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Sample records for multiple chiral centers

  1. (Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

    PubMed Central

    Koutoulogenis, Giorgos; Kaplaneris, Nikolaos

    2016-01-01

    Summary Organocatalysis, now running its second decade of life, is being considered one of the main tools a synthetic chemist has to perform asymmetric catalysis. In this review the synthesis of six-membered rings, that contain multiple chiral centers, either by a ring closing process or by a functionalization reaction on an already existing six-membered ring, utilizing bifunctional (thio)ureas will be summarized. Initially, the use of primary amine-thioureas as organocatalysts for the above transformation is being discussed, followed by the examples employing secondary amine-thioureas. Finally, the use of tertiary amine-thioureas and miscellaneous examples are presented. PMID:27340441

  2. (Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers.

    PubMed

    Koutoulogenis, Giorgos; Kaplaneris, Nikolaos; Kokotos, Christoforos G

    2016-01-01

    Organocatalysis, now running its second decade of life, is being considered one of the main tools a synthetic chemist has to perform asymmetric catalysis. In this review the synthesis of six-membered rings, that contain multiple chiral centers, either by a ring closing process or by a functionalization reaction on an already existing six-membered ring, utilizing bifunctional (thio)ureas will be summarized. Initially, the use of primary amine-thioureas as organocatalysts for the above transformation is being discussed, followed by the examples employing secondary amine-thioureas. Finally, the use of tertiary amine-thioureas and miscellaneous examples are presented. PMID:27340441

  3. Chiral geometry in multiple chiral doublet bands

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Chen, Qibo

    2016-02-01

    The chiral geometry of multiple chiral doublet bands with identical configuration is discussed for different triaxial deformation parameters γ in the particle rotor model with . The energy spectra, electromagnetic transition probabilities B(M1) and B(E2), angular momenta, and K-distributions are studied. It is demonstrated that the chirality still remains not only in the yrast and yrare bands, but also in the two higher excited bands when γ deviates from 30°. The chiral geometry relies significantly on γ, and the chiral geometry of the two higher excited partner bands is not as good as that of the yrast and yrare doublet bands. Supported by Plan Project of Beijing College Students’ Scientific Research and Entrepreneurial Action, Major State 973 Program of China (2013CB834400), National Natural Science Foundation of China (11175002, 11335002, 11375015, 11461141002), National Fund for Fostering Talents of Basic Science (NFFTBS) (J1103206), Research Fund for Doctoral Program of Higher Education (20110001110087) and China Postdoctoral Science Foundation (2015M580007)

  4. How center vortices break chiral symmetry

    NASA Astrophysics Data System (ADS)

    Faber, Manfried; Höllwieser, Roman

    2016-01-01

    We investigate the chiral properties of near-zero modes for thick classical center vortices in SU(2) lattice gauge theory as examples of the phenomena which may arise in a vortex vacuum. In particular we analyze the creation of near-zero modes from would-be zero modes of various topological charge contributions from center vortices. We show that classical colorful spherical vortex and instanton ensembles have almost identical Dirac spectra and the low-lying eigenmodes from spherical vortices show all characteristic properties for chiral symmetry breaking. We further show that also vortex intersections are able to give rise to a finite density of near-zero modes, leading to chiral symmetry breaking via the Banks-Casher formula. We discuss the mechanism by which center vortex fluxes contribute to chiral symmetry breaking.

  5. Multiple chiral doublet bands of identical configuration in 103Rh.

    PubMed

    Kuti, I; Chen, Q B; Timár, J; Sohler, D; Zhang, S Q; Zhang, Z H; Zhao, P W; Meng, J; Starosta, K; Koike, T; Paul, E S; Fossan, D B; Vaman, C

    2014-07-18

    Three sets of chiral doublet band structures have been identified in the ^{103}Rh nucleus. The properties of the observed chiral doublet bands are in good agreement with theoretical results obtained using constrained covariant density functional theory and particle rotor model calculations. Two of them belong to an identical configuration and provide the first experimental evidence for a novel type of multiple chiral doublets, where an "excited" chiral doublet of a configuration is seen together with the "yrast" one. This observation shows that the chiral geometry in nuclei can be robust against the increase of the intrinsic excitation energy. PMID:25083635

  6. Multiple spectra of electron spin resonance in chiral molecule-based magnets networked by a single chiral ligand

    NASA Astrophysics Data System (ADS)

    Mito, M.; Nagano, T.; Tsuruta, K.; Deguchi, H.; Takagi, S.; Kishine, J.; Yoshida, Y.; Inoue, K.

    2013-10-01

    A molecule-based magnet [Cr(CN)6][Mn(R/S)-pnH(H2O)](H2O) (termed R/S-GN) is a chiral crystal without an inversion center and mirror reflection, and its structural network is constructed using a chiral ligand diaminopropane (R/S)-pn. In S-GN, multiple spectra of ESR were observed below the magnetic ordering temperature by Morgunov et al. [Phys. Rev. B 77, 184419 (2008)]. They concluded that the phenomenon at the high field side occurred because the incommensurate magnetic structure resulted in a length-controllable superlattice of domain walls (the so-called chiral soliton lattice, CSL) under a dc magnetic field H applied perpendicular to the magnetic chiral axis. However, there multiple spectra were observed even for H nearly parallel to the chiral axis, a-axis, and their interpretation is unreasonable. Thus, we conducted an X-band electron spin resonance (ESR) measurement of R-GN under conditions similar to those of their experiment and performed Fourier spectrum analyses for the data of R-GN as an approach of physical characterization. By using two Lorentz spectra, the main ESR spectra for H // a were reproduced, and furthermore two prominent periodic modes were found by spectrum analyses based on Fourier transform. Two characteristic periods, p1 and p2 (multiplicity can be physically characterized with those of p1 and p2. The unique spectra observed below the magnetic ordering temperature are due not to hyperfine structure but magnetic fine structure, and it certainly originates from the existence of plural nonequivalent magnetic sites. Thus, it is unreasonable to consider CSL to explain the multiple ESR spectra observed independently of the field direction, whereas the observed complex spectra appeal wealthy scientific potentiality in chiral crystals.

  7. Evidence for Octupole Correlations in Multiple Chiral Doublet Bands

    NASA Astrophysics Data System (ADS)

    Liu, C.; Wang, S. Y.; Bark, R. A.; Zhang, S. Q.; Meng, J.; Qi, B.; Jones, P.; Wyngaardt, S. M.; Zhao, J.; Xu, C.; Zhou, S.-G.; Wang, S.; Sun, D. P.; Liu, L.; Li, Z. Q.; Zhang, N. B.; Jia, H.; Li, X. Q.; Hua, H.; Chen, Q. B.; Xiao, Z. G.; Li, H. J.; Zhu, L. H.; Bucher, T. D.; Dinoko, T.; Easton, J.; Juhász, K.; Kamblawe, A.; Khaleel, E.; Khumalo, N.; Lawrie, E. A.; Lawrie, J. J.; Majola, S. N. T.; Mullins, S. M.; Murray, S.; Ndayishimye, J.; Negi, D.; Noncolela, S. P.; Ntshangase, S. S.; Nyakó, B. M.; Orce, J. N.; Papka, P.; Sharpey-Schafer, J. F.; Shirinda, O.; Sithole, P.; Stankiewicz, M. A.; Wiedeking, M.

    2016-03-01

    Two pairs of positive-and negative-parity doublet bands together with eight strong electric dipole transitions linking their yrast positive- and negative-parity bands have been identified in 78Br. They are interpreted as multiple chiral doublet bands with octupole correlations, which is supported by the microscopic multidimensionally-constrained covariant density functional theory and triaxial particle rotor model calculations. This observation reports the first example of chiral geometry in octupole soft nuclei.

  8. Evidence for Octupole Correlations in Multiple Chiral Doublet Bands.

    PubMed

    Liu, C; Wang, S Y; Bark, R A; Zhang, S Q; Meng, J; Qi, B; Jones, P; Wyngaardt, S M; Zhao, J; Xu, C; Zhou, S-G; Wang, S; Sun, D P; Liu, L; Li, Z Q; Zhang, N B; Jia, H; Li, X Q; Hua, H; Chen, Q B; Xiao, Z G; Li, H J; Zhu, L H; Bucher, T D; Dinoko, T; Easton, J; Juhász, K; Kamblawe, A; Khaleel, E; Khumalo, N; Lawrie, E A; Lawrie, J J; Majola, S N T; Mullins, S M; Murray, S; Ndayishimye, J; Negi, D; Noncolela, S P; Ntshangase, S S; Nyakó, B M; Orce, J N; Papka, P; Sharpey-Schafer, J F; Shirinda, O; Sithole, P; Stankiewicz, M A; Wiedeking, M

    2016-03-18

    Two pairs of positive-and negative-parity doublet bands together with eight strong electric dipole transitions linking their yrast positive- and negative-parity bands have been identified in ^{78}Br. They are interpreted as multiple chiral doublet bands with octupole correlations, which is supported by the microscopic multidimensionally-constrained covariant density functional theory and triaxial particle rotor model calculations. This observation reports the first example of chiral geometry in octupole soft nuclei. PMID:27035296

  9. Multiple Intelligences Centers and Projects.

    ERIC Educational Resources Information Center

    Chapman, Carolyn; Freeman, Lynn

    Based upon Gardner's theory of multiple intelligences, this book guides elementary school teachers through the process of using classroom learning centers and projects by providing choices for students. The guide is divided into two sections, providing the theoretical background and information on how to develop multiple intelligences learning…

  10. Indirect chiral separation and analyses in human biological fluids of the stereoisomers of a thienothiopyran-2-sulfonamide (TRUSOPT), a novel carbonic anhydrase inhibitor with two chiral centers in the molecule.

    PubMed

    Matuszewski, B K; Constanzer, M L

    1992-01-01

    The indirect chiral separation of the four stereoisomers (1)-(4) of a novel carbonic anhydrase inhibitor with two chiral centers in the molecule is reported. The method is based on chemical derivatization of the secondary amino group of the inhibitor with chiral isocyanate, formation of diastereomeric urea derivatives, each with three chiral centers in the molecule, and their separation under nonchiral HPLC conditions. The attempts to separate racemic mixture (1) + (2) from its diastereomeric counterpart (3) + (4) under nonchiral conditions, and to separate enantiomers (1) and (2) directly on a chiral stationary phase (CSP) are also reported. The indirect method was utilized for the assessment of an in vivo inversion of configuration at either one or both chiral centers of the molecule of (1). Analyses of selected whole blood and urine samples from human subjects after multiple bilateral topical ocular dosing with (1) did not reveal the presence of any of the three possible stereoisomers (2)-(4) of (1) indicating that the inversion of configuration at neither one nor two chiral centers of (1) occurs in vivo. PMID:1476862

  11. Search for multiple chiral doublets in rhodium isotopes

    SciTech Connect

    Peng, J.; Sagawa, H.; Zhang, S. Q.; Yao, J. M.; Zhang, Y.; Meng, J.

    2008-02-15

    The deformation in rhodium isotopes is investigated using adiabatic and configuration-fixed constrained triaxial relativistic mean field (RMF) approaches. The triaxial deformations are found in the ground states of {sup 102,104,106,108,110}Rh, which is consistent with triaxial Skyrme Hartree-Fock calculations. Several minima with triaxial deformation in {sup 104,106,108,110}Rh are obtained by the configuration-fixed constrained calculations. The corresponding configurations are characterized by the quantum numbers |nljm> obtained by transforming wave functions from a Cartesian basis to a spherical basis. The possible existence of multiple chiral doublets (M{chi}D) is demonstrated in {sup 104,106,108,110}Rh isotopes, based on different particle-hole configurations and triaxial deformations.

  12. Enantiomeric resolution of multiple chiral centres racemates by capillary electrophoresis.

    PubMed

    Ali, Imran; Suhail, Mohd; Al-Othman, Zeid A; Alwarthan, Abdulrahman; Aboul-Enein, Hassan Y

    2016-05-01

    Enantiomeric resolution of multichiral centre racemates is an important area as some multichiral centre racemates are of great medicinal importance. However, enantioseparation of such types of racemates is a challenging task. Amongst many analytical techniques, capillary electrophoresis is a powerful technique and may be used to resolve such racemates. Only few papers are available describing enantiomeric resolution of such racemates. Therefore, efforts have been made to describe the enantiomeric resolution of multichiral centre racemates by capillary electrophoresis. This article discusses the importance of multichiral racemates, the need for capillary electrophoresis in enantiomeric resolution and chiral resolution of multichiral centre racemates using various chiral selectors. Further, attempts have been made to discuss the future challenges and prospects of enantiomeric resolution of multichiral racemates. The various chiral selectors used for the purpose are chiral crown ether, cyclodextrins, polysaccharides, macrocyclic glycopeptide antibiotics and ligand exchange. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26840015

  13. Multiple chiral doublet candidate nucleus {sup 105}Rh in a relativistic mean-field approach

    SciTech Connect

    Li Jian; Zhang, S. Q.; Meng, J.

    2011-03-15

    Following the reports of two pairs of chiral doublet bands observed in {sup 105}Rh, the adiabatic and configuration-fixed constrained triaxial relativistic mean-field calculations are performed to investigate their triaxial deformations with the corresponding configuration and the possible multiple chiral doublet (M{chi}D) phenomenon. The existence of the M{chi}D phenomenon in {sup 105}Rh is highly expected.

  14. Enantioselective synthesis of cyclopropanes that contain fluorinated tertiary stereogenic carbon centers: a chiral α-fluoro carbanion strategy.

    PubMed

    Shen, Xiao; Zhang, Wei; Zhang, Lei; Luo, Tao; Wan, Xiaolong; Gu, Yucheng; Hu, Jinbo

    2012-07-01

    Chiral transfer: the fluorinated sulfoximine (see scheme; Ts=p-toluenesulfonyl) was synthesized and used as the first chiral fluoromethylenation reagent for the synthesis of cyclopropanes that contain fluorinated tertiary stereogenic carbon centers in good yields, good diastereoselectivity, and excellent enantioselectivity. PMID:22689532

  15. Remote control of helical chirality: thermodynamic resolution of a racemic mixture of CTV units by remote stereogenic centers.

    PubMed

    Chatelet, Bastien; Joucla, Lionel; Padula, Daniele; Di Bari, Lorenzo; Pilet, Guillaume; Robert, Vincent; Dufaud, Véronique; Dutasta, Jean-Pierre; Martinez, Alexandre

    2015-02-01

    Enantiopure hemicryptophanes designed from the cyclotriveratrylene (CTV) unit display remarkable properties in selective host-guest recognition or as supramolecular catalysts. The unprecedented control of the helical chirality of the CTV unit by remote stereogenic centers of a tren moiety is reported, providing an original access to this highly promising class of host molecules. Although the chiral centers and the CTV unit are separated by more than 10 Å, one single diastereomer is formed; the nature of the diastereoselective process is discussed and the procedure is exemplified using different enantiopure tren derivatives. This work also highlights the influence of the chirality of the CTV unit on the whole cage structure. PMID:25629235

  16. Combined heterogeneous metal/chiral amine: multiple relay catalysis for versatile eco-friendly synthesis.

    PubMed

    Deiana, Luca; Jiang, Yan; Palo-Nieto, Carlos; Afewerki, Samson; Incerti-Pradillos, Celia A; Verho, Oscar; Tai, Cheuk-Wai; Johnston, Eric V; Córdova, Armando

    2014-03-24

    Herein is described a versatile and broad synergistic strategy for expansion of chemical space and the synthesis of valuable molecules (e.g. carbocycles and heterocycles), with up to three quaternary stereocenters, in a highly enantioselective fashion from simple alcohols (31 examples, 95:5 to >99.5:0.5 e.r.) using integrated heterogeneous metal/chiral amine multiple relay catalysis and air/O₂ as the terminal oxidant. A novel highly 1,4-selective heterogeneous metal/amine co-catalyzed hydrogenation of enals was also added to the relay catalysis sequences. PMID:24677482

  17. Stereogenic Centers and Axes: A Comparison of the Chiral Topologies Available to Cabcd and AbC=C=Ccd

    ERIC Educational Resources Information Center

    Lloyd-Williams, Paul; Giralt, Ernest

    2005-01-01

    A clarification of concepts and a comparative analysis of chirality as a consequence of stereogenic center and axes are provided by considering the different possibilities for the archetypical molecule Cabcd. The key difference between Cabcd and abC=C=Ccd and, by extension, between molecules incorporating a stereogenic axis, is in the number of…

  18. Multiple scattering in chiral media: border effects, reduced depolarization, and sensitivity limit

    NASA Astrophysics Data System (ADS)

    Delplancke, Francoise; Badoz, Jacques P.; Boccara, A. Claude

    1997-10-01

    Suspensions of polystyrene latex beads in chiral solutions were investigated. The rotatory power, induced by solubilized sucrose, in near-forward scattering was measured via a method using polarization modulation by photo-elastic modulator. The sensitivity of the measurement was enhanced and optimized in order to measure sucrose concentrations as low as 5 mg/ml in a cell 5 mm thick only. Different concentrations and diameters of latex particles were used in combination with different sucrose concentrations going from 1 mg/ml up to saturation. The experiments showed that the apparent rotatory power is enhanced by multiple scattering, that depolarization effects are less important with highly concentrated sucrose solutions and that attention has to be paid to cell border effects in order to avoid important artifacts, in case of highly scattering suspensions. Qualitative and theoretical explanations of those observations are presented. One possible application of this method is to measure the sugar content in human blood, in vivo, non-invasively, through the skin. The concentration to be evaluated is at the sensitivity limit. So any artifact has to be removed carefully, e.g. skin cell birefringence or chirality.

  19. An In-tether Chiral Center Modulates the Helicity, Cell Permeability, and Target Binding Affinity of a Peptide.

    PubMed

    Hu, Kuan; Geng, Hao; Zhang, Qingzhou; Liu, Qisong; Xie, Mingsheng; Sun, Chengjie; Li, Wenjun; Lin, Huacan; Jiang, Fan; Wang, Tao; Wu, Yun-Dong; Li, Zigang

    2016-07-01

    The addition of a precisely positioned chiral center in the tether of a constrained peptide is reported, yielding two separable peptide diastereomers with significantly different helicity, as supported by circular dichroism (CD) and NMR spectroscopy. Single crystal X-ray diffraction analysis suggests that the absolute configuration of the in-tether chiral center in helical form is R, which is in agreement with theoretical simulations. The relationship between the secondary structure of the short peptides and their biochemical/biophysical properties remains elusive, largely because of the lack of proper controls. The present strategy provides the only method for investigating the influence of solely conformational differences upon the biochemical/biophysical properties of peptides. The significant differences in permeability and target binding affinity between the peptide diastereomers demonstrate the importance of helical conformation. PMID:27167181

  20. Multiple chiral topological states in liquid crystals from unstructured light beams

    SciTech Connect

    Loussert, Charles; Brasselet, Etienne

    2014-02-03

    It is shown experimentally that unstructured light beams can generate a wealth of distinct metastable defect structures in thin films of chiral liquid crystals. Various kinds of individual chiral topological states are obtained as well as dimers and trimers, which correspond to the entanglement of several topological unit cells. Self-assembled nested assemblies of several metastable particle-like topological states can also be formed. Finally, we propose and experimentally demonstrate an opto-electrical approach to generate tailor-made architectures.

  1. Multiple Determinants of Caregiver Behavior in Child Care Centers

    ERIC Educational Resources Information Center

    de Schipper, Elles J.; Riksen-Walraven, J. Marianne; Geurts, Sabine A. E.

    2007-01-01

    In this study of the multiple determinants of professional caregiving, 237 caregivers (age range: 18-56 years) from 64 Dutch child care centers were extensively observed during their interactions with the children (0-4 years) in their usual care group. The choice of potential determinants of the caregiving quality was guided by Belsky's [Belsky,…

  2. Eight Biblical Interactive Learning Centers (Based on Gardner's Multiple Intelligences).

    ERIC Educational Resources Information Center

    Goldstein, Semadar

    This report describes how to implement Howard Gardner's multiple intelligences (MI) into Israel's Tanakh classrooms and includes samples of implemented materials. It also notes goals and obstacles encountered during this process and how they were overcome. To illustrate this process, the report provides an overview of Tanakh-centered activities…

  3. Phosphine-Catalyzed β,γ-Umpolung Domino Reaction of Allenic Esters: Facile Synthesis of Tetrahydrobenzofuranones Bearing a Chiral Tetrasubstituted Stereogenic Carbon Center.

    PubMed

    Takizawa, Shinobu; Kishi, Kenta; Yoshida, Yasushi; Mader, Steffen; Arteaga, Fernando Arteaga; Lee, Shoukou; Hoshino, Manabu; Rueping, Magnus; Fujita, Makoto; Sasai, Hiroaki

    2015-12-14

    An enantio-, diastereo-, regio-, and chemoselective phosphine-catalyzed β,γ-umpolung domino reaction of allenic esters with dienones has been developed for the first time. The designed sequence, involving oxy-Michael and Rauhut-Currier reactions, produced highly functionalized tetrahydrobenzofuranones, bearing a chiral tetrasubstituted stereogenic center, in up to 96 % ee. PMID:26537173

  4. Chiral four-dimensional F-theory compactifications with SU(5) and multiple U(1)-factors

    NASA Astrophysics Data System (ADS)

    Cvetič, Mirjam; Grassi, Antonella; Klevers, Denis; Piragua, Hernan

    2014-04-01

    We develop geometric techniques to determine the spectrum and the chiral indices of matter multiplets for four-dimensional F-theory compactifications on elliptic Calabi-Yau fourfolds with rank two Mordell-Weil group. The general elliptic fiber is the Calabi-Yau onefold in dP 2. We classify its resolved elliptic fibrations over a general base B. The study of singularities of these fibrations leads to explicit matter representations, that we determine both for U(1) × U(1) and SU(5) × U(1) × U(1) constructions. We determine for the first time certain matter curves and surfaces using techniques involving prime ideals. The vertical cohomology ring of these fourfolds is calculated for both cases and general formulas for the Euler numbers are derived. Explicit calculations are presented for a specific base B = ℙ3. We determine the general G 4-flux that belongs to of the resolved Calabi-Yau fourfolds. As a by-product, we derive for the first time all conditions on G 4-flux in general F-theory compactifications with a non-holomorphic zero section. These conditions have to be formulated after a circle reduction in terms of Chern-Simons terms on the 3D Coulomb branch and invoke M-theory/F-theory duality. New Chern-Simons terms are generated by Kaluza-Klein states of the circle compactification. We explicitly perform the relevant field theory computations, that yield non-vanishing results precisely for fourfolds with a non-holomorphic zero section. Taking into account the new Chern-Simons terms, all 4D matter chiralities are determined via 3D M-theory/F-theory duality. We independently check these chiralities using the subset of matter surfaces we determined. The presented techniques are general and do not rely on toric data.

  5. Engineering chiral density waves and topological band structures by multiple-Q superpositions of collinear up-up-down-down orders

    NASA Astrophysics Data System (ADS)

    Hayami, Satoru; Ozawa, Ryo; Motome, Yukitoshi

    2016-07-01

    Magnetic orders characterized by multiple ordering vectors harbor noncollinear and noncoplanar spin textures and can be a source of unusual electronic properties through the spin Berry phase mechanism. We theoretically show that such multiple-Q states are stabilized in itinerant magnets in the form of superpositions of collinear up-up-down-down (UUDD) spin states, which accompany the density waves of vector and scalar chirality. The result is drawn by examining the ground state of the Kondo lattice model with classical localized moments, especially when the Fermi surface is tuned to be partially nested by the symmetry-related commensurate vectors. We unveil the instability toward a double-Q UUDD state with vector chirality density waves on the square lattice and a triple-Q UUDD state with scalar chirality density waves on the triangular lattice, using the perturbative theory and variational calculations. The former double-Q state is also confirmed by large-scale Langevin dynamics simulations. We also show that, for a sufficiently large exchange coupling, the chirality density waves can induce rich nontrivial topology of electronic structures, such as the massless Dirac semimetal, Chern insulator with quantized topological Hall response, and peculiar edge states which depend on the phase of chirality density waves at the edges.

  6. GMTI Direction of Arrival Measurements from Multiple Phase Centers.

    SciTech Connect

    Doerry, Armin W.; Bickel, Douglas L.

    2015-03-01

    Ground Moving Target Indicator (GMTI) radar attempts to detect and locate targets with unknown motion. Very slow-moving targets are difficult to locate in the presence of surrounding clutter. This necessitates multiple antenna phase centers (or equivalent) to offer independent Direction of Arrival (DOA) measurements. DOA accuracy and precision generally remains dependent on target Signal-to-Noise Ratio (SNR), Clutter-toNoise Ratio (CNR), scene topography, interfering signals, and a number of antenna parameters. This is true even for adaptive techniques like Space-Time-AdaptiveProcessing (STAP) algorithms.

  7. A norepinephrine coated magnetic molecularly imprinted polymer for simultaneous multiple chiral recognition.

    PubMed

    Chen, Juan; Liang, Ru-Ping; Wang, Xiao-Ni; Qiu, Jian-Ding

    2015-08-28

    A newly designed molecularly imprinted polymer (MIP) material was developed and successfully used as recognition element for enantioselective recognition by microchip electrophoresis. In this work, molecularly imprinted polymers were facilely prepared employing Fe3O4 nanoparticles (NPs) as the supporting substrate and norepinephrine as the functional monomer in the presence of template molecule in a weak alkaline solution. After extracting the embedded template molecules, the produced imprinted Fe3O4@polynorepinephrine (MIP-Fe3O4@PNE) NPs have cavities complementary to three dimensional shape of template molecules favoring high binding capacity and magnetism property for easy manipulation. The MIP-Fe3O4@PNE NPs prepared with l-tryptophan, l-valine, l-threonine, Gly-l-Phe, S-(-)-ofloxacin or S-(-)-binaphthol as template molecules were packed in the polydimethylsiloxane microchannel via magnetic field as novel stationary phase to successful enantioseparation of corresponding target analysts. The MIP-Fe3O4@PNE NPs-based microchip electrophoresis system exhibited strong recognition ability, excellent high-performance, admirable reproducibility and stability, which provided a powerful protocol for separation enantiomers within a short analytical time and opened up an avenue for multiplex chiral compound assay in various systems. PMID:26206627

  8. The ribosome can discriminate the chirality of amino acids within its peptidyl-transferase center.

    PubMed

    Englander, Michael T; Avins, Joshua L; Fleisher, Rachel C; Liu, Bo; Effraim, Philip R; Wang, Jiangning; Schulten, Klaus; Leyh, Thomas S; Gonzalez, Ruben L; Cornish, Virginia W

    2015-05-12

    The cellular translational machinery (TM) synthesizes proteins using exclusively L- or achiral aminoacyl-tRNAs (aa-tRNAs), despite the presence of D-amino acids in nature and their ability to be aminoacylated onto tRNAs by aa-tRNA synthetases. The ubiquity of L-amino acids in proteins has led to the hypothesis that D-amino acids are not substrates for the TM. Supporting this view, protein engineering efforts to incorporate D-amino acids into proteins using the TM have thus far been unsuccessful. Nonetheless, a mechanistic understanding of why D-aa-tRNAs are poor substrates for the TM is lacking. To address this deficiency, we have systematically tested the translation activity of D-aa-tRNAs using a series of biochemical assays. We find that the TM can effectively, albeit slowly, accept D-aa-tRNAs into the ribosomal aa-tRNA binding (A) site, use the A-site D-aa-tRNA as a peptidyl-transfer acceptor, and translocate the resulting peptidyl-D-aa-tRNA into the ribosomal peptidyl-tRNA binding (P) site. During the next round of continuous translation, however, we find that ribosomes carrying a P-site peptidyl-D-aa-tRNA partition into subpopulations that are either translationally arrested or that can continue translating. Consistent with its ability to arrest translation, chemical protection experiments and molecular dynamics simulations show that P site-bound peptidyl-D-aa-tRNA can trap the ribosomal peptidyl-transferase center in a conformation in which peptidyl transfer is impaired. Our results reveal a novel mechanism through which D-aa-tRNAs interfere with translation, provide insight into how the TM might be engineered to use D-aa-tRNAs, and increase our understanding of the physiological role of a widely distributed enzyme that clears D-aa-tRNAs from cells. PMID:25918365

  9. The ribosome can discriminate the chirality of amino acids within its peptidyl-transferase center

    PubMed Central

    Englander, Michael T.; Avins, Joshua L.; Fleisher, Rachel C.; Liu, Bo; Effraim, Philip R.; Wang, Jiangning; Schulten, Klaus; Leyh, Thomas S.; Gonzalez, Ruben L.; Cornish, Virginia W.

    2015-01-01

    The cellular translational machinery (TM) synthesizes proteins using exclusively L- or achiral aminoacyl-tRNAs (aa-tRNAs), despite the presence of D-amino acids in nature and their ability to be aminoacylated onto tRNAs by aa-tRNA synthetases. The ubiquity of L-amino acids in proteins has led to the hypothesis that D-amino acids are not substrates for the TM. Supporting this view, protein engineering efforts to incorporate D-amino acids into proteins using the TM have thus far been unsuccessful. Nonetheless, a mechanistic understanding of why D-aa-tRNAs are poor substrates for the TM is lacking. To address this deficiency, we have systematically tested the translation activity of D-aa-tRNAs using a series of biochemical assays. We find that the TM can effectively, albeit slowly, accept D-aa-tRNAs into the ribosomal aa-tRNA binding (A) site, use the A-site D-aa-tRNA as a peptidyl-transfer acceptor, and translocate the resulting peptidyl-D-aa-tRNA into the ribosomal peptidyl-tRNA binding (P) site. During the next round of continuous translation, however, we find that ribosomes carrying a P-site peptidyl-D-aa-tRNA partition into subpopulations that are either translationally arrested or that can continue translating. Consistent with its ability to arrest translation, chemical protection experiments and molecular dynamics simulations show that P site-bound peptidyl-D-aa-tRNA can trap the ribosomal peptidyl-transferase center in a conformation in which peptidyl transfer is impaired. Our results reveal a novel mechanism through which D-aa-tRNAs interfere with translation, provide insight into how the TM might be engineered to use D-aa-tRNAs, and increase our understanding of the physiological role of a widely distributed enzyme that clears D-aa-tRNAs from cells. PMID:25918365

  10. The Decker Family Development Center: Supportive Data of an Intervention Model for Multiple-Risk Families.

    ERIC Educational Resources Information Center

    Newman, Carole; And Others

    The Decker Family Development Center in Barberton (Ohio) is a holistic "one-stop shop" that provides services to families who are at multiple risk. During its 5 years of operation, this center has developed a model that goes beyond cooperation into co-construction to empower stakeholders. This paper describes the center and its successes and…

  11. Simultaneous chiral discrimination of multiple profens by cyclodextrin-modified capillary electrophoresis in normal and reversed polarity modes.

    PubMed

    La, Sookie; Kim, Jiyung; Kim, Jung-Han; Goto, Junichi; Kim, Kyoung-Rae

    2003-08-01

    Simultaneous enantioseparations of nine profens for their accurate chiral discrimination were achieved by capillary electrophoresis (CE) in the normal polarity (NP) mode with a single cyclodextrin (CD) system and in the reversed polarity (RP) mode with a dual CD system. The single CD system in the NP mode employed heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TMbetaCD) added at 75 mM-100 mM 2-(N-morpholino)ethanesulfonic acid buffer (pH 6.0) as the optimum run buffer. The dual CD system operated in the RP mode used 30 mM TMbetaCD and 1.0% anionic carboxymethyl-beta-cyclodextrin dissolved in pH 3.0, 100 mM phosphoric acid-triethanolamine buffer containing 0.01% hexadimethrine bromide added to reverse the electroosmotic flow. Fairly good enantiomeric resolutions and the opposite enantiomer migration orders were achieved in the two modes. Relative migration times to internal standard under respective optimum conditions were characteristic of each enantiomer with good precision (< 2% relative standard deviation, RSD), thereby enabling to crosscheck the chemical identification of profens and also their accurate chiralities. The method linearity in the two modes was found to be adequate (r > or = 0.9991) for the chiral assay of the profens investigated. Simultaneous enantiomeric purity test of ibuprofen, ketoprofen and flurbiprofen in a mixture was feasible in a single analysis by the present method. PMID:12900877

  12. Supporting Multiple Programs and Projects at NASA's Kennedy Space Center

    NASA Technical Reports Server (NTRS)

    Stewart, Camiren L.

    2014-01-01

    With the conclusion of the shuttle program in 2011, the National Aeronautics and Space Administration (NASA) had found itself at a crossroads for finding transportation of United States astronauts and experiments to space. The agency would eventually hand off the taxiing of American astronauts to the International Space Station (ISS) that orbits in Low Earth Orbit (LEO) about 210 miles above the earth under the requirements of the Commercial Crew Program (CCP). By privatizing the round trip journey from Earth to the ISS, the space agency has been given the additional time to focus funding and resources to projects that operate beyond LEO; however, adding even more stress to the agency, the premature cancellation of the program that would succeed the Shuttle Program - The Constellation Program (CxP) -it would inevitably delay the goal to travel beyond LEO for a number of years. Enter the Space Launch System (SLS) and the Orion Multipurpose Crew Vehicle (MPCV). Currently, the SLS is under development at NASA's Marshall Spaceflight Center in Huntsville, Alabama, while the Orion Capsule, built by government contractor Lockheed Martin Corporation, has been assembled and is currently under testing at the Kennedy Space Center (KSC) in Florida. In its current vision, SLS will take Orion and its crew to an asteroid that had been captured in an earlier mission in lunar orbit. Additionally, this vehicle and its configuration is NASA's transportation to Mars. Engineers at the Kennedy Space Center are currently working to test the ground systems that will facilitate the launch of Orion and the SLS within its Ground Services Development and Operations (GSDO) Program. Firing Room 1 in the Launch Control Center (LCC) has been refurbished and outfitted to support the SLS Program. In addition, the Spaceport Command and Control System (SCCS) is the underlying control system for monitoring and launching manned launch vehicles. As NASA finds itself at a junction, so does all of its

  13. Rational Design of Chiral Nanostructures from Self-Assembly of a Ferrocene-Modified Dipeptide.

    PubMed

    Wang, Yuefei; Qi, Wei; Huang, Renliang; Yang, Xuejiao; Wang, Mengfan; Su, Rongxin; He, Zhimin

    2015-06-24

    We report a new paradigm for the rational design of chiral nanostructures that is based on the hierarchical self-assembly of a ferrocene (Fc)-modified dipeptide, ferrocene-L-Phe-L-Phe-OH (Fc-FF). Compared to other chiral self-assembling systems, Fc-FF is unique because of its smaller size, biocompatibility, multiple functions (a redox center), and environmental responsiveness. X-ray and spectroscopic analyses showed that the incorporation of counterions during the hierarchical self-assembly of Fc-FF changed the conformations of the secondary structures from flat β sheets into twisted β sheets. This approach enables chiral self-assembly and the formation of well-defined chiral nanostructures composed of helical twisted β sheets. We identified two elementary forms for the helical twist of the β sheets, which allowed us to create a rich variety of rigid chiral nanostructures over a wide range of scales. Furthermore, through subtle modulations in the counterions, temperature, and solvent, we are able to precisely control the helical pitch, diameter, and handedness of the self-assembled chiral nanostructures. This unprecedented level of control not only offers insights into how rationally designed chiral nanostructures can be formed from simple molecular building blocks but also is of significant practical value for the use in chiroptics, templates, chiral sensing, and separations. PMID:26018930

  14. Chiral superconductors.

    PubMed

    Kallin, Catherine; Berlinsky, John

    2016-05-01

    Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from μSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed. PMID:27088452

  15. Chiral squaring

    NASA Astrophysics Data System (ADS)

    Nagy, S.

    2016-07-01

    We construct the states and symmetries of N = 4 super-Yang-Mills by tensoring two N = 1 chiral multiplets and introducing two extra SUSY generators. This allows us to write the maximal N = 8 supergravity as four copies of the chiral multiplet. We extend this to higher dimensions and discuss applications to scattering amplitudes.

  16. Chiral superconductors

    NASA Astrophysics Data System (ADS)

    Kallin, Catherine; Berlinsky, John

    2016-05-01

    Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from μSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed.

  17. The Multiple Facets of Iodine(III) Compounds in an Unprecedented Catalytic Auto-amination for Chiral Amine Synthesis.

    PubMed

    Buendia, Julien; Grelier, Gwendal; Darses, Benjamin; Jarvis, Amanda G; Taran, Frédéric; Dauban, Philippe

    2016-06-20

    Iodine(III) reagents are used in catalytic one-pot reactions, first as both oxidants and substrates, then as cross-coupling partners, to afford chiral polyfunctionalized amines. The strategy relies on an initial catalytic auto C(sp(3) )-H amination of the iodine(III) oxidant, which delivers an amine-derived iodine(I) product that is subsequently used in palladium-catalyzed cross-couplings to afford a variety of useful building blocks with high yields and excellent stereoselectivities. This study demonstrates the concept of self-amination of the hypervalent iodine reagents, which increases the value of the aryl moiety. PMID:27158802

  18. A Chiral Granular Gas

    NASA Astrophysics Data System (ADS)

    Tsai, J.-C.; Ye, Fangfu; Rodriguez, Juan; Gollub, J. P.; Lubensky, T. C.

    2005-05-01

    Inspired by rattleback toys, we created small chiral wires that rotate in a preferred direction on a vertically oscillating platform and quantified their motion with experiment and simulation. We demonstrate experimentally that angular momentum of rotation about particle centers of mass is converted to collective angular momentum of center-of-mass motion in a granular gas of these wires, and we introduce a continuum model that explains our observations.

  19. A chiral granular gas.

    PubMed

    Tsai, J-C; Ye, Fangfu; Rodriguez, Juan; Gollub, J P; Lubensky, T C

    2005-06-01

    Inspired by rattleback toys, we created small chiral wires that rotate in a preferred direction on a vertically oscillating platform and quantified their motion with experiment and simulation. We demonstrate experimentally that angular momentum of rotation about particle centers of mass is converted to collective angular momentum of center-of-mass motion in a granular gas of these wires, and we introduce a continuum model that explains our observations. PMID:16090323

  20. Chiral Graphene Quantum Dots.

    PubMed

    Suzuki, Nozomu; Wang, Yichun; Elvati, Paolo; Qu, Zhi-Bei; Kim, Kyoungwon; Jiang, Shuang; Baumeister, Elizabeth; Lee, Jaewook; Yeom, Bongjun; Bahng, Joong Hwan; Lee, Jaebeom; Violi, Angela; Kotov, Nicholas A

    2016-02-23

    Chiral nanostructures from metals and semiconductors attract wide interest as components for polarization-enabled optoelectronic devices. Similarly to other fields of nanotechnology, graphene-based materials can greatly enrich physical and chemical phenomena associated with optical and electronic properties of chiral nanostructures and facilitate their applications in biology as well as other areas. Here, we report that covalent attachment of l/d-cysteine moieties to the edges of graphene quantum dots (GQDs) leads to their helical buckling due to chiral interactions at the "crowded" edges. Circular dichroism (CD) spectra of the GQDs revealed bands at ca. 210-220 and 250-265 nm that changed their signs for different chirality of the cysteine edge ligands. The high-energy chiroptical peaks at 210-220 nm correspond to the hybridized molecular orbitals involving the chiral center of amino acids and atoms of graphene edges. Diverse experimental and modeling data, including density functional theory calculations of CD spectra with probabilistic distribution of GQD isomers, indicate that the band at 250-265 nm originates from the three-dimensional twisting of the graphene sheet and can be attributed to the chiral excitonic transitions. The positive and negative low-energy CD bands correspond to the left and right helicity of GQDs, respectively. Exposure of liver HepG2 cells to L/D-GQDs reveals their general biocompatibility and a noticeable difference in the toxicity of the stereoisomers. Molecular dynamics simulations demonstrated that d-GQDs have a stronger tendency to accumulate within the cellular membrane than L-GQDs. Emergence of nanoscale chirality in GQDs decorated with biomolecules is expected to be a general stereochemical phenomenon for flexible sheets of nanomaterials. PMID:26743467

  1. Evaluation of immunomodulatory drugs in multiple myeloma: single center experience

    PubMed Central

    Ozkan, Melda Comert; Tombuloglu, Murat; Sahin, Fahri; Saydam, Guray

    2015-01-01

    Objective: Multiple myeloma (MM) comprises 1% of all cancers and 10% of hematologic malignancies and known as an incurable disease. The introduction of immunomodulatory drugs (IMiDs) has brought a major shift in therapeutic paradigm in the treatment of newly diagnosed and relapsed/refractory MM patients. The aim of this study was to evaluate the relationship between response status and hematological parameters in patients with MM treated with thalidomide or lenalidomide. Methods: Sixty-eight patients who were treated with IMiDs in Ege University, School of Medicine, Department of Hematology, between 2005 and 2012, were evaluated, retrospectively. Results and Conclusion: We could not find any difference between the hematological parameters before and after the treatment neither with thalidomide nor lenalidomide. However, the heterogenity of our groups, the difference in treatment strategies and potential side effects would have an impact on this result. It is needed to perform prospective clinical trials to prove that whether correction of hematological parameters would reflect the response status in patients with myeloma that treated with IMiDs. PMID:27069758

  2. One-pot multiple reactions: asymmetric synthesis of 2,6-cis-disubstituted piperidine alkaloids from chiral aziridine.

    PubMed

    Yadav, Nagendra Nath; Choi, Jihye; Ha, Hyun-Joon

    2016-07-01

    A divergent, new, and highly stereoselective synthesis of cis-2,6-disubstituted piperidine natural products including isosolenopsins, deoxocassine, and spectaline was achieved from chiral aziridine decorated with appropriate alkyl chains for isosolenopsins or alkynyl groups for deoxocassine and spectaline at C2. The characteristic feature of this synthesis is one-pot sequential reactions under atmospheric hydrogen including the reduction of alkyne (for deoxocassine and spectaline), reductive ring-opening of aziridine, debenzylation, and intramolecular reductive amination in high yields. The prerequisite aziridines were elaborated from commercially available (2S)-hydroxymethylaziridine through oxidation, Wittig olefination, and the Grignard reaction for isosolenopsins or substrate-controlled lithium alkynylate addition for deoxocassine and spectaline. PMID:27189444

  3. Isotopic chirality

    SciTech Connect

    Floss, H.G.

    1994-12-01

    This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.

  4. Importance of the Chiral Centers of Jasmonic Acid in the Responses of Plants (Activities and Antagonism between Natural and Synthetic Analogs).

    PubMed Central

    Holbrook, L.; Tung, P.; Ward, K.; Reid, D. M.; Abrams, S.; Lamb, N.; Quail, J. W.; Moloney, M. M.

    1997-01-01

    The importance of the two chiral centers at C-3 and C-7 in the molecular structure of jasmonic acid in plant responses was investigated. We separated methyl jasmonate (MeJA) into (3R)- and (3S)-isomers with a fixed stereochemistry at C-3, but epimerization at C-7 is possible. The four isomers of the nonepimerizable analog 7-methyl MeJA were synthesized. These six esters and their corresponding acids were tested in three bioassays: (a) senescence in sunflower (Helianthus annuus) cotyledons; (b) proteinase inhibitor II gene expression in transgenic tobacco (Nicotiana tabacum) with [beta]-glucuronidase as a biochemical reporter; and (c) seed germination in Brassica napus and wheat (Triticum aestivum). The esters and acids had similar activities in the three assays, with the ester being more effective than its acid. The (3R)-stereochemistry was critical for jasmonate activity. Although activity was reduced after substituting the C-7 proton with a methyl group, the analogs with (3R,7R)- or (3R,7S)-stereochemistry were active in some of the assays. Although the four isomers of 7-methyl MeJA were inactive or only weakly active in the senescence assay, they could overcome the senescence-promoting effect of (3R)-MeJA. The strongest antagonistic effect was observed with the (3R,7S)-isomer. PMID:12223716

  5. Inherently Chiral Calixarenes: Synthesis, Optical Resolution, Chiral Recognition and Asymmetric Catalysis

    PubMed Central

    Li, Shao-Yong; Xu, Yao-Wei; Liu, Jun-Min; Su, Cheng-Yong

    2011-01-01

    Inherently chiral calixarenes, whose chirality is based on the absence of a planar symmetry or an inversion center in the molecules as a whole through the asymmetric array of several achiral groups upon the three-dimensional calix-skeletons, are challenging and attractive chiral molecules, because of their potential in supramolecular chemistry. The synthesis and optical resolution of all varieties of inherently chiral calixarenes are systematically discussed and classified, and their applications in chiral recognition and asymmetric catalysis are thoroughly illustrated in this review. PMID:21339996

  6. NATIONAL SURVEYS OF MULTIPLE ENVIRONMENTAL HAZARDS TO YOUNG CHILDREN IN HOMES AND CHILD CARE CENTERS

    EPA Science Inventory

    The Department of Housing and Urban Development (HUD) has teamed with other federal agencies to characterize exposure of multiple environmental hazards to young children in two main indoor environments, homes and daycare centers. Under the co-sponsorship of HUD and the Nationa...

  7. Leaders' Experiences with High School-College Writing Center Collaborations: A Qualitative Multiple-Case Study

    ERIC Educational Resources Information Center

    Story, Julie A.

    2014-01-01

    The purpose of this qualitative multiple-case study was to explore academic leaders' experiences with the organizational elements of their own high school-college writing center collaborations. Conjoining theories framed this study: collaborative leadership theory, Kenneth Bruffee's notion of social constructionism and collaborative learning…

  8. Excitation of surface plasmon polariton modes with multiple nitrogen vacancy centers in single nanodiamonds

    NASA Astrophysics Data System (ADS)

    Kumar, Shailesh; Lausen, Jens L.; Garcia-Ortiz, Cesar E.; Andersen, Sebastian K. H.; Roberts, Alexander S.; Radko, Ilya P.; Smith, Cameron L. C.; Kristensen, Anders; Bozhevolnyi, Sergey I.

    2016-02-01

    Nitrogen-vacancy (NV) centers in diamonds are interesting due to their remarkable characteristics that are well suited to applications in quantum-information processing and magnetic field sensing, as well as representing stable fluorescent sources. Multiple NV centers in nanodiamonds (NDs) are especially useful as biological fluorophores due to their chemical neutrality, brightness and room-temperature photostability. Furthermore, NDs containing multiple NV centers also have potential in high-precision magnetic field and temperature sensing. Coupling NV centers to propagating surface plasmon polariton (SPP) modes gives a base for lab-on-a-chip sensing devices, allows enhanced fluorescence emission and collection which can further enhance the precision of NV-based sensors. Here, we investigate coupling of multiple NV centers in individual NDs to the SPP modes supported by silver surfaces protected by thin dielectric layers and by gold V-grooves (VGs) produced via the self-terminated silicon etching. In the first case, we concentrate on monitoring differences in fluorescence spectra obtained from a source ND, which is illuminated by a pump laser, and from a scattering ND illuminated only by the fluorescence-excited SPP radiation. In the second case, we observe changes in the average NV lifetime when the same ND is characterized outside and inside a VG. Fluorescence emission from the VG terminations is also observed, which confirms the NV coupling to the VG-supported SPP modes.

  9. Punctuated Chirality

    NASA Astrophysics Data System (ADS)

    Gleiser, Marcelo; Thorarinson, Joel; Walker, Sara Imari

    2008-12-01

    Most biomolecules occur in mirror, or chiral, images of each other. However, life is homochiral: proteins contain almost exclusively L-amino acids, while only D-sugars appear in RNA and DNA. The mechanism behind this fundamental asymmetry of life remains an open problem. Coupling the spatiotemporal evolution of a general autocatalytic polymerization reaction network to external environmental effects, we show through a detailed statistical analysis that high intensity and long duration events may drive achiral initial conditions towards chirality. We argue that life’s homochirality resulted from sequential chiral symmetry breaking triggered by environmental events, thus extending the theory of punctuated equilibrium to the prebiotic realm. Applying our arguments to other potentially life-bearing planetary platforms, we predict that a statistically representative sampling will be racemic on average.

  10. Punctuated chirality.

    PubMed

    Gleiser, Marcelo; Thorarinson, Joel; Walker, Sara Imari

    2008-12-01

    Most biomolecules occur in mirror, or chiral, images of each other. However, life is homochiral: proteins contain almost exclusively L-amino acids, while only D-sugars appear in RNA and DNA. The mechanism behind this fundamental asymmetry of life remains an open problem. Coupling the spatiotemporal evolution of a general autocatalytic polymerization reaction network to external environmental effects, we show through a detailed statistical analysis that high intensity and long duration events may drive achiral initial conditions towards chirality. We argue that life's homochirality resulted from sequential chiral symmetry breaking triggered by environmental events, thus extending the theory of punctuated equilibrium to the prebiotic realm. Applying our arguments to other potentially life-bearing planetary platforms, we predict that a statistically representative sampling will be racemic on average. PMID:18841492

  11. Prebiotic chirality

    NASA Astrophysics Data System (ADS)

    Mekki-Berrada, Ali

    Bringing closer phospholipids each other on a bilayer of liposome, causes their rotation around their fatty acids axis, generating a force which brings closer the two sheets of the bilayer. In this theoretical study I show that for getting the greater cohesion of the liposome, by these forces, the serine in the hydrophilic head must have a L chirality. In the case where the hydrophilic head is absent amino acids with L chirality could contribute to this cohesion by taking the place of L-serine. Some coenzymes having a configuration similar to ethanolamine may also contribute. This is the case of pyridoxamine, thiamine and tetrahydrofolic acid. The grouping of amino acids of L chirality and pyridoxamine on the wall could initialize the prebiotic metabolism of these L amino acids only. This would explain the origin of the homo-chirality of amino acids in living world. Furthermore I show that in the hydrophilic head, the esterification of glycerol-phosphate by two fatty acids go through the positioning of dihydroxyacetone-phosphate and L-glyceraldehyde-3-phosphate, but not of D-glyceraldehyde-3-phosphate, prior their hydrogenation to glycerol-3- phosphate. The accumulation of D-glyceraldehyde-3-phosphate in the cytoplasm displace the thermodynamic equilibria towards the synthesis of D-dATP from D-glyceraldehyde-3-phosphate, acetaldehyde and prebiotic adenine, a reaction which does not require a coenzyme in the biotic metabolism. D-dATP and thiamine, more prebiotic metabolism of L-amino acids on the wall, would initialize D-pentoses phosphate and D-nucleotides pathways from the reaction of D-glyceraldehyde-3-phosphate + dihydroxyacetone-phosphate + prebiotic nucleic bases. The exhaustion of the prebiotic glyceraldehyde (racemic) and the nascent biotic metabolism dominated by D-glyceraldehyde-3-phosphate, would explain the origin of homo-chirality of sugars in living world. References: http://en.wikiversity.org/wiki/Prebiotic_chirality

  12. Multiple emotions: a person-centered approach to the relationship between intergroup emotion and action orientation.

    PubMed

    Fernando, Julian W; Kashima, Yoshihisa; Laham, Simon M

    2014-08-01

    Although a great deal of research has investigated the relationship between emotions and action orientations, most studies to date have used variable-centered techniques to identify the best emotion predictor(s) of a particular action. Given that people frequently report multiple or blended emotions, a profitable area of research may be to adopt person-centered approaches to examine the action orientations elicited by a particular combination of emotions or "emotion profile." In two studies, across instances of intergroup inequality in Australia and Canada, we examined participants' experiences of six intergroup emotions: sympathy, anger directed at three targets, shame, and pride. In both studies, five groups of participants with similar emotion profiles were identified by cluster analysis and their action orientations were compared; clusters indicated that the majority of participants experienced multiple emotions. Each action orientation was also regressed on the six emotions. There were a number of differences in the results obtained from the person-centered and variable-centered approaches. This was most apparent for sympathy: the group of participants experiencing only sympathy showed little inclination to perform prosocial actions, yet sympathy was a significant predictor of numerous action orientations in regression analyses. These results imply that sympathy may only prompt a desire for action when experienced in combination with other emotions. We suggest that the use of person-centered and variable-centered approaches as complementary analytic strategies may enrich research into not only the affective predictors of action, but emotion research in general. PMID:24749637

  13. Chiral streamers

    SciTech Connect

    Zou, Dandan; Cao, Xin; Lu, Xinpei; Ostrikov, Kostya

    2015-10-15

    The interaction of time-varying electromagnetic fields and solid, liquid, and gaseous matter may lead to electrical breakdown phenomena through the excitation of ionization waves or streamers that control the dynamics of localized plasma propagation through the media. The streamers usually propagate along straight lines, either between random points in space or along a certain direction in a guided mode. Here, we report on a new type of plasma discharges with the regular helical propagation pattern driven by a pulsed dc voltage in nitrogen at sub-atmospheric-pressure conditions. The helical guided streamers, named chiral streamers or chi-streamers, are excited without any external magnetic fields, which commonly cause helical plasma motions. We also demonstrate a hybrid propagation mode involving the interchangeable chiral streamers and the straight-line propagating plasmas. High-speed, time-resolved optical imaging reveals that the chiral streamers and the hybrid patterns are made of spatially localized discrete plasma bullets, similar to the straight-line guided streamers. These results may enable effective control of propagation of confined plasmas and electromagnetic energy along pre-determined, potentially deterministic paths, which have important implications for the development of next-generation plasma-based radiation sources, communication devices, and medical treatments.

  14. Chiral streamers

    NASA Astrophysics Data System (ADS)

    Zou, Dandan; Cao, Xin; Lu, Xinpei; Ostrikov, Kostya Ken

    2015-10-01

    The interaction of time-varying electromagnetic fields and solid, liquid, and gaseous matter may lead to electrical breakdown phenomena through the excitation of ionization waves or streamers that control the dynamics of localized plasma propagation through the media. The streamers usually propagate along straight lines, either between random points in space or along a certain direction in a guided mode. Here, we report on a new type of plasma discharges with the regular helical propagation pattern driven by a pulsed dc voltage in nitrogen at sub-atmospheric-pressure conditions. The helical guided streamers, named chiral streamers or chi-streamers, are excited without any external magnetic fields, which commonly cause helical plasma motions. We also demonstrate a hybrid propagation mode involving the interchangeable chiral streamers and the straight-line propagating plasmas. High-speed, time-resolved optical imaging reveals that the chiral streamers and the hybrid patterns are made of spatially localized discrete plasma bullets, similar to the straight-line guided streamers. These results may enable effective control of propagation of confined plasmas and electromagnetic energy along pre-determined, potentially deterministic paths, which have important implications for the development of next-generation plasma-based radiation sources, communication devices, and medical treatments.

  15. Improved accuracy of acute graft-versus-host disease staging among multiple centers.

    PubMed

    Levine, John E; Hogan, William J; Harris, Andrew C; Litzow, Mark R; Efebera, Yvonne A; Devine, Steven M; Reshef, Ran; Ferrara, James L M

    2014-01-01

    The clinical staging of acute graft-versus-host disease (GVHD) varies significantly among bone marrow transplant (BMT) centers, but adherence to long-standing practices poses formidable barriers to standardization among centers. We have analyzed the sources of variability and developed a web-based remote data entry system that can be used by multiple centers simultaneously and that standardizes data collection in key areas. This user-friendly, intuitive interface resembles an online shopping site and eliminates error-prone entry of free text with drop-down menus and pop-up detailed guidance available at the point of data entry. Standardized documentation of symptoms and therapeutic response reduces errors in grade assignment and allows creation of confidence levels regarding the diagnosis. Early review and adjudication of borderline cases improves consistency of grading and further enhances consistency among centers. If this system achieves widespread use it may enhance the quality of data in multicenter trials to prevent and treat acute GVHD. PMID:25455279

  16. Improved accuracy of acute graft-versus-host disease staging among multiple centers

    PubMed Central

    Levine, John E.; Hogan, William J.; Harris, Andrew C.; Litzow, Mark R.; Efebera, Yvonne A.; Devine, Steven M.; Reshef, Ran; Ferrara, James L.M.

    2015-01-01

    The clinical staging of acute graft-versus-host disease (GVHD) varies significantly among bone marrow transplant (BMT) centers, but adherence to long-standing practices poses formidable barriers to standardization among centers. We have analyzed the sources of variability and developed a web-based remote data entry system that can be used by multiple centers simultaneously and that standardizes data collection in key areas. This user-friendly, intuitive interface resembles an online shopping site and eliminates error-prone entry of free text with drop-down menus and pop-up detailed guidance available at the point of data entry. Standardized documentation of symptoms and therapeutic response reduces errors in grade assignment and allows creation of confidence levels regarding the diagnosis. Early review and adjudication of borderline cases improves consistency of grading and further enhances consistency among centers. If this system achieves widespread use it may enhance the quality of data in multicenter trials to prevent and treat acute GVHD. PMID:25455279

  17. Multiplicity of europium centers in doped stoichiometric crystals of lithium niobate

    NASA Astrophysics Data System (ADS)

    Kaplyanskii, A. A.; Kapphan, S.; Kutsenko, A. B.; Polgar, K.; Skvortsov, A. P.

    2007-04-01

    The optical spectra of europium-doped stoichiometric lithium niobate (LiNbO3:Eu3+) crystals have been studied using combined excitation-luminescence spectroscopy in the range of 5D0 → 7F1, 7F0 optical transitions. Analysis of the results shows that Eu3+ ions can occupy 14 energetically nonequivalent positions in the LiNbO3 crystal lattice. This multiplicity of impurity centers is related to possible variants of the incorporation of Eu3+ ions into the LiNbO3 crystal lattice and the compensation of excess charge. Energy positions of the 5D0 level and the lowest sublevel of the 7F1 Stark multiplet are determined for Eu3+ centers of all 14 types.

  18. Worldwide phylogeography of wild boar reveals multiple centers of pig domestication.

    PubMed

    Larson, Greger; Dobney, Keith; Albarella, Umberto; Fang, Meiying; Matisoo-Smith, Elizabeth; Robins, Judith; Lowden, Stewart; Finlayson, Heather; Brand, Tina; Willerslev, Eske; Rowley-Conwy, Peter; Andersson, Leif; Cooper, Alan

    2005-03-11

    Mitochondrial DNA (mtDNA) sequences from 686 wild and domestic pig specimens place the origin of wild boar in island Southeast Asia (ISEA), where they dispersed across Eurasia. Previous morphological and genetic evidence suggested pig domestication took place in a limited number of locations (principally the Near East and Far East). In contrast, new genetic data reveal multiple centers of domestication across Eurasia and that European, rather than Near Eastern, wild boar are the principal source of modern European domestic pigs. PMID:15761152

  19. Multiple Bragg diffraction at W point in the face centered cubic photonic crystals

    NASA Astrophysics Data System (ADS)

    Nair, Rajesh V.; Jagatap, Bhagawantrao N.

    2015-01-01

    We report the experimental observation of multiple Bragg diffraction that occurs when the tip of the incident wave vector lies on a line joining the L and W points in the Brillouin zone of a face-centered cubic (FCC) photonic crystal. The multiple Bragg diffraction is analyzed for photonic crystals with different lattice constants and refractive index contrasts. Angle-dependent reflectance spectroscopy indicates strong hybridization of diffraction resonances when the tip of the incident wave vector crosses the W point and the multiple Bragg diffraction is seen to be extended over an angular range of 8 deg around the W point. We also observe a new diffraction resonance in the short-wavelength region for wave vectors shifting toward the W point in the hexagonal facet of the FCC Brillouin zone. Each diffraction resonance is fitted using the Bragg's law for different planes in the FCC photonic crystal taking into account the internal angle between the planes. The diffraction resonances in the multiple Bragg diffraction regime are assigned to FCC crystal planes with Miller indices (111), (200), (1¯11), and (220). Our results have implications for diverse kinds of wave propagations in periodic structures and applications in light emission, sensing, and structural color pigments.

  20. Chiral mirrors

    SciTech Connect

    Plum, Eric; Zheludev, Nikolay I.

    2015-06-01

    Mirrors are used in telescopes, microscopes, photo cameras, lasers, satellite dishes, and everywhere else, where redirection of electromagnetic radiation is required making them arguably the most important optical component. While conventional isotropic mirrors will reflect linear polarizations without change, the handedness of circularly polarized waves is reversed upon reflection. Here, we demonstrate a type of mirror reflecting one circular polarization without changing its handedness, while absorbing the other. The polarization-preserving mirror consists of a planar metasurface with a subwavelength pattern that cannot be superimposed with its mirror image without being lifted out of its plane, and a conventional mirror spaced by a fraction of the wavelength from the metasurface. Such mirrors enable circularly polarized lasers and Fabry-Pérot cavities with enhanced tunability, gyroscopic applications, polarization-sensitive detectors of electromagnetic waves, and can be used to enhance spectroscopies of chiral media.

  1. Enantioselective Recognition for Many Different Kinds of Chiral Guests by One Chiral Receptor Based on Tetraphenylethylene Cyclohexylbisurea.

    PubMed

    Xiong, Jia-Bin; Xie, Wen-Zhao; Sun, Jian-Ping; Wang, Jin-Hua; Zhu, Zhi-Hua; Feng, Hai-Tao; Guo, Dong; Zhang, Hui; Zheng, Yan-Song

    2016-05-01

    A neutral chiral receptor based on TPE cyclohexylbisurea was synthesized and could discriminate the enantiomers of many different kinds of chiral reagents, including chiral acidic compounds, basic compounds, amino acids, and even neutral alcohols. The (1)H NMR spectra disclosed that the ability of chiral recognition could be ascribed to the multiple hydrogen bonds and CH-π interactions between the TPE urea receptor and the enantiomer of the chiral guest, which led to the selective aggregation of the receptor with one of the two enantiomers. This result exhibited a great potential in enantiomer discernment and high-throughput analysis of enantiomer composition of these chiral analytes by one chiral AIE molecule. PMID:27032054

  2. Chirality of Viral Capsids

    NASA Astrophysics Data System (ADS)

    Dharmavaram, Sanjay; Xie, Fangming; Bruinsma, Robijn; Klug, William; Rudnick, Joseph

    Most icosahedral viruses are classified by their T-number which identifies their capsid in terms of the number of capsomers and their relative arrangement. Certain T-numbers (T = 7 for instance) are inherently chiral (with no reflection planes) while others (e.g. T = 1) are achiral. We present a Landau-Brazovskii (LB) theory for weak crystallization in which a scalar order parameter that measures density of capsid proteins successfully predicts the various observed T-numbers and their respective chiralities. We find that chiral capsids gain stability by spontaneously breaking symmetry from an unstable chiral state. The inherently achiral LB-free energy does not preferentially select a particular chiral state from its mirror reflection. Based on the physical observation that proteins are inherently chiral molecules with directional interactions, we propose a new chiral term to the LB energy as a possible selection mechanism for chirality.

  3. Chiral structures from achiral liquid crystals in cylindrical capillaries

    PubMed Central

    Jeong, Joonwoo; Kang, Louis; Davidson, Zoey S.; Collings, Peter J.; Lubensky, Tom C.; Yodh, A. G.

    2015-01-01

    We study chiral symmetry-broken configurations of nematic liquid crystals (LCs) confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls (i.e., perpendicular surface alignment). Interestingly, achiral nematic LCs with comparatively small twist elastic moduli relieve bend and splay deformations by introducing twist deformations. In the resulting twisted and escaped radial (TER) configuration, LC directors are parallel to the cylindrical axis near the center, but to attain radial orientation near the capillary wall, they escape along the radius through bend and twist distortions. Chiral symmetry-breaking experiments in polymer-coated capillaries are carried out using Sunset Yellow FCF, a lyotropic chromonic LC with a small twist elastic constant. Its director configurations are investigated by polarized optical microscopy and explained theoretically with numerical calculations. A rich phenomenology of defects also arises from the degenerate bend/twist deformations of the TER configuration, including a nonsingular domain wall separating domains of opposite twist handedness but the same escape direction and singular point defects (hedgehogs) separating domains of opposite escape direction. We show the energetic preference for singular defects separating domains of opposite twist handedness compared with those of the same handedness, and we report remarkable chiral configurations with a double helix of disclination lines along the cylindrical axis. These findings show archetypally how simple boundary conditions and elastic anisotropy of confined materials lead to multiple symmetry breaking and how these broken symmetries combine to create a variety of defects. PMID:25825733

  4. Chiral structures from achiral liquid crystals in cylindrical capillaries.

    PubMed

    Jeong, Joonwoo; Kang, Louis; Davidson, Zoey S; Collings, Peter J; Lubensky, Tom C; Yodh, A G

    2015-04-14

    We study chiral symmetry-broken configurations of nematic liquid crystals (LCs) confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls (i.e., perpendicular surface alignment). Interestingly, achiral nematic LCs with comparatively small twist elastic moduli relieve bend and splay deformations by introducing twist deformations. In the resulting twisted and escaped radial (TER) configuration, LC directors are parallel to the cylindrical axis near the center, but to attain radial orientation near the capillary wall, they escape along the radius through bend and twist distortions. Chiral symmetry-breaking experiments in polymer-coated capillaries are carried out using Sunset Yellow FCF, a lyotropic chromonic LC with a small twist elastic constant. Its director configurations are investigated by polarized optical microscopy and explained theoretically with numerical calculations. A rich phenomenology of defects also arises from the degenerate bend/twist deformations of the TER configuration, including a nonsingular domain wall separating domains of opposite twist handedness but the same escape direction and singular point defects (hedgehogs) separating domains of opposite escape direction. We show the energetic preference for singular defects separating domains of opposite twist handedness compared with those of the same handedness, and we report remarkable chiral configurations with a double helix of disclination lines along the cylindrical axis. These findings show archetypally how simple boundary conditions and elastic anisotropy of confined materials lead to multiple symmetry breaking and how these broken symmetries combine to create a variety of defects. PMID:25825733

  5. Chiral structures from achiral liquid crystals in cylindrical capillaries

    NASA Astrophysics Data System (ADS)

    Jeong, Joonwoo; Kang, Louis; Davidson, Zoey S.; Collings, Peter J.; Lubensky, Tom C.; Yodh, A. G.

    2015-04-01

    We study chiral symmetry-broken configurations of nematic liquid crystals (LCs) confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls (i.e., perpendicular surface alignment). Interestingly, achiral nematic LCs with comparatively small twist elastic moduli relieve bend and splay deformations by introducing twist deformations. In the resulting twisted and escaped radial (TER) configuration, LC directors are parallel to the cylindrical axis near the center, but to attain radial orientation near the capillary wall, they escape along the radius through bend and twist distortions. Chiral symmetry-breaking experiments in polymer-coated capillaries are carried out using Sunset Yellow FCF, a lyotropic chromonic LC with a small twist elastic constant. Its director configurations are investigated by polarized optical microscopy and explained theoretically with numerical calculations. A rich phenomenology of defects also arises from the degenerate bend/twist deformations of the TER configuration, including a nonsingular domain wall separating domains of opposite twist handedness but the same escape direction and singular point defects (hedgehogs) separating domains of opposite escape direction. We show the energetic preference for singular defects separating domains of opposite twist handedness compared with those of the same handedness, and we report remarkable chiral configurations with a double helix of disclination lines along the cylindrical axis. These findings show archetypally how simple boundary conditions and elastic anisotropy of confined materials lead to multiple symmetry breaking and how these broken symmetries combine to create a variety of defects.

  6. Introduction to chiral symmetry

    SciTech Connect

    Koch, V.

    1996-01-08

    These lectures are an attempt to a pedagogical introduction into the elementary concepts of chiral symmetry in nuclear physics. Effective chiral models such as the linear and nonlinear sigma model will be discussed as well as the essential ideas of chiral perturbation theory. Some applications to the physics of ultrarelativistic heavy ion collisions will be presented.

  7. Model of complex chiral drug metabolic systems and numerical simulation of the remaining chirality toward analysis of dynamical pharmacological activity.

    PubMed

    Ogino, Yoshiyuki; Asahi, Toru

    2015-05-21

    In this study, systems of complicated pathways involved in chiral drug metabolism were investigated. The development of chiral drugs resulted in significant improvement in the remedies available for the treatment of various severe sicknesses. Enantiopure drugs undergo various biological transformations that involve chiral inversion and thus result in the generation of multiple enantiomeric metabolites. Identification of the specific active substances determining a given drug׳s efficacy among such a mixture of different metabolites remains a challenge. To comprehend this complexity, we constructed a mathematical model representing the complicated metabolic pathways simultaneously involving chiral inversion. Moreover, this model is applied to the metabolism of thalidomide, which has recently been revived as a potentially effective prescription drug for a number of intractable diseases. The numerical simulation results indicate that retained chirality in the metabolites reflects the original chirality of the unmetabolized drug, and a higher level of enantiomeric purity is preserved during spontaneous degradation. In addition, chirality remaining after equilibration is directly related to the rate constant not only for chiral inversion but also for generation and degradation. Furthermore, the retention of chirality is quantitatively predictable using this combination of kinetic parameters. Our simulation results well explain the behavior of thalidomide in the practical biological experimental data. Therefore, this model promises a comprehensive understanding of dynamic metabolic systems involving chiral drugs that express multiple enantiospecific drug efficacies. PMID:25791284

  8. Controlling and imaging chiral spin textures

    NASA Astrophysics Data System (ADS)

    Chen, Gong

    Chirality in magnetic materials is fundamentally interesting and holds potential for logic and memory applications. Using spin-polarized low-energy electron microscopy at National Center for Electron Microscopy, we recently observed chiral domain walls in thin films. We developed ways to tailor the Dzyaloshinskii-Moriya interaction, which drives the chirality, by interface engineering and by forming ternary superlattices. We find that spin-textures can be switched between left-handed, right-handed, cycloidal, helical and mixed domain wall structures by controlling uniaxial strain in magnetic films. We also demonstrate an experimental approach to stabilize skyrmions in magnetic multilayers without external magnetic field. These results exemplify the rich physics of chirality associated with interfaces of magnetic materials

  9. Electronic circular dichroism behavior of chiral Phthiobuzone

    PubMed Central

    Li, Li; Wang, Lin; Si, Yikang

    2014-01-01

    Phthiobuzone is a bis(thiosemicarbazone) derivative with a single chiral center which has been used as a racemate in the clinical treatment of herpes and trachoma diseases. In this study, its two enantiomers were prepared from chiral amino acids and their absolute configurations were investigated by electronic circular dichroism (ECD) combined with modern quantum-chemical calculations using time-dependent density functional theory. It was found that solvation changed both the conformational distribution and the ECD spectrum of each conformer. The theoretical ECD spectra of the two enantiomers were in good agreement with the experimentally determined spectra of the corresponding isomers in dimethyl sulfoxide. The ECD behavior of the bis(thiosemicarbazone) chromophore in a chiral environment is also discussed. Our results indicate that ECD spectroscopy may be a useful tool for the stereochemical evaluation of chiral drugs. PMID:26579380

  10. Massive parallel IGHV gene sequencing reveals a germinal center pathway in origins of human multiple myeloma

    PubMed Central

    Bryant, Dean; Seckinger, Anja; Hose, Dirk; Zojer, Niklas; Sahota, Surinder S.

    2015-01-01

    Human multiple myeloma (MM) is characterized by accumulation of malignant terminally differentiated plasma cells (PCs) in the bone marrow (BM), raising the question when during maturation neoplastic transformation begins. Immunoglobulin IGHV genes carry imprints of clonal tumor history, delineating somatic hypermutation (SHM) events that generally occur in the germinal center (GC). Here, we examine MM-derived IGHV genes using massive parallel deep sequencing, comparing them with profiles in normal BM PCs. In 4/4 presentation IgG MM, monoclonal tumor-derived IGHV sequences revealed significant evidence for intraclonal variation (ICV) in mutation patterns. IGHV sequences of 2/2 normal PC IgG populations revealed dominant oligoclonal expansions, each expansion also displaying mutational ICV. Clonal expansions in MM and in normal BM PCs reveal common IGHV features. In such MM, the data fit a model of tumor origins in which neoplastic transformation is initiated in a GC B-cell committed to terminal differentiation but still targeted by on-going SHM. Strikingly, the data parallel IGHV clonal sequences in some monoclonal gammopathy of undetermined significance (MGUS) known to display on-going SHM imprints. Since MGUS generally precedes MM, these data suggest origins of MGUS and MM with IGHV gene mutational ICV from the same GC B-cell, arising via a distinctive pathway. PMID:25929340

  11. Asymmetric Synthesis of Chiral Atropisomeric Bis-Aryl Organophosphorus from Menthyl H-Phosphinate.

    PubMed

    Ma, Yan-Na; Yang, Shang-Dong

    2016-04-01

    This review describes new methods for the synthesis of chiral monophosphine ligands with menthyl phenylphosphinate as a chiral auxiliary through asymmetric Suzuki-Miyaura cross-coupling reactions and asymmetric C-H functionalization. The chiral menthyl phenylphosphinate as a chiral auxiliary is easy to prepare and the menthyl group can easily be transformed into other functional groups, with the chiral center synchronously remaining. These methodologies provide highly efficient and practical strategies for the synthesis of novel axially chiral biaryl monophosphine oxides and their corresponding phosphines. Meanwhile, these reactions are easy to handle and exhibit wide scope for substrates with excellent diastereomeric ratios. PMID:26991107

  12. Chirality in nonlinear optics.

    PubMed

    Haupert, Levi M; Simpson, Garth J

    2009-01-01

    The past decade has witnessed the emergence of new measurement approaches and applications for chiral thin films and materials enabled by the observations of the high sensitivity of second-order nonlinear optical measurements to chirality. In thin films, the chiral response to second harmonic generation and sum frequency generation (SFG) from a single molecular monolayer is often comparable with the achiral response. The chiral specificity also allows for symmetry-allowed SFG in isotropic chiral media, confirming predictions made approximately 50 years ago. With these experimental demonstrations in hand, an important challenge is the construction of intuitive predictive models that allow the measured chiral response to be meaningfully related back to molecular and macromolecular structure. This review defines and considers three distinct mechanisms for chiral effects in uniaxially oriented assemblies: orientational chirality, intrinsic chirality, and isotropic chirality. The role of each is discussed in experimental and computational studies of bacteriorhodopsin films, binaphthol, and collagen. Collectively, these three model systems support a remarkably simple framework for quantitatively recovering the measured chiral-specific activity. PMID:19046125

  13. Chirality in Nonlinear Optics

    NASA Astrophysics Data System (ADS)

    Haupert, Levi M.; Simpson, Garth J.

    2009-05-01

    The past decade has witnessed the emergence of new measurement approaches and applications for chiral thin films and materials enabled by the observations of the high sensitivity of second-order nonlinear optical measurements to chirality. In thin films, the chiral response to second harmonic generation and sum frequency generation (SFG) from a single molecular monolayer is often comparable with the achiral response. The chiral specificity also allows for symmetry-allowed SFG in isotropic chiral media, confirming predictions made ˜50 years ago. With these experimental demonstrations in hand, an important challenge is the construction of intuitive predictive models that allow the measured chiral response to be meaningfully related back to molecular and macromolecular structure. This review defines and considers three distinct mechanisms for chiral effects in uniaxially oriented assemblies: orientational chirality, intrinsic chirality, and isotropic chirality. The role of each is discussed in experimental and computational studies of bacteriorhodopsin films, binaphthol, and collagen. Collectively, these three model systems support a remarkably simple framework for quantitatively recovering the measured chiral-specific activity.

  14. Chiral symmetry and chiral-symmetry breaking

    SciTech Connect

    Peskin, M.E.

    1982-12-01

    These lectures concern the dynamics of fermions in strong interaction with gauge fields. Systems of fermions coupled by gauge forces have a very rich structure of global symmetries, which are called chiral symmetries. These lectures will focus on the realization of chiral symmetries and the causes and consequences of thier spontaneous breaking. A brief introduction to the basic formalism and concepts of chiral symmetry breaking is given, then some explicit calculations of chiral symmetry breaking in gauge theories are given, treating first parity-invariant and then chiral models. These calculations are meant to be illustrative rather than accurate; they make use of unjustified mathematical approximations which serve to make the physics more clear. Some formal constraints on chiral symmetry breaking are discussed which illuminate and extend the results of our more explicit analysis. Finally, a brief review of the phenomenological theory of chiral symmetry breaking is presented, and some applications of this theory to problems in weak-interaction physics are discussed. (WHK)

  15. Improving the Spelling of High Frequency Words in Daily Writing through the Use of Multiple Intelligence Centers.

    ERIC Educational Resources Information Center

    Shah, Tejal; Thomas, Alexis

    This study describes a 12-week program developed with the intent of improving the spelling of high frequency words using centers that will activate each of the eight multiple intelligences. The targeted population consists of second and third graders in a suburban community in northeast Illinois. Parent surveys, teacher interviews, observations,…

  16. Development of chiral sulfoxide ligands for asymmetric catalysis.

    PubMed

    Trost, Barry M; Rao, Meera

    2015-04-20

    Nitrogen-, phosphorus-, and oxygen-based ligands with chiral backbones have been the historic workhorses of asymmetric transition-metal-catalyzed reactions. On the contrary, sulfoxides containing chirality at the sulfur atom have mainly been used as chiral auxiliaries for diastereoselective reactions. Despite several distinct advantages over traditional ligand scaffolds, such as the proximity of the chiral information to the metal center and the ability to switch between S and O coordination, these compounds have only recently emerged as a versatile class of chiral ligands. In this Review, we detail the history of the development of chiral sulfoxide ligands for asymmetric catalysis. We also provide brief descriptions of metal-sulfoxide bonding and strategies for the synthesis of enantiopure sulfoxides. Finally, insights into the future development of this underutilized ligand class are discussed. PMID:25801825

  17. Automated vessel shadow segmentation of fovea-centered spectral-domain images from multiple OCT devices

    NASA Astrophysics Data System (ADS)

    Wu, Jing; Gerendas, Bianca S.; Waldstein, Sebastian M.; Simader, Christian; Schmidt-Erfurth, Ursula

    2014-03-01

    ground truth vessel shadow regions identified by expert graders at the Vienna Reading Center (VRC). The results presented here are intended to show the feasibility of this method for the accurate and precise extraction of suitable retinal vessel shadows from multiple vendor 3D SD-OCT scans for use in intra-vendor and cross-vendor 3D OCT registration, 2D fundus registration and actual retinal vessel segmentation. The resulting percentage of true vessel shadow segments to false positive segments identified by the proposed system compared to mean grader ground truth is 95%.

  18. Safety and efficacy of dimethyl fumarate in multiple sclerosis: a multi-center observational study.

    PubMed

    Miclea, A; Leussink, V I; Hartung, H P; Gold, R; Hoepner, R

    2016-08-01

    Dimethyl fumarate (DMF) was recently approved for treating patients with relapsing-remitting multiple sclerosis (RRMS) based on two phase III clinical trials demonstrating its efficacy. This prompts the need for demonstrating the clinical efficacy and safety of DMF in the real world. By retrospective analysis of medical records at two German MS centers, 644 MS patients treated with DMF were identified. All were included in a safety analysis, and a subgroup of patients with available efficacy data during previous MS therapies (n = 352) was further analyzed for annualized relapse rate and disability progression assessed by the EDSS. In the overall DMF population studied, the annualized relapse rate decreased from 0.52 at baseline to 0.35, and the annualized disability progression from 0.15 to 0.10. Patients who were switched from interferons or glatiramer acetate to DMF revealed a greater benefit, whereas patients pretreated with more potent immunotherapies did not respond that well. Interestingly, patients with a lymphocyte count ≥2000/µl after 0.52 years (mean, SD 0.2) of DMF treatment did not benefit compared to those with lower lymphocyte counts. In total, 22.2 % of the patients withdrew from DMF due to side effects, with gastrointestinal discomfort (12.7 %) and lymphopenia (5.3 %) as most frequently reported reasons. Our study corroborates that DMF is an overall safe and effective drug that reduces relapse rate as well as disability progression in MS patients. Further prospective studies are warranted to establish the additional parameters predicting DMF response, especially in patients switching from other first-line immunotherapies. PMID:27260297

  19. Regional Gray Matter Atrophy in Relapsing Remitting Multiple Sclerosis: Baseline Analysis of Multi-Center Data

    PubMed Central

    Datta, Sushmita; Staewen, Terrell D.; Cofield, Stacy S.; Cutter, Gary R.; Lublin, Fred D.; Wolinsky, Jerry S.; Narayana, Ponnada A.

    2015-01-01

    Regional gray matter (GM) atrophy in multiple sclerosis (MS) at disease onset and its temporal variation can provide objective information regarding disease evolution. An automated pipeline for estimating atrophy of various GM structures was developed using tensor based morphometry (TBM) and implemented on a multi-center sub-cohort of 1008 relapsing remitting MS (RRMS) patients enrolled in a Phase 3 clinical trial. Four hundred age and gender matched healthy controls were used for comparison. Using the analysis of covariance, atrophy differences between MS patients and healthy controls were assessed on a voxel-by-voxel analysis. Regional GM atrophy was observed in a number of deep GM structures that included thalamus, caudate nucleus, putamen, and cortical GM regions. General linear regression analysis was performed to analyze the effects of age, gender, and scanner field strength, and imaging sequence on the regional atrophy. Correlations between regional GM volumes and expanded disability status scale (EDSS) scores, disease duration (DD), T2 lesion load (T2 LL), T1 lesion load (T1 LL), and normalized cerebrospinal fluid (nCSF) were analyzed using Pearson’s correlation coefficient. Thalamic atrophy observed in MS patients compared to healthy controls remained consistent within subgroups based on gender and scanner field strength. Weak correlations between thalamic volume and EDSS (r = −0.133; p < 0.001) and DD (r = −0.098; p = 0.003) were observed. Of all the structures, thalamic volume moderately correlated with T2 LL (r = −0.492; p-value < 0.001), T1 LL (r = −0.473; p-value < 0.001) and nCSF (r = −0.367; p-value < 0.001). PMID:25787188

  20. Regional gray matter atrophy in relapsing remitting multiple sclerosis: baseline analysis of multi-center data.

    PubMed

    Datta, Sushmita; Staewen, Terrell D; Cofield, Stacy S; Cutter, Gary R; Lublin, Fred D; Wolinsky, Jerry S; Narayana, Ponnada A

    2015-03-01

    Regional gray matter (GM) atrophy in multiple sclerosis (MS) at disease onset and its temporal variation can provide objective information regarding disease evolution. An automated pipeline for estimating atrophy of various GM structures was developed using tensor based morphometry (TBM) and implemented on a multi-center sub-cohort of 1008 relapsing remitting MS (RRMS) patients enrolled in a Phase 3 clinical trial. Four hundred age and gender matched healthy controls were used for comparison. Using the analysis of covariance, atrophy differences between MS patients and healthy controls were assessed on a voxel-by-voxel analysis. Regional GM atrophy was observed in a number of deep GM structures that included thalamus, caudate nucleus, putamen, and cortical GM regions. General linear regression analysis was performed to analyze the effects of age, gender, and scanner field strength, and imaging sequence on the regional atrophy. Correlations between regional GM volumes and expanded disability status scale (EDSS) scores, disease duration (DD), T2 lesion load (T2 LL), T1 lesion load (T1 LL), and normalized cerebrospinal fluid (nCSF) were analyzed using Pearson׳s correlation coefficient. Thalamic atrophy observed in MS patients compared to healthy controls remained consistent within subgroups based on gender and scanner field strength. Weak correlations between thalamic volume and EDSS (r=-0.133; p<0.001) and DD (r=-0.098; p=0.003) were observed. Of all the structures, thalamic volume moderately correlated with T2 LL (r=-0.492; P-value<0.001), T1 LL (r=-0.473; P-value<0.001) and nCSF (r=-0.367; P-value<0.001). PMID:25787188

  1. A molecular propeller effect for chiral separation and analysis.

    PubMed

    Clemens, Jonathon B; Kibar, Osman; Chachisvilis, Mirianas

    2015-01-01

    Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved. PMID:26216219

  2. A molecular propeller effect for chiral separation and analysis

    PubMed Central

    Clemens, Jonathon B.; Kibar, Osman; Chachisvilis, Mirianas

    2015-01-01

    Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved. PMID:26216219

  3. A molecular propeller effect for chiral separation and analysis

    NASA Astrophysics Data System (ADS)

    Clemens, Jonathon B.; Kibar, Osman; Chachisvilis, Mirianas

    2015-07-01

    Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved.

  4. Planar plasmonic chiral nanostructures.

    PubMed

    Zu, Shuai; Bao, Yanjun; Fang, Zheyu

    2016-02-21

    A strong chiral optical response induced at a plasmonic Fano resonance in a planar Au heptamer nanostructure was experimentally and theoretically demonstrated. The scattering spectra show the characteristic narrow-band feature of Fano resonances for both left and right circular polarized lights, with a chiral response reaching 30% at the Fano resonance. Specifically, we systematically investigate the chiral response of planar heptamers with gradually changing the inter-particle rotation angles and separation distance. The chiral spectral characteristics clearly depend on the strength of Fano resonances and the associated near-field optical distributions. Finite element method simulations together with a multipole expansion method demonstrate that the enhanced chirality is caused by the excitation of magnetic quadrupolar and electric toroidal dipolar modes. Our work provides an effective method for the design of 2D nanostructures with a strong chiral response. PMID:26818746

  5. Axially chiral BODIPYs.

    PubMed

    Lerrick, Reinner I; Winstanley, Thomas P L; Haggerty, Karen; Wills, Corinne; Clegg, William; Harrington, Ross W; Bultinck, Patrick; Herrebout, Wouter; Benniston, Andrew C; Hall, Michael J

    2014-05-11

    The synthesis and resolution of a class of chiral organic fluorophores, axially chiral 4,4-difluoro-4-bora-3a,4a-diaza-s-indacenes (Ax*-BODIPY), is described. Ax*-BODIPYs were prepared through a modular synthesis combined with a late stage Heck functionalisation. Resolution was achieved by preparative chiral HPLC. Absolute stereochemical assignment was performed by comparison of experimental ECD spectra with TD-DFT calculations. PMID:24676233

  6. Chiral atomically thin films

    NASA Astrophysics Data System (ADS)

    Kim, Cheol-Joo; Sánchez-Castillo, A.; Ziegler, Zack; Ogawa, Yui; Noguez, Cecilia; Park, Jiwoong

    2016-06-01

    Chiral materials possess left- and right-handed counterparts linked by mirror symmetry. These materials are useful for advanced applications in polarization optics, stereochemistry and spintronics. In particular, the realization of spatially uniform chiral films with atomic-scale control of their handedness could provide a powerful means for developing nanodevices with novel chiral properties. However, previous approaches based on natural or grown films, or arrays of fabricated building blocks, could not offer a direct means to program intrinsic chiral properties of the film on the atomic scale. Here, we report a chiral stacking approach, where two-dimensional materials are positioned layer-by-layer with precise control of the interlayer rotation (θ) and polarity, resulting in tunable chiral properties of the final stack. Using this method, we produce left- and right-handed bilayer graphene, that is, a two-atom-thick chiral film. The film displays one of the highest intrinsic ellipticity values (6.5 deg μm–1) ever reported, and a remarkably strong circular dichroism (CD) with the peak energy and sign tuned by θ and polarity. We show that these chiral properties originate from the large in-plane magnetic moment associated with the interlayer optical transition. Furthermore, we show that we can program the chiral properties of atomically thin films layer-by-layer by producing three-layer graphene films with structurally controlled CD spectra.

  7. Chiral atomically thin films.

    PubMed

    Kim, Cheol-Joo; Sánchez-Castillo, A; Ziegler, Zack; Ogawa, Yui; Noguez, Cecilia; Park, Jiwoong

    2016-06-01

    Chiral materials possess left- and right-handed counterparts linked by mirror symmetry. These materials are useful for advanced applications in polarization optics, stereochemistry and spintronics. In particular, the realization of spatially uniform chiral films with atomic-scale control of their handedness could provide a powerful means for developing nanodevices with novel chiral properties. However, previous approaches based on natural or grown films, or arrays of fabricated building blocks, could not offer a direct means to program intrinsic chiral properties of the film on the atomic scale. Here, we report a chiral stacking approach, where two-dimensional materials are positioned layer-by-layer with precise control of the interlayer rotation (θ) and polarity, resulting in tunable chiral properties of the final stack. Using this method, we produce left- and right-handed bilayer graphene, that is, a two-atom-thick chiral film. The film displays one of the highest intrinsic ellipticity values (6.5 deg μm(-1)) ever reported, and a remarkably strong circular dichroism (CD) with the peak energy and sign tuned by θ and polarity. We show that these chiral properties originate from the large in-plane magnetic moment associated with the interlayer optical transition. Furthermore, we show that we can program the chiral properties of atomically thin films layer-by-layer by producing three-layer graphene films with structurally controlled CD spectra. PMID:26900756

  8. Multiple-order resonant Raman scattering of the localized molecular rose center in BaF 2

    NASA Astrophysics Data System (ADS)

    Deyhimi, Farzad; Bill, Hans

    1983-11-01

    The rose center in BaF 2 is investigated by resonant Raman scattering. The spectra obtained at liquid-helium temperature show multiple order and combination bands of the internal local modes (up to the sixth order), and associated side bands of the lattice. The temperature dependence of the linewidth of the local-mode transitions has been investigated and is explained as being due to anharmonic coupling to the lattice.

  9. Molecular-Level Design of Heterogeneous Chiral Catalysis

    SciTech Connect

    Francisco Zaera

    2012-03-21

    , and the development of ways to imprint chiral centers on achiral solid surfaces. Chiral catalysis is not only a problem of great importance in its own right, but also the ultimate test of how to control selectivity in catalysis. The time is ripe for fundamental work in heterogeneous chiral catalysis to provide the U.S. with a leadership role in developing the next generation of catalytic processes for medicinal and agrochemical manufacturing. Our team provides the required expertise for a synergistic and comprehensive integration of physical and chemical experimentation with solid state and molecular reactivity theories to solve this problem.

  10. Religious-Centered Multiethnic Societies: Multiple Identities and Ethnopolitics in Latvia.

    ERIC Educational Resources Information Center

    Karklins, Rasma; Zepa, Brigita

    1996-01-01

    Maintains that people have multiple identities and discusses how these differential identities were realigned in Latvia during and after the collapse of the Soviet Union. Survey data suggests current ethnopolitical identity incorporates multiple dimensions and a strong contextual component. Includes graphs and tables of statistical data. (MJP)

  11. Chiral Drugs: An Overview

    PubMed Central

    Nguyen, Lien Ai; He, Hua; Pham-Huy, Chuong

    2006-01-01

    About more than half of the drugs currently in use are chiral compounds and near 90% of the last ones are marketed as racemates consisting of an equimolar mixture of two enantiomers. Although they have the same chemical structure, most isomers of chiral drugs exhibit marked differences in biological activities such as pharmacology, toxicology, pharmacokinetics, metabolism etc. Some mechanisms of these properties are also explained. Therefore, it is important to promote the chiral separation and analysis of racemic drugs in pharmaceutical industry as well as in clinic in order to eliminate the unwanted isomer from the preparation and to find an optimal treatment and a right therapeutic control for the patient. In this article, we review the nomenclature, pharmacology, toxicology, pharmacokinetics, metabolism etc of some usual chiral drugs as well as their mechanisms. Different techniques used for the chiral separation in pharmaceutical industry as well as in clinical analyses are also examined. PMID:23674971

  12. A study of steric chirality: the chiral nematic phase of a system of chiral two-site HGO molecules

    NASA Astrophysics Data System (ADS)

    Varga, Szabolcs; Jackson, George

    2011-03-01

    The liquid crystalline phase behaviour of a chiral two-site hard Gaussian overlap fluid is examined using the well-known Parsons-Lee extension of the theory of Onsager. The hard-core model is constructed such that the vector connecting the centers of two hard Gaussian segments is perpendicular to the long axes of both segments. The microscopic chirality of the particle can be controlled with the dihedral angle between the long axes of the hard Gaussian segments, the distance between the two segments, and the length-to-breath ratios of each segment. In the framework of the Parsons-Lee approach three different types of phases are considered, namely, the isotropic liquid state, and the nematic and the chiral nematic (cholesteric) liquid crystalline states. For simplicity, the orientation of the particles is restricted to the plane perpendicular to the twist axis, and the particles do not have internal freedom to rotate around their main symmetry axes. The geometric condition for the formation of a chiral nematic phase, the properties of the helical structure, and the phase boundary of the ordering transition are determined by means of a free energy minimization. It is shown that steric (shape) chirality always gives rise to a helical structure in the nematic phase, and that the low density chiral systems can undergo a transition from an isotropic liquid to a twisted nematic phase on increasing the density. Analytical expressions are obtained for the twist period (pitch) in the limit of parallel stacking of the rod-like segments in layers normal to the helical axis, which are only valid for systems characterized by weak chiral strengths. A key finding of the numerical calculations is that the pitch is very sensitive to the segment separation, but not to the density or aspect ratio. It is interesting to note that the inverse of the pitch is predicted to depend linearly on the dihedral angle in all of the cases studied.

  13. Chiral Perturbation Theory

    NASA Astrophysics Data System (ADS)

    Tiburzi, Brian C.

    The era of high-precision lattice QCD has led to synergy between lattice computations and phenomenological input from chiral perturbation theory. We provide an introduction to chiral perturbation theory with a bent towards understanding properties of the nucleon and other low-lying baryons. Four main topics are the basis for this chapter. We begin with a discussion of broken symmetries and the procedure to construct the chiral Lagrangian. The second topic concerns specialized applications of chiral perturbation theory tailored to lattice QCD, such as partial quenching, lattice discretization, and finite-volume effects. We describe inclusion of the nucleon in chiral perturbation theory using a heavy-fermion Euclidean action. Issues of convergence are taken up as our final topic. We consider expansions in powers of the strange-quark mass, and the appearance of unphysical singularities in the heavy-particle formulation. Our aim is to guide lattice practitioners in understanding the predictions chiral perturbation theory makes for baryons, and show how the lattice will play a role in testing the rigor of the chiral expansion at physical values of the quark masses.

  14. Applications of chiral symmetry

    SciTech Connect

    Pisarski, R.D.

    1995-03-01

    The author discusses several topics in the applications of chiral symmetry at nonzero temperature. First, where does the rho go? The answer: up. The restoration of chiral symmetry at a temperature T{sub {chi}} implies that the {rho} and a{sub 1} vector mesons are degenerate in mass. In a gauged linear sigma model the {rho} mass increases with temperature, m{sub {rho}}(T{sub {chi}}) > m{sub {rho}}(0). The author conjectures that at T{sub {chi}} the thermal {rho} - a{sub 1}, peak is relatively high, at about {approximately}1 GeV, with a width approximately that at zero temperature (up to standard kinematic factors). The {omega} meson also increases in mass, nearly degenerate with the {rho}, but its width grows dramatically with temperature, increasing to at least {approximately}100 MeV by T{sub {chi}}. The author also stresses how utterly remarkable the principle of vector meson dominance is, when viewed from the modern perspective of the renormalization group. Secondly, he discusses the possible appearance of disoriented chiral condensates from {open_quotes}quenched{close_quotes} heavy ion collisions. It appears difficult to obtain large domains of disoriented chiral condensates in the standard two flavor model. This leads to the last topic, which is the phase diagram for QCD with three flavors, and its proximity to the chiral critical point. QCD may be very near this chiral critical point, and one might thereby generated large domains of disoriented chiral condensates.

  15. Evaluation of Multiple Outcomes in the Child Parent Center Compensatory Education Program: Year II.

    ERIC Educational Resources Information Center

    Eash, Maurice J.; And Others

    Results are reported from the second year of a longitudinal evaluation of Child Parent Centers (CPC's) serving low-income urban children. Six-year-old participants and nine-year-old former participants and comparison groups were analyzed on measures including reading and mathematics achievement, internal-external control belief, and…

  16. Chirality control in oligothiophene through chiral wrapping.

    PubMed

    Sanji, Takanobu; Kato, Nobu; Tanaka, Masato

    2006-01-19

    [structure: see text] Mixing oligothiophenes and polysaccharides, such as amylose and schizophyllan, affords novel inclusion complexes, in which oligothiophene guests adopt twisted conformation in the chiral channel created by left- or right-handed helical wrapping with the polysaccharide host polymers, leading to optical activity. PMID:16408883

  17. Synthesis of Chiral Cyclopentenones.

    PubMed

    Simeonov, Svilen P; Nunes, João P M; Guerra, Krassimira; Kurteva, Vanya B; Afonso, Carlos A M

    2016-05-25

    The cyclopentenone unit is a very powerful synthon for the synthesis of a variety of bioactive target molecules. This is due to the broad diversity of chemical modifications available for the enone structural motif. In particular, chiral cyclopentenones are important precursors in the asymmetric synthesis of target chiral molecules. This Review provides an overview of reported methods for enantioselective and asymmetric syntheses of cyclopentenones, including chemical and enzymatic resolution, asymmetric synthesis via Pauson-Khand reaction, Nazarov cyclization and organocatalyzed reactions, asymmetric functionalization of the existing cyclopentenone unit, and functionalization of chiral building blocks. PMID:27101336

  18. The covariant chiral ring

    NASA Astrophysics Data System (ADS)

    Bourget, Antoine; Troost, Jan

    2016-03-01

    We construct a covariant generating function for the spectrum of chiral primaries of symmetric orbifold conformal field theories with N = (4 , 4) supersymmetry in two dimensions. For seed target spaces K3 and T 4, the generating functions capture the SO(21) and SO(5) representation theoretic content of the chiral ring respectively. Via string dualities, we relate the transformation properties of the chiral ring under these isometries of the moduli space to the Lorentz covariance of perturbative string partition functions in flat space.

  19. The significance of chirality in drug design and development.

    PubMed

    Brooks, W H; Guida, W C; Daniel, K G

    2011-01-01

    Proteins are often enantioselective towards their binding partners. When designing small molecules to interact with these targets, one should consider stereoselectivity. As considerations for exploring structure space evolve, chirality is increasingly important. Binding affinity for a chiral drug can differ for diastereomers and between enantiomers. For the virtual screening and computational design stage of drug development, this problem can be compounded by incomplete stereochemical information in structure libraries leading to a "coin toss" as to whether or not the "ideal" chiral structure is present. Creating every stereoisomer for each chiral compound in a structure library leads to an exponential increase in the number of structures resulting in potentially unmanageable file sizes and screening times. Therefore, only key chiral structures, enantiomeric pairs based on relative stereochemistry need be included, and lead to a compromise between exploration of chemical space and maintaining manageable libraries. In clinical environments, enantiomers of chiral drugs can have reduced, no, or even deleterious effects. This underscores the need to avoid mixtures of compounds and focus on chiral synthesis. Governmental regulations emphasizing the need to monitor chirality in drug development have increased. The United States Food and Drug Administration issued guidelines and policies in 1992 concerning the development of chiral compounds. These guidelines require that absolute stereochemistry be known for compounds with chiral centers and that this information should be established early in drug development in order that the analysis can be considered valid. From exploration of structure space to governmental regulations it is clear that the question of chirality in drug design is of vital importance. PMID:21291399

  20. Large-scale green chemical synthesis of adjacent quaternary chiral centers by continuous flow photodecarbonylation of aqueous suspensions of nanocrystalline ketones.

    PubMed

    Hernández-Linares, María Guadalupe; Guerrero-Luna, Gabriel; Pérez-Estrada, Salvador; Ellison, Martha; Ortin, Maria-Mar; Garcia-Garibay, Miguel A

    2015-02-01

    To demonstrate the ease of scale-up and synthetic potential of some organic solid state reactions, we report the synthesis, crystallization, and solid state photochemistry of acyclic, homochiral, hexasubstituted (+)-(2R,4S)-2-carbomethoxy-4-cyano-2,4-diphenyl-3-pentanone 1. We demonstrate that solid state photodecarbonylation of (+)-(2R,4S)-1 affords (+)-(2R,3R)-2-carbomethoxy-3-cyano-2,3-diphenyl-butane 2 with two adjacent stereogenic, all-carbon substituted quaternary centers, in quantitative chemical yield and 100% diastereoselectivity and enantiomeric excess. The efficient multigram photodecarbonylation of (+)-(2R,4S)-1 as a nanocrystalline suspension in water using a continuous flow photoreactor shows that the large-scale synthesis of synthetically challenging compounds using photochemical synthesis in the solid state can be executed in a remarkably simple manner. PMID:25578232

  1. Nonlinear chiral transport phenomena

    NASA Astrophysics Data System (ADS)

    Chen, Jiunn-Wei; Ishii, Takeaki; Pu, Shi; Yamamoto, Naoki

    2016-06-01

    We study the nonlinear responses of relativistic chiral matter to the external fields such as the electric field E , gradients of temperature and chemical potential, ∇T and ∇μ . Using the kinetic theory with Berry curvature corrections under the relaxation time approximation, we compute the transport coefficients of possible new electric currents that are forbidden in usual chirally symmetric matter but are allowed in chirally asymmetric matter by parity. In particular, we find a new type of electric current proportional to ∇μ ×E due to the interplay between the effects of the Berry curvature and collisions. We also derive an analog of the "Wiedemann-Franz" law specific for anomalous nonlinear transport in relativistic chiral matter.

  2. Spintronics: Chiral damping

    PubMed Central

    Kim, Kyoung-Whan; Lee, Hyun-Woo

    2016-01-01

    The analysis of the magnetic domain wall motion in a nanostructured magnetic system with strong spin-orbit coupling shows that the energy dissipation can be chiral when the inversion symmetry is broken. PMID:26906956

  3. Efficient Molecular Dynamics Simulations of Multiple Radical Center Systems Based on the Fragment Molecular Orbital Method

    SciTech Connect

    Nakata, Hiroya; Schmidt, Michael W; Fedorov, Dmitri G; Kitaura, Kazuo; Nakamura, Shinichiro; Gordon, Mark S

    2014-10-16

    The fully analytic energy gradient has been developed and implemented for the restricted open-shell Hartree–Fock (ROHF) method based on the fragment molecular orbital (FMO) theory for systems that have multiple open-shell molecules. The accuracy of the analytic ROHF energy gradient is compared with the corresponding numerical gradient, illustrating the accuracy of the analytic gradient. The ROHF analytic gradient is used to perform molecular dynamics simulations of an unusual open-shell system, liquid oxygen, and mixtures of oxygen and nitrogen. These molecular dynamics simulations provide some insight about how triplet oxygen molecules interact with each other. Timings reveal that the method can calculate the energy gradient for a system containing 4000 atoms in only 6 h. Therefore, it is concluded that the FMO-ROHF method will be useful for investigating systems with multiple open shells.

  4. Scalemic and racemic imprinting with a chiral crosslinker.

    PubMed

    Hebert, Britney; Meador, Danielle S; Spivak, David A

    2015-08-26

    The development of molecularly imprinted chiral stationary phases has traditionally been limited by the need for a chiral pure template. Paradoxically, availability of a chiral pure template largely defeats the purpose of developing a chiral stationary phase. To solve this paradox, imprinting of scalemic and racemic template mixtures was investigated using both chiral (N-α-bismethacryloyl-L-alanine) and achiral (N,O-bisacrylamide ethanolamine) crosslinkers. Imprinting of scalemic mixtures provided polymers capable of partial separation of Boc-tyrosine enantiomers with virtually the same results when using either the chiral or achiral crosslinker. However, the chiral crosslinker was required for chiral differentiation by the racemic imprinted polymers which were evaluated in both batch rebinding and chromatographic modes. Batch rebinding analysis revealed intersecting binding isotherms for the L- and D-Boc-tyrosine, indicating bias for the D or L enantiomer is concentration dependent. Partial chromatographic separation was achieved by the racemic imprinted polymers providing variable D or L bias in equal probability over multiple replicates of polymer synthesis. Correlation of enantiomer bias with the batch rebinding results and optimization of HPLC parameters are discussed. PMID:26347178

  5. Luminescent chiral lanthanide(III) complexes as potential molecular probes

    PubMed Central

    Muller, Gilles

    2009-01-01

    This perspective gives an introduction into the design of luminescent lanthanide(III)-containing complexes possessing chiral properties and used to probe biological materials. The first part briefly describes general principles, focusing on the optical aspect (i.e. lanthanide luminescence, sensitization processes) of the most emissive trivalent lanthanide ions, europium and terbium, incorporated into molecular luminescent edifices. This is followed by a short discussion on the importance of chirality in the biological and pharmaceutical fields. The second part is devoted to the assessment of the chiroptical spectroscopic tools available (typically circular dichroism and circularly polarized luminescence) and the strategies used to introduce a chiral feature into luminescent lanthanide(III) complexes (chiral structure resulting from a chiral arrangement of the ligand molecules surrounding the luminescent center or presence of chiral centers in the ligand molecules). Finally, the last part illustrates these fundamental principles with recent selected examples of such chiral luminescent lanthanide-based compounds used as potential probes of biomolecular substrates. PMID:19885510

  6. Chiral plasma instabilities.

    PubMed

    Akamatsu, Yukinao; Yamamoto, Naoki

    2013-08-01

    We study the collective modes in relativistic electromagnetic or quark-gluon plasmas with an asymmetry between left- and right-handed chiral fermions, based on the recently formulated kinetic theory with Berry curvature corrections. We find that there exists an unstable mode, signaling the presence of a plasma instability. We argue the fate of this "chiral plasma instability" including the effect of collisions, and briefly discuss its relevance in heavy ion collisions and compact stars. PMID:23952387

  7. Chiral pesticides: identification, description, and environmental implications.

    PubMed

    Ulrich, Elin M; Morrison, Candice N; Goldsmith, Michael R; Foreman, William T

    2012-01-01

    , synthetic musks, and their degradates (Kallenborn and Hiihnerfuss 2001;Heeb et al. 2007; Hihnerfuss and Shah 2009). The stereoisomers of pesticides can have widely different efficacy, toxicity to nontarget organisms, and metabolic rates in biota. For these reasons, it is important to first be aware of likely fate and effect differences, to incorporate molecular asymmetry insights into research projects, and to study the individual stereoisomers of the applied pesticide material.With the advent of enantioselective chromatography techniques, the chirality of pesticides has been increasingly studied. While the ChirBase (Advanced ChemistryDevelopment 1997-2010) database does not include all published chiral analytical separations, it does contain more than 3,500 records for 146 of the 482 chiral pesticides (30%). The majority of the records are found in the liquid chromatography database (2,677 or 76%), followed by the gas chromatography database (652 or 18%),and the capillary electrophoresis database (203 or 6%). The finding that only 30% of the chiral pesticides covered in this review have entries in ChirBase highlights the need for expanded efforts to develop additional enantioselective chromatographic methods. Other techniques (e.g., nuclear magnetic resonance and other spectroscopy)are available for investigation of chiral compounds, but often are not utilized because of cost, complexity, or simply not recognizing that a pesticide is chiral.In this review, we have listed and have briefly described the general nature of chiral fungicides, herbicides, insecticides, and other miscellaneous classes. A data-set generated for this review contains 1,693 pesticides, the number of enantioselective separation records in ChirBase, pesticide usage class, SMILES structure string and counts of stereogenic centers. This dataset is publically available for download at the following website: http://www.epa.gov/heasd/products/products.html. With the information herein coupled to the

  8. Structural reconstruction of the catalytic center of LiPDF through multiple scattering calculation with MXAN

    NASA Astrophysics Data System (ADS)

    Guo, Xiaoyun; Chu, Wangsheng; Ma, Sixuan; Gong, Weimin; Benfatto, Maurizio; Hu, Tiandou; Xie, Yaning; Wu, ZiYu

    2006-11-01

    Peptide deformylase (PDF, EC 3.5.1.27) is essential for the normal growth of eubacterium but not for mammalians. Recently, PDF has been studied as a target for new antibiotics. In this paper, X-ray absorption spectroscopy was employed to determine the local structure around the zinc ion of PDF from Leptospira Interrogans in dry powder, because it is very difficult to obtain the crystallized sample of LiPDF. We performed X-ray absorption near edge structure (XANES) calculation and reconstructed successfully the local geometry of the active center, and the results from calculations show that a water molecule (Wat1) has moved towards the zinc ion and lies in the distance range to coordinate with the zinc ion weakly. In addition, the sensitivity of theoretical spectra to the different ligand bodies was evaluated in terms of goodness-of-fit.

  9. Myelomatous pleural effusion involvement in 23 patients with multiple myeloma: A single-center clinical analysis.

    PubMed

    Zhong, Yuping; Zhang, Jiajia; Wang, Huan

    2015-05-01

    We investigated the treatment and prognosis of pleural effusion (PE) in multiple myeloma (MM) patients. From June 2005 to December 2013, 296 MM patients participated in this study. There were 23 PE patients, including 11 men and 12 women, with a median age of 56.8 years (range 37-68 years). A diagnosis of PE was based on physical examination, chest X-ray or computed tomography, and pleural fluid analysis. All patients demonstrated myeloma cells in the pleural fluid, and six patients were positive for PE M protein. PE patients received bortezomib combined with other drugs. Only one patient demonstrated a complete response; 10 patients showed partial responses, and 12 patients developed progressive disease and died. MM linked with myelomatous PE is associated with a poor prognosis. Myelomatous PE is likely a late manifestation of the natural history of MM or an expression of the aggressive behavior of the disease. PMID:26273384

  10. Multiple Shh signaling centers participate in fungiform papilla and taste bud formation and maintenance

    PubMed Central

    Liu, H-X; Ermilov, A; Grachtchouk, M; Li, L; Gumucio, DL; Dlugosz, AA; Mistretta, CM

    2014-01-01

    The adult fungiform taste papilla is a complex of specialized cell types residing in the stratified squamous tongue epithelium. This unique sensory organ includes taste buds, papilla epithelium and lateral walls that extend into underlying connective tissue to surround a core of lamina propria cells. Fungiform papillae must contain long-lived, sustaining or stem cells and short-lived, maintaining or transit amplifying cells that support the papilla and specialized taste buds. Shh signaling has established roles in supporting fungiform induction, development and patterning. However, for a full understanding of how Shh transduced signals act in tongue, papilla and taste bud formation and maintenance, it is necessary to know where and when the Shh ligand and pathway components are positioned. We used immunostaining, in situ hybridization and mouse reporter strains for Shh, Ptch1, Gli1 and Gli2-expression and proliferation markers to identify cells that participate in hedgehog signaling. Whereas there is a progressive restriction in location of Shh ligand-expressing cells, from placode and apical papilla cells to taste bud cells only, a surrounding population of Ptch1 and Gli1 responding cells is maintained in signaling centers throughout papilla and taste bud development and differentiation. The Shh signaling targets are in regions of active cell proliferation. Using genetic-inducible lineage tracing for Gli1-expression, we found that Shh-responding cells contribute not only to maintenance of filiform and fungiform papillae, but also to taste buds. A requirement for normal Shh signaling in fungiform papilla, taste bud and filiform papilla maintenance was shown by Gli2 constitutive activation. We identified proliferation niches where Shh signaling is active and suggest that epithelial and mesenchymal compartments harbor potential stem and/or progenitor cell zones. In all, we report a set of hedgehog signaling centers that regulate development and maintenance of taste

  11. Syntheses and some features of five new cyclohexane-1,3-dicarboxylates with multiple stereogenic centers

    NASA Astrophysics Data System (ADS)

    Ismiyev, Arif M.; Maharramov, Abel M.; Aliyeva, Rafiga A.; Askerov, Rizvan K.; Mahmudov, Kamran T.; Kopylovich, Maximilian N.; Naïli, Houcine; Pombeiro, Armando J. L.

    2013-01-01

    The condensation of diethyl 4-hydroxy-4-methyl-6-oxo-2-(4-substitutedphenyl)-cyclohexane-1,3-dicarboxylates and N'-(2-chloropropyl)ethane-1,2-diamine leads to diethyl 1-(2-chloropropyl)-9-hydroxy-9-methyl-7-phenyl-1,4-diazaspiro[4.5]decane-6,8-dicarboxylate (2) and its para-substituted methyl (1), chloro (3), bromo (4), and nitro (5) derivatives with a new stereogenic center, which were fully characterized by elemental analysis, ESI-MS, IR, 1H and 13C NMR spectroscopies and X-ray single-crystal analysis (for 2). The condensation reaction is regioselective, only cyclohexanone carbonyl moiety undergoes the transformation, leaving the β-keto ester carbonyls unreacted. Withing the compounds 1-5, the increase in the Hammett's σp, related normal σpn, inductive σI, negative σp- and positive σp+ polar conjugation and Taft's σpo substituent constants generally leads to the corresponding drift of δOsbnd H and δNsbnd H NMR chemical shifts to lower field.

  12. Chiral quirkonium decays

    NASA Astrophysics Data System (ADS)

    Fok, R.; Kribs, Graham D.

    2011-08-01

    We calculate the two-body decay rates of quirkonium states formed from quirks that acquire mass solely through electroweak symmetry breaking. We consider SU(N)ic infracolor with two flavors of quirks transforming under the electroweak group (but not QCD) of the standard model. In one case, the quirks are in a chiral representation of the electroweak group, while in the other case, a vectorlike representation. The differences in the dominant decay channels between “chiral quirkonia” versus “vectorlike quirkonia” are striking. Several chiral quirkonia states can decay into the unique two-body resonance channels WH, ZH, tt¯, tb¯/bt¯, and γH, which never dominate for vectorlike quirkonia. Additionally, the channels WW, WZ, ZZ, and Wγ, are shared among both chiral and vectorlike quirkonia. Resonances of dileptons or light quarks (dijets) can dominate for some vectorlike quirkonia states throughout their mass range, while these modes never dominate for chiral quirkonia unless the decays into pairs of gauge or Higgs bosons are kinematically forbidden.

  13. Chiral Quirkonium Decays

    SciTech Connect

    Fok, R.; Kribs, Graham D.; /Fermilab

    2011-06-01

    We calculate the two-body decay rates of quirkonium states formed from quirks that acquire mass solely through electroweak symmetry breaking. We consider SU(N){sub ic} infracolor with two flavors of quirks transforming under the electroweak group (but not QCD) of the standard model. In one case, the quirks are in a chiral representation of the electroweak group, while in the other case, a vectorlike representation. The differences in the dominant decay channels between 'chiral quirkonia' versus 'vectorlike quirkonia' are striking. Several chiral quirkonia states can decay into the unique two-body resonance channels WH, ZH, t{bar t}, t{bar b}/b{bar t}, and {gamma}H, which never dominate for vectorlike quirkonia. Additionally, the channels WW, WZ, ZZ, and W{gamma}, are shared among both chiral and vectorlike quirkonia. Resonances of dileptons or light quarks (dijets) can dominate for some vectorlike quirkonia states throughout their mass range, while these modes never dominate for chiral quirkonia unless the decays into pairs of gauge or Higgs bosons are kinematically forbidden.

  14. Spontaneous chirality in simple systems

    PubMed

    Pickett; Gross; Okuyama

    2000-10-23

    Two simple examples of spontaneous chiral symmetry breaking are presented. The first is close-packed cylindrically confined spheres. As the cylinder diameter is varied, one obtains a variety of chiral phases. The second example involves unconfined dipolar particles with an isotropic attraction, which also exhibits chiral ground states. We speculate that a dilute magnetorheological fluid film, with the addition of smaller particles to provide an attractive entropic interaction, will exhibit a chiral columnar ground state. PMID:11030973

  15. Application of rifampicin as a chiral selector for enantioresolution of basic drugs using capillary electrophoresis.

    PubMed

    Dixit, Shuchi; Park, Jung Hag

    2016-07-01

    Rifampicin, a member of rifamycin sub-class of antibiotics which belongs to the naphthalenic ansamycin class of antibiotics, has a characteristic ansa structure, i.e., a ring structure or chromophore spanned by an aliphatic chain. The present work was designed to evaluate its potential as a chiral selector (CS) as its structure consisting of nine stereogenic centers, an aromatic moiety and several functional groups (i.e., one imine, one amide, one acetoxy residue, two aliphatic hydroxyl and three phenolic hydroxyl groups) was expected to instigate multiple enantioselective interactions, namely, hydrogen bonding and inclusion complexation with chiral analytes, and therefore resulting in efficient enantioseparations. Systematic experiments were performed to investigate the effects of concentration of CS, composition of background electrolyte (BGE) and applied voltage on chiral separation. Enantiomers of propranolol and metoprolol were baseline resolved using a BGE consisting of 20mM CS and 50/50 (v/v) iso-propanol/phosphate buffer (100mM, pH 7.0) whereas for enantiomers of sertraline, a BGE consisting of 23mM CS and 40/60 (v/v) iso-propanol/phosphate buffer (100mM, pH 7.0) resulted in baseline resolutions. PMID:27240943

  16. Rationalization of chirality induction and inversion in a zinc trisporphyrinate by a chiral monoalcohol.

    PubMed

    Li, Li; Hu, Chuanjiang; Shi, Bo; Wang, Yong

    2016-05-10

    A new host-guest system is formed between a benzene tricarboxamide linked zinc trisporphyrinate and a chiral monoalcohol (1-phenylethylalcohol). CD spectra show the chirality induction and inversion processes, which are controlled by the corresponding 1 : 1 and 1 : 2 coordination complexes. The binding constants calculated by UV-vis and CD spectral data are much larger than that for [Zn(TPP)] (TPP = tetraphenylporphyrin). The crystallographic structure of the host-guest complex reveals that multiple intramolecular hydrogen bonds and π-π interactions could contribute to its high binding affinity to 1-phenylethylalcohol. The DFT calculations suggest that the spatial orientations of porphyrin moieties change from the 1 : 1 complex to the 1 : 2 complex. The chirality induction and inversion processes are rationalized by the summation of pairwise interactions among multichromophores according to pairwise additivity. PMID:27074900

  17. Chiral Sensitivity in the Dissociative Electron Attachment of Halocamphor Molecules

    NASA Astrophysics Data System (ADS)

    Dreiling, Joan

    2016-05-01

    We have demonstrated chirally-dependent molecular destruction when incident longitudinally-spin-polarized (chiral) electrons break bonds in chiral molecules. This chiral sensitivity was observed through an asymmetry in the dissociative electron attachment (DEA) reaction rate with chiral 3-bromocamphor (C10 H15 BrO). Such an observation provides an unambiguous demonstration of the idea underlying the Vester-Ulbricht hypothesis, which attempts to explain the origins of the homochirality that is observed in many biological systems. While the lack of inversion symmetry in these reactions allows the effects we observe to occur, their dynamic causes are poorly understood. We have further studied the asymmetries in the DEA rates for two additional halocamphor molecules, 3-iodocamphor (C10 H15 IO) and 10-iodocamphor, in a systematic effort to illuminate the mechanisms responsible for the chiral sensitivity. The DEA signal depends on the sign of the incident electron helicity for a given target handedness in all molecules, and it varies with both the atomic number and the location of the heaviest atom in the molecule. Surprisingly, the DEA asymmetries for 10-iodocamphor, in which the heaviest atom is farther from a chiral center than for the other molecules, produced the largest asymmetries. This work was performed at the University of Nebraska-Lincoln. This project was funded by NSF Grant PHY-1206067.

  18. An Aligned-Gap and Centered-Gap Rectangular Multiple Split Ring Resonator for Dielectric Sensing Applications

    PubMed Central

    Rusni, Izyani Mat; Ismail, Alyani; Alhawari, Adam Reda Hasan; Hamidon, Mohd Nizar; Yusof, Nor Azah

    2014-01-01

    This paper presents the design and development of a planar Aligned-Gap and Centered-Gap Rectangular Multiple Split Ring Resonator (SRR) for microwave sensors that operates at a resonance frequency around 5 GHz. The sensor consists of a microstrip transmission line loaded with two elements of rectangular SRR on both sides. The proposed metamaterial sensors were designed and fabricated on Rogers RT5880 substrate having dielectric constant of 2.2 and thickness of 0.787 mm. The final dimension of the proposed sensor was measured at 35 × 14 mm2. Measured results show good agreement with simulated ones as well as exhibiting high Q-factor for use in sensing application. A remarkably shift of resonance frequency is observed upon introduction of several sample with different dielectric value. PMID:25051036

  19. The derivation of a chiral substituent code for secondary alcohols and its application to the prediction of enantioselectivity.

    PubMed

    Suo, Jing-Jie; Zhang, Qing-You; Li, Jing-Ya; Zhou, Yan-Mei; Xu, Lu

    2013-06-01

    A chiral substituent code was proposed based on the features of secondary alcohols, in which a chiral center is attached to two substituents in addition to OH and H substituents. The new chirality code, which was generated by predefining positional information of four substituents attached to stereocenter, was applied to two datasets composed of secondary alcohols as the enantioselective products of asymmetric reactions. In the first dataset, the chemical reaction was catalyzed by a biocatalyst, lipase from Candida rugosa. The catalyst for the second dataset was (-)-diisopinocampheylchloroborane. The structure-enantioselectivity relationship models were constructed using random forests with the chiral substituent code as the input. The resulting models were assessed both in terms of single enantiomers and pairs of enantiomers. Satisfactory results were obtained for both datasets. Although the chiral substituent code was specifically developed for secondary alcohols, it can easily be extended to represent chiral compounds possessing a specific chiral center bonded to two variable substituents. PMID:23666031

  20. Quantum phenomenology for the disoriented chiral condensate

    SciTech Connect

    Amado, R.D. ); Kogan, I.I. )

    1995-01-01

    We consider the quantum state describing the disoriented chiral condensate (DCC), which may be produced in high energy collisions. We show how a mean field treatment of the quantum equations corresponding to the classical linear [sigma] model leads to a squeezed state description of the pions emerging from the DCC. We examine various squeezed and coherent state descriptions of those pions with particular attention to charge and number fluctuations. We also study the phenomenology of multiple DCC domains.

  1. Baryon chiral perturbation theory

    NASA Astrophysics Data System (ADS)

    Scherer, S.

    2012-03-01

    We provide a short introduction to the one-nucleon sector of chiral perturbation theory and address the issue of power counting and renormalization. We discuss the infrared regularization and the extended on-mass-shell scheme. Both allow for the inclusion of further degrees of freedom beyond pions and nucleons and the application to higher-loop calculations. As applications we consider the chiral expansion of the nucleon mass to order Script O(q6) and the inclusion of vector and axial-vector mesons in the calculation of nucleon form factors. Finally, we address the complex-mass scheme for describing unstable particles in effective field theory.

  2. Diastereodivergent Catalytic Asymmetric Michael Addition of 2-Oxindoles to α,β-Unsaturated Ketones by Chiral Diamine Catalysts.

    PubMed

    Wei, Yuan; Wen, Shigang; Liu, Zunwu; Wu, Xinxin; Zeng, Bubing; Ye, Jinxing

    2015-06-01

    A diastereodivergent catalytic asymmetric Michael addition of 2-oxindoles to α,β-unsaturated ketones has been successfully developed with two complementary chiral diamine catalysts, affording chiral 3,3-disubstituted oxindoles with two adjacent chiral centers. Diastereodivergence has been realized through modifying substrates and utilizing different catalysts. Either anti-or syn-configured products possessing vicinal quaternary and tertiary stereogenic centers were produced with high enantioselectivities. PMID:25973971

  3. Patient- and family-centered care coordination: a framework for integrating care for children and youth across multiple systems.

    PubMed

    2014-05-01

    Understanding a care coordination framework, its functions, and its effects on children and families is critical for patients and families themselves, as well as for pediatricians, pediatric medical subspecialists/surgical specialists, and anyone providing services to children and families. Care coordination is an essential element of a transformed American health care delivery system that emphasizes optimal quality and cost outcomes, addresses family-centered care, and calls for partnership across various settings and communities. High-quality, cost-effective health care requires that the delivery system include elements for the provision of services supporting the coordination of care across settings and professionals. This requirement of supporting coordination of care is generally true for health systems providing care for all children and youth but especially for those with special health care needs. At the foundation of an efficient and effective system of care delivery is the patient-/family-centered medical home. From its inception, the medical home has had care coordination as a core element. In general, optimal outcomes for children and youth, especially those with special health care needs, require interfacing among multiple care systems and individuals, including the following: medical, social, and behavioral professionals; the educational system; payers; medical equipment providers; home care agencies; advocacy groups; needed supportive therapies/services; and families. Coordination of care across settings permits an integration of services that is centered on the comprehensive needs of the patient and family, leading to decreased health care costs, reduction in fragmented care, and improvement in the patient/family experience of care. PMID:24777209

  4. Clinical and epidemiological profile of multiple sclerosis in a reference center in the State of Bahia, Brazil.

    PubMed

    Cardoso, Eduardo; Fukuda, Thiago; Pereira, Júlio; Seixas, Jamile; Miranda, Rafael; Rodrigues, Bernardo; Saback, Thaís; Andrade, Renata; Cardoso, Grace; Martinez, Rosa; Avena, Juliane; Melo, Ailton

    2006-09-01

    Multiple sclerosis (MS) is an autoimmune, demyelinating and degenerative disease that affects the central nervous system. Its prevalence and clinical aspects vary according to the continent considered, being more frequent in Caucasians and young individuals aged 20 to 40 years. Epidemiological data from Brazil show that prevalence is variable, being more frequent in the Southern and Southeastern areas of the country, rather than in the Northern and Northeastern areas. The purpose of this paper is to describe MS clinical and epidemiological features in the State of Bahia, in the Brazilian Northeastern region. Thus, we held a cross-sectional study over the period from February to May, 2005, in the Multiple Sclerosis Patient Support Center ("Núcleo de Apoio aos Pacientes com Esclerose Múltipla") of Bahia, which included all patients with a diagnosis of MS seen over this period of time. A total of 121 patients were investigated, being 80.2% females (female:male ratio=4:1), with higher frequency in mulatto individuals (64%), and the relapsing-remitting type (91.3%). Most patients (68.7%) had mild MS, and blacks were prone to worse prognosis compared to other patients. PMID:17057875

  5. Multiple perpetrator rape among girls evaluated at a hospital-based Child Advocacy Center: Seven years of reviewed cases

    PubMed Central

    Edinburgh, Laurel; Pape-Blabolil, Julie; Harpin, Scott B.; Saewyc, Elizabeth

    2015-01-01

    The aim of this study was to describe contextual events, abuse experiences, and disclosure processes of adolescents who presented to a hospital-based Child Advocacy Center for medical evaluation and evidentiary collection as indicated after experiencing multiple perpetrator rape during a single event (n = 32) and to compare these findings to a group of single perpetrator sexual assaults (n = 534). This study used a retrospective mixed-methods design with in-depth, forensic interviews and complete physical examinations of gang-raped adolescents. Patients ranged from 12 to 17 years (M = 14 years). Girls who experienced multiple perpetrator rape during a single event were more likely to have run away, to have drunk alcohol in the past month, and to have participated in binge drinking in the past 2 weeks. Acute presentation of these victims were rare but 30% had hymenal transections and 38% had sexually transmitted infections (STIs). Forensic interviews revealed alcohol was a common weapon used by offenders, and its use resulted in victims experiencing difficulty in remembering and reporting details for police investigation or physical and mental health care. Most victims were raped at parties they attended with people they thought they could trust, and they felt let down by witnesses who could have helped but did not intervene. Although relatively rare, multiple perpetrator rape during a single event is a type of severe sexual assault experience and has significant risks for deleterious health outcomes. These victims require health care by trained providers to diagnose physical findings, treat STIs, screen for trauma, and support victims. PMID:24933707

  6. Contesting the paradigm of chirality

    NASA Astrophysics Data System (ADS)

    Efrati, Efi

    2012-02-01

    In 1893 Lord Kelvin coined the term chirality, and stated what is to become the elementary paradigm of chirality: 'I call any geometrical figure, or any group of points, chiral, and say it has chirality, if its image in a plane mirror , ideally realized cannot be brought to coincide with itself'. While the notion of chirality has greatly advanced our understanding of the structures of molecules and crystals, it has been shown to be inconsistent with every pseudo-scalar quantification. In this talk I will present a tabletop demonstration of a chiral structure which is constructed through the achiral summation of identical elementary units which are symmetric under reflection. The seeming contradiction to the definition of chirality is reconciled by proposing an alternative definition, relying on the physicist interpretation of the right hand rule.

  7. Chiral holmium complex-catalyzed Diels-Alder reaction of silyloxyvinylindoles: stereoselective synthesis of hydrocarbazoles.

    PubMed

    Harada, Shinji; Morikawa, Takahiro; Nishida, Atsushi

    2013-10-18

    The catalytic and asymmetric cycloaddition between 3-[1-(silyloxy)vinyl]indoles and electron-deficient olefins gave substituted hydrocarbazoles in up to 99% yield and 94% ee. This reaction was catalyzed by a novel chiral holmium(III) complex. Alkylation of the cycloadduct gave a tricyclic compound with four continuous chiral centers, one of which was a quaternary carbon. PMID:24079531

  8. Comparison of positively and negatively charged achiral co-monomers added to cyclodextrin monolith: improved chiral separations in capillary electrochromatography.

    PubMed

    Lu, Yang; Shamsi, Shahab A

    2014-10-01

    Cyclodextrins (CDs) and their derivatives have been one of the most popular and successful chiral additives used in electrokinetic chromatography because of the presence of multiple chiral centers, which leads to multiple chiral interactions. However, there has been relatively less published work on the use of CDs as monolithic media for capillary electrochromatography (CEC). The goal of this study was to show how the addition of achiral co-monomer to a polymerizable CD such as glycidyl methacrylate β-cyclodextrin (GMA/β-CD) can affect the enantioselective separations in monolithic CEC. To achieve this goal, polymeric monoliths columns were prepared by co-polymerizing GMA/β-CD with cationic or anionic achiral co-monomers [(2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and vinyl benzyltrimethyl-ammonium (VBTA)] in the presence of conventional crosslinker (ethylene dimethacrylate) and ternary porogen system including butanediol, propanol and water. A total of 34 negatively charged compounds, 30 positively charged compounds and 33 neutral compounds were screened to compare the enantioresolution capability on the GMA/β-CD, GMA/β-CD-VBTA and GMA/β-CD-AMPS monolithic columns. PMID:24108813

  9. Full quantum theory of the chiral anomaly transport in a Weyl semimetal

    NASA Astrophysics Data System (ADS)

    Lee, Woo-Ram; Park, Kwon; KIAS Team

    In relativistic field theory, the chiral anomaly means a violation of the number conservation of chiral fermions. In condensed matter physics, the chiral anomaly can be manifested in a Weyl semimetal as a negative magnetoresistance in the presence of parallel electric and magnetic fields. In this work, we use the Keldysh-Floquet Green's function formalism to develop a full quantum theory of the chiral anomaly transport, which can be valid in a broad range of both electric and magnetic field strengths. The authors thank KIAS Center for Advanced Computation (CAC) for providing computing resources.

  10. Prediction of enantiomeric selectivity in chromatography. Application of conformation-dependent and conformation-independent descriptors of molecular chirality.

    PubMed

    Aires-de-Sousa, João; Gasteiger, Johann

    2002-03-01

    In order to process molecular chirality by computational methods and to obtain predictions for properties that are influenced by chirality, a fixed-length conformation-dependent chirality code is introduced. The code consists of a set of molecular descriptors representing the chirality of a 3D molecular structure. It includes information about molecular geometry and atomic properties, and can distinguish between enantiomers, even if chirality does not result from chiral centers. The new molecular transform was applied to two datasets of chiral compounds, each of them containing pairs of enantiomers that had been separated by chiral chromatography. The elution order within each pair of isomers was predicted by means of Kohonen neural networks (NN) using the chirality codes as input. A previously described conformation-independent chirality code was also applied and the results were compared. In both applications clustering of the two classes of enantiomers (first eluted and last eluted enantiomers) could be successfully achieved by NN and accurate predictions could be obtained for independent test sets. The chirality code described here has a potential for a broad range of applications from stereoselective reactions to analytical chemistry and to the study of biological activity of chiral compounds. PMID:11885960

  11. Chiral electron-chiral target scattering

    SciTech Connect

    Trantham, K.W.; Gay, T.J. Johnston, M.E.

    1996-05-01

    It is possible to have an electronic counterpart to the well known effect of optical circular dichroism: electron circular dichroism (ECD) is the preferential scattering of longitudinally polarized electrons by a chiral target. Resulting essentially from a difference in total scattering cross section for different incident electron helicities, this {open_quotes}parity-violating{close_quotes} effect is allowed by symmetry because the scattering target is handed. The authors have searched for ECD in camphor by measuring the transmitted intensity of electrons with positive (negative) helicity I{sub +({minus})} through a gas cell containing stereoisomers of camphor vapor and constructing the asymmetry A = (I{sub +} {minus} I{sub {minus}}). Within their sensitivity (2x10{sup {minus}4}) the authors were not able to detect ECD at the energies investigated (10 eV). Prospects for future investigations, particularly in light of the recent positive results measured in Muenster, will be discussed.

  12. Multiple Interconversions of the E' and Oxygen-Hole Defect Centers in High-Purity Amorphous Silica during Anneal-Interrupted x Irradiation

    NASA Astrophysics Data System (ADS)

    Zhang, Lin; Mashkov, V. A.; Leisure, R. G.

    1995-02-01

    Multiple interconversions of E' centers and peroxy radicals have been observed for the first time by means of anneal-interrupted x-irradiation experiments. It is shown that each of these defects can serve as the precursor of the other; under thermal anneal an E' center can convert to a peroxy radical due to the capture of an oxygen molecule, and under irradiation the peroxy radical can covert to an E' center due to irradiation-induced release of oxygen. The results for the defect production and anneal behavior are well described in terms of simple stretched-exponential defect-reaction kinetics.

  13. Three-Month Test-Retest Reliability of Center of Pressure Motion During Standing Balance in Individuals with Multiple Sclerosis

    PubMed Central

    Wajda, Douglas A.; Motl, Robert W.

    2016-01-01

    Background: Balance impairment and an increased rate of falls are commonly reported in individuals with multiple sclerosis (MS). Force platform–generated center of pressure (COP) metrics have previously been recommended as an outcome measure to quantify balance deficits and distinguish between fallers and nonfallers in MS. Information is limited regarding the preservation of postural control in individuals with MS over extended time frames in the absence of an intervention. This report examines the test-retest reliability and magnitude of change of COP motion during standing balance over 3 months. Methods: Twenty individuals with MS and a history of falling underwent testing on two occasions 3 months apart in the absence of an intervention. On both occasions, participants completed two 30-second trials of three conditions: eyes open, eyes closed, and eyes open with concurrent cognitive challenge (dual task). Measures of COP area, velocity, and temporal structure were calculated and included in the reliability analysis. Results: The COP metrics displayed fair-to-excellent reliability over 3 months without an intervention. Reliability was maintained across the three commonly used balance conditions. Conclusions: These results offer insight into the reliability of COP measures over a 3-month period in MS and can inform the use of COP metrics for future study design (eg, sample size estimates) and balance outcome assessment during randomized controlled trials and fall-prevention studies in individuals with MS. PMID:27134578

  14. A retrospective analysis of cytogenetic alterations in patients with newly diagnosed multiple myeloma: a single center study in Korea

    PubMed Central

    Li, Shuhua; Lim, Hyeon-Ho; Woo, Kwang-Sook; Kim, Sung-Hyun

    2016-01-01

    Background The accurate identification of cytogenetic abnormalities in multiple myeloma (MM) has become more important over recent years for the development of new diagnostic and prognostic markers. In this study, we retrospectively analyzed the cytogenetic aberrations in MM cases as an initial assessment in a single institute. Methods We reviewed the cytogenetic results from 222 patients who were newly diagnosed with MM between January 2000 and December 2015. Chromosomal analysis was performed on cultured bone marrow samples by standard G-banding technique. At least 20 metaphase cells were analyzed for karyotyping. Results Clonal chromosome abnormalities were detected in 45.0% (100/222) of the patients. Among these results, 80 cases (80.0%) had both numerical and structural chromosome abnormalities. Overall hyperdiploidy with structural cytogenetic aberrations was the most common finding (44.0%), followed by hypodiploidy with structural aberrations (28.0%). Amplification of the long arm of chromosome 1 and -13/del(13q) were the most frequent recurrent abnormalities, and were detected in 50 patients (50.0%) and 40 patients (40.0%) with clonal abnormalities, respectively. The most common abnormality involving 14q32 was t(11;14)(q13;q32), which was observed in 19 cases. Conclusion These findings demonstrate that myeloma cells exhibit complex aberrations regardless of ploidy, even from a single center in Korea. Conventional cytogenetic analysis should be included in the initial diagnostic work-up for patients suspected of having MM. PMID:27382557

  15. Separation mechanisms for palonosetron stereoisomers at different chiral selector concentrations in MEKC.

    PubMed

    Hu, Shao-Qiang; Guo, Xu-Ming; Shi, Hai-Jun; Luo, Rong-Jie

    2015-03-01

    The separation mechanisms for palonosetron (PALO) stereoisomers in MEKC using sodium cholate (SC) as surfactant and chiral selector have been studied, in a wide range of concentrations below and above the CMC. It was found that SC micelles only provide chirally selective recognition for 3a carbon chiral center in PALO molecules. The resolution of the configurations of 2 carbon chiral center is achieved by the difference of mobility in continuous phase. A schematic diagram depicting the separation mechanisms and the corresponding migration orders among all of four stereoisomers was proposed based on the measured separation parameters. A MEKC method to achieve the complete separation of four stereoisomers in very short time using a very low chiral selector concentration, instead of high concentrations generally considered, was developed based on the understanding of the mechanisms. PMID:25404138

  16. Chiral Dynamics 2006

    NASA Astrophysics Data System (ADS)

    Ahmed, Mohammad W.; Gao, Haiyan; Weller, Henry R.; Holstein, Barry

    2007-10-01

    pt. A. Plenary session. Opening remarks: experimental tests of chiral symmetry breaking / A. M. Bernstein. [Double pie symbols] scattering / H. Leutwyler. Chiral effective field theory in a [Triangle]-resonance region / V. Pascalutsa. Some recent developments in chiral perturbation theory / Ulf-G. Mei ner. Chiral extrapolation and nucleon structure from the lattice / R.D. Young. Recent results from HAPPEX / R. Michaels. Chiral symmetries and low energy searches for new physics / M.J. Ramsey-Musolf. Kaon physics: recent experimental progress / M. Moulson. Status of the Cabibbo angle / V. Cirigliano. Lattice QCD and nucleon spin structure / J.W. Negele. Spin sum rules and polarizabilities: results from Jefferson lab / J-P Chen. Compton scattering and nucleon polarisabilities / Judith A. McGovern. Virtual compton scattering at MIT-bates / R. Miskimen. Physics results from the BLAST detector at the BATES accelerator / R.P. Redwine. The [Pie sympbol]NN system, recent progress / C. Hanhart. Application of chiral nuclear forces to light nuclei / A. Nogga. New results on few-body experiments at low energy / Y. Nagai. Few-body lattice calculations / M.J. Savage. Research opportunities at the upgraded HI?S facility / H.R. Weller -- pt. B. Goldstone boson dynamics. Working group summary: Goldstone Boson dynamics / G. Colangelo and S. Giovannella. Recent results on radiative Kaon decays from NA48 and NA48/2 / S.G. López. Cusps in K-->3 [Pie symbol] decays / B. Kubis. Recent KTeV results on radiative Kaon decays / M.C. Ronquest. The [Double pie symbols] scattering amplitude / J.R. Peláez. Determination of the Regge parameters in the [Double pie symbols] scattering amplitude / I. Caprini. e+e- Hadronic cross section measurement at DA[symbol]NE with the KLOE detector / P. Beltrame. Measurement of the form factors of e+e- -->2([Pie symbol]+[Pie symbol]-), pp and the resonant parameters of the heavy charmonia at BES / H. Hu. Measurement of e+e- multihadronic cross section below 4

  17. Chiral symmetry and pentaquarks

    SciTech Connect

    Dmitri Diakonov

    2004-07-01

    Spontaneous chiral symmetry breaking, mesons and baryons are illustrated in the language of the Dirac theory. Various forces acting between quarks inside baryons are discussed. I explain why the naive quark models typically overestimate pentaquark masses by some 500 MeV and why in the fully relativistic approach to baryons pentaquarks turn out to be light. I discuss briefly why it can be easier to produce pentaquarks at low than at high energies.

  18. Chiral Biomarkers in Meteorites

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    2010-01-01

    The chirality of organic molecules with the asymmetric location of group radicals was discovered in 1848 by Louis Pasteur during his investigations of the rotation of the plane of polarization of light by crystals of sodium ammonium paratartrate. It is well established that the amino acids in proteins are exclusively Levorotary (L-aminos) and the sugars in DNA and RNA are Dextrorotary (D-sugars). This phenomenon of homochirality of biological polymers is a fundamental property of all life known on Earth. Furthermore, abiotic production mechanisms typically yield recemic mixtures (i.e. equal amounts of the two enantiomers). When amino acids were first detected in carbonaceous meteorites, it was concluded that they were racemates. This conclusion was taken as evidence that they were extraterrestrial and produced by abiologically. Subsequent studies by numerous researchers have revealed that many of the amino acids in carbonaceous meteorites exhibit a significant L-excess. The observed chirality is much greater than that produced by any currently known abiotic processes (e.g. Linearly polarized light from neutron stars; Circularly polarized ultraviolet light from faint stars; optically active quartz powders; inclusion polymerization in clay minerals; Vester-Ulbricht hypothesis of parity violations, etc.). This paper compares the measured chirality detected in the amino acids of carbonaceous meteorites with the effect of these diverse abiotic processes. IT is concluded that the levels observed are inconsistent with post-arrival biological contamination or with any of the currently known abiotic production mechanisms. However, they are consistent with ancient biological processes on the meteorite parent body. This paper will consider these chiral biomarkers in view of the detection of possible microfossils found in the Orgueil and Murchison carbonaceous meteorites. Energy dispersive x-ray spectroscopy (EDS) data obtained on these morphological biomarkers will be

  19. Chirality and protein folding

    NASA Astrophysics Data System (ADS)

    Kwiecinska, Joanna I.; Cieplak, Marek

    2005-05-01

    There are several simple criteria of folding to a native state in model proteins. One of them involves crossing of a threshold value of the root mean square deviation distance away from the native state. Another checks whether all native contacts are established, i.e. whether the interacting amino acids come closer than some characteristic distance. We use Go-like models of proteins and show that such simple criteria may prompt one to declare folding even though fragments of the resulting conformations have a wrong sense of chirality. We propose that a better condition of folding should augment the simple criteria with the requirement that most of the local values of the chirality should be nearly native. The kinetic discrepancy between the simple and compound criteria can be substantially reduced in the Go-like models by providing the Hamiltonian with a term which favours native values of the local chirality. We study the effects of this term as a function of its amplitude and compare it to other models such as ones with side groups and ones with angle-dependent potentials.

  20. Increasing Retention of Adult Learners in Telecourses through the Incorporation of Learning-Centered Instructional Strategies and the Use of Multiple Modalities for Content Delivery and Interaction.

    ERIC Educational Resources Information Center

    Nelson, Lin M.

    A project was undertaken to increase retention in a health education telecourse by incorporating a competency-based orientation to distance learning and learner-centered instructional strategies into the telecourse, and by using multiple media for content delivery and interaction. A general orientation to distance learning was developed that…

  1. Electronic and chiroptical properties of chiral cycloiridiated complexes bearing helicenic NHC ligands.

    PubMed

    Hellou, Nora; Jahier-Diallo, Claire; Baslé, Olivier; Srebro-Hooper, Monika; Toupet, Loïc; Roisnel, Thierry; Caytan, Elsa; Roussel, Christian; Vanthuyne, Nicolas; Autschbach, Jochen; Mauduit, Marc; Crassous, Jeanne

    2016-07-28

    The first helicene-NHC-iridium complexes have been prepared in enantiopure forms. Their stereochemical, electronic, and chiroptical features were characterized experimentally and via first-principles calculations, highlighting the helical and iridium-centered chirality. PMID:27354241

  2. Chirality and equilibrium biopolymer bundles.

    PubMed

    Grason, Gregory M; Bruinsma, Robijn F

    2007-08-31

    We use continuum theory to show that chirality is a key thermodynamic control parameter for the aggregation of biopolymers: chirality produces a stable disperse phase of hexagonal bundles under moderately poor solvent conditions, as has been observed in in vitro studies of F actin [O. Pelletier et al., Phys. Rev. Lett. 91, 148102 (2003)]. The large characteristic radius of these chiral bundles is not determined by a mysterious long-range molecular interaction but by in-plane shear elastic stresses generated by the interplay between a chiral torque and an unusual, but universal, nonlinear gauge term in the strain tensor of ordered chains that is imposed by rotational invariance. PMID:17931038

  3. Chiral drag force

    NASA Astrophysics Data System (ADS)

    Rajagopal, Krishna; Sadofyev, Andrey V.

    2015-10-01

    We provide a holographic evaluation of novel contributions to the drag force acting on a heavy quark moving through strongly interacting plasma. The new contributions are chiral in the sense that they act in opposite directions in plasmas containing an excess of left- or right-handed quarks. The new contributions are proportional to the coefficient of the axial anomaly, and in this sense also are chiral. These new contributions to the drag force act either parallel to or antiparallel to an external magnetic field or to the vorticity of the fluid plasma. In all these respects, these contributions to the drag force felt by a heavy quark are analogous to the chiral magnetic effect (CME) on light quarks. However, the new contribution to the drag force is independent of the electric charge of the heavy quark and is the same for heavy quarks and antiquarks, meaning that these novel effects do not in fact contribute to the CME current. We show that although the chiral drag force can be non-vanishing for heavy quarks that are at rest in the local fluid rest frame, it does vanish for heavy quarks that are at rest in a suitably chosen frame. In this frame, the heavy quark at rest sees counterpropagating momentum and charge currents, both proportional to the axial anomaly coefficient, but feels no drag force. This provides strong concrete evidence for the absence of dissipation in chiral transport, something that has been predicted previously via consideration of symmetries. Along the way to our principal results, we provide a general calculation of the corrections to the drag force due to the presence of gradients in the flowing fluid in the presence of a nonzero chemical potential. We close with a consequence of our result that is at least in principle observable in heavy ion collisions, namely an anticorrelation between the direction of the CME current for light quarks in a given event and the direction of the kick given to the momentum of all the heavy quarks and

  4. Multiple Scattering X-Ray Absorption Studies of Zn2+ Binding Sites in Bacterial Photosynthetic Reaction Centers

    PubMed Central

    Giachini, Lisa; Francia, Francesco; Mallardi, Antonia; Palazzo, Gerardo; Carpenè, Emilio; Boscherini, Federico; Venturoli, Giovanni

    2005-01-01

    Binding of transition metal ions to the reaction center (RC) protein of the photosynthetic bacterium Rhodobacter sphaeroides has been previously shown to slow light-induced electron and proton transfer to the secondary quinone acceptor molecule, QB. On the basis of x-ray diffraction at 2.5 Å resolution a site, formed by AspH124, HisH126, and HisH128, has been identified at the protein surface which binds Cd2+ or Zn2+. Using Zn K-edge x-ray absorption fine structure spectroscopy we report here on the local structure of Zn2+ ions bound to purified RC complexes embedded into polyvinyl alcohol films. X-ray absorption fine structure data were analyzed by combining ab initio simulations and multiparameter fitting; structural contributions up to the fourth coordination shell and multiple scattering paths (involving three atoms) have been included. Results for complexes characterized by a Zn to RC stoichiometry close to one indicate that Zn2+ binds two O and two N atoms in the first coordination shell. Higher shell contributions are consistent with a binding cluster formed by two His, one Asp residue, and a water molecule. Analysis of complexes characterized by ∼2 Zn ions per RC reveals a second structurally distinct binding site, involving one O and three N atoms, not belonging to a His residue. The local structure obtained for the higher affinity site nicely fits the coordination geometry proposed on the basis of x-ray diffraction data, but detects a significant contraction of the first shell. Two possible locations of the second new binding site at the cytoplasmic surface of the RC are proposed. PMID:15613631

  5. Diastereodivergent asymmetric sulfa-Michael additions of α-branched enones using a single chiral organic catalyst.

    PubMed

    Tian, Xu; Cassani, Carlo; Liu, Yankai; Moran, Antonio; Urakawa, Atsushi; Galzerano, Patrizia; Arceo, Elena; Melchiorre, Paolo

    2011-11-01

    A significant limitation of modern asymmetric catalysis is that, when applied to processes that generate chiral molecules with multiple stereogenic centers in a single step, researchers cannot selectively access the full matrix of all possible stereoisomeric products. Mirror image products can be discretely provided by the enantiomeric pair of a chiral catalyst. But modulating the enforced sense of diastereoselectivity using a single catalyst is a largely unmet challenge. We document here the possibility of switching the catalytic functions of a chiral organic small molecule (a quinuclidine derivative with a pendant primary amine) by applying an external chemical stimulus, in order to induce diastereodivergent pathways. The strategy can fully control the stereochemistry of the asymmetric conjugate addition of alkyl thiols to α-substituted α,β-unsaturated ketones, a class of carbonyls that has never before succumbed to a catalytic approach. The judicious choice of acidic additives and reaction media switches the sense of the catalyst's diastereoselection, thereby affording either the syn or anti product with high enantioselectivity. PMID:21936561

  6. CHIRAL POLLUTANTS: OCCURRENCE AND SIGNIFICANCE

    EPA Science Inventory

    This task involves process research to determine the environmental occurrence and fate of enantiomers of selected chiral pesticides, PCBs and other chiral pollutants with an emphasis on currently-used modern pesticides expected to have short to intermediate environmental half-liv...

  7. Chiral Crystallization of Ethylenediamine Sulfate

    ERIC Educational Resources Information Center

    Koby, Lawrence; Ningappa, Jyothi B.; Dakesssian, Maria; Cuccia, Louis A.

    2005-01-01

    The optimal conditions for the crystallization of achiral ethylenediamine sulfate into large chiral crystals that are ideal for polarimetry studies and observation using Polaroid sheets are presented. This experiment is an ideal undergraduate experiment, which clearly demonstrates the chiral crystallization of an achiral molecule.

  8. CHIRAL PESTICIDES: OCCURRENCE AND SIGNIFICANCE

    EPA Science Inventory

    Like amino acids, certain pesticides exist in "left-handed" and "right-handed" (chiral) forms. Commercially available chiral pesticides are produced as racemic mixtures in which the ratio of the two forms (or enantiomers) is 1:1. Enantiomers have the same ...

  9. A search for disoriented chiral condensate at Fermilab

    SciTech Connect

    Bjorken, J.D.

    1996-10-01

    A small test/experiment at the Fermilab Collider which measures charged particle and photon multiplicities in the forward direction, {eta} {approx} 4.1, has been carried out, with the primary goal being the search for disoriented chiral condensate (DCC). The author describes the experiment and analysis methods, together with preliminary results.

  10. Controlling Chirality of Entropic Crystals

    NASA Astrophysics Data System (ADS)

    Damasceno, Pablo F.; Karas, Andrew S.; Schultz, Benjamin A.; Engel, Michael; Glotzer, Sharon C.

    2015-10-01

    Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams.

  11. Mass-Selective Chiral Analysis.

    PubMed

    Boesl, Ulrich; Kartouzian, Aras

    2016-06-12

    Three ways of realizing mass-selective chiral analysis are reviewed. The first is based on the formation of diastereomers that are of homo- and hetero- type with respect to the enantiomers of involved chiral molecules. This way is quite well-established with numerous applications. The other two ways are more recent developments, both based on circular dichroism (CD). In one, conventional or nonlinear electronic CD is linked to mass spectrometry (MS) by resonance-enhanced multiphoton ionization. The other is based on CD in the angular distribution of photoelectrons, which is measured in combination with MS via photoion photoelectron coincidence. Among the many important applications of mass-selective chiral analysis, this review focuses on its use as an analytical tool for the development of heterogeneous enantioselective chemical catalysis. There exist other approaches to combine chiral analysis and mass-selective detection, such as chiral chromatography MS, which are not discussed here. PMID:27070181

  12. Mass-Selective Chiral Analysis

    NASA Astrophysics Data System (ADS)

    Boesl, Ulrich; Kartouzian, Aras

    2016-06-01

    Three ways of realizing mass-selective chiral analysis are reviewed. The first is based on the formation of diastereomers that are of homo- and hetero- type with respect to the enantiomers of involved chiral molecules. This way is quite well-established with numerous applications. The other two ways are more recent developments, both based on circular dichroism (CD). In one, conventional or nonlinear electronic CD is linked to mass spectrometry (MS) by resonance-enhanced multiphoton ionization. The other is based on CD in the angular distribution of photoelectrons, which is measured in combination with MS via photoion photoelectron coincidence. Among the many important applications of mass-selective chiral analysis, this review focuses on its use as an analytical tool for the development of heterogeneous enantioselective chemical catalysis. There exist other approaches to combine chiral analysis and mass-selective detection, such as chiral chromatography MS, which are not discussed here.

  13. Controlling Chirality of Entropic Crystals.

    PubMed

    Damasceno, Pablo F; Karas, Andrew S; Schultz, Benjamin A; Engel, Michael; Glotzer, Sharon C

    2015-10-01

    Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams. PMID:26550757

  14. Chirality-Dependent Hall Effect in Weyl Semimetals.

    PubMed

    Yang, Shengyuan A; Pan, Hui; Zhang, Fan

    2015-10-01

    We generalize a semiclassical theory and use the argument of angular momentum conservation to examine the ballistic transport in lightly doped Weyl semimetals, taking into account various phase-space Berry curvatures. We predict universal transverse shifts of the wave-packet center in transmission and reflection, perpendicular to the direction in which the Fermi energy or velocities change adiabatically. The anomalous shifts are opposite for electrons with different chirality, and they can be made imbalanced by breaking inversion symmetry. We discuss how to utilize local gates, strain effects, and circularly polarized lights to generate and probe such a chirality-dependent Hall effect. PMID:26550743

  15. Chirality-dependent Hall Effect in Weyl Semimetals

    NASA Astrophysics Data System (ADS)

    Yang, Shengyuan; Pan, Hui; Zhang, Fan

    We generalize a semiclassical theory and use the argument of angular momentum conservation to examine the ballistic transport in lightly-doped Weyl semimetals, taking into account various phase-space Berry curvatures. We predict universal transverse shifts of the wave-packet center in transmission and reflection, perpendicular to the direction in which the Fermi energy or velocities change adiabatically. The anomalous shifts are opposite for electrons with different chirality, and can be made imbalanced by breaking inversion symmetry. We discuss how to utilize local gates, strain effects, and circularly polarized lights to generate and probe such a chirality-dependent Hall effect. Journal Ref: Phys. Rev. Lett. 115 , 156603 (2015).

  16. Systems engineering and integration of control centers in support of multiple programs. [ground control for STS payloads and unmanned vehicles

    NASA Technical Reports Server (NTRS)

    Miller, David N.

    1989-01-01

    The NASA Johnson Space Center's new Multiprogram Control Center (MPCC) addresses the control requirements of complex STS payloads as well as unmanned vehicles. An account is given of the relationship of the MPCC to the STS Mission Control Center, with a view to significant difficulties that may be encountered and solutions thus far devised for generic problems. Examples of MPCC workstation applications encompass telemetry decommutation, engineering unit conversion, data-base management, trajectory processing, and flight design.

  17. Structural studies on the chiral selector capacity of cyclodextrin derivatives.

    PubMed

    Tokés, Béla; Ferencz, László; Buchwald, Peter; Donáth-Nagy, Gabriella; Vancea, Szende; Sánta, Nándor; Kis, Erika Lilla

    2008-04-24

    Chromatographic separation of enantiomers to assure or enhance chiral purity is of considerable importance and can be achieved by the use of selectors of great structural variety. Cyclodextrins are an important and frequently used class, and they are multimodal selectors since multiple chiral interactions are possible by very different mechanisms. Here, the results of a preliminary examination on the possible value of computational molecular modeling approaches for the predictability of cyclodextrin selector effects for compounds that possess both geometrical and optical isomerism are presented. Interactions between various cyclodextrins and pyrethroic acids are modeled, interpreted, and compared to experimental capillary electrophoresis data. PMID:18280575

  18. Chiral fiber optical isolator

    NASA Astrophysics Data System (ADS)

    Kopp, Victor I.; Zhang, Guoyin; Zhang, Sheng; Genack, Azriel Z.; Neugroschl, Dan

    2009-02-01

    We propose an in-fiber chiral optical isolator based on chiral fiber polarizer technology and calculate its performance by incorporating the magnetic field into the scattering matrix. The design will be implemented in a special preform, which is passed through a miniature heat zone as it is drawn and twisted. The birefringence of the fiber is controlled by adjusted the diameter of a dual-core optical fiber. By adjusting the twist, the fiber can convert linear to circular polarization and reject one component of circular polarization. In the novel central portion of the isolator, the fiber diameter is large. The effective birefringence of the circular central core with high Verdet constant embedded in an outer core of slightly smaller index of refraction is small. The central potion is a non-reciprocal polarization converter which passes forward traveling left circularly polarized (LCP) light as LCP, while converting backward propagating LCP to right circularly polarized (RCP) light. Both polarizations of light traveling backwards are scattered out of the isolator. Since it is an all-glass structure, we anticipate that the isolator will be able to handle several watts of power and will be environmentally robust.

  19. Candidates for twin chiral bands in 102Rh.

    PubMed

    Tonev, D; Yavahchova, M S; Goutev, N; de Angelis, G; Petkov, P; Bhowmik, R K; Singh, R P; Muralithar, S; Madhavan, N; Kumar, R; Kumar Raju, M; Kaur, J; Mohanto, G; Singh, A; Kaur, N; Garg, R; Shukla, A; Marinov, Ts K; Brant, S

    2014-02-01

    Excited states in 102Rh, populated in the fusion-evaporation reaction Zr94(11B,3n)102Rh at a beam energy of 36 MeV, were studied using the Indian National Gamma Array spectrometer at Inter University Accelerator Center, New Delhi. The angular correlations and the electromagnetic character of some of the gamma-ray transitions observed were investigated in detail. A new chiral candidate sister band was found. Lifetimes of exited states in both chiral candidate bands of 102Rh were measured for the first time in the A∼100 mass region by means of the Doppler-shift attenuation technique. The derived reduced transition probabilities are compared to the predictions of the two quasiparticles plus triaxial rotor model. Both experimental results and calculations do not support the presence of static chirality in 102Rh. PMID:24580588

  20. Molecular self-assemblies might discriminate the diffusion of chiral molecules.

    PubMed

    Galstian, Tigran; Allahverdyan, Karen

    2015-06-01

    Biological tissue has many self-aligned anisotropic molecular organizations, which are able to undergo reversible orientational deformations and spatially transfer them. At the same time, the majority of drugs and many biologically important molecules contain chiral centers. It is therefore important to understand the factors affecting the diffusion of chiral molecules in such elastic environments. We experimentally study the diffusion of chiral molecules in a nematic liquid crystal host representing the model of biological tissue. The analogy of Cano's quantization effect is observed (due to the gradient of the chiral dopant) and used to estimate the corresponding diffusion coefficients. It is shown that thanks to the collective orientational correlation of host molecules the diffusion of chiral dopants is noticeably reduced (by a factor of ≈1.6) for the case of rigid alignment of host molecules compared to the case when the same matrix is free to adjust that alignment. PMID:25902722

  1. Phase diagrams for the blue phases of highly chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Bowling, Miriam B.; Collings, Peter J.; Booth, Christopher J.; Goodby, John W.

    1993-11-01

    Polarizing microscopy and optical-activity measurements are used to determine the phase diagram for the blue phases of chiral-racemic mixtures of terephthaloyloxy-bis-4-(2'-methylbutyl) benzoate. Contrary to an earlier report, it is the second blue phase (BP II) rather than the first blue phase (BP I) that is not stable relative to the other blue phases at high chirality. With this development, all phase diagrams for the blue phases reported to date have the same topology. Using similar data for two other highly chiral systems, it is found that a simple scaling of the temperature and chiral-fraction axes produces phase diagrams in quantitative agreement with the present results. Thus, in spite of differences in molecular structure, the number of chiral centers, and phase-transition temperatures, these three systems possess remarkably similar phase diagrams and lend evidence for a universal phase diagram for the blue phases.

  2. Chiral quantum dot based materials

    NASA Astrophysics Data System (ADS)

    Govan, Joseph; Loudon, Alexander; Baranov, Alexander V.; Fedorov, Anatoly V.; Gun'ko, Yurii

    2014-05-01

    Recently, the use of stereospecific chiral stabilising molecules has also opened another avenue of interest in the area of quantum dot (QD) research. The main goal of our research is to develop new types of technologically important quantum dot materials containing chiral defects, study their properties and explore their applications. The utilisation of chiral penicillamine stabilisers allowed the preparation of new water soluble white emitting CdS quantum nanostructures which demonstrated circular dichroism in the band-edge region of the spectrum. It was also demonstrated that all three types of QDs (D-, L-, and Rac penicillamine stabilised) show very broad emission bands between 400 and 700 nm due to defects or trap states on the surfaces of the nanocrystals. In this work the chiral CdS based quantum nanostructures have also been doped by copper metal ions and new chiral penicilamine stabilized CuS nanoparticles have been prepared and investigated. It was found that copper doping had a strong effect at low levels in the synthesis of chiral CdS nanostructures. We expect that this research will open new horizons in the chemistry of chiral nanomaterials and their application in biotechnology, sensing and asymmetric synthesis.

  3. Chiral perturbation theory with nucleons

    SciTech Connect

    Meissner, U.G.

    1991-09-01

    I review the constraints posed on the interactions of pions, nucleons and photons by the spontaneously broken chiral symmetry of QCD. The framework to perform these calculations, chiral perturbation theory, is briefly discussed in the meson sector. The method is a simultaneous expansion of the Greens functions in powers of external moments and quark masses around the massless case, the chiral limit. To perform this expansion, use is made of a phenomenological Lagrangian which encodes the Ward-identities and pertinent symmetries of QCD. The concept of chiral power counting is introduced. The main part of the lectures of consists in describing how to include baryons (nucleons) and how the chiral structure is modified by the fact that the nucleon mass in the chiral limit does not vanish. Particular emphasis is put on working out applications to show the strengths and limitations of the methods. Some processes which are discussed are threshold photopion production, low-energy compton scattering off nucleons, {pi}N scattering and the {sigma}-term. The implications of the broken chiral symmetry on the nuclear forces are briefly described. An alternative approach, in which the baryons are treated as very heavy fields, is touched upon.

  4. Nuclear chiral and magnetic rotation in covariant density functional theory

    NASA Astrophysics Data System (ADS)

    Meng, Jie; Zhao, Pengwei

    2016-05-01

    Excitations of chiral rotation observed in triaxial nuclei and magnetic and/or antimagnetic rotations (AMR) seen in near-spherical nuclei have attracted a lot of attention. Unlike conventional rotation in well-deformed or superdeformed nuclei, here the rotational axis is not necessary coinciding with any principal axis of the nuclear density distribution. Thus, tilted axis cranking (TAC) is mandatory to describe these excitations self-consistently in the framework of covariant density functional theory (CDFT). We will briefly introduce the formalism of TAC–CDFT and its application for magnetic and AMR phenomena. Configuration-fixed CDFT and its predictions for nuclear chiral configurations and for favorable triaxial deformation parameters are also presented, and the discoveries of the multiple chiral doublets in 133Ce and 103Rh are discussed.

  5. The Ridged Cross-Junction Multiple-Way Power Divider for Small Blockage and Symmetrical Slot Arrangement in the Center Feed Single-Layer Slotted Waveguide Array

    NASA Astrophysics Data System (ADS)

    Tsunemitsu, Yasuhiro; Yoshida, Goro; Goto, Naohisa; Hirokawa, Jiro; Ando, Makoto

    The center-feed in a single-layer slotted waveguide array [1]-[3] is one of the key components in polarization division duplex (PDD) wireless systems. Two center-feed arrays with orthogonal polarization and boresight beams are orthogonally arranged side-by-side for transmission and reception, simultaneously. Each antenna has extremely high XPD (almost 50dB in measurement) and a very high isolation (over 80dB in measurement) between two arrays is observed provided the symmetry of slot arrangement is preserved [4]. Unfortunately, the area blocked by the center feed causes high sidelobe levels. This paper proposes the ridged cross-junction multiple-way power divider for realizing blockage reduction and symmetrical slot arrangement at the same time.

  6. Cellular and Nuclear Alignment Analysis for Determining Epithelial Cell Chirality.

    PubMed

    Raymond, Michael J; Ray, Poulomi; Kaur, Gurleen; Singh, Ajay V; Wan, Leo Q

    2016-05-01

    Left-right (LR) asymmetry is a biologically conserved property in living organisms that can be observed in the asymmetrical arrangement of organs and tissues and in tissue morphogenesis, such as the directional looping of the gastrointestinal tract and heart. The expression of LR asymmetry in embryonic tissues can be appreciated in biased cell alignment. Previously an in vitro chirality assay was reported by patterning multiple cells on microscale defined geometries and quantified the cell phenotype-dependent LR asymmetry, or cell chirality. However, morphology and chirality of individual cells on micropatterned surfaces has not been well characterized. Here, a Python-based algorithm was developed to identify and quantify immunofluorescence stained individual epithelial cells on multicellular patterns. This approach not only produces results similar to the image intensity gradient-based method reported previously, but also can capture properties of single cells such as area and aspect ratio. We also found that cell nuclei exhibited biased alignment. Around 35% cells were misaligned and were typically smaller and less elongated. This new imaging analysis approach is an effective tool for measuring single cell chirality inside multicellular structures and can potentially help unveil biophysical mechanisms underlying cellular chiral bias both in vitro and in vivo. PMID:26294010

  7. Connections between chiral Lagrangians and QCD sum-rules

    NASA Astrophysics Data System (ADS)

    Fariborz, Amir H.; Pokraka, A.; Steele, T. G.

    2016-01-01

    In this paper, it is shown how a chiral Lagrangian framework can be used to derive relationships connecting quark-level QCD correlation functions to mesonic-level two-point functions. Crucial ingredients of this connection are scale factor matrices relating each distinct quark-level substructure (e.g. quark-antiquark, four-quark) to its mesonic counterpart. The scale factors and mixing angles are combined into a projection matrix to obtain the physical (hadronic) projection of the QCD correlation function matrix. Such relationships provide a powerful bridge between chiral Lagrangians and QCD sum-rules that are particularly effective in studies of the substructure of light scalar mesons with multiple complicated resonance shapes and substantial underlying mixings. The validity of these connections is demonstrated for the example of the isotriplet a0(980)-a0(1450) system, resulting in an unambiguous determination of the scale factors from the combined inputs of QCD sum-rules and chiral Lagrangians. These scale factors lead to a remarkable agreement between the quark condensates in QCD and the mesonic vacuum expectation values that induce spontaneous chiral symmetry breaking in chiral Lagrangians. This concrete example shows a clear sensitivity to the underlying a0-system mixing angle, illustrating the value of this methodology in extensions to more complicated mesonic systems.

  8. Amino Acids and Chirality

    NASA Technical Reports Server (NTRS)

    Cook, Jamie E.

    2012-01-01

    Amino acids are among the most heavily studied organic compound class in carbonaceous chondrites. The abundance, distributions, enantiomeric compositions, and stable isotopic ratios of amino acids have been determined in carbonaceous chondrites fi'om a range of classes and petrographic types, with interesting correlations observed between these properties and the class and typc of the chondritcs. In particular, isomeric distributions appear to correlate with parent bodies (chondrite class). In addition, certain chiral amino acids are found in enantiomeric excess in some chondrites. The delivery of these enantiomeric excesses to the early Earth may have contributed to the origin of the homochirality that is central to life on Earth today. This talk will explore the amino acids in carbonaceous chondritcs and their relevance to the origin of life.

  9. Chiral Bosonization of Superconformal Ghosts

    NASA Technical Reports Server (NTRS)

    Shi, Deheng; Shen, Yang; Liu, Jinling; Xiong, Yongjian

    1996-01-01

    We explain the difference of the Hilbert space of the superconformal ghosts (beta,gamma) system from that of its bosonized fields phi and chi. We calculate the chiral correlation functions of phi, chi fields by inserting appropriate projectors.

  10. Life's chirality from prebiotic environments

    NASA Astrophysics Data System (ADS)

    Gleiser, Marcelo; Walker, Sara Imari

    2012-10-01

    A key open question in the study of life is the origin of biomolecular homochirality: almost every life-form on Earth has exclusively levorotary amino acids and dextrorotary sugars. Will the same handedness be preferred if life is found elsewhere? We review some of the pertinent literature and discuss recent results suggesting that life's homochirality resulted from sequential chiral symmetry breaking triggered by environmental events. In one scenario, autocatalytic prebiotic reactions undergo stochastic fluctuations due to environmental disturbances, in a mechanism reminiscent of evolutionary punctuated equilibrium: short-lived destructive events may lead to long-term enantiomeric excess. In another, chiral-selective polymerization reaction rates influenced by environmental effects lead to substantial chiral excess even in the absence of autocatalysis. Applying these arguments to other potentially life-bearing platforms has implications to the search for extraterrestrial life: we predict that a statistically representative sampling of extraterrestrial stereochemistry will be racemic (chirally neutral) on average.

  11. The management of multiple sclerosis by reference centers in south of Italy: a 2011 survey on health demands and needs in Campania region.

    PubMed

    de Waure, Chiara; Di Nardo, Francesco; Mazzucco, Walter; Nedovic, Darko; Battaglia, Mario Alberto; Busillo, Vincenzo; Di Iorio, Walter; Gallo, Antonio; Lanzillo, Roberta; Lombardi, Emilio; Maniscalco, Giorgia Teresa; Orefice, Giuseppe; Petracca, Maria; Romano, Felice; Sinisi, Leonardo; Spadera, Anna Pia; Spitaleri, Daniele; Vivo, Pasquale; Ricciardi, Walter

    2016-02-01

    This cross-sectional study has investigated the diagnostic and therapeutic management of patients suffering from multiple sclerosis (MS) in the Campania Region (Italy). A survey involving all the reference centers for MS in Campania Region was conducted from March to August 2011. Centers responded to a web-administered questionnaire on management and clinical characteristics of MS patients. In the study period, 3263 patients (mean age 37 years, 66 % females) accessed the centers. Patients received a first diagnosis of MS in 161 cases (4.9 %). About 37 % of the subjects without a previous diagnosis came to the centers on their own initiative. All patients underwent a complete neurological examination and expanded disability status scale. The other most common investigations were magnetic resonance imaging (44.0 %) and evoked potentials (22.1 %). The number of treated patients was 2797 (87.1 %). The most used drugs were interferon β and glatiramer acetate. The time between diagnosis and initiation of therapy exceeded 6 months in 32 % of cases. Second-line drugs were under-used: 16 % of patients who might benefit from them show high clinical and radiological disease activity despite treatment with immunomodulant drugs. The MS care management of the surveyed centers showed consistent margins for improvement in 2011. Even though these data do not represent the current situation, they can be used to monitor improvements in MS care. PMID:26439919

  12. Critical dimensions for chiral bosons

    SciTech Connect

    Mezincescu, L.; Nepomechie, R.I.

    1988-05-15

    We give the Lagrangian formulation of a Bose model in 1+1 dimensions which describes a free chiral Lie-algebra-valued current. This model is a non-Abelian generalization of the chiral scalar model of Siegel. Both the Abelian and non-Abelian actions have a gauge invariance, which becomes anomalous when the models are quantized. The condition that this anomaly be canceled coincides with the string no-ghost condition.

  13. Application of chiral critical clusters to assymetric synthesis

    DOEpatents

    Ferrieri, Richard A.

    2002-01-01

    Disclosed is a composition, a method of making and a method of using critical clusters for asymmetric synthesis using substantially optically-pure chiral solvent molecules in a supercritical fluid. The solvent molecules are capable of forming a multipoint hydrogen bonded solvate as they encage at least one solute molecule. The encaged solute molecule is capable of reacting to form an optically active chiral center. In another aspect, there is disclosed a method of directing the position of bonding between a solute molecule and a ligand involving encaging the solute molecule and the ligand with polar solvent molecules in a supercritical fluid under conditions of temperature and pressure sufficient to change electric charge distribution in the solute molecule. In yet another aspect, disclosed is a method of making pharmaceutical compounds involving encaging a solute molecule, which is capable of forming a chiral center, and a ligand with polar solvent molecules in a supercritical fluid under conditions of temperature and pressure sufficient to change electric charge distribution of the solute molecule. The solute molecule and ligand are then reacted whereby the ligand bonds to the solute molecule forming a chiral center. Also disclosed is a method for racemic resolution using critical clusters involving encaging racemic mixtures of solute molecules with substantially optically-pure chiral solvent molecules in a supercritical fluid under conditions of temperature and pressure sufficient to form critical clusters. The solvent molecules are capable of multipoint hydrogen bonding with the solute molecules. The encaged solute molecules are then nonenzymatically reacted to enhance the optical purity of the solute molecules.

  14. Discovery of the interstellar chiral molecule propylene oxide (CH3CHCH2O)

    NASA Astrophysics Data System (ADS)

    McGuire, Brett A.; Carroll, P. Brandon; Loomis, Ryan A.; Finneran, Ian A.; Jewell, Philip R.; Remijan, Anthony J.; Blake, Geoffrey A.

    2016-06-01

    Life on Earth relies on chiral molecules—that is, species not superimposable on their mirror images. This manifests itself in the selection of a single molecular handedness, or homochirality, across the biosphere. We present the astronomical detection of a chiral molecule, propylene oxide (CH3CHCH2O), in absorption toward the Galactic center. Propylene oxide is detected in the gas phase in a cold, extended molecular shell around the embedded, massive protostellar clusters in the Sagittarius B2 star-forming region. This material is representative of the earliest stage of solar system evolution in which a chiral molecule has been found.

  15. Discovery of the interstellar chiral molecule propylene oxide (CH₃CHCH₂O).

    PubMed

    McGuire, Brett A; Carroll, P Brandon; Loomis, Ryan A; Finneran, Ian A; Jewell, Philip R; Remijan, Anthony J; Blake, Geoffrey A

    2016-06-17

    Life on Earth relies on chiral molecules-that is, species not superimposable on their mirror images. This manifests itself in the selection of a single molecular handedness, or homochirality, across the biosphere. We present the astronomical detection of a chiral molecule, propylene oxide (CH3CHCH2O), in absorption toward the Galactic center. Propylene oxide is detected in the gas phase in a cold, extended molecular shell around the embedded, massive protostellar clusters in the Sagittarius B2 star-forming region. This material is representative of the earliest stage of solar system evolution in which a chiral molecule has been found. PMID:27303055

  16. Bottom-up synthesis of chiral covalent organic frameworks and their bound capillaries for chiral separation

    PubMed Central

    Qian, Hai-Long; Yang, Cheng-Xiong; Yan, Xiu-Ping

    2016-01-01

    Covalent organic frameworks (COFs) are a novel class of porous materials, and offer great potential for various applications. However, the applications of COFs in chiral separation and chiral catalysis are largely underexplored due to the very limited chiral COFs available and their challenging synthesis. Here we show a bottom-up strategy to construct chiral COFs and an in situ growth approach to fabricate chiral COF-bound capillary columns for chiral gas chromatography. We incorporate the chiral centres into one of the organic ligands for the synthesis of the chiral COFs. We subsequently in situ prepare the COF-bound capillary columns. The prepared chiral COFs and their bound capillary columns give high resolution for the separation of enantiomers with excellent repeatability and reproducibility. The proposed strategy provides a promising platform for the synthesis of chiral COFs and their chiral separation application. PMID:27401541

  17. Bottom-up synthesis of chiral covalent organic frameworks and their bound capillaries for chiral separation

    NASA Astrophysics Data System (ADS)

    Qian, Hai-Long; Yang, Cheng-Xiong; Yan, Xiu-Ping

    2016-07-01

    Covalent organic frameworks (COFs) are a novel class of porous materials, and offer great potential for various applications. However, the applications of COFs in chiral separation and chiral catalysis are largely underexplored due to the very limited chiral COFs available and their challenging synthesis. Here we show a bottom-up strategy to construct chiral COFs and an in situ growth approach to fabricate chiral COF-bound capillary columns for chiral gas chromatography. We incorporate the chiral centres into one of the organic ligands for the synthesis of the chiral COFs. We subsequently in situ prepare the COF-bound capillary columns. The prepared chiral COFs and their bound capillary columns give high resolution for the separation of enantiomers with excellent repeatability and reproducibility. The proposed strategy provides a promising platform for the synthesis of chiral COFs and their chiral separation application.

  18. Bottom-up synthesis of chiral covalent organic frameworks and their bound capillaries for chiral separation.

    PubMed

    Qian, Hai-Long; Yang, Cheng-Xiong; Yan, Xiu-Ping

    2016-01-01

    Covalent organic frameworks (COFs) are a novel class of porous materials, and offer great potential for various applications. However, the applications of COFs in chiral separation and chiral catalysis are largely underexplored due to the very limited chiral COFs available and their challenging synthesis. Here we show a bottom-up strategy to construct chiral COFs and an in situ growth approach to fabricate chiral COF-bound capillary columns for chiral gas chromatography. We incorporate the chiral centres into one of the organic ligands for the synthesis of the chiral COFs. We subsequently in situ prepare the COF-bound capillary columns. The prepared chiral COFs and their bound capillary columns give high resolution for the separation of enantiomers with excellent repeatability and reproducibility. The proposed strategy provides a promising platform for the synthesis of chiral COFs and their chiral separation application. PMID:27401541

  19. Correlation between structures of chiral polymers and their efficiency for chiral resolution by crystallization.

    PubMed

    Menahem, Tali; Pravda, Martin; Mastai, Yitzhak

    2009-10-01

    In this work, we describe the correlation between chiral polymer structures, particularly alpha-helical and random coil conformations, and their efficiency as chiral resolving agents in crystallization processes. A set of chiral block copolymers based on polyethylene oxide with chiral glutamic acid oligopeptide segments (PEG(113)-b-(+)-(S)-Glu(20)) were synthesized and employed as additives in the crystallization of rac-threonine. CD spectroscopy demonstrates that structures of chiral polymers could be switched between a helical and a disordered random coil by pH. The effect of these polymers at different conformations on the crystallization kinetics, crystal morphology, and chiral resolution of rac-threonine is reported. Our study demonstrates that only chiral polymers with alpha-helical conformations of the chiral segment are effective as additives for chiral resolution throughout crystallization. Overall, our results provide useful guidelines for the selection and design of chiral polymer additives that will act efficiently for chiral resolution by crystallization. PMID:19455618

  20. A Person-Centered Approach to P-E Fit Questions Using a Multiple-Trait Model.

    ERIC Educational Resources Information Center

    De Fruyt, Filip

    2002-01-01

    Employed college students (n=401) completed the Self-Directed Search and NEO Personality Inventory-Revised. Person-environment fit across Holland's six personality types predicted job satisfaction and skill development. Five-Factor Model traits significantly predicted intrinsic career outcomes. Use of the five-factor, person-centered approach to…

  1. Implementation of a Community-Based Family-Centered Program in Portugal: A Multiple Case Study Evaluation

    ERIC Educational Resources Information Center

    Teixeira de Melo, Ana; Alarcao, Madalena

    2012-01-01

    Family-centered, community-based programs are particularly suited to support families with at-risk children or maltreated children and achieve family preservation or reunification. In these child protection and child welfare cases, assessment is of great importance to inform decision making. But the implementation of services to support the…

  2. Treatment Verification: Multiple Analytical Methods and a Search for Causality in the Child Parent Center Compensatory Education Program.

    ERIC Educational Resources Information Center

    Conrad, Kendon J.; And Others

    Treatment verification methodology was employed in studying the Chicago Child Parent Center (CPC) compensatory education program. Established in disadvantaged areas by the Chicago public schools, CPCs are designed to break the cycle of poverty through educational intervention with children at ages 3 through 8. An element of evaluation studies that…

  3. Enantioselective Synthesis of Isoquinolines: Merging Chiral-Phosphine and Gold Catalysis.

    PubMed

    Gao, Yu-Ning; Shi, Feng-Chen; Xu, Qin; Shi, Min

    2016-05-10

    The highly enantioselective synthesis of dihydroisoquinoline derivatives from aromatic sulfonated imines tethered with an alkyne moiety, through a one-pot asymmetric relay catalysis of chiral-phosphine and gold catalysts, is reported. Enantiomerically enriched dihydroisoquinoline derivatives were afforded in good yields and good-to-excellent ee values under mild conditions, based on the asymmetric aza-Morita-Baylis-Hillman reaction. Dihydroisoquinoline derivatives containing two chiral centers were also synthesized through further transformations. PMID:26990120

  4. Characterization of the particulate methane monooxygenase metal centers in multiple redox states by X-ray absorption spectroscopy.

    PubMed

    Lieberman, Raquel L; Kondapalli, Kalyan C; Shrestha, Deepak B; Hakemian, Amanda S; Smith, Stephen M; Telser, Joshua; Kuzelka, Jane; Gupta, Rajeev; Borovik, A S; Lippard, Stephen J; Hoffman, Brian M; Rosenzweig, Amy C; Stemmler, Timothy L

    2006-10-01

    The integral membrane enzyme particulate methane monooxygenase (pMMO) converts methane, the most inert hydrocarbon, to methanol under ambient conditions. The 2.8-A resolution pMMO crystal structure revealed three metal sites: a mononuclear copper center, a dinuclear copper center, and a nonphysiological mononuclear zinc center. Although not found in the crystal structure, solution samples of pMMO also contain iron. We have used X-ray absorption spectroscopy to analyze the oxidation states and coordination environments of the pMMO metal centers in as-isolated (pMMO(iso)), chemically reduced (pMMO(red)), and chemically oxidized (pMMO(ox)) samples. X-ray absorption near-edge spectra (XANES) indicate that pMMO(iso) contains both Cu(I) and Cu(II) and that the pMMO Cu centers can undergo redox chemistry. Extended X-ray absorption fine structure (EXAFS) analysis reveals a Cu-Cu interaction in all redox forms of the enzyme. The Cu-Cu distance increases from 2.51 to 2.65 A upon reduction, concomitant with an increase in the average Cu-O/N bond lengths. Appropriate Cu2 model complexes were used to refine and validate the EXAFS fitting protocols for pMMO(iso). Analysis of Fe EXAFS data combined with electron paramagnetic resonance (EPR) spectra indicates that Fe, present as Fe(III), is consistent with heme impurities. These findings are complementary to the crystallographic data and provide new insight into the oxidation states and possible electronic structures of the pMMO Cu ions. PMID:16999437

  5. Chiral symmetry in rotating systems

    NASA Astrophysics Data System (ADS)

    Malik, Sham S.

    2015-08-01

    The triaxial rotating system at critical angular momentum I ≥Iband exhibits two enatiomeric (the left- and right-handed) forms. These enatiomers are related to each other through dynamical chiral symmetry. The chiral symmetry in rotating system is defined by an operator χ ˆ =Rˆy (π) T ˆ, which involves the product of two distinct symmetries, namely, continuous and discrete. Therefore, new guidelines are required for testing its commutation with the system Hamiltonian. One of the primary objectives of this study is to lay down these guidelines. Further, the possible impact of chiral symmetry on the geometrical arrangement of angular momentum vectors and investigation of observables unique to nuclear chiral-twins is carried out. In our model, the angular momentum components (J1, J2, J3) occupy three mutually perpendicular axes of triaxial shape and represent a non-planar configuration. At certain threshold energy, the equation of motion in angular momentum develops a second order phase transition and as a result two distinct frames (i.e., the left- and right-handed) are formed. These left- and right-handed states correspond to a double well system and are related to each other through chiral operator. At this critical angular momentum, the centrifugal and Coriolis interactions lower the barrier in the double well system. The tunneling through the double well starts, which subsequently lifts the degeneracy among the rotational states. A detailed analysis of the behavior of rotational energies, spin-staggering, and the electromagnetic transition probabilities of the resulting twin-rotational bands is presented. The ensuing model results exhibit similarities with many observed features of the chiral-twins. An advantage of our formalism is that it is quite simple and it allows us to pinpoint the understanding of physical phenomenon which lead to chiral-twins in rotating systems.

  6. Enhancing the ACE control center for the multiple uses of spacecraft integration and test and mission and science operations

    NASA Technical Reports Server (NTRS)

    Snow, Frank; Garrard, Thomas L.; Steck, Jane A.; Maury, Jesse L.

    1996-01-01

    In relation to the mandate to reduce space mission development and operations costs, the advanced composition explorer (ACE) will use a version of the Transportable Payload Operations Control Center (TPOCC) for its mission operations. It was determined during the phase B of the ACE project that a potential existed for substantial savings if the adaptation of the TPOCC for the ACE mission operations could include its adaptation for use as the primary component in the ground support equipment for the integration and testing of the ACE spacecraft, and for use as the basic component in the ACE science center. The implementation of this approach required the enhancement of the TPOCC requirements, changes in the development schedule and changes in the allocation and activities of the personnel responsible for the development of ACE operations. It is discussed how these issues, and the problems that arose, were addressed.

  7. Can a Non-Chiral Object Be Made of Two Identical Chiral Moieties?

    ERIC Educational Resources Information Center

    LeMarechal, Jean Francois

    2008-01-01

    Several pedagogical objects can be used to discuss chirality. Here, we use the cut of an apple to show that the association of identical chiral moieties can form a non-chiral object. Octahedral chirality is used to find situations equivalent to the cut of the apple. (Contains 5 figures.)

  8. Chiral Chlordane Components in Environmental Matrices

    EPA Science Inventory

    Chlordane, a persistent, bioaccumulative and toxic organochlorine pesticide, has been studied for many years. Since the advent of chiral analysis for environmental samples, over 2,400 measurements have been made of various chiral chlordane components. Chlordane enantiomer fractio...

  9. Effects of chirality and surface stresses on the bending and buckling of chiral nanowires

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Shan; Shimada, Takahiro; Wang, Gang-Feng; Kitamura, Takayuki

    2014-01-01

    Due to their superior optical, elastic and electrical properties, chiral nanowires have many applications as sensors, probes, and building blocks of nanoelectromechanical systems. In this paper, we develop a refined Euler-Bernoulli beam model for chiral nanowires with surface effects and material chirality incorporated. This refined model is employed to investigate the bending and buckling of chiral nanowires. It is found that surface effects and material chirality significantly affect the elastic behaviour of chiral nanowires. This study is helpful not only for understanding the size-dependent behaviour of chiral nanowires, but also for characterizing their mechanical properties.

  10. Controlling Chirality of Entropic Crystals

    NASA Astrophysics Data System (ADS)

    Damasceno, Pablo; Karas, Andrew; Schultz, Benjamin; Engel, Michael; Glotzer, Sharon

    Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams. Work supported by the National Science Foundation, Division of Materials Research Award No. DMR 1120923, U.S. Army Research Office under Grant Award No. W911NF-10-1-0518, and also by the DOD/ASD (R&E) under Award No. N00244-09-1-0062.

  11. Hydrogen-Regulated Chiral Nanoplasmonics.

    PubMed

    Duan, Xiaoyang; Kamin, Simon; Sterl, Florian; Giessen, Harald; Liu, Na

    2016-02-10

    Chirality is a highly important topic in modern chemistry, given the dramatically different pharmacological effects that enantiomers can have on the body. Chirality of natural molecules can be controlled by reconfiguration of molecular structures through external stimuli. Despite the rapid progress in plasmonics, active regulation of plasmonic chirality, particularly in the visible spectral range, still faces significant challenges. In this Letter, we demonstrate a new class of hybrid plasmonic metamolecules composed of magnesium and gold nanoparticles. The plasmonic chirality from such plasmonic metamolecules can be dynamically controlled by hydrogen in real time without introducing macroscopic structural reconfiguration. We experimentally investigate the switching dynamics of the hydrogen-regulated chiroptical response in the visible spectral range using circular dichroism spectroscopy. In addition, energy dispersive X-ray spectroscopy is used to examine the morphology changes of the magnesium particles through hydrogenation and dehydrogenation processes. Our study can enable plasmonic chiral platforms for a variety of gas detection schemes by exploiting the high sensitivity of circular dichroism spectroscopy. PMID:26745446

  12. Tactoids of chiral liquid crystals

    NASA Astrophysics Data System (ADS)

    Palacio-Betancur, Viviana; Villada-Gil, Stiven; Zhou, Ye; Armas-Pérez, Julio C.; de Pablo, Juan José; Hernández-Ortiz, Juan Pablo

    The phase diagram of chiral liquid crystals confined in ellipsoids is obtained, by following a theoretically informed Monte Carlo relaxation of the tensor alignment field Q. The free energy of the system is described by a functional in the framework of the Landau-de Gennes formalism. This study also includes the effect of anchoring strength, curvature, and chirality of the system. In the low chirality region of the phase diagram we found the twist bipolar (BS) phase and some cholesteric phases such as the radial spherical structure (RSS), twist cylinder (TC) and double twist cylinder (DTC) whose axis of rotation is not necessarily aligned with the major axis of the geometry. For high chirality scenarios, the disclination lines are twisted or bent near the surface preventing the formation of symmetric networks of defects, although an hexagonal pattern is formed on the surface which might serve as open sites for collocation of colloids. By analyzing the free energies of isochoric systems, prolate geometries tend to be more favorable for high chirality and low anchoring conditions. Universidad Nacional de Colombia Ph.D. grant and COLCIENCIAS under the Contract No. 110-165-843-748. CONACYT for Postdoctoral Fellowships Nos. 186166 and 203840.

  13. Chiral Thirring–Wess model

    SciTech Connect

    Rahaman, Anisur

    2015-10-15

    The vector type of interaction of the Thirring–Wess model was replaced by the chiral type and a new model was presented which was termed as chiral Thirring–Wess model in Rahaman (2015). The model was studied there with a Faddeevian class of regularization. Few ambiguity parameters were allowed there with the apprehension that unitarity might be threatened like the chiral generation of the Schwinger model. In the present work it has been shown that no counter term containing the regularization ambiguity is needed for this model to be physically sensible. So the chiral Thirring–Wess model is studied here without the presence of any ambiguity parameter and it has been found that the model not only remains exactly solvable but also does not lose the unitarity like the chiral generation of the Schwinger model. The phase space structure and the theoretical spectrum of this new model have been determined in the present scenario. The theoretical spectrum is found to contain a massive boson with ambiguity free mass and a massless boson.

  14. Multispectral Chiral Imaging with a Metalens.

    PubMed

    Khorasaninejad, M; Chen, W T; Zhu, A Y; Oh, J; Devlin, R C; Rousso, D; Capasso, F

    2016-07-13

    The vast majority of biologically active compounds, ranging from amino acids to essential nutrients such as glucose, possess intrinsic handedness. This in turn gives rise to chiral optical properties that provide a basis for detecting and quantifying enantio-specific concentrations of these molecules. However, traditional chiroptical spectroscopy and imaging techniques require cascading of multiple optical components in sophisticated setups. Here, we present a planar lens with an engineered dispersive response, which simultaneously forms two images with opposite helicity of an object within the same field-of-view. In this way, chiroptical properties can be probed across the visible spectrum using only the lens and a camera without the addition of polarizers or dispersive optical devices. We map the circular dichroism of the exoskeleton of a chiral beetle, Chrysina gloriosa, which is known to exhibit high reflectivity of left-circularly polarized light, with high spatial resolution limited by the numerical aperture of the planar lens. Our results demonstrate the potential of metasurfaces in realizing a compact and multifunctional device with unprecedented imaging capabilities. PMID:27267137

  15. Field induced spin chirality and chirality switching in magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Tartakovskaya, Elena V.

    2015-05-01

    The physical origin of the field-induced spin chirality experimentally observed in rare earth multilayers is determined. It is shown that the effect is possible due to the interplay between solid-state exchange interactions (the Ruderman-Kittel-Kasuya-Yosida and the Dsyaloshinsky-Moriya interactions), the external magnetic field and a special confinement of magnetic constituents. The presented model describes a certain temperature dependence of the chirality factor in agreement with experimental data and opens a new way to design nanostructured objects with predicted handedness.

  16. Chiral lattice fermions with correct vacuum polarization and chiral anomaly

    SciTech Connect

    Pryor, C. )

    1991-04-15

    An action for chiral lattice fermions is proposed, which avoids the Nielsen-Ninomiya theorem by virtue of its nonlocality and nonbilinearity. The action is constructed by eliminating the extra fermion modes with a gauge-violating Majorana-type Wilson mass, which is then rendered invariant by an integration over gauge transformations. The free propagator is calculated, and the one-loop vacuum polarization is shown to be identical to that for Wilson fermions, even at nonzero lattice spacing. Also the chiral anomaly is shown to be the same as for Wilson fermions in the continuum limit.

  17. Repulsive Casimir force in chiral metamaterials.

    PubMed

    Zhao, R; Zhou, J; Koschny, Th; Economou, E N; Soukoulis, C M

    2009-09-01

    We demonstrate theoretically that one can obtain repulsive Casimir forces and stable nanolevitations by using chiral metamaterials. By extending the Lifshitz theory to treat chiral metamaterials, we find that a repulsive force and a minimum of the interaction energy possibly exist for strong chirality, under realistic frequency dependencies and correct limiting values (for zero and infinite frequencies) of the permittivity, permeability, and chiral coefficients. PMID:19792309

  18. Chiral Sensor for Enantiodiscrimination of Varied Acids.

    PubMed

    Huang, Huayin; Bian, Guangling; Zong, Hua; Wang, Yabai; Yang, Shiwei; Yue, Huifeng; Song, Ling; Fan, Hongjun

    2016-06-01

    A chiral thiophosphoroamide 4 derived from (1R,2R)-1,2-diaminocyclohexane is used as a highly effective chiral sensor for the chiral recognition of varied acids via ion-pairing and hydrogen-bonding interactions using (1)H, (19)F and (31)P NMR. PMID:27192021

  19. Structure Study of the Chiral Lactide Molecules by Chirped-Pulse Ftmw Spectroscopy

    NASA Astrophysics Data System (ADS)

    Zaleski, Daniel P.; Neill, Justin L.; Pate, Brooks H.; Bialkowska-Jaworska, Ewa; Kisiel, Zbigniew

    2011-06-01

    Lactide is a six member cyclic diester with two chiral centers that forms from lactic acid in the presence of heat and an acid catalyst. It can form either a homo-chiral (RR) structure with both methyl groups equatorial or a hetero-chiral (RS) structure where one methyl group is equatorial and the other methyl group is axial. Structurally lactide is similar to lactic acid dimer; however, the kinked ring is covalently bonded and two waters are lost. And unlike lactic acid dimer, which has a very small dipole moment, the dipole moment of lactide is on the order of 3 Debye. Here the microwave spectra of the highly rigid homo- and hetero-chiral lactides are presented, which were first assigned in a heated lactic acid spectrum where the chemistry took place in the reservoir nozzles. Further isotopic information from a commercial sample of predominately homo-chiral lactide was obtained leading to a Kraitchman substitution structure of the homo-chiral lactide. Preliminary results of the cluster of homo-chiral lactide with one water molecule attached are also presented.

  20. A disoriented chiral condensate search at the Fermilab Tevatron

    SciTech Connect

    Convery, M.E.

    1997-05-01

    MiniMax (Fermilab T-864) was a small test/experiment at the Tevatron designed to search for disoriented chiral condensates (DCC) in the forward direction. Relativistic quantum field theory treats the vacuum as a medium, with bulk properties characterized by long-range order parameters. This has led to suggestions that regions of {open_quotes}disoriented vacuum{close_quotes} might be formed in high-energy collision processes. In particular, the approximate chiral symmetry of QCD could lead to regions of vacuum which have chiral order parameters disoriented to directions which have non-zero isospin, i.e. disoriented chiral condensates. A signature of DCC is the resulting distribution of the fraction of produced pions which are neutral. The MiniMax detector at the C0 collision region of the Tevatron was a telescope of 24 multi-wire proportional chambers (MWPC`s) with a lead converter behind the eighth MWPC, allowing the detection of charged particles and photon conversions in an acceptance approximately a circle of radius 0.6 in pseudorapidity-azimuthal-angle space, centered on pseudorapidity {eta} {approx} 4. An electromagnetic calorimeter was located behind the MWPC telescope, and hadronic calorimeters and scintillator were located in the upstream anti-proton direction to tag diffractive events.

  1. Chirality and gravitational parity violation.

    PubMed

    Bargueño, Pedro

    2015-06-01

    In this review, parity-violating gravitational potentials are presented as possible sources of both true and false chirality. In particular, whereas phenomenological long-range spin-dependent gravitational potentials contain both truly and falsely chiral terms, it is shown that there are models that extend general relativity including also coupling of fermionic degrees of freedom to gravity in the presence of torsion, which give place to short-range truly chiral interactions similar to that usually considered in molecular physics. Physical mechanisms which give place to gravitational parity violation together with the expected size of the effects and their experimental constraints are discussed. Finally, the possible role of parity-violating gravity in the origin of homochirality and a road map for future research works in quantum chemistry is presented. PMID:25919812

  2. Total parathyroidectomy in a large cohort of cases with hyperparathyroidism associated with multiple endocrine neoplasia type 1: experience from a single academic center

    PubMed Central

    de Menezes Montenegro, Fabio Luiz; Lourenço, Delmar Muniz; Tavares, Marcos Roberto; Arap, Sergio Samir; Nascimento, Climerio Pereira; Neto, Ledo Mazzei Massoni; D'Alessandro, André; Toledo, Rodrigo Almeida; Coutinho, Flávia Lima; Brandão, Lenine Garcia; de Britto e Silva Filho, Gilberto; Cordeiro, Anói Castro; Toledo, Sergio Pereira Almeida

    2012-01-01

    Most cases of sporadic primary hyperparathyroidism present disturbances in a single parathyroid gland and the surgery of choice is adenomectomy. Conversely, hyperparathyroidism associated with multiple endocrine neoplasia type 1 (hyperparathyroidism/multiple endocrine neoplasia type 1) is an asynchronic, asymmetrical multiglandular disease and it is surgically approached by either subtotal parathyroidectomy or total parathyroidectomy followed by parathyroid auto-implant to the forearm. In skilful hands, the efficacy of both approaches is similar and both should be complemented by prophylactic thymectomy. In a single academic center, 83 cases of hyperparathyroidism/multiple endocrine neoplasia type 1 were operated on from 1987 to 2010 and our first surgical choice was total parathyroidectomy followed by parathyroid auto-implant to the non-dominant forearm and, since 1997, associated transcervical thymectomy to prevent thymic carcinoid. Overall, 40% of patients were given calcium replacement (mean intake 1.6 g/day) during the first months after surgery, and this fell to 28% in patients with longer follow-up. These findings indicate that several months may be needed in order to achieve a proper secretion by the parathyroid auto-implant. Hyperparathyroidism recurrence was observed in up to 15% of cases several years after the initial surgery. Thus, long-term follow-up is recommended for such cases. We conclude that, despite a tendency to subtotal parathyroidectomy worldwide, total parathyroidectomy followed by parathyroid auto-implant is a valid surgical option to treat hyperparathyroidism/multiple endocrine neoplasia type 1. Larger comparative systematic studies are needed to define the best surgical approach to hyperparathyroidism/multiple endocrine neoplasia type 1. PMID:22584718

  3. Microwave propagation in chiral metamaterials

    NASA Astrophysics Data System (ADS)

    Prybylski, Aida; Yon, Luis; Noginova, Natalia

    Chiral hyperbolic metamaterials are predicted to show interesting properties associated with possible topological photonic states in these materials, which present new opportunities for light control and manipulation. As prototypes, we consider two metal-dielectric systems designed for microwave range: a twisted wires array, where chirality is associated with shape of metal inclusions, and a rotated layer system, with parallel wires in each layer, and direction of the wires orientation rotated from layer to layer. Systems with different content of metal and layer-to-layer distance were fabricated and studied in the free space propagation experiment. The results were discussed in terms of effective media consideration.

  4. Collisions in Chiral Kinetic Theory.

    PubMed

    Chen, Jing-Yuan; Son, Dam T; Stephanov, Mikhail A

    2015-07-10

    Using a covariant formalism, we construct a chiral kinetic theory Lorentz invariant to order O(ℏ), which includes collisions. We find a new contribution to the particle number current due to the side jumps required by the conservation of angular momentum during collisions. We also find a conserved symmetric stress-energy tensor as well as the H function obeying Boltzmann's H theorem. We demonstrate their use by finding a general equilibrium solution and the values of the anomalous transport coefficients characterizing the chiral vortical effect. PMID:26207458

  5. Constructing diabatic states from adiabatic states: Extending generalized Mulliken-Hush to multiple charge centers with Boys localization

    NASA Astrophysics Data System (ADS)

    Subotnik, Joseph E.; Yeganeh, Sina; Cave, Robert J.; Ratner, Mark A.

    2008-12-01

    This article shows that, although Boys localization is usually applied to single-electron orbitals, the Boys method itself can be applied to many electron molecular states. For the two-state charge-transfer problem, we show analytically that Boys localization yields the same charge-localized diabatic states as those found by generalized Mulliken-Hush theory. We suggest that for future work in electron transfer, where systems have more than two charge centers, one may benefit by using a variant of Boys localization to construct diabatic potential energy surfaces and extract electronic coupling matrix elements. We discuss two chemical examples of Boys localization and propose a generalization of the Boys algorithm for creating diabatic states with localized spin density that should be useful for Dexter triplet-triplet energy transfer.

  6. Mechanical chirality: A chiral catalyst with a ring to it

    NASA Astrophysics Data System (ADS)

    Goldup, Stephen M.

    2016-05-01

    A chiral [2]rotaxane in which the asymmetry is derived from the way in which the two components are mechanically interlocked -- rather than being encoded in the covalent connectivity of the components themselves -- has been shown to act as an enantioselective organocatalyst.

  7. Shared Service Center vs. Shared Service Network: A Multiple Case Study Analysis of Factors Impacting on Shared Service Configurations

    NASA Astrophysics Data System (ADS)

    Becker, Jörg; Niehaves, Björn; Krause, Andreas

    Shared services have proven to be a key element when it comes to increasing government efficiency by collaboration. Here, we seek to investigate into the shared services phenomenon in the context of government reforms. For this purpose, an interview and document analysis-based multiple case study has been conducted in Germany. The qualitative analysis covers two shared service implementations on the local government level and identifies important preconditions for shared service emergence, namely cost pressure as motive, the existence of key actors promoting the topic and the existence of prior cooperation. Moreover, it is shown that the structure of such previous cooperation determines, if shared services are being organised in a centralised (shared service centre) or decentralised format (shared service network).

  8. Brilliant Sm, Eu, Tb and Dy chiral lanthanide complexes withstrong circularly polarized luminescence

    SciTech Connect

    Petoud, Stephane; Muller, Gilles; Moore, Evan G.; Xu, Jide; Sokolnicki, Jurek; Riehl, James P.; Le, Uyen; Cohen, Seth M.; Raymond,Kenneth N.

    2006-07-10

    The synthesis, characterization and luminescent behavior of trivalent Sm, Eu, Dy and Tb complexes of two enantiomeric, octadentate, chiral, 2-hydroxyisophthalamide ligands are reported. These complexes are highly luminescent in solution. Functionalization of the achiral parent ligand with a chiral 1-phenylethylamine substituent on the open face of the complex in close proximity to the metal center yields complexes with strong circularly polarized luminescence (CPL) activity. This appears to be the first example of a system utilizing the same ligand architecture to sensitize four different lanthanide cations and display CPL activity. The luminescence dissymmetry factor, g{sub lum}, recorded for the Eu(III) complex is one of the highest values reported, and this is the first time the CPL effect has been demonstrated for a Sm(III) complex with a chiral ligand. The combination of high luminescence intensity with CPL activity should enable new bioanalytical applications of macromolecules in chiral environments.

  9. Coherent perfect absorption in chiral metamaterials.

    PubMed

    Ye, Yuqian; Hay, Darrick; Shi, Zhimin

    2016-07-15

    We study the coherent perfect absorption (CPA) of a chiral structure and derive analytically the CPA condition for transversely isotropic chiral structures in circular polarization bases. The coherent absorption of such a chiral system is generally polarization dependent and can be tuned by the relative phase between the coherent input beams. To demonstrate our theoretical predictions, a chiral metamaterial absorber operating in the terahertz frequency range is optimized. We numerically demonstrate that a coherent absorption of 99.5% can be achieved. Moreover, we show that an optimized CPA chiral structure can be used as an interferometric control of polarization state of the output beams with constant output intensity. PMID:27420535

  10. Scaling laws in chiral hydrodynamic turbulence

    NASA Astrophysics Data System (ADS)

    Yamamoto, Naoki

    2016-06-01

    We study the turbulent regime of chiral (magneto)hydrodynamics for charged and neutral matter with chirality imbalance. We find that the chiral magnetohydrodynamics for charged plasmas possesses a unique scaling symmetry, only without fluid helicity under the local charge neutrality. We also find a different type of unique scaling symmetry in the chiral hydrodynamics for neutral matter with fluid helicity in the inertial range. We show that these symmetries dictate the self-similar inverse cascade of the magnetic and kinetic energies. Our results imply the possible inverse energy cascade in core-collapse supernovae due to the chiral transport of neutrinos.

  11. Chiral xenobiotics bioaccumulations and environmental health prospectives.

    PubMed

    Hussain, Iqbal; ALOthman, Zeid A; Alwarthan, Abdulrahman A; Sanagi, Mohd Marsin; Ali, Imran

    2015-08-01

    The chiral xenobiotics are very dangerous for all of us due to the different enantioselective toxicities of the enantiomers. Besides, these have different enantioselective bioaccumulations and behaviors in our body and other organisms. It is of urgent need to understand the enantioselective bioaccumulations, toxicities, and the health hazards of the chiral xenobiotics. The present article describes the classification, sources of contamination, distribution, enantioselective bioaccumulation, and the toxicities of the chiral xenobiotics. Besides, the efforts are also made to discuss the prevention and remedial measures of the havoc of the chiral xenobiotics. The challenges of the chiral xenobiotics have also been highlighted. Finally, future prospectives are also discussed. PMID:26148690

  12. Open Repair Versus Thoracic Endovascular Aortic Repair in Multiple-Injured Patients: Observations From a Level-1 Trauma Center

    PubMed Central

    Brand, Stephan; Breitenbach, Ingo; Bolzen, Philipp; Petri, Maximilian; Krettek, Christian; Teebken, Omke

    2015-01-01

    Background: Blunt trauma of the thoracic aorta is a rare but potentially life-threatening entity. Intimal tears are a domain of non-operative management, whereas all other types of lesions should be repaired urgently. There is now a clear trend favoring minimally invasive stent grafting over open surgical repair. Objectives: The aim of the present study was to retrospectively evaluate the mortality and morbidity with either treatment option. Therefore, a retrospective observational study was performed to compare two different treatment methods at two different time periods at one trauma center. Patients and Methods: Between 1977 and 2012, all severely injured patients referred to our level 1 trauma center were screened for blunt aortic injuries. We compared baseline characteristics, 30-day and overall mortality, morbidity, duration of intensive care treatment, procedure time, and transfusion of packed red blood between patients who underwent open surgical or stent repair. Results: During the observation period, 45 blunt aortic injuries were recorded. The average Injury Severity Score (ISS) was 41.8 (range 29 - 68). Twenty-five patients underwent Open Repair (OR), and another 20 patients were scheduled to emergency stent grafting. The 30-day mortality in the surgical and stent groups were 5/25 (20%) and 2/20 (10%), respectively. The average time for open surgery was 151 minutes; the mean time for stent grafting was 67 minutes (P = 0.001). Postoperative stay on the intensive care unit was between one and 59 days (median 10) in group one and between four and 50 days in group two (median 26)(P = 0.03). Patients undergoing OR required transfusion of 6.0 units of packed red cells in median; patients undergoing stent grafting required a median of 2.0 units of packed red cells (P < 0.001). In the stent grafting group, 30-day mortality was 10% (2/20). Conclusions: Due to more sophisticated diagnostic tools and surgical approaches, mortality and morbidity of blunt aortic

  13. Helical motion of chiral liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takaki; Sano, Masaki

    Artificial swimmers have been intensively studied to understand the mechanism of the locomotion and collective behaviors of cells and microorganisms. Among them, most of the artificial swimmers are designed to move along the straight path. However, in biological systems, chiral dynamics such as circular and helical motion are quite common because of the chirality of their bodies, which are made of chiral biomolecules. To understand the role of the chirality in the physics of microswimmers, we designed chiral artificial swimmers and the theoretical model for the chiral motion. We found that chiral liquid crystal droplets, when dispersed in surfactant solutions, swim in the helical path induced by the Marangoni effect. We will discuss the mechanism of the helical motion with our phenomenological model. This work is supported by Grant-in-Aid for JSPS Fellows (Grant No. 26.9814), and MEXT KAKENHI Grant No. 25103004.

  14. Chirality effect in disordered graphene ribbon junctions

    NASA Astrophysics Data System (ADS)

    Long, Wen

    2012-05-01

    We investigate the influence of edge chirality on the electronic transport in clean or disordered graphene ribbon junctions. By using the tight-binding model and the Landauer-Büttiker formalism, the junction conductance is obtained. In the clean sample, the zero-magnetic-field junction conductance is strongly chirality-dependent in both unipolar and bipolar ribbons, whereas the high-magnetic-field conductance is either chirality-independent in the unipolar or chirality-dependent in the bipolar ribbon. Furthermore, we study the disordered sample in the presence of magnetic field and find that the junction conductance is always chirality-insensitive for both unipolar and bipolar ribbons with adequate disorders. In addition, the disorder-induced conductance plateaus can exist in all chiral bipolar ribbons provided the disorder strength is moderate. These results suggest that we can neglect the effect of edge chirality in fabricating electronic devices based on the magnetotransport in a disordered graphene ribbon.

  15. Micropatterning of cells reveals chiral morphogenesis

    PubMed Central

    2013-01-01

    Invariant left-right (LR) patterning or chirality is critical for embryonic development. The loss or reversal of LR asymmetry is often associated with malformations and disease. Although several theories have been proposed, the exact mechanism of the initiation of the LR symmetry has not yet been fully elucidated. Recently, chirality has been detected within single cells as well as multicellular structures using several in vitro approaches. These studies demonstrated the universality of cell chirality, its dependence on cell phenotype, and the role of physical boundaries. In this review, we discuss the theories for developmental LR asymmetry, compare various in vitro cell chirality model systems, and highlight possible roles of cell chirality in stem cell differentiation. We emphasize that the in vitro cell chirality systems have great promise for helping unveil the nature of chiral morphogenesis in development. PMID:23672821

  16. On the tensorial nature of chirality

    NASA Astrophysics Data System (ADS)

    Efrati, Efi; Irvine, William

    2013-03-01

    Chirality occupies a central role in fields ranging from biological self assembly to the design of optical meta-materials. The definition of chirality, as given by lord Kelvin in 1893, associates handedness with the lack of mirror symmetry. However, the quantification of chirality based on this definition has proven to be an elusive task. The difficulty in quantifying chirality is contrasted by the ease with which one determines the handedness of objects with a well defined axis such as screws and helices. In this talk I will present table-top demonstrations that show that a single object can simultaneously be left handed and right handed when considered from different directions. The orientation dependence of handedness motivates a tensorial quantification of chirality relating directions to rotations. I will give an explicit example of such a tensorial measure of chirality for embedded surfaces, and show how the tensorial nature of chirality can be probed in experiments and exploited as a design principle.

  17. Construction of a tunable multi-enzyme-coordinate expression system for biosynthesis of chiral drug intermediates

    PubMed Central

    Jiang, Wei; Fang, Baishan

    2016-01-01

    Systems that can regulate and coordinate the expression of multiple enzymes for metabolic regulation and synthesis of important drug intermediates are poorly explored. In this work, a strategy for constructing a tunable multi-enzyme-coordinate expression system for biosynthesis of chiral drug intermediates was developed and evaluated by connecting protein-protein expressions, regulating the strength of ribosome binding sites (RBS) and detecting the system capacity for producing chiral amino acid. Results demonstrated that the dual-enzyme system had good enantioselectivity, low cost, high stability, high conversion rate and approximately 100% substrate conversion. This study has paved a new way of exploring metabolic mechanism of functional genes and engineering whole cell-catalysts for synthesis of chiral α-hydroxy acids or chiral amino acids. PMID:27456301

  18. Chiral phosphines in nucleophilic organocatalysis

    PubMed Central

    Xiao, Yumei; Sun, Zhanhu

    2014-01-01

    Summary This review discusses the tertiary phosphines possessing various chiral skeletons that have been used in asymmetric nucleophilic organocatalytic reactions, including annulations of allenes, alkynes, and Morita–Baylis–Hillman (MBH) acetates, carbonates, and ketenes with activated alkenes and imines, allylic substitutions of MBH acetates and carbonates, Michael additions, γ-umpolung additions, and acylations of alcohols. PMID:25246969

  19. Baryon and chiral symmetry breaking

    SciTech Connect

    Gorsky, A.; Krikun, A.

    2014-07-23

    We briefly review the generalized Skyrmion model for the baryon recently suggested by us. It takes into account the tower of vector and axial mesons as well as the chiral symmetry breaking. The generalized Skyrmion model provides the qualitative explanation of the Ioffe’s formula for the baryon mass.

  20. Dynamics of the chiral transition

    SciTech Connect

    Gavin, S.

    1994-07-01

    Measurements of disoriented chiral condensates (DCC) in heavy ion collisions at RHIC can yield fundamental information on the nature of the QCD phase transition. I review theoretical efforts to understand DCC formation and present work in progress on possible experimental ramifications.

  1. Dynamics of the chiral transition

    SciTech Connect

    Gavin, S.

    1995-07-10

    Measurements of disoriented chiral condensates (DCC) in heavy ion collisions at RHIC can yield fundamental information on the nature of the QCD phase transition. I review theoretical efforts to understand DCC formation and present work in progress on their possible experimental ramifications. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  2. A single-center retrospective analysis of first-line therapy of multiple myeloma with bendamustine-bortezomib-dexamethasone.

    PubMed

    Zwickl, Hannes; Zwickl-Traxler, Elisabeth; Pecherstorfer, Martin

    2016-09-01

    The aim of this retrospective study was to evaluate the efficacy and toxicity profile of bendamustine, bortezomib, and dexamethasone (BBD) combination treatment of patients with newly diagnosed multiple myeloma (MM). BBD treatment had a response rate of 80% regarding patients with ≥ partial response (PR). Median time to best response was 87.5 days and PFS was 22 months. Median of OS was not reached. PFS of non-responding patients was significantly shortened compared to those with ≥ PR. No statistically significant differences were determined concerning age (≥ vs. < 68 years) and ISS stage (ISS stage I/II vs. III). Grade 3 hematological effects and grade 3/4 non-hematological effects occurred in 20% and 35% of patients, respectively. Most pronounced hematological adverse event was leukopenia, the most severe non-hematological ones affected the cardiovascular system. In summary, BBD treatment was of acceptable efficacy in patients with newly diagnosed MM and exhibited rather low toxicity. PMID:26901249

  3. Spherical β-cyclodextrin-silica hybrid materials for multifunctional chiral stationary phases.

    PubMed

    Wang, Litao; Dong, Shuqing; Han, Feng; Zhao, Yingwei; Zhang, Xia; Zhang, Xiaoli; Qiu, Hongdeng; Zhao, Liang

    2015-02-27

    Spherical β-CD-silica hybrid materials have been prepared successfully by simple one-pot polymerization, which provide a new strategy to construct new type of HPLC chiral stationary phases. Various β-CD, ethane, triazinyl and 3,5-dimethylphenyl functional groups that can provide multiple interactions were introduced into the pore channels and pore wall framework of mesoporous materials, respectively. The materials towards some chiral, acidic, anilines and phenols compounds showed multiple chromatographic separation functions including racemic resolution, anion exchange and achiral separations with a typical feature of normal/reversed phase chromatography. Multi-tasking including racemic resolution and achiral separations for selected compounds were performed simultaneously on a chiral chromatographic column. The multifunctional character of materials arises from the multiple interactions including hydrophobic interaction, π-π interaction, anion exchange, inclusion interaction and hydrogen bonding interaction. PMID:25637012

  4. Nuclear chiral dynamics and thermodynamics

    NASA Astrophysics Data System (ADS)

    Holt, Jeremy W.; Kaiser, Norbert; Weise, Wolfram

    2013-11-01

    This presentation reviews an approach to nuclear many-body systems based on the spontaneously broken chiral symmetry of low-energy QCD. In the low-energy limit, for energies and momenta small compared to a characteristic symmetry breaking scale of order 1 GeV, QCD is realized as an effective field theory of Goldstone bosons (pions) coupled to heavy fermionic sources (nucleons). Nuclear forces at long and intermediate distance scales result from a systematic hierarchy of one- and two-pion exchange processes in combination with Pauli blocking effects in the nuclear medium. Short distance dynamics, not resolved at the wavelengths corresponding to typical nuclear Fermi momenta, are introduced as contact interactions between nucleons. Apart from a set of low-energy constants associated with these contact terms, the parameters of this theory are entirely determined by pion properties and low-energy pion-nucleon scattering observables. This framework (in-medium chiral perturbation theory) can provide a realistic description of both isospin-symmetric nuclear matter and neutron matter, with emphasis on the isospin-dependence determined by the underlying chiral NN interaction. The importance of three-body forces is emphasized, and the role of explicit Δ(1232)-isobar degrees of freedom is investigated in detail. Nuclear chiral thermodynamics is developed and a calculation of the nuclear phase diagram is performed. This includes a successful description of the first-order phase transition from a nuclear Fermi liquid to an interacting Fermi gas and the coexistence of these phases below a critical temperature Tc. Density functional methods for finite nuclei based on this approach are also discussed. Effective interactions, their density dependence and connections to Landau Fermi liquid theory are outlined. Finally, the density and temperature dependences of the chiral (quark) condensate are investigated.

  5. Chiral selectivity of amino acid adsorption on chiral surfaces—The case of alanine on Pt

    SciTech Connect

    Franke, J.-H.; Kosov, D. S.

    2015-02-07

    We study the binding pattern of the amino acid alanine on the naturally chiral Pt surfaces Pt(531), Pt(321), and Pt(643). These surfaces are all vicinal to the (111) direction but have different local environments of their kink sites and are thus a model for realistic roughened Pt surfaces. Alanine has only a single methyl group attached to its chiral center, which makes the number of possible binding conformations computationally tractable. Additionally, only the amine and carboxyl group are expected to interact strongly with the Pt substrate. On Pt(531), we study the molecule in its pristine as well as its deprotonated form and find that the deprotonated one is more stable by 0.47 eV. Therefore, we study the molecule in its deprotonated form on Pt(321) and Pt(643). As expected, the oxygen and nitrogen atoms of the deprotonated molecule provide a local binding “tripod” and the most stable adsorption configurations optimize the interaction of this “tripod” with undercoordinated surface atoms. However, the interaction of the methyl group plays an important role: it induces significant chiral selectivity of about 60 meV on all surfaces. Hereby, the L-enantiomer adsorbs preferentially to the Pt(321){sup S} and Pt(643){sup S} surfaces, while the D-enantiomer is more stable on Pt(531){sup S}. The binding energies increase with increasing surface density of kink sites, i.e., they are largest for Pt(531){sup S} and smallest for Pt(643){sup S}.

  6. Redox-Triggered Helicity Inversion in Chiral Cobalt Complexes in Combination with H(+) and NO3(-) Stimuli.

    PubMed

    Gregoliński, Janusz; Hikita, Masahiro; Sakamoto, Tatsuya; Sugimoto, Hideki; Tsukube, Hiroshi; Miyake, Hiroyuki

    2016-01-19

    Three chiral ligands with variable denticity, H2L2-H2L4, conjugated by N,N'-ethylenebis[N-methyl-(S)-alanine] and an ortho-heterosubstituted aromatic amine, were newly synthesized as analogues of previously reported H2L1. Four contracted-Λoxo cobalt(III) complexes [Co(L)](+) with left-handed helical structure of Λ4Δ2 configuration were prepared by one-electron oxidation of the corresponding contracted-Λred cobalt(II) complexes [Co(L)], which were generated from chiral ligands and Co(ClO4)2·6H2O or Co(CF3SO3)2·5.2H2O in the presence of an organic base. Although the prepared cobalt(III) complexes were very inert and kinetically stable against protonation and NO3(-) complexation, cobalt(III) reduction in the presence of CF3SO3H and/or Bu4NNO3 allowed immediate changing of their three-dimensional structures from the contracted-Λoxo form to the extended-Λ [Co(H2L)Y2](n+) (Y = solvent and/or anion, n = 0-2) form with left-handed helicity or to the extended-Δ [Co(H2L)(NO3)](+) form with right-handed helicity via N- to O-amide coordination switching. Both extended forms were contracted to the original Λoxo form by oxidation of the cobalt(II) center in the presence of an organic base. Thus, redox reactions triggered dynamic helicity inversion of the chiral cobalt complexes, via multiple molecular motions consisting of relaxation/compression, extension/contraction, and helicity inversion motions in combination with deprotonation/protonation of amide linkages and NO3(-) anion complexation. PMID:26731008

  7. Chirality at metal and helical ligand folding in optical isomers of chiral bis(naphthaldiminato)nickel(II) complexes.

    PubMed

    Enamullah, Mohammed; Quddus, Mohammad Abdul; Hasan, Mohammad Rezabul; Pescitelli, Gennaro; Berardozzi, Roberto; Makhloufi, Gamall; Vasylyeva, Vera; Janiak, Christoph

    2016-01-14

    Enantiopure bis[{(R or S)-N-1-(Ar)ethyl-2-oxo-1-naphthaldiminato-κ(2)N,O}]nickel(ii) complexes {Ar = C6H5 ( or ), p-OMeC6H4 ( or ), and p-BrC6H4 ( or )} are synthesized from the reactions between (R or S)-N-1-(Ar)ethyl-2-oxo-1-naphthaldimine and nickel(ii) acetate. Circular-dichroism spectra and their density-functional theoretical simulation reveal the expected mirror image relationship between the enantiomeric pairs / and / in solution. CD spectra are dominated by the metal-centered Λ- or Δ-chirality of non-planar four-coordinated nickel, this latter being in turn dictated by the ligand chirality. Single crystal structure determination for and shows that there are two symmetry-independent molecules (A and B) in each asymmetric unit that give a Z' = 2 structure. Two asymmetric and chiral bidentate N^O-chelate Schiff base ligands coordinate to the nickel atom in a distorted square planar N2O2-coordination sphere. The conformational difference between the symmetry-independent molecules arises from the "up-or-down" folding of the naphthaldiminato ligand with respect to the coordination plane, which creates right- (P) or left-handed (M) helical conformations. Overall, the combination of ligand chirality, chirality at the metal and ligand folding gives rise to discrete metal helicates of preferred helicity in a selective way. Cyclic voltammograms (CV) show an oxidation wave at ca. 1.30 V for the [Ni(L)2]/[Ni(L)2](+) couple, and a reduction wave at ca. -0.35 V for the [Ni(L)2]/[Ni(L)2](-) couple in acetonitrile. PMID:26619269

  8. Probing the chiral anomaly and transport in Weyl semimetals

    NASA Astrophysics Data System (ADS)

    Parameswaran, Siddharth

    2014-03-01

    The topological nature of Weyl semimetals is reflected in the Adler-Bell-Jackiw anomaly, an unusual bulk response where applying parallel electric (E) and magnetic (B) fields pumps electrons between nodes of opposite chirality at a rate proportional to E . B . We argue that this pumping is measurable via nonlocal transport experiments, in the limit of weak internode scattering. Such nonlocal transport vanishes when the injected current and magnetic field are orthogonal, and therefore serves as a test of the chiral anomaly. I will also comment on the possibility of observing similar physics in the three-dimensional Dirac semimetallic phase proposed to exist in Na3Bi and Cd3As2, which have been the subject of recent photoemission and transport experiments. We acknowledge support from the Simons Foundation, NSF Grant PHYS-1066293 (Aspen Center for Physics), DOE Contract No. DEAC02- 05CH11231, and the Gordon and Betty Moore Foundation Grant GBMF1250 (IQIM at Caltech).

  9. Chiral sensing by nonchiral tetrapyrroles.

    PubMed

    Labuta, Jan; Hill, Jonathan P; Ishihara, Shinsuke; Hanyková, Lenka; Ariga, Katsuhiko

    2015-03-17

    Enantiomeric excess (ee) is a measure of the purity of an enantiomer of a chiral compound with respect to the presence of the complementary enantiomer. It is an important aspect of chemistry, especially in the fields of pharmaceuticals and asymmetric catalysis. Existing methods for determination of enantiomeric excesses using nuclear magnetic resonance (NMR) spectroscopy mostly rely on special chiral reagents (auxiliaries) that form two or more diastereomeric complexes with a chiral compound. As a result of this, the NMR spectrum of each enantiomer is different, allowing the determination of enantiomeric excess. In this Account, we describe a molecular design process that has allowed us to prepare prochiral solvating agents for NMR determination of ee of a wide variety of analyte types. At the outset of this work, we initially encountered the phenomenon of NMR peak splitting in the oxoporphyrinogen (OxP) host component of a supramolecular host-guest complex, where the extent of the splitting is apparently proportional to the guests' ee. Upon closer examination of the mechanism of action, it was found that several complicating factors, including prototropic tautomerism, macrocyclic inversion (ring-flipping), and 1:2 host-guest stoichiometry, obstruct potential applications of OxP as a chiral solvating agent. By considering the molecular conformation of the OxP host, a saddle-shaped calix[4]pyrrole, we moved to study the tetraphenylporphyrin (TPP) dication since it has a similar form, and it was found that it could also be used to probe ee. However, although TPP does not suffer from disadvantageous tautomeric processes, it is still subject to macrocyclic inversion and has the additional serious disadvantage of operating for ee sensing only at depressed temperatures. The intrinsic disadvantages of the OxP and TPP systems were finally overcome by covalently modifying the OxP chromophore by regioselective N-alkylation at one face of the molecule. This procedure yields a

  10. Chiral logarithms in quenched QCD

    SciTech Connect

    Y. Chen; S. J. Dong; T. Draper; I. Horvath; F. X. Lee; K. F. Liu; N. Mathur; and J. B. Zhang

    2004-08-01

    The quenched chiral logarithms are examined on a 163x28 lattice with Iwasaki gauge action and overlap fermions. The pion decay constant fpi is used to set the lattice spacing, a = 0.200(3) fm. With pion mass as low as {approx}180 MeV, we see the quenched chiral logarithms clearly in mpi2/m and fP, the pseudoscalar decay constant. The authors analyze the data to determine how low the pion mass needs to be in order for the quenched one-loop chiral perturbation theory (chiPT) to apply. With the constrained curve-fitting method, they are able to extract the quenched chiral logarithmic parameter delta together with other low-energy parameters. Only for mpi<=300 MeV do we obtain a consistent and stable fit with a constant delta which they determine to be 0.24(3)(4) (at the chiral scale Lambdachi = 0.8 GeV). By comparing to the 123x28 lattice, they estimate the finite volume effect to be about 2.7% for the smallest pion mass. They also fitted the pion mass to the form for the re-summed cactus diagrams and found that its applicable region is extended farther than the range for the one-loop formula, perhaps up to mpi {approx}500-600 MeV. The scale independent delta is determined to be 0.20(3) in this case. The authors study the quenched non-analytic terms in the nucleon mass and find that the coefficient C1/2 in the nucleon mass is consistent with the prediction of one-loop chiPT. They also obtain the low energy constant L5 from fpi. They conclude from this study that it is imperative to cover only the range of data with the pion mass less than {approx}300 MeV in order to examine the chiral behavior of the hadron masses and decay constants in quenched QCD and match them with quenched one-loop chiPT.

  11. Chirality and catalysis with aromatic N-fused heterobicyclic carbenes.

    PubMed

    Iglesias-Sigüenza, Javier; Izquierdo, Cristina; Díez, Elena; Fernández, Rosario; Lassaletta, José M

    2016-06-21

    The benzoannulation of the most common families of aromatic NHCs, imidazol-2-ylidenes and 1,2,4-triazol-3-ylidenes, results in heterobicyclic imidazo[1,5-a]pyridin-3-ylidenes ('s) and [1,2,4]triazolo[4,3-a]pyridin-3-ylidenes ('s), characterized by a bridged N atom. These are versatile platforms that offer multiple possibilities for the modulation of the steric and electronic properties of the carbene ligand and/or organocatalyst, and offer also diverse opportunities for the introduction of several types of chiralities. In this paper the different families of chiral and carbenes and their application in asymmetric catalysis will be discussed. PMID:27254732

  12. Asymmetric Ugi 3CR on isatin-derived ketimine: synthesis of chiral 3,3-disubstituted 3-aminooxindole derivatives

    PubMed Central

    Lesma, Giordano; Meneghetti, Fiorella; Sacchetti, Alessandro; Stucchi, Mattia

    2014-01-01

    Summary An efficient Ugi three-component reaction of a preformed chiral ketimine derived from isatin with various isonitrile and acid components has been developed. The reactions proceeded smoothly and in a stereocontrolled manner with regard to the new center of the Ugi products due to the stereoinduction of the amine chiral residue. A wide variety of novel chiral 3,3-disubstituted 3-aminooxindoles were obtained, a selection of which were subjected to post-Ugi transformations, paving the way to application as peptidomimetics. PMID:24991292

  13. Copper-Catalyzed Intramolecular Desymmetric Aryl C-O Coupling for the Enantioselective Construction of Chiral Dihydrobenzofurans and Dihydrobenzopyrans.

    PubMed

    Yang, Wenqiang; Liu, Yangyuan; Zhang, Shasha; Cai, Qian

    2015-07-20

    O-Heterocyclic structures such as 2,3-dihydrobenzofurans are key motifs in many natural compounds and pharmaceuticals. Enantioselective formation of chiral dihydrobenzofurans and analogues was achieved through a copper-catalyzed desymmetrization strategy with a chiral cyclic 1,2-diamine. A broad range of substrates are compatible with this Cu(I)-diamine catalytic system and afford the desired coupling products with chiral tertiary or quaternary carbon centers in high yields and good to excellent enantioselectivities under mild conditions. PMID:26060986

  14. Mechanism of chirality conversion by periodic change of temperature: Role of chiral clusters

    NASA Astrophysics Data System (ADS)

    Katsuno, Hiroyasu; Uwaha, Makio

    2016-01-01

    By grinding crystals in a solution, the chirality of crystal structure (and the molecular chirality for the case of chiral molecules as well) can be converted, and the cause of the phenomenon is attributed to crystal growth with chiral clusters. We show that the recently found chirality conversion with a periodic change of temperature can also be explained by crystal growth with chiral clusters. With the use of a generalized Becker-Döring model, which includes enantio-selective incorporation of small chiral clusters to large solid clusters, the change of cluster distribution and the mass flow between clusters are studied. The chiral clusters act as a reservoir to pump out the minority species to the majority, and the exponential amplification of the enantiomeric excess found in the experiment is reproduced in the numerical calculation.

  15. Asymmetric synthesis using chiral-encoded metal.

    PubMed

    Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2016-01-01

    The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity. PMID:27562028

  16. Asymmetric synthesis using chiral-encoded metal

    PubMed Central

    Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2016-01-01

    The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity. PMID:27562028

  17. Molecular chirality: language, history, and significance.

    PubMed

    Gal, Joseph

    2013-01-01

    In this chapter some background material concerning molecular chirality and enantiomerism is presented. First some basic chemical-molecular aspects of chirality are reviewed, after which certain relevant terminology whose use in the literature has been problematic is discussed. Then an overview is provided of some of the early discoveries that laid the foundations of the science of molecular chirality in chemistry and biology, including the discovery of the phenomenon of molecular chirality by L. Pasteur, the proposals for the asymmetric carbon atom by J.H. van 't Hoff and J.A. Lebel, Pasteur's discovery of biological enantioselectivity, the discovery of enantioselectivity at biological receptors by A. Piutti, the studies of enzymatic stereoselectivity by E. Fischer, and the work on enantioselectivity in pharmacology by A. Cushny. Finally, the role of molecular chirality in pharmacotherapy and new-drug development, arguably one of the main driving forces for the current intense interest in the phenomenon of molecular chirality, is discussed. PMID:23666078

  18. Stable Pentaquarks from Strange Chiral Multiplets

    SciTech Connect

    Silas Beane

    2004-12-01

    The assumption of strong diquark correlations in the QCD spectrum suggests flavor multiplets of hadrons that are degenerate in the chiral limit. Generally it would be unnatural for there to be degeneracy in the hadron spectrum that is not protected by a QCD symmetry. Here we show--for pentaquarks constructed from diquarks--that these degeneracies can be naturally protected by the full chiral symmetry of QCD. The resulting chiral multiplet structure recovers the ideally-mixed pentaquark mass spectrum of the diquark model, and interestingly, requires that the axial couplings of the pentaquarks to states outside the degenerate multiplets vanish in the chiral limit. This result suggests that if these hadrons exist, they are stable in the chiral limit and therefore have widths that scale as the fourth power of the kaon mass over the chiral symmetry breaking scale. Natural-size widths are of order a few MeV.

  19. Enantioselective recognition at mesoporous chiral metal surfaces

    PubMed Central

    Wattanakit, Chularat; Côme, Yémima Bon Saint; Lapeyre, Veronique; Bopp, Philippe A.; Heim, Matthias; Yadnum, Sudarat; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2014-01-01

    Chirality is widespread in natural systems, and artificial reproduction of chiral recognition is a major scientific challenge, especially owing to various potential applications ranging from catalysis to sensing and separation science. In this context, molecular imprinting is a well-known approach for generating materials with enantioselective properties, and it has been successfully employed using polymers. However, it is particularly difficult to synthesize chiral metal matrices by this method. Here we report the fabrication of a chirally imprinted mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and chiral template molecules. The porous platinum retains a chiral character after removal of the template molecules. A matrix obtained in this way exhibits a large active surface area due to its mesoporosity, and also shows a significant discrimination between two enantiomers, when they are probed using such materials as electrodes. PMID:24548992

  20. Anomalous Maxwell equations for inhomogeneous chiral plasma

    NASA Astrophysics Data System (ADS)

    Gorbar, E. V.; Shovkovy, I. A.; Vilchinskii, S.; Rudenok, I.; Boyarsky, A.; Ruchayskiy, O.

    2016-05-01

    Using the chiral kinetic theory we derive the electric and chiral current densities in inhomogeneous relativistic plasma. We also derive equations for the electric and chiral chemical potentials that close the Maxwell equations in such a plasma. The analysis is done in the regimes with and without a drift of the plasma as a whole. In addition to the currents present in the homogeneous plasma (Hall current, chiral magnetic, chiral separation, and chiral electric separation effects, as well as Ohm's current) we derive several new terms associated with inhomogeneities of the plasma. Apart from various diffusionlike terms, we find also new dissipationless terms that are independent of relaxation time. Their origin can be traced to the Berry curvature modifications of the kinetic theory.

  1. On lattice chiral gauge theories

    NASA Technical Reports Server (NTRS)

    Maiani, L.; Rossi, G. C.; Testa, M.

    1991-01-01

    The Smit-Swift-Aoki formulation of a lattice chiral gauge theory is presented. In this formulation the Wilson and other non invariant terms in the action are made gauge invariant by the coupling with a nonlinear auxilary scalar field, omega. It is shown that omega decouples from the physical states only if appropriate parameters are tuned so as to satisfy a set of BRST identities. In addition, explicit ghost fields are necessary to ensure decoupling. These theories can give rise to the correct continuum limit. Similar considerations apply to schemes with mirror fermions. Simpler cases with a global chiral symmetry are discussed and it is shown that the theory becomes free at decoupling. Recent numerical simulations agree with those considerations.

  2. Bootstrapping N=2 chiral correlators

    NASA Astrophysics Data System (ADS)

    Lemos, Madalena; Liendo, Pedro

    2016-01-01

    We apply the numerical bootstrap program to chiral operators in four-dimensional N=2 SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of N=2 SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.

  3. Chiral description of massive gravity

    NASA Astrophysics Data System (ADS)

    Alexandrov, Sergei; Krasnov, Kirill; Speziale, Simone

    2013-06-01

    We propose and study a new first order version of the ghost-free massive gravity. Instead of metrics or tetrads, it uses a connection together with Plebanski's chiral 2-forms as fundamental variables, rendering the phase space structure similar to that of SU(2) gauge theories. The chiral description simplifies computations of the constraint algebra, and allows us to perform the complete canonical analysis of the system. In particular, we explicitly compute the secondary constraint and carry out the stabilization procedure, thus proving that in general the theory propagates 7 degrees of freedom, consistently with previous claims. Finally, we point out that the description in terms of 2-forms opens the door to an infinite class of ghost-free massive bi-gravity actions. Our results apply directly to Euclidean signature. The reality conditions to be imposed in the Lorentzian signature appear to be more complicated than in the usual gravity case and are left as an open issue.

  4. On chirality of slime mould.

    PubMed

    Dimonte, Alice; Adamatzky, Andrew; Erokhin, Victor; Levin, Michael

    2016-02-01

    Left-right patterning and lateralised behaviour is an ubiquitous aspect of plants and animals. The mechanisms linking cellular chirality to the large-scale asymmetry of multicellular structures are incompletely understood, and it has been suggested that the chirality of living cells is hardwired in their cytoskeleton. We examined the question of biased asymmetry in a unique organism: the slime mould Physarum polycephalum, which is unicellular yet possesses macroscopic, complex structure and behaviour. In laboratory experiment using a T-shape, we found that Physarum turns right in more than 74% of trials. The results are in agreement with previously published studies on asymmetric movement of muscle cells, neutrophils, liver cells and growing neural filaments, and for the first time reveal the presence of consistently-biased laterality in the fungi kingdom. Exact mechanisms of the slime mould's direction preference remain unknown. PMID:26747637

  5. Microfluidic Separation of Chiral Particles

    NASA Astrophysics Data System (ADS)

    Marcos; Fu, Henry; Powers, Thomas; Stocker, Roman

    2008-11-01

    We present a combined theoretical and experimental investigation of the fluid mechanics of a helix exposed to a shear flow. In addition to classic Jeffery orbits, Resistive Force Theory predicts a drift of the helix across streamlines, perpendicular to the shear plane. The direction of the drift is determined by the direction of the shear and the chirality of the helix. We verify this prediction experimentally using microfluidics, by exposing Leptospira biflexa, a non-motile strain of helical-shaped bacteria, to a plane parabolic flow. As the shear in the top and bottom halves of the microchannel has opposite sign, we predict and observe the bacteria in these two regions to drift in opposite directions. The magnitude of the separation is in good quantitative agreement with theory. This setup can be used to separate microscale chiral objects.

  6. ENANTIOMERIC RATIOS OF CHIRAL PCB ATROPISOMERS IN RADIODATED SEDIMENT CORES

    EPA Science Inventory

    Enantiomeric ratios (ERs)) of chiral polychlorinated biphenyl (PCB) atropisomers were quantified in radiodated sediment cores of Lake Hartwell SC, a reservoir heavily impacted by PCBS, to study spatial and temporal changes in chirality. A chiral analysis of cores showed accumulat...

  7. Anomalies and Discrete Chiral Symmetries

    SciTech Connect

    Creutz, M.

    2009-09-07

    The quantum anomaly that breaks the U(1) axial symmetry of massless multi-flavored QCD leaves behind a discrete flavor-singlet chiral invariance. With massive quarks, this residual symmetry has a close connection with the strong CP-violating parameter theta. One result is that if the lightest quarks are degenerate, then a first order transition will occur when theta passes through pi. The resulting framework helps clarify when the rooting prescription for extrapolating in the number of flavors is valid.

  8. Chiral particle separation by a nonchiral microlattice.

    PubMed

    Bogunovic, Lukas; Fliedner, Marc; Eichhorn, Ralf; Wegener, Sonja; Regtmeier, Jan; Anselmetti, Dario; Reimann, Peter

    2012-09-01

    We conceived a model experiment for a continuous separation strategy of chiral molecules (enantiomers) without the need of any chiral selector structure or derivatization agents: Microparticles that only differ by their chirality are shown to migrate along different directions when driven by a steady fluid flow through a square lattice of cylindrical posts. In accordance with our numerical predictions, the transport directions of the enantiomers depend very sensitively on the orientation of the lattice relative to the fluid flow. PMID:23005274

  9. Chiral Particle Separation by a Nonchiral Microlattice

    NASA Astrophysics Data System (ADS)

    Bogunovic, Lukas; Fliedner, Marc; Eichhorn, Ralf; Wegener, Sonja; Regtmeier, Jan; Anselmetti, Dario; Reimann, Peter

    2012-09-01

    We conceived a model experiment for a continuous separation strategy of chiral molecules (enantiomers) without the need of any chiral selector structure or derivatization agents: Microparticles that only differ by their chirality are shown to migrate along different directions when driven by a steady fluid flow through a square lattice of cylindrical posts. In accordance with our numerical predictions, the transport directions of the enantiomers depend very sensitively on the orientation of the lattice relative to the fluid flow.

  10. Chiral anomaly, bosonization, and fractional charge

    SciTech Connect

    Mignaco, J.A.; Monteiro, M.A.R.

    1985-06-15

    We present a method to evaluate the Jacobian of chiral rotations, regulating determinants through the proper-time method and using Seeley's asymptotic expansion. With this method we compute easily the chiral anomaly for ..nu.. = 4,6 dimensions, discuss bosonization of some massless two-dimensional models, and handle the problem of charge fractionization. In addition, we comment on the general validity of Fujikawa's approach to regulate the Jacobian of chiral rotations with non-Hermitian operators.