measure an upward shift of (0.6 ± 0.05) eV in the Dirac point from -0.43 eV to +0.17 eV relative to the Fermi level. The carrier density is observed to change from n ˜ (1 × 1013 ± 0.1 × 1013) cm-2 to p ˜ (2 × 1012 ± 1 × 1012) cm-2. We introduce a doping model employing Fermi-Dirac statistics which explicitly takes temperature and the highly correlated nature of molecular orbitals into account. The model describes the observed doping behaviour in our experiment and readily explains why net p-type doping was not achieved in a previous study [Coletti et al., Phys. Rev. B 81, 8 (2010)] which used tetrafluorotetra-cyanoquinodimethane (F4-TCNQ).

  12. Responsive small molecular hydrogels based on adamantane-peptides for cell culture.

    PubMed

    Yang, Cuihong; Li, Dongxia; Liu, Zheng; Hong, Ge; Zhang, Jun; Kong, Deling; Yang, Zhimou

    2012-01-12

    The development of responsive small molecular hydrogels that can be applied for recovery of cells postculture attract extensive interests for researchers in fields of cell biology, stem cell differentiation, and tissue engineering. We report in this study several responsive small molecular hydrogels based on adamantane-peptides whose gel to clear solution phase transition can be achieved by addition of β-cyclodextrin (β-CD) derivatives. The small molecular hydrogels are formed by our recently developed method of disulfide bond cleavage by glutathione (GSH). Mouse fibroblast 3T3 cells attach and grow well at the surface of hydrogels. Furthermore, 3T3 cells postculture can be recovered from the gels by the addition of a β-CD derivative due to formation of clear solutions by the adamantane-β-CD interaction. The culture on hydrogels and recovery process do not cause obvious effects on behaviors of 3T3 cells. The results shown in this study indicate that small molecular hydrogels based on adamantane-peptides have great potentials in research fields where further analysis of cells is needed.

  13. Impurity distribution and microstructure of Ga-doped ZnO films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Kvit, A. V.; Yankovich, A. B.; Avrutin, V.; Liu, H.; Izyumskaya, N.; Özgür, Ü.; Morkoç, H.; Voyles, P. M.

    2012-12-01

    We report microstructural characterization of heavily Ga-doped ZnO (GZO) thin films on GaN and sapphire by aberration-corrected scanning transmission electron microscopy. Growth under oxygen-rich and metal-rich growth conditions leads to changes in the GZO polarity and different extended defects. For GZO layers on sapphire, the primary extended defects are voids, inversion domain boundaries, and low-angle grain boundaries. Ga doping of ZnO grown under metal-rich conditions causes a switch from pure oxygen polarity to mixed oxygen and zinc polarity in small domains. Electron energy loss spectroscopy and energy dispersive spectroscopy spectrum imaging show that Ga is homogeneous, but other residual impurities tend to accumulate at the GZO surface and at extended defects. GZO grown on GaN on c-plane sapphire has Zn polarity and no voids. There are misfit dislocations at the interfaces between GZO and an undoped ZnO buffer layer and at the buffer/GaN interface. Low-angle grain boundaries are the only threading microstructural defects. The potential effects of different extended defects and impurity distributions on free carrier scattering are discussed.

  14. Hopping charge transport in molecularly doped polymers: Polymer matrix dependence of the hole drift mobility

    NASA Astrophysics Data System (ADS)

    Kanemitsu, Yoshihiko

    1992-03-01

    Effects of the polymer matrix on the drift mobility of holes in polymers doped with 2-(p-dipropylaminophenyl)-4-(p-dimethylaminophenyl)-5-(o-chlorophenyl)-1, 3-oxazole were studied by means of time-of-flight photoconductivity measurements. The drift mobility at zero field, the activation energy for hopping, and the electric field dependence of the mobility strongly depend on the polymer composition. These polymer matrix dependence of the drift mobility are largely related to energetic disorder of hopping sites in binary solid solution.

  15. Efficient Triplet Exciton Fusion in Molecularly Doped Polymer Light-Emitting Diodes.

    PubMed

    Di, Dawei; Yang, Le; Richter, Johannes M; Meraldi, Lorenzo; Altamimi, Rashid M; Alyamani, Ahmed Y; Credgington, Dan; Musselman, Kevin P; MacManus-Driscoll, Judith L; Friend, Richard H

    2017-04-01

    Solution-processed polymer organic light-emitting diodes (OLEDs) doped with triplet-triplet annihilation (TTA)-upconversion molecules, including 9,10-diphenylanthracene, perylene, rubrene and TIPS-pentacene, are reported. The fraction of triplet-generated electroluminescence approaches the theoretical limit. Record-high efficiencies in solution-processed OLEDs based on these materials are achieved. Unprecedented solid-state TTA-upconversion quantum yield of 23% (TTA-upconversion reaction efficiency of 70%) at electrical excitation well below one-sun equivalent is observed.

  16. Small Gold Nanoparticles Interfaced to Electrodes through Molecular Linkers: A Platform to Enhance Electron Transfer and Increase Electrochemically Active Surface Area.

    PubMed

    Young, Samantha L; Kellon, Jaclyn E; Hutchison, James E

    2016-10-17

    For the smallest nanostructures (<5 nm), small changes in structure can lead to significant changes in properties and reactivity. In the case of nanoparticle (NP)-functionalized electrodes, NP structure and composition, and the nature of the NP-electrode interface have a strong influence upon electrochemical properties that are critical in applications such as amperometric sensing, photocatalysis and electrocatalysis. Existing methods to fabricate NP-functionalized electrodes do not allow for precise control over all these variables, especially the NP-electrode interface, making it difficult to understand and predict how structural changes influence NP activity. We investigated the electrochemical properties of small (dcore < 2.5 nm) gold nanoparticles (AuNPs) on boron doped diamond electrodes using three different electrode fabrication techniques with varying degrees of nanoparticle-electrode interface definition. Two methods to attach AuNPs to the electrode through a covalently bound molecular linker were developed and compared to NP-functionalized electrodes fabricated using solution deposition methods (drop-casting and physiadsorption of a monolayer). In each case, a ferrocene redox probe was tethered to the AuNP surface to evaluate electron transfer through the AuNPs. The AuNPs that were molecularly interfaced with the electrode exhibited nearly ideal, reproducible electrochemical behavior with narrow redox peaks and small peak separations, whereas the solution deposited NPs had broader redox peaks with large peak separations. These data suggest that the molecular tether facilitates AuNP-mediated electron transfer. Interestingly, the molecularly tethered NPs also had significantly more electrochemically active surface area than the solution deposited NPs. The enhanced electrochemical behavior of the molecularly interfaced NPs demonstrates the significant influence of the interface on NP-mediated electron transfer and suggests that similar modified electrodes

  17. A tetraphenylethylene core-based 3D structure small molecular acceptor enabling efficient non-fullerene organic solar cells.

    PubMed

    Liu, Yuhang; Mu, Cheng; Jiang, Kui; Zhao, Jingbo; Li, Yunke; Zhang, Lu; Li, Zhengke; Lai, Joshua Yuk Lin; Hu, Huawei; Ma, Tingxuan; Hu, Rongrong; Yu, Demei; Huang, Xuhui; Tang, Ben Zhong; Yan, He

    2015-02-01

    A tetraphenylethylene core-based small molecular acceptor with a unique 3D molecular structure is developed. Bulk-heterojunction blend films with a small feature size (≈20 nm) are obtained, which lead to non-fullerene organic solar cells (OSCs) with 5.5% power conversion efficiency. The work provides a new molecular design approach to efficient non-fullerene OSCs based on 3D-structured small-molecule acceptors.

  18. Linearly and circularly polarized laser photoinduced molecular order in azo dye doped polymer films

    NASA Astrophysics Data System (ADS)

    Saad, Bendaoud

    2017-03-01

    Photo-induced behavior of Azo Disperse one (AZD1) doped Poly(Methyl MethAcrylate) (PMMA) using both linear and circular polarized light is studied. The anisotropy is not erased by the circular polarization light. The circular polarization light combined with relatively long lifetime of the cis state in azo dye doped polymers activate all transverse directions of the angular hole burning through the spot in the film inducing anisotropy. Under circular polarized light, there is no orientation perpendicularly to the helex described by the rotating electric field vector, trans molecules reorients in the propagation direction of the pump beam. The polarization state of the probe beam after propagation through the pumped spot depends strongly on the angle of incidence of both pump and probe beams on the input face. In the case where circular polarized pump and probe beams are under the same angle of incidence, the probe beam "sees" anisotropic film as if it is isotropic. Results of this work shows the possibility to reorient azobenzene-type molecules in two orthogonal directions using alternately linearly and circularly polarized beams.

  19. Fe-doped semi-insulating GaN with solid Fe source grown on (110) Si substrates by NH3 molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Noh, Young Kyun; Lee, Sang Tae; Kim, Moon Deock; Oh, Jae Eung

    2017-02-01

    Iron doped GaN layers were grown on (110) Si substrates by ammonia molecular beam epitaxy (MBE) using solid elemental iron as a source. Specular films with concentrations up to 1×1020 cm-3, as determined by secondary ion mass spectroscopy, were grown, unlike a limited incorporation of Fe into GaN by metal-rich rf plasma MBE. The Fe concentration in the film showed an exponential dependence on the inverse of source temperature with an activation energy of 3.4 eV, which agrees well to the reported value for the sublimation of Fe. A 1.5 μm thick GaN film with a sheet resistance of 1 GΩ/sq. was obtained by compensating unintentional residual donors with a small Fe concentration of 1×1017 cm-3. X-ray diffraction rocking curves indicated high crystalline quality, very similar to an undoped film, showing that the Fe incorporation required to obtain the semi-insulating film properties did not affect the structural properties of the film. The low-temperature PL spectra of highly resistive and semi-insulating Fe:GaN in the range of 1017 1018 cm-3 show dominant exciton emissions and enhanced donor-acceptor-pair (DAP) emissions, implying that Fe ions contribute to the DAP transition between donor levels and Fe-related acceptor levels, possibly compensating the residual donors to achieve the semi-insulating electrical properties.

  20. Selective room temperature phosphorescence sensing of target protein using Mn-doped ZnS QDs-embedded molecularly imprinted polymer.

    PubMed

    Tan, Lei; Kang, Chengcheng; Xu, Shiying; Tang, Youwen

    2013-10-15

    The direct correlation between disease states and protein levels makes the sensitive, convenient, and precise detection of proteins the focus of scientific research. This paper demonstrates a new strategy for producing phosphorescent molecularly imprinted polymer (MIP) for specific recognition of a target protein. The technique provides surface graft imprinting in aqueous solutions using vinyl modified Mn-doped ZnS QDs as supports, methacrylic acid and acrylamide as functional monomers, and bovine hemoglobin as a template. The QDs act as antennae for recognition signal amplification and optical readout, and the MIP shell provides analyte selectivity and prevents interfering molecules from coming into contact with the QDs. The small particle sizes and the nontoxicity of the MIP-QDs composites allows for good dispersibility and stability in an aqueous solution. Under optimal conditions, good linear correlations were obtained for bovine hemoglobin over the concentration range from 1.0×10⁻⁷ to 5.0×10⁻⁶ mol L⁻¹ and with recoveries of 96.7-103.8% and 92.6-94.2% for urine and serum samples, respectively. The long lifetime of the MIP-QDs composites phosphorescence avoids interference due to autofluorescence and scattering of the biomatrix, facilitating composites' application for detection of bovine hemoglobin in biological fluids. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. A novel mechanism for small heat shock proteins to function as molecular chaperones.

    PubMed

    Zhang, Kaiming; Ezemaduka, Anastasia N; Wang, Zhao; Hu, Hongli; Shi, Xiaodong; Liu, Chuang; Lu, Xinping; Fu, Xinmiao; Chang, Zengyi; Yin, Chang-Cheng

    2015-03-06

    Small heat shock proteins (sHSPs) are molecular chaperones ubiquitously present in all forms of life, but their function mechanisms remain controversial. Here we show by cryo-electron microscopy and single particle 3D reconstruction that, at the low temperatures (4-25°C), CeHSP17 (a sHSP from Caenorhabditis elegans) exists as a 24-subunit spherical oligomer with tetrahedral symmetry. Our studies demonstrate that CeHSP17 forms large sheet-like super-molecular assemblies (SMAs) at the high temperatures (45-60°C), and such SMAs are apparently the form that exhibits chaperone-like activity. Our findings suggest a novel molecular mechanism for sHSPs to function as molecular chaperones.

  2. Molecular targeted therapy in the treatment of advanced stage non-small cell lung cancer (NSCLC).

    PubMed

    Kumarakulasinghe, Nesaretnam Barr; van Zanwijk, Nico; Soo, Ross A

    2015-04-01

    Historically, patients with advanced stage non-small cell lung cancer (NSCLC) were treated with chemotherapy alone, but a therapeutic plateau has been reached. Advances in the understanding of molecular genetics have led to the recognition of multiple molecularly distinct subsets of NSCLC. This in turn has led to the development of rationally directed molecular targeted therapy, leading to improved clinical outcomes. Tumour genotyping for EGFR mutations and ALK rearrangement has meant chemotherapy is no longer given automatically as first-line treatment but reserved for when patients do not have a 'druggable' driver oncogene. In this review, we will address the current status of clinically relevant driver mutations and emerging new molecular subsets in lung adenocarcinoma and squamous cell carcinoma, and the role of targeted therapy and mechanisms of acquired resistance to targeted therapy.

  3. Improving molecular testing and personalized medicine in non-small-cell lung cancer in Ontario.

    PubMed

    Lim, C; Sekhon, H S; Cutz, J C; Hwang, D M; Kamel-Reid, S; Carter, R F; Santos, G da Cunha; Waddell, T; Binnie, M; Patel, M; Paul, N; Chung, T; Brade, A; El-Maraghi, R; Sit, C; Tsao, M S; Leighl, N B

    2017-04-01

    Although molecular testing has become standard in managing advanced nonsquamous non-small-cell lung cancer (nsclc), most patients undergo minimally invasive procedures, and the diagnostic tumour specimens available for testing are usually limited. A knowledge translation initiative to educate diagnostic specialists about sampling techniques and laboratory processes was undertaken to improve the uptake and application of molecular testing in advanced lung cancer. A multidisciplinary panel of physician experts including pathologists, respirologists, interventional thoracic radiologists, thoracic surgeons, medical oncologists, and radiation oncologists developed a specialty-specific education program, adapting international clinical guidelines to the local Ontario context. Expert recommendations from the program are reported here. Panel experts agreed that specialists procuring samples for lung cancer diagnosis should choose biopsy techniques that maximize tumour cellularity, and that conservation strategies to maximize tissue for molecular testing should be used in tissue processing. The timeliness of molecular reporting can be improved by pathologist-initiated reflex testing upon confirmation of nonsquamous nsclc and by prompt transportation of specimens to designated molecular diagnostic centres. To coordinate timely molecular testing and optimal treatment, collaboration and communication between all clinicians involved in diagnosing patients with advanced lung cancer are mandatory. Knowledge transfer to diagnostic lung cancer specialists could potentially improve molecular testing and treatment for advanced lung cancer patients.

  4. Focused molecular analysis of small cell lung cancer: feasibility in routine clinical practice.

    PubMed

    Abdelraouf, Fatma; Sharp, Adam; Maurya, Manisha; Mair, Debbie; Wotherspoon, Andrew; Leary, Alex; Gonzalez de Castro, David; Bhosle, Jaishree; Nassef, Ayatallah; Gaafar, Taghrid; Popat, Sanjay; Yap, Timothy A; O'Brien, Mary

    2015-11-18

    There is an urgent need to identify molecular signatures in small cell lung cancer (SCLC) that may select patients who are likely to respond to molecularly targeted therapies. In this study, we investigate the feasibility of undertaking focused molecular analyses on routine diagnostic biopsies in patients with SCLC. A series of histopathologically confirmed formalin-fixed, paraffin-embedded SCLC specimens were analysed for epidermal growth factor receptors (EGFR), KRAS, NRAS and BRAF mutations, ALK gene rearrangements and MET amplification. EGFR and KRAS mutation testing was evaluated using real time polymerase chain reaction (RT-PCR cobas(®)), BRAF and NRAS mutations using multiplex PCR and capillary electrophoresis-single strand conformation analysis, and ALK and MET aberrations with fluorescent in situ hybridization. All genetic aberrations detected were validated independently. A total of 105 patients diagnosed with SCLC between July 1990 and September 2006 were included. 60 (57 %) patients had suitable tumour tissue for molecular testing. 25 patients were successfully evaluated for all six pre-defined molecular aberrations. Eleven patients failed all molecular analysis. No mutations in EGFR, KRAS and NRAS were detected, and no ALK gene rearrangements or MET gene amplifications were identified. A V600E substitution in BRAF was detected in a Caucasian male smoker diagnosed with SCLC with squamoid and glandular features. The paucity of patients with sufficient tumour tissue, quality of DNA extracted and low frequency of aberrations detected indicate that alternative molecular characterisation approaches are necessary, such as the use of circulating plasma DNA in patients with SCLC.

  5. Improving molecular testing and personalized medicine in non-small-cell lung cancer in Ontario

    PubMed Central

    Lim, C.; Sekhon, H.S.; Cutz, J.C.; Hwang, D.M.; Kamel-Reid, S.; Carter, R.F.; Santos, G. da Cunha; Waddell, T.; Binnie, M.; Patel, M.; Paul, N.; Chung, T.; Brade, A.; El-Maraghi, R.; Sit, C.; Tsao, M.S.; Leighl, N.B.

    2017-01-01

    Background Although molecular testing has become standard in managing advanced nonsquamous non-small-cell lung cancer (nsclc), most patients undergo minimally invasive procedures, and the diagnostic tumour specimens available for testing are usually limited. A knowledge translation initiative to educate diagnostic specialists about sampling techniques and laboratory processes was undertaken to improve the uptake and application of molecular testing in advanced lung cancer. Methods A multidisciplinary panel of physician experts including pathologists, respirologists, interventional thoracic radiologists, thoracic surgeons, medical oncologists, and radiation oncologists developed a specialty-specific education program, adapting international clinical guidelines to the local Ontario context. Expert recommendations from the program are reported here. Results Panel experts agreed that specialists procuring samples for lung cancer diagnosis should choose biopsy techniques that maximize tumour cellularity, and that conservation strategies to maximize tissue for molecular testing should be used in tissue processing. The timeliness of molecular reporting can be improved by pathologist-initiated reflex testing upon confirmation of nonsquamous nsclc and by prompt transportation of specimens to designated molecular diagnostic centres. To coordinate timely molecular testing and optimal treatment, collaboration and communication between all clinicians involved in diagnosing patients with advanced lung cancer are mandatory. Conclusions Knowledge transfer to diagnostic lung cancer specialists could potentially improve molecular testing and treatment for advanced lung cancer patients. PMID:28490924

  6. A Experimental Study of Indium-Doped Mercury Cadmium Telluride Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Sou, Iam-Keong

    Indium doping of HgCdTe has been successfully carried out during growth by MBE. According to Hall Effect measurements, indium acts as n-type dopant for HgCdTe as expected. The absence of carrier freeze-out indicates that the donor energy level of indium is probably merged with the conduction band. By the combination of the Hall effect and SIMS the incorporation mechanisms of indium are found to be different between the (111)B and (100) growth orientations. In the (111)B case, part of the indium is incorporated in the metal sites and the rest of its precipitates in the form of In_2Te _3. In the (100) case, most of the indium atoms are believed to be incorporated interstitially in the lattice, and the other indium might occupy the metal sites (this is true at least for indium atomic concentration less than 10^{17}cm ^{-3}). This study indicates that the diffusion of indium is also dependent upon growth orientation. Two different diffusion components were observed in both the (111)B and (100) epilayers, but their characteristics are distinguishable. In the (111)B materials, the slow component is believed to be contributed by the In_2Te _3 neutral complexes. The fast component diffuses along the high-diffusivity paths via dislocation and/or grain boundaries. In the (100) materials, the results seem to imply that for heavily doped region (~ 10^{19}cm ^{-3}) part of the indium content is incorporated interstitially and the rest of it forms neutral complexes. During diffusion annealing, these interstitial indium ions gradually move to the metal sites via interstitialcy mechanism. The fast component is related to the diffusion of In_2Te_3 neutral complexes. The diffusion mechanism of the slow component has not yet been established. Indium doping during MBE growth has been used to fabricate HgCdTe:InCdTe-HgCdTe:In single barrier structures. Negative differential resistance was observed in these structures at low temperature. The valence band offset Delta E_{v} in the Hg

  7. Small unilamellar vesicles: a platform technology for molecular imaging of brain tumors

    NASA Astrophysics Data System (ADS)

    Iqbal, Umar; Albaghdadi, Homam; Nieh, Mu-Ping; Tuor, Ursula I.; Mester, Zoltan; Stanimirovic, Danica; Katsaras, John; Abulrob, Abedelnasser

    2011-05-01

    Molecular imaging enables the non-invasive investigation of cellular and molecular processes. Although there are challenges to overcome, the development of targeted contrast agents to increase the sensitivity of molecular imaging techniques is essential for their clinical translation. In this study, spontaneously forming, small unilamellar vesicles (sULVs) (30 nm diameter) were used as a platform to build a bimodal (i.e., optical and magnetic resonance imaging (MRI)) targeted contrast agent for the molecular imaging of brain tumors. sULVs were loaded with a gadolinium (Gd) chelated lipid (Gd-DPTA-BOA), functionalized with targeting antibodies (anti-EGFR monoclonal and anti-IGFBP7 single domain), and incorporated a near infrared dye (Cy5.5). The resultant sULVs were characterized in vitro using small angle neutron scattering (SANS), phantom MRI and dynamic light scattering (DLS). Antibody targeted and nontargeted Gd loaded sULVs labeled with Cy5.5 were assessed in vivo in a brain tumor model in mice using time domain optical imaging and MRI. The results demonstrated that a spontaneously forming, nanosized ULVs loaded with a high payload of Gd can selectively target and image, using MR and optical imaging, brain tumor vessels when functionalized with anti-IGFBP7 single domain antibodies. The unique features of these targeted sULVs make them promising molecular MRI contrast agents.

  8. Small Unilamellar Vesicles: A Platform Technology for Molecular Imaging of Brain Tumors

    SciTech Connect

    Iqbal, U; Albaghdadi, H; Nieh, Mu-Ping; Tuor, U.I; Mester, Z; Stanimirovic, D; Katsaras, John; Abulrob, A

    2011-01-01

    Molecular imaging enables the non-invasive investigation of cellular and molecular processes. Although there are challenges to overcome, the development of targeted contrast agents to increase the sensitivity of molecular imaging techniques is essential for their clinical translation. In this study, spontaneously forming, small unilamellar vesicles (sULVs) (30 nm diameter) were used as a platform to build a bimodal (i.e., optical and magnetic resonance imaging (MRI)) targeted contrast agent for the molecular imaging of brain tumors. sULVs were loaded with a gadolinium (Gd) chelated lipid (Gd-DPTA-BOA), functionalized with targeting antibodies (anti-EGFR monoclonal and anti-IGFBP7 single domain), and incorporated a near infrared dye (Cy5.5). The resultant sULVs were characterized in vitro using small angle neutron scattering (SANS), phantom MRI and dynamic light scattering (DLS). Antibody targeted and nontargeted Gd loaded sULVs labeled with Cy5.5 were assessed in vivo in a brain tumor model in mice using time domain optical imaging and MRI. The results demonstrated that a spontaneously forming, nanosized ULVs loaded with a high payload of Gd can selectively target and image, using MR and optical imaging, brain tumor vessels when functionalized with anti-IGFBP7 single domain antibodies. The unique features of these targeted sULVs make them promising molecular MRI contrast agents.

  9. Boron doped graphene wrapped silver nanowires as an efficient electrocatalyst for molecular oxygen reduction

    PubMed Central

    Nair, Anju K.; Thazhe veettil, Vineesh; Kalarikkal, Nandakumar; Thomas, Sabu; Kala, M. S.; Sahajwalla, Veena; Joshi, Rakesh K.; Alwarappan, Subbiah

    2016-01-01

    Metal nanowires exhibit unusually high catalytic activity towards oxygen reduction reaction (ORR) due to their inherent electronic structures. However, controllable synthesis of stable nanowires still remains as a daunting challenge. Herein, we report the in situ synthesis of silver nanowires (AgNWs) over boron doped graphene sheets (BG) and demonstrated its efficient electrocatalytic activity towards ORR for the first time. The electrocatalytic ORR efficacy of BG-AgNW is studied using various voltammetric techniques. The BG wrapped AgNWs shows excellent ORR activity, with very high onset potential and current density and it followed four electron transfer mechanism with high methanol tolerance and stability towards ORR. The results are comparable to the commercially available 20% Pt/C in terms of performance. PMID:27941954

  10. Nonnuclear Nearly Free Electron Conduction Channels Induced by Doping Charge in Nanotube–Molecular Sheet Composites

    SciTech Connect

    Zhao, Jin; Zheng, Qijing; Petek, Hrvoje; Yang, Jinlong

    2014-09-04

    Nearly free electron (NFE) states with density maxima in nonnuclear (NN) voids may have remarkable electron transport properties ranging from suppressed electron–phonon interaction to Wigner crystallization. Such NFE states, however, usually exist near the vacuum level, which makes them unsuitable for transport. Through first principles calculations on nanocomposites consisting of carbon nanotube (CNT) arrays sandwiched between boron nitride (BN) sheets, we describe a stratagem for stabilizing the NN-NFE states to below the Fermi level. By doping the CNTs with negative charge, we establish Coulomb barriers at CNTs walls that, together with the insulating BN sheets, define the transverse potentials of one-dimensional (1D) transport channels, which support the NN-NFE states.

  11. Dual origin of defect magnetism in graphene and its reversible switching by molecular doping.

    PubMed

    Nair, R R; Tsai, I-L; Sepioni, M; Lehtinen, O; Keinonen, J; Krasheninnikov, A V; Castro Neto, A H; Katsnelson, M I; Geim, A K; Grigorieva, I V

    2013-01-01

    Control of magnetism by applied voltage is desirable for spintronics applications. Finding a suitable material remains an elusive goal, with only a few candidates found so far. Graphene is one of them and attracts interest because of its weak spin-orbit interaction, the ability to control electronic properties by the electric field effect and the possibility to introduce paramagnetic centres such as vacancies and adatoms. Here we show that the magnetism of adatoms in graphene is itinerant and can be controlled by doping, so that magnetic moments are switched on and off. The much-discussed vacancy magnetism is found to have a dual origin, with two approximately equal contributions; one from itinerant magnetism and the other from dangling bonds. Our work suggests that graphene's spin transport can be controlled by the field effect, similar to its electronic and optical properties, and that spin diffusion can be significantly enhanced above a certain carrier density.

  12. Boron doped graphene wrapped silver nanowires as an efficient electrocatalyst for molecular oxygen reduction

    NASA Astrophysics Data System (ADS)

    Nair, Anju K.; Thazhe Veettil, Vineesh; Kalarikkal, Nandakumar; Thomas, Sabu; Kala, M. S.; Sahajwalla, Veena; Joshi, Rakesh K.; Alwarappan, Subbiah

    2016-12-01

    Metal nanowires exhibit unusually high catalytic activity towards oxygen reduction reaction (ORR) due to their inherent electronic structures. However, controllable synthesis of stable nanowires still remains as a daunting challenge. Herein, we report the in situ synthesis of silver nanowires (AgNWs) over boron doped graphene sheets (BG) and demonstrated its efficient electrocatalytic activity towards ORR for the first time. The electrocatalytic ORR efficacy of BG-AgNW is studied using various voltammetric techniques. The BG wrapped AgNWs shows excellent ORR activity, with very high onset potential and current density and it followed four electron transfer mechanism with high methanol tolerance and stability towards ORR. The results are comparable to the commercially available 20% Pt/C in terms of performance.

  13. Tellurium n-type doping of highly mismatched amorphous GaN1-xAsx alloys in plasma-assisted molecular beam epitaxy

    DOE PAGES

    Novikov, S. V.; Ting, M.; Yu, K. M.; ...

    2014-10-01

    In this paper we report our study on n-type Te doping of amorphous GaN1-xAsx layers grown by plasma-assisted molecular beam epitaxy. We have used a low temperature PbTe source as a source of tellurium. Reproducible and uniform tellurium incorporation in amorphous GaN1-xAsx layers has been successfully achieved with a maximum Te concentration of 9×10²⁰ cm⁻³. Tellurium incorporation resulted in n-doping of GaN1-xAsx layers with Hall carrier concentrations up to 3×10¹⁹ cm⁻³ and mobilities of ~1 cm²/V s. The optimal growth temperature window for efficient Te doping of the amorphous GaN1-xAsx layers has been determined.

  14. Development of Ultra Small Shock Tube for High Energy Molecular Beam Source

    SciTech Connect

    Miyoshi, Nobuya; Nagata, Shuhei; Kinefuchi, Ikuya; Shimizu, Kazuya; Matsumoto, Yoichiro; Takagi, Shu

    2008-12-31

    A molecular beam source exploiting a small shock tube is described for potential generation of high energy beam in a range of 1-5 eV without any undesirable impurities. The performance of a non-diaphragm type shock tube with an inner diameter of 2 mm was evaluated by measuring the acceleration and attenuation process of shock waves. With this shock tube installed in a molecular beam source, we measured the time-of-flight distributions of shock-heated beams, which demonstrated the ability of controlling the beam energy with the initial pressure ratio of the shock tube.

  15. A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

    PubMed Central

    2016-01-01

    Summary This review summarizes part of the author’s research in the area of supramolecular chemistry, beginning with his early life influences and early career efforts in molecular recognition, especially molecular tweezers. Although designed to complex DNA, these hosts proved more applicable to the field of host–guest chemistry. This early experience and interest in intercalation ultimately led to the current efforts to develop small molecule therapeutic agents for myotonic dystrophy using a rational design approach that heavily relies on principles of supramolecular chemistry. How this work was influenced by that of others in the field and the evolution of each area of research is highlighted with selected examples. PMID:26877815

  16. Studies of arsenic incorporation and P-type doping in epitaxial mercury cadmium telluride thin films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Zandian, Majid

    Doped layer semiconductor structures provide possibilities for novel electronic devices. Growth of Hg1-xCdxTe by molecular beam epitaxy (MBE) allows precise control over the doping profile and position of heterojunctions as well as structural properties of this ternary alloy. Even though n-type doping using indium is well established, little is known about p-type doping in this material system by MBE. Several elements such as Ag, Au, Sb, Bi and P have been previously used, however high diffusion coefficient and amphoteric behavior of these atoms in HgCdTe has restricted their use in heterojunction devices where control over doping profiles and concentrations is needed. We investigated arsenic incorporation efficiency as a function of As 4 flux and growth temperature. The sticking coefficient of As is substantially higher at lower growth temperature compared to growth at 190°C. For samples grown at 170°C, the etch pit density (EPD) is higher compared to p-type As doped samples grown at 190°C. Higher EPD is associated with columnar twin defects observed in transmission electron microscopy (TEM) studies of low growth temperature samples. Growth at low temperature of 170°C causes Hg rich condition promoting twin formation. Therefore, growth of p-type layers doped with As at low temperatures require optimization of II/VI flux ratio to eliminate columnar twin defects. It is possible to incorporate As at normal MBE growth temperature of 190°C but very high flux of As has to used to overcome low sticking coefficient of As at these temperatures. We proposed a mechanism for the activation of As involving Hg vacancies (VHg··) where Te is moved to a Hg vacancy, leaving behind a Te vacancy, which is then filled by an As atom. The Te that is now on a Hg site (i.e., Te antisite) migrates to the surface and leaves the crystal.

  17. Ultra-small Nd3+-doped nanoparticles as near-infrared luminescent biolabels of hemin in bacteria

    NASA Astrophysics Data System (ADS)

    Xi, Yonglan; Chang, Zhizhou; Ye, Xiaomei; Huang, Hongying; Huang, Yanan; Xiao, Qingbo; Lin, Hongzhen

    2016-01-01

    Near-infrared (NIR) luminescent Nd3+-doped nanoparticles (NPs) have attracted considerable attention in bioimaging and biodetection. Here, we demonstrate sub-6 nm NaGdF4:Nd3+,Fe3+ NPs as luminescent biolabels of hemin molecules that act as the exogenous electron carriers in microbial communities. Contrary to the severe quenching of the visible luminescence for either upconverting or downconverting NPs, the Nd3+-doped NPs show superior properties in avoiding the optical absorption of hemin within the UV and visible spectral regions. A detailed examination showed that the Nd3+-doped NPs exhibit no obvious toxic effects on the microbial communities and show scarce influence on the characteristics of labeled hemin molecules in enhancing the reducing power of the fermentation system. More importantly, by monitoring the NIR luminescence of Nd3+-doped NPs, the selective accumulation of exogenous electron carriers in bacteria that are lacking reducing power has been revealed for the first time. The application of Nd3+-doped NPs as biolabels in bacteria would provide new opportunities for further unravelling the role of exogenous electron carriers in anaerobic digestion.Near-infrared (NIR) luminescent Nd3+-doped nanoparticles (NPs) have attracted considerable attention in bioimaging and biodetection. Here, we demonstrate sub-6 nm NaGdF4:Nd3+,Fe3+ NPs as luminescent biolabels of hemin molecules that act as the exogenous electron carriers in microbial communities. Contrary to the severe quenching of the visible luminescence for either upconverting or downconverting NPs, the Nd3+-doped NPs show superior properties in avoiding the optical absorption of hemin within the UV and visible spectral regions. A detailed examination showed that the Nd3+-doped NPs exhibit no obvious toxic effects on the microbial communities and show scarce influence on the characteristics of labeled hemin molecules in enhancing the reducing power of the fermentation system. More importantly, by

  18. Molecular identification of chlamydial cause of abortion in small ruminants in Jordan.

    PubMed

    Ababneh, Huthaifa Salah; Ababneh, Mustafa Mohammed Kheir; Hananeh, Wael Mahmoud; Alsheyab, Fawzi Mohammad; Jawasreh, Khaleel Ibraheem; Al-Gharaibeh, Moath Ahmad; Ababneh, Mohammed Mahmoud

    2014-12-01

    Chlamydophila abortus (Ch. abortus) is the etiological agent of ovine enzootic abortion (OEA) and one of the most common infectious agents of abortion in small ruminants worldwide. RFLP-PCR analysis of the outer membrane protein gene (OMP2 gene) was used for diagnosis and characterization of chlamydial causes of abortion in small ruminants in Jordan. Sixty-six placental tissues and 15 vaginal swabs were collected from aborted ewes and does to identify cause of abortion in Jordan. Thirty-eight placental samples (58 %) and 13 vaginal swabs (87 %) were positive for chlamydial DNA. Shedding of bacteria in vaginal swabs was detected within 7 days after abortion. The results of this study showed that chlamydiosis is one of the important causes of abortion in small ruminants in Jordan. In addition, vaginal swab is an excellent sample for molecular diagnosis of chlamydiosis. DNA sequencing and RFLP analysis of the OMP2 reveal that all chlamydial cause of abortion in small ruminants in Jordan are due to Ch. abortus. While, Ch. pecorum was not detected in any sample. OMP2 gene of the isolated Jordanian strain was identical (100 %) to Ch. abortus FAS strain. In conclusion, Ch. abortus is an important cause of abortion in Jordan; vaginal swab within 7 days of abortion can be used for molecular diagnosis of chlamydiosis in small ruminants.

  19. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Structural and Electrical Properties of Single Crystalline Ga-Doped ZnO Thin Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Lu, Zhong-Lin; Zou, Wen-Qin; Xu, Ming-Xiang; Zhang, Feng-Ming; Du, You-Wei

    2009-11-01

    High-quality Ga-doped ZnO (ZnO:Ga) single crystalline films with various Ga concentrations are grown on a-plane sapphire substrates using molecular-beam epitaxy. The site configuration of doped Ga atoms is studied by means of x-ray absorption spectroscopy. It is found that nearly all Ga can substitute into ZnO lattice as electrically active donors, a generating high density of free carriers with about one electron per Ga dopant when the Ga concentration is no more than 2%. However, further increasing the Ga doping concentration leads to a decrease of the conductivity due to partial segregation of Ga atoms to the minor phase of the spinel ZnGa2O4 or other intermediate phase. It seems that the maximum solubility of Ga in the ZnO single crystalline film is about 2 at.% and the lowest resistivity can reach 1.92 × 10-4 Ω·cm at room temperature, close to the best value reported. In contrast to ZnO:Ga thin film with 1% or 2% Ga doping, the film with 4% Ga doping exhibits a metal semiconductor transition at 80 K. The scattering mechanism of conducting electrons in single crystalline ZnO:Ga thin film is discussed.

  20. Following the nanostructural molecular orientation guidelines for sulfur versus thiophene units in small molecule photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Kim, Yu Jin; Park, Chan Eon

    2016-03-01

    In bulk heterojunction (BHJ) organic photovoltaics, particularly those using small molecules, electron donor and/or electron acceptor materials form a distributed network in the photoactive layer where critical photo-physical processes occur. Extensive research has recently focused on the importance of sulfur atoms in the small molecules. Little is known about the three-dimensional orientation of these sulfur atom-containing molecules. Herein, we report on our research concerning the heterojunction textures of the crystalline molecular orientation of small compounds having sulfur-containing units in the side chains, specifically, compounds known as DR3TSBDT that contain the alkylthio group and DR3TBDTT that does not. The improved performance of the DR3TBDTT-based devices, particularly in the photocurrent and the fill factor, was attributed to the large population of donor compound crystallites with a favorable face-on orientation along the perpendicular direction. This orientation resulted in efficient charge transport and a reduction in charge recombination. These findings underscore the great potential of small-molecule solar cells and suggest that even higher efficiencies can be achieved through materials development and molecular orientation control.In bulk heterojunction (BHJ) organic photovoltaics, particularly those using small molecules, electron donor and/or electron acceptor materials form a distributed network in the photoactive layer where critical photo-physical processes occur. Extensive research has recently focused on the importance of sulfur atoms in the small molecules. Little is known about the three-dimensional orientation of these sulfur atom-containing molecules. Herein, we report on our research concerning the heterojunction textures of the crystalline molecular orientation of small compounds having sulfur-containing units in the side chains, specifically, compounds known as DR3TSBDT that contain the alkylthio group and DR3TBDTT that does not

  1. Correlating Molecular Structures with Transport Dynamics in High-Efficiency Small-Molecule Organic Photovoltaics.

    PubMed

    Peng, Jiajun; Chen, Yani; Wu, Xiaohan; Zhang, Qian; Kan, Bin; Chen, Xiaoqing; Chen, Yongsheng; Huang, Jia; Liang, Ziqi

    2015-06-24

    Efficient charge transport is a key step toward high efficiency in small-molecule organic photovoltaics. Here we applied time-of-flight and organic field-effect transistor to complementarily study the influences of molecular structure, trap states, and molecular orientation on charge transport of small-molecule DRCN7T (D1) and its analogue DERHD7T (D2). It is revealed that, despite the subtle difference of the chemical structures, D1 exhibits higher charge mobility, the absence of shallow traps, and better photosensitivity than D2. Moreover, charge transport is favored in the out-of-plane structure within D1-based organic solar cells, while D2 prefers in-plane charge transport.

  2. Small Molecular-Sized Artesunate Attenuates Ocular Neovascularization via VEGFR2, PKCα, and PDGFR Targets

    PubMed Central

    Zong, Yao; Yuan, Yongguang; Qian, Xiaobing; Huang, Zhen; Yang, Wei; Lin, Leilei; Zheng, Qishan; Li, Yujie; He, Huining; Gao, Qianying

    2016-01-01

    Ocular neovascularization (NV) is the primary cause of blindness in many ocular diseases. Large molecular weight anti- vascular endothelial growth factor (VEGF) protein drugs, such as Avastin and Lucentis, have saved the vision of millions. However, approximately 20–30% of patients respond poorly to anti-VEGF treatment. We found that artesunate (ART), a small molecular derivative of artemisinin, had a significant inhibitory effect on ocular NV by downregulating the expression of VEGFR2, PKCα, and PDGFR. ART significantly inhibited retinal NV in rabbits and macular edema in monkeys with greater anterior chamber penetrability and more durable efficacy than Avastin. Our pilot study showed that intravitreal injection of 80 μg ART significantly inhibited iris and corneal NV in a severe retinal detachment case. Our results suggest that ART might be a potential persistent small-molecule drug to manage ocular NV via multi-targets. PMID:27480521

  3. Photocatalytic evolution of molecular hydrogen and oxygen over La-doped NaTaO3 particles: Effect of different cocatalysts (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Ivanova, Irina; Kandiel, Tarek; Hakki, Amer; Dillert, Ralf; Bahnemann, Detlef W.

    2015-09-01

    To solve the global energy and environmental issues highly efficient systems for solar energy conversion and storage are needed. One of them involves the photocatalytic conversion of solar energy into the storable fuel molecular hydrogen via the water splitting process utilizing metal-oxide semiconductors as catalysts. Since photocatalytic water splitting is still a rather poorly understood reaction, fundamental research in this field is required. Herein, the photocatalytic activity for water splitting was investigated utilizing La-doped NaTaO3 as a model photocatalyst. The activity of La-doped NaTaO3 was assessed by the determination of the overall quantum yield of molecular hydrogen and molecular oxygen evolution. In pure water La-doped NaTaO3 exhibits rather poor activity for the photocatalytic H2 evolution whereby no O2 was detected. To enhance the photocatalytic activity the surface of La-doped NaTaO3 was modified with various cocatalysts including noble metals (Pt, Au and Rh) and metal oxides (NiO, CuO, CoO, AgO and RuO2). The photocatalytic activity was evaluated in pure water, in aqueous methanol solution, and in aqueous silver nitrate solution. The results reveal that cocatalysts such as RuO2 or CuO exhibiting the highest catalytic activity for H2 evolution from pure water, possess, however, the lowest activity for O2 evolution from aqueous silver nitrate solution. La-doped NaTaO3 modified with Pt shows the highest quantum yield of 33 % with respect to the H2 evolution in the presence of methanol. To clarify the role of methanol in such a photocatalytic system, long-term investigations and isotopic studies were performed. The underlying mechanisms of methanol oxidation were elucidated.

  4. Why nanoscale tank treads move? Structures, chemical bonding, and molecular dynamics of a doped boron cluster B10C.

    PubMed

    Wang, Ying-Jin; Guo, Jin-Chang; Zhai, Hua-Jin

    2017-07-13

    Planar boron clusters form dynamic rotors, either as molecular Wankel motors or subnanoscale tank treads, the latter being exemplified by an elongated B11(-) cluster. For an in-depth mechanistic understanding of the rotors, we investigate herein a doped boron cluster, B10C, in which a C atom isovalently substitutes B(-) in the B11(-) tank tread. Two critical structures are achieved: the Cs ((1)A') global minimum (GM) with C positioned in the peripheral ring and the C2v ((1)A1) local minimum (LM) with C in the diatomic core. In the GM the C atom completely halts the rotation of B10C, whereas in the LM the dynamic fluxionality remains. The energy barriers for in-plane rotation differ markedly: 12.93/18.31 kcal mol(-1) for GM versus 1.84 kcal mol(-1) for LM at the single-point CCSD(T) level. The GM rotates via two transition states (TS), compared to one for the LM. Chemical bonding in the structures is elucidated via canonical molecular orbital (CMO) analysis, adaptive natural density partitioning (AdNDP), electron localization functions (ELFs), and Wiberg bond indices (WBI). Electron delocalization is shown to be essential for structural fluxionality. In particular, the variation of WBI from the GM or LM geometries to their TS structures correlates positively with the energy barrier, which offers a quasi-quantitative measure of the barrier height and hence controls the dynamics. This finding may be extended to all molecular rotors. It also helps rationalize why a strongly covalently bound system can behave dynamically in a manner similar to a weakly bound one; it is the latter that is generally anticipated to be structurally fluxional.

  5. Mosaic small supernumerary marker chromosome 1 at amniocentesis: prenatal diagnosis, molecular genetic analysis and literature review.

    PubMed

    Chen, Chih-Ping; Chen, Ming; Su, Yi-Ning; Huang, Jian-Pei; Chern, Schu-Rern; Wu, Peih-Shan; Su, Jun-Wei; Chang, Shun-Ping; Chen, Yu-Ting; Lee, Chen-Chi; Chen, Li-Feng; Pan, Chen-Wen; Wang, Wayseen

    2013-10-15

    We present prenatal diagnosis and molecular cytogenetic analysis of mosaic small supernumerary marker chromosome 1 [sSMC(1)]. We review the literature of sSMC(1) at amniocentesis and chromosome 1p21.1-p12 duplication syndrome. We discuss the genotype-phenotype correlation of the involved genes of ALX3, RBM15, NTNG1, SLC25A24, GPSM2, TBX15 and NOTCH2 in this case.

  6. The Formation of Molecular Clouds in the Galaxy and the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Lee, Min-Young

    In this thesis, I provide observational constraints on the formation of molecular clouds, precursors of star formation, by conducting high-resolution, multi-wavelength investigations of dense gas in the Galaxy and the Small Magellanic Cloud (SMC). By applying the unsharp-masking technqiue to the mid-infrared image obtained with the Spitzer Space Telescope , I identify 55 high-contrast regions (HCRs) in the SMC. The follow-up molecular line observations toward one of the HCRs suggest that the HCRs are likely moderately dense and trace regions where the transition from atomic to molecular hydrogen occurs in this low-metallicity galaxy. Motivated by this result, I investigate the transition from atomic to molecular hydrogen at high resolution across the Perseus molecular cloud in the Galaxy. By deriving the atomic and molecular hydrogen column density images on sub-parsec scales, I find that the atomic gas distribution is relatively uniform across Perseus and as a result, the ratio of molecular to atomic hydrogen linearly increases with the total gas column density. These results are consistent with the theoretical perspective that formation and photodissociation of molecular hydrogen are in balance and the abundance of molecular hydrogen is controlled by the minimum gas column density required for shielding of molecular hydrogen. Finally, I perform a detailed study of the relation between the molecular hydrogen column density and the carbon monoxide integrated intensity in Perseus and show that the ratio of the two, so called X-factor, varies spatially by up to a factor of 100. I compare the atomic/molecular hydrogen, carbon monoxide, and X-factor data with two contrasting theoretical models. I find that the steady state and equilibrium chemistry model reproduces the observations very well but requires an extended, diffuse halo around a dense core. While agreeing with the observations reasonably well, the macroturbulent and non-equilibrium chemistry model shows

  7. Molecular dynamics study of the mechanical loss in amorphous pure and doped silica.

    PubMed

    Hamdan, Rashid; Trinastic, Jonathan P; Cheng, H P

    2014-08-07

    Gravitational wave detectors and other precision measurement devices are limited by the thermal noise in the oxide coatings on the mirrors of such devices. We have investigated the mechanical loss in amorphous oxides by calculating the internal friction using classical, atomistic molecular dynamics simulations. We have implemented the trajectory bisection method and the non-local ridge method in the DL-POLY molecular dynamics simulation software to carry out those calculations. These methods have been used to locate the local potential energy minima that a system visits during a molecular dynamics trajectory and the transition state between any two consecutive minima. Using the numerically calculated barrier height distributions, barrier asymmetry distributions, relaxation times, and deformation potentials, we have calculated the internal friction of pure amorphous silica and silica mixed with other oxides. The results for silica compare well with experiment. Finally, we use the numerical calculations to comment on the validity of previously used theoretical assumptions.

  8. Molecular dynamics study of the mechanical loss in amorphous pure and doped silica

    NASA Astrophysics Data System (ADS)

    Hamdan, Rashid; Trinastic, Jonathan P.; Cheng, H. P.

    2014-08-01

    Gravitational wave detectors and other precision measurement devices are limited by the thermal noise in the oxide coatings on the mirrors of such devices. We have investigated the mechanical loss in amorphous oxides by calculating the internal friction using classical, atomistic molecular dynamics simulations. We have implemented the trajectory bisection method and the non-local ridge method in the DL-POLY molecular dynamics simulation software to carry out those calculations. These methods have been used to locate the local potential energy minima that a system visits during a molecular dynamics trajectory and the transition state between any two consecutive minima. Using the numerically calculated barrier height distributions, barrier asymmetry distributions, relaxation times, and deformation potentials, we have calculated the internal friction of pure amorphous silica and silica mixed with other oxides. The results for silica compare well with experiment. Finally, we use the numerical calculations to comment on the validity of previously used theoretical assumptions.

  9. Ultra-small Nd(3+)-doped nanoparticles as near-infrared luminescent biolabels of hemin in bacteria.

    PubMed

    Xi, Yonglan; Chang, Zhizhou; Ye, Xiaomei; Huang, Hongying; Huang, Yanan; Xiao, Qingbo; Lin, Hongzhen

    2016-01-21

    Near-infrared (NIR) luminescent Nd(3+)-doped nanoparticles (NPs) have attracted considerable attention in bioimaging and biodetection. Here, we demonstrate sub-6 nm NaGdF4:Nd(3+),Fe(3+) NPs as luminescent biolabels of hemin molecules that act as the exogenous electron carriers in microbial communities. Contrary to the severe quenching of the visible luminescence for either upconverting or downconverting NPs, the Nd(3+)-doped NPs show superior properties in avoiding the optical absorption of hemin within the UV and visible spectral regions. A detailed examination showed that the Nd(3+)-doped NPs exhibit no obvious toxic effects on the microbial communities and show scarce influence on the characteristics of labeled hemin molecules in enhancing the reducing power of the fermentation system. More importantly, by monitoring the NIR luminescence of Nd(3+)-doped NPs, the selective accumulation of exogenous electron carriers in bacteria that are lacking reducing power has been revealed for the first time. The application of Nd(3+)-doped NPs as biolabels in bacteria would provide new opportunities for further unravelling the role of exogenous electron carriers in anaerobic digestion.

  10. An anchor-dependent molecular docking process for docking small flexible molecules into rigid protein receptors.

    PubMed

    Lin, Thy-Hou; Lin, Guan-Liang

    2008-08-01

    A molecular docking method designated as ADDock, anchor-dependent molecular docking process for docking small flexible molecules into rigid protein receptors, is presented in this article. ADDock makes the bond connection lists for atoms based on anchors chosen for building molecular structures for docking small flexible molecules or ligands into rigid active sites of protein receptors. ADDock employs an extended version of piecewise linear potential for scoring the docked structures. Since no translational motion for small molecules is implemented during the docking process, ADDock searches the best docking result by systematically changing the anchors chosen, which are usually the single-edge connected nodes or terminal hydrogen atoms of ligands. ADDock takes intact ligand structures generated during the docking process for computing the docked scores; therefore, no energy minimization is required in the evaluation phase of docking. The docking accuracy by ADDock for 92 receptor-ligand complexes docked is 91.3%. All these complexes have been docked by other groups using other docking methods. The receptor-ligand steric interaction energies computed by ADDock for some sets of active and inactive compounds selected and docked into the same receptor active sites are apparently separated. These results show that based on the steric interaction energies computed between the docked structures and receptor active sites, ADDock is able to separate active from inactive compounds for both being docked into the same receptor.

  11. Efficient bulk heterojunction photovoltaic cells using small-molecular-weight organic thin films.

    PubMed

    Peumans, Peter; Uchida, Soichi; Forrest, Stephen R

    2003-09-11

    The power conversion efficiency of small-molecular-weight and polymer organic photovoltaic cells has increased steadily over the past decade. This progress is chiefly attributable to the introduction of the donor-acceptor heterojunction that functions as a dissociation site for the strongly bound photogenerated excitons. Further progress was realized in polymer devices through use of blends of the donor and acceptor materials: phase separation during spin-coating leads to a bulk heterojunction that removes the exciton diffusion bottleneck by creating an interpenetrating network of the donor and acceptor materials. The realization of bulk heterojunctions using mixtures of vacuum-deposited small-molecular-weight materials has, on the other hand, posed elusive: phase separation induced by elevating the substrate temperature inevitably leads to a significant roughening of the film surface and to short-circuited devices. Here, we demonstrate that the use of a metal cap to confine the organic materials during annealing prevents the formation of a rough surface morphology while allowing for the formation of an interpenetrating donor-acceptor network. This method results in a power conversion efficiency 50 per cent higher than the best values reported for comparable bilayer devices, suggesting that this strained annealing process could allow for the formation of low-cost and high-efficiency thin film organic solar cells based on vacuum-deposited small-molecular-weight organic materials.

  12. A non-diaphragm type small shock tube for application to a molecular beam source.

    PubMed

    Yoshimoto, Yuta; Osuka, Kenichi; Miyoshi, Nobuya; Kinefuchi, Ikuya; Takagi, Shu; Matsumoto, Yoichiro

    2013-07-01

    A non-diaphragm type small shock tube was developed for application to a molecular beam source, which can generate beams in the energy range from 1 to several electron volts and beams containing dissociated species such as atomic oxygen. Since repetitive high-frequency operation is indispensable for rapid signal acquisition in beam scattering experiments, the dimensions of the shock tube were miniaturized to reduce the evacuation time between shots. The designed shock tube is 2-4 mm in diameter and can operate at 0.5 Hz. Moreover, a high shock Mach number at the tube end is required for high-energy molecular beam generation. To reduce the shock attenuation caused by the wall boundary layer, which becomes significant in small-diameter tubes, we developed a high-speed response valve employing the current-loop mechanism. The response time of this mechanism is about 100 μs, which is shorter than the rupture time of conventional diaphragms. We show that the current-loop valve generates shock waves with shorter formation distances (about 200-300 mm) than those of conventional shock tubes. In addition, the converging geometry efficiently accelerates shock wave in the small-diameter tubes. The optimal geometry of the shock tube yields shock Mach number around 7, which indicates that the translation energy of molecular beams can exceed 1 eV even in the presence of the real gas effect.

  13. A non-diaphragm type small shock tube for application to a molecular beam source

    NASA Astrophysics Data System (ADS)

    Yoshimoto, Yuta; Osuka, Kenichi; Miyoshi, Nobuya; Kinefuchi, Ikuya; Takagi, Shu; Matsumoto, Yoichiro

    2013-07-01

    A non-diaphragm type small shock tube was developed for application to a molecular beam source, which can generate beams in the energy range from 1 to several electron volts and beams containing dissociated species such as atomic oxygen. Since repetitive high-frequency operation is indispensable for rapid signal acquisition in beam scattering experiments, the dimensions of the shock tube were miniaturized to reduce the evacuation time between shots. The designed shock tube is 2-4 mm in diameter and can operate at 0.5 Hz. Moreover, a high shock Mach number at the tube end is required for high-energy molecular beam generation. To reduce the shock attenuation caused by the wall boundary layer, which becomes significant in small-diameter tubes, we developed a high-speed response valve employing the current-loop mechanism. The response time of this mechanism is about 100 μs, which is shorter than the rupture time of conventional diaphragms. We show that the current-loop valve generates shock waves with shorter formation distances (about 200-300 mm) than those of conventional shock tubes. In addition, the converging geometry efficiently accelerates shock wave in the small-diameter tubes. The optimal geometry of the shock tube yields shock Mach number around 7, which indicates that the translation energy of molecular beams can exceed 1 eV even in the presence of the real gas effect.

  14. Comprehensive molecular pathology analysis of small bowel adenocarcinoma reveals novel targets with potential for clinical utility.

    PubMed

    Alvi, Muhammad A; McArt, Darragh G; Kelly, Paul; Fuchs, Marc-Aurel; Alderdice, Matthew; McCabe, Clare M; Bingham, Victoria; McGready, Claire; Tripathi, Shailesh; Emmert-Streib, Frank; Loughrey, Maurice B; McQuaid, Stephen; Maxwell, Perry; Hamilton, Peter W; Turkington, Richard; James, Jacqueline A; Wilson, Richard H; Salto-Tellez, Manuel

    2015-08-28

    Small bowel accounts for only 0.5% of cancer cases in the US but incidence rates have been rising at 2.4% per year over the past decade. One-third of these are adenocarcinomas but little is known about their molecular pathology and no molecular markers are available for clinical use. Using a retrospective 28 patient matched normal-tumor cohort, next-generation sequencing, gene expression arrays and CpG methylation arrays were used for molecular profiling. Next-generation sequencing identified novel mutations in IDH1, CDH1, KIT, FGFR2, FLT3, NPM1, PTEN, MET, AKT1, RET, NOTCH1 and ERBB4. Array data revealed 17% of CpGs and 5% of RNA transcripts assayed to be differentially methylated and expressed respectively (p < 0.01). Merging gene expression and DNA methylation data revealed CHN2 as consistently hypermethylated and downregulated in this disease (Spearman -0.71, p < 0.001). Mutations in TP53 which were found in more than half of the cohort (15/28) and Kazald1 hypomethylation were both were indicative of poor survival (p = 0.03, HR = 3.2 and p = 0.01, HR = 4.9 respectively). By integrating high-throughput mutational, gene expression and DNA methylation data, this study reveals for the first time the distinct molecular profile of small bowel adenocarcinoma and highlights potential clinically exploitable markers.

  15. [Effects of UV radiation on the aggregation performance of small molecular organic acids].

    PubMed

    Wang, Wen-Dong; Wang, Ya-Bo; Fan, Qing-Hai; Ding, Zhen-Zhen; Wang, Wen; Song, Shan; Zhang, Yin-Ting

    2014-10-01

    This study systematically investigated the effects of UV radiation on the aggregation of small molecular aliphatic carboxylic acids and phenolic acids by jar test. Experimental results show that solution pH has little effect on the coagulation of small molecular aliphatic carboxylic acids including citric acid, oxalic acid, tartaric acid, and succinic acid. For the solutions pretreated with UV light, the removal rates of the selected aliphatic carboxylic acids in coagulation are higher than that without UV radiation. Further study shows that photochemical reactions occur during UV radiation which decreases the negative charge in aliphatic carboxylic acids, and thereby increases their aggregation properties. Different from aliphatic carboxylic acids, phenol, salicylic acid, and benzoic acid have poor coagulation properties, and UV radiation does not have notable effects on their aggregation in the coagulation process. The coagulation performance of tannic acid is better than the other phenolic acids. At pH = 6, its removal rate is above 90%, which may be contributed to the aliphatic carboxylic acid structure in its molecular. Meanwhile, the large molecular of tannic acid is also easier to be adsorbed by the hydrolysis products of PAC1.

  16. Comprehensive molecular pathology analysis of small bowel adenocarcinoma reveals novel targets with potential for clinical utility

    PubMed Central

    Kelly, Paul; Fuchs, Marc-Aurel; Alderdice, Matthew; McCabe, Clare M.; Bingham, Victoria; McGready, Claire; Tripathi, Shailesh; Emmert-Streib, Frank; Loughrey, Maurice B.; McQuaid, Stephen; Maxwell, Perry; Hamilton, Peter W.; Turkington, Richard; James, Jacqueline A.; Wilson, Richard H.; Salto-Tellez, Manuel

    2015-01-01

    Small bowel accounts for only 0.5% of cancer cases in the US but incidence rates have been rising at 2.4% per year over the past decade. One-third of these are adenocarcinomas but little is known about their molecular pathology and no molecular markers are available for clinical use. Using a retrospective 28 patient matched normal-tumor cohort, next-generation sequencing, gene expression arrays and CpG methylation arrays were used for molecular profiling. Next-generation sequencing identified novel mutations in IDH1, CDH1, KIT, FGFR2, FLT3, NPM1, PTEN, MET, AKT1, RET, NOTCH1 and ERBB4. Array data revealed 17% of CpGs and 5% of RNA transcripts assayed to be differentially methylated and expressed respectively (p < 0.01). Merging gene expression and DNA methylation data revealed CHN2 as consistently hypermethylated and downregulated in this disease (Spearman −0.71, p < 0.001). Mutations in TP53 which were found in more than half of the cohort (15/28) and Kazald1 hypomethylation were both were indicative of poor survival (p = 0.03, HR = 3.2 and p = 0.01, HR = 4.9 respectively). By integrating high-throughput mutational, gene expression and DNA methylation data, this study reveals for the first time the distinct molecular profile of small bowel adenocarcinoma and highlights potential clinically exploitable markers. PMID:26315110

  17. STM Observation of Molecular Adsorption on Graphene and Nitrogen Doped Graphene

    NASA Astrophysics Data System (ADS)

    Obata, Seiji; Saiki, Koichiro

    2014-03-01

    Carbon alloy catalyst (CAC) shows catalytic activity to oxygen reduction reaction (ORR) and it is expected as a substitution of Pt in fuel cells due to its catalytic property. At present CAC are synthesized by burning organic compounds which contain nitrogen atoms such as phthalocyanine. The catalytic activity of CAC is lower than Pt. Since catalytic sites and oxygen reduction process is still unknown, elucidation of catalytic sites of CAC helps to synthesize high performance CAC. STM is a useful tool to investigate adsorption and reaction at atomic level. However, disordered structure of CAC makes it difficult to use STM for catalytic site observation. To overcome this difficulty, we synthesized nitrogen doped graphene (NG) and and pristine graphene (PG) on Pt (111) and used it as model catalyst to study the catalytic property of CAC. Oxygen adsorption is the first step of oxygen reduction reaction. Therefore we investigated the oxygen adsorption to NG and PG by STM. Oxygen adsorbed at domain boundary (DB) of NG?According to XPS measurement nitrogen atoms exist at edge site preferably. These results indicate that nitrogen atom enhances oxygen adsorption activity. In addition, actual reaction process occurs in H2O. Thus we also investigated H2O adsorption on NG.

  18. Following the nanostructural molecular orientation guidelines for sulfur versus thiophene units in small molecule photovoltaic cells.

    PubMed

    Kim, Yu Jin; Park, Chan Eon

    2016-04-14

    In bulk heterojunction (BHJ) organic photovoltaics, particularly those using small molecules, electron donor and/or electron acceptor materials form a distributed network in the photoactive layer where critical photo-physical processes occur. Extensive research has recently focused on the importance of sulfur atoms in the small molecules. Little is known about the three-dimensional orientation of these sulfur atom-containing molecules. Herein, we report on our research concerning the heterojunction textures of the crystalline molecular orientation of small compounds having sulfur-containing units in the side chains, specifically, compounds known as DR3TSBDT that contain the alkylthio group and DR3TBDTT that does not. The improved performance of the DR3TBDTT-based devices, particularly in the photocurrent and the fill factor, was attributed to the large population of donor compound crystallites with a favorable face-on orientation along the perpendicular direction. This orientation resulted in efficient charge transport and a reduction in charge recombination. These findings underscore the great potential of small-molecule solar cells and suggest that even higher efficiencies can be achieved through materials development and molecular orientation control.

  19. Stopping cancer in its tracks: using small molecular inhibitors to target glioblastoma migrating cells.

    PubMed

    Mattox, Austin K; Li, Jing; Adamson, David C

    2012-12-01

    Glioblastoma multiforme (GBM) represents one of the most common aggressive types of primary brain tumors. Despite advances in surgical resection, novel neuroimaging procedures, and the most recent adjuvant radiotherapy and chemotherapy, the median survival after diagnosis is about 12-14 months. Targeting migrating GBM cells is a key research strategy in the fight against this devastating cancer. Though the vast majority of the primary tumor focus can be surgically resected, these migrating cells are responsible for its universal recurrence. Numerous strategies and technologies are being explored to target migrating glioma cells, with small molecular inhibitors as one of the most commonly studied. Small molecule inhibitors, such as protein kinase inhibitors, phosphorylation site inhibitors, protease inhibitors, and antisense oligonucleotides show promise in slowing the progression of this disease. A better understanding of these small molecule inhibitors and how they target various extra- and intracellular signaling pathways may eventually lead to a cure for GBM.

  20. Hyperthermal molecular beam source using a non-diaphragm-type small shock tube

    NASA Astrophysics Data System (ADS)

    Yoshimoto, Yuta; Osuka, Kenichi; Miyoshi, Nobuya; Kinefuchi, Ikuya; Takagi, Shu; Matsumoto, Yoichiro

    2016-10-01

    We have developed a hyperthermal molecular beam source employing a non-diaphragm-type small shock tube for gas-surface interaction studies. Unlike conventional shock-heated beam sources, the capability of repetitive beam generation without the need for replacing a diaphragm makes our beam source suitable for scattering experiments, which require signal accumulation for a large number of beam pulses. The short duration of shock heating alleviates the usual temperature limit due to the nozzle material, enabling the generation of a molecular beam with higher translational energy or that containing dissociated species. The shock-heated beam is substantially free from surface-contaminating impurities that are pronounced in arc-heated beams. We characterize the properties of nitrogen and oxygen molecular beams using the time-of-flight method. When both the timing of beam extraction and the supply quantity of nitrogen gas are appropriately regulated, our beam source can generate a nitrogen molecular beam with translational energy of approximately 1 eV, which corresponds to the typical activation energy of surface reactions. Furthermore, our beam source can generate an oxygen molecular beam containing dissociated oxygen atoms, which can be a useful probe for surface oxidation. The dissociation fraction along with the translational energy can be adjusted through the supply quantity of oxygen gas.

  1. Hyperthermal molecular beam source using a non-diaphragm-type small shock tube.

    PubMed

    Yoshimoto, Yuta; Osuka, Kenichi; Miyoshi, Nobuya; Kinefuchi, Ikuya; Takagi, Shu; Matsumoto, Yoichiro

    2016-10-01

    We have developed a hyperthermal molecular beam source employing a non-diaphragm-type small shock tube for gas-surface interaction studies. Unlike conventional shock-heated beam sources, the capability of repetitive beam generation without the need for replacing a diaphragm makes our beam source suitable for scattering experiments, which require signal accumulation for a large number of beam pulses. The short duration of shock heating alleviates the usual temperature limit due to the nozzle material, enabling the generation of a molecular beam with higher translational energy or that containing dissociated species. The shock-heated beam is substantially free from surface-contaminating impurities that are pronounced in arc-heated beams. We characterize the properties of nitrogen and oxygen molecular beams using the time-of-flight method. When both the timing of beam extraction and the supply quantity of nitrogen gas are appropriately regulated, our beam source can generate a nitrogen molecular beam with translational energy of approximately 1 eV, which corresponds to the typical activation energy of surface reactions. Furthermore, our beam source can generate an oxygen molecular beam containing dissociated oxygen atoms, which can be a useful probe for surface oxidation. The dissociation fraction along with the translational energy can be adjusted through the supply quantity of oxygen gas.

  2. Multiscale Molecular Simulation of Solution Processing of SMDPPEH: PCBM Small-Molecule Organic Solar Cells.

    PubMed

    Lee, Cheng-Kuang; Pao, Chun-Wei

    2016-08-17

    Solution-processed small-molecule organic solar cells are a promising renewable energy source because of their low production cost, mechanical flexibility, and light weight relative to their pure inorganic counterparts. In this work, we developed a coarse-grained (CG) Gay-Berne ellipsoid molecular simulation model based on atomistic trajectories from all-atom molecular dynamics simulations of smaller system sizes to systematically study the nanomorphology of the SMDPPEH/PCBM/solvent ternary blend during solution processing, including the blade-coating process by applying external shear to the solution. With the significantly reduced overall system degrees of freedom and computational acceleration from GPU, we were able to go well beyond the limitation of conventional all-atom molecular simulations with a system size on the order of hundreds of nanometers with mesoscale molecular detail. Our simulations indicate that, similar to polymer solar cells, the optimal blending ratio in small-molecule organic solar cells must provide the highest specific interfacial area for efficient exciton dissociation, while retaining balanced hole/electron transport pathway percolation. We also reveal that blade-coating processes have a significant impact on nanomorphology. For given donor/acceptor blending ratios, applying an external shear force can effectively promote donor/acceptor phase segregation and stacking in the SMDPPEH domains. The present study demonstrated the capability of an ellipsoid-based coarse-grained model for studying the nanomorphology evolution of small-molecule organic solar cells during solution processing/blade-coating and provided links between fabrication protocols and device nanomorphologies.

  3. TOPICAL REVIEW: Small animal SPECT and its place in the matrix of molecular imaging technologies

    NASA Astrophysics Data System (ADS)

    Meikle, Steven R.; Kench, Peter; Kassiou, Michael; Banati, Richard B.

    2005-11-01

    Molecular imaging refers to the use of non-invasive imaging techniques to detect signals that originate from molecules, often in the form of an injected tracer, and observe their interaction with a specific cellular target in vivo. Differences in the underlying physical principles of these measurement techniques determine the sensitivity, specificity and length of possible observation of the signal, characteristics that have to be traded off according to the biological question under study. Here, we describe the specific characteristics of single photon emission computed tomography (SPECT) relative to other molecular imaging technologies. SPECT is based on the tracer principle and external radiation detection. It is capable of measuring the biodistribution of minute (<10-10 molar) concentrations of radio-labelled biomolecules in vivo with sub-millimetre resolution and quantifying the molecular kinetic processes in which they participate. Like some other imaging techniques, SPECT was originally developed for human use and was subsequently adapted for imaging small laboratory animals at high spatial resolution for basic and translational research. Its unique capabilities include (i) the ability to image endogenous ligands such as peptides and antibodies due to the relative ease of labelling these molecules with technetium or iodine, (ii) the ability to measure relatively slow kinetic processes (compared with positron emission tomography, for example) due to the long half-life of the commonly used isotopes and (iii) the ability to probe two or more molecular pathways simultaneously by detecting isotopes with different emission energies. In this paper, we review the technology developments and design tradeoffs that led to the current state-of-the-art in SPECT small animal scanning and describe the position SPECT occupies within the matrix of molecular imaging technologies.

  4. Surface segregation and structure of Sb-doped Si(100) films grown at low temperature by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Hobart, K. D.; Godbey, D. J.; Twigg, M. E.; Fatemi, M.; Thompson, P. E.; Simons, D. S.

    1995-07-01

    Sb surface segregation and doping during Si(100) molecular beam epitaxy were studied for growth temperatures of 320-500°C. Surface segregation was analyzed by depth profiling with secondary ion mass spectrometry and the results indicate the existence of several distinct dopant concentration- and temperature-dependent surface segregation regimes: (1) For dilute Sb surface concentrations the measurements reveal a region where bulk and surface concentrations are linearly related, and the surface segregation is described by a constant. However, the experimentally determined temperature dependence of the segregation does not follow simple kinetics theory, and appreciable surface segregation is observed at temperatures ≤ 400°C. (2) At temperatures ≥ 350°C, the surface segregation reaches a maximum for Sb surface concentrations of 0.5 monolayers. (3) For surface concentrations near 1 monolayer, the surface segregation decreases with increasing surface Sb coverage due to dopant interaction within surface and subsurface layers. In cases where films were grown under very high dopant fluxes, we have identified cone-like defects and stacking faults that are the result of the apparent surface concentration exceeding 1 monolayer.

  5. Effects of growth temperature on Mg-doped GaN grown by ammonia molecular beam epitaxy

    SciTech Connect

    Hurni, Christophe A.; Lang, Jordan R.; Burke, Peter G.; Speck, James S.

    2012-09-03

    The hole concentration p in Mg-doped GaN films grown by ammonia molecular beam epitaxy depends strongly on the growth temperature T{sub GR}. At T{sub GR}=760 Degree-Sign C, GaN:Mg films showed a hole concentration of p=1.2 Multiplication-Sign 10{sup 18} cm{sup -3} for [Mg]=4.5 Multiplication-Sign 10{sup 19} cm{sup -3}, while at T{sub GR}=840 Degree-Sign C, p=4.4 Multiplication-Sign 10{sup 16} cm{sup -3} for [Mg]=7 Multiplication-Sign 10{sup 19} cm{sup -3}. Post-growth annealing did not increase p. The sample grown at 760 Degree-Sign C exhibited a low resistivity of 0.7 {Omega}cm. The mobility for all the samples was around 3-7 cm{sup 2}/V s. Temperature-dependent Hall measurements and secondary ion mass spectroscopy suggest that the samples grown at T{sub GR}>760 Degree-Sign C are compensated by an intrinsic donor rather than hydrogen.

  6. Sustained molecular oxygen activation by solid iron doped silicon carbide under microwave irradiation: Mechanism and application to norfloxacin degradation.

    PubMed

    Li, Hongbo; Chen, Jing; Hou, Huijie; Pan, Hong; Ma, Xiaoxue; Yang, Jiakuan; Wang, Linling; Crittenden, John C

    2017-09-11

    Sustained molecular oxygen activation by iron doped silicon carbide (Fe/SiC) was investigated under microwave (MW) irradiation. The catalytic performance of Fe/SiC for norfloxacin (NOR) degradation was also studied. Rapid mineralization in neutral solution was observed with a pseudo-first-order rate constant of 0.2239 min(-1) under 540 W of MW irradiation for 20 min. Increasing Fe/SiC rod and MW power significantly enhanced the degradation and mineralization rate with higher yield of reactive oxygen species (ROS). Fe shell corrosion and subsequent Fe(0/II) oxidation by molecular oxygen with MW activation was the key factor for NOR degradation through two-electron-transfer by Fe(0) under acidic conditions and single-electron-transfer by Fe(II) under neutral-alkaline solution. Removal rate of NOR was significantly affected by solution pH, showing higher degradation rates at both acidic and alkaline conditions. The highest removal efficiencies and rates at alkaline pH values were ascribed to the contribution of bound Fe(II) species on the Fe shell surface due to the hydroxylation of Fe/SiC. ·OH was the main oxidizing specie for NOR degradation, confirmed by density functional theory (DFT) calculations and radical scavenger tests. DFT calculations were conducted on the reaction/activation energies of the transition/final states of NOR/degradation products, combined with intermediate identification with high performance liquid chromatography coupled with a triple-quadruple mass spectrometer (HPLC-MS/MS), the piperazinyl ring was the most reactive site for ·OH attack, followed by further ring-opening and stepwise oxidation. In this study, Fe/SiC were proved to be an excellent catalyst for the treatment of fluoroquinolone antibiotics with MW activation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Molecular dynamics simulations of small DNA plasmids: effects of sequence and supercoiling on intramolecular motions.

    PubMed

    Tan, R K; Sprous, D; Harvey, S C

    1996-08-01

    Small (600 base pair) DNA plasmids were modeled with a simplified representation (3DNA) and the intramolecular motions were studied using molecular mechanics and molecular dynamics techniques. The model is detailed enough to incorporate sequence effects. At the same time, it is simple enough to allow long molecular dynamics simulations. The simulations revealed that large-scale slithering occurs in a homogeneous sequence. In a heterogeneous sequence, containing numerous small intrinsic curves, the centers of the curves are preferentially positioned at the tips of loops. With more curves than loop tips (two in unbranched supercoiled DNA), the heterogeneous sequence plasmid slithers short distances to reposition other curves into the loop tips. However, the DNA is immobilized most of the time, with the loop tips positioned over a few favored curve centers. Branching or looping also appears in the heterogeneous sequence as a new method of repositioning the loop tips. Instead of a smooth progression of increasing writhing with increasing linking difference, theoretical studies have predicted that there is a threshold between unwrithed and writhed DNA at a linking difference between one and two. This has previously been observed in simulations of static structures and is demonstrated here for dynamic homogeneous closed DNA. Such an abrupt transition is not found in the heterogeneous sequence in both the static and dynamic cases.

  8. Investigating molecular interactions and surface morphology of wax-doped asphaltenes.

    PubMed

    Pahlavan, Farideh; Mousavi, Masoumeh; Hung, Albert; Fini, Ellie H

    2016-04-07

    The nature and origin of bee-like microstructures (bees) in asphalt binders and their impact on asphalt oxidation have been the subject of extensive discussions in recent years. While several studies refer to the bees as solely surface features, some others consider them to be bulk microcrystalline components that are formed due to co-precipitation of wax and asphaltene molecules. In this study, we use a rigorous theoretical and experimental approach to investigate the interplay of asphalt components (mainly asphaltene and wax) and their impact on bee formation. In the theoretical section, quantum-mechanical calculations using density functional theory (DFT) are used to evaluate the strength of interactions between asphaltene unit sheets in the presence and absence of a wax component, as well as the mutual interactions between asphaltene molecules (monomers and dimers) and paraffin wax. The results of this section reveal that paraffin waxes not only do not reinforce the interaction between the asphaltene unit sheets, they destabilize asphaltene assembly and dimerization. AIM (Atom in Molecules) analysis shows the destabilizing effect of wax on asphaltene assembly as a reduction in the number of cage and bond critical points between asphaltenes. This destabilization effect among interacting systems (asphaltene-asphaltene and wax-asphaltene) does not support the hypothesis that interaction between paraffin waxes and non-wax components, such as asphaltene, is responsible for their co-precipitation and bee formation. To further examine the effect of wax component on asphalt microstructure experimentally, we used atomic force microscopy (AFM) to study the surface morphology of an asphalt sample doped with 1% to 25% paraffin wax. In agreement with the conclusions drawn from the DFT approach, our experiments indicate that paraffin wax tends to crystallize separately and form lamellar paraffin wax crystal inclusions with 10 nm thickness. Moreover, the addition of 3% wax

  9. In vitro synthesis of high molecular weight rubber by Hevea small rubber particles.

    PubMed

    Rojruthai, Porntip; Sakdapipanich, Jitladda Tangpakdee; Takahashi, Seiji; Hyegin, Lee; Noike, Motoyoshi; Koyama, Tanetoshi; Tanaka, Yasuyuki

    2010-02-01

    Hevea brasiliensis is one of few higher plants producing the commercial natural rubber used in many significant applications. The biosynthesis of high molecular weight rubber molecules by the higher plants has not been clarified yet. Here, the in vitro rubber biosynthesis was performed by using enzymatically active small rubber particles (SRP) from Hevea. The mechanism of the in vitro rubber synthesis was investigated by the molecular weight distribution (MWD). The highly purified SRP prepared by gel filtration and centrifugation in the presence of Triton((R)) X-100 showed the low isopentenyl diphosphate (IPP) incorporation for the chain extension mechanism of pre-existing rubber. The MWD of in vitro rubber elongated from the pre-existing rubber chains in SRP was analyzed for the first time in the case of H. brasiliensis by incubating without the addition of any initiator. The rubber transferase activity of 70% incorporation of the added IPP (w/w) was obtained when farnesyl diphosphate was present as the allylic diphosphate initiator. The in vitro synthesized rubber showed a typical bimodal MWD of high and low molecular weight fractions in GPC analysis, which was similar to that of the in vivo rubber with peaks at around 10(6) and 10(5) Da or lower. The reaction time independence and dependence of molecular weight of high and low molecular weight fractions, respectively, indicated that the high molecular weight rubber was synthesized from the chain extension of pre-existing rubber molecules whereas the lower one was from the chain elongation of rubber molecules newly synthesized from the added allylic substrates.

  10. Ovarian proteomic study reveals the possible molecular mechanism for hyperprolificacy of Small Tail Han sheep

    PubMed Central

    Miao, Xiangyang; Luo, Qingmiao; Zhao, Huijing; Qin, Xiaoyu

    2016-01-01

    Small Tail Han sheep is a widely bred farm animal in China which has attracted lots of attention due to their high prolificacy and year-round estrus. However, the molecular mechanism of its fecundity remains unrevealed. The FecB gene polymorphism has been found to be associated with the ovulation rate and litter size of sheep. In the present study, we constructed an iTRAQ-based quantitative proteomics analysis to compare the ovarian proteomes of FecB+FecB+ genotype Small Tail Han sheep ewes (Han ++), FecBBFecBB Han ewes (Han BB) and Dorset ewes (Dorset). Hundreds of differentially expressed proteins between each two groups were identified; GO and KEGG pathway analysis indicated that the expressions of those proteins involved in ribosome assembly, protein translation and mTOR pathway between Dorset and both Han groups were highly different. Between Han ++ and Han BB groups, higher level of protein expressions were related to mitochondrial oxidation functions such as oxidoreductase activity, cytochrome-c oxidase activity and electron carrier activity. This was identified in Han BB group, which may contribute to the elevated ovulation rate of Han BB ewes. In conclusion, our work provided a prospective understanding of the molecular mechanism for high prolificacy of Small Tail Han sheep. PMID:27271055

  11. Molecular approaches to p- and n-nanoscale doping of Ge 1-ySn y semiconductors: Structural, electrical and transport properties

    NASA Astrophysics Data System (ADS)

    Xie, Junqi; Tolle, J.; D'Costa, V. R.; Weng, C.; Chizmeshya, A. V. G.; Menendez, J.; Kouvetakis, J.

    2009-08-01

    We report the development of practical doping protocols via designer molecular sources to create n- and p-type doped Ge 1-ySn y layers grown directly upon Si(1 0 0). These materials will have applications in the fabrication of advanced PIN devices that are intended to extend the infrared optical response beyond that of Ge by utilizing the Sn composition as an additional design parameter. Highly controlled and efficient n-doping of single-layer structures is achieved using custom built P(GeH 3) 3 and As(GeH 3) 3, precursors containing preformed Ge-As and Ge-P near-tetrahedral bonding arrangements compatible with the structure of the host Ge-Sn lattice. Facile substitution and complete activation of the P and As atoms at levels ˜10 17-10 19 cm -3 is obtained via in situ depositions at low temperatures (350 °C). Acceptor doping is readily achieved using conventional diborane yielding carrier concentrations between 10 17-10 19 cm -3 under similar growth conditions. Full activation of the as-grown dopant concentrations is demonstrated by combined SIMS and Hall experiments, and corroborated using a contactless spectroscopic ellipsometry approach. RTA processing of the samples leads to a significant increase in carrier mobility comparable to that of bulk Ge containing similar doping levels. The alloy scattering contribution appears to be negligible for electron carrier concentrations beyond 10 19 cm -3 in n-type samples and hole concentrations beyond 10 18 cm -3 in p-type samples. A comparative study using the classical lower-order hydrides PH 3 and AsH 3 produced n-doped films with carrier densities (up to 9 × 10 19 cm -3) similar to those afforded by P(GeH 3) 3 and As(GeH 3) 3. However, early results indicate that the simpler PH 3 and AsH 3 sources yield materials with inferior morphology and microstructure. Calculations of surface energetics using bond enthalpies suggest that the latter massive compounds bind to the surface via strong Ge-Ge bonds and likely act as

  12. Molecular-targeted therapy for elderly patients with advanced non-small cell lung cancer

    PubMed Central

    ANTONELLI, GIOVANNA; LIBRA, MASSIMO; PANEBIANCO, VINCENZO; RUSSO, ALESSIA ERIKA; VITALE, FELICE VITO; COLINA, PAOLO; D'ANGELO, ALESSANDRO; ROSSELLO, ROSALBA; FERRAÙ, FRANCESCO

    2016-01-01

    Lung cancer is the most common cause of cancer-related mortality in men and women. Non-small cell lung cancer (NSCLC) represents close to 90% of all lung cancers. When diagnosed, >50% of patients are >65 years old. Through an improved understanding of the molecular mechanisms involved in lung oncogenesis, molecular-targeted approaches have become an essential element for the treatment of patients with NSCLC. As the toxicity profiles of the techniques are definitely more favorable compared with chemotherapy, they are particularly attractive for use in elderly patients, who are potentially more susceptible to the toxicity of systemic oncological therapies. However, studies on the activity of molecular-targeted agents in this aged patient setting are much more limited compared with those in their younger counterparts. In the present review, the literature on molecular-targeted therapy for elderly patients with advanced NSCLC is discussed. It is concluded that bevacizumab should be reserved only for highly select elderly patients with advanced NSCLC when the clinician deems it useful in the face of acceptable toxicities. In elderly patients with advanced epidermal growth factor receptor mutation-positive NSCLC, erlotinib and gefitinib appear to repeat the same favorable performance as that documented on a larger scale in the overall population of patients with activating mutations. A good toxicity profile is also confirmed for active molecules on different pathways, such as crizotinib. PMID:26870160

  13. Molecular-targeted therapy for elderly patients with advanced non-small cell lung cancer.

    PubMed

    Antonelli, Giovanna; Libra, Massimo; Panebianco, Vincenzo; Russo, Alessia Erika; Vitale, Felice Vito; Colina, Paolo; D'Angelo, Alessandro; Rossello, Rosalba; Ferraù, Francesco

    2016-01-01

    Lung cancer is the most common cause of cancer-related mortality in men and women. Non-small cell lung cancer (NSCLC) represents close to 90% of all lung cancers. When diagnosed, >50% of patients are >65 years old. Through an improved understanding of the molecular mechanisms involved in lung oncogenesis, molecular-targeted approaches have become an essential element for the treatment of patients with NSCLC. As the toxicity profiles of the techniques are definitely more favorable compared with chemotherapy, they are particularly attractive for use in elderly patients, who are potentially more susceptible to the toxicity of systemic oncological therapies. However, studies on the activity of molecular-targeted agents in this aged patient setting are much more limited compared with those in their younger counterparts. In the present review, the literature on molecular-targeted therapy for elderly patients with advanced NSCLC is discussed. It is concluded that bevacizumab should be reserved only for highly select elderly patients with advanced NSCLC when the clinician deems it useful in the face of acceptable toxicities. In elderly patients with advanced epidermal growth factor receptor mutation-positive NSCLC, erlotinib and gefitinib appear to repeat the same favorable performance as that documented on a larger scale in the overall population of patients with activating mutations. A good toxicity profile is also confirmed for active molecules on different pathways, such as crizotinib.

  14. Screening Molecular Chaperones Similar to Small Heat Shock Proteins in Schizosaccharomyces pombe

    PubMed Central

    Han, Jiyoung; Kim, Kanghwa

    2015-01-01

    To screen molecular chaperones similar to small heat shock proteins (sHsps), but without α-crystalline domain, heat-stable proteins from Schizosaccharomyces pombe were analyzed by 2-dimensional electrophoresis and matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Sixteen proteins were identified, and four recombinant proteins, including cofilin, NTF2, pyridoxin biosynthesis protein (Snz1) and Wos2 that has an α-crystalline domain, were purified. Among these proteins, only Snz1 showed the anti-aggregation activity against thermal denaturation of citrate synthase. However, pre-heating of NTF2 and Wos2 at 70℃ for 30 min, efficiently prevented thermal aggregation of citrate synthase. These results indicate that Snz1 and NTF2 possess molecular chaperone activity similar to sHsps, even though there is no α-crystalline domain in their sequences. PMID:26539043

  15. Communication: Kirkwood-Buff integrals in the thermodynamic limit from small-sized molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Cortes-Huerto, R.; Kremer, K.; Potestio, R.

    2016-10-01

    We present an accurate and efficient method to obtain Kirkwood-Buff (KB) integrals in the thermodynamic limit from small-sized molecular dynamics simulations. By introducing finite size effects into integral equations of statistical mechanics, we derive an analytical expression connecting the KB integrals of the bulk system with the fluctuations of the number of molecules in the corresponding closed system. We validate the method by calculating the activity coefficients of aqueous urea mixtures and the KB integrals of Lennard-Jones fluids. Moreover, our results demonstrate how to identify simulation conditions under which computer simulations reach the thermodynamic limit.

  16. MOLECULARLY TARGETED THERAPIES IN NON-SMALL CELL LUNG CANCER ANNUAL UPDATE 2014

    PubMed Central

    Morgensztern, Daniel; Campo, Meghan J.; Dahlberg, Suzanne E.; Doebele, Robert C.; Garon, Edward; Gerber, David E.; Goldberg, Sarah B.; Hammerman, Peter S.; Heist, Rebecca; Hensing, Thomas; Horn, Leora; Ramalingam, Suresh S.; Rudin, Charles M.; Salgia, Ravi; Sequist, Lecia; Shaw, Alice T.; Simon, George R.; Somaiah, Neeta; Spigel, David R.; Wrangle, John; Johnson, David; Herbst, Roy S.; Bunn, Paul; Govindan, Ramaswamy

    2015-01-01

    There have been significant advances in the understanding of the biology and treatment of non-small cell lung cancer (NSCLC) over the past few years. A number of molecularly targeted agents are in the clinic or in development for patients with advanced NSCLC (Table 1). We are beginning to understand the mechanisms of acquired resistance following exposure to tyrosine kinase inhibitors in patients with oncogene addicted NSCLC. The advent of next generation sequencing has enabled to study comprehensively genomic alterations in lung cancer. Finally, early results from immune checkpoint inhibitors are very encouraging. This review summarizes recent advances in the area of cancer genomics, targeted therapies and immunotherapy. PMID:25535693

  17. Genetic and molecular coordinates of neuroendocrine lung tumors, with emphasis on small-cell lung carcinomas.

    PubMed Central

    Koutsami, Marilena K.; Doussis-Anagnostopoulou, Ipatia; Papavassiliou, Athanasios G.; Gorgoulis, Vassilis G.

    2002-01-01

    The aim of this review is to present the advances in our understanding of the progression of tumorigenesis in neuroendocrine lung tumors. Current information on established and putative diagnostic and prognostic markers of neuroendocrine tumors are evaluated, with a special reference to small-cell lung carcinoma, due to its higher incidence and aggressive behavior. The genetic and molecular changes that accompany these neoplasms are highlighted, and factors that influence cell-cycle progression, apoptosis, drug resistance, and escape from immune surveillance are critically assessed. PMID:12435853

  18. Small Animal Imaging Center Design: The Facility at the UCLA Crump Institute for Molecular Imaging

    PubMed Central

    Stout, David B.; Chatziioannou, Arion F.; Lawson, Timothy P.; Silverman, Robert W.; Gambhir, Sanjiv S.; Phelps, Michael E.

    2010-01-01

    Purpose The growing number of mouse and rat experiments, coupled with advances in small-animal imaging systems such as microPET®, optical, microCAT™, microMR, ultrasound and microSPECT, has necessitated a common technical center for imaging small animals. Procedures At the UCLA Crump Institute for Molecular Imaging, we have designed and built a facility to support the research interests of a wide range of investigators from multiple disciplines. Requirements to satisfy both research and regulatory oversight have been critically examined. Support is provided for investigator training, study scheduling, data acquisition, archiving, image display, and analysis. Results The center has been in operation for more than 18 months, supporting more than 13,000 individual imaging procedures. Conclusions We have created a facility that maximizes our resource utilization while providing optimal investigator support, as well as the means to continually improve the quality and diversity of the science by integrating physical and biological sciences. PMID:16261425

  19. Nonlocal strain gradient theory calibration using molecular dynamics simulation based on small scale vibration of nanotubes

    NASA Astrophysics Data System (ADS)

    Mehralian, Fahimeh; Tadi Beni, Yaghoub; Karimi Zeverdejani, Mehran

    2017-06-01

    Featured by two small length scale parameters, nonlocal strain gradient theory is utilized to investigate the free vibration of nanotubes. A new size-dependent shell model formulation is developed by using the first order shear deformation theory. The governing equations and boundary conditions are obtained using Hamilton's principle and solved for simply supported boundary condition. As main purpose of this study, since the values of two small length scale parameters are still unknown, they are calibrated by the means of molecular dynamics simulations (MDs). Then, the influences of different parameters such as nonlocal parameter, scale factor, length and thickness on vibration characteristics of nanotubes are studied. It is also shown that increase in thickness and decrease in length parameters intensify the effect of nonlocal parameter and scale factor.

  20. Small-angle X-ray scattering method to characterize molecular interactions: Proof of concept.

    PubMed

    Allec, Nicholas; Choi, Mina; Yesupriya, Nikhil; Szychowski, Brian; White, Michael R; Kann, Maricel G; Garcin, Elsa D; Daniel, Marie-Christine; Badano, Aldo

    2015-07-10

    Characterizing biomolecular interactions is crucial to the understanding of biological processes. Existing characterization methods have low spatial resolution, poor specificity, and some lack the capability for deep tissue imaging. We describe a novel technique that relies on small-angle X-ray scattering signatures from high-contrast molecular probes that correlate with the presence of biomolecular interactions. We describe a proof-of-concept study that uses a model system consisting of mixtures of monomer solutions of gold nanoparticles (GNPs) as the non-interacting species and solutions of GNP dimers linked with an organic molecule (dimethyl suberimidate) as the interacting species. We report estimates of the interaction fraction obtained with the proposed small-angle X-ray scattering characterization method exhibiting strong correlation with the known relative concentration of interacting and non-interacting species.

  1. Molecular characterization of small peripheral lung tumors based on the analysis of fine needle aspirates.

    PubMed

    Zudaire, I; Lozano, M D; Vazquez, M F; Pajares, M J; Agorreta, J; Pio, R; Zulueta, J J; Yankelevitz, D F; Henschke, C I; Montuenga, L M

    2008-01-01

    The computed tomography (CT)-based early lung cancer diagnostic technologies allow the detection of very small stage I lung tumors. As part of these screening protocols any suspicious nodule has to be diagnosed morphologically, which requires CT-guided Fine Needle Aspiration, open biopsy or surgery. Fine Needle Aspiration (FNA) cytology is a well-recognised method for a rapid and accurate diagnosis of small lung tumors. Molecular analysis of the FNA specimens could complement cytology diagnosis by the characterization of the biological traits at the preoperative stage. In this study, we aimed to characterize the biological profile of 33 paraffin-embedded transthoracic FNA samples obtained from three groups of lung cancer patients: two groups of small early-detected lung adenocarcinomas (radiologically subsolid and solid nodules) and a third group of small metastatic adenocarcinomas. Genetic analysis was performed by fluorescence in situ hybridization using the four-color LAVysion probe. p53 and Ki-67 protein expression was also evaluated by immunocytochemistry. The samples showed gains for all targets analyzed; two cases had EGFR gene amplification and two cases had MYC amplification. There were no significant differences in the percentage of genetically malignant cells and the expression of Ki-67 among the three groups. However, p53 accumulation was significantly higher in the metastatic group compared to the subsolid early-detected group (P = 0.001). In conclusion, molecular analysis of FNA specimens may provide useful information at preoperative stages. In our series, a good prognostic profile in subsolid early detected adenocarcinomas is suggested.

  2. Multiplatform-based molecular subtypes of non-small-cell lung cancer.

    PubMed

    Chen, F; Zhang, Y; Parra, E; Rodriguez, J; Behrens, C; Akbani, R; Lu, Y; Kurie, J M; Gibbons, D L; Mills, G B; Wistuba, I I; Creighton, C J

    2017-03-01

    Non-small-cell lung cancer (NSCLC) demonstrates remarkable molecular diversity. With the completion of The Cancer Genome Atlas (TCGA), there is opportunity for systematic analyses of the entire TCGA NSCLC cohort, including comparisons and contrasts between different disease subsets. On the basis of multidimensional and comprehensive molecular characterization (including DNA methylation and copy, and RNA and protein expression), 1023 NSCLC cases-519 from TCGA adenocarcinoma (AD) project and 504 from TCGA squamous cell carcinoma (SQCC) project-were classified using a 'cluster-of-clusters' analytic approach. Patterns from TCGA NSCLC subsets were examined in independent external databases, including the PROSPECT (Profiling of Resistance patterns and Oncogenic Signaling Pathways in Evaluation of Cancers of the Thorax) NSCLC data set. Nine genomic subtypes of NSCLC were identified, three within SQCC and six within AD. SQCC subtypes were associated with transcriptional targets of SOX2 or p63. One predominately AD subtype (with a large proportion of SQCC) shared molecular features with neuroendocrine tumors. Two AD subtypes manifested a CpG island methylator phenotype. Three AD subtypes showed high p38 and mTOR pathway activation. AD subtypes associated with low differentiation showed relatively worse prognosis. SQCC subtypes and two of the AD subtypes expressed cancer testis antigen genes, whereas three AD subtypes expressed several immune checkpoint genes including PDL1 and PDL2, corresponding with patterns of greater immune cell infiltration. Subtype associations for several immune-related markers-including PD1, PDL1, CD3 and CD8-were confirmed in the PROSPECT cohort using immunohistochemistry. NSCLC molecular subtypes have therapeutic implications and lend support to a personalized approach to NSCLC management based on molecular characterization.

  3. Melting and superionic transition of Gd-doped ceria nanocrystals: Molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Kovalenko, M. A.; Kupryazhkin, A. Ya.

    2012-11-01

    Molecular dynamics program for simulation of nanocrystals in vacuum, with ionic model approximation, was developed. The use of graphics processor allows us to speed up calculation by two orders of magnitude in comparison with CPU realization. For Ce1-XGdXO2-X/2 system by fitting to experimental data pair interaction potentials were obtained, comparison with existing potential set was carried out. Melting temperature of CeO2 nanocrystal depends on its octahedron diagonal size as Тm(L,nm) = Тm(∞) - (5534 ± 153)ṡL-2. Structural disorder of Ce1-XGdXO2-X/2 nanocrystals (X = 0-0.3) in superionic transition and melting regimes was investigated. Dependences of melting temperature and specific volume change at melting from gadolinium dopant quantity have downward trend. It is shown, that oxygen sublattice disorder ("melting") in crystallites takes place at about 0.7Tm. The contribution of intrinsic disorder to anion diffusion coefficient in systems with gadolinium dopant was extracted and the presence of superionic transition is shown. Comparison with high-temperature ionic conductivity data was carried out.

  4. Molecular Dynamics Simulations of Dislocation Activity in Single-Crystal and Nanocrystalline Copper Doped with Antimony

    NASA Astrophysics Data System (ADS)

    Rajgarhia, Rahul K.; Spearot, Douglas E.; Saxena, Ashok

    2010-04-01

    Recent experimental and simulation results have indicated that high-temperature grain growth in nanocrystalline (NC) materials can be suppressed by introducing dopant atoms at the grain boundaries. However, the influence of grain boundary dopants on the mechanical behavior of stabilized NC materials is less clear. In this work, molecular dynamics (MD) simulations are used to study the impact of very low dopant concentrations (<1.0 at. pct Sb) on plastic deformation in single-crystal and NC Cu. A new interatomic potential for low Sb concentration Cu-Sb solid-solution alloys is used to model dopant/host and dopant/dopant interatomic interactions within the MD framework. In single-crystal models, the strained regions around the Sb atoms act as heterogeneous sources for partial dislocation nucleation; the stress associated with this process decreases with increasing Sb concentration. In NC models, MD simulations indicate that Sb dopants randomly dispersed at the grain boundaries cause an increase in the flow stress in NC Cu, implying that Sb atoms at the grain boundaries retard both grain boundary sliding and dislocation nucleation from grain boundary regions.

  5. Molecularly imprinted polymer doped with Hectorite for selective recognition of sinomenine hydrochloride.

    PubMed

    Zhang, W; Fu, H L; Li, X Y; Zhang, H; Wang, N; Li, W; Zhang, X X

    2016-01-01

    In this work, a new and facile method was introduced to prepare molecularly imprinted polymers (MIPs) based on nano clay hectorite (Hec) for sinomenine hydrochloride (SM) analysis. Hec was firstly dissolved in distilled water in order to swell adequately, followed by a common precipitation polymerization with SM as the template, methacrylic acid as monomer, ethylene glycol dimethacrylate as a crosslinker and 2,2-azobisisobutyronitrile as an initiator. Hec@SM-MIPs were characterized by Fourier transform infrared spectrometer, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The maximum binding capacity of Hec@SM-MIPs, SM-MIPs and non-imprinted polymers (NIPs) (Hec@NIPs) was 57.4, 16.8 and 11.6 mg/g, respectively. The reason for this result may be that Hec@SM-MIPs have more binding sites and imprinted cavities for template molecule. Equilibrium data were described by the Langmuir and Freundlich isotherm models. The results showed that the Hec@SM-MIPs adsorption data correlated better with the Langmuir equation than the Freundlich equation under the studied concentration range. In vitro drug release experiment, Hec@SM-MIPs have a better ability to control SM release than SM-MIPs. Therefore, Hec@SM-MIPs were successfully applied to extraction of SM and used as the materials for drug delivery system.

  6. Electron Impact Ionization and Fragmentation Dynamics of Small Atomic and Molecular Clusters

    NASA Astrophysics Data System (ADS)

    Dorn, Alexander

    2016-09-01

    New ionization and fragmentation reactions emerge if target atoms or molecules are embedded in an environment as it is the case in small clusters or in the condensed phase. These can be intermolecular energy and charge transfer processes or a completely modified fragmentation behavior of the molecular ions. Here we study low energy electron impact induced ionization with a multi-electron and ion imaging spectrometer (reaction microscope) and a supersonic gas jet target which can produce small clusters of various target species. Interatomic reactions are studied for the model system of weakly bound Ar2 dimers. Here, the coincident detection of three electrons and two ions gives detailed insight in interatomic Coulombic decay and radiative charge transfer processes. Such processes were also found in bio-relevant systems like water clusters. We studied pure and water-mixed clusters of tetrahydrofuran (C4H8O, THF) which is the simplest analog of deoxyribose in the DNA backbone. One observation is that ionization of the outermost valence orbital for the monomer leads to stable THF ions. In contrast if THF is bound to another THF or a water molecule the molecular ring breaks. In addition we identify intermolecular Coulombic decay induced by energy transfer from a water molecule ionized in the inner valence shell to the neighboring THF molecule.

  7. Silicon Phthalocyanines Axially Disubstituted with Erlotinib toward Small-Molecular-Target-Based Photodynamic Therapy.

    PubMed

    Chen, Juan-Juan; Huang, Yi-Zhen; Song, Mei-Ru; Zhang, Zhi-Hong; Xue, Jin-Ping

    2017-09-21

    Small-molecular-target-based photodynamic therapy-a promising targeted anticancer strategy-was developed by conjugating zinc(II) phthalocyanine with a small-molecular-target-based anticancer drug. To prevent self-aggregation and avoid problems of phthalocyanine isomerization, two silicon phthalocyanines di-substituted axially with erlotinib have been synthesized and fully characterized. These conjugates are present in monomeric form in various solvents as well as culture media. Cell-based experiments showed that these conjugates localize in lysosomes and mitochondria, while maintaining high photodynamic activities (IC50 values as low as 8 nm under a light dose of 1.5 J cm(-2) ). With erlotinib as the targeting moiety, two conjugates were found to exhibit high specificity for EGFR-overexpressing cancer cells. Various poly(ethylene glycol) (PEG) linker lengths were shown to have an effect on the photophysical/photochemical properties and on in vitro phototoxicity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Ultrastructural and molecular changes in the developing small intestine of the toad Bufo regularis.

    PubMed

    Sakr, S A; Badawy, G M; El-Borm, H T

    2014-01-01

    The ontogenetic development of the small intestine of the toad Bufo regularis was investigated using twofold approaches, namely, ultrastructural and molecular. The former has been done using transmission electron microscope and utilizing the developmental stages 42, 50, 55, 60, 63, and 66. The most prominent ultrastructural changes were recorded at stage 60 and were more evident at stage 63. These included the appearance of apoptotic bodies/nuclei within the larval epithelium, the presence of macrophages, swollen mitochondria, distorted rough endoplasmic reticulum, chromatin condensation, and irregular nuclear envelop, and the presence of large vacuoles and lysosomes. The molecular investigation involved examining DNA content and fragmentation. The results showed that the DNA content decreased significantly during the metamorphic stages 60 and 63 compared with both larval (50 and 55) and postmetamorphic (66) stages. The metamorphic stages (60 and 63) displayed extensive DNA laddering compared with stages 50, 55, and 66. The percentage of DNA damage was 0.00%, 12.91%, 57.26%, 45.48%, and 4.43% for the developmental stages 50, 55, 60, 63, and 66, respectively. In conclusion, the recorded remodeling of the small intestine represents a model for clarifying the mechanism whereby cell death and proliferation are controlled.

  9. Radiation-associated small cell neuroendocrine carcinoma of the thyroid: a case report with molecular analyses.

    PubMed

    Mussazhanova, Zhanna; Miura, Shiro; Stanojevic, Boban; Rougounovitch, Tatiana; Saenko, Vladimir; Shiraishi, Toshio; Kurashige, Tomomi; Shichijo, Kazuko; Kaneko, Kenichi; Takahashi, Haruo; Ito, Masahiro; Nakashima, Masahiro

    2014-03-01

    Neuroendocrine tumor (NET) of the thyroid other than medullary carcinoma is extremely rare. We describe here a case of calcitonin-negative small cell neuroendocrine carcinoma (SCNEC), which occurred in a thyroid gland that had previously been irradiated at high dose (60 Gy) for pharyngeal cancer, with molecular analyses for follicular cell origin. The tumor cells were small with fine chromatin, inconspicuous nucleoli, and inapparent cytoplasm, and showed neuroendocrine architectures such as palisading, rosettes, and trabeculae. Mitotic figures were numerous exceeding 10 mitoses per 10 high-power fields. The tumor cells invaded into several vessels and metastasized to regional lymph nodes. Immunohistochemically, the tumor cells were strongly positive for neuroendocrine markers and thyroglobulin (Tg), a marker of thyroid follicular cells but negative for calcitonin and carcinoembryonic antigen (CEA). Expression of Tg and thyrotropin receptor (TSHR) were confirmed by quantitative real-time polymerase chain reaction (RT-PCR). Ki-67 labeling index was more than 70% in the tumor cells. Taken together, the tumor was diagnosed as SCNEC of the thyroid. Genetic analyses also revealed microsatellite abnormalities of the phosphatase and tensin homolog (PTEN) gene, suggesting that functional loss of PTEN contributes to carcinogenesis. This is the first report describing a SCNEC of the thyroid with molecular analyses that provide evidence for a follicular epithelial origin.

  10. Progress of small molecular inhibitors in the development of anti-influenza virus agents

    PubMed Central

    Wu, Xiaoai; Wu, Xiuli; Sun, Qizheng; Zhang, Chunhui; Yang, Shengyong; Li, Lin; Jia, Zhiyun

    2017-01-01

    The influenza pandemic is a major threat to human health, and highly aggressive strains such as H1N1, H5N1 and H7N9 have emphasized the need for therapeutic strategies to combat these pathogens. Influenza anti-viral agents, especially active small molecular inhibitors play important roles in controlling pandemics while vaccines are developed. Currently, only a few drugs, which function as influenza neuraminidase (NA) inhibitors and M2 ion channel protein inhibitors, are approved in clinical. However, the acquired resistance against current anti-influenza drugs and the emerging mutations of influenza virus itself remain the major challenging unmet medical needs for influenza treatment. It is highly desirable to identify novel anti-influenza agents. This paper reviews the progress of small molecular inhibitors act as antiviral agents, which include hemagglutinin (HA) inhibitors, RNA-dependent RNA polymerase (RdRp) inhibitors, NA inhibitors and M2 ion channel protein inhibitors etc. Moreover, we also summarize new, recently reported potential targets and discuss strategies for the development of new anti-influenza virus drugs. PMID:28382157

  11. Ultrastructural and Molecular Changes in the Developing Small Intestine of the Toad Bufo regularis

    PubMed Central

    Sakr, S. A.; Badawy, G. M.; El-Borm, H. T.

    2014-01-01

    The ontogenetic development of the small intestine of the toad Bufo regularis was investigated using twofold approaches, namely, ultrastructural and molecular. The former has been done using transmission electron microscope and utilizing the developmental stages 42, 50, 55, 60, 63, and 66. The most prominent ultrastructural changes were recorded at stage 60 and were more evident at stage 63. These included the appearance of apoptotic bodies/nuclei within the larval epithelium, the presence of macrophages, swollen mitochondria, distorted rough endoplasmic reticulum, chromatin condensation, and irregular nuclear envelop, and the presence of large vacuoles and lysosomes. The molecular investigation involved examining DNA content and fragmentation. The results showed that the DNA content decreased significantly during the metamorphic stages 60 and 63 compared with both larval (50 and 55) and postmetamorphic (66) stages. The metamorphic stages (60 and 63) displayed extensive DNA laddering compared with stages 50, 55, and 66. The percentage of DNA damage was 0.00%, 12.91%, 57.26%, 45.48%, and 4.43% for the developmental stages 50, 55, 60, 63, and 66, respectively. In conclusion, the recorded remodeling of the small intestine represents a model for clarifying the mechanism whereby cell death and proliferation are controlled. PMID:24715821

  12. Enhancement of photoluminescence in various Eu x Re(1- x)TTA3Phen (Re = Y, Tb) complexes molecularly doped in PMMA

    NASA Astrophysics Data System (ADS)

    Thejo Kalyani, N.; Dhoble, S. J.; Pode, R. B.

    2012-07-01

    Europium β-diketonate complexes Eu x Re(1- x)(TTA)3Phen, (Re = Y/Tb, TTA: thenoyl trifluro acetone, Phen: 1-10 Phenanthroline; x = 0.5) have been molecularly doped in poly methyl methacrylate matrix to study the concentration effect on the optical properties such as optical absorption and photoluminescence spectra for four different amounts of weight % (10, 25, 50 and 60 %). All these doped complexes show strong absorption peaks at 334 and 280 nm attributed to n-π* and π-π* transitions of β-diketonate ligand TTA respectively. The close absorptivity of all the complexes is due to the same tris chelated core TTA. Among the three complexes doped in PMMA matrix Eu0.5Tb0.5(TTA)3Phen complex shows hyper chromic shift with enhancement in the luminescent intensity. Enhancement of red light emission have been observed with the increase in wt% of all pure and doped systems in the order of Eu(TTA)3Phen, < Eu0.5Y0.5(TTA)3Phen < Eu0.5Tb0.5(TTA)3Phen. It has been observed that their PL intensity increases in the order of 10 > 25 > 50-60 %. However the luminescence intensity of these blended films with 50 and 60 % of rare earth complexes shows nearly equal value, indicating that the optimal doping concentration is about 50 % under the chosen experimental conditions. Hence these complexes are best suitable in fabricating eco-friendly organic light-emitting devices and displays by solution techniques, which can be operated at very low voltage.

  13. Application of a continuous-wave tunable erbium-doped fiber laser to molecular spectroscopy in the near infrared

    NASA Astrophysics Data System (ADS)

    Cousin, J.; Masselin, P.; Chen, W.; Boucher, D.; Kassi, S.; Romanini, D.; Szriftgiser, P.

    2006-05-01

    Development of a continuous-wave tunable fiber laser-based spectrometer for applied spectroscopy is reported. Wide wavelength tunability of an erbium-doped fiber laser (EDFL) was investigated in the near-infrared region of 1543-1601 nm. Continuous mode-hop free fine frequency tuning has been accomplished by temperature tuning in conjunction with mechanical tuning. The overall spectroscopic performance of the EDFL was evaluated in terms of frequency tunability along with its suitability for molecular spectroscopy. High-resolution absorption spectra of acetylene (C2H2) were recorded near 1544 nm with a minimum measurable absorption coefficient of about 3.5×10-7 cm-1/Hz1/2 for direct absorption spectroscopy associated with a 100-m long multipass cell. Detections of C2H2 at different concentration levels were performed as well with high dynamic detection range varying from 100% purity to sub ppmv using cavity ring down spectroscopy. A 3σ-detection-limited minimum detectable concentration (MDC) of 400 ppbv has been obtained by using the transition line Pe(22) of the ν1+ν3+ν5 1(Πg)-ν5 1(Πu) hot band near 1543.92 nm with a detection bandwidth of 2.3 Hz. This corresponds to a minimum detectable absorption coefficient of 6.6×10-11 cm-1/Hz1/2. The sensitivity limit could be further improved by almost one order of magnitude (down to ˜60 ppbv) by use of the Pe(27) line of the ν1+ν3(Σu +)-0(Σg +)combination band near 1543.68 nm.

  14. Electrical properties of C-doped p-type GaP and GaPN grown by molecular beam epitaxy

    SciTech Connect

    Liu Zhengxin; Kawanami, Hitoshi; Sakata, Isao

    2010-01-18

    The electrical properties of C-doped p-type GaP and GaPN epilayers grown by molecular beam epitaxy using CBr{sub 4} as a doping source have been investigated. C is shown to be a relatively shallow acceptor both in GaP and GaPN, with the activation energy in the regions of 16-33 and 18-35 meV, respectively. GaP demonstrates ordinary conduction characteristics, whereas GaPN has a typical mixed conduction effect and the impurity conduction becomes dominant at low temperatures. It is conjectured that impurity conduction and ionized impurity scattering mechanisms in GaPN may be related to the inactivated C and N radicals.

  15. Growth of a delta-doped silicon layer by molecular beam epitaxy on a charge-coupled device for reflection-limited ultraviolet quantum efficiency

    NASA Technical Reports Server (NTRS)

    Hoenk, Michael E.; Grunthaner, Paula J.; Grunthaner, Frank J.; Terhune, R. W.; Fattahi, Masoud; Tseng, Hsin-Fu

    1992-01-01

    Low-temperature silicon molecular beam epitaxy is used to grow a delta-doped silicon layer on a fully processed charge-coupled device (CCD). The measured quantum efficiency of the delta-doped backside-thinned CCD is in agreement with the reflection limit for light incident on the back surface in the spectral range of 260-600 nm. The 2.5 nm silicon layer, grown at 450 C, contained a boron delta-layer with surface density of about 2 x 10 exp 14/sq cm. Passivation of the surface was done by steam oxidation of a nominally undoped 1.5 nm Si cap layer. The UV quantum efficiency was found to be uniform and stable with respect to thermal cycling and illumination conditions.

  16. Non-adiabatic molecular dynamics investigation of photoionization state formation and lifetime in Mn²⁺-doped ZnO quantum dots.

    PubMed

    Fischer, Sean A; Lingerfelt, David B; May, Joseph W; Li, Xiaosong

    2014-09-07

    The unique electronic structure of Mn(2+)-doped ZnO quantum dots gives rise to photoionization states that can be used to manipulate the magnetic state of the material and to generate zero-reabsorption luminescence. Fast formation and long non-radiative decay of this photoionization state is a necessary requirement for these important applications. In this work, surface hopping based non-adiabatic molecular dynamics are used to demonstrate the fast formation of a metal-to-ligand charge transfer state in a Mn(2+)-doped ZnO quantum dot. The formation occurs on an ultrafast timescale and is aided by the large density of states and significant mixing of the dopant Mn(2+) 3dt2 levels with the valence-band levels of the ZnO lattice. The non-radiative lifetime of the photoionization states is also investigated.

  17. Increased effective barrier heights in Schottky diodes by molecular-beam epitaxy of CoSi2 and Ga-doped Si on Si(111)

    NASA Technical Reports Server (NTRS)

    Fathauer, R. W.; Lin, T. L.; Grunthaner, P. J.; Andersson, P. O.; Iannelli, J. M.

    1988-01-01

    Increasing the effective Schottky-barrier height of epitaxial CoSi2/Si(111) diodes by the use of thin, highly doped Si layers in close proximity to the metal-semiconductor interface has been studied. Intrinsic Si, Si doped by coevaporation of Ga, and epitaxial CoSi2 layers have all been grown in the same molecular-beam epitaxy system. Current-voltage and photoresponse characterization yield barrier heights ranging from 0.61 eV for a sample with no p(+) layer to 0.89 eV for a sample with a 20-nm-thick p(+) layer. These results are compared to theoretical values based on a one-dimensional solution of Poisson's equation under the depletion approximation.

  18. Molecular aluminum hydrides identified by inelastic neutron scattering during H2 regeneration of catalyst-doped NaAlH4.

    PubMed

    Fu, Qi Jia; Ramirez-Cuesta, A J; Tsang, Shik Chi

    2006-01-19

    Catalyst-doped sodium aluminum hydrides have been intensively studied as solid hydrogen carriers for onboard proton-exchange membrane (PEM) fuel cells. Although the importance of catalyst choice in enhancing kinetics for both hydrogen uptake and release of this hydride material has long been recognized, the nature of the active species and the mechanism of catalytic action are unclear. We have shown by inelastic neutron scattering (INS) spectroscopy that a volatile molecular aluminum hydride is formed during the early stage of H2 regeneration of a depleted, catalyst-doped sodium aluminum hydride. Computational modeling of the INS spectra suggested the formation of AlH3 and oligomers (AlH3)n (Al2H6, Al3H9, and Al4H12 clusters), which are pertinent to the mechanism of hydrogen storage. This paper demonstrates, for the first time, the existence of these volatile species.

  19. Non-conjugated small molecule FRET for differentiating monomers from higher molecular weight amyloid beta species.

    PubMed

    Ran, Chongzhao; Zhao, Wei; Moir, Robert D; Moore, Anna

    2011-04-29

    Systematic differentiation of amyloid (Aβ) species could be important for diagnosis of Alzheimer's disease (AD). In spite of significant progress, controversies remain regarding which species are the primary contributors to the AD pathology, and which species could be used as the best biomarkers for its diagnosis. These controversies are partially caused by the lack of reliable methods to differentiate the complicated subtypes of Aβ species. Particularly, differentiation of Aβ monomers from toxic higher molecular weight species (HrMW) would be beneficial for drug screening, diagnosis, and molecular mechanism studies. However, fast and cheap methods for these specific aims are still lacking. We demonstrated the feasibility of a non-conjugated FRET (Förster resonance energy transfer) technique that utilized amyloid beta (Aβ) species as intrinsic platforms for the FRET pair assembly. Mixing two structurally similar curcumin derivatives that served as the small molecule FRET pair with Aβ40 aggregates resulted in a FRET signal, while no signal was detected when using Aβ40 monomer solution. Lastly, this FRET technique enabled us to quantify the concentrations of Aβ monomers and high molecular weight species in solution. We believe that this FRET technique could potentially be used as a tool for screening for inhibitors of Aβ aggregation. We also suggest that this concept could be generalized to other misfolded proteins/peptides implicated in various pathologies including amyloid in diabetes, prion in bovine spongiform encephalopathy, tau protein in AD, and α-synuclein in Parkinson disease.

  20. Molecular dynamics investigation of separation of hydrogen sulfide from acidic gas mixtures inside metal-doped graphite micropores.

    PubMed

    Huang, Pei-Hsing

    2015-09-21

    The separation of poisonous compounds from various process fluids has long been highly intractable, motivating the present study on the dynamic separation of H2S in acidic-gas-mixture-filled micropores. The molecular dynamics approach, coupled with the isothermal-isochoric ensemble, was used to model the molecular interactions and adsorption of H2S/CO2/CO/H2O mixtures inside metal-doped graphite slits. Due to the difference in the adsorption characteristics between the two distinct adsorbent materials, the metal dopant in the graphitic micropores leads to competitive adsorption, i.e. the Au and graphite walls compete to capture free adsorbates. The effects of competitive adsorption, coupled with changes in the gas temperature, concentration, constituent ratio and slit width on the constituent separation of mixtures were systematically studied. The molecule-wall binding energies calculated in this work (those of H2S, H2O and CO on Au walls and those of H2O, CO and CO2 on graphite walls) show good agreement with those obtained using density functional theory (DFT) and experimental results. The z-directional self-diffusivities (Dz) for adsorbates inside the slit ranged from 10(-9) to 10(-7) m(2) s(-1) as the temperature was increased from 10 to 500 K. The values are comparable with those for a typical microporous fluid (10(-8)-10(-9) m(2) s(-1) in a condensed phase and 10(-6)-10(-7) m(2) s(-1) in the gaseous state). The formation of H-bonding networks and hydrates of H2S is disadvantageous for the separation of mixtures. The results indicate that H2S can be efficiently separated from acidic gas mixtures onto the Au(111) surface by (i) reducing the mole fraction of H2S and H2O in the mixtures, (ii) raising the gas temperature to the high temperature limit (≥400 K), and (iii) lowering the slit width to below the threshold dimension (≤23.26 Å).

  1. Validation and extraction of molecular-geometry information from small-molecule databases

    PubMed Central

    Long, Fei; Emsley, Paul; Gražulis, Saulius; Merkys, Andrius; Vaitkus, Antanas

    2017-01-01

    A freely available small-molecule structure database, the Crystallography Open Database (COD), is used for the extraction of molecular-geometry information on small-molecule compounds. The results are used for the generation of new ligand descriptions, which are subsequently used by macromolecular model-building and structure-refinement software. To increase the reliability of the derived data, and therefore the new ligand descriptions, the entries from this database were subjected to very strict validation. The selection criteria made sure that the crystal structures used to derive atom types, bond and angle classes are of sufficiently high quality. Any suspicious entries at a crystal or molecular level were removed from further consideration. The selection criteria included (i) the resolution of the data used for refinement (entries solved at 0.84 Å resolution or higher) and (ii) the structure-solution method (structures must be from a single-crystal experiment and all atoms of generated molecules must have full occupancies), as well as basic sanity checks such as (iii) consistency between the valences and the number of connections between atoms, (iv) acceptable bond-length deviations from the expected values and (v) detection of atomic collisions. The derived atom types and bond classes were then validated using high-order moment-based statistical techniques. The results of the statistical analyses were fed back to fine-tune the atom typing. The developed procedure was repeated four times, resulting in fine-grained atom typing, bond and angle classes. The procedure will be repeated in the future as and when new entries are deposited in the COD. The whole procedure can also be applied to any source of small-molecule structures, including the Cambridge Structural Database and the ZINC database. PMID:28177306

  2. Molecular dynamics of glycine ions in alanine doped TGS single crystal as probed by polarized laser raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Bajpai, P. K.; Verma, A. L.

    2012-10-01

    Polarized Raman spectra of pure and alanine doped tri-glycine sulfate (TGS) single crystals at 12 K in different scattering geometries are analyzed. Sub species modes due to three crystallographically distinguishable glycine ions G (I), G (II) and G (III) are assigned. It is observed that alanine doping does not change the crystalline field and acts as local perturbation only. The major changes due to doping are observed in the relative intensities of different modes; most of the modes associated with G (I) and SO42- ions show reversal behavior in relative intensity at high doping concentration. The observed spectral changes are analyzed in terms of reorientation of G (I) ions with sub species modes of G (II)/ G (III) following the reorientation due to complex hydrogen bonding network.

  3. Molecular dynamics of glycine ions in alanine doped TGS single crystal as probed by polarized laser Raman spectroscopy.

    PubMed

    Bajpai, P K; Verma, A L

    2012-10-01

    Polarized Raman spectra of pure and alanine doped tri-glycine sulfate (TGS) single crystals at 12 K in different scattering geometries are analyzed. Sub species modes due to three crystallographically distinguishable glycine ions G (I), G (II) and G (III) are assigned. It is observed that alanine doping does not change the crystalline field and acts as local perturbation only. The major changes due to doping are observed in the relative intensities of different modes; most of the modes associated with G (I) and SO(4)(2-) ions show reversal behavior in relative intensity at high doping concentration. The observed spectral changes are analyzed in terms of reorientation of G (I) ions with sub species modes of G (II)/ G (III) following the reorientation due to complex hydrogen bonding network.

  4. Theoretical investigations on enhancing the performance of terminally diketopyrrolopyrrole-based small-molecular donors in organic solar cell applications.

    PubMed

    Liu, Xiaorui; Huang, Chengzhi; Shen, Wei; He, Rongxing; Li, Ming

    2016-01-01

    Diketopyrrolopyrrole (DPP)-based small molecules with acceptor-core-acceptor (A-core-A) type as donor materials have been used successfully in organic solar cells (OSC). In this work, based on the DPP-core-DPP type molecule SM1 consisting of a DPP unit as acceptor and benzene as the core, we replaced the benzene core with more electron-withdrawing groups in SM1 and further designed four new small-molecular donors (SM2-SM5) in order to improve the electrical properties, optical absorption and performance in OSC applications. The calculated results indicate that the designed small-molecular donors SM2-SM5 exhibit better performances in comparison with SM1, such as lower highest occupied molecular orbital (HOMO), narrower energy gap, larger absorption range, better electronic transfer between donor and acceptor and higher hole mobility. Moreover, the decreased HOMO levels and transition energy of small-molecular donors in OSC applications play an important role in the parameters of open-current voltage, fill factor and short-circuit current. Consequently, adjusting the electron-deficient ability of cores in DPP-core-DPP type small-molecular donors is an efficient approach that can be used to obtain high-efficiency DPP-based small-molecular donors for OSC applications. Graphical Abstract The designed small-molecules with good electronic and photophysical properties will act as a promising donor candidate for organic solar cell applications. Moreover, The decreased HOMO levels and transition energy of small-molecular donors in OSC applications play an important role in the parameters of open-current voltage, fill factor and short-circuit current.

  5. Small-molecule G-quadruplex interactions: Systematic exploration of conformational space using multiple molecular dynamics.

    PubMed

    Husby, Jarmila; Todd, Alan K; Platts, James A; Neidle, Stephen

    2013-12-01

    G-quadruplexes are higher-order four-stranded structures formed from repetitive guanine-containing tracts in nucleic acids. They comprise a core of stacked guanine-quartets linked by loops of length and sequence that vary with the context in which the quadruplex sequence occurs. Such sequences can be found in a number of genomic environments; at the telomeric ends of eukaryotic chromosomes, in promoter regions, in untranslated sequences and in open reading frames. Quadruplex formation can inhibit telomere maintenance, transcription and translation, especially when enhanced by quadruplex-binding small molecules, and quadruplex targeting is currently of considerable interest. The available experimental structural data shows that quadruplexes can have high conformational flexibility, especially in loop regions, which has hampered attempts to use high-throughput docking to find quadruplex-binding small-molecules with new scaffolds or to optimize existing ones with structure-based design methods. An approach to overcome the challenge of quadruplex conformational flexibility is presented here, which uses a combined multiple molecular dynamics and sampling approach. Two test small molecules have been used, RHPS4 and pyridostatin, which themselves have contrasting degrees of conformational flexibility. Copyright © 2013 Wiley Periodicals, Inc.

  6. Acidolysis small molecular phenolic ether used as accelerator in photosensitive diazonaphthaquinone systems

    NASA Astrophysics Data System (ADS)

    Zhou, Haihua; Zou, Yingquan

    2006-03-01

    The photosensitive compounds in the photosensitive coatings of positive PS plates are the diazonaphthaquinone derivatives. Some acidolysis small molecular phenolic ethers, which were synthesized by some special polyhydroxyl phenols with vinyl ethyl ether, are added in the positive diazonaphthaquinone photosensitive composition to improve its sensitivity, composed with photo-acid-generators. The effects to the photosensitivity, anti-alkali property, anti-isopropyl alcohol property, dot resolution and line resolution of the coatings are studied with different additive percent of the special phenolic ethers. In the conventional photosensitive diazonaphthaquinone systems for positive PS plates, the photosensitivity is improved without negative effects to resolution, anti-alkali and anti-isopropyl alcohol properties when added about 5% of the special acidolysis phenolic ethers, EAAE or DPHE, composed with photo-acid-generators.

  7. Small-angle neutron scattering and molecular dynamics structural study of gelling DNA nanostars

    NASA Astrophysics Data System (ADS)

    Fernandez-Castanon, J.; Bomboi, F.; Rovigatti, L.; Zanatta, M.; Paciaroni, A.; Comez, L.; Porcar, L.; Jafta, C. J.; Fadda, G. C.; Bellini, T.; Sciortino, F.

    2016-08-01

    DNA oligomers with properly designed sequences self-assemble into well defined constructs. Here, we exploit this methodology to produce bulk quantities of tetravalent DNA nanostars (each one composed of 196 nucleotides) and to explore the structural signatures of their aggregation process. We report small-angle neutron scattering experiments focused on the evaluation of both the form factor and the temperature evolution of the scattered intensity at a nanostar concentration where the system forms a tetravalent equilibrium gel. We also perform molecular dynamics simulations of one isolated tetramer to evaluate the form factor numerically, without resorting to any approximate shape. The numerical form factor is found to be in very good agreement with the experimental one. Simulations predict an essentially temperature-independent form factor, offering the possibility to extract the effective structure factor and its evolution during the equilibrium gelation.

  8. Elucidating the Molecular Deformation Mechanism of Entangled Polymers in Fast Flow by Small Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Wang, Yangyang; Sanchez-Diaz, Luis; Cheng, Shiwang; Hong, Kunlun; Chen, Wei-Ren; Liu, Jianning; Lin, Panpan; Wang, Shi-Qing

    Understanding the viscoelastic properties of polymers is of fundamental and practical importance because of the vast and ever expanding demand of polymeric materials in daily life. Our current theoretical framework for describing the nonlinear flow behavior of entangled polymers is built upon the tube model pioneered by de Gennes, Doi, and Edwards. In this work, we critically examine the central hypothesis of the tube model for nonlinear rheology using small angle neutron scattering (SANS). While the tube model envisions a unique non-affine elastic deformation mechanism for entangled polymers, our SANS measurements show that the evolution of chain conformation of a well-entangled polystyrene melt closely follows the affine deformation mechanism in uniaxial extension, even when the Rouse Weissenberg number is much smaller than unity. This result provides a key clue for understanding the molecular deformation mechanism of entangled polymers in fast flow. Several implications from our analysis will be discussed in this talk.

  9. Low energy emission bands in a small molecular fluorene derivative for organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Lou, S. L.; Yu, H. S.; Ma, W. M.; Jiang, Y.; Zhang, Q.

    2008-11-01

    6,6'-(9H-fluoren-9,9-diyl)bis(2,3-bis(9,9-dihexyl-9H-fluoren-2-yl)quinoxaline) (BFLBBFLYQ) was a novel small molecular fluorene material with fluorescence maxima at 450 nm in spin cast films. Compared to spin cast films, BFLBBFLYQ vacuum evaporated deposition films exhibited different photo-physical properties. The low energy emission bands from 530 to 570 nm were observed from the electroluminescence (EL) and photoluminescence (PL) spectra of BFLBBFLYQ films evaporated deposition in ultrahigh vacuum circumstance, and the origin of these emission features were investigated and discussed. Also, the emissive properties of BFLBBFLYQ spin cast films upon thermal annealing and under UV irradiation in air were characterized for the effect of thermal oxidization and photo-oxidization.

  10. Skin: Major target organ of allergic reactions to small molecular weight compounds

    SciTech Connect

    Merk, Hans F. Baron, Jens M.; Neis, Mark M.; Obrigkeit, Daniela Hoeller; Karlberg, Ann-Therese

    2007-11-01

    Skin is a major target organ for allergic reactions to small molecular weight compounds. Drug allergic reactions may be life-threatening such as in the case of anaphylactic reactions or bullous drug reactions and occur in about 5% of all hospitalized patients. Allergic contact dermatitis has an enormous influence on the social life of the patient because it is the most frequent reason for occupational skin diseases and the treatment and prevention of this disease cost approximately Euro 3 billion per year in Germany. The different proposed pathophysiological pathways leading to a drug eruption are discussed in this paper. All major enzymes which are involved in the metabolism of xenobiotica were shown to be present in skin. Evidence supporting the role of metabolism in the development of drug allergy and allergic contact dermatitis is demonstrated in the example of sulphonamides and fragrances.

  11. Molecularly targeted therapies for advanced or metastatic non-small-cell lung carcinoma

    PubMed Central

    Bayraktar, Soley; Rocha-Lima, Caio M

    2013-01-01

    Non-small-cell lung cancer (NSCLC) remains the leading cause of cancer-related death in both men and women in the United States. Platinum-based doublet chemotherapy has been a standard for patients with advanced stage disease. Improvements in overall survival and quality of life have been modest. Improved knowledge of the aberrant molecular signaling pathways found in NSCLC has led to the development of biomarkers with associated targeted therapeutics, thus changing the treatment paradigm for many NSCLC patients. In this review, we present a summary of many of the currently investigated biologic targets in NSCLC, discuss their current clinical trial status, and also discuss the potential for development of other targeted agents. PMID:23696960

  12. Transient electroluminescence dynamics in small molecular organic light-emitting diodes

    SciTech Connect

    Gan, Z; Liu, R; Shinar, R; Shinar, J

    2010-09-14

    Intriguing electroluminescence (EL) spikes, following a voltage pulse applied to small molecular OLEDs, are discussed, elucidating carrier and exciton quenching dynamics and their relation to device structure. At low temperatures, all devices exhibit spikes at {approx} 70-300 ns and {mu}s-long tails. At 295 K only those with a hole injection barrier, carrier-trapping guest-host emitting layer, and no strong hole-blocking layer exhibit the spikes. They narrow and appear earlier under post-pulse reverse bias. The spikes and tails are in agreement with a revised model of recombination of correlated charge pairs (CCPs) and initially unpaired charges. Decreased post-pulse field-induced dissociative quenching of singlet excitons and CCPs, and possibly increased post-pulse current of holes that 'turn back' toward the recombination zone after having drifted beyond it are suspected to cause the spikes amplitude, which exceeds the dc EL.

  13. Organic oxide/Al composite cathode in small molecular organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Guo, Tzung-Fang; Yang, Fuh-Shun; Tsai, Zen-Jay; Wen, Ten-Chin; Wu, Ching-In; Chung, Chia-Tin

    2006-07-01

    This study addresses the feasibility of using an organic oxide/Al composite cathode to fabricate the small molecular organic light-emitting diodes (OLEDs). A supplementary organic buffer film is placed at the interface between the tris(8-hydroxyquinoline) aluminum (Alq3) and the organic oxide/Al complex layers. Incorporating the rubrene/poly(ethylene glycol) dimethyl ether (PEGDE) buffer layers into the composite cathode structure markedly improves the performance of devices. The luminous efficiencies of Alq3-based OLEDs biased at ˜100mA /cm2 are 4.8 and 5.1cd/A for rubrene (50Å)/PEGDE (15Å)/Al and rubrene (50Å)/PEGDE (15Å)/LiF (5Å)/Al cathode devices, and 1.3 and 3.8cd/A for devices with Al and LiF (5Å)/Al cathodes, respectively.

  14. The small molecular mass antifungal protein of Penicillium chrysogenum--a mechanism of action oriented review.

    PubMed

    Hegedus, Nikoletta; Leiter, Eva; Kovács, Barbara; Tomori, Valéria; Kwon, Nak-Jung; Emri, Tamás; Marx, Florentine; Batta, Gyula; Csernoch, László; Haas, Hubertus; Yu, Jae-Hyuk; Pócsi, István

    2011-12-01

    The β-lactam producing filamentous fungus Penicillium chrysogenum secretes a 6.25 kDa small molecular mass antifungal protein, PAF, which has a highly stable, compact 3D structure and is effective against a wide spectrum of plant and zoo pathogenic fungi. Its precise physiological functions and mode of action need to be elucidated before considering possible biomedical, agricultural or food technological applications. According to some more recent experimental data, PAF plays an important role in the fine-tuning of conidiogenesis in Penicillium chrysogenum. PAF triggers apoptotic cell death in sensitive fungi, and cell death signaling may be transmitted through two-component systems, heterotrimeric G protein coupled signal transduction and regulatory networks as well as via alteration of the Ca(2+) -homeostasis of the cells. Possible biotechnological applications of PAF are also outlined in the review.

  15. Small molecular donors for organic solar cells obtained by simple and clean synthesis.

    PubMed

    Demeter, Dora; Mohamed, Salma; Diac, Andreea; Grosu, Ion; Roncali, Jean

    2014-04-01

    A small donor-acceptor molecule is synthesized in a two-step procedure involving reaction of N,N-diphenylhydrazine on 2,5-diformylthiophene and Knoevenagel condensation. Results of UV/Vis absorption spectroscopy and cyclic voltammetry show that replacement of the phenyl ring bridge of a reference compound 2 by an azo group produces a slight red-shift of λmax, an enhancement of the molecular absorption coefficient, and a decrease of the energy level of the frontier orbitals. A preliminary evaluation of the potentialities of compound 1 as donor material in a basic bilayer planar heterojunction cell of 28 mm(2) active area using C60 as acceptor gave a short-circuit current density of 6.32 mA cm(-2) and a power conversion efficiency of 2.07 %.

  16. Donor and acceptor levels in ZnO homoepitaxial thin films grown by molecular beam epitaxy and doped with plasma-activated nitrogen

    SciTech Connect

    Muret, Pierre; Tainoff, Dimitri; Morhain, Christian; Chauveau, Jean-Michel

    2012-09-17

    Deep level transient spectroscopy of both majority and minority carrier traps is performed in a n-type, nitrogen doped homoepitaxial ZnO layer grown on a m-plane by molecular beam epitaxy. Deep levels, most of them being not detected in undoped ZnO, lie close to the band edges with ionization energies in the range 0.12-0.60 eV. The two hole traps with largest capture cross sections are likely acceptors, 0.19 and 0.48 eV from the valence band edge, able to be ionized below room temperature. These results are compared with theoretical predictions and other experimental data.

  17. Molecular Beam Epitaxy growth and characterization of silicon - Doped InAs dot in a well quantum dot infrared photo detector (DWELL-QDIP)

    NASA Astrophysics Data System (ADS)

    Srinivasan, T.; Mishra, P.; Jangir, S. K.; Raman, R.; Sridhara Rao, D. V.; Rawal, D. S.; Muralidharan, R.

    2015-05-01

    We report the growth by Molecular Beam Epitaxy (MBE), fabrication and characterization of silicon doped 20 layer InAs dot in a well quantum dot infrared photo detector (DWELL-QDIP) device structures. Two structures with InAs dots of vertical heights of 50 Å and 40 Å were compared. A 2-8 μm band normal incidence photo response of the detector with polarization and bias dependence was obtained at 77 K. The specific peak detectivity D∗ be 0.8 × 109 Jones for one of the detectors.

  18. Investigation of the optical properties of GaAs with δ-Si doping grown by molecular-beam epitaxy at low temperatures

    SciTech Connect

    Lavrukhin, D. V. Yachmenev, A. E.; Bugaev, A. S.; Galiev, G. B.; Klimov, E. A.; Khabibullin, R. A.; Ponomarev, D. S.; Maltsev, P. P.

    2015-07-15

    Molecular-beam epitaxy is used for the preparation of structures based on “low-temperature” grown GaAs with introduced d-Si doping. Specific features in the photon-energy range of 1.28–1.48 eV are observed in the photoluminescence spectrum after structures annealing at temperatures of 520 and 580°C; these features are related to the formation of point defects and their complexes. The “pump–probe” light transmission measurements reveal that the characteristic lifetimes of nonequilibrium carriers in the fabricated structures amount to T{sup c} ≈ 1.2–1.5 ps.

  19. Path integral molecular dynamics simulation of quasi-free rotational motion of CO doped in a large para-hydrogen cluster

    NASA Astrophysics Data System (ADS)

    Mizumoto, Yoshihiko; Ohtsuki, Yukiyoshi

    2011-01-01

    Path integral molecular dynamics simulation is used to study the rotational motion of a CO molecule doped in a large para-hydrogen (p-H2) cluster. The quasi-free rotational motion of CO in a p-H2 cluster with a reduced rotational constant is derived from the imaginary-time orientational correlation functions, and is in good agreement with recent experimental observations. We attribute the reduced rotational constant to the low-viscous fluid-like behavior of the host p-H2 cluster.

  20. Small-Animal Molecular Imaging for Preclinical Cancer Research: .μPET and μ.SPECT.

    PubMed

    Cuccurullo, Vincenzo; Di Stasio, Giuseppe D; Schillirò, Maria L; Mansi, Luigi

    2016-01-01

    Due to different sizes of humans and rodents, the performance of clinical imaging devices is not enough for a scientifically reliable evaluation in mice and rats; therefore dedicated small-animal systems with a much higher sensitivity and spatial resolution, compared to the ones used in humans, are required. Smallanimal imaging represents a cutting-edge research method able to approach an enormous variety of pathologies in which animal models of disease may be used to elucidate the mechanisms underlying the human condition and/or to allow a translational pharmacological (or other) evaluation of therapeutic tools. Molecular imaging, avoiding animal sacrifice, permits repetitive (i.e. longitudinal) studies on the same animal which becomes its own control. In this way also the over time evaluation of disease progression or of the treatment response is enabled. Many different rodent models have been applied to study almost all kind of human pathologies or to experiment a wide series of drugs and/or other therapeutic instruments. In particular, relevant information has been achieved in oncology by in vivo neoplastic phenotypes, obtained through procedures such as subcutaneous tumor grafts, surgical transplantation of solid tumor, orthotopic injection of tumor cells into specific organs/sites of interest, genetic modification of animals to promote tumor-genesis; in this way traditional or innovative treatments, also including gene therapy, of animals with a cancer induced by a known carcinogen may be experimented. Each model has its own disadvantage but, comparing different studies, it is possible to achieve a panoramic and therefore substantially reliable view on the specific subject. Small-animal molecular imaging has become an invaluable component of modern biomedical research that will gain probably an increasingly important role in the next few years.

  1. Ab Initio Computational Study of Chromate Molecular Anion Adsorption on the Surfaces of Pristine and B- or N-Doped Carbon Nanotubes and Graphene

    NASA Astrophysics Data System (ADS)

    Hizhnyi, Yuriy; Nedilko, Sergii; Borysiuk, Viktor; Shyichuk, Andrii

    2017-01-01

    Density functional theory (DFT) computations of the electronic structures of undoped, B- and N-doped CNT(3,3), CNT(5,5) carbon nanotubes, and graphene with adsorbed chromate anions CrO4 2- were performed within molecular cluster approach. Relaxed geometries, binding energies, charge differences of the adsorbed CrO4 2- anions, and electronic wave function contour plots were calculated using B3LYP hybrid exchange-correlation functional. Oscillator strengths of electronic transitions of CrO4 2- anions adsorbed on the surfaces of studied carbon nanostructures were calculated by the TD-DFT method. Calculations reveal covalent bonding between the anion and the adsorbents in all studied adsorption configurations. For all studied types of adsorbent structures, doping with N strengthens chemical bonding with CrO4 2- anions, providing a 2-eV increase in binding energies comparatively to adsorption of the anion on undoped adsorbents. Additional electronic transitions of CrO4 2- anions appear in the orange-green spectral region when the anions are adsorbed on the N-doped low-diameter carbon nanotubes CNT(3,3) and CNT(5,5).

  2. Ab Initio Computational Study of Chromate Molecular Anion Adsorption on the Surfaces of Pristine and B- or N-Doped Carbon Nanotubes and Graphene.

    PubMed

    Hizhnyi, Yuriy; Nedilko, Sergii; Borysiuk, Viktor; Shyichuk, Andrii

    2017-12-01

    Density functional theory (DFT) computations of the electronic structures of undoped, B- and N-doped CNT(3,3), CNT(5,5) carbon nanotubes, and graphene with adsorbed chromate anions CrO4(2-) were performed within molecular cluster approach. Relaxed geometries, binding energies, charge differences of the adsorbed CrO4(2-) anions, and electronic wave function contour plots were calculated using B3LYP hybrid exchange-correlation functional. Oscillator strengths of electronic transitions of CrO4(2-) anions adsorbed on the surfaces of studied carbon nanostructures were calculated by the TD-DFT method. Calculations reveal covalent bonding between the anion and the adsorbents in all studied adsorption configurations. For all studied types of adsorbent structures, doping with N strengthens chemical bonding with CrO4(2-) anions, providing a ~2-eV increase in binding energies comparatively to adsorption of the anion on undoped adsorbents. Additional electronic transitions of CrO4(2-) anions appear in the orange-green spectral region when the anions are adsorbed on the N-doped low-diameter carbon nanotubes CNT(3,3) and CNT(5,5).

  3. Development of molecularly targeted agents and immunotherapies in small cell lung cancer.

    PubMed

    Sharp, Adam; Bhosle, Jaishree; Abdelraouf, Fatma; Popat, Sanjay; O'Brien, Mary; Yap, Timothy A

    2016-06-01

    Small cell lung cancer (SCLC) is a smoking-induced malignancy with multiple toxin-associated mutations, which accounts for 15% of all lung cancers. It remains a clinical challenge with a rapid doubling time, early dissemination and poor prognosis. Despite multiple clinical trials in SCLC, platinum-based chemotherapy remains the mainstay of treatment in the first line advanced disease setting; good initial responses are nevertheless inevitably followed by disease relapse and survival ultimately remains poor. There are currently no molecularly targeted agents licenced for use in SCLC. Advances in sequencing the cancer genome and other high-throughput profiling technologies have identified aberrant pathways and mechanisms implicated in SCLC development and progression. Novel anti-tumour therapeutics that impact these putative targets are now being developed and investigated in SCLC. In this review, we discuss novel anti-tumour agents assessed in SCLC with reference to the complex molecular mechanisms implicated in SCLC development and progression. We focus on novel DNA damage response inhibitors, immune checkpoint modulators and antibody-drug conjugates that have shown promise in SCLC, and which may potentially transform treatment strategies in this disease. Finally, we envision the future management of SCLC and propose a biomarker-driven translational treatment paradigm for SCLC that incorporates next generation sequencing studies with patient tumours, circulating plasma DNA and functional imaging. Such modern strategies have the potential to transform the management and improve patient outcomes in SCLC.

  4. Molecular phylogeny of the small carpenter bees (Hymenoptera: Apidae: Ceratinini) indicates early and rapid global dispersal.

    PubMed

    Rehan, Sandra M; Chapman, Tom W; Craigie, Andrew I; Richards, Miriam H; Cooper, Steven J B; Schwarz, Michael P

    2010-06-01

    The small carpenter bees (tribe Ceratinini, family Apidae) are recorded from all continents except Antarctica. The Ceratinini have a near-global distribution which contrasts strongly with their sister tribe, the Allodapini which has a largely southern Old World distribution. The Ceratinini therefore provides an excellent group to understand the factors that help determine the biogeography and radiation of the bees. This is the first molecular study of ceratinine bees covering representatives from both northern and southern hemisphere Old and New World regions. We use two mitochondrial and one nuclear marker (totalling 2807 nucleotides) to examine the age, cladogenesis and historical biogeography of this tribe. Tree topology and molecular dating support an African origin at about 47 Mya with subsequent dispersal into Eurasia 44 Mya, and followed by an American invasion 32 Mya. Concentrated African and Malagasy sampling revealed there were two or three dispersals events into Madagascar ranging from 25 to 9 Mya. Lineage through time analyses suggest higher rates of cladogenesis close to the origin of the tribe, and this corresponds to both major dispersal events and divergences of lineages leading to extant subgenera. Ceratinini have potentially great importance for future studies to understand the relative roles of dispersal ability and time of origin in determining bee biogeography.

  5. First molecular isolation of Mycoplasma ovis from small ruminants in North Africa.

    PubMed

    Rjeibi, Mohamed R; Darghouth, Mohamed A; Omri, Houda; Souidi, Khemaïs; Rekik, Mourad; Gharbi, Mohamed

    2015-06-08

    Eperythrozoonosis is a small ruminant disease caused by the bacterium Mycoplasma ovis (formerly known as Eperythrozoon ovis). Whilst acute infection in sheep may result in an anaemia and ill thrift syndrome, most animals do not develop clinical signs. Molecular methods were used to compare and evaluate the prevalence of infection with M. ovis in sheep and goats in Tunisia. A total of 739 whole blood samples from 573 sheep and 166 goats were tested for the M. ovis 16S rRNA gene using PCR. The overall prevalence was 6.28% ± 0.019 (36/573). Only sheep were infected with M. ovis (p < 0.001), and the prevalence was significantly higher in central Tunisia (29.2%) compared with other regions (p < 0.05). The prevalence revealed significant differences according to breed and bioclimatic zones (p < 0.001). Furthermore, the prevalence in young sheep (35/330; 10.6%) was higher than in adults (1/243; 0.41%) (p < 0.001). Only sheep of the Barbarine breed were infected, with a prevalence of 11.8% (p < 0.001). This is the first molecular study and genetic characterisation of M. ovis in North African sheep breeds.

  6. Small molecular weight proteins/peptides present in the in vivo formed human acquired enamel pellicle.

    PubMed

    Siqueira, Walter L; Oppenheim, Frank G

    2009-05-01

    The aim of this study was to investigate the type and the nature of peptides present in the in vivo formed human acquired enamel pellicle. Pellicle material was collected from 10 volunteers and subjected to sample preparations consisting of centrifugal filtration using a 10 kDa molecular weight cut-off membrane and high-resolution gel filtration chromatography. The fractions containing peptides <10 kDa obtained by both methods were analyzed by LC-ESI-MS/MS. 78 natural pellicle peptides with molecular weights ranging from 766.9 Da to 3981.4 Da were identified originating from 29 different proteins. The number of peptides present in acquired enamel pellicle appears to be large and this is likely to enhance the functional spectrum of this protein film. The presence of small peptides in pellicle may be functionally important since structure/function studies of many salivary proteins have shown that specific domains within these native proteins retain or even exhibit enhanced biological activities. The data present the basis for determining the precise function of these pellicle peptides and for gaining insights into the role pellicle plays in the oral cavity.

  7. Structural and functional homology between periplasmic bacterial molecular chaperones and small heat shock proteins.

    PubMed

    Zav'yalov, V P; Zav'yalova, G A; Denesyuk, A I; Gaestel, M; Korpela, T

    1995-07-01

    The periplasmic Yersinia pestis molecular chaperone Caf1M belongs to a superfamily of bacterial proteins for one of which (PapD protein of Escherichia coli) the immunoglobulin-like fold was solved by X-ray analysis. The N-terminal domain of Caf1M was found to share a 20% amino acid sequence identity with an inclusion body-associated protein IbpB of Escherichia coli. One of the regions that was compared, was 32 amino acids long, and displayed more than 40% identity, probability of random coincidence was 1.2 x 10(-4). IbpB is involved in a superfamily of small heat shock proteins which fulfil the function of molecular chaperone. On the basis of the revealed homology, an immunoglobulin-like one-domain model of IbpB three-dimensional structure was designed which could be a prototype conformation of sHsp's. The structure suggested is in good agreement with the known experimental data obtained for different members of sHsp's superfamily.

  8. Advances in the Development of Molecularly Targeted Agents in Non-Small-Cell Lung Cancer.

    PubMed

    Dolly, Saoirse O; Collins, Dearbhaile C; Sundar, Raghav; Popat, Sanjay; Yap, Timothy A

    2017-04-04

    Non-small-cell lung cancer (NSCLC) remains a significant global health challenge and the leading cause of cancer-related mortality. The traditional 'one-size-fits-all' treatment approach has now evolved into one that involves personalized strategies based on histological and molecular subtypes. The molecular era has revolutionized the treatment of patients harboring epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK) and ROS1 gene aberrations. In the appropriately selected population, anti-tumor agents against these molecular targets can significantly improve progression-free survival. However, the emergence of acquired resistance is inevitable. Novel potent compounds with much improved and rational selectivity profiles, such as third-generation EGFR T790M resistance mutation-specific inhibitors, have been developed and added to the NSCLC armamentarium. To date, attempts to overcome resistance bypass pathways through downstream signaling blockade has had limited success. Furthermore, the majority of patients still do not harbor known driver genetic or epigenetic alterations and/or have no new available treatment options, with chemotherapy remaining their standard of care. Several potentially actionable driver aberrations have recently been identified, with the early clinical development of multiple inhibitors against these promising targets currently in progress. The advent of immune checkpoint inhibitors has led to significant benefit for advanced NSCLC patients with durable responses observed. Further interrogation of the underlying biology of NSCLC, coupled with modern clinical trial designs, is now required to develop novel targeted therapeutics rationally matched with predictive biomarkers of response, so as to further advance NSCLC therapeutics through the next decade.

  9. Molecular architecture of the 90S small subunit pre-ribosome

    PubMed Central

    Sun, Qi; Zhu, Xing; Qi, Jia; An, Weidong; Lan, Pengfei; Tan, Dan; Chen, Rongchang; Wang, Bing; Zheng, Sanduo; Zhang, Cheng; Chen, Xining; Zhang, Wei; Chen, Jing; Dong, Meng-Qiu; Ye, Keqiong

    2017-01-01

    Eukaryotic small ribosomal subunits are first assembled into 90S pre-ribosomes. The complete 90S is a gigantic complex with a molecular mass of approximately five megadaltons. Here, we report the nearly complete architecture of Saccharomyces cerevisiae 90S determined from three cryo-electron microscopy single particle reconstructions at 4.5 to 8.7 angstrom resolution. The majority of the density maps were modeled and assigned to specific RNA and protein components. The nascent ribosome is assembled into isolated native-like substructures that are stabilized by abundant assembly factors. The 5' external transcribed spacer and U3 snoRNA nucleate a large subcomplex that scaffolds the nascent ribosome. U3 binds four sites of pre-rRNA, including a novel site on helix 27 but not the 3' side of the central pseudoknot, and crucially organizes the 90S structure. The 90S model provides significant insight into the principle of small subunit assembly and the function of assembly factors. DOI: http://dx.doi.org/10.7554/eLife.22086.001 PMID:28244370

  10. Molecular architecture of the 90S small subunit pre-ribosome.

    PubMed

    Sun, Qi; Zhu, Xing; Qi, Jia; An, Weidong; Lan, Pengfei; Tan, Dan; Chen, Rongchang; Wang, Bing; Zheng, Sanduo; Zhang, Cheng; Chen, Xining; Zhang, Wei; Chen, Jing; Dong, Meng-Qiu; Ye, Keqiong

    2017-02-28

    Eukaryotic small ribosomal subunits are first assembled into 90S pre-ribosomes. The complete 90S is a gigantic complex with a molecular mass of approximately five megadaltons. Here, we report the nearly complete architecture of Saccharomyces cerevisiae 90S determined from three cryo-electron microscopy single particle reconstructions at 4.5 to 8.7 angstrom resolution. The majority of the density maps were modeled and assigned to specific RNA and protein components. The nascent ribosome is assembled into isolated native-like substructures that are stabilized by abundant assembly factors. The 5' external transcribed spacer and U3 snoRNA nucleate a large subcomplex that scaffolds the nascent ribosome. U3 binds four sites of pre-rRNA, including a novel site on helix 27 but not the 3' side of the central pseudoknot, and crucially organizes the 90S structure. The 90S model provides significant insight into the principle of small subunit assembly and the function of assembly factors.

  11. Molecular dynamics study of contact mechanics: contact area and interfacial separation from small to full contact

    NASA Astrophysics Data System (ADS)

    Yang, Chunyan; Persson, Bo

    2008-03-01

    We report a molecular dynamics study of the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. We study the contact area and the interfacial separation from small contact (low load) to full contact (high load). For small load the contact area varies linearly with the load and the interfacial separation depends logarithmically on the load [1-4]. For high load the contact area approaches to the nominal contact area (i.e., complete contact), and the interfacial separation approaches to zero. The present results may be very important for soft solids, e.g., rubber, or for very smooth surfaces, where complete contact can be reached at moderate high loads without plastic deformation of the solids. References: [1] C. Yang and B.N.J. Persson, arXiv:0710.0276, (to appear in Phys. Rev. Lett.) [2] B.N.J. Persson, Phys. Rev. Lett. 99, 125502 (2007) [3] L. Pei, S. Hyun, J.F. Molinari and M.O. Robbins, J. Mech. Phys. Sol. 53, 2385 (2005) [4] M. Benz, K.J. Rosenberg, E.J. Kramer and J.N. Israelachvili, J. Phy. Chem. B.110, 11884 (2006)

  12. Effectiveness of beads for tracking small-scale molecular motor dynamics

    NASA Astrophysics Data System (ADS)

    Lade, Steven J.; Craig, Erin M.; Linke, Heiner

    2011-08-01

    Investigations into molecular motor dynamics are increasingly focused on small-scale features of the motor’s motion. We define performance measures of a common type of single-molecule motility assay, the bead assay, for its ability to detect such features. Using numerical models, we explore the dependence of assay performance on a number of experimentally controllable parameters, including bead size, optical force, and the method of attaching the bead to the motor. We find that the best parameter choice depends on the objective of the experiments, and give a guide to parameter selection. Comparison of the models against experimental data from a recent bead assay of myosin V exemplifies how our methods can also be used to extract additional information from bead assays, particularly that related to small-scale features. By analyzing the experimental data we find evidence for previously undetected multiple waiting states of the bead-motor complex. Furthermore, from numerical simulations we find that equilibrium bead dynamics display features previously attributed to aborted motor steps, and that bead dynamics alone can produce multiple subphases during a step.

  13. Enhancing Antibody Response against Small Molecular Hapten with Tobacco Mosaic Virus as a Polyvalent Carrier.

    PubMed

    Zhao, Xia; Chen, Limin; Luckanagul, Jittima Amie; Zhang, Xiaolei; Lin, Yuan; Wang, Qian

    2015-06-15

    Virus nanoparticles (VNPs) have been applied as carrier proteins for effective vaccine development. In this paper, we report the usage of tobacco mosaic virus (TMV) as a carrier for the display of the small molecule estriol (E3), a weakly immunogenic hapten. A highly efficient copper (I)-catalyzed azide-alkyne cycloaddition reaction (CuAAC) was performed for the conjugation of E3 onto TMV capsid at tyrosine (Tyr) 139, by which the antigen density could be controlled. The immune properties of these constructs were evaluated in mice. We found that a strong and long-term antibody response was elicited by conjugating a high density of small molecular haptens on TMV through an oligo(ethylene glycol) (OEG) linker, likely due to the effective activation of B-cells. This study suggests that TMV can serve as a promising platform to induce strong humoral immune responses and that the optimized conjugation strategy was critical to produce high quality antibodies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Ultrahigh density array of vertically aligned small-molecular organic nanowires on arbitrary substrates.

    PubMed

    Starko-Bowes, Ryan; Pramanik, Sandipan

    2013-06-18

    In recent years π-conjugated organic semiconductors have emerged as the active material in a number of diverse applications including large-area, low-cost displays, photovoltaics, printable and flexible electronics and organic spin valves. Organics allow (a) low-cost, low-temperature processing and (b) molecular-level design of electronic, optical and spin transport characteristics. Such features are not readily available for mainstream inorganic semiconductors, which have enabled organics to carve a niche in the silicon-dominated electronics market. The first generation of organic-based devices has focused on thin film geometries, grown by physical vapor deposition or solution processing. However, it has been realized that organic nanostructures can be used to enhance performance of above-mentioned applications and significant effort has been invested in exploring methods for organic nanostructure fabrication. A particularly interesting class of organic nanostructures is the one in which vertically oriented organic nanowires, nanorods or nanotubes are organized in a well-regimented, high-density array. Such structures are highly versatile and are ideal morphological architectures for various applications such as chemical sensors, split-dipole nanoantennas, photovoltaic devices with radially heterostructured "core-shell" nanowires, and memory devices with a cross-point geometry. Such architecture is generally realized by a template-directed approach. In the past this method has been used to grow metal and inorganic semiconductor nanowire arrays. More recently π-conjugated polymer nanowires have been grown within nanoporous templates. However, these approaches have had limited success in growing nanowires of technologically important π-conjugated small molecular weight organics, such as tris-8-hydroxyquinoline aluminum (Alq3), rubrene and methanofullerenes, which are commonly used in diverse areas including organic displays, photovoltaics, thin film transistors

  15. Ultrahigh Density Array of Vertically Aligned Small-molecular Organic Nanowires on Arbitrary Substrates

    PubMed Central

    Starko-Bowes, Ryan; Pramanik, Sandipan

    2013-01-01

    In recent years π-conjugated organic semiconductors have emerged as the active material in a number of diverse applications including large-area, low-cost displays, photovoltaics, printable and flexible electronics and organic spin valves. Organics allow (a) low-cost, low-temperature processing and (b) molecular-level design of electronic, optical and spin transport characteristics. Such features are not readily available for mainstream inorganic semiconductors, which have enabled organics to carve a niche in the silicon-dominated electronics market. The first generation of organic-based devices has focused on thin film geometries, grown by physical vapor deposition or solution processing. However, it has been realized that organic nanostructures can be used to enhance performance of above-mentioned applications and significant effort has been invested in exploring methods for organic nanostructure fabrication. A particularly interesting class of organic nanostructures is the one in which vertically oriented organic nanowires, nanorods or nanotubes are organized in a well-regimented, high-density array. Such structures are highly versatile and are ideal morphological architectures for various applications such as chemical sensors, split-dipole nanoantennas, photovoltaic devices with radially heterostructured "core-shell" nanowires, and memory devices with a cross-point geometry. Such architecture is generally realized by a template-directed approach. In the past this method has been used to grow metal and inorganic semiconductor nanowire arrays. More recently π-conjugated polymer nanowires have been grown within nanoporous templates. However, these approaches have had limited success in growing nanowires of technologically important π-conjugated small molecular weight organics, such as tris-8-hydroxyquinoline aluminum (Alq3), rubrene and methanofullerenes, which are commonly used in diverse areas including organic displays, photovoltaics, thin film transistors

  16. Noise-like femtosecond pulse in passively mode-locked Tm-doped NALM-based oscillator with small net anomalous dispersion

    NASA Astrophysics Data System (ADS)

    Liu, Shuo; Yan, Feng-Ping; Zhang, Lu-Na; Han, Wen-Guo; Bai, Zhuo-Ya; Zhou, Hong

    2016-01-01

    A passively mode-locked thulium-doped fiber laser (TDFL) based on a nonlinear amplifying loop mirror (NALM) is presented. By adjusting the polarization controllers, stable noise-like (NL) mode-locked femtosecond pulse operation is obtained at the 2 μm band. In the experimental period of 200 min, the output power fluctuation is less than 0.06 dB and the 3 dB spectral bandwidth variation is less than 0.02 nm, indicating that the pulsed TDFL possesses good long-term stability. To the best of our knowledge, this is the first 2 μm band NALM-based TDFL with small net anomalous dispersion for a NL femtosecond pulse. At the maximum pump power of 3.52 W, the emitting laser has a NL pulse width of 460 fs, the repetition rate of 9.1 MHz, and the NL pulse energy of 32.72 nJ.

  17. Nitrogen-doped MOF-derived micropores carbon as immobilizer for small sulfur molecules as a cathode for lithium sulfur batteries with excellent electrochemical performance.

    PubMed

    Li, Zhaoqiang; Yin, Longwei

    2015-02-25

    Nitrogen-doped carbon (NDC) spheres with abundant 22 nm mesopores and 0.5 nm micropores are obtained by directly carbonization of nitrogen-contained metal organic framework (MOF) nanocrystals. Large S8 and small S2-4 molecules are successfully infiltrated into 22 nm mesopores and 0.5 nm micropores, respectively. We successfully investigate the effect of sulfur immobilization in mesopores and micropores on the electrochemical performance of lithium-sulfur (Li-S) battery based on NDC-sulfur hybrid cathodes. The large S8 molecules in 22 nm mesopores can be removed by a prolonged heat treatment, with only small molecules of S2-4 immobilized in micropores of NDC matrices. The NDC/S2-4 hybrid exhibits excellent cycling performance, high Coulombic efficiency, and good rate capability as cathode for Li-S batteries. The confinement of smaller S2-4 molecules in the micropores of NDS efficiently avoids the loss of active sulfur and formation of soluble high-order Li polysulfides. The porous carbon can buffer the volume expansion and contraction changes, promising a stable structure for cathode. Furthermore, N doping in MOF-derived carbon not only facilitates the fast charge transfer but also is helpful in building a stronger interaction between carbon and sulfur, strengthening immobilization ability of S2-4 in micropores. The NDS-sulfur hybrid cathode exhibits a reversible capacity of 936.5 mAh g(-1) at 100th cycle with a Coulombic efficiency of 100% under a current density of 335 mA g(-1). It displays a superior rate capability performance, delivering a capacity of 632 mAh g(-1) at a high rate of 5 A g(-1). This uniquely porous NDC derived from MOF nanocrystals could be applied in related high-energy storage devices.

  18. Improving biogas separation and methane storage with multilayer graphene nanostructure via layer spacing optimization and lithium doping: a molecular simulation investigation.

    PubMed

    Chen, Jie-Jie; Li, Wen-Wei; Li, Xue-Liang; Yu, Han-Qing

    2012-09-18

    Methane is a desirable alternative to conventional fossil fuels, and also a main component of biogas from anaerobic fermentation of organic wastes. However, its relatively lower purity and poor storage by existing adsorbent materials negatively affect its wide application. Thus, efficient, cost-effective, and safe adsorbent materials for methane purification and storage are highly desired. In this study, multilayer graphene nanostructures (MGNs) with optimized structure are investigated as a potential adsorbent for this purpose. The effects of layer distance and Li doping on MGN performance in terms of methane storage and acid gas (H(2)S and CO(2)) separation from biogas are examined by molecular simulations. The mechanisms for the interactions between gas molecules and substrates are elucidated by analyzing the binding energy, geometric structures, and charge distribution from the first-principles calculations. The results show that nonhydrocarbons in biogas can be effectively separated using Li-doped MGNs with the optimal layer distance of 0.68 nm, and then the pure methane gas can be stored in MGNs with capacity satisfying the DOE target. This work offers a molecular-level insight into the interactions between gas molecules and MGNs and might provide useful information for development of new materials for methane purification and storage.

  19. Dissipative structures of diffuse molecular gas. III. Small-scale intermittency of intense velocity-shears

    NASA Astrophysics Data System (ADS)

    Hily-Blant, P.; Falgarone, E.; Pety, J.

    2008-04-01

    Aims: We further characterize the structures tentatively identified on thermal and chemical grounds as the sites of dissipation of turbulence in molecular clouds (Papers I and II). Methods: Our study is based on two-point statistics of line centroid velocities (CV), computed from three large 12CO maps of two fields. We build the probability density functions (PDF) of the CO line centroid velocity increments (CVI) over lags varying by an order of magnitude. Structure functions of the line CV are computed up to the 6th order. We compare these statistical properties in two translucent parsec-scale fields embedded in different large-scale environments, one far from virial balance and the other virialized. We also address their scale dependence in the former, more turbulent, field. Results: The statistical properties of the line CV bear the three signatures of intermittency in a turbulent velocity field: (1) the non-Gaussian tails in the CVI PDF grow as the lag decreases, (2) the departure from Kolmogorov scaling of the high-order structure functions is more pronounced in the more turbulent field, (3) the positions contributing to the CVI PDF tails delineate narrow filamentary structures (thickness ~0.02 pc), uncorrelated to dense gas structures and spatially coherent with thicker ones (~0.18 pc) observed on larger scales. We show that the largest CVI trace sharp variations of the extreme CO linewings and that they actually capture properties of the underlying velocity field, uncontaminated by density fluctuations. The confrontation with theoretical predictions leads us to identify these small-scale filamentary structures with extrema of velocity-shears. We estimate that viscous dissipation at the 0.02 pc-scale in these structures is up to 10 times higher than average, consistent with their being associated with gas warmer than the bulk. Last, their average direction is parallel (or close) to that of the local magnetic field projection. Conclusions: Turbulence in these

  20. Doping-free white organic light-emitting diodes without blue molecular emitter: An unexplored approach to achieve high performance via exciplex emission

    NASA Astrophysics Data System (ADS)

    Luo, Dongxiang; Xiao, Ye; Hao, Mingming; Zhao, Yu; Yang, Yibin; Gao, Yuan; Liu, Baiquan

    2017-02-01

    Doping-free white organic light-emitting diodes (DF-WOLEDs) are promising for the low-cost commercialization because of their simplified device structures. However, DF-WOLEDs reported thus far in the literature are based on the use of blue single molecular emitters, whose processing can represent a crucial point in device manufacture. Herein, DF-WOLEDs without the blue single molecular emitter have been demonstrated by managing a blue exciplex system. For the single-molecular-emitter (orange or yellow emitter) DF-WOLEDs, (i) a color rendering index (CRI) of 81 at 1000 cd/m2 can be obtained, which is one of the highest for the single-molecular-emitter WOLEDs, or (ii) a high efficiency of 35.4 lm/W can be yielded. For the dual-molecular-emitter (yellow/red emitters) DF-WOLED, a high CRI of 85 and low correlated color temperature of 2376 K at 1000 cd/m2 have been simultaneously achieved, which has not been reported by previous DF-WOLEDs. Such presented findings may unlock an alternative avenue to the simplified but high-performance WOLEDs.

  1. Tuning the threshold voltage of carbon nanotube transistors by n-type molecular doping for robust and flexible complementary circuits

    PubMed Central

    Wang, Huiliang; Wei, Peng; Li, Yaoxuan; Han, Jeff; Lee, Hye Ryoung; Naab, Benjamin D.; Liu, Nan; Wang, Chenggong; Adijanto, Eric; Tee, Benjamin C.-K.; Morishita, Satoshi; Li, Qiaochu; Gao, Yongli; Cui, Yi; Bao, Zhenan

    2014-01-01

    Tuning the threshold voltage of a transistor is crucial for realizing robust digital circuits. For silicon transistors, the threshold voltage can be accurately controlled by doping. However, it remains challenging to tune the threshold voltage of single-wall nanotube (SWNT) thin-film transistors. Here, we report a facile method to controllably n-dope SWNTs using 1H-benzoimidazole derivatives processed via either solution coating or vacuum deposition. The threshold voltages of our polythiophene-sorted SWNT thin-film transistors can be tuned accurately and continuously over a wide range. Photoelectron spectroscopy measurements confirmed that the SWNT Fermi level shifted to the conduction band edge with increasing doping concentration. Using this doping approach, we proceeded to fabricate SWNT complementary inverters by inkjet printing of the dopants. We observed an unprecedented noise margin of 28 V at VDD = 80 V (70% of 1/2VDD) and a gain of 85. Additionally, robust SWNT complementary metal−oxide−semiconductor inverter (noise margin 72% of 1/2VDD) and logic gates with rail-to-rail output voltage swing and subnanowatt power consumption were fabricated onto a highly flexible substrate. PMID:24639537

  2. N-type molecular electrical doping in organic semiconductors: formation and dissociation efficiencies of charge transfer complex

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Min; Yoo, Seung-Jun; Moon, Chang-Ki; Sim, Bomi; Lee, Jae-Hyun; Lim, Heeseon; Kim, Jeong Won; Kim, Jang-Joo

    2016-09-01

    Electrical doping is an important method in organic electronics to enhance device efficiency by controlling Fermi level, increasing conductivity, and reducing injection barrier from electrode. To understand the charge generation process of dopant in doped organic semiconductors, it is important to analyze the charge transfer complex (CTC) formation and dissociation into free charge carrier. In this paper, we correlate charge generation efficiency with the CTC formation and dissociation efficiency of n-dopant in organic semiconductors (OSs). The CTC formation efficiency of Rb2CO3 linearly decreases from 82.8% to 47.0% as the doping concentration increases from 2.5 mol% to 20 mol%. The CTC formation efficiency and its linear decrease with doping concentration are analytically correlated with the concentration-dependent size and number of dopant agglomerates by introducing the degree of reduced CTC formation. Lastly, the behavior of dissociation efficiency is discussed based on the picture of the statistical semiconductor theory and the frontier orbital hybridization model.

  3. Fabrication of Composite Films by Controlling Molecular Doping Processes between Polyaniline and Soluble Multiwalled Nanotubes and Their Optical Characteristics

    NASA Astrophysics Data System (ADS)

    Feng, Wei; Zhou, Feng; Wang, Xiaogong; Bai, Xiaodong; Liang, Ji; Yoshino, Katsumi

    2003-09-01

    An efficient approach to composite film fabrication that involves the control of doping processes between soluble multiwalled nanotubes (s-MWNTs) and polyaniline (PAN) molecules has been developed in this work. The s-MWNTs were prepared by introducing carboxylic acid and sulfonic acid groups to the surfaces of nanotubes. The s-MWNT was used as a dopant to react with the imine nitrogens of emeraldine PAN via the protonation doping process in a layer-by-layer manner. The resultant composite films on the quartz substrates were characterized by UV/Vis spectroscopy, photoluminescence, Fourier-transform infrared spectroscopy, scanning electron micrograph and X-ray diffraction. Results showed that s-MWNTs were doped into polyaniline layers, which caused changes in the composite film characteristics such as electrical properties, spectroscopic features and morphology. Unlike the already-used layer-by-layer process based on electrostatic attraction, our process is based on the acid-base reaction between emeraldine and s-MWNT. Owing to the protonation doping, the bond between the carboxyl group and the imine nitrogen group becomes covalent, which enhances the stability of the film.

  4. Progress in the development of immunoanalytical methods incorporating recombinant antibodies to small molecular weight biotoxins.

    PubMed

    Kavanagh, Owen; Elliott, Christopher T; Campbell, Katrina

    2015-04-01

    Rapid immunoanalytical screening of food and environmental samples for small molecular weight (hapten) biotoxin contaminations requires the production of antibody reagents that possess the requisite sensitivity and specificity. To date animal-derived polyclonal (pAb) and monoclonal (mAb) antibodies have provided the binding element of the majority of these assays but recombinant antibodies (rAb) isolated from in vitro combinatorial phage display libraries are an exciting alternative due to (1) circumventing the need for experimental animals, (2) speed of production in commonly used in vitro expression systems and (3) subsequent molecular enhancement of binder performance. Short chain variable fragments (scFv) have been the most commonly employed rAb reagents for hapten biotoxin detection over the last two decades but antibody binding fragments (Fab) and single domain antibodies (sdAb) are increasing in popularity due to increased expression efficiency of functional binders and superior resistance to solvents. rAb-based immunochromatographic assays and surface plasmon resonance (SPR) biosensors have been reported to detect sub-regulatory levels of fungal (mycotoxins), marine (phycotoxins) and aquatic biotoxins in a wide range of food and environmental matrices, however this technology has yet to surpass the performances of the equivalent mAb- and pAb-based formats. As such the full potential of rAb technology in hapten biotoxin detection has yet to be achieved, but in time the inherent advantages of engineered rAb are set to provide the next generation of ultra-high performing binder reagents for the rapid and specific detection of hapten biotoxins.

  5. Histopathological and molecular characterization of encephalitic listeriosis in small ruminants from northern Paraná, Brazil

    PubMed Central

    Headley, Selwyn Arlington; Bodnar, Lívia; Fritzen, Juliana T.T.; Bronkhorst, Dalton Evert; Alfieri, Alice Fernandes; Okano, Werner; Alfieri, Amauri Alcindo

    2013-01-01

    Listeriosis is a disease primarily of ruminants caused by the Gram-positive bacterium Listeria monocytogenes. Ruminants either demonstrate manifestations of the encephalitic, septicemic, or reproductive form of listeriosis. The pathological and molecular findings with encephalitic listeriosis in a 5.5-month-old, male, mixed-breed goat and a 3-year-old Texel-crossed sheep from northern Paraná, Brazil are described. Clinically, the kid demonstrated circling, lateral protrusion of the tongue, head tilt, and convulsions; the ewe presented ataxia, motor incoordination, and lateral decumbency. Brainstem dysfunctions were diagnosed clinically and listeriosis was suspected. Necropsy performed on both animals did not reveal remarkable gross lesions; significant histopathological alterations were restricted to the brainstem (medulla oblongata; rhombencephalitis) and were characterized as meningoencephalitis that consisted of extensive mononuclear perivascular cuffings, neutrophilic and macrophagic microabscesses, and neuroparenchymal necrosis. PCR assay and direct sequencing, using genomic bacterial DNA derived from the brainstem of both animals, amplified the desired 174 base pairs length amplicon of the listeriolysin O gene of L. monocytogenes. Phylogenetic analyses demonstrated that the strains associated with rhombencephalitis during this study clustered with known strains of L. monocytogenes lineage I from diverse geographical locations and from cattle of the state of Paraná with encephalitic listeriosis. Consequently, these strains should be classified as L. monocytogenes lineage I. These results confirm the active participation of lineage I strains of L. monocytogenes in the etiopathogenesis of the brainstem dysfunctions observed during this study, probably represent the first characterization of small ruminant listeriosis by molecular techniques in Latin America, and suggest that ruminants within the state of Paraná were infected by the strains of the same lineage

  6. Electrostatic Interactions Mediate Binding of Obscurin to Small Ankyrin 1: Biochemical and Molecular Modeling Studies

    PubMed Central

    Busby, Ben; Oashi, Taiji; Willis, Chris D.; Ackermann, Maegen A.; Kontrogianni-Konstantopoulos, Aikaterini; MacKerell, Alexander D.; Bloch, Robert J.

    2012-01-01

    Small ankyrin 1 (sAnk1; also Ank1.5) is an integral protein of the sarcoplasmic reticulum in skeletal and cardiac muscle cells, where it is thought to bind to the C-terminal region of obscurin, a large modular protein that surrounds the contractile apparatus. Using fusion proteins in vitro, in combination with site directed mutagenesis and surface plasmon resonance measurements, we previously showed that the binding site on sAnk1 for obscurin consists in part of six lysine and arginine residues. Here we show that four charged residues in the high affinity binding site on obscurin for sAnk1, between residues 6316-6345, consisting of three glutamates and a lysine, are necessary, but not sufficient, for this site on obscurin to bind with high affinity to sAnk1. We also identify specific complementary mutations in sAnk1 that can partially or completely compensate for the changes in binding caused by charge-switching mutations in obscurin. We used molecular modeling to develop structural models of residues 6322-6339 of obscurin bound to sAnk1. The models, based on a combination of Brownian and molecular dynamics simulations, predict that the binding site on sAnk1 for obscurin is organized as two ankyrin-like repeats, with the last α-helical segment oriented at an angle to the nearby helices, allowing lysine-6338 of obscurin to form an ionic interaction with aspartate-111 of sAnk1. This prediction was validated by double mutant cycle experiments. Our results are consistent with a model in which electrostatic interactions between specific pairs of side chains on obscurin and sAnk1 promote binding and complex formation. PMID:21333652

  7. Histopathological and molecular characterization of encephalitic listeriosis in small ruminants from northern Paraná, Brazil.

    PubMed

    Headley, Selwyn Arlington; Bodnar, Lívia; Fritzen, Juliana T T; Bronkhorst, Dalton Evert; Alfieri, Alice Fernandes; Okano, Werner; Alfieri, Amauri Alcindo

    2013-01-01

    Listeriosis is a disease primarily of ruminants caused by the Gram-positive bacterium Listeria monocytogenes. Ruminants either demonstrate manifestations of the encephalitic, septicemic, or reproductive form of listeriosis. The pathological and molecular findings with encephalitic listeriosis in a 5.5-month-old, male, mixed-breed goat and a 3-year-old Texel-crossed sheep from northern Paraná, Brazil are described. Clinically, the kid demonstrated circling, lateral protrusion of the tongue, head tilt, and convulsions; the ewe presented ataxia, motor incoordination, and lateral decumbency. Brainstem dysfunctions were diagnosed clinically and listeriosis was suspected. Necropsy performed on both animals did not reveal remarkable gross lesions; significant histopathological alterations were restricted to the brainstem (medulla oblongata; rhombencephalitis) and were characterized as meningoencephalitis that consisted of extensive mononuclear perivascular cuffings, neutrophilic and macrophagic microabscesses, and neuroparenchymal necrosis. PCR assay and direct sequencing, using genomic bacterial DNA derived from the brainstem of both animals, amplified the desired 174 base pairs length amplicon of the listeriolysin O gene of L. monocytogenes. Phylogenetic analyses demonstrated that the strains associated with rhombencephalitis during this study clustered with known strains of L. monocytogenes lineage I from diverse geographical locations and from cattle of the state of Paraná with encephalitic listeriosis. Consequently, these strains should be classified as L. monocytogenes lineage I. These results confirm the active participation of lineage I strains of L. monocytogenes in the etiopathogenesis of the brainstem dysfunctions observed during this study, probably represent the first characterization of small ruminant listeriosis by molecular techniques in Latin America, and suggest that ruminants within the state of Paraná were infected by the strains of the same lineage

  8. Toxoplasma gondii in free-ranging wild small felids from Brazil: molecular detection and genotypic characterization.

    PubMed

    Cañón-Franco, W A; Araújo, F A P; López-Orozco, N; Jardim, M M A; Keid, L B; Dalla-Rosa, C; Cabral, A D; Pena, H F J; Gennari, S M

    2013-11-08

    Brazil harbors the largest number of wild Neotropical felid species, with ten of the twelve species recorded in the American continent. Although these animals are considered to be definitive hosts for Toxoplasma gondii, there are few descriptions of the parasite in these species. Here, we performed a molecular detection of T. gondii by amplification of the marker ITS-1 from tissue samples obtained from 90 free-ranging wild small Neotropical felids from Rio Grande do Sul - Brazil. Of the sampled animals, 34.4% (n=31) were positive including the species Puma yagouaroundi - jaguarondi (9/22), Leopardus geoffroyi - Geoffroy's cat (6/22), Leopardus tigrinus - oncilla (8/28), Leopardus wiedii - margay (6/10), Leopardus pardalis - ocelot (1/1) and Leopardus colocolo - Pampas cat (1/7). Toxoplasma DNA was detected with a frequency of 14.6% (63/433) in primary samples of tongue (16/56), brain (8/43), skeletal muscle (15/83), heart (7/63), diaphragm (3/56), vitreous humor (2/44), eye muscle (6/44) and eyeball (6/44). Multilocus PCR-RFLP genotyping of eleven small Neotropical felids using the molecular markers SAG1, 5'3'SAG2, alt. SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, Apico and CS3 allowed the partial characterization of eight genotypes. We fully characterized two new genotypes that have not been described previously in Brazil (Lw#31Tn from L. wiedii and Py#21Sm from P. yagouaroundi) and one genotype Py#56Br from P. yagouaroundi that has been described previously in isolates from cats, dogs and capybaras from São Paulo state. This study constitutes the first detection and genotypic characterization of T. gondii in free-ranging felids in Brazil, demonstrating the occurrence of the parasite in wild populations and suggesting its potential transmissibility to humans and other domestic and wild animals. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Computer Molecular Dynamics Simulation Study of Isomerization and Melting of Small Alkali-Halide Clusters.

    NASA Astrophysics Data System (ADS)

    Luo, Jia

    1987-09-01

    In this study we have systematically investigated, using Molecular Dynamics simulations, the energetics, structure and dynamics of alkali-halide clusters of variable sizes ((NaCl)_{n}, for n = 4, 16 and 108) over a wide temperature range. Our simulations show that the very nature of the phase transformation and the underlying physical processes involved, depend on the size of the system. We conclude that at the lower end of the size spectrum, the phase space of the system is characterized by a small number of stable configuration (solid isomers) between which the system transforms in a diffusionless manner, with temperature dependent rates and branching ratios. As the system size is increased the number of accessible conformers increases leading to a hierarchical kinetics of isomerization events which exhibits itself as a broadening of the transition region. For these small clusters coexistence is between solid isomers rather than inter-phase (solid-liquid) coexistence. The latter develops for clusters of sufficient size, characterized by a dense spectrum of accessible states, separated by thermally surmountable barriers. Under these circumstances conventional melting is observed as a sharp transition, the separation of time-scales for inter-well and intra -well dynamics ceases, and true solid-liquid coexistence is found. In the Methods section of the text, we describe the potential model, the computer program algorithm, the molecular dynamics running initial conditions, and the method of temperature control. In the Results section, we discuss and demonstrate the structures of alkali-halide clusters as a function of temperature and the curves of the caloric equation of state; the time evolution of the kinetic energy and the distribution of short time average of the kinetic energy; the coordination number function and the function n(r), which is related to the pair correlation function, as a function of temperature and size; the mean square displacement, the

  10. The physics and chemistry of small molecular clouds in the Galactic plane. 2: H2CO

    NASA Astrophysics Data System (ADS)

    Turner, B. E.

    1994-12-01

    We have made extensive observations of 2 and 6 cm H2CO in all 27 of the Clemens-Barvainis small molecular clouds for which several structural models including hydrostatic equilibrium polytropes were developed in an earlier paper based on C(18)O and (13)CO observations. We have observed the 211-110 line at 2.0 mm in 11 of the CB objects and in 10 of 11 cirrus cores earlier studied in C(18)O, (13)CO, and H2CO. As with the cirrus cores, the three H2CO lines in CB objects are all well fitted by both polytropic models and ad hoc n approximately r-1 models, using the external UV fields derived in the earlier papers. The reanalysis of the cirrus cores includes the 2 mm H2CO lines as well as treating the C-12/C-13 ratio as a variable, and yields approximately 40% higher fractional abundances than the earlier analysis, as well as giving equal preference to both centrally peaked and radially flat distributions of the H2CO fractional abundance. The same central H2CO abundances are found for the CB objects, but these objects favor radially flat abundance distributions, possibly because of beam dilution of the 6 cm lines speculated as unaccounted for in the detailed estimates made using maps of every source. As before, no clear preference is shown for polytropic or r-1 structures although r-1 is favored for a subset of 11 objects with 211-110 data. The large central abundances derived for both types of object (mean value 1.4 x 10-8 for ortho H2CO) are too large by a factor 104 to be compatible with gas-phase formation of H2CO. Grain formation is indicated, as concluded earlier for cirrus cores. It is argued that photocatalysis on grains is consistent with either peaked or flat H2CO abundance distributions, but this cannot be tested conclusively within the uncertainties of determining the structures or the abundance distributions. By including consistently the effects of UV radiation fields and electron excitation, our models fit accurately all four lines of C(18)O and (13)CO

  11. Molecular Markers as Prognostic Factors in DCIS and Small Invasive Breast Cancers.

    PubMed

    Sänger, N; Engels, K; Graf, A; Ruckhäberle, E; Effenberger, K E; Fehm, T; Holtrich, U; Becker, S; Karn, T

    2014-11-01

    Ductal carcinoma in situ (DCIS) accounts for up to half of screen-detected breast cancers and thus constitutes a major public health problem. Despite effective current treatment many patients with DCIS are either over- or undertreated because of the paucity of precise models to predict recurrence or progression. The combination of clinical and molecular factors as already applied for invasive disease may help to build such models also for DCIS. We compared 53 DCIS (36.6 %) and 92 (63.4 %) invasive breast cancer cases and found no significant differences in age, receptor status of ER, PR, and HER2, and the use of radiotherapy. Interestingly, the proportion of disseminated tumor cells (DTC) did also not significantly differ between DCIS and invasive cases (p = 0.57). A negative PR status was associated with the detection of DTCs (p = 0.026). We then compared relationships of clinical parameters and biomarkers with patients' prognosis in 43 DCIS and 40 small invasive tumors ≤ 5 mm (T1a). ER negativity was associated with shorter relapse free survival in the complete cohort (p = 0.004) and showed a trend in both subgroups (p = 0.053 for DCIS and p = 0.046 for T1a, respectively). In conclusion, we found markedly similar properties of both DCIS and small invasive breast cancers with respect to the distribution of several parameters as well as to the prognostic value of biomarkers. DCIS with a luminal phenotype seem to be characterized by a favourable prognosis.

  12. Stochastic dynamics of small ensembles of non-processive molecular motors: the parallel cluster model.

    PubMed

    Erdmann, Thorsten; Albert, Philipp J; Schwarz, Ulrich S

    2013-11-07

    Non-processive molecular motors have to work together in ensembles in order to generate appreciable levels of force or movement. In skeletal muscle, for example, hundreds of myosin II molecules cooperate in thick filaments. In non-muscle cells, by contrast, small groups with few tens of non-muscle myosin II motors contribute to essential cellular processes such as transport, shape changes, or mechanosensing. Here we introduce a detailed and analytically tractable model for this important situation. Using a three-state crossbridge model for the myosin II motor cycle and exploiting the assumptions of fast power stroke kinetics and equal load sharing between motors in equivalent states, we reduce the stochastic reaction network to a one-step master equation for the binding and unbinding dynamics (parallel cluster model) and derive the rules for ensemble movement. We find that for constant external load, ensemble dynamics is strongly shaped by the catch bond character of myosin II, which leads to an increase of the fraction of bound motors under load and thus to firm attachment even for small ensembles. This adaptation to load results in a concave force-velocity relation described by a Hill relation. For external load provided by a linear spring, myosin II ensembles dynamically adjust themselves towards an isometric state with constant average position and load. The dynamics of the ensembles is now determined mainly by the distribution of motors over the different kinds of bound states. For increasing stiffness of the external spring, there is a sharp transition beyond which myosin II can no longer perform the power stroke. Slow unbinding from the pre-power-stroke state protects the ensembles against detachment.

  13. Long-Term Retention of Small, Volatile Molecular Species within Metallic Microcapsules.

    PubMed

    Hitchcock, James P; Tasker, Alison L; Baxter, Elaine A; Biggs, Simon; Cayre, Olivier J

    2015-07-15

    Encapsulation and full retention of small molecular weight active ingredients is a challenging task that remains unsolved by current technologies used in industry and academia. In particular, certain everyday product formulations provide difficult environments in which preventing active leakage through capsule walls is not feasible. For example, a continuous phase that can fully dissolve an encapsulated active will typically force full release over a fraction of the intended lifetime of a product. This is due to the inherent porosity of polymeric membranes typically used as capsule wall material in current technologies. In this study, we demonstrate a method for preventing undesired loss of encapsulated actives under these extreme conditions using a simple threestep process. Our developed methodology, which forms an impermeable metal film around polymer microcapsules, prevents loss of small, volatile oils within an ethanol continuous phase for at least 21 days while polymeric capsules lose their entire content in less than 30 min under the same conditions. Polymer shell-oil core microcapsules are produced using a well-known cosolvent extraction method to precipitate a polymeric shell around the oil core. Subsequently, metallic catalytic nanoparticles are physically adsorbed onto the microcapsule polymeric shells. Finally, this nanoparticle coating is used to catalyze the growth of a secondary metallic film. Specifically, this work shows that it is possible to coat polymeric microcapsules containing a model oil system or a typical fragrance oil with a continuous metal shell. It also shows that the coverage of nanoparticles on the capsule surface can be controlled, which is paramount for obtaining a continuous impermeable metal film. In addition, control over the metal shell thickness is demonstrated without altering the capability of the metal film to retain the encapsulated oils.

  14. Emission from small dust particles in diffuse and molecular cloud medium

    NASA Technical Reports Server (NTRS)

    Bernard, J. P.; Desert, X.

    1990-01-01

    Infrared Astronomy Satellite (IRAS) observations of the whole galaxy has shown that long wavelength emission (100 and 60 micron bands) can be explained by thermal emission from big grains (approx 0.1 micron) radiating at their equilibrium temperature when heated by the InterStellar Radiation Field (ISRF). This conclusion has been confirmed by continuum sub-millimeter observations of the galactic plane made by the EMILIE experiment at 870 microns (Pajot et al. 1986). Nevertheless, shorter wavelength observations like 12 and 25 micron IRAS bands, show an emission from the galactic plane in excess with the long wavelength measurements which can only be explained by a much hotter particles population. Because dust at equilibrium cannot easily reach high temperatures required to explain this excess, this component is thought to be composed of very small dust grains or big molecules encompassing thermal fluctuations. Researchers present here a numerical model that computes emission, from Near Infrared Radiation (NIR) to Sub-mm wavelengths, from a non-homogeneous spherical cloud heated by the ISRF. This model fully takes into account the heating of dust by multi-photon processes and back-heating of dust in the Visual/Infrared Radiation (VIS-IR) so that it is likely to describe correctly emission from molecular clouds up to large A sub v and emission from dust experiencing temperature fluctuations. The dust is a three component mixture of polycyclic aromatic hydrocarbons, very small grains, and classical big grains with independent size distributions (cut-off and power law index) and abundances.

  15. Stochastic dynamics of small ensembles of non-processive molecular motors: The parallel cluster model

    SciTech Connect

    Erdmann, Thorsten; Albert, Philipp J.; Schwarz, Ulrich S.

    2013-11-07

    Non-processive molecular motors have to work together in ensembles in order to generate appreciable levels of force or movement. In skeletal muscle, for example, hundreds of myosin II molecules cooperate in thick filaments. In non-muscle cells, by contrast, small groups with few tens of non-muscle myosin II motors contribute to essential cellular processes such as transport, shape changes, or mechanosensing. Here we introduce a detailed and analytically tractable model for this important situation. Using a three-state crossbridge model for the myosin II motor cycle and exploiting the assumptions of fast power stroke kinetics and equal load sharing between motors in equivalent states, we reduce the stochastic reaction network to a one-step master equation for the binding and unbinding dynamics (parallel cluster model) and derive the rules for ensemble movement. We find that for constant external load, ensemble dynamics is strongly shaped by the catch bond character of myosin II, which leads to an increase of the fraction of bound motors under load and thus to firm attachment even for small ensembles. This adaptation to load results in a concave force-velocity relation described by a Hill relation. For external load provided by a linear spring, myosin II ensembles dynamically adjust themselves towards an isometric state with constant average position and load. The dynamics of the ensembles is now determined mainly by the distribution of motors over the different kinds of bound states. For increasing stiffness of the external spring, there is a sharp transition beyond which myosin II can no longer perform the power stroke. Slow unbinding from the pre-power-stroke state protects the ensembles against detachment.

  16. Stochastic dynamics of small ensembles of non-processive molecular motors: The parallel cluster model

    NASA Astrophysics Data System (ADS)

    Erdmann, Thorsten; Albert, Philipp J.; Schwarz, Ulrich S.

    2013-11-01

    Non-processive molecular motors have to work together in ensembles in order to generate appreciable levels of force or movement. In skeletal muscle, for example, hundreds of myosin II molecules cooperate in thick filaments. In non-muscle cells, by contrast, small groups with few tens of non-muscle myosin II motors contribute to essential cellular processes such as transport, shape changes, or mechanosensing. Here we introduce a detailed and analytically tractable model for this important situation. Using a three-state crossbridge model for the myosin II motor cycle and exploiting the assumptions of fast power stroke kinetics and equal load sharing between motors in equivalent states, we reduce the stochastic reaction network to a one-step master equation for the binding and unbinding dynamics (parallel cluster model) and derive the rules for ensemble movement. We find that for constant external load, ensemble dynamics is strongly shaped by the catch bond character of myosin II, which leads to an increase of the fraction of bound motors under load and thus to firm attachment even for small ensembles. This adaptation to load results in a concave force-velocity relation described by a Hill relation. For external load provided by a linear spring, myosin II ensembles dynamically adjust themselves towards an isometric state with constant average position and load. The dynamics of the ensembles is now determined mainly by the distribution of motors over the different kinds of bound states. For increasing stiffness of the external spring, there is a sharp transition beyond which myosin II can no longer perform the power stroke. Slow unbinding from the pre-power-stroke state protects the ensembles against detachment.

  17. Delta-doping of Semiconductors

    NASA Astrophysics Data System (ADS)

    Schubert, E. F.

    2005-08-01

    Part I: 1. Introduction E. F. Schubert; Part II: 2. Electronic structure of delta-doped semiconductors C. R. Proetto; Part III: 3. Recent progress in delta-like confinement of impurities in GaAs K. H. Ploog; 4. Flow-rate modulation epitaxy (FME) of III-V semiconductors T. Makimoto and Y. Horikoshi; 5. Gas source molecular beam epitaxy (MBE) of delta-doped III-V semiconductors D. Ritter; 6. Solid phase epitaxy for delta-doping in silicon I. Eisele; 7. Low temperature MBE of silicon H.-J. Gossmann; Part IV: 8. Secondary ion mass spectrometry of delta-doped semiconductors H. S. Luftmann; 9. Capacitance-voltage profiling E. F. Schubert; 10. Redistribution of impurities in III-V semiconductors E. F. Schubert; 11. Dopant diffusion and segregation in delta-doped silicon films H.-J. Gossmann; 12. Characterisation of silicon and delta-doped structures in GaAs R. C. Newman; 13. The DX-center in silicon delta-doped GaAs and AlxGa1-xAs P. M. Koenraad; Part V: 14. Luminescence and ellipsometry spectroscopy H. Yao and E. F. Schubert; 15. Photoluminescence and Raman spectroscopy of single delta-doped III-V semiconductor heterostructures J. Wagner and D. Richards; 16. Electron transport in delta-doped quantum wells W. T. Masselink; 17. Electron mobility in delta-doped layers P. M. Koenraad; 18. Hot electrons in delta-doped GaAs M. Asche; 19. Ordered delta-doping R. L. Headrick, L. C. Feldman and B. E. Weir; Part IV: 20. Delta-doped channel III-V field effect transistors (FETs) W.-P. Hong; 21. Selectively doped heterostructure devices E. F. Schubert; 22. Silicon atomic layer doping FET K. Nakagawa and K. Yamaguchi; 23. Planar doped barrier devices R. J. Malik; 24. Silicon interband and intersubband photodetectors I. Eisele; 25. Doping superlattice devices E. F. Schubert.

  18. Quantum solvent states and rovibrational spectra of small doped 3He clusters through the full-configuration-interaction nuclear orbital approach: The (3He)N-Cl2(X) case (N<=4)

    NASA Astrophysics Data System (ADS)

    de Lara-Castells, María Pilar; Aguirre, Néstor F.; Villarreal, Pablo; Barrio, Gerardo Delgado; Mitrushchenkov, Alexander O.

    2010-05-01

    A full-configuration-interaction nuclear orbital treatment has been recently developed as a benchmark quantum-chemistry-like method to study small doped H3e clusters [M. P. de Lara-Castells et al., J. Chem. Phys. 125, 221101 (2006)]. Our objective in this paper is to extend our previous study on (H3e)N-Cl2(B) clusters, using an enhanced implementation that allows employing very large one-particle basis sets [M. P. de Lara-Castells et al., J. Chem. Phys. 131, 194101 (2009)], and apply the method to the (H3e)N-Cl2(X) case, using both a semiempirical T-shaped and an ab initio He-dopant potential with minima at both T-shaped and linear conformations. Calculations of the ground and low-lying excited solvent states stress the key role played by the anisotropy of the He-dopant interaction in determining the global energies and the structuring of the H3e atoms around the dopant. Whereas H3e atoms are localized in a broad belt around the molecular axis in ground-state N-sized complexes with N =1-3, irrespective of using the T-shaped or the ab initio He-dopant potential function, the dopant species becomes fully coated by just four H3e atoms when the He-dopant potential also has a minimum at linear configurations. However, excited solvent states with a central ring-type clustering of the host molecule are found to be very close in energy with the ground state by using the ab initio potential function. A microscopic analysis of this behavior is provided. Additional simulations of the molecular rovibrational Raman spectra, also including excited solvent states, provide further insights into the importance of proper modeling the anisotropy of the He-dopant interaction in these weakly bound systems and of taking into account the low-lying excitations.

  19. Molecular Dynamics Study of Small PNA Molecules in Lipid-Water System

    PubMed Central

    Weroński, Paweł; Jiang, Yi; Rasmussen, Steen

    2007-01-01

    We present the results of molecular dynamics simulations of small peptide nucleic acid (PNA) molecules, synthetic analogs of DNA, at a lipid bilayer in water. At neutral pH, without any salt, and in the NPnγT ensemble, two similar PNA molecules (6-mers) with the same nucleic base sequence and different terminal groups are investigated at the interface between water and a 1-palmitoyl-2-oleoylphosphatidylcholine lipid bilayer. The results of our simulations suggest that at low ionic strength of the solution, both PNA molecules adsorb at the lipid-water interface. In the case where the PNA molecule has charged terminal groups, the main driving force of adsorption is the electrostatic attraction between the charged groups of PNA and the lipid heads. The main driving force of adsorption of the PNA molecule with neutral terminal groups is the hydrophobic interaction of the nonpolar groups. Our simulations suggest that the system free energy change associated with PNA adsorption at the lipid-water interface is on the order of several tens of kT per PNA molecule in both cases. PMID:17307825

  20. Advanced evolutionary molecular engineering to produce thermostable cellulase by using a small but efficient library.

    PubMed

    Ito, Y; Ikeuchi, A; Imamura, C

    2013-01-01

    We aimed at constructing thermostable cellulase variants of cellobiohydrolase II, derived from the mesophilic fungus Phanerochaete chrysosporium, by using an advanced evolutionary molecular engineering method. By aligning the amino acid sequences of the catalytic domains of five thermophilic fungal CBH2 and PcCBH2 proteins, we identified 45 positions where the PcCBH2 genes differ from the consensus sequence of two to five thermophilic fungal CBH2s. PcCBH2 variants with the consensus mutations were obtained by a cell-free translation system that was chosen for easy evaluation of thermostability. From the small library of consensus mutations, advantageous mutations for improving thermostability were found to occur with much higher frequency relative to a random library. To further improve thermostability, advantageous mutations were accumulated within the wild-type gene. Finally, we obtained the most thermostable variant Mall4, which contained all 15 advantageous mutations found in this study. This variant had the same specific cellulase activity as the wild type and retained sufficient activity at 50°C for >72 h, whereas wild-type PcCBH2 retained much less activity under the same conditions. The history of the accumulation process indicated that evolution of PcCBH2 toward improved thermostability was ideally and rapidly accomplished through the evolutionary process employed in this study.

  1. Small animal optoacoustic tomography system for molecular imaging of contrast agents

    NASA Astrophysics Data System (ADS)

    Su, Richard; Liopo, Anton; Ermilov, Sergey A.; Oraevsky, Alexander A.

    2016-03-01

    We developed a new and improved Laser Optoacoustic Imaging System, LOIS-3D for preclinical research applications in small animal models. The advancements include (i) a new stabilized imaging module with a more homogeneous illumination of the mouse yielding a better spatial resolution (<0.2 mm) and (ii) a new low noise amplifier incorporated into the ultrasonic probe and providing the noise equivalent pressure around 2 Pa resulting in increased signal-to-noise ratio and the optical absorption sensitivity of about 0.15 cm-1. We also improved scan time and the image reconstruction times. This prototype has been commercialized for a number of biomedical research applications, such as imaging vascularization and measuring hemoglobin / oxyhemoglobin distribution in the organs as well as imaging exogenous or endogenous optoacoustic contrast agents. As examples, we present in vivo experiments using phantoms and mice with and without tumor injected with contrast agents with indocyanine green (ICG). LOIS-3D was capable of detecting ~1-2 pmole of the ICG, in tissues with relatively low blood content. With its high sensitivity and excellent spatial resolution LOIS-3D is an advanced alternative to fluorescence and bioluminescence based modalities for molecular imaging in live mice.

  2. Predicting Adsorption Affinities of Small Molecules on Carbon Nanotubes Using Molecular Dynamics Simulation.

    PubMed

    Comer, Jeffrey; Chen, Ran; Poblete, Horacio; Vergara-Jaque, Ariela; Riviere, Jim E

    2015-12-22

    Computational techniques have the potential to accelerate the design and optimization of nanomaterials for applications such as drug delivery and contaminant removal; however, the success of such techniques requires reliable models of nanomaterial surfaces as well as accurate descriptions of their interactions with relevant solutes. In the present work, we evaluate the ability of selected models of naked and hydroxylated carbon nanotubes to predict adsorption equilibrium constants for about 30 small aromatic compounds with a variety of functional groups. The equilibrium constants determined using molecular dynamics coupled with free-energy calculation techniques are directly compared to those derived from experimental measurements. The calculations are highly predictive of the relative adsorption affinities of the compounds, with excellent correlation (r ≥ 0.9) between calculated and measured values of the logarithm of the adsorption equilibrium constant. Moreover, the agreement in absolute terms is also reasonable, with average errors of less than one decade. We also explore possible effects of surface loading, although we demonstrate that they are negligible for the experimental conditions considered. Given the degree of reliability demonstrated, we move on to employing the in silico techniques in the design of nanomaterials, using the optimization of adsorption affinity for the herbacide atrazine as an example. Our simulations suggest that, compared to other modifications of graphenic carbon, polyvinylpyrrolidone conjugation gives the highest affinity for atrazine-substantially greater than that of graphenic carbon alone-and may be useful as a nanomaterial for delivery or sequestration of atrazine.

  3. Antidiabetic effects of pterosin A, a small-molecular-weight natural product, on diabetic mouse models.

    PubMed

    Hsu, Feng-Lin; Huang, Chun-Fa; Chen, Ya-Wen; Yen, Yuan-Peng; Wu, Cheng-Tien; Uang, Biing-Jiun; Yang, Rong-Sen; Liu, Shing-Hwa

    2013-02-01

    The therapeutic effect of pterosin A, a small-molecular-weight natural product, on diabetes was investigated. Pterosin A, administered orally for 4 weeks, effectively improved hyperglycemia and glucose intolerance in streptozotocin, high-fat diet-fed, and db/db diabetic mice. There were no adverse effects in normal or diabetic mice treated with pterosin A for 4 weeks. Pterosin A significantly reversed the increased serum insulin and insulin resistance (IR) in dexamethasone-IR mice and in db/db mice. Pterosin A significantly reversed the reduced muscle GLUT-4 translocation and the increased liver phosphoenolpyruvate carboxyl kinase (PEPCK) expression in diabetic mice. Pterosin A also significantly reversed the decreased phosphorylations of AMP-activated protein kinase (AMPK) and Akt in muscles of diabetic mice. The decreased AMPK phosphorylation and increased p38 phosphorylation in livers of db/db mice were effectively reversed by pterosin A. Pterosin A enhanced glucose uptake and AMPK phosphorylation in cultured human muscle cells. In cultured liver cells, pterosin A inhibited inducer-enhanced PEPCK expression, triggered the phosphorylations of AMPK, acetyl CoA carboxylase, and glycogen synthase kinase-3, decreased glycogen synthase phosphorylation, and increased the intracellular glycogen level. These findings indicate that pterosin A may be a potential therapeutic option for diabetes.

  4. Small molecule kinase inhibitors alleviate different molecular features of myotonic dystrophy type 1.

    PubMed

    Wojciechowska, Marzena; Taylor, Katarzyna; Sobczak, Krzysztof; Napierala, Marek; Krzyzosiak, Wlodzimierz J

    2014-01-01

    Expandable (CTG)n repeats in the 3' UTR of the DMPK gene are a cause of myotonic dystrophy type 1 (DM1), which leads to a toxic RNA gain-of-function disease. Mutant RNAs with expanded CUG repeats are retained in the nucleus and aggregate in discrete inclusions. These foci sequester splicing factors of the MBNL family and trigger upregulation of the CUGBP family of proteins resulting in the mis-splicing of their target transcripts. To date, many efforts to develop novel therapeutic strategies have been focused on disrupting the toxic nuclear foci and correcting aberrant alternative splicing via targeting mutant CUG repeats RNA; however, no effective treatment for DM1 is currently available. Herein, we present results of culturing of human DM1 myoblasts and fibroblasts with two small-molecule ATP-binding site-specific kinase inhibitors, C16 and C51, which resulted in the alleviation of the dominant-negative effects of CUG repeat expansion. Reversal of the DM1 molecular phenotype includes a reduction of the size and number of foci containing expanded CUG repeat transcripts, decreased steady-state levels of CUGBP1 protein, and consequent improvement of the aberrant alternative splicing of several pre-mRNAs misregulated in DM1.

  5. Monitoring the Spatiotemporal Activities of miRNAs in Small Animal Models Using Molecular Imaging Modalities

    PubMed Central

    Baril, Patrick; Ezzine, Safia; Pichon, Chantal

    2015-01-01

    MicroRNAs (miRNAs) are a class of small non-coding RNAs that regulate gene expression by binding mRNA targets via sequence complementary inducing translational repression and/or mRNA degradation. A current challenge in the field of miRNA biology is to understand the functionality of miRNAs under physiopathological conditions. Recent evidence indicates that miRNA expression is more complex than simple regulation at the transcriptional level. MiRNAs undergo complex post-transcriptional regulations such miRNA processing, editing, accumulation and re-cycling within P-bodies. They are dynamically regulated and have a well-orchestrated spatiotemporal localization pattern. Real-time and spatio-temporal analyses of miRNA expression are difficult to evaluate and often underestimated. Therefore, important information connecting miRNA expression and function can be lost. Conventional miRNA profiling methods such as Northern blot, real-time PCR, microarray, in situ hybridization and deep sequencing continue to contribute to our knowledge of miRNA biology. However, these methods can seldom shed light on the spatiotemporal organization and function of miRNAs in real-time. Non-invasive molecular imaging methods have the potential to address these issues and are thus attracting increasing attention. This paper reviews the state-of-the-art of methods used to detect miRNAs and discusses their contribution in the emerging field of miRNA biology and therapy. PMID:25749473

  6. High Sensitivity Method to Estimate Distribution of Hyaluronan Molecular Sizes in Small Biological Samples Using Gas-Phase Electrophoretic Mobility Molecular Analysis

    PubMed Central

    Do, Lan; Dahl, Christen P.; Kerje, Susanne; Hansell, Peter; Mörner, Stellan; Lindqvist, Ulla; Engström-Laurent, Anna; Larsson, Göran; Hellman, Urban

    2015-01-01

    Hyaluronan is a negatively charged polydisperse polysaccharide where both its size and tissue concentration play an important role in many physiological and pathological processes. The various functions of hyaluronan depend on its molecular size. Up to now, it has been difficult to study the role of hyaluronan in diseases with pathological changes in the extracellular matrix where availability is low or tissue samples are small. Difficulty to obtain large enough biopsies from human diseased tissue or tissue from animal models has also restricted the study of hyaluronan. In this paper, we demonstrate that gas-phase electrophoretic molecular mobility analyzer (GEMMA) can be used to estimate the distribution of hyaluronan molecular sizes in biological samples with a limited amount of hyaluronan. The low detection level of the GEMMA method allows for estimation of hyaluronan molecular sizes from different parts of small organs. Hence, the GEMMA method opens opportunity to attain a profile over the distribution of hyaluronan molecular sizes and estimate changes caused by disease or experimental conditions that has not been possible to obtain before. PMID:26448761

  7. Fe₃O₄@rGO doped molecularly imprinted polymer membrane based on magnetic field directed self-assembly for the determination of amaranth.

    PubMed

    Han, Qing; Wang, Xi; Yang, Zaiyue; Zhu, Wanying; Zhou, Xuemin; Jiang, Huijun

    2014-06-01

    Based on magnetic field directed self-assembly (MDSA) of Fe3O4@rGO composites, a novel magnetic molecularly imprinted electrochemical sensor (MIES) was fabricated and developed for the determination of the azo dye amaranth. Fe3O4@rGO composites were obtained by a one-step approach involving the initial intercalating of iron ions between the graphene oxide layers via the electrostatic interaction, followed by the reduction with hydrazine hydrate to deposit Fe3O4 nanoparticles onto the reduced oxide graphene nanosheets. In molecular imprinting, the complex including the function monomer of aniline, the template of amaranth and Fe3O4@rGO was pre-assembled through π-π stacking and hydrogen bonding interactions, and then was self-assembled on the surface of magnetic glassy carbon electrode (MGCE) with the help of magnetic field induction before electropolymerization. The structures and morphologies of Fe3O4@rGO and the doped molecularly imprinted polymers (MIPs) were investigated by Fourier transform infrared spectrometer (FT-IR), Raman spectra and scanning electron microscope (SEM). Besides, the characterization by differential pulse voltammetry (DPV) showed that Fe3O4@rGO composites promoted the electrical conductivity of the imprinted sensors when doped into the MIPs. The adsorption isotherms and adsorption kinetics were employed to evaluate the performances of MIES. The detection of amaranth was achieved via the redox probe K3[Fe(CN)6] by blocking the imprinted cavities, which avoided the interferences of oxidation products and analogs of amaranth. Furthermore, the prepared MIES exhibited good sensitivity, selectivity, reproducibility and efficiency for detecting amaranth in fruit drinks. The average recoveries were 93.15-100.81% with the RSD <3.0%.

  8. Ex vivo inhibition of Clostridium botulinum neurotoxin types B, C, E, and F by small molecular weight inhibitors.

    PubMed

    Montgomery, Vicki A; Ahmed, S Ashraf; Olson, Mark A; Mizanur, Rahman M; Stafford, Robert G; Roxas-Duncan, Virginia I; Smith, Leonard A

    2015-05-01

    Two small molecular weight inhibitors, compounds CB7969312 and CB7967495, that displayed inhibition of botulinum neurotoxin serotype A in a previous study, were evaluated for inhibition of botulinum neurotoxin serotypes B, C, E, and F. The small molecular weight inhibitors were assessed by molecular modeling, UPLC-based peptide cleavage assay; and an ex vivo assay, the mouse phrenic nerve - hemidiaphragm assay (MPNHDA). While both compounds were inhibitors of botulinum neurotoxin (BoNT) serotypes B, C, and F in the MPNHDA, compound CB7969312 was effective at lower molar concentrations than compound CB7967495. However, compound CB7967495 was significantly more effective at preventing BoNTE intoxication than compound CB7969312. In the UPLC-based peptide cleavage assay, CB7969312 was also more effective against LcC. Both compounds inhibited BoNTE, but not BoNTF, LcE, or LcF in the UPLC-based peptide cleavage assay. Molecular modeling studies predicted that both compounds would be effective inhibitors of BoNTs B, C, E, and F. But CB7967495 was predicted to be a more effective inhibitor of the four serotypes (B, C, E, and F) than CB7969312. This is the first report of a small molecular weight compound that inhibits serotypes B, C, E, and F in the ex vivo assay.

  9. Molecular geometry and polarizability of small cadmium selenide clusters from all-electron ab initio and Density Functional Theory calculations.

    PubMed

    Karamanis, Panaghiotis; Maroulis, George; Pouchan, Claude

    2006-02-21

    We have calculated molecular geometries and electric polarizabilities for small cadmium selenide clusters. Our calculations were performed with conventional ab initio and density functional theory methods and Gaussian-type basis sets especially designed for (CdSe)(n). We find that the dipole polarizability per atom converges rapidly to the bulk value.

  10. Optical and electrical properties of Mg-doped AlN nanowires grown by molecular beam epitaxy

    SciTech Connect

    Connie, Ashfiqua Tahseen; Zhao, Songrui; Sadaf, Sharif Md.; Shih, Ishiang; Mi, Zetian; Du, Xiaozhang; Lin, Jingyu; Jiang, Hongxing

    2015-05-25

    In this paper, the optical and electrical properties of Mg-doped AlN nanowires are discussed. At room temperature, with the increase of Mg-doping concentration, the Mg-acceptor energy level related optical transition can be clearly measured, which is separated about 0.6 eV from the band-edge transition, consistent with the Mg activation energy in AlN. The electrical conduction measurements indicate an activation energy of 23 meV at 300 K–450 K temperature range, which is significantly smaller than the Mg-ionization energy in AlN, suggesting the p-type conduction being mostly related to hopping conduction. The free hole concentration of AlN:Mg nanowires is estimated to be on the order of 10{sup 16 }cm{sup −3}, or higher.

  11. Thin-film growth and patterning techniques for small molecular organic compounds used in optoelectronic device applications.

    PubMed

    Biswas, Shaurjo; Shalev, Olga; Shtein, Max

    2013-01-01

    Rapid advances in research and development in organic electronics have resulted in many exciting discoveries and applications, including organic light-emitting devices for information display and illumination, solar cells, photodetectors, chemosensors, and logic. Organic optoelectronic materials are broadly classified as polymeric or small molecular. For the latter category, solvent-free deposition techniques are generally preferred to form well-defined interfaces and improve device performance. This article reviews several deposition and patterning methods for small molecular thin films and devices, including organic molecular beam deposition, vacuum thermal evaporation, organic vapor phase deposition, and organic vapor jet printing, and compares them to several other methods that have been proposed recently. We hope this review provides a compact but informative summary of the state of the art in organic device processing and addresses the various techniques' governing physical principles.

  12. TMDB: a literature-curated database for small molecular compounds found from tea.

    PubMed

    Yue, Yi; Chu, Gang-Xiu; Liu, Xue-Shi; Tang, Xing; Wang, Wei; Liu, Guang-Jin; Yang, Tao; Ling, Tie-Jun; Wang, Xiao-Gang; Zhang, Zheng-Zhu; Xia, Tao; Wan, Xiao-Chun; Bao, Guan-Hu

    2014-09-16

    Tea is one of the most consumed beverages worldwide. The healthy effects of tea are attributed to a wealthy of different chemical components from tea. Thousands of studies on the chemical constituents of tea had been reported. However, data from these individual reports have not been collected into a single database. The lack of a curated database of related information limits research in this field, and thus a cohesive database system should necessarily be constructed for data deposit and further application. The Tea Metabolome database (TMDB), a manually curated and web-accessible database, was developed to provide detailed, searchable descriptions of small molecular compounds found in Camellia spp. esp. in the plant Camellia sinensis and compounds in its manufactured products (different kinds of tea infusion). TMDB is currently the most complete and comprehensive curated collection of tea compounds data in the world. It contains records for more than 1393 constituents found in tea with information gathered from 364 published books, journal articles, and electronic databases. It also contains experimental 1H NMR and 13C NMR data collected from the purified reference compounds or collected from other database resources such as HMDB. TMDB interface allows users to retrieve tea compounds entries by keyword search using compound name, formula, occurrence, and CAS register number. Each entry in the TMDB contains an average of 24 separate data fields including its original plant species, compound structure, formula, molecular weight, name, CAS registry number, compound types, compound uses including healthy benefits, reference literatures, NMR, MS data, and the corresponding ID from databases such as HMDB and Pubmed. Users can also contribute novel regulatory entries by using a web-based submission page. The TMDB database is freely accessible from the URL of http://pcsb.ahau.edu.cn:8080/TCDB/index.jsp. The TMDB is designed to address the broad needs of tea biochemists

  13. Replica exchange molecular dynamics simulations provide insight into substrate recognition by small heat shock proteins.

    PubMed

    Patel, Sunita; Vierling, Elizabeth; Tama, Florence

    2014-06-17

    The small heat shock proteins (sHSPs) are a virtually ubiquitous and diverse group of molecular chaperones that can bind and protect unfolding proteins from irreversible aggregation. It has been suggested that intrinsic disorder of the N-terminal arm (NTA) of sHSPs is important for substrate recognition. To investigate conformations of the NTA that could recognize substrates we performed replica exchange molecular dynamics simulations. Behavior at normal and stress temperatures of the dimeric building blocks of dodecameric HSPs from wheat (Ta16.9) and pea (Ps18.1) were compared because they display high sequence similarity, but Ps18.1 is more efficient in binding specific substrates. In our simulations, the NTAs of the dimer are flexible and dynamic; however, rather than exhibiting highly extended conformations they retain considerable α-helical character and contacts with the conserved α-crystallin domain (ACD). Network analysis and clustering methods reveal that there are two major conformational forms designated either "open" or "closed" based on the relative position of the two NTAs and their hydrophobic solvent accessible surface area. The equilibrium constant for the closed to open transition is significantly different for Ta16.9 and Ps18.1, with the latter showing more open conformations at elevated temperature correlated with its more effective chaperone activity. In addition, the Ps18.1 NTAs have more hydrophobic solvent accessible surface than those of Ta16.9. NTA hydrophobic patches are comparable in size to the area buried in many protein-protein interactions, which would enable sHSPs to bind early unfolding intermediates. Reduced interactions of the Ps18.1 NTAs with each other and with the ACD contribute to the differences in dynamics and hydrophobic surface area of the two sHSPs. These data support a major role for the conformational equilibrium of the NTA in substrate binding and indicate features of the NTA that contribute to sHSP chaperone

  14. Potentiometric sensors doped with biomolecules as a new approach to small molecule/biomolecule binding kinetics analysis.

    PubMed

    Daems, D; De Wael, K; Vissenberg, K; Van Camp, G; Nagels, L

    2014-04-15

    The most successful binding kinetics analysis systems at this moment include surface plasmon resonance (SPR), quartz microcrystal balance (QMB) and surface acoustic wave (SAW). Although these are powerful methods, they generally are complex, expensive and require the use of monolayers. Here, we report on potentiometric sensors as an inexpensive and simple alternative to do binding kinetics analysis between small molecules in solution and biomolecules (covalently) attached in a biopolymer sensor coating layer. As an example, dopamine and an anti-dopamine aptamer were used as the small molecule and the biomolecule respectively. Binding between both follows a Langmuir adsorption type model and creates a surface potential. The system operates in Flow Injection Analysis mode (FIA). Besides being an interesting new binding kinetics tool, the approach allows systematic design of potentiometric biosensors (in the present study a dopamine sensor), and gives new insights into the functioning of ion-selective electrodes (ISE's).

  15. Vacancy-type defects in Mg-doped GaN grown by ammonia-based molecular beam epitaxy probed using a monoenergetic positron beam

    SciTech Connect

    Uedono, Akira; Malinverni, Marco; Martin, Denis; Grandjean, Nicolas; Okumura, Hironori; Ishibashi, Shoji

    2016-06-28

    Vacancy-type defects in Mg-doped GaN were probed using a monoenergetic positron beam. GaN films with a thickness of 0.5–0.7 μm were grown on GaN/sapphire templates using ammonia-based molecular beam epitaxy and characterized by measuring Doppler broadening spectra. Although no vacancies were detected in samples with a Mg concentration [Mg] below 7 × 10{sup 19 }cm{sup −3}, vacancy-type defects were introduced starting at above [Mg] = 1 × 10{sup 20 }cm{sup −3}. The major defect species was identified as a complex between Ga vacancy (V{sub Ga}) and multiple nitrogen vacancies (V{sub N}s). The introduction of vacancy complexes was found to correlate with a decrease in the net acceptor concentration, suggesting that the defect introduction is closely related to the carrier compensation. We also investigated Mg-doped GaN layers grown using In as the surfactant. The formation of vacancy complexes was suppressed in the subsurface region (≤80 nm). The observed depth distribution of defects was attributed to the thermal instability of the defects, which resulted in the introduction of vacancy complexes during the deposition process.

  16. Vacancy-type defects in Mg-doped GaN grown by ammonia-based molecular beam epitaxy probed using a monoenergetic positron beam

    NASA Astrophysics Data System (ADS)

    Uedono, Akira; Malinverni, Marco; Martin, Denis; Okumura, Hironori; Ishibashi, Shoji; Grandjean, Nicolas

    2016-06-01

    Vacancy-type defects in Mg-doped GaN were probed using a monoenergetic positron beam. GaN films with a thickness of 0.5-0.7 μm were grown on GaN/sapphire templates using ammonia-based molecular beam epitaxy and characterized by measuring Doppler broadening spectra. Although no vacancies were detected in samples with a Mg concentration [Mg] below 7 × 1019 cm-3, vacancy-type defects were introduced starting at above [Mg] = 1 × 1020 cm-3. The major defect species was identified as a complex between Ga vacancy (VGa) and multiple nitrogen vacancies (VNs). The introduction of vacancy complexes was found to correlate with a decrease in the net acceptor concentration, suggesting that the defect introduction is closely related to the carrier compensation. We also investigated Mg-doped GaN layers grown using In as the surfactant. The formation of vacancy complexes was suppressed in the subsurface region (≤80 nm). The observed depth distribution of defects was attributed to the thermal instability of the defects, which resulted in the introduction of vacancy complexes during the deposition process.

  17. Fluorine-doped nanocrystalline SnO{sub 2} powders prepared via a single molecular precursor method as anode materials for Li-ion batteries

    SciTech Connect

    Ha, Hyung-Wook; Kim, Keon . E-mail: kkim@korea.ac.kr; Borniol, Mervyn de; Toupance, Thierry . E-mail: t.toupance@lcoo.u-bordeaux1.fr

    2006-03-15

    Fluorine-doped nanocrystalline tin dioxide materials (F:SnO{sub 2}) have been successfully prepared by the sol-gel process from a single molecular precursor followed by a thermal treatment at 450-650 deg. C. The resulting materials were characterized by FTIR spectroscopy, powder X-ray diffraction, nitrogen adsorption porosimetry (BET) and transmission electron microscopy (TEM). The mean particle size increased from 5 to 20 nm and the specific surface area decreased from 123 to 37 m{sup 2}/g as the temperature of heat treatment was risen from 450 to 650 deg. C. Fluorine-doped nanocrystalline SnO{sub 2} exhibited capacity of 560, 502, and 702 mA h/g with 48%, 50%, and 40% capacity retention after 25 cycles between 1.2 V and 50 mV at the rate of 25 mA/g, respectively. In comparison, commercial SnO{sub 2} showed an initial capacity of 388 mA h/g, with only 23% capacity retention after 25 cycles.

  18. Synthesis and characterization of novel molecularly imprinted polymer - coated Mn-doped ZnS quantum dots for specific fluorescent recognition of cocaine.

    PubMed

    Chantada-Vázquez, María Pilar; Sánchez-González, Juan; Peña-Vázquez, Elena; Tabernero, María Jesús; Bermejo, Ana María; Bermejo-Barrera, Pilar; Moreda-Piñeiro, Antonio

    2016-01-15

    Mn-doped ZnS quantum dots (QDs) coated with a molecularly imprinted polymer (MIP) material selective toward cocaine and its metabolites have been prepared and applied to cocaine (COC) and metabolites assessment by spectrofluorimetry. Ultrasound irradiation (37kHz) was novelty used for performing the Mn-doped ZnS QDs synthesis as well as for preparing the QD based MIP-coated composite by precipitation polymerization (imprinting process). This fact allowed the synthesis to be accomplished in four hours. In addition, the use of ultrasound irradiation during MIP-QDs synthesis increased the homogeneity of the QDs size, and reduced nanoparticles agglomeration. MIP was synthesized using COC as a template molecule, ethylene dimethacrylate (EDMA) as a functional monomer, divinylbenzene (DVB) as a cross-linker, and 2,2'-azobisisobutyronitrile (AIBN) as an initiator. The fluorescence of MIP-coated QDs was quenched by the template (COC) and also by metabolites from COC such as benzoylecgonine (BZE), and ecgonine methyl ester (EME). Quenching was not observed when performing experiments with non-imprinted polymer (NIP)-coated QDs; and also, fluorescence quenching of MIP-coated QDs was not observed by other drugs of abuse and metabolites (heroin and cannabis abuse). This fact indicates that the prepared material recognize only COC (template) and metabolites. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Precipitation control and activation enhancement in boron-doped p{sup +}-BaSi{sub 2} films grown by molecular beam epitaxy

    SciTech Connect

    Khan, M. Ajmal; Nakamura, K.; Du, W.; Toko, K.; Usami, N.; Suemasu, T.

    2014-06-23

    Precipitation free boron (B)-doped as-grown p{sup +}-BaSi{sub 2} layer is essential for the BaSi{sub 2} p-n junction solar cells. In this article, B-doped p-BaSi{sub 2} layers were grown by molecular beam epitaxy on Si(111) substrates, and the influence of substrate growth temperature (T{sub S}) and B temperature (T{sub B}) in the Knudsen cell crucible were investigated on the formation of B precipitates and the activation efficiency. The hole concentration, p, reached 1.0 × 10{sup 19 }cm{sup −3} at room temperature for T{sub S} = 600 and T{sub B} = 1550 °C. However, the activation rate of B was only 0.1%. Furthermore, the B precipitates were observed by transmission electron microscopy (TEM). When the T{sub S} was raised to 650 °C and the T{sub B} was decreased to 1350 °C, the p reached 6.8 × 10{sup 19 }cm{sup −3}, and the activation rate increased to more than 20%. No precipitation of B was also confirmed by TEM.

  20. Molecular Characterisation of Small Molecule Agonists Effect on the Human Glucagon Like Peptide-1 Receptor Internalisation

    PubMed Central

    Thompson, Aiysha; Stephens, Jeffrey W.; Bain, Stephen C.

    2016-01-01

    The glucagon-like peptide receptor (GLP-1R), which is a G-protein coupled receptor (GPCR), signals through both Gαs and Gαq coupled pathways and ERK phosphorylation to stimulate insulin secretion. The aim of this study was to determine molecular details of the effect of small molecule agonists, compounds 2 and B, on GLP-1R mediated cAMP production, intracellular Ca2+ accumulation, ERK phosphorylation and its internalisation. In human GLP-1R (hGLP-1R) expressing cells, compounds 2 and B induced cAMP production but caused no intracellular Ca2+ accumulation, ERK phosphorylation or hGLP-1R internalisation. GLP-1 antagonists Ex(9–39) and JANT-4 and the orthosteric binding site mutation (V36A) in hGLP-1R failed to inhibit compounds 2 and B induced cAMP production, confirming that their binding site distinct from the GLP-1 binding site on GLP-1R. However, K334A mutation of hGLP-1R, which affects Gαs coupling, inhibited GLP-1 as well as compounds 2 and B induced cAMP production, indicating that GLP-1, compounds 2 and B binding induce similar conformational changes in the GLP-1R for Gαs coupling. Additionally, compound 2 or B binding to the hGLP-1R had significantly reduced GLP-1 induced intracellular Ca2+ accumulation, ERK phosphorylation and hGLP-1R internalisation. This study illustrates pharmacology of differential activation of GLP-1R by GLP-1 and compounds 2 and B. PMID:27100083

  1. Photocatalytic reduction of Cr(VI) by small molecular weight organic acids over schwertmannite.

    PubMed

    Jiang, Danjun; Li, Ying; Wu, Yong; Zhou, Pei; Lan, Yeqing; Zhou, Lixiang

    2012-10-01

    In this study, a series of bath experiments was carried out to investigate the photoreduction of Cr(VI) by small molecular weight organic acids (SOAs) over schwertmannite, a mineral found in acid mine drainage (AMD). The results demonstrated that schwertmannite or SOAs alone was unable to effectively transform Cr(VI) to Cr(III) even if exposed to an illumination of mimic solar light. However, an addition of schwertmannite significantly enhanced the reduction of Cr(VI) by SOAs under the same condition. For example, 100μM Cr(VI) was almost completely removed within 50min in the presence of both schwertmannite (0.6gL(-1)) and oxalic acid (300μM) at pH 3.0. The photocatalytic reduction of Cr(VI) was strongly influenced by pH, the initial concentrations and the structures of SOAs. Of the tested three SOAs, the reaction rates of photocatalytic reduction of Cr(VI) were in the order of oxalic acid>citric acid>tartaric acid. The reaction obeyed to zero-order kinetics with respect to Cr(VI) with excess SOAs. A possible mechanism for photoreduction of Cr(VI) by SOAs over schwertmannite was proposed. Fe(III) on the surface of schwertmannite was dissolved by SOAs, and then Fe(III)-SOA complexes with high photochemical activity formed. Further, Fe(II) together with organic acid radicals, CO(2)(-) and O(2)(-), was generated through a metal-ligand-charge-transfer pathway (MLCT), leading to a rapid reduction of Cr(VI). Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Morphological and molecular analyses of larval taeniid species in small mammals from contrasting habitats in Denmark.

    PubMed

    Al-Sabi, M N S; Jensen, P M; Christensen, M U; Kapel, C M O

    2015-01-01

    Taeniid infections in intermediate hosts manifest themselves as extraintestinal larval stages which, in early development, lack species-specific characteristics. The inability to distinguish infections of zoonotic importance such as Echinococcus multilocularis from other taeniid infections that have mainly veterinary significance stimulated the development of species-specific molecular diagnostics. In this study, the prevalence of taeniid infections in potential intermediate hosts was evaluated using both morphological diagnosis and a newly described multiplex polymerase chain reaction (PCR) for species determination. Small mammals (N= 719) were trapped in three different types of habitats in north-east Zealand, Denmark. The sensitivity of the multiplex PCR (90.5%) exceeded that of morphological examination (57.9%) for identifying 95 taeniid infections. The use of the multiplex PCR resulted in higher prevalence rates due to improved detection of immature liver infections with Hydatigera taeniaeformis and Versteria mustelae, but did not affect the observed prevalence rates of peritoneal metacestodes of Taenia polyacantha. The prevalence of taeniid infections showed a significant difference according to habitat type, potentially identifying a 'sylvatic' transmission and an 'urban' transmission, with marked variation among different taeniid species. Versteria mustelae and T. polyacantha were more prevalent in rural forests, while infections with H. taeniaeformis were dominant in urban parks/forests and in residential and farm gardens. The multiplex PCR facilitated a better utilization of wildlife samples by yielding a higher number of definitive diagnoses of ambiguous taeniid infections in liver lesions, allowing for more accurate epidemiological data and, hence, a more accurate risk assessment.

  3. Rhamnetin induces sensitization of hepatocellular carcinoma cells to a small molecular kinase inhibitor or chemotherapeutic agents.

    PubMed

    Jia, Hui; Yang, Qian; Wang, Tao; Cao, Yu; Jiang, Qi-Yu; Ma, Hong-da; Sun, Hui-Wei; Hou, Ming-Xiao; Yang, Yong-Ping; Feng, Fan

    2016-07-01

    The rapid development of multi-drug resistance (MDR) process has hindered the effectiveness of advanced hepatocellular carcinoma (HCC) treatments. Notch-1 pathway, which mediates the stress-response, promotes cell survival, EMT (epithelial-mesenchymal transition) process and induces anti-apoptosis in cancer cells, would be a potential target for overcoming MDR process. This study investigated the potential application of rhamnetin, a specific inhibitor of Notch-1 pathway, in anti-tumor drug sensitization of HCC treatment. The expression of miR-34a, proteins belonging to Notch-1 signaling pathway or MDR-related proteins was detected by quantitative polymerase chain reaction (qPCR) and western blot assay. To identify whether rhamnetin induces the chemotherapeutic sensitization in HCC cells, the MTT-assays, flow cytometry, soft agar, trans-well and nude mice assays were performed. The endogenous expression of miR-34a was significantly increased and the expression of Notch-1 and Survivin was downregulated after rhamnetin treatment. Treatment of rhamnetin also reduced the expression of MDR related proteins P-GP (P-glycoprotein) and BCRP (breast cancer resistance protein). Rhamnetin increased the susceptibility of HCC cells and especially HepG2/ADR, a MDR HCC cell line, to a small molecular kinase inhibitor sorafenib or chemotherapeutic drugs etoposide and paclitaxel. The IC(50) value of those drugs correspondingly decreased. Together, our findings suggest that rhamnetin treatment may attenuate the MDR process in HCC cells. These findings may contribute to more effective strategies for HCC therapy. Rhamnetin acts as a promising sensitizer to chemotherapy and may be a novel approach to overcome the MDR process of HCC. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Inhibition of non-small cell lung cancer (NSCLC) growth by a novel small molecular inhibitor of EGFR.

    PubMed

    Li, Jinsong; Deng, Huayun; Hu, Meichun; Fang, Yuanzhang; Vaughn, Amanda; Cai, Xiaopan; Xu, Leqin; Wan, Wei; Li, Zhenxi; Chen, Shijie; Yang, Xinghai; Wu, Song; Xiao, Jianru

    2015-03-30

    The epidermal growth factor receptor (EGFR) is a therapeutic target (oncotarget) in NSCLC. Using in vitro EGFR kinase activity system, we identified a novel small molecule, WB-308, as an inhibitor of EGFR. WB-308 decreased NSCLC cell proliferation and colony formation, by causing G2/M arrest and apoptosis. Furthermore, WB-308 inhibited the engraft tumor growths in two animal models in vivo (lung orthotopic transplantation model and patient-derived engraft mouse model). WB-308 impaired the phosphorylation of EGFR, AKT, and ERK1/2 protein. WB-308 was less cytotoxic than Gefitinib. Our study suggests that WB-308 is a novel EGFR-TKI and may be considered to substitute for Gefitinib in clinical therapy for NSCLC.

  5. Alloy formation during molecular beam epitaxy growth of Si-doped InAs nanowires on GaAs[111]B

    PubMed Central

    Davydok, Anton; Rieger, Torsten; Biermanns, Andreas; Saqib, Muhammad; Grap, Thomas; Lepsa, Mihail Ion; Pietsch, Ullrich

    2013-01-01

    Vertically aligned InAs nanowires (NWs) doped with Si were grown self-assisted by molecular beam epitaxy on GaAs[111]B substrates covered with a thin SiOx layer. Using out-of-plane X-ray diffraction, the influence of Si supply on the growth process and nanostructure formation was studied. It was found that the number of parasitic crystallites grown between the NWs increases with increasing Si flux. In addition, the formation of a Ga0.2In0.8As alloy was observed if the growth was performed on samples covered by a defective oxide layer. This alloy formation is observed within the crystallites and not within the nanowires. The Ga concentration is determined from the lattice mismatch of the crystallites relative to the InAs nanowires. No alloy formation is found for samples with faultless oxide layers. PMID:24046494

  6. Nucleation and growth of GaN nanorods on Si (111) surfaces by plasma-assisted molecular beam epitaxy - The influence of Si- and Mg-doping

    NASA Astrophysics Data System (ADS)

    Furtmayr, Florian; Vielemeyer, Martin; Stutzmann, Martin; Arbiol, Jordi; Estradé, Sònia; Peirò, Francesca; Morante, Joan Ramon; Eickhoff, Martin

    2008-08-01

    The self-assembled growth of GaN nanorods on Si (111) substrates by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions is investigated. An amorphous silicon nitride layer is formed in the initial stage of growth that prevents the formation of a GaN wetting layer. The nucleation time was found to be strongly influenced by the substrate temperature and was more than 30 min for the applied growth conditions. The observed tapering and reduced length of silicon-doped nanorods is explained by enhanced nucleation on nonpolar facets and proves Ga-adatom diffusion on nanorod sidewalls as one contribution to the axial growth. The presence of Mg leads to an increased radial growth rate with a simultaneous decrease of the nanorod length and reduces the nucleation time for high Mg concentrations.

  7. Alloy formation during molecular beam epitaxy growth of Si-doped InAs nanowires on GaAs[111]B.

    PubMed

    Davydok, Anton; Rieger, Torsten; Biermanns, Andreas; Saqib, Muhammad; Grap, Thomas; Lepsa, Mihail Ion; Pietsch, Ullrich

    2013-08-01

    Vertically aligned InAs nanowires (NWs) doped with Si were grown self-assisted by molecular beam epitaxy on GaAs[111]B substrates covered with a thin SiO x layer. Using out-of-plane X-ray diffraction, the influence of Si supply on the growth process and nanostructure formation was studied. It was found that the number of parasitic crystallites grown between the NWs increases with increasing Si flux. In addition, the formation of a Ga0.2In0.8As alloy was observed if the growth was performed on samples covered by a defective oxide layer. This alloy formation is observed within the crystallites and not within the nanowires. The Ga concentration is determined from the lattice mismatch of the crystallites relative to the InAs nanowires. No alloy formation is found for samples with faultless oxide layers.

  8. The Art of Building Small: From Molecular Switches to Motors (Nobel Lecture).

    PubMed

    Feringa, Ben L

    2017-09-04

    A journey into the nano-world: The ability to design, use and control motor-like functions at the molecular level sets the stage for numerous dynamic molecular systems. In his Nobel Lecture, B. L. Feringa describes the evolution of the field of molecular motors and explains how to program and control molecules by incorporating responsive and adaptive properties. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. X-ray and molecular modelling in fragment-based design of three small quinoline scaffolds for HIV integrase inhibitors.

    PubMed

    Majerz-Maniecka, Katarzyna; Musiol, Robert; Skórska-Stania, Agnieszka; Tabak, Dominik; Mazur, Pawel; Oleksyn, Barbara J; Polanski, Jaroslaw

    2011-03-01

    Crystal structures of three small molecular scaffolds based on quinoline, 2-methylquinoline-5,8-dione, 5-hydroxy-quinaldine-6-carboxylic acid and 8-hydroxy-quinaldine-7-carboxylic acid, were characterised. 5-Hydroxy-quinaldine-6-carboxylic acid was co-crystallized with cobalt(II) chloride to form a model of divalent metal cation-ligand interactions for potential HIV integrase inhibitors. Molecular docking into active site of HIV IN was also performed on 1WKN PDB file. Selected ligand-protein interactions have been found specific for active compounds. Studied structures can be used as scaffolds in fragment-based design of new potent drugs.

  10. Molecular ecology of Listeria monocytogenes and other Listeria species in small and very small ready-to-eat meat processing plants.

    PubMed

    Williams, Shanna K; Roof, Sherry; Boyle, Elizabeth A; Burson, Dennis; Thippareddi, Harshavardhan; Geornaras, Ifigenia; Sofos, John N; Wiedmann, Martin; Nightingale, Kendra

    2011-01-01

    A longitudinal study was conducted to track Listeria contamination patterns in ready-to-eat meats from six small or very small meat processing plants located in three states over 1 year. A total of 688 environmental sponge samples were collected from nonfood contact surfaces during bimonthly visits to each plant. Overall, L. monocytogenes was isolated from 42 (6.1%) environmental samples, and its prevalence ranged from 1.7 to 10.8% across different plants. Listeria spp., other than L. monocytogenes, were isolated from 9.5% of samples overall, with the prevalence ranging from 1.5 to 18.3% across different plants. The prevalence of L. monocytogenes correlated well with that of other Listeria spp. for some but not all plants. One L. monocytogenes isolate representing each positive sample was characterized by molecular serotyping, EcoRI ribotyping, and pulsed-field gel electrophoresis typing. Seven sample sites tested positive for L. monocytogenes on more than one occasion, and the same ribotype was detected more than once at five of these sites. Partial sigB sequencing was used to speciate other Listeria spp. isolates and assign an allelic type to each isolate. Other Listeria spp. were isolated more than once from 14 sample sites, and the same sigB allelic type was recovered at least twice from seven of these sites. One plant was colonized by an atypical hemolytic L. innocua strain. Our findings indicate that small and very small meat processing plants that produce ready-to-eat meat products are characterized by a varied prevalence of Listeria, inconsistent correlation between contamination by L. monocytogenes and other Listeria spp., and a unique Listeria molecular ecology.

  11. The improved efficiency of low molecular weight organic solar cells doped with a Cu(I) triplet material

    NASA Astrophysics Data System (ADS)

    Su, Bin; Gao, Lin; Li, Xiuying; Che, Guangbo; Zhu, Enwei; Wang, Bo; Yan, Yongsheng

    2016-08-01

    We developed a method to improve the performance of the copper phthalocyanine (CuPc)/fullerene (C60) organic solar cells (OSCs) by doping CuPc with a long triplet lifetime material. By doping [Cu(bis[2-(diphenylphosphino)phenyl]ether)(benzo[i]dipyrido[3,2-a:2',3'-c]phenazine)]BF4 (CuDB) into CuPc, the enhanced short-circuit current density ( J SC) of 6.213 mA/cm2, open-circuit voltage ( V OC) of 0.39 V and a peak power conversion efficiency (PCE) of 0.92% compared to 0.79% of the standard CuPc/C60 OSCs are achieved under 1 sun AM 1.5 G illumination at an intensity of 100 mW/cm2. The performance improvement is mainly attributed to the long triplet lifetime of CuDB (τ = 70.05 μs) which leads to more effective exciton dissociation.

  12. Conversion process of the dominant electroluminescence mechanism in a molecularly doped organic light-emitting device with only electron trapping

    NASA Astrophysics Data System (ADS)

    Zhou, Liang; Zhang, Hongjie; Deng, Ruiping; Li, Zhefeng; Yu, Jiangbo; Guo, Zhiyong

    2007-09-01

    In this work, the detailed conversion process of the dominant electroluminescence (EL) mechanism in a device with Eu(TTA)3phen (TTA =thenoyltrifluoroacetone, phen =1,10-phenanthroline) doped CBP (4,4'-N,N'-dicarbazole-biphenyl) film as the emitting layer was investigated by analyzing the evolution of carrier distribution on dye and host molecules with increasing voltage. Firstly, it was confirmed that only electrons can be trapped in Eu(TTA)3phen doped CBP. As a result, holes and electrons would be situated on CBP and Eu(TTA)3phen molecules, respectively, and thus creates an unbalanced carrier distribution on both dye and host molecules. With the help of EL and photoluminescence spectra, the distribution of holes and electrons on both Eu(TTA)3phen and CBP molecules was demonstrated to change gradually with increasing voltage. Therefore, the dominant EL mechanism in this device changes gradually from carrier trapping at relatively low voltage to Förster energy transfer at relatively high voltage.

  13. One-step ethanolysis of lignin into small-molecular aromatic hydrocarbons over nano-SiC catalyst.

    PubMed

    Chen, Yigang; Wang, Fang; Jia, Yingjie; Yang, Nan; Zhang, Xianming

    2017-02-01

    Catalytic depolymerization of lignin for preparation of aromatic hydrocarbons without external hydrogen was first carried out over nano-SiC catalyst in supercritical ethanol. Mixture of the catalyst and lignin was innovatively suspended in a closed reactor and small-molecular aromatic hydrocarbons were successfully achieved at 500°C. Results revealed that not only did conversion of lignin increase sharply under the nano-SiC catalyst, but also phenols were not detected. The increase of residence time under the Fe-SiC catalyst did not change distribution of the liquid products besides the yield improvement, suggesting that the catalyst was suitable and selective towards formation of small-molecular benzenes, especially C6-C8 benzenes. Preliminary studies found that lignin depolymerization and deoxygenation were successfully fulfilled during the reactions, which provided a very effective route to conversion of lignin into high added-value molecules as transportation fuel additives.

  14. Molecular diagnostics for infectious disease in small animal medicine: an overview from the laboratory.

    PubMed

    Daniels, Joshua B

    2013-11-01

    Molecular diagnostic tests have augmented the way in which veterinary practitioners approach the diagnosis of infectious disease. The technical bases of these tests are explained in addition to the general clinical applications for which they are most aptly suited, as individual assays are best discussed in the context of their respective diseases. In this article, an emphasis is placed on validation of molecular tests so that practitioners can be educated consumers of molecular diagnostics. The relationships between disease prevalence and positive and negative predictive values are discussed. Finally, examples of the pitfalls of multiplex polymerase chain reaction testing are illustrated.

  15. Deformation of poly(methyl methacrylate)-poly(ethylene oxide) blends: a molecular characterization by small-angle neutron scattering

    SciTech Connect

    Lefebvre, J.M.R.; Porter, S.; Wignall, G.D.

    1986-01-01

    The deformation behavior of miscible amorphous/amorphous PMMA/PEO blends has been compared to that of pure PMMA. Small-angle neutron scattering experiments have been performed on labeled systems made of PEO + D-PMMA + H-PMMA. Characteristic molecular parameters such as radius of gyration R/sub g/, molecular weight M/sub w/ and interaction parameter X have been extracted from the coherent scattering cross sections. Molecular anisotropy is measured on the solid state coextruded samples and the observed drawing efficiency is compared to the results of shrinkage tests. In the case of PMMA/PEO blends, anomalous scattering behavior precludes any quantitative interpretation of the scattering patterns, but revealed important structural changes upon drawing, namely a deformation-induced phase separation.

  16. DFT, NBO and molecular docking studies of the adsorption of fluoxetine into and on the surface of simple and sulfur-doped carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Shahabi, Dana; Tavakol, Hossein

    2017-10-01

    In this study, noncovalent interactions between Fluoxetine (FX) and different carbon nanotubes (CNTs) or sulfur doped carbon nanotubes (SCNTs) were fully considered using DFT, natural bond orbital (NBO) and molecular docking calculations. Two different CNTs (and SCNTs) with 7,7 and 8,8 chiralities were considered as the adsorbents and the adsorption of FX by these adsorbents were studied in two cases: into the nanotubes and on their surfaces. The results of DFT and NBO calculations proposed that the 8,8 nanotubes are more suitable adsorbents for FX because the energies of their adsorptions are minimum. Population: analyses were also proposed that the adsorption of FX by SCNTs lead to more changes in electronic and sensing properties than the adsorption by CNTs. Moreover, the adsorption energies, obtained from molecular docking calculations (using 94 different models), proposed that the adsorption of FX into (versus out of) the nanotubes, adsorption processes by double-walled or triple-walled (versus single-walled) nanotubes and the adsorption by nanotubes with 8,8 chiralities are the most favorable adsorption processes.

  17. Molecular Breast Imaging: Use of a Dual-Head Dedicated Gamma Camera to Detect Small Breast Tumors

    PubMed Central

    Hruska, Carrie B.; Phillips, Stephen W.; Whaley, Dana H.; Rhodes, Deborah J.; O’Connor, Michael K.

    2014-01-01

    OBJECTIVE Molecular breast imaging with a single-head cadmium zinc telluride (CZT) gamma camera has previously been shown to have good sensitivity for the detection of small lesions. To further improve sensitivity, we developed a dual-head molecular breast imaging system using two CZT detectors to simultaneously acquire opposing breast views and reduce lesion-to-detector distance. We determined the incremental gain in sensitivity of molecular breast imaging with dual detectors. SUBJECTS AND METHODS Patients with BI-RADS category 4 or 5 lesions < 2 cm that were identified on mammography or sonography and scheduled for biopsy underwent molecular breast imaging as follows: After injection of 740 MBq of technetium-99m (99mTc) sestamibi, 10-minute craniocaudal and mediolateral oblique views of each breast were acquired. Blinded reviews were performed using images from both detectors 1 and 2 and images from detector 1 only (simulating a single-head system). Lesions were scored on a scale of 1–5; 2 or higher was considered positive. RESULTS Of the 150 patients in the study, 128 cancers were confirmed in 88 patients. Averaging the results from the three blinded readers, the sensitivity of dual-head molecular breast imaging was 90% (115/128), whereas the sensitivity from review of only single-head molecular breast imaging was 80% (102/128). The sensitivity for the detection of cancers ≤ 10 mm in diameter was 82% (50/61) for dual-head molecular breast imaging and 68% (41/61) for single-head molecular breast imaging. On average, 13 additional cancers were seen on dual-head images and the tumor uptake score increased by 1 or more in 60% of the identified tumors. CONCLUSION Gains in sensitivity with the dual-head system molecular breast imaging are partially due to increased confidence in lesion detection. Molecular breast imaging can reliably detect breast lesions < 2 cm and dual-head molecular breast imaging can significantly increase sensitivity for subcentimeter lesions

  18. Measurement of Small Molecular Dopant F4TCNQ and C60F36 Diffusion in Organic Bilayer Architectures.

    PubMed

    Li, Jun; Rochester, Chris W; Jacobs, Ian E; Friedrich, Stephan; Stroeve, Pieter; Riede, Moritz; Moulé, Adam J

    2015-12-30

    The diffusion of molecules through and between organic layers is a serious stability concern in organic electronic devices. In this work, the temperature-dependent diffusion of molecular dopants through small molecule hole transport layers is observed. Specifically we investigate bilayer stacks of small molecules used for hole transport (MeO-TPD) and p-type dopants (F4TCNQ and C60F36) used in hole injection layers for organic light emitting diodes and hole collection electrodes for organic photovoltaics. With the use of absorbance spectroscopy, photoluminescence spectroscopy, neutron reflectometry, and near-edge X-ray absorption fine structure spectroscopy, we are able to obtain a comprehensive picture of the diffusion of fluorinated small molecules through MeO-TPD layers. F4TCNQ spontaneously diffuses into the MeO-TPD material even at room temperature, while C60F36, a much bulkier molecule, is shown to have a substantially higher morphological stability. This study highlights that the differences in size/geometry and thermal properties of small molecular dopants can have a significant impact on their diffusion in organic device architectures.

  19. Toward molecular mechanism of xenon anesthesia: a link to studies of xenon complexes with small aromatic molecules.

    PubMed

    Andrijchenko, Natalya N; Ermilov, Alexander Yu; Khriachtchev, Leonid; Räsänen, Markku; Nemukhin, Alexander V

    2015-03-19

    The present study illustrates the steps toward understanding molecular mechanism of xenon anesthesia by focusing on a link to the structures and spectra of intermolecular complexes of xenon with small aromatic molecules. A primary cause of xenon anesthesia is attributed to inhibition of N-methyl-D-aspartate (NMDA) receptors by an unknown mechanism. Following the results of quantum mechanics/molecular mechanics (QM/MM) and molecular dynamics (MD) calculations we report plausible xenon action sites in the ligand binding domain of the NMDA receptor, which are due to interaction of xenon atoms with aromatic amino-acid residues. We rely in these calculations on computational protocols adjusted in combined experimental and theoretical studies of intermolecular complexes of xenon with phenol. Successful reproduction of vibrational shifts in molecular species upon complexation with xenon measured in low-temperature matrices allowed us to select a proper functional form in density functional theory (DFT) approach for use in QM subsystems, as well as to calibrate force field parameters for MD simulations. The results of molecular modeling show that xenon atoms can compete with agonists for a place in the corresponding protein cavity, thus indicating their active role in anesthetic action.

  20. Advances in preclinical therapeutics development using small animal imaging and molecular analyses: the gastrointestinal stromal tumors model.

    PubMed

    Pantaleo, M A; Landuzzi, L; Nicoletti, G; Nanni, C; Boschi, S; Piazzi, G; Santini, D; Di Battista, M; Castellucci, P; Lodi, F; Fanti, S; Lollini, P-L; Biasco, G

    2009-09-01

    The large use of target therapies in the treatment of gastrointestinal stromal tumors (GISTs) highlighted the urgency to integrate new molecular imaging technologies, to develop new criteria for tumor response evaluation and to reach a more comprehensive definition of the molecular target. These aspects, which come from clinical experiences, are not considered enough in preclinical research studies which aim to evaluate the efficacy of new drugs or new combination of drugs with molecular target. We developed a xenograft animal model GIST882 using nude mice. We evaluated both the molecular and functional characterization of the tumor mass. The mutational analysis of KIT receptor of the GIST882 cell lines and tumor mass showed a mutation on exon 13 that was still present after in vivo cell growth. The glucose metabolism and cell proliferation was evaluated with a small animal PET using both FDG and FLT. The experimental development of new therapies for GIST treatment requires sophisticated animal models in order to represent the tumor molecular heterogeneity already demonstrated in the clinical setting and in order to evaluate the efficacy of the treatment also considering the inhibition of tumor metabolism, and not only considering the change in size of tumors. This approach of cancer research on GISTs is crucial and essential for innovative perspectives that could cross over to other types of cancer.

  1. Structural Evolution of Polylactide Molecular Bottlebrushes: Kinetics Study by Size Exclusion Chromatography, Small Angle Neutron Scattering and Simulations

    SciTech Connect

    Pickel, Deanna L; Kilbey, II, S Michael; Uhrig, David; Hong, Kunlun; Carrillo, Jan-Michael Y; Sumpter, Bobby G; Ahn, Suk-Kyun; Han, Youngkyu; Kim, Dr. Tae-Hwan; Smith, Gregory Scott; Do, Changwoo

    2014-01-01

    Structural evolution from poly(lactide) (PLA) macromonomer to resultant PLA molecular bottlebrush during ring opening metathesis polymerization (ROMP) was investigated for the first time by combining size exclusion chromatography (SEC), small-angle neutron scattering (SANS) and coarse-grained molecular dynamics (CG-MD) simulations. Multiple aliquots were collected at various reaction times during ROMP, and subsequently analyzed by SEC and SANS. The two complementary techniques enable the understanding of systematic changes in conversion, molecular weight and dispersity as well as structural details of PLA molecular bottlebrushes. CG-MD simulation not only predicts the experimental observations, but it also provides further insight into the analysis and interpretation of data obtained in SEC and SANS experiments. We find that PLA molecular bottlebrushes undergo three conformational transitions with increasing conversion (i.e., increasing the backbone length): (1) from an elongated to a globular shape due to longer side chain at lower conversion, (2) from a globular to an elongated shape at intermediate conversion caused by excluded volume of PLA side chain, and (3) the saturation of contour length at higher conversion due to chain transfer reactions.

  2. Structural Evolution of Polylactide Molecular Bottlebrushes: Kinetics Study by Size Exclusion Chromatography, Small Angle Neutron Scattering, and Simulations

    SciTech Connect

    Ahn, Suk-kyun; Carrillo, Jan-Michael Y.; Han, Youngkyu; Kim, Tae-Hwan; Uhrig, David; Pickel, Deanna L.; Hong, Kunlun; S. Michael Kilbey; Sumpter, Bobby G.; Smith, Gregory Scott; Do, Changwoo

    2014-08-18

    In this paper, structural evolution from poly(lactide) (PLA) macromonomer to resultant PLA molecular bottlebrush during ring opening metathesis polymerization (ROMP) was investigated for the first time by combining size exclusion chromatography (SEC), small-angle neutron scattering (SANS), and coarse-grained molecular dynamics (CG-MD) simulations. Multiple aliquots were collected at various reaction times during ROMP and subsequently analyzed by SEC and SANS. These complementary techniques enable the understanding of systematic changes in conversion, molecular weight and dispersity as well as structural details of PLA molecular bottlebrushes. CG-MD simulation not only predicts the experimental observations, but it also provides further insight into the analysis and interpretation of data obtained in SEC and SANS experiments. Finally, we find that PLA molecular bottlebrushes undergo three conformational transitions with increasing conversion (i.e., increasing the backbone length): (1) from an elongated to a globular shape due to longer side chain at low conversion, (2) from a globular to an elongated shape at intermediate conversion caused by excluded volume of PLA side chain, and (3) the saturation of contour length at high conversion due to chain transfer reactions.

  3. A new molecular precursor route for the synthesis of Bi-Y, Y-Nb and Bi-doped Y-Nb oxides at moderate temperatures

    SciTech Connect

    Bayot, D.A.; Dupont, A.M.; Devillers, Michel M.

    2007-03-15

    Yttrium-based multimetallic oxides containing bismuth and/or niobium were prepared by a method starting from pre-isolated stable water-soluble precursors which are complexes with the ethylenediaminetetraacetate ligand (edta). The cubic Bi{sub 1-} {sub x} Y {sub x} O{sub 1.5} (x=0.22, 0.25 and 0.3) and Y{sub 3}NbO{sub 7} oxides were obtained in a pure form in a range of moderate temperatures (600-650 deg. C). This preparation method also allowed to stabilize at room temperature, without quenching, the tetragonal YNbO{sub 4} oxide in a distorted form (T'-phase) by calcining the precursor at 800 deg. C. When heated up to 1000 deg. C, this metastable T'-phase transforms into the metastable 'high-temperature' T oxide, which converts on cooling down to room temperature into the thermodynamically stable monoclinic M oxide. Doping the YNbO{sub 4} oxide with Bi{sup 3+} cations (0.5% and 1% Bi with respect to total Bi+Y amount) led at 800 deg. C to a mixture of the T'-phase and the thermodynamically stable monoclinic one. At 900 deg. C, the almost pure monoclinic structure was obtained. - Graphical abstract: Bi-Y, Nb-Y and Bi-doped Nb-Y oxides were prepared by a molecular precursors method from pre-isolated water-soluble edta-based complexes. The cubic Bi{sub 1-} {sub x} Y {sub x} O{sub 1.5} and Y{sub 3}NbO{sub 7} oxides were obtained in a pure form at the moderate temperature of 650 deg. C. A distorted tetragonal YNbO{sub 4} phase was also stabilized at room temperature by calcining the precursor at 800 deg. C, and the pure corresponding monoclinic oxide has been obtained near 1100 deg. C.

  4. Simple and Sensitive Molecularly Imprinted Polymer - Mn-Doped ZnS Quantum Dots Based Fluorescence Probe for Cocaine and Metabolites Determination in Urine.

    PubMed

    Chantada-Vázquez, María Pilar; Sánchez-González, Juan; Peña-Vázquez, Elena; Tabernero, María Jesús; Bermejo, Ana María; Bermejo-Barrera, Pilar; Moreda-Piñeiro, Antonio

    2016-03-01

    A new molecularly imprinted polymer (MIP)-based fluorescent artificial receptor has been prepared by anchoring a selective MIP for cocaine (COC) on the surface of polyethylene glycol (PEG) modified Mn-doped ZnS quantum dots (QDs). The prepared material combines the high selectivity attributed to MIPs and the sensitive fluorescent property of the Mn-doped ZnS QDs. Simple and low cost methods have therefore been optimized for assessing cocaine abuse in urine by monitoring the fluorescence quenching when the template (COC) and also metabolites from COC [benzoylecgonine (BZE) and ecgonine methyl ester (EME)] are present. Fluorescence quenching was not observed when performing experiments with other drugs of abuse (and their metabolites) or when using nonimprinted polymer (NIP)-coated QDs. Under optimized operating conditions (1.5 mL of 200 mg L(-1) MIP-coated QDs solution, pH 5.5, and 15 min before fluorescence scanning) two analytical methods were developed/validated. One of the procedures (direct method) consisted of urine sample 1:20 dilution before fluorescence measurements. The method has been found to be fast, precise, and accurate, but the standard addition technique for performing the analysis was required because of the existence of matrix effect. The second procedure performed a solid phase extraction (SPE) first, avoiding matrix effect and allowing external calibration. The limits of detection of the methods were 0.076 mg L(-1) (direct method) and 0.0042 mg L(-1) (SPE based method), which are lower than the cutoff values for confirmative conclusions regarding cocaine abuse.

  5. Molecular Profiling of Malignant Pleural Effusion in Metastatic Non-Small-Cell Lung Carcinoma. The Effect of Preanalytical Factors.

    PubMed

    Carter, Jamal; Miller, James Adam; Feller-Kopman, David; Ettinger, David; Sidransky, David; Maleki, Zahra

    2017-07-01

    Non-small-cell lung cancer (NSCLC)-associated malignant pleural effusions (MPEs) are sometimes the only available specimens for molecular analysis. This study evaluates diagnostic yield of NSCLC-associated MPE, its adequacy for molecular profiling and the potential influence of MPE volume/cellularity on the analytic sensitivity of our assays. Molecular results of 50 NSCLC-associated MPE cases during a 5-year period were evaluated. Molecular profiling was performed on cell blocks and consisted of fluorescent in situ hybridization (FISH) for ALK gene rearrangements and the following sequencing platforms: Sanger sequencing (for EGFR) and high-throughput pyrosequencing (for KRAS and BRAF) during the first 4 years of the study period, and targeted next-generation sequencing performed thereafter. A total of 50 NSCLC-associated MPE cases were identified where molecular testing was requested. Of these, 17 cases were excluded: 14 cases (28%) due to inadequate tumor cellularity and 3 cases due to unavailability of the slides to review. A total of 27 out of 50 MPE cases (54%) underwent at least EGFR and KRAS sequencing and FISH for ALK rearrangement. Of the 27 cases with molecular testing results available, a genetic abnormality was detected in 16 cases (59%). The most common genetic aberrations identified involved EGFR ( 9 ) and KRAS ( 7 ). Six cases had ALK FISH only, of which one showed rearrangement. MPE volume was not associated with overall cellularity or tumor cellularity (P = 0.360). Molecular profiling of MPE is a viable alternative to testing solid tissue in NSCLC. This study shows successful detection of genetic aberrations in 59% of samples with minimal risk of false negative.

  6. Effects of nitrogen-doped multi-walled carbon nanotubes compared to pristine multi-walled carbon nanotubes on human small airway epithelial cells

    PubMed Central

    Mihalchik, Amy L.; Ding, Weiqiang; Porter, Dale W.; McLoughlin, Colleen; Schwegler-Berry, Diane; Sisler, Jennifer D.; Stefaniak, Aleksandr B.; Snyder-Talkington, Brandi N.; Cruz-Silva, Rodolfo; Terrones, Mauricio; Tsuruoka, Shuji; Endo, Morinobu; Castranova, Vincent; Qian, Yong

    2015-01-01

    Nitrogen-doped multi-walled carbon nanotubes (ND-MWCNTs) are modified multi-walled carbon nanotubes (MWCNTs) with enhanced electrical properties that are used in a variety of applications, including fuel cells and sensors; however, the mode of toxic action of ND-MWCNT has yet to be fully elucidated. In the present study, we compared the interaction of ND-MWCNT or pristine MWCNT-7 with human small airway epithelial cells (SAEC) and evaluated their subsequent bioactive effects. Transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction suggested the presence of N-containing defects in the lattice of the nanotube. The ND-MWCNTs were determined to be 93.3% carbon, 3.8% oxygen, and 2.9% nitrogen. A dose–response cell proliferation assay showed that low doses of ND-MWCNT (1.2 mg/ml) or MWCNT-7 (0.1 mg/ml) increased cellular proliferation, while the highest dose of 120 mg/ml of either material decreased proliferation. ND-MWCNT and MWCNT-7 appeared to interact with SAEC at 6 h and were internalized by 24 h. ROS were elevated at 6 and 24 h in ND-MWCNT exposed cells, but only at 6 h in MWCNT-7 exposed cells. Significant alterations to the cell cycle were observed in SAEC exposed to either 1.2 mg/ml of ND-MWCNT or MWCNT-7 in a time and material-dependent manner, possibly suggesting potential damage or alterations to cell cycle machinery. Our results indicate that ND-MWCNT induce effects in SAEC over a time and dose-related manner which differ from MWCNT-7. Therefore, the physicochemical characteristics of the materials appear to alter their biological effects. PMID:25797581

  7. Effects of nitrogen-doped multi-walled carbon nanotubes compared to pristine multi-walled carbon nanotubes on human small airway epithelial cells.

    PubMed

    Mihalchik, Amy L; Ding, Weiqiang; Porter, Dale W; McLoughlin, Colleen; Schwegler-Berry, Diane; Sisler, Jennifer D; Stefaniak, Aleksandr B; Snyder-Talkington, Brandi N; Cruz-Silva, Rodolfo; Terrones, Mauricio; Tsuruoka, Shuji; Endo, Morinobu; Castranova, Vincent; Qian, Yong

    2015-07-03

    Nitrogen-doped multi-walled carbon nanotubes (ND-MWCNTs) are modified multi-walled carbon nanotubes (MWCNTs) with enhanced electrical properties that are used in a variety of applications, including fuel cells and sensors; however, the mode of toxic action of ND-MWCNT has yet to be fully elucidated. In the present study, we compared the interaction of ND-MWCNT or pristine MWCNT-7 with human small airway epithelial cells (SAEC) and evaluated their subsequent bioactive effects. Transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction suggested the presence of N-containing defects in the lattice of the nanotube. The ND-MWCNTs were determined to be 93.3% carbon, 3.8% oxygen, and 2.9% nitrogen. A dose-response cell proliferation assay showed that low doses of ND-MWCNT (1.2μg/ml) or MWCNT-7 (0.12μg/ml) increased cellular proliferation, while the highest dose of 120μg/ml of either material decreased proliferation. ND-MWCNT and MWCNT-7 appeared to interact with SAEC at 6h and were internalized by 24h. ROS were elevated at 6 and 24h in ND-MWCNT exposed cells, but only at 6h in MWCNT-7 exposed cells. Significant alterations to the cell cycle were observed in SAEC exposed to either 1.2μg/ml of ND-MWCNT or MWCNT-7 in a time and material-dependent manner, possibly suggesting potential damage or alterations to cell cycle machinery. Our results indicate that ND-MWCNT induce effects in SAEC over a time and dose-related manner which differ from MWCNT-7. Therefore, the physicochemical characteristics of the materials appear to alter their biological effects.

  8. Targeting the molecular chaperone SlyD to inhibit bacterial growth with a small molecule

    PubMed Central

    Kumar, Amit; Balbach, Jochen

    2017-01-01

    Molecular chaperones are essential molecules for cell growth, whereby they maintain protein homeostasis. Because of their central cellular function, bacterial chaperones might be potential candidates for drug targets. Antimicrobial resistance is currently one of the greatest threats to human health, with gram-negative bacteria being of major concern. We found that a Cu2+ complex readily crosses the bacterial cell wall and inhibits SlyD, which is a molecular chaperone, cis/trans peptidyl prolyl isomerise (PPIase) and involved in various other metabolic pathways. The Cu2+ complex binds to the active sites of SlyD, which suppresses its PPIase and chaperone activities. Significant cell growth retardation could be observed for pathogenic bacteria (e.g., Staphylococcus aureus and Pseudomonas aeruginosa). We anticipate that rational development of drugs targeting molecular chaperones might help in future control of pathogenic bacterial growth, in an era of rapidly increasing antibiotic resistance. PMID:28176839

  9. Infrared absorption spectra of molecular crystals: Possible evidence for small-polaron formation?

    NASA Astrophysics Data System (ADS)

    Pržulj, Željko; Čevizović, Dalibor; Zeković, Slobodan; Ivić, Zoran

    2008-09-01

    The temperature dependence of the position of the so-called anomalous band peaked at 1650cm in the IR-absorption spectrum of crystalline acetanilide (ACN) is theoretically investigated within the small-polaron theory. Its pronounced shift towards the position of the normal band is predicted with the rise of temperature. Interpretation of the IR-absorption spectra in terms of small-polaron model has been critically assessed on the basis of these results.

  10. LETTER TO THE EDITOR: Small molecular white organic light emitting devices with a single emission layer

    NASA Astrophysics Data System (ADS)

    Duan, Yu; Zhao, Yi; Cheng, Gang; Jiang, Wenlong; Li, Jiang; Wu, Zhijun; Hou, Jingying; Liu, Shiyong

    2004-03-01

    An organic white light emitting device has been demonstrated by mixing two colours from a single emissive layer. The device structure included indium tin oxide glass substrate/40 nm N,N-diphenyl-N,N-bis1-naphthyl-1, 1-biphenyl-4,4-diamine as hole transparent layer/20 nm 4,48-bis(2,28-diphenylvinyl)-1,18-biphenyl doped with 0.8% rubrene as emitting layer/30 nm tris-8-hydroxyquinoline aluminium as electron transport layer/0.6 nm LiF/aluminium. A stable white emission Commission Internationale de 1'Eclairage chromaticity coordinate range from (0.34, 0.36) to (0.32, 0.32) for forward bias voltage changes from 5 to 13 V has been achieved. Its maximum luminance was 15840 cd m-2 at 17 V, and the maximum power and current efficiencies were 3.1 lw W-1 and 5.8 cd A-1 at 6 V, respectively.

  11. Small Molecular White Organic Light Emitting Devices with Single Emission Zone

    NASA Astrophysics Data System (ADS)

    Duan, Yu; Jiang, Wenlong; Li, Jiang; Chen, Gang; Zhao, Yi; Hou, Jingying; Liu, Shiyong

    2004-11-01

    An organic white-light-emitting device has been demonstrated by mixing two colors from a single emissive layer. The device structure included indium tin oxide glass (ITO) substrate/30 nm 4,4',4''-tris{N,-(3-methylphenyl)-N-phenylamino}triphenylamine (m-MTDATA) as hole injection layer/10 nm N,N-diphenyl-N,N-bis1-naphthy l-1,1-biphenyl-4,4-diamine (NPB) as hole transparent layer/30 nm bis [2-(2-hydroxyphenyl)-pyridine]beryllium (Bepp2) doped with 0.2% rubrene as emitting layer/40 nm tris-8-hydroxyquinoline aluminum (Alq3) as electron transport layer/0.8 nm LiF/aluminum (Al). A stable white emission Commission Internationale de 1’Eclairage (CIE) chromaticity coordinate range from (0.38, 0.36) to (0.31, 0.31) for forward bias voltage which changing from 6 to 17 V has been achieved. Its maximum luminance was 29000 cd/m2 at 15v, and the maximum power and current efficiencies were 3.0 lm/W at 5 V and 6.3 cd/A at 7 V, respectively.

  12. Design rules for rational control of polymer glass formation behavior and mechanical properties with small molecular additives

    NASA Astrophysics Data System (ADS)

    Mangalara, Jayachandra Hari; Simmons, David

    Small molecule additives have long been employed to tune polymers' glass formation, mechanical and transport properties. For example, plasticizers are commonly employed to suppress polymer Tg and soften the glassy state, while antiplasticizers, which stiffen the glassy state of a polymer while suppressing its Tg, are employed to enhance protein and tissue preservation in sugar glasses. Recent literature indicates that additives can have a wide range of possible effects, but all of these have not been clearly understood and well appreciated. Here we employ molecular dynamics simulations to establish design rules for the selection of small molecule additives with size, molecular stiffness, and interaction energy chosen to achieve targeted effects on polymer properties. We furthermore find that a given additive's effect on a polymer's Tg can be predicted from its Debye-Waller factor via a function previously found to describe nanoconfinement effects on the glass transition. These results emphasize the potential for a new generation of targeted molecular additives to contribute to more targeted rational design of polymers. We acknowledge the Keck Foundation and the Ohio Supercomputing Center for financial and computational support of this effort, respectively.

  13. Treatment algorithm in 2014 for advanced non-small cell lung cancer: therapy selection by tumour histology and molecular biology.

    PubMed

    Manegold, Christian

    2014-09-01

    The availability of antineoplastic monoclonal antibodies, small molecules and newer cytotoxics such as pemetrexed, the EGFR-tyrosine kinase inhibitors erlotinib, gefitinib, afatinib as well as the anti-angiogenic bevacizumab and the ALK-inhibitor crizotinib has recently changes the treatment algorithm of advanced non-small cell lung cancer. Decision making in 2014 is characterized by customizing therapy, by selecting a specific therapeutic regimen based on the histotype and the genotype of the tumour. This refers to first-line induction therapy and maintenance therapy as well, but also to subsequent lines of therapy since anti-neoplastic drugs and regimens used upfront clinically influence the selection of agents/regimes considered for second-/third-line treatment. Consequently, therapy customization through tumour histology and molecular markers has significantly influenced the work of pathologists around the globe and the process of obtaining an extended therapeutically relevant tumour diagnosis. Not only histological sub-typing became standard but molecular information is also considered of increasing importance for treatment selection. Routine molecular testing in certified laboratories must be established, and the diagnostic process should ideally be performed under the guidance of evidence based recommendation. The process of investigating and implementing medical targeting in lung cancer therefore, requires advanced diagnostic techniques and expertise and because of its large dimension is costly and influenced by the limitation of financial and clinical resources. Copyright © 2014. Published by Elsevier Urban & Partner Sp. z o.o.

  14. The small contribution of molecular Bremsstrahlung radiation to the air-fluorescence yield of cosmic ray shower particles

    NASA Astrophysics Data System (ADS)

    Al Samarai, Imen; Deligny, Olivier; Rosado, Jaime

    2016-10-01

    A small contribution of molecular Bremsstrahlung radiation to the air-fluorescence yield in the UV range is estimated based on an approach previously developed in the framework of the radio-detection of showers in the gigahertz frequency range. First, this approach is shown to provide an estimate of the main contribution of the fluorescence yield due to the de-excitation of the C 3Πu electronic level of nitrogen molecules to the B 3Πg one amounting to Y[ 337 ] =(6.05 ± 1.50) MeV-1 at 800 hPa pressure and 293 K temperature conditions, which compares well to previous dedicated works and to experimental results. Then, under the same pressure and temperature conditions, the fluorescence yield induced by molecular Bremsstrahlung radiation is found to be Y[330-400]MBR = 0.10 MeV-1 in the wavelength range of interest for the air-fluorescence detectors used to detect extensive air showers induced in the atmosphere by ultra-high energy cosmic rays. This means that out of ≃175 photons with wavelength between 330 and 400 nm detected by fluorescence detectors, one of them has been produced by molecular Bremsstrahlung radiation. Although small, this contribution is not negligible in regards to the total budget of systematic uncertainties when considering the absolute energy scale of fluorescence detectors.

  15. Direct prediction of residual dipolar couplings of small molecules in a stretched gel by stochastic molecular dynamics simulations.

    PubMed

    Frank, Andreas O; Freudenberger, J Christoph; Shaytan, Alexey K; Kessler, Horst; Luy, Burkhard

    2015-03-01

    Residual dipolar couplings are highly useful NMR parameters for calculating and refining molecular structures, dynamics, and interactions. For some applications, however, it is inevitable that the preferred orientation of a molecule in an alignment medium is calculated a priori. Several methods have been developed to predict molecular orientations and residual dipolar couplings. Being beneficial for macromolecules and selected small-molecule applications, such approaches lack sufficient accuracy for a large number of organic compounds for which the fine structure and eventually the flexibility of all involved molecules have to be considered or are limited to specific, well-studied liquid crystals. We introduce a simplified model for detailed all-atom molecular dynamics calculations with a polymer strand lined up along the principal axis as a new approach to simulate the preferred orientation of small to medium-sized solutes in polymer-based, gel-type alignment media. As is shown by a first example of strychnine in a polystyrene/CDCl3 gel, the simulations potentially enable the accurate prediction of residual dipolar couplings taking into account structural details and dynamic averaging effects of both the polymer and the solute.

  16. High-throughput screening identifies small molecule inhibitors of molecular chaperones.

    PubMed

    Kondoh, Yasumitsu; Osada, Hiroyuki

    2013-01-01

    Heat shock proteins (HSPs) are involved in a number of cellular processes, including cell cycle, growth, and survival, apoptosis, stress responses, angiogenesis, and oncogenesis. Among the characterized HSPs, the molecular chaperone HSP90 has emerged as an exciting molecular target for cancer therapy since its discovery as the target protein of the antibiotic geldanamycin. The stress-inducible HSP70, which is upregulated in many cancers, contributing to tumor cell survival and resistance to therapy, has important roles as a housekeeper in the cell, assisting in the correct folding, trafficking, and degradation of many proteins. 2-Phenylethynesulfonamide (PES) physically interacts with HSP70 and disrupts the association between HSP70 and several of its cofactors and client proteins, leading to cancer cell death that is selectively mediated through caspase-independent mechanisms involving increased protein aggregation, impairment of lysosomal functions, and inhibition of autophagy. Mammalian HSP60 has several functions in the cell, including apoptosis, an immune-regulatory function, and cell spreading. HSP60 is a mitochondrial protein that is essential for the folding and assembly of newly imported proteins in the mitochondria. Epolactaene/ETB covalently binds to HSP60, inhibiting its chaperone activity. Molecular chaperone inhibitors are significantly valuable not only as tools to reveal the unknown cellular functions of molecular chaperones, but also as lead compounds for drug discovery. Thus, high-throughput screening systems are necessary for the discovery of more effective inhibitors. Here, we describe the methodology for 4 characteristic types of high-throughput screening systems for inhibitors of molecular chaperones, mainly HSP90 and HSP70: the colorimetric method, the fluorescence polarization method, the chemical array method, and the AlphaScreen® method.

  17. Generation of 6.8 W of CW output power at 1550 nm using small mode field diameter Er:Yb co-doped double clad fiber in laser oscillator configuration

    NASA Astrophysics Data System (ADS)

    Gurram, Srikanth; Kuruvilla, A.; Singh, Rajpal; Bindra, K. S.

    2017-06-01

    We report studies on erbium:ytterbium doped fiber laser, that uses a commercially available off-the-shelf Er:Yb co-doped single mode fiber with small mode field diameter of 7 µm, which is compatible with single mode fibers used in most of the communication systems. In a FBG based laser oscillator configuration pumped at 976 nm, the single transverse mode fiber laser emitted more than 6.87 Watts of output power at 1550 nm with a conversion efficiency of ~32% over a narrow line width. The pump radiation is coupled into active fiber using free-space optics. To the best of our knowledge, this is the highest power reported in the 1.55 µm region by using commercially available off-the-shelf active fiber of small mode field diameter (~7 µm) in a simple laser oscillator configuration with 9×× nm pumping. We also observed the effect of weak secondary grating structure in FBGs on the spectral characteristics of EYDFLs and explained its significance for co-doped fiber lasers such as erbium-ytterbium fiber lasers.

  18. Electric field poled polymeric nonlinear optical systems: molecular dynamics simulations of poly(methyl methacrylate) doped with disperse red chromophores.

    PubMed

    Tu, Yaoquan; Zhang, Qiong; Agren, Hans

    2007-04-12

    We demonstrate a complete procedure for simulations of electric field poled polymeric nonlinear optical systems with the purpose to evaluate the macroscopic electro-optic coefficients. The simulations cover the electric field poling effects on the chromophore order at the liquid state, the cooling procedure from the liquid to the solid state in the presence of the poling field, and the back-relaxation of the system after the removal of the field. We use Disperse Red chromophore molecules doped in a poly(methyl methacrylate) matrix for a numerical demonstration of the total procedure. On the basis of the simulation results, the polymer mobility and the static properties of the dopant chromophores are derived. In the liquid state, the chromophore molecules are closer to the side chains than to the backbones of the polymer matrix, and after the simulated annealing, the polymer matrix tends to be closely packed, leading to a significant change in the polymer structure around the chromophore molecules. Besides predicting the absolute macroscopic electro-optic coefficient values, the results are used to derive the microscopic origin of these values in terms of geometric and electronic structure, loading, poling, and back-relaxation effects, thereby aiding to establish design principles for optimum guest-host configurations.

  19. A Biphasic Pleural Tumor with Features of an Epithelioid and Small Cell Mesothelioma: Morphologic and Molecular Findings

    PubMed Central

    2016-01-01

    Malignant mesotheliomas are generally classified into epithelioid, sarcomatoid, desmoplastic, and biphasic types with rare reports of a small cell form. These small cell variants display some morphologic overlap with desmoplastic small round cell tumors (DSRCTs) which generally occur within the abdominal cavity of young males and are defined by a characteristic t(11;22)(p13;q12) translocation. However, there are rare reports of DSRCTs lacking this translocation. We present a 78-year-old man with a pleura-based biphasic neoplasm with features of both epithelioid mesothelioma and a small cell blastema-like neoplasm. The epithelioid portion showed IHC reactivity for pan cytokeratin, CK5/6, D2-40, and calretinin and the small cell portion marked with CD99, pan cytokeratin, WT1, FLI1, S100, CD200, MyoD1, and CD15. Fluorescence in situ hybridization testing for the t(11;22)(p13;q12) translocation disclosed loss of the EWSR1 gene in 94% of tumor cell nuclei, but there was no evidence of the classic translocation. Array based-comparative genomic hybridization (a-CGH) confirmed the tumor had numerous chromosome copy number losses, including 11p15.5-p11.12 and 22q12.1-q13.33, with loss of the EWSR1 and WT1 gene regions. Herein, we report novel complex CGH findings in a biphasic tumor and review the molecular genetic alterations in both mesothelioma and DSRCTs. PMID:27403364

  20. Molecular entrapment of small molecules within the interior of horse spleen ferritin.

    PubMed

    Webb, B; Frame, J; Zhao, Z; Lee, M L; Watt, G D

    1994-02-15

    A procedure for trapping small molecules inside the interior of horse spleen ferritin (HoSF) and methods for characterizing HoSF and its small entrapped molecules are described. HoSF is first dissociated into subunits by adjustment to pH 2 in the presence of the small molecules to be trapped. The pH of the dissociated HoSF is then increased to 7 at which time the dissociated subunits reassemble reforming the 24-mer HoSF, thereby trapping solvent within its interior. HoSF is then separated from unbound molecules by dialysis, ultrafiltration, and/or ammonium sulfate precipitation. Sephadex G-25 and DEAE chromatographic methods were also used to separate HoSF from unbound small molecules. Capillary electrophoresis (CE) was used to demonstrate the association of small molecules with HoSF after the pH-induced unfolding-refolding process. The pH indicator neutral red was clearly associated with HoSF and presumed trapped within the ferritin interior. Acid/base titrations suggested that the trapped indicator had a different pKa than the free indicator, a result which indicates that the ferritin interior is different than the external solution. The utility of using trapped molecules for gaining information on ferritin function is proposed and discussed.

  1. Molecular profiling in Italian patients with advanced non-small-cell lung cancer: An observational prospective study.

    PubMed

    Gobbini, Elisa; Galetta, Domenico; Tiseo, Marcello; Graziano, Paolo; Rossi, Antonio; Bria, Emilio; Di Maio, Massimo; Rossi, Giulio; Gregorc, Vanesa; Riccardi, Ferdinando; Scotti, Vieri; Ceribelli, Anna; Buffoni, Lucio; Delmonte, Angelo; Franchina, Tindara; Migliorino, Maria Rita; Cortinovis, Diego; Pisconti, Salvatore; Bordi, Paola; Catino, Annamaria; Maiello, Evaristo; Arizio, Francesca; Novello, Silvia

    2017-09-01

    Molecular profiling of advanced non-small-cell lung cancer (NSCLC) is recommended according to European and Italian guidelines. However, molecular routine assessment remains still heterogeneous. This observational study aimed to take a picture of the real clinical practice in molecular testing and therapeutic choices in advanced Italian NSCLCs. This study prospectively enrolled newly diagnosed advanced or recurrent NSCLCs referred to 38 Italian centres, from November 2014 to November 2015. Information regarding molecular profiling and treatment choices were collected. Description of patients' outcome included overall survival (OS), progression-free survival in first (PFS1) and second-line (PFS2). Among 1787 patients enrolled, 1388 (78%) performed at least one molecular analysis during the history of disease: 76% were tested for EGFR, 53% for ALK, 27% for KRAS, 16% for ROS1, 14% for BRAF, 5% for HER2, 4% for MET and 1% for FGFR. The remaining 399 patients (22.3%) did not receive any molecular test. Among patients receiving at least one molecular analysis, 583 (42%) presented a molecular alteration. Considering EGFR mutated and/or ALK rearranged patients (402), for which target agents were routinely reimbursed at time of study in Italy, the 86% received a personalized treatment as first and/or second line: the 90% (286) of EGFR mutants received an EGFR tyrosine kinase inhibitor, mostly gefitinib (41.1%) or afatinib (36.4%) while 74% (62) of ALK translocated patients received an ALK inhibitor, mostly crizotinib (64%). Median OS was 9.34 months (95% CI 8.62-10.0), median PFS1 was 4.61 months (95%CI 4.31-4.84) and median PFS2 was 2.76 months (95%CI 2.57-3.19). In the Italian clinical practice, routine molecular assessment was largely applied in NSCLC patients, according to national guidelines, but a low level of ALK test was reached. Most of EGFR mutants an ALK rearranged patients received a personalized treatment as first and/or second line. Copyright © 2017 Elsevier

  2. Spatial variability of organic matter molecular composition and elemental geochemistry in surface sediments of a small boreal Swedish lake

    NASA Astrophysics Data System (ADS)

    Tolu, Julie; Rydberg, Johan; Meyer-Jacob, Carsten; Gerber, Lorenz; Bindler, Richard

    2017-04-01

    The composition of sediment organic matter (OM) exerts a strong control on biogeochemical processes in lakes, such as those involved in the fate of carbon, nutrients and trace metals. While between-lake spatial variability of OM quality is increasingly investigated, we explored in this study how the molecular composition of sediment OM varies spatially within a single lake and related this variability to physical parameters and elemental geochemistry. Surface sediment samples (0-10 cm) from 42 locations in Härsvatten - a small boreal forest lake with a complex basin morphometry - were analyzed for OM molecular composition using pyrolysis gas chromatography mass spectrometry for the contents of 23 major and trace elements and biogenic silica. We identified 162 organic compounds belonging to different biochemical classes of OM (e.g., carbohydrates, lignin and lipids). Close relationships were found between the spatial patterns of sediment OM molecular composition and elemental geochemistry. Differences in the source types of OM (i.e., terrestrial, aquatic plant and algal) were linked to the individual basin morphometries and chemical status of the lake. The variability in OM molecular composition was further driven by the degradation status of these different source pools, which appeared to be related to sedimentary physicochemical parameters (e.g., redox conditions) and to the molecular structure of the organic compounds. Given the high spatial variation in OM molecular composition within Härsvatten and its close relationship with elemental geochemistry, the potential for large spatial variability across lakes should be considered when studying biogeochemical processes involved in the cycling of carbon, nutrients and trace elements or when assessing lake budgets.

  3. Syntheses of D-A-A Type Small Molecular Donor Materials Having Various Electron Accepting Moiety for Organic Photovoltaic Application.

    PubMed

    Kim, Nahyeon; Park, Sangman; Lee, Myong-Hoon; Lee, Jaemin; Lee, Changjin; Yoon, Sung Cheol

    2016-03-01

    Small molecular donor, DTDCTB achieved a high power conversion efficiency (PCE) value of 6.6 ± 0.2% in vacuum-deposited planar mixed heterojunction (PMHJ) structure. However, the same material just recorded PCE of 0.34% in solution processed small molecule based bulk heterjunction (BHJ) organic photovoltaic cells. For the improvement of organic photovoltaic cells (OPVs), In this study, we designed and synthesized several D-A-A (donor-acceptor-acceptor) type molecular electron donating materials. Ditolylaminothienyl moiety as an electron donating group connected to 1,2,5-benzothiadiazole as a conjugated electron accepting unit, simultaneously with an electron accepting terminal group such as cyano alkyl acetate and N-alkyl rhodanine. The thermal, photophysical, and electrochemical properties of prepared small molecules were investigated by DSC, UV/Vis spectroscopy and Cyclic Voltametry, respectively. As a result, 0.89% of PCE can be obtained from OPV using a mixture of DTATBTER and PCBM as an active layer with a Voc of 0.87 V, a Jsc of 3.20 mA/cm2, and a fill factor of 31.9%.

  4. Purification, concentration and recovery of small fragments of DNA from Giardia lamblia and their use for other molecular techniques.

    PubMed

    Santos, Fabiola; Gómez-Manzo, Saúl; Sierra-Palacios, Edgar; González-Valdez, Abigail; Castillo-Villanueva, Adriana; Reyes-Vivas, Horacio; Marcial-Quino, Jaime

    2017-01-01

    Purification of nucleic acids is an essential procedure for most experiments in molecular biology. In this paper, the freeze-squeeze method with some modifications is proposed as an alternative methodology for the purification, concentration and recovery of small DNA fragments from agarose gels. The advantage of this alternative methodology is that it enables the recovery of fragments that are less than 100 bp in length and enables suspension of products in smaller volumes compared to several commercially available kits. In addition, the purified fragments were re-amplified by PCR and used for cloning and sequencing. Moreover, this protocol was used to perform the isolation and identification of microRNAs from Giardia lamblia, as previously reported. This protocol has the advantage of being inexpensive and easy and can be employed for various molecular applications. The advantages of this protocol include •A modified classical method was used for purification of small DNA fragments from G. lamblia.•The modified freeze-squeeze method was more efficient in cleaning up small DNA fragments from agarose gels compared to commercial kits.•The modified method allows concentration and recovery of fragments up to 60 bp in length.•The modified freeze-squeeze method allows re-suspension of the products in volumes of up to 2.5 μL.

  5. Molecular genetics of pediatric brain stem gliomas. Application of PCR techniques to small and archival brain tumor specimens

    SciTech Connect

    Louis, D.N.; Rubio, M.P.; Correa, K.M.; Gusella, J.F.; Deimling, A. von )

    1993-09-01

    Brain stem gliomas are pediatric astrocytomas that histologically resemble adult supratentorial astrocytomas such as gliobastomas multiforme (GBM). The molecular genetic studies have suggested that adult GBM can be divided into two genetic subsets: Tumors with p53 tumor suppressor gene mutations and chromosome 17p loss that occur more commonly in younger patients; and tumors with epidermal growth factor receptor (EGFR) gene amplification that occur more commonly in older patients. Brain stem gliomas have not been studied since biopsies of these tumors are rare and extremely small. The authors investigated the molecular genetic composition of seven brain stem glioblastomas (two small biopsies, five autopsies) using polymerase chain reaction (PCR) assays for chromosomal loss, gene mutation and gene amplification. Four cases lost portions of chromosome 17p that included the 53p gene. These four cases and one additional case had mutations in the p53 gene. None of the cases showed amplification of the EGFR gene. Allelic losses of the long arm of chromosome 10 were noted in four cases. These results suggest similarities between pediatric brain stem glioblastomas and those GBM that occur in younger adult patients, and confirm the utility of PCR-based means of studying small and archival brain tumor specimens. 47 refs., 7 figs., 2 tabs.

  6. Atomic Spectral Methods for Ab Initio Molecular Electronic Energy Surfaces: Transitioning From Small-Molecule to Biomolecular-Suitable Approaches.

    PubMed

    Mills, Jeffrey D; Ben-Nun, Michal; Rollin, Kyle; Bromley, Michael W J; Li, Jiabo; Hinde, Robert J; Winstead, Carl L; Sheehy, Jeffrey A; Boatz, Jerry A; Langhoff, Peter W

    2016-08-25

    Continuing attention has addressed incorportation of the electronically dynamical attributes of biomolecules in the largely static first-generation molecular-mechanical force fields commonly employed in molecular-dynamics simulations. We describe here a universal quantum-mechanical approach to calculations of the electronic energy surfaces of both small molecules and large aggregates on a common basis which can include such electronic attributes, and which also seems well-suited to adaptation in ab initio molecular-dynamics applications. In contrast to the more familiar orbital-product-based methodologies employed in traditional small-molecule computational quantum chemistry, the present approach is based on an "ex-post-facto" method in which Hamiltonian matrices are evaluated prior to wave function antisymmetrization, implemented here in the support of a Hilbert space of orthonormal products of many-electron atomic spectral eigenstates familiar from the van der Waals theory of long-range interactions. The general theory in its various forms incorporates the early semiempirical atoms- and diatomics-in-molecules approaches of Moffitt, Ellison, Tully, Kuntz, and others in a comprehensive mathematical setting, and generalizes the developments of Eisenschitz, London, Claverie, and others addressing electron permutation symmetry adaptation issues, completing these early attempts to treat van der Waals and chemical forces on a common basis. Exact expressions are obtained for molecular Hamiltonian matrices and for associated energy eigenvalues as sums of separate atomic and interaction-energy terms, similar in this respect to the forms of classical force fields. The latter representation is seen to also provide a long-missing general definition of the energies of individual atoms and of their interactions within molecules and matter free from subjective additional constraints. A computer code suite is described for calculations of the many-electron atomic eigenspectra and

  7. Inhibitory monoclonal antibody against a (myristylated) small-molecular-weight antigen from Plasmodium falciparum associated with the parasitophorous vacuole membrane.

    PubMed

    Kara, U A; Stenzel, D J; Ingram, L T; Bushell, G R; Lopez, J A; Kidson, C

    1988-04-01

    A small-molecular-weight antigen that occurs in asexual blood stages in synchronized cultures of Plasmodium falciparum was detected by a monoclonal antibody which inhibits parasite growth in vitro. This antigen, QF116, showed a molecular weight of 15,000 in parasite strain FCR-3K+ from The Gambia and 19,000 in strain FCQ-27 from Papua New Guinea. The protein did not show significant glycosylation by galactose or glucosamine labeling but was found to be acylated by myristic acid. By using immunogold labeling and electron microscopy, the location of the antigen could be attributed to the parasitophorous vacuole membrane and to inclusions and vesicles residing within the cytoplasm of the erythrocyte host cell.

  8. Molecular docking studies of Traditional Chinese Medicinal compounds against known protein targets to treat non-small cell lung carcinomas

    PubMed Central

    Zhao, Guo-Fang; Huang, Zuo-An; Du, Xue-Kui; Yang, Ming-Lei; Huang, Dan-Dan; Zhang, Shun

    2016-01-01

    In silico drug design using virtual screening, absorption, distribution, metabolism and excretion (ADME)/Tox data analysis, automated docking and molecular dynamics simulations for the determination of lead compounds for further in vitro analysis is a cost effective strategy. The present study used this strategy to discover novel lead compounds from an in-house database of Traditional Chinese Medicinal (TCM) compounds against epithelial growth factor receptor (EGFR) protein for targeting non-small cell lung cancer (NSCLC). After virtual screening of an initial dataset of 2,242 TCM compounds, leads were identified based on binding energy and ADME/Tox data and subjected to automated docking followed by molecular dynamics simulation. Triptolide, a top compound identified by this vigorous in silico screening, was then tested in vitro on the H2347 cell line carrying wild-type EGFR, revealing an anti-proliferative potency similar to that of known drugs against NSCLC. PMID:27279494

  9. Molecular analysis of lungworms from European bison (Bison bonasus) on the basis of small subunit ribosomal RNA gene (SSU).

    PubMed

    Pyziel, Anna M

    2014-03-01

    Dictyocaulosis (Nematoda: Trichostrongyloidea) is a widespread parasitosis of the European bison (Bison bonasus) inhabiting Bialowieza Primeval Forest. Bearing in mind the current coexistence of bison with wild cervids, and with domestic ruminants in the 19th and 20th century, the need arose for molecular identification of lungworm species. Molecular analysis was done on adult lungworms that were obtained from the respiratory track of four free-roaming bison euthanized as a part of the population health control program. As the result of the study four identical small subunit-ribosomal RNA gene sequences from the lungworms were obtained and deposited in GenBank as sequence, 1708 bp long (GenBank KC771250). Comparative analysis of the SSU rRNA sequences revealed the European bison to be a host for the bovine lungworm Dictyocaulus viviparus.

  10. A highly efficient molecular cloning platform that utilises a small bacterial toxin gene.

    PubMed

    Mok, Wendy W K; Li, Yingfu

    2013-04-15

    Molecular cloning technologies that have emerged in recent years are more efficient and simpler to use than traditional strategies, but many have the disadvantages of requiring multiple steps and expensive proprietary enzymes. We have engineered cloning vectors containing variants of IbsC, a 19-residue toxin from Escherichia coli K-12. These toxic peptides offer selectivity to minimise the background, labour, and cost associated with conventional molecular cloning. As demonstrated with the cloning of reporter genes, this "detox cloning" system consistently produced over 95 % positive clones. Purification steps between digestion and ligation are not necessary, and the total time between digestion and plating of transformants can be as little as three hours. Thus, these IbsC-based cloning vectors are as reliable and amenable to high-throughput cloning as commercially available systems, and have the advantage of being more time-efficient and cost-effective.

  11. Systematic Identification of Molecular Subtype-Selective Vulnerabilities in Non Small Cell Lung Cancer

    PubMed Central

    Kim, Hyun Seok; Mendiratta, Saurabh; Kim, Jiyeon; Pecot, Chad Victor; Larsen, Jill E.; Zubovych, Iryna; Seo, Bo Yeun; Kim, Jimi; Eskiocak, Banu; Chung, Hannah; McMillan, Elizabeth; Wu, Sherry; De Brabander, Jef; Komurov, Kakajan; Toombs, Jason E.; Wei, Shuguang; Peyton, Michael; Williams, Noelle; Gazdar, Adi F.; Posner, Bruce A.; Brekken, Rolf; Sood, Anil K.; Deberardinis, Ralph J.; Roth, Michael G.; Minna, John D.; White, Michael A.

    2013-01-01

    SUMMARY Context-specific molecular vulnerabilities that arise during tumor evolution represent an attractive intervention target class. However, the frequency and diversity of somatic lesions detected among lung tumors can confound efforts to identify these targets. To confront this challenge, we have applied parallel screening of chemical and genetic perturbations within a panel of molecularly annotated NSCLC lines to identify intervention opportunities tightly linked to molecular response indicators predictive of target sensitivity. Anchoring this analysis on a matched tumor/normal cell model from a lung adenocarcinoma patient identified three distinct target/response-indicator pairings that are represented with significant frequencies (6–16%) in the patient population. These include NLRP3 mutation/inflammasome activation-dependent FLIP addiction, co-occuring KRAS and LKB1 mutation-driven COPI addiction, and selective sensitivity to a synthetic indolotriazine that is specified by a 7-gene expression signature. Target efficacies were validated in vivo, and mechanism of action studies uncovered new cancer cell biology. PMID:24243015

  12. Molecular-sized fluorescent nanodiamonds

    NASA Astrophysics Data System (ADS)

    Vlasov, Igor I.; Shiryaev, Andrey A.; Rendler, Torsten; Steinert, Steffen; Lee, Sang-Yun; Antonov, Denis; Vörös, Márton; Jelezko, Fedor; Fisenko, Anatolii V.; Semjonova, Lubov F.; Biskupek, Johannes; Kaiser, Ute; Lebedev, Oleg I.; Sildos, Ilmo; Hemmer, Philip. R.; Konov, Vitaly I.; Gali, Adam; Wrachtrup, Jörg

    2014-01-01

    Doping of carbon nanoparticles with impurity atoms is central to their application. However, doping has proven elusive for very small carbon nanoparticles because of their limited availability and a lack of fundamental understanding of impurity stability in such nanostructures. Here, we show that isolated diamond nanoparticles as small as 1.6 nm, comprising only ~400 carbon atoms, are capable of housing stable photoluminescent colour centres, namely the silicon vacancy (SiV). Surprisingly, fluorescence from SiVs is stable over time, and few or only single colour centres are found per nanocrystal. We also observe size-dependent SiV emission supported by quantum-chemical simulation of SiV energy levels in small nanodiamonds. Our work opens the way to investigating the physics and chemistry of molecular-sized cubic carbon clusters and promises the application of ultrasmall non-perturbative fluorescent nanoparticles as markers in microscopy and sensing.

  13. Molecular characterization and pathogenicity of fungal isolates for use against the small hive beetle (Aethina tumida)

    USDA-ARS?s Scientific Manuscript database

    The analysis of DNA sequences from fungal pathogens obtained from cadavers of the small hive beetle (SHB) collected from several apiaries in Florida revealed a mixture of saprobes and two potential primary entomopathogens, Metarhizium anisopliae and Beauveria bassiana. Spray tower bioassays indicate...

  14. CT-guided transthoracic core needle biopsy for small pulmonary lesions: diagnostic performance and adequacy for molecular testing

    PubMed Central

    Tian, Panwen; Wang, Ye; Li, Lei; Zhou, Yongzhao; Luo, Wenxin

    2017-01-01

    Background Computed tomography (CT)-guided transthoracic needle biopsy is a well-established, minimally invasive diagnostic tool for pulmonary lesions. Few large studies have been conducted on the diagnostic performance and adequacy for molecular testing of transthoracic core needle biopsy (TCNB) for small pulmonary lesions. Methods This study included CT-guided TCNB with 18-gauge cutting needles in 560 consecutive patients with small (≤3 cm) pulmonary lesions from January 2012 to January 2015. There were 323 males and 237 females, aged 51.8±12.7 years. The size of the pulmonary lesions was 1.8±0.6 cm. The sensitivity, specificity, accuracy and complications of the biopsies were investigated. The risk factors of diagnostic failure were assessed using univariate and multivariate analyses. The sample’s adequacy for molecular testing of non-small cell lung cancer (NSCLC) was analyzed. Results The overall sensitivity, specificity, and accuracy for diagnosis of malignancy were 92.0% (311/338), 98.6% (219/222), and 94.6% (530/560), respectively. The incidence of bleeding complications was 22.9% (128/560), and the incidence of pneumothorax was 10.4% (58/560). Logistic multivariate regression analysis showed that the independent risk factors for diagnostic failure were a lesion size ≤1 cm [odds ratio (OR), 3.95; P=0.007], lower lobe lesions (OR, 2.83; P=0.001), and pneumothorax (OR, 1.98; P=0.004). Genetic analysis was successfully performed on 95.45% (168/176) of specimens diagnosed as NSCLC. At least 96.8% of samples with two or more passes from a lesion were sufficient for molecular testing. Conclusions The diagnostic yield of small pulmonary lesions by CT-guided TCNB is high, and the procedure is relatively safe. A lesion size ≤1 cm, lower lobe lesions, and pneumothorax are independent risk factors for biopsy diagnostic failure. TCNB specimens could provide adequate tissues for molecular testing. PMID:28275482

  15. Experiments and molecular-dynamics simulation of elastic waves in a plasma crystal radiated from a small dipole source.

    PubMed

    Piel, A; Nosenko, V; Goree, J

    2002-08-19

    The radiation of elastic waves from a localized source is observed experimentally in a two-dimensional plasma crystal. An initial shear stress applied by a laser forms a small dipole source. The emerging complex wave pattern is shown to consist of outgoing compressional and shear wave pulses. Subsequent structures are identified as inward-going waves due to the finite size of the source region, which reappear on the opposite side. The compressional wave forms a trailing wave train due to strong dispersion, while the nondispersive shear wave evolves into a vortex-antivortex pair on either side. The experiments are compared with a molecular-dynamics simulation.

  16. A Novel and Non-Cytotoxic Self-Healing Supramolecular Elastomer Synthesized with Small Molecular Biological Acids.

    PubMed

    Liu, Ling; Pan, Cheng; Zhang, Liqun; Guo, Baochun

    2016-10-01

    A novel and non-cytotoxic self-healing supramolecular elastomer (SE) is synthesized with small-molecular biological acids by hydrogen-bonding interactions. The synthesized SEs behave as rubber at room temperature without additional plasticizers or crosslinkers, which is attributed to the phase-separated structure. The SE material exhibits outstanding self-healing capability at room temperature and essential non-cytotoxicity, which makes it a potential candidate for biomedical applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Anti-localization caused by small doping of heavy-mass impurity-atoms in carbon nanotubes and a novel spintronics device

    NASA Astrophysics Data System (ADS)

    Haruyama, Junji; Takesue, Izumi; Hasegawa, Tetsuro

    2002-01-01

    Multi-walled carbon nanotubes (MWNTs), standing in nanoporous alumina membranes, are doped at one end by impurity atoms from electrode materials. Doping of the light-mass materials (carbon and aluminum) leads to weak localization in Altshuler-Aronov-Spivak oscillation, consistent with past reports. In contrast, we find that doping of heavy-mass materials (gold and platinum) at a volume ratio of only about 5% changes this weak localization to anti-localization. It is understood by a drastic change of the phase interference, caused by the polarized injection of spin-flipped electrons due to spin-orbit interaction in the diffusion region, in the bulk of the MWNTs. We also propose a novel spintronics (electron-wave phase switching) circuit using this effect.

  18. Molecular Signature of Pseudomonas aeruginosa with Simultaneous Nanomolar Detection of Quorum Sensing Signaling Molecules at a Boron-Doped Diamond Electrode

    NASA Astrophysics Data System (ADS)

    Buzid, Alyah; Shang, Fengjun; Reen, F. Jerry; Muimhneacháin, Eoin Ó.; Clarke, Sarah L.; Zhou, Lin; Luong, John H. T.; O’Gara, Fergal; McGlacken, Gerard P.; Glennon, Jeremy D.

    2016-07-01

    Electroanalysis was performed using a boron-doped diamond (BDD) electrode for the simultaneous detection of 2-heptyl-3-hydroxy-4-quinolone (PQS), 2-heptyl-4-hydroxyquinoline (HHQ) and pyocyanin (PYO). PQS and its precursor HHQ are two important signal molecules produced by Pseudomonas aeruginosa, while PYO is a redox active toxin involved in virulence and pathogenesis. This Gram-negative and opportunistic human pathogen is associated with a hospital-acquired infection particularly in patients with compromised immunity and is the primary cause of morbidity and mortality in cystic fibrosis (CF) patients. Early detection is crucial in the clinical management of this pathogen, with established infections entering a biofilm lifestyle that is refractory to conventional antibiotic therapies. Herein, a detection procedure was optimized and proven for the simultaneous detection of PYO, HHQ and PQS in standard mixtures, biological samples, and P. aeruginosa spiked CF sputum samples with remarkable sensitivity, down to nanomolar levels. Differential pulse voltammetry (DPV) scans were also applicable for monitoring the production of PYO, HHQ and PQS in P. aeruginosa PA14 over 8 h of cultivation. The simultaneous detection of these three compounds represents a molecular signature specific to this pathogen.

  19. The development of a new optical sensor based on the Mn doped ZnS quantum dots modified with the molecularly imprinted polymers for sensitive recognition of florfenicol

    NASA Astrophysics Data System (ADS)

    Sadeghi, Susan; Jahani, Moslem; Belador, Foroogh

    2016-04-01

    The Mn doped ZnS quantum dots (Mn:ZnS QDs) capped with the florfenicol molecularly imprinted polymer (Mn:ZnS QDs@MIP) were prepared via the sol-gel surface imprinting approach using 3-aminopropyltriethoxysilane (APTES) as the functional monomer and tetraethoxysilane (TEOS) as the cross-linker for the optosensing of the florfenicol. Transmission electron microscopy (TEM), X-ray diffractometer, IR spectroscopy, UV-Vis absorption spectrophotometry, and spectrofluorometry were used to elucidate the formation, morphology, and identification of the products. To illustrate the usefulness of the new imprinted material, the non-imprinted coated Mn:ZnS QDs (Mn:ZnS QDs@NIP) were synthesized without the presence of the florfenicol. It was revealed that the fluorescence (FL) intensity of the Mn:ZnS QDs@MIP increased with increasing the FF concentration. Under the optimal conditions, changes in the FL intensity in the presence of the target molecule showed a linear response in the concentration range of 30-700 μmol L- 1 with a detection limit of 24 μmol L- 1. The developed method was finally applied successfully to the determination of FF in different meat samples with satisfactory recoveries.

  20. Molecular Signature of Pseudomonas aeruginosa with Simultaneous Nanomolar Detection of Quorum Sensing Signaling Molecules at a Boron-Doped Diamond Electrode

    PubMed Central

    Buzid, Alyah; Shang, Fengjun; Reen, F. Jerry; Muimhneacháin, Eoin Ó; Clarke, Sarah L.; Zhou, Lin; Luong, John H. T.; O’Gara, Fergal; McGlacken, Gerard P.; Glennon, Jeremy D.

    2016-01-01

    Electroanalysis was performed using a boron-doped diamond (BDD) electrode for the simultaneous detection of 2-heptyl-3-hydroxy-4-quinolone (PQS), 2-heptyl-4-hydroxyquinoline (HHQ) and pyocyanin (PYO). PQS and its precursor HHQ are two important signal molecules produced by Pseudomonas aeruginosa, while PYO is a redox active toxin involved in virulence and pathogenesis. This Gram-negative and opportunistic human pathogen is associated with a hospital-acquired infection particularly in patients with compromised immunity and is the primary cause of morbidity and mortality in cystic fibrosis (CF) patients. Early detection is crucial in the clinical management of this pathogen, with established infections entering a biofilm lifestyle that is refractory to conventional antibiotic therapies. Herein, a detection procedure was optimized and proven for the simultaneous detection of PYO, HHQ and PQS in standard mixtures, biological samples, and P. aeruginosa spiked CF sputum samples with remarkable sensitivity, down to nanomolar levels. Differential pulse voltammetry (DPV) scans were also applicable for monitoring the production of PYO, HHQ and PQS in P. aeruginosa PA14 over 8 h of cultivation. The simultaneous detection of these three compounds represents a molecular signature specific to this pathogen. PMID:27427496

  1. Molecular Dynamics Study of Poly And Monocrystalline CdS/CdTe Junctions and Cu Doped Znte Back Contacts for Solar Cell Applications

    NASA Astrophysics Data System (ADS)

    Aguirre, Rodolfo, II

    Cadmium telluride (CdTe) is a material used to make solar cells because it absorbs the sunlight very efficiently and converts it into electricity. However, CdTe modules suffer from degradation of 1% over a period of 1 year. Improvements on the efficiency and stability can be achieved by designing better materials at the atomic scale. Experimental techniques to study materials at the atomic scale, such as Atomic Probe Tomography (APT) and Transmission Electron Microscope (TEM) are expensive and time consuming. On the other hand, Molecular Dynamics (MD) offers an inexpensive and fast computer simulation technique to study the growth evolution of materials with atomic scale resolution. In combination with advance characterization software, MD simulations provide atomistic visualization, defect analysis, structure maps, 3-D atomistic view, and composition profiles. MD simulations help to design better quality materials by predicting material behavior at the atomic scale. In this work, a new MD method to study several phenomena such as polycrystalline growth of CdTe-based materials, interdiffusion of atoms at interfaces, and deposition of a copper doped ZnTe back contact is established. Results are compared with experimental data found in the literature and experiments performed and shown to be in remarkably good agreement.

  2. Low temperature p-type doping of (Al)GaN layers using ammonia molecular beam epitaxy for InGaN laser diodes

    NASA Astrophysics Data System (ADS)

    Malinverni, M.; Lamy, J.-M.; Martin, D.; Feltin, E.; Dorsaz, J.; Castiglia, A.; Rossetti, M.; Duelk, M.; Vélez, C.; Grandjean, N.

    2014-12-01

    We demonstrate state-of-the-art p-type (Al)GaN layers deposited at low temperature (740 °C) by ammonia molecular beam epitaxy (NH3-MBE) to be used as top cladding of laser diodes (LDs) with the aim of further reducing the thermal budget on the InGaN quantum well active region. Typical p-type GaN resistivities and contact resistances are 0.4 Ω cm and 5 × 10-4 Ω cm2, respectively. As a test bed, we fabricated a hybrid laser structure emitting at 400 nm combining n-type AlGaN cladding and InGaN active region grown by metal-organic vapor phase epitaxy, with the p-doped waveguide and cladding layers grown by NH3-MBE. Single-mode ridge-waveguide LD exhibits a threshold voltage as low as 4.3 V for an 800 × 2 μm2 ridge dimension and a threshold current density of ˜5 kA cm-2 in continuous wave operation. The series resistance of the device is 6 Ω and the resistivity is 1.5 Ω cm, confirming thereby the excellent electrical properties of p-type Al0.06Ga0.94N:Mg despite the low growth temperature.

  3. Photoluminescence of Ga-doped ZnO film grown on c-Al2O3 (0001) by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Park, H. C.; Byun, D.; Angadi, B.; Hee Park, D.; Choi, W. K.; Choi, J. W.; Jung, Y. S.

    2007-10-01

    High quality gallium doped ZnO (Ga:ZnO) thin films were grown on c-Al2O3(1000) by plasma-assisted molecular beam epitaxy, and Ga concentration NGa was controlled in the range of 1×1018-2.5×1020/cm3 by adjusting/changing the Ga cell temperature. From the low-temperature photoluminescence at 10K, the donor bound exciton I8 related to Ga impurity was clearly observed and confirmed by comparing the calculated activation energy of 16.8meV of the emission peak intensity with the known localization energy, 16.1meV. Observed asymmetric broadening with a long tail on the lower energy side in the photoluminescence (PL) emission line shape could be fitted by the Stark effect and the compensation ratio was approximately 14-17% at NGa⩾1×1020/cm3. The measured broadening of photoluminescence PL emission is in good agreement with the total thermal broadening and potential fluctuations caused by random distribution of impurity at NGa lower than the Mott critical density.

  4. Evaluation of Luminescence Decay Measurements Probed on Pure and Doped Pt(IV) Hexahalogeno Complexes. II. Molecular Properties Obtained from Temperature Dependent Lifetime Curves

    NASA Astrophysics Data System (ADS)

    Biertümpel, Ingo; Schmidtke, Hans-Herbert

    1997-05-01

    Lifetime measurements down to nearly liquid helium temperatures are used for determining energy levels and transition rates between excited levels and relaxations into the ground state. Energies are obtained from temperature dependent lifetimes by fitting experimental curves to model functions pertinent for thermally activated processes. Rates are calculated from solutions of rate equations. Similar parameters for pure and doped Pt(IV) hexahalogeno complexes indicate that excited levels largely belong to molecular units. Some of the rates between excited states are only somewhat larger than decay rates into the ground state, which is a consequence of the polyexponential decay measured also at low temperature (2 K). In the series of halogen complexes, the rates between spinorbit levels resulting from 3T1g increase from fluorine to bromine, although energy splittings become larger. Due to the decreasing population of higher excited states in this series, K^PtFö shows a tri-exponential, K2PtCl6 a bi-exponential and FoPtBr6 a mono-exponential decay. In the latter case the population density of higher excited states relaxes so fast that emission occurs primarily from the lowest excited Γ3(3T1g) level. Phase transitions and emission from chromophores on different sites can also be observed.

  5. Molecular Signature of Pseudomonas aeruginosa with Simultaneous Nanomolar Detection of Quorum Sensing Signaling Molecules at a Boron-Doped Diamond Electrode.

    PubMed

    Buzid, Alyah; Shang, Fengjun; Reen, F Jerry; Muimhneacháin, Eoin Ó; Clarke, Sarah L; Zhou, Lin; Luong, John H T; O'Gara, Fergal; McGlacken, Gerard P; Glennon, Jeremy D

    2016-07-18

    Electroanalysis was performed using a boron-doped diamond (BDD) electrode for the simultaneous detection of 2-heptyl-3-hydroxy-4-quinolone (PQS), 2-heptyl-4-hydroxyquinoline (HHQ) and pyocyanin (PYO). PQS and its precursor HHQ are two important signal molecules produced by Pseudomonas aeruginosa, while PYO is a redox active toxin involved in virulence and pathogenesis. This Gram-negative and opportunistic human pathogen is associated with a hospital-acquired infection particularly in patients with compromised immunity and is the primary cause of morbidity and mortality in cystic fibrosis (CF) patients. Early detection is crucial in the clinical management of this pathogen, with established infections entering a biofilm lifestyle that is refractory to conventional antibiotic therapies. Herein, a detection procedure was optimized and proven for the simultaneous detection of PYO, HHQ and PQS in standard mixtures, biological samples, and P. aeruginosa spiked CF sputum samples with remarkable sensitivity, down to nanomolar levels. Differential pulse voltammetry (DPV) scans were also applicable for monitoring the production of PYO, HHQ and PQS in P. aeruginosa PA14 over 8 h of cultivation. The simultaneous detection of these three compounds represents a molecular signature specific to this pathogen.

  6. Doping control of GaAsPN alloys by molecular beam epitaxy for monolithic III-V/Si tandem solar cells

    NASA Astrophysics Data System (ADS)

    Yamane, Keisuke; Sato, Kento; Sekiguchi, Hiroto; Okada, Hiroshi; Wakahara, Akihiro

    2017-09-01

    This paper presents intentional doping of n- and p-type GaAs0.19P0.76N0.05 alloys by molecular beam epitaxy, followed by rapid thermal annealing (RTA). Sulfur and magnesium were respectively used as n- and p-type dopants. The carrier concentrations were controllable between 1017 and 1019 cm-3 by adjusting the dopant cell temperature. It was revealed that Hall mobility of the n-type GaAsPN alloys was increased by the RTA process compared to as-grown ones, whereas no significant difference was apparent in the p-type alloys. It is believed that improvement of the conduction band spatial uniformity was mainly responsible for the Hall mobility increase of the n-type GaAsPN alloys by RTA. Finally, a p-i-n GaAsPN diode structure was grown on n-type GaP substrates. A current-voltage characteristic showed a typical rectifying curve with a built-in voltage of 1.8 V and an ideality factor of 1.45. The reverse saturation current was estimated to be less than 10 nA/cm2.

  7. Alkaline Earth Metal Zirconate Perovskites MZrO3 (M=Ba(2+), Sr(2+), Ca(2+)) Derived from Molecular Precursors and Doped with Eu(3+) Ions.

    PubMed

    Drąg-Jarząbek, Anna; John, Łukasz; Petrus, Rafał; Kosińska-Klähn, Magdalena; Sobota, Piotr

    2016-03-24

    The effect of alkaline earth metal alkoxides on the protonation of zirconocene dichloride was investigated. This approach enabled the design of compounds with preset molecular structures for generating high-purity binary metal oxide perovskites MZrO3 (M=Ba(2+), Sr(2+), Ca(2+)). Single-source molecular precursors [Ba4 Zr2 (μ6 -O)(μ3 ,η(2)-OR)8 (OR)2(η(2) -HOR)2 (HOR)2 Cl4], [Sr4 Zr2 (μ6 -O)(μ3 ,η(2)-OR)8 (OR)2 (HOR)4 Cl4], [Ca4 Zr2 (μ6-O)(μ3 ,η(2)-OR)8 (OR)2 Cl4], and [Ca6 Zr2 (μ2 ,η(2)-OR)12 (μ-Cl)2 (η(2) -HOR)4 Cl6 ]⋅8 CH2 Cl2 were prepared via elimination of the cyclopentadienyl ring from Cp2 ZrCl2 as CpH in the presence of M(OR)2 and alcohol ROH (ROH=CH3OCH2 CH2OH) as a source of protons. The resulting complexes were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray diffraction. The compounds were then thermally decomposed to MCl2 /MZrO3 mixtures. Leaching of MCl2 from the raw powder with deionized water produced highly pure perovskite-like oxide particles of 40-80 nm in size. Luminescence studies on Eu(3+)-doped MZrO3 revealed that the perovskites are attractive host lattices for potential applications in display technology.

  8. Supramolecular assemblies with tunable morphologies from homopolymeric and small organic molecular building blocks.

    PubMed

    Peng, Huisheng; Lu, Yunfeng

    2006-06-20

    This work demonstrates the formation of micrometer-sized supramolecular assemblies with tunable morphologies using a homopolymer, poly(4-vinylpyridine), and a small organic acid, 5,7-dodecadiynedioic acid, as the building molecules. Three different morphologies (hollow spheres, solid spheres, and rods) were obtained, depending on the molar ratio of the building molecules. It is proposed that hydrogen bonding between P4VP and DCDA and the pi-pi stacking of the diacetylenic moieties are responsible for the formation of these assemblies. Interestingly, ordered hexagonal and lamellar mesostructures were also formed within the microstructure during the co-assembly process. As a result, UV irradiation of the supramolecular assemblies polymerized the diacetylenic moieties, resulting in cross-linked and responsive blue polydiacetylenic assemblies that can change color to red upon external stimuli (e.g., thermal stimuli). This work provides a novel concept of the synthesis of responsive supramolecular assemblies from a homopolymer and small organic molecules.

  9. Note: Molecular diffusivity in a small pore zeolite measured by a variable pressure (piezometric) uptake method

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Kobayashi, Yasukazu; Muhammad, Usman; Wang, Dezheng; Wang, Yao

    2016-03-01

    The use of numerical analysis to solve the diffusion equation in the uptake method allowed the measurement of molecular diffusivity in a zeolite with a variable pressure around it. The diffusivity was obtained from the data in the measurement of the adsorption isotherm, which means that the diffusivity measurement now needs neither a special instrument nor procedure. The diffusivities of all the gases are readily available from the measurement of their adsorption isotherms and these data include how the diffusivity changes versus adsorbed concentration. The modeling introduced can also be used for a zeolite with a surface barrier.

  10. New Neurons in Aging Brains: Molecular Control by Small Non-Coding RNAs

    PubMed Central

    Schouten, Marijn; Buijink, M. Renate; Lucassen, Paul J.; Fitzsimons, Carlos P.

    2012-01-01

    Adult neurogenesis generates functional neurons from neural stem cells present in specific brain regions. It is largely confined to two main regions: the subventricular zone of the lateral ventricle, and the subgranular zone of the dentate gyrus (DG), in the hippocampus. With age, the function of the hippocampus and particularly the DG is impaired. For instance, adult neurogenesis is decreased with aging, in both proliferating and differentiation of newborn cells, while in parallel an age-associated decline in cognitive performance is often seen. Surprisingly, the synaptogenic potential of adult-born neurons is only marginally influenced by aging. Therefore, although proliferation, differentiation, and synaptogenesis of adult-born new neurons in the DG are closely related to each other, they are differentially affected by aging. In this review we discuss the crucial roles of a novel class of recently discovered modulators of gene expression, the small non-coding RNAs, in the regulation of adult neurogenesis. Multiple small non-coding RNAs are differentially expressed in the hippocampus. In particular a subgroup of the small non-coding RNAs, the microRNAs, fine-tune the progression of adult neurogenesis. This makes small non-coding RNAs appealing candidates to orchestrate the functional alterations in adult neurogenesis and cognition associated with aging. Finally, we summarize observations that link changes in circulating levels of steroid hormones with alterations in adult neurogenesis, cognitive decline, and vulnerability to psychopathology in advanced age, and discuss a potential interplay between steroid hormone receptors and microRNAs in cognitive decline in aging individuals. PMID:22363255

  11. The role of additive in diketopyrrolopyrrole-based small molecular bulk heterojunction solar cells.

    PubMed

    Wang, Hongyu; Liu, Feng; Bu, Laju; Gao, Jun; Wang, Cheng; Wei, Wei; Russell, Thomas P

    2013-12-03

    A new diketopyrrolopyrrole-based small molecule for solution-processed OPVs is synthesized. The chemical additive has a profound effect in refining the morphology and, thus, significantly increases the efficiencies of the devices. The role of the additive is characterized by various techniques and the additive-driven structure-property relationship is established, which reveals that the additive affects the crystallization, PCBM aggregation, and phase separation. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Small copper-doped silicon clusters CuSin (n = 4-10) and their anions: structures, thermochemistry, and electron affinities.

    PubMed

    Lin, Lin; Yang, Jucai

    2015-06-01

    The structures and energies of copper-doped small silicon clusters CuSi n (n = 4-10) and their anions were investigated systematically using CCSD(T)/aug-cc-pVTZ-DK//MP2/6-31G(2df,p), G4//MP2/6-31G(2df,p), and the B3LYP/6-311+G* basis set. The performance of the methods used for the prediction of energetic and thermodynamic properties was evaluated. Comparing experimental [Xu et al. (2012) J Chem Phys 136:104308] and theoretical calculations, it was concluded that the CCSD(T) results are very accurate and exhibit the best performance; the mean absolute deviation from experimental data was 0.043 eV. The excellent agreement of vertical detachment energy (VDE) between experimental results and CCSD(T) calculations indicates that the ground state structures of CuSi n (-) (n = 4-10) presented in this paper are reliable. For CuSi10, assigning 2.90±0.08 eV to the experimental adiabatic electron affinity (AEA) and 3.90±0.08 eV to the VDE is more reasonable than to 3.46±0.08 eV and 3.62±0.08 eV, respectively, based on the CCSD(T) calculations and the previous photoelectron spectrum of CuSi10 (-) (Xu et al., op. cit.). The AEAs of CuSi n (n = 4-10), excluding CuSi7, are in excellent agreement with experimental data, showing that the ground state structures of CuSi n (n = 4-6, 8-10) reported in this paper are reliable. CuSi10 is suggested to be the smallest endohedral ground state structure. However, adding an additional electron to CuSi10 pulls out the Cu atom from the center location, forming an exohedral ground state structure of CuSi10 (-). The charge transfer and dissociation energy of Cu from CuSi n and their anions determined to examine the nature of bonding and their relative stabilities.

  13. Molecular Identification of Echinococcus multilocularis Infection in Small Mammals from Northeast, Iran

    PubMed Central

    Beiromvand, Molouk; Akhlaghi, Lame; Fattahi Massom, Seyed Hossein; Meamar, Ahmad Reza; Darvish, Jamshid; Razmjou, Elham

    2013-01-01

    Background Alveolar echinococcosis is a zoonotic disease caused by the metacestode of Echinococcus multilocularis. Many species of small mammals, including arvicolid rodents or Ochotona spp., are natural intermediate hosts of the cestode. The main aim of this study was to identify natural intermediate hosts of E. multilocularis in Chenaran County, Razavi Khorasan Province, northeastern Iran, where the prevalence of infected wild and domestic carnivores is high. Methodology/Principal Findings A program of trapping was carried out in five villages in which this cestode was reported in carnivores. The livers of 85 small mammals were investigated for the presence of E. multilocularis infection using multiplex PCR of mitochondrial genes. Infections were identified in 30 specimens: 23 Microtus transcaspicus, three Ochotona rufescens, two Mus musculus, one Crocidura gmelini, and one Apodemus witherbyi. Conclusions/Significance A range of small mammals therefore act as natural intermediate hosts for the transmission of E. multilocularis in Chenaran County, and the prevalence suggested that E. multilocularis infection is endemic in this region. The existence of the life cycle of this potentially lethal cestode in the vicinity of human habitats provides a significant risk of human infection. PMID:23875048

  14. Airplane dopes and doping

    NASA Technical Reports Server (NTRS)

    Smith, W H

    1919-01-01

    Cellulose acetate and cellulose nitrate are the important constituents of airplane dopes in use at the present time, but planes were treated with other materials in the experimental stages of flying. The above compounds belong to the class of colloids and are of value because they produce a shrinking action on the fabric when drying out of solution, rendering it drum tight. Other colloids possessing the same property have been proposed and tried. In the first stages of the development of dope, however, shrinkage was not considered. The fabric was treated merely to render it waterproof. The first airplanes constructed were covered with cotton fabric stretched as tightly as possible over the winds, fuselage, etc., and flying was possible only in fine weather. The necessity of an airplane which would fly under all weather conditions at once became apparent. Then followed experiments with rubberized fabrics, fabrics treated with glue rendered insoluble by formaldehyde or bichromate, fabrics treated with drying and nondrying oils, shellac, casein, etc. It was found that fabrics treated as above lost their tension in damp weather, and the oil from the motor penetrated the proofing material and weakened the fabric. For the most part the film of material lacked durability. Cellulose nitrate lacquers, however were found to be more satisfactory under varying weather conditions, added less weight to the planes, and were easily applied. On the other hand, they were highly inflammable, and oil from the motor penetrated the film of cellulose nitrate, causing the tension of the fabric to be relaxed.

  15. CO near the Pleiades: Encounter of a star cluster with a small molecular cloud

    NASA Technical Reports Server (NTRS)

    Bally, J.; White, R. E.

    1986-01-01

    Although there is a large amount of interstellar matter near the Pleiades star cluster, the observed dust and gas is not a remnant of the placental molecular cloud from which the star cluster was formed. Carbon monoxide (CO) associated with the visible reflection nebulae was discovered by Cohen (1975). Its radial velocity differs from that of the cluster by many times the cluster escape velocity, which implies that the cloud-cluster association is the result of a chance encounter. This circumstance and the proximity of the Pleiades to the sun creates an unique opportunity for study of interstellar processes at high spatial resolution. To study the molecular component of the gas, a 1.7 square degree field was mapped with the AT&T Bell Laboratories 7-meter antenna (1.7' beam) on a 1' grid in the J=1.0 C(12)O line, obtaining over 6,000 spectra with 50 kHz resolution. The cloud core was mapped in the J=1-0 line of C(13)O. Further observations include an unsuccessful search for CS (J=2-1) at AT&T BL, and some C(12)O J=2-1 spectra obtained at the Millimeter Wave Observatory of the University of Texas.

  16. Molecular dynamics simulation studies of hyperbranched polyglycerols and their encapsulation behaviors of small drug molecules.

    PubMed

    Yu, Chunyang; Ma, Li; Li, Ke; Li, Shanlong; Liu, Yannan; Zhou, Yongfeng; Yan, Deyue

    2016-08-10

    Hyperbranched polyglycerol (HPG) is one of the most important hyperbranched polymers (HBPs) due to its interesting properties and applications. Herein, the conformation of HPGs depending on the degree of polymerization (DP) and the degree of branching (DB) is investigated explicitly by molecular dynamics simulations. This study shows that the radius of gyration (Rg) scales as Rg ∼ DP(1/3), which is in close agreement with the result of the SANS experiment. For HPGs with the same DP, the radius of gyration, asphericities and solvent accessible surface area all monotonically decrease with the increase of DB; while for HPGs with the same DB, the molecular anisotropy decreases with the increase of DP. The radial density investigation discloses that the cavities are randomly distributed in the interior of the HPG core to support the "dendritic box effect", which can be used to encapsulate the guest molecules. Interestingly, the terminal groups of HPGs with a high Wiener index (WI) are more favorable to fold back into the interiors than those with the low WI when in water. For the hyperbranched multi-arm copolymer with a HPG core and many polyethylene glycol (PEG) arms, drug encapsulation studies show that the PEG caps can not only effectively prevent tamoxifen from leaving the HPG core, but also encapsulate tamoxifen inside the PEG chains. These simulation results have provided more details for understanding the structure-property relationships of HPGs in water.

  17. Conserved molecular mechanisms underlying the effects of small molecule xenobiotic chemotherapeutics on cells

    PubMed Central

    SARIN, HEMANT

    2016-01-01

    For proper determination of the apoptotic potential of chemoxenobiotics in synergism, it is important to understand the modes, levels and character of interactions of chemoxenobiotics with cells in the context of predicted conserved biophysical properties. Chemoxenobiotic structures are studied with respect to atom distribution over molecular space, the predicted overall octanol-to-water partition coefficient (Log OWPC; unitless) and molecular size viz a viz van der Waals diameter (vdWD). The Log OWPC-to-vdWD (nm−1) parameter is determined, and where applicable, hydrophilic interacting moiety/core-to-vdWD (nm−1) and lipophilic incorporating hydrophobic moiety/core-to-vdWD (nm−1) parameters of their part-structures are determined. The cellular and sub-cellular level interactions of the spectrum of xenobiotic chemotherapies have been characterized, for which a classification system has been developed based on predicted conserved biophysical properties with respect to the mode of chemotherapeutic effect. The findings of this study are applicable towards improving the effectiveness of existing combination chemotherapy regimens and the predictive accuracy of personalized cancer treatment algorithms as well as towards the selection of appropriate novel xenobiotics with the potential to be potent chemotherapeutics for dendrimer nanoparticle-based effective transvascular delivery. PMID:26998284

  18. Fabrication of water-dispersible and highly conductive PSS-doped PANI/graphene nanocomposites using a high-molecular weight PSS dopant and their application in H2S detection

    NASA Astrophysics Data System (ADS)

    Cho, Sunghun; Lee, Jun Seop; Jun, Jaemoon; Kim, Sung Gun; Jang, Jyongsik

    2014-11-01

    This work describes the fabrication of poly(4-styrenesulfonic acid)-doped polyaniline/graphene (PSS-doped PANI/graphene) nanocomposites and their use as sensing elements for hydrogen sulfide (H2S) detection. PSS with a weight-average molecular weight (Mw) of 1.96 × 106 was synthesized using low-temperature free-radical polymerization. The PSS was used as both a doping agent and a binding agent for the polymerization of aniline monomers in a biphasic system (water-chloroform) at -50 °C. The high Mw of PSS resulted in relatively large particle sizes and smooth surfaces of the PSS-doped PANI. These physical characteristics, in turn, resulted in low interparticle resistance and high conductivity. In addition, the PSS allowed homogeneous dispersion of reduced graphene sheets through electrostatic repulsion. The prepared PSS-doped PANI/graphene solutions showed good compatibility with flexible poly(ethylene terephthalate) (PET) substrates, making them suitable for flexible sensor electrodes. Changes in the charge-transport properties, such as protonation level, conjugation length, crystalline structure, and charge-transfer resistance, of the electrode materials were the main factors influencing the electrical and sensor performance of the PSS-doped PANI-based electrodes. PSS-doped PANI/graphene composites containing 30 wt% graphene showed the highest conductivity (168.4 S cm-1) and the lowest minimum detection level (MDL) for H2S gas (1 ppm). This result is consistent with the observed improvements in charge transport in the electrode materials via strong π-π stacking interactions between the PANI and the graphene sheets.This work describes the fabrication of poly(4-styrenesulfonic acid)-doped polyaniline/graphene (PSS-doped PANI/graphene) nanocomposites and their use as sensing elements for hydrogen sulfide (H2S) detection. PSS with a weight-average molecular weight (Mw) of 1.96 × 106 was synthesized using low-temperature free-radical polymerization. The PSS was

  19. Small Bowel Carcinomas in Coeliac or Crohn's Disease: Clinico-pathological, Molecular, and Prognostic Features. A Study From the Small Bowel Cancer Italian Consortium.

    PubMed

    Vanoli, Alessandro; Di Sabatino, Antonio; Furlan, Daniela; Klersy, Catherine; Grillo, Federica; Fiocca, Roberto; Mescoli, Claudia; Rugge, Massimo; Nesi, Gabriella; Fociani, Paolo; Sampietro, Gianluca; Ardizzone, Sandro; Luinetti, Ombretta; Calabrò, Antonio; Tonelli, Francesco; Volta, Umberto; Santini, Donatella; Caio, Giacomo; Giuffrida, Paolo; Elli, Luca; Ferrero, Stefano; Latella, Giovanni; Ciardi, Antonio; Caronna, Roberto; Solina, Gaspare; Rizzo, Aroldo; Ciacci, Carolina; D'Armiento, Francesco P; Salemme, Marianna; Villanacci, Vincenzo; Cannizzaro, Renato; Canzonieri, Vincenzo; Reggiani Bonetti, Luca; Biancone, Livia; Monteleone, Giovanni; Orlandi, Augusto; Santeusanio, Giuseppe; Macciomei, Maria C; D'Incà, Renata; Perfetti, Vittorio; Sandri, Giancarlo; Silano, Marco; Florena, Ada M; Giannone, Antonino G; Papi, Claudio; Coppola, Luigi; Usai, Paolo; Maccioni, Antonio; Astegiano, Marco; Migliora, Paola; Manca, Rachele; Martino, Michele; Trapani, Davide; Cerutti, Roberta; Alberizzi, Paola; Riboni, Roberta; Sessa, Fausto; Paulli, Marco; Solcia, Enrico; Corazza, Gino R

    2017-08-01

    An increased risk of small bowel carcinoma [SBC] has been reported in coeliac disease [CD] and Crohn's disease [CrD]. We explored clinico-pathological, molecular, and prognostic features of CD-associated SBC [CD-SBC] and CrD-associated SBC [CrD-SBC] in comparison with sporadic SBC [spo-SBC]. A total of 76 patients undergoing surgical resection for non-familial SBC [26 CD-SBC, 25 CrD-SBC, 25 spo-SBC] were retrospectively enrolled to investigate patients' survival and histological and molecular features including microsatellite instability [MSI] and KRAS/NRAS, BRAF, PIK3CA, TP53, HER2 gene alterations. CD-SBC showed a significantly better sex-, age-, and stage-adjusted overall and cancer-specific survival than CrD-SBC, whereas no significant difference was found between spo-SBC and either CD-SBC or CrD-SBC. CD-SBC exhibited a significantly higher rate of MSI and median tumour-infiltrating lymphocytes [TIL] than CrD-SBC and spo-SBC. Among the whole SBC series, both MSI─which was the result of MLH1 promoter methylation in all but one cases─and high TIL density were associated with improved survival at univariable and stage-inclusive multivariable analysis. However, only TILs retained prognostic power when clinical subgroups were added to the multivariable model. KRAS mutation and HER2 amplification were detected in 30% and 7% of cases, respectively, without prognostic implications. In comparison with CrD-SBC, CD-SBC patients harbour MSI and high TILs more frequently and show better outcome. This seems mainly due to their higher TIL density, which at multivariable analysis showed an independent prognostic value. MSI/TIL status, KRAS mutations and HER2 amplification might help in stratifying patients for targeted anti-cancer therapy.

  20. Growth and Doping of Al(x)Ga(1-x)N Films by Electron Cyclotron Resonance Assisted Molecular Beam

    DTIC Science & Technology

    1994-08-31

    of GaN film arom n on (00~ 1) St. sho%%ine, a -stakire :_ mirk...d .is S. a micritn~in. markcd as T: and j hexaeunatl %urritue regzion, marked a-, It...might expect that the hydrogen-donor state concentration is small in the p-type material. However, the chemistry of hydrogen in GaN is clearly a

  1. Molecular characterization and phylogenetic analysis of the causative agent of hemoplasma infection in small Indian Mongoose (Herpestes Javanicus).

    PubMed

    Sharifiyazdi, Hassan; Nazifi, Saeed; Shirzad Aski, Hesamaddin; Shayegh, Hossein

    2014-09-01

    Hemoplasmas are the trivial name for a group of erythrocyte-parasitizing bacteria of the genus Mycoplasma. This study is the first report of hemoplasma infection in Small Indian Mongoose (Herpestes Javanicus) based on molecular analysis of 16S rDNA. Whole blood samples were collected by sterile methods, from 14 live captured mongooses, in the south of Iran. Candidatus Mycoplasma turicensis (CMt)-like hemoplasma was detected in blood samples from one animal tested. BLAST search and phylogenetic analysis of partial 16S rDNA sequence (933bp) of the hemoplasma from Small Indian mongoose (KJ530704) revealed only 96-97% identity to the previously described CMt followed by 95% and 91% similarity with Mycoplasma coccoides and Mycoplasma haemomuris, respectively. Accordingly, the Iranian mongoose CMt isolate showed a high intra-specific genetic variation compared to all previously reported CMt strains in GenBank. Further molecular studies using multiple phylogenetic markers are required to characterize the exact species of Mongoose-derived hemoplasma.

  2. Advances in molecular biology of lung disease: aiming for precision therapy in non-small cell lung cancer.

    PubMed

    Rooney, Claire; Sethi, Tariq

    2015-10-01

    Lung cancer is the principal cause of cancer-related mortality in the developed world, accounting for almost one-quarter of all cancer deaths. Traditional treatment algorithms have largely relied on histologic subtype and have comprised pragmatic chemotherapy regimens with limited efficacy. However, because our understanding of the molecular basis of disease in non-small cell lung cancer (NSCLC) has improved exponentially, it has become apparent that NSCLC can be radically subdivided, or molecularly characterized, based on recurrent driver mutations occurring in specific oncogenes. We know that the presence of such mutations leads to constitutive activation of aberrant signaling proteins that initiate, progress, and sustain tumorigenesis. This persistence of the malignant phenotype is referred to as "oncogene addiction." On this basis, a paradigm shift in treatment approach has occurred. Rational, targeted therapies have been developed, the first being tyrosine kinase inhibitors (TKIs), which entered the clinical arena > 10 years ago. These were tremendously successful, significantly affecting the natural history of NSCLC and improving patient outcomes. However, the benefits of these drugs are somewhat limited by the emergence of adaptive resistance mechanisms, and efforts to tackle this phenomenon are ongoing. A better understanding of all types of oncogene-driven NSCLC and the occurrence of TKI resistance will help us to further develop second- and third-generation small molecule inhibitors and will expand our range of precision therapies for this disease.

  3. 7,7,8,8-Tetracyanoquinodimethane based molecular dopants for p-type doping of OLEDs: A theoretical investigation

    SciTech Connect

    Cosimbescu, Lelia; Padmaperuma, Asanga B.; Gaspar, Daniel J.

    2011-11-15

    The array of organic conductivity dopants used for organic light emitting devices (OLED) to reduce the operating voltage and improve power efficiency is extremely limited. Here we report a comparative theoretical study between newly proposed analogs and the standard state-of-the-art conductivity dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). We used density functional theory to determine the bond lengths, bond angles and electronic properties, such as the energy of the highest occupied molecular orbital (E{sub HOMO}) and lowest occupied molecular orbital (E{sub LUMO}) states, as well as the triplet energies of the novel structures (ET). The ground state structures of the proposed molecules were optimized at the B3LYP/6-31G* level. The results show that substitution of one or two fluorine groups in the F4-TCNQ core with a substituted phenyl ring or other electron withdrawing moieties, will not substantially affect the geometry of the molecule or its electronic ability to accept electrons. The most significant finding was that the phenyl substitutions onto the TCNQ core are nearly perpendicular to the TCNQ plane, and thus there is no electronic communication between the two rings. This is extremely important, as such extension of the {pi} conjugated system would negatively affect the E{sub LUMO} and thus the electron affinity of the molecule.

  4. Molecular conformation of the full-length tumor suppressor NF2/Merlin—a small angle neutron scattering study

    PubMed Central

    Khajeh, Jahan Ali; Ju, Jeong Ho; Atchiba, Moussoubaou; Allaire, Marc; Stanley, Christopher; Heller, William T.; Callaway, David J.E.; Bu, Zimei

    2014-01-01

    Summary The tumor suppressor protein Merlin inhibits cell proliferation upon establishing cell-cell contacts. Because Merlin has high sequence similarity to the Ezrin-Radixin-Moesin (ERM) family of proteins, the structural model of ERM protein autoinhibition and cycling between closed/resting and open/active conformational states is often employed to explain Merlin function. However, recent biochemical studies suggest alternative molecular models of Merlin function. Here, we have determined the low resolution molecular structure and binding activity of Merlin and a Merlin(S518D) mutant that mimics the inactivating phosphorylation at S518 using small angle neutron scattering (SANS) and binding experiments. SANS shows that in solution both Merlin and Merlin(S518D) adopt a closed conformation, but binding experiments indicate that a significant fraction of either Merlin or Merlin(S518D) is capable of binding to the target protein NHERF1. Upon binding to the phosphatidylinositol 4,5-bisphosphate lipid, the wild-type Merlin adopts a more open conformation than in solution, but Merlin(S518D) remains in a closed conformation. This study supports a rheostat model of Merlin in NHERF1 binding, and contributes to resolve a controversy about the molecular conformation and binding activity of Merlin. PMID:24882693

  5. Pick-up, transport and release of a molecular cargo using a small-molecule robotic arm.

    PubMed

    Kassem, Salma; Lee, Alan T L; Leigh, David A; Markevicius, Augustinas; Solà, Jordi

    2016-02-01

    Modern-day factory assembly lines often feature robots that pick up, reposition and connect components in a programmed manner. The idea of manipulating molecular fragments in a similar way has to date only been explored using biological building blocks (specifically DNA). Here, we report on a wholly artificial small-molecule robotic arm capable of selectively transporting a molecular cargo in either direction between two spatially distinct, chemically similar, sites on a molecular platform. The arm picks up/releases a 3-mercaptopropanehydrazide cargo by formation/breakage of a disulfide bond, while dynamic hydrazone chemistry controls the cargo binding to the platform. Transport is controlled by selectively inducing conformational and configurational changes within an embedded hydrazone rotary switch that steers the robotic arm. In a three-stage operation, 79-85% of 3-mercaptopropanehydrazide molecules are transported in either (chosen) direction between the two platform sites, without the cargo at any time fully dissociating from the machine nor exchanging with other molecules in the bulk.

  6. Pick-up, transport and release of a molecular cargo using a small-molecule robotic arm

    NASA Astrophysics Data System (ADS)

    Kassem, Salma; Lee, Alan T. L.; Leigh, David A.; Markevicius, Augustinas; Solà, Jordi

    2016-02-01

    Modern-day factory assembly lines often feature robots that pick up, reposition and connect components in a programmed manner. The idea of manipulating molecular fragments in a similar way has to date only been explored using biological building blocks (specifically DNA). Here, we report on a wholly artificial small-molecule robotic arm capable of selectively transporting a molecular cargo in either direction between two spatially distinct, chemically similar, sites on a molecular platform. The arm picks up/releases a 3-mercaptopropanehydrazide cargo by formation/breakage of a disulfide bond, while dynamic hydrazone chemistry controls the cargo binding to the platform. Transport is controlled by selectively inducing conformational and configurational changes within an embedded hydrazone rotary switch that steers the robotic arm. In a three-stage operation, 79-85% of 3-mercaptopropanehydrazide molecules are transported in either (chosen) direction between the two platform sites, without the cargo at any time fully dissociating from the machine nor exchanging with other molecules in the bulk.

  7. Molecular Dynamics Simulations on Parallel Computers: a Study of Polar Versus Nonpolar Media Effects in Small Molecule Solvation.

    NASA Astrophysics Data System (ADS)

    Debolt, Stephen Edward

    Solvent effects were studied and described via molecular dynamics (MD) and free energy perturbation (FEP) simulations using the molecular mechanics program AMBER. The following specific topics were explored:. Polar solvents cause a blue shift of the rm nto pi^* transition band of simple alkyl carbonyl compounds. The ground- versus excited-state solvation effects responsible for the observed solvatochromism are described in terms of the molecular level details of solute-solvent interactions in several modeled solvents spanning the range from polar to nonpolar, including water, methanol, and carbon tetrachloride. The structure and dynamics of octanol media were studied to explore the question: "why is octanol/water media such a good biophase analog?". The formation of linear and cyclic polymers of hydrogen-bonded solvent molecules, micelle-like clusters, and the effects of saturating waters are described. Two small drug-sized molecules, benzene and phenol, were solvated in water-saturated octanol. The solute-solvent structure and dynamics were analysed. The difference in their partitioning free energies was calculated. MD and FEP calculations were adapted for parallel computation, increasing their "speed" or the time span accessible by a simulation. The non-cyclic polyether ionophore salinomycin was studied in methanol solvent via parallel FEP. The path of binding and release for a potassium ion was investigated by calculating the potential of mean force along the "exit vector".

  8. Small renal masses: The molecular markers associated with outcome of patients with kidney tumors 7 cm or less

    NASA Astrophysics Data System (ADS)

    Spirina, L. V.; Usynin, Y. A.; Kondakova, I. V.; Yurmazov, Z. A.; Slonimskaya, E. M.; Pikalova, L. V.

    2016-08-01

    The investigation of molecular mechanisms of tumor cell behavior in small renal masses is required to achieve the better cancer survival. The aim of the study is to find molecular markers associated with outcome of patients with kidney tumors 7 cm or less. A homogenous group of 20 patients T1N0M0-1 (mean age 57.6 ± 2.2 years) with kidney cancer was selected for the present analysis. The content of transcription and growth factors was determined by ELISA. The levels of AKT-mTOR signaling pathway components were measured by Western blotting analysis. The molecular markers associated with unfavorable outcome of patients with kidney tumors 7 cm or less were high levels of NF-kB p50, NF-kB p65, HIF-1, HIF-2, VEGF and CAIX. AKT activation with PTEN loss also correlated with the unfavorable outcome of kidney cancer patients with tumor size 7 cm or less. It is observed that the biological features of kidney cancer could predict the outcome of patients.

  9. Molecular characteristics of non-small cell lung cancer with reduced CHFR expression in The Cancer Genome Atlas (TCGA) project.

    PubMed

    Brodie, Seth A; Li, Ge; Brandes, Johann C

    2015-01-01

    CHFR expression has previously been established as a powerful predictor for response to taxane based first-line chemotherapy in non-small cell lung cancer. It is currently unknown however, if reduced CHFR expression correlates with certain molecular subtypes of lung cancer. In order to determine which patients may benefit from CHFR biomarker testing we conducted the present study to characterize clinical and molecular characteristics of patients with reduced vs. high CHFR expression. We utilized the extensive molecular and clinical data of the most recent adeno- and squamous cell carcinoma datasets from The Cancer Genome Atlas (TCGA) project. CHFR expression, analyzed by RNA-seq, was classified as high vs. low based on the median CHFR expression level and correlated with the presence or absence of lung cancer specific mutations (EGFR, KRAS, ALK, MET, ERBB2, TP53, STK11, ROS1, RET, NF1, Pik3CA for adenocarcinomas and FGFR1, FGFR2, FGFR3, TP53, STK11, EGFR for squamous cell carcinomas). Reduced CHFR expression was associated with EGFR exon19/21 mutations in adenocarcinoma OR 0.23 (95%CI: 0.06-0.88) and male gender in squamous cell carcinoma (OR 0.46 (95%CI 0.23-0.92), p = 0.02). Published by Elsevier Ltd.

  10. Molecular theory for the phase equilibria and cluster distribution of associating fluids with small bond angles.

    PubMed

    Marshall, Bennett D; Chapman, Walter G

    2013-08-07

    We develop a new theory for associating fluids with multiple association sites. The theory accounts for small bond angle effects such as steric hindrance, ring formation, and double bonding. The theory is validated against Monte Carlo simulations for the case of a fluid of patchy colloid particles with three patches and is found to be very accurate. Once validated, the theory is applied to study the phase diagram of a fluid composed of three patch colloids. It is found that bond angle has a significant effect on the phase diagram and the very existence of a liquid-vapor transition.

  11. Cellular and molecular biology of small cell lung cancer: an overview

    PubMed Central

    Karachaliou, Niki; Pilotto, Sara; Lazzari, Chiara; Bria, Emilio; de Marinis, Filippo

    2016-01-01

    Although the incidence of small cell lung cancer (SCLC) has declined during the past 30 years, it remains a frustrating disease to research and treat. Numerous attempts to enhance the anti-tumor effects of traditional chemotherapy for SCLC have not been successful. For any tumor to become cancerous, various genetic mutations and biologic alterations must occur in the cell that, when combined, render it a malignant neoplasm. New and novel therapies based on understanding these mechanisms of transformation are needed. Herein we provide an in-depth view of some of the genomic alterations in SCLC that have emerged as potential targets for therapeutic intervention. PMID:26958489

  12. Biomolecular Crowding Arising from Small Molecules, Molecular Constraints, Surface Packing, and Nano-Confinement.

    PubMed

    Hilaire, Mary Rose; Abaskharon, Rachel M; Gai, Feng

    2015-07-02

    The effect of macromolecular crowding on the structure, dynamics, and reactivity of biomolecules is well established and the relevant research has been extensively reviewed. Herein, we focus our discussion on crowding effects arising from small cosolvent molecules and densely packed surface conditions. In addition, we highlight recent efforts that capitalize on the excluded volume effect for various tailored biochemical and biophysical applications. Specifically, we discuss how a targeted increase in local mass density can be exploited to gain insight into the folding dynamics of the protein of interest and how confinement via reverse micelles can be used to study a range of biophysical questions, from protein hydration dynamics to amyloid formation.

  13. Sampling small-scale and large-scale conformational changes in proteins and molecular complexes

    NASA Astrophysics Data System (ADS)

    Yun, Mi-Ran; Mousseau, N.; Derreumaux, P.

    2007-03-01

    Sampling of small-scale and large-scale motions is important in various computational tasks, such as protein-protein docking and ligand binding. Here, we report further development and applications of the activation-relaxation technique for internal coordinate space trajectories (ARTIST). This method generates conformational moves of any complexity and size by identifying and crossing well-defined saddle points connecting energy minima. Simulations on two all-atom proteins and three protein complexes containing between 70 and 300 amino acids indicate that ARTIST opens the door to the full treatment of all degrees of freedom in dense systems such as protein-protein complexes.

  14. Water activity and mobility in solutions of glycerol and small molecular weight sugars: Implication for cryo- and lyopreservation

    NASA Astrophysics Data System (ADS)

    He, Xiaoming; Fowler, Alex; Toner, Mehmet

    2006-10-01

    In this study, the free volume models, originally developed for large molecular weight polymer-solvent systems, were used to study the water activity and mobility in solutions of four small molecular weight cryo-/lyoprotectants, viz., glycerol, a monosaccharide (fructose), and two disaccharides (sucrose and trehalose). The free volume model parameters were determined by fitting the models to available experimental data using a nonlinear optimization procedure. It was found that free volume models could accurately predict the available experimental data, which suggests that the free volume models might be generally applicable to aqueous solutions of small molecular weight cryo-/lyoprotectants. Furthermore, several models for estimating the mutual diffusion coefficient were tested using available experimental data for aqueous solutions of glycerol and a better method to estimate the mutual diffusion coefficient was proposed. Free volume models were used to predict and analyze the water activity and mobility in solutions of four cryo-/lyoprotectants under conditions frequently encountered in cryo-/lyopreservation applications. It was found that the water mobility in the glassy state of the above four solutions is essentially negligible in the case of cryopreservation with storage temperature lower than -110°C. However, the water mobility in a glass at higher temperature (>-80°C) may be significant. As a result, a subcooling of up to 50°C may be necessary for the long-term cryo-/lyopreservation of biomaterials depending on the water content and the type of cryo-/lyoprotectants. It was further shown that trehalose might be the best of the four protectants studied for lyopreservation (water mass fraction ⩽0.1) when the storage temperature is above the room temperature. The results from this study might be useful for the development of more effective protocols for both cryopreservation and lyopreservation of living cells and other biomaterials.

  15. Stability of small molecular clusters modelled with stochastic and deterministic dynamics

    NASA Astrophysics Data System (ADS)

    Natarajan, Sukina

    This investigation concerns the transition pathway of the condensation phase transition. Under certain conditions condensation is initiated by nucleation events, which are driven by fluctuations or instabilities in the vapour phase. This involves the spontaneous formation of groups of particles, which we refer to as clusters. The clusters have a highly unstable nature and exist momentarily, before breaking up. This makes them difficult to study experimentally and model mathematically, in comparison to larger more stable systems. The aim of this study is to explore the stability of these tiny molecular clusters that exist momentarily within their environment, in terms of the time taken for the cluster to lose particles (decay). To do this we employ a microscopic cluster model of n-nonane molecules in which the cluster is treated in isolation from the vapour particles that would normally surround it. The interactions between cluster particles are modelled using empirical potentials. The cluster's dynamics is modelled using deterministic molecular dynamics simulations. The simulations generate a time evolved trajectory of all the positions, velocities and forces of all the atoms in the cluster. The process of cluster decay in n-nonane clusters is modelled using a Langevin interpretation of the decay mechanism. This treatment views cluster decay as a process of single particle escape from a confining potential of mean force, driven by a particle's interactions with the surrounding cluster particles. The motion of a cluster particle is modelled using a Langevin equation, which is parameterised using the MD generated data in order to extract the decay related parameters. The decay parameters are used to evaluate an Arrhenius type equation for the kinetic decay rate. This is used to calculate the mean timescale of cluster decay for n-nonane clusters, which we refer to as the mean cluster lifetime. We compare the dynamically generated lifetimes calculated from the model to

  16. Geometric isotope effects on small chloride ion water clusters with path integral molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Suzuki, Kimichi; Nagashima, Umpei; Tachikawa, Masanori; Yan, Shiwei

    2013-11-01

    The geometric isotope effects on the structures of hydrated chloride ionic hydrogen bonded clusters are explored by carrying out path integral molecular dynamics simulations. First, an outer shell coordinate is selected to display the rearrangement of single and multi hydration shell cluster structures. Next, to show the competition of intramolecular and intermolecular nuclear quantum effects, the intramolecular OH∗ stretching and intermolecular ion-water wagging motions are studied for single and multi shell structures, respectively. The results indicate that the intermolecular nuclear quantum effects stabilize the ionic hydrogen bonds in single shell structures, while they are destabilized through the competition with intramolecular nuclear quantum effects in multi shell structures. In addition, the correlations between ion-water stretching motion and other cluster vibrational coordinates are discussed. The results indicate that the intermolecular nuclear quantum effects on the cluster structures are strongly related to the cooperation of the water-water hydrogen bond interactions.

  17. Molecular Evidence for Gender Differences in the Migratory Behaviour of a Small Seabird

    PubMed Central

    Medeiros, Renata J.; King, R. Andrew; Symondson, William O. C.; Cadiou, Bernard; Zonfrillo, Bernard; Bolton, Mark; Morton, Rab; Howell, Stephen; Clinton, Anthony; Felgueiras, Marcial; Thomas, Robert J.

    2012-01-01

    Molecular sexing revealed an unexpectedly strong female bias in the sex ratio of pre-breeding European Storm Petrels (Hydrobates pelagicus), attracted to playback of conspecific calls during their northwards migration past SW Europe. This bias was consistent across seven years, ranging from 80.8% to 89.7% female (mean annual sex ratio ± SD = 85.5% female ±4.1%). The sex ratio did not differ significantly from unity (i.e., 50% female) among (i) Storm Petrel chicks at a breeding colony in NW France, (ii) adults found dead on beaches in Southern Portugal, (iii) breeding birds attending nest burrows in the UK, captured by hand, and (iv) adults captured near a breeding colony in the UK using copies of the same sound recordings as used in Southern Europe, indicating that females are not inherently more strongly attracted to playback calls than males. A morphological discriminant function analysis failed to provide a good separation of the sexes, showing the importance of molecular sexing for this species. We found no sex difference in the seasonal or nocturnal timing of migration past Southern Europe, but there was a significant tendency for birds to be caught in sex-specific aggregations. The preponderance of females captured in Southern Europe suggests that the sexes may differ in migration route or in their colony-prospecting behaviour during migration, at sites far away from their natal colonies. Such differences in migration behaviour between males and females are poorly understood but have implications for the vulnerability of seabirds to pollution and environmental change at sea during the non-breeding season. PMID:23029481

  18. Molecular evidence for gender differences in the migratory behaviour of a small seabird.

    PubMed

    Medeiros, Renata J; King, R Andrew; Symondson, William O C; Cadiou, Bernard; Zonfrillo, Bernard; Bolton, Mark; Morton, Rab; Howell, Stephen; Clinton, Anthony; Felgueiras, Marcial; Thomas, Robert J

    2012-01-01

    Molecular sexing revealed an unexpectedly strong female bias in the sex ratio of pre-breeding European Storm Petrels (Hydrobates pelagicus), attracted to playback of conspecific calls during their northwards migration past SW Europe. This bias was consistent across seven years, ranging from 80.8% to 89.7% female (mean annual sex ratio ± SD = 85.5% female ±4.1%). The sex ratio did not differ significantly from unity (i.e., 50% female) among (i) Storm Petrel chicks at a breeding colony in NW France, (ii) adults found dead on beaches in Southern Portugal, (iii) breeding birds attending nest burrows in the UK, captured by hand, and (iv) adults captured near a breeding colony in the UK using copies of the same sound recordings as used in Southern Europe, indicating that females are not inherently more strongly attracted to playback calls than males. A morphological discriminant function analysis failed to provide a good separation of the sexes, showing the importance of molecular sexing for this species. We found no sex difference in the seasonal or nocturnal timing of migration past Southern Europe, but there was a significant tendency for birds to be caught in sex-specific aggregations. The preponderance of females captured in Southern Europe suggests that the sexes may differ in migration route or in their colony-prospecting behaviour during migration, at sites far away from their natal colonies. Such differences in migration behaviour between males and females are poorly understood but have implications for the vulnerability of seabirds to pollution and environmental change at sea during the non-breeding season.

  19. One-step pyrolytic synthesis of nitrogen and sulfur dual-doped porous carbon with high catalytic activity and good accessibility to small biomolecules.

    PubMed

    Gao, Weiwei; Feng, Xun; Zhang, Tianyi; Huang, Hao; Li, Jin; Song, Wenbo

    2014-01-01

    As one of promising catalysts that contain high density of active sites, N doped carbons have been extensively researched, while the reports for N, S dual-doped carbon materials are far less exhaustive. Herein, devoid of activation process and template, N, S dual-doped porous carbon (N-S-PC) was prepared for the first time via one-step pyrolysis of sodium citrate and cysteine. Possessing unique porous structure and large pore volume as well as good accessibility, N-S-PC demonstrates significantly improved electrocatalytic activity toward oxidation of ascorbic acid (AA), dopamine (DA), and uric acid (UA). In the coexisting system, the peak potential separation between AA and DA is up to 251 mV, which is much larger than for most of the other carbons. On the basis of large potential separation and high current response, selective and sensitive simultaneous determination of AA, DA, and UA was successfully accomplished by differential pulse voltammetry, displaying a linear response from 50 to 2000 μM, from 0.1 to 50 μM, and from 0.1 to 50 μM with a detection limit (S/N = 3) of 0.78, 0.02, and 0.06 μM. This work highlights the importance of N, S dual doping and hierarchical porous carbons for efficient catalysis.

  20. Stable and controlled amphoteric doping by encapsulation of organic molecules inside carbon nanotubes.

    PubMed

    Takenobu, Taishi; Takano, Takumi; Shiraishi, Masashi; Murakami, Yousuke; Ata, Masafumi; Kataura, Hiromichi; Achiba, Yohji; Iwasa, Yoshihiro

    2003-10-01

    Single-walled carbon nanotubes (SWNTs) have strong potential for molecular electronics, owing to their unique structural and electronic properties. However, various outstanding issues still need to be resolved before SWNT-based devices can be made. In particular, large-scale, air-stable and controlled doping is highly desirable. Here we present a method for integrating organic molecules into SWNTs that promises to push the performance limit of these materials for molecular electronics. Reaction of SWNTs with molecules having large electron affinity and small ionization energy achieved p- and n-type doping, respectively. Optical characterization revealed that charge transfer between SWNTs and molecules starts at certain critical energies. X-ray diffraction experiments revealed that molecules are predominantly encapsulated inside SWNTs, resulting in an improved stability in air. The simplicity of the synthetic process offers a viable route for the large-scale production of SWNTs with controlled doping states.

  1. Molecular investigation of Cryptosporidium in small caged pets in northeast China: host specificity and zoonotic implications.

    PubMed

    Li, Qiao; Li, Lu; Tao, Wei; Jiang, Yanxue; Wan, Qiang; Lin, Yongchao; Li, Wei

    2016-07-01

    This study screened 151 pet-derived fecal specimens randomly collected from four commercial markets in northeast China for the presence of Cryptosporidium by genus-specific nested PCRs of the small subunit rRNA gene. Of these, 14 specimens (9.3 %) from nine species of birds, two types of rodents, and a hedgehog were positive for Cryptosporidium. Sequence analysis on the PCR-positive isolates facilitated identification of three Cryptosporidium species (C. baileyi, C. galli, and C. ubiquitum) and two Cryptosporidium genotypes (ferret genotype and avian genotype V). The study birds were affected predominantly with bird-specific C. baileyi (Atlantic canary, budgerigar, crested myna, rock dove, and silky fowl), C. galli (Chinese hwamei), and Cryptosporidium avian genotype V (Fischer's lovebird and rosy-faced lovebird). Cryptosporidium ferret genotype previously considered rodent-adapted was identified in three specimens from budgerigar, chipmunk, and red squirrel. Two specimens collected from common hill myna and hedgehog were positive for C. ubiquitum. The species of birds that can be colonized by Cryptosporidium were extended. Moreover, the data expanded the host range of Cryptosporidium ferret genotype and C. ubiquitum, especially the birds. The carriage of zoonotic C. ubiquitum in small caged pets is of public health importance.

  2. Selective-area growth of heavily n–doped GaAs nanostubs on Si(001) by molecular beam epitaxy

    SciTech Connect

    Chang, Yoon Jung Woo, Jason C. S.; Simmonds, Paul J.

    2016-04-18

    Using an aspect ratio trapping technique, we demonstrate molecular beam epitaxy of GaAs nanostubs on Si(001) substrates. Nanoholes in a SiO{sub 2} mask act as a template for GaAs-on-Si selective-area growth (SAG) of nanostubs 120 nm tall and ≤100 nm in diameter. We investigate the influence of growth parameters including substrate temperature and growth rate on SAG. Optimizing these parameters results in complete selectivity with GaAs growth only on the exposed Si(001). Due to the confined-geometry, strain and defects in the GaAs nanostubs are restricted in lateral dimensions, and surface energy is further minimized. We assess the electrical properties of the selectively grown GaAs nanostubs by fabricating heterogeneous p{sup +}–Si/n{sup +}–GaAs p–n diodes.

  3. Selective-area growth of heavily n-doped GaAs nanostubs on Si(001) by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Chang, Yoon Jung; Simmonds, Paul J.; Beekley, Brett; Goorsky, Mark S.; Woo, Jason C. S.

    2016-04-01

    Using an aspect ratio trapping technique, we demonstrate molecular beam epitaxy of GaAs nanostubs on Si(001) substrates. Nanoholes in a SiO2 mask act as a template for GaAs-on-Si selective-area growth (SAG) of nanostubs 120 nm tall and ≤100 nm in diameter. We investigate the influence of growth parameters including substrate temperature and growth rate on SAG. Optimizing these parameters results in complete selectivity with GaAs growth only on the exposed Si(001). Due to the confined-geometry, strain and defects in the GaAs nanostubs are restricted in lateral dimensions, and surface energy is further minimized. We assess the electrical properties of the selectively grown GaAs nanostubs by fabricating heterogeneous p+-Si/n+-GaAs p-n diodes.

  4. Direct optical carbon dioxide sensing based on a polymeric film doped with a selective molecular tweezer-type ionophore.

    PubMed

    Xie, Xiaojiang; Pawlak, Marcin; Tercier-Waeber, Mary-Lou; Bakker, Eric

    2012-04-03

    A novel optical method for the determination of CO(2) concentration in aqueous and gaseous samples of plasticized PVC film is presented. The detection principle makes use of a direct molecular recognition of the carbonate ion by a molecular tweezer-type ionophore, which has previously been demonstrated to exhibit excellent carbonate selectivity. The carbonate ion is extracted together with hydrogen ions into a polymeric film that contains the anion exchanger tridodecylmethylammonium chloride, a lipophilic, electrically charged, and highly basic pH indicator, which is used for the readout in absorbance mode, in addition to the lipophilic carbonate ionophore. According to known bulk optode principles, such an optical sensor responds to the product of the carbonate ion activity and the square of hydrogen ion activity. This quantity is thermodynamically linked to the activity of carbon dioxide. This allows one to realize a direct carbon dioxide sensor that does not make use of the traditional Severinghaus sensing principle of measuring a pH change upon CO(2) equilibration across a membrane. A selectivity analysis shows that common ions such as chloride are sufficiently suppressed for direct PCO(2) measurements in freshwater samples at pH 8. Chloride interference, however, is too severe for direct seawater measurements at the same pH. This may be overcome by placing a gas-permeable membrane over the optode sensing film. This is conceptually confirmed by establishing that the sensor is equally useful for gas-phase PCO(2) measurements. As expected, humid air samples are required for proper sensor functioning, as dry CO(2) gas will not cause any signal change. The sensor showed acceptable response times and good reproducibility under both conditions.

  5. Role of Molecular Flexibility and Colloidal Descriptions of Proteins in Crowded Environments from Small-Angle Scattering.

    PubMed

    Castellanos, Maria Monica; Clark, Nicholas J; Watson, Max C; Krueger, Susan; McAuley, Arnold; Curtis, Joseph E

    2016-12-15

    Small-angle scattering is a powerful technique to study molecular conformation and interactions of proteins in solution and in amorphous solids. We have investigated the role of multiple protein configurations in the interaction parameters derived from small-angle scattering for proteins in concentrated solutions. In order to account for the wide configurational space sampled by proteins, we generate ensembles of atomistic structures for lysozyme and monoclonal antibodies, representing globular and flexible proteins, respectively. While recent work has argued that a colloidal approach is inadequate to model proteins, because of the large configurational space that they sample in solution, we find a range of length scales where colloidal models can be used to describe solution scattering data while simultaneously accounting for structural flexibility. We provide insights to determine the length scales where isotropic colloidal models can be used, and find smoothly varying sets of interaction parameters that encompass ensembles of structures. This approach may play an important role in the definition of long-range interactions in coarse-grained models of flexible proteins with experimental scattering constraints. Additionally, we apply the decoupling approximation to ensembles of lysozyme structures with atomistic detail and observe remarkably different results when using geometric solids, such as ellipsoids. The insights from this study provide guidelines for the analysis of small-angle scattering profiles of proteins in crowded environments.

  6. Small-angle scattering from phospholipid nanodiscs: derivation and refinement of a molecular constrained analytical model form factor.

    PubMed

    Skar-Gislinge, Nicholas; Arleth, Lise

    2011-02-28

    Nanodiscs™ consist of small phospholipid bilayer discs surrounded and stabilized by amphiphilic protein belts. Nanodiscs and their confinement and stabilization of nanometer sized pieces of phospholipid bilayer are highly interesting from a membrane physics point of view. We demonstrate how the detailed structure of Di-Lauroyl-Phosphatidyl Choline (DLPC) nanodiscs may be determined by simultaneous fitting of a structural model to small-angle scattering data from the nanodiscs as investigated in three different contrast situations, respectively two SANS contrasts and one SAXS contrast. The article gives a detailed account of the underlying structural model for the nanodiscs and describe how additional chemical and biophysical information can be incorporated in the model in terms of molecular constraints. We discuss and quantify the contribution from the different elements of the structural model and provide very strong experimental support for the nanodiscs as having an elliptical cross-section and with poly-histidine tags protruding out from the rim of the protein belt. The analysis also provides unprecedented information about the structural conformation of the phospholipids when these are localized in the nanodiscs. The model paves the first part of the way in order to reach our long term goal of using the nanodiscs as a platform for small-angle scattering based structural investigations of membrane proteins in solution.

  7. Serologic and Molecular Evidence of Vaccinia Virus Circulation among Small Mammals from Different Biomes, Brazil

    PubMed Central

    Miranda, Júlia B.; Borges, Iara A.; Campos, Samantha P.S.; Vieira, Flávia N.; de Ázara, Tatiana M.F.; Marques, Fernanda A.; Costa, Galileu B.; Luis, Ana Paula M.F.; de Oliveira, Jaqueline S.; Ferreira, Paulo César P.; Bonjardim, Cláudio Antônio; da Silva, Silvio L.M.; Eiras, Álvaro E.; Abrahão, Jônatas S.; Kroon, Erna G.; Drumond, Betânia P.; Paglia, Adriano P.

    2017-01-01

    Vaccinia virus (VACV) is a zoonotic agent that causes a disease called bovine vaccinia, which is detected mainly in milking cattle and humans in close contact with these animals. Even though many aspects of VACV infection have been described, much is still unknown about its circulation in the environment and its natural hosts/reservoirs. To investigate the presence of Orthopoxvirus antibodies or VACV DNA, we captured small rodents and marsupials in 3 areas of Minas Gerais state, Brazil, and tested their samples in a laboratory. A total of 336 animals were tested; positivity ranged from 18.1% to 25.5% in the 3 studied regions located in different biomes, including the Atlantic Forest and the Cerrado. Analysis of nucleotide sequences indicated co-circulation of VACV groups I and II. Our findings reinforce the possible role played by rodents and marsupials in VACV maintenance and its transmission chain. PMID:28518030

  8. Results from a 'small box' realtime molecular contamination monitor on STS-3

    NASA Technical Reports Server (NTRS)

    Triolo, J.; Kruger, R.; Mcintosh, R.; Maag, C.

    1983-01-01

    On the basis of early estimates of the Shuttle induced environment, Scialdone (1979) concluded that in the vicinity of the cargo, the cargo would have the largest influence on the environment. As a contamination control device, realtime monitors can indicate safe operational periods for sensitive attached payloads. It was, therefore, decided to develop the OSS-1/Contamination Monitor Package (CMP) experiment which was seen as a forerunner of an operational monitor. A description of the CMP is provided, taking into account four actively temperature controlled quartz crystal microbalances (TQCM). The TQCM temperatures could be varied from -60 C to +80 C. The sensor consisted of a matched pair of quartz crystals. The crystals were designated as a sensor and reference crystal. Results obtained during the STS-3 mission are discussed. These results show the feasibility and advantages of a small real-time contamination monitor.

  9. Small-molecule compounds that modulate lipolysis in adipose tissue: targeting strategies and molecular classes.

    PubMed

    Wang, Minghan; Fotsch, Christopher

    2006-10-01

    Lipolysis is an important pathway in maintaining energy homeostasis through the degradation of triglycerides in adipose tissue and the release of fatty acids into the circulation as an energy source. However, an elevated level of circulating fatty acids leads to unfavorable metabolic effects such as insulin resistance and dyslipidemia. Cell surface receptors and intracellular components of the lipolytic pathway have been targeted to develop antilipolytic agents, among which are G-protein-coupled receptor agonists and lipase inhibitors. In addition, molecules that stimulate lipolysis have been tested in clinical trials as a treatment for obesity. Together, these molecules represent a diverse group of regulators for this pathway. This review will discuss strategies to target lipolysis and the major issues with representative small-molecule modulators of this pathway.

  10. Molecular Characterization of the Small Nonstructural Proteins of Parvovirus Aleutian Mink Disease Virus (AMDV) During Infection

    PubMed Central

    Huang, Qinfeng; Luo, Yong; Cheng, Fang; Best, Sonja M.; Bloom, Marshall E.; Qiu, Jianming

    2014-01-01

    Aleutian mink disease virus (AMDV) is the only member in genus Amdovirus of the family Parvoviridae. During AMDV infection, six species of viral transcripts are generated from one precursor mRNA through alternative splicing and alternative polyadenylation. In addition to the large non-structural protein NS1, two small non-structural proteins, NS2 and NS3, are putatively encoded (Qiu J, et al: Journal of Virology, 80:654–62, 2006). However, these two proteins have not been experimentally demonstrated during virus infection, and nothing is known about their function. Here, we studied the nonstructural protein expression profile of AMDV, and for the first time, confirmed expression of NS2 and NS3 during infection, and identified their intracellular localization. More importantly, we provided evidence that both NS2 and NS3 are necessary for AMDV replication. PMID:24606679

  11. Molecular characterization of Leptospira spp. strains isolated from small rodents in Croatia.

    PubMed Central

    Turk, N.; Milas, Z.; Margaletic, J.; Staresina, V.; Slavica, A.; Riquelme-Sertour, N.; Bellenger, E.; Baranton, G.; Postic, D.

    2003-01-01

    We report the isolation and characterization of 16 Leptospira spp. strains isolated from small rodents captured in 11 different regions of inland Croatia. Large NotI and SgrAI restriction fragment allowed us to assign 10 isolates to the serovar istrica, 5 isolates to the serovar tsaratsovo and 1 isolate to the serovar lora. The phylogenetic analysis conducted from the sequences of the first 330 bp from the 16S rDNA gene revealed that the strains belonged to three different species, L. borgpetersenii, L. kirschneri and L. interrogans. Carrier rates in eight rodent species varied from 0 to 71.4%. Mus musculus showed the highest infection level and confirmed its role as a major reservoir of the serogroup Sejroë. For the first time we reported the occurrence of serovars tsaratsovo and lora in Croatia. PMID:12613757

  12. Molecular locks and keys: the role of small molecules in phytohormone research.

    PubMed

    Fonseca, Sandra; Rosado, Abel; Vaughan-Hirsch, John; Bishopp, Anthony; Chini, Andrea

    2014-01-01

    Plant adaptation, growth and development rely on the integration of many environmental and endogenous signals that collectively determine the overall plant phenotypic plasticity. Plant signaling molecules, also known as phytohormones, are fundamental to this process. These molecules act at low concentrations and regulate multiple aspects of plant fitness and development via complex signaling networks. By its nature, phytohormone research lies at the interface between chemistry and biology. Classically, the scientific community has always used synthetic phytohormones and analogs to study hormone functions and responses. However, recent advances in synthetic and combinational chemistry, have allowed a new field, plant chemical biology, to emerge and this has provided a powerful tool with which to study phytohormone function. Plant chemical biology is helping to address some of the most enduring questions in phytohormone research such as: Are there still undiscovered plant hormones? How can we identify novel signaling molecules? How can plants activate specific hormone responses in a tissue-specific manner? How can we modulate hormone responses in one developmental context without inducing detrimental effects on other processes? The chemical genomics approaches rely on the identification of small molecules modulating different biological processes and have recently identified active forms of plant hormones and molecules regulating many aspects of hormone synthesis, transport and response. We envision that the field of chemical genomics will continue to provide novel molecules able to elucidate specific aspects of hormone-mediated mechanisms. In addition, compounds blocking specific responses could uncover how complex biological responses are regulated. As we gain information about such compounds we can design small alterations to the chemical structure to further alter specificity, enhance affinity or modulate the activity of these compounds.

  13. Human, rat and chicken small intestinal Na+-Cl−-creatine transporter: functional, molecular characterization and localization

    PubMed Central

    Peral, M J; García-Delgado, M; Calonge, M L; Durán, J M; De La Horra, M C; Wallimann, T; Speer, O; Ilundáin, A A

    2002-01-01

    In spite of all the fascinating properties of oral creatine supplementation, the mechanism(s) mediating its intestinal absorption has(have) not been investigated. The purpose of this study was to characterize intestinal creatine transport. [14C]Creatine uptake was measured in chicken enterocytes and rat ileum, and expression of the creatine transporter CRT was examined in human, rat and chicken small intestine by reverse transcription-polymerase chain reaction, Northern blot, in situ hybridization, immunoblotting and immunohistochemistry. Results show that enterocytes accumulate creatine against its concentration gradient. This accumulation was electrogenic, Na+- and Cl−-dependent, with a probable stoichiometry of 2 Na+: 1 Cl−: 1 creatine, and inhibited by ouabain and iodoacetic acid. The kinetic study revealed a Km for creatine of 29 μm. [14C]Creatine uptake was efficiently antagonized by non-labelled creatine, guanidinopropionic acid and cyclocreatine. More distant structural analogues of creatine, such as GABA, choline, glycine, β-alanine, taurine and betaine, had no effect on intestinal creatine uptake, indicating a high substrate specificity of the creatine transporter. Consistent with these functional data, messenger RNA for CRT was detected only in the cells lining the intestinal villus. The sequences of partial clones, and of the full-length cDNA clone, isolated from human and rat small intestine were identical to previously cloned CRT cDNAs. Immunological analysis revealed that CRT protein was mainly associated with the apical membrane of the enterocytes. This study reports for the first time that mammalian and avian enterocytes express CRT along the villus, where it mediates high-affinity, Na+- and Cl−-dependent, apical creatine uptake. PMID:12433955

  14. Novel method to estimate solubility of small molecules in cis-polyisoprene by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Kikuchi, Hiroaki; Kuwajima, Satoru; Fukuda, Mitsuhiro

    2001-10-01

    A novel method to predict gas solubility in cis-1,4-polyisoprene is developed using molecular dynamics (MD) simulations under constant particle number, constant pressure and constant temperature (NPT) conditions. Analogous to the experimental sorption technique, the binary-phase model constructed of gas/polymer was prepared. In order to maintain external pressure of the whole system during long NPT-MD runs, the vapor phase was filled with virtual liquid which has no interaction with the gas molecules and has only a repulsive interaction with the polymer. After attaining equilibration of the system, the solubility of oxygen and carbon dioxide in the polymer phase were estimated in the temperature range from 273 K to 373 K by counting the number of gas molecules inside the polymer phase. The average solubility linearly increased with the increase in the external pressure, indicating that Henry's Law was satisfied. The solubility coefficient obtained from the present method showed good agreement with the experimental data. Concentration profiles of gas molecule showed that it was significantly higher near the interface than both in the gas phase and inside the polymer phase. The distinction between "adsorbed" and "absorbed" gas molecules and also their effect on the solubility was discussed.

  15. Evaluation of Three Small Molecular Drugs for Targeted Therapy to Treat Nonsmall Cell Lung Cancer

    PubMed Central

    Ni, Jun; Zhang, Li

    2016-01-01

    Objective: To guide the optimal selection among first-generation epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) in clinical practice. This review attempted to provide a thorough comparison among three first-generation EGFR-TKIs, namely icotinib, erlotinib, and gefitinib, with regard to their molecular structure, pharmacokinetic parameters, clinical data, adverse reactions, and contraindications. Data Sources: An electronic literature search of the PubMed database and Google Scholar for all the available articles regarding gefitinib, icotinib, and erlotinib in the English language from January 2005 to December 2014 was used. Study Selection: The search terms or keywords included but not limited to “lung cancer”, “nonsmall cell lung cancer (NSCLC)”, “epidemiology”, “EGFR”, “TKIs”, and “optimal selection”. Results: As suggested by this review, even though the three first-generation EGFR-TKIs share the quinazoline structure, erlotinib had the strongest apoptosis induction activity because of its use of a different side-chain. The pharmacokinetic parameters indicated that both erlotinib and icotinib are affected by food. The therapeutic window of erlotinib is narrow, and the recommended dosage is close to the maximum tolerable dosage. Icotinib enjoys a wider therapeutic window, and its concentration in the blood is within a safe dosage range even if it is administered with food. Based on multiple large-scale clinical trials, erlotinib is universally applied as the first-line treatment. In marked contrast, icotinib is available only in China as the second- or third-line therapeutic approach for treating advanced lung cancer. In addition, it exhibits a similar efficacy but better safety profile than gefitinib. Conclusions: Although there is a paucity of literature regarding whether icotinib is superior to erlotinib, its superior toxicity profile, noninferior efficacy, and lower cost indicate that it is a better alternative

  16. Reducing THMFP by H2O2/UV oxidation for humic acid of small molecular weight.

    PubMed

    Yen, Hsing Yuan; Yen, Li Shuang

    2015-01-01

    In this study, the merits of using H2O2/UV oxidation for reducing trihalomethane formation potential (THMFP), colour, and dissolved organic carbon (DOC) of smaller molecular humic acid were investigated, especially the energy consumption based on EEO. The results show that THMFP decreases by increasing oxidation time, H2O2 dose and UV intensity. The reaction constant in descending order is kColour>kDOC>kTHMFP. Furthermore, EEO shows three trends. First, it decreases as H2O2 dose increases. That is, by increasing the amount of H2O2 dose, the electrical energy efficiency becomes better. Second, EEO,9 W>EEO,13 W, implying that higher UV power would result in a higher electrical energy efficiency. Third, EEO,THMFP>EEO,DOC>EEO,colour. That is, the electric energy efficiency is the best for colour removal, second for DOC removal, and third for THMFP reduction. The operation costs for 90% removal of colour, DOC, and THMFP are from 0.31 to 0.69, from 0.78 to 1.72, and from 1.11 to 2.29 US$/m3, respectively. However, reducing THMs to Taiwan's drinking water standard of 80 µg/L needs only 0.25-0.60 US$/m3. Therefore, the condition with UV of 9 W, H2O2 of 50 mg/L, and oxidation time of 23 min can be applied for THMs reduction as the cost is the smallest of 0.25 US$/m3, even lower than current Taiwan's drinking water price of 0.3 US$/m3.

  17. Molecular imaging in small animals--roles for micro-CT.