WorldWideScience

Sample records for cell linear dichroism

  1. Linear dichroism and circular dichroism in photosynthesis research

    NARCIS (Netherlands)

    Garab, G.; Amerongen, van H.

    2009-01-01

    The efficiency of photosynthetic light energy conversion depends largely on the molecular architecture of the photosynthetic membranes. Linear- and circular-dichroism (LD and CD) studies have contributed significantly to our knowledge of the molecular organization of pigment systems at different lev

  2. Circular and linear dichroism of periodical helical media with large dielectric anisotropy

    CERN Document Server

    Arakelian, H M; Eritsyan, H S

    2000-01-01

    The interaction of light with a layer of periodical helical media is considered. Features of circular and linear dichroism at large dielectric anisotropy are studied. Influence of dielectric boundaries on circular and linear dichroism is investigated.

  3. Linear and Chiral Dichroism in the Electron Microscope

    CERN Document Server

    Schattschneider, Peter

    2012-01-01

    The growing interest in the miniaturization of magnetic storage media and the quest for novel spintronics applications rely on element specific detection of spin and orbital magnetic moments in a solid. The most sophisticated technique to reach this aim has been XMCD (X-ray magnetic circular dichroism), largely used in synchrotron beam lines. The spatial resolution limit of this technique is of the order of 20 - 50 nm. This poses a sensible limit for the study of nanostructured devices. This book describes EMCD (energy loss magnetic chiral dichroism), a phenomenon in energy loss spectroscopy d

  4. Magnetic x-ray linear dichroism of ultrathin Fe-Ni alloy films

    Energy Technology Data Exchange (ETDEWEB)

    Schumann, F.O.; Willis, R.F. [Pennsylvania State Univ., University Park, PA (United States); Goodman, K.W. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    The authors have studied the magnetic structure of ultrathin Fe-Ni alloy films as a function of Fe concentration by measuring the linear dichroism of the 3p-core levels in angle-resolved photoemission spectroscopy. The alloy films, grown by molecular-beam epitaxy on Cu(001) surfaces, were fcc and approximately four monolayers thick. The intensity of the Fe dichroism varied with Fe concentration, with larger dichroisms at lower Fe concentrations. The implication of these results to an ultrathin film analogue of the bulk Invar effect in Fe-Ni alloys will be discussed. These measurements were performed at the Spectromicroscopy Facility (Beamline 7.0.1) of the Advanced Light Source.

  5. Magnetic x-ray linear dichroism in resonant and non-resonant Gd 4f photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, S.; Gammon, W.J.; Pappas, D.P. [Virginia Commonwealth Univ., Richmond, VA (United States)] [and others

    1997-04-01

    The enhancement of the magnetic linear dichroism in resonant 4f photoemission (MLDRPE) is studied from a 50 monolayer film of Gd/Y(0001). The ALS at beamline 7.0.1 provided the source of linearly polarized x-rays used in this study. The polarized light was incident at an angle of 30 degrees relative to the film plane, and the sample magnetization was perpendicular to the photon polarization. The linear dichroism of the 4f core levels is measured as the photon energy is tuned through the 4d-4f resonance. The authors find that the MLDRPE asymmetry is strongest at the resonance. Near the threshold the asymmetry has several features which are out of phase with the fine structure of the total yield.

  6. Linear dichroism and optical anisotropy of silver nanoprisms in polymer films

    Science.gov (United States)

    Requena, S.; Doan, H.; Raut, S.; D'Achille, A.; Gryczynski, Z.; Gryczynski, I.; Strzhemechny, Y. M.

    2016-08-01

    We present optical studies of two different size distributions of silver triangular nanoprisms, one with a dipole resonance at 520 nm and the other with a dipole resonance at 650 nm, placed in different media. Significant wavelength-dependent depolarization of scattered light from the silver nanoprisms suspended in water indicates strong interference of multiple surface plasmon resonant modes in the same particle. We use this depolarization as a probe of light scattering by the nanoprisms in a lipid solution due to the rejection of a polarized background scattering. Also, the silver nanoprisms were embedded in a polyvinyl alcohol polymer matrix and oriented by stretching the polymer/nanoprism nanocomposite films. We observe significantly increased linear dichroism in the region associated with the plasmonic in-plane dipole mode upon stretching. Additionally, there is a weaker linear dichroism in the region associated with out-of-plane modes, which vanish in the extinction spectrum of the stretched nanocomposite film.

  7. Inversed linear dichroism in F K-edge NEXAFS spectra of fluorinated planar aromatic molecules

    DEFF Research Database (Denmark)

    de Oteyza, D. G.; Sakko, A.; El-Sayed, A.;

    2012-01-01

    orbitals with significant density of states on the fluorine atoms show different symmetry from those mainly located on C and N atoms. As a result, the angle-dependent linear dichroism in NEXAFS F K-edge spectra is inversed with respect to that in the C and N K-edges. In addition, the significant overlap...... in energy of π* and σ* orbitals throughout the F K-edge spectrum hampers its use for analysis of molecular orientations from angle-dependent NEXAFS measurements....

  8. Synchrotron radiation linear dichroism (SRLD) investigation of the electronictransitions of quinizarin, chrysazin, and anthrarufin

    DEFF Research Database (Denmark)

    Nguyen, Duy Duc; Jones, Nykola C.; Hoffmann, Søren Vrønning;

    2010-01-01

    The electronic transitions of the three , (alpha), (alphaPrime) -dihydroxy derivatives of anthraquinone, 1,4-dihydroxy-, 1,8-dihydroxy-, and 1,5-dihydroxy-9,10-anthraquinone (quinizarin, chrysazin, and anthrarufin), were investigated by synchrotron radiation linear dichroism (SRLD) spectroscopy...... the investigated region (15,000-58,000cm-1), essentially similar wavenumbers, intensities, and transition moment directions were determined for chrysazin and anthrarufin, while the spectrum of quinizarin deviated significantly. The results of time-dependent density functional theory (TD-DFT) calculations were...

  9. Determining Molecular Orientations in Disordered Materials from X-ray Linear Dichroism at the Iodine L1-Edge.

    Science.gov (United States)

    Palmer, Benjamin A; Collins, Stephen P; Hulliger, Jürg; Hughes, Colan E; Harris, Kenneth D M

    2016-12-21

    To demonstrate that measurements of X-ray linear dichroism are effective for determining bond orientations in disordered materials, we report the first observation of X-ray linear dichroism at the iodine L1-edge. The iodine-containing molecular solid studied in this work was the inclusion compound containing 4,4'-diiodobiphenyl guest molecules in the perhydrotriphenylene host structure. In this material, the guest substructure does not exhibit three-dimensional ordering, and thus diffraction-based techniques do not provide insights on the orientational properties of the guest molecules. Iodine L1-edge X-ray absorption spectra, recorded as a function of orientation of a single crystal of the material, exhibit significant dichroism (whereas no dichroism is observed at the iodine L2- and L3-edges). From quantitative analysis of the X-ray dichroism, the orientational properties of the C-I bonds within this material are established. The results pave the way for applying X-ray dichroism to determine molecular orientational properties of other materials, especially for partially ordered materials such as liquid crystals, confined liquids, and disordered crystalline phases, for which diffraction techniques may not be applicable.

  10. Theory for magnetic linear dichroism of electronic transitions between twofold-degenerate molecular spin levels

    Science.gov (United States)

    Bominaar, Emile L.; Achim, Catalina; Peterson, Jim

    1998-07-01

    Magnetic linear dichroism (MLD) spectroscopy is a relatively new technique which previously has been almost exclusively applied to atoms. These investigations have revealed that the study of MLD, in conjunction with electronic absorption and magnetic circular dichroism (MCD) spectroscopies, provides significant additional information concerning the electronic structure of atoms. More recent measurements have indicated that MLD is also observable from transition ions in inorganic compounds and metalloproteins. While the theory for atomic MLD has been worked out in considerable detail during the last two decades, an MLD theory of practical utility for the analysis of the spectra derived from the majority of paramagnetic molecules is not available. In the present contribution, the MLD of an electric-dipole-allowed transition between twofold-degenerate molecular spin levels is analyzed, assuming nonsaturating conditions. As for atomic systems, it is found that the MLD of a single molecule is dominated by the term G0. However, this term vanishes in the powder average evaluated for a randomly oriented ensemble of molecules, leading to a drastic reduction of the MLD differential absorption for systems with spin S=1/2 compared to that observed for systems with higher ground-state spin. It is found that MLD and MCD spectroscopies on solution samples have complementary spin-state specific sensitivities which suggest that the two methods can be used to selectively probe the individual metal sites in multicenter metalloprotein assemblies.

  11. In situ azimuthal rotation device for linear dichroism measurements in scanning transmission x-ray microscopy

    Science.gov (United States)

    Hernández-Cruz, D.; Hitchcock, A. P.; Tyliszczak, T.; Rousseau, M.-E.; Pézolet, M.

    2007-03-01

    A novel miniature rotation device used in conjunction with a scanning transmission x-ray microscope is described. It provides convenient in situ sample rotation to enable measurements of linear dichroism at high spatial resolution. The design, fabrication, and mechanical characterization are presented. This device has been used to generate quantitative maps of the spatial distribution of the orientation of proteins in several different spider and silkworm silks. Specifically, quantitative maps of the dichroic signal at the C 1s→π*amide transition in longitudinal sections of the silk fibers give information about the spatial orientation, degree of alignment, and spatial distribution of protein peptide bonds. A new approach for analyzing the dichroic signal to extract orientation distributions, in addition to magnitudes of aligned components, is presented and illustrated with results from Nephila clavipes dragline spider silk measured using the in situ rotation device.

  12. Electronic states of the fluorophore 9,10-bis(phenylethynyl)anthracene (BPEA). A synchrotron radiation linear dichroism investigation

    DEFF Research Database (Denmark)

    Thulstrup, Peter Waaben; Jones, Nykola; Hoffmann, Søren Vrønning

    2013-01-01

    The electronic transitions of 9,10-bis(phenylethynyl)anthracene (BPEA) were investigated by synchrotron radiation linear dichroism (SRLD) spectroscopy in the range 20000–58000 cm1 (500–170 nm) on molecular samples aligned in stretched polyethylene. The investigation was supported by variable...

  13. Soft-x-ray linear-dichroism and magnetic-circular-dichroism studies of CeRh3B2: Large crystal-field splitting and anomalous ferromagnetism

    Science.gov (United States)

    Yamaguchi, K.; Namatame, H.; Fujimori, A.; Koide, T.; Shidara, T.; Nakamura, M.; Misu, A.; Fukutani, H.; Yuri, M.; Kasaya, M.; Suzuki, H.; Kasuya, T.

    1995-05-01

    CeRh3B2 shows an anomalously high Curie temperature (Tc=115 K) for a Ce compound with nonmagnetic constituents, strong anisotropy in the magnetic susceptibility, and ferromagnetic ordering. We have studied its electronic structure by measuring linear dichroism (LD) and magnetic circular dichroism (MCD) in the Ce 4d core-level x-ray-absorption spectra. The result for LD indicates a highly anisotropic distribution of Ce 4f electrons along the hexagonal c axis, while the MCD result shows that the magnetic moment of the Ce 4f electron is dominated by the orbital moment as in the case of a small crystal field. Using the Anderson-impurity model including the axial crystal field, the strong interatomic Ce 4f-Ce 5d hybridization and the Ce 4f-Rh 4d hybridization, we show that there is a range of parameter sets for the axial crystal field and the Ce 4f-valence-band transfer integral which explains the results of the LD and MCD experiments. Using the same parameter set, we have also attempted to explain the Kondo temperature and the unusually high Curie temperature.

  14. Combined SERS and flow linear dichroism approach to monitoring the interaction of pharmaceuticals with their target

    Science.gov (United States)

    Ianoul, Anatoli I.; Fleury, Fabrice; Duval, Olivier; Jardillier, Jean-Claude; Alix, Alain J.; Nabiev, Igor R.

    1999-04-01

    Surface-Enhanced Raman Scattering (SERS) spectroscopy and Flow Linear Dichroism (FLD) technique have been employed to study the anticancer agent fagaronine and its derivative ethoxidine - double inhibitors of DNA topoisomerases I and II. Cooperative use of two methods permitted (i) to determine the molecular determinants of the drug-DNA interactions; (ii) to monitor in real time the process of topo I inhibition by these anticancer agents. FLD technique allowed us to identify the mode of drug interactions with the DNA as a 'major groove intercalation' and to determine orientation of the drugs chromophores within the complexes. Using SERS spectroscopy we have determined the drugs molecular determinants interacting with the DNA. FLD was also used for real time monitoring of the process of sc DNA relaxation by topo I and of inhibition of relaxation with the pharmaceuticals. Ethoxidine was found to exhibit the same activity of inhibition of sc DNA relaxation as fagaronine at the 10-fold less concentration. The proposed SERS-FLD combined approach demonstrates the new perspectives for screening new pharmaceuticals due to its relative simplicity and low expense, high sensitivity and selectivity, and, finally, possibility of real-time monitoring of the structure-function correlation within the series of drug derivatives.

  15. Theory of Kerr and Faraday rotations and linear dichroism in Topological Weyl Semimetals.

    Science.gov (United States)

    Kargarian, Mehdi; Randeria, Mohit; Trivedi, Nandini

    2015-08-03

    We consider the electromagnetic response of a topological Weyl semimetal (TWS) with a pair of Weyl nodes in the bulk and corresponding Fermi arcs in the surface Brillouin zone. We compute the frequency-dependent complex conductivities σαβ(ω) and also take into account the modification of Maxwell equations by the topological θ-term to obtain the Kerr and Faraday rotations in a variety of geometries. For TWS films thinner than the wavelength, the Kerr and Faraday rotations, determined by the separation between Weyl nodes, are significantly larger than in topological insulators. In thicker films, the Kerr and Faraday angles can be enhanced by choice of film thickness and substrate refractive index. We show that, for radiation incident on a surface with Fermi arcs, there is no Kerr or Faraday rotation but the electric field develops a longitudinal component inside the TWS, and there is linear dichroism signal. Our results have implications for probing the TWS phase in various experimental systems.

  16. A new highly adaptable design of shear-flow device for orientation of macromolecules for Linear Dichroism (LD) measurement

    KAUST Repository

    Lundahl, P. Johan

    2011-01-01

    This article presents a new design of flow-orientation device for the study of bio-macromolecules, including DNA and protein complexes, as well as aggregates such as amyloid fibrils and liposome membranes, using Linear Dichroism (LD) spectroscopy. The design provides a number of technical advantages that should make the device inexpensive to manufacture, easier to use and more reliable than existing techniques. The degree of orientation achieved is of the same order of magnitude as that of the commonly used concentric cylinders Couette flow cell, however, since the device exploits a set of flat strain-free quartz plates, a number of problems associated with refraction and birefringence of light are eliminated, increasing the sensitivity and accuracy of measurement. The device provides similar shear rates to those of the Couette cell but is superior in that the shear rate is constant across the gap. Other major advantages of the design is the possibility to change parts and vary sample volume and path length easily and at a low cost. © 2011 The Royal Society of Chemistry.

  17. Linear dichroism studies of tryptophanase and its quasisubstrate complexes oriented in polyacrylamide gel.

    Science.gov (United States)

    Zakomirdina, L N; Sakharova, I S; Torchinsky, Y M

    1990-10-01

    Tryptophanase from Escherichia coli was oriented in a compressed slab of polyacrylamide gel and its linear dichroism (LD) and absorption spectra have been measured. The free enzyme displays four LD bands at 305, 340, 425 and 490 nm. Two bands at 340 and 425 nm belong to the internal coenzyme-lysine aldimine. The 305-nm band apparently belongs to an aromatic amino acid residue. The 490-nm band disappears after treatment with NaBH4 or after incubation with L-alanine and subsequent dialysis. It is suggested that the 490-nm band belongs to a quinonoid enzyme subform. The reaction of tryptophanase with threo-3-phenyl-DL-serine, L-threonine and D-alanine leads to formation of an external aldimine with an intense absorption band at 420-425 nm. The values of reduced LD (delta A/A) in this band strongly differ from that in the 420-nm band of the free enzyme. The LD value of the complex with D-alanine is intermediate between those of the free enzyme and the complex with 3-phenylserine. In the presence of indole the complex with D-alanine displays the same LD as that observed with 3-phenylserine. The reaction of tryptophanase with L-alanine or oxindolyl-L-alanine leads to formation of a quinonoid intermediate with an absorption band near 500 nm. The LD value in this band is close to that of an external aldimine with L-threonine. It is concluded that reorientations of the coenzyme occur in the course of the tryptophanase reaction.

  18. Linear birefringence and dichroism in citric acid coated Fe{sub 3}O{sub 4} magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Jing-Fung, E-mail: jacklin@cc.feu.edu.tw [Graduate School of Computer Application Engineering, Far East University, No. 49, Zhonghua Road, Xinshi District, Tainan, Taiwan, ROC (China); Tsai, Chun-Chin [Department of Optoelectronic Engineering, Far East University, No. 49, Zhonghua Road, Xinshi District, Tainan, Taiwan, ROC (China); Lee, Meng-Zhe [Graduate School of Computer Application Engineering, Far East University, No. 49, Zhonghua Road, Xinshi District, Tainan, Taiwan, ROC (China)

    2014-12-15

    To prepare highly dispersed water-based Fe{sub 3}O{sub 4} magnetic nanoparticles (MNPs), we adopted the co-precipitation method and used citric acid (CA) as the surfactant. Via transmission electronic microscopy, dynamic light scattering, and X-ray diffractometry, we characterized the dispersibility and size of the products. Through two single-parameter experiments, including the pH value of suspension and the action of double centrifugations, the appropriate parameters' values were determined. Further, to produce CA coated MNPs with good magneto-optical properties as high retardance and low dichroism, the orthogonal design method was used to find the optimal parameters' values, including pH value of suspension after coating was 5, molar ratio of CA to Fe{sub 3}O{sub 4} MNPs was 0.06, volume of CA was 40 ml, and coating temperature was 70 °C. Above all, the linear birefringence and dichroism of the best CA coated ferrofluid we produced were measured by a Stokes polarimeter as 23.6294° and 0.3411 under 64.5 mT, respectively. Thus, the biomedical applications could be performed hereafter. - Highlights: • We examine pH changes about retardance/dichroism of citric acid coated ferrofluid. • We examine centrifugal action about dispersity of citric acid coated ferrofluid. • Dispersity of coated suspensions with different pH is investigated by DLS results. • Optimum combination and influence sequence obtained by Taguchi method is found. • Molar ratio of CA to Fe{sub 3}O{sub 4} deeply influences the retardance and dichroism of FFs.

  19. Domain imaging on multiferroic BiFeO{sub 3}(001) by linear and circular dichroism in threshold photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Sander, Anke; Christl, Maik [Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle(Saale) (Germany); Chiang, Cheng-Tien [Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle(Saale) (Germany); Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle(Saale) (Germany); Alexe, Marin [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Widdra, Wolf, E-mail: wolf.widdra@physik.uni-halle.de [Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Von-Danckelmann-Platz 3, 06120 Halle(Saale) (Germany); Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle(Saale) (Germany)

    2015-12-14

    We demonstrate ferroelectric domain imaging at BiFeO{sub 3}(001) single crystal surfaces with laser-based threshold photoemission electron microscopy (PEEM). Work function differences and linear dichroism allow for the identification of the eight independent ferroelectric domain configurations in the PEEM images. There, the determined domain structure is consistent with piezoresponse force microscopy of the sample surface and can also be related to the circular dichroic PEEM images. Our results provide a method for efficient mapping of complex ferroelectric domains with laser-excited PEEM and may allow lab-based time-resolved studies of the domain dynamics in the future.

  20. Investigation of chromophore-chromophore interaction by electro-optic measurements, linear dichroism, x-ray scattering, and density-functional calculations

    DEFF Research Database (Denmark)

    Apitz, Dirk; Bertram, R.P.; Benter, N.;

    2005-01-01

    Free-beam interferometry and angle-resolved absorption spectra are used to investigate the linear electro-optic coefficients and the linear dichroism in photoaddressable bis-azo copolymer thin films. From the first- and second order parameters deduced, the chromophore orientation distribution is ...

  1. Linear Dichroism of Cyanine Dyes in Stretched Polyvinyl Alcohol Films: A Physical Chemistry Laboratory Experiment.

    Science.gov (United States)

    Natarajan, L. V.; And Others

    1983-01-01

    Provides background information, procedures, and results of an undergraduate physical chemistry experiment on the polarization of absorption spectra of cyanine dyes in stretched polyvinyl alcohol films. The experiment gives a simple demonstration of the concept of linear dichromism and the validity of the TEM method used in the analyses. (JN)

  2. Structural analysis of RecA protein-DNA complexes by fluorescence-detected linear dichroism: absence of structural change of filament for pairing of complementary DNA strands.

    Science.gov (United States)

    Morimatsu, Katsumi; Takahashi, Masayuki

    2006-11-15

    We have developed a simple measuring system for fluorescence-detected linear dichroism and applied it to the structural analysis of the RecA-DNA complex filaments, which are intermediates of the homologous recombination reaction. Taking advantage of the selectivity of fluorescence signals, we distinguished the linear dichroism signals of ethidium bromide and tryptophan residues in the RecA-DNA-ethidium bromide complex, whereas the conventional (absorption-detected) linear dichroism measurement provides only the sum of the signals because signals overlap each other and that of DNA. We further observed that the tryptophan residue at position 290 of RecA in the RecA-DNA-adenosine-5'-O-(3-thiotriphosphate) complex was oriented parallel to the long axis of the filament, in good agreement with the previous site-specific linear dichroism analysis, and that this orientation was not significantly modified by the pairing of the complementary DNA strand. These results suggest that the pairing reaction occurs without a large structural change of the RecA filament.

  3. Molecular and vibrational structure of diphenylether and its 4,4' -dibromo derivative. Infrared linear dichroism spectroscopy and density functional theory calculations

    DEFF Research Database (Denmark)

    Eriksen, Troels K; Karlsen, Eva; Spanget-Larsen, Jens

    2015-01-01

    The title compounds were investigated by means of Linear Dichroism (LD) IR spectroscopy on samples partially aligned in uniaxially stretched low-density polyethylene and by density functional theory calculations. Satisfactory overall agreement between observed and calculated vibrational wavenumbe...... and IR intensities are obtained, allowing a fairly detailed assignment of the observed transitions in terms of individual nuclear motions....

  4. Itinerant and localized magnetic moments in ferrimagnetic Mn{sub 2}CoGa thin films identified with x-ray magnetic linear dichroism: experiment and ab initio theory

    Energy Technology Data Exchange (ETDEWEB)

    Meinert, M.; Schmalhorst, J; Klewe, C.; Reiss, G.; Arenholz, E.; Bohnert, T.; Nielsch, K.

    2011-08-08

    Epitaxial thin films of the half-metallic X{sub a}-compound Mn{sub 2}CoGa (Hg{sub 2}CuTi prototype) were prepared by dc magnetron co-sputtering with different heat treatments on MgO (001) substrates. High-quality lms with a bulk magnetization of 1.95(5) {mu}{sub }B per unit cell were obtained. The average Mn magnetic moment and the Co moment are parallel, in agreement with theory. The x-ray magnetic circular dichroism spectra agree with calculations based on density functional theory and reveal the antiparallel alignment of the two inequivalent Mn moments. X-ray magnetic linear dichroism allows to distinguish between itinerant and localized Mn moments. It is shown that one of the two Mn moments has localized character, whereas the other Mn moment and the Co moment are itinerant.

  5. Structure of human Rad51 protein filament from molecular modeling and site-specific linear dichroism spectroscopy

    KAUST Repository

    Reymer, A.

    2009-07-08

    To get mechanistic insight into the DNA strand-exchange reaction of homologous recombination, we solved a filament structure of a human Rad51 protein, combining molecular modeling with experimental data. We build our structure on reported structures for central and N-terminal parts of pure (uncomplexed) Rad51 protein by aid of linear dichroism spectroscopy, providing angular orientations of substituted tyrosine residues of Rad51-dsDNA filaments in solution. The structure, validated by comparison with an electron microscopy density map and results from mutation analysis, is proposed to represent an active solution structure of the nucleo-protein complex. An inhomogeneously stretched double-stranded DNA fitted into the filament emphasizes the strategic positioning of 2 putative DNA-binding loops in a way that allows us speculate about their possibly distinct roles in nucleo-protein filament assembly and DNA strand-exchange reaction. The model suggests that the extension of a single-stranded DNA molecule upon binding of Rad51 is ensured by intercalation of Tyr-232 of the L1 loop, which might act as a docking tool, aligning protein monomers along the DNA strand upon filament assembly. Arg-235, also sitting on L1, is in the right position to make electrostatic contact with the phosphate backbone of the other DNA strand. The L2 loop position and its more ordered compact conformation makes us propose that this loop has another role, as a binding site for an incoming double-stranded DNA. Our filament structure and spectroscopic approach open the possibility of analyzing details along the multistep path of the strand-exchange reaction.

  6. Calculation of Linear Dichroism in the Ce 4d-Core XAS and 4f Electronic State of CeRh3B2

    Science.gov (United States)

    Jo, Takeo; Imada, Shin

    1990-07-01

    Linear dichroism in Ce 4d-core photoabsorption for CeRh3B2 with a hexagonal structure is discussed on the basis of an impurity Anderson model. The model takes into account the hybridization between the 4f orbit and conduction band states, multiplets arising from electrostatic interactions between electrons and crystalline anisotropy. In the paramagnetic state of the compound, the difference in the multiplet structure of 4d XAS is calculated between two incident beams with polarizations parallel and perpendicular to the c-axis with varying the crystalline field to increase the occupancy of the 4f state with the azimuthal quantum number m{=}0. The result shows that the dichroism is a promising characteristic to check recent theoretical predictions on the occupancy of the 4f state with m{=}0 in CeRh3B2 and therefore, to measure the crystal anisotropy.

  7. Giant crystal field and ferromagnetism in the Kondo system CeRh3B2: Soft-x-ray linear-dichroism study

    Science.gov (United States)

    Yamaguchi, K.; Namatame, H.; Hase, I.; Fujimori, A.; Misu, A.; Kasaya, M.; Kasuya, T.

    1992-10-01

    We have studied the electronic structure of CeRh3B2, which has an anomalously high ferromagnetic ordering temperature, by linear dichroism in the Ce 4d core-level x-ray-absorption spectra. The result indicates an unusually large axial crystal field of order 0.1-0.2 eV along the hexagonal c axis. We propose a possible origin of the giant crystal field and the anomalous ferromagnetism in terms of the strong interatomic Ce 4f-Ce 5d hybridization.

  8. Measuring circular dichroism in a capillary cell using the b23 synchrotron radiation CD beamline at diamond light source.

    Science.gov (United States)

    Jávorfi, Tamás; Hussain, Rohanah; Myatt, Daniel; Siligardi, Giuliano

    2010-01-01

    Synchrotron radiation circular dichroism (SRCD) is a well-established method in structural biology. The first UV-VIS beamline dedicated to circular dichroism at Diamond Light Source, a third generation synchrotron facility in South Oxfordshire, has recently become operational and it is now available for the user community. Herein we present an important application of SRCD: the CD measurement of protein solutions in fused silica rectangular capillary cells. This was achieved without the use of any lens between the photoelastic modulator and the photomultiplier tube detectors by exploiting the high photon flux of the collimated beam that can be as little as half a millimeter squared. Measures to minimize or eliminate vacuum-UV protein denaturation effects are discussed. The CD spectra measured in capillaries is a proof of principle to address CD measurements in microdevice systems using the new B23 SRCD beamline.

  9. The vibrational structure of (E,E’)-1,4-diphenyl-1,3-butadiene. Linear dichroism FTIR spectroscopy and quantum chemical calculations

    DEFF Research Database (Denmark)

    Hansen, Bjarke Knud Vilster; Møller, Søren; Spanget-Larsen, Jens

    2006-01-01

    The title compound (DPB) was investigated by FTIR spectroscopy in liquid solutions and by FTIR linear dichroism (LD) measurements on samples aligned in stretched polyethylene. The LD data provided experimental assignments of molecular transition moment directions and vibrational symmetries for more...... than 40 vibrational transitions. The observed IR wavenumbers, relative intensities, and polarization directions were generally well reproduced by the results of a harmonic analysis based on B3LYP/cc-pVTZ density functional theory (DFT). The combined experimental and theoretical results led to proposal...... of a nearly complete assignment of the IR active fundamentals of DPB, involving reassignment of a number of transitions. In addition, previously published Raman spectra of DPB were well predicted by the B3LYP/cc-pVTZ calculations....

  10. X-ray natural linear dichroism of graphitic materials across the carbon K-edge: Correction for perturbing high-order harmonics

    Science.gov (United States)

    Jansing, C.; Mertins, H. C.; Gaupp, A.; Sokolov, A.; Gilbert, M. C.; Wahab, H.; Timmers, H.

    2016-05-01

    Reflectivity measurements on graphitic materials such as graphene at energies across the carbon K-edge are frustrated by significant intensity loss due to adventitious carbon on beamline mirrors. Such intensity reduction enhances effects due to perturbing high-order harmonics in the beam. These effects distort the actual structure of the reflectance curve. In order to overcome this limitation, a correction technique has been developed and demonstrated first with measurements for highly ordered pyrolytic graphite. The same approach may be applied to other graphitic materials such as graphene and it may be used with other synchrotron beamlines. The fraction of high-order harmonics was determined by passing the incident beam through a 87 nm thin silicon nitride absorber that can be well modeled. Using the corrected measurements the x-ray natural linear dichroism of the sample has been determined.

  11. Linearity Testing of Photovoltaic Cells

    Energy Technology Data Exchange (ETDEWEB)

    Pinegar, S.; Nalley, D.; Emery, K.

    2006-01-01

    Photovoltaic devices are rated in terms of their power output or efficiency with respect to a specific spectrum, total irradiance, and temperature. In order to rate photovoltaic devices, a reference detector whose response is linear with total irradiance is needed. This procedure documents a procedure to determine if a detector is linear over the irradiance range of interest. Testing the short circuit current versus the total irradiance is done by illuminating a reference cell candidate with two lamps that are fitted with programmable filter wheels. The purpose is to reject nonlinear samples as determined by national and international standards from being used as primary reference cells. A calibrated linear reference cell tested by the two lamp method yields a linear result.

  12. Photo-physics study of an hydroxy-quinoline derivative as inhibitor of Pim-1 kinase: ultraviolet-visible linear dichroism spectroscopy and quantum chemical calculations.

    Science.gov (United States)

    Lamhasni, T; Ait Lyazidi, S; Hnach, M; Haddad, M; Desmaële, D; Spanget-Larsen, J; Nguyen, D D; Ducasse, L

    2013-09-01

    The photophysical properties of the antiviral 7-nicotinoyl-styrylquinoline (MB96) were investigated by means of UV-Vis linear dichroism (LD) spectroscopy on molecular samples aligned in stretched polyvinylalcohol (PVA), supported by time dependent density functional theory (TD-DFT) calculations. Experimentally, the directions of the transitions moments with respect to the long axis of the molecule were deduced from the orientation K factors, determined by means of "trial-and-error" procedure. The absorption spectrum presents two parts. The main transition in the lowest energy part, observed around 365 nm and showing the highest K value 0.8, is longitudinally in-plane polarized. The highest energy part which is extended between 230 and 320 nm, large, diffuse, and of weak intensity, shows estimated K values between 0.2 and 0.5. This complex structure is transversally polarized with some contamination by the longitudinal character of the first strong band. The TD-DFT results agree fairly well with the LD measurements.

  13. Towards an exact theory of linear absorbance and circular dichroism of pigment-protein complexes: Importance of non-secular contributions

    Energy Technology Data Exchange (ETDEWEB)

    Dinh, Thanh-Chung; Renger, Thomas, E-mail: thomas.renger@jku.at [Institut für Theoretische Physik, Johannes Kepler University Linz, Altenberger Str. 69, 4040 Linz (Austria)

    2015-01-21

    A challenge for the theory of optical spectra of pigment-protein complexes is the equal strength of the pigment-pigment and the pigment-protein couplings. Treating both on an equal footing so far can only be managed by numerically costly approaches. Here, we exploit recent results on a normal mode analysis derived spectral density that revealed the dominance of the diagonal matrix elements of the exciton-vibrational coupling in the exciton state representation. We use a cumulant expansion technique that treats the diagonal parts exactly, includes an infinite summation of the off-diagonal parts in secular and Markov approximations, and provides a systematic perturbative way to include non-secular and non-Markov corrections. The theory is applied to a model dimer and to chlorophyll (Chl) a and Chl b homodimers of the reconstituted water-soluble chlorophyll-binding protein (WSCP) from cauliflower. The model calculations reveal that the non-secular/non-Markov effects redistribute oscillator strength from the strong to the weak exciton transition in absorbance and they diminish the rotational strength of the exciton transitions in circular dichroism. The magnitude of these corrections is in a few percent range of the overall signal, providing a quantitative explanation of the success of time-local convolution-less density matrix theory applied earlier. A close examination of the optical spectra of Chl a and Chl b homodimers in WSCP suggests that the opening angle between Q{sub y} transition dipole moments in Chl b homodimers is larger by about 9{sup ∘} than for Chl a homodimers for which a crystal structure of a related WSCP complex exists. It remains to be investigated whether this change is due to a different mutual geometry of the pigments or due to the different electronic structures of Chl a and Chl b.

  14. Non linear behaviour of cell tensegrity models

    Science.gov (United States)

    Alippi, A.; Bettucci, A.; Biagioni, A.; Conclusio, D.; D'Orazio, A.; Germano, M.; Passeri, D.

    2012-05-01

    Tensegrity models for the cytoskeleton structure of living cells is largely used nowadays for interpreting the biochemical response of living tissues to mechanical stresses. Microtubules, microfilaments and filaments are the microscopic cell counterparts of struts (microtubules) and cables (microfilaments and filaments) in the macroscopic world: the formers oppose to compression, the latters to tension, thus yielding an overall structure, light and highly deformable. Specific cell surface receptors, such as integrins, act as the coupling elements that transmit the outside mechanical stress state into the cell body. Reversible finite deformations of tensegrity structures have been widely demonstrated experimentally and in a number of living cell simulations. In the present paper, the bistability behaviour of two general models, the linear bar oscillator and the icosahedron, is studied, as they are both obtained from mathematical simulation, the former, and from larger scale experiments, the latter. The discontinuity in the frequency response of the oscillation amplitude and the lateral bending of the resonance curves are put in evidence, as it grows larger as the driving amplitude increases, respectively.

  15. Direct surface magnetometry with photoemission magnetic x-ray dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J.G.; Goodman, K.W. [Lawrence Berkeley National Lab., CA (United States); Schumann, F.O. [Pennsylvania State Univ., University Park, PA (United States)] [and others

    1997-04-01

    Element specific surface magnetometry remains a central goal of synchrotron radiation based studies of nanomagnetic structures. One appealing possibility is the combination of x-ray absorption dichroism measurements and the theoretical framework provided by the {open_quotes}sum rules.{close_quotes} Unfortunately, sum rule analysis are hampered by several limitations including delocalization of the final state, multi-electronic phenomena and the presence of surface dipoles. An alternative experiment, Magnetic X-Ray Dichroism in Photoelectron Spectroscopy, holds out promise based upon its elemental specificity, surface sensitivity and high resolution. Computational simulations by Tamura et al. demonstrated the relationship between exchange and spin orbit splittings and experimental data of linear and circular dichroisms. Now the authors have developed an analytical framework which allows for the direct extraction of core level exchange splittings from circular and linear dichroic photoemission data. By extending a model initially proposed by Venus, it is possible to show a linear relation between normalized dichroism peaks in the experimental data and the underlying exchange splitting. Since it is reasonable to expect that exchange splittings and magnetic moments track together, this measurement thus becomes a powerful new tool for direct surface magnetometry, without recourse to time consuming and difficult spectral simulations. The theoretical derivation will be supported by high resolution linear and circular dichroism data collected at the Spectromicroscopy Facility of the Advanced Light Source.

  16. Transient vibrational circular dichroism spectrometer: technical development

    Directory of Open Access Journals (Sweden)

    Helbing J.

    2010-06-01

    Full Text Available We recently reported the first measurements of transient VCD in the C-H-stretch region following visible excitation of cobalt(--spartein complex (Co(spCl2 with picosecond time resolution [1]. This poster presents the detailed description of the setup based on the synchronization of a femtosecond laser system with a photo elastic modulator [2]. A very precise control of the probe pulse polarization is a requirement to avoid linear dichroism artefacts. This is particularly important in crossed polarizer “quasi-null” technique which can be used to significantly enhance chiral signals [3].

  17. Zero-Field Dichroism in the Solar Chromosphere

    CERN Document Server

    Sainz, R M

    2003-01-01

    We explain the linear polarization of the Ca II infrared triplet observed close to the edge of the solar disk. In particular, we demonstrate that the physical origin of the enigmatic polarizations of the 866.2 nm and 854.2 nm lines lies in the existence of atomic polarization in their metastable lower levels, which produces differential absorption of polarization components (dichroism). To this end, we have solved the problem of the generation and transfer of polarized radiation by taking fully into account all the relevant optical pumping mechanisms in multilevel atomic models. We argue that `zero-field' dichroism may be of great diagnostic value in astrophysics.

  18. Photoelectron circular dichroism of isopropanolamine

    Science.gov (United States)

    Catone, D.; Turchini, S.; Contini, G.; Prosperi, T.; Stener, M.; Decleva, P.; Zema, N.

    2017-01-01

    Spectroscopies based on circular polarized light are sensitive to the electronic and structural properties of chiral molecules. Photoelectron circular dichroism (PECD) is a powerful technique that combines the chiral sensitivity of the circular polarized light and the electronic information obtained by photoelectron spectroscopy. An experimental and theoretical PECD study of the outer valence and C 1s core states of 1-amino-2-propanol in the gas phase is presented. The experimental dichroic dispersions in the photoelectron kinetic energy are compared with theoretical calculations employing a multicentric basis set of B-spline functions and a Kohn-Sham Hamiltonian. In order to understand analogies and differences in the dichroism of structural isomers bearing the same functional groups, a comparison with previous PECD study of valence band of 2-amino-1-propanol is carried out.

  19. Linear aggregation theory in cell biology

    Energy Technology Data Exchange (ETDEWEB)

    Hill, T.L.

    1987-01-01

    This is an account of the theory, probability, and thermodynamics of linear aggregation. The emphasis is on basic principles illustrated by simple models, not on particular applications or polymers. The general physical aggregate systems - attached single-stranded polymers, single-stranded polymers modified by a second component, long multistranded polymers, attached multistranded polymers - are given extensive treatment. Also included are a discussion of the GTPase and ATPase activity accompanying the aggregation of microtubules and action, and the properties of the kinetic two-phase model of the end of a microtubule.

  20. Anisotropic elliptical dichroism and influence of imperfection of circular polarization upon anisotropic circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Wakabayashi, Masamitsu [Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501 (Japan); RIKEN, Research Cluster for Innovation, Nakamura Lab, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Yokojima, Satoshi, E-mail: yokojima@toyaku.ac.jp [Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachiouji-shi, Tokyo 192-0392 (Japan); RIKEN, Research Cluster for Innovation, Nakamura Lab, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Fukaminato, Tuyoshi [Research Institute for Electronic Science, Hokkaido University, N20, W10, Kita-ku, Sapporo 001-0020 (Japan); PRESTO, Japan Science and Technology Agency (JST), Sanbancho, Chiyoda-ku, Tokyo 102-0075 (Japan); Ohtani, Hiroyuki [Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8501 (Japan); Nakamura, Shinichiro, E-mail: snakamura@riken.jp [RIKEN, Research Cluster for Innovation, Nakamura Lab, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)

    2015-04-21

    In spite of the importance of anisotropic circular dichroism, in practice, it is difficult to get rid of the artifacts that arise from the imperfection of the circular polarization. Undesirable linear dichroism, interference of two orthogonal polarization states, and linear birefringence prevent us from making accurate measurements. We propose a theoretical method for evaluating the contributions of the first two, which are thought to be the main artifacts when specimens are not thick enough. Using the time-dependent perturbation theory and taking into account the direction of light propagation toward an orientationally fixed molecule, we formulated the transition probability of systems perturbed by arbitrarily polarized light and the absorption difference associated with two kinds of polarized light. We also formulated, as an extension of the dissymmetry factor of circular dichroism, a newly defined dissymmetry factor associated with two arbitrary polarization states. Furthermore, we considered a mixed-state of photon ensemble in which polarization states distribute at a certain width around a certain average. Although the purity of polarization and ellipticity does not correspond immediately, by considering the mixed state it is possible to treat them consistently. We used quantum statistical mechanics to describe the absorption difference for two kinds of photon ensembles and applied the consequent formula to examine the reported experimental results of single-molecule chiroptical responses under discussion in the recent past. The artifacts are theoretically suggested to be sensitive to the incident direction of elliptically polarized light and to the oriented systems, the ellipticity, and the orientation of ellipse. The mixed state has little, if any, effect when the polarization state distribution is narrow.

  1. Controllability analysis of decentralised linear controllers for polymeric fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Serra, Maria; Aguado, Joaquin; Ansede, Xavier; Riera, Jordi [Institut de Robotica i Informatica Industrial, Universitat Politecnica de Catalunya - Consejo Superior de Investigaciones Cientificas, C. Llorens i Artigas 4, 08028 Barcelona (Spain)

    2005-10-10

    This work deals with the control of polymeric fuel cells. It includes a linear analysis of the system at different operating points, the comparison and selection of different control structures, and the validation of the controlled system by simulation. The work is based on a complex non linear model which has been linearised at several operating points. The linear analysis tools used are the Morari resiliency index, the condition number, and the relative gain array. These techniques are employed to compare the controllability of the system with different control structures and at different operating conditions. According to the results, the most promising control structures are selected and their performance with PI based diagonal controllers is evaluated through simulations with the complete non linear model. The range of operability of the examined control structures is compared. Conclusions indicate good performance of several diagonal linear controllers. However, very few have a wide operability range. (author)

  2. Simulation of magnetic circular dichroism in the electron microscope

    Science.gov (United States)

    Rubino, Stefano; Schattschneider, Peter; Rusz, Jan; Verbeeck, Johan; Leifer, Klaus

    2010-12-01

    As electron energy-loss spectroscopy (EELS) and x-ray absorption spectroscopy (XAS) probe the same transitions from core-shell states to unoccupied states above the Fermi energy, it should always be possible to apply the two techniques to the same physical phenomena, such as magnetic dichroism, and obtain the same information. Indeed, the similarity in the expression of the electron and x-ray cross-sections had been already exploited to prove the equivalence of x-ray magnetic linear dichroism and anisotropy in EELS, by noting that the polarization vector of a photon plays the same role as the momentum transfer in electron scattering. Recently, the same was proven true for x-ray magnetic circular dichroism (XMCD) by establishing a new TEM technique called EMCD (electron energy-loss magnetic chiral dichroism) (Schattschneider P et al 2006 Nature 441 486-8), which makes use of special electron scattering conditions to force the absorption of a circularly polarized virtual photon. The intrinsic advantage of EMCD over XMCD is the high spatial resolution of electron microscopes, which are readily available. Among the particular obstacles in EMCD that do not exist for synchrotron radiation, is the notoriously low signal and the very particular scattering conditions necessary to observe a chiral dichroic signal. In spite of that, impressive progress has been made in recent years. The signal strength could be considerably increased, and some innovations such as using a convergent beam have been introduced. EMCD has evolved into several techniques, which make full use of the versatility of the TEM and energy filtering, spectroscopy or STEM conditions (Rubino S 2007 Magnetic circular dichroism in the transmission electron microscope PhD Thesis Vienna University of Technology, Vienna, Austria).

  3. Magnetic x-ray dichroism in ultrathin epitaxial films

    Energy Technology Data Exchange (ETDEWEB)

    Tobin, J.G.; Goodman, K.W. [Lawrence Berkeley National Lab., CA (United States); Cummins, T.R. [Univ. of Missouri, Rolla, MO (United States)] [and others

    1997-04-01

    The authors have used Magnetic X-ray Linear Dichroism (MXLD) and Magnetic X-ray Circular Dichroism (MXCD) to study the magnetic properties of epitaxial overlayers in an elementally specific fashion. Both MXLD and MXCD Photoelectron Spectroscopy were performed in a high resolution mode at the Spectromicroscopy Facility of the ALS. Circular Polarization was obtained via the utilization of a novel phase retarder (soft x-ray quarter wave plate) based upon transmission through a multilayer film. The samples were low temperature Fe overlayers, magnetic alloy films of NiFe and CoNi, and Gd grown on Y. The authors results include a direct comparison of high resolution angle resolved Photoelectron Spectroscopy performed in MXLD and MXCD modes as well as structural studies with photoelectron diffraction.

  4. Three-dimensional structural imaging of starch granules by second-harmonic generation circular dichroism.

    Science.gov (United States)

    Zhuo, G-Y; Lee, H; Hsu, K-J; Huttunen, M J; Kauranen, M; Lin, Y-Y; Chu, S-W

    2014-03-01

    Chirality is one of the most fundamental and essential structural properties of biological molecules. Many important biological molecules including amino acids and polysaccharides are intrinsically chiral. Conventionally, chiral species can be distinguished by interaction with circularly polarized light, and circular dichroism is one of the best-known approaches for chirality detection. As a linear optical process, circular dichroism suffers from very low signal contrast and lack of spatial resolution in the axial direction. It has been demonstrated that by incorporating nonlinear interaction with circularly polarized excitation, second-harmonic generation circular dichroism can provide much higher signal contrast. However, previous circular dichroism and second-harmonic generation circular dichroism studies are mostly limited to probe chiralities at surfaces and interfaces. It is known that second-harmonic generation, as a second-order nonlinear optical effect, provides excellent optical sectioning capability when combined with a laser-scanning microscope. In this work, we combine the axial resolving power of second-harmonic generation and chiral sensitivity of second-harmonic generation circular dichroism to realize three-dimensional chiral detection in biological tissues. Within the point spread function of a tight focus, second-harmonic generation circular dichroism could arise from the macroscopic supramolecular packing as well as the microscopic intramolecular chirality, so our aim is to clarify the origins of second-harmonic generation circular dichroism response in complicated three-dimensional biological systems. The sample we use is starch granules whose second-harmonic generation-active molecules are amylopectin with both microscopic chirality due to its helical structure and macroscopic chirality due to its crystallized packing. We found that in a starch granule, the second-harmonic generation for right-handed circularly polarized excitation is

  5. Linear and Non-Linear Optical Imaging of Cancer Cells with Silicon Nanoparticles

    Science.gov (United States)

    Tolstik, Elen; Osminkina, Liubov A.; Akimov, Denis; Gongalsky, Maksim B.; Kudryavtsev, Andrew A.; Timoshenko, Victor Yu.; Heintzmann, Rainer; Sivakov, Vladimir; Popp, Jürgen

    2016-01-01

    New approaches for visualisation of silicon nanoparticles (SiNPs) in cancer cells are realised by means of the linear and nonlinear optics in vitro. Aqueous colloidal solutions of SiNPs with sizes of about 10–40 nm obtained by ultrasound grinding of silicon nanowires were introduced into breast cancer cells (MCF-7 cell line). Further, the time-varying nanoparticles enclosed in cell structures were visualised by high-resolution structured illumination microscopy (HR-SIM) and micro-Raman spectroscopy. Additionally, the nonlinear optical methods of two-photon excited fluorescence (TPEF) and coherent anti-Stokes Raman scattering (CARS) with infrared laser excitation were applied to study the localisation of SiNPs in cells. Advantages of the nonlinear methods, such as rapid imaging, which prevents cells from overheating and larger penetration depth compared to the single-photon excited HR-SIM, are discussed. The obtained results reveal new perspectives of the multimodal visualisation and precise detection of the uptake of biodegradable non-toxic SiNPs by cancer cells and they are discussed in view of future applications for the optical diagnostics of cancer tumours. PMID:27626408

  6. Linear and Non-Linear Optical Imaging of Cancer Cells with Silicon Nanoparticles.

    Science.gov (United States)

    Tolstik, Elen; Osminkina, Liubov A; Akimov, Denis; Gongalsky, Maksim B; Kudryavtsev, Andrew A; Timoshenko, Victor Yu; Heintzmann, Rainer; Sivakov, Vladimir; Popp, Jürgen

    2016-09-12

    New approaches for visualisation of silicon nanoparticles (SiNPs) in cancer cells are realised by means of the linear and nonlinear optics in vitro. Aqueous colloidal solutions of SiNPs with sizes of about 10-40 nm obtained by ultrasound grinding of silicon nanowires were introduced into breast cancer cells (MCF-7 cell line). Further, the time-varying nanoparticles enclosed in cell structures were visualised by high-resolution structured illumination microscopy (HR-SIM) and micro-Raman spectroscopy. Additionally, the nonlinear optical methods of two-photon excited fluorescence (TPEF) and coherent anti-Stokes Raman scattering (CARS) with infrared laser excitation were applied to study the localisation of SiNPs in cells. Advantages of the nonlinear methods, such as rapid imaging, which prevents cells from overheating and larger penetration depth compared to the single-photon excited HR-SIM, are discussed. The obtained results reveal new perspectives of the multimodal visualisation and precise detection of the uptake of biodegradable non-toxic SiNPs by cancer cells and they are discussed in view of future applications for the optical diagnostics of cancer tumours.

  7. Configuration of singular optical cones in gyrotropic crystals with dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Merkulov, V. S., E-mail: merkul@physics.by [National Academy of Sciences of Belarus, Material Science Applied Research Center (Belarus)

    2015-02-15

    Optical conic singularities in crystals with linear dichroism and natural optical activity at the point of intersection of dispersion curves for the main refractive indices are considered. The possible existence of singularities like a nodal point, tangency point, triple point, and cusps of the first and second order is demonstrated. Forty-nine different types of irreducible fourth-order optical cones obtained by sequential bifurcations of eight main singular cones are established. The classification is based on the concept of roughness of systems depending on parameters.

  8. How pathogens use linear motifs to perturb host cell networks

    KAUST Repository

    Via, Allegra

    2015-01-01

    Molecular mimicry is one of the powerful stratagems that pathogens employ to colonise their hosts and take advantage of host cell functions to guarantee their replication and dissemination. In particular, several viruses have evolved the ability to interact with host cell components through protein short linear motifs (SLiMs) that mimic host SLiMs, thus facilitating their internalisation and the manipulation of a wide range of cellular networks. Here we present convincing evidence from the literature that motif mimicry also represents an effective, widespread hijacking strategy in prokaryotic and eukaryotic parasites. Further insights into host motif mimicry would be of great help in the elucidation of the molecular mechanisms behind host cell invasion and the development of anti-infective therapeutic strategies.

  9. Magnetic dichroism and spin structure of antiferromagnetic NiO(001) films

    NARCIS (Netherlands)

    Altieri, S; Finazzi, M; Hsieh, HH; Lin, HJ; Chen, CT; Hibma, T; Valeri, S; Sawatzky, GA

    2003-01-01

    We find that Ni L-2 edge x-ray magnetic linear dichroism is fully reversed for NiO(001) films on materials with reversed lattice mismatch. We relate this phenomenon to a preferential stabilization of magnetic S domains with main spin component either in or out of the plane, via dipolar interactions.

  10. All-dielectric metasurface circular dichroism waveplate

    Science.gov (United States)

    Hu, Jingpei; Zhao, Xiaonan; Lin, Yu; Zhu, Aijiao; Zhu, Xiaojun; Guo, Peiji; Cao, Bing; Wang, Chinhua

    2017-01-01

    We propose and experimentally demonstrate a high efficient circularly polarizing dichroism waveplate (CPDW) using a Si-based all-dielectric 2Dchiral metasurface. We demonstrate that the CPDW exhibits a unique dichroism in that it functions as a transmissive quarter waveplate for one of either left-or right-handed circularly polarized incident lightand a reflective mirror for the opposite polarization. The circular polarization dichroism (CPD = IRCP ‑ ILCP) in transmission at wavelength ~1.5 μm reaches 97% and the extinction ratio (ER = IRCP/ILCP) is as high as 345:1. Experimental fabrications and measurements of the proposed all-dielectric metasurface are implemented and found to be in excellent agreement with the simulations. The proposed all-dielectric chiral metasurface is of advantages of high-dichroism, easy-fabrication and standard semiconductor fabrication techniques compatible, which could lead to enhanced security in fiber and free-space communications, as well as imaging and sensing applications for circularly polarized light with a highly integrated photonic platform.

  11. All-dielectric metasurface circular dichroism waveplate

    Science.gov (United States)

    Hu, Jingpei; Zhao, Xiaonan; Lin, Yu; Zhu, Aijiao; Zhu, Xiaojun; Guo, Peiji; Cao, Bing; Wang, Chinhua

    2017-01-01

    We propose and experimentally demonstrate a high efficient circularly polarizing dichroism waveplate (CPDW) using a Si-based all-dielectric 2Dchiral metasurface. We demonstrate that the CPDW exhibits a unique dichroism in that it functions as a transmissive quarter waveplate for one of either left-or right-handed circularly polarized incident lightand a reflective mirror for the opposite polarization. The circular polarization dichroism (CPD = IRCP − ILCP) in transmission at wavelength ~1.5 μm reaches 97% and the extinction ratio (ER = IRCP/ILCP) is as high as 345:1. Experimental fabrications and measurements of the proposed all-dielectric metasurface are implemented and found to be in excellent agreement with the simulations. The proposed all-dielectric chiral metasurface is of advantages of high-dichroism, easy-fabrication and standard semiconductor fabrication techniques compatible, which could lead to enhanced security in fiber and free-space communications, as well as imaging and sensing applications for circularly polarized light with a highly integrated photonic platform. PMID:28139753

  12. Polarimetric investigation of materials with both linear and circular anisotropy

    DEFF Research Database (Denmark)

    Naydenova, I.; Nikolova, L.; Todorov, T.;

    1997-01-01

    We investigate light propagation through materials with both linear and circular anisotropy and find the relation of the amplitude and polarization transfer functions to the four anisotropic characteristics: linear circular birefringence, and linear and circular dichroism. We determine these four...

  13. Linear and Planar Variable Reluctance Motors for Flexible Manufactoring Cells

    Directory of Open Access Journals (Sweden)

    Imre Szepi

    2004-01-01

    Full Text Available Most advances manufactoring processes require precise linear motion for several tasks as material transfer, packaging, assembly or electrical wiring. To achieve precise linear motion, most of the usual high-performance manufactoring machines use X-Y sliding tables with rotary motors and rotary - to - linear couplers. Though this method is the most widely used, it has disadvantages of low ccuracy, complex mechanical adjustments, hogh cost, and low reliability. This paper describes a novel modular construction which can be used to build up linear surface direct - driven motors for high performance motions in flexible manufactoring automation. The proposed motors have simple modular structure and they have no limitation on the travel distance. Simulated results of the linear and planar motion systems indicate that the motion systems has good accurancy.

  14. Chiral Surface Waves for Enhanced Circular Dichroism

    CERN Document Server

    Pellegrini, Giovanni; Celebrano, Michele; Duò, Lamberto; Biagioni, Paolo

    2016-01-01

    We present a novel chiral sensing platform that combines a one-dimensional photonic crystal design with a birefringent surface defect. The platform sustains simultaneous transverse electric and transverse magnetic surface modes, which are exploited to generate chiral surface waves. The present design provides homogeneous and superchiral fields of both handednesses over arbitrarily large areas in a wide spectral range, resulting in the enhancement of the circular dichroism signal by two orders of magnitude, thus paving the road toward the successful combination of surface-enhanced spectroscopies and electromagnetic superchirality.

  15. Linear IgA dermatosis, coeliac disease, and extraintestinal B cell lymphoma.

    OpenAIRE

    Kapur, A.; Isaacs, P E; Kelsey, P R

    1995-01-01

    Linear IgA dermatosis is a malignancy associated rare bullous disorder similar to dermatitis herpetiformis. Linear IgA dermatosis differs from dermatitis herpetiformis in that the IgA deposits in the epidermal basement membrane are linear rather than granular. A patient is presented with coeliac disease who presented with linear IgA dermatosis and anaemia caused by chronic low grade B cell lymphoma.

  16. Resonant second-harmonic-generation circular-dichroism microscopy reveals molecular chirality in native biological tissues

    CERN Document Server

    Chen, Mei-Yu; Kan, Che-Wei; Lin, Yen-Yin; Ye, Cin-Wei; Wu, Meng-Jer; Liu, Hsiang-Lin; Chu, Shi-Wei

    2016-01-01

    Conventional linear optical activity effects are widely used for studying chiral materials. However, poor contrast and artifacts due to sample anisotropy limit the applicability of these methods. Here we demonstrate that nonlinear second-harmonic-generation circular dichroism spectral microscopy can overcome these limits. In intact collagenous tissues, clear spectral resonance is observed with sub-micrometer spatial resolution. By performing gradual protein denaturation studies, we show that the resonant responses are dominantly due to the molecular chirality.

  17. X-ray magnetic circular dichroism in Co2FeGa: First-principles calculations

    Science.gov (United States)

    Kukusta, D. A.; Antonov, V. N.; Yaresko, A. N.

    2011-08-01

    The electronic structure and x-ray magnetic circular dichroism (XMCD) spectra of the Heusler alloy Co2FeGa were investigated theoretically from first principles, using the fully relativistic Dirac linear MT-orbital (LMTO) band structure method. Densities of valence states, orbital and spin magnetic moments are analyzed and discussed. The origin of the XMCD spectra in the Co2FeGa compound is examined. The calculated results are compared with available experimental data.

  18. Quantification of stromal vascular cell mechanics with a linear cell monolayer rheometer

    Energy Technology Data Exchange (ETDEWEB)

    Elkins, Claire M., E-mail: cma9@stanford.edu; Fuller, Gerald G. [Department of Chemical Engineering, Stanford University, Stanford, California 94305 (United States); Shen, Wen-Jun; Khor, Victor K.; Kraemer, Fredric B. [Division of Endocrinology, Gerontology and Metabolism, Stanford University, Stanford, California 94305 and Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304 (United States)

    2015-01-15

    Over the past few decades researchers have developed a variety of methods for measuring the mechanical properties of whole cells, including traction force microscopy, atomic force microscopy (AFM), and single-cell tensile testing. Though each of these techniques provides insight into cell mechanics, most also involve some nonideal conditions for acquiring live cell data, such as probing only one portion of a cell at a time, or placing the cell in a nonrepresentative geometry during testing. In the present work, we describe the development of a linear cell monolayer rheometer (LCMR) and its application to measure the mechanics of a live, confluent monolayer of stromal vascular cells. In the LCMR, a monolayer of cells is contacted on both top and bottom by two collagen-coated plates and allowed to adhere. The top plate then shears the monolayer by stepping forward to induce a predetermined step strain, while a force transducer attached to the top plate collects stress information. The stress and strain data are then used to determine the maximum relaxation modulus recorded after step-strain, G{sub r}{sup 0}, referred to as the zero-time relaxation modulus of the cell monolayer. The present study validates the ability of the LCMR to quantify cell mechanics by measuring the change in G{sub r}{sup 0} of a confluent cell monolayer upon the selective inhibition of three major cytoskeletal components (actin microfilaments, vimentin intermediate filaments, and microtubules). The LCMR results indicate that both actin- and vimentin-deficient cells had ∼50% lower G{sub r}{sup 0} values than wild-type, whereas tubulin deficiency resulted in ∼100% higher G{sub r}{sup 0} values. These findings constitute the first use of a cell monolayer rheometer to quantitatively distinguish the roles of different cytoskeletal elements in maintaining cell stiffness and structure. Significantly, they are consistent with results obtained using single-cell mechanical testing methods

  19. Calculations of magnetic x-ray dichroism in the 3d absorption spectra of rare-earth compounds

    NARCIS (Netherlands)

    GOEDKOOP, JB; THOLE, BT; VANDERLAAN, G; SAWATZKY, GA; DEGROOT, FMF; FUGGLE, JC; de Groot, Frank

    1988-01-01

    We present atomic calculations for the recently discovered magnetic x-ray dichroism (MXD) displayed by the 3d x-ray-absorption spectra of rare-earth compounds. The spectral shapes expected at T=0 K for linear polarization parallel and normal to the local magnetic field is given, together with the te

  20. Linear Look-ahead in Conjunctive Cells: An Entorhinal Mechanism for Vector-Based Navigation

    Directory of Open Access Journals (Sweden)

    John L Kubie

    2012-04-01

    Full Text Available The crisp organization of the firing bumps of entorhinal grid cells and conjunctive cells leads to the notion that the entorhinal cortex may compute linear navigation routes. Specifically, we propose a process, termed linear look-ahead, by which a stationary animal could compute a series of locations in the direction it is facing. We speculate that this computation could be achieved through learned patterns of connection strengths among entorhinal neurons. This paper has three sections. First, we describe the minimal grid cell properties that will be built into our network. Specifically, the network relies of rigid modules of neurons, where all members have identical grid scale and orientation, but differ in spatial phase. Additionally, these neurons must be densely interconnected with synapses that are modifiable early in the animal’s life. Second, we investigate whether plasticity during short bouts of locomotion could induce patterns of connections amongst grid cells or conjunctive cells. Finally, we run a simulation to test whether the learned connection patterns can exhibit linear look-ahead. Our results are straightforward. A simulated 30-minute walk produces weak strengthening of synapses between grid cells that do not support linear look-ahead. Similar training in a conjunctive-cell module produces a small subset of very strong connections between cells. These strong pairs have three properties: The pre- and post-synaptic cells have similar heading direction. The cell pairs have neighboring grid bumps. Finally, the spatial offset of firing bumps of the cell pair is in the direction of the common heading preference. Such a module can produce strong and accurate linear look ahead starting in any location and extending in any direction. We speculate that this process may: 1. compute linear paths to goals; 2. update grid cell firing during navigation; and 3. stabilize the rigid modules of grid cells and conjunctive cells.

  1. Linear IgA bullous dermatosis in a patient with renal cell carcinoma

    NARCIS (Netherlands)

    Van der Waal, RIF; Van de Scheur, MR; Pas, HH; Jonkman, MF; Van Groeningen, CJ; Nieboer, C; Starink, TM

    2001-01-01

    Linear IgA bullous dermatosis (LABD) is an autoimmune subepidermal bullous disease with heterogeneous clinical manifestations, characterized by linear deposition of IgA along the epidermal basement membrane zone. We report a patient with a metastasized renal cell carcinoma who developed an extensive

  2. BBU design of linear induction accelerator cells for radiography application

    Energy Technology Data Exchange (ETDEWEB)

    Shang, C.C.; Chen, Y.J.; Gaporaso, G.J.; Houck, T.L.; Molau, N.E.; Focklen, J.; Gregory, S.

    1997-05-06

    There is an ongoing effort to develop accelerating modules for high-current electron accelerators for advanced radiography application. Accelerating modules with low beam-cavity coupling impedances along with gap designs with acceptable field stresses comprise a set of fundamental design criteria. We examine improved cell designs which have been developed for accelerator application in several radiographic operating regimes. We evaluate interaction impedances, analyze the effects of beam structure coupling on beam dynamics (beam break-up instability and corkscrew motion). We also provide estimates of coupling through interesting new high-gradient insulators and evaluate their potential future application in induction cells.

  3. DEIMOS: A beamline dedicated to dichroism measurements in the 350–2500 eV energy range

    Energy Technology Data Exchange (ETDEWEB)

    Ohresser, P., E-mail: philippe.ohresser@synchrotron-soleil.fr; Otero, E.; Choueikani, F.; Chen, K.; Stanescu, S.; Deschamps, F.; Moreno, T.; Polack, F.; Lagarde, B.; Daguerre, J.-P.; Marteau, F. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette (France); Scheurer, F.; Joly, L.; Muller, B. [Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 UdS-CNRS, 67034 Strasbourg Cedex 2 (France); Kappler, J.-P. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette (France); Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504 UdS-CNRS, 67034 Strasbourg Cedex 2 (France); Bunau, O.; Sainctavit, Ph. [Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin - BP 48, 91192 Gif-sur-Yvette (France); Institut de Minéralogie et de Physique des Milieux Condensés, CNRS UMR 7590, Université Pierre et Marie Curie, 75252 Paris Cedex 5 (France)

    2014-01-15

    The DEIMOS (Dichroism Experimental Installation for Magneto-Optical Spectroscopy) beamline was part of the second phase of the beamline development at French Synchrotron SOLEIL (Source Optimisée de Lumière à Energie Intermédiaire du LURE) and opened to users in March 2011. It delivers polarized soft x-rays to perform x-ray absorption spectroscopy, x-ray magnetic circular dichroism, and x-ray linear dichroism in the energy range 350–2500 eV. The beamline has been optimized for stability and reproducibility in terms of photon flux and photon energy. The main end-station consists in a cryo-magnet with 2 split coils providing a 7 T magnetic field along the beam or 2 T perpendicular to the beam with a controllable temperature on the sample from 370 K down to 1.5 K.

  4. Non-modal linear stability analysis of miscible viscous fingering in a Hele-Shaw cell

    CERN Document Server

    Hota, Tapan Kumar; Mishra, Manoranjan

    2015-01-01

    For miscible viscous fingering (VF) in a Hele-Shaw cell or in two dimensional homogeneous porous media, the transient growth of disturbances is investigated by non-modal linear stability analysis (NMA). Due to the non-autonomous nature of the linearized perturbed equations, the linear stability theory prohibits using the normal mode analysis. The linearized perturbed equations for Darcy's law coupled with a convection-diffusion equation is discretized using finite difference method. The resultant matrix valued initial value problem is then solved by fourth order Runge-Kutta method, followed by a singular value decomposition (SVD) of the propagator matrix. We demonstrate the dominant perturbation that experiences the maximum amplification within the linear regime which lead to the transient growth. This feature was previously unattained in the existing linear stability methods for miscible VF. To explore the relevance of the optimal perturbation obtained from non-modal analysis of the physical system, we perfo...

  5. Where the linearized Poisson-Boltzmann cell model fails: Spurious phase separation in charged colloidal suspensions

    Science.gov (United States)

    Tamashiro, M. N.; Schiessel, H.

    2003-07-01

    The Poisson-Boltzmann (PB) spherical Wigner-Seitz cell model—introduced to theoretically describe suspensions of spherical charged colloidal particles—is investigated at the nonlinear and linearized levels. The linearization of the mean-field PB functional yields linearized Debye-Hückel-type equations agreeing asymptotically with the nonlinear PB results in the weak-coupling (high-temperature) limit. Both the canonical (fixed number of microions) as well as the semigrand-canonical (in contact with an infinite salt reservoir) cases are considered and discussed in a unified linearized framework. In disagreement with the exact nonlinear PB solution inside a Wigner-Seitz cell, the linearized theory predicts the occurrence of a thermodynamical instability with an associated phase separation of the homogeneous suspension into dilute (gas) and dense (liquid) phases, being thus a spurious result of the linearization. We show that these artifacts, although thermodynamically consistent with quadratic expansions of the nonlinear functional and osmotic pressure, may be traced back to the nonfulfillment of the underlying assumptions of the linearization. This raises questions about the reliability of the prediction of gas/liquid-like phase separation in deionized aqueous suspensions of charged colloids mediated by monovalent counterions obtained by linearized theories.

  6. Using the group of non-linear cells design metamaterial bar

    Science.gov (United States)

    Sun, Hongwei; Song, Xin; Hu, Xiaolei; Gu, Jinliang

    2016-04-01

    The paper presents the wave propagation in one-dimensional metamaterial bar with attached group of non-linear local oscillators by using analytical and numerical models. The focus is on the influence of group of non-linear cells on the filtering properties of the bar in the 1000Hz to 2000Hz range. Group of Periodic cells with alternating properties exhibit interesting dynamic characteristics that enable them to act as filters. Waves can propagate along bars within specific bands of frequencies called pass bands, and attenuate within bands of frequencies called gaps. Gaps in structures with group of periodic cells are located according on the frequency of cells. From the cell, we can yield the effect negative stiffness and effect negative mass. We can also design the gaps from attached oscillators or cells. In the uniform case the gap is located around the resonant frequency of the oscillators, and thus a stop band can be created in the lower frequency range. In the case with group of non-linear cells the results show that the position of the gap can be designed, and the design depends on the amplitude and the degree of non-linear cells.

  7. SIMULTANEOUS MEASUREMENT OF CIRCULAR DICHROISM AND FLUORESCENCE POLARIZATION ANISOTROPY.

    Energy Technology Data Exchange (ETDEWEB)

    SUTHERLAND,J.C.

    2002-01-19

    Circular dichroism and fluorescence polarization anisotropy are important tools for characterizing biomolecular systems. Both are used extensively in kinetic experiments involving stopped- or continuous flow systems as well as titrations and steady-state spectroscopy. This paper presents the theory for determining circular dichroism and fluorescence polarization anisotropy simultaneously, thus insuring the two parameters are recorded under exactly the same conditions and at exactly the same time in kinetic experiments. The approach to measuring circular dichroism is that used in almost all conventional dichrographs. Two arrangements for measuring fluorescence polarization anisotropy are described. One uses a single fluorescence detector and signal processing with a lock-in amplifier that is similar to the measurement of circular dichroism. The second approach uses classic ''T'' format detection optics, and thus can be used with conventional photon-counting detection electronics. Simple extensions permit the simultaneous measurement of the absorption and excitation intensity corrected fluorescence intensity.

  8. On the existence of Jones birefringence and Jones dichroism.

    Science.gov (United States)

    Arteaga, Oriol

    2010-05-01

    We claim that the so-called Jones birefringence and Jones dichroism effects, understood as new optical phenomena of difficult experimental observation, cannot be deduced from Jones publications and were proposed due to a misinterpretation of his original work.

  9. Dichroism in the photoionisation of atoms at XUV free-electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Mazza, T., E-mail: tommaso.mazza@xfel.eu [European XFEL GmbH, Albert-Einstein-Ring 19, D-22761 Hamburg (Germany); Gryzlova, E.V.; Grum-Grzhimailo, A.N. [Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Kazansky, A.K. [Departamento de Fisica de Materiales, UPV/EHU, E-20018 San Sebastian/Donostia (Spain); IKERBASQUE, Basque Foundation for Science, E-48011 Bilbao (Spain); Donostia International Physics Center (DIPC), E-20018 San Sebastian/Donostia (Spain); Kabachnik, N.M. [European XFEL GmbH, Albert-Einstein-Ring 19, D-22761 Hamburg (Germany); Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, Moscow 119991 (Russian Federation); Donostia International Physics Center (DIPC), E-20018 San Sebastian/Donostia (Spain); Meyer, M., E-mail: michael.meyer@xfel.eu [European XFEL GmbH, Albert-Einstein-Ring 19, D-22761 Hamburg (Germany)

    2015-10-15

    Highlights: • We studied 2-color photoionization of He by angle-resolved electron spectroscopy. • Beta-parameters contain information about the symmetry of outgoing electron waves. • Experiments are compared to strong field approximation and perturbation theory. • 2-Photon measurements can be used to characterize FEL radiation properties. • Non-dipole contributions are predicted to produce new features in the dichroism. - Abstract: Two-color photoionization of atomic He has been investigated by angle-integrated and angle-resolved electron spectroscopy. The combined action of intense radiation pulses from the XUV free-electron laser (FEL), FERMI or FLASH, and a synchronized optical laser on the target atom gives rise to a rich sideband structure in the photoemission spectrum. Measurements of the angular distribution parameters and the determination of the circular and linear dichroism for the two-color photoionization enable a detailed analysis of the symmetry of the outgoing electron waves and of the dynamics underlying the multi-photon processes. The experimental results are in excellent agreement with theoretical results obtained using perturbation theory (low intensity regime) and the strong field approximation. For the particular case of two-photon ionization the measurements represent an ideal tool for characterizing certain FEL parameters, here for example the degree and the sign of circular polarization. Finally, new features of the dichroism are theoretically predicted originating from the non-dipole contribution into the photoionization amplitudes.

  10. Circular dichroism induced by Fano resonances in planar chiral oligomers

    CERN Document Server

    Hopkins, Ben; Miroshnichenko, Andrey E; Kivshar, Yuri S

    2016-01-01

    We present a general theory of circular dichroism induced in planar chiral nanostructures with rotational symmetry. It is demonstrated, analytically, that the handedness of the incident field's polarization can control whether a nanostructure induces either absorption or scattering losses, even when the total loss (extinction) is polarization-independent. We then show that this effect is a consequence of modal interference so that strong circular dichroism in absorption and scattering can be engineered by combining Fano resonances with chiral nanoparticle clusters.

  11. Circular dichroism beamline B23 at the Diamond Light Source.

    Science.gov (United States)

    Hussain, Rohanah; Jávorfi, Tamás; Siligardi, Giuliano

    2012-01-01

    Synchrotron radiation circular dichroism (SRCD) is a well established technique in structural biology. The first UV-VIS beamline, dedicated to circular dichroism, at Diamond Light Source Ltd, a third-generation synchrotron facility in south Oxfordshire, UK, has recently become operational and it is now available for the user community. Herein the main characteristics of the B23 SRCD beamline, the ancillary facilities available for users, and some of the recent advances achieved are summarized.

  12. The circular dichroism of ribosomal ribonucleic acids.

    Science.gov (United States)

    Cox, R A; Hirst, W; Godwin, E; Kaiser, I

    1976-05-01

    1. The c.d. (circular dichroism) of Drosophila melanogaster rRNA (42% G+C) and of G+C-rich fragments (78% G+C) obtained by partial hydrolysis of rabbit L-rRNA (the largest RNA species isolated from the large subribosomal particle) were measured and found to differ substantially. 2. To interpret these spectra a relation between c.d. of bihelical RNA and % G+C was derived, namely delta epsilonfG = AFG2+bfG+c, where deltaepsilonfG is the c.d. of RNA characterized by a mole fraction, fG, of guanine nucleotides and a, b and c are constants. 3. A frame of reference was established by studying the c.d. of a range of rRNA species, including S-rRNA (the RNA species isolated from the smaller subribosomal particle) and L-rRNA of Escherichia coli. 4. It was found for the rRNA species studied that 0.60+/-0.05 of residues appear to form bihelical secondary structure. 5. A higher helical content, 0.66+/-0.05, was found for the G+C-rich fragment of L-rRNA. The difference in the c.d. of rabbit L-rRNA and of D. melanogaster rRNA is attributable to the dependence of c.d. of the bihelical parts on %G+C. 6. The minimum in c.d. at 295 nm increases with increasing %G+C. The c.d. of rRNA was compared with that of the parent subparticle in this region of the spectrum, where high precision may be attained.

  13. PCR-based detection of a rare linear DNA in cell culture

    Directory of Open Access Journals (Sweden)

    Saveliev Sergei V.

    2002-01-01

    Full Text Available The described method allows for detection of rare linear DNA fragments generated during genomic deletions. The predicted limit of the detection is one DNA molecule per 107 or more cells. The method is based on anchor PCR and involves gel separation of the linear DNA fragment and chromosomal DNA before amplification. The detailed chemical structure of the ends of the linear DNA can be defined with the use of additional PCR-based protocols. The method was applied to study the short-lived linear DNA generated during programmed genomic deletions in a ciliate. It can be useful in studies of spontaneous DNA deletions in cell culture or for tracking intracellular modifications at the ends of transfected DNA during gene therapy trials.

  14. Numerical estimation of 3D mechanical forces exerted by cells on non-linear materials.

    Science.gov (United States)

    Palacio, J; Jorge-Peñas, A; Muñoz-Barrutia, A; Ortiz-de-Solorzano, C; de Juan-Pardo, E; García-Aznar, J M

    2013-01-04

    The exchange of physical forces in both cell-cell and cell-matrix interactions play a significant role in a variety of physiological and pathological processes, such as cell migration, cancer metastasis, inflammation and wound healing. Therefore, great interest exists in accurately quantifying the forces that cells exert on their substrate during migration. Traction Force Microscopy (TFM) is the most widely used method for measuring cell traction forces. Several mathematical techniques have been developed to estimate forces from TFM experiments. However, certain simplifications are commonly assumed, such as linear elasticity of the materials and/or free geometries, which in some cases may lead to inaccurate results. Here, cellular forces are numerically estimated by solving a minimization problem that combines multiple non-linear FEM solutions. Our simulations, free from constraints on the geometrical and the mechanical conditions, show that forces are predicted with higher accuracy than when using the standard approaches.

  15. Circular dichroism in free-free transitions of high energy electron-atom scattering

    CERN Document Server

    Cionga, Aurelia; Zloh, Gabriela; 10.1103/PhysRevA.62.063406

    2013-01-01

    We consider high energy electron scattering by hydrogen atoms in the presence of a laser field of moderate power and higher frequencies. If the field is a superposition of a linearly and a circularly polarized laser beam in a particular configuration, then we can show that circular dichroism in two photon transitions can be observed not only for the differential but also for the integrated cross sections, provided the laser-dressing of the atomic target is treated in second order perturbation theory and the coupling between hydrogenic bound and continuum states is involved.

  16. Circular dichroism in the two-colour two-photon ionization of hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Cionga, Aurelia [Institute of Space Sciences, PO Box MG-23, R-76900 Bucharest-Magurele (Romania); Fifirig, Magda [Department of Chemistry, University of Bucharest, Bd Regina Elisabeta 4-12, R-70346 Bucharest (Romania); Ehlotzky, Fritz [Institute for Theoretical Physics, University of Innsbruck, Technikerstrasse 25, A-6020 Innsbruck (Austria)

    2002-12-14

    We study dichroic effects in the two-photon ionization of hydrogen from its ground state due to the interaction with a bichromatic field of commensurate frequencies. The two field components have different polarization: one is linearly polarized and the other is circularly polarized (CP). Circular dichroism (CD) in the angular distribution of the photoelectrons appears if the helicity of the CP field is reversed. Numerical results reveal the influence of the photon frequencies chosen on the CD in the azimuthal angular distribution of the ejected photoelectrons.

  17. Effects of graphene quantum dots on linear and nonlinear optical behavior of malignant ovarian cells

    Science.gov (United States)

    Mohajer, Salman; Ara, Mohammad Hossein Majles; Serahatjoo, Leila

    2016-07-01

    We investigate linear and nonlinear optical properties of standard human ovarian cancer cells (cell line: A2780cp) in vitro. Cells were treated by graphene quantum dots (GQDs) with two special concentrations. Nontoxicity of GQDs was examined in standard biological viability tests. Cancerous cells were fixed on a glass slide; then, interaction of light with biofilms was studied in linear and nonlinear regimes. Absorption spectra of untreated biofilms and biofilms with two different concentrations of GQDs was studied by UV-visible spectrophotometer. Optical behavior of biofilms in a linear regime of intensity (with low-intensity laser exposure) was reported using a simple optical setup. After that, we compared the attenuation of light in biofilm of cancerous cells with and without GQDs. Nonlinear behavior of these biofilms was investigated by a Z-scan setup using a continued wave He-Ne laser. Results showed that GQDs decreased the extinction coefficient and changed the sign and exact value of the nonlinear refractive index of malignant ovarian cells noticeably. The nonlinear refractive index of studied cells with no GQDs treatment was in the order of 10-8 (cm2/w) with a positive sign. This quantity changed to the same order of magnitude with a negative sign after GQDs treatment. Thus, GQDs can be used for cancer diagnosis under laser irradiation.

  18. The design of the HOM-damping cells for the S-band linear collider

    OpenAIRE

    Müller, Wolfgang F. O.; Hülsmann, Peter; Kurz, Martin; Glock, Hans-Walter; Klein, Horst

    2005-01-01

    Damping cells for the higher order modes are necessary for the S-band linear collider to minimize BBU (Beam-Break-Up). The construction of the damper cells has to take into account the different field geometries of the higher order modes. So two different types of dampers have been designed: a wall slotted an an iris slotted cell. In order to optimize the two types of damping cells with respect to damping strength, impedance matching between coupling system and waveguide dampers and between d...

  19. Modeling the Non-Linear Behavior of Library Cells for an Accurate Static Noise Analysis

    CERN Document Server

    Forzan, Cristiano

    2011-01-01

    In signal integrity analysis, the joint effect of propagated noise through library cells, and of the noise injected on a quiet net by neighboring switching nets through coupling capacitances, must be considered in order to accurately estimate the overall noise impact on design functionality and performances. In this work the impact of the cell non-linearity on the noise glitch waveform is analyzed in detail, and a new macromodel that allows to accurately and efficiently modeling the non-linear effects of the victim driver in noise analysis is presented. Experimental results demonstrate the effectiveness of our method, and confirm that existing noise analysis approaches based on linear superposition of the propagated and crosstalk-injected noise can be highly inaccurate, thus impairing the sign-off functional verification phase.

  20. Single-tube linear DNA amplification for genome-wide studies using a few thousand cells

    NARCIS (Netherlands)

    Shankaranarayanan, P.; Mendoza-Parra, M.A.; Gool, van W.; Trindade, L.M.; Gronemeyer, H.

    2012-01-01

    Linear amplification of DNA (LinDA) by T7 polymerase is a versatile and robust method for generating sufficient amounts of DNA for genome-wide studies with minute amounts of cells. LinDA can be coupled to a great number of global profiling technologies. Indeed, chromatin immunoprecipitation coupled

  1. Enabling linear alkyl carbonate electrolytes for high voltage Li-ion cells

    Science.gov (United States)

    Xia, Jian; Petibon, Remi; Xiong, Deijun; Ma, Lin; Dahn, J. R.

    2016-10-01

    Some of the problems of current electrolytes for high voltage Li-ion cells originate from ethylene carbonate (EC) which is thought to be an essential electrolyte component for Li-ion cells. Ethylene carbonate-free electrolytes containing 1 M LiPF6 in ethylmethyl carbonate (EMC) with small loadings of vinylene carbonate, fluoroethylene carbonate, or (4R,5S)-4,5-Difluoro-1,3-dioxolan-2-one acting as "enablers" were developed. These electrolytes used in Li(Ni0.4Mn0.4Co0.2)O2/graphite pouch type Li-ion cells tested at 4.2 V and 4.5 V yielded excellent charge-discharge cycling and storage properties. The results for cells containing linear alkyl carbonate electrolytes with no EC were compared to those of cells with EC-containing electrolytes incorporating additives proven to enhance cyclability of cells. The combination of EMC with appropriate amounts of these enablers yields cells with better performance than cells with EC-containing electrolytes incorporating additives tested to 4.5 V. Further optimizing these linear alkyl carbonate electrolytes with appropriate co-additives may represent a viable path to the successful commercial utilization of NMC/graphite Li-ion cells operated to 4.5 V and above.

  2. Anisotropic Circular Dichroism Signatures of Oriented Thylakoid Membranes and Lamellar Aggregates of LHCII

    Energy Technology Data Exchange (ETDEWEB)

    Miloslavina, Y.; Hind, G.; Lambrev, P. H.; Javorfi, T.; Varkonyi, Z.; Karlicky, V.; Wall, J. S.; Garab, G.

    2011-06-12

    In photosynthesis research, circular dichroism (CD) spectroscopy is an indispensable tool to probe molecular architecture at virtually all levels of structural complexity. At the molecular level, the chirality of the molecule results in intrinsic CD; pigment-pigment interactions in protein complexes and small aggregates can give rise to excitonic CD bands, while 'psi-type' CD signals originate from large, densely packed chiral aggregates. It has been well established that anisotropic CD (ACD), measured on samples with defined non-random orientation relative to the propagation of the measuring beam, carries specific information on the architecture of molecules or molecular macroassemblies. However, ACD is usually combined with linear dichroism and can be distorted by instrumental imperfections, which given the strong anisotropic nature of photosynthetic membranes and complexes, might be the reason why ACD is rarely studied in photosynthesis research. In this study, we present ACD spectra, corrected for linear dichroism, of isolated intact thylakoid membranes of granal chloroplasts, washed unstacked thylakoid membranes, photosystem II (PSII) membranes (BBY particles), grana patches, and tightly stacked lamellar macroaggregates of the main light-harvesting complex of PSII (LHCII). We show that the ACD spectra of face- and edge-aligned stacked thylakoid membranes and LHCII lamellae exhibit profound differences in their psi-type CD bands. Marked differences are also seen in the excitonic CD of BBY and washed thylakoid membranes. Magnetic CD (MCD) spectra on random and aligned samples, and the largely invariable nature of the MCD spectra, despite dramatic variations in the measured isotropic and anisotropic CD, testify that ACD can be measured without substantial distortions and thus employed to extract detailed information on the (supra)molecular organization of photosynthetic complexes. An example is provided showing the ability of CD data to indicate such an

  3. Anisotropic Circular Dichroism Signatures of Oriented Thylakoid Membranes and Lamellar Aggregates of LHCII

    Energy Technology Data Exchange (ETDEWEB)

    Miloslavina Y.; Hind G.; Lambrev, P. H.; Javorfi, T.; Varkonyi, Z.; Karlicky, V.; Wall, J. S.; Garab, G.

    2012-03-01

    In photosynthesis research, circular dichroism (CD) spectroscopy is an indispensable tool to probe molecular architecture at virtually all levels of structural complexity. At the molecular level, the chirality of the molecule results in intrinsic CD; pigment-pigment interactions in protein complexes and small aggregates can give rise to excitonic CD bands, while 'psi-type' CD signals originate from large, densely packed chiral aggregates. It has been well established that anisotropic CD (ACD), measured on samples with defined non-random orientation relative to the propagation of the measuring beam, carries specific information on the architecture of molecules or molecular macroassemblies. However, ACD is usually combined with linear dichroism and can be distorted by instrumental imperfections, which given the strong anisotropic nature of photosynthetic membranes and complexes, might be the reason why ACD is rarely studied in photosynthesis research. In this study, we present ACD spectra, corrected for linear dichroism, of isolated intact thylakoid membranes of granal chloroplasts, washed unstacked thylakoid membranes, photosystem II (PSII) membranes (BBY particles), grana patches, and tightly stacked lamellar macroaggregates of the main light-harvesting complex of PSII (LHCII). We show that the ACD spectra of face- and edge-aligned stacked thylakoid membranes and LHCII lamellae exhibit profound differences in their psi-type CD bands. Marked differences are also seen in the excitonic CD of BBY and washed thylakoid membranes. Magnetic CD (MCD) spectra on random and aligned samples, and the largely invariable nature of the MCD spectra, despite dramatic variations in the measured isotropic and anisotropic CD, testify that ACD can be measured without substantial distortions and thus employed to extract detailed information on the (supra)molecular organization of photosynthetic complexes. An example is provided showing the ability of CD data to indicate such an

  4. Kinetic flow dichroism study of conformational changes in supercoiled DNA induced by ethidium bromide and noncovalent and covalent binding of benz[a]pyrene diol epoxide.

    Science.gov (United States)

    Yoshida, H; Swenberg, C E; Geacintov, N E

    1987-03-10

    The dynamic conformational changes due to the noncovalent intercalative binding of ethidium bromide and racemic trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE), and the covalent binding of BPDE to supercoiled phi X174 DNA, have been studied by gel electrophoresis and a novel application of a kinetic flow linear dichroism technique. The magnitude of the linear dichroism (delta A) of the DNA oriented in the flow gradient is sensitive to the hydrodynamic shape of the DNA molecule which is affected by the binding of the drug or the carcinogen BPDE. While the linear dichroism of ethidium bromide supercoiled DNA is time independent, the delta A spectra of BPDE-DNA reaction mixtures vary on time scales of minutes, which correspond to the reaction rate constant of BPDE to form 7,8,9,10-tetrahydroxytetrahydrobenzo[a]pyrene hydrolysis products and covalent DNA adducts. The rapid noncovalent intercalation of BPDE causes an initial large increase in delta A (up to 250%, corresponding to the dichroism observed with relaxed circular DNA), followed by a slower decrease in the linear dichroism signal. This decrease in delta A is attributed to the removal of intercalated diol epoxide molecules and the resulting reversible increase in the number of superhelical turns. The kinetic flow dichroism spectra indicate that the noncovalent BPDE-DNA complexes are intercalative in nature, while the covalent adducts are characterized by a very different conformation in which the long axes of the pyrenyl residues are oriented at a large angle with respect to the average orientation of the planes of the DNA bases.(ABSTRACT TRUNCATED AT 250 WORDS)

  5. Large Enhancement of Circular Dichroism Using an Embossed Chiral Metamaterial

    CERN Document Server

    Mousavi, S Hamed Shams; El-Sayed, Mostafa A; Eftekhar, Ali A; Adibi, Ali

    2016-01-01

    In the close vicinity of a chiral nanostructure, the circular dichroism of a biomolecule could be greatly enhanced, due to the interaction with the local superchiral fields. Modest enhancement of optical activity using a planar metamaterial, with some chiral properties, and achiral nanoparticles has been previously reported. A more substantial chirality enhancement can be achieved in the local filed of a chiral nanostructure with a three-dimensional arrangement. Using an embossed chiral nanostructure designed for chiroptical sensing, we measure the circular dichroism spectra of two biomolecules, Chlorophylls A and B, at the molecular level, using a simple polarization resolved reflection measurement. This experiment is the first realization of the on-resonance surface-enhanced circular dichroism, achieved by matching the chiral resonances of a strongly chiral metamaterial with that of a chiral molecule, resulting in an unprecedentedly large differential CD spectrum from a monolayer of a chiral material.

  6. Variable conformation of GAP junctions linking bone cells: a transmission electron microscopic study of linear, stacked linear, curvilinear, oval, and annular junctions.

    Science.gov (United States)

    Shapiro, F

    1997-10-01

    There is a marked variability in the conformation of bone cell gap junctions in newborn murine cortical bone as defined by transmission electron microscopy (TEM). Studies were done in newborn BALB/c mouse and Sprague-Dawley rat femurs and tibias. Femoral and tibial cortices were dissected into 1 mm3 fragments and prepared in standardized fashion using modified Karnovsky fixation, 7.5% EDTA decalcification, 1% osmium tetroxide-sym collidine buffer with 1% lanthanum nitrate postfixation, Epon resin, 60 nm sections, lead citrate/uranyl acetate staining, and examination at 60 kV. Previous TEM descriptions of bone junctions have, with rare exceptions, noted only isolated linear or mildly curvilinear structures. In this study we noted gap junctional shapes on thin-section TEM preparations of osteoblasts and osteocytes to be extremely variable and complex encompassing linear, curvilinear, stacked linear, oval, and annular conformations. Multiple observations revealed linear gap junctions linking surface osteoblast cell bodies; linear, curvilinear, stacked linear, and oval junctions linking osteoblast processes in osteoid; linear and curvilinear junctions where cell processes joined with osteocyte cell bodies and each of the five conformations linking osteocyte processes within canaliculi. The annular junctions were found within osteoblast and osteocyte cytoplasm and in osteocyte cell processes within canaliculi. The annular junctions are intracellular, degenerating structures which appear as ultrastructural markers of gap junction involution. The more complex shapes reported here must be considered in (1) interpreting quantitative studies using freeze-fracture replicas, thin sections, and confocal microscopy immunolabeled junction connexin-43 components and (2) assessing gap junction biogenesis and turnover. 3-D reconstruction of bone junctions will enhance our understanding of these complex conformations.

  7. Reload Purified Melittin and Lactoferrin on Perfluorooctyl Bromide Nanoparticles (PFOB-Nps and Examine the Distribution of Particle Size, Zeta Potential and Confirmation of Their Accession on the Nanoparticles Via Tryptophan Fluorescence and Circular Dichroism (CD and its Anti-Cancer Effects on Human Breast Cancer Cell Line MCF7

    Directory of Open Access Journals (Sweden)

    Hadis Rahmani Incheh Keykanlu

    2016-12-01

    Full Text Available Acording to the prevalence of cancer in today's societies, it is too important to find new drugs for that treatment. Cationic antimicrobial peptides that are able to eliminate a wide range of bacteria, fungi, parasites, viruses and unicellular, are natural anti-cancer agents. In the present study, the effect of cationic peptides of bee venom Melittin (ML and Lactoferrin (LF of camel milk which was loaded on the Perfluorooctyl Bromide (PFOB nanoparticles, were examined on MCF7 cells. Nanoparticles using oil in water emulsion was prepared by ultra-thoracic and ultrasonic. Then ML and LF were separately added to the nanoparticles then incorporation of them were confirmed by tryptophan fluorescence and circular dichroism (CD spectra. The mean diameter of the nanoparticles did not change after addition of ML and LF (~100 nm, but as expected, the zeta potential of the nanoparticles with increasing of ML and LF concentrations to the preformed nanoparticles increased from -18.43(without ML and LF to +21.61(LF 110.66µg/ml and +20.93(ML 0.1µg/ml and +23.75(LF 110.66µg/ml and ML 0.1µg/ml. By using of scanning electron microscopy (SEM, the morphology and structure of nanoparticles was investigated, homogeneity and uniformity during processing and loading of ML and LF was observed. Effectiveness of nanoparticles loaded on cancer cells was performed with MTT test. The results showed that ML and LF had a positive effect on cancer cell death. Percent of cell death was higher when ML and LF was loaded on nanoparticles. With increase of ML and LF concentration loading on nanoparticles, increases cancer cell death. Minitab software was used to analyze some data.

  8. Non-linear elasticity of extracellular matrices enables contractile cells to communicate local position and orientation.

    Directory of Open Access Journals (Sweden)

    Jessamine P Winer

    Full Text Available Most tissue cells grown in sparse cultures on linearly elastic substrates typically display a small, round phenotype on soft substrates and become increasingly spread as the modulus of the substrate increases until their spread area reaches a maximum value. As cell density increases, individual cells retain the same stiffness-dependent differences unless they are very close or in molecular contact. On nonlinear strain-stiffening fibrin gels, the same cell types become maximally spread even when the low strain elastic modulus would predict a round morphology, and cells are influenced by the presence of neighbors hundreds of microns away. Time lapse microscopy reveals that fibroblasts and human mesenchymal stem cells on fibrin deform the substrate by several microns up to five cell lengths away from their plasma membrane through a force limited mechanism. Atomic force microscopy and rheology confirm that these strains locally and globally stiffen the gel, depending on cell density, and this effect leads to long distance cell-cell communication and alignment. Thus cells are acutely responsive to the nonlinear elasticity of their substrates and can manipulate this rheological property to induce patterning.

  9. Optically-driven red blood cell rotor in linearly polarized laser tweezers

    Indian Academy of Sciences (India)

    Manas Khan; Samarendra K Mohanty; A K Sood

    2005-11-01

    We have constructed a dual trap optical tweezers set-up around an inverted microscope where both the traps can be independently controlled and manipulated in all the three dimensions. Here we report our observations on rotation of red blood cells (RBCs) in a linearly polarized optical trap. Red blood cells deform and become twisted in hypertonic phosphate buffer saline and when trapped, experience an unbalanced radiation pressure force. The torque generated from the unbalanced force causes the trapped RBC to rotate. Addition of Ca++ ions in the solution, keeping the osmolarity same, makes the cell membranes stiffer and the cells deform less. Thus the speed of rotation of the red blood cells can be controlled, as less deformation and in turn less asymmetry in shape produces less torque under the radiation pressure resulting in slower rotation at the same laser power.

  10. Cytotoxic Impacts of Linear and Branched Polyethylenimine Nanostructures in A431 Cells

    Directory of Open Access Journals (Sweden)

    Yadollah Omidi

    2011-06-01

    Full Text Available Introduction: Polyethylenimine (PEI, as a nonviral cationic polymer, has been widely used as gene delivery nanosystem. Although a number of investigations have highlighted its toxic impacts on target cells through induction of apoptosis/necrosis, still it is essential to look at its structural impacts on target cells. Methods: In this current study, cytogenomic impacts of 25 kD linear and branched PEI (LPEI and BPEI, respectively in A431 cells are reported to address possible mechanism for induction of apoptosis. At 40-50% confluency, A431 cells were exposed to PEI at a recommended concentration for 4 hr. After 24 hr, to detect apoptosis and DNA damage, the treated cells were subjected to MTT assay, FITC-labeled annexin V flow cytometry and comet assay. Results: Flow cytometry assessments revealed that the BPEI can result in greater internalization than the linear PEI, which also induced greater cytotoxicity. Annexin V assay confirmed early and late apoptosis by BPEI, imposing somewhat DNA damage detected by comet assay. Western blot analysis resulted in induction of Akt-kinase which is possibly one of biomolecules affected by PEI. Conclusion: These results highlight that, despite induction of Akt-kinase, the BPEI can elicit apoptosis in target cells.

  11. Circular dichroism of graphene oxide: the chiral structure model

    Institute of Scientific and Technical Information of China (English)

    Jing CAO; Hua-Jie YIN; Rui SONG

    2013-01-01

    We have observed the circular dichroism signal of dilute graphene oxide (GO), then systematically investigated the chirality of GO and established a probable chiral unit model, This study may open up a new field for understanding the structure of GO and lay the foundation for fabrication of GO-based materials.

  12. Enhanced circular dichroism via slow light in dispersive structured media

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Mortensen, Asger

    2007-01-01

    Circular dichroism (CD) is in widespread use as a means of determining enantiomeric excess. We show how slow-light phenomena in dispersive structured media allow for a reduction in the required optical path length of an order of magnitude. The same ideas may be used to enhance the sensitivity of CD...

  13. Cyanobacterial phycobilisomes: selective dissociation monitored by fluorescence and circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Rigbi, M.; Rosinski, J.; Siegelman, H.W.; Sutherland, J.C.

    1980-04-01

    Phycobilisomes are supramolecular assemblies of phycobiliproteins responsible for photosynthetic light collection in red algae and cyanobacteria. They can be selectively dissociated by reduction of temperature and buffer concentration. Phycobilisomes isolated from Fremyella diplosiphon transfer energy collected by C-phycoerythrin and C-phycocyanin to allophycocyanin. The energy transfer to allophycocyanin is nearly abolished at 2/sup 0/C, as indicated by a blue shift in fluorescence emission, and is accompanied by a decrease in the circular dichroism in the region of allophycocyanin absorbance. Further dissociation of the phycobilisomes can be attained by reduction of buffer concentration and holding at 2/sup 0/C. Energy transfer to C-phycocyanin is nearly abolished, and decreases occur in the circular dichroism in the region of C-phycocyanin and C-phycoerythrin absorbance. Complete dissociation of the phycobilisomes at low buffer concentration and 2/sup 0/C requires extended time. Energy transfer to C-phycocyanin is further reduced and the circular dichroism maximum of C-phycoerythrin at 575 nm is lost. Circular dichroism provides information on the hexamer-monomer transitions of the phycobiliproteins, whereas fluorescence is indicative of hexamer-hexamer interactions. We consider that hydrophobic interactions are fundamental to the maintenance of the structure and function of phycobilisomes.

  14. Circular dichroism spectroscopic studies on structures formed by telomeric DNA sequences in vitro

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Telomere plays an important role in cellular processes, such as cell aging, death and carcinogenisis. Having special sequences, it can form quadruplex structure in vitro. Circular dichroism (CD) spectroscopic studies show that TTAGGG, (TTAGGG)2 and (TTAGGG)4 can all form quadruplex in vitro and exist mainly as parallel quadruplex without metal ions. Both K+ and Na+ can stabilize the tetrameric structure and facilitate the forming of anti-parallel conformation. Furthermore, the conformations of quadruplex can also be affected by sequence length, the nature and concentration of metal ions.

  15. X-ray magnetic dichroism in (Zn,Mn)O diluted magnetic semiconductors: First-principles calculations

    Science.gov (United States)

    Antonov, V. N.; Bekenov, L. V.; Mazur, D. V.; Germash, L. P.

    2012-06-01

    The electronic structure of (Zn,Mn)O diluted magnetic semiconductors was investigated theoretically from first principles by using the fully-relativistic Dirac linear muffin-tin orbital band structure method with the local spin-density approximation (LSDA) and the LSDA+ U approach. The X-ray magnetic circular dichroism (XMCD) spectra at the Mn, Zn, and O K and Mn L 2,3 edges were investigated theoretically from first principles. The origin of the XMCD spectra in these compounds was examined. The effect of oxygen vacancy atoms was found to be crucial for the X-ray magnetic dichroism at the Mn L 2,3 edges. The calculated results are compared with available experimental data.

  16. Systematic Perturbation of Cytoskeletal Function Reveals a Linear Scaling Relationship between Cell Geometry and Fitness

    Directory of Open Access Journals (Sweden)

    Russell D. Monds

    2014-11-01

    Full Text Available Diversification of cell size is hypothesized to have occurred through a process of evolutionary optimization, but direct demonstrations of causal relationships between cell geometry and fitness are lacking. Here, we identify a mutation from a laboratory-evolved bacterium that dramatically increases cell size through cytoskeletal perturbation and confers a large fitness advantage. We engineer a library of cytoskeletal mutants of different sizes and show that fitness scales linearly with respect to cell size over a wide physiological range. Quantification of the growth rates of single cells during the exit from stationary phase reveals that transitions between “feast-or-famine” growth regimes are a key determinant of cell-size-dependent fitness effects. We also uncover environments that suppress the fitness advantage of larger cells, indicating that cell-size-dependent fitness effects are subject to both biophysical and metabolic constraints. Together, our results highlight laboratory-based evolution as a powerful framework for studying the quantitative relationships between morphology and fitness.

  17. Linear porokeratosis with multiple squamous cell carcinomas successfully treated by electrochemotherapy.

    Science.gov (United States)

    Sommerlad, M; Lock, A; Moir, G; McGregor, J; Bull, R; Cerio, R; Harwood, C

    2016-12-01

    Porokeratosis is a clonal epidermal disorder of keratinization characterized by annular lesions with an atrophic centre and a hyperkeratotic edge. The cornoid lamella is the histopathological hallmark. Six clinical variants are recognized: porokeratosis of Mibelli; disseminated superficial porokeratosis; disseminated superficial actinic porokeratosis (DSAP); porokeratosis plantaris et palmaris disseminata; punctate porokeratosis and linear porokeratosis. Linear porokeratosis is the type most frequently associated with malignant transformation into squamous cell carcinoma (SCC). It is thought to represent a mosaic form of DSAP and has an incidence of less than 1 in 200 000; treatment options are limited. We describe a patient with systematized linear porokeratosis and multiple SCCs who was successfully treated with bleomycin electrochemotherapy (ECT), a form of intralesional chemotherapy. In view of their large number, the individual SCCs were treated with bleomycin ECT. One year post-treatment the patient remains tumour free. To our knowledge, this is the first case of multiple SCCs treated by ECT in the context of systematized linear porokeratosis. Our case highlights the challenges associated with diagnosing and managing this unusual form of porokeratosis.

  18. [Cells in the system of multicelular organisms from positions of non-linear dynamics].

    Science.gov (United States)

    Kotolupov, V A; Isaeva, V V

    2012-01-01

    The organism physiological systems forming a hierarchic network with mutual dependence and subordination can be considered as systems with non-linear dynamics including positive and negative feedbacks. In the course of evolution there occurred selection of robust, flexible, modular systems capable for adaptive self-organization by non-linear interaction of components, which leads to formation of the ordered in space and time robust and plastic organization of the whole. Cells of multicellular organisms are capable for coordinated "social" behavior with formation of ordered cell assemblies, which provides a possibility of morphological and functional variability correlating with manifestations of the large spectrum of adaptive reactions. The multicellular organism is the multilevel system with hierarchy of numerous subsystems capable for adaptive self-organization; disturbance of their homeostasis can lead to pathological changes. The healthy organism regulates homeostasis, self-renewal, differentiation, and apoptosis of cells serving its parts and construction blocks by preserving its integrity and controlling behavior of cells. The systemic approach taking into account biological regularities of the appearance and development of functions in evolution of multicellular organisms opens new possibilities for diagnostics and treatment of many diseases.

  19. Nonlinear robust control of proton exchange membrane fuel cell by state feedback exact linearization

    Energy Technology Data Exchange (ETDEWEB)

    Li, Q.; Chen, W. [School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan Province (China); Wang, Y.; Jia, J. [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue 639798, Singapore (Singapore); Han, M. [School of Engineering, Temasek Polytechnic, Tampines 529757, Singapore (Singapore)

    2009-10-20

    By utilizing the state feedback exact linearization approach, a nonlinear robust control strategy is designed based on a multiple-input multiple-output (MIMO) dynamic nonlinear model of proton exchange membrane fuel cell (PEMFC). The state feedback exact linearization approach can achieve the global exact linearization via the nonlinear coordinate transformation and the dynamic extension algorithm such that H{sub {infinity}} robust control strategy can be directly utilized to guarantee the robustness of the system. The proposed dynamic nonlinear model is tested by comparing the simulation results with the experimental data in Fuel Cell Application Centre in Temasek Polytechnic. The comprehensive results of simulation manifest that the dynamic nonlinear model with nonlinear robust control law has better transient and robust stability when the vehicle running process is simulated. The proposed nonlinear robust controller will be very useful to protect the membrane damage by keeping the pressure deviations as small as possible during large disturbances and prolong the stack life of PEMFC. (author)

  20. Optical analysis and thermal management of 2-cell strings linear concentrating photovoltaic system

    Science.gov (United States)

    Reddy, K. S.; Kamnapure, Nikhilesh R.

    2015-09-01

    This paper presents the optical and thermal analyses for a linear concentrating photovoltaic/thermal collector under different operating conditions. Linear concentrating photovoltaic system (CPV) consists of a highly reflective mirror, a receiver and semi-dual axis tracking mechanism. The CPV receiver embodies two strings of triple-junction cells (100 cells in each string) adhered to a mild steel circular tube mounted at the focal length of trough. This system provides 560 W of electricity and 1580 W of heat which needs to be dissipated by active cooling. The Al2O3/Water nanofluid is used as heat transfer fluid (HTF) flowing through circular receiver for CPV cells cooling. Optical analysis of linear CPV system with 3.35 m2 aperture and geometric concentration ratio (CR) of 35 is carried out using Advanced System Analysis Program (ASAP) an optical simulation tool. Non-uniform intensity distribution model of solar disk is used to model the sun in ASAP. The impact of random errors including slope error (σslope), tracking error (σtrack) and apparent change in sun's width (σsun) on optical performance of collector is shown. The result from the optical simulations shows the optical efficiency (ηo) of 88.32% for 2-cell string CPV concentrator. Thermal analysis of CPV receiver is carried out with conjugate heat transfer modeling in ANSYS FLUENT-14. Numerical simulations of Al2O3/Water nanofluid turbulent forced convection are performed for various parameters such as nanoparticle volume fraction (φ), Reynolds number (Re). The addition of the nanoparticle in water enhances the heat transfer in the ranges of 3.28% - 35.6% for φ = 1% - 6%. Numerical results are compared with literature data which shows the reasonable agreement.

  1. Cell protection by low doses of ionizing radiation challenges the concept of linearity

    Energy Technology Data Exchange (ETDEWEB)

    Feinendegen, L.E. [Brookhaven National Lab., Upton, NY (United States). Medical Dept.; Bond, V.P. [Washington State Univ., Richland, WA (United States). Research Faculty; Sondhaus, C.A. [Arizona Univ., Tucson, AZ (United States). Dept. of Radiology and Radiation Control Office; Altman, K.I.

    1999-07-01

    Ionizing radiation is known to potentially interfere with cellular functions at all levels. Cell death and late effects such as malignant tumors may result. These stem from permanent damage to cellular DNA, which may lead to maligant transformation of the affected cells. Most such studies have used relatively high values of an absorbed dose, D, above about 0.3 Gy. After acute exposures of humans to between 0.3 and 2 Gy, the risk of cancer in the exposed individuals seems proportional to tissue D. For the purpose of radiation protection, this proportionality is assumed to extend down to zero D. This assumption defines the linear-no-threshold, LNT, hypothesis. In addition to DNA damage, altered intracellular signaling results from acute exposure to cell doses below about 0.3 Gy, and involves radiation-induced reactive oxygen species, ROS. In consequence, different mechanisms of protection against DNA lesions may be induced and last from hours to weeks in different cell types. Damage to DNA is continuously and endogenously produced mainly by ROS generated in a normal oxidative metabolism. This DNA damage quantitatively exceeds by several orders of magnitude that caused by low-dose irradiation. Thus, the protective responses following acute low-dose irradiation may be presumed to mainly prevent and reduce endogenously caused DNA damage. Protective responses are physiological and ubiquitous, albeit differently expressed in various cell types and species. Only in few cases has the induction of such responses been studied that occur after acute low-dose irradiation. Their incidence has been described to be nonlinear, increasing initially with D, beginning to decrease with D when D exceeds about 0.1-0.2 Gy, and eventually disappearing at higher D. Accordingly, the model described here uses two dose-effect functions, one linear for causing and a nonlinear one for reducing DNA damage in the irradiated cells and tissues. The resulting net dose-risk function strongly suggests

  2. 光系统Ⅱ反应中心CP47/D1/D2/Cyt b-559复合物中色素分子空间取向的线二色光谱研究%Orientation of Pigments in the Isolated Photosystem Ⅱ Sub-core Reaction Center CP47/D1/D2/Cyt b-559 Complexes: A Linear Dichroism Study

    Institute of Scientific and Technical Information of China (English)

    侯建敏; Dominique DEJONGHE; 单际修; 李良璧; 匡廷云

    2000-01-01

    Linear dichroism (LD) spectroscopy is an important technique in the study of the orientation andorganization of pigments in the photosynthetic membrane complexes in vivo and in vitro. In this work, the ori-entation of the pigments in the isolated photosystem Ⅱ (PS Ⅱ) sub-core reaction center complexes was ana-lyzed and characterized by means of low temperature absorption and LD spectroscopy. The preparations con-taining different amounts of CP47 isolated from spinach (Spinacia oleracea L.) chloroplast were used in orderto investigate the orientation of pigments in the PS Ⅱ sub-core CP47/D1/D2/Cyt b-559 (CP47/D1/D2) com-plexes. Chlorophyll a (Chl a) absorbing at 680 nm in CP47/D1/D2/Cyt b-559 complex showed an orientationof the Qy transition parallel to the membrane plane. It is proposed that there are two forms of β-carotene (β-Car) in CP47/D1/D2/Cyt b-559 complex, denoted as β-Car (Ⅰ) and β-Car (Ⅱ), with different orienta-tions, β-Car (Ⅰ) at 470 and 505 nm is roughly parallel to the membrane plane, and β-Car (Ⅱ) at 460 and490 nm seems to be perpendicular orientation. Upon the photoinhibitory experiment β-Car (Ⅱ) was found tobe photosensitive and easily photodamaged. It also showed that the positive LD signal observed at 680 nm wasquite complicated. This signal is tentatively attributed to P680 and some Chl a of antenna in CP47 proteinbased upon our measurements.%线二色光谱(LD)是研究色素分子在光合膜上空间取向和排布的重要手段.采用低温(100K)吸收光谱和线二色光谱技术研究光系统Ⅱ核心复合物CP47/D1/D2/Cyt b-559中色素分子的空间取向.结果表明,在光系统Ⅱ核心复合物CP47/D1/D2/Cyt b-559中680 nm处有吸收的叶绿素分子Qy跃迁与光合膜平面平行.β-胡萝卜素分子有两种不同的空间取向,其中在470和505nm处有吸收的β-胡萝卜素分子(Ⅰ)与光合膜平面近似平行,而在460和490nm处有吸收的β-胡萝卜素分子(Ⅱ)与光合膜垂直.光

  3. Electronic and vibrational circular dichroism spectra of (R)-(-)-apomorphine

    Energy Technology Data Exchange (ETDEWEB)

    Abbate, Sergio, E-mail: abbate@med.unibs.it [Dipartimento di Scienze Biomediche e Biotecnologie, Universita di Brescia, Viale Europa 11, 25123 Brescia (Italy); CNISM, Consorzio Interuniversitario Scienze Fisiche della Materia, Via della Vasca Navale 84, 00146 Roma (Italy); Longhi, Giovanna; Lebon, France [Dipartimento di Scienze Biomediche e Biotecnologie, Universita di Brescia, Viale Europa 11, 25123 Brescia (Italy); CNISM, Consorzio Interuniversitario Scienze Fisiche della Materia, Via della Vasca Navale 84, 00146 Roma (Italy); Tommasini, Matteo [Dipartimento di Chimica, Materiali e Ingegneria Chimica ' G. Natta' , Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Consorzio Interuniversitario per la Scienza e Tecnologia dei Materiali (INSTM), Unita di Ricerca del Politecnico di Milano (Dip. CMIC), Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

    2012-09-11

    Highlights: Black-Right-Pointing-Pointer ECD and VCD Spectra of (R)-(-)-apomorphine measured in various solvents. Black-Right-Pointing-Pointer DFT calculations allow to study the protonation state and conformations. Black-Right-Pointing-Pointer Contributions from catechol OH vibrations to the VCD spectra is studied. -- Abstract: Apomorphine is a chiral drug molecule; notwithstanding its extraordinary importance, little attention has been paid to the characterization of its chiroptical properties. Here we report on its electronic circular dichroism (ECD) spectra, recorded in methanol and water, and vibrational circular dichroism (VCD) in methanol and dimethyl sulfoxide (DMSO) solutions. Density functional theory (DFT) calculations have allowed us to interpret the spectra and to evaluate the role of possible conformations, charge-states and interactions with counter ions.

  4. Structural characterization of chiral molecules using vibrational circular dichroism spectroscopy

    DEFF Research Database (Denmark)

    Lassen, Peter Rygaard

    2006-01-01

    compounds of pharmaceutical interest. Others are transition metal complexes relevant for the search for parity-violation effects in vibrational spectroscopy (rhenium complexes), for asymmetric catalysis (Schiff-base complexes), or as model systems for metal centres in biology (Schiff-bases and heme....... Currently, only part of the enhancement can be reproduced theoretically, as demonstrated for the Schiff-bases. Their conformers and absolute configurations were also identified. As for proteins, the interpretation of their spectra is different, because the immense number of overlapping vibrational modes...... chiral molecules. This project is about application of one such technique, circular dichroism (CD) spectroscopy, which measures the difference in absorption of left- and right circularly polarized light - hence the name circular dichroism. This study has focused on the infrared (IR) range because...

  5. Stereochemistry of the tadalafil diastereoisomers: a critical assessment of vibrational circular dichroism, electronic circular dichroism, and optical rotatory dispersion.

    Science.gov (United States)

    Qiu, Shi; De Gussem, Ewoud; Tehrani, Kourosch Abbaspour; Sergeyev, Sergey; Bultinck, Patrick; Herrebout, Wouter

    2013-11-14

    The stereochemistry of all four stereoisomers of tadalafil is determined using vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and optical rotatory dispersion (ORD) spectroscopy. By comparing experimentally obtained VCD spectra to computationally simulated ones, the absolute configuration of the enantiomeric pair (6R, 12aR)/(6S, 12aS) can be confidently assigned without prior knowledge of their relative stereochemistry. IR and NMR spectra are used to aid the assignment of the relative stereochemistry. The IR and VCD difference spectra further confirm the assignment of all stereoisomers. ECD and ORD spectra are used to investigate the complementarity of the three chiroptical techniques. VCD spectroscopy itself is found to have the ability to identify diastereoisomers, and simultaneous use of these chiroptical spectroscopic methods and NMR chemical shifts aids in increasing the reliability of stereochemistry assignment of diastereoisomers.

  6. High linear-energy-transfer radiation can overcome radioresistance of glioma stem-like cells to low linear-energy-transfer radiation

    Science.gov (United States)

    Hirota, Yuki; Masunaga, Shin-Ichiro; Kondo, Natsuko; Kawabata, Shinji; Hirakawa, Hirokazu; Yajima, Hirohiko; Fujimori, Akira; Ono, Koji; Kuroiwa, Toshihiko; Miyatake, Shin-Ichi

    2014-01-01

    Ionizing radiation is applied as the standard treatment for glioblastoma multiforme (GBM). However, radiotherapy remains merely palliative, not curative, because of the existence of glioma stem cells (GSCs), which are regarded as highly radioresistant to low linear-energy-transfer (LET) photons. Here we analyzed whether or not high-LET particles can overcome the radioresistance of GSCs. Glioma stem-like cells (GSLCs) were induced from the GBM cell line A172 in stem cell culture medium. The phenotypes of GSLCs and wild-type cells were confirmed using stem cell markers. These cells were irradiated with 60Co gamma rays or reactor neutron beams. Under neutron-beam irradiation, high-LET proton particles can be produced through elastic scattering or nitrogen capture reaction. Radiosensitivity was assessed by a colony-forming assay, and the DNA double-strand breaks (DSBs) were assessed by a histone gamma-H2AX focus detection assay. In stem cell culture medium, GSLCs could form neurosphere-like cells and express neural stem cell markers (Sox2 and Musashi) abundantly in comparison with their parental cells. GSLCs were significantly more radioresistant to gamma rays than their parental cells, but neutron beams overcame this resistance. There were significantly fewer gamma-H2AX foci in the A172 GSLCs 24 h after irradiation with gamma rays than in their parental cultured cells, while there was no apparent difference following neutron-beam irradiation. High-LET radiation can overcome the radioresistance of GSLCs by producing unrepairable DNA DSBs. High-LET radiation therapy might have the potential to overcome GBM's resistance to X-rays in a clinical setting. PMID:23955054

  7. Linear identification and model adjustment of a PEM fuel cell stack

    Energy Technology Data Exchange (ETDEWEB)

    Kunusch, C.; Puleston, P.F.; More, J.J. [LEICI, Departamento de Electrotecnia, Universidad Nacional de La Plata, calle 1 esq. 47 s/n, 1900 La Plata (Argentina); Consejo de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina); Husar, A. [Institut de Robotica i Informatica Industrial (CSIC-UPC), c/ Llorens i Artigas 4-6, 08028 Barcelona (Spain); Mayosky, M.A. [LEICI, Departamento de Electrotecnia, Universidad Nacional de La Plata, calle 1 esq. 47 s/n, 1900 La Plata (Argentina); Comision de Investigaciones Cientificas (CIC), Provincia de Buenos Aires (Argentina)

    2008-07-15

    In the context of fuel cell stack control a mayor challenge is modeling the interdependence of various complex subsystem dynamics. In many cases, the states interaction is usually modeled through several look-up tables, decision blocks and piecewise continuous functions. Many internal variables are inaccessible for measurement and cannot be used in control algorithms. To make significant contributions in this area, it is necessary to develop reliable models for control and design purposes. In this paper, a linear model based on experimental identification of a 7-cell stack was developed. The procedure followed to obtain a linear model of the system consisted in performing spectroscopy tests of four different single-input single-output subsystems. The considered inputs for the tests were the stack current and the cathode oxygen flow rate, while the measured outputs were the stack voltage and the cathode total pressure. The resulting model can be used either for model-based control design or for on-line analysis and errors detection. (author)

  8. Measurement of the polarization for soft x-ray magnetic circular dichroism at the BSRF beamline 4B7B

    CERN Document Server

    Zhi-Ying, Guo; Jing-Tao, Zhu; YI-Dong, Zhao; Lei, Zheng; Cai-Hao, Hong; Kun, Tang; Dong-Liang, Yang; Ming-Qi, Cui

    2012-01-01

    Three ultra-short-period W/B4C multilayers (1.244nm, 1.235nm and 1.034nm) have been fabricated and used for polarization measurement at the 4B7B Beamline of Beijing Synchrotron Radiation Facility (BSRF). By rotating analyzer ellipsometry method, the linear polarization degree of light emerging from this beamline has been measured and the circular polarization evaluated for 700eV-860eV. The first soft x-ray magnetic circular dichroism measurements are carried out at BSRF by positioning the beamline aperture out of the plane of the electron storage ring.

  9. Intermediate regime and a phase diagram of red blood cell dynamics in a linear flow

    Science.gov (United States)

    Levant, Michael; Steinberg, Victor

    2016-12-01

    In this paper we investigate the in vitro dynamics of a single rabbit red blood cell (RBC) in a planar linear flow as a function of a shear stress σ and the dynamic viscosity of outer fluid ηo. A linear flow is a generalization of previous studies dynamics of soft objects including RBC in shear flow and is realized in the experiment in a microfluidic four-roll mill device. We verify that the RBC stable orientation dynamics is found in the experiment being the in-shear-plane orientation and the RBC dynamics is characterized by observed three RBC dynamical states, namely tumbling (TU), intermediate (INT), and swinging (SW) [or tank-treading (TT)] on a single RBC. The main results of these studies are the following. (i) We completely characterize the RBC dynamical states and reconstruct their phase diagram in the case of the RBC in-shear-plane orientation in a planar linear flow and find it in a good agreement with that obtained in early experiments in a shear flow for human RBCs. (ii) The value of the critical shear stress σc of the TU-TT(SW) transition surprisingly coincides with that found in early experiments in spite of a significant difference in the degree of RBC shape deformations in both the SW and INT states. (iii) We describe the INT regime, which is stationary, characterized by strong RBC shape deformations and observed in a wide range of the shear stresses. We argue that our observations cast doubts on the main claim of the recent numerical simulations that the only RBC spheroidal stress-free shape is capable to explain the early experimental data. Finally, we suggest that the amplitude dependence of both θ and the shape deformation parameter D on σ can be used as the quantitative criterion to determine the RBC stress-free shape.

  10. Linearized texture of three-dimensional extracellular matrix is mandatory for bladder cancer cell invasion

    Science.gov (United States)

    Alfano, Massimo; Nebuloni, Manuela; Allevi, Raffaele; Zerbi, Pietro; Longhi, Erika; Lucianò, Roberta; Locatelli, Irene; Pecoraro, Angela; Indrieri, Marco; Speziali, Chantal; Doglioni, Claudio; Milani, Paolo; Montorsi, Francesco; Salonia, Andrea

    2016-01-01

    In the fields of biomaterials and tissue engineering simulating the native microenvironment is of utmost importance. As a major component of the microenvironment, the extracellular matrix (ECM) contributes to tissue homeostasis, whereas modifications of native features are associated with pathological conditions. Furthermore, three-dimensional (3D) geometry is an important feature of synthetic scaffolds favoring cell stemness, maintenance and differentiation. We analyzed the 3D structure, geometrical measurements and anisotropy of the ECM isolated from (i) human bladder mucosa (basal lamina and lamina propria) and muscularis propria; and, (ii) bladder carcinoma (BC). Next, binding and invasion of bladder metastatic cell line was observed on synthetic scaffold recapitulating anisotropy of tumoral ECM, but not on scaffold with disorganized texture typical of non-neoplastic lamina propria. This study provided information regarding the ultrastructure and geometry of healthy human bladder and BC ECMs. Likewise, using synthetic scaffolds we identified linearization of the texture as a mandatory feature for BC cell invasion. Integrating microstructure and geometry with biochemical and mechanical factors could support the development of an innovative synthetic bladder substitute or a tumoral scaffold predictive of chemotherapy outcomes. PMID:27779205

  11. Effect of linear alkylbenzene sulfonate (LAS) on human intestinal Caco-2 cells at non cytotoxic concentrations.

    Science.gov (United States)

    Bradai, Mohamed; Han, Junkyu; Omri, Abdelfatteh El; Funamizu, Naoyuki; Sayadi, Sami; Isoda, Hiroko

    2016-08-01

    Linear alkylbenzene sulfonate (LAS) is a cytotoxic synthetic anionic surfactant widely present in the environment due to its large-scale production and intensive use in the detergency field. In this study, we investigated the effect of LAS (CAS No. 25155-30-0) at non cytotoxic concentrations on human intestinal Caco-2 cells using different in vitro bioassays. As results, LAS increased Caco-2 cell proliferation at concentrations ranging from 1 to 15 ppm, more significantly for shorter exposure time (24 h), confirmed using flow cytometry and trypan blue exclusion methods. Moreover, proteomics analysis revealed that this effect was associated with an over-expression of elongation factor 2 and dipeptidyl peptidase 3, and a down-regulation of 14-3-3 protein theta, confirmed at mRNA level using real-time PCR. These findings suggest that LAS at non cytotoxic concentrations, similar to those observed at wastewater treatment plants outlets, increases the growth rate of colon cancer cells, raising thereby its tumor promotion effect potential.

  12. Linear gyrokinetic particle-in-cell simulations of Alfven instabilities in tokamaks

    CERN Document Server

    Biancalani, A; Briguglio, S; Koenies, A; Lauber, Ph; Mishchenko, A; Poli, E; Scott, B D; Zonca, F

    2015-01-01

    The linear dynamics of Alfven modes in tokamaks is investigated here by means of the global gyrokinetic particle-in-cell code NEMORB. The model equations are shown and the local shear Alfven wave dispersion relation is derived, recovering the continuous spectrum in the incompressible ideal MHD limit. A verification and benchmark analysis is performed for continuum modes in a cylinder and for toroidicity-induced Alfven Eigenmodes. Modes in a reversed-shear equilibrium are also investigated, and the dependence of the spatial structure in the poloidal plane on the equilibrium parameters is described. In particular, a phase-shift in the poloidal angle is found to be present for modes whose frequency touches the continuum, whereas a radial symmetry is found to be characteristic of modes in the continuum gap.

  13. Circular Dichroism in Multiphoton Ionization of Resonantly Excited He+ Ions

    Science.gov (United States)

    Ilchen, M.; Douguet, N.; Mazza, T.; Rafipoor, A. J.; Callegari, C.; Finetti, P.; Plekan, O.; Prince, K. C.; Demidovich, A.; Grazioli, C.; Avaldi, L.; Bolognesi, P.; Coreno, M.; Di Fraia, M.; Devetta, M.; Ovcharenko, Y.; Düsterer, S.; Ueda, K.; Bartschat, K.; Grum-Grzhimailo, A. N.; Bozhevolnov, A. V.; Kazansky, A. K.; Kabachnik, N. M.; Meyer, M.

    2017-01-01

    Intense, circularly polarized extreme-ultraviolet and near-infrared (NIR) laser pulses are combined to double ionize atomic helium via the oriented intermediate He+(3 p ) resonance state. Applying angle-resolved electron spectroscopy, we find a large photon helicity dependence of the spectrum and the angular distribution of the electrons ejected from the resonance by NIR multiphoton absorption. The measured circular dichroism is unexpectedly found to vary strongly as a function of the NIR intensity. The experimental data are well described by theoretical modeling and possible mechanisms are discussed.

  14. Characterization of magnetic domain walls using electron magnetic chiral dichroism

    Directory of Open Access Journals (Sweden)

    Ren Chao Che, Chong Yun Liang, Xiang He, Hai Hua Liu and Xiao Feng Duan

    2011-01-01

    Full Text Available Domain walls and spin states of permalloy were investigated by electron magnetic chiral dichroism (EMCD technique in Lorentz imaging mode using a JEM-2100F transmission electron microscope. EMCD signals from both Fe and Ni L3,2 edges were detected from the Bloch lines but not from the adjacent main wall. The magnetic polarity orientation of the circular Bloch line is opposite to that of the cross Bloch line. The orientations of Fe and Ni spins are parallel rather than antiparallel, both at the cross Bloch line and circular Bloch line.

  15. A novel methodology for non-linear system identification of battery cells used in non-road hybrid electric vehicles

    Science.gov (United States)

    Unger, Johannes; Hametner, Christoph; Jakubek, Stefan; Quasthoff, Marcus

    2014-12-01

    An accurate state of charge (SoC) estimation of a traction battery in hybrid electric non-road vehicles, which possess higher dynamics and power densities than on-road vehicles, requires a precise battery cell terminal voltage model. This paper presents a novel methodology for non-linear system identification of battery cells to obtain precise battery models. The methodology comprises the architecture of local model networks (LMN) and optimal model based design of experiments (DoE). Three main novelties are proposed: 1) Optimal model based DoE, which aims to high dynamically excite the battery cells at load ranges frequently used in operation. 2) The integration of corresponding inputs in the LMN to regard the non-linearities SoC, relaxation, hysteresis as well as temperature effects. 3) Enhancements to the local linear model tree (LOLIMOT) construction algorithm, to achieve a physical appropriate interpretation of the LMN. The framework is applicable for different battery cell chemistries and different temperatures, and is real time capable, which is shown on an industrial PC. The accuracy of the obtained non-linear battery model is demonstrated on cells with different chemistries and temperatures. The results show significant improvement due to optimal experiment design and integration of the battery non-linearities within the LMN structure.

  16. Complex polarization propagator calculations of magnetic circular dichroism spectra

    Science.gov (United States)

    Solheim, Harald; Ruud, Kenneth; Coriani, Sonia; Norman, Patrick

    2008-03-01

    It is demonstrated that the employment of the nonlinear complex polarization propagator enables the calculation of the complete magnetic circular dichroism spectra of closed-shell molecules, including at the same time both the so-called Faraday A and B terms. In this approach, the differential absorption of right and left circularly polarized light in the presence of a static magnetic field is determined from the real part of the magnetic field-perturbed electric dipole polarizability. The introduction of the finite lifetimes of the electronically excited states into the theory results in response functions that are well behaved in the entire spectral region, i.e., the divergencies that are found in conventional response theory approaches at the transition energies of the system are not present. The applicability of the approach is demonstrated by calculations of the ultraviolet magnetic circular dichroism spectra of para-benzoquinone, tetrachloro-para-benzoquinone, and cyclopropane. The present results are obtained with the complex polarization propagator approach in conjunction with Kohn-Sham density functional theory and the standard adiabatic density functionals B3LYP, CAM-B3LYP, and BHLYP.

  17. Circular dichroism in drug discovery and development: an abridged review.

    Science.gov (United States)

    Bertucci, Carlo; Pistolozzi, Marco; De Simone, Angela

    2010-09-01

    Chirality plays a fundamental role in determining the pharmacodynamic and pharmacokinetic properties of drugs, and contributes significantly to our understanding of the mechanisms that lie behind biorecognition phenomena. Circular dichroism spectroscopy is the technique of choice for determining the stereochemistry of chiral drugs and proteins, and for monitoring and characterizing molecular recognition phenomena in solution. The role of chirality in our understanding of recognition phenomena at the molecular level is discussed here via several selected systems of interest in the drug discovery and development area. The examples were selected in order to underline the utility of circular dichroism in emerging studies of protein-protein interactions in biological context. In particular, the following aspects are discussed here: the relationship between stereochemistry and pharmacological activity--stereochemical characterization of new leads and drugs; stereoselective binding of leads and drugs to target proteins--the binding of drugs to serum albumins; conformational transitions of peptides and proteins of physiological relevance, and the stereochemical characterization of therapeutic peptides.

  18. Structural characterization of recombinant therapeutic proteins by circular dichroism.

    Science.gov (United States)

    Bertucci, Carlo; Pistolozzi, Marco; De Simone, Angela

    2011-10-01

    Most of the protein therapeutics are now produced by recombinant DNA technology. The advantages of recombinant proteins are related to their higher specificity and to their safety as exposure to animal or human diseases. However, several problems are still present in development of recombinant proteins as therapeutics, such as low bioavailability, short serum half-life, and immune response. Their successful application hinges on the protein stereochemical stability, and on the folding and the tendency to aggregate induced by purification steps and storage. All these aspects determine the failure of many potential protein therapies, and limitations in the development of the formulation. The application of multiple analytical techniques is important in order to obtain a detailed product profile and to understand how manufacturing can influence product structure and activity. Surely the protein conformation is a key aspect to be assessed, because a specific conformation is often essential for the biological function of the protein. Thus, there is a growing need to perform structural studies under the conditions in which the proteins operate, and to monitor the structural changes of the protein. Circular dichroism has been increasingly recognised as a valuable and reliable technique to get this information. In particular, examples will be here reported on the use of circular dichroism spectroscopy in the structural characterization of free and formulated recombinant proteins, looking at the prediction of the secondary structure, propensity to conformational changes, stability, and tendency to aggregate.

  19. A circular dichroism sensor for Ni(2+) and Co(2+) based on L-cysteine capped cadmium sulfide quantum dots.

    Science.gov (United States)

    Tedsana, Wimonsiri; Tuntulani, Thawatchai; Ngeontae, Wittaya

    2015-03-31

    A new circular dichroism sensor for detecting Ni(2+) and Co(2+) was proposed for the first time using chiral chelating quantum dots. The detection principle was based on changing of circular dichroism signals of the chiral quantum dots when forming a chiral complex with Ni(2+) or Co(2+). L-Cysteine capped cadmium sulfide quantum dots (L-Cyst-CdS QDs) were proposed as a chiral probe. The CD spectrum of L-Cyst-CdS QDs was significantly changed in the presence of Ni(2+) and Co(2+). On the other hand, other studied cations did not alter the original CD spectrum. Moreover, when increasing the concentration of Ni(2+) or Co(2+), the intensity of the CD spectrum linearly increased as a function of concentration and could be useful for the quantitative analysis. The proposed CD sensor showed linear working concentration ranges of 10-60 μM and 4-80 μM with low detection limits of 7.33 μМ and 1.13 μM for the detection of Ni(2+) and Co(2+), respectively. Parameters possibly affected the detection sensitivity such as solution pH and incubation time were studied and optimized. The proposed sensor was applied to detect Ni(2+) and Co(2+) in real water samples, and the results agreed well with the analysis using the standard ICP-OES.

  20. Flow Linear Dichroism Spectroscopic Studies of the Natural Product Curcumin and Double Stranded DNA

    DEFF Research Database (Denmark)

    Leth, Rasmus; Thulstrup, Peter Waaben

    2011-01-01

    Curcumin is a polyphenol found in the rhizomes of the plant Curcuma Longa, commonly known as turmeric. Curcumin has a bright yellow color, and in turmeric, curcumin exists along with two other curcuminoids: desmethoxy curcumin and bisdesmethoxy curcumin [1]. Curcumin has shown multiple biological...

  1. Identification of critical residues of linear B cell epitope on Goodpasture autoantigen.

    Directory of Open Access Journals (Sweden)

    Xiao-yu Jia

    Full Text Available The autoantigen of anti-glomerular basement membrane (GBM disease has been identified as the non-collagenous domain 1 of α3 chain of type IV collagen, α3(IVNC1. Our previous study revealed a peptide on α3(IVNC1 as a major linear epitope for B cells and potentially nephrogenic, designated as P14 (α3129-150. This peptide has also been proven to be the epitope of auto-reactive T cells in anti-GBM patients. This study was aimed to further characterize the critical motif of P14.16 patients with anti-GBM disease and positive anti-P14 antibodies were enrolled. A set of truncated and alanine substituted peptides derived from P14 were synthesized. Circulating antibodies against the peptides were detected by enzyme linked immunosorbent assay (ELISA.We found that all sera with anti-P14 antibodies reacted with the 13-mer sequence in the C-terminus of P14 (P14c exclusively. The level of antibodies against P14 was highly correlated with the level of antibodies against P14c (r=0.970, P<0.001. P14c was the core immunogenic region and the amino acid sequence (ISLWKGFSFIMFT was highly hydrophobic. Each amino acid residue in P14c was sequentially replaced by alanine. Three residues of glycine142, phenylalanine143, and phenylalanine145 were identified crucial for antibody binding based on the remarkable decline (P<0.001 of antibody reaction after each residue replacement.We defined GFxF (α3142, 143,145 as the critical motif of P14. It may provide some clues for understanding the etiology of anti-GBM disease.

  2. Kinetics of linear rouleaux formation studied by visual monitoring of red cell dynamic organization.

    Science.gov (United States)

    Barshtein, G; Wajnblum, D; Yedgar, S

    2000-05-01

    Red blood cells (RBCs) in the presence of plasma proteins or other macromolecules may form aggregates, normally in rouleaux formations, which are dispersed with increasing blood flow. Experimental observations have suggested that the spontaneous aggregation process involves the formation of linear rouleaux (FLR) followed by formation of branched rouleaux networks. Theoretical models for the spontaneous rouleaux formation were formulated, taking into consideration that FLR may involve both "polymerization," i.e., interaction between two single RBCs (e + e) and the addition of a single RBC to the end of an existing rouleau (e + r), as well as "condensation" between two rouleaux by end-to-end addition (r + r). The present study was undertaken to experimentally examine the theoretical models and their assumptions, by visual monitoring of the spontaneous FLR (from singly dispersed RBC) in plasma, in a narrow gap flow chamber. The results validate the theoretical model, showing that FLR involves both polymerization and condensation, and that the kinetic constants for the above three types of intercellular interactions are the same, i.e., k(ee) = k(er) = k(rr) = k, and for all tested hematocrits (0.625-6%) k < 0.13 +/- 0.03 s(-1).

  3. Uncertainty in measurement of protein circular dichroism spectra

    Science.gov (United States)

    Cox, Maurice G.; Ravi, Jascindra; Rakowska, Paulina D.; Knight, Alex E.

    2014-02-01

    Circular dichroism (CD) spectroscopy of proteins is widely used to measure protein secondary structure, and to detect changes in secondary and higher orders of structure, for applications in research and in the quality control of protein products such as biopharmaceuticals. However, objective comparison of spectra is challenging because of a limited quantitative understanding of the sources of error in the measurement. Statistical methods can be used for comparisons, but do not provide a mechanism for dealing with systematic, as well as random, errors. Here we present a measurement model for CD spectroscopy of proteins, incorporating the principal sources of uncertainty, and use the model in conjunction with experimental data to derive an uncertainty budget. We show how this approach could be used in practice for the objective comparison of spectra, and discuss the benefits and limitations of this strategy.

  4. Using Circular Dichroism Spectra to Estimate Protein Secondary Structure

    Energy Technology Data Exchange (ETDEWEB)

    Greenfield, N.

    2006-01-01

    Circular dichroism (CD) is an excellent tool for rapid determination of the secondary structure and folding properties of proteins that have been obtained using recombinant techniques or purified from tissues. The most widely used applications of protein CD are to determine whether an expressed, purified protein is folded, or if a mutation affects its conformation or stability. In addition, it can be used to study protein interactions. This protocol details the basic steps of obtaining and interpreting CD data and methods for analyzing spectra to estimate the secondary structural composition of proteins. CD has the advantage that it is that measurements may be made on multiple samples containing 20 {mu}g or less of proteins in physiological buffers in a few hours. However, it does not give the residue-specific information that can be obtained by X-ray crystallography or NMR.

  5. Roles of linear ubiquitinylation, a crucial regulator of NF-κB and cell death, in the immune system.

    Science.gov (United States)

    Sasaki, Katsuhiro; Iwai, Kazuhiro

    2015-07-01

    Linear ubiquitinylation, a newly identified post-translational modification, is catalyzed by the linear ubiquitin assembly complex (LUBAC), which is composed of three different subunits, HOIL-1L (heme-oxidized IRP2 ligase 1L), HOIP (HOIL-1 interacting protein), and SHARPIN (SHANK-associated RH domain-interacting protein). LUBAC plays a critical role in the activation of nuclear factor-κB (NF-κB) signaling triggered by a variety of stimuli, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and pathogen-derived components, and in the protection from cell death. Loss of function of SHARPIN in mice triggers chronic inflammation in multiple organs including the skin, as well as immunodeficiency. In humans, mutations in the gene encoding HOIL-1L cause chronic hyperinflammation and immunodeficiency, which are both associated with decreased levels of LUBAC. The linear ubiquitinylation activity of LUBAC is indispensable for B-cell function in mice, and hyperactivation of LUBAC is associated with oncogenesis in certain forms of B-cell lymphoma. In this review, the current understanding of the biochemistry of LUBAC-mediated linear ubiquitinylation and its involvement in the immune system are discussed.

  6. Pancreatic β-cell function increases in a linear dose-response manner following exercise training in adults with prediabetes

    DEFF Research Database (Denmark)

    Malin, Steven K; Solomon, Thomas P J; Blaszczak, Alecia;

    2013-01-01

    composition (dual-energy X-ray absorptiometry and computed tomography) were also measured before and after the intervention. Exercise dose was computed using Vo2/heart-rate derived linear regression equations. Subjects expended 474.5 ± 8.8 kcal/session (2,372.5 ± 44.1 kcal/wk) during the intervention and lost......Although some studies suggest that a linear dose-response relationship exists between exercise and insulin sensitivity, the exercise dose required to enhance pancreatic β-cell function is unknown. Thirty-five older obese adults with prediabetes underwent a progressive 12-wk supervised exercise...

  7. Improved flow cytometric method to enumerate residual cells: minimal linear detection limits for platelets, erythrocytes, and leukocytes.

    Science.gov (United States)

    Pichler, J; Printz, D; Scharner, D; Trbojevic, D; Siekmann, J; Fritsch, G

    2002-08-15

    Increasing demand for quality control of blood products requires more sensitive methods to enumerate residual cells. Presently, the reported threshold (in cells per microliter) is 400 for red blood cells, 30-500 for platelets, and 1 for leukocytes. To examine precision and linearity in enumerating residual platelets and red blood cells, EDTA-anticoagulated blood from healthy donors was serially diluted with serum, stained in TruCount tubes using a no-lyse/no-wash procedure and a monoclonal antibody cocktail against the CD42a (FL1) and glycophorin-A (FL2) epitopes, and analyzed by flow cytometry. Leukocyte counts were determined in separate tubes. Cell preparation and analysis were performed once for 20 blood samples each and 20 times using the same specimen. Acquisition from the same tube was performed separately for platelets (threshold on FL1) and red blood cells (threshold on FL2). Multiparameter analysis was used for data evaluation. Linear results were obtained for platelets per microliter between 3,410 and 5 and for red blood cells per microliter between 54,000 and 3. For the lower cell concentrations, the coefficient of variation was 16.7% for platelets and 10.9% for red blood cells. The presented method allows the distinction between physiologically intact and ghost red blood cells. The method represents a reliable, sensitive, and accurate approach to quantify platelets and red blood cells in diluted blood. It can be applied to enumerate residual cells in plasma products and meets the increasing demand for quality control in blood components.

  8. Studies on fish and pork paste gelation by dynamic rheology and circular dichroism.

    Science.gov (United States)

    Liu, R; Zhao, S-M; Xiong, S-B; Xie, B-J; Liu, H-M

    2007-09-01

    The muscle paste of fish, pork, and their mixtures were prepared to study the gelling characteristics by dynamic rheological measurement. The gelation mechanisms of muscle paste were also investigated by circular dichroism. Gel formation of fish paste occurred in 2 steps of 5 to 35 and 51 to 90 degrees C respectively, while pork paste mainly in 1 step of 49 to 72 degrees C. Gel formation was relative to the alpha-helix unfolding of myosin, which responded the melting temperatures of 40 and 50 degrees C for fish myosin and 50 and 60 degrees C for pork myosin, respectively. Alpha-helix unfolding of myosin was beneficial for gel formation. During gel formation, G' of muscle paste was linearly related to alpha-helical content of myosin. The interactions of fish and pork proteins at high temperature (>35 degrees C) could change the gel forming characteristics of muscle paste. Mixed paste exhibited a similar gelation pattern to individual fish paste with 2 visible increases in G'. Addition of pork could suppress the breakdown of fish gel structure at approximately 50 degrees C. Mixing pork and silver carp in a certain ratio could improve the gel properties of silver carp products.

  9. Applied Circular Dichroism: A Facile Spectroscopic Tool for Configurational Assignment and Determination of Enantiopurity

    Directory of Open Access Journals (Sweden)

    Macduff O. Okuom

    2015-01-01

    Full Text Available In order to determine if electronic circular dichroism (ECD is a good tool for the qualitative evaluation of absolute configuration and enantiopurity in the absence of chiral high performance liquid chromatography (HPLC, ECD studies were performed on several prescriptions and over-the-counter drugs. Cotton effects (CE were observed for both S and R isomers between 200 and 300 nm. For the drugs examined in this study, the S isomers showed a negative CE, while the R isomers displayed a positive CE. The ECD spectra of both enantiomers were nearly mirror images, with the amplitude proportional to the enantiopurity. Plotting the differential extinction coefficient (Δε versus enantiopurity at the wavelength of maximum amplitude yielded linear standard curves with coefficients of determination (R2 greater than 97% for both isomers in all cases. As expected, Equate, Advil, and Motrin, each containing a racemic mixture of ibuprofen, yielded no chiroptical signal. ECD spectra of Suphedrine and Sudafed revealed that each of them is rich in 1S,2S-pseudoephedrine, while the analysis of Equate vapor inhaler is rich in R-methamphetamine.

  10. A complex-polarization-propagator protocol for magneto-chiral axial dichroism and birefringence dispersion

    DEFF Research Database (Denmark)

    Cukras, Janusz; Kauczor, Joanna; Norman, Patrick

    2016-01-01

    A computational protocol for magneto-chiral dichroism and magneto-chiral birefringence dispersion is presented within the framework of damped response theory, also known as complex polarization propagator theory, at the level of time-dependent Hartree–Fock and time-dependent density functional...... theory. Magneto-chiral dichroism and magneto-chiral birefringence spectra in the (resonant) frequency region below the first ionization threshold of R-methyloxirane and L-alanine are presented and compared with the corresponding results obtained for both the electronic circular dichroism and the magnetic...

  11. FTIR Vibrational Circular Dichroism Of Oligopeptides Related To Polyproline

    Science.gov (United States)

    Dukor, R. K.; Keiderling, Timothy A.

    1989-12-01

    Vibrational Circular Dichroism (VCD) data can be routinely measured by FTIR. On our FTIR VCD instrument it is possible to obtain a spectrum where baseline correction is accomplished with solvent only. Such capability is important for measuring biological systems. Several polypeptides that have been assigned to be in 'random coil' conformation all give an amide I VCD pattern which has the same sign and bandshape as poly-L-proline II but a smaller magnitude. This is consistent with a previous proposal by Tiffany & Krimm that the 'random coil' conformation of charged polypeptides actually has a significant local ordering in the form of a left-handed extended helix. To investigate this problem further we have studied the effects of temperature and chain length on the VCD bandshape of this conformational type. The latter studies were done with (Pro)n, n=2-7. Our results indicate that even at the level of (Pro)4 the VCD spectrum has the same bandshape, sign and intensity as found in the 'random coil' poly-L-glutamic acid spectrum. Data on various 'random coil' systems will be compared to the model studies we have done.

  12. Circular dichroism in laser-assisted proton-hydrogen collisions

    Science.gov (United States)

    Niederhausen, Thomas; Feuerstein, Bernold; Thumm, Uwe

    2004-08-01

    We investigate the effects of a strong laser field on the dynamics of electron capture and emission in ion-atom collisions within a reduced dimensionality model of the scattering system in which the motion of the active electron and the laser electric field vector are confined to the scattering plane. We examine the probabilities for electron capture and ionization as a function of the laser intensity, the projectile impact parameter b , and the laser phase ϕ that determines the orientation of the laser electric field with respect to the internuclear axis at the time of closest approach between target and projectile. Our results for the b -dependent ionization and capture probabilities show a strong dependence on both ϕ and the helicity of the circularly polarized laser light. For intensities above 5×1012W/cm2 our model predicts a noticeable circular dichroism in the capture probability for slow proton-hydrogen collisions, which persists after averaging over ϕ . Capture and electron emission probabilities defer significantly from results for laser-unassisted collisions. Furthermore, we find evidence for a charge-resonance-enhanced ionization mechanism that may enable the measurement of the absolute laser phase ϕ .

  13. Molecular Magnetic Dichroism in Spectra of White Dwarfs

    Science.gov (United States)

    Berdyugina, S. V.; Berdyugin, A. V.; Piirola, V.

    2007-08-01

    We present novel calculations of the magnetic dichroism appearing in molecular bands in the presence of a strong magnetic field, which perturbs the internal structure of the molecule and results in net polarization due to the Paschen-Back effect. Based on that, we analyze new spectropolarimetric observations of the cool magnetic helium-rich white dwarf G99-37, which shows strongly polarized molecular bands in its spectrum. In addition to previously known molecular bands of the C2 Swan and CH A-X systems, we find a firm evidence for the violet CH B-X bands at 390 nm and C2 Deslandres-d’Azambuja bands at 360 nm. Combining the polarimetric observations with our model calculations, we deduce a dipole magnetic field of 7.5±0.5MG with the positive pole pointing towards the Earth. We conclude that the developed technique is an excellent tool for studying magnetic fields on cool magnetic stars.

  14. Magnetic circular dichroism of porphyrin lanthanide M3+ complexes.

    Science.gov (United States)

    Andrushchenko, Valery; Padula, Daniele; Zhivotova, Elena; Yamamoto, Shigeki; Bouř, Petr

    2014-10-01

    Lanthanide complexes exhibit interesting spectroscopic properties yielding many applications as imaging probes, natural chirality amplifiers, and therapeutic agents. However, many properties are not fully understood yet. Therefore, we applied magnetic circular dichroism (MCD) spectroscopy, which provides enhanced information about the underlying electronic structure to a series of lanthanide compounds. The metals in the M(3+) state included Y, La, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu; the spectra were collected for selected tetraphenylporphin (TPP) and octaethylporphin (OEP) complexes in chloroform. While the MCD and UV-VIS absorption spectra were dominated by the porphyrin signal, metal binding significantly modulated them. MCD spectroscopy was found to be better suited to discriminate between various species than absorption spectroscopy alone. The main features and trends in the lanthanide series observed in MCD and absorption spectra of the complexes could be interpreted at the Density Functional Theory (DFT) level, with effective core potentials on metal nuclei. The sum over state (SOS) method was used for simulation of the MCD intensities. The combination of the spectroscopy and quantum-chemical computations is important for understanding the interactions of the metals with the organic compounds.

  15. Optical properties and circular dichroism of chiral metal nanoparticles

    Science.gov (United States)

    Fan, Zhiyuan; Govorov, Alexander; OU Team

    2013-03-01

    In nature, biological systems are built up by homochiral building blocks, such as a sugar and protein. Circular dichroism (CD) is an effective tool of resolving molecular conformations. It utilizes circularly polarized light to detect differential absorption of chiral materials. In medicine, it will help us to develop new drugs and therapies, if we understand the connection between the physical or chemical properties of drug molecules and their conformations. With the rapid development of nanotechnologies, chiral nanomaterials attract lots of attention nowadays. CD signals of chiral molecules can be enhanced or shifted to the visible band in the presence of plasmonic nanocrystals. Here we present a plasmonic CD mechanism from a single chiral metal nanocrystal. The mechanism is essentially different from the dipolar plasmon-plasmon interaction in a chiral NP assembly, which mimics the CD mechanism of chiral molecules. Chiral metal nanocrystals are expected to have promising applications in biosensing. Recently a few experimental papers reported successful realizations of chiral nanocrystals in a macroscopic ensemble in solution. Particularly the paper described silver nanoparticles grown on chiral template molecules and demonstrating characteristic CD signals at a plasmonic wavelength. The plasmonic CD signals in Ref. can come from a dipolar plasmon-molecule interaction or from a chiral shape of nanocrystals. This work was supported by the NSF (project: CBET- 0933782) and by the Volkswagen Foundation.

  16. Structures of plant viruses from vibrational circular dichroism.

    Science.gov (United States)

    Shanmugam, Ganesh; Polavarapu, Prasad L; Kendall, Amy; Stubbs, Gerald

    2005-08-01

    Vibrational circular dichroism (VCD) spectra in the amide I and II regions have been measured for viruses for the first time. VCD spectra were recorded for films prepared from aqueous buffer solutions and also for solutions using D(2)O buffers at pH 8. Investigations of four filamentous plant viruses, Tobacco mosaic virus (TMV), Papaya mosaic virus, Narcissus mosaic virus (NMV) and Potato virus X (PVX), as well as a deletion mutant of PVX, are described in this paper. The film VCD spectra of the viruses clearly revealed helical structures in the virus coat proteins; the nucleic acid bases present in the single-stranded RNA could also be characterized. In contrast, the solution VCD spectra showed the characteristic VCD bands for alpha-helical structures in the coat proteins but not for RNA. Both sets of results clearly indicated that the coat protein conformations are dominated by helical structures, in agreement with earlier reports. VCD results also indicated that the coat protein structures in PVX and NMV are similar to each other and somewhat different from that of TMV. The present study demonstrates the feasibility of measuring VCD spectra for viruses and extracting structural information from these spectra.

  17. Fine mapping and conservation analysis of linear B-cell epitopes of peste des petits ruminants virus nucleoprotein.

    Science.gov (United States)

    Yu, Ruisong; Fan, Xiaoming; Xu, Wanxiang; Li, Wentao; Dong, Shijuan; Zhu, Yumin; He, Yaping; Tang, Haiping; Du, Rong; Li, Zhen

    2015-01-30

    Nucleoprotein (NP) is the most abundant and highly immunogenic protein of morbillivirus, and is presently the basis of most diagnostic assays for peste des petits ruminants virus (PPRV). In this study, fine epitope mapping and conservation analysis of linear B-cell epitopes on the PPRV NP has been undertaken using biosynthetic peptides. Nineteen linear B-cell epitopes were identified and their corresponding minimal motifs were located on the NP of PPRV China/Tibet/Geg/07-30. Conservation analysis indicated that ten of the 19 minimal motifs were conserved among 46 PPRV strains. Peptides containing the minimal motifs were recognized using anti-PPRV serum from a goat immunized with PPRV vaccine strain Nigeria 75/1. Identified epitopes and their motifs improve our understanding of the antigenic characteristics of PPRV NP and provide a basis for the development of epitope-based diagnostic assays.

  18. Non-linear elasticity of core/shell spun PGS/PLLA fibres and their effect on cell proliferation.

    Science.gov (United States)

    Xu, Bing; Rollo, Ben; Stamp, Lincon A; Zhang, Dongcheng; Fang, Xiya; Newgreen, Donald F; Chen, Qizhi

    2013-09-01

    An efficient delivery system is critical for the success of cell therapy. To deliver cells to a dynamic organ, the biomaterial vehicle should mechanically match with the non-linearly elastic host tissue. In this study, non-linearly elastic biomaterials have been fabricated from a chemically crosslinked elastomeric poly(glycerol sebacate) (PGS) and thermoplastic poly(l-lactic acid) (PLLA) using the core/shell electrospinning technique. The spun fibrous materials containing a PGS core and PLLA shell demonstrate J-shaped stress-strain curves, having ultimate tensile strength (UTS), rupture elongation and stiffness constants of 1 ± 0.2 MPa, 25 ± 3% and 12 ± 2, respectively, which are comparable to skin tissue properties reported previously. Our ex vivo and in vivo trials have shown that the elastomeric mesh supports and fosters the growth of enteric neural crest (ENC) progenitor cells, and that the cell-seeded elastomeric fibrous sheet physically remains in intimate contact with guts after grafting, providing the effective delivery of the progenitor cells to an embryonic and post-natal gut environment.

  19. Structure and Absolute Configuration of Nyasol and Hinokiresinol via Synthesis and Vibrational Circular Dichroism Spectroscopy

    DEFF Research Database (Denmark)

    Lassen, Peter Rygaard

    2005-01-01

    The absolute configuration of the norlignan (+)-nyasol was determined to be S by comparison of the experimental vibrational circular dichroism data with first-principle calculations taking into account the eight lowest energy conformations. The established absolute configuration of (+)-nyasol...

  20. Applications of Circular Dichroism for Structural Analysis of Gelatin and Antimicrobial Peptides

    Directory of Open Access Journals (Sweden)

    Yoonkyung Park

    2012-03-01

    Full Text Available Circular dichroism (CD is a useful technique for monitoring changes in the conformation of antimicrobial peptides or gelatin. In this study, interactions between cationic peptides and gelatin were observed without affecting the triple helical content of the gelatin, which was more strongly affected by anionic surfactant. The peptides did not adopt a secondary structure in the presence of aqueous solution or Tween 80, but a peptide secondary structure formed upon the addition of sodium dodecyl sulfate (SDS. The peptides bound to the phosphate group of lipopolysaccharide (LPS and displayed an alpha-helical conformation while (KW4 adopted a folded conformation. Further, the peptides did not specifically interact with the fungal cell wall components of mannan or laminarin. Tryptophan blue shift assay indicated that these peptides interacted with SDS, LPS, and gelatin but not with Tween 80, mannan, or laminarin. The peptides also displayed antibacterial activity against P. aeruginosa without cytotoxicity against HaCaT cells at MIC, except for HPA3NT3-analog peptide. In this study, we used a CD spectroscopic method to demonstrate the feasibility of peptide characterization in numerous environments. The CD method can thus be used as a screening method of gelatin-peptide interactions for use in wound healing applications.

  1. Photoemission and magnetic circular dichroism studies of magnetic semiconductors

    Science.gov (United States)

    Fujimori, Atsushi

    2005-03-01

    Recently, a series of novel ferromagnetic semiconductors have been synthesized using MBE and related techniques and have attracted much attention because of unknown mechanisms of carrier-induced ferromagnetism and potential applications as "spin electronics" devices. Some new materials show ferromagnetism even well above room temperature. Photoemission spectroscopy has been used to study the d orbitals of the dilute transition-metal atoms, mostly Mn, and their hybridization with the host band states [1]. Soft x-ray absorption spectroscopy (XAS) and magnetic circular dichroism (MCD) at the transition-metal 2p-3d absorption edges are useful techniques to study the valence and spin states of the transition-metal atoms. Furthermore, since MCD has different sensitivities to the ferromagnetic and paramagnetic components at different temperatures and magnetic fileds, if the sample is a mixture of ferromagnetic and non-ferromagnetic transition- metal atoms, it can be used to separate the two components and to study their electronic structures. In this talk, results are presented for the prototypical diluted ferromagnetic semiconductor Ga1-xMnxAs [2] and the room-temperature ferromagnets Zn1-xCoxO and Ti1-xCoxO2.I acknowledge collaboration with Y. Ishida, J.-I. Hwang, M. Kobayashi, Y. Takeda, Y. Saitoh, J. Okamoto, T. Okane, Y. Muramatsu, K. Mamiya, T. Koide, A. Tanaka, M. Tanaka, Hayashi, S. Ohya, T. Kondo, H. Munekata, H. Saeki, H. Tabata, T. Kawai, Y. Matsumoto, H. Koinuma, T. Fukumura and M. Kawasaki. This work was supported by a Grant-in-Aid for Scientific Research in Priority Area "Semiconductor nano-spintronics" (14076209) from MEXT, Japan.1. J. Okabayashi et al., Phys. Rev. B 64, 125304 (2001).2. A. Fujimori et al., J. Electron Spectrosc. Relat. Phenom., in press.

  2. Non-linear Membrane Properties in Entorhinal Cortical Stellate Cells Reduce Modulation of Input-Output Responses by Voltage Fluctuations.

    Science.gov (United States)

    Fernandez, Fernando R; Malerba, Paola; White, John A

    2015-04-01

    The presence of voltage fluctuations arising from synaptic activity is a critical component in models of gain control, neuronal output gating, and spike rate coding. The degree to which individual neuronal input-output functions are modulated by voltage fluctuations, however, is not well established across different cortical areas. Additionally, the extent and mechanisms of input-output modulation through fluctuations have been explored largely in simplified models of spike generation, and with limited consideration for the role of non-linear and voltage-dependent membrane properties. To address these issues, we studied fluctuation-based modulation of input-output responses in medial entorhinal cortical (MEC) stellate cells of rats, which express strong sub-threshold non-linear membrane properties. Using in vitro recordings, dynamic clamp and modeling, we show that the modulation of input-output responses by random voltage fluctuations in stellate cells is significantly limited. In stellate cells, a voltage-dependent increase in membrane resistance at sub-threshold voltages mediated by Na+ conductance activation limits the ability of fluctuations to elicit spikes. Similarly, in exponential leaky integrate-and-fire models using a shallow voltage-dependence for the exponential term that matches stellate cell membrane properties, a low degree of fluctuation-based modulation of input-output responses can be attained. These results demonstrate that fluctuation-based modulation of input-output responses is not a universal feature of neurons and can be significantly limited by subthreshold voltage-gated conductances.

  3. TiO2 dye sensitized solar cell (DSSC): linear relationship of maximum power point and anthocyanin concentration

    Science.gov (United States)

    Ahmadian, Radin

    2010-09-01

    This study investigated the relationship of anthocyanin concentration from different organic fruit species and output voltage and current in a TiO2 dye-sensitized solar cell (DSSC) and hypothesized that fruits with greater anthocyanin concentration produce higher maximum power point (MPP) which would lead to higher current and voltage. Anthocyanin dye solution was made with crushing of a group of fresh fruits with different anthocyanin content in 2 mL of de-ionized water and filtration. Using these test fruit dyes, multiple DSSCs were assembled such that light enters through the TiO2 side of the cell. The full current-voltage (I-V) co-variations were measured using a 500 Ω potentiometer as a variable load. Point-by point current and voltage data pairs were measured at various incremental resistance values. The maximum power point (MPP) generated by the solar cell was defined as a dependent variable and the anthocyanin concentration in the fruit used in the DSSC as the independent variable. A regression model was used to investigate the linear relationship between study variables. Regression analysis showed a significant linear relationship between MPP and anthocyanin concentration with a p-value of 0.007. Fruits like blueberry and black raspberry with the highest anthocyanin content generated higher MPP. In a DSSC, a linear model may predict MPP based on the anthocyanin concentration. This model is the first step to find organic anthocyanin sources in the nature with the highest dye concentration to generate energy.

  4. Circular dichroism sensor based on cadmium sulfide quantum dots for chiral identification and detection of penicillamine

    Energy Technology Data Exchange (ETDEWEB)

    Ngamdee, Kessarin [Materials Chemistry Research Center, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen, 40002 (Thailand); Puangmali, Theerapong [Department of Physics, Faculty of Science, Khon Kaen University, Khon Kaen, 40002 (Thailand); Tuntulani, Thawatchai [Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, 10330 (Thailand); Ngeontae, Wittaya, E-mail: wittayange@kku.ac.th [Materials Chemistry Research Center, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen, 40002 (Thailand)

    2015-10-22

    A new chemical sensor based on the measuring of circular dichroism signal (CD) was fabricated from cysteamine capped cadmium sulfide quantum dots (Cys-CdS QDs). The chiral-thiol molecules, D-penicillamine (DPA) and L-penicillamine (LPA), were used to evaluate potentials of this sensor. Basically, DPA and LPA provide very low CD signals. However, the CD signals of DPA and LPA can be enhanced in the presence of Cys-CdS QDs. The CD spectra of DPA and LPA exhibited a mirror image profile. Parameters affecting the determination of DPA and LPA were thoroughly investigated in details. Under the optimized condition, the CD signals of DPA and LPA displayed a linear relationship with the concentrations of both enantiomers, ranging from 1 to 35 μM. Detection limits of this sensor were 0.49 and 0.74 μM for DPA and LPA, respectively. To demonstrate a potential application of this sensor, the proposed sensor was used to determine DPA and LPA in real urine samples. It was confirmed that the proposed detection technique was reliable and could be utilized in a broad range of applications. - Highlights: • This paper demonstrates a new CD sensor based on cadmium sulfide quantum dots. • Achiral quantum dots are used for the detection and chiral identification of thiol-chiral containing compounds. • The sensor show highest selectivity towards penicillamine. • The detection limits of the sensor less than 1 μM. • The sensor can potentially be used in physiological urine samples.

  5. 980-nm infrared laser modulation of sodium channel kinetics in a neuron cell linearly mediated by photothermal effect

    Science.gov (United States)

    Li, Xinyu; Liu, Jia; Liang, Shanshan; Sun, Changsen

    2014-10-01

    Photothermal effect (PE) plays a major role in the near-infrared laser interaction with biological tissue. But, quite few interactions can be quantitatively depicted. Here, a two-step model is proposed to describe a 980-nm infrared laser interaction with neuron cell in vitro. First, the laser-induced temperature rises in the cell surrounding area were measured by using an open pipette method and also calculated by solving the heat conduction equation. Second, we recorded the modifications on sodium (Na) channel current in neuron cells directly by using a patch clamp to synchronize the 980-nm laser irradiation and obtained how the electrophysiological function of neuron cells respond to the temperature rise. Then, the activation time constants, τm, were extracted by fitting the sodium currents with the Hodgkin-Huxley model. The infrared laser modulation effect on sodium currents kinetics was examined by taking a ratio between the time constants with and without the laser irradiations. The analysis revealed that the averaged ratio at a specific laser exposure could be well related to the temperature properties of the Na channel protein. These results proved that the modulation of sodium current kinetics of a neuron cell in vitro by 980-nm laser with different-irradiation levels was linearly mediated corresponding to the laser-induced PE.

  6. Linear microrheology with optical tweezers of living cells 'is not an option'!

    Science.gov (United States)

    Tassieri, Manlio

    2015-08-07

    Optical tweezers have been successfully adopted as exceptionally sensitive transducers for microrheology studies of complex fluids. Despite the general trend, in this article I explain why a similar approach should not be adopted for microrheology studies of living cells. This conclusion is acheived on the basis of statistical mechanics principles that indicate the unsuitability of optical tweezers for such purpose.

  7. Non-linear model reduction and control of molten carbonate fuel cell systems with internal reforming

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Min

    2007-10-12

    Currently, the process design of fuel cells and the development of control strategies is mainly based on heuristic methods. Fuel cell models are often too complex for control purposes, or they are developed for a specific type of fuel cell and valid only in a small range of operation conditions. The application of fuel cell models to controller design is still limited. Furthermore, suitable and simple-to-implement design strategies for fuel cell control remain an open area. There is thus a motivation for simplifying dynamic models for process control applications and for designing suitable control strategies for fuel cells. This is the main objective of this work. As an application example, the 250 kW industrial molten carbonate fuel cell (MCFC) system HotModule by MTU CFC Solutions, Germany is considered. A detailed dynamic two-dimensional spatially distributed cross-flow model of a MCFC from literature is taken as a starting point for the investigation. In Chapter 2, two simplified model versions are derived by incorporating additional physical assumptions. One of the simplified models is extended to a three-dimensional stack model to deal with physical and chemical phenomena in the stack. Simulations of the stack model are performed in Chapter 3 in order to calculate the mass and temperature distributions in the direction perpendicular to the electrode area. The other simplified model forms the basis for a low order reduced model that is derived in Chapter 4. The reduced-order model is constructed by application of the Karhunen-Loeve Galerkin method. The spatial temperature, concentration and potential profiles are approximated by a set of orthogonal time independent spatial basis functions. Problem specific basis functions are generated numerically from simulation data of the detailed reference model. The advantage of this approach is that a small number of basis functions suffices in order to approximate the solution of the detailed model very well. The

  8. Linearization Techniques

    Directory of Open Access Journals (Sweden)

    Gildeberto S. Cardoso

    2011-01-01

    Full Text Available This paper presents a study of linear control systems based on exact feedback linearization and approximate feedback linearization. As exact feedback linearization is applied, a linear controller can perform the control objectives. The approximate feedback linearization is required when a nonlinear system presents a noninvolutive property. It uses a Taylor series expansion in order to compute a nonlinear transformation of coordinates to satisfy the involutivity conditions.

  9. Cytotoxic effect of linear alkylbenzene sulfonate on human intestinal Caco-2 cells: associated biomarkers for risk assessment.

    Science.gov (United States)

    Bradai, Mohamed; Han, Junkyu; El Omri, Abdelfatteh; Funamizu, Naoyuki; Sayadi, Sami; Isoda, Hiroko

    2014-09-01

    Linear alkylbenzene sulfonate (LAS) is a synthetic anionic surfactant widely present in the environment due to its intensive production and use in the detergency field. Admitting that current procedure of risk assessment has limits in providing realistic risk assessment data and predicting the cumulative effect of the toxicant mixtures, the incorporation of information regarding the mode of action and cell response mechanism seems to be a potential solution to overcome these limits. In this regard, we investigated in this study the LAS cytotoxicity on human intestinal Caco-2 cells, trying to unveil the protein actors implicated in the cell response using proteomics approach in order to give a better understanding of the toxicological effect and allow the identification of appropriate biomarkers reflecting the mode of action associated with LAS. As results, we demonstrated that LAS induces a time- and dose-dependent cytotoxicity in Caco-2 cells accompanied by an induction of oxidative stress followed by an excessive increase of intracellular calcium level. Proteomics approach helped in discovering three informative biomarkers of effect associated with LAS cytotoxic effect, reported for the first time: calreticulin, thioredoxin, and heat shock cognate 71 (HSP7C), confirmed by real-time PCR and western blot analysis. These biomarkers could serve for more reliable future risk assessment studies that consider the toxicants mode of action in order to help in the prediction of potential cumulative effects of environmentally coexisting contaminants.

  10. Experimental determination of excitonic band structures of single-walled carbon nanotubes using circular dichroism spectra

    Science.gov (United States)

    Wei, Xiaojun; Tanaka, Takeshi; Yomogida, Yohei; Sato, Naomichi; Saito, Riichiro; Kataura, Hiromichi

    2016-10-01

    Experimental band structure analyses of single-walled carbon nanotubes have not yet been reported, to the best of our knowledge, except for a limited number of reports using scanning tunnelling spectroscopy. Here we demonstrate the experimental determination of the excitonic band structures of single-chirality single-walled carbon nanotubes using their circular dichroism spectra. In this analysis, we use gel column chromatography combining overloading selective adsorption with stepwise elution to separate 12 different single-chirality enantiomers. Our samples show higher circular dichroism intensities than the highest values reported in previous works, indicating their high enantiomeric purity. Excitonic band structure analysis is performed by assigning all observed Eii and Eij optical transitions in the circular dichroism spectra. The results reproduce the asymmetric structures of the valence and conduction bands predicted by density functional theory. Finally, we demonstrate that an extended empirical formula can estimate Eij optical transition energies for any (n,m) species.

  11. Linear gyrokinetic particle-in-cell simulations for small to large toroidal wavenumbers

    Energy Technology Data Exchange (ETDEWEB)

    Fivaz, M.; Tran, T.M.; Villard, L.; Appert, K.; Brunner, S.; Vaclavik, J. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP); Parker, S.E. [Colorado Univ., Boulder, CO (United States). Dept. of Physics

    1996-09-01

    We study here low frequency electrostatic microinstabilities driven by ion temperature gradients (ITG instabilities) relevant to anomalous ion heat transport in tokamaks. The plasma is modelled with gyrokinetic ions and adiabatic electrons. An axisymmetric equilibrium magnetic structure is provided by the MHD equilibrium code CHEASE. The full plasma cross-section is considered in the simulation. We follow the time-evolution of electrostatic, quasineutral perturbations of a local Maxwellian equilibrium distribution function, using two different particle-in-cell (PIC) codes running on a massively parallel CRAY-T3D. (author) 4 figs., 9 refs.

  12. No Evidence for a Low Linear Energy Transfer Adaptive Response in Irradiated RKO Cells

    Energy Technology Data Exchange (ETDEWEB)

    Sowa, Marianne B.; Goetz, Wilfried; Baulch, Janet E.; Lewis, Adam J.; Morgan, William F.

    2011-01-06

    It has become increasingly evident from reports in the literature that there are many confounding factors that are capable of modulating radiation induced non-targeted responses such as the bystander effect and the adaptive response. In this paper we examine recent data that suggest that the observation of non-targeted responses may not be universally observable for differing radiation qualities. We have conducted a study of the adaptive response following low LET exposures for human colon carcinoma cells and failed to observe adaption for the endpoints of clonogenic survival or micronucleus formation.

  13. A UV-prepared linear polymer electrolyte membrane for dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Imperiyka, M., E-mail: imperiyka@gmail.com [Faculty of Arts and Sciences, Kufra Campus, University of Benghazi, Al Kufrah (Libya); Ahmad, A.; Hanifah, S.A. [School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Polymer Research Center, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia); Bella, F. [Center for Space Human Robotics @Polito, Istituto Italiano di Tecnologia, Corso Trento 21, 10129 Torino (Italy); Department of Applied Science and Technology – DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy)

    2014-10-01

    The effects of LiClO{sub 4} and LiFS{sub 3}SO{sub 3} on poly(glycidyl methacrylate)-based solid polymer electrolyte and its photoelectrochemical performance in a dye sensitized solar cell consisting of FTO/TiO{sub 2}–dye/P(GMA)–LiClO{sub 4}–EC/Pt were investigated. The electrochemical stability of films was studied by cyclic voltammetry (CV). The highest ionic conductivities obtained were 4.2×10{sup −5} and 3.7×10{sup −6} S cm{sup −1} for the film containing 30 wt% LiClO{sub 4} and 25 wt% LiCF{sub 3}SO{sub 3}, respectively. The polymer electrolytes showed electrochemical stability windows up to 3 V and 2.8 V for LiClO{sub 4} and LiCF{sub 3}SO{sub 3}, respectively. The assembled dye-sensitized solar cell showed a sunlight conversion efficiency of 0.679% (J{sub sc}=3 mA cm{sup −2}, V{sub oc}=0.48 V and FF=0.47), under light intensity of 100 mW cm{sup −2}.

  14. Development of a relativistic Particle In Cell code PARTDYN for linear accelerator beam transport

    Science.gov (United States)

    Phadte, D.; Patidar, C. B.; Pal, M. K.

    2017-04-01

    A relativistic Particle In Cell (PIC) code PARTDYN is developed for the beam dynamics simulation of z-continuous and bunched beams. The code is implemented in MATLAB using its MEX functionality which allows both ease of development as well higher performance similar to a compiled language like C. The beam dynamics calculations carried out by the code are compared with analytical results and with other well developed codes like PARMELA and BEAMPATH. The effect of finite number of simulation particles on the emittance growth of intense beams has been studied. Corrections to the RF cavity field expressions were incorporated in the code so that the fields could be calculated correctly. The deviations of the beam dynamics results between PARTDYN and BEAMPATH for a cavity driven in zero-mode have been discussed. The beam dynamics studies of the Low Energy Beam Transport (LEBT) using PARTDYN have been presented.

  15. Linear Psoriasis

    Directory of Open Access Journals (Sweden)

    Agarwalla Arun

    2001-01-01

    Full Text Available Linear psoriasis, inflammatory linear varrucous epidermal naevus (ILVEN. Lichen straitus, linear lichen planus and invasion of epidermal naevi by psoriasis have clinical and histopathological overlap. We report two young male patients of true linear psoriasis without classical lesions elsewhere which were proved histopathologically. Seasonal variation and good response to topical antipsoriatic treatment supported the diagnosis.

  16. Linear algebra

    CERN Document Server

    Shilov, Georgi E

    1977-01-01

    Covers determinants, linear spaces, systems of linear equations, linear functions of a vector argument, coordinate transformations, the canonical form of the matrix of a linear operator, bilinear and quadratic forms, Euclidean spaces, unitary spaces, quadratic forms in Euclidean and unitary spaces, finite-dimensional space. Problems with hints and answers.

  17. Protecting effects specifically from low doses of ionizing radiation to mammalian cells challenge the concept of linearity

    Energy Technology Data Exchange (ETDEWEB)

    Feinendegen, L.E. [Brookhaven National Lab., Upton, NY (United States). Medical Dept.; Bond, V.P. [Washington State Univ., Richland, WA (United States); Sondhaus, C.A. [Univ. of Arizona, Tucson, AZ (United States). Dept. of Radiology and Radiation Control Office; Altman, K.I. [Univ. of Rochester Medical Center, NY (United States). Dept. of Biochemistry and Biophysics

    1998-12-31

    This report examines the origin of tissue effects that may follow from different cellular responses to low-dose irradiation, using published data. Two principal categories of cellular responses are considered. One response category relates to the probability of radiation-induced DNA damage. The other category consists of low-dose induced changes in intracellular signaling that induce mechanisms of DNA damage control different from those operating at high levels of exposure. Modeled in this way, tissue is treated as a complex adaptive system. The interaction of the various cellular responses results in a net tissue dose-effect relation that is likely to deviate from linearity in the low-dose region. This suggests that the LNT hypothesis should be reexamined. The aim of this paper is to demonstrate that by use of microdosimetric concepts, the energy deposited in cell mass can be related to the occurrence of cellular responses, both damaging and defensive.

  18. Non-linear relationship of cell hit and transformation probabilities in low dose of inhaled radon progenies

    CERN Document Server

    Balásházy, Imre; Madas, Balázs Gergely; Hofmann, Werner

    2013-01-01

    Cellular hit probabilities of alpha particles emitted by inhaled radon progenies in sensitive bronchial epithelial cell nuclei were simulated at low exposure levels to obtain useful data for the rejection or in support of the linear-non-threshold (LNT) hypothesis. In this study, local distributions of deposited inhaled radon progenies in airway bifurcation models were computed at exposure conditions, which are characteristic of homes and uranium mines. Then, maximum local deposition enhancement factors at bronchial airway bifurcations, expressed as the ratio of local to average deposition densities, were determined to characterize the inhomogeneity of deposition and to elucidate their effect on resulting hit probabilities. The results obtained suggest that in the vicinity of the carinal regions of the central airways the probability of multiple hits can be quite high even at low average doses. Assuming a uniform distribution of activity there are practically no multiple hits and the hit probability as a funct...

  19. Classifying the Progression of Ductal Carcinoma from Single-Cell Sampled Data via Integer Linear Programming: A Case Study.

    Science.gov (United States)

    Catanzaro, Daniele; Shackney, Stanley E; Schaffer, Alejandro A; Schwartz, Russell

    2016-01-01

    Ductal Carcinoma In Situ (DCIS) is a precursor lesion of Invasive Ductal Carcinoma (IDC) of the breast. Investigating its temporal progression could provide fundamental new insights for the development of better diagnostic tools to predict which cases of DCIS will progress to IDC. We investigate the problem of reconstructing a plausible progression from single-cell sampled data of an individual with synchronous DCIS and IDC. Specifically, by using a number of assumptions derived from the observation of cellular atypia occurring in IDC, we design a possible predictive model using integer linear programming (ILP). Computational experiments carried out on a preexisting data set of 13 patients with simultaneous DCIS and IDC show that the corresponding predicted progression models are classifiable into categories having specific evolutionary characteristics. The approach provides new insights into mechanisms of clonal progression in breast cancers and helps illustrate the power of the ILP approach for similar problems in reconstructing tumor evolution scenarios under complex sets of constraints.

  20. Identification of a highly antigenic linear B cell epitope within Plasmodium vivax apical membrane antigen 1 (AMA-1.

    Directory of Open Access Journals (Sweden)

    Lilian Lacerda Bueno

    Full Text Available Apical membrane antigen 1 (AMA-1 is considered to be a major candidate antigen for a malaria vaccine. Previous immunoepidemiological studies of naturally acquired immunity to Plasmodium vivax AMA-1 (PvAMA-1 have shown a higher prevalence of specific antibodies to domain II (DII of AMA-1. In the present study, we confirmed that specific antibody responses from naturally infected individuals were highly reactive to both full-length AMA-1 and DII. Also, we demonstrated a strong association between AMA-1 and DII IgG and IgG subclass responses. We analyzed the primary sequence of PvAMA-1 for B cell linear epitopes co-occurring with intrinsically unstructured/disordered regions (IURs. The B cell epitope comprising the amino acid sequence 290-307 of PvAMA-1 (SASDQPTQYEEEMTDYQK, with the highest prediction scores, was identified in domain II and further selected for chemical synthesis and immunological testing. The antigenicity of the synthetic peptide was identified by serological analysis using sera from P. vivax-infected individuals who were knowingly reactive to the PvAMA-1 ectodomain only, domain II only, or reactive to both antigens. Although the synthetic peptide was recognized by all serum samples specific to domain II, serum with reactivity only to the full-length protein presented 58.3% positivity. Moreover, IgG reactivity against PvAMA-1 and domain II after depletion of specific synthetic peptide antibodies was reduced by 18% and 33% (P = 0.0001 for both, respectively. These results suggest that the linear epitope SASDQPTQYEEEMTDYQK is highly antigenic during natural human infections and is an important antigenic region of the domain II of PvAMA-1, suggesting its possible future use in pre-clinical studies.

  1. A Simple Spreadsheet Program to Simulate and Analyze the Far-UV Circular Dichroism Spectra of Proteins

    Science.gov (United States)

    Abriata, Luciano A.

    2011-01-01

    A simple algorithm was implemented in a spreadsheet program to simulate the circular dichroism spectra of proteins from their secondary structure content and to fit [alpha]-helix, [beta]-sheet, and random coil contents from experimental far-UV circular dichroism spectra. The physical basis of the method is briefly reviewed within the context of…

  2. Characterization of dry globular proteins and protein fibrils by synchrotron radiation vacuum UV circular dichroism

    DEFF Research Database (Denmark)

    Nesgaard, Lise W.; Hoffmann, Søren Vrønning; Andersen, Christian Beyschau

    2008-01-01

    Circular dichroism using synchrotron radiation (SRCD) can extend the spectral range down to approximately 130 nm for dry proteins, potentially providing new structural information. Using a selection of dried model proteins, including alpha-helical, beta-sheet, and mixed-structure proteins, we obs...

  3. Energetics, structures, vibrational frequencies, vibrational absorption, vibrational circular dichroism and Raman intensities of Leu-enkephalin

    DEFF Research Database (Denmark)

    Jalkanen, Karl J.

    2003-01-01

    , similar to the characteristic features in electronic circular dichroism spectra with respect to those in the UV-vis electronic absorption spectra. Finally, we have also attempted to stabilize the zwitterionic species by treating the aqueous environment by using a continuum solvent approach, the Onsager...

  4. Circular dichroism as a means to follow DNA gymnastics: on the shoulders of giants

    Directory of Open Access Journals (Sweden)

    H.H. Klump

    2010-01-01

    Full Text Available This is the first report of DNA stem-loops self-assembled by ‘foot-loop’ interactions into either two-dimensional strings or three-dimensional spirals, distinguished by circular dichroism spectroscopy. All subunits are linked by cooperative Watson-Crick hydrogen bonds.

  5. Circular Dichroism Investigation of Dess-Martin Periodinane Oxidation in the Organic Chemistry Laboratory

    Science.gov (United States)

    Reed, Nicole A.; Rapp, Robert D.; Hamann, Christian S.; Artz, Pamela G.

    2005-01-01

    Dess-Martin periodinane oxidation is an experiment that provides an avenue to the introduction of Circular Dichroism (CD) spectroscopy in organic chemistry curriculum as a diagnostic tool for examination of the results of a familiar reaction, and absolute configuration. From the experiment, students increased their understanding of CD theory and…

  6. Protein Circular Dichroism Data Bank (PCDDB): data bank and website design.

    Science.gov (United States)

    Whitmore, Lee; Janes, Robert W; Wallace, B A

    2006-06-01

    The Protein Circular Dichroism Data Bank (PCDDB) is a new deposition data bank for validated circular dichroism spectra of biomacromolecules. Its aim is to be a resource for the structural biology and bioinformatics communities, providing open access and archiving facilities for circular dichroism and synchrotron radiation circular dichroism spectra. It is named in parallel with the Protein Data Bank (PDB), a long-existing valuable reference data bank for protein crystal and NMR structures. In this article, we discuss the design of the data bank structure and the deposition website located at http://pcddb.cryst.bbk.ac.uk. Our aim is to produce a flexible and comprehensive archive, which enables user-friendly spectral deposition and searching. In the case of a protein whose crystal structure and sequence are known, the PCDDB entry will be linked to the appropriate PDB and sequence data bank files, respectively. It is anticipated that the PCDDB will provide a readily accessible biophysical catalogue of information on folded proteins that may be of value in structural genomics programs, for quality control and archiving in industrial and academic labs, as a resource for programs developing spectroscopic structural analysis methods, and in bioinformatics studies.

  7. Strong K-edge Magnetic Circular Dichroism Observed in Photon-in-Photon-out Spectroscopy

    NARCIS (Netherlands)

    Sikora, Marcin; Juhin, Amelie; Weng, Tsu-Chien; Sainctavit, Philippe; Detlefs, Carsten; de Groot, Frank; Glatzel, Pieter

    2010-01-01

    A large enhancement of the x-ray magnetic circular dichroism is observed at the iron K absorption preedge of magnetite. This is achieved by performing resonant inelastic x-ray scattering (RIXS) experiments with a 2p hole in the final state of the second-order optical process. We measured and calcula

  8. Probing electronic coupling between adenine bases in RNA strands from synchrotron radiation circular dichroism experiments

    DEFF Research Database (Denmark)

    Nielsen, Lisbeth Munksgård; Hoffmann, Søren Vrønning; Nielsen, Steen Brøndsted

    2012-01-01

    Circular dichroism spectra (176–330 nm) of RNA adenine oligomers, (rA)n (n = 1–10, 12, 15, and 20), reveal electronic coupling between two bases in short strands. The number of interacting bases in long strands is more and larger than that reported previously for the corresponding DNA strands....

  9. Detection Limits for Natural Circular Dichroism of Chiral Complexes in the X-ray Range

    NARCIS (Netherlands)

    Goulon, José; Sette, Francesco; Moise, Claude; Fontaine, Alain; Perey, Danièle; Rudolf, Petra; Baudelet, François

    1993-01-01

    Whereas both Magnetic Circular Dichroism and Faraday Rotation studies have been successfully carried out at the K-, L- and M- absorption edges of metal atoms in ferromagnetic systems, Natural optical activity of chiral complexes has not yet been detected quite unambiguously in the X-ray range. We re

  10. SPIN POLARIZATION AND MAGNETIC DICHROISM IN PHOTOEMISSION FROM CORE AND VALENCE STATES IN LOCALIZED MAGNETIC SYSTEMS

    NARCIS (Netherlands)

    THOLE, BT; VANDERLAAN, G

    1991-01-01

    Using group theory we derive a general model for spin polarization and magnetic dichroism in photo-emission in the presence of atomic interactions between the hole created and the valence holes. We predict strong effects in the photoemission from core levels and localized valence levels of transitio

  11. Systematic Bioinformatic Approach for Prediction of Linear B-Cell Epitopes on Dengue E and prM Protein.

    Science.gov (United States)

    Nadugala, Mahesha N; Premaratne, Prasad H; Goonasekara, Charitha L

    2016-01-01

    B-cell epitopes on the envelope (E) and premembrane (prM) proteins of dengue virus (DENV) were predicted using bioinformatics tools, BepiPred, Ellipro, and SVMTriP. Predicted epitopes, 32 and 17 for E and prM proteins, respectively, were then characterized for their level of conservations. The epitopes, EP4/E (48-55), epitope number 4 of E protein at amino acids 48-55, EP9/E (165-182), EP11/E (218-233), EP20/E (322-349), EP21/E (326-353), EP23/E (356-365), and EP25/E (380-386), showed a high intraserotype conservancy with very low pan-serotype conservancy, demonstrating a potential target as serotype specific diagnostic markers. EP3 (30-41) located in domain-I and EP26/E (393-409), EP27/E (416-435), EP28/E (417-430) located in the stem region of E protein, and EP8/prM (93-112) from the prM protein have a pan-serotype conservancy higher than 70%. These epitopes indicate a potential use as universal vaccine candidates, subjected to verification of their potential in viral neutralization. EP2/E (16-21), EP5/E (62-123), EP6/E (63-89), EP19/E (310-329), and EP24/E (371-402), which have more than 50% pan-serotype conservancies, were found on E protein regions that are important in host cell attachment. Previous studies further show evidence for some of these epitopes to generate cross-reactive neutralizing antibodies, indicating their importance in antiviral strategies for DENV. This study suggests that bioinformatic approaches are attractive first line of screening for identification of linear B-cell epitopes.

  12. Proton velocity ring-driven instabilities in the inner magnetosphere: Linear theory and particle-in-cell simulations

    Science.gov (United States)

    Min, Kyungguk; Liu, Kaijun

    2016-01-01

    Linear dispersion theory and electromagnetic particle-in-cell (PIC) simulations are used to investigate linear growth and nonlinear saturation of the proton velocity ring-driven instabilities, namely, ion Bernstein instability and Alfvén-cyclotron instability, which lead to fast magnetosonic waves and electromagnetic ion cyclotron waves in the inner magnetosphere, respectively. The proton velocity distribution is assumed to consist of 10% of a ring distribution and 90% of a low-temperature Maxwellian background. Here two cases with ring speeds vr/vA=1 and 2 (vA is the Alfvén speed) are examined in detail. For the two cases, linear theory predicts that the maximum growth rate γm of the Bernstein instability is 0.16Ωp and 0.19Ωp, respectively, and γm of the Alfvén-cyclotron instability is 0.045Ωp and 0.15Ωp, respectively, where Ωp is the proton cyclotron frequency. Two-dimensional PIC simulations are carried out for the two cases to examine the instability development and the corresponding evolution of the particle distributions. Initially, Bernstein waves develop and saturate with strong electrostatic fluctuations. Subsequently, electromagnetic Alfvén-cyclotron waves grow and saturate. Despite their smaller growth rate, the saturation levels of the Alfvén-cyclotron waves for both cases are larger than those of the Bernstein waves. Resonant interactions with the Bernstein waves lead to scattering of ring protons predominantly along the perpendicular velocity component (toward both decreasing and, at a lesser extent, increasing speeds) without substantial change of either the parallel temperature or the temperature anisotropy. Consequently, the Alfvén-cyclotron instability can still grow. Furthermore, the free energy resulting from the pitch angle scattering by the Alfvén-cyclotron waves is larger than the free energy resulting from the perpendicular energy scattering, thereby leading to the larger saturation level of the Alfvén-cyclotron waves.

  13. Recombineering linear BACs.

    Science.gov (United States)

    Chen, Qingwen; Narayanan, Kumaran

    2015-01-01

    Recombineering is a powerful genetic engineering technique based on homologous recombination that can be used to accurately modify DNA independent of its sequence or size. One novel application of recombineering is the assembly of linear BACs in E. coli that can replicate autonomously as linear plasmids. A circular BAC is inserted with a short telomeric sequence from phage N15, which is subsequently cut and rejoined by the phage protelomerase enzyme to generate a linear BAC with terminal hairpin telomeres. Telomere-capped linear BACs are protected against exonuclease attack both in vitro and in vivo in E. coli cells and can replicate stably. Here we describe step-by-step protocols to linearize any BAC clone by recombineering, including inserting and screening for presence of the N15 telomeric sequence, linearizing BACs in vivo in E. coli, extracting linear BACs, and verifying the presence of hairpin telomere structures. Linear BACs may be useful for functional expression of genomic loci in cells, maintenance of linear viral genomes in their natural conformation, and for constructing innovative artificial chromosome structures for applications in mammalian and plant cells.

  14. Effect of linear alkylbenzene sulfonate (LAS) on ion transport and intracellular calcium in kidney distal epithelial cells (A6).

    Science.gov (United States)

    Bjerregaard, H F; Staermose, S; Vang, J

    2001-01-01

    Linear alkylbenzene sulfonate (LAS) is found in near-shore environments receiving wastewater from urban treatment plants in a concentration reported to have physiological and toxic effect on aquatic organisms. The aim of this study was to investigate the effect LAS on ion transport and homeostasis in epithelia cells. A6 cells form a polarised epithelium when grown on permeable supports, actively absorb sodium and secrete chloride. Only the addition of LAS (100 microM) to the apical solution of A6 epithelia resulted in an increase in the active ion transport measured as short circuit current (SCC) and transepithelial conductance (G(t)). This increase could not be affected by the sodium channel inhibitor amiloride (100 microM), indicating that LAS stimulated the chloride secretion. Change in the intracellular calcium concentration (Ca(2+))(i) was measured in fura-2 loaded A6 cells, since it known that increase in (Ca(2+))(i) stimulate chloride secretion. LAS induced a concentration-dependent increase in (Ca(2+))(i) from 5 to 200 microM, where the half-maximal stimulating concentration on 100 mM resulted in an increase in (Ca(2+))(i) from 108+/-15 to 570+/-26 nM (n=4; P<0.01). The increase in (Ca(2+))(i) could be blocked by the calcium chelator ethylenebis(5-oxyethylenenitrilo)tetraacetic acid (EGTA), showing that the effect of LAS was due to influx of extracellular calcium. Furthermore, it was shown that the calcium channel inhibitor verapamil (0.2 mM) abolished the LAS induced increase in (Ca(2+))(i) and Gt when applied to the apical solution. However, verapamil has no inhibitory effect on these parameters when the non-ionic detergent Triton X-100 (100 microM) was added to A6 cells. These results indicate that LAS induced a specific activation of calcium channels in the apical membrane of A6 epithelia, leading to increase in (Ca(2+))(i) and thereby increased chloride secretion as a result of stimulation of calcium-dependent chloride channels in the apical membrane

  15. Sorption-desorption kinetics and toxic cell concentration in marine phytoplankton microalgae exposed to Linear Alkylbenzene Sulfonate.

    Science.gov (United States)

    Renaud, Florent; Oberhänsli, François; Teyssié, Jean-Louis; Miramand, Pierre; Temara, Ali; Warnau, Michel

    2011-05-01

    Linear Alkylbenzene Sulfonates (LAS) are ubiquitous surfactants. Traces can be found in coastal environments. Sorption and toxicity of C(12)-LAS congeners were studied in controlled conditions (2-3500 μg C(12)LAS/L) in five marine phytoplanktonic species, using standardized methods. IC(50) values ranged from 0.5 to 2 mg LAS/L. Sorption of (14)C(12)-6 LAS isomer was measured at environmentally relevant trace levels (4μg/L) using liquid scintillation counting. Steady-state sorption on algae was reached within 5h in the order dinoflagellate>diatoms>green algae. The sorption data, fitted a L-type Freundlich isotherm, indicating saturation. Desorption was rapid but a low LAS fraction was still sorbed after 24h. Toxic cell concentration was 0.38±0.09 mg/g for the studied species. LAS toxicity results from sorption on biological membranes leading to non-specific disturbance of algal growth. Results indicate that LAS concentrations in coastal environments do not represent a risk for these organisms.

  16. An atomic orbital based real-time time-dependent density functional theory for computing electronic circular dichroism band spectra.

    Science.gov (United States)

    Goings, Joshua J; Li, Xiaosong

    2016-06-21

    One of the challenges of interpreting electronic circular dichroism (ECD) band spectra is that different states may have different rotatory strength signs, determined by their absolute configuration. If the states are closely spaced and opposite in sign, observed transitions may be washed out by nearby states, unlike absorption spectra where transitions are always positive additive. To accurately compute ECD bands, it is necessary to compute a large number of excited states, which may be prohibitively costly if one uses the linear-response time-dependent density functional theory (TDDFT) framework. Here we implement a real-time, atomic-orbital based TDDFT method for computing the entire ECD spectrum simultaneously. The method is advantageous for large systems with a high density of states. In contrast to previous implementations based on real-space grids, the method is variational, independent of nuclear orientation, and does not rely on pseudopotential approximations, making it suitable for computation of chiroptical properties well into the X-ray regime.

  17. Validation of a method using an achiral liquid chromatography sorbent and a circular dichroism detector. Analysis of the efaroxan enantiomers.

    Science.gov (United States)

    Lorin, Marie; Delépée, Raphaël; Ribet, Jean-Paul; Morin, Philippe

    2007-02-01

    The known HPLC method using an achiral C8 silica sorbent and a circular dichroism (CD) detector for the determination of efaroxan enantiomeric excess has been validated. After optimization of the mobile phase, the enantiomers were detected at 278 nm offering maximum ellipticity between two optically active forms. The calibration curve of the anisotropy factor (g) versus the enantiomeric excess was linear with a correlation coefficient (r2) of 0.9985. The accuracy of the method was assessed by comparing the enantiomeric excess obtained by measuring the g factor (C8 column, CD and UV detections) with those determined by enantioselective HPLC (Chiralpak AD-H column, UV detection). Statistical tests (level of confidence of 95%) were assessed to compare the two orthogonal methods. The straight line gave a correlation coefficient of 0.9995, an intercept not significantly different from zero (0.0549) and a slope of 1.026. The precision evaluated on retention time (RSDmethod has the advantages of being fast and precise without using expensive chiral column. Non-enantioselective HPLC-CD was suitable for the simultaneous determination of the optical and chemical purity of efaroxan.

  18. Electrically induced circular dichroism of multi-domain layers of a long-pitch cholesteric liquid crystal

    Science.gov (United States)

    Yakovlev, Dmitry D.; Sherman, Maria M.; Yakovlev, Dmitry A.

    2014-01-01

    Circular dichroism is typical of cholesteric materials with a cholesteric pitch of the order of light wavelength, where it is connected with selective reflection of one of the circularly polarized components of light. In this work we report, for the first time, on our observations of circular dichroism on multi-domain layers of a nonabsorbing cholesteric LC material whose natural cholesteric pitch is much larger than the wavelength of incident light. It is demonstrated that the degree of manifestation of the circular dichroism depends heavily on the LC layer thickness, voltage applied to the layer, and wavelength.

  19. The use of Coulomb-attenuated methods for the calculation of electronic circular dichroism spectra

    Science.gov (United States)

    Shcherbin, Dmitry; Ruud, Kenneth

    2008-06-01

    We explore different parametrizations of the Coulomb-attenuated method B3LYP functional (CAM-B3LYP) for the calculation of circular dichroism spectra. In order to assess the performance of the different parametrizations, the calculated results are compared with high-level coupled-cluster calculations at the CC2 and CCSD levels of theory. We demonstrate that it is not possible to directly obtain good results both for the excitation energies and the rotational strengths simultaneously for any of the parametrizations of the CAM-B3LYP functional that we have tested. However, using the lowest excited state as a reference instead of the ground state—that is, shifting uniformly all excitation energies—leads to one parametrization which performs better than the others and thus can be recommended for studies of circular dichroism using the CAM-B3LYP functional.

  20. The use of Coulomb-attenuated methods for the calculation of electronic circular dichroism spectra

    Energy Technology Data Exchange (ETDEWEB)

    Shcherbin, Dmitry [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromso, N-9037 Tromso (Norway); Ruud, Kenneth [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromso, N-9037 Tromso (Norway)], E-mail: kenneth.ruud@chem.uit.no

    2008-06-16

    We explore different parametrizations of the Coulomb-attenuated method B3LYP functional (CAM-B3LYP) for the calculation of circular dichroism spectra. In order to assess the performance of the different parametrizations, the calculated results are compared with high-level coupled-cluster calculations at the CC2 and CCSD levels of theory. We demonstrate that it is not possible to directly obtain good results both for the excitation energies and the rotational strengths simultaneously for any of the parametrizations of the CAM-B3LYP functional that we have tested. However, using the lowest excited state as a reference instead of the ground state-that is, shifting uniformly all excitation energies-leads to one parametrization which performs better than the others and thus can be recommended for studies of circular dichroism using the CAM-B3LYP functional.

  1. An X-ray magnetic circular dichroism study of the interface Magnetism in titanate Heterostructures

    Science.gov (United States)

    Salluzzo, Marco; CNR-SPIN Team

    2014-03-01

    The 2D-electron system (2DES) created at the interface between LaAlO3 and SrTiO3 have attracted strong interest in recent years. This system shows an intriguing inversion the Ti3d bands hierarchy at the interface respect the bulk, and some reports even suggested coexistence between ferromagnetism and superconductivity. By using x-ray magnetic circular dichroism we show that oxygen vacancies induce magnetic interfacial localized Ti3 + states, which couple to the 2DES, with a negative exchange interaction. The magnetic dichroism signal is quenched in standard LAO/STO interfaces annealed in high oxygen pressure after the deposition and showing a homogeneous superconducting ground state, suggesting a decisive role of oxygen vacancies in the magnetism of these oxide interfaces.

  2. Chiral optical fields: A unified formulation of helicity scattered from particles and dichroism enhancement

    CERN Document Server

    Nieto-Vesperinas, Manuel

    2016-01-01

    We establish a general unified formulation which, using the optical theorem of electromagnetic helicity, shows that dichorism is a phenomenon arising in any scattering -or diffraction- process, elastic or not, of chiral electromagnetic fields by objects either chiral or achiral. It is shown how this approach paves the way to overcoming well-known limitations of standard circular dichroism, like its weak signal or the difficulties of using it with magnetodielectric particles. Based on the angular spectrum representation of optical fields with only right circular or left circular plane waves, we introduce beams with transverse elliptic polarization and posessing a longitudinal component. Then our formulation for general optical fields shows how to enhance the helicity, (and therefore the dichroism signal), versus the energy of the light scattered or emitted by a particle, or viceversa.

  3. Levels of Supramolecular Chirality of Polyglutamine Aggregates Revealed by Vibrational Circular Dichroism

    OpenAIRE

    Kurouski, Dmitry; Kar, Karunakar; Wetzel, Ronald; Dukor, Rina K.; Lednev, Igor K.; Nafie, Laurence A.

    2013-01-01

    Polyglutamine (PolyQ) aggregates are a hallmark of several severe neurodegenerative diseases, expanded CAG-repeat diseases in which inheritance of an expanded polyQ sequence above a pathological threshold is associated with a high risk of disease. Application of vibrational circular dichroism (VCD) reveals that these PolyQ fibril aggregates exhibit a chiral supramolecular organization that is distinct from the supramolecular organization of previously observed amyloid fibrils. PolyQ fibrils g...

  4. Magnetic moments in a gadolinium iron garnet studied by soft-X-ray magnetic circular dichroism

    NARCIS (Netherlands)

    Rudolf, P.; Sette, F.; Tjeng, L.H.; Meigs, G.; Chen, C.T.

    1992-01-01

    The magnetic moments of Gd and Fe in gadolinium iron garnet (Gd3Fe5O12) were probed at 77 and 300 K by soft-X-ray magnetic circular dichroism (SXMCD) measurements at the GdMa4,5 and at the FeL2,3 absorption edges. The SXMCD signal at each edge allows one to independently determine the magnetic order

  5. Experimental demonstration of the microscopic origin of circular dichroism (Conference Presentation)

    Science.gov (United States)

    Shvets, Gennady B.

    2016-09-01

    Fully two-dimensional metamaterials, also known as metasurfaces comprised of planar-chiral plasmonic metamolecules that are just nanometers thick, have been shown to exhibit chiral dichroism in transmission. The origin of the resulting circular dichroism is rather subtle. Theoretical calculations indicate that this surprising effect relies on finite non-radiative (Ohmic) losses of the metasurface. In the absence of such losses on the nanoscale, the chiral dichroism in transmission (CDT) defined as the difference between the transmission coefficients of the RCP and LCP waves, must identically vanish. This surprising theoretical prediction has never been experimentally verified because of the challenge of measuring non-radiative loss on the nanoscale. We use a combination of nanoscale characterization techniques to demonstrate that the RCP and LCP states of the incident light produce drastically different distributions of optical energy and Ohmic heat dissipation in the two-dimensional chiral nanoantennas, thereby producing a strong chiral dichroism in absorption (CDA). A planar-chiral metasurface, along with its chiral enantiomer, was designed to maximize the CDA in mid-IR range. The CDA gives rise to the CDT observed experimentally in the far-field measurements. We then use scattering-type near-field scanning optical microscopy to map the optical energy distribution on the nanoantennas and their enantiomers in response to the RCP and LCP light. Photo-expansion microscopy, also known as AFM-IR, was then utilized to experimentally demonstrate drastically different Ohmic heating of the nanoantennas under RCP and LCP light illumination. In collaboration with: A.B.Khanikaev, N.Arju, Z.Fan, D.Purtseladze, F.Lu, J.Lee, P.Sarriugarte, M.Schnell, R.Hillenbrand, M.A.Belkin

  6. Analysis of boundary point (break point) in Linear Delay Model for nanoscale VLSI standard cell library characterization at PVT corners

    CERN Document Server

    Agarwal, Gaurav Kumar

    2014-01-01

    In VLSI chip design flow, Static Timing Analysis (STA) is used for fast and accurate analysis of data-path delay. This process is fast because delay is picked from Look Up Tables (LUT) rather than conventional SPICE simulations. But accuracy of this method depends upon the underlying delay model with which LUT was characterized. Non Linear Delay Model (NLDM) based LUTs are quite common in industries. These LUT requires huge amount to time during characterization because of huge number of SPICE simulations done at arbitrary points. To improve this people proposed various other delay models like alpha-power and piecewise linear delay models. Bulusu et al proposed Linear Delay Model(LDM) which reduces LUT generation time to 50 percent. LDM divides delay curve w.r.t input rise time(trin) into two different region one is linear and other is non-linear. This boundary point between linear and non- linear region was called break point (trb). Linear region will be done if we simulate at only two points. This advantage...

  7. Synchrotron Radiation Linear Dichroism (SRLD) and Time Dependent Density Functional Theory (TD-DFT) Calculations on Dihydroxy-Anthraquinones

    DEFF Research Database (Denmark)

    Nguyen, Duy Duc; Spanget-Larsen, Jens

    SRLD spectra of Quinizarin, Anthrarufin, and Chrysazin partially aligned in stretched polyethylene were measured at the ASTRID synchrotron UV1 beamline (ISA, Aarhus University), yielding absorbance and polarization data up to 57000 cm-1. The observed absorption bands were assigned to electronic t...

  8. Electronic states of model hydrocarbon chromophores investigated by Synchrotron Radiation Linear Dichroism (SRLD) spectroscopy on aligned samples

    DEFF Research Database (Denmark)

    Nguyen, Duy Duc; Hoffmann, Søren Vrønning; Jones, Nykola;

    2010-01-01

    , differently polarized absorption bands, and to symmetry assignments of the observed molecular states. This information is highly useful in the study of molecular symmetry and reactivity. Partially aligned molecular samples may be produced in a simple fashion by the use of stretched polymers as anisotropic...

  9. Electronic properties of Co{sub 2}FeSi investigated by X-ray magnetic linear dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Emmel, M. [Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, D-55128 Mainz (Germany); Alfonsov, A. [IFW Dresden, Institute for Solid State Research, D-01069 Dresden (Germany); Legut, D. [VSB - Technical University of Ostrava, 17. Listopadu 15, CZ-70833 Ostrava (Czech Republic); Kehlberger, A.; Vilanova, E. [Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, D-55128 Mainz (Germany); Krug, I.P. [Peter Grünberg Institut PGI-6, Forschungszentrum Jülich, D-52425 Jülich (Germany); Gottlob, D.M. [Peter Grünberg Institut PGI-6, Forschungszentrum Jülich, D-52425 Jülich (Germany); Fakultät für Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), D-47048 Duisburg (Germany); Belesi, M. [IFW Dresden, Institute for Solid State Research, D-01069 Dresden (Germany); Büchner, B. [IFW Dresden, Institute for Solid State Research, D-01069 Dresden (Germany); Institut für Physik, TU Dresden, D-01062 Dresden (Germany); Kläui, M. [Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, D-55128 Mainz (Germany); Oppeneer, P.M. [Department of Physics and Astronomy, Uppsala University, P. O. Box 516, S-751 20 Uppsala (Sweden); Wurmehl, S. [IFW Dresden, Institute for Solid State Research, D-01069 Dresden (Germany); Institut für Physik, TU Dresden, D-01062 Dresden (Germany); and others

    2014-11-15

    We present experimental XMLD spectra measured on epitaxial (001)-oriented thin Co{sub 2}FeSi films, which are rich in features and depend sensitively on the degree of atomic order and interdiffusion from capping layers. Al- and Cr-capped films with different degrees of atomic order were prepared by DC magnetron sputtering by varying the deposition temperatures. The local structural properties of the film samples were additionally investigated by nuclear magnetic resonance (NMR) measurements. The XMLD spectra of the different samples show clear and uniform trends at the L{sub 3,2} edges. The Al-capped samples show similar behavior as previous measured XMLD spectra of Co{sub 2}FeSi{sub 0.6}Al{sub 0.4}. Thus, we assume that during deposition Al atoms are being implanted into the subsurface of Co{sub 2}FeSi. Such an interdiffusion is not observed for the corresponding Cr-capped films, which makes Cr the material of choice for capping Co{sub 2}FeSi films. We report stronger XMLD intensities at the L{sub 3,2} Co and Fe egdes for films with a higher saturation magnetization. Additionally, we compare the spectra with ab initio predictions and obtain a reasonably good agreement. Furthermore, we were able to detect an XMCD signal at the Si L-edge, indicating the presence of a magnetic moment at the Si atoms. - Highlights: • Co{sub 2}FeSi thin films with different degree ordering were grown by DC sputtering. • The films were structurally investigated by NMR, XMLD and XMCD. • We see a relation between the saturation magnetization and the XMLD strength. • We notice an intermixing of the Al capping with the film material. • We detect a magnetic moment at the Si atom probed with XMCD.

  10. Linear Systems.

    Science.gov (United States)

    The report documents a series of seminars at Rome Air Development Center with the content equivalent to an intense course in Linear Systems . Material...is slanted toward the practicing engineer and introduces some of the fundamental concepts and techniques for analyzing linear systems . Techniques for

  11. Correction: Absolute stereochemistry and preferred conformations of urate degradation intermediates from computed and experimental circular dichroism spectra.

    Science.gov (United States)

    Pipolo, Silvio; Percudani, Riccardo; Cammi, Roberto

    2016-04-14

    Correction for 'Absolute stereochemistry and preferred conformations of urate degradation intermediates from computed and experimental circular dichroism spectra' by Silvio Pipolo et al., Org. Biomol. Chem., 2011, 9, 5149-5155.

  12. Direct determination of absolute configuration: a vibrational circular dichroism study on dimethyl-substituted phenyloxiranes synthesized by Shi epoxidation

    DEFF Research Database (Denmark)

    Fristrup, Peter; Lassen, Peter Rygaard; Tanner, David Ackland;

    2008-01-01

    The three possible dimethylsubstituted phenyloxiranes (cis, trans and geminal) were synthesized in both racemic (mCPBA) and enantiomerically enriched forms (Shi epoxidation) and subjected to a vibrational circular dichroism study. The experimental spectra were compared to theoretical spectra obta...

  13. First observation of spin dichroism with deuterons up to 20 MeV in a carbon target

    CERN Document Server

    Baryshevsky, V; Engels, R; Rathmann, F; Seyfarth, H; Ströher, H; Ullrich, T; D"uweke, C; Emmerich, R; Imig, A; Ley, J; Schieck, H P; Schulze, R; Tenckhoff, G; Weske, C; Mikirtytchiants, M; Vasilev, A

    2005-01-01

    The first observation of the phenomenom of deuteron spin dichroism in the energy region of 6-20 MeV is described. Experimental values of this effect for deuterons after passage of an unpolarized carbon target are reported.

  14. Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

    Science.gov (United States)

    Lee, Geon Joon; Sim, Geon Bo; Choi, Eun Ha; Kwon, Young-Wan; Kim, Jun Young; Jang, Siun; Kim, Seong Hwan

    2015-01-01

    To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.

  15. Optical and structural properties of plasma-treated Cordyceps bassiana spores as studied by circular dichroism, absorption, and fluorescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Geon Joon, E-mail: gjlee@kw.ac.kr; Sim, Geon Bo; Choi, Eun Ha [Plasma Bioscience Research Center/Department of Electrical and Biological Physics, Kwangwoon University, Seoul 139-701 (Korea, Republic of); Kwon, Young-Wan [KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 136-701 (Korea, Republic of); Kim, Jun Young; Jang, Siun; Kim, Seong Hwan, E-mail: piceae@naver.com [Department of Microbiology and Institute of Basic Sciences, Dankook University, Cheonan 330-714 (Korea, Republic of)

    2015-01-14

    To understand the killing mechanism of fungal spores by plasma treatment, the optical, structural, and biological properties of the insect pathogenic fungus Cordyceps bassiana spores were studied. A nonthermal atmospheric-pressure plasma jet (APPJ) was used to treat the spores in aqueous solution. Optical emission spectra of the APPJ acquired in air indicated emission peaks corresponding to hydroxyl radicals and atomic oxygen. When the APPJ entered the aqueous solution, additional reactive species were derived from the interaction of plasma radicals with the aqueous solution. Fluorescence and absorption spectroscopy confirmed the generation of hydroxyl radicals and hydrogen peroxide in the plasma-activated water (PAW). Spore counting showed that plasma treatment significantly reduced spore viability. Absorption spectroscopy, circular dichroism (CD) spectroscopy, and agarose gel electrophoresis of the DNA extracted from plasma-treated spores showed a reduction in spore DNA content. The magnitude of the dip in the CD spectrum was lower in the plasma-treated spores than in the control, indicating that plasma treatment causes structural modifications and/or damage to cellular components. Tryptophan fluorescence intensity was lower in the plasma-treated spores than in the control, suggesting that plasma treatment modified cell wall proteins. Changes in spore viability and DNA content were attributed to structural modification of the cell wall by reactive species coming from the APPJ and the PAW. Our results provided evidence that the plasma radicals and the derived reactive species play critical roles in fungal spore inactivation.

  16. Linear algebra

    CERN Document Server

    Stoll, R R

    1968-01-01

    Linear Algebra is intended to be used as a text for a one-semester course in linear algebra at the undergraduate level. The treatment of the subject will be both useful to students of mathematics and those interested primarily in applications of the theory. The major prerequisite for mastering the material is the readiness of the student to reason abstractly. Specifically, this calls for an understanding of the fact that axioms are assumptions and that theorems are logical consequences of one or more axioms. Familiarity with calculus and linear differential equations is required for understand

  17. Linear algebra

    CERN Document Server

    Liesen, Jörg

    2015-01-01

    This self-contained textbook takes a matrix-oriented approach to linear algebra and presents a complete theory, including all details and proofs, culminating in the Jordan canonical form and its proof. Throughout the development, the applicability of the results is highlighted. Additionally, the book presents special topics from applied linear algebra including matrix functions, the singular value decomposition, the Kronecker product and linear matrix equations. The matrix-oriented approach to linear algebra leads to a better intuition and a deeper understanding of the abstract concepts, and therefore simplifies their use in real world applications. Some of these applications are presented in detailed examples. In several ‘MATLAB-Minutes’ students can comprehend the concepts and results using computational experiments. Necessary basics for the use of MATLAB are presented in a short introduction. Students can also actively work with the material and practice their mathematical skills in more than 300 exerc...

  18. Linear Models

    CERN Document Server

    Searle, Shayle R

    2012-01-01

    This 1971 classic on linear models is once again available--as a Wiley Classics Library Edition. It features material that can be understood by any statistician who understands matrix algebra and basic statistical methods.

  19. Linear DNA for rapid prototyping of synthetic biological circuits in an Escherichia coli based TX-TL cell-free system.

    Science.gov (United States)

    Sun, Zachary Z; Yeung, Enoch; Hayes, Clarmyra A; Noireaux, Vincent; Murray, Richard M

    2014-06-20

    Accelerating the pace of synthetic biology experiments requires new approaches for rapid prototyping of circuits from individual DNA regulatory elements. However, current testing standards require days to weeks due to cloning and in vivo transformation. In this work, we first characterized methods to protect linear DNA strands from exonuclease degradation in an Escherichia coli based transcription-translation cell-free system (TX-TL), as well as mechanisms of degradation. This enabled the use of linear DNA PCR products in TX-TL. We then compared expression levels and binding dynamics of different promoters on linear DNA and plasmid DNA. We also demonstrated assembly technology to rapidly build circuits entirely in vitro from separate parts. Using this strategy, we prototyped a four component genetic switch in under 8 h entirely in vitro. Rapid in vitro assembly has future applications for prototyping multiple component circuits if combined with predictive computational models.

  20. International comparability in spectroscopic measurements of protein structure by circular dichroism: CCQM-P59.1

    Science.gov (United States)

    Ravi, Jascindra; Rakowska, Paulina D.; Garfagnini, Tommaso; Baron, Bruno; Charlet, Philippe; Jones, Christopher; Milev, Stoyan; DeSa Lorenz, Julie; Plusquellic, David; Wien, Frank; Wu, Liqing; Meuse, Curtis W.; Knight, Alex E.

    2010-12-01

    Circular dichroism (CD) is a spectroscopic technique that is widely used to obtain information about protein structure, and hence is an important tool with many applications, including the characterization of biopharmaceuticals. A previous inter-laboratory study, CCQM-P59, showed that there was a poor level of comparability between laboratories in CD spectroscopy. In a follow-up study reported here, we achieved our goal of demonstrating improved comparability and data quality, primarily by addressing the problems identified in the previous study, which included cell path-length measurement, instrument calibration and good practice in general. Multivariate analysis techniques (principal component analysis and soft independent modelling of class analogies) were shown to be useful in comparing large spectral data sets and in classifying spectra. However, our results also show that there is more work to be done to improve confidence in the technique as the discrepancies observed were partially due to systematic effects, which the statistical approaches do not consider. We therefore conclude that there is a need for an improved understanding of the uncertainties in CD measurement.

  1. Linear algebra

    CERN Document Server

    Edwards, Harold M

    1995-01-01

    In his new undergraduate textbook, Harold M Edwards proposes a radically new and thoroughly algorithmic approach to linear algebra Originally inspired by the constructive philosophy of mathematics championed in the 19th century by Leopold Kronecker, the approach is well suited to students in the computer-dominated late 20th century Each proof is an algorithm described in English that can be translated into the computer language the class is using and put to work solving problems and generating new examples, making the study of linear algebra a truly interactive experience Designed for a one-semester course, this text adopts an algorithmic approach to linear algebra giving the student many examples to work through and copious exercises to test their skills and extend their knowledge of the subject Students at all levels will find much interactive instruction in this text while teachers will find stimulating examples and methods of approach to the subject

  2. Linear algebra

    CERN Document Server

    Sahai, Vivek

    2013-01-01

    Beginning with the basic concepts of vector spaces such as linear independence, basis and dimension, quotient space, linear transformation and duality with an exposition of the theory of linear operators on a finite dimensional vector space, this book includes the concept of eigenvalues and eigenvectors, diagonalization, triangulation and Jordan and rational canonical forms. Inner product spaces which cover finite dimensional spectral theory and an elementary theory of bilinear forms are also discussed. This new edition of the book incorporates the rich feedback of its readers. We have added new subject matter in the text to make the book more comprehensive. Many new examples have been discussed to illustrate the text. More exercises have been included. We have taken care to arrange the exercises in increasing order of difficulty. There is now a new section of hints for almost all exercises, except those which are straightforward, to enhance their importance for individual study and for classroom use.

  3. Linear algebra

    CERN Document Server

    Allenby, Reg

    1995-01-01

    As the basis of equations (and therefore problem-solving), linear algebra is the most widely taught sub-division of pure mathematics. Dr Allenby has used his experience of teaching linear algebra to write a lively book on the subject that includes historical information about the founders of the subject as well as giving a basic introduction to the mathematics undergraduate. The whole text has been written in a connected way with ideas introduced as they occur naturally. As with the other books in the series, there are many worked examples.Solutions to the exercises are available onlin

  4. Vibrational circular dichroism spectra for large molecules and molecules with heavy elements

    Science.gov (United States)

    Reiter, Kevin; Kühn, Michael; Weigend, Florian

    2017-02-01

    We present an implementation of vibrational circular dichroism (VCD) spectra in TURBOMOLE. We mainly followed the route proposed by Cheeseman [Chem. Phys. Lett. 252, 211 (1996)] and extended the modules for calculating the magnetic response and vibrational frequencies accordingly. The implementation allows for gauge origin invariant employment of effective core potentials, as demonstrated for Co(ppy)3, ppy = 2-Phenylpyridine. In this way, scalar relativistic effects are covered and heavy elements can be treated. Further, with the present implementation molecular symmetry may be efficiently exploited, which makes the calculation of large (symmetric) systems feasible. The calculation of the VCD spectrum of icosahedral C6202+ is shown as an illustrative application.

  5. Magnetic circular dichroism spectroscopy as a probe of the structures of the metal sites in metalloproteins.

    Science.gov (United States)

    McMaster, Jonathan; Oganesyan, Vasily S

    2010-10-01

    Magnetic circular dichroism (MCD) is a powerful probe of the electronic and geometric structures of metal centres in metalloproteins. MCD has provided significant insight into the nature of the axial donors at haem centres and, more recently, sophisticated methods for the analysis of MCD spectra have had a major impact on the study of the electronic structures of the ground states of a range of Cu, non-haem iron and Mo-containing active sites. This detail, together with data from other complimentary spectroscopies, has played a major role in defining the chemistry underpinning the catalysis achieved by these metal centres.

  6. Circular dichroism and superdiffusive transport at the surface of BiTeI.

    Science.gov (United States)

    Mauchain, J; Ohtsubo, Y; Hajlaoui, M; Papalazarou, E; Marsi, M; Taleb-Ibrahimi, A; Faure, J; Kokh, K A; Tereshchenko, O E; Eremeev, S V; Chulkov, E V; Perfetti, L

    2013-09-20

    We investigate the electronic states of BiTeI after the optical pumping with circularly polarized photons. Our data show that photoexcited electrons reach an internal thermalization within 300 fs of the arrival of the pump pulse. Instead, the dichroic contrast generated by the circularly polarized light relaxes on a time scale shorter than 80 fs. This result implies that orbital and spin polarization created by the circular pump pulse rapidly decays via manybody interaction. The persistent dichroism at longer delay times is due to the helicity dependence of superdiffussive transport. We ascribe it to the lack of inversion symmetry in an electronic system far from equilibrium conditions.

  7. Assignment of absolute stereostructures through quantum mechanics electronic and vibrational circular dichroism calculations.

    Science.gov (United States)

    Dai, Peng; Jiang, Nan; Tan, Ren-Xiang

    2016-01-01

    Elucidation of absolute configuration of chiral molecules including structurally complex natural products remains a challenging problem in organic chemistry. A reliable method for assigning the absolute stereostructure is to combine the experimental circular dichroism (CD) techniques such as electronic and vibrational CD (ECD and VCD), with quantum mechanics (QM) ECD and VCD calculations. The traditional QM methods as well as their continuing developments make them more applicable with accuracy. Taking some chiral natural products with diverse conformations as examples, this review describes the basic concepts and new developments of QM approaches for ECD and VCD calculations in solution and solid states.

  8. Comparison of Behaviour in Different Liquids and in Cells of Gold Nanorods and Spherical Nanoparticles Modified by Linear Polyethyleneimine and Bovine Serum Albumin

    Directory of Open Access Journals (Sweden)

    Inna A. Pyshnaya

    2014-01-01

    Full Text Available Gold nanorods (GNRs are considered one of the most promising forms of nanoparticles for nanobiotechnology; however, the problem of their toxicity is currently not resolved. We synthesised GNRs, modified with linear polyethyleneimine (PEI-GNRs, and examined their physicochemical and some biological properties in comparison with GNRs modified with BSA and spherical gold nanoparticles (sGNPs modified with the same agents. The influence of the buffer, cell culture media, and serum on hydrodynamic diameter and zeta potential of all GNPs was studied. Simultaneously, the size, shape, and formation of a corona were examined by transmission electron microscopy (TEM. PEI-GNRs and GNPs were nontoxic for BHK-21 and HeLa cells (MTT test. Penetration of all GNPs into BHK-21, melanoma B16, and HeLa cells was examined after 30 min, 3 h, and 24 h of incubation using TEM ultrathin sections. PEI-GNRs and PEI-sGNPs demonstrated fast and active penetration into cells by caveolin-dependent and lipid raft-mediated endocytosis and accumulated in endosomes and lysosomes. BSA-modified GNPs showed prolonged flotation and a significant delay in cell penetration. The results show that the charge of initial NPs determines penetration into cells. Thus, the designed PEI-GNRs were nontoxic and stable in cell culture media and could efficiently penetrate cells.

  9. Q & A Experiment to Search for Vacuum Dichroism, Pseudoscalar-Photon Interaction and Millicharged Fermions

    CERN Document Server

    Chen, S J; Ni, W T; Chen, Sheng-Jui; Mei, Hsien-Hao; Ni, Wei-Tou

    2006-01-01

    A number of experiments are underway to detect vacuum birefringence and dichroism -- PVLAS, Q & A, and BMV. Recently, PVLAS experiment has observed optical rotation in vacuum by a magnetic field (vacuum dichroism). Theoretical interpretations of this result include a possible pseudoscalar-photon interaction and the existence of millicharged fermions. Here, we report the progress and first results of Q & A (QED [quantum electrodynamics] and Axion) experiment proposed and started in 1994. A 3.5-m high-finesse (around 30,000) Fabry-Perot prototype detector extendable to 7-m has been built and tested. We use X-pendulums and automatic control schemes developed by the gravitational-wave detection community for mirror suspension and cavity control. To polarize the vacuum, we use a 2.3-T dipole permanent magnet, with 27-mm-diameter clear borehole and 0.6-m field length,. In the experiment, the magnet is rotated at 5-10 rev/s to generate time-dependent polarization signal with twice the rotation frequency. Our...

  10. A molecular dynamics and circular dichroism study of a novel synthetic antimicrobial peptide

    Science.gov (United States)

    Rodina, N. P.; Yudenko, A. N.; Terterov, I. N.; Eliseev, I. E.

    2013-08-01

    Antimicrobial peptides are a class of small, usually positively charged amphiphilic peptides that are used by the innate immune system to combat bacterial infection in multicellular eukaryotes. Antimicrobial peptides are known for their broad-spectrum antimicrobial activity and thus can be used as a basis for a development of new antibiotics against multidrug-resistant bacteria. The most challengeous task on the way to a therapeutic use of antimicrobial peptides is a rational design of new peptides with enhanced activity and reduced toxicity. Here we report a molecular dynamics and circular dichroism study of a novel synthetic antimicrobial peptide D51. This peptide was earlier designed by Loose et al. using a linguistic model of natural antimicrobial peptides. Molecular dynamics simulation of the peptide folding in explicit solvent shows fast formation of two antiparallel beta strands connected by a beta-turn that is confirmed by circular dichroism measurements. Obtained from simulation amphipatic conformation of the peptide is analysed and possible mechanism of it's interaction with bacterial membranes together with ways to enhance it's antibacterial activity are suggested.

  11. Photon energy dependence of circular dichroism of the Au(111) surface state

    Science.gov (United States)

    Ärrälä, M.; Nieminen, J.; Braun, J.; Ebert, H.; Lindroos, M.

    2013-11-01

    Through relativistic photoemission calculations for the Au(111) surface state at the Fermi level, we study the photon energy dependence of circular dichroism. The dichromatic signal (DS) pattern changes 23 times with photon energies between 7 and 100 eV, and we have found 13 different patterns in the k∥ map at the Fermi level for the DS from the Au(111) surface state with normal incidence light. We show that the photon energy dependence of DS is very complex even in the simplest case. The sign change in the circular dichroism as a function of photon energy is related to the relative phases of the complex expansion coefficients of different outgoing partial waves in a time-reversed low-energy electron diffraction state. With off-normal incidence, the z component of the incoming photon field is dominant, and the fine structure seen in the DS in the normal incidence case is lost very rapidly, moving from a normal to an off-normal incidence. We also report that the Rashba split surface state of Au(111) has a significant component of d-type orbital due to relativistic effects and the computational setup used.

  12. Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism.

    Science.gov (United States)

    Fan, Tingting; Grychtol, Patrik; Knut, Ronny; Hernández-García, Carlos; Hickstein, Daniel D; Zusin, Dmitriy; Gentry, Christian; Dollar, Franklin J; Mancuso, Christopher A; Hogle, Craig W; Kfir, Ofer; Legut, Dominik; Carva, Karel; Ellis, Jennifer L; Dorney, Kevin M; Chen, Cong; Shpyrko, Oleg G; Fullerton, Eric E; Cohen, Oren; Oppeneer, Peter M; Milošević, Dejan B; Becker, Andreas; Jaroń-Becker, Agnieszka A; Popmintchev, Tenio; Murnane, Margaret M; Kapteyn, Henry C

    2015-11-17

    We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform.

  13. Identification of a linear B-cell epitope on the avian leukosis virus P27 protein using monoclonal antibodies.

    Science.gov (United States)

    Li, Xiaofei; Qin, Liting; Zhu, Haibo; Sun, Yingjun; Cui, Xuezhi; Gao, Yadong; Qi, Xiaole; Wang, Yongqiang; Gao, Honglei; Gao, Yulong; Wang, Xiaomei

    2016-10-01

    Avian leukosis virus (ALV) is an avian oncogenic retrovirus that can induce various clinical tumors. The capsid protein P27 is the group-specific antigen of ALV and has many viral antigen sites that are easy to detect. In this study, we produced a monoclonal antibody (mAb), 3A9, that is specific for the P27 protein. A series of partially overlapping peptides were screened to define (181)PPSAR(185) as the minimal linear epitope recognized by mAb 3A9. The identified epitope could be recognized by chicken anti-ALV and mouse anti-ALV P27 sera. The epitope was highly conserved among a number of ALV-A, ALV-B and ALV-J strains. MAb 3A9 might be a valuable tool for the development of new immunodiagnostic approaches for ALV, and the defined linear epitope might help further our understanding of the antigenic structure of the P27 protein.

  14. Linear programming

    CERN Document Server

    Karloff, Howard

    1991-01-01

    To this reviewer’s knowledge, this is the first book accessible to the upper division undergraduate or beginning graduate student that surveys linear programming from the Simplex Method…via the Ellipsoid algorithm to Karmarkar’s algorithm. Moreover, its point of view is algorithmic and thus it provides both a history and a case history of work in complexity theory. The presentation is admirable; Karloff's style is informal (even humorous at times) without sacrificing anything necessary for understanding. Diagrams (including horizontal brackets that group terms) aid in providing clarity. The end-of-chapter notes are helpful...Recommended highly for acquisition, since it is not only a textbook, but can also be used for independent reading and study. —Choice Reviews The reader will be well served by reading the monograph from cover to cover. The author succeeds in providing a concise, readable, understandable introduction to modern linear programming. —Mathematics of Computing This is a textbook intend...

  15. [The Analysis for Probable Reasons of Cd4+ T-Cell Activation Non-Linear Dependence on Extra Cellular Calcium Ion Concentration in Human Peripheral Blood in vitro].

    Science.gov (United States)

    Litvinov, I S

    2015-01-01

    The analysis for probable reasons of CD4+ T-cell activation non-linear dependence on [Ca2+]o in HPB in vitro is the general aim of current work. At the beginning we pursued the analysis of receptor-dependent (the mixture of monoclonal antibodies (mAbs) to CD3 and CD28 molecules) and receptor-independent (phorbol-myristate-acetate and ionomycin mixture) means to activate T cells in vitro with different [Ca2+]o in HPB. The key role of intracellular T-cell signaling systems in activated T cells in their non-similar sensitivity to calcium ions in the blood was shown. The analysis of differentiation next stages of CD4+ T-cell activation in vitro relatively [Ca2+]o in PHB demonstrates the key role of the earliest induction stages in non-similar sensitivity to calcium ions in CD4+ T-cell activation in vitro. According to the pursued analysis; the non-similar sensitivity of CD4+ T-cell in vitro to activation is in no-way connected with pace differences on the primary stages of activation process. The comparison of CD4+ memory T cells with their naive T-cell precursors in the cell activation process in hypocalcemia conditions was made in the separate experimental series. The 1st maximum consists in average of 85% CD4+CD45R0high CD69+ memory T cells. Naive CD4+CD45RAlowCD69+ T cells constitute the remainder 15%. The 2nd maximum almost completely consists of CD4+CD45R0+CD69+ memory T cells. The ratio between CD4+CD69+ T cell maximums depends on donor ages and represents linear dependence with R = -0.981. The most probable candidate on the role of CD4+ T cell, being capable of activation in hypocalcemia conditions, are memory T lymphocytes, being resistant to ionomycin action (I R) subset. To check this assumption the mononuclear cells and their IR-fraction were prepared from donor PB. Then the mononuclear cells and their IR-fraction were activated by mAbs mixture at different [EGTA] values. For IR-fraction, enriched with CD4+CD45RA-CD45R0+ memory T cells, slightly seen 1st

  16. Similar structures, different characteristics: circular dichroism of metallic helix arrays with single-, double-, and triple-helical structures.

    Science.gov (United States)

    Zhang, Peng; Yang, Zhenyu; Zhao, Ming; Wu, Lin; Lu, Zeqin; Cheng, Yongzhi; Gong, Rongzhou; Zheng, Yu; Duan, Jian

    2013-04-01

    We fabricated three-dimensional metallic helix arrays with single-, double-, and triple-helical structures. The transmission performances with the normal incident angle were measured in the microwave frequency of 12-18 GHz. For the single- and double-helical structures, giant circular dichroism with fairly wide bands is observed in the transmission spectra. However, the triple-helical structure does not exhibit circular dichroism. Based on the phenomenon of circular dichroism, the single- and double-helical structures can be used as broadband circular polarizers in the microwave region, but triple-helical ones cannot. The experiments have a good agreement with our simulation results, which were studied by the finite-difference time domain method.

  17. Star-shaped and linear π-conjugated oligomers consisting of a tetrathienoanthracene core and multiple diketopyrrolopyrrole arms for organic solar cells.

    Science.gov (United States)

    Komiyama, Hideaki; Adachi, Chihaya; Yasuda, Takuma

    2016-01-01

    Solution-processable star-shaped and linear π-conjugated oligomers consisting of an electron-donating tetrathienoanthracene (TTA) core and electron-accepting diketopyrrolopyrrole (DPP) arms, namely, TTA-DPP4 and TTA-DPP2, were designed and synthesized. Based on density functional theory calculations, the star-shaped TTA-DPP4 has a larger oscillator strength than the linear TTA-DPP2, and consequently, better photoabsorption property over a wide range of visible wavelengths. The photovoltaic properties of organic solar cells based on TTA-DPP4 and TTA-DPP2 with a fullerene derivative were evaluated by varying the thickness of the bulk heterojunction active layer. As a result of the enhanced visible absorption properties of the star-shaped π-conjugated structure, better photovoltaic performances were obtained with relatively thin active layers (40-60 nm).

  18. Star-shaped and linear π-conjugated oligomers consisting of a tetrathienoanthracene core and multiple diketopyrrolopyrrole arms for organic solar cells

    Science.gov (United States)

    Adachi, Chihaya

    2016-01-01

    Summary Solution-processable star-shaped and linear π-conjugated oligomers consisting of an electron-donating tetrathienoanthracene (TTA) core and electron-accepting diketopyrrolopyrrole (DPP) arms, namely, TTA-DPP4 and TTA-DPP2, were designed and synthesized. Based on density functional theory calculations, the star-shaped TTA-DPP4 has a larger oscillator strength than the linear TTA-DPP2, and consequently, better photoabsorption property over a wide range of visible wavelengths. The photovoltaic properties of organic solar cells based on TTA-DPP4 and TTA-DPP2 with a fullerene derivative were evaluated by varying the thickness of the bulk heterojunction active layer. As a result of the enhanced visible absorption properties of the star-shaped π-conjugated structure, better photovoltaic performances were obtained with relatively thin active layers (40–60 nm). PMID:27559398

  19. In silico Identification and Validation of a Linear and Naturally Immunogenic B-Cell Epitope of the Plasmodium vivax Malaria Vaccine Candidate Merozoite Surface Protein-9

    Science.gov (United States)

    Rodrigues-da-Silva, Rodrigo Nunes; Martins da Silva, João Hermínio; Singh, Balwan; Jiang, Jianlin; Meyer, Esmeralda V. S.; Santos, Fátima; Banic, Dalma Maria; Moreno, Alberto; Galinski, Mary R.; Oliveira-Ferreira, Joseli; Lima-Junior, Josué da Costa

    2016-01-01

    Synthetic peptide vaccines provide the advantages of safety, stability and low cost. The success of this approach is highly dependent on efficient epitope identification and synthetic strategies for efficacious delivery. In malaria, the Merozoite Surface Protein-9 of Plasmodium vivax (PvMSP9) has been considered a vaccine candidate based on the evidence that specific antibodies were able to inhibit merozoite invasion and recombinant proteins were highly immunogenic in mice and humans. However the identities of linear B-cell epitopes within PvMSP9 as targets of functional antibodies remain undefined. We used several publicly-available algorithms for in silico analyses and prediction of relevant B cell epitopes within PMSP9. We show that the tandem repeat sequence EAAPENAEPVHENA (PvMSP9E795-A808) present at the C-terminal region is a promising target for antibodies, given its high combined score to be a linear epitope and located in a putative intrinsically unstructured region of the native protein. To confirm the predictive value of the computational approach, plasma samples from 545 naturally exposed individuals were screened for IgG reactivity against the recombinant PvMSP9-RIRII729-972 and a synthetic peptide representing the predicted B cell epitope PvMSP9E795-A808. 316 individuals (58%) were responders to the full repetitive region PvMSP9-RIRII, of which 177 (56%) also presented total IgG reactivity against the synthetic peptide, confirming it validity as a B cell epitope. The reactivity indexes of anti-PvMSP9-RIRII and anti-PvMSP9E795-A808 antibodies were correlated. Interestingly, a potential role in the acquisition of protective immunity was associated with the linear epitope, since the IgG1 subclass against PvMSP9E795-A808 was the prevalent subclass and this directly correlated with time elapsed since the last malaria episode; however this was not observed in the antibody responses against the full PvMSP9-RIRII. In conclusion, our findings identified and

  20. Enantioselective semi-preparative HPLC separation of PCB metabolites and their absolute structures determined by electronic and vibrational circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Tuan, H.P.; Larsson, C.; Huehnerfuss, H. [Hamburg Univ. (Germany). Inst. fuer Organische Chemie; Hoffmann, F.; Froeba, M. [Giessen Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Bergmann, Aa. [Stockholm Univ. (Sweden). Dept. of Environmental Chemistry

    2004-09-15

    The present paper represents a first result of an ongoing systematic study of atropisomeric methylsulfonyl, methylthionyl, hydroxy, and methoxy metabolites of environmentally most relevant PCBs. This involves semi-preparative enantioselective HPLC separation to obtain pure atropisomers from synthesized PCB metabolite standards, their configuration estimation using the electronic circular dichroism (UV-CD) method and the determination / confirmation of these absolute configurations applying the combined vibrational circular dichroism (VCD) / ab initio approach. The following substances have been investigated: 4-HO-, 4-MeO-, 4-MeS-, 4-MeSO2-, 3-MeS- and 3-MeSO{sub 2}-CB149.

  1. Linear systems

    CERN Document Server

    Bourlès, Henri

    2013-01-01

    Linear systems have all the necessary elements (modeling, identification, analysis and control), from an educational point of view, to help us understand the discipline of automation and apply it efficiently. This book is progressive and organized in such a way that different levels of readership are possible. It is addressed both to beginners and those with a good understanding of automation wishing to enhance their knowledge on the subject. The theory is rigorously developed and illustrated by numerous examples which can be reproduced with the help of appropriate computation software. 60 exe

  2. Identification of two linear B-cell epitopes from West Nile virus NS1 by screening a phage-displayed random peptide library

    Directory of Open Access Journals (Sweden)

    Qin Yong-Li

    2011-07-01

    Full Text Available Abstract Background The West Nile virus (WNV nonstructural protein 1 (NS1 is an important antigenic protein that elicits protective antibody responses in animals and can be used for the serological diagnosis of WNV infection. Although previous work has demonstrated the vital role of WNV NS1-specific antibody responses, the specific epitopes in the NS1 have not been identified. Results The present study describes the identification of two linear B-cell epitopes in WNV NS1 through screening a phage-displayed random 12-mer peptide library with two monoclonal antibodies (mAbs 3C7 and 4D1 that directed against the NS1. The mAbs 3C7 and 4D1 recognized phages displaying peptides with the consensus motifs LTATTEK and VVDGPETKEC, respectively. Exact sequences of both motifs were found in the NS1 (895LTATTEK901 and 925VVDGPETKEC934. Further identification of the displayed B cell epitopes were conducted using a set of truncated peptides expressed as MBP fusion proteins. The data indicated that 896TATTEK901 and925VVDGPETKEC934 are minimal determinants of the linear B cell epitopes recognized by the mAbs 3C7 and 4D1, respectively. Antibodies present in the serum of WNV-positive horses recognized the minimal linear epitopes in Western blot analysis, indicating that the two peptides are antigenic in horses during infection. Furthermore, we found that the epitope recognized by 3C7 is conserved only among WNV strains, whereas the epitope recognized by 4D1 is a common motif shared among WNV and other members of Japanese encephalitis virus (JEV serocomplex. Conclusions We identified TATTEK and VVDGPETKEC as NS1-specific linear B-cell epitopes recognized by the mAbs 3C7 and 4D1, respectively. The knowledge and reagents generated in this study may have potential applications in differential diagnosis and the development of epitope-based marker vaccines against WNV and other viruses of JEV serocomplex.

  3. Characteristics of myeloid differentiation and maturation pathway derived from human hematopoietic stem cells exposed to different linear energy transfer radiation types.

    Directory of Open Access Journals (Sweden)

    Satoru Monzen

    Full Text Available Exposure of hematopoietic stem/progenitor cells (HSPCs to ionizing radiation causes a marked suppression of mature functional blood cell production in a linear energy transfer (LET- and/or dose-dependent manner. However, little information about LET effects on the proliferation and differentiation of HSPCs has been reported. With the aim of characterizing the effects of different types of LET radiations on human myeloid hematopoiesis, in vitro hematopoiesis in Human CD34(+ cells exposed to carbon-ion beams or X-rays was compared. Highly purified CD34(+ cells exposed to each form of radiation were plated onto semi-solid culture for a myeloid progenitor assay. The surviving fractions of total myeloid progenitors, colony-forming cells (CFC, exposed to carbon-ion beams were significantly lower than of those exposed to X-rays, indicating that CFCs are more sensitive to carbon-ion beams (D(0 = 0.65 than to X-rays (D(0 = 1.07. Similar sensitivities were observed in granulocyte-macrophage and erythroid progenitors, respectively. However, the sensitivities of mixed-type progenitors to both radiation types were similar. In liquid culture for 14 days, no significant difference in total numbers of mononuclear cells was observed between non-irradiated control culture and cells exposed to 0.5 Gy X-rays, whereas 0.5 Gy carbon-ion beams suppressed cell proliferation to 4.9% of the control, a level similar to that for cells exposed to 1.5 Gy X-rays. Cell surface antigens associated with terminal maturation, such as CD13, CD14, and CD15, on harvest from the culture of X-ray-exposed cells were almost the same as those from the non-irradiated control culture. X-rays increased the CD235a(+ erythroid-related fraction, whereas carbon-ion beams increased the CD34(+CD38(- primitive cell fraction and the CD13(+CD14(+/-CD15(- fraction. These results suggest that carbon-ion beams inflict severe damage on the clonal growth of myeloid HSPCs, although the intensity of cell

  4. Characteristics of myeloid differentiation and maturation pathway derived from human hematopoietic stem cells exposed to different linear energy transfer radiation types.

    Science.gov (United States)

    Monzen, Satoru; Yoshino, Hironori; Kasai-Eguchi, Kiyomi; Kashiwakura, Ikuo

    2013-01-01

    Exposure of hematopoietic stem/progenitor cells (HSPCs) to ionizing radiation causes a marked suppression of mature functional blood cell production in a linear energy transfer (LET)- and/or dose-dependent manner. However, little information about LET effects on the proliferation and differentiation of HSPCs has been reported. With the aim of characterizing the effects of different types of LET radiations on human myeloid hematopoiesis, in vitro hematopoiesis in Human CD34(+) cells exposed to carbon-ion beams or X-rays was compared. Highly purified CD34(+) cells exposed to each form of radiation were plated onto semi-solid culture for a myeloid progenitor assay. The surviving fractions of total myeloid progenitors, colony-forming cells (CFC), exposed to carbon-ion beams were significantly lower than of those exposed to X-rays, indicating that CFCs are more sensitive to carbon-ion beams (D(0) = 0.65) than to X-rays (D(0) = 1.07). Similar sensitivities were observed in granulocyte-macrophage and erythroid progenitors, respectively. However, the sensitivities of mixed-type progenitors to both radiation types were similar. In liquid culture for 14 days, no significant difference in total numbers of mononuclear cells was observed between non-irradiated control culture and cells exposed to 0.5 Gy X-rays, whereas 0.5 Gy carbon-ion beams suppressed cell proliferation to 4.9% of the control, a level similar to that for cells exposed to 1.5 Gy X-rays. Cell surface antigens associated with terminal maturation, such as CD13, CD14, and CD15, on harvest from the culture of X-ray-exposed cells were almost the same as those from the non-irradiated control culture. X-rays increased the CD235a(+) erythroid-related fraction, whereas carbon-ion beams increased the CD34(+)CD38(-) primitive cell fraction and the CD13(+)CD14(+/-)CD15(-) fraction. These results suggest that carbon-ion beams inflict severe damage on the clonal growth of myeloid HSPCs, although the intensity of cell surface

  5. Polyglutamine- and temperature-dependent conformational rigidity in mutant huntingtin revealed by immunoassays and circular dichroism spectroscopy.

    Directory of Open Access Journals (Sweden)

    Valentina Fodale

    Full Text Available BACKGROUND: In Huntington's disease, expansion of a CAG triplet repeat occurs in exon 1 of the huntingtin gene (HTT, resulting in a protein bearing>35 polyglutamine residues whose N-terminal fragments display a high propensity to misfold and aggregate. Recent data demonstrate that polyglutamine expansion results in conformational changes in the huntingtin protein (HTT, which likely influence its biological and biophysical properties. Developing assays to characterize and measure these conformational changes in isolated proteins and biological samples would advance the testing of novel therapeutic approaches aimed at correcting mutant HTT misfolding. Time-resolved Förster energy transfer (TR-FRET-based assays represent high-throughput, homogeneous, sensitive immunoassays widely employed for the quantification of proteins of interest. TR-FRET is extremely sensitive to small distances and can therefore provide conformational information based on detection of exposure and relative position of epitopes present on the target protein as recognized by selective antibodies. We have previously reported TR-FRET assays to quantify HTT proteins based on the use of antibodies specific for different amino-terminal HTT epitopes. Here, we investigate the possibility of interrogating HTT protein conformation using these assays. METHODOLOGY/PRINCIPAL FINDINGS: By performing TR-FRET measurements on the same samples (purified recombinant proteins or lysates from cells expressing HTT fragments or full length protein at different temperatures, we have discovered a temperature-dependent, reversible, polyglutamine-dependent conformational change of wild type and expanded mutant HTT proteins. Circular dichroism spectroscopy confirms the temperature and polyglutamine-dependent change in HTT structure, revealing an effect of polyglutamine length and of temperature on the alpha-helical content of the protein. CONCLUSIONS/SIGNIFICANCE: The temperature- and polyglutamine

  6. Chirality study inside biological tissue by second harmonic generation circular dichroism

    Science.gov (United States)

    Hsu, Kuo-Jen; Lee, Hsuan; Zhuo, Guan-Yu; Chao, Pen-Hsiu; Chu, Shi-Wei

    2013-02-01

    Many biological systems are composed of chiral molecules and their functions depend strongly on their chirality. For example, most amino acids are of left-handed chirality while most polysaccharides are of right-handed chirality. Both of them are vital for human life, so it is important to perform chiral detection inside bio-tissues. Here we demonstrated second harmonic generation circular dichroism (SHG-CD) as a novel chiral imaging contrast in thick biotissue. Compared with conventional chiral detection, SHG-CD provides at least three orders higher contrast. In addition, due to the nonlinear nature of SHG, this technique provides optical sectioning capability, so the axial contrast is much better. The advantages of nonlinear optical microscopy are optical sectioning and deep penetration capabilities. The SHG-CD achieved 100% signal contrast with sub-micrometer spatial resolution. This method is expected to offer a novel contrast mechanism of imaging chirality inside complex bio-tissues.

  7. Detection of magnetic circular dichroism on the two-nanometer scale

    Science.gov (United States)

    Schattschneider, Peter; Stöger-Pollach, Michael; Rubino, Stefano; Sperl, Matthias; Hurm, Christian; Zweck, Josef; Rusz, Ján

    2008-09-01

    Magnetic circular dichroism (MCD) is a standard technique for the study of magnetic properties of materials in synchrotron beamlines. We present here a scattering geometry in the transmission electron microscope through which MCD can be observed with unprecedented spatial resolution. A convergent electron beam is used to scan a cross sectional preparation of a Fe/Au multilayer sample. Differences in the energy-loss spectra induced by the magnetic moments of the Fe atoms can be resolved with a resolution of better than 2 nm. This is a breakthrough achievement when compared both to the previous energy-loss MCD resolution (200 nm) or the best x-ray MCD experiments (approximately 20 nm).

  8. Levels of Supramolecular Chirality of Polyglutamine Aggregates Revealed by Vibrational Circular Dichroism

    Science.gov (United States)

    Kurouski, Dmitry; Kar, Karunakar; Wetzel, Ronald; Dukor, Rina K.; Lednev, Igor K.; Nafie, Laurence A.

    2013-01-01

    Polyglutamine (PolyQ) aggregates are a hallmark of several severe neurodegenerative diseases, expanded CAG-repeat diseases in which inheritance of an expanded polyQ sequence above a pathological threshold is associated with a high risk of disease. Application of vibrational circular dichroism (VCD) reveals that these PolyQ fibril aggregates exhibit a chiral supramolecular organization that is distinct from the supramolecular organization of previously observed amyloid fibrils. PolyQ fibrils grown from monomers with Q repeats 35 and above (Q≥35) exhibit approximately 10-fold enhancement of the same VCD spectrum compared to the already enhanced VCD of fibrils formed from Q repeats 30 and below (Q≤30). PMID:23583713

  9. Stereochemical study of tolperisone, a muscle relaxant agent, by circular dichroism and ultraviolet spectroscopy.

    Science.gov (United States)

    Zsila, F; Hollósi, M; Gergely, A

    2000-11-01

    The stereochemistry of tolperisone, a chiral aryl-alkyl basic ketone was investigated by means of circular dichroism (CD) and ultraviolet (UV) spectroscopy. The unusually high optical activity of tolperisone hydrochloride in the n-->pi* region is interpreted by the presence of a chiral conformer in solution. For stereochemical reasons, the C = O group and the aromatic moiety lack coplanarity by forming an inherently dissymetric chromophore, of M helicity. Similar helicity prevails in the crystal phase, according to the solid-state CD spectrum of (-)-tolperisone HCl salt. The chirality rule proposed by Snatzke for nonplanar benzoyl chromophores predicts the absolute configuration of (-)-tolperisone hydrochloride to be R, in agreement with other alpha-methyl-beta-amino-ketones.

  10. Feasibility of non-invasive optical blood-glucose detection using overtone circular dichroism

    CERN Document Server

    Hokr, Brett H; Meng, Zhaokai; Petrov, Georgi I; Yakovlev, Vladislav V

    2016-01-01

    Diabetes is one of the most debilitating and costly diseases currently plaguing humanity. It is a leading cause of death and dismemberment in the world, and we know how to treat it. Accurate, continuous monitoring and control of blood glucose levels via insulin treatments are widely known to mitigate the majority of detrimental effects caused by the disease. The primary limitation of continuous glucose monitoring is patient non-compliance due to the unpleasant nature of "finger-stick" testing methods. This limitation can be largely, or even completely, removed by non-invasive testing methods. In this report, we demonstrate the vibrational overtone circular dichroism properties of glucose and analyze its use as a method of non-invasive glucose monitoring, capable of assuaging this trillion dollar scourge.

  11. Conformational effects on the circular dichroism of Human Carbonic Anhydrase II: a multilevel computational study.

    Directory of Open Access Journals (Sweden)

    Tatyana G Karabencheva-Christova

    Full Text Available Circular Dichroism (CD spectroscopy is a powerful method for investigating conformational changes in proteins and therefore has numerous applications in structural and molecular biology. Here a computational investigation of the CD spectrum of the Human Carbonic Anhydrase II (HCAII, with main focus on the near-UV CD spectra of the wild-type enzyme and it seven tryptophan mutant forms, is presented and compared to experimental studies. Multilevel computational methods (Molecular Dynamics, Semiempirical Quantum Mechanics, Time-Dependent Density Functional Theory were applied in order to gain insight into the mechanisms of interaction between the aromatic chromophores within the protein environment and understand how the conformational flexibility of the protein influences these mechanisms. The analysis suggests that combining CD semi empirical calculations, crystal structures and molecular dynamics (MD could help in achieving a better agreement between the computed and experimental protein spectra and provide some unique insight into the dynamic nature of the mechanisms of chromophore interactions.

  12. X-Ray Magnetic Circular Dichroism Measurement of Fe-Co Alloy Films Prepared by Electrodeposition

    Institute of Scientific and Technical Information of China (English)

    LI Zong-Mu; XU Fa-Qiang; WANG Li-Wu; WANG Jie; ZHU Jun-Fa; ZHANG Wen-Hua

    2007-01-01

    The macro- and micro-magnetic properties of Fe-Co alloy films eletrodeposited on GaAs(100) are studied by synchrotron radiation x-ray magnetic circular dichroism (XMCD) in combination with the magneto-optical Kerr effect (MOKE) measurements and magnetic force microscopy (MFM). The orbital and spin magnetic moments of each element in the Fe-Co alloy are determined by the sum rules of XMCD. Element-specific hysteresis loops (ESHL) are obtained by recording the La MCD signals as a function of applied magnetic field. MOKE results reveal that the amorphous films are magnetically isotropic in the surface plane. The MFM image shows that the dimension of the magnetic domains is about 1-2 μm, which is much larger than that of the grains, indicating that there are intergranular correlations among these grains. Both ESHL and MOKE hysteresis loops indicate the strong ferromagnetic coupling of Fe and Co in the alloy films.

  13. Optically detected electron paramagnetic resonance by microwave modulated magnetic circular dichroism

    Science.gov (United States)

    Börger, Birgit; Bingham, Stephen J.; Gutschank, Jörg; Schweika, Marc Oliver; Suter, Dieter; Thomson, Andrew J.

    1999-11-01

    Electron paramagnetic resonance (EPR) can be detected optically, with a laser beam propagating perpendicular to the static magnetic field. As in conventional EPR, excitation uses a resonant microwave field. The detection process can be interpreted as coherent Raman scattering or as a modulation of the laser beam by the circular dichroism of the sample oscillating at the microwave frequency. The latter model suggests that the signal should show the same dependence on the optical wavelength as the MCD signal. We check this for two different samples [cytochrome c-551, a metalloprotein, and ruby (Cr3+:Al2O3)]. In both cases, the observed wavelength dependence is almost identical to that of the MCD signal. A quantitative estimate of the amplitude of the optically detected EPR signal from the MCD also shows good agreement with the experimental results.

  14. Helical Inversion of Gel Fibrils by Elongation of Perfluoroalkyl Chains as Studied by Vibrational Circular Dichroism.

    Science.gov (United States)

    Sato, Hisako; Yajima, Tomoko; Yamagishi, Akihiko

    2016-05-01

    Vibrational circular dichroism (VCD) spectroscopy was applied to gelation by a chiral low-molecular mass weight gelator, N,N'-diperfluoroalkanoyl-1,2-trans-diaminocyclohexane. Attention was focused on the winding effects of (-CF2 )n chains on the gelating ability. For this purpose, a series of gelators were synthesized with perfluoroalkyl chains of different length (n = 6-8). When gelation was studied using acetonitrile as a solvent, the fibrils took different morphologies, depending on the chain length: twisted saddle-like ribbon or helical ribbon from fibril (n = 6) and a helical ribbon from platelet (n = 8). The signs of VCD peaks assigned to the couplet of C=O stretching and to the C-F stretching were also dependent on n, indicating that a gelator molecule changed conformation on elongating perfluoroalkyl chains. A model is proposed for the aggregation modes in fibrils. Chirality 28:361-364, 2016. © 2016 Wiley Periodicals, Inc.

  15. Photoemission and core-level magnetic circular dichroism studies of diluted magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Fujimori, A. [Department of Complexity Science and Engineering, Universtiy of Tokyo, 1-5-1 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan) and Synchrotron Radiation Research Center, Japan Atomic Energy Research Institute, SPring-8, Mikazuki, Hyogo 679-5148 (Japan)]. E-mail: fujimori@phys.s.u-tokyo.ac.jp; Okabayashi, J. [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyou-ku, Tokyo 113-8656 (Japan); Takeda, Y. [Synchrotron Radiation Research Center, Japan Atomic Energy Research Institute, SPring-8, Mikazuki, Hyogo 679-5148 (Japan); Mizokawa, T. [Department of Complexity Science and Engineering, Universtiy of Tokyo, 1-5-1 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Okamoto, J. [Synchrotron Radiation Research Center, Japan Atomic Energy Research Institute, SPring-8, Mikazuki, Hyogo 679-5148 (Japan); Mamiya, K. [Photon Factory, IMSS, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305 (Japan); Saitoh, Y. [Synchrotron Radiation Research Center, Japan Atomic Energy Research Institute, SPring-8, Mikazuki, Hyogo 679-5148 (Japan); Muramatsu, Y. [Synchrotron Radiation Research Center, Japan Atomic Energy Research Institute, SPring-8, Mikazuki, Hyogo 679-5148 (Japan); Oshima, M. [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyou-ku, Tokyo 113-8656 (Japan); Ohya, S. [Department of Electronic Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Tanaka, M. [Department of Electronic Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2005-06-15

    An overview is given on the photoemission studies of the electronic structure of diluted magnetic semiconductors (DMS's), in particular of the prototypical ferromagnetic DMS Ga{sub 1-x}Mn{sub x}As. Configuration-interaction cluster-model analyses of the photoemission data allow us to estimate the p-d exchange coupling constant and hence to predict how to increase the Curie temperature in new materials. Spectra near the Fermi level combined with the transport and optical properties suggest a highly incoherent metallic state for the ferromagnetic metallic phase. It is shown that new insight into the chemically and magnetically inhomogeneous states of DMS's can be gained by the temperature and magnetic field dependence of core-level magnetic circular dichroism signals.

  16. Stability of some Cactaceae proteins based on fluorescence, circular dichroism, and differential scanning calorimetry measurements.

    Science.gov (United States)

    Gorinstein, S; Zemser, M; Vargas-Albores, F; Ochoa, J L; Paredes-Lopez, O; Scheler, C; Aksu, S; Salnikow, J

    1999-02-01

    Characterization of three cactus proteins (native and denatured) from Machaerocereus gummosus (Pitahaya agria), Lophocereu schottii (Garambullo), and Cholla opuntia (Cholla), was based on electrophoretic, fluorescence, CD (circular dichroism), DSC (differential scanning calorimetry), and FT-IR (Fourier transform infrared) measurements. The obtained results of intrinsic fluorescence, DSC, and CD were dissimilar for the three species of cactus, providing evidence of differences in secondary and tertiary structures. Cactus proteins may be situated in the following order corresponding to their relative stability: Machaerocereus gummosus (Pitahaya agria) > Cholla opuntia (Cholla) > Lophocereu schottii (Garambullo). Thermodynamic properties of proteins and their changes upon denaturation (temperature of denaturation, enthalphy, and the number of ruptured hydrogen bonds) were correlated with the secondary structure of proteins and disappearance of alpha-helix.

  17. Effects of Trehalose on Thermodynamic Properties of Alpha-synuclein Revealed through Synchrotron Radiation Circular Dichroism

    Directory of Open Access Journals (Sweden)

    Paolo Ruzza

    2015-05-01

    Full Text Available Many neurodegenerative diseases, including Huntington’s, Alzheimer’s and Parkinson’s diseases, are characterized by protein misfolding and aggregation. The capability of trehalose to interfere with protein misfolding and aggregation has been recently evaluated by several research groups. In the present work, we studied, by means of synchrotron radiation circular dichroism (SRCD spectroscopy, the dose-effect of trehalose on α-synuclein conformation and/or stability to probe the capability of this osmolyte to interfere with α-synuclein’s aggregation. Our study indicated that a low trehalose concentration stabilized α-synuclein folding much better than at high concentration by blocking in vitro α-synuclein’s polymerisation. These results suggested that trehalose could be associated with other drugs leading to a new approach for treating Parkinson’s and other brain-related diseases.

  18. Fano resonance assisting plasmonic circular dichroism from nanorice heterodimers for extrinsic chirality

    CERN Document Server

    Hu, Li; Fang, Liang; Chen, Guo; Wei, Hua; Fang, Yurui

    2015-01-01

    In this work, the circular dichroisms (CD) of nanorice heterodimers consisting of two parallel arranged nanorices with the same size but different materials are investigated theoretically. Symmetry-breaking is introduced by using different materials and oblique incidence to achieve strong CD at the vicinity of Fano resonance peaks. We demonstrate that all Au-Ag heterodimers exhibit multipolar Fano resonances and strong CD effect. A simple quantitative analysis shows that the structure with larger Fano asymmetry factor has stronger CD. The intensity and peak positions of the CD effect can be flexibly tuned in a large range by changing particle size, shape, the inter-particle distance and surroundings. Furthermore, CD spectra exhibit high sensitivity to ambient medium in visible and near infrared regions. Our results here are beneficial for the design and application of high sensitive CD sensors and other related fields.

  19. Large circular dichroism and optical rotation in titanium doped chiral silver nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Titus, Jitto; Perera, A.G. Unil [Department of Physics and Astronomy, Optoelectronics Laboratory, GSU, Atlanta, GA (United States); Larsen, George; Zhao, Yiping [Department of Physics and Astronomy, Nanolab, UGA, Athens, GA (United States)

    2016-10-15

    The circular dichroism of titanium-doped silver chiral nanorod arrays grown using the glancing angle deposition (GLAD) method is investigated in the visible and near infrared ranges using transmission ellipsometry and spectroscopy. These films are found to have significant circular polarization effects across broad ranges of the visible to NIR spectrum, including large values for optical rotation. The characteristics of these circular polarization effects are strongly influenced by the morphology of the deposited arrays. Thus, the morphological control of the optical activity in these nanostructures demonstrates significant optimization capability of the GLAD technique for fabricating chiral plasmonic materials. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Dichroism, chirality, and polarization eigenstates in Babinet nanoslot-dimer membrane metamaterials

    DEFF Research Database (Denmark)

    Zhukovsky, Sergei; Chigrin, Dmitry N.; Kremers, Christian;

    2013-01-01

    We present a detailed theoretical description of the optical properties of planar metamaterials comprising a metal membrane patterned with openings (microslots) arranged in closely located couples (dimers). Using the covariant coupled-dipole approach, the effective material tensors of such a meta......We present a detailed theoretical description of the optical properties of planar metamaterials comprising a metal membrane patterned with openings (microslots) arranged in closely located couples (dimers). Using the covariant coupled-dipole approach, the effective material tensors...... of such a metamaterial are recovered, and contributions responsible for elliptical dichroism and optical activity are identified. Polarization conversion properties of II-shaped and V-shaped dimers are determined and explained in terms of elliptically polarized eigenmodes of the metamaterial. Good agreement with direct...

  1. Crystal structures, circular dichroism spectra and absolute configurations of some ?-ascorbic acid derivatives

    Science.gov (United States)

    Wittine, Karlo; Gazivoda, Tatjana; Markuš, Marko; Mrvoš-Sermek, Draginja; Hergold-Brundić, Antonija; Cetina, Mario; Žiher, Dinko; Gabelica, Vesna; Mintas, Mladen; Raić-Malić, Silvana

    2004-01-01

    Chiral 2,3-O,O-dibenzyl ethers of L-ascorbic acid with 4-(5,6-epoxy)- (4) and 6-O-tosyl- (8) functional groups were studied by X-ray crystallography and circular dichroism (CD) spectroscopy. The stereostructure of 2,3-O,O-dibenzyl-5,6-isopropylidene-L-ascorbic acid (6) and 8 was determined by X-ray crystal structure analysis. Comparison of the CD-spectra of 4 and 8 with the CD-spectra of their synthetic precursors (2-3, 5-7) and L-ascorbic acid (1) itself, as well as crystal structures of 6 and 8 permitted to deduce the absolute configuration of 4. Thus, the chiral atoms C-4 and C-5 in 4 have R and S configurations, which is consistent with the configuration of 1.

  2. Circular dichroism and Raman spectroscopic study of the spider venom toxin V50F17

    Science.gov (United States)

    Alix, A. J. P.; Berjot, M.; Dauchez, M. A. M.; Dhalluin, C.; Lippens, G.

    1999-05-01

    V50F17 is a small 45 amino acid neurotoxin fractionated (F17) from the venom V50 of the spider Segestria florentina, which has eight cysteine residues constituting four disulfide bridges. Using circular dichroism data and vibrational Raman data at both pH 2.9 and 7.0 and preliminary NMR results obtained at pH 2.9, we derived structural information for this small protein. From these data, it is seen that it is possible to characterise well the local conformation of the disulfide bridges and the overall shape of the globular protein. Moreover, using optical spectroscopic data, it is shown that consequent local and/or global modifications are obtained on changing the pH. Results of the secondary structure states, the local conformations of the disulfide bridges, the exposure of side chains of residues and particularly of Tyr41 are discussed.

  3. Light flux density threshold at which protein denaturation is induced by synchrotron radiation circular dichroism beamlines.

    Science.gov (United States)

    Miles, A J; Janes, Robert W; Brown, A; Clarke, D T; Sutherland, J C; Tao, Y; Wallace, B A; Hoffmann, S V

    2008-07-01

    New high-flux synchrotron radiation circular dichroism (SRCD) beamlines are providing important information for structural biology, but can potentially cause denaturation of the protein samples under investigation. This effect has been studied at the new CD1 dedicated SRCD beamline at ISA in Denmark, where radiation-induced thermal damage effects were observed, depending not only on the radiation flux but also on the focal spot size of the light. Comparisons with similar studies at other SRCD facilities worldwide has lead to the estimation of a flux density threshold under which SRCD beamlines should be operated when samples are to be exposed to low-wavelength vacuum ultraviolet radiation for extended periods of time.

  4. Spin polarization and magnetic dichroism in core-level photoemission from ferromagnets

    Energy Technology Data Exchange (ETDEWEB)

    Menchero, Jose Gabriel [Univ. of California, Berkeley, CA (United States). Dept. of Physics

    1997-05-01

    In this thesis we present a theoretical investigation of angle- and spin-resolved core-level photoemission from ferromagnetic Fe and Ni. We also consider magneto-dichroic effects due to reversal of the photon helicity or reversal of the sample magnetization direction. In chapter 1, we provide a brief outline of the history of photoemission, and show how it has played an important role in the development of modern physics. We then review the basic elements of the theory of core-level photoemission, and discuss the validity of the some of the commonly-used approximations. In chapter 2, we present a one-electron theory to calculate spin- and angle-resolved photoemission spectra for an arbitrary photon polarization. The Hamiltonian includes both spin-orbit and exchange interactions. As test cases for the theory, we calculate the spin polarization and magnetic dichroism for the Fe 2p core level, and find that agreement with experiment is very good.

  5. A study of aliphatic amino acids using simulated vibrational circular dichroism and Raman optical activity spectra

    CERN Document Server

    Ganesan, Aravindhan; Wang, Feng

    2013-01-01

    Vibrational optical activity (VOA) spectra, such as vibrational circular dichroism (VCD) and Raman optical activity (ROA) spectra, of aliphatic amino acids are simulated using density functional theory (DFT) methods in both gas phase (neutral form) and solution (zwitterionic form), together with their respective infrared (IR) and Raman spectra of the amino acids. The DFT models, which are validated by excellent agreements with the available experimental Raman and ROA spectra of alanine in solution, are employed to study other aliphatic amino acids. The inferred (IR) intensive region (below 2000 cm-1) reveals the signature of alkyl side chains, whereas the Raman intensive region (above 3000 cm-1) contains the information of the functional groups in the amino acids. Furthermore, the chiral carbons of the amino acids (except for glycine) dominate the VCD and ROA spectra in the gas phase, but the methyl group vibrations produce stronger VCD and ROA signals in solution. The C-H related asymmetric vibrations domina...

  6. Influence of hybridization in the Magnetic Circular X-ray Dichroism at the Ce-M4,5 absorption edges of Ce-Fe systems

    NARCIS (Netherlands)

    Finazzi, M.; de Groot, F.M.F.; Dias, A.-M.; Kappler, J.-P.; Schulte, O.; Felsch, W.; Krill, G.

    2013-01-01

    We have performed a Magnetic Circular X-ray Dichroism (XMCD) study at the Ce-M*,s absorption edges on some Ce-Fe systems. We find that the dichroism signal in these systems is very sensitive to the degree of hybridization of the 4f electrons with the valence band. XMCD is able to demonstrate that th

  7. Influence of hybridization in the magnetic circular X-ray dichroism at the Ce-M(4,5) absorption edges of Ce-Fe systems

    NARCIS (Netherlands)

    Finazzi, M; deGroot, FMF; Dias, AM; Kappler, JP; Schulte, O; Felsch, W; Krill, G

    1996-01-01

    We have performed a Magnetic Circular X-ray Dichroism (XMCD) study at the Ce-M(4,5) absorption edges on some Ce-Fe systems. We find that the dichroism signal in these systems is very sensitive to the degree of hybridization of the 4f electrons with the valence band. XMCD is able to demonstrate that

  8. 4-Arylflavan-3-ols as Proanthocyanidin Models: Absolute Configuration via Density Functional Calculation of Electronic Circular Dichroism

    Science.gov (United States)

    Density functional theory/B3LYP has been employed to optimize the conformations of selected 4-arylflavan-3-ols and their phenolic methyl ether 3-O-acetates. The electronic circular dichroism spectra of the major conformers have been calculated using time-dependent density functional theory to valida...

  9. Circular dichroism spectrum of [Co(en)(3)](3+) in water : A discrete solvent reaction field study

    NARCIS (Netherlands)

    Jensen, L.; Swart, Marcel; Van Duijnen, Piet Th.; Autschbach, J.

    2006-01-01

    In this work we investigate the circular dichroism (CD) spectrum of [Co(en)(3)](3+) in water, using the discrete solvent reaction field (DRF) model. The DRF model is a polarizable quantum mechanics/molecular mechanics (QM/MM) model. The implementation of the DRF model for CD spectra calculations bas

  10. Soft-X-ray magnetic circular dichroism : a new technique for probing magnetic properties of magnetic surfaces and ultrathin films

    NARCIS (Netherlands)

    Tjeng, L.H.; Idzerda, Y.U.; Rudolf, P.; Sette, F.; Chen, C.T.

    1992-01-01

    We demonstrate the feasibility of applying the novel soft-X-ray magnetic circular dichroism (SXMCD) technique to investigate the magnetic properties of magnetic surfaces and uitrathin films. Measurements have been carried out on Ni films of various thickness on a Cu(100) substrate at the Ni L2,3 abs

  11. Vibrational Circular Dichroism Absolute Configuration of 9,12-Cyclomulin-13-ol, a Diterpene from Azorella and Laretia Species.

    Science.gov (United States)

    Muñoz, Marcelo A; San-Martín, Aurelio; Joseph-Nathan, Pedro

    2015-08-01

    The absolute configuration of the diterpenoid 9,12-cyclomulin-13-ol (1), a constituent of Azorella and Laretia species, has been established by vibrational circular dichroism spectroscopy in combination with density functional theory calculations. The obtained normal diterpene absolute configuration confirms that of azorellanol (2), which was determined by single crystal X-ray diffraction.

  12. X-ray magnetic circular dichroism spectra and distortions at Fe2+ L(2,3) edges

    NARCIS (Netherlands)

    Wang, X.; de Groot, F.M.F.; Cramer, S.P.

    1996-01-01

    We have shown from ligand field multiplet calculations that the shape of X-ray magnetic circular dichroism (XMCD) spectra changes drastically with the distortion parameter Ds. The temperature dependence study of XMCD makes it possible to determine both Ds and spin-orbit coupling.

  13. Understanding the changes in the circular dichroism of light harvesting complex IIupon varying its pigment composition and organization

    NARCIS (Netherlands)

    Georgakopoulou, S.; Zwan, van der G.; Bassi, R.; Grondelle, van R.; Amerongen, van H.; Croce, R.

    2007-01-01

    In this work we modeled the circular dichroism (CD) spectrum of LHCII, the main light harvesting antenna of photosystem II of higher plants. Excitonic calculations are performed for a monomeric subunit, taken from the crystal structure of trimeric LHCII from spinach. All of the major features of the

  14. Identification of linear B-cell epitopes on myotoxin II, a Lys49 phospholipase A₂ homologue from Bothrops asper snake venom.

    Science.gov (United States)

    Lomonte, Bruno

    2012-10-01

    Knowledge on toxin immunogenicity at the molecular level can provide valuable information for the improvement of antivenoms, as well as for understanding toxin structure-function relationships. The aims of this study are two-fold: first, to identify the linear B-cell epitopes of myotoxin II from Bothrops asper snake venom, a Lys49 phospholipase A₂ homologue; and second, to use antibodies specifically directed against an epitope having functional relevance in its toxicity, to probe the dimeric assembly mode of this protein in solution. Linear B-cell epitopes were identified using a library of overlapping synthetic peptides spanning its complete sequence. Epitopes recognized by a rabbit antiserum to purified myotoxin II, and by three batches of a polyvalent (Crotalidae) therapeutic antivenom (prepared in horses immunized with a mixture of B. asper, Crotalus simus, and Lachesis stenophrys venoms) were mapped using an enzyme-immunoassay based on the capture of biotinylated peptides by immobilized streptavidin. Some of the epitopes identified were shared between the two species, whereas others were unique. Differences in epitope recognition were observed not only between the two species, but also within the three batches of equine antivenom. Epitope V, located at the C-terminal region of this protein, is known to be relevant for toxicity and neutralization. Affinity-purified rabbit antibodies specific for this site were able to immunoprecipitate myotoxin II, suggesting that the two copies of epitope V are simultaneously available to antibody binding, which would be compatible with the mode of dimerization known as "conventional" dimer.

  15. Identification of a conserved neutralizing linear B-cell epitope in the VP1 proteins of duck hepatitis A virus type 1 and 3.

    Science.gov (United States)

    Zhang, Ruihua; Zhou, Guomei; Xin, Yinghao; Chen, Junhao; Lin, Shaoli; Tian, Ye; Xie, Zhijing; Jiang, Shijin

    2015-11-18

    Duck virus hepatitis (DVH), mainly caused by duck hepatitis A virus (DHAV), is a severe disease threaten to duck industry and has worldwide distribution. As the major structural protein, the VP1 protein of DHAV is able to induce neutralizing antibody in ducks. In this study, a monoclonal antibody (mAb) 4F8 against the intact DHAV-1 particles was used to identify the possible epitope in the three serotypes of DHAV. The mAb 4F8 had weak neutralizing activities to both DHAV-1 and DHAV-3, and reacted with the conserved linear B-cell epitopes of (75)GEIILT(80) in DHAV-1 VP1 and (75)GEVILT(80) in DHAV-3 VP1 protein, respectively, while not with DHAV-2 VP1. This was the first report about identification of the common conserved neutralizing linear B-cell epitope of DHAV-1 and DHAV-3, which will facilitate understanding of the antigenic structure of VP1 and the serologic diagnosis of DHAV infection.

  16. Electronic structure and x-ray magnetic circular dichroism in A2FeReO6 (A =Ca ,Sr ,andBa ) oxides

    Science.gov (United States)

    Antonov, V. N.; Bekenov, L. V.; Ernst, A.

    2016-07-01

    A systematic electronic structure study of A2FeReO6 (A =Ba ,Sr ,andCa ) has been performed by employing the local-spin-density approximation (LSDA) and LSDA +U methods using the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. We investigated the effects of the subtle interplay between spin-orbit coupling, electron correlations, and lattice distortion on the electronic structure of double perovskites. Ca2FeReO6 has a large distortion in the Fe-O-Re bond, and the electronic structure is mainly determined by electron correlations and lattice distortion. In the Ba -Sr -Ca row, the correlation effects at the Fe site are increased. The correlations at the Re site are small in the Ba- and Sr-based compounds but significant in Ca2FeReO6 . Ca2FeReO6 behaves like an insulator only if considered with a relatively large value of Coulomb repulsion Ueff=2.3 eV at the Re site in addition to Ueff=3.1 eV at the Fe site. Ca2FeReO6 possesses a phase transition at 140 K where the metal-insulator transition (MIT) occurs between metallic high-temperature and insulating low-temperature phases. The spin and orbital magnetic moments are linear functions of temperature before and after the MIT but change abruptly at the point of the phase transition. From theoretically calculated magnetocrystalline anisotropy energy (MAE), we found that the easy axis of magnetization for the low-temperature phase is along the b direction, in agreement with experimental data. We found that the major contribution to the MAE is due to the orbital magnetic anisotropy at the Re site. X-ray-absorption spectra and x-ray magnetic circular dichroism at the Re, Fe, and Ba L2 ,3 and Fe, Ca, and O K edges were investigated theoretically in the frame of the LSDA +U method. A qualitative explanation of the x-ray magnetic circular dichroism spectra shape is provided by an analysis of the corresponding selection rules, orbital character, and occupation numbers of individual orbitals

  17. A circular dichroism sensor for Ni{sup 2+} and Co{sup 2+} based on L-cysteine capped cadmium sulfide quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Tedsana, Wimonsiri [Materials Chemistry Research Center, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand); Tuntulani, Thawatchai [Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Ngeontae, Wittaya, E-mail: wittayange@kku.ac.th [Materials Chemistry Research Center, Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Khon Kaen University, Khon Kaen 40002 (Thailand)

    2015-03-31

    Highlights: • Demonstrated a new efficient sensor platform based quantum dots. • Used chiral quantum dots as CD sensor for the detection of heavy metal ions for the first time. • The proposed CD sensor showed highest selectivity towards Ni{sup 2+} and Co{sup 2+}. • Low detection limits of 7.33 μM and 1.13 μM for Ni{sup 2+} and Co{sup 2+}, respectively. • Can be used in real water samples comparing with ICP-OES. - Abstract: A new circular dichroism sensor for detecting Ni{sup 2+} and Co{sup 2+} was proposed for the first time using chiral chelating quantum dots. The detection principle was based on changing of circular dichroism signals of the chiral quantum dots when forming a chiral complex with Ni{sup 2+} or Co{sup 2+}. L-Cysteine capped cadmium sulfide quantum dots (L-Cyst-CdS QDs) were proposed as a chiral probe. The CD spectrum of L-Cyst-CdS QDs was significantly changed in the presence of Ni{sup 2+} and Co{sup 2+}. On the other hand, other studied cations did not alter the original CD spectrum. Moreover, when increasing the concentration of Ni{sup 2+} or Co{sup 2+}, the intensity of the CD spectrum linearly increased as a function of concentration and could be useful for the quantitative analysis. The proposed CD sensor showed linear working concentration ranges of 10–60 μM and 4–80 μM with low detection limits of 7.33 μM and 1.13 μM for the detection of Ni{sup 2+} and Co{sup 2+}, respectively. Parameters possibly affected the detection sensitivity such as solution pH and incubation time were studied and optimized. The proposed sensor was applied to detect Ni{sup 2+} and Co{sup 2+} in real water samples, and the results agreed well with the analysis using the standard ICP-OES.

  18. General characterization of Tityus fasciolatus scorpion venom. Molecular identification of toxins and localization of linear B-cell epitopes.

    Science.gov (United States)

    Mendes, T M; Guimarães-Okamoto, P T C; Machado-de-Avila, R A; Oliveira, D; Melo, M M; Lobato, Z I; Kalapothakis, E; Chávez-Olórtegui, C

    2015-06-01

    This communication describes the general characteristics of the venom from the Brazilian scorpion Tityus fasciolatus, which is an endemic species found in the central Brazil (States of Goiás and Minas Gerais), being responsible for sting accidents in this area. The soluble venom obtained from this scorpion is toxic to mice being the LD50 is 2.984 mg/kg (subcutaneally). SDS-PAGE of the soluble venom resulted in 10 fractions ranged in size from 6 to 10-80 kDa. Sheep were employed for anti-T. fasciolatus venom serum production. Western blotting analysis showed that most of these venom proteins are immunogenic. T. fasciolatus anti-venom revealed consistent cross-reactivity with venom antigens from Tityus serrulatus. Using known primers for T. serrulatus toxins, we have identified three toxins sequences from T. fasciolatus venom. Linear epitopes of these toxins were localized and fifty-five overlapping pentadecapeptides covering complete amino acid sequence of the three toxins were synthesized in cellulose membrane (spot-synthesis technique). The epitopes were located on the 3D structures and some important residues for structure/function were identified.

  19. Linear methods in band theory

    DEFF Research Database (Denmark)

    Andersen, O. Krogh

    1975-01-01

    of Korringa-Kohn-Rostoker, linear-combination-of-atomic-orbitals, and cellular methods; the secular matrix is linear in energy, the overlap integrals factorize as potential parameters and structure constants, the latter are canonical in the sense that they neither depend on the energy nor the cell volume...

  20. LINEAR SYSTEMS AND LINEAR INTERPOLATION I

    Institute of Scientific and Technical Information of China (English)

    丁立峰

    2001-01-01

    he linear interpolation of linear system on a family of linear systems is introduced and discussed. Some results and examples on singly generated systems on a finite dimensional vector space are given.

  1. The joint statistics of mildly non-linear cosmological densities and slopes in count-in-cells

    CERN Document Server

    Bernardeau, Francis; Pichon, Christophe

    2015-01-01

    In the context of count-in-cells statistics, the joint probability distribution of the density in two concentric spherical shells is predicted from first first principle for sigmas of the order of one. The agreement with simulation is found to be excellent. This statistics allows us to deduce the conditional one dimensional probability distribution function of the slope within under dense (resp. overdense) regions, or of the density for positive or negative slopes. The former conditional distribution is likely to be more robust in constraining the cosmological parameters as the underlying dynamics is less evolved in such regions. A fiducial dark energy experiment is implemented on such counts derived from Lambda-CDM simulations.

  2. Non-Linearity of dose-effect relationship on the example of cytogenetic effects in plant cells at low level exposure to ionising radiation

    Energy Technology Data Exchange (ETDEWEB)

    Oudalova, Alla; Geras' kin, Stanislav; Dikarev, Vladimir; Dikareva, Nina; Chernonog, Elena [Russian Institute of Agricultural Radiology and Agroecology, RIARAE, 249032 Obninsk (Russian Federation); Copplestone, David [Environment Agency, Millbank Tower, 25th. Floor, 21/24 Millbank, London, SW1P 4XL (United Kingdom); Evseeva, Tatyana [Institute of Biology, Kommunisticheskaya st., 28 Syktyvkar 167610, Komi Republic (Russian Federation)

    2006-07-01

    Over several decades, modelling the effects of ionizing radiation on biological system has relied on the target principle [Timofeeff-Ressovsky et al., 1935], which assumes that cell damage or modification to genes appear as a direct consequence of the exposure of biological macromolecules to charged particles. Furthermore, it is assumed that there is no threshold for the induction of biological damage and that the effects observed are proportional to the energy absorbed. Following this principle, the average number of hits per target should increase linearly with dose, and the yield of mutations per unit of dose is assumed to be the same at both low and high doses (linearity of response). This principle has served as the scientific background for the linear no-threshold (LNT) concept that forms the basis for the radiological protection for the public and the environment [ICRP, 1990]. It follows from the LNT that there is an additional risk for human health from exposure to any radiation level, even below natural background. Since the mid 50's, however, the scientific basis for the LNT concept has been challenged as experimental data have shown that, at low doses, there was a non linear relationship in the dose response. Luchnik and Timofeeff-Ressovsky were the first who showed a non-linear response to a low dose exposure [Luchnik, 1957; Timofeeff-Ressovsky and Luchnik, 1960]. Since then, many data have been accumulated which contradict the LNT model at low doses and dose rates. However, the hit-effect paradigm has become such a strong and indissoluble fact that it has persisted even under the growing pressure of scientific evidence for phenomena at low dose exposure that can not be successfully accounted for by the LNT concept. In recent years, additional information on non-targeted effects of radiation has been accumulated following the first reports of an adaptive response in human lymphocytes [Olivieri et al., 1984] as well as bystander mutagenic effect of

  3. Assessment of the hemolysis and endothelial cell cytotoxicity induced by residual linear alkylbenzene sulfonates on pharmaceutical rubber stoppers based on HPLC-ESI-MS.

    Science.gov (United States)

    Li, Xianghui; Qiu, Lu; Li, Yueyue; Chen, Xiaofei; Zhu, Zhenyu; Chai, Yifeng

    2015-09-01

    This study was designed to develop a high-performance liquid chromatographic-electrospray ionization-mass spectrometry (HPLC-ESI-MS) method for quantitative determination of residual surfactant linear alkylbenzene sulfonate (LAS) compounds on pharmaceutical rubber stoppers. An HPLC-ESI-MS method was developed for separation and determination of five LAS homologs (C10-C14) under gradient conditions using methanol and ammonium acetate as mobile phases. Hemolysis activity of residual LAS compounds was analyzed by spectrophotometry. Expression of interleukin (IL)-6 and tumor necrosis factor (TNF)-α in human umbilical vein endothelial cells (HUVECs) after LAS compound treatment was examined by enzyme-linked sorbent assay. LAS compounds were well separated and determined by the established gradient conditions. The linear range was 0.05-8 µg/mL with correlation coefficients ≥0.997. Recoveries were from 73 to 134% and the relative standard deviation was <13.7%. There was a correlation between hemolysis rate and LAS compounds concentration when it was ≥0.8 µg/cm(2). LAS compounds decreased the viability of HUVECs and promoted the production of IL-6 and TNF-α. The developed analytical method was successful for quantitative determination of residual LAS compounds on pharmaceutical rubber stoppers and it is important to monitor and control the amount of LAS compounds on rubber stoppers.

  4. Quantitative shearing linear amplification polymerase chain reaction: an improved method for quantifying lentiviral vector insertion sites in transplanted hematopoietic cell systems.

    Science.gov (United States)

    Zhou, Sheng; Bonner, Melissa A; Wang, Yong-Dong; Rapp, Samuel; De Ravin, Suk See; Malech, Harry L; Sorrentino, Brian P

    2015-02-01

    In gene therapy trials targeting blood disorders, it is important to detect dominance of transduced hematopoietic stem cell (HSC) clones arising from vector insertion site (VIS) effects. Current methods for VIS analysis often do not have defined levels of quantitative accuracy and therefore can fail to detect early clonal dominance. We have developed a rapid and inexpensive method for measuring clone size based on random shearing of genomic DNA, minimal exponential PCR amplification, and shear site counts as a quantitative endpoint. This quantitative shearing linear amplification PCR (qsLAM PCR) assay utilizes an internal control sample containing 19 lentiviral insertion sites per cell that is mixed with polyclonal samples derived from transduced human CD34+ cells. Samples were analyzed from transplanted pigtail macaques and from a participant in our X-linked severe combined immunodeficiency (XSCID) lentiviral vector trial and yielded controlled and quantitative results in all cases. One case of early clonal dominance was detected in a monkey transplanted with limiting numbers of transduced HSCs, while the clinical samples from the XSCID trial participant showed highly diverse clonal representation. These studies demonstrate that qsLAM PCR is a facile and quantitative assay for measuring clonal repertoires in subjects enrolled in human gene therapy trials using lentiviral-transduced HSCs.

  5. Principle component analysis and linear discriminant analysis of multi-spectral autofluorescence imaging data for differentiating basal cell carcinoma and healthy skin

    Science.gov (United States)

    Chernomyrdin, Nikita V.; Zaytsev, Kirill I.; Lesnichaya, Anastasiya D.; Kudrin, Konstantin G.; Cherkasova, Olga P.; Kurlov, Vladimir N.; Shikunova, Irina A.; Perchik, Alexei V.; Yurchenko, Stanislav O.; Reshetov, Igor V.

    2016-09-01

    In present paper, an ability to differentiate basal cell carcinoma (BCC) and healthy skin by combining multi-spectral autofluorescence imaging, principle component analysis (PCA), and linear discriminant analysis (LDA) has been demonstrated. For this purpose, the experimental setup, which includes excitation and detection branches, has been assembled. The excitation branch utilizes a mercury arc lamp equipped with a 365-nm narrow-linewidth excitation filter, a beam homogenizer, and a mechanical chopper. The detection branch employs a set of bandpass filters with the central wavelength of spectral transparency of λ = 400, 450, 500, and 550 nm, and a digital camera. The setup has been used to study three samples of freshly excised BCC. PCA and LDA have been implemented to analyze the data of multi-spectral fluorescence imaging. Observed results of this pilot study highlight the advantages of proposed imaging technique for skin cancer diagnosis.

  6. Copper(II) complex formation with a linear peptide encompassing the putative cell binding site of angiogenin.

    Science.gov (United States)

    La Mendola, Diego; Magrì, Antonio; Vagliasindi, Laura I; Hansson, Örjan; Bonomo, Raffaele P; Rizzarelli, Enrico

    2010-11-28

    Angiogenin is one of the more potent angiogenic factors known, whose activity may be affected by the presence of copper ions. Copper(II) complexes with the peptides encompassing the putative endothelial cell binding domain of angiogenin, Ac-KNGNPHREN-NH(2) and Ac-PHREN-NH(2), have been characterized by potentiometric, UV-vis, CD and EPR spectroscopic methods. The coordination features of all the copper complex species derived by both peptides are practically the same, as predictable because of the presence of a proline residue within their aminoacidic sequence. In particular, Ac-PHREN-NH(2) is really the aminoacidic sequence involved in the binding to copper(II). Thermodynamic and spectroscopic evidence are given that side chain oxygen donor atom of glutamyl residue is involved in the copper binding up to physiological pH. EPR parameters suggest that the carboxylate group is still involved also in the predominant species [Cu(L)H(-2)], the metal coordination environment being probably formed by N(Im), 2N(-), H(2)O in equatorial plane and an oxygen atom from COO(-) in apical position, or vice versa, with the carboxylate oxygen atom in the copper coordination plane and the water molecule confined to one of the apical positions. Moreover, the comparison with the thermodynamic and spectroscopic results in the case of the copper(ii) complex species formed by the single point mutated peptide, Ac-PHRQN-NH(2), provides further evidence of the presence of carboxylate oxygen atom in the copper coordination sphere.

  7. Can circular dichroism in core-level photoemission provide a spectral fingerprint of adsorbed chiral molecules?

    Energy Technology Data Exchange (ETDEWEB)

    Allegretti, F [Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom); Polcik, M [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D 14195 Berlin (Germany); Sayago, D I [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D 14195 Berlin (Germany); Demirors, F [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D 14195 Berlin (Germany); O' Brien, S [Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom); Nisbet, G [Centre for Applied Catalysis, Department of Chemical and Biological Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH (United Kingdom); Lamont, C L A [Centre for Applied Catalysis, Department of Chemical and Biological Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH (United Kingdom); Woodruff, D P [Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2005-04-01

    The results of experimental measurements and theoretical simulations of circular dichroism in the angular distribution (CDAD) of photoemission from atomic core levels of each of the enantiomers of a chiral molecule, alanine, adsorbed on Cu(1 1 0) are presented. Measurements in, and out of, substrate mirror planes allow one to distinguish the CDAD due to the chirality of the sample from that due to a chiral experimental geometry. For these studies of oriented chiral molecules, the CDAD is seen not only in photoemission from the molecular chiral centre, but also from other atoms which have chiral geometries as a result of the adsorption. The magnitude of the CDAD due to the sample chirality differs for different adsorption phases of alanine, and for different emission angles and energies, but is generally small compared with CDAD out of the substrate mirror planes which is largely unrelated to the molecular chirality. While similar measurements of other molecules may reveal larger CDAD due to molecular chirality, the fact that the results for one chiral molecule show weak effects means that such CDAD is unlikely to provide a simple and routine general spectral fingerprint of adsorbed molecular chirality.

  8. [Study of collagen mimetic peptide's triple-helix structure and its thermostability by circular dichroism].

    Science.gov (United States)

    Zhang, Zhi-Bao; Wang, Jing-Jie; Chen, Hui-Juan; Xiong, Qing-Qing; Liu, Ling-Rong; Zhang, Qi-Qing

    2014-04-01

    In the present study, the authors explore the triple-helix conformation and thermal stability of collagen mimetic peptides (CMPs) as a function of peptide sequence and/or chain length by circular dichroism(CD). Five CMPs were designed and synthetized varying the number of POG triplets or incorporating an integrin alpha2beta1 binding motif Gly-Phe-Hyp-Gly-Glu-Arg (GFOGER). CD spectroscopy from 260 to 190 nm was recorded to confirm the existence of triple-helix conformation at room temperature, while thermal melting and thermal annealing of triple-helix (thermal unfolding and refolding of triple-helix, respectively) was characterized by monitoring ellipticity at 225 nm as a function of temperature. The results demonstrated that all the CMPs adopted triple-helix conformation, and the thermal stability of the CMPs was enhanced with increasing the number of POG triplets. In contrast to natural collagen, the thermal denaturation processes of CMPs were reversible, i. e. the triple-helix unfolded upon heating while refolded upon cooling. Meanwhile, the phenomenon of "hysteresis" was observed by comparing melting and thermal curves. These findings add new insights to the mechanisms of collagen and CMPs assembly, as well as provide an alternative approach to the fabrication of artificial collagen-likes biomaterials.

  9. Study of Structural Stability of Cyclophilin A by NMR and Circular Dichroism Spectra

    Institute of Scientific and Technical Information of China (English)

    SHI, Yan-Hong; LIN, Dong-Hai; HUANG, Jian-Ying; SHEN, Xu

    2006-01-01

    The structural stability of cyclophilin A (CypA) was investigated using H/D exchange and temperature coefficients of chemical shifts of amide protons, monitored by 2D heteronuclear NMR spectroscopy. Amide proton exchange rates were measured by H/D exchange experiments for slow-exchange protons and measured by SEA (Solvent Exposed Amides)-HSQC experiments for fast-exchange protons. Temperature coefficients of chemical shifts and hydrogen exchange rates of amide protons show reasonably good correlation with the protein structure. Totally,44 out of 153 non-proline assigned residues still exist in 86 d of hydrogen-deuterium exchange at 4 ℃, suggesting that CypA structure should be highly stable. Residues in secondary structures of α2, β1, β2, β5,β6 and β7 might constitute the hydrophobic core of the protein. The change in free energy of unfolding ( AGuH2O ) of CypA was estimated to be (21.99± 1.53) kJ·mol-1 by circular dichroism (CD). The large free energy change is also an indicator of the high structural stability.

  10. Induced circular dichroism of the interaction between pinacyanol and algal alginates.

    Science.gov (United States)

    Khouri, Sa'ib J; Knierim, Robert; Buss, Volker

    2009-09-08

    The interaction between pinacyanol chloride and sodium alginate or guluronate-rich alginate is found to effect profound changes in the visible absorbance and circular dichroism spectra. Two different types of aggregates are observed depending on the relative dye/alginate concentrations. With a dye/alginate ratio at 1:1, a complex is deduced based on an analysis of Job's method and conductometric titrations. Another complex forms at 1:10 dye/alginate ratio and only in the presence of alginate or guluronate-rich alginate. The two aggregates are in dynamic equilibrium according to the presence of isosbestic points in the visible spectra. The effects of pH and divalent cations on the spectra are studied. The 1:10 complex is damaged by addition of hydrochloric acid and divalent cations; however, at low concentration of these agents the spectra indicate conversion of the complex into the 1:1 aggregate. Models for the two complexes are proposed taking into account the preference of guluronate binding sites for chelating ions.

  11. Elucidating second coordination sphere effects in heme proteins using low-temperature magnetic circular dichroism spectroscopy.

    Science.gov (United States)

    Lehnert, Nicolai

    2012-05-01

    This paper reviews recent findings on how the second coordination sphere of heme proteins fine-tunes the properties of the heme active site via hydrogen bonding. This insight is obtained from low-temperature magnetic circular dichroism (MCD) spectroscopy. In the case of high-spin ferric hemes, MCD spectroscopy allows for the identification of a multitude of charge-transfer (CT) transitions. Using optically-detected magnetic saturation curves, out-of-plane polarized CT transitions between the heme and its axial ligand(s) can be identified. In the case of ferric Cytochrome P450cam, the corresponding S(σ)→Fe(III) CT transition can be used as a probe for the {Fe(III)-axial ligand} interaction, indicating that the hydrogen bonding network of the proximal Cys only plays a limited role for fine-tuning the Fe(III)-S(Cys) interaction. In the case of high-spin ferrous hemes with axial His/imidazole coordination, our MCD-spectroscopic investigations have uncovered a direct correlation between the strength of the hydrogen bond to the proximal imidazole ligand and the ground state of the complexes. With neutral imidazole coordination, the doubly occupied d-orbital of high-spin iron(II) is of d(π) character, located orthogonal to the heme plane. As the strength of the hydrogen bond increases, this orbital rotates into the heme plane, changing the ground state of the complex.

  12. Reversible Plasmonic Circular Dichroism via Hybrid Supramolecular Gelation of Achiral Gold Nanorods.

    Science.gov (United States)

    Jin, Xue; Jiang, Jian; Liu, Minghua

    2016-12-27

    The fabrication of chiroptical plasmonic nanomaterials such as chiral plasmonic gold nanorods (GNRs) has been attracting great interest. Generally, in order to realize the plasmonic circular dichroism (PCD) from achiral GNRs, it is necessary to partially replace the surface-coated cetyltrimethylammonium bromide with chiral molecules. Here, we present a supramolecular approach to generate and modulate the PCD of GNRs through the hybrid gelation of GNRs with an amphiphilic chiral dendron gelator. Upon gelation, the PCD could be produced and further regulated depending on the ratio of the dendrons to GNRs. It was revealed that the wrapping of the self-assembled nanofibers around the GNRs is crucial for generating the PCD. Furthermore, the hybrid gel underwent a thermotriggered gel-sol and sol-gel transformation, during which the PCD can disappear (solution) and reappear (gel), respectively, and such process can be repeated many times. In addition, the hybrid gel could also undergo shrinkage upon addition of a slight amount of Mg(2+) ions, during which the PCD disappeared also. Thus, through the gel formation and subsequent metal ion- or temperature-triggered phase transition, PCD can be reversibly modulated. The results not only clarified the generation mechanism of PCD from the achiral GNRs without the chiral modification on the surface but also offered a simple and efficient way to modulate the PCD.

  13. The thermal and storage stability of bovine haemoglobin by ultraviolet–visible and circular dichroism spectroscopies

    Directory of Open Access Journals (Sweden)

    Ruchir Bhomia

    2016-08-01

    Full Text Available The effects of temperature, pH and long-term storage on the secondary structure and conformation changes of bovine haemoglobin (bHb were studied using circular dichroism (CD and ultraviolet--visible (UV–vis spectroscopies. Neural network software was used to deconvolute the CD data to obtain the fractional content of the five secondary structures. The storage stability of bHb solutions in pH 6, 7 and 8 buffers was significantly higher at 4 °C than at 23 °C for the first 3 days. A complete denaturation of bHb was observed after 40 days irrespective of storage temperature or pH. The bHb solutions were also exposed to heating and cooling cycles between 25 and 65 °C and structural changes were followed by UV–vis and CD spectroscopies. These experiments demonstrated that α-helix content of bHb decreased steadily with the increasing temperature above 35 °C at all pH values. The loss in α-helicity and gain in random coil conformations was pH-dependent and the greatest under alkaline conditions. Furthermore, there was minimal recovery of the secondary structure content upon cooling to 25 °C. The use of bHb as a model drug is very common and this study elucidates the significance of storage and processing conditions on its stability.

  14. Simultaneous Analysis of Secondary Structure and Light Scattering from Circular Dichroism Titrations: Application to Vectofusin-1

    Science.gov (United States)

    Vermeer, Louic S.; Marquette, Arnaud; Schoup, Michel; Fenard, David; Galy, Anne; Bechinger, Burkhard

    2016-12-01

    Circular Dichroism data are often decomposed into their constituent spectra to quantify the secondary structure of peptides or proteins but the estimation of the secondary structure content fails when light scattering leads to spectral distortion. If peptide-induced liposome self-association occurs, subtracting control curves cannot correct for this. We show that if the cause of the light scattering is independent from the peptide structural changes, the CD spectra can be corrected using principal component analysis (PCA). The light scattering itself is analysed and found to be in good agreement with backscattering experiments. This method therefore allows to simultaneously follow structural changes related to peptide-liposome binding as well as peptide induced liposome self-association. We apply this method to study the structural changes and liposome binding of vectofusin-1, a transduction enhancing peptide used in lentivirus based gene therapy. Vectofusin-1 binds to POPC/POPS liposomes, causing a reversal of the negative liposome charge at high peptide concentrations. When the peptide charges exactly neutralise the lipid charges on both leaflets reversible liposome self-association occurs. These results are in good agreement with biological observations and provide further insight into the conditions required for efficent transduction enhancement.

  15. Interaction of polyphenolic metabolites with human serum albumin: a circular dichroism study.

    Science.gov (United States)

    Nozaki, Akiko; Kimura, Toshikiro; Ito, Hideyuki; Hatano, Tsutomu

    2009-09-01

    Binding sites of polyphenolic compounds on human serum albumin (HSA) were investigated using induced Cotton effects on the circular dichroism (CD) spectra. Polyphenolic compounds used in this study are known to be metabolites from tannins and their related polyphenols in food and medicinal plants. The present investigation revealed that the structural differences markedly affected the binding of the compounds to HSA. Protocatechuic acid, together with its methylated compounds vanillic and isovanillic acids, were assigned to be bound to sites I and II of HSA, based on the competitive relationships with site-I-binding phenylbutazone (PB) and site-II-binding diazepam (DP). 4-O-Methylgallic acid, which is the metabolite from gallic acid, was bound to site I on HSA, while gallic acid did not affect the binding of PB and DP at the concentration examined. Neither ellagic acid nor its metabolite urolithin A was competitive with PB and DP on HSA. The addition of digitoxin did not affect the induced CD of the polyphenolic acids examined.

  16. Utilization of circular dichroism experiment to distinguish acanthoside D and eleutheroside E.

    Science.gov (United States)

    Kil, Yun-Seo; Park, Ji-Yeon; Kim, Youngmee; Nam, Sang-Jip; Kim, Sung-Jin; Kim, Yeong Shik; Seo, Eun Kyoung

    2015-11-01

    Two lignan glycosides, acanthoside D (1) (=liriodendrin, (+)-syringaresinol di-O-β-D-glucopyranoside) and eleutheroside E (2) have been confused each other for so long time, and hard to be distinguished each other. Now, this two compounds need to be defined properly so that all the commercial mistakes and confusions should not be made. They have identical planar structures except for the configurations at C-7 and C-8 in each structure according to the chemistry database, SciFinder(®). The systematic name of acanthoside D is [(1S,3aR,4S,6aR)-tetrahydro-1H,3H-furo[3,4-c]furan-1,4-diyl]bis(2,6-dimethoxy-4,1-phenylene) bis-β-D-glucopyranoside (1), and the name of eleutheroside E is [(1R,3aR,4S,6aS)-tetrahydro-1H,3H-furo[3,4-c]furan-1,4-diyl]bis(2,6-dimethoxy-4,1-phenylene) bis-β-D-glucopyranoside (2). The differences at two chiral centers do not make any differences in the NMR spectra. Thus, the circular dichroism were utilized to dissolve this difficult problem. Acanthoside D (1) showed a positive Cotton effect at 200 nm, whereas eleutheroside E (2) exhibited a negative cotton effect at 200 nm. The absolute structure of acanthoside D was also confirmed by X-ray crystallography.

  17. Circular dichroism measurements at an x-ray free-electron laser with polarization control

    Science.gov (United States)

    Hartmann, G.; Lindahl, A. O.; Knie, A.; Hartmann, N.; Lutman, A. A.; MacArthur, J. P.; Shevchuk, I.; Buck, J.; Galler, A.; Glownia, J. M.; Helml, W.; Huang, Z.; Kabachnik, N. M.; Kazansky, A. K.; Liu, J.; Marinelli, A.; Mazza, T.; Nuhn, H.-D.; Walter, P.; Viefhaus, J.; Meyer, M.; Moeller, S.; Coffee, R. N.; Ilchen, M.

    2016-08-01

    A non-destructive diagnostic method for the characterization of circularly polarized, ultraintense, short wavelength free-electron laser (FEL) light is presented. The recently installed Delta undulator at the LCLS (Linac Coherent Light Source) at SLAC National Accelerator Laboratory (USA) was used as showcase for this diagnostic scheme. By applying a combined two-color, multi-photon experiment with polarization control, the degree of circular polarization of the Delta undulator has been determined. Towards this goal, an oriented electronic state in the continuum was created by non-resonant ionization of the O2 1s core shell with circularly polarized FEL pulses at hν ≃ 700 eV. An also circularly polarized, highly intense UV laser pulse with hν ≃ 3.1 eV was temporally and spatially overlapped, causing the photoelectrons to redistribute into so-called sidebands that are energetically separated by the photon energy of the UV laser. By determining the circular dichroism of these redistributed electrons using angle resolving electron spectroscopy and modeling the results with the strong-field approximation, this scheme allows to unambiguously determine the absolute degree of circular polarization of any pulsed, ultraintense XUV or X-ray laser source.

  18. Ligand induced circular dichroism and circularly polarized luminescence in CdSe quantum dots.

    Science.gov (United States)

    Tohgha, Urice; Deol, Kirandeep K; Porter, Ashlin G; Bartko, Samuel G; Choi, Jung Kyu; Leonard, Brian M; Varga, Krisztina; Kubelka, Jan; Muller, Gilles; Balaz, Milan

    2013-12-23

    Chiral thiol capping ligands L- and D-cysteines induced modular chiroptical properties in achiral cadmium selenide quantum dots (CdSe QDs). Cys-CdSe prepared from achiral oleic acid capped CdSe by postsynthetic ligand exchange displayed size-dependent electronic circular dichroism (CD) and circularly polarized luminescence (CPL). Opposite CPL signals were measured for the CdSe QDs capped with D- and L-cysteine. The CD profile and CD anisotropy varied with size of CdSe nanocrystals with largest anisotropy observed for CdSe nanoparticles of 4.4 nm. Magic angle spinning solid state NMR (MAS ssNMR) experiments suggested bidentate interaction between cysteine and the surface of CdSe. Time Dependent Density Functional Theory (TDDFT) calculations verified that attachment of L- and D-cysteine to the surface of model (CdSe)13 nanoclusters induces measurable opposite CD signals for the exitonic band of the nanocluster. The origin of the induced chirality is consistent with the hybridization of highest occupied CdSe molecular orbitals with those of the chiral ligand.

  19. Magnetic circular dichroism spectroscopy of weakly exchange coupled transition metal dimers: A model study

    DEFF Research Database (Denmark)

    Piligkos, S.; Slep, L.D.; Weyhermuller, T.

    2009-01-01

    bands of the minority spin Ni(II) ligand field bands were observed to change sign relative to the parent complex 2. This behavior has been analyzed. The present work hence provides a benchmark study for the application of MCD spectroscopy to weakly interacting transition metal dinners. (C) 2008 Elsevier......A detailed study of the magnetic circular dichroism (MCD) spectra of weakly exchange coupled transition metal heterodimers is reported. The systems consist of three isostructural complexes of the type [LM(III)(PyA)(3)M(II)](ClO4)(2) where L represents 1,4,7-trimethyl-1,4,7-triazacyclonanane and Py......A- is the monoanion of pyridine-2-aldoxime. The trivalent metal ion M(III) is either diamagnetic Ga(III) or paramagnetic Cr(III) (S-Cr = 3/2). The divalent metal ion M(II) is either diamagnetic Zn(II) or paramagnetic Ni(II) (S-Ni = 1). The three systems 1 (CrZn), 2 (GaNi) and 3 (CrNi) have been structurally...

  20. Conformational flexibility of a scorpion toxin active on mammals and insects: a circular dichroism study.

    Science.gov (United States)

    Loret, E P; Sampieri, F; Roussel, A; Granier, C; Rochat, H

    1990-01-01

    Three scorpion toxins have been analyzed by circular dichroism in water and in 2,2,2-trifluoroethanol (TFE) solutions. These toxins were chosen because they are representative of three kinds of pharmacological activities: (1) toxin AaH IT2, an antiinsect toxin purified from the venom of Androctonus australis Hector, which is able to bind to insect nervous system preparation, (2) toxin Css II, from the venom of Centruroides suffusus suffusus, which is a beta-type antimammal toxin capable of binding to mammal nervous system preparation, and (3) the toxin Ts VII from the venom of Tityus serrulatus, which is able to bind to both types of nervous systems. In order to minimize bias, CD data were analyzed by a predictive algorithm to assess secondary structure content. Among the three molecules, Ts VII presented the most unordered secondary structure in water, but it gained in ordered forms when solubilized in TFE. These results indicated that the Ts VII backbone is the most flexible, which might result in a more pronounced tendency for this toxin molecule to undergo conformational changes. This is consistent with the fact that it competes with both antiinsect and beta-type antimammal toxins for the binding to the sodium channel.

  1. Density functional calculations on electronic circular dichroism spectra of chiral transition metal complexes.

    Science.gov (United States)

    Autschbach, Jochen; Jorge, Francisco E; Ziegler, Tom

    2003-05-05

    Time-dependent density functional theory (TD-DFT) has for the first time been applied to the computation of circular dichroism (CD) spectra of transition metal complexes, and a detailed comparison with experimental spectra has been made. Absorption spectra are also reported. Various Co(III) complexes as well as [Rh(en)(3)](3+) are studied in this work. The resulting simulated CD spectra are generally in good agreement with experimental spectra after corrections for systematic errors in a few of the lowest excitation energies are applied. This allows for an interpretation and assignment of the spectra for the whole experimentally accessible energy range (UV/vis). Solvent effects on the excitations are estimated via inclusion of a continuum solvent model. This significantly improves the computed excitation energies for charge-transfer bands for complexes of charge +3, but has only a small effect on those for neutral or singly charged complexes. The energies of the weak d-to-d transitions of the Co complexes are systematically overestimated due to deficiencies of the density functionals. These errors are much smaller for the 4d metal complex. Taking these systematic errors and the effect of a solvent into consideration, TD-DFT computations are demonstrated to be a reliable tool in order to assist with the assignment and interpretation of CD spectra of chiral transition metal complexes.

  2. First-principles analysis of X-ray magnetic circular dichroism for transition metal complex oxides

    Science.gov (United States)

    Ikeno, Hidekazu

    2016-10-01

    X-ray magnetic circular dichroism (XMCD) is widely used for the characterization of magnetism of materials. However, information from XMCD related to the atomic, electronic, and magnetic structures is not fully utilized due to the lack of reliable theoretical tools for spectral analysis. In this work, the first-principles configuration interaction (CI) calculations for X-ray absorption spectra developed by the author were extended for the calculation of XMCD, where the Zeeman energy was taken into the Hamiltonian of the CI to mimic magnetic polarization in the solid state. This technique was applied to interpret the L2,3 XMCD from 3d transition metal complex oxides, such as NiFe2O4 and FeTiO3. The experimental XMCD spectra were quantitatively reproduced using this method. The oxidation states as well as the magnetic ordering between transition metal ions on crystallographically different sites in NiFe2O4 can be unambiguously determined. A first-principles analysis of XMCD in FeTiO3 revealed the presence of Fe3+ and Ti3+ ions, which indicates that the charge transfer from Fe to Ti ions occurs. The origin of magnetic polarization of Ti ions in FeTiO3 was also discussed.

  3. Circular dichroism measured on single chlorosomal light-harvesting complexes of green photosynthetic bacteria

    KAUST Repository

    Furumaki, Shu

    2012-12-06

    We report results on circular dichroism (CD) measured on single immobilized chlorosomes of a triple mutant of green sulfur bacterium Chlorobaculum tepidum. The CD signal is measured by monitoring chlorosomal bacteriochlorphyll c fluorescence excited by alternate left and right circularly polarized laser light with a fixed wavelength of 733 nm. The excitation wavelength is close to a maximum of the negative CD signal of a bulk solution of the same chlorosomes. The average CD dissymmetry parameter obtained from an ensemble of individual chlorosomes was gs = -0.025, with an intrinsic standard deviation (due to variations between individual chlorosomes) of 0.006. The dissymmetry value is about 2.5 times larger than that obtained at the same wavelength in the bulk solution. The difference can be satisfactorily explained by taking into account the orientation factor in the single-chlorosome experiments. The observed distribution of the dissymmetry parameter reflects the well-ordered nature of the mutant chlorosomes. © 2012 American Chemical Society.

  4. The thermal and storage stability of bovine haemoglobin by ultraviolet-visible and circular dichroism spectroscopies$

    Institute of Scientific and Technical Information of China (English)

    Ruchir Bhomia; Vivek Trivedi n; Nichola J. Coleman; John C. Mitchell

    2016-01-01

    The effects of temperature, pH and long-term storage on the secondary structure and conformation changes of bovine haemoglobin (bHb) were studied using circular dichroism (CD) and ultraviolet–visible (UV–vis) spectroscopies. Neural network software was used to deconvolute the CD data to obtain the fractional content of the five secondary structures. The storage stability of bHb solutions in pH 6, 7 and 8 buffers was significantly higher at 4 °C than at 23 °C for the first 3 days. A complete denaturation of bHb was observed after 40 days irrespective of storage temperature or pH. The bHb solutions were also ex-posed to heating and cooling cycles between 25 and 65 °C and structural changes were followed by UV–vis and CD spectroscopies. These experiments demonstrated that α-helix content of bHb decreased steadily with the increasing temperature above 35 °C at all pH values. The loss inα-helicity and gain in random coil conformations was pH-dependent and the greatest under alkaline conditions. Furthermore, there was minimal recovery of the secondary structure content upon cooling to 25 °C. The use of bHb as a model drug is very common and this study elucidates the significance of storage and processing con-ditions on its stability.

  5. Introducing DInaMo: A Package for Calculating Protein Circular Dichroism Using Classical Electromagnetic Theory

    Directory of Open Access Journals (Sweden)

    Igor V. Uporov

    2015-09-01

    Full Text Available The dipole interaction model is a classical electromagnetic theory for calculating circular dichroism (CD resulting from the π-π* transitions of amides. The theoretical model, pioneered by J. Applequist, is assembled into a package, DInaMo, written in Fortran allowing for treatment of proteins. DInaMo reads Protein Data Bank formatted files of structures generated by molecular mechanics or reconstructed secondary structures. Crystal structures cannot be used directly with DInaMo; they either need to be rebuilt with idealized bond angles and lengths, or they need to be energy minimized to adjust bond lengths and bond angles because it is common for crystal structure geometries to have slightly short bond lengths, and DInaMo is sensitive to this. DInaMo reduces all the amide chromophores to points with anisotropic polarizability and all nonchromophoric aliphatic atoms including hydrogens to points with isotropic polarizability; all other atoms are ignored. By determining the interactions among the chromophoric and nonchromophoric parts of the molecule using empirically derived polarizabilities, the rotational and dipole strengths are determined leading to the calculation of CD. Furthermore, ignoring hydrogens bound to methyl groups is initially explored and proves to be a good approximation. Theoretical calculations on 24 proteins agree with experiment showing bands with similar morphology and maxima.

  6. Linear Algebra and Smarandache Linear Algebra

    OpenAIRE

    Vasantha, Kandasamy

    2003-01-01

    The present book, on Smarandache linear algebra, not only studies the Smarandache analogues of linear algebra and its applications, it also aims to bridge the need for new research topics pertaining to linear algebra, purely in the algebraic sense. We have introduced Smarandache semilinear algebra, Smarandache bilinear algebra and Smarandache anti-linear algebra and their fuzzy equivalents. Moreover, in this book, we have brought out the study of linear algebra and ve...

  7. A computational protocol for the study of circularly polarized phosphorescence and circular dichroism in spin-forbidden absorption

    DEFF Research Database (Denmark)

    Kaminski, Maciej; Cukras, Janusz; Pecul, Magdalena;

    2015-01-01

    on the response function formalism and is implemented at the level of time-dependent density functional theory. It has been employed to calculate the spin-forbidden circular dichroism and circularly polarized phosphorescence signals of valence n - p* and n ’ p* transitions, respectively, in several chiral enones......We present a computational methodology to calculate the intensity of circular dichroism (CD) in spinforbidden absorption and of circularly polarized phosphorescence (CPP) signals, a manifestation of the optical activity of the triplet–singlet transitions in chiral compounds. The protocol is based...... structure. In many cases the sign of the spin-forbidden CD and CPP signals are opposite. For the b,g-enones under investigation, where there are two minima on the lowest triplet excited state potential energy surface, each minimum exhibits a CPP signal of a different sign....

  8. Interaction of fisetin with human serum albumin by fluorescence, circular dichroism spectroscopy and DFT calculations: binding parameters and conformational changes

    Energy Technology Data Exchange (ETDEWEB)

    Matei, Iulia; Ionescu, Sorana [Department of Physical Chemistry, Faculty of Chemistry, University of Bucharest, Bd. Regina Elisabeta 4-12, 030018 Bucharest (Romania); Hillebrand, Mihaela, E-mail: mihh@gw-chimie.math.unibuc.ro [Department of Physical Chemistry, Faculty of Chemistry, University of Bucharest, Bd. Regina Elisabeta 4-12, 030018 Bucharest (Romania)

    2011-08-15

    The interaction between fisetin, an antioxidant and neuroprotective flavonoid, and human serum albumin (HSA) is investigated by means of fluorescence (steady-state, synchronous, time-resolved) and circular dichroism (CD) spectroscopy. The formation of a 1:1 complex with a constant of about 10{sup 5} M{sup -1} was evidenced. Foerster's resonance energy transfer and competitive binding with site markers warfarin and ibuprofen were considered and discussed. Changes in the CD band of HSA indicate a decrease in the {alpha}-helix content upon binding. An induced CD signal for bound fisetin was observed and rationalized in terms of density functional theory calculations. - Highlights: > Fisetin-BSA system was studied by fluorescence spectroscopy. > Binding parameters, association constant and number of sites were estimated. > Binding site of fisetin was identified by competitive experiments. > Conformational changes in HSA and fisetin were evidenced by circular dichroism. > TDDFT calculated CD spectra supported the experimental data.

  9. A new soft X-ray magnetic circular dichroism facility at the BSRF beamline 4B7B

    CERN Document Server

    Guo, Zhi-Ying; Xing, Hai-Ying; Tang, Kun; Xui, Wei; Chen, Dong-liang; Cui, Ming-Qi; Zhao, YI-Dong

    2014-01-01

    X-ray magnetic circular dichroism (XMCD) has become an important and powerful tool because it allows the study of material properties in combination with elemental specificity, chemical state specificity, and magnetic specificity. A new soft X-ray magnetic circular dichroism apparatus has been developed at the Beijing Synchrotron Radiation Facility (BSRF). The apparatus combines three experimental conditions: ultra-high-vacuum environment, moderate magnetic fields and in-situ sample preparation to measure the absorption signal. We designed a C type dipole electromagnet that provides magnetic fields up to 0.5T in parallel (or anti-parallel) direction relative to the incoming X-ray beam. The performances of the electromagnet are measured and the results show good agreement with the simulation ones. Following film grown in situ by evaporation methods, XMCD measurements are performed. Combined polarization corrections, the magnetic moments of the Fe and Co films determined by sum rules are consistent with other t...

  10. Photoelectron circular dichroism of chiral molecules studied with a continuum-state-corrected strong-field approximation

    Science.gov (United States)

    Dreissigacker, Ingo; Lein, Manfred

    2014-05-01

    Motivated by recent experiments on circular dichroism in the photoelectron momentum distributions from strong-field ionization of chiral molecules [C. Lux et al., Angew. Chem. Int. Ed. 51, 5001 (2012), 10.1002/anie.201109035; C. S. Lehmann et al., J. Chem. Phys. 139, 234307 (2013), 10.1063/1.4844295], we investigate the origin of this effect theoretically. We show that it is not possible to describe photoelectron circular dichroism with the commonly used strong-field approximation due to its plane-wave nature. We therefore apply the Born approximation to the scattering state and use this as a continuum-state correction in the strong-field approximation. We obtain electron distributions for the molecules camphor and fenchone. In order to gain physical insight into the process, we study the contributions of individual molecular orientations.

  11. Simulations of circular dichroism spectra of a pair of diterpene enantiomers by time-dependent density functional theory

    Science.gov (United States)

    Liaw, Chih-Chuang; Chang, Jia-Lin; Chen, Shou-Fong; Huang, Jhih-Hong; Sie, Jyun-Fu; Cheng, Yung-Yi

    2011-11-01

    We present the first theoretical study on a pair of diterpene enantiomers of formula C 21H 34O 5, which were newly isolated from plants and identified as 3β,5β-dihydroxy-16 α/ β-methoxyhalima-13(14)-en-15,16-olide. The equilibrium geometries and harmonic vibrational frequencies of their low-lying conformers were obtained by using the AM1 and B3LYP/6-31+G(d) methods. At the optimized geometries, rotatory strengths of six excited states of each conformer were computed by the time-dependent density functional theory. The electronic circular dichroism spectra were simulated by taking Boltzmann averaging and considering the solvent effect, from which the absolute configurations of the enantiomers were determined. Their vibrational circular dichroism spectra were also predicted.

  12. Absolute Configuration Assignment of a Paraconic Acid Derivative via Vibrational Circular Dichroism Spectroscopy and Density Functional Theory Calculation.

    Science.gov (United States)

    Meninno, Sara; Rizzo, Paola; Abbate, Sergio; Longhi, Giovanna; Mazzeo, Giuseppe; Monaco, Guglielmo; Lattanzi, Alessandra; Zanasi, Riccardo

    2016-02-01

    Density functional theory calculation of the vibrational circular dichroism spectrum was used to assign the absolute configuration of an all-carbon quaternary β-stereocenter of a γ-butyrolactone recently synthesized through an asymmetric organocatalytic tandem aldol/lactonization sequence. Comparison with the experimental spectrum is satisfactory, on account of the fact that spectroscopic features are weak due to the presence of multiple conformers. As a result, the (R) absolute configuration was assigned to the (+) optical isomer.

  13. Linear B-cell epitope mapping of MAPK3 and MAPK4 from Leishmania braziliensis: implications for the serodiagnosis of human and canine leishmaniasis.

    Science.gov (United States)

    Menezes-Souza, Daniel; de Oliveira Mendes, Tiago Antônio; de Araújo Leão, Ana Carolina; de Souza Gomes, Matheus; Fujiwara, Ricardo Toshio; Bartholomeu, Daniella Castanheira

    2015-02-01

    The correct and early identification of humans and dogs infected with Leishmania are key steps in the control of leishmaniasis. Additionally, a method with high sensitivity and specificity at low cost that allows the screening of a large number of samples would be extremely valuable. In this study, we analyzed the potential of mitogen-activated protein kinase 3 (MAPK3) and mitogen-activated protein kinase 4 (MAPK4) proteins from Leishmania braziliensis to serve as antigen candidates for the serodiagnosis of human visceral and tegumentary leishmaniasis, as well as canine visceral disease. Moreover, we mapped linear B-cell epitopes in these proteins and selected those epitopes with sequences that were divergent in the corresponding orthologs in Homo sapiens, in Canis familiaris, and in Trypanosoma cruzi. We compared the performance of these peptides with the recombinant protein using ELISA. Both MAPK3 and MAPK4 recombinant proteins showed better specificity in the immunodiagnosis of human and canine leishmaniasis than soluble parasite antigens and the EIE-leishmaniose-visceral-canina-bio-manguinhos (EIE-LVC) kit. Furthermore, the performance of this serodiagnosis assay was improved using synthetic peptides corresponding to B-cell epitopes derived from both proteins.

  14. Identification of in vivo nitrosylated phytochelatins in Arabidopsis thaliana cells by liquid chromatography-direct electrospray-linear ion trap-mass spectrometry.

    Science.gov (United States)

    Elviri, L; Speroni, F; Careri, M; Mangia, A; di Toppi, L Sanità; Zottini, M

    2010-06-18

    Reversed-phase liquid chromatography (RPLC) and electrospray (ESI)-linear ion trap (LIT) mass spectrometry was applied to the direct characterization of in vivo S-nitrosylated (SNO) phytochelatins (PCs) expressed in cadmium-stressed Arabidopsis thaliana cells. Cys-nitrosylation is under discussion as in vivo redox-based post-translational modification of proteins and peptides in plants in which the -NO group is involved as signal molecule in different biological functions. The gas-phase ion chemistry of in vivo and in vitro generated SNO-PC(s) was compared with the aim of evaluating NO binding stability and improving MS knowledge about peptide nitrosation. Using RPLC separation and ESI-LIT-MS, mono-nitrosylated PCs were identified in in vivo cadmium treated A. thaliana cells without derivatization. The in vivo binding of the NO group to PC(2), PC(3) and PC(4) resulted to occur selectively on only one cystein residue. The fragmentation pathway energies of the in vitro GSNO-generated NO-PCs with respect to the in vivo NO-PCs were investigated, suggesting the presence of a different internal stability for these molecules. By carrying out MS(2) experiments on these quasi-symmetric peptides, the different stability degree of the NO group was demonstrated to be correlated with the PC chain length. In addition, the data obtained highlight a putative role of the adjacent Glu/Cys motif in the gas-phase stability of the NO-containing molecule.

  15. Ab initio study of the one- and two-photon circular dichroism of R-(+)-3-methyl-cyclopentanone

    Science.gov (United States)

    Rizzo, Antonio; Lin, Na; Ruud, Kenneth

    2008-04-01

    One- and two-photon circular dichroism spectra of R-(+)-3-methyl-cyclopentanone, a system that has been the subject of recent experimental studies of (2+1) resonance-enhanced multiphoton ionization circular dichroism, have been calculated with an origin-invariant density functional theory approximation in the region of the lowest electronic excited states, both for the gas phase and for a selection of solvents. A polarizable continuum model is used in the calculations performed on the solvated system. Two low-lying conformers are analyzed, and a comparison of the intensities and characteristic features is made with the corresponding two-photon absorption for each species, also for the Boltzmann-averaged spectra. The effect of the choice of geometry, basis set, and exchange-correlation functional is carefully analyzed. It is found that a density functional theory approach using the Coulomb attenuating method variant of Becke's three-parameter exchange and the Lee-Yang-Parr correlation functionals with correlation-consistent basis sets of double-zeta quality can reproduce the experimental electronic circular dichroism spectra very well. The features appearing in experiment are characterized in terms of molecular excitations, and the differences in the response of each state in the one- and two-photon processes are highlighted.

  16. Raman, SERS, and induced circular dichroism techniques as a probe of pharmaceuticals in their interactions with the human serum albumin and p-glycoprotein

    Science.gov (United States)

    Fleury, Fabrice; Ianoul, Anatoli I.; Baggetto, Loris; Jardillier, Jean-Claude; Alix, Alain J.; Nabiev, Igor R.

    1999-04-01

    Camptothecin (CPT) derivatives are the well known inhibitors of the human DNA topoisomerase (topo) I. Two of them, irinotecan and topotecan, are just in the clinics; 9-amino- CPT is on the stage II of clinical trials, and the active search for new derivatives is now in progress. Stability of the CPT derivatives on their way to the target and resistance of cancer cells to these drugs present the crucial problem of the chemotherapy. Human serum albumin (HSA) is the mediator of transport and metabolism of numerous pharmaceuticals in the blood and P-glycoprotein (P- gp) plays a crucial role of the mediator of the multidrug resistance (MDR) of the cancer cells. This paper present the result of analysis of molecular interactions of some drugs of CPT family with the HSA and P-gp. Induced circular dichroism (CD) and Raman techniques have been applied for monitoring molecular interaction of drugs with HSA as well as to identify the conformational transition of the protein induced by the drug binding. Drug molecular determinants responsible for interaction have been identified and their binding sites within the HSA have been localized. New cancer cells lines exhibiting an extremely high level of MDR resistance have been established and were shown to contain the P-gp overproduced in the quantities of 35 percent from the all membrane proteins. The membrane fractions of these cells with the controls presented by the membranes of the parental membrane proteins. The membrane fractions of these cells with the controls presented by the membranes of the parental sensitive cells may be used as a model system for spectroscopic analysis of the specific pharmaceuticals/P-gp interactions.

  17. Regulation of ATM in DNA double strand break repair accounts for the radiosensitivity in human cells exposed to high linear energy transfer ionizing radiation

    Energy Technology Data Exchange (ETDEWEB)

    Xue Lian, E-mail: xuelian@suda.edu.cn [School of Radiation Medicine and Public Health, Medical College of Soochow University, No. 199, Ren' ai Road, Suzhou 215123 (China); Yu Dong, E-mail: ydong@ncc.go.jp [Tumor Endocrinology Project, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045 (Japan); Furusawa, Yoshiya; Okayasu, Ryuichi [Heavy-Ion Radiobiology Research Group, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba-shi 263-8555 (Japan); Tong Jian; Cao Jianping; Fan Saijun [School of Radiation Medicine and Public Health, Medical College of Soochow University, No. 199, Ren' ai Road, Suzhou 215123 (China)

    2009-11-02

    High linear energy transfer (LET) radiation shows different biological effects from low-LET radiation. The complex nature of high LET radiation-induced damage, especially the clustered DNA damage, brings about slow repair of DNA double strand breaks (DSBs), which finally lead to higher lethality and chromosome aberration. Ionizing radiation (IR) induced DNA DSBs are repaired by both non-homologous end-joining (NHEJ) and homologous recombination repair (HRR) pathways in mammalian cells. The novel function of ataxia telangiectasia-mutated (ATM) protein is its involvement in the DSB repair of slow kinetics for 'dirty' breaks rejoining by NHEJ, this suggests that ATM may play a more important role in high LET radiation-induced DNA damage. We show here that KU55933, an ATM inhibitor could distinctly lower the clonogenic survival in normal human skin fibroblast cells exposed to carbon ion radiation and dramatically impair the normal process for DSB repair. We also implicated the involvement of ATM in the two pathways of DNA DSB repair, with DNA-PKcs and Rad51 as the representative proteins. The phosphorylation of DNA-PKcs at Thr-2609 with both immunoblotting and immunofluorescent staining indicated an ATM-dependent change, while for Rad51, KU55933 pretreatment could postpone the formation of nuclear Rad51 foci. Interestingly, we also found that pretreatment with chloroquine, an ATM stimulator could protect cells from carbon ion radiation only at lower doses. For doses over 1 Gy, protection was no longer observed. There was a dose-dependent increase for ATM kinase activity, with saturation at about 1 Gy. Chloroquine pretreatment prior to 1 Gy of carbon ion radiation did not enhance the autophosphorylation of ATM at serine 1981. The function of ATM in G2/M checkpoint arrest facilitated DSB repair in high-LET irradiation. Our results provide a possible mechanism for the direct involvement of ATM in DSB repair by high-LET irradiation.

  18. Species-dependent stereoselective drug binding to albumin: a circular dichroism study.

    Science.gov (United States)

    Pistolozzi, Marco; Bertucci, Carlo

    2008-03-01

    Drug binding to albumins from different mammalian species was investigated to disclose evidence of species-dependent stereoselectivity in drug-binding processes and affinities. This aspect is important for evaluating the reliability of extrapolating distribution data among species. The circular dichroism (CD) signal induced by drug binding to the albumins [human serum albumin (HSA), bovine serum albumin (BSA), rat serum albumin (RSA), and dog serum albumin (DSA)] were measured and analyzed. The binding of selected drugs and metabolites to HSA significantly differed from the binding to the other albumins in terms of affinity and conformation of the bound ligands. In particular, phenylbutazone, a marker of site one on HSA, showed a higher affinity for binding to BSA with respect to RSA, HSA, and DSA, respectively. In the case of diazepam, a marker of site two on HSA, the affinity decreased in order from HSA to DSA, RSA, and BSA. The induced CD spectra were similar in terms of energy and band signs, suggesting almost the same conformation for the bound drug to the different albumins. Stereoselectivity was high for the binding of ketoprofen to HSA and RSA. A different sign was observed for the CD spectra induced by the drug to the two albumins because of the prevalence of a different conformation of the bound drug. Interestingly, the same induced CD spectra were obtained using either the racemic form or the (S)-enantiomer. Finally, significant differences were observed in the affinity of bilirubin, being highest for BSA, then decreasing for RSA, HSA, and DSA. A more complex conformational equilibrium was observed for bound bilirubin.

  19. Prediction of protein secondary structure from circular dichroism using theoretically derived spectra.

    Science.gov (United States)

    Louis-Jeune, Caroline; Andrade-Navarro, Miguel A; Perez-Iratxeta, Carol

    2012-02-01

    Circular dichroism (CD) is a spectroscopic technique commonly used to investigate the structure of proteins. Major secondary structure types, alpha-helices and beta-strands, produce distinctive CD spectra. Thus, by comparing the CD spectrum of a protein of interest to a reference set consisting of CD spectra of proteins of known structure, predictive methods can estimate the secondary structure of the protein. Currently available methods, including K2D2, use such experimental CD reference sets, which are very small in size when compared to the number of tertiary structures available in the Protein Data Bank (PDB). Conversely, given a PDB structure, it is possible to predict a theoretical CD spectrum from it. The methodological framework for this calculation was established long ago but only recently a convenient implementation called DichroCalc has been developed. In this study, we set to determine whether theoretically derived spectra could be used as reference set for accurate CD based predictions of secondary structure. We used DichroCalc to calculate the theoretical CD spectra of a nonredundant set of structures representing most proteins in the PDB, and applied a straightforward approach for predicting protein secondary structure content using these theoretical CD spectra as reference set. We show that this method improves the predictions, particularly for the wavelength interval between 200 and 240 nm and for beta-strand content. We have implemented this method, called K2D3, in a publicly accessible web server at http://www. ogic.ca/projects/k2d3.

  20. Theoretical modeling of peptide α-helical circular dichroism in aqueous solution.

    Science.gov (United States)

    Kaminský, Jakub; Kubelka, Jan; Bour, Petr

    2011-03-10

    Reliable modeling of protein and peptide circular dichroism (CD) spectra in the far UV presents a challenge for current theoretical approaches. In this study, the time-dependent density functional theory (TDDFT), configuration interaction with single excitation (CIS), and transition dipole coupling (TDC) were used to assess the most important factors contributing to the CD spectra of the α-helical secondary structure. The dependence on the peptide chain length and also the role of the flexibility and solvent environment were investigated with a model oligopeptide Ac-(Ala)(N)-NH-Me, (N = 1, ..., 18). Both the TDDFT and TDC-like methods suggest that the CD curve typical for the α-helix arises gradually, but its basic characteristic is discernible already for peptides with 4-5 amino acid residues. The calculated dependence was in a qualitative agreement with experimental spectra of short α-helices stabilized by the histidine-metal binding. The TDDFT computations of the CD were found to be unusually sensitive to the basis set and solvent model. Explicit hydration and temperature fluctuations of the peptide geometry, simulated with the aid of molecular dynamics (MD), significantly influenced the CD and absorption spectral shapes. An extensive averaging over MD configurations is thus required to obtain a converged spectral profile in cluster simulations. On the other hand, both the TDDFT and TDC models indicate only a minor influence of the alanine side chains. The CIS and TDC calculations also point toward a relatively small effect of the helix-helix interaction on the CD spectral profiles. For a model system of two helices, the CIS method predicted larger changes in the spectra than TDC. This suggests other than interactions between peptide chains, such as mutual polarization, can have a minor, but measurable, effect on the CD spectrum.

  1. Core-level magnetic circular dichroism in 3d and 4f magnetic systems (invited) (abstract)

    Science.gov (United States)

    Koide, T.

    1994-05-01

    With the recent availability of circulary polarized synchrotron radiation over a wide photon energy range from VUV to hard X rays, the magnetic circular dichroism (MCD) in core-level photoabsorption has rapidly attracted growing interest, both experimentally and theoretically. This novel technique can provide element-specific and site-selective information about the magnetic and the electronic states in various magnetic substances because the core-level MCD process involves optical transitions in which the one-electron initial states are well localized and have well-defined angular momenta. In order to get insight into the local magnetic states in 3d and 4f magnetic systems, we have studied MCD of ferrites, Fe1-xPtx alloys, and mixed-valence CeRh3B2 at the core-absorption edges in the VUV˜soft x-ray region. The experiments were performed by utilizing directly characterized, circularly polarized undulator radiation and off-plane synchrotron radiation1 in conjunction with an ultrahigh vacuum compatible superconducting magnet of special design.2 Clear MCD signals were observed for CeRh3B2 in the prethreshold region of the Ce 4d→4f (N4,5) edges. A comparison of the experimental MCD spectrum with theoretical ones3 for uniaxial crystal fields of Δc=0 and 0.2 eV shows that the experimental spectrum qualitatively agrees with the theoretical one for Δc=0 eV. Theory predicts that the MCD pattern for ΔcCeRh3B2. We will also present the MCD data in the M2,3 core-absorption region for ferrites (Fe3O4 and CoFe2O4) and Fe1-xPtx alloys, discussing the results.

  2. Vibronic coupling effect on circular dichroism spectrum: Carotenoid-retinal interaction in xanthorhodopsin

    Science.gov (United States)

    Fujimoto, Kazuhiro J.; Balashov, Sergei P.

    2017-03-01

    The role of vibronic coupling of antenna carotenoid and retinal in xanthorhodopsin (XR) in its circular dichroism (CD) spectrum is examined computationally. A vibronic exciton model combined with a transition-density-fragment interaction (TDFI) method is developed, and applied to absorption and CD spectral calculations of XR. The TDFI method is based on the electronic Coulomb and exchange interactions between transition densities for individual chromophores [K. J. Fujimoto, J. Chem. Phys. 137, 034101 (2012)], which provides a quantitative description of electronic coupling energy. The TDFI calculation reveals a dominant contribution of the Coulomb interaction to the electronic coupling energy and a negligible contribution of the exchange interaction, indicating that the antenna function of carotenoid results from the Förster type of excitation-energy transfer, not from the Dexter one. The calculated absorption and CD spectra successfully reproduce the main features of the experimental results, which allow us to investigate the mechanism of biphasic CD spectrum observed in XR. The results indicate that vibronic coupling between carotenoid and retinal plays a significant role in the shape of the CD spectrum. Further analysis reveals that the negative value of electronic coupling directly contributes to the biphasic shape of CD spectrum. This study also reveals that the C6—C7 bond rotation of salinixanthin is not the main factor for the biphasic CD spectrum although it gives a non-negligible contribution to the spectral shift. The present method is useful for analyzing the molecular mechanisms underlying the chromophore-chromophore interactions in biological systems.

  3. Cloning of linear T-cell epitops of EG95 antigen of Echinococcus granulosus into pGEX4t1 vector and expression analysis by SDS-PAGE

    Directory of Open Access Journals (Sweden)

    Roghayeh Mesri

    2016-12-01

    Full Text Available Background & Objectives: Echinococcus granulosus causes a common disease between humans and animals that called hydatid cyst or hydatidosis. The recombinant EG95 vaccine based on cloning of the 25 KD oncospheral antigen-Eg95- in pGEX stimulated significant humoral and cellular immunity in sheep, but regarding the effect of TH1cell immunity against this parasite and the influence of the linear T-cell epitopes in stimulating this immunity, only the coding sequence of linear T Cell epitopes of EG95 was cloned in pGEX and analyzed it's expression to optimize the qualification of this available vaccine in this study. Materials & Methods: The coding sequence of EG95 linear epitopes by IEDB software were predicted and synthesized. After PCR, the amplicon and pGEX4T1 were digested by xhoI restriction enzyme, the fragment was cloned into pGEX4T1 by heat shock method, and Positive colonies were selected by direct PCR with specific primers. The recombinant protein expression was evaluated in BL21 cells by 10% SDS-PAGE. Results: The coding sequence of EG95 linear T-cell epitopes was amplified by PCR and cloned into pGEX4T1 vector.  The recombinant plasmid was selected with Colony PCR and size difference between intact and recombinant purificated vectors. Recombinant protein expression with high significant concentration was recognized by SDS-PAGE. Conclusion: The EG95 linear T-cell epitopes coding sequence has been successfully cloned into pGEX4T1 vector and expressed into BL21 cells.

  4. Induction and Persistence of Large γH2AX Foci by High Linear Energy Transfer Radiation in DNA-Dependent protein kinase–Deficient Cells

    Energy Technology Data Exchange (ETDEWEB)

    Bracalente, Candelaria; Ibañez, Irene L. [Departamento de Micro y Nanotecnología, Comisión Nacional de Energía Atómica, San Martín, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires (Argentina); Molinari, Beatriz [Departamento de Radiobiología, Comisión Nacional de Energía Atómica, San Martín, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires (Argentina); Palmieri, Mónica [Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires (Argentina); Kreiner, Andrés [Consejo Nacional de Investigaciones Científicas y Técnicas, Buenos Aires (Argentina); Gerencia de Investigación y Aplicaciones, Comisión Nacional de Energía Atómica, San Martín, Buenos Aires (Argentina); Escuela de Ciencia y Tecnología, Universidad Nacional de San Martín, San Martín, Buenos Aires (Argentina); Valda, Alejandro [Escuela de Ciencia y Tecnología, Universidad Nacional de San Martín, San Martín, Buenos Aires (Argentina); and others

    2013-11-15

    Purpose: To evaluate the cell response to DNA double-strand breaks induced by low and high linear energy transfer (LET) radiations when the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), an essential protein of the nonhomologous end-joining repair pathway, lacks kinase activity. Methods and Materials: CHO10B2, a Chinese hamster ovary cell line, and its derived radiosensitive mutant cell line, irs-20, lacking DNA-PKcs activity, were evaluated after 0 to 3 Gy of γ-rays, plateau and Bragg peak protons, and lithium beams by clonogenic assay, and as a measurement of double-strand breaks, phosphorylated H2AX (γH2AX) foci number and size were quantified by immunocytofluorescence. Results: Irs-20 exhibited greater radiosensitivity and a higher amount of γH2AX foci than CHO10B2 at 6 hours after irradiation for all types of radiations. Remarkably, CHO10B2 and irs-20 maintained their difference in radiosensitivity after high-LET radiation. Six hours after low-LET radiations, irs-20 did not reach basal levels of γH2AX at high doses, whereas CHO10B2 recovered basal levels for all doses. After high-LET radiation, only CHO10B2 exhibited a reduction in γH2AX foci, but it never reached basal levels. Persistent foci in irs-20 confirmed a repair deficiency. Interestingly, after 30 minutes of high-LET radiation both cell lines exhibited large foci (size >0.9 μm{sup 2}) related to the damage nature, whereas at 6 hours irs-20 showed a higher amount of large foci than CHO10B2, with a 7-fold increase at 3 Gy, that could also be associated to radiosensitivity. Conclusions: We demonstrated, for the first time, an association between deficient DNA-PKcs activity and not only high levels of H2AX phosphorylation but also persistence and size increase of γH2AX foci after high-LET irradiation.

  5. Fully non-linear multi-species Fokker-Planck-Landau collisions for gyrokinetic particle-in-cell simulations of fusion plasma

    Science.gov (United States)

    Hager, Robert; Yoon, E. S.; Ku, S.; D'Azevedo, E. F.; Worley, P. H.; Chang, C. S.

    2015-11-01

    We describe the implementation, and application of a time-dependent, fully nonlinear multi-species Fokker-Planck-Landau collision operator based on the single-species work of Yoon and Chang [Phys. Plasmas 21, 032503 (2014)] in the full-function gyrokinetic particle-in-cell codes XGC1 [Ku et al., Nucl. Fusion 49, 115021 (2009)] and XGCa. XGC simulations include the pedestal and scrape-off layer, where significant deviations of the particle distribution function from a Maxwellian can occur. Thus, in order to describe collisional effects on neoclassical and turbulence physics accurately, the use of a non-linear collision operator is a necessity. Our collision operator is based on a finite volume method using the velocity-space distribution functions sampled from the marker particles. Since the same fine configuration space mesh is used for collisions and the Poisson solver, the workload due to collisions can be comparable to or larger than the workload due to particle motion. We demonstrate that computing time spent on collisions can be kept affordable by applying advanced parallelization strategies while conserving mass, momentum, and energy to reasonable accuracy. We also show results of production scale XGCa simulations in the H-mode pedestal and compare to conventional theory. Work supported by US DOE OFES and OASCR.

  6. Highly Efficient p-i-n Perovskite Solar Cells Utilizing Novel Low-Temperature Solution-Processed Hole Transport Materials with Linear π-Conjugated Structure.

    Science.gov (United States)

    Li, Yang; Xu, Zheng; Zhao, Suling; Qiao, Bo; Huang, Di; Zhao, Ling; Zhao, Jiao; Wang, Peng; Zhu, Youqin; Li, Xianggao; Liu, Xicheng; Xu, Xurong

    2016-09-01

    Alternative low-temperature solution-processed hole-transporting materials (HTMs) without dopant are critical for highly efficient perovskite solar cells (PSCs). Here, two novel small molecule HTMs with linear π-conjugated structure, 4,4'-bis(4-(di-p-toyl)aminostyryl)biphenyl (TPASBP) and 1,4'-bis(4-(di-p-toyl)aminostyryl)benzene (TPASB), are applied as hole-transporting layer (HTL) by low-temperature (sub-100 °C) solution-processed method in p-i-n PSCs. Compared with standard poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS) HTL, both TPASBP and TPASB HTLs can promote the growth of perovskite (CH3 NH3 PbI3 ) film consisting of large grains and less grain boundaries. Furthermore, the hole extraction at HTL/CH3 NH3 PbI3 interface and the hole transport in HTL are also more efficient under the conditions of using TPASBP or TPASB as HTL. Hence, the photovoltaic performance of the PSCs is dramatically enhanced, leading to the high efficiencies of 17.4% and 17.6% for the PSCs using TPASBP and TPASB as HTL, respectively, which are ≈40% higher than that of the standard PSC using PEDOT:PSS HTL.

  7. Circular dichroism, molecular modeling, and serology indicate that the structural basis of antigenic variation in foot-and-mouth disease virus is [alpha]-helix formation

    Energy Technology Data Exchange (ETDEWEB)

    France, L.L.; Piatti, P.G.; Newman, J.F.E.; Brown, F. (Plum Island Animal Disease Center, Greenport, NY (United States)); Toth, I.; Gibbons, W.A. (Univ. of London (United Kingdom))

    1994-08-30

    Seven antigenic variants obtained from a single field isolate of foot-and-mouth disease virus, serotype A12, differ only at residues 148 and 153 in the immunodominant loop of viral protein VP1. Synthetic peptides corresponding to the region 141-160 are highly immunogenic. UV circular dichroism shows that (i) in aqueous solution of the peptides are nearly identical, but in 100% trifluoroethanol they display helix-forming properties which correlate well with their serological crossreactivities for anti-peptide sera, and (ii) these properties are insensitive to substitutions at position 153, except for proline, but are highly sensitive to substitutions at position 148. This pattern can be explained by the effects of these substitutions on the amphiphilic character and positions of helices postulated in the region 146-156. Molecular models indicate that residues 147, 148, 150, 151, 153-155, and 157 are most likely to interact with residues of the antibody paratopes. The data are consistent with the existence of an inverse [gamma]-turn around Pro-153, and a [beta]-turn at the cell-attachment site at residues 145-147. 31 refs., 5 figs.

  8. Linearly constrained minimax optimization

    DEFF Research Database (Denmark)

    Madsen, Kaj; Schjær-Jacobsen, Hans

    1978-01-01

    We present an algorithm for nonlinear minimax optimization subject to linear equality and inequality constraints which requires first order partial derivatives. The algorithm is based on successive linear approximations to the functions defining the problem. The resulting linear subproblems...

  9. Calcium Binding Ability of Recombinant Buffalo Regucalcin: A Study Using Circular Dichroism Spectroscopy.

    Science.gov (United States)

    Harikrishna, P; Thomas, Jobin; Shende, A M; Bhure, S K

    2017-02-13

    Regucalcin is a calcium regulating multifunctional protein reported to have many important functions like calcium homeostasis, anti-oxidative, anti-apoptotic and anti-cancerous functions. Although it is demonstrated as a calcium regulating protein, the calcium binding ability of regucalcin is still a controversy. The main reason for the controversy is that it lacks a typical EF hand motif which is common to most of the calcium binding proteins. Even though many studies reported regucalcin as a calcium binding protein, there are some studies reporting regucalcin as non-calcium binding also. In the present study, we investigated the calcium binding ability of recombinant buffalo regucalcin by assessing the secondary structural changes of the protein using circular dichroism spectroscopy after adding Ca(2+) to the protein solution. Two types of calcium binding studies were done, one with different concentration of calcium chloride (0.5 mM CaCl2, 1 mM CaCl2, 2 mM CaCl2) and other at different time interval (no incubation and 10 min incubation) after addition of calcium chloride. Significant structural changes were observed in both studies which prove the calcium binding ability of recombinant regucalcin. A constant increase in the α-helix (1.1% with 0.5 mM CaCl2, 1.4% with 1 mM CaCl2, 3.5% with 2 mM CaCl2) and a decrease in β-sheets (78.5% with 0.5 mM CaCl2, 77.4% with 1 mM CaCl2, 75.7% with 2 mM CaCl2) were observed with the increase in calcium chloride concentration. There was a rapid increase in α-helix and decrease in β-sheets immediately after addition of calcium chloride, which subsides after 10 min incubation.

  10. Circular dichroism spectroscopic investigation of double-decker phthalocyanine with G-Quadruplex as promising telomerase inhibitor

    Science.gov (United States)

    Baǧda, Efkan; Baǧda, Esra; Yabaş, Ebru

    2017-01-01

    In the present study, interaction of a double-decker phthalocyanine with two G-quadruplex DNA, Tel 21 and cMYC, was investigated. To the best of our knowledge, this is the first study about G-quadruplex-double decker phthalocyanine interaction. The spectrophotometric titration method was used for binding constant calculations. From the binding constants, it can be said that double-decker phthalocyanine more likely to bind Tel 21 rather than cMYC. The conformational changes upon binding were monitored via circular dichroism spectroscopy. The ethidium bromide replacement assay was investigated spectrofluorometrically.

  11. STUDY ON MAGNETIC FIELD-INDUCED ORIENTATION OF A CHIRAL SIDE-CHAIN LIQUID CRYSTAL POLYACRYLATE USING INFRARED DICHROISM

    Institute of Scientific and Technical Information of China (English)

    HE Liu; JIN Shunzi; ZHANG Shufan; QI Zongneng; WANG Fosong

    1996-01-01

    Magnetic field-induced orientation of a chiral side chain liquid crystalline polyacrylate (P-11) was studied by using IR dichroism. For the investigated P-11, it has been shown that the magnetic alignment takes place over the entire temperature range between its melting point and clearing point and the orientation level is strongly temperature-dependent, the development with time of the magnetic orientation follows an exponential-type relation,and the smectic phase state influences the thermal relaxation process in the absence of the magnetic field.

  12. Expedient synthesis of novel pregnane-NSAIDs prodrugs, XRD, stereochemistry of their C-20 derivatives by circular dichroism, conformational analysis, their DFT and TD-DFT studies

    Science.gov (United States)

    Singh, Ranvijay Pratap; Sharma, Sonia; Kant, Rajni; Amandeep; Singh, Praveer; Sethi, Arun

    2016-02-01

    Four novel pregnane-NSAIDs prodrugs 3β-(2-(6-methoxynaphthalene-2yl) propionoxy)-16α-methoxy-pregn-5-ene-20-one (3), 16α-methoxy-pregn-5-ene-20-one-3yl-2(4-iso butyl phenyl) propanoate (4), 3β-(2-(6-methoxynaphthalene-2yl) propionoxy) 20-hydroxy-16α-methoxy-pregn-5-ene (5) and 20-hydroxy-16α-methoxy-pregn-5-ene-20-one-3yl-2(4-iso butyl phenyl) propanoate (6) have been synthesized. They were analyzed experimentally by spectroscopic techniques like 1H, 13C NMR, FT-IR, UV-visible spectroscopy, mass spectrometry and correlated by theoretical calculations. The structure and conformations of 3 was established by single crystal X-ray diffraction, which crystallized in orthorhombic form having P212121 space group. Absolute configuration of C-20 hydroxy derivatives 5 and 6 was established by circular dichroism (CD) analysis. Conformational analysis of 5 was carried out to determine the most stable conformation. The electronic properties, such as frontier orbitals, band gap energies, oscillator strength and wavelength have been calculated using time dependent density functional theory (TD-DFT). The vibrational wavenumbers have been calculated using DFT method and assigned with the help of potential energy distribution (PED). Global and local reactivity descriptors have been computed to predict reactivity and reactive sites in the molecule. First hyperpolarizability (β0) of synthesized compounds has been computed to evaluate non-linear optical (NLO) response. Molecular electrostatic potential (MEP) for synthesized compounds have also been determined to check their electrophilic or nucleophilic reactivity as well as reaction path.

  13. Foundations of linear and generalized linear models

    CERN Document Server

    Agresti, Alan

    2015-01-01

    A valuable overview of the most important ideas and results in statistical analysis Written by a highly-experienced author, Foundations of Linear and Generalized Linear Models is a clear and comprehensive guide to the key concepts and results of linear statistical models. The book presents a broad, in-depth overview of the most commonly used statistical models by discussing the theory underlying the models, R software applications, and examples with crafted models to elucidate key ideas and promote practical model building. The book begins by illustrating the fundamentals of linear models,

  14. Mechanisms of Cell Killing Response from Low Linear Energy Transfer (LET Radiation Originating from 177Lu Radioimmunotherapy Targeting Disseminated Intraperitoneal Tumor Xenografts

    Directory of Open Access Journals (Sweden)

    Kwon Joong Yong

    2016-05-01

    Full Text Available Radiolabeled antibodies (mAbs provide efficient tools for cancer therapy. The combination of low energy β−-emissions (500 keVmax; 130 keVave along with a γ-emission for imaging makes 177Lu (T1/2 = 6.7 day a suitable radionuclide for radioimmunotherapy (RIT of tumor burdens possibly too large to treat with α-particle radiation. RIT with 177Lu-trastuzumab has proven to be effective for treatment of disseminated HER2 positive peritoneal disease in a pre-clinical model. To elucidate mechanisms originating from this RIT therapy at the molecular level, tumor bearing mice (LS-174T intraperitoneal xenografts were treated with 177Lu-trastuzumab comparatively to animals treated with a non-specific control, 177Lu-HuIgG, and then to prior published results obtained using 212Pb-trastuzumab, an α-particle RIT agent. 177Lu-trastuzumab induced cell death via DNA double strand breaks (DSB, caspase-3 apoptosis, and interfered with DNA-PK expression, which is associated with the repair of DNA non-homologous end joining damage. This contrasts to prior results, wherein 212Pb-trastuzumab was found to down-regulate RAD51, which is involved with homologous recombination DNA damage repair. 177Lu-trastuzumab therapy was associated with significant chromosomal disruption and up-regulation of genes in the apoptotic process. These results suggest an inhibition of the repair mechanism specific to the type of radiation damage being inflicted by either high or low linear energy transfer radiation. Understanding the mechanisms of action of β−- and α-particle RIT comparatively through an in vivo tumor environment offers real information suitable to enhance combination therapy regimens involving α- and β−-particle RIT for the management of intraperitoneal disease.

  15. Feedback linearization of piecewise linear systems

    NARCIS (Netherlands)

    Camlibel, Kanat; Ustoglu, Ilker

    2005-01-01

    One of the classical problems of nonlinear systems and control theory is feedback linearization. Its obvious motivation is that one can utilize linear control theory if the nonlinear system at hand is linearizable by feedback. This problem is well-understood for the smooth nonlinear systems. In the

  16. PILOT STUDY International comparability in spectroscopic measurements of protein structure by circular dichroism: CCQM-P59

    Science.gov (United States)

    Ravi, Jascindra; Schiffmann, David; Tantra, Ratna; Cox, Simon; Eady, Jonathan; Jones, Christopher; Vrettos, John S.; Affleck, Richard P.; DeSa Lorenz, Julie; Shigeri, Yasushi; Linghui, Sheng; Jun, Liu; Willows, Robert; Charlet, Philippe; Dupont, Yves; Meuse, Curtis W.; Bailey, Marc J. A.; Knight, Alex E.

    2010-01-01

    Circular dichroism is a spectroscopic technique that is widely used to obtain information about protein structure, and hence is an important tool with many applications, including the characterization of biopharmaceuticals. However, there is a lack of confidence in the technique, arising from an observed lack of comparability in the data obtained by different laboratories, or even different operators. In this study, we set out to determine the extent of comparability in the technique, by comparing the results obtained from identical protein samples by a panel of worldwide laboratories. The laboratories chosen were either national measurement institutes (NMIs) or expert laboratories nominated by an NMI. We also aimed to identify the main factors contributing to any lack of measurement comparability. Data were analysed using PCA and SIMCA methods, and we show these statistical techniques are ideal for analysing large amounts of this type of spectroscopic data. We found a startling lack of comparability among laboratories, but we also found that most of the variability arose from relatively simple problems, which can be avoided by following simple guidelines. We believe that the lack of an absolute reference or measurement traceability in circular dichroism contributes to a lack of confidence in the technique. Main text. To reach the main text of this paper, click on Final Report. The final report has been peer-reviewed and approved for publication by the CCQM Working Group on Bioanalysis (BAWG).

  17. Lipid membrane association of myelin proteins and peptide segments studied by oriented and synchrotron radiation circular dichroism spectroscopy.

    Science.gov (United States)

    Muruganandam, Gopinath; Bürck, Jochen; Ulrich, Anne S; Kursula, Inari; Kursula, Petri

    2013-12-01

    Myelin-specific proteins are either integral or peripheral membrane proteins that, in complex with lipids, constitute a multilayered proteolipid membrane system, the myelin sheath. The myelin sheath surrounds the axons of nerves and enables rapid conduction of axonal impulses. Myelin proteins interact intimately with the lipid bilayer and play crucial roles in the assembly, function, and stability of the myelin sheath. Although myelin proteins have been investigated for decades, their structural properties upon membrane surface binding are still largely unknown. In this study, we have used simplified model systems consisting of synthetic peptides and membrane mimics, such as detergent micelles and/or lipid vesicles, to probe the conformation of peptides using synchrotron radiation circular dichroism spectroscopy (SRCD). Additionally, oriented circular dichroism spectroscopy (OCD) was employed to examine the orientation of myelin peptides in macroscopically aligned lipid bilayers. Various representative peptides from the myelin basic protein (MBP), P0, myelin/oligodencrocyte glycoprotein, and connexin32 (cx32) were studied. A helical peptide from the central immunodominant epitope of MBP showed a highly tilted orientation with respect to the membrane surface, whereas the N-terminal cytoplasmic segment of cx32 folded into a helical structure that was only slightly tilted. The folding of full-length myelin basic protein was, furthermore, studied in a bicelle environment. Our results provide information on the conformation and membrane alignment of important membrane-binding peptides in a membrane-mimicking environment, giving novel insights into the mechanisms of membrane binding and stacking by myelin proteins.

  18. Room temperature high circular dichroism ultraviolet lasing from planar spiral metal-GaN nanowire cavity (Conference Presentation)

    Science.gov (United States)

    Shih, Min-Hsiung

    2016-09-01

    Circularly polarized light and chiroptical effect have received considerable attention in advanced photonic and electronic technologies including optical spintronics, quantum-based optical information processing and communication, and high-efficiency liquid crystal display backlights. Moreover, the development of circularly polarized photon sources has played a major role in circular dichroism (CD) spectroscopy, which is important for analyses of optically active molecules, chiral synthesis in biology and chemistry, and ultrafast magnetization control. However, the conventional collocation of light-emitting devices and additional circular-polarization converters that produce circularly polarized beams makes the setup bulky and hardly compatible with nanophotonic devices in ultrasmall scales. In fact, the direct generation of circularly polarized photons may simplify the system integration, compact the setup, lower the cost of external components, and perhaps enhance the power efficiency. In this work, with the spiral-type metal-gallium nitride (GaN) nanowire cavity, we demonstrated an ultrasmall semiconductor laser capable of emitting circularly-polarized photons. The left- and right-hand spiral metal nanowire cavities with varied periods were designed at ultraviolet wavelengths to achieve the high quality factor circular dichroism metastructures. The dissymmetry factors characterizing the degrees of circular polarizations of the left- and right-hand chiral lasers were 1.4 and -1.6 (2 if perfectly circular polarized), respectively. The results show that the chiral cavities with only 5 spiral periods can achieve lasing signals with decently high degrees of circular polarizations.

  19. Optimized Spiral Metal-Gallium-Nitride Nanowire Cavity for Ultra-High Circular Dichroism Ultraviolet Lasing at Room Temperature.

    Science.gov (United States)

    Liao, Wei-Chun; Liao, Shu-Wei; Chen, Kuo-Ju; Hsiao, Yu-Hao; Chang, Shu-Wei; Kuo, Hao-Chung; Shih, Min-Hsiung

    2016-05-25

    Circularly polarized laser sources with small footprints and high efficiencies can possess advanced functionalities in optical communication and biophotonic integrated systems. However, the conventional lasers with additional circular-polarization converters are bulky and hardly compatible with nanophotonic circuits, and most active chiral plasmonic nanostructures nowadays exhibit broadband emission and low circular dichroism. In this work, with spirals of gallium nitride (GaN) nanowires (NWRs) covered by a metal layer, we demonstrated an ultrasmall semiconductor laser capable of emitting circularly-polarized photons. The left- and right-hand spiral metal nanowire cavities with varied periods were designed at ultraviolet wavelengths to achieve the high quality factor circular dichroism metastructures. The dissymmetry factors characterizing the degrees of circular polarizations of the left- and right-hand chiral lasers were 1.4 and -1.6 (±2 if perfectly circular polarized), respectively. The results show that the chiral cavities with only 5 spiral periods can achieve lasing signals with the high degrees of circular polarizations.

  20. Surface characterization of human serum albumin and sodium perfluorooctanoate mixed solutions by pendant drop tensiometry and circular dichroism.

    Science.gov (United States)

    Messina, Paula; Prieto, Gerardo; Dodero, Verónica; Cabrerizo-Vílchez, M A; Maldonado-Valderrama, J; Ruso, Juan M; Sarmiento, Félix

    2006-06-15

    The interfacial behavior of mixed human serum albumin (HSA)/sodium perfluorooctanoate (C8FONa) solutions is examined by using two experimental techniques, pendant drop tensiometry and circular dichroism spectroscopy. Through the analysis of the surface tension of the mixed solutions, surface competitive adsorption at the air-water interface between C8FONa and HSA is detected. The dynamic adsorption curves exhibit the distinct regimes in their time-dependent surface tension. The nature of these regimes is further analyzed in terms of the variation of the molecules surface areas. As a consequence, a compact and dense structure was formed where protein molecules were interconnected and overlapped. Thus, a reduction of the area occupied per molecule from 100 to 0.2 nm(2) is interpreted as a gel-like structure at the surface. The presence of the surfactant seems to favor the formation of this interfacial structure. Finally, measurements of circular dichroism suggests a compaction of the protein due to the association with the surfactant given by an increase of alpha-helix structure in the complexes as compared to that of pure protein.

  1. Structural alterations of human serum albumin caused by glycative and oxidative stressors revealed by circular dichroism analysis.

    Science.gov (United States)

    Monacelli, Fiammetta; Storace, Daniela; D'Arrigo, Cristina; Sanguineti, Roberta; Borghi, Roberta; Pacini, Davide; Furfaro, Anna L; Pronzato, Maria A; Odetti, Patrizio; Traverso, Nicola

    2013-01-01

    The aim of this work was to evaluate the ability of oxidative and glycative stressors to modify properties of human serum albumin (HSA) by analyzing markers of glycation (pentosidine) and oxidation (advanced oxidative protein products (AOPPs)) and assessing fluorescence and circular dichroism. HSA was incubated for up to 21 days with ribose, ascorbic acid (AA) and diethylenetriamine pentacetate (DTPA) in various combinations in order to evaluate influences of these substances on the structure of HSA. Ribose was included as a strong glycative molecule, AA as a modulator of oxidative stress, and DTPA as an inhibitor of metal-catalyzed oxidation. Ribose induced a significant increase in pentosidine levels. AA and DTPA prevented the accumulation of pentosidine, especially at later time points. Ribose induced a mild increase in AOPP formation, while AA was a strong inducer of AOPP formation. Ribose, in combination with AA, further increased the formation of AOPP. DTPA prevented the AA-induced generation of AOPP. Ribose was also a potent inducer of fluorescence at 335nm ex/385nm em, which is typical of pentosidine. AA and DTPA prevented this fluorescence. Circular dichroism showed complex results, in which AA and DTPA were strong modifiers of the percentages of the alpha-helical structure of HSA, while ribose affected the structure of HSA only at later time points.

  2. A new soft X-ray magnetic circular dichroism facility at the BSRF beamline 4B7B

    Science.gov (United States)

    Guo, Zhi-Ying; Hong, Cai-Hao; Xing, Hai-Ying; Tang, Kun; Zheng, Lei; Xui, Wei; Chen, Dong-Liang; Cui, Ming-Qi; Zhao, Yi-Dong

    2015-04-01

    X-ray magnetic circular dichroism (XMCD) has become an important and powerful tool because it allows the study of material properties in combination with elemental specificity, chemical state specificity, and magnetic specificity. A new soft X-ray magnetic circular dichroism apparatus has been developed at the Beijing Synchrotron Radiation Facility (BSRF). The apparatus combines three experimental conditions: an ultra-high-vacuum environment, moderate magnetic fields and in-situ sample preparation to measure the absorption signal. We designed a C-type dipole electromagnet that provides magnetic fields up to 0.5 T in parallel (or anti-parallel) direction relative to the incoming X-ray beam. The performances of the electromagnet are measured and the results show good agreement with the simulation ones. Following film grown in situ by evaporation methods, XMCD measurements are performed. Combined polarization corrections, the magnetic moments of the Fe and Co films determined by sum rules are consistent with other theoretical predictions and experimental measurements. Supported by National Natural Science Foundation of China (61204008)

  3. Combination of chemometrically assisted voltammetry, calorimetry, and circular dichroism as a new method for the study of bioinorganic substances: application to selenocystine metal complexes.

    Science.gov (United States)

    Gusmão, Rui; Prohens, Rafel; Díaz-Cruz, José Manuel; Ariño, Cristina; Esteban, Miquel

    2012-02-01

    Selenium-containing compounds play an important role in antioxidant defense systems, binding to toxic metals, preventing their uptake into cells, and thus protecting cells from metal-induced formation of reactive oxygen species. Here, we present a proposal for a relatively new method as a complement to the more usual methods used in selenium studies. A systematic study of the metal-binding properties of selenocystine (SeCyst) in the presence of divalent metal cations (Cd, Co, Hg, Ni, and Zn) is reported. Isothermal titration calorimetry provides thermodynamic parameters of the systems. Titrations produced curves that could be fit reasonably well to the one set of sites model. The data clearly demonstrate that one M(2+) binds one SeCyst molecule, and the stable M(SeCyst) complex is formed under these conditions. The order of the SeCyst binding constant for the metal ions is Hg(2+) > Cd(2+) ~ Zn(2+) > Ni(2+)> Co(2+). Cadmium ion was selected as a modulator for the behavior of SeCyst in the presence of a nonessential metal, and zinc was selected for the case of an essential element. These interactions of SeCyst with Cd(2+) and Zn(2+), either individually or combined, were studied in aqueous buffered solutions at physiological pH by differential pulse polarography and circular dichroism spectroscopy. Furthermore, recently developed chemometric tools were applied to differential pulse polarography data obtained in mixtures of SeCyst and glutathione in the presence of Cd(2+) at physiological pH.

  4. Linear side chains in benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c] pyrrole-4,6-dione polymers direct self-assembly and solar cell performance

    KAUST Repository

    Cabanetos, Clement

    2013-03-27

    While varying the size and branching of solubilizing side chains in π-conjugated polymers impacts their self-assembling properties in thin-film devices, these structural changes remain difficult to anticipate. This report emphasizes the determining role that linear side-chain substituents play in poly(benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers for bulk heterojunction (BHJ) solar cell applications. We show that replacing branched side chains by linear ones in the BDT motifs induces a critical change in polymer self-assembly and backbone orientation in thin films that correlates with a dramatic drop in solar cell efficiency. In contrast, we show that for polymers with branched alkyl-substituted BDT motifs, controlling the number of aliphatic carbons in the linear N-alkyl-substituted TPD motifs is a major contributor to improved material performance. With this approach, PBDTTPD polymers were found to reach power conversion efficiencies of 8.5% and open-circuit voltages of 0.97 V in BHJ devices with PC71BM, making PBDTTPD one of the best polymer donors for use in the high-band-gap cell of tandem solar cells. © 2013 American Chemical Society.

  5. Radiotherapy treatment planning linear-quadratic radiobiology

    CERN Document Server

    Chapman, J Donald

    2015-01-01

    Understand Quantitative Radiobiology from a Radiation Biophysics PerspectiveIn the field of radiobiology, the linear-quadratic (LQ) equation has become the standard for defining radiation-induced cell killing. Radiotherapy Treatment Planning: Linear-Quadratic Radiobiology describes tumor cell inactivation from a radiation physics perspective and offers appropriate LQ parameters for modeling tumor and normal tissue responses.Explore the Latest Cell Killing Numbers for Defining Iso-Effective Cancer TreatmentsThe book compil

  6. The search for circular dichroism in high-Tc superconductors (abstract)

    Science.gov (United States)

    Lyons, K. B.; Kwo, J.; Dillon, J. F., Jr.; Espinosa, G. P.; McGlashan-Powell, M.; Ramirez, A. P.; Schneemeyer, L. F.

    1991-04-01

    Stimulated by recent predictions of broken time reversal symmetry in cuprate superconductors, we have carried out a study of the polar Kerr ellipticity (the ellipticity of normally reflected light with the incident beam linearly polarized) for various cuprate materials, both superconducting and nonsuperconducting. The technique used employs a rotating half-wave retardation plate in order to discriminate against linear polarization effects. The results reveal a signature of a nonzero polar Kerr ellipticity which appears on cooling near 200 K in a variety of superconducting materials, and which is not observed in the corresponding insulating compounds. In this talk, in addition to summarizing these results, we plan to discuss the measurement technique itself in some detail. Measurements on both thin films and bulk samples will be discussed, together with a variety of tests on unrelated materials, which serve to eliminate various possible experimental artifacts.

  7. A linear programming manual

    Science.gov (United States)

    Tuey, R. C.

    1972-01-01

    Computer solutions of linear programming problems are outlined. Information covers vector spaces, convex sets, and matrix algebra elements for solving simultaneous linear equations. Dual problems, reduced cost analysis, ranges, and error analysis are illustrated.

  8. Magnetism of unconventional nanoscaled materials. An X-ray circular dichroism and muon spin rotation study

    Energy Technology Data Exchange (ETDEWEB)

    Tietze, Thomas Hermann

    2014-12-15

    The physical properties of nanoparticles deviate strongly from its bulk counterparts. In particular, the magnetic properties change strongly due to an elevated number of surface compared to bulk atoms. As a consequence the orbital magnetic moment in nanoparticles as well as the magnetic anisotropy is enhanced. Therefore, such nanoparticles have great potential in e.g. next generation high density data storage devices. A promising way to realize such devices is to deposit nanoparticles on graphene. Depending on the preparation conditions the templated growth of nanocluster arrays with different particle size and shape is possible. Since graphene possesses outstanding properties as well it is congruous to combine the advantages of both systems and to investigate its principle properties in more detail. Thus, one part of this work is dedicated to the size and shape dependence of electronic and magnetic properties of Ni nanoclusters on graphene. The magnetic properties were investigated using X-ray Magnetic Circular Dichroism (XMCD). From the corresponding absorption spectra, the electronic structure and the nanoparticle substrate interaction could be determined. Two sets of nanoparticles were investigated, with triangular and spherical shape. For each set the size was varied. Nonmagnetic absorption spectra indicate a strong interaction between the Ni nanoclusters and the graphene substrate. The integrated absorption signal which is a measure of the number of unoccupied states in the Ni d shell decreases strongly with decreasing cluster size. This means an enhanced occupancy of the Ni d states, most likely caused by charge transfer at the Ni nanocluster/graphene interface. As a consequence the magnetic moment was much smaller than expected for nanoclusters for all samples investigated. The smallest value obtained was only 50% of the respective bulk magnetic moment. The magnetic moment increases disproportionally and converges towards bulk properties above 2 ML. No

  9. On Regular Linear Relations

    Institute of Scientific and Technical Information of China (English)

    T. (A)LVAREZ

    2012-01-01

    For a closed linear relation in a Banach space the concept of regularity is introduced and studied.It is shown that many of the results of Mbekhta and other authors for operators remain valid in the context of multivalued linear operators.We also extend the punctured neighbourhood theorem for operators to linear relations and as an application we obtain a characterization of semiFredholm linear relations which are regular.

  10. Classifying Linear Canonical Relations

    OpenAIRE

    Lorand, Jonathan

    2015-01-01

    In this Master's thesis, we consider the problem of classifying, up to conjugation by linear symplectomorphisms, linear canonical relations (lagrangian correspondences) from a finite-dimensional symplectic vector space to itself. We give an elementary introduction to the theory of linear canonical relations and present partial results toward the classification problem. This exposition should be accessible to undergraduate students with a basic familiarity with linear algebra.

  11. Comparison of Linear Array and Line Blot Assay for Detection of Human Papillomavirus and Diagnosis of Cervical Precancer and Cancer in the Atypical Squamous Cell of Undetermined Significance and Low-Grade Squamous Intraepithelial Lesion Triage Study▿

    OpenAIRE

    Castle, Philip E.; Gravitt, Patti E.; Solomon, Diane; Wheeler, Cosette M.; Schiffman, Mark

    2007-01-01

    We evaluated Linear Array (LA), a newly commercialized PGMY09/11 L1 consensus primer PCR test that detects 37 human papillomavirus (HPV) genotypes by reverse line blot hybridization, for the detection of individual HPV genotypes and carcinogenic HPV and its clinical performance for detecting 2-year cumulative cervical precancer and cancer using archived specimens from the Atypical Squamous Cell of Undetermined Significance (ASCUS) and Low-Grade Squamous Intraepithelial Lesion Triage Study. LA...

  12. Linear-Algebra Programs

    Science.gov (United States)

    Lawson, C. L.; Krogh, F. T.; Gold, S. S.; Kincaid, D. R.; Sullivan, J.; Williams, E.; Hanson, R. J.; Haskell, K.; Dongarra, J.; Moler, C. B.

    1982-01-01

    The Basic Linear Algebra Subprograms (BLAS) library is a collection of 38 FORTRAN-callable routines for performing basic operations of numerical linear algebra. BLAS library is portable and efficient source of basic operations for designers of programs involving linear algebriac computations. BLAS library is supplied in portable FORTRAN and Assembler code versions for IBM 370, UNIVAC 1100 and CDC 6000 series computers.

  13. Studying the Stability of S-Layer Protein of Lactobacillus Acidophilus ATCC 4356 in Simulated Gastrointestinal Fluids Using SDS-PAGE and Circular Dichroism.

    Science.gov (United States)

    Eslami, Neda; Kermanshahi, Rouha Kasra; Erfan, Mohammad

    2013-01-01

    Crystalline arrays of proteinaceous subunits forming surface layers (S-layers) are now recognized as one of the most common outermost cell envelope components of prokaryotic organisms. The surface layer protein of Lactobacillus acidophilus ATCC4356 is composed of a single species of protein of apparent molecular weight of 43-46 KDa. Considering the Lactobacillus acidophilus ATCC4356 having the S-layer is stable in harsh gastrointestinal (GI) conditions, a protective role against destructive GI factors which has been proposed for these nanostructures. It opens interesting perspectives in the using and development of this S-layer as a protective coat for oral administration of unstable drug nanocarriers. To achieve this goal, it is necessary to study the in-vitro stability of the S-layers in the simulated gastrointestinal fluids (SGIF). This study was planned to evaluate the in-vitro stability of the extracted S-layer protein of Lactobacillus acidophilus ATCC4356 in SGIF using it as a protective coat in oral drug delivery. Sodium dodecyl sulfate gel electrophoresis (SDS-PAGE) and circular dichroism (CD) spectroscopy were used to study the stability of the S-layer protein incubated in SGIF. Both the SDS-PAGE and CD spectra results showed that Lactobacillus acidophilus ATCC4356 S-layer protein is stable in simulated gastric fluid (SGF) with pH = 2 up to 5 min. It is stable in SGF pH = 3.2 and above it, with and without pepsin. It is also stable in all the simulated intestinal fluids. This S-layer is also stable in all of the simulated intestinal fluids.

  14. Kaempferol-human serum albumin interaction: Characterization of the induced chirality upon binding by experimental circular dichroism and TDDFT calculations

    Science.gov (United States)

    Matei, Iulia; Ionescu, Sorana; Hillebrand, Mihaela

    2012-10-01

    The experimental induced circular dichroism (ICD) and absorption spectra of the achiral flavonoid kaempferol upon binding to human serum albumin (HSA) were correlated to electronic CD and UV-vis spectra theoretically predicted by time-dependent density functional theory (TDDFT). The neutral and four anionic species of kaempferol in various conformations were considered in the calculations. The appearance of the experimental ICD signal was rationalized in terms of kaempferol binding to HSA in a distorted, chiral, rigid conformation. The comparison between the experimental and simulated spectra allowed for the identification of the kaempferol species that binds to HSA, namely the anion generated by deprotonation of the hydroxyl group in position 7. This approach constitutes a convenient method for evidencing the binding species and for determining its conformation in the binding pocket of the protein. Its main advantage over the UV-vis absorption method lays in the fact that only the bound ligand species gives an ICD signal.

  15. Circular dichroism and infrared spectroscopic characterization of secondary structure components of protein Z during mashing and boiling processes.

    Science.gov (United States)

    Han, Yupeng; Wang, Jinjing; Li, Yongxian; Hang, Yu; Yin, Xiangsheng; Li, Qi

    2015-12-01

    In beer brewing, protein Z is hypothesized to stabilize beer foam. However, few investigations have revealed the relationship between conformational alterations to protein Z during the brewing process and beer foam. In this report, protein Z from sweet wort was isolated during mashing and boiling processes. Circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR) were used to monitor the structural characteristics of protein Z. The results showed that the α-helix and β-sheet content decreased, whereas the content of β-turn and random coil increased. The complex environment rich in polysaccharides may facilitate conformational alterations and modifications to protein Z. Additionally, the formation of extended structural features to protein Z provides access to reactive amino acid side chains that can undergo modifications and the exposure of hydrophobic core regions of the protein. Analyzing structural transformations should provide a deeper understanding of the mechanism of protein Z on maintaining beer foam.

  16. A QM/MM-MD study on protein electronic properties: Circular dichroism spectra of oxytocin and insulin

    Science.gov (United States)

    Kitagawa, Yuya; Akinaga, Yoshinobu; Kawashima, Yukio; Jung, Jaewoon; Ten-no, Seiichiro

    2012-06-01

    A QM/MM (quantum-mechanical/molecular-mechanical) molecular-dynamics approach based on the generalized hybrid-orbital (GHO) method, in conjunction with the second-order perturbation (MP2) theory and the second-order approximate coupled-cluster (CC2) model, is employed to calculate electronic property accounting for a protein environment. Circular dichroism (CD) spectra originating from chiral disulfide bridges of oxytocin and insulin at room temperature are computed. It is shown that the sampling of thermal fluctuation of molecular geometries facilitated by the GHO-MD method plays an important role in the obtained spectra. It is demonstrated that, while the protein environments in an oxytocin molecule have significant electrostatic influence on its chiral center, it is compensated by solvent induced charges. This gives a reasonable explanation to experimental observations. GHO-MD simulations starting from different experimental structures of insulin indicate that existence of the disulfide bridges with negative dihedral angles is crucial.

  17. A QM/MM-MD study on protein electronic properties: Circular dichroism spectra of oxytocin and insulin

    Energy Technology Data Exchange (ETDEWEB)

    Kitagawa, Yuya [Graduate School of System Informatics, Kobe University, Kobe 657-8501 (Japan); CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012 (Japan); Akinaga, Yoshinobu [RIKEN Advanced Institute for Computational Science, Kobe 650-0047 (Japan); Kawashima, Yukio [Department of Chemistry, Graduate School of Sciences, Kyushu University, Fukuoka 812-8581 (Japan); Institute of Advanced Research, Kyushu University, Fukuoka 812-8581 (Japan); Jung, Jaewoon [RIKEN Advanced Institute for Computational Science, Kobe 650-0047 (Japan); Ten-no, Seiichiro, E-mail: tenno@cs.kobe-u.ac.jp [Graduate School of System Informatics, Kobe University, Kobe 657-8501 (Japan); CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012 (Japan)

    2012-06-05

    A QM/MM (quantum-mechanical/molecular-mechanical) molecular-dynamics approach based on the generalized hybrid-orbital (GHO) method, in conjunction with the second-order perturbation (MP2) theory and the second-order approximate coupled-cluster (CC2) model, is employed to calculate electronic property accounting for a protein environment. Circular dichroism (CD) spectra originating from chiral disulfide bridges of oxytocin and insulin at room temperature are computed. It is shown that the sampling of thermal fluctuation of molecular geometries facilitated by the GHO-MD method plays an important role in the obtained spectra. It is demonstrated that, while the protein environments in an oxytocin molecule have significant electrostatic influence on its chiral center, it is compensated by solvent induced charges. This gives a reasonable explanation to experimental observations. GHO-MD simulations starting from different experimental structures of insulin indicate that existence of the disulfide bridges with negative dihedral angles is crucial.

  18. On the interplay between chirality and exciton coupling: a DFT calculation of the circular dichroism in π-stacked ethylene.

    Science.gov (United States)

    Norman, Patrick; Linares, Mathieu

    2014-09-01

    The chirality of stacked weakly interacting π-systems was interpreted in terms of Frenkel exciton states and the formation of excitonic circular dichroism (CD) bands was monitored for ethylene stacks of varying sizes. Convergence of CD bands with respect to the system size was observed for stacks involving around 10 molecules. By means of rotation around the C-C double bond in ethylene, chirality was induced in the monomeric system and which was shown to dominate the spectral responses, even for polymer aggregates. In helical assemblies of chiral entities, there will always be a mix of excitonic and monomeric contributions to the CD signal and it is demonstrated that the complex polarization propagator approach in combination with Density Functional Theory is a suitable method to address this situation.

  19. Drug binding to human serum albumin: abridged review of results obtained with high-performance liquid chromatography and circular dichroism.

    Science.gov (United States)

    Ascoli, Giorgio A; Domenici, Enrico; Bertucci, Carlo

    2006-09-01

    The drug binding to plasma and tissue proteins are fundamental factors in determining the overall pharmacological activity of a drug. Human serum albumin (HSA), together with alpha1-acid glycoprotein (AGP), are the most important plasma proteins, which act as drug carriers, with drug pharmacokinetic implications, resulting in important clinical impacts for drugs that have a relatively narrow therapeutic index. This review focuses on the combination of biochromatography and circular dichroism as an effective approach for the characterization of albumin binding sites and their enantioselectivity. Furthermore, their applications to the study of changes in the binding properties of the protein arising by the reversible or covalent binding of drugs are discussed, and examples of physiological relevance reported. Perspectives of these studies reside in supporting the development of new drugs, which require miniaturization to facilitate the screening of classes of compounds for their binding to the target protein, and a deeper characterization of the mechanisms involved in the molecular recognition processes.

  20. Toroidal Interaction and Propeller Chirality of Hexaarylbenzenes. Dynamic Domino Inversion Revealed by Combined Experimental and Theoretical Circular Dichroism Studies.

    Science.gov (United States)

    Kosaka, Tomoyo; Inoue, Yoshihisa; Mori, Tadashi

    2016-03-01

    Hexaarylbenzenes (HABs) have greatly attracted much attention due to their unique propeller-shaped structure and potential application in materials science, such as liquid crystals, molecular capsules/rotors, redox materials, nonlinear optical materials, as well as molecular wires. Less attention has however been paid to their propeller chirality. By introducing small point-chiral group(s) at the periphery of HABs, propeller chirality was effectively induced, provoking strong Cotton effects in the circular dichroism (CD) spectrum. Temperature and solvent polarity manipulate the dynamics of propeller inversion in solution. As such, whizzing toroids become more substantial in polar solvents and at an elevated temperature, where radial aromatic rings (propeller blades) prefer orthogonal alignment against the central benzene ring (C6 core), maximizing toroidal interactions.

  1. Present status of vacuum ultraviolet natural circular dichroism measurement system using polarizing undulator at TERAS BL5 beamline

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Masahito, E-mail: masahito-tanaka@aist.go.j [Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Umezono 1-1-1, Tsukuba, Ibaraki 305-8568 (Japan); Yagi-Watanabe, Kazutoshi; Kaneko, Fusae [Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology (AIST), Central 2, Umezono 1-1-1, Tsukuba, Ibaraki 305-8568 (Japan); Nakagawa, Kazumichi [Graduate School of Human Development and Environment, Kobe University, Tsurukabuto 3-11, Nada-ku, Kobe 657-8501 (Japan)

    2010-08-15

    The study of natural circular dichroism (CD) in the vacuum and extreme ultraviolet (VUV and EUV) regions has been providing us with chirality and structural information on biomolecules. We have developed the beamline BL5 at TERAS, Tsukuba, which is equipped with a compact Onuki-type polarizing undulator. This beamline is dedicated to measuring the CD spectra in the VUV and EUV regions for the photon energy region of 5-40 eV. The use of a polarization modulation technique with a polarizing undulator is essential for detecting a weak CD signal. Using this CD system, the natural CD spectrum has been measured in the EUV region up to 40 eV for the first time. In addition, the differences and the similarities between the CD spectra of four amino acid films (alanine, valine, leucine, and phenylalanine) in the VUV region up to 9.5 eV are determined.

  2. Domain wall velocity measurement in permalloy nanowires with X-ray magnetic circular dichroism imaging and single shot Kerr microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Moore, T.A., E-mail: t.a.moore@physics.or [Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Klaeui, M.; Heyne, L.; Moehrke, P. [Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Backes, D.; Rhensius, J. [Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Ruediger, U. [Fachbereich Physik, Universitaet Konstanz, Universitaetsstrasse 10, 78457 Konstanz (Germany); Heyderman, L.J. [Laboratory for Micro- and Nanotechnology, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Mentes, T.O.; Nino, M.A.; Locatelli, A. [Sincrotrone Trieste, 34012 Basovizza-Trieste (Italy); Potenza, A.; Marchetto, H.; Cavill, S.; Dhesi, S.S. [Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE (United Kingdom)

    2010-05-15

    Domain walls (DWs) propagated along nanoscale magnetic wires by current or field pulses could potentially be used for data storage or logic applications, but the understanding of the DW dynamics, particularly under the influence of spin-polarized current, is incomplete. Measuring the velocity can give insights into the physics of the DW motion. Here we demonstrate DW velocity measurements in permalloy (Ni{sub 80}Fe{sub 20}) nanowires (1500 nm width and 20 nm thickness) using the techniques of X-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM) to image the magnetic contrast in the nanowires, and single shot Kerr microscopy, which allows for dynamic measurements. The magnetic imaging yields the average velocity as well as information on the DW spin structure, whereas the single shot method highlights the stochastic nature of the DW motion.

  3. X-ray magnetic circular dichroism and small angle neutron scattering study of thiol capped gold nanoparticles.

    Energy Technology Data Exchange (ETDEWEB)

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M. A.; Haskel, D.; Pinel, E. F.; te Velthuis, S. G. E.; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian, C.; Garcia, M. A.; Univ. Complutense de Madrid; Inst. de Magnetismo Aplicado UCM; Univ. Pisa; Univ. di Padova

    2009-11-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 {center_dot} 10{sup -4} was found at the Au L{sub 3} edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M{sub s}, of 0.06 emu/g{sub Au}. SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences.

  4. X-ray magnetic circular dichroism and small angle neutron scattering studies of thiol capped gold nanoparticles.

    Energy Technology Data Exchange (ETDEWEB)

    de la Venta, J.; Bouzas, V.; Pucci, A.; Laguna-Marco, M. A.; Haskel, D.; te Velthuis, S. G. E; Hoffmann, A.; Lal, J.; Bleuel, M.; Ruggeri, G.; de Julian Fernandez, C.; Garcia, M. A.; Univ.Complutense de Madrid; Inst. de Magnetismo Aplicado; Univ. of Pisa; Lab. di Magnetismo Molecolare

    2009-01-01

    X-ray magnetic circular dichroism (XMCD) and Small Angle Neutron Scattering (SANS) measurements were performed on thiol capped Au nanoparticles (NPs) embedded into polyethylene. An XMCD signal of 0.8 {center_dot} 10{sup -4} was found at the Au L{sub 3} edge of thiol capped Au NPs embedded in a polyethylene matrix for which Superconducting Quantum Interference Device (SQUID) magnetometry yielded a saturation magnetization, M{sub s}, of 0.06 emu/g{sub Au}. SANS measurements showed that the 3.2 nm average-diameter nanoparticles are 28% polydispersed, but no detectable SANS magnetic signal was found with the resolution and sensitivity accessible with the neutron experiment. A comparison with previous experiments carried out on Au NPs and multilayers, yield to different values between XMCD signals and magnetization measured by SQUID magnetometer. We discuss the origin of those differences.

  5. Non-reciprocal directional dichroism in the AFM phase of BiFeO3 at THz frequencies

    Science.gov (United States)

    Nagel, Urmas; Rõõm, T.; Farkas, D.; Szaller, D.; Bordács, S.; Kézsmárki, I.; Engelkamp, H.; Ozaki, Y.; Tomiaki, Y.; Ito, T.; Fishman, Randy S.

    We did THz absorption spectroscopy of BiFeO3 single crystals in the AFM phase, where the spin cycloid is destroyed in magnetic fields between 18 T and 32 T in Voigt geometry at 1.6 K. If B0 ∥ [ 1 1 0 ] , we see strong directional dichroism (DD) of absorption of the magnon mode with light propagating along the direction of the ferroelectric polarization k ∥ P ∥ [ 111 ] and eω ∥ [ 1 1 0 ] , bω ∥ [ 1 1 2 ] . The sign of DD can be reversed (i) by reversing the direction of B0 or (ii) by flipping the sample, thus reversing the propagation direction of light. The observed effect is caused by the strong magneto-electric coupling in the collinear AFM phase. Research sponsored by the Estonian Ministry of Education and Research (IUT23-3).

  6. Soft x-ray circular dichroism and scattering using a modulated elliptically polarizing wiggler and double synchronous detection

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, J.C.; Polewski, K.; Monteleone, D.C. [and others

    1998-01-23

    We have constructed an experimental station (beamline) at the National Synchrotron Light Source to measure circular dichroism (CD) using soft x-rays (250 {le} hv {le} 900 eV) from a time modulated elliptically polarizing wiggler. The polarization of the soft x-ray beam switches periodically between two opposite polarizations, hence permitting the use of phase-sensitive (lock-in) detection. While the wiggler can be modulated at frequencies up to 100 Hz, switching transients limit the actual practical frequency to {approx}25 Hz. With analog detection, switching transients are blocked by a chopper synchronized to the frequency and phase of the wiggler. The CD is obtained from the ratio of the signal recovered at the frequency of polarization modulation, f, to the average beam intensity, which is recovered by synchronous detection at frequency 2f.

  7. Theoretical description of circular dichroism in photoelectron angular distributions of randomly oriented chiral molecules after multi-photon photoionization

    CERN Document Server

    Goetz, R E; Nikoobakht, B; Berger, R; Koch, C P

    2016-01-01

    Photoelectron circular dichroism refers to the forward/backward asymmetry in the photoelectron angular distribution with respect to the propagation axis of circularly polarized light. It has recently been demonstrated in femtosecond multi-photon photoionization experiments with randomly oriented camphor and fenchone molecules [C. Lux et al., Angew. Chem. Int. Ed. 51, 5001 (2012);C. S. Lehmann et al., J. Chem. Phys. 139, 234307 (2013)]. A theoretical framework describing this process as (2+1) resonantly enhanced multi-photon ionization is constructed, which consists of two-photon photoselection from randomly oriented molecules and successive one-photon ionisation of the photoselected molecules. It combines perturbation theory for the light-matter interaction with ab initio calculations for the two-photon absorption and a single-center expansion of the photoelectron wavefunction in terms of hydrogenic continuum functions. It is verified that the model correctly reproduces the basic symmetry behavior expected un...

  8. Relaxation Dynamics in Photoexcited Chiral Molecules Studied by Time-Resolved Photoelectron Circular Dichroism: Toward Chiral Femtochemistry

    CERN Document Server

    Comby, Antoine; Boggio-Pasqua, Martial; Descamps, Dominique; Légaré, Francois; Nahon, Laurent; Petit, Stéphane; Pons, Bernard; Fabre, Baptiste; Mairesse, Yann; Blanchet, Valérie

    2016-01-01

    Unravelling the main initial dynamics responsible for chiral recognition is a key stepin the understanding of many biological processes. However this challenging task requires a sensitive enantiospecic probe to investigate molecular dynamics on their natural femtosecond timescale. Here we show that, in the gas phase, the ultrafast relaxationdynamics of photoexcited chiral molecules can be tracked by recording Time-ResolvedPhotoElectron Circular Dichroism (TR-PECD) resulting from the photoionisation bya circularly polarized probe pulse. A large forward/backward asymmetry along theprobe propagation axis is observed in the photoelectron angular distribution. Its evolution with pump-probe delay reveals ultrafast dynamics that are inaccessible in theangle-integrated photoelectron spectrum nor via the usual electron emission anisotropyparameter ($\\beta$). PECD, which originates from the electron scattering in the chiral molecular potential, appears as a new sensitive observable for ultrafast molecular dynamicsin ch...

  9. 4f orbital and spin magnetism in cerium intermetallic compounds studied by magnetic circular x-ray dichroism

    Science.gov (United States)

    Schillé, J. Ph.; Bertran, F.; Finazzi, M.; Brouder, Ch.; Kappler, J. P.; Krill, G.

    1994-08-01

    Magnetic circular x-ray dichroism experiments at the M4,5 absorption edges of cerium in the intermetallic compounds CeCuSi, CeRh3B2, and CeFe2 are reported. By applying general sum rules, it is shown that these experiments are able to yield both the magnitude and the direction of the 4f magnetic moment on Ce. An estimation of the orbital contribution to those 4f moments is given. Our experiments demonstrate the existence of a 4f magnetic moment on Ce in CeFe2 and confirm the extreme sensitivity of the 4f orbital contribution to the degree of localization of the 4f electrons. This 4f orbital contribution is significantly higher than the one predicted from spin-resolved band-structure calculations.

  10. Local X-ray magnetic circular dichroism study of Fe/Cu(111) using a tunneling smart tip

    Energy Technology Data Exchange (ETDEWEB)

    DiLullo, Andrew; Shirato, Nozomi; Cummings, Marvin [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Kersell, Heath; Chang, Hao [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Ohio University, Athens, OH 45701 (United States); Rosenmann, Daniel; Miller, Dean; Freeland, John W. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Hla, Saw-Wai [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Ohio University, Athens, OH 45701 (United States); Rose, Volker, E-mail: vrose@anl.gov [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

    2016-01-28

    A tunneling smart tip of a synchrotron X-ray scanning tunneling microscope provides simultaneously localized topographic, elemental and magnetic information. Localized spectroscopy with simultaneous topographic, elemental and magnetic information is presented. A synchrotron X-ray scanning tunneling microscope has been employed for the local study of the X-ray magnetic circular dichroism at the Fe L{sub 2,3}-edges of a thin iron film grown on Cu(111). Polarization-dependent X-ray absorption spectra have been obtained through a tunneling smart tip that serves as a photoelectron detector. In contrast to conventional spin-polarized scanning tunneling microscopy, X-ray excitations provide magnetic contrast even with a non-magnetic tip. Intensity variations in the photoexcited tip current point to chemical variations within a single magnetic Fe domain.

  11. Conformational analysis of quinine and its pseudo enantiomer quinidine: a combined jet-cooled spectroscopy and vibrational circular dichroism study.

    Science.gov (United States)

    Sen, Ananya; Bouchet, Aude; Lepère, Valeria; Le Barbu-Debus, Katia; Scuderi, D; Piuzzi, F; Zehnacker-Rentien, A

    2012-08-16

    Laser-desorbed quinine and quinidine have been studied in the gas phase by combining supersonic expansion with laser spectroscopy, namely, laser-induced fluorescence (LIF), resonance-enhanced multiphoton ionization (REMPI), and IR-UV double resonance experiments. Density funtional theory (DFT) calculations have been done in conjunction with the experimental work. The first electronic transition of quinine and quinidine is of π-π* nature, and the studied molecules weakly fluoresce in the gas phase, in contrast to what was observed in solution (Qin, W. W.; et al. J. Phys. Chem. C2009, 113, 11790). The two pseudo enantiomers quinine and quinidine show limited differences in the gas phase; their main conformation is of open type as it is in solution. However, vibrational circular dichroism (VCD) experiments in solution show that additional conformers exist in condensed phase for quinidine, which are not observed for quinine. This difference in behavior between the two pseudo enantiomers is discussed.

  12. Determination of levamisole and tetramisole in seized cocaine samples by enantioselective high-performance liquid chromatography and circular dichroism detection.

    Science.gov (United States)

    Bertucci, Carlo; Tedesco, Daniele; Fabini, Edoardo; Di Pietra, Anna Maria; Rossi, Francesca; Garagnani, Marco; Del Borrello, Elia; Andrisano, Vincenza

    2014-10-10

    Levamisole, an anthelmintic drug, has been increasingly employed as an adulterant of illicit street cocaine over the last decade; recently, the use of tetramisole, the racemic mixture of levamisole and its enantiomer dexamisole, was also occasionally observed. A new enantioselective high-performance liquid chromatography (HPLC) method, performed on cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phases in normal-phase mode, was validated to determine the enantiomeric composition of tetramisole enantiomers in seized cocaine samples. Furthermore, the hyphenation of the validated HPLC method with a circular dichroism (CD) detection system allowed the direct determination of elution order and a selective monitoring of levamisole and dexamisole in the presence of possible interferences. The method was applied to the identification and quantitation of the two enantiomers of tetramisole in seized street cocaine samples.

  13. Wavelength dependent photoelectron circular dichroism of limonene studied by femtosecond multiphoton laser ionization and electron-ion coincidence imaging

    Science.gov (United States)

    Rafiee Fanood, Mohammad M.; Janssen, Maurice H. M.; Powis, Ivan

    2016-09-01

    Enantiomers of the monoterpene limonene have been investigated by (2 + 1) resonance enhanced multiphoton ionization and photoelectron circular dichroism employing tuneable, circularly polarized femtosecond laser pulses. Electron imaging detection provides 3D momentum measurement while electron-ion coincidence detection can be used to mass-tag individual electrons. Additional filtering, by accepting only parent ion tagged electrons, can be then used to provide discrimination against higher energy dissociative ionization mechanisms where more than three photons are absorbed to better delineate the two photon resonant, one photon ionization pathway. The promotion of different vibrational levels and, tentatively, different electronic ion core configurations in the intermediate Rydberg states can be achieved with different laser excitation wavelengths (420 nm, 412 nm, and 392 nm), in turn producing different state distributions in the resulting cations. Strong chiral asymmetries in the lab frame photoelectron angular distributions are quantified, and a comparison made with a single photon (synchrotron radiation) measurement at an equivalent photon energy.

  14. Advanced linear algebra

    CERN Document Server

    Cooperstein, Bruce

    2010-01-01

    Vector SpacesFieldsThe Space FnVector Spaces over an Arbitrary Field Subspaces of Vector SpacesSpan and IndependenceBases and Finite Dimensional Vector SpacesBases and Infinite Dimensional Vector SpacesCoordinate VectorsLinear TransformationsIntroduction to Linear TransformationsThe Range and Kernel of a Linear TransformationThe Correspondence and Isomorphism TheoremsMatrix of a Linear TransformationThe Algebra of L(V, W) and Mmn(F)Invertible Transformations and MatricesPolynomialsThe Algebra of PolynomialsRoots of PolynomialsTheory of a Single Linear OperatorInvariant Subspaces of an Operator

  15. Spectral characteristics of fluorescence and circular dichroism of aflatoxin B1 reaction with its anti-idiotypic antibody

    Science.gov (United States)

    Liu, Aiping; Yang, Hongxiu; Wang, Xiaohong; Chen, Fusheng

    2012-11-01

    Aflatoxin B1 (AFB1) is a toxic secondary metabolite and sensitive methods for its analysis have been developed. In our lab, a number of works have been carried out, including exploitation of detection methods and production of anti-idiotypic antibody (Ab2) against Fab fragment of anti-AFB1 antibody (Ab1). In this paper, Ab2 was generated upon the immunization of mice with F(ab')2 fragment, which was specific to AFB1 and obtained by pepsin digestion of Ab1. The characteristics of Ab2 was primarily investigated by indirect competitive enzyme-linked immunosorbent assay (icELISA), which indicated that Ab2, might bear an internal image of antigen AFB1 and was able to combine to F(ab')2 in competition with AFB1, and the concentration of Ab2 to cause 50% inhibition of binding (IC50) was 131.8 μg/mL. In addition, fluorescence and circular dichroism studies were designed to explore the mutual relationship among AFB1, F(ab')2 and Ab2. The fluorescence spectroscopy implied that both AFB1 and Ab2 act as a quencher upon F(ab')2, and the Ab2 could compete with AFB1 when both of Ab2 and AFB1 reacted with F(ab')2. The circular dichroism (CD) spectrum suggested that both the binding of Ab2 and AFB1 on F(ab')2 brought secondary conformation change of F(ab')2, especially in the changes of α helix and β sheet. The research performed would provide unique insight into the comprehension of interaction among AFB1, F(ab')2 and Ab2 as well as offer structural information for substitution researches of toxic antigen like AFB1.

  16. Circular dichroism study of the interaction between mutagens and bilirubin bound to different binding sites of serum albumins

    Science.gov (United States)

    Orlov, Sergey; Goncharova, Iryna; Urbanová, Marie

    Although recent investigations have shown that bilirubin not only has a negative role in the organism but also exhibits significant antimutagenic properties, the mechanisms of interactions between bilirubin and mutagens are not clear. In this study, interaction between bilirubin bound to different binding sites of mammalian serum albumins with structural analogues of the mutagens 2-aminofluorene, 2,7-diaminofluorene and mutagen 2,4,7-trinitrofluorenone were investigated by circular dichroism and absorption spectroscopy. Homological human and bovine serum albumins were used as chiral matrices, which preferentially bind different conformers of bilirubin in the primary binding sites and make it observable by circular dichroism. These molecular systems approximated a real system for the study of mutagens in blood serum. Differences between the interaction of bilirubin bound to primary and to secondary binding sites of serum albumins with mutagens were shown. For bilirubin bound to secondary binding sites with low affinity, partial displacement and the formation of self-associates were observed in all studied mutagens. The associates of bilirubin bound to primary binding sites of serum albumins are formed with 2-aminofluorene and 2,4,7-trinitrofluorenone. It was proposed that 2,7-diaminofluorene does not interact with bilirubin bound to primary sites of human and bovine serum albumins due to the spatial hindrance of the albumins binding domains. The spatial arrangement of the bilirubin bound to serum albumin along with the studied mutagens was modelled using ligand docking, which revealed a possibility of an arrangement of the both bilirubin and 2-aminofluorene and 2,4,7-trinitrofluorenone in the primary binding site of human serum albumin.

  17. Linear Systems on Tropical Curves

    CERN Document Server

    Haase, Christian; Yu, Josephine

    2009-01-01

    A tropical curve \\Gamma is a metric graph with possibly unbounded edges, and tropical rational functions are continuous piecewise linear functions with integer slopes. We define the complete linear system |D| of a divisor D on a tropical curve \\Gamma analogously to the classical counterpart. We investigate the structure of |D| as a cell complex and show that linear systems are quotients of tropical modules, finitely generated by vertices of the cell complex. Using a finite set of generators, |D| defines a map from \\Gamma to a tropical projective space, and the image can be extended to a tropical curve of degree equal to \\deg(D). The tropical convex hull of the image realizes the linear system |D| as a polyhedral complex. We show that curves for which the canonical divisor is not very ample are hyperelliptic. We also show that the Picard group of a \\Q-tropical curve is a direct limit of critical groups of finite graphs converging to the curve.

  18. A vibrational circular dichroism implementation within a Slater-type-orbital based density functional framework and its application to hexa- and hepta-helicenes

    NARCIS (Netherlands)

    Baerends, Evert; Neugebauer, Johannes; Nicu, Valentin; Wolff, Stephen

    2008-01-01

    We describe the implementation of the rotational strengths for vibrational circular dichroism (VCD) in the Slater-type orbital based Amsterdam Density Functional (ADF) package. We show that our implementation, which makes use of analytical derivative techniques and London atomic orbitals, yields o

  19. Prediction and cloning linear Tcell epitopes of P14-3-3 antigen into pEGFP–N1 as a DNA vaccine model to induse immuno response against hydatidosis and it\\'s expression in CHO cell line

    Directory of Open Access Journals (Sweden)

    R mesri

    2015-11-01

    Full Text Available ABSTRACT Background & purpose: Hydatidosis is a zoonotic disease that caused by infection with the larvae of Echinococcus granulosus. Different antigens produced in larval stage of this parasite that recombinant vaccine base these antigens created significant immunity in infected animals. One of the important antigens is p14-3-3 that it's recombinant antigen created considerable immunity in mouse models. In this study according to the high immunity of antigen epitopes region the coding sequence of T-cell epitopes of P14-3-3 was cloned into pEGFP-N1vector in order to produce an effective DNA vaccine model to stimulate high level of Th1 immune response.   Material and method: In this study bioinformatics tools were used to prediction of linear T-Cell epitopes of Echinococcus granulosus P14-3-3 &zeta antigen. The nucleotide coding sequence of these epitopes was synthesized by PCR. the ampliqon was digested with XhoI restriction enzyme and cloned into pEGFP–N1 vector That has been purificated by modified sambrook method with CaCl2 and PEG6000..Positive colony was selected by direct colony PCR and confirmed by the sequencing.and evaluation of it's expression in Eukaryotic cells was done by transformed to CHO cell line with electroporation. Results: Linear T-cell epitopes of Echinococcus granulosus P14-3-3 after prediction,synthesis and amplification wae successfully cloned into pEGFP-N1 vector that purificated by new method with maximum vector and minimum RNA concentration.The expression of new constract in CHO cell line as a eukaryotic cells achivment by fluorescent microscope and will be used as a DNA vaccine model to evaluation immuno response in mouse models.   Discussion: Successfully cloning of The linear T-cell epitppes coding sequence of Echinococcus granulosus P14-3-3&zeta antigen into pEGFP-N1 verificated by sequencing and fluorscent microscope images demonstrated expression of recombinant protein in CHO cell line

  20. Non linear system become linear system

    Directory of Open Access Journals (Sweden)

    Petre Bucur

    2007-01-01

    Full Text Available The present paper refers to the theory and the practice of the systems regarding non-linear systems and their applications. We aimed the integration of these systems to elaborate their response as well as to highlight some outstanding features.

  1. Basic linear algebra

    CERN Document Server

    Blyth, T S

    2002-01-01

    Basic Linear Algebra is a text for first year students leading from concrete examples to abstract theorems, via tutorial-type exercises. More exercises (of the kind a student may expect in examination papers) are grouped at the end of each section. The book covers the most important basics of any first course on linear algebra, explaining the algebra of matrices with applications to analytic geometry, systems of linear equations, difference equations and complex numbers. Linear equations are treated via Hermite normal forms which provides a successful and concrete explanation of the notion of linear independence. Another important highlight is the connection between linear mappings and matrices leading to the change of basis theorem which opens the door to the notion of similarity. This new and revised edition features additional exercises and coverage of Cramer's rule (omitted from the first edition). However, it is the new, extra chapter on computer assistance that will be of particular interest to readers:...

  2. Linear collider: a preview

    Energy Technology Data Exchange (ETDEWEB)

    Wiedemann, H.

    1981-11-01

    Since no linear colliders have been built yet it is difficult to know at what energy the linear cost scaling of linear colliders drops below the quadratic scaling of storage rings. There is, however, no doubt that a linear collider facility for a center of mass energy above say 500 GeV is significantly cheaper than an equivalent storage ring. In order to make the linear collider principle feasible at very high energies a number of problems have to be solved. There are two kinds of problems: one which is related to the feasibility of the principle and the other kind of problems is associated with minimizing the cost of constructing and operating such a facility. This lecture series describes the problems and possible solutions. Since the real test of a principle requires the construction of a prototype I will in the last chapter describe the SLC project at the Stanford Linear Accelerator Center.

  3. Linearity in Process Languages

    DEFF Research Database (Denmark)

    Nygaard, Mikkel; Winskel, Glynn

    2002-01-01

    The meaning and mathematical consequences of linearity (managing without a presumed ability to copy) are studied for a path-based model of processes which is also a model of affine-linear logic. This connection yields an affine-linear language for processes, automatically respecting open-map bisi......The meaning and mathematical consequences of linearity (managing without a presumed ability to copy) are studied for a path-based model of processes which is also a model of affine-linear logic. This connection yields an affine-linear language for processes, automatically respecting open......-map bisimulation, in which a range of process operations can be expressed. An operational semantics is provided for the tensor fragment of the language. Different ways to make assemblies of processes lead to different choices of exponential, some of which respect bisimulation....

  4. Adding linear orders

    CERN Document Server

    Shelah, Saharon

    2011-01-01

    We address the following question: Can we expand an NIP theory by adding a linear order such that the expansion is still NIP? Easily, if acl(A)=A for all A, then this is true. Otherwise, we give counterexamples. More precisely, there is a totally categorical theory for which every expansion by a linear order has IP. There is also an \\omega-stable NDOP theory for which every expansion by a linear order interprets bounded arithmetic.

  5. Matrices and linear transformations

    CERN Document Server

    Cullen, Charles G

    1990-01-01

    ""Comprehensive . . . an excellent introduction to the subject."" - Electronic Engineer's Design Magazine.This introductory textbook, aimed at sophomore- and junior-level undergraduates in mathematics, engineering, and the physical sciences, offers a smooth, in-depth treatment of linear algebra and matrix theory. The major objects of study are matrices over an arbitrary field. Contents include Matrices and Linear Systems; Vector Spaces; Determinants; Linear Transformations; Similarity: Part I and Part II; Polynomials and Polynomial Matrices; Matrix Analysis; and Numerical Methods. The first

  6. Linear models with R

    CERN Document Server

    Faraway, Julian J

    2014-01-01

    A Hands-On Way to Learning Data AnalysisPart of the core of statistics, linear models are used to make predictions and explain the relationship between the response and the predictors. Understanding linear models is crucial to a broader competence in the practice of statistics. Linear Models with R, Second Edition explains how to use linear models in physical science, engineering, social science, and business applications. The book incorporates several improvements that reflect how the world of R has greatly expanded since the publication of the first edition.New to the Second EditionReorganiz

  7. Linear integrated circuits

    CERN Document Server

    Carr, Joseph

    1996-01-01

    The linear IC market is large and growing, as is the demand for well trained technicians and engineers who understand how these devices work and how to apply them. Linear Integrated Circuits provides in-depth coverage of the devices and their operation, but not at the expense of practical applications in which linear devices figure prominently. This book is written for a wide readership from FE and first degree students, to hobbyists and professionals.Chapter 1 offers a general introduction that will provide students with the foundations of linear IC technology. From chapter 2 onwa

  8. Charges for linearized gravity

    CERN Document Server

    Aksteiner, Steffen

    2013-01-01

    Maxwell test fields as well as solutions of linearized gravity on the Kerr exterior admit non-radiating modes, i.e. non-trivial time-independent solutions. These are closely related to conserved charges. In this paper we discuss the non-radiating modes for linearized gravity, which may be seen to correspond to the Poincare Lie-algebra. The 2-dimensional isometry group of Kerr corresponds to a 2-parameter family of gauge-invariant non-radiating modes representing infinitesimal perturbations of mass and azimuthal angular momentum. We calculate the linearized mass charge in terms of linearized Newman-Penrose scalars.

  9. X-ray magnetic dichroism: from quantitative determination of magnetic moments to imaging of magnetization dynamics; Dichroisme magnetique des rayons X: de la determination quantitative des moments magnetiques a l'imagerie de la dynamique de l'aimantation

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, J

    2006-03-15

    In this document, I use some results of my research activities of the last ten years to show the power of x-ray magnetic dichroism for determining magnetic properties of thin layers, multilayers and nano-structures. The use of sum rules for x-ray dichroism allows a quantitative determination of the spin and orbital contributions to the magnetic moment, for each element of a heterogeneous material separately. Used in a qualitative way, x-ray dichroism allows monitoring the magnetization of the different layers in a multilayer material as a function of applied field. In combination with the temporal structure of synchrotron radiation, it is possible to study fast magnetization reversal with element selectivity, which is important for devices like spin valves and magnetic tunnel junctions. Adding the spatial resolution of a photoelectron emission microscope (PEEM), it becomes possible to study all the details of the fast magnetization reversal in complex magnetic systems. (author)

  10. Linear Rogue waves

    CERN Document Server

    Yuce, C

    2015-01-01

    We predict the existence of linear discrete rogue waves. We discuss that Josephson effect is the underlying reason for the formation of such waves. We study linear rogue waves in continuous system and present an exact analytical rogue wave solution of the Schrodinger-like equation.

  11. Linearized Wenger graphs

    OpenAIRE

    2014-01-01

    © 2015 Elsevier B.V. Motivated by recent extensive studies on Wenger graphs, we introduce a new infinite class of bipartite graphs of a similar type, called linearized Wenger graphs. The spectrum, diameter and girth of these linearized Wenger graphs are determined.

  12. Efficient Non Linear Loudspeakers

    DEFF Research Database (Denmark)

    Petersen, Bo R.; Agerkvist, Finn T.

    2006-01-01

    Loudspeakers have traditionally been designed to be as linear as possible. However, as techniques for compensating non linearities are emerging, it becomes possible to use other design criteria. This paper present and examines a new idea for improving the efficiency of loudspeakers at high levels...... by changing the voice coil layout. This deliberate non-linear design has the benefit that a smaller amplifier can be used, which has the benefit of reducing system cost as well as reducing power consumption.......Loudspeakers have traditionally been designed to be as linear as possible. However, as techniques for compensating non linearities are emerging, it becomes possible to use other design criteria. This paper present and examines a new idea for improving the efficiency of loudspeakers at high levels...

  13. Linear algebra done right

    CERN Document Server

    Axler, Sheldon

    2015-01-01

    This best-selling textbook for a second course in linear algebra is aimed at undergrad math majors and graduate students. The novel approach taken here banishes determinants to the end of the book. The text focuses on the central goal of linear algebra: understanding the structure of linear operators on finite-dimensional vector spaces. The author has taken unusual care to motivate concepts and to simplify proofs. A variety of interesting exercises in each chapter helps students understand and manipulate the objects of linear algebra. The third edition contains major improvements and revisions throughout the book. More than 300 new exercises have been added since the previous edition. Many new examples have been added to illustrate the key ideas of linear algebra. New topics covered in the book include product spaces, quotient spaces, and dual spaces. Beautiful new formatting creates pages with an unusually pleasant appearance in both print and electronic versions. No prerequisites are assumed other than the ...

  14. Direct evidence of Ni magnetic moment in TbNi{sub 2}Mn—X-ray magnetic circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Yu, D.H., E-mail: dyu@ansto.gov.au [Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, Sydney, NSW 2234 (Australia); Huang, Meng-Jie [National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China); Wang, J.L. [Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, Sydney, NSW 2234 (Australia); School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Canberra at the Australian Defense Force Academy, Sydney, ACT 2600 (Australia); Institute for Superconductivity and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); Su, Hui-Chia; Lin, Hong-Ji; Chen, Chien-Te [National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu 30076, Taiwan (China); Campbell, S.J. [School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Canberra at the Australian Defense Force Academy, Sydney, ACT 2600 (Australia)

    2014-12-15

    We have investigated the individual magnetic moments of Ni, Mn and Tb atoms in the intermetallic compound TbNi{sub 2}Mn in the Laves phase (magnetic phase transition temperature T{sub C} ∼131 K) by X-ray magnetic circular dichroism (XMCD) studies at 300 K, 80 K and 20 K. Analyses of the experimental results reveal that Ni atoms at 20 K in an applied magnetic field of 1 T carry an intrinsic magnetic moment of spin and orbital magnetic moment contributions 0.53±0.01 μ{sub B} and 0.05±0.01 μ{sub B}, respectively. These moment values are similar to those of the maximum saturated moment of Ni element. A very small magnetic moment of order <0.1 μ{sub B} has been measured for Mn. This suggests that Mn is antiferromagnetically ordered across the two nearly equally occupied sites of 16d and 8a. A magnetic moment of up to ∼0.3 μ{sub B} has been observed for the Tb atoms. Identification of a magnetic moment on the Ni atoms has provided further evidence for the mechanism of enhancement of the magnetic phase transition temperature in TbNi{sub 2}Mn compared with TbNi{sub 2} (T{sub C}∼37.5 K) and TbMn{sub 2} (T{sub C}∼54 K) due to rare earth–transition metal (R–T) and transition metal–transition metal (T–T) interactions. The behaviour of the X-ray magnetic circular dichroism spectra of TbNi{sub 2}Mn at 300 K, 80 K and 20 K – above and below the magnetic ordering temperature T{sub C} ∼131 K – is discussed. - Highlights: • We study the magnetic moment of TbNi{sub 2}Mn with XMCD. • We observe directly the Ni intrinsic magnetic moment in TbNi{sub 2}Mn. • We find that Mn ordered antiferromagnetically across the 16d and 8a sites. • We confirm the mechanism for increasing the magnetic phase transition temperature.

  15. SU-F-BRD-16: Relative Biological Effectiveness of Double-Strand Break Induction for Modeling Cell Survival in Pristine Proton Beams of Different Dose-Averaged Linear Energy Transfers

    Energy Technology Data Exchange (ETDEWEB)

    Peeler, C; Bronk, L [UT MD Anderson Cancer Center, Houston, TX (United States); UT Graduate School of Biomedical Sciences at Houston, Houston, TX (United States); Taleei, R; Guan, F; Patel, D; Titt, U; Mirkovic, D; Grosshans, D; Mohan, R [UT MD Anderson Cancer Center, Houston, TX (United States); Stewart, R [University of Washington School of Medicine, Seattle, WA (United States)

    2015-06-15

    Purpose: High throughput in vitro experiments assessing cell survival following proton radiation indicate that both the alpha and the beta parameters of the linear quadratic model increase with increasing proton linear energy transfer (LET). We investigated the relative biological effectiveness (RBE) of double-strand break (DSB) induction as a means of explaining the experimental results. Methods: Experiments were performed with two lung cancer cell lines and a range of proton LET values (0.94 – 19.4 keV/µm) using an experimental apparatus designed to irradiate cells in a 96 well plate such that each column encounters protons of different dose-averaged LET (LETd). Traditional linear quadratic survival curve fitting was performed, and alpha, beta, and RBE values obtained. Survival curves were also fit with a model incorporating RBE of DSB induction as the sole fit parameter. Fitted values of the RBE of DSB induction were then compared to values obtained using Monte Carlo Damage Simulation (MCDS) software and energy spectra calculated with Geant4. Other parameters including alpha, beta, and number of DSBs were compared to those obtained from traditional fitting. Results: Survival curve fitting with RBE of DSB induction yielded alpha and beta parameters that increase with proton LETd, which follows from the standard method of fitting; however, relying on a single fit parameter provided more consistent trends. The fitted values of RBE of DSB induction increased beyond what is predicted from MCDS data above proton LETd of approximately 10 keV/µm. Conclusion: In order to accurately model in vitro proton irradiation experiments performed with high throughput methods, the RBE of DSB induction must increase more rapidly than predicted by MCDS above LETd of 10 keV/µm. This can be explained by considering the increased complexity of DSBs or the nature of intra-track pairwise DSB interactions in this range of LETd values. NIH Grant 2U19CA021239-35.

  16. Structure Effect of Some New Anticancer Pt(II) Complexes of Amino Acid Derivatives with Small Branched or Linear Hydrocarbon Chains on Their DNA Interaction.

    Science.gov (United States)

    Kantoury, Mahshid; Eslami Moghadam, Mahboube; Tarlani, Ali Akbar; Divsalar, Adeleh

    2016-07-01

    The aim of this study was to investigate the structure effect and identify the modes of binding of amino acid-Pt complexes to DNA molecule for cancer treatment. Hence, three novel water soluble platinum complexes, [Pt(phen)(R-gly)]NO3 (where phen is 1,10-phenanthroline, R-gly is methyl, amyl, and isopentyl-glycine), have been synthesized and characterized by spectroscopic methods, conductivity measurements, and chemical analysis. The anticancer activities of synthesized complexes were investigated against human breast cancer cell line of MDA-MB 231. The 50% cytotoxic concentration values were determined to be 42.5, 58, and 70 μm for methyl-, amyl-, and isopentyl-gly complexes, respectively. These complexes were interacted with calf thymus DNA (ct-DNA) via positive cooperative interaction. The modes of binding of the complexes to DNA were investigated by fluorescence spectroscopy and circular dichroism in combination with a molecular docking study. The result indicates that complexes with small or branched hydrocarbon chains can intercalate with DNA. This is while amyl complexes with linear chains interacted additionally via groove binding. The results of the negative value of Gibbs energy for binding of isopentyl-platinum to DNA and those of the molecular docking were coherent. Furthermore, the docking results demonstrated that hydrophobic interaction plays an important role in the complex-DNA interaction.

  17. UV-visible microscope spectrophotometric polarization and dichroism with increased discrimination power in forensic analysis

    Science.gov (United States)

    Purcell, Dale Kevin

    merit investigated included: 1) wavelength accuracy, 2) wavelength precision, 3) wavelength resolution stability, 4) photometric accuracy, 5) photometric precision, 6) photometric linearity, 7) photometric noise, and 8) short-term baseline stability. In addition, intrinsic instrument polarization effects were investigated to determine the impact of these properties on spectral interpretation and data quality. Finally, a set of recommendations were developed which describe instrument performance characteristics for microscope and spectrometer features and functions, and specific instrument parameters that must be controlled in order to acquire high quality data from an ultraviolet-visible forensic microscope spectrophotometer system for increased discrimination power.

  18. Applied linear regression

    CERN Document Server

    Weisberg, Sanford

    2005-01-01

    Master linear regression techniques with a new edition of a classic text Reviews of the Second Edition: ""I found it enjoyable reading and so full of interesting material that even the well-informed reader will probably find something new . . . a necessity for all of those who do linear regression."" -Technometrics, February 1987 ""Overall, I feel that the book is a valuable addition to the now considerable list of texts on applied linear regression. It should be a strong contender as the leading text for a first serious course in regression analysis."" -American Scientist, May-June 1987

  19. Linear associative algebras

    CERN Document Server

    Abian, Alexander

    1973-01-01

    Linear Associative Algebras focuses on finite dimensional linear associative algebras and the Wedderburn structure theorems.The publication first elaborates on semigroups and groups, rings and fields, direct sum and tensor product of rings, and polynomial and matrix rings. The text then ponders on vector spaces, including finite dimensional vector spaces and matrix representation of vectors. The book takes a look at linear associative algebras, as well as the idempotent and nilpotent elements of an algebra, ideals of an algebra, total matrix algebras and the canonical forms of matrices, matrix

  20. Applied linear regression

    CERN Document Server

    Weisberg, Sanford

    2013-01-01

    Praise for the Third Edition ""...this is an excellent book which could easily be used as a course text...""-International Statistical Institute The Fourth Edition of Applied Linear Regression provides a thorough update of the basic theory and methodology of linear regression modeling. Demonstrating the practical applications of linear regression analysis techniques, the Fourth Edition uses interesting, real-world exercises and examples. Stressing central concepts such as model building, understanding parameters, assessing fit and reliability, and drawing conclusions, the new edition illus

  1. Elements of linear space

    CERN Document Server

    Amir-Moez, A R; Sneddon, I N

    1962-01-01

    Elements of Linear Space is a detailed treatment of the elements of linear spaces, including real spaces with no more than three dimensions and complex n-dimensional spaces. The geometry of conic sections and quadric surfaces is considered, along with algebraic structures, especially vector spaces and transformations. Problems drawn from various branches of geometry are given.Comprised of 12 chapters, this volume begins with an introduction to real Euclidean space, followed by a discussion on linear transformations and matrices. The addition and multiplication of transformations and matrices a

  2. Matrices and linear algebra

    CERN Document Server

    Schneider, Hans

    1989-01-01

    Linear algebra is one of the central disciplines in mathematics. A student of pure mathematics must know linear algebra if he is to continue with modern algebra or functional analysis. Much of the mathematics now taught to engineers and physicists requires it.This well-known and highly regarded text makes the subject accessible to undergraduates with little mathematical experience. Written mainly for students in physics, engineering, economics, and other fields outside mathematics, the book gives the theory of matrices and applications to systems of linear equations, as well as many related t

  3. Multiband Circular Polarizer Based on Fission Transmission of Linearly Polarized Wave for X-Band Applications

    Directory of Open Access Journals (Sweden)

    Farman Ali Mangi

    2016-01-01

    Full Text Available A multiband circular polarizer based on fission transmission of linearly polarized wave for x-band application is proposed, which is constructed of 2 × 2 metallic strips array. The linear-to-circular polarization conversion is obtained by decomposing the linearly incident x-polarized wave into two orthogonal vector components of equal amplitude and 90° phase difference between them. The innovative approach of “fission transmission of linear-to-circular polarized wave” is firstly introduced to obtain giant circular dichroism based on decomposition of orthogonal vector components through the structure. It means that the incident linearly polarized wave is converted into two orthogonal components through lower printed metallic strips layer and two transmitted waves impinge on the upper printed strips layer to convert into four orthogonal vector components at the end of structure. This projection and transmission sequence of orthogonal components sustain the chain transmission of electromagnetic wave and can achieve giant circular dichroism. Theoretical analysis and microwave experiments are presented to validate the performance of the structure. The measured results are in good agreement with simulation results. In addition, the proposed circular polarizer exhibits the optimal performance with respect to the normal incidence. The right handed circularly polarized wave is emitted ranging from 10.08 GHz to 10.53 GHz and 10.78 GHz to 11.12 GHz, while the left handed circular polarized wave is excited at 10.54 GHz–10.70 GHz and 11.13 GHz–11.14 GHz, respectively.

  4. Evaluation of cathepsin B activity for degrading collagen IV using a surface plasmon resonance method and circular dichroism spectroscopy.

    Science.gov (United States)

    Shoji, Atsushi; Kabeya, Mitsutaka; Ishida, Yuuki; Yanagida, Akio; Shibusawa, Yoichi; Sugawara, Masao

    2014-07-01

    Evaluation of cathepsin B activities for degrading collagen IV and heat-denatured collagen IV (gelatin) were performed by surface plasmon resonance (SPR) and circular dichroism (CD) measurements. The optimal pH of cathepsin B activity for degrading each substrate was around 4.0. The ΔRU(15 min), which is a decrease in the SPR signal at 15 min after injection of cathepsin B, was smaller for collagen IV than for heat-denatured collagen IV owing to the presence of triple-helical conformation. An unstable nature of the triple-helical conformation of collagen IV at pH 4.0 was shown by the CD study. Degrading collagen IV by cathepsin B was facilitated owing to a local unwinding of the triple-helical conformation caused by proteolytic cleavage of the non-helical region. The concentration dependence of the initial velocity for degrading collagen IV by cathepsin B at pH 4.0 was biphasic, showing that cathepsin B at low concentration exhibits exopeptidase activity, while the enzyme at high concentration exhibits endopeptidase activity. The kinetic parameters for the exopeptidase activity of cathepsin B toward collagen IV and heat-treated collagen IV were evaluated and discussed in terms of the protease mechanism.

  5. Plasmonic circular dichroism of 310- and α-helix using a discrete interaction model/quantum mechanics method.

    Science.gov (United States)

    Chulhai, Dhabih V; Jensen, Lasse

    2015-05-28

    Plasmonic circular dichroism (CD) of chiral molecules in the near field of plasmonic nanoparticles (NPs) may be used to enhance molecular CD signatures or to induce a CD signal at the plasmon resonance. A recent few-states theory explored these effects for model systems and showed an orientation dependence of the sign of the induced CD signal for spherical NPs. Here, we use the discrete interaction model/quantum mechanical (DIM/QM) method to simulate the CD and plasmonic CD of the 310- and α-helix conformations of a short alanine peptide. We find that the interactions between the molecule and the plasmon lead to significant changes in the CD spectra. In the plasmon region, we find that the sign of the CD depends strongly on the orientation of the molecule as well as specific interactions with the NP through image dipole effects. A small enhancement of the CD is found in the molecular region of the spectrum, however, the molecular signatures may be significantly altered through interactions with the NP. We also show that the image dipole effect can result in induced plasmonic CD even for achiral molecules. Overall, we find that the specific interactions with the NP can lead to large changes to the CD spectrum that complicates the interpretation of the results.

  6. IR and Vibrational Circular Dichroism Spectroscopy of Matrine- and Artemisinin-Type Herbal Products: Stereochemical Characterization and Solvent Effects.

    Science.gov (United States)

    Zhang, Yuefei; Poopari, M Reza; Cai, Xiaoli; Savin, Aliaksandr; Dezhahang, Zahra; Cheramy, Joseph; Xu, Yunjie

    2016-04-22

    Five Chinese herbal medicines--matrine, oxymatrine, sophoridine, artemisinin, and dihydroartemisinin--were investigated using vibrational circular dichroism (VCD) experiments and density functional theory calculations to extract their stereochemical information. The three matrine-type alkaloids are available from the dry roots of Sophora flavescens and have long been used in various traditional Chinese herbal medicines to combat diseases such as cancer and cardiac arrhythmia. Artemisinin and the related dihydroartemisinin, discovered in 1979 by Professor Youyou Tu, a 2015 Nobel laureate in medicine, are effective drugs for the treatment of malaria. The VCD measurements were carried out in CDCl3 and DMSO-d6, two solvents with different dielectric constants and hydrogen-bonding characteristics. A "clusters-in-a-liquid" approach was used to model both explicit and implicit solvent effects. The studies show that effectively accounting for solvent effects is critical to using IR and VCD spectroscopy to provide unique spectroscopic features to differentiate the potential stereoisomers of these Chinese herbal medicines.

  7. X-ray absorption spectroscopy and magnetic circular dichroism studies of L10-Mn-Ga thin films

    Science.gov (United States)

    Glas, M.; Sterwerf, C.; Schmalhorst, J. M.; Ebke, D.; Jenkins, C.; Arenholz, E.; Reiss, G.

    2013-11-01

    Tetragonally distorted Mn3-xGax thin films with 0.1magnetic anisotropy and low magnetization and thus have the potential to serve as electrodes in spin transfer torque magnetic random access memory. Because a direct capping of these films with MgO is problematic due to oxide formation, we examined the influence of a CoFeB interlayer and of two different deposition methods for the MgO barrier on the formation of interfacial Mn-O for Mn62Ga38 by element specific X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD). A highly textured L10 crystal structure of the Mn-Ga films was verified by X-ray diffraction measurements. For samples with e-beam evaporated MgO barrier no evidence for Mn-O was found whereas in samples with magnetron sputtered MgO, Mn-O was detected, even for the thickest interlayer thickness. Both XAS and XMCD measurements showed an increasing interfacial Mn-O amount with decreasing CoFeB interlayer thickness. Additional element specific full hysteresis loops determined an out-of-plane magnetization axis for the Mn and Co, respectively.

  8. Alkali-hydrolysis of D-glucono-delta-lactone studied by chiral Raman and circular dichroism spectroscopies

    Institute of Scientific and Technical Information of China (English)

    JIA GuoQing; QIU Shi; LI GuanNa; ZHOU Jun; FENG ZhaoChi; LI Can

    2009-01-01

    The alkali-hydrolysis of D-glucono-delta-lactone (GDL) was investigated by chiral Raman and circular dichroism (CD) spectroecopies in combination with density functional theory calculation. Based on the characteristic CD bands of GDL and its hydrolysis product, the dynamics of hydrolysis was studied using stopped-flow CD method. Using chiral Raman spectroscopy (CRS), the stereochemical change of GDL owing to the hydrolysis reaction was discussed on the vibrational scale. The CRS results show that the ring-opening due to hydrolysis has a great influence on the chiral structure around the cer-bonyl group, which was evidenced by the disappearance of the CRS band at 1735 cm-1 (C=0 stretching vibrational mode). In addition, the change of positions and intensity of CRS bands was also observed, which was ascribed to the perturbation around the C2, C3, C4 and C5 carbons due to ring-opening. It is worthy to note that the stereochemistry of C2, C3, C4 and C5 had no fundamental change during the hydrolysis reaction, which was reflected in the maintenance of the signs of the CRS bands. Our results demonstrate that in comparison with CD technique, CRS may provide more detailed structural infor-mation of chiral molecules and open up new vistas of research for chirel reactions.

  9. Alkali-hydrolysis of D-glucono-delta-lactone studied by chiral Raman and circular dichroism spectroscopies

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The alkali-hydrolysis of D-glucono-delta-lactone (GDL) was investigated by chiral Raman and circular dichroism (CD) spectroscopies in combination with density functional theory calculation. Based on the characteristic CD bands of GDL and its hydrolysis product, the dynamics of hydrolysis was studied using stopped-flow CD method. Using chiral Raman spectroscopy (CRS), the stereochemical change of GDL owing to the hydrolysis reaction was discussed on the vibrational scale. The CRS results show that the ring-opening due to hydrolysis has a great influence on the chiral structure around the car-bonyl group, which was evidenced by the disappearance of the CRS band at 1735 cm-1 (C== O stretching vibrational mode). In addition, the change of positions and intensity of CRS bands was also observed, which was ascribed to the perturbation around the C2, C3, C4 and C5 carbons due to ring-opening. It is worthy to note that the stereochemistry of C2, C3, C4 and C5 had no fundamental change during the hydrolysis reaction, which was reflected in the maintenance of the signs of the CRS bands. Our results demonstrate that in comparison with CD technique, CRS may provide more detailed structural information of chiral molecules and open up new vistas of research for chiral reactions.

  10. Competitive binding of (-)-epigallocatechin-3-gallate and 5-fluorouracil to human serum albumin: A fluorescence and circular dichroism study

    Science.gov (United States)

    Yuan, Lixia; Liu, Min; Liu, Guiqin; Li, Dacheng; Wang, Zhengping; Wang, Bingquan; Han, Jun; Zhang, Min

    2017-02-01

    Combination therapy with more than one therapeutic agent can improve therapeutic efficiency and decrease drug resistance. In this study, the interactions of human serum albumin (HSA) with individual or combined anticancer drugs, (-)-epigallocatechin-3-gallate (EGCG) and 5-fluorouracil (FU), were investigated by fluorescence and circular dichroism (CD) spectroscopy. The results demonstrated that the interaction of EGCG or FU with HSA is a process of static quenching and EGCG formed a more stable complex. The competitive experiments of site markers suggested that both anti-carcinogens mainly bound to site I (subdomain IIA). The interaction forces which play important roles in the binding process were discussed based on enthalpy and entropy changes. Moreover, the competition binding model for a ternary system was proposed so as to precisely calculate the binding parameters. The results demonstrated that one drug decreased the binding affinity of another drug with HSA, resulting in the increasing free drug concentration at the action sites. CD studies indicated that there was an alteration in HSA secondary structure due to the binding of EGCG and FU. It can be concluded that the combination of EGCG with FU may enhance anticancer efficacy. This finding may provide a theoretical basis for clinical treatments.

  11. Vibrational circular dichroism from ab initio molecular dynamics and nuclear velocity perturbation theory in the liquid phase

    Science.gov (United States)

    Scherrer, Arne; Vuilleumier, Rodolphe; Sebastiani, Daniel

    2016-08-01

    We report the first fully ab initio calculation of dynamical vibrational circular dichroism spectra in the liquid phase using nuclear velocity perturbation theory (NVPT) derived electronic currents. Our approach is rigorous and general and thus capable of treating weak interactions of chiral molecules as, e.g., chirality transfer from a chiral molecule to an achiral solvent. We use an implementation of the NVPT that is projected along the dynamics to obtain the current and magnetic dipole moments required for accurate intensities. The gauge problem in the liquid phase is resolved in a twofold approach. The electronic expectation values are evaluated in a distributed origin gauge, employing maximally localized Wannier orbitals. In a second step, the gauge invariant spectrum is obtained in terms of a scaled molecular moments, which allows to systematically include solvent effects while keeping a significant signal-to-noise ratio. We give a thorough analysis and discussion of this choice of gauge for the liquid phase. At low temperatures, we recover the established double harmonic approximation. The methodology is applied to chiral molecules ((S)-d2-oxirane and (R)-propylene-oxide) in the gas phase and in solution. We find an excellent agreement with the theoretical and experimental references, including the emergence of signals due to chirality transfer from the solute to the (achiral) solvent.

  12. Photoinduced dichroism and surface-relief-gratings of hyperbranched azo polymers synthesized by azo-coupling reaction

    Institute of Scientific and Technical Information of China (English)

    CHE Pengchao; HE Yaning; WANG Xiaogong

    2007-01-01

    This article reports the synthesis and photoresponsive properties of a hyperbranched azo polymer containing electron donor-acceptor type azo chromophores both in backbone and peripheral positions.For the synthesis,a hyperbranched azo precursor polymer was synthesized by step-growth polymerization of an AB2 monomer,bis[2-(N-ethylanilino)ethyl] 5-aminoisophthalate,through azocoupling reaction.The hyperbranched precursor polymer was then reacted with the diazonium salt from 4-cyanoaniline to introduce donor-acceptor azo chromophores in the peripheral groups.The resulting azo polymers were characterized by the spectroscopic methods and thermal analysis.The photo-induced dichroism of the hyperbranched polymer was studied and its orientation order parameter was estimated to be 0.063.Thin films of the hyperbranched azo polymers were used to fabricate surface-relief-gratings (SRGs) by exposing them to an interference pattern of Ar+ laser beam at modest intensities (150 mW/cm2).The azo chromophores introduced by postazo-coupling reaction at the para-positions of the peripheral azobenzenes shows a significant effect on the SRG inscription rate.The hyperbranched azo polymers can potentially be used for applications such as reversible optical data storage,photoswitch,sensors,and other photo-driven devices.

  13. Co K-edge magnetic circular dichroism across the spin state transition in LaCoO3 single crystal

    Science.gov (United States)

    Efimov, V.; Ignatov, A.; Troyanchuk, I. O.; Sikolenko, V. V.; Rogalev, A.; Wilhelm, F.; Efimova, E.; Tiutiunnikov, S. I.; Karpinsky, D.; Kriventsov, V.; Yakimchuk, E.; Molodtsov, S.; Sainctavit, P.; Prabhakaran, D.

    2016-05-01

    We report on Co K-edge x-ray magnetic circular dichroism (XMCD) measurements of LaCoO3 single crystal in temperature range from 5 to 300 K and external magnetic field of 17 T. The response consists of pre-edge (at 7712 eV) and bi-polar peak (up at 7727, down at 7731 eV) with amplitudes, respectively, less than 10-3 and 10-2 of the Co K-edge jump. Using the sum rule the orbital magnetic moment of 4p Co is evaluated. Its temperature dependence reaches a maximum of (2.7 ± 0.9) x10-3 μB at 120 K, following the trend for the total magnetic moment on the Co obtained from the superconducting quantum interference device measurements. However, on warming from 25 to 120 K, the orbital magnetic moment of the 4p Co doubles while total magnetic moment of Co increases 10 times. First principle calculations are in order to relate the Co K-edge XMCD results to the orbital and spin moment of 3d Co.

  14. X-ray magnetic circular dichroism and reflection anisotropy spectroscopy Kerr effect studies of capped magnetic nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Cunniffe, J. P.; McNally, D.E.; Liberati, M.; Arenholz, E.; McGuinness, C.; McGilp, J. F.

    2010-03-02

    Aligned Co wires grown on Pt(997) under ultra-high vacuum conditions have been capped successfully by the epitaxial growth of Au monolayers (ML) at room temperature. The samples were kept under vacuum except when transferring between apparatus or when making some of the measurements. No degradation of the Co wires was detected during the measurements. The magneto-optic response of the system was measured using X-ray magnetic circular dichroism (XMCD) at the Co L{sub 2,3} edge and reflection anisotropy spectroscopy (RAS) at near normal incidence, which is sensitive to the normal component of the out-of-plane magnetization via the Kerr effect (MOKE). Capping the wires significantly impacts their magnetic properties. Comparison of the magneto-optic response of the system at X-ray and optical energies reveals small differences that are attributed to the induced moment in the Pt substrate and Au capping layer not picked up by the element specific XMCD measurements. The sensitivity of RAS-MOKE is sufficient to allow the determination of the easy axis direction of the capped wires to within a few degrees. The results for a 6-atom-wide Co wire sample, capped with 6 ML of Au, are consistent with the capped wires possessing perpendicular magnetization.

  15. Silica as a Matrix for Encapsulating Proteins: Surface Effects on Protein Structure Assessed by Circular Dichroism Spectroscopy

    Directory of Open Access Journals (Sweden)

    Genet H. Zemede

    2012-08-01

    Full Text Available The encapsulation of biomolecules in solid materials that retain the native properties of the molecule is a desired feature for the development of biosensors and biocatalysts. In the current study, protein entrapment in silica-based materials is explored using the sol-gel technique. This work surveys the effects of silica confinement on the structure of several model polypeptides, including apomyoglobin, copper-zinc superoxide dismutase, polyglutamine, polylysine, and type I antifreeze protein. Changes in the secondary structure of each protein following encapsulation are monitored by circular dichroism spectroscopy. In many cases, silica confinement reduces the fraction of properly-folded protein relative to solution, but addition of a secondary solute or modification of the silica surface leads to an increase in structure. Refinement of the glass surface by addition of a monosubstituted alkoxysilane during sol-gel processing is shown to be a valuable tool for testing the effects of surface chemistry on protein structure. Because silica entrapment prevents protein aggregation by isolating individual protein molecules in the pores of the glass material, one may monitor aggregation-prone polypeptides under solvent conditions that are prohibited in solution, as demonstrated with polyglutamine and a disease-related variant of superoxide dismutase.

  16. X-ray absorption spectroscopy and magnetic circular dichroism studies of L1{sub 0}-Mn-Ga thin films

    Energy Technology Data Exchange (ETDEWEB)

    Glas, M., E-mail: mglas@physik.uni-bielefeld.de; Sterwerf, C.; Schmalhorst, J. M.; Reiss, G. [Thin Films and Physics of Nanostructures, Bielefeld University, Bielefeld (Germany); Ebke, D. [Thin Films and Physics of Nanostructures, Bielefeld University, Bielefeld (Germany); Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Jenkins, C.; Arenholz, E. [ALS Berkeley, California 94720-8229 (United States)

    2013-11-14

    Tetragonally distorted Mn{sub 3−x}Ga{sub x} thin films with 0.1dichroism (XMCD). A highly textured L1{sub 0} crystal structure of the Mn-Ga films was verified by X-ray diffraction measurements. For samples with e-beam evaporated MgO barrier no evidence for Mn-O was found whereas in samples with magnetron sputtered MgO, Mn-O was detected, even for the thickest interlayer thickness. Both XAS and XMCD measurements showed an increasing interfacial Mn-O amount with decreasing CoFeB interlayer thickness. Additional element specific full hysteresis loops determined an out-of-plane magnetization axis for the Mn and Co, respectively.

  17. Dumbbell-type fullerene-steroid hybrids: a join experimental and theoretical investigation for conformational, configurational, and circular dichroism assignments.

    Science.gov (United States)

    Ruíz, Alberto; Morera-Boado, Cercis; Almagro, Luis; Coro, Julieta; Maroto, Enrique E; Herranz, María Ángeles; Filippone, Salvatore; Molero, Dolores; Martínez-Álvarez, Roberto; Garcia de la Vega, José M; Suárez, Margarita; Martín, Nazario

    2014-04-18

    New [60]fullerene-steroid conjugates (4-6) have been synthesized by 1,3-dipolar cycloaddition and Bingel-Hirsch cyclopropanation reactions from suitably functionalized epiandrosterone and [60]fullerene. Since a new stereocenter is created in the formation of the Prato monoaduct, two different diastereomers were isolated by HPLC (4, 5) whose absolute configurations were assigned according to the highly reliable "sector rule" on fullerenes. A further reaction of the malonate-containing diastereomer 5 with a second C60 molecule has afforded dumbbell fullerene 6 in which the two fullerene units are covalently connected through an epiandrosterone moiety. The new compounds have been spectroscopically characterized and their redox potentials, determined by cyclic voltametry, reveal three reversible reduction waves for hybrids 4 and 5, whereas these signals are split in dumbbell 6. Theoretical calculations at semiempirical (AM1) and single point B3LYP/6-31G(d) levels have predicted the most stable conformations for the hybrid compounds (4-6), showing the importance of the chlorine atom on the D ring of the steroid. Furthermore, TDDFT calculations have allowed assignments of the experimentally determined circular dichroism (CD) of the [60]fullerene-steroid hybrids based on the sign and position of the Cotton effects, despite the exceptionally large systems under study.

  18. Electrochemical reduction of the biliverdin-serum albumin complex as monitored by absorption and circular dichroism spectroscopy.

    Science.gov (United States)

    Claret, J; Ibars, O; Lang, K; Trull, F R; Lightner, D A

    1995-02-23

    The cathodic reduction at the mercury electrode of a biliverdin IX alpha-serum albumin complex at physiological pH in an aqueous buffer containing percentages of DMSO ranging from 4% to 20% is studied by cyclic voltametry and controlled potential coulometry. The progression of pigment disappearance and the (stereochemical) nature of the product are monitored by chromatography, UV-visible absorption and circular dichroism spectroscopy. Upon reduction, albumin-bound biliverdin IX alpha, with a slight preference for the P-helicity, affords the corresponding bound bilirubin IX alpha -with an M-chirality conformation. The complex is reduced at -0.64 V (vs. SCE; 8% DMSO), only a little shifted compared to reduction of free biliverdin IX alpha under the same conditions. In contrast, an analogous bilirubin IX alpha-serum albumin complex is essentially inert towards cathodic reduction under conditions where free bilirubin IX alpha is reduced, indicating a better shielding by the protein of the bilirubin IX alpha molecule from the electrode surface. The presence of relative position (as in the biliverdins IX alpha and XIII alpha) or absence (as in mesobiliverdin IX alpha) of vinyl groups in the pigment does not have a significant effect upon its electroreduction behaviour, indicating that the process is not sensitive to the subtle differences imposed by vinyl groups upon the structure of the corresponding biliverdin-albumin complexes.

  19. X-ray magnetic circular dichroism study of epitaxial magnetite ultrathin film on MgO(100)

    Energy Technology Data Exchange (ETDEWEB)

    Liu, W. Q.; Xu, Y. B., E-mail: yongbing.xu@york.ac.uk, E-mail: rzhang@nju.edu.cn [York-Nanjing International Center for Spintronics (YNICS), School of Electronics Science and Engineering, Nanjing University, Nanjing 210093 (China); Spintronics and Nanodevice Laboratory, Department of Electronics, University of York, York YO10 5DD (United Kingdom); Song, M. Y.; Lin, J. G. [Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan (China); Maltby, N. J.; Li, S. P. [Spintronics and Nanodevice Laboratory, Department of Electronics, University of York, York YO10 5DD (United Kingdom); Samant, M. G.; Parkin, S. S. P. [IBM Research Division, Almaden Research Center, San Jose, California 95120 (United States); Bencok, P.; Steadman, Paul; Dobrynin, Alexey [Diamond Light Source, Didcot OX11 0DE (United Kingdom); Zhang, R., E-mail: yongbing.xu@york.ac.uk, E-mail: rzhang@nju.edu.cn [York-Nanjing International Center for Spintronics (YNICS), School of Electronics Science and Engineering, Nanjing University, Nanjing 210093 (China)

    2015-05-07

    The spin and orbital magnetic moments of the Fe{sub 3}O{sub 4} epitaxial ultrathin film synthesized by plasma assisted simultaneous oxidization on MgO(100) have been studied with X-ray magnetic circular dichroism. The ultrathin film retains a rather large total magnetic moment, i.e., (2.73 ± 0.15) μ{sub B}/f.u., which is ∼70% of that for the bulk-like Fe{sub 3}O{sub 4}. A significant unquenched orbital moment up to 0.54 ± 0.05 μ{sub B}/f.u. was observed, which could come from the symmetry breaking at the Fe{sub 3}O{sub 4}/MgO interface. Such sizable orbital moment will add capacities to the Fe{sub 3}O{sub 4}-based spintronics devices in the magnetization reversal by the electric field.

  20. Unraveling the thermodynamics and kinetics of RNA assembly: surface plasmon resonance, isothermal titration calorimetry, and circular dichroism.

    Science.gov (United States)

    Hoogstraten, Charles G; Sumita, Minako; White, Neil A

    2014-01-01

    The mechanisms and driving forces of the assembly of RNA tertiary structure are a topic of much current interest. In several systems, including our own work in the docking transition of the hairpin ribozyme, intramolecular RNA tertiary folding has been converted into an intermolecular binding event, allowing the full power of contemporary biophysical techniques to be brought to bear on the analysis. We review the use of three such methods: circular dichroism to isolate the binding of multivalent cations coupled to tertiary assembly, surface plasmon resonance to determine the rates of association and dissociation, and isothermal titration calorimetry to dissect the thermodynamic contributions to RNA assembly events. We pay particular attention to practical aspects of these studies, such as careful preparation of samples with fixed free concentrations of cations in order to avoid errors due to ion depletion effects that are common in RNA systems. Examples of applications from our own work with the hairpin ribozyme are shown. Distinctions among the data handling procedures for the various techniques used and solution conditions encountered are also discussed.

  1. Theoretical description of circular dichroism in photoelectron angular distributions of randomly oriented chiral molecules after multi-photon photoionization

    Science.gov (United States)

    Goetz, R. E.; Isaev, T. A.; Nikoobakht, B.; Berger, R.; Koch, C. P.

    2017-01-01

    Photoelectron circular dichroism refers to the forward/backward asymmetry in the photoelectron angular distribution with respect to the propagation axis of circularly polarized light. It has recently been demonstrated in femtosecond multi-photon photoionization experiments with randomly oriented camphor and fenchone molecules [C. Lux et al., Angew. Chem., Int. Ed. 51, 4755 (2012) and C. S. Lehmann et al., J. Chem. Phys. 139, 234307 (2013)]. A theoretical framework describing this process as (2+1) resonantly enhanced multi-photon ionization is constructed, which consists of two-photon photoselection from randomly oriented molecules and successive one-photon ionization of the photoselected molecules. It combines perturbation theory for the light-matter interaction with ab initio calculations for the two-photon absorption and a single-center expansion of the photoelectron wavefunction in terms of hydrogenic continuum functions. It is verified that the model correctly reproduces the basic symmetry behavior expected under exchange of handedness and light helicity. When applied to fenchone and camphor, semi-quantitative agreement with the experimental data is found, for which a sufficient d wave character of the electronically excited intermediate state is crucial.

  2. Ultraviolet-circular dichroism spectroscopy and potentiometric study of the interaction between human serum albumin and sodium perfluorooctanoate.

    Science.gov (United States)

    Messina, Paula; Prieto, Gerardo; Dodero, Verónica; Ruso, Juan M; Schulz, Pablo; Sarmiento, Félix

    2005-12-15

    The interaction of a fluorinated surfactant, sodium perfluorooctanoate, with human serum albumin (HSA) has been investigated by a combination of ultraviolet-circular dichroism (UV-CD) spectroscopy and potentiometry (by a home-built ion-selective electrode) techniques to detect and characterize the conformational transitions of HSA. By using difference spectroscopy, the transition was followed as a function of temperature, and the data were analyzed to obtain the parameters characterizing the thermodynamics of unfolding. The results indicate that the presence of surfactant drastically changes the melting unfolding, acting as a structure stabilizer and delaying the unfolding process. Potentiometric measurements were used to determine the binding isotherms and binding capacity for this system. The isotherm shows a high affinity of surfactant molecules for HSA. The average number of surfactant molecules absorbed per protein molecule (at 28 mM of surfactant concentration) was found to be approximately 900, about 6 g of surfactant per gram of protein. The shape of the binding capacity curve and the relation between binding capacity and extend of cooperativity were examined. From these analysis, the values of g (number of ligand-binding sites), KH (Hill binding constant), and nH (Hill coefficient) were determined.

  3. Site-specific conformational determination in thermal unfolding studies of helical peptides using vibrational circular dichroism with isotopic substitution

    Science.gov (United States)

    Silva, R. A. G. D.; Kubelka, Jan; Bour, Petr; Decatur, Sean M.; Keiderling, Timothy A.

    2000-01-01

    Understanding the detailed mechanism of protein folding requires dynamic, site-specific stereochemical information. The short time response of vibrational spectroscopies allows evaluation of the distribution of populations in rapid equilibrium as the peptide unfolds. Spectral shifts associated with isotopic labels along with local stereochemical sensitivity of vibrational circular dichroism (VCD) allow determination of the segment sequence of unfolding. For a series of alanine-rich peptides that form α-helices in aqueous solution, we used isotopic labeling and VCD to demonstrate that the α-helix noncooperatively unwinds from the ends with increasing temperature. For these blocked peptides, the C-terminal is frayed at 5°C. Ab initio level theoretical simulations of the IR and VCD band shapes are used to analyze the spectra and to confirm the conformation of the labeled components. The VCD signals associated with the labeled residues are amplified by coupling to the nonlabeled parts of the molecule. Thus small labeled segments are detectable and stereochemically defined in moderately large peptides in this report of site-specific peptide VCD conformational analysis. PMID:10880566

  4. Multireference ab initio studies of zero-field splitting and magnetic circular dichroism spectra of tetrahedral Co(II) complexes.

    Science.gov (United States)

    Sundararajan, Mahesh; Ganyushin, Dmitry; Ye, Shengfa; Neese, Frank

    2009-08-14

    A newly developed multireference (MR) ab initio method for the calculation of magnetic circular dichroism (MCD) spectra was calibrated through the calculation of the ground- and excited state properties of seven high-spin (S = 3/2) Co(II) complexes. The MCD spectra were computed by the explicit treatment of spin-orbit coupled (SOC) and spin-spin coupled (SSC) N-electron states. For the complexes studied in this work, we found that the SOC is more important than the SSC for determining the ground state zero field splitting (ZFS). Our computed ZFS parameter D for the [Co(PPh(3))(2)Cl(2)] model complex is -17.6 cm(-1), which is reasonably close to the experimental value of -14.8 cm(-1). Generally, the computed absorption and MCD spectra are in fair agreement with experiment for all investigated complexes. Thus, reliable electronic structure and spectroscopic predictions for medium sized transition metal complexes are feasible on the basis of this methodology. This characterizes the presented method as a promising tool for MCD spectra interpretations of transition metal complexes in a variety of areas of chemistry and biology.

  5. Complexation behavior of gelatin with amphiphilic drug imipramine hydrochloride as studied by conductimetry, surface tensiometry and circular dichroism studies.

    Science.gov (United States)

    Ali, Mohd Sajid; Anjum, Kahkashan; Khan, Javed M; Khan, Rizwan H; Kabir-ud-Din

    2011-01-01

    Herein we report our studies carried out on the interaction between IMP and gelatin in aqueous medium at 25°C using conductimetry, surface tensiometry and circular dichroism (CD) techniques. Both surface tensiometry and conductimetry results indicate that the drug interacts with the gelatin in a surfactant-like manner, i.e., both critical aggregation (cac) and polymer saturation points (psp) were observed. The interaction starts with the formation of a highly surface-active complex as revealed by the lowering of surface tension on the addition of drug to the macromolecule. The decrease in cac on increasing gelatin concentration is an indication of the strong interaction between gelatin and IMP. However, at low concentration of gelatin the interaction was not much strong as exposed by surface tension study, i.e., the cac was not very clear (as with higher gelatin concentrations). As usual, the psp increased on increasing the gelatin concentration and was always higher than the critical micelle concentration of the drug in pure aqueous medium. Using CD measurements the influence of IMP on the secondary structure of gelatin in aqueous solutions was also investigated. CD studies (performed at very low drug concentrations) illustrated that the random coil content of gelatin increases with increasing drug concentration. Free energies of aggregation (ΔG(agg)) and micellization (ΔG(mic)) were computed with the help of degrees of micelle ionization obtained from the specific conductivity - [IMP] plots.

  6. Determining the polarization state of an extreme ultraviolet free-electron laser beam using atomic circular dichroism.

    Science.gov (United States)

    Mazza, T; Ilchen, M; Rafipoor, A J; Callegari, C; Finetti, P; Plekan, O; Prince, K C; Richter, R; Danailov, M B; Demidovich, A; De Ninno, G; Grazioli, C; Ivanov, R; Mahne, N; Raimondi, L; Svetina, C; Avaldi, L; Bolognesi, P; Coreno, M; O'Keeffe, P; Di Fraia, M; Devetta, M; Ovcharenko, Y; Möller, Th; Lyamayev, V; Stienkemeier, F; Düsterer, S; Ueda, K; Costello, J T; Kazansky, A K; Kabachnik, N M; Meyer, M

    2014-04-16

    Ultrafast extreme ultraviolet and X-ray free-electron lasers are set to revolutionize many domains such as bio-photonics and materials science, in a manner similar to optical lasers over the past two decades. Although their number will grow steadily over the coming decade, their complete characterization remains an elusive goal. This represents a significant barrier to their wider adoption and hence to the full realization of their potential in modern photon sciences. Although a great deal of progress has been made on temporal characterization and wavefront measurements at ultrahigh extreme ultraviolet and X-ray intensities, only few, if any progress on accurately measuring other key parameters such as the state of polarization has emerged. Here we show that by combining ultra-short extreme ultraviolet free electron laser pulses from FERMI with near-infrared laser pulses, we can accurately measure the polarization state of a free electron laser beam in an elegant, non-invasive and straightforward manner using circular dichroism.

  7. Dimethyl Sulfoxide Induced Destabilization and Disassembly of Various Structural Variants of Insulin Fibrils Monitored by Vibrational Circular Dichroism.

    Science.gov (United States)

    Zhang, Ge; Babenko, Viktoria; Dzwolak, Wojciech; Keiderling, Timothy A

    2015-12-15

    Dimethyl sulfoxide (DMSO) induced destabilization of insulin fibrils has been previously studied by Fourier transform infrared spectroscopy and interpreted in terms of secondary structural changes. The variation of this process for fibrils with different types of higher-order morphological structures remained unclear. Here, we utilize vibrational circular dichroism (VCD), which has been reported to provide a useful biophysical probe of the supramolecular chirality of amyloid fibrils, to characterize changes in the macroscopic chirality following DMSO-induced disassembly for two types of insulin fibrils formed under different conditions, at different reduced pH values with and without added salt and agitation. We confirm that very high concentrations of DMSO can disaggregate both types of insulin fibrils, which initially maintained a β-sheet conformation and eventually changed their secondary structure to a disordered form. The two types responded to varying concentrations of DMSO, and disaggregation followed different mechanisms. Interconversion of specific insulin fibril morphological types also occurred during the destabilization process as monitored by VCD. With transmission electron microscopy, we were able to correlate the changes in VCD sign patterns to alteration of morphology of the insulin fibrils.

  8. Enhanced biocatalysis mechanism under microwave irradiation in isoquercitrin production revealed by circular dichroism and surface plasmon resonance spectroscopy.

    Science.gov (United States)

    Gong, An; Zhu, Dan; Mei, Yi-Yuan; Xu, Xiao-Hui; Wu, Fu-An; Wang, Jun

    2016-04-01

    An efficient and rapid process for isoquercitrin production by hesperidinase-catalyzed hydrolysis of rutin was successfully developed under microwave irradiation detecting the affinity by circular dichroism (CD) and surface plasmon resonance (SPR) spectroscopy. A maximum isoquercitrin yield of 91.5±2.7% was obtained in 10min with the conditions of 10g/L hesperidinase, 2g/L rutin, 30°C and microwave power density 88.9W/L. Enzymatic reaction rate and Vm/Km in the microwave reactor were 6.34-fold higher than in a continuous flow microreactor and 1.24-fold higher than in a biphasic system. CD and SPR analysis results also showed that hesperidinase has a better selectivity and affinity (3.3-fold than in a batch reactor) to generate isoquercitrin under microwave irradiation. Microwave irradiation greatly improved the reaction efficiency and productivity, leading to a more positive economical assessment. The binding affinity indicates the presence of strong multivalent interactions between rutin and hesperidinase under microwave irradiation.

  9. Vibrational circular dichroism from ab initio molecular dynamics and nuclear velocity perturbation theory in the liquid phase.

    Science.gov (United States)

    Scherrer, Arne; Vuilleumier, Rodolphe; Sebastiani, Daniel

    2016-08-28

    We report the first fully ab initio calculation of dynamical vibrational circular dichroism spectra in the liquid phase using nuclear velocity perturbation theory (NVPT) derived electronic currents. Our approach is rigorous and general and thus capable of treating weak interactions of chiral molecules as, e.g., chirality transfer from a chiral molecule to an achiral solvent. We use an implementation of the NVPT that is projected along the dynamics to obtain the current and magnetic dipole moments required for accurate intensities. The gauge problem in the liquid phase is resolved in a twofold approach. The electronic expectation values are evaluated in a distributed origin gauge, employing maximally localized Wannier orbitals. In a second step, the gauge invariant spectrum is obtained in terms of a scaled molecular moments, which allows to systematically include solvent effects while keeping a significant signal-to-noise ratio. We give a thorough analysis and discussion of this choice of gauge for the liquid phase. At low temperatures, we recover the established double harmonic approximation. The methodology is applied to chiral molecules ((S)-d2-oxirane and (R)-propylene-oxide) in the gas phase and in solution. We find an excellent agreement with the theoretical and experimental references, including the emergence of signals due to chirality transfer from the solute to the (achiral) solvent.

  10. Microscopic Magnetic Properties of the Itinerant Metamagnet UCoAl by X-ray Magnetic Circular Dichroism

    Science.gov (United States)

    Combier, Tristan; Palacio-Morales, Alexandra; Sanchez, Jean-Pierre; Wilhelm, Fabrice; Pourret, Alexandre; Brison, Jean-Pascal; Aoki, Dai; Rogalev, Andrei

    2017-02-01

    The itinerant metamagnet UCoAl has been investigated by high field X-ray magnetic circular dichroism (XMCD) at the U M4,5 and Co K edges. The orbital and spin moments of U at 2.1 K for H || c applied below and above the first order metamagnetic transition field (HM) have been determined. The magnetism of UCoAl is dominated by the U moment. There is no evidence for any change of the orbital to spin moment ratio (˜-2.05) across HM and within the ferromagnetic phase up to 17 T. The possibility of a Fermi surface reconstruction at HM remains an open option. XMCD at the Co K-edge reveals the presence of a small Co 4p-orbital moment parallel to the macroscopic magnetization. In addition, the Co 3d-moment is estimated to be at most 0.1 μB at 17 T. The similar field dependence of the U and Co magnetizations indicates that the Co moment is induced by the U moment.

  11. X-ray magnetic circular dichroism study of Dy-doped Bi2Te3 topological insulator thin films

    Science.gov (United States)

    Figueroa, A. I.; Baker, A. A.; Harrison, S. E.; Kummer, K.; van der Laan, G.; Hesjedal, T.

    2017-01-01

    Magnetic doping of topological insulators (TIs) is crucial for unlocking novel quantum phenomena, paving the way for spintronics applications. Recently, we have shown that doping with rare earth ions introduces large magnetic moments and allows for high doping concentrations without the loss of crystal quality, however no long range magnetic order was observed. In Dy-doped Bi2Te3 we found a band gap opening above a critical doping concentration, despite the paramagnetic bulk behavior. Here, we present a surface-sensitive x-ray magnetic circular dichroism (XMCD) study of an in situ cleaved film in the cleanest possible environment. The Dy M4,5 absorption spectra measured with circularly polarized x-rays are fitted using multiplet calculations to obtain the effective magnetic moment. Arrott-Noakes plots, measured by the Dy M5 XMCD as a function of field at low temperatures, give a negative transition temperature. The evaporation of a ferromagnetic Co thin film did not introduce ferromagnetic ordering of the Dy dopants either; instead a lowering of the transition temperature was observed, pointing towards an antiferromagnetic ordering scenario. This result shows that there is a competition between the magnetic exchange interaction and the Zeeman interaction. The latter favors the Co and Dy magnetic moments to be both aligned along the direction of the applied magnetic field, while the exchange interaction is minimized if the Dy and Co atoms are antiferromagnetically coupled, as in zero applied field.

  12. Linear systems theory revisited

    NARCIS (Netherlands)

    Willigenburg, van L.G.; Koning, de W.L.

    2008-01-01

    This paper investigates and clarifies how different definitions of reachability, observability, controllability, reconstructability and minimality that appear in the control literature, may be equivalent or different, depending on the type of linear system. The differences are caused by (1) whether

  13. Unsupervised Linear Discriminant Analysis

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    An algorithm for unsupervised linear discriminant analysis was presented. Optimal unsupervised discriminant vectors are obtained through maximizing covariance of all samples and minimizing covariance of local k-nearest neighbor samples. The experimental results show our algorithm is effective.

  14. Linear system theory

    Science.gov (United States)

    Callier, Frank M.; Desoer, Charles A.

    1991-01-01

    The aim of this book is to provide a systematic and rigorous access to the main topics of linear state-space system theory in both the continuous-time case and the discrete-time case; and the I/O description of linear systems. The main thrusts of the work are the analysis of system descriptions and derivations of their properties, LQ-optimal control, state feedback and state estimation, and MIMO unity-feedback systems.

  15. Elementary linear algebra

    CERN Document Server

    Andrilli, Stephen

    2010-01-01

    Elementary Linear Algebra develops and explains in careful detail the computational techniques and fundamental theoretical results central to a first course in linear algebra. This highly acclaimed text focuses on developing the abstract thinking essential for further mathematical study. The authors give early, intensive attention to the skills necessary to make students comfortable with mathematical proofs. The text builds a gradual and smooth transition from computational results to general theory of abstract vector spaces. It also provides flexbile coverage of practical applications, expl

  16. Spin state transition in LaCoO3 studied using soft x-ray absorption spectroscopy and magnetic circular dichroism.

    Science.gov (United States)

    Haverkort, M W; Hu, Z; Cezar, J C; Burnus, T; Hartmann, H; Reuther, M; Zobel, C; Lorenz, T; Tanaka, A; Brookes, N B; Hsieh, H H; Lin, H-J; Chen, C T; Tjeng, L H

    2006-10-27

    Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-L(2,3) edge, we reveal that the spin state transition in LaCoO3 can be well described by a low-spin ground state and a triply degenerate high-spin first excited state. From the temperature dependence of the spectral line shapes, we find that LaCoO3 at finite temperatures is an inhomogeneous mixed-spin state system. It is crucial that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low- or intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance, and inelastic neutron data.

  17. Circular Dichroism in the 3d and 4d Core Photoabsorption for Ferromagnetic Ce Compounds —Interplay of Hybridization, Spin Orbit Interaction and Crystal Field—

    Science.gov (United States)

    Jo, Takeo; Imada, Shin

    1990-04-01

    The Ce 3d- and 4d-core photoabsorption spectra (3d XAS and 4d XAS) of ferromagnetic mixed valent Ce compounds are calculated on the basis of the impurity Anderson model. The model takes into account the Coulomb interaction producing multiplet structures, the spin-orbit interaction, the crystal field effect and the molecular field acting on the 4f spin. The calculation shows a strong circular dichroism even for the Ce magnetic moment of ˜0.5 μB. The dichroism is furthermore shown to be a powerful method to measure the spin and orbital contributions to the 4f moment. On the basis of the calculation, the 4f magnetic state of the ferromagnet CeRh3B2 is discussed.

  18. Structures and short linear motif of disordered transcription factor regions provide clues to the interactome of the cellular hub Radical-Induced Cell Death1

    DEFF Research Database (Denmark)

    O'Shea, Charlotte; Staby, Lasse; Bendsen, Sidsel Krogh;

    2017-01-01

    point to larger networks of interactions, such as with proteins that serve as hubs for essential cellular functions. The stress-associated plant protein Radical-Induced Cell Death1 (RCD1) is one such hub, interacting with many transcription factors via their flexible IDRs. To identify the SLiM bound...

  19. X-ray magnetic circular dichroism: Orbital and spin moments of iron single-crystal thin film deposited on MgO substrate

    Institute of Scientific and Technical Information of China (English)

    LI Honghong; WANG Jie; LI Ruipeng; GUO Yuxian; WANG Feng; HU Zhiwei

    2005-01-01

    X-ray magnetic circular dichroism in absorption of the single-crystal iron layer deposited epitaxially on MgO substrate is studied. Spin and orbital moment, 0.069 and 2.33 -B, respectively, are calculated in terms of the XMCD sum rules. Our results are accordant to those published. Experiments show that the orbital moment would be decreased to that in bulk materials as iron film is thinned down, but spin moment changes little.

  20. Circular dichroism anisotrophy of DNA with different modifications at N7 of guanine.

    Science.gov (United States)

    Zavriev, S K; Minchenkova, L E; Vorlícková, M; Kolchinsky, A M; Volkenstein, M V; Ivanov, V I

    1979-09-27

    The complexex DNA-Ag1+, DNA-Cu1+, protonated DNA and DNA methylated at N7 of guanine were oriented by pumping the solutions through a multicapillary cell in the direction of a light beam. The CD components along the DNA axis, delta epsilon parallel, and normal to it, 2 delta epsilon perpendicular, were calculated from the CD spectra of the oriented samples by the method of Chung and Holzwarth, (1975) J. Mol. Biol. 92, 449--466. It was shown that in most cases, except that of the protonated DNA, the degree of orientation was only slightly less than that for pure DNA. This demonstrated the absence of aggregation and of appreciable denaturation. In all cases the modifications of DNA give rise to a negative component 2 delta epsilon perpendicular, whose magnitude increased as the extent of modification increased. From both the CD spectra of non-oriented samples and the absorption spectra, an inference is drawn that Ag1+ and Cu1+ are attached to the same site as CH3 groups i.e., to the N7 atom of guanine. Proton transfer along the H-bond from the N1 atom of G to the N3 atom of the complementary cytosine is suggested to be a result of the modifications, although the case of H+-DNA may differ from the others. Based on the CD spectra for the anisotropic components, delta epsilon parallel and 2 delta epsilon perpendicular, it is proposed that ligand binding is accompanied by winding of the DNA helix.

  1. Extraction of linear anisotropic parameters using optical coherence tomography and hybrid Mueller matrix formalism.

    Science.gov (United States)

    Liao, Chia-Chi; Lo, Yu-Lung

    2015-04-20

    A method is proposed for extracting the linear birefringence (LB) and linear dichroism (LD) properties of an anisotropic optical sample using reflection-mode optical coherence tomography (OCT) and a hybrid Mueller matrix formalism. To ensure the accuracy of the extracted parameter values, a method is proposed for calibrating and compensating the polarization distortion effect induced by the beam splitters in the OCT system using a composite quarter-waveplate / half-waveplate / quarter-waveplate structure. The validity of the proposed method is confirmed by extracting the LB and LD properties of a quarter-wave plate and a defective polarizer. To the best of the authors' knowledge, the method proposed in this study represents the first reported attempt to utilize an inverse Mueller matrix formalism and a reflection-mode OCT structure to extract the LB and LD parameters of optically anisotropic samples.

  2. Non-Markovian Quantum State Diffusion for Temperature-Dependent Linear Spectra of Light Harvesting Aggregates

    CERN Document Server

    Ritschel, Gerhard; Möbius, Sebastian; Strunz, Walter T; Eisfeld, Alexander

    2014-01-01

    Non-Markovian Quantum State Diffusion (NMQSD) has turned out to be an effective method to calculate excitonic properties of aggregates composed of organic chromophores, taking into account the strong coupling of electronic transitions to vibrational modes of the chromophores. In this paper we show how to calculate linear optical spectra at finite temperatures in an efficient way. To this end we map a finite temperature environment to the zero temperature case using the so-called thermofield method. The zero temperature case equations can then be solved efficiently by standard integrators. As an example we calculate absorption and circular dichroism spectra of a linear aggregate. The formalism developed can be applied to calculate arbitrary correlation functions.

  3. On Linear Algebra Education

    Directory of Open Access Journals (Sweden)

    Sinan AYDIN

    2009-04-01

    Full Text Available Linear algebra is a basic course followed in mathematics, science, and engineering university departments.Generally, this course is taken in either the first or second year but there have been difficulties in teachingand learning. This type of active algebra has resulted in an increase in research by mathematics educationresearchers. But there is insufficient information on this subject in Turkish and therefore it has not beengiven any educational status. This paper aims to give a general overview of this subject in teaching andlearning. These education studies can be considered quadruple: a the history of linear algebra, b formalismobstacles of linear algebra and cognitive flexibility to improve teaching and learning, c the relation betweenlinear algebra and geometry, d using technology in the teaching and learning linear algebra.Mathematicseducation researchers cannot provide an absolute solution to overcome the teaching and learning difficultiesof linear algebra. Epistemological analyses and experimental teaching have shown the learning difficulties.Given these results, further advice and assistance can be offered locally.

  4. Further linear algebra

    CERN Document Server

    Blyth, T S

    2002-01-01

    Most of the introductory courses on linear algebra develop the basic theory of finite­ dimensional vector spaces, and in so doing relate the notion of a linear mapping to that of a matrix. Generally speaking, such courses culminate in the diagonalisation of certain matrices and the application of this process to various situations. Such is the case, for example, in our previous SUMS volume Basic Linear Algebra. The present text is a continuation of that volume, and has the objective of introducing the reader to more advanced properties of vector spaces and linear mappings, and consequently of matrices. For readers who are not familiar with the contents of Basic Linear Algebra we provide an introductory chapter that consists of a compact summary of the prerequisites for the present volume. In order to consolidate the student's understanding we have included a large num­ ber of illustrative and worked examples, as well as many exercises that are strategi­ cally placed throughout the text. Solutions to the ex...

  5. Evaluation of the automated hematology analyzer Sysmex XT-2000iV™ compared to the ADVIA® 2120 for its use in dogs, cats, and horses: Part I--precision, linearity, and accuracy of complete blood cell count.

    Science.gov (United States)

    Bauer, Natali; Nakagawa, Julia; Dunker, Cathrin; Failing, Klaus; Moritz, Andreas

    2011-11-01

    The automated laser-based hematology analyzer Sysmex XT-2000iV™ providing a complete blood cell count (CBC) and 5-part differential has been introduced in large veterinary laboratories. The aim of the current study was to determine precision, linearity, and accuracy of the Sysmex analyzer. Reference method for the accuracy study was the laser-based hematology analyzer ADVIA® 2120. For evaluation of accuracy, consecutive fresh blood samples from healthy and diseased cats (n = 216), dogs (n = 314), and horses (n = 174) were included. A low intra-assay coefficient of variation (CV) of approximately 1% was seen for the CBC except platelet count (PLT). An intra-assay CV ranging between 2% and 5.5% was evident for the differential count except for feline and equine monocytes (7.7%) and horse eosinophils (15.7%). Linearity was excellent for white blood cell count (WBC), hematocrit value, red blood cell count (RBC), and PLT. For all evaluated species, agreement was excellent for WBC and RBC, with Spearman rank correlation coefficients (r(s)) ranging from >0.99 to 0.98. Hematocrit value correlated excellently in cats and dogs, whereas for horses, a good correlation was evident. A good correlation between both analyzers was seen in feline and equine PLT (r(s) = 0.89 and 0.92, respectively), whereas correlation was excellent for dogs (r(s) = 0.93). Biases were close to 0 except for mean corpuscular hemoglobin concentration (4.11 to -7.25 mmol/l) and canine PLT (57 × 10(9)/l). Overall, the performance of the Sysmex analyzer was excellent and compared favorably with the ADVIA analyzer.

  6. Theory of linear operations

    CERN Document Server

    Banach, S

    1987-01-01

    This classic work by the late Stefan Banach has been translated into English so as to reach a yet wider audience. It contains the basics of the algebra of operators, concentrating on the study of linear operators, which corresponds to that of the linear forms a1x1 + a2x2 + ... + anxn of algebra.The book gathers results concerning linear operators defined in general spaces of a certain kind, principally in Banach spaces, examples of which are: the space of continuous functions, that of the pth-power-summable functions, Hilbert space, etc. The general theorems are interpreted in various mathematical areas, such as group theory, differential equations, integral equations, equations with infinitely many unknowns, functions of a real variable, summation methods and orthogonal series.A new fifty-page section (``Some Aspects of the Present Theory of Banach Spaces'''') complements this important monograph.

  7. A combined binding mechanism of nonionic ethoxylated surfactants to bovine serum albumin revealed by fluorescence and circular dichroism.

    Science.gov (United States)

    Iovescu, Alina; Băran, Adriana; Stîngă, Gabriela; Cantemir-Leontieş, Anca Ruxandra; Maxim, Monica Elisabeta; Anghel, Dan Florin

    2015-12-01

    The study systematically investigates aqueous mixtures of fixed bovine serum albumin (BSA) and various ethoxylated nonionic surfactants belonging to a homologous series or not. Mono-disperse tetra-(C12E4), hexa-(C12E6) and octa-ethyleneglycol mono-n-dodecyl ether (C12E8), and poly-disperse eicosa-ethyleneglycol mono-n-tetradecyl ether (C14EO20) are respectively employed. Fluorescence and circular dichroism measurements are performed at surfactant/protein molar ratios (rm)s lower and higher than one. We aim to get new insights into the binding mechanism of these species and to differentiate among the interaction abilities of these surfactants. The relative magnitude of the binding thermodynamic parameters by fluorescence, and the increase of α-helix prove that hydrogen bonding drives the interaction next to the hydrophobic attraction. C12En (n=4,6,8) develop more H bonds with the albumin than C14EO20 owing to a zigzag conformation of their short ethyleneoxide chains. Among the homologous surfactants, C12E6 has a slightly stronger interaction with BSA due to a maximal number of H bonds at a minimal hindering. Static fluorescence and dynamic fluorescence indicate an inter-conversion between the tryptophan (Trp) rotamers which happens around the surfactants critical micellar concentration. For C14EO20, the meander conformation of the polar group determines a less evident conversion of the Trp rotamers and smaller α-helix rise. Binding isotherms of the homologous surfactants and the fluorescence quenching mechanism by C12E6 are also provided.

  8. Conformational analysis of XA and AX dipeptides in water by electronic circular dichroism and 1H NMR spectroscopy.

    Science.gov (United States)

    Hagarman, Andrew; Measey, Thomas; Doddasomayajula, Ravi S; Dragomir, Isabelle; Eker, Fatma; Griebenow, Kai; Schweitzer-Stenner, Reinhard

    2006-04-06

    We measured the temperature-dependent electronic circular dichroism (ECD) spectra of AX, XA, and XG dipeptides in D2O. The spectra of all XA and AX peptides indicate a substantial population of the polyproline II (PPII) conformation, while the ECD spectra of LG, KG, PG, and AG were found to be quantitatively different from the alanine-based dipeptides. Additional UV absorption data indicate that the ECD spectra of the XG peptides stem from electronic coupling between the peptide and the C-terminal group, and that spectral differences reflect different orientations of the latter. We also measured the 1H NMR spectra of the investigated dipeptides to determine the 3JHalphaNH coupling constants for the C-terminal residue. The observed temperature dependence of the ECD spectra and the respective room-temperature 3JHalphaNH coupling constants were analyzed by a two-state model encompassing PPII and a beta-like conformation. The PPII propensity of alanine in the XA series is only slightly modulated by the N-terminal side chain, and is larger than 50%. As compared to AA, XA peptides containing L, P, S, K V, E, T, and I all cause a relative stabilization of the extended beta-strand conformation. The PPII fractions of XA peptides varied between 0.64 for AA and 0.58 for DA, whereas the PPII fractions of AX peptides were much lower. From the investigated AX peptides, only AL and AQ showed the expected PPII propensity. We found that AT, AI, and AV clearly prefer an extended beta-strand conformation. A quantitative comparison of AA, AAA, and AAAA revealed a hierarchy AAAA > AAA approximately AA for the PPII population, in agreement with predictions from MD calculations and results from Raman optical activity studies (McColl et al. J. Am. Chem. Soc. 2004, 126, 5076).

  9. Analysis of exact linearization and aproximate feedback linearization techniques

    OpenAIRE

    Schnitman, Leizer; Cardoso, Gildeberto de Souza

    2011-01-01

    p. 1-17 This paper presents a study of linear control systems based on exact feedback linearization and approximate feedback linearization. As exact feedback linearization is applied, a linear controller can perform the control objectives. The approximate feedback linearization is required when a nonlinear system presents a noninvolutive property. It uses a Taylor series expansion in order to compute a nonlinear transformation of coordinates to satisfy the involutivity conditions.

  10. Analysis of Exact Linearization and Aproximate Feedback Linearization Techniques

    OpenAIRE

    Cardoso, Gildeberto S.; Leizer Schnitman

    2011-01-01

    This paper presents a study of linear control systems based on exact feedback linearization and approximate feedback linearization. As exact feedback linearization is applied, a linear controller can perform the control objectives. The approximate feedback linearization is required when a nonlinear system presents a noninvolutive property. It uses a Taylor series expansion in order to compute a nonlinear transformation of coordinates to satisfy the involutivity conditions.

  11. Handbook of linear algebra

    CERN Document Server

    Hogben, Leslie

    2013-01-01

    With a substantial amount of new material, the Handbook of Linear Algebra, Second Edition provides comprehensive coverage of linear algebra concepts, applications, and computational software packages in an easy-to-use format. It guides you from the very elementary aspects of the subject to the frontiers of current research. Along with revisions and updates throughout, the second edition of this bestseller includes 20 new chapters.New to the Second EditionSeparate chapters on Schur complements, additional types of canonical forms, tensors, matrix polynomials, matrix equations, special types of

  12. Advanced linear algebra

    CERN Document Server

    Cooperstein, Bruce

    2015-01-01

    Advanced Linear Algebra, Second Edition takes a gentle approach that starts with familiar concepts and then gradually builds to deeper results. Each section begins with an outline of previously introduced concepts and results necessary for mastering the new material. By reviewing what students need to know before moving forward, the text builds a solid foundation upon which to progress. The new edition of this successful text focuses on vector spaces and the maps between them that preserve their structure (linear transformations). Designed for advanced undergraduate and beginning graduate stud

  13. Linear Algebra Thoroughly Explained

    CERN Document Server

    Vujičić, Milan

    2008-01-01

    Linear Algebra Thoroughly Explained provides a comprehensive introduction to the subject suitable for adoption as a self-contained text for courses at undergraduate and postgraduate level. The clear and comprehensive presentation of the basic theory is illustrated throughout with an abundance of worked examples. The book is written for teachers and students of linear algebra at all levels and across mathematics and the applied sciences, particularly physics and engineering. It will also be an invaluable addition to research libraries as a comprehensive resource book for the subject.

  14. Linear Logical Voting Protocols

    DEFF Research Database (Denmark)

    DeYoung, Henry; Schürmann, Carsten

    2012-01-01

    . In response, we promote linear logic as a high-level language for both specifying and implementing voting protocols. Our linear logical specifications of the single-winner first-past-the-post (SW- FPTP) and single transferable vote (STV) protocols demonstrate that this approach leads to concise......Current approaches to electronic implementations of voting protocols involve translating legal text to source code of an imperative programming language. Because the gap between legal text and source code is very large, it is difficult to trust that the program meets its legal specification...... implementations that closely correspond to their legal specification, thereby increasing trust....

  15. Linear- rubbing Manipulation

    Institute of Scientific and Technical Information of China (English)

    SHEN Guo-quan; XIAO Yuan-chun

    2003-01-01

    @@ Linear-rubbing is a characteristic technique in the academic school of internal exercise massage in Shanghai. It was known as "flat pushing method" in the past times. The academic school of internal exercise Tuina finds, in the clinical practice of flat pushing, that if the internal exercise accumuhtes in the palm and one-way movement is replaced by two-way movement, the kinetic energy may be transformed into heat energy, bringing about a new unique manipulating technique, which is rather different from the usual flat pushing no longer and now called linear-rubbing therapy.

  16. Linear Mappings of Quaternion Algebra

    OpenAIRE

    Kleyn, Aleks

    2011-01-01

    In the paper I considered linear and antilinear automorphisms of quaternion algebra. I proved the theorem that there is unique expansion of R-linear mapping of quaternion algebra relative to the given set of linear and antilinear automorphisms.

  17. About Some Linear Operators

    Directory of Open Access Journals (Sweden)

    Ovidiu T. Pop

    2007-01-01

    Full Text Available Using the method of Jakimovski and Leviatan from their work in 1969, we construct a general class of linear positive operators. We study the convergence, the evaluation for the rate of convergence in terms of the first modulus of smoothness and we give a Voronovskaja-type theorem for these operators.

  18. Finite-dimensional linear algebra

    CERN Document Server

    Gockenbach, Mark S

    2010-01-01

    Some Problems Posed on Vector SpacesLinear equationsBest approximationDiagonalizationSummaryFields and Vector SpacesFields Vector spaces Subspaces Linear combinations and spanning sets Linear independence Basis and dimension Properties of bases Polynomial interpolation and the Lagrange basis Continuous piecewise polynomial functionsLinear OperatorsLinear operatorsMore properties of linear operatorsIsomorphic vector spaces Linear operator equations Existence and uniqueness of solutions The fundamental theorem; inverse operatorsGaussian elimination Newton's method Linear ordinary differential eq

  19. Inferring polymorphism-induced regulatory gene networks active in human lymphocyte cell lines by weighted linear mixed model analysis of multiple RNA-Seq datasets.

    Directory of Open Access Journals (Sweden)

    Wensheng Zhang

    Full Text Available Single-nucleotide polymorphisms (SNPs contribute to the between-individual expression variation of many genes. A regulatory (trait-associated SNP is usually located near or within a (host gene, possibly influencing the gene's transcription or/and post-transcriptional modification. But its targets may also include genes that are physically farther away from it. A heuristic explanation of such multiple-target interferences is that the host gene transfers the SNP genotypic effects to the distant gene(s by a transcriptional or signaling cascade. These connections between the host genes (regulators and the distant genes (targets make the genetic analysis of gene expression traits a promising approach for identifying unknown regulatory relationships. In this study, through a mixed model analysis of multi-source digital expression profiling for 140 human lymphocyte cell lines (LCLs and the genotypes distributed by the international HapMap project, we identified 45 thousands of potential SNP-induced regulatory relationships among genes (the significance level for the underlying associations between expression traits and SNP genotypes was set at FDR < 0.01. We grouped the identified relationships into four classes (paradigms according to the two different mechanisms by which the regulatory SNPs affect their cis- and trans- regulated genes, modifying mRNA level or altering transcript splicing patterns. We further organized the relationships in each class into a set of network modules with the cis- regulated genes as hubs. We found that the target genes in a network module were often characterized by significant functional similarity, and the distributions of the target genes in three out of the four networks roughly resemble a power-law, a typical pattern of gene networks obtained from mutation experiments. By two case studies, we also demonstrated that significant biological insights can be inferred from the identified network modules.

  20. Piecewise Linear Wilson lines

    CERN Document Server

    Van der Veken, Frederik F

    2014-01-01

    Wilson lines, being comparators that render non-local operator products gauge invariant, are extensively used in QCD calculations, especially in small-$x$ calculations, calculations concerning validation of factorisation schemes and in calculations for constructing or modelling parton density functions. We develop an algorithm to express piecewise path ordered exponentials as path ordered integrals over the separate segments, and apply it on linear segments, reducing the number of diagrams needed to be calculated. We show how different linear path topologies can be related using their colour structure. This framework allows one to easily switch results between different Wilson line structures, which is especially useful when testing different structures against each other, e.g. when checking universality properties of non-perturbative objects.

  1. Scaled Sparse Linear Regression

    CERN Document Server

    Sun, Tingni

    2011-01-01

    Scaled sparse linear regression jointly estimates the regression coefficients and noise level in a linear model. It chooses an equilibrium with a sparse regression method by iteratively estimating the noise level via the mean residual squares and scaling the penalty in proportion to the estimated noise level. The iterative algorithm costs nearly nothing beyond the computation of a path of the sparse regression estimator for penalty levels above a threshold. For the scaled Lasso, the algorithm is a gradient descent in a convex minimization of a penalized joint loss function for the regression coefficients and noise level. Under mild regularity conditions, we prove that the method yields simultaneously an estimator for the noise level and an estimated coefficient vector in the Lasso path satisfying certain oracle inequalities for the estimation of the noise level, prediction, and the estimation of regression coefficients. These oracle inequalities provide sufficient conditions for the consistency and asymptotic...

  2. Linear recursive distributed representations.

    Science.gov (United States)

    Voegtlin, Thomas; Dominey, Peter F

    2005-09-01

    Connectionist networks have been criticized for their inability to represent complex structures with systematicity. That is, while they can be trained to represent and manipulate complex objects made of several constituents, they generally fail to generalize to novel combinations of the same constituents. This paper presents a modification of Pollack's Recursive Auto-Associative Memory (RAAM), that addresses this criticism. The network uses linear units and is trained with Oja's rule, in which it generalizes PCA to tree-structured data. Learned representations may be linearly combined, in order to represent new complex structures. This results in unprecedented generalization capabilities. Capacity is orders of magnitude higher than that of a RAAM trained with back-propagation. Moreover, regularities of the training set are preserved in the new formed objects. The formation of new structures displays developmental effects similar to those observed in children when learning to generalize about the argument structure of verbs.

  3. Linearizing nonlinear optics

    CERN Document Server

    Schmidt, Bruno E; Ernotte, Guilmot; Clerici, Matteo; Morandotti, Roberto; Ibrahim, Heide; Legare, Francois

    2016-01-01

    In the framework of linear optics, light fields do not interact with each other in a medium. Yet, when their field amplitude becomes comparable to the electron binding energies of matter, the nonlinear motion of these electrons emits new dipole radiation whose amplitude, frequency and phase differ from the incoming fields. Such high fields are typically achieved with ultra-short, femtosecond (1fs = 10-15 sec.) laser pulses containing very broad frequency spectra. Here, the matter not only couples incoming and outgoing fields but also causes different spectral components to interact and mix through a convolution process. In this contribution, we describe how frequency domain nonlinear optics overcomes the shortcomings arising from this convolution in conventional time domain nonlinear optics1. We generate light fields with previously inaccessible properties because the uncontrolled coupling of amplitudes and phases is turned off. For example, arbitrary phase functions are transferred linearly to the second har...

  4. Extended linear chain compounds

    CERN Document Server

    Linear chain substances span a large cross section of contemporary chemistry ranging from covalent polymers, to organic charge transfer com­ plexes to nonstoichiometric transition metal coordination complexes. Their commonality, which coalesced intense interest in the theoretical and exper­ imental solid state physics/chemistry communities, was based on the obser­ vation that these inorganic and organic polymeric substrates exhibit striking metal-like electrical and optical properties. Exploitation and extension of these systems has led to the systematic study of both the chemistry and physics of highly and poorly conducting linear chain substances. To gain a salient understanding of these complex materials rich in anomalous aniso­ tropic electrical, optical, magnetic, and mechanical properties, the conver­ gence of diverse skills and talents was required. The constructive blending of traditionally segregated disciplines such as synthetic and physical organic, inorganic, and polymer chemistry, crystallog...

  5. Redesigning linear algebra algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Dongarra, J.J.

    1983-01-01

    Many of the standard algorithms in linear algebra as implemented in FORTRAN do not achieve maximum performance on today's large-scale vector computers. The author examines the problem and constructs alternative formulations of algorithms that do not lose the clarity of the original algorithm or sacrifice the FORTRAN portable environment, but do gain the performance attainable on these supercomputers. The resulting implementation not only performs well on vector computers but also increases performance on conventional sequential computers. 13 references.

  6. Redesigning linear algebra algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Dongarra, J.J.

    1983-01-01

    Many of the standard algorithms in linear algebra as implemented in FORTRAN do not achieve maximum performance on today's large-scale vector computers. In this paper we examine the problem and construct alternative formulations of algorithms that do not lose the clarity of the original algorithm or sacrifice the Fortran portable environment, but do gain the performance attainable on these supercomputers. The resulting implementation not only performs well on vector computers but also increases performance on conventional sequential computers.

  7. Linear abdominal trauma.

    Science.gov (United States)

    Danto, L A; Wolfman, E F

    1976-03-01

    Three cases of blunt abdominal trauma are presented to exemplify the mechanism of trauma and the problems of diagnosis associated with any linear blow to the abdomen. The mechanisms of visceral injury are reviewed, and special attention is directed to the abdominal wall injury that can be present in these patients. This injury has special implications in directing the operative approach and repair. An unusual aortic occlusion is described which is peculiar to this type of injury.

  8. Fundamentals of linear algebra

    CERN Document Server

    Dash, Rajani Ballav

    2008-01-01

    FUNDAMENTALS OF LINEAR ALGEBRA is a comprehensive Text Book, which can be used by students and teachers of All Indian Universities. The Text has easy, understandable form and covers all topics of UGC Curriculum. There are lots of worked out examples which helps the students in solving the problems without anybody's help. The Problem sets have been designed keeping in view of the questions asked in different examinations.

  9. Relativistic Linear Restoring Force

    Science.gov (United States)

    Clark, D.; Franklin, J.; Mann, N.

    2012-01-01

    We consider two different forms for a relativistic version of a linear restoring force. The pair comes from taking Hooke's law to be the force appearing on the right-hand side of the relativistic expressions: d"p"/d"t" or d"p"/d["tau"]. Either formulation recovers Hooke's law in the non-relativistic limit. In addition to these two forces, we…

  10. Linear network theory

    CERN Document Server

    Sander, K F

    1964-01-01

    Linear Network Theory covers the significant algebraic aspect of network theory, with minimal reference to practical circuits. The book begins the presentation of network analysis with the exposition of networks containing resistances only, and follows it up with a discussion of networks involving inductance and capacity by way of the differential equations. Classification and description of certain networks, equivalent networks, filter circuits, and network functions are also covered. Electrical engineers, technicians, electronics engineers, electricians, and students learning the intricacies

  11. Dimension of linear models

    DEFF Research Database (Denmark)

    Høskuldsson, Agnar

    1996-01-01

    of these criteria are widely used ones, while the remaining four are ones derived from the H-principle of mathematical modeling. Many examples from practice show that the criteria derived from the H-principle function better than the known and popular criteria for the number of components. We shall briefly review...... the basic problems in determining the dimension of linear models. Then each of the eight measures are treated. The results are illustrated by examples....

  12. Linearized Kernel Dictionary Learning

    Science.gov (United States)

    Golts, Alona; Elad, Michael

    2016-06-01

    In this paper we present a new approach of incorporating kernels into dictionary learning. The kernel K-SVD algorithm (KKSVD), which has been introduced recently, shows an improvement in classification performance, with relation to its linear counterpart K-SVD. However, this algorithm requires the storage and handling of a very large kernel matrix, which leads to high computational cost, while also limiting its use to setups with small number of training examples. We address these problems by combining two ideas: first we approximate the kernel matrix using a cleverly sampled subset of its columns using the Nystr\\"{o}m method; secondly, as we wish to avoid using this matrix altogether, we decompose it by SVD to form new "virtual samples," on which any linear dictionary learning can be employed. Our method, termed "Linearized Kernel Dictionary Learning" (LKDL) can be seamlessly applied as a pre-processing stage on top of any efficient off-the-shelf dictionary learning scheme, effectively "kernelizing" it. We demonstrate the effectiveness of our method on several tasks of both supervised and unsupervised classification and show the efficiency of the proposed scheme, its easy integration and performance boosting properties.

  13. Linear algebraic groups

    CERN Document Server

    Springer, T A

    1998-01-01

    "[The first] ten chapters...are an efficient, accessible, and self-contained introduction to affine algebraic groups over an algebraically closed field. The author includes exercises and the book is certainly usable by graduate students as a text or for self-study...the author [has a] student-friendly style… [The following] seven chapters... would also be a good introduction to rationality issues for algebraic groups. A number of results from the literature…appear for the first time in a text." –Mathematical Reviews (Review of the Second Edition) "This book is a completely new version of the first edition. The aim of the old book was to present the theory of linear algebraic groups over an algebraically closed field. Reading that book, many people entered the research field of linear algebraic groups. The present book has a wider scope. Its aim is to treat the theory of linear algebraic groups over arbitrary fields. Again, the author keeps the treatment of prerequisites self-contained. The material of t...

  14. Lanthanide tris(β-diketonates) as useful probes for chirality determination of biological amino alcohols in vibrational circular dichroism: ligand to ligand chirality transfer in lanthanide coordination sphere.

    Science.gov (United States)

    Miyake, Hiroyuki; Terada, Keiko; Tsukube, Hiroshi

    2014-06-01

    A series of lanthanide tris(β-diketonates) functioned as useful chirality probes in the vibrational circular dichroism (VCD) characterization of biological amino alcohols. Various chiral amino alcohols induced intense VCD signals upon ternary complexation with racemic lanthanide tris(β-diketonates). The VCD signals observed around 1500 cm(-1) (β-diketonate IR absorption region) correlated well with the stereochemistry and enantiomeric purity of the targeted amino alcohol, while the corresponding monoalcohol, monoamine, and diol substrates induced very weak VCD signals. The high-coordination number and dynamic property of the lanthanide complex offer an effective chirality VCD probing of biological substrates.

  15. Magnetic anisotropy in Ta/CoFeB/MgO investigated by x-ray magnetic circular dichroism and first-principles calculation

    Energy Technology Data Exchange (ETDEWEB)

    Kanai, Shun [Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Tsujikawa, Masahito; Shirai, Masafumi [Center for Spintronics Integrated Systems, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Miura, Yoshio [Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Department of Electronics and Information Science, Kyoto Institute of Technology, Kyoto (Japan); Matsukura, Fumihiro, E-mail: f-matsu@wpi-aimr.tohoku.ac.jp; Ohno, Hideo [Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); WPI-Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2014-12-01

    We study the spin and orbital magnetic moments in Ta/Co{sub 0.4}Fe{sub 0.4}B{sub 0.2}/MgO by x-ray magnetic circular dichroism measurements as well as first-principles calculations, in order to clarify the origin of the perpendicular magnetic anisotropy. Both experimental and theoretical results show that orbital magnetic moment of Fe is more anisotropic than that of Co with respect to the magnetization direction. The anisotropy is larger for thinner CoFeB, indicating that Fe atoms at the interface with MgO contribute more than Co to the observed perpendicular magnetic anisotropy.

  16. Perpendicular magnetic anisotropy at the interface between ultrathin Fe film and MgO studied by angular-dependent x-ray magnetic circular dichroism

    Energy Technology Data Exchange (ETDEWEB)

    Okabayashi, J. [Research Center for Spectrochemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Koo, J. W.; Mitani, S. [National Institute for Materials Science (NIMS), Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8577 (Japan); Sukegawa, H. [National Institute for Materials Science (NIMS), Tsukuba 305-0047 (Japan); Takagi, Y.; Yokoyama, T. [Institute of Molecular Science, Okazaki, Aichi 444-8585 (Japan)

    2014-09-22

    Interface perpendicular magnetic anisotropy (PMA) in ultrathin Fe/MgO (001) has been investigated using angular-dependent x-ray magnetic circular dichroism (XMCD). We found that anisotropic orbital magnetic moments deduced from the analysis of XMCD contribute to the large PMA energies, whose values depend on the annealing temperature. The large PMA energies determined from magnetization measurements are related to those estimated from the XMCD and the anisotropic orbital magnetic moments through the spin-orbit interaction. The enhancement of anisotropic orbital magnetic moments can be explained mainly by the hybridization between the Fe 3d{sub z}{sup 2} and O 2p{sub z} states.

  17. Differential Equations with Linear Algebra

    CERN Document Server

    Boelkins, Matthew R; Potter, Merle C

    2009-01-01

    Linearity plays a critical role in the study of elementary differential equations; linear differential equations, especially systems thereof, demonstrate a fundamental application of linear algebra. In Differential Equations with Linear Algebra, we explore this interplay between linear algebra and differential equations and examine introductory and important ideas in each, usually through the lens of important problems that involve differential equations. Written at a sophomore level, the text is accessible to students who have completed multivariable calculus. With a systems-first approach, t

  18. Crab Cavities for Linear Colliders

    Energy Technology Data Exchange (ETDEWEB)

    Burt, G.; Ambattu, P.; Carter, R.; Dexter, A.; Tahir, I.; /Cockcroft Inst. Accel. Sci. Tech. /Lancaster U.; Beard, C.; Dykes, M.; Goudket, P.; Kalinin, A.; Ma, L.; McIntosh, P.; /Daresbury; Shulte, D.; /CERN; Jones, Roger M.; /Cockcroft Inst. Accel. Sci. Tech. /Manchester U.; Bellantoni, L.; Chase, B.; Church, M.; Khabouline, T.; Latina, A.; /Fermilab; Adolphsen, C.; Li, Z.; Seryi, Andrei; /SLAC

    2011-11-08

    Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favour a 3.9 GHz superconducting, multi-cell cavity as the solution for ILC, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are fundamental issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders.

  19. Crab cavities for linear colliders

    CERN Document Server

    Burt, G; Carter, R; Dexter, A; Tahir, I; Beard, C; Dykes, M; Goudket, P; Kalinin, A; Ma, L; McIntosh, P; Shulte, D; Jones, Roger M; Bellantoni, L; Chase, B; Church, M; Khabouline, T; Latina, A; Adolphsen, C; Li, Z; Seryi, Andrei; Xiao, L

    2008-01-01

    Crab cavities have been proposed for a wide number of accelerators and interest in crab cavities has recently increased after the successful operation of a pair of crab cavities in KEK-B. In particular crab cavities are required for both the ILC and CLIC linear colliders for bunch alignment. Consideration of bunch structure and size constraints favour a 3.9 GHz superconducting, multi-cell cavity as the solution for ILC, whilst bunch structure and beam-loading considerations suggest an X-band copper travelling wave structure for CLIC. These two cavity solutions are very different in design but share complex design issues. Phase stabilisation, beam loading, wakefields and mode damping are fundamental issues for these crab cavities. Requirements and potential design solutions will be discussed for both colliders.

  20. Optical linear algebra

    Energy Technology Data Exchange (ETDEWEB)

    Casasent, D.; Ghosh, A.

    1983-01-01

    Many of the linear algebra operations and algorithms possible on optical matrix-vector processors are reviewed. Emphasis is given to the use of direct solutions and their realization on systolic optical processors. As an example, implicit and explicit solutions to partial differential equations are considered. The matrix-decomposition required is found to be the major operation recommended for optical realization. The pipelining and flow of data and operations are noted to be key issues in the realization of any algorithm on an optical systolic array processor. A realization of the direct solution by householder qr decomposition is provided as a specific case study. 19 references.

  1. Linear right ideal nearrings

    Directory of Open Access Journals (Sweden)

    Kenneth D. Magill

    2001-01-01

    Full Text Available We determine, up to isomorphism, all those topological nearrings n whose additive groups are the n-dimensional Euclidean groups, n>1, and which contain n one-dimensional linear subspaces {Ji}i=1n which are also right ideals of the nearring satisfying several additional properties. Specifically, for each w∈n, we require that there exist wi∈Ji, 1≤i≤n, such that w=w1+w2+⋯+wn and multiplication on the left of w yields the same result as multiplication by the same element on the left of wn. That is, vw=vwn for each v∈n.

  2. Matlab linear algebra

    CERN Document Server

    Lopez, Cesar

    2014-01-01

    MATLAB is a high-level language and environment for numerical computation, visualization, and programming. Using MATLAB, you can analyze data, develop algorithms, and create models and applications. The language, tools, and built-in math functions enable you to explore multiple approaches and reach a solution faster than with spreadsheets or traditional programming languages, such as C/C++ or Java. MATLAB Linear Algebra introduces you to the MATLAB language with practical hands-on instructions and results, allowing you to quickly achieve your goals. In addition to giving an introduction to

  3. Variations in clinical estimates of tumor volume regression parameters and time factor during external radiotherapy in cancer cervix: Does it mimic the linear-quadratic model of cell survival?

    Directory of Open Access Journals (Sweden)

    Datta N

    2005-01-01

    Full Text Available BACKGROUND: Tumor regression parameters and time factor during external radiotherapy (EXTRT are of paramount importance. AIMS: To quantify the parameters of tumor regression and time factor during EXTRT in cancer cervix. SETTINGS AND DESIGN: Patients, treated solely with radiotherapy and enrolled for other prospective studies having weekly tumor regressions recorded were considered. MATERIALS AND METHODS: Seventy-seven patients received 50Gy of EXTRT followed by intracavitary brachytherapy. Loco-regional regressions were assessed clinically and regression fraction (RF was represented as RF = c + a1D + a2D2- a3T, with c, D and T as constant, cumulative EXTRT dose and treatment time respectively. STATISTICAL ANALYSIS USED: Step wise linear regression was performed for RF. Scatter plots were fitted using linear-quadratic fit. RESULTS: Coefficients of parameters D, D2 and T were computed for various dose intervals, namely 0-20 Gy, 0-30 Gy, 0-40 Gy and 0-50 Gy. At 0-20 Gy and 0-30 Gy, only the coefficient of D2 was significant (P < 0.001, while both D2 and T turned significant (P < 0.001 at 0-40 Gy. For the entire range of 0-50 Gy, all the coefficients of D, D2 and T showed significance, leading to an estimate of 26 Gy for a1/a2 and 0.96 Gy/day for a3/a1. CONCLUSIONS: As with a/β and g/a of post-irradiation cell survival curves, a1/a2 and a3/a1 represents the cumulative effect of various radiobiological factors influencing clinical regression of tumor during the course of EXTRT. The dynamic changes in the coefficients of D, D2sub and T, indicate their relative importance during various phases of EXTRT.

  4. Linear atomic quantum coupler

    CERN Document Server

    El-Orany, Faisal A A

    2009-01-01

    In this paper, we develop the notion of the linear atomic quantum coupler. This device consists of two modes propagating into two waveguides, each of them includes a localized and/or a trapped atom. These waveguides are placed close enough to allow exchanging energy between them via evanescent waves. Each mode interacts with the atom in the same waveguide in the standard way, i.e. as the Jaynes-Cummings model (JCM), and with the atom-mode in the second waveguide via evanescent wave. We present the Hamiltonian for the system and deduce the exact form for the wavefunction. We investigate the atomic inversions and the second-order correlation function. In contrast to the conventional linear coupler, the atomic quantum coupler is able to generate nonclassical effects. The atomic inversions can exhibit long revival-collapse phenomenon as well as subsidiary revivals based on the competition among the switching mechanisms in the system. Finally, under certain conditions, the system can yield the results of the two-m...

  5. Comet LINEAR Splits Further

    Science.gov (United States)

    2001-05-01

    Third Nucleus Observed with the VLT Summary New images from the VLT show that one of the two nuclei of Comet LINEAR (C/2001 A2), now about 100 million km from the Earth, has just split into at least two pieces . The three fragments are now moving through space in nearly parallel orbits while they slowly drift apart. This comet will pass through its perihelion (nearest point to the Sun) on May 25, 2001, at a distance of about 116 million kilometres. It has brightened considerably due to the splitting of its "dirty snowball" nucleus and can now be seen with the unaided eye by observers in the southern hemisphere as a faint object in the southern constellation of Lepus (The Hare). PR Photo 18a/01 : Three nuclei of Comet LINEAR . PR Photo 18b/01 : The break-up of Comet LINEAR (false-colour). Comet LINEAR splits and brightens ESO PR Photo 18a/01 ESO PR Photo 18a/01 [Preview - JPEG: 400 x 438 pix - 55k] [Normal - JPEG: 800 x 875 pix - 136k] ESO PR Photo 18b/01 ESO PR Photo 18b/01 [Preview - JPEG: 367 x 400 pix - 112k] [Normal - JPEG: 734 x 800 pix - 272k] Caption : ESO PR Photo 18a/01 shows the three nuclei of Comet LINEAR (C/2001 A2). It is a reproduction of a 1-min exposure in red light, obtained in the early evening of May 16, 2001, with the 8.2-m VLT YEPUN (UT4) telescope at Paranal. ESO PR Photo 18b/01 shows the same image, but in a false-colour rendering for more clarity. The cometary fragment "B" (right) has split into "B1" and "B2" (separation about 1 arcsec, or 500 km) while fragment "A" (upper left) is considerably fainter. Technical information about these photos is available below. Comet LINEAR was discovered on January 3, 2001, and designated by the International Astronomical Union (IAU) as C/2001 A2 (see IAU Circular 7564 [1]). Six weeks ago, it was suddenly observed to brighten (IAUC 7605 [1]). Amateurs all over the world saw the comparatively faint comet reaching naked-eye magnitude and soon thereafter, observations with professional telescopes indicated

  6. On the linear programming bound for linear Lee codes.

    Science.gov (United States)

    Astola, Helena; Tabus, Ioan

    2016-01-01

    Based on an invariance-type property of the Lee-compositions of a linear Lee code, additional equality constraints can be introduced to the linear programming problem of linear Lee codes. In this paper, we formulate this property in terms of an action of the multiplicative group of the field [Formula: see text] on the set of Lee-compositions. We show some useful properties of certain sums of Lee-numbers, which are the eigenvalues of the Lee association scheme, appearing in the linear programming problem of linear Lee codes. Using the additional equality constraints, we formulate the linear programming problem of linear Lee codes in a very compact form, leading to a fast execution, which allows to efficiently compute the bounds for large parameter values of the linear codes.

  7. Linear algebra, geometry and transformation

    CERN Document Server

    Solomon, Bruce

    2014-01-01

    Vectors, Mappings and Linearity Numeric Vectors Functions Mappings and Transformations Linearity The Matrix of a Linear Transformation Solving Linear Systems The Linear SystemThe Augmented Matrix and RRE Form Homogeneous Systems in RRE Form Inhomogeneous Systems in RRE Form The Gauss-Jordan Algorithm Two Mapping Answers Linear Geometry Geometric Vectors Geometric/Numeric Duality Dot-Product Geometry Lines, Planes, and Hyperplanes System Geometry and Row/Column Duality The Algebra of Matrices Matrix Operations Special Matrices Matrix Inversion A Logical Digression The Logic of the Inversion Alg

  8. Photoinduced dichroism and optical anisotropy in a liquid-crystalline azobenzene side chain polymer caused by anisotropic angular distribution of trans and cis isomers

    Science.gov (United States)

    Blinov, Lev M.; Kozlovsky, Mikhail V.; Ozaki, Masanori; Skarp, Kent; Yoshino, Katsumi

    1998-10-01

    Photochromism has been studied for two comb-like liquid-crystalline copolymers (I) and (II) containing azobenzene chromophores in their side chains. In a smectic glass phase of both copolymers, upon short-time irradiation by UV light, long-living cis isomers are observed. Both copolymers manifest the photoinduced anisotropy, the physical mechanisms of which seem to be quite different. In spin-coated films of polymer (II), the origin of the anisotropy is a strong stable dichroism, which is due to an enrichment and depletion of the chosen angular direction, correspondingly, with trans and cis isomers of the azobenzene chromophores. Polymer (I) manifests no dichroism at all, and its induced optical anisotropy may be accounted for by a rather slow chromophore reorientation. In copolymer (II) a considerable reorientation of the mesogenic groups also occurs as a secondary phenomenon at the stage of the cis isomer formation only. This observation shed more light on the general process of the light-induced molecular reorientation in polymers, liquid crystals, and Langmuir-Blodgett films, which is of great importance for holographic information recording.

  9. Absorption spectra of adenocarcinoma and squamous cell carcinoma cervical tissues

    Science.gov (United States)

    Ivashko, Pavlo; Peresunko, Olexander; Zelinska, Natalia; Alonova, Marina

    2014-08-01

    We studied a methods of assessment of a connective tissue of cervix in terms of specific volume of fibrous component and an optical density of staining of connective tissue fibers in the stroma of squamous cancer and cervix adenocarcinoma. An absorption spectra of blood plasma of the patients suffering from squamous cancer and cervix adenocarcinoma both before the surgery and in postsurgical periods were obtained. Linear dichroism measurements transmittance in polarized light at different orientations of the polarization plane relative to the direction of the dominant orientation in the structure of the sample of biotissues of stroma of squamous cancer and cervix adenocarcinoma were carried. Results of the investigation of the tumor tissues showed that the magnitude of the linear dichroism Δ is insignificant in the researched spectral range λ=280-840 nm and specific regularities in its change observed short-wave ranges.

  10. Linear control theory for gene network modeling.

    Science.gov (United States)

    Shin, Yong-Jun; Bleris, Leonidas

    2010-09-16

    Systems biology is an interdisciplinary field that aims at understanding complex interactions in cells. Here we demonstrate that linear control theory can provide valuable insight and practical tools for the characterization of complex biological networks. We provide the foundation for such analyses through the study of several case studies including cascade and parallel forms, feedback and feedforward loops. We reproduce experimental results and provide rational analysis of the observed behavior. We demonstrate that methods such as the transfer function (frequency domain) and linear state-space (time domain) can be used to predict reliably the properties and transient behavior of complex network topologies and point to specific design strategies for synthetic networks.

  11. Linear geometry thyratron

    Science.gov (United States)

    Byron, S.

    1985-03-01

    The low pressure gas-filled thyratron is scalable in the long dimension. Internally the tube is formed as a tetrode, with an auxiliary grid placed between the cathode and the control grid. A dc or pulsed power source drives the auxiliary grid both to insure uniform cathode emission and to provide a grid-cathode plasma prior to commutation. The high voltage holdoff structure consists of the anode, the control grid and its electrostatic shielding baffles, and a main quartz insulator. A small gas flow supply and exhaust system is used that eliminates the need for a hydrogen reservoir and permits other gases, such as helium, to be used. The thyratron provides a low inductance, high current, long lifetime switch configuration: useful for switch-on applications involving large scale lasers and other similar loads that are distributed in a linear geometry.

  12. Introduction to linear elasticity

    CERN Document Server

    Gould, Phillip L

    2013-01-01

    Introduction to Linear Elasticity, 3rd Edition, provides an applications-oriented grounding in the tensor-based theory of elasticity for students in mechanical, civil, aeronautical, and biomedical engineering, as well as materials and earth science. The book is distinct from the traditional text aimed at graduate students in solid mechanics by introducing the subject at a level appropriate for advanced undergraduate and beginning graduate students. The author's presentation allows students to apply the basic notions of stress analysis and move on to advanced work in continuum mechanics, plasticity, plate and shell theory, composite materials, viscoelasticity and finite method analysis. This book also:  Emphasizes tensor-based approach while still distilling down to explicit notation Provides introduction to theory of plates, theory of shells, wave propagation, viscoelasticity and plasticity accessible to advanced undergraduate students Appropriate for courses following emerging trend of teaching solid mechan...

  13. Novel cyclen-based linear polymer as a high-affinity binding material for DNA condensation

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A novel cyclen-based linear polyamine (POGEC) was designed and synthesized from the reaction between 1,3-propanediol diglycidyl ether and 1,7-bis(diethoxyphosphory)-1,4,7,10-tetraazacyclod-odecane. High-affinity binding between POGEC and DNA was demonstrated by agarose gel electrophoresis and scanning electron microscopy (SEM). Moreover,the formed POGEC/DNA complex (termed polyplex) could be disassociated to release the free DNA through addition of the physiological concentration of NaCl solution. Fluorescence spectrum was used to measure the high-affinity binding and DNA condensation capability of POGEC. Circular dichroism (CD) spectrum indicates that the DNA conformation did not change after binding to POEGC.

  14. Novel cyclen-based linear polymer as a high-affinity binding material for DNA condensation

    Institute of Scientific and Technical Information of China (English)

    XIANG YongZhe; WANG Na; ZHANG Ji; LI Kun; ZHANG ZhongWei; LIN HongHui; YU XiaoQi

    2009-01-01

    A novel cyclen-based linear polyamine (POGEC) was designed and synthesized from the reaction be-tween 1,3-propanediol diglycidyl ether and 1,7-bis(diethoxyphosphory)-1,4,7,10-tetraazacyclod- odecane.High-affinity binding between POGEC and DNA was demonstrated by agarose gel electrophoresis and scanning electron microscopy (SEM). Moreover, the formed POGEC/DNA complex (termed polyplex) could be disassociated to release the free DNA through addition of the physiological concentration of NaCl solution. Fluorescence spectrum was used to measure the high-affinity binding and DNA con-densation capability of POGEC. Circular dichroism (CD) spectrum indicates that the DNA conformation did not change after binding to POEGC.

  15. Non-Markovian Quantum State Diffusion for temperature-dependent linear spectra of light harvesting aggregates

    Science.gov (United States)

    Ritschel, Gerhard; Suess, Daniel; Möbius, Sebastian; Strunz, Walter T.; Eisfeld, Alexander

    2015-01-01

    Non-Markovian Quantum State Diffusion (NMQSD) has turned out to be an efficient method to calculate excitonic properties of aggregates composed of organic chromophores, taking into account the coupling of electronic transitions to vibrational modes of the chromophores. NMQSD is an open quantum system approach that incorporates environmental degrees of freedom (the vibrations in our case) in a stochastic way. We show in this paper that for linear optical spectra (absorption, circular dichroism), no stochastics is needed, even for finite temperatures. Thus, the spectra can be obtained by propagating a single trajectory. To this end, we map a finite temperature environment to the zero temperature case using the so-called thermofield method. The resulting equations can then be solved efficiently by standard integrators.

  16. Recursive Algorithm For Linear Regression

    Science.gov (United States)

    Varanasi, S. V.

    1988-01-01

    Order of model determined easily. Linear-regression algorithhm includes recursive equations for coefficients of model of increased order. Algorithm eliminates duplicative calculations, facilitates search for minimum order of linear-regression model fitting set of data satisfactory.

  17. Computer Program For Linear Algebra

    Science.gov (United States)

    Krogh, F. T.; Hanson, R. J.

    1987-01-01

    Collection of routines provided for basic vector operations. Basic Linear Algebra Subprogram (BLAS) library is collection from FORTRAN-callable routines for employing standard techniques to perform basic operations of numerical linear algebra.

  18. Linear connections on matrix geometries

    CERN Document Server

    Madore, J; Mourad, J; Madore, John; Masson, Thierry; Mourad, Jihad

    1994-01-01

    A general definition of a linear connection in noncommutative geometry has been recently proposed. Two examples are given of linear connections in noncommutative geometries which are based on matrix algebras. They both possess a unique metric connection.

  19. A primer on linear models

    CERN Document Server

    Monahan, John F

    2008-01-01

    Preface Examples of the General Linear Model Introduction One-Sample Problem Simple Linear Regression Multiple Regression One-Way ANOVA First Discussion The Two-Way Nested Model Two-Way Crossed Model Analysis of Covariance Autoregression Discussion The Linear Least Squares Problem The Normal Equations The Geometry of Least Squares Reparameterization Gram-Schmidt Orthonormalization Estimability and Least Squares Estimators Assumptions for the Linear Mean Model Confounding, Identifiability, and Estimability Estimability and Least Squares Estimators F

  20. 基于手性金纳米粒子圆二色光谱法识别与检测银离子%Recognition and Detection of Silver Ion by Circular Dichroism Spectrum Based on Chiral Gold Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    韦克毅; 王猛; 杜宇; 蔡波; 江云宝

    2016-01-01

    In this work,chiral gold particles with optical activity can be obtained by a facile liquid phase method.The textural proper-ties of the as-prepared samples were characterized by high resolution transmission electron microscopy,circular dichroism spectrum and absorption spectrum.The results show that the average particle size for the production is 3.6 nm and silver ion can be selectively recognized from 1 3 kinds of metal ions in 1 2 min with universal recurrence.We also established the standard curve for detecting silver ion.This study demonstrates that the linear range for this curve is 0.2-30μmol/L,the linearly dependent coefficient is 0.995(n=15),which supplies a simple new environmentally friendly method for quickly detecting and recognizing silver ion in environmental water samples with high precision.%采用液相制备方法获得具有光学活性的手性金纳米粒子,通过吸收光谱和圆二色光谱及高分辨透射电镜对手性金纳米粒子进行表征.利用圆二色光谱法建立手性金纳米粒子对 Ag+选择性识别方法,结果表明手性金纳米粒子对Ag+响应时间仅需12 min,手性金纳米粒子能够从13种常见金属离子中选择性识别 Ag+,并对多种常见金属离子具有较好的抗干扰能力,检测灵敏度高并且具有良好的重现性.所建立标准曲线线性范围为0.2~30μmol/L,线性相关系数R2=0.995(n=15),Ag+的检测限为0.2μmol/L;为环境水样中 Ag+的识别和检测提供了一种简单、精确、快速、环境友好的新方法.

  1. Templates for Linear Algebra Problems

    NARCIS (Netherlands)

    Bai, Z.; Day, D.; Demmel, J.; Dongarra, J.; Gu, M.; Ruhe, A.; Vorst, H.A. van der

    2001-01-01

    The increasing availability of advanced-architecture computers is having a very signicant eect on all spheres of scientic computation, including algorithm research and software development in numerical linear algebra. Linear algebra {in particular, the solution of linear systems of equations and eig

  2. Linear Logic on Petri Nets

    DEFF Research Database (Denmark)

    Engberg, Uffe Henrik; Winskel, Glynn

    This article shows how individual Petri nets form models of Girard's intuitionistic linear logic. It explores questions of expressiveness and completeness of linear logic with respect to this interpretation. An aim is to use Petri nets to give an understanding of linear logic and give some apprai...

  3. Random linear codes in steganography

    Directory of Open Access Journals (Sweden)

    Kamil Kaczyński

    2016-12-01

    Full Text Available Syndrome coding using linear codes is a technique that allows improvement in the steganographic algorithms parameters. The use of random linear codes gives a great flexibility in choosing the parameters of the linear code. In parallel, it offers easy generation of parity check matrix. In this paper, the modification of LSB algorithm is presented. A random linear code [8, 2] was used as a base for algorithm modification. The implementation of the proposed algorithm, along with practical evaluation of algorithms’ parameters based on the test images was made.[b]Keywords:[/b] steganography, random linear codes, RLC, LSB

  4. On constructing disjoint linear codes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Weiguo; CAI Mian; XIAO Guozhen

    2007-01-01

    To produce a highly nonlinear resilient function,the disjoint linear codes were originally proposed by Johansson and Pasalic in IEEE Trans.Inform.Theory,2003,49(2):494-501.In this paper,an effective method for finding a set of such disjoint linear codes is presented.When n≥2k,we can find a set of[n,k] disjoint linear codes with joint linear codes exists with cardinality at least 2.We also describe a result on constructing a set of [n,k] disjoint linear codes with minimum distance at least some fixed positive integer.

  5. Linear Rogowski coil

    Science.gov (United States)

    Nassisi, V.; Delle Side, D.

    2017-02-01

    Nowadays, the employment and development of fast current pulses require sophisticated systems to perform measurements. Rogowski coils are used to diagnose cylindrical shaped beams; therefore, they are designed and built with a toroidal structure. Recently, to perform experiments of radiofrequency biophysical stresses, flat transmission lines have been developed. Therefore, in this work we developed a linear Rogowski coil to detect current pulses inside flat conductors. The system is first approached by means of transmission line theory. We found that, if the pulse width to be diagnosed is comparable with the propagation time of the signal in the detector, it is necessary to impose a uniform current as input pulse, or to use short coils. We further analysed the effect of the resistance of the coil and the influence of its magnetic properties. As a result, the device we developed is able to record pulses lasting for some hundreds of nanoseconds, depending on the inductance, load impedance, and resistance of the coil. Furthermore, its response is characterized by a sub-nanosecond rise time (˜100 ps). The attenuation coefficient depends mainly on the turn number of the coil, while the fidelity of the response depends both on the magnetic core characteristics and on the current distribution along the plane conductors.

  6. Linear dilaton black holes

    CERN Document Server

    Clément, G; Leygnac, C; Clement, Gerard; Gal'tsov, Dmitri; Leygnac, Cedric

    2003-01-01

    We present new solutions to Einstein-Maxwell-dilaton-axion (EMDA) gravity in four dimensions describing black holes which asymptote to the linear dilaton background. In the non-rotating case they can be obtained as the limiting geometry of dilaton black holes. The rotating solutions (possibly endowed with a NUT parameter) are constructed using a generating technique based on the Sp(4,R) duality of the EMDA system. In a certain limit (with no event horizon present) our rotating solutions coincide with supersymmetric Israel-Wilson-Perjes type dilaton-axion solutions. In presence of an event horizon supersymmetry is broken. The temperature of the static black holes is constant, and their mass does not depend on it, so the heat capacity is zero. We investigate geodesics and wave propagation in these spacetimes and find superradiance in the rotating case. Because of the non-asymptotically flat nature of the geometry, certain modes are reflected from infinity, in particular, all superradiant modes are confined. Thi...

  7. Berkeley Proton Linear Accelerator

    Science.gov (United States)

    Alvarez, L. W.; Bradner, H.; Franck, J.; Gordon, H.; Gow, J. D.; Marshall, L. C.; Oppenheimer, F. F.; Panofsky, W. K. H.; Richman, C.; Woodyard, J. R.

    1953-10-13

    A linear accelerator, which increases the energy of protons from a 4 Mev Van de Graaff injector, to a final energy of 31.5 Mev, has been constructed. The accelerator consists of a cavity 40 feet long and 39 inches in diameter, excited at resonance in a longitudinal electric mode with a radio-frequency power of about 2.2 x 10{sup 6} watts peak at 202.5 mc. Acceleration is made possible by the introduction of 46 axial "drift tubes" into the cavity, which is designed such that the particles traverse the distance between the centers of successive tubes in one cycle of the r.f. power. The protons are longitudinally stable as in the synchrotron, and are stabilized transversely by the action of converging fields produced by focusing grids. The electrical cavity is constructed like an inverted airplane fuselage and is supported in a vacuum tank. Power is supplied by 9 high powered oscillators fed from a pulse generator of the artificial transmission line type.

  8. Design of scratch detector for cell phone screen based on linear array CCD%基于线阵CCD的手机屏幕瑕疵检测器的设计

    Institute of Scientific and Technical Information of China (English)

    董恒平; 刘增元; 易阳; 薛斌

    2012-01-01

    以改善手机屏幕质量传统人工检测方法的稳定性和可靠性为目的,制作了1款基于线阵CCD的手机屏幕划痕类瑕疵检测器.采用CCD相机和单稳态触发器为核心器件对信号采集、信号处理和功能模块电路进行了设计,可单独提取出划痕信号并将其整形为矩形脉冲.基于此,可以对手机屏幕表面3cm×3cm区域内,宽度≥0.08mm的划痕进行快速识别并报警,并能实现对0~9以内,最小间距达0.5mm的划痕数目进行准确分辨和实时统计.该检测器可应用于手机生产流水线,实现对手机屏幕质量的在线实时、高效检测.%With the purpose of improving stability and reliability in traditional artificial methods of quality detection, scratch detector for cell phone screen is fabricated based on linear array CCD. By employing CCD camera and monostable flip-flop as core components, signal acquisition, signal processing and functional modular circuits are designed. Signal corresponding to scratches is extracted seperately and transformed into rectangular pulses. An alarm is quickly given when scatch with linewidth greater than 0. 08 mm is identified on the screen surface within the area of 3 cm X 3 cm. Besides, the number of scatches with minumum spacing of 0. 5 mm can be accurately distinguished and instantaneously counted within the range of 0-9. In this case,this detector can be applied in assembly line of cell phone for realizing online real-time and high-efficient quality detection of cell phone screen.

  9. Linear Algebraic Method for Non-Linear Map Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Yu,L.; Nash, B.

    2009-05-04

    We present a newly developed method to analyze some non-linear dynamics problems such as the Henon map using a matrix analysis method from linear algebra. Choosing the Henon map as an example, we analyze the spectral structure, the tune-amplitude dependence, the variation of tune and amplitude during the particle motion, etc., using the method of Jordan decomposition which is widely used in conventional linear algebra.

  10. Direct observation of high-spin states in manganese dimer and trimer cations by x-ray magnetic circular dichroism spectroscopy in an ion trap

    Energy Technology Data Exchange (ETDEWEB)

    Zamudio-Bayer, V. [Physikalisches Institut, Universität Freiburg, Stefan-Meier-Straße 21, 79104 Freiburg (Germany); Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin (Germany); Hirsch, K.; Langenberg, A.; Kossick, M. [Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin (Germany); Institut für Optik und Atomare Physik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin (Germany); Ławicki, A.; Lau, J. T., E-mail: tobias.lau@helmholtz-berlin.de [Institut für Methoden und Instrumentierung der Forschung mit Synchrotronstrahlung, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin (Germany); Terasaki, A. [Cluster Research Laboratory, Toyota Technological Institute, 717-86 Futamata, Ichikawa, Chiba 272-0001 (Japan); Department of Chemistry, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581 (Japan); Issendorff, B. von [Physikalisches Institut, Universität Freiburg, Stefan-Meier-Straße 21, 79104 Freiburg (Germany)

    2015-06-21

    The electronic structure and magnetic moments of free Mn{sub 2}{sup +} and Mn{sub 3}{sup +} are characterized by 2p x-ray absorption and x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap that is coupled to a synchrotron radiation beamline. Our results directly show that localized magnetic moments of 5 μ{sub B} are created by 3d{sup 5}({sup 6}S) states at each ionic core, which are coupled ferromagnetically to form molecular high-spin states via indirect exchange that is mediated in both cases by a delocalized valence electron in a singly occupied 4s derived antibonding molecular orbital with an unpaired spin. This leads to total magnetic moments of 11 μ{sub B} for Mn{sub 2}{sup +} and 16 μ{sub B} for Mn{sub 3}{sup +}, with no contribution of orbital angular momentum.

  11. Large anisotropic Fe orbital moments in perpendicularly magnetized Co2FeAl Heusler alloy thin films revealed by angular-dependent x-ray magnetic circular dichroism

    Science.gov (United States)

    Okabayashi, Jun; Sukegawa, Hiroaki; Wen, Zhenchao; Inomata, Koichiro; Mitani, Seiji

    2013-09-01

    Perpendicular magnetic anisotropy (PMA) in Heusler alloy Co2FeAl thin films sharing an interface with a MgO layer is investigated by angular-dependent x-ray magnetic circular dichroism. Orbital and spin magnetic moments are deduced separately for Fe and Co 3d electrons. In addition, the PMA energies are estimated using the orbital magnetic moments parallel and perpendicular to the film surfaces. We found that PMA in Co2FeAl is determined mainly by the contribution of Fe atoms with large orbital magnetic moments, which are enhanced at the interface between Co2FeAl and MgO. Furthermore, element specific magnetization curves of Fe and Co are found to be similar, suggesting the existence of ferromagnetic coupling between Fe and Co PMA directions.

  12. A high-performance liquid chromatography with circular dichroism detector for determination of stereochemistry of 6, 9-oxygen bridge dibenzocyclooctadiene lignans from kadsura coccinea.

    Science.gov (United States)

    Zhu, Hui; Xu, Liang; Yang, Shi-Lin; Li, He-Ran

    2015-10-01

    The stereochemistry of two 6, 9-oxygen bridge dibenzocyclooctadiene lignans from Kadsura coccinea, are difficult to separate and very unstable. The present study was designed to develop a high-performance liquid chromatography using circular dichroism detection for the analysis of the stereochemistry. A new 6, 9-oxygen bridge dibenzocyclooctadiene lignans named Kadsulignan Q was firstly found with an S-biphenyl configuration. The other compound was identified as Kadsulignan L with an R- biphenyl configuration. In order to obtain kinetic data on their reversible interconversion, the stability was measured at different deuterated solvents such as deuterated methanol, deuterated chloroform and deuterated dimethylsulfoxide. The lignans were more unstable and converted more easily in deuterated methanol than in deuterated chloroform and deuterated dimethylsulfoxide.

  13. Effect of colloidal gold size on the conformational changes of adsorbed cytochrome c: probing by circular dichroism, UV-visible, and infrared spectroscopy.

    Science.gov (United States)

    Jiang, Xiue; Jiang, Junguang; Jin, Yongdong; Wang, Erkang; Dong, Shaojun

    2005-01-01

    The conformational changes of bovine heart cytochrome c (cyt c) induced by the adsorption on gold nanoparticles with different sizes have been investigated by electronic absorption, circular dichroism (CD), and Fourier transform infrared spectra. The combination of these techniques can give complementary information about adsorption-induced conformational changes. The results show that there are different conformational changes for cyt c adsorbed on gold nanoparticles with different sizes due to the different interaction forces between cyt c and gold nanoparticles. The colloidal gold concentration-dependent conformation distribution curves of cyt c obtained by analysis of CD spectra using the singular value decomposition least-squares method show that the coverage of cyt c on the gold nanoparticles surface also affects the conformational changes of the adsorbed cyt c.

  14. Soft x-ray magnetic circular dichroism of L2{sub 1}-type Co{sub 2}FeGa Heusler alloy

    Energy Technology Data Exchange (ETDEWEB)

    Umetsu, R Y; Kainuma, R; Fukamichi, K [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Sendai 980-8577 (Japan); Nakamura, T [JASRI/SPring-8, 1-1-1 Kouto, Sayo, Hyogo 679-5198 (Japan); Kobayashi, K; Ishida, K [Department of Materials Science, Graduate School of Engineering, Tohoku University, 6-6-02 Aoba, Sendai 980-8579 (Japan); Sakuma, A, E-mail: rie@tagen.tohoku.ac.j [Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-08 Aoba, Sendai 980-8579 (Japan)

    2010-03-17

    Spin and orbital magnetic moments of the L2{sub 1}-type Co{sub 2}FeGa Heusler alloy have been investigated using x-ray magnetic circular dichroism spectra in the soft x-ray region. From the spectra of the L{sub 2,3}-edge of Co and Fe, the ratios of the orbital magnetic moment to the spin magnetic moment M{sub orb}/M{sub spin} are estimated to be 0.06 for Co and 0.02 for Fe, in agreement with the available theoretical values. The orbital magnetic moments of these two elements are small in line with theoretical results, reflecting the high symmetry of the L2{sub 1}-type crystal structure. Furthermore, it has been confirmed that the magnetic moment of Ga is induced in the present alloy.

  15. Quantitative x-ray magnetic circular dichroism mapping with high spatial resolution full-field magnetic transmission soft x-ray spectro-microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, MacCallum J. [Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Physics Department, University of California, Berkeley, California 94720 (United States); Agostino, Christopher J. [Physics Department, University of California, Berkeley, California 94720 (United States); National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); N' Diaye, Alpha T. [Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Chen, Gong [National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Im, Mi-Young [Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology, Daegu 711-873 (Korea, Republic of); Fischer, Peter, E-mail: PJFischer@lbl.gov [Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Physics Department, University of California, Santa Cruz, California 94056 (United States)

    2015-05-07

    The spectroscopic analysis of X-ray magnetic circular dichroism (XMCD), which serves as strong and element-specific magnetic contrast in full-field magnetic transmission soft x-ray microscopy, is shown to provide information on the local distribution of spin (S) and orbital (L) magnetic moments down to a spatial resolution of 25 nm limited by the x-ray optics used in the x-ray microscope. The spatially resolved L/S ratio observed in a multilayered (Co 0.3 nm/Pt 0.5 nm) × 30 thin film exhibiting a strong perpendicular magnetic anisotropy decreases significantly in the vicinity of domain walls, indicating a non-uniform spin configuration in the vertical profile of a domain wall across the thin film. Quantitative XMCD mapping with x-ray spectro-microscopy will become an important characterization tool for systems with topological or engineered magnetization inhomogeneities.

  16. Ga+ ion irradiation-induced changes in magnetic anisotropy of a Pt/Co/Pt thin film studied by X-ray magnetic circular dichroism

    Directory of Open Access Journals (Sweden)

    Liedke M. O.

    2013-01-01

    Full Text Available Ga+ ion irradiation-induced changes in magnetic anisotropy of a Pt/Co/Pt ultrathin film are investigated by means of the X-ray magnetic circular dichroism (XMCD technique. A large difference in the Co orbital moment is observed between out-of-plane and in-plane directions of the film at moderate Ga+ fluences of ~1-2×1014 ions/cm2, which corresponds to the perpendicular magnetic anisotropy (PMA, while further increased fluences reduce the orbital moment difference, resulting in in-plane magnetization. In contrast, at much higher Ga+ fluences of ~5×1015 ions/cm2, at which PMA is observed again, no significant difference is found in the orbital moment of Co between out-of-plane and in-plane directions. Different origins are thus suggested for the appearance of PMA induced by the irradiation between moderate and high Ga+ fluences.

  17. Nuclear velocity perturbation theory for vibrational circular dichroism: An approach based on the exact factorization of the electron-nuclear wave function

    Energy Technology Data Exchange (ETDEWEB)

    Scherrer, Arne [Martin-Luther-University Halle-Wittenberg, von-Danckelmann-Platz 4, D-06120 Halle (Germany); UMR 8640 ENS-CNRS-UPMC, Département de Chimie, 24 rue Lhomond, École Normale Supérieure, 75005 Paris (France); UPMC Université Paris 06, 4, Place Jussieu, 75005 Paris (France); Agostini, Federica; Gross, E. K. U. [Max-Planck-Institute of Microstructure Physics, Weinberg 2, D-06120 Halle (Germany); Sebastiani, Daniel [Martin-Luther-University Halle-Wittenberg, von-Danckelmann-Platz 4, D-06120 Halle (Germany); Vuilleumier, Rodolphe [UMR 8640 ENS-CNRS-UPMC, Département de Chimie, 24 rue Lhomond, École Normale Supérieure, 75005 Paris (France); UPMC Université Paris 06, 4, Place Jussieu, 75005 Paris (France)

    2015-08-21

    The nuclear velocity perturbation theory (NVPT) for vibrational circular dichroism (VCD) is derived from the exact factorization of the electron-nuclear wave function. This new formalism offers an exact starting point to include correction terms to the Born-Oppenheimer (BO) form of the molecular wave function, similar to the complete-adiabatic approximation. The corrections depend on a small parameter that, in a classical treatment of the nuclei, is identified as the nuclear velocity. Apart from proposing a rigorous basis for the NVPT, we show that the rotational strengths, related to the intensity of the VCD signal, contain a new contribution beyond-BO that can be evaluated with the NVPT and that only arises when the exact factorization approach is employed. Numerical results are presented for chiral and non-chiral systems to test the validity of the approach.

  18. Valence-state Model of Strain-dependent Mn L2,3 X-ray Magnetic Circular Dichroism from Ferromagnetic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    van der Laan, G.; Edmonds, K. W.; Arenholz, E.; Farley, N. R. S.; Gallagher, B. L.

    2010-03-30

    We present a valence-state model to explain the characteristics of a recently observed pre-edge feature in Mn L{sub 3} x-ray magnetic circular dichroism (XMCD) of ferromagnetic (Ga,Mn)As and (Al,Ga,Mn)As thin films. The prepeak XMCD shows a uniaxial anisotropy, contrary to the cubic symmetry of the main structures induced by the crystalline electric field. Reversing the strain in the host lattice reverses the sign of the uniaxial anisotropy. With increasing carrier localization, the prepeak height increases, indicating an increasing 3d character of the hybridized holes. Hence, the feature is ascribed to transitions from the Mn 2p core level to unoccupied p-d hybridized valence states. The characteristics of the prepeak are readily reproduced by the model calculation taking into account the symmetry of the strain-, spin-orbit-, and exchange-split valence states around the zone center.

  19. A vibrational circular dichroism approach to the determination of the absolute configurations of flavorous 5-substituted-2(5H)-furanones.

    Science.gov (United States)

    Nakahashi, Atsufumi; Yaguchi, Yoshihiro; Miura, Nobuaki; Emura, Makoto; Monde, Kenji

    2011-04-25

    Sotolon (1) and maple furanone (2) are naturally occurring chiral furanones. These 5-substituted-2(5H)-furanones are industrially significant aroma compounds due to their characteristic organoleptic properties and extraordinarily low odor thresholds. Each enantiomer of 1 and 2 was successfully obtained by preparative enantioselective supercritical fluid chromatography. The absolute configuration of 1 was confirmed as (R)-(-)-1 and (S)-(+)-1 by adopting the vibrational circular dichroism (VCD) approach. The absolute configuration of 2, which has remained ambiguous since its discovery in 1957, was determined as (R)-(+)-2 and (S)-(-)-2 for the first time by the VCD technique. Surprisingly, the signs of the optical rotation of 2 are opposite of those of 1 regardless of their identical absolute configurations. This observation emphasizes the risk in absolute configurational assignments based on comparison of optical rotation signs of similar structures. Odor evaluation of the enantiomers of 2 revealed different odor intensities.

  20. Angle-resolved soft X-ray magnetic circular dichroism in a monatomic Fe layer facing an MgO(0 0 1) tunnel barrier

    Energy Technology Data Exchange (ETDEWEB)

    Mamiya, K. [Photon Factory, Institute of Materials Structure Science (IMSS), High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Koide, T. [Photon Factory, Institute of Materials Structure Science (IMSS), High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)]. E-mail: tsuneharu.koide@kek.jp; Ishida, Y. [Department of Complexity Science and Engineering, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Osafune, Y. [Department of Complexity Science and Engineering, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Fujimori, A. [Department of Complexity Science and Engineering, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Suzuki, Y. [Graduate School of Engineering Science, Osaka University, 1-3 Toyonaka, Osaka 560-8531 (Japan); NanoElectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Katayama, T. [NanoElectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Yuasa, S. [NanoElectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan)

    2006-11-15

    The electronic and magnetic states of a monatomic Fe(0 0 1) layer directly facing an MgO(0 0 1) tunnel barrier were studied by angle-resolved X-ray magnetic circular dichroism (XMCD) at the Fe L {sub 2,3} edges in the longitudinal (L) and transverse (T) arrangements. A strong XMCD reveals no oxidation of the 1-ML Fe, showing its crucial role in giant tunnel magnetoresistance effects in Fe/MgO/Fe magnetic tunnel junctions. Sum-rule analyses of the angle-resolved XMCD give values of a spin moment, in-plane and out-of-plane orbital and magnetic dipole moments. Argument is given on their physical implication.