Structure determination of helical filaments by solid-state NMR spectroscopy

Science.gov (United States)

Ahmed, Mumdooh; Spehr, Johannes; König, Renate; Lünsdorf, Heinrich; Rand, Ulfert; Lührs, Thorsten; Ritter, Christiane

2016-01-01

The controlled formation of filamentous protein complexes plays a crucial role in many biological systems and represents an emerging paradigm in signal transduction. The mitochondrial antiviral signaling protein (MAVS) is a central signal transduction hub in innate immunity that is activated by a receptor-induced conversion into helical superstructures (filaments) assembled from its globular caspase activation and recruitment domain. Solid-state NMR (ssNMR) spectroscopy has become one of the most powerful techniques for atomic resolution structures of protein fibrils. However, for helical filaments, the determination of the correct symmetry parameters has remained a significant hurdle for any structural technique and could thus far not be precisely derived from ssNMR data. Here, we solved the atomic resolution structure of helical MAVSCARD filaments exclusively from ssNMR data. We present a generally applicable approach that systematically explores the helical symmetry space by efficient modeling of the helical structure restrained by interprotomer ssNMR distance restraints. Together with classical automated NMR structure calculation, this allowed us to faithfully determine the symmetry that defines the entire assembly. To validate our structure, we probed the protomer arrangement by solvent paramagnetic resonance enhancement, analysis of chemical shift differences relative to the solution NMR structure of the monomer, and mutagenesis. We provide detailed information on the atomic contacts that determine filament stability and describe mechanistic details on the formation of signaling-competent MAVS filaments from inactive monomers. PMID:26733681

High-Temperature Wide Thermal Hysteresis of an Iron(II Dinuclear Double Helicate

Directory of Open Access Journals (Sweden)

Shiori Hora

2017-07-01

Full Text Available Two new dinuclear iron(II complexes (1·PF6 and 1·AsF6 of the general formula [FeII2(L2C32](X4·nH2O·mMeCN (X = PF6, n = m = 1.5 for 1·PF6 and X = AsF6, n = 3, m = 1 for 1·AsF6 have been prepared and structurally characterized, where L2C3 is a bis-1,2,3-triazolimine type Schiff-base ligand, 1,1′-[propane-1,3-diylbis(1H-1,2,3-triazole-1,4-diyl]bis{N-[2-(pyridin-2-ylethyl]methanimine}. Single crystal X-ray structure analyses revealed that 1·PF6 and 1·AsF6 are isostructural. The complex-cation [FeII2(L2C32]4+ of both has the same dinuclear double helicate architecture, in which each iron(II center has an N6 octahedral coordination environment. Neighboring helicates are connected by intermolecular π–π interactions to give a chiral one-dimensional (1D structure, and cationic 1D chains with the opposite chirality exist in the crystal lattice to give a heterochiral crystal. Magnetic and differential scanning calorimetry (DSC studies were performed only for 1·AsF6, since the thermal stability in a high-temperature spin crossover (SCO region of 1·PF6 is poorer than that of 1·AsF6. 1·AsF6 shows an unsymmetrical hysteretic SCO between the low-spin–low-spin (LS–LS and high-spin–high-spin (HS–HS states at above room temperature. The critical temperatures of warming (Tc↑ and cooling (Tc↓ modes in the abrupt spin transition area are 485 and 401 K, respectively, indicating the occurrence of 84 K-wide thermal hysteresis in the first thermal cycle.

Salt-bridging effects on short amphiphilic helical structure and introducing sequence-based short beta-turn motifs.

Science.gov (United States)

Guarracino, Danielle A; Gentile, Kayla; Grossman, Alec; Li, Evan; Refai, Nader; Mohnot, Joy; King, Daniel

2018-02-01

Determining the minimal sequence necessary to induce protein folding is beneficial in understanding the role of protein-protein interactions in biological systems, as their three-dimensional structures often dictate their activity. Proteins are generally comprised of discrete secondary structures, from α-helices to β-turns and larger β-sheets, each of which is influenced by its primary structure. Manipulating the sequence of short, moderately helical peptides can help elucidate the influences on folding. We created two new scaffolds based on a modestly helical eight-residue peptide, PT3, we previously published. Using circular dichroism (CD) spectroscopy and changing the possible salt-bridging residues to new combinations of Lys, Arg, Glu, and Asp, we found that our most helical improvements came from the Arg-Glu combination, whereas the Lys-Asp was not significantly different from the Lys-Glu of the parent scaffold, PT3. The marked 3 10 -helical contributions in PT3 were lessened in the Arg-Glu-containing peptide with the beginning of cooperative unfolding seen through a thermal denaturation. However, a unique and unexpected signature was seen for the denaturation of the Lys-Asp peptide which could help elucidate the stages of folding between the 3 10 and α-helix. In addition, we developed a short six-residue peptide with β-turn/sheet CD signature, again to help study minimal sequences needed for folding. Overall, the results indicate that improvements made to short peptide scaffolds by fine-tuning the salt-bridging residues can enhance scaffold structure. Likewise, with the results from the new, short β-turn motif, these can help impact future peptidomimetic designs in creating biologically useful, short, structured β-sheet-forming peptides.

Structural details (kinks and non-alpha conformations) in transmembrane helices are intrahelically determined and can be predicted by sequence pattern descriptors.

Science.gov (United States)

Rigoutsos, Isidore; Riek, Peter; Graham, Robert M; Novotny, Jiri

2003-08-01

One of the promising methods of protein structure prediction involves the use of amino acid sequence-derived patterns. Here we report on the creation of non-degenerate motif descriptors derived through data mining of training sets of residues taken from the transmembrane-spanning segments of polytopic proteins. These residues correspond to short regions in which there is a deviation from the regular alpha-helical character (i.e. pi-helices, 3(10)-helices and kinks). A 'search engine' derived from these motif descriptors correctly identifies, and discriminates amongst instances of the above 'non-canonical' helical motifs contained in the SwissProt/TrEMBL database of protein primary structures. Our results suggest that deviations from alpha-helicity are encoded locally in sequence patterns only about 7-9 residues long and can be determined in silico directly from the amino acid sequence. Delineation of such variations in helical habit is critical to understanding the complex structure-function relationships of polytopic proteins and for drug discovery. The success of our current methodology foretells development of similar prediction tools capable of identifying other structural motifs from sequence alone. The method described here has been implemented and is available on the World Wide Web at http://cbcsrv.watson.ibm.com/Ttkw.html.

Magnetohydrodynamic helical structures in nominally axisymmetric low-shear tokamak plasmas

International Nuclear Information System (INIS)

Graves, J P; Brunetti, D; Cooper, W A; Reimerdes, H; Halpern, F; Pochelon, A; Sauter, O; Chapman, I T

2013-01-01

The primary goal of hybrid scenarios in tokamaks is to enable high performance operation with large plasma currents whilst avoiding MHD instabilities. However, if a local minimum in the safety factor is allowed to approach unity, the energy required to overcome stabilizing magnetic field line bending is very small, and as a consequence, large MHD structures can be created, with typically dominant m = n = 1 helical component. If there is no exact q = 1 rational surface the essential character of these modes can be modelled assuming ideal nested magnetic flux surfaces. The methods used to characterize these structures include linear and non-linear ideal MHD stability calculations which evaluate the departure from an axisymmetric plasma state, and also equilibrium calculations using a 3D equilibrium code. While these approaches agree favourably for simulations of ITER relevant hybrid regimes in this paper, the relevance of the ideal MHD model itself is tested through empirical examination of helical states in MAST and TCV. While long lived modes in MAST do not have island structures, some of the continuous mode oscillations exhibited in high elongation experiments in TCV indicate that resistivity may play a role in further weakening the ability of the tokamak core to remain axisymmetric. The simulations and experiments consistently highlight the need to control the safety factor in hybrid scenarios planned for future fusion grade tokamaks such as ITER. (paper)

Synthesis and optical resolution of a Cu(I) double-stranded helicate with ketimine-bridged tris(bipyridine) ligands.

Science.gov (United States)

Furusho, Yoshio; Goto, Hidetoshi; Itomi, Ken; Katagiri, Hiroshi; Miyagawa, Toyoharu; Yashima, Eiji

2011-09-21

A tetranuclear Cu(I) double-stranded helicate was synthesized from ketimine-bridged tris(bipyridine) ligands and Cu(I) ions, and the racemate was successfully resolved by diastereomeric salt formation using an optically pure phosphate anion followed by anion exchange with NaPF(6) without racemization.

Structural details (kinks and non-α conformations) in transmembrane helices are intrahelically determined and can be predicted by sequence pattern descriptors

Science.gov (United States)

Rigoutsos, Isidore; Riek, Peter; Graham, Robert M.; Novotny, Jiri

2003-01-01

One of the promising methods of protein structure prediction involves the use of amino acid sequence-derived patterns. Here we report on the creation of non-degenerate motif descriptors derived through data mining of training sets of residues taken from the transmembrane-spanning segments of polytopic proteins. These residues correspond to short regions in which there is a deviation from the regular α-helical character (i.e. π-helices, 310-helices and kinks). A ‘search engine’ derived from these motif descriptors correctly identifies, and discriminates amongst instances of the above ‘non-canonical’ helical motifs contained in the SwissProt/TrEMBL database of protein primary structures. Our results suggest that deviations from α-helicity are encoded locally in sequence patterns only about 7–9 residues long and can be determined in silico directly from the amino acid sequence. Delineation of such variations in helical habit is critical to understanding the complex structure–function relationships of polytopic proteins and for drug discovery. The success of our current methodology foretells development of similar prediction tools capable of identifying other structural motifs from sequence alone. The method described here has been implemented and is available on the World Wide Web at http://cbcsrv.watson.ibm.com/Ttkw.html. PMID:12888523

Energy landscape, structure and rate effects on strength properties of alpha-helical proteins

International Nuclear Information System (INIS)

Bertaud, Jeremie; Hester, Joshua; Jimenez, Daniel D; Buehler, Markus J

2010-01-01

The strength of protein domains is crucial to identify the mechanical role of protein domains in biological processes such as mechanotransduction, tissue mechanics and tissue remodeling. Whereas the concept of strength has been widely investigated for engineered materials, the strength of fundamental protein material building blocks and how it depends on structural parameters such as the chemical bonding, the protein filament length and the timescale of observation or deformation velocity remains poorly understood. Here we report a systematic analysis of the influence of key parameters that define the energy landscape of the strength properties of alpha-helical protein domains, including energy barriers, unfolding and refolding distances, the locations of folded and unfolded states, as well as variations of the length and pulling velocity of alpha-helical protein filaments. The analysis is facilitated by the development of a double-well mesoscale potential formulation, utilized here to carry out a systematic numerical analysis of the behavior of alpha-helices. We compare the results against widely used protein strength models based on the Bell model, one of the simplest models used to characterize the strength of protein filaments. We find that, whereas Bell-type models are a reasonable approximation to describe the rupture of alpha-helical protein domains for a certain range of pulling speeds and values of energy barriers, the model ceases to hold for very large energy barriers and for very small pulling speeds, in agreement with earlier findings. We conclude with an application of our mesoscale model to investigate the effect of the length of alpha-helices on their mechanical strength. We find a weakening effect as the length of alpha-helical proteins increases, followed by an asymptotic regime in which the strength remains constant. We compare strand lengths found in biological proteins with the scaling law of strength versus alpha-helix filament length. The

Diffraction by DNA, carbon nanotubes and other helical nanostructures

International Nuclear Information System (INIS)

Lucas, Amand A; Lambin, Philippe

2005-01-01

This review discusses the diffraction patterns of x-rays or electrons scattered by fibres of helical biological molecules and by carbon nanotubes (CNTs) from the unified point of view of the Fourier-Bessel transform of an atomic helix. This paper is intended for scientists who are not professional crystallographers. X-ray fibre diffraction patterns of Pauling's protein α-helix and of Crick and Pauling's protein coiled-coil are revisited. This is followed by a non-technical comparison between the historic x-ray diffraction patterns of the A and B conformations of DNA, which were crucial for the discovery of the double helix. The qualitative analysis of the diffraction images is supported by novel optical simulation experiments designed to pinpoint the gross structural informational content of the patterns. The spectacular helical structure of the tobacco mosaic virus determined by Rosalind Franklin and co-workers will then be described as an early example of the great power of x-ray crystallography in determining the structure of a large biomolecular edifice. After these mostly historical and didactic case studies, this paper will consider electron diffraction and transmission electron microscopy of CNTs of great current interest, focusing particularly on recent data obtained for single-wall, double-wall and scrolled nanotubes. Several points of convergence between the interpretations of the diffraction patterns of biological helices and CNTs will be emphasized

The Cu2+-nitrilotriacetic acid complex improves loading of α-helical double histidine site for precise distance measurements by pulsed ESR

Science.gov (United States)

Ghosh, Shreya; Lawless, Matthew J.; Rule, Gordon S.; Saxena, Sunil

2018-01-01

Site-directed spin labeling using two strategically placed natural histidine residues allows for the rigid attachment of paramagnetic Cu2+. This double histidine (dHis) motif enables extremely precise, narrow distance distributions resolved by Cu2+-based pulsed ESR. Furthermore, the distance measurements are easily relatable to the protein backbone-structure. The Cu2+ ion has, till now, been introduced as a complex with the chelating agent iminodiacetic acid (IDA) to prevent unspecific binding. Recently, this method was found to have two limiting concerns that include poor selectivity towards α-helices and incomplete Cu2+-IDA complexation. Herein, we introduce an alternative method of dHis-Cu2+ loading using the nitrilotriacetic acid (NTA)-Cu2+ complex. We find that the Cu2+-NTA complex shows a four-fold increase in selectivity toward α-helical dHis sites. Furthermore, we show that 100% Cu2+-NTA complexation is achievable, enabling precise dHis loading and resulting in no free Cu2+ in solution. We analyze the optimum dHis loading conditions using both continuous wave and pulsed ESR. We implement these findings to show increased sensitivity of the Double Electron-Electron Resonance (DEER) experiment in two different protein systems. The DEER signal is increased within the immunoglobulin binding domain of protein G (called GB1). We measure distances between a dHis site on an α-helix and dHis site either on a mid-strand or a non-hydrogen bonded edge-strand β-sheet. Finally, the DEER signal is increased twofold within two α-helix dHis sites in the enzymatic dimer glutathione S-transferase exemplifying the enhanced α-helical selectivity of Cu2+-NTA.

Rational assembly of Pb(II)/Cd(II)/Mn(II) coordination polymers based on flexible V-shaped dicarboxylate ligand: Syntheses, helical structures and properties

Energy Technology Data Exchange (ETDEWEB)

Yang, Gao-Shan [School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Liu, Chong-Bo, E-mail: cbliu@nchu.edu.cn [School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 330063 (China); School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Liu, Hong [School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Robbins, Julianne; Zhang, Z. John [School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Yin, Hong-Shan [School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Wen, Hui-Liang [State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047 (China); Wang, Yu-Hua [School of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 330063 (China)

2015-05-15

Six new coordination polymers, namely, [Pb(L)(H{sub 2}O)] (1), [Pb(L)(phen)] (2), [Pb{sub 2}(L){sub 2}(4,4′-bipy){sub 0.5}] (3), [Cd(L)(phen)] (4), [Cd(L)(4,4′-bipy)]·H{sub 2}O (5) and [Mn(L)(4,4′-bipy)]·H{sub 2}O (6) have been synthesized by the hydrothermal reaction of 2,2′-[hexafluoroisopropylidenebis(p-phenyleneoxy)]diacetic acid (H{sub 2}L) with Pb(II)/Cd(II)/Mn(II) in the presence of ancillary ligands 4,4′-bipyridine (4,4′-bipy) or 1,10-phenanthroline (phen). Complexes 1 and 4–6 exhibit 2-D structures, and complexes 2–3 display 3-D frameworks, of which L{sup 2−} ligands join metal ions to single-stranded helical chains of 1, 3–6 and double-stranded helical chains of 2. Complexes 2 and 3 also contain double-stranded Metal–O helices. Topology analysis reveals that complexes 1 and 4 both represent 4-connected sql net, 2 represents 6-connected pcu net, 3 exhibits a novel (3,12)-connected net, while 5 and 6 display (3,5)-connected gek1 net. The six complexes exhibit two kinds of inorganic–organic connectivities: I{sup 0}O{sup 2} for 1, 4–6, and I{sup 1}O{sup 2} for 2–3. The photoluminescent properties of 4–5 and the magnetic properties of 6 have been investigated. - Graphical abstract: Six new Pb(II)/Cd(II)/Mn(II) coordination polymers with helical structures based on flexible V-shaped dicarboxylate ligand have been synthesized and structurally characterized. Photoluminescent and magnetic properties have been investigated. - Highlights: • Six novel M(II) coordination polymers with 2,2′-[hexafluoroisopropylidenebis(p-phenyleneoxy)]diacetic acid and N-donor ligands. • Complexes 1–6 show diverse intriguing helical characters. • The luminescent properties of complexes 1–5 were investigated. • Complex 6 shows antiferromagnetic coupling.

Interactions between Radial Electric Field, Transport and Structure in Helical Plasmas

International Nuclear Information System (INIS)

Ida, Katsumi and others

2006-01-01

Control of the radial electric field is considered to be important in helical plasmas, because the radial electric field and its shear are expected to reduce neoclassical and anomalous transport, respectively. Particle and heat transport, that determines the radial structure of density and electron profiles, sensitive to the structure of radial electric field. On the other hand, the radial electric field itself is determined by the plasma parameters. In general, the sign of the radial electric field is determined by the plasma collisionality, while the magnitude of the radial electric field is determined by the temperature and/or density gradients. Therefore the structure of radial electric field and temperature and density are strongly coupled through the particle and heat transport and formation mechanism of radial electric field. Interactions between radial electric field, transport and structure in helical plasmas is discussed based on the experiments on Large Helical Device

HANFORD DOUBLE-SHELL TANK THERMAL and SEISMIC PROJECT. DYTRAN ANALYSIS OF SEISMICALLY INDUCED FLUID-STRUCTURE INTERACTION IN A HANFORD DOUBLE-SHELL PRIMARY TANK

International Nuclear Information System (INIS)

MACKEY, T.C.

2006-01-01

M and D Professional Services, Inc. (M and D) is under subcontract to Pacific Northwest National Laboratories (PNNL) to perform seismic analysis of the Hanford Site Double-Shell Tanks (DSTs) in support of a project entitled ''Double-Shell Tank (DSV Integrity Project-DST Thermal and Seismic Analyses)''. The overall scope of the project is to complete an up-to-date comprehensive analysis of record of the DST System at Hanford in support of Tri-Party Agreement Milestone M-48-14. The work described herein was performed in support of the seismic analysis of the DSTs. The thermal and operating loads analysis of the DSTs is documented in Rinker et al. (2004). The overall seismic analysis of the DSTs is being performed with the general-purpose finite element code ANSYS'. The global model used for the seismic analysis of the DSTs includes the DST structure, the contained waste, and the surrounding soil. The seismic analysis of the DSTs must address the fluid-structure interaction behavior and sloshing response of the primary tank and contained liquid. ANSYS has demonstrated capabilities for structural analysis, but has more limited capabilities for fluid-structure interaction analysis. The purpose of this study is to demonstrate the capabilities and investigate the limitations of the finite element code MSC.Dytranz for performing a dynamic fluid-structure interaction analysis of the primary tank and contained waste. To this end, the Dytran solutions are benchmarked against theoretical solutions appearing in BNL 1995, when such theoretical solutions exist. When theoretical solutions were not available, comparisons were made to theoretical solutions to similar problems, and to the results from ANSYS simulations. Both rigid tank and flexible tank configurations were analyzed with Dytran. The response parameters of interest that are evaluated in this study are the total hydrodynamic reaction forces, the impulsive and convective mode frequencies, the waste pressures, and slosh

From plasma crystals and helical structures towards inorganic living matter

International Nuclear Information System (INIS)

Tsytovich, V N; Morfill, G E; Fortov, V E; Gusein-Zade, N G; Klumov, B A; Vladimirov, S V

2007-01-01

Complex plasmas may naturally self-organize themselves into stable interacting helical structures that exhibit features normally attributed to organic living matter. The self-organization is based on non-trivial physical mechanisms of plasma interactions involving over-screening of plasma polarization. As a result, each helical string composed of solid microparticles is topologically and dynamically controlled by plasma fluxes leading to particle charging and over-screening, the latter providing attraction even among helical strings of the same charge sign. These interacting complex structures exhibit thermodynamic and evolutionary features thought to be peculiar only to living matter such as bifurcations that serve as 'memory marks', self-duplication, metabolic rates in a thermodynamically open system, and non-Hamiltonian dynamics. We examine the salient features of this new complex 'state of soft matter' in light of the autonomy, evolution, progenity and autopoiesis principles used to define life. It is concluded that complex self-organized plasma structures exhibit all the necessary properties to qualify them as candidates for inorganic living matter that may exist in space provided certain conditions allow them to evolve naturally

alpha-helical structural elements within the voltage-sensing domains of a K(+) channel.

Science.gov (United States)

Li-Smerin, Y; Hackos, D H; Swartz, K J

2000-01-01

Voltage-gated K(+) channels are tetramers with each subunit containing six (S1-S6) putative membrane spanning segments. The fifth through sixth transmembrane segments (S5-S6) from each of four subunits assemble to form a central pore domain. A growing body of evidence suggests that the first four segments (S1-S4) comprise a domain-like voltage-sensing structure. While the topology of this region is reasonably well defined, the secondary and tertiary structures of these transmembrane segments are not. To explore the secondary structure of the voltage-sensing domains, we used alanine-scanning mutagenesis through the region encompassing the first four transmembrane segments in the drk1 voltage-gated K(+) channel. We examined the mutation-induced perturbation in gating free energy for periodicity characteristic of alpha-helices. Our results are consistent with at least portions of S1, S2, S3, and S4 adopting alpha-helical secondary structure. In addition, both the S1-S2 and S3-S4 linkers exhibited substantial helical character. The distribution of gating perturbations for S1 and S2 suggest that these two helices interact primarily with two environments. In contrast, the distribution of perturbations for S3 and S4 were more complex, suggesting that the latter two helices make more extensive protein contacts, possibly interfacing directly with the shell of the pore domain.

Antimicrobial peptides: the role of hydrophobicity in the alpha helical structure

Directory of Open Access Journals (Sweden)

Pandurangan Perumal

2013-12-01

Full Text Available The antimicrobial peptides (AMPs are a class of molecule obtained from plants, insects, animals, and humans. These peptides have been classified into five categories: 1. Anionic peptide, 2. Linear alpha helical cationic peptide, 3. Cationic peptide, 4. Anionic and cationic peptides with disulphide bonds, and 5. Anionic and cationic peptide fragments of larger proteins. Factors affecting AMPs are sequence, size, charge, hydrophobicity, amphipathicity, structure and conformation. Synthesis of these peptides is convenient by using solid phase peptide synthesis by using FMOC chemistry protocol. The secondary structures of three synthetic peptides were determined by circular dichroism. Also, it was compared the stability of the α-helical structure and confirmed the percentage of helix of these peptides by using circular dichroism. Some of these AMPs show therapeutic properties like antimicrobial, antiviral, contraceptive, and anticancer. The formulations of some peptides have been entered into the phase I, II, or III of clinical trials. This article to review briefly the sources, classification, factors affecting AMPs activity, synthesis, characterization, mechanism of action and therapeutic concern of AMPs and mainly focussed on percentage of α-helical structure in various medium.

Robust integer and fractional helical modes in the quantum Hall effect

Science.gov (United States)

Ronen, Yuval; Cohen, Yonatan; Banitt, Daniel; Heiblum, Moty; Umansky, Vladimir

2018-04-01

Electronic systems harboring one-dimensional helical modes, where spin and momentum are locked, have lately become an important field of their own. When coupled to a conventional superconductor, such systems are expected to manifest topological superconductivity; a unique phase hosting exotic Majorana zero modes. Even more interesting are fractional helical modes, yet to be observed, which open the route for realizing generalized parafermions. Possessing non-Abelian exchange statistics, these quasiparticles may serve as building blocks in topological quantum computing. Here, we present a new approach to form protected one-dimensional helical edge modes in the quantum Hall regime. The novel platform is based on a carefully designed double-quantum-well structure in a GaAs-based system hosting two electronic sub-bands; each tuned to the quantum Hall effect regime. By electrostatic gating of different areas of the structure, counter-propagating integer, as well as fractional, edge modes with opposite spins are formed. We demonstrate that, due to spin protection, these helical modes remain ballistic over large distances. In addition to the formation of helical modes, this platform can serve as a rich playground for artificial induction of compounded fractional edge modes, and for construction of edge-mode-based interferometers.

α-Helical Structural Elements within the Voltage-Sensing Domains of a K+ Channel

Science.gov (United States)

Li-Smerin, Yingying; Hackos, David H.; Swartz, Kenton J.

2000-01-01

Voltage-gated K+ channels are tetramers with each subunit containing six (S1–S6) putative membrane spanning segments. The fifth through sixth transmembrane segments (S5–S6) from each of four subunits assemble to form a central pore domain. A growing body of evidence suggests that the first four segments (S1–S4) comprise a domain-like voltage-sensing structure. While the topology of this region is reasonably well defined, the secondary and tertiary structures of these transmembrane segments are not. To explore the secondary structure of the voltage-sensing domains, we used alanine-scanning mutagenesis through the region encompassing the first four transmembrane segments in the drk1 voltage-gated K+ channel. We examined the mutation-induced perturbation in gating free energy for periodicity characteristic of α-helices. Our results are consistent with at least portions of S1, S2, S3, and S4 adopting α-helical secondary structure. In addition, both the S1–S2 and S3–S4 linkers exhibited substantial helical character. The distribution of gating perturbations for S1 and S2 suggest that these two helices interact primarily with two environments. In contrast, the distribution of perturbations for S3 and S4 were more complex, suggesting that the latter two helices make more extensive protein contacts, possibly interfacing directly with the shell of the pore domain. PMID:10613917

Role of the Coulomb interaction in the low-frequency density of states of DNA double helices

International Nuclear Information System (INIS)

Garcia, A.E.; Krumhansl, J.A.

1988-01-01

The complete vibrational frequency spectrum of several DNA double-helical oligomers is calculated using established pair potentials. Various cutoff values are used for the range of the Coulomb interactions. At very low frequency the integrated density of states shows a noninteger exponent with values ranging from 0.75 to 1.55, depending on the cutoff value for the Coulomb interactions. We conclude that the cumulative densities of states in those molecules depend more on competing interactions than on various proposed universal laws

DNA-like double helix formed by peptide nucleic acid

DEFF Research Database (Denmark)

Wittung, P; Nielsen, Peter E.; Buchardt, O

1994-01-01

Although the importance of the nucleobases in the DNA double helix is well understood, the evolutionary significance of the deoxyribose phosphate backbone and the contribution of this chemical entity to the overall helical structure and stability of the double helix is not so clear. Peptide nucleic...

Chiral Organic Cages with a Triple-Stranded Helical Structure Derived from Helicene.

Science.gov (United States)

Malik, Abaid Ullah; Gan, Fuwei; Shen, Chengshuo; Yu, Na; Wang, Ruibin; Crassous, Jeanne; Shu, Mouhai; Qiu, Huibin

2018-02-28

We report the use of helicene with an intrinsic helical molecular structure to prepare covalent organic cages via imine condensation. The organic cages revealed a [3+2]-type architecture containing a triple-stranded helical structure with three helicene units arranged in a propeller-like fashion with the framework integrally twisted. Such structural chirality was retained upon dissolution in organic solvents, as indicated by a strong diastereotopy effect in proton NMR and unique Cotton effects in circular dichroism spectra. Further study on chiral adsorption showed that the chiral organic cages possess considerable enantioselectivity toward a series of aromatic racemates.

Study on the structure optimization scheme design of a double-tube once-through steam

International Nuclear Information System (INIS)

Wei, Xinyu; Wu, Shifa; Wang, Pengfei; Zhao, Fuyu

2016-01-01

A double-tube once-through steam generator (DOTSG) consisting of an outer straight tube and an inner helical tube is studied in this work. First, the structure of the DOTSG is optimized by considering two different objective functions. The tube length and the total pressure drop are considered as the first and second objective functions, respectively. Because the DOTSG is divided into the subcooled, boiling, and superheated sections according to the different secondary fluid states, the pitches in the three sections are defined as the optimization variables. A multi-objective optimization model is established and solved by particle swarm optimization. The optimization pitch is small in the subcooled region and superheated region, and large in the boiling region. Considering the availability of the optimum structure at power levels below 100% full power, we propose a new operating scheme that can fix the boundaries between the three heat-transfer sections. The operation scheme is proposed on the basis of data for full power, and the operation parameters are calculated at low power level. The primary inlet and outlet temperatures, as well as flow rate and secondary outlet temperature are changed according to the operation procedure

Study on the structure optimization scheme design of a double-tube once-through steam

Energy Technology Data Exchange (ETDEWEB)

Wei, Xinyu; Wu, Shifa; Wang, Pengfei; Zhao, Fuyu [Dept. of Nuclear Science and Technology, Xi' an Jiaotong University, Xi' an (China)

2016-08-15

A double-tube once-through steam generator (DOTSG) consisting of an outer straight tube and an inner helical tube is studied in this work. First, the structure of the DOTSG is optimized by considering two different objective functions. The tube length and the total pressure drop are considered as the first and second objective functions, respectively. Because the DOTSG is divided into the subcooled, boiling, and superheated sections according to the different secondary fluid states, the pitches in the three sections are defined as the optimization variables. A multi-objective optimization model is established and solved by particle swarm optimization. The optimization pitch is small in the subcooled region and superheated region, and large in the boiling region. Considering the availability of the optimum structure at power levels below 100% full power, we propose a new operating scheme that can fix the boundaries between the three heat-transfer sections. The operation scheme is proposed on the basis of data for full power, and the operation parameters are calculated at low power level. The primary inlet and outlet temperatures, as well as flow rate and secondary outlet temperature are changed according to the operation procedure.

Diagnostic value of triphasic incremental helical CT in early and progressive gastric carcinoma

International Nuclear Information System (INIS)

Gao Jianbo; Yan Xuehua; Li Mengtai; Guo Hua; Chen Xuejun; Guan Sheng; Zhang Xiefu; Li Shuxin; Yang Xiaopeng

2001-01-01

Objective: To investigate helical CT enhancement characteristics of gastric carcinoma, and the diagnostic value and preoperative staging of gastric carcinoma with triphasic incremental helical CT of the stomach with water-filling method. Methods: Both double-contrast barium examination and triphasic incremental helical CT of the stomach with water-filling method were performed in 46 patients with gastric carcinoma. Results: (1) Among these patients, normal gastric wall exhibited one layered structure in 18 patients, two or three layered structure in 28 patients in the arterial and portal venous phase. (2) Two cases of early stomach cancer showed marked enhancement in the arterial and portal venous phase and obvious attenuation of enhancement in the equilibrium phase. On the contrary, 32 of the 44 advanced gastric carcinoma was showed marked enhancement in the venous phase compared with the arterial phase ( t = 4.226, P < 0.05). (3) The total accuracy of triphasic incremental helical CT in determining TNM-staging was 81.0%. Conclusion: Different types of gastric carcinoma have different enhancement features. Triphases incremental helical CT is more accurate than conventional CT in the preoperative staging of gastric carcinoma

Space confinement and rotation stress induced self-organization of double-helix nanostructure: a nanotube twist with a moving catalyst head.

Science.gov (United States)

Zhao, Meng-Qiang; Zhang, Qiang; Tian, Gui-Li; Huang, Jia-Qi; Wei, Fei

2012-05-22

Inorganic materials with double-helix structure have attracted intensive attention due to not only their elegant morphology but also their amazing morphology-related potential applications. The investigation on the formation mechanism of the inorganic double-helix nanostructure is the first step for the fundamental studies of their materials or physical properties. Herein, we demonstrated the space confinement and rotation stress induced self-organization mechanism of the carbon nanotube (CNT)-array double helices under scanning electron microscopy by directly observing their formation process from individual layered double hydroxide flakes, which is a kind of hydrotalcite-like material composed of positively charged layers and charge-balancing interlayer anions. Space confinement is considered to be the most important extrinsic factor for the formation of CNT-array double helices. Synchronous growth of the CNT arrays oppositely from LDH flakes with space confinement on both sides at the same time is essential for the growth of CNT-array double helices. Coiling of the as-grown CNT arrays into double helices will proceed by self-organization, tending to the most stable morphology in order to release their internal rotation stress. Based on the demonstrated mechanism, effective routes were carried out to improve the selectivity for CNT-array double helices. The work provides a promising method for the fabrication of double-helix nanostructures with their two helices connected at the end by self-assembly.

Folding control in cyclic peptides through N-methylation pattern selection: formation of antiparallel beta-sheet dimers, double reverse turns and supramolecular helices by 3alpha,gamma cyclic peptides.

Science.gov (United States)

Amorín, Manuel; Castedo, Luis; Granja, Juan R

2008-01-01

Peptide foldamers constitute a growing class of nanomaterials with potential applications in a wide variety of chemical, medical and technological fields. Here we describe the preparation and structural characteristics of a new class of cyclic peptide foldamers (3alpha,gamma-CPs) that, depending on their backbone N-methylation patterns and the medium, can either remain as flat rings that dimerize through arrays of hydrogen bonds of antiparallel beta-sheet type, or can fold into twisted double reverse turns that, in the case of double gamma-turns, associate in nonpolar solvents to form helical supramolecular structures. A 3alpha,gamma-CP consists of a number of multiples of a repeat unit made up of four amino acid residues of alternating chirality: three corresponding to alpha-amino acids and one to a gamma-amino acid (a cis-3-aminocycloalkanecarboxylic acid).

Investigation of FIV Characteristics on a Coaxial Double-tube Structure

Energy Technology Data Exchange (ETDEWEB)

Song, Kee Nam; Kim, Yong Wan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Park, Sang Chul [ABLEMAX Co., Seoul (Korea, Republic of)

2009-10-15

A Very High Temperature Gas Cooled Reactor (VHTR) has been selected as a high energy heat source of the order of 950 .deg. C for nuclear hydrogen generation, which can produce hydrogen from water or natural gas. A primary hot gas duct (HGD) as a coaxial double-tube type cross vessel is a key component connecting a reactor pressure vessel and an intermediate heat exchanger in the VHTR. In this study, a structural sizing methodology for the primary HGD of the VHTR is suggested in order to modulate a flow-induced vibration (FIV). And as an example, a structural sizing of the horizontal HGD with a coaxial double-tube structure was carried out using the suggested method. These activities include a decision of the geometric dimensions, a selection of the material, and an evaluation of the strength of the coaxial double-tube type cross vessel components. Also in order to compare the FIV characteristics of the proposed design cases, a fluid-structure interaction (FSI) analysis was carried out using the ADINA code.

Chirality and helicity of poly-benzyl-L-glutamate in liquid crystals and a wave structure that mimics collagen helicity in crimp

Directory of Open Access Journals (Sweden)

Vidal Benedicto de Campos

2001-01-01

Full Text Available Ideal biocompatible polymers must show a mimetic superstructure with biological supra-organization. Collagen-rich structures like tendons and ligaments are materials with various levels of order, from molecules to bundles of fibers, which affect their biomechanical properties and cellular interactions. Poly-benzyl-L-glutamate (PBLG displaying helicity was used here to test the development of wave-like structures as those occurring in collagen fibers. Birefringence of PBLG under various crystallization conditions was studied with a lambda/4 compensator according to Sénarmont. Qualitative observations were plainly sufficient to conclude that the PBLG fibrils were supra-organized helically as a chiral object. During crystallization stretched PBLG formed a helical superstructure with characteristic striation resembling waves (crimp. Supported by optical anisotropy findings, a twisted grain boundary liquid crystal type is proposed as a transition phase in the formation of the PBLG chiral object. A similarity with the wavy organization (crimp of collagen bundles is proposed.

HIFLUX: OBLATE FRCS, DOUBLE HELICES,SPHEROMAKS AND RFPS IN ONE SYSTEM

International Nuclear Information System (INIS)

SCHAFFER, M.J.; BOEDO, J.A.

2003-01-01

OAK-B135 High magnetic flux is required for thermonuclear FRC reactors and, more immediately, to advance the FRC experimental program in general. Oblate FRCs are of special interest because they are predicted to have certain improved MHD stability over elongated FRCs, and oblate FRCs may yield the most compact, magnetically confined fusion reactors. Neither oblate nor high-flux FRCs have been investigated experimentally to date. Our presently proposed technique is to make two high-flux, oppositely-handed plasmas by a pair of large, external, reversed-field pinch (RFP) sources. The plasmas would propagate as two Taylor-relaxed double-helix plasmas, to an oblate main plasma chamber, where they would relax further to a counter-helicity pair of spheromaks, which would finally merge into a single high-flux FRC. A concept for a new experimental facility, HIFLUX, to make and study high-magnetic-flux oblate Field-Reversed Configuration (FRC) plasmas, is described. Similar principles might also enable high flux non-inductive startup of other plasma devices

Conversion from mutual helicity to self-helicity observed with IRIS

Science.gov (United States)

Li, L. P.; Peter, H.; Chen, F.; Zhang, J.

2014-10-01

Context. In the upper atmosphere of the Sun observations show convincing evidence for crossing and twisted structures, which are interpreted as mutual helicity and self-helicity. Aims: We use observations with the new Interface Region Imaging Spectrograph (IRIS) to show the conversion of mutual helicity into self-helicity in coronal structures on the Sun. Methods: Using far UV spectra and slit-jaw images from IRIS and coronal images and magnetograms from SDO, we investigated the evolution of two crossing loops in an active region, in particular, the properties of the Si IV line profile in cool loops. Results: In the early stage two cool loops cross each other and accordingly have mutual helicity. The Doppler shifts in the loops indicate that they wind around each other. As a consequence, near the crossing point of the loops (interchange) reconnection sets in, which heats the plasma. This is consistent with the observed increase of the line width and of the appearance of the loops at higher temperatures. After this interaction, the two new loops run in parallel, and in one of them shows a clear spectral tilt of the Si IV line profile. This is indicative of a helical (twisting) motion, which is the same as to say that the loop has self-helicity. Conclusions: The high spatial and spectral resolution of IRIS allowed us to see the conversion of mutual helicity to self-helicity in the (interchange) reconnection of two loops. This is observational evidence for earlier theoretical speculations. Movie associated with Fig. 1 and Appendix A are available in electronic form at http://www.aanda.org

Computational Prediction of Atomic Structures of Helical Membrane Proteins Aided by EM Maps

Science.gov (United States)

Kovacs, Julio A.; Yeager, Mark; Abagyan, Ruben

2007-01-01

Integral membrane proteins pose a major challenge for protein-structure prediction because only ≈100 high-resolution structures are available currently, thereby impeding the development of rules or empirical potentials to predict the packing of transmembrane α-helices. However, when an intermediate-resolution electron microscopy (EM) map is available, it can be used to provide restraints which, in combination with a suitable computational protocol, make structure prediction feasible. In this work we present such a protocol, which proceeds in three stages: 1), generation of an ensemble of α-helices by flexible fitting into each of the density rods in the low-resolution EM map, spanning a range of rotational angles around the main helical axes and translational shifts along the density rods; 2), fast optimization of side chains and scoring of the resulting conformations; and 3), refinement of the lowest-scoring conformations with internal coordinate mechanics, by optimizing the van der Waals, electrostatics, hydrogen bonding, torsional, and solvation energy contributions. In addition, our method implements a penalty term through a so-called tethering map, derived from the EM map, which restrains the positions of the α-helices. The protocol was validated on three test cases: GpA, KcsA, and MscL. PMID:17496035

Control of Helical Chirality of Ferrocene-Dipeptide Conjugates by the Secondary Structure of Dipeptide Chains.

Science.gov (United States)

Moriuchi, Toshiyuki; Nishiyama, Taiki; Nobu, Masaki; Hirao, Toshikazu

2017-09-18

Controlling helical chirality and creating protein secondary structures in cyclic/acyclic ferrocene-dipeptide bioorganometallic conjugates were achieved by adjusting the conformational flexibility of the dipeptide chains. In systems reported to date, the helical chirality of a conjugate was determined by the absolute configuration of the adjacent amino acid reside. In contrast, it was possible to induce both M- and P-helical chirality, even when the configuration of the adjacent amino acid was the same. It is particularly interesting to note that M-helical chirality was produced in a cyclic ferrocene-dipeptide conjugate composed of the l-Ala-d-Pro-cystamine-d-Pro-l-Ala dipeptide sequence (1), in which a type II β-turn-like secondary structure was established. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Potential Magnetic Field around a Helical Flux-rope Current Structure in the Solar Corona

OpenAIRE

Petrie, G. J. D.

2007-01-01

We consider the potential magnetic field associated with a helical electric line current flow, idealizing the near-potential coronal field within which a highly localized twisted current structure is embedded. It is found that this field has a significant axial component off the helical magnetic axis where there is no current flow, such that the flux winds around the axis. The helical line current field, in including the effects of flux rope writhe, is therefore more topologically complex tha...

After the double helix: Rosalind Franklin's research on Tobacco mosaic virus.

Science.gov (United States)

Creager, Angela N H; Morgan, Gregory J

2008-06-01

Rosalind Franklin is best known for her informative X-ray diffraction patterns of DNA that provided vital clues for James Watson and Francis Crick's double-stranded helical model. Her scientific career did not end when she left the DNA work at King's College, however. In 1953 Franklin moved to J. D. Bernal's crystallography laboratory at Birkbeck College, where she shifted her focus to the three-dimensional structure of viruses, obtaining diffraction patterns of Tobacco mosaic virus (TMV) of unprecedented detail and clarity. During the next five years, while making significant headway on the structural determination of TMV, Franklin maintained an active correspondence with both Watson and Crick, who were also studying aspects of virus structure. Developments in TMV research during the 1950s illustrate the connections in the emerging field of molecular biology between structural studies of nucleic acids and of proteins and viruses. They also reveal how the protagonists of the "race for the double helix" continued to interact personally and professionally during the years when Watson and Crick's model for the double-helical structure of DNA was debated and confirmed.

HANFORD DOUBLE-SHELL TANK THERMAL and SEISMIC PROJECT-ANSYS BENCHMARK ANALYSIS OF SEISMICALLY INDUCED FLUID-STRUCTURE INTERACTION IN A HANFORD DOUBLE-SHELL PRIMARY TANK

International Nuclear Information System (INIS)

MACKEY, T.C.

2006-01-01

M and D Professional Services, Inc. (M and D) is under subcontract to Pacific Northwest National Laboratories (PNNL) to perform seismic analysis of the Hanford Site Double-Shell Tanks (DSTs) in support of a project entitled ''Double-Shell Tank (DSV Integrity Project-DST Thermal and Seismic Analyses)''. The overall scope of the project is to complete an up-to-date comprehensive analysis of record of the DST System at Hanford in support of Tri-Party Agreement Milestone M-48-14. The work described herein was performed in support of the seismic analysis of the DSTs. The thermal and operating loads analysis of the DSTs is documented in Rinker et al. (2004). The overall seismic analysis of the DSTs is being performed with the general-purpose finite element code ANSYS. The overall model used for the seismic analysis of the DSTs includes the DST structure, the contained waste, and the surrounding soil. The seismic analysis of the DSTs must address the fluid-structure interaction behavior and sloshing response of the primary tank and contained liquid. ANSYS has demonstrated capabilities for structural analysis, but the capabilities and limitations of ANSYS to perform fluid-structure interaction are less well understood. The purpose of this study is to demonstrate the capabilities and investigate the limitations of ANSYS for performing a fluid-structure interaction analysis of the primary tank and contained waste. To this end, the ANSYS solutions are benchmarked against theoretical solutions appearing in BNL 1995, when such theoretical solutions exist. When theoretical solutions were not available, comparisons were made to theoretical solutions of similar problems and to the results from Dytran simulations. The capabilities and limitations of the finite element code Dytran for performing a fluid-structure interaction analysis of the primary tank and contained waste were explored in a parallel investigation (Abatt 2006). In conjunction with the results of the global ANSYS

Magnetic field structure near the plasma boundary in helical systems and divertor tokamaks

International Nuclear Information System (INIS)

Nagasaki, Kazunobu; Itoh, Kimitaka

1990-02-01

Magnetic field structure of the scrape off layer (SOL) region in both helical systems and divertor tokamaks is studied numerically by using model fields. The connection length of the field line to the wall is calculated. In helical systems, the connection length, L, has a logarithmic dependence on the distance from the outermost magnetic surface or that from the residual magnetic islands. The effect of axisymmetric fields on the field structure is also determined. In divertor tokamaks, the connection length also has logarithmic properties near the separatrix. Even when the perturbations, which resonate to rational surfaces near the plasma boundary, are added, logarithmic properties still remain. We compare the connection length of torsatron/helical-heliotron systems with that of divertor tokamaks. It is found that the former is shorter than the latter by one order magnitude with similar aspect ratio. (author)

Determining the helicity structure of third generation resonances

International Nuclear Information System (INIS)

Papaefstathiou, Andreas

2011-11-01

We examine methods that have been proposed for determining the helicity structure of decays of new resonances to third generation quarks and/or leptons. We present analytical and semi-analytical predictions and assess the applicability of the relevant variables in realistic reconstruction scenarios using Monte Carlo-generated events, including the effects of QCD radiation and multiple parton interactions, combinatoric ambiguities and fast detector simulation. (orig.)

Preparation of CuO nanoparticles by thermal decomposition of double-helical dinuclear copper(II Schiff-base complexes

Directory of Open Access Journals (Sweden)

Aliakbar Dehno Khalaji

2015-12-01

Full Text Available In this paper, two double helical dinuclear copper(II complexes of bis-N,O-bidentate Schiff base ligands bis(3-methoxy-N-salicylidene-4,4'-diaminodiphenylsulfone (L1 and bis(5-bromo-N-salicylidene-4,4'-diaminodiphenylsulfone (L2 were prepared and characterized by elemental analyses (CHN, as well as thermal analysis. Elemental analyses (CHN suggested that the reaction between ligands and copper salt has been occurred in 1:1 molar ratio. In these complexes the Schiff base ligands behaves as an anionic and bis-bidentate chelate and is coordinated to the copper(II ion via two phenolic oxygen and two iminic nitrogen atoms. In these double helical dinuclear complexes, each copper(II center has a pseudo-tetrahedral coordination sphere two-wrapped ligands. Thermal analysis of ligands and their complexes were studied in the range of room temperature to 750 °C with a heating rate of 10 °C min-1. TG plots show that the ligands and their complexes are thermally decomposed via 2 and 3 thermal steps, respectively. In addition, the complexes thermally decomposed in air at 520 °C for 3 h. The obtained solids characterized by Fourier transform infrared spectroscopy (FT-IR, X-ray powder diffraction (XRD and transmission electron microscopy (TEM. The X-ray pattern result shows that the CuO nanoparticles are pure and single phase. The TEM result shows the as prepared CuO nanoparticles were very small and similar shape with particle size about

Numerical modeling of formation of helical structures in reversed-field-pinch plasma

International Nuclear Information System (INIS)

Mizuguchi, N.; Ichiguchi, K.; Todo, Y.; Sanpei, A.; Oki, K.; Masamune, S.; Himura, H.

2012-11-01

Nonlinear three-dimensional magnetohydrodynamic(MHD) simulations have been executed for the low-aspect-ratio reversed-field-pinch (RFP) plasma to reveal the physical mechanism of the formation processes of helical structures. The simulation results show a clear formation of n=4 structure as a result of dominant growth of resistive modes, where n represents the toroidal mode number. The resultant relaxed helical state consists of a unique bean-shaped and hollow pressure profile in the poloidal cross section for both cases of resonant and non-resonant triggering instability modes. The results are partially comparable to the experimental observations. The physical mechanisms of those processes are examined. (author)

Helical Birods: An Elastic Model of Helically Wound Double-Stranded Rods

KAUST Repository

Prior, Christopher

2014-03-11

© 2014, Springer Science+Business Media Dordrecht. We consider a geometrically accurate model for a helically wound rope constructed from two intertwined elastic rods. The line of contact has an arbitrary smooth shape which is obtained under the action of an arbitrary set of applied forces and moments. We discuss the general form the theory should take along with an insight into the necessary geometric or constitutive laws which must be detailed in order for the system to be complete. This includes a number of contact laws for the interaction of the two rods, in order to fit various relevant physical scenarios. This discussion also extends to the boundary and how this composite system can be acted upon by a single moment and force pair. A second strand of inquiry concerns the linear response of an initially helical rope to an arbitrary set of forces and moments. In particular we show that if the rope has the dimensions assumed of a rod in the Kirchhoff rod theory then it can be accurately treated as an isotropic inextensible elastic rod. An important consideration in this demonstration is the possible effect of varying the geometric boundary constraints; it is shown the effect of this choice becomes negligible in this limit in which the rope has dimensions similar to those of a Kirchhoff rod. Finally we derive the bending and twisting coefficients of this effective rod.

Particle-in-cell simulation of helical structure onset in plasma fiber with dust grains

International Nuclear Information System (INIS)

Kulhanek, Petr; Bren, David; Kaizr, Vaclav; Pasek, Jan

2002-01-01

Fully three dimensional PIC program package for the helical pinch numerical simulation was developed in our department. Both electromagnetic and gravitational interactions are incorporated into the model. Collisions are treated via Monte Carlo methods. The program package enabled to prove the conditions of onset of spiral and helical structures in the pinch

Numerical Analysis of Helical Pile-Soil Interaction under Compressive Loads

Science.gov (United States)

Polishchuk, A. I.; Maksimov, F. A.

2017-11-01

The results of the field tests of full-scale steel helical piles in clay soils intended for prefabricated temporary buildings foundations are presented in this article. The finite element modeling was used for the evaluation of stress distribution of the clay soil around helical piles. An approach of modeling of the screw-pile geometry has been proposed through the Finite Element Analysis. Steel helical piles with a length of 2.0 m, shaft diameter of 0.108 m and a blade diameter of 0.3 m were used in the experiments. The experiments have shown the efficiency of double-bladed helical piles in the clay soils compared to single-bladed piles. It has been experimentally established that the introduction of the second blade into the pile shaft provides an increase of the bearing capacity in clay soil up to 30% compared to a single-bladed helical pile with similar geometrical dimensions. The numerical results are compared with the measurements obtained by a large scale test and the bearing capacity has been estimated. It has been found that the model results fit the field results. For a double-bladed helical pile it was revealed that shear stresses upon pile loading are formed along the lateral surface forming a cylindrical failure surface.

Crystal structures and thermodynamics/kinetics of Zn(II) coordination polymers with helical chains

Energy Technology Data Exchange (ETDEWEB)

He, Tian [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi’an 710069 (China); Yue, Ke-Fen, E-mail: ykflyy@nwu.edu.cn [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi’an 710069 (China); Zhao, Yi-xing; Chen, San-Ping [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi’an 710069 (China); Zhou, Chun-sheng, E-mail: slzhoucs@126.com.cn [Shaanxi Key Laboratory of Comprehensive Utilization of Tailings Resources, College of Chemical Engineering and Modern Materials, Shangluo University, Shangluo 726000 (China); Yan, Ni [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi’an 710069 (China)

2016-07-15

Solvothermal reactions of Zn(II) acetates and four V-shaped carboxylates ligands in the presence of 1,4-Bis(2-methyl-imidazol-1-yl)butane afforded four interesting Zn(II) coordination polymers with helical chains, namely, {[Zn(bib)(atibdc)]·2H_2O}{sub n} (1), {[Zn(bib)(atbip)]·H_2O}{sub n} (2), {[Zn(bib)(2,2′-tda)]}{sub n} (3) and {[Zn(bib)(5-tbipa)]·EtOH}{sub n} (4), (H{sub 2}atibdc=5-amino-2,4,6-triiodoisophthalic acid, H{sub 2}atbip=5-amino-2,4,6-tribromoisophthalic acid, 2,2′-H{sub 2}tad=2,2′-thiodiacetic acid, 5-H{sub 2}tbipa=5-tert-butyl-isophthalic acid). 1 reveals a 3D chiral framework with three kinds of helical chains along a, b and c axis. 2 shows a 2D step-type chiral framework with right-handed helical chains. 3 displays a wavelike 2D layer network possessing alternate left- and right-handed helical chains. 4 presents a four-connected 3D framework with zigzag and meso-helical chains. The different spacers and substituent group of carboxylic acid ligands may lead to the diverse network structures of 1–4. The fluorescent properties of complexes 1−4 were studied. In addition, the thermal decompositions properties of 1–4 were investigated by simultaneous TG/DTG–DSC technique. The apparent activation energy E and the pre-exponential factor (A) of skeleton collapse for the complexes 1–4 are calculated by the integral Kissinger's method and Ozawa–Doyle's method. The activation energy E (E{sub 1}=209.658 kJ·mol{sup −1}, E{sub 2}=250.037 kJ mol{sup −1}, E{sub 3}=225.300 kJ mol{sup −1}, E{sub 4}=186.529 kJ·mol{sup −1}) demonstrates that the reaction rate of the melting decomposition is slow. The thermodynamic parameters (ΔH{sup ‡}, ΔG{sup ‡} and ΔS{sup ‡}) at the peak temperatures of the DTG curves were also calculated. ΔG{sup ‡}>0 indicates that the skeleton collapse is not spontaneous. ΔH{sub d}>0 suggests that the skeleton collapse is endothermic, corresponding to the intense endothermic peak of the DSC

Triple helical DNA in a duplex context and base pair opening

Science.gov (United States)

Esguerra, Mauricio; Nilsson, Lennart; Villa, Alessandra

2014-01-01

It is fundamental to explore in atomic detail the behavior of DNA triple helices as a means to understand the role they might play in vivo and to better engineer their use in genetic technologies, such as antigene therapy. To this aim we have performed atomistic simulations of a purine-rich antiparallel triple helix stretch of 10 base triplets flanked by canonical Watson–Crick double helices. At the same time we have explored the thermodynamic behavior of a flipping Watson–Crick base pair in the context of the triple and double helix. The third strand can be accommodated in a B-like duplex conformation. Upon binding, the double helix changes shape, and becomes more rigid. The triple-helical region increases its major groove width mainly by oversliding in the negative direction. The resulting conformations are somewhere between the A and B conformations with base pairs remaining almost perpendicular to the helical axis. The neighboring duplex regions maintain a B DNA conformation. Base pair opening in the duplex regions is more probable than in the triplex and binding of the Hoogsteen strand does not influence base pair breathing in the neighboring duplex region. PMID:25228466

Variation in the Helical Structure of Native Collagen

Science.gov (United States)

2014-02-24

notochord were obtained in previous studies [4,10,20–22]. The scaled amplitudes of the central, meridional section of each data set were used to...including helical, structure) from rat tail tendon (collagen type I) and lamprey notochord (collagen type II) show several common features (Figure 5). Of...also a possible consequence of the type II collagen notochord samples being stretched, perhaps to a greater extant then the type I tendon samples to aid

RNAHelix: computational modeling of nucleic acid structures with Watson-Crick and non-canonical base pairs.

Science.gov (United States)

Bhattacharyya, Dhananjay; Halder, Sukanya; Basu, Sankar; Mukherjee, Debasish; Kumar, Prasun; Bansal, Manju

2017-02-01

Comprehensive analyses of structural features of non-canonical base pairs within a nucleic acid double helix are limited by the availability of a small number of three dimensional structures. Therefore, a procedure for model building of double helices containing any given nucleotide sequence and base pairing information, either canonical or non-canonical, is seriously needed. Here we describe a program RNAHelix, which is an updated version of our widely used software, NUCGEN. The program can regenerate duplexes using the dinucleotide step and base pair orientation parameters for a given double helical DNA or RNA sequence with defined Watson-Crick or non-Watson-Crick base pairs. The original structure and the corresponding regenerated structure of double helices were found to be very close, as indicated by the small RMSD values between positions of the corresponding atoms. Structures of several usual and unusual double helices have been regenerated and compared with their original structures in terms of base pair RMSD, torsion angles and electrostatic potentials and very high agreements have been noted. RNAHelix can also be used to generate a structure with a sequence completely different from an experimentally determined one or to introduce single to multiple mutation, but with the same set of parameters and hence can also be an important tool in homology modeling and study of mutation induced structural changes.

Amphipathic alpha-helices and putative cholesterol binding domains of the influenza virus matrix M1 protein are crucial for virion structure organisation.

Science.gov (United States)

Tsfasman, Tatyana; Kost, Vladimir; Markushin, Stanislav; Lotte, Vera; Koptiaeva, Irina; Bogacheva, Elena; Baratova, Ludmila; Radyukhin, Victor

2015-12-02

The influenza virus matrix M1 protein is an amphitropic membrane-associated protein, forming the matrix layer immediately beneath the virus raft membrane, thereby ensuring the proper structure of the influenza virion. The objective of this study was to elucidate M1 fine structural characteristics, which determine amphitropic properties and raft membrane activities of the protein, via 3D in silico modelling with subsequent mutational analysis. Computer simulations suggest the amphipathic nature of the M1 α-helices and the existence of putative cholesterol binding (CRAC) motifs on six amphipathic α-helices. Our finding explains for the first time many features of this protein, particularly the amphitropic properties and raft/cholesterol binding potential. To verify these results, we generated mutants of the A/WSN/33 strain via reverse genetics. The M1 mutations included F32Y in the CRAC of α-helix 2, W45Y and W45F in the CRAC of α-helix 3, Y100S in the CRAC of α-helix 6, M128A and M128S in the CRAC of α-helix 8 and a double L103I/L130I mutation in both a putative cholesterol consensus motif and the nuclear localisation signal. All mutations resulted in viruses with unusual filamentous morphology. Previous experimental data regarding the morphology of M1-gene mutant influenza viruses can now be explained in structural terms and are consistent with the pivotal role of the CRAC-domains and amphipathic α-helices in M1-lipid interactions. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of temperature on DNA double helix: An insight from ...

Indian Academy of Sciences (India)

The three-dimensional structure of DNA contains various sequence-dependent structural information, which control many cellular processes in life, such as replication, transcription, DNA repair, etc. For the above functions, DNA double helices need to unwind or melt locally, which is different from terminal melting, as often ...

6,6″-Dimethyl-2,2':6',2″-terpyridine revisited: new fluorescent silver(I) helicates with in vitro antiproliferative activity via selective nucleoli targeting.

Science.gov (United States)

Fik, Marta A; Gorczyński, Adam; Kubicki, Maciej; Hnatejko, Zbigniew; Fedoruk-Wyszomirska, Agnieszka; Wyszko, Eliza; Giel-Pietraszuk, Małgorzata; Patroniak, Violetta

2014-10-30

6,6″-Dimethyl-2,2':6',2″-terpyridine ligand (L) reacts in equimolar ratio with Ag(I) ions what results in formation of dinuclear double helicates, which differ in terms of framework and complexity in accordance to counterions and solvent applied. Obtained complexes were thoroughly studied in terms of their biological activity, with the positive antiproliferative outcome on three human cancer cell lines: human breast cancer (T47D), human cervical carcinoma (HeLa) and human lung cancer (A-549). Performed DNA binding experiments showed that given Ag(I) species specifically interact with DNA double helix via intercalation and were visualized by confocal microscopy to specifically bind to the nuclei. All newly synthesized helical systems exhibit promising antimicrobial activity against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacterial strains. Spectrophotometric properties were described as fulfilment of structural studies of newly presented complexes confirming their helical structure in solution. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Observation of helical structure in a low energy plasma focus pinch

International Nuclear Information System (INIS)

Rout, R.K.; Shyam, A.

1989-01-01

Helical structure and hot spots were observed in a Mather-type plasma focus operated at 3 KJ of bank energy. The experiments were carried out with the help of a fast optical framing camera and two X-ray pin-hole cameras with different filters. It was observed that initially a conical pinch (with base diameter of 6 mm and length of 14 mm) with temperature of ≅ 10 2 eV was formed. This pinch disintegrated after ≅ 50 ns by a single lobe sausage instability into a central high temperature (≅ 10 3 eV) filament of 1 mm diameter and 8 mm length containing a high emissivity helical structure. This helix is probably responsible for generation of axial magnetic field and relaxation of the focus pinch. Hot spots of high X-ray intensity and temperature (≅ 10 3 eV) were also observed much beyond the filament region. (author)

Induced helical backbone conformations of self-organizable dendronized polymers.

Science.gov (United States)

Rudick, Jonathan G; Percec, Virgil

2008-12-01

Control of function through the primary structure of a molecule presents a significant challenge with valuable rewards for nanoscience. Dendritic building blocks encoded with information that defines their three-dimensional shape (e.g., flat-tapered or conical) and how they associate with each other are referred to as self-assembling dendrons. Self-organizable dendronized polymers possess a flat-tapered or conical self-assembling dendritic side chain on each repeat unit of a linear polymer backbone. When appended to a covalent polymer, the self-assembling dendrons direct a folding process (i.e., intramolecular self-assembly). Alternatively, intermolecular self-assembly of dendrons mediated by noncovalent interactions between apex groups can generate a supramolecular polymer backbone. Self-organization, as we refer to it, is the spontaneous formation of periodic and quasiperiodic arrays from supramolecular elements. Covalent and supramolecular polymers jacketed with self-assembling dendrons self-organize. The arrays are most often comprised of cylindrical or spherical objects. The shape of the object is determined by the primary structure of the dendronized polymer: the structure of the self-assembling dendron and the length of the polymer backbone. It is therefore possible to predictably generate building blocks for single-molecule nanotechnologies or arrays of supramolecules for bottom-up self-assembly. We exploit the self-organization of polymers jacketed with self-assembling dendrons to elucidate how primary structure determines the adopted conformation and fold (i.e., secondary and tertiary structure), how the supramolecules associate (i.e., quaternary structure), and their resulting functions. A combination of experimental techniques is employed to interrogate the primary, secondary, tertiary, and quaternary structure of the self-organizable dendronized polymers. We refer to the process by which we interpolate between the various levels of structural

High-resolution crystal structures of protein helices reconciled with three-centered hydrogen bonds and multipole electrostatics.

Science.gov (United States)

Kuster, Daniel J; Liu, Chengyu; Fang, Zheng; Ponder, Jay W; Marshall, Garland R

2015-01-01

Theoretical and experimental evidence for non-linear hydrogen bonds in protein helices is ubiquitous. In particular, amide three-centered hydrogen bonds are common features of helices in high-resolution crystal structures of proteins. These high-resolution structures (1.0 to 1.5 Å nominal crystallographic resolution) position backbone atoms without significant bias from modeling constraints and identify Φ = -62°, ψ = -43 as the consensus backbone torsional angles of protein helices. These torsional angles preserve the atomic positions of α-β carbons of the classic Pauling α-helix while allowing the amide carbonyls to form bifurcated hydrogen bonds as first suggested by Némethy et al. in 1967. Molecular dynamics simulations of a capped 12-residue oligoalanine in water with AMOEBA (Atomic Multipole Optimized Energetics for Biomolecular Applications), a second-generation force field that includes multipole electrostatics and polarizability, reproduces the experimentally observed high-resolution helical conformation and correctly reorients the amide-bond carbonyls into bifurcated hydrogen bonds. This simple modification of backbone torsional angles reconciles experimental and theoretical views to provide a unified view of amide three-centered hydrogen bonds as crucial components of protein helices. The reason why they have been overlooked by structural biologists depends on the small crankshaft-like changes in orientation of the amide bond that allows maintenance of the overall helical parameters (helix pitch (p) and residues per turn (n)). The Pauling 3.6(13) α-helix fits the high-resolution experimental data with the minor exception of the amide-carbonyl electron density, but the previously associated backbone torsional angles (Φ, Ψ) needed slight modification to be reconciled with three-atom centered H-bonds and multipole electrostatics. Thus, a new standard helix, the 3.6(13/10)-, Némethy- or N-helix, is proposed. Due to the use of constraints from

Heat transfer of a helical double-pipe vertical evaporator: Theoretical analysis and experimental validation

Energy Technology Data Exchange (ETDEWEB)

Colorado-Garrido, D.; Santoyo-Castelazo, E. [Posgrado en Ingenieria y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001. Col. Chamilpa, C.P. 62209 Cuernavaca, Morelos (Mexico); Hernandez, J.A.; Siqueiros, J.; Juarez-Romero, D. [Centro de Investigacion en Ingenieria y Ciencia Aplicadas, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001. Col. Chamilpa, C.P. 62209 Cuernavaca, Morelos (Mexico); Garcia-Valladares, O. [Centro de Investigacion en Energia (CIE), Universidad Nacional Autonoma de Mexico(UNAM), Privada Xochicalco S/N, Temixco, 62580 Morelos (Mexico)

2009-07-15

A predictive model is developed to describe heat transfer and fluid dynamic behavior of a helical double-pipe vertical evaporator used in an absorption heat transformer integrated to a water purification process. The evaporator uses water as working fluid connected in countercurrent. Heat transfer by conduction in the internal tube wall is considered; in addition the change of phase is carried out into the internal tube. The dynamic model considers equations of continuity, momentum and energy in each flow. The discretized governing equations are coupled using an implicit step by step method. The results of this model are compared with the experimental data in steady state, obtaining good agreement in the evaporation process. The model is also evaluated of form dynamic to determine the principal operation variables that affect the evaporator with the main objective to optimize and control the system. (author)

Ac-induced disruption of the doubleDs structure in tomato

NARCIS (Netherlands)

Rommens, Caius M.T.; Biezen, Erik A. van der; Ouwerkerk, Pieter B.F.; Nijkamp, H. John J.; Hille, Jacques

1991-01-01

The maize doubleDs element is stably maintained in the tomato genome. Upon the subsequent introduction of Ac into a plant containing doubleDs, disruption of the doubleDs structure and DNA rearrangements at the site of the doubleDs element were observed. No indications were obtained for excision of

A numerical study of the stabilitiy of helical vortices using vortex methods

International Nuclear Information System (INIS)

Walther, J H; Guenot, M; Machefaux, E; Rasmussen, J T; Chatelain, P; Okulov, V L; Soerensen, J N; Bergdorf, M; Koumoutsakos, P

2007-01-01

We present large-scale parallel direct numerical simulations using particle vortex methods of the instability of the helical vortices. We study the instability of a single helical vortex and find good agreement with inviscid theory. We outline equilibrium configurations for three double helical vortices-similar to those produced by three blade wind turbines. The simulations confirm the stability of the inviscid model, but predict a breakdown of the vortical system due to viscosity

A numerical study of the stabilitiy of helical vortices using vortex methods

Energy Technology Data Exchange (ETDEWEB)

Walther, J H [Department of Mechanical Engineering, Technical University of Denmark, DK-2800 Lyngby (Denmark); Guenot, M [Enginering College in Industrial Systems, FR-17041, La Rochelle (France); Machefaux, E [Enginering College in Industrial Systems, FR-17041, La Rochelle (France); Rasmussen, J T [Department of Mechanical Engineering, Technical University of Denmark, DK-2800 Lyngby (Denmark); Chatelain, P [Computational Laboratory, ETH Zurich, CH-8092 Zurich (Switzerland); Okulov, V L [Department of Mechanical Engineering, Technical University of Denmark, DK-2800 Lyngby (Denmark); Soerensen, J N [Department of Mechanical Engineering, Technical University of Denmark, DK-2800 Lyngby (Denmark); Bergdorf, M [Computational Laboratory, ETH Zurich, CH-8092 Zurich (Switzerland); Koumoutsakos, P [Computational Laboratory, ETH Zurich, CH-8092 Zurich (Switzerland)

2007-07-15

We present large-scale parallel direct numerical simulations using particle vortex methods of the instability of the helical vortices. We study the instability of a single helical vortex and find good agreement with inviscid theory. We outline equilibrium configurations for three double helical vortices-similar to those produced by three blade wind turbines. The simulations confirm the stability of the inviscid model, but predict a breakdown of the vortical system due to viscosity.

Dynamics and deformability of α-, 310- and π-helices

Directory of Open Access Journals (Sweden)

Narwani Tarun Jairaj

2018-01-01

Full Text Available Protein structures are often represented as seen in crystals as (i rigid macromolecules (ii with helices, sheets and coils. However, both definitions are partial because (i proteins are highly dynamic macromolecules and (ii the description of protein structures could be more precise. With regard to these two points, we analyzed and quantified the stability of helices by considering α-helices as well as 310- and π-helices. Molecular dynamic (MD simulations were performed on a large set of 169 representative protein domains. The local protein conformations were followed during each simulation and analyzed. The classical flexibility index (B-factor was confronted with the MD root mean square flexibility (RMSF index. Helical regions were classified according to their level of helicity from high to none. For the first time, a precise quantification showed the percentage of rigid and flexible helices that underlie unexpected behaviors. Only 76.4% of the residues associated with α-helices retain the conformation, while this tendency drops to 40.5% for 310-helices and is never observed for π-helices. α-helix residues that do not remain as an α-helix have a higher tendency to assume β-turn conformations than 310- or π-helices. The 310-helices that switch to the α-helix conformation have a higher B-factor and RMSF values than the average 310-helix but are associated with a lower accessibility. Rare π-helices assume a β-turn, bend and coil conformations, but not α- or 310-helices. The view on π-helices drastically changes with the new DSSP (Dictionary of Secondary Structure of Proteins assignment approach, leading to behavior similar to 310-helices, thus underlining the importance of secondary structure assignment methods.

Electronic Band Structure of Helical Polyisocyanides.

Science.gov (United States)

Champagne, Benoît; Liégeois, Vincent; Fripiat, Joseph G; Harris, Frank E

2017-10-19

Restricted Hartree-Fock computations are reported for a methyl isocyanide polymer (repeating unit -C═N-CH 3 ), whose most stable conformation is expected to be a helical chain. The computations used a standard contracted Gaussian orbital set at the computational levels STO-3G, 3-21G, 6-31G, and 6-31G**, and studies were made for two line-group configurations motivated by earlier work and by studies of space-filling molecular models: (1) A structure of line-group symmetry L9 5 , containing a 9-fold screw axis with atoms displaced in the axial direction by 5/9 times the lattice constant, and (2) a structure of symmetry L4 1 that had been proposed, containing a 4-fold screw axis with translation by 1/4 of the lattice constant. Full use of the line-group symmetry was employed to cause most of the computational complexity to depend only on the size of the asymmetric repeating unit. Data reported include computed bond properties, atomic charge distribution, longitudinal polarizability, band structure, and the convoluted density of states. Most features of the description were found to be insensitive to the level of computational approximation. The work also illustrates the importance of exploiting line-group symmetry to extend the range of polymer structural problems that can be treated computationally.

Stretchable Helical Architecture Inorganic-Organic Hetero Thermoelectric Generator

KAUST Repository

Rojas, Jhonathan Prieto; Singh, Devendra; Conchouso Gonzalez, David; Carreno, Armando Arpys Arevalo; Foulds, Ian G.; Hussain, Muhammad Mustafa

2016-01-01

To achieve higher power output from a thermoelectric generator (TEG), one needs to maintain a larger temperature difference between hot and cold end. In that regard, a stretchable TEG can be interesting to adaptively control the temperature difference. Here we show, the development of simple yet versatile and highly stretchable thermoelectric generators (TEGs), by combining well-known inorganic thermoelectric materials Bismuth Telluride and Antimony Telluride (Bi2Te3 and Sb2Te3) with organic substrates (Off-Stoichiometry Thiol-Enes polymer platform – OSTE, polyimide or paper) and novel helical architecture (double-arm spirals) to achieve over 100% stretchability. First, an OSTE-based TEG design demonstrates higher open circuit voltage generation at 100% strain than at rest, although it exhibits high internal resistance and a relatively complex fabrication process. The second, simpler TEG design, achieves a significant resistance reduction and two different structural substrates (PI and paper) are compared. The paper-based TEG generates 17 nW (ΔT = 75 °C) at 60% strain, which represents more than twice the power generation while at rest (zero strain). On the other hand, polyimide produces more conductive TE films and higher power (~35 nW at ΔT = 75 °C) but due to its higher thermal conductivity, power does not increase at stretch. In conclusion, highly stretchable TEGs can lead to higher temperature gradients (thus higher power generation), given that thermal conductivity of the structural material is low enough. Furthermore, either horizontal or vertical displacement can be achieved with double-arm helical architecture, hence allowing to extend the device to any nearby and mobile heat sink for continuous, effectively higher power generation.

Stretchable Helical Architecture Inorganic-Organic Hetero Thermoelectric Generator

KAUST Repository

Rojas, Jhonathan Prieto

2016-10-26

To achieve higher power output from a thermoelectric generator (TEG), one needs to maintain a larger temperature difference between hot and cold end. In that regard, a stretchable TEG can be interesting to adaptively control the temperature difference. Here we show, the development of simple yet versatile and highly stretchable thermoelectric generators (TEGs), by combining well-known inorganic thermoelectric materials Bismuth Telluride and Antimony Telluride (Bi2Te3 and Sb2Te3) with organic substrates (Off-Stoichiometry Thiol-Enes polymer platform – OSTE, polyimide or paper) and novel helical architecture (double-arm spirals) to achieve over 100% stretchability. First, an OSTE-based TEG design demonstrates higher open circuit voltage generation at 100% strain than at rest, although it exhibits high internal resistance and a relatively complex fabrication process. The second, simpler TEG design, achieves a significant resistance reduction and two different structural substrates (PI and paper) are compared. The paper-based TEG generates 17 nW (ΔT = 75 °C) at 60% strain, which represents more than twice the power generation while at rest (zero strain). On the other hand, polyimide produces more conductive TE films and higher power (~35 nW at ΔT = 75 °C) but due to its higher thermal conductivity, power does not increase at stretch. In conclusion, highly stretchable TEGs can lead to higher temperature gradients (thus higher power generation), given that thermal conductivity of the structural material is low enough. Furthermore, either horizontal or vertical displacement can be achieved with double-arm helical architecture, hence allowing to extend the device to any nearby and mobile heat sink for continuous, effectively higher power generation.

Estimation of strength in different extra Watson-Crick hydrogen bonds in DNA double helices through quantum chemical studies.

Science.gov (United States)

Bandyopadhyay, D; Bhattacharyya, D

2006-10-15

It was shown earlier, from database analysis, model building studies, and molecular dynamics simulations that formation of cross-strand bifurcated or Extra Watson-Crick hydrogen (EWC) bonds between successive base pairs may lead to extra rigidity to DNA double helices of certain sequences. The strengths of these hydrogen bonds are debatable, however, as they do not have standard linear geometry criterion. We have therefore carried out detailed ab initio quantum chemical studies using RHF/6-31G(2d,2p) and B3LYP/6-31G(2p,2d) basis sets to determine strengths of several bent hydrogen bonds with different donor and acceptors. Interaction energy calculations, corrected for the basis set superposition errors, suggest that N-H...O type bent EWC hydrogen bonds are possible along same strands or across the strands between successive base pairs, leading to significant stability (ca. 4-9 kcal/mol). The N-H...N and C-H...O type interactions, however, are not so stabilizing. Hence, consideration of EWC N-H...O H-bonds can lead to a better understanding of DNA sequence directed structural features. Copyright (c) 2006 Wiley Periodicals, Inc.

Helical structures in vertically aligned dust particle chains in a complex plasma

Science.gov (United States)

Hyde, Truell W.; Kong, Jie; Matthews, Lorin S.

2013-05-01

Self-assembly of structures from vertically aligned, charged dust particle bundles within a glass box placed on the lower, powered electrode of a Gaseous Electronics Conference rf reference cell were produced and examined experimentally. Self-organized formation of one-dimensional vertical chains, two-dimensional zigzag structures, and three-dimensional helical structures of triangular, quadrangular, pentagonal, hexagonal, and heptagonal symmetries are shown to occur. System evolution is shown to progress from a one-dimensional chain structure, through a zigzag transition to a two-dimensional, spindlelike structure, and then to various three-dimensional, helical structures exhibiting multiple symmetries. Stable configurations are found to be dependent upon the system confinement, γ2=ω0h/ω0v2 (where ω0h,v are the horizontal and vertical dust resonance frequencies), the total number of particles within a bundle, and the rf power. For clusters having fixed numbers of particles, the rf power at which structural phase transitions occur is repeatable and exhibits no observable hysteresis. The critical conditions for these structural phase transitions as well as the basic symmetry exhibited by the one-, two-, and three-dimensional structures that subsequently develop are in good agreement with the theoretically predicted configurations of minimum energy determined employing molecular dynamics simulations for charged dust particles confined in a prolate, spheroidal potential as presented theoretically by Kamimura and Ishihara [Kamimura and Ishihara, Phys. Rev. EPLEEE81063-651X10.1103/PhysRevE.85.016406 85, 016406 (2012)].

Self-Assembling Peptide Surfactants A6K and A6D Adopt a-Helical Structures Useful for Membrane Protein Stabilization

Directory of Open Access Journals (Sweden)

Furen Zhuang

2011-10-01

Full Text Available Elucidation of membrane protein structures have been greatly hampered by difficulties in producing adequately large quantities of the functional protein and stabilizing them. A6D and A6K are promising solutions to the problem and have recently been used for the rapid production of membrane-bound G protein-coupled receptors (GPCRs. We propose that despite their short lengths, these peptides can adopt α-helical structures through interactions with micelles formed by the peptides themselves. These α-helices are then able to stabilize α-helical motifs which many membrane proteins contain. We also show that A6D and A6K can form β-sheets and appear as weak hydrogels at sufficiently high concentrations. Furthermore, A6D and A6K together in sodium dodecyl sulfate (SDS can form expected β-sheet structures via a surprising α-helical intermediate.

Stiffness versus architecture of single helical polyisocyanopeptides

NARCIS (Netherlands)

Buul, van A.M.; Schwartz, E.; Brocorens, P.; Koepf, M.; Beljonne, D.; Maan, J.C.; Christianen, P.C.M.; Kouwer, P.H.J.; Nolte, R.J.M.; Engelkamp, H.; Blank, K.; Rowan, A.E.

2013-01-01

Helical structures play a vital role in nature, offering mechanical rigidity, chirality and structural definition to biological systems. Little is known about the influence of the helical architecture on the intrinsic properties of polymers. Here, we offer an insight into the nano architecture of

Stochastic field line structures appearing in field line tracing calculations for a helical magnetic limiter on TORE SUPRA

International Nuclear Information System (INIS)

Fuchs, G.; Steffen, B.; Blenski, T.; Grosman, A.; Samain, A.

1985-05-01

The influence on the structure of the magnetic field of a tokamak produced by small helical currents flowing near the plasma in TORE SUPRA was investigated numerically by drawing Poincare plots. The current in the helical conductors, the pitch of the windings, the rotational transform and the plasma pressure have been varied. The topology of the magnetic field line structure is discussed in some detail and simple examples are given for illustration. (orig.)

Measurements of double-helicity asymmetries in inclusive J /ψ production in longitudinally polarized p +p collisions at √{s }=510 GeV

Science.gov (United States)

Adare, A.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Akimoto, R.; Alfred, M.; Apadula, N.; Aramaki, Y.; Asano, H.; Atomssa, E. T.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Bandara, N. S.; Bannier, B.; Barish, K. N.; Bathe, S.; Bazilevsky, A.; Beaumier, M.; Beckman, S.; Belmont, R.; Berdnikov, A.; Berdnikov, Y.; Black, D.; Blau, D. S.; Bok, J. S.; Boyle, K.; Brooks, M. L.; Bryslawskyj, J.; Buesching, H.; Bumazhnov, V.; Campbell, S.; Chen, C.-H.; Chi, C. Y.; Chiu, M.; Choi, I. J.; Choi, J. B.; Chujo, T.; Citron, Z.; Csanád, M.; Csörgő, T.; Danley, T. W.; Datta, A.; Daugherity, M. S.; David, G.; Deblasio, K.; Dehmelt, K.; Denisov, A.; Deshpande, A.; Desmond, E. J.; Ding, L.; Dion, A.; Diss, P. B.; Do, J. H.; Drees, A.; Drees, K. A.; Durham, J. M.; Durum, A.; Enokizono, A.; En'yo, H.; Esumi, S.; Fadem, B.; Feege, N.; Fields, D. E.; Finger, M.; Finger, M.; Fokin, S. L.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Gal, C.; Gallus, P.; Garg, P.; Ge, H.; Giordano, F.; Glenn, A.; Goto, Y.; Grau, N.; Greene, S. V.; Grosse Perdekamp, M.; Gu, Y.; Gunji, T.; Guragain, H.; Hachiya, T.; Haggerty, J. S.; Hahn, K. I.; Hamagaki, H.; Hamilton, H. F.; Han, S. Y.; Hanks, J.; Hasegawa, S.; Haseler, T. O. S.; Hashimoto, K.; He, X.; Hemmick, T. K.; Hill, J. C.; Hollis, R. S.; Homma, K.; Hong, B.; Hoshino, T.; Hotvedt, N.; Huang, J.; Huang, S.; Ikeda, Y.; Imai, K.; Imazu, Y.; Inaba, M.; Iordanova, A.; Isenhower, D.; Ivanishchev, D.; Jacak, B. V.; Jeon, S. J.; Jezghani, M.; Jia, J.; Jiang, X.; Johnson, B. M.; Joo, E.; Joo, K. S.; Jouan, D.; Jumper, D. S.; Kanda, S.; Kang, J. H.; Kang, J. S.; Kawall, D.; Kazantsev, A. V.; Key, J. A.; Khachatryan, V.; Khanzadeev, A.; Kihara, K.; Kim, C.; Kim, D. H.; Kim, D. J.; Kim, E.-J.; Kim, G. W.; Kim, H.-J.; Kim, M.; Kim, Y. K.; Kimelman, B.; Kistenev, E.; Kitamura, R.; Klatsky, J.; Kleinjan, D.; Kline, P.; Koblesky, T.; Kofarago, M.; Komkov, B.; Koster, J.; Kotov, D.; Kurita, K.; Kurosawa, M.; Kwon, Y.; Lacey, R.; Lajoie, J. G.; Lebedev, A.; Lee, K. B.; Lee, S.; Lee, S. H.; Leitch, M. J.; Leitgab, M.; Li, X.; Lim, S. H.; Liu, M. X.; Lynch, D.; Makdisi, Y. I.; Makek, M.; Manion, A.; Manko, V. I.; Mannel, E.; McCumber, M.; McGaughey, P. L.; McGlinchey, D.; McKinney, C.; Meles, A.; Mendoza, M.; Meredith, B.; Miake, Y.; Mignerey, A. C.; Miller, A. J.; Milov, A.; Mishra, D. K.; Mitchell, J. T.; Miyasaka, S.; Mizuno, S.; Mohanty, A. K.; Montuenga, P.; Moon, T.; Morrison, D. P.; Moukhanova, T. V.; Murakami, T.; Murata, J.; Mwai, A.; Nagamiya, S.; Nagashima, K.; Nagle, J. L.; Nagy, M. I.; Nakagawa, I.; Nakagomi, H.; Nakano, K.; Nattrass, C.; Netrakanti, P. K.; Nihashi, M.; Niida, T.; Nishimura, S.; Nouicer, R.; Novák, T.; Novitzky, N.; Nyanin, A. S.; O'Brien, E.; Ogilvie, C. A.; Orjuela Koop, J. D.; Osborn, J. D.; Oskarsson, A.; Ozawa, K.; Pak, R.; Pantuev, V.; Papavassiliou, V.; Park, J. S.; Park, S.; Pate, S. F.; Patel, L.; Patel, M.; Peng, J.-C.; Perepelitsa, D. V.; Perera, G. D. N.; Peressounko, D. Yu.; Perry, J.; Petti, R.; Pinkenburg, C.; Pinson, R.; Pisani, R. P.; Purschke, M. L.; Rak, J.; Ramson, B. J.; Ravinovich, I.; Read, K. F.; Reynolds, D.; Riabov, V.; Riabov, Y.; Rinn, T.; Riveli, N.; Roach, D.; Rolnick, S. D.; Rosati, M.; Rowan, Z.; Rubin, J. G.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Sako, H.; Samsonov, V.; Sarsour, M.; Sato, S.; Sawada, S.; Schaefer, B.; Schmoll, B. K.; Sedgwick, K.; Seele, J.; Seidl, R.; Sen, A.; Seto, R.; Sett, P.; Sexton, A.; Sharma, D.; Shein, I.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shukla, P.; Sickles, A.; Silva, C. L.; Silvermyr, D.; Singh, B. K.; Singh, C. P.; Singh, V.; Slunečka, M.; Snowball, M.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Sourikova, I. V.; Stankus, P. W.; Stepanov, M.; Stoll, S. P.; Sugitate, T.; Sukhanov, A.; Sumita, T.; Sun, J.; Sziklai, J.; Takahara, A.; Taketani, A.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tieulent, R.; Timilsina, A.; Todoroki, T.; Tomášek, M.; Torii, H.; Towell, C. L.; Towell, M.; Towell, R.; Towell, R. S.; Tserruya, I.; van Hecke, H. W.; Vargyas, M.; Velkovska, J.; Virius, M.; Vrba, V.; Vznuzdaev, E.; Wang, X. R.; Watanabe, D.; Watanabe, Y.; Watanabe, Y. S.; Wei, F.; Whitaker, S.; White, A. S.; Wolin, S.; Woody, C. L.; Wysocki, M.; Xia, B.; Xue, L.; Yalcin, S.; Yamaguchi, Y. L.; Yanovich, A.; Yoo, J. H.; Yoon, I.; Younus, I.; Yu, H.; Yushmanov, I. E.; Zajc, W. A.; Zelenski, A.; Zhou, S.; Zou, L.; Phenix Collaboration

2016-12-01

We report the double-helicity asymmetry, ALL J /ψ, in inclusive J /ψ production at forward rapidity as a function of transverse momentum pT and rapidity |y |. The data analyzed were taken during √{s }=510 GeV longitudinally polarized p +p collisions at the Relativistic Heavy Ion Collider in the 2013 run using the PHENIX detector. At this collision energy, J /ψ particles are predominantly produced through gluon-gluon scatterings, thus ALL J /ψ is sensitive to the gluon polarization inside the proton. We measured ALL J /ψ by detecting the decay daughter muon pairs μ+μ- within the PHENIX muon spectrometers in the rapidity range 1.2 <|y |<2.2 . In this kinematic range, we measured the ALL J /ψ to be 0.012 ±0.010 (stat) ±0.003 (syst). The ALL J /ψ can be expressed to be proportional to the product of the gluon polarization distributions at two distinct ranges of Bjorken x : one at moderate range x ≈5 ×10-2 where recent data of jet and π0 double helicity spin asymmetries have shown evidence for significant gluon polarization, and the other one covering the poorly known small-x region x ≈2 ×10-3. Thus our new results could be used to further constrain the gluon polarization for x <5 ×10-2.

Helicity in proton–proton elastic scattering and the spin structure of the pomeron

Directory of Open Access Journals (Sweden)

Carlo Ewerz

2016-12-01

Full Text Available We discuss different models for the spin structure of the nonperturbative pomeron: scalar, vector, and rank-2 symmetric tensor. The ratio of single-helicity-flip to helicity-conserving amplitudes in polarised high-energy proton–proton elastic scattering, known as the complex r5 parameter, is calculated for these models. We compare our results to experimental data from the STAR experiment. We show that the spin-0 (scalar pomeron model is clearly excluded by the data, while the vector pomeron is inconsistent with the rules of quantum field theory. The tensor pomeron is found to be perfectly consistent with the STAR data.

Beta-helical polymers from isocyanopeptides

NARCIS (Netherlands)

Cornelissen, J.J.L.M.; Donners, J.J.J.M.; Gelder, de R.; Graswinckel, W.S.; Metselaar, G.A.; Rowan, A.E.; Sommerdijk, N.A.J.M.; Nolte, R.J.M.

2001-01-01

Polymerization of isocyanopeptides results in the formation of high molecular mass polymers that fold in a proteinlike fashion to give helical strands in which the peptide chains are arranged in ß-sheets. The ß-helical polymers retain their structure in water and unfold in a cooperative process at

Assembly of alginate microfibers to form a helical structure using micromanipulation with a magnetic field

International Nuclear Information System (INIS)

Sun, Tao; Huang, Qiang; Shi, Qing; Wang, Huaping; Li, Pengyun; Fukuda, Toshio; Hu, Chengzhi; Nakajima, Masahiro

2016-01-01

Helical structures assembled using alginate microfibers have a promising spatial architecture mimicking in vivo vessels for culturing vascular cells. However, the helical structure can only be assembled at the macroscale, since a microassembly-based approach has not yet been developed. In this paper, we propose a magnetic-field-based micromanipulation method to fabricate a helical microstructure. By microfluidic spinning, alginate microfibers encapsulating magnetic nanoparticles are synthesized to enable the control of an electromagnetic needle (EMN). We developed a microrobotic system to actuate a micropipette to fix a free end of the microfiber, and then move the EMN to reel the microfiber around a micropillar. The motion of the EMN is guided using an upright microscope and a side-view camera. Because of the limitation of operation space, a spacer sleeve was designed to keep the tip of the EMN attracted to the microfiber, and simultaneously to keep the other part of the EMN isolated from the microfiber. To ensure the availability of the microfiber for continuously coiling, we enable the EMN tip to slide on the surface of the microfiber without changing the tensioning of the microfiber for positioning control. Furthermore, stable and repeatable micromanipulation was achieved to form multi-turn microfiber coils based on the motion planning of the EMN. Finally, we successfully fabricated a helical microstructure that can be applied in vascular tissue engineering in the future. (paper)

Measurements of double-helicity asymmetries in inclusive $J/\\psi$ production in longitudinally polarized $p+p$ collisions at $\\sqrt{s}=510$ GeV

OpenAIRE

Adare, A.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Akimoto, R.; Alfred, M.; Apadula, N.; Aramaki, Y.; Asano, H.; Atomssa, E. T.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Bandara, N. S.

2016-01-01

We report the double helicity asymmetry, $A_{LL}^{J/\\psi}$, in inclusive $J/\\psi$ production at forward rapidity as a function of transverse momentum $p_T$ and rapidity $|y|$. The data analyzed were taken during $\\sqrt{s}=510$ GeV longitudinally polarized $p$$+$$p$ collisions at the Relativistic Heavy Ion Collider (RHIC) in the 2013 run using the PHENIX detector. At this collision energy, $J/\\psi$ particles are predominantly produced through gluon-gluon scatterings, thus $A_{LL}^{J/\\psi}$ is ...

General architecture of the alpha-helical globule.

Science.gov (United States)

Murzin, A G; Finkelstein, A V

1988-12-05

A model is presented for the arrangement of alpha-helices in globular proteins. In the model, helices are placed on certain ribs of "quasi-spherical" polyhedra. The polyhedra are chosen so as to allow the close packing of helices around a hydrophobic core and to stress the collective interactions of the individual helices. The model predicts a small set of stable architectures for alpha-helices in globular proteins and describes the geometries of the helix packings. Some of the predicted helix arrangements have already been observed in known protein structures; others are new. An analysis of the three-dimensional structures of all proteins for which co-ordinates are available shows that the model closely approximates the arrangements and packing of helices actually observed. The average deviations of the real helix axes from those in the model polyhedra is +/- 20 degrees in orientation and +/- 2 A in position (1 A = 0.1 nm). We also show that for proteins that are not homologous, but whose helix arrangements are described by the same polyhedron, the root-mean-square difference in the position of the C alpha atoms in the helices is 1.6 to 3.0 A.

New helical-shape magnetic pole design for Magnetic Lead Screw enabling structure simplification

DEFF Research Database (Denmark)

Lu, Kaiyuan; Xia, Yongming; Wu, Weimin

2015-01-01

Magnetic lead screw (MLS) is a new type of high performance linear actuator that is attractive for many potential applications. The main difficulty of the MLS technology lies in the manufacturing of its complicated helical-shape magnetic poles. Structure simplification is, therefore, quite...

Cryogenic structural material and design of support structures for the Large Helical Device

International Nuclear Information System (INIS)

Nishimura, Arata; Imagawa, Shinsaku; Tamura, Hitoshi

1997-01-01

This paper describes a short history of material selection for the cryogenic support structures for the Large Helical Device (LHD) which has superconducting coils. Since the support structures are cooled down to 4.4 K together with the coils, SUS 316 was chosen because of its stable austenitic phase, sufficient mechanical properties at cryogenic temperature and good weldability. Also, outlines of the design and fabrication processes of the support structures are summarized. On the design of the support structures, a deformation analysis was carried out to maintain the proper magnetic field during operation. Afterwards, a stress analysis was performed. During machining and assembling, tolerance was noticed to keep coil positions accurate. Special welding grooves and fabrication processes were considered and achieved successfully. Finally, a cryogenic supporting post which sustains the cryogenic structures and superconducting coils is presented. CFRP was used in this specially developed supporting post to reduce the heat conduction from ambient 300 K structures. (author)

Sharp kink of DNA at psoralen-cross-link site deduced from crystal structure of psoralen-thymine monoadduct

International Nuclear Information System (INIS)

Kim, S.H.; Peckler, S.; Graves, B.; Kanne, D.; Rapoport, H.; Hearst, J.E.

1983-01-01

Light-induced cross-linking of double-stranded nucleic acids by psoralens has been exploited to locate, in vivo or in vitro, those double-helical regions of DNA or RNA that can accommodate any structural changes caused by the psoralen cross-links. To determine three-dimensional structural parameters of the cross-link, we have solved the crystal structure of the psoralen-thymine monoadduct formed in photoreaction between calf thymus DNA and 8-methoxypsoralen (8MOP). There are eight possible configurations for psoralen-thymine monoadducts and 64 for diadducts. We describe here the structural details of a psoralen-thymine monoadduct obtained in a biological environment and the consequences of the photo-cross-link between 8MOP and double-helical DNA

Helical self-organization and hierarchical self-assembly of an oligoheterocyclic pyridine-pyridazine strand into extended supramolecular fibers.

Science.gov (United States)

Cuccia, Louis A; Ruiz, Eliseo; Lehn, Jean-Marie; Homo, Jean-Claude; Schmutz, Marc

2002-08-02

The synthesis and characterization of an alternating pyridine-pyridazine strand comprising thirteen heterocycles are described. Spontaneous folding into a helical secondary structure is based on a general molecular self-organization process enforced by the conformational information encoded within the primary structure of the molecular strand itself. Conformational control based on heterocyclic "helicity codons" illustrates a strategy for designing folding properties into synthetic oligomers (foldamers). Strong intermolecular interactions of the highly ordered lock-washer subunits of compound 3 results in hierarchical supramolecular self-assembly into protofibrils and fibrils. Compound 3 also forms mechanically stable two-dimensional Langmuir-Blodgett and cast thin films.

Hydrodynamic studies of CNT nanofluids in helical coil heat exchanger

Science.gov (United States)

Babita; Sharma, S. K.; Mital Gupta, Shipra; Kumar, Arinjay

2017-12-01

Helical coils are extensively used in several industrial processes such as refrigeration systems, chemical reactors, recovery processes etc to accommodate a large heat transfer area within a smaller space. Nanofluids are getting great attention due to their enhanced heat transfer capability. In heat transfer equipments, pressure drop is one of the major factors of consideration for pumping power calculations. So, the present work is aimed to study hydrodynamics of CNT nanofluids in helical coils. In this study, pressure drop characteristics of CNT nanofluid flowing inside horizontal helical coils are investigated experimentally. The helical coil to tube diameter was varied from 11.71 to 27.34 keeping pitch of the helical coil constant. Double distilled water was used as basefluid. SDBS and GA surfactants were added to stablilize CNT nanofluids. The volumetric fraction of CNT nanofluid was varied from 0.003 vol% to 0.051 vol%. From the experimental data, it was analyzed that the friction factor in helical coils is greater than that of straight tubes. Concentration of CNT in nanofluids also has a significant influence on the pressure drop/friction factor of helical coils. At a constant concentration of CNT, decreasing helical coil to tube diameter from 27.24 to 11.71, fanning friction factor of helical coil; f c increases for a constant value of p/d t. This increase in the value of fanning friction factor can be attributed to the secondary flow of CNT nanofluid in helical coils.

Dynamic and Progressive Control of DNA Origami Conformation by Modulating DNA Helicity with Chemical Adducts.

Science.gov (United States)

Chen, Haorong; Zhang, Hanyu; Pan, Jing; Cha, Tae-Gon; Li, Shiming; Andréasson, Joakim; Choi, Jong Hyun

2016-05-24

DNA origami has received enormous attention for its ability to program complex nanostructures with a few nanometer precision. Dynamic origami structures that change conformation in response to environmental cues or external signals hold great promises in sensing and actuation at the nanoscale. The reconfiguration mechanism of existing dynamic origami structures is mostly limited to single-stranded hinges and relies almost exclusively on DNA hybridization or strand displacement. Here, we show an alternative approach by demonstrating on-demand conformation changes with DNA-binding molecules, which intercalate between base pairs and unwind DNA double helices. The unwinding effect modulates the helicity mismatch in DNA origami, which significantly influences the internal stress and the global conformation of the origami structure. We demonstrate the switching of a polymerized origami nanoribbon between different twisting states and a well-constrained torsional deformation in a monomeric origami shaft. The structural transformation is shown to be reversible, and binding isotherms confirm the reconfiguration mechanism. This approach provides a rapid and reversible means to change DNA origami conformation, which can be used for dynamic and progressive control at the nanoscale.

Light scattering measurements supporting helical structures for chromatin in solution.

Science.gov (United States)

Campbell, A M; Cotter, R I; Pardon, J F

1978-05-01

Laser light scattering measurements have been made on a series of polynucleosomes containing from 50 to 150 nucleosomes. Radii of gyration have been determined as a function of polynucleosome length for different ionic strength solutions. The results suggest that at low ionic strength the chromatin adopts a loosely helical structure rather than a random coil. The helix becomes more regular on increasing the ionic strength, the dimension resembling those proposed by Finch and Klug for their solenoid model.

Helicity-flip in particle production on nuclei

International Nuclear Information System (INIS)

Faeldt, G.

1977-01-01

Coherent nuclear production processes are generally analyzed assuming helicity conserving production amplitudes. In view of the uncertainties of the actual helicity structure this could be a dangerous assumption. It is shown that helicity-flip contributions might be part of the explanation of the small effective (pππ)-nucleon cross sections observed in coherent production. (Auth.)

Fifty years of coiled-coils and alpha-helical bundles: a close relationship between sequence and structure.

Science.gov (United States)

Parry, David A D; Fraser, R D Bruce; Squire, John M

2008-09-01

alpha-Helical coiled coils are remarkable for the diversity of related conformations that they adopt in both fibrous and globular proteins, and for the range of functions that they exhibit. The coiled coils are based on a heptad (7-residue), hendecad (11-residue) or a related quasi-repeat of apolar residues in the sequences of the alpha-helical regions involved. Most of these, however, display one or more sequence discontinuities known as stutters or stammers. The resulting coiled coils vary in length, in the number of chains participating, in the relative polarity of the contributing alpha-helical regions (parallel or antiparallel), and in the pitch length and handedness of the supercoil (left- or right-handed). Functionally, the concept that a coiled coil can act only as a static rod is no longer valid, and the range of roles that these structures have now been shown to exhibit has expanded rapidly in recent years. An important development has been the recognition that the delightful simplicity that exists between sequence and structure, and between structure and function, allows coiled coils with specialized features to be designed de novo.

Clinical Significance of "Double-hit" and "Double-protein" expression in Primary Gastric B-cell Lymphomas.

Science.gov (United States)

He, Miaoxia; Chen, Keting; Li, Suhong; Zhang, Shimin; Zheng, Jianming; Hu, Xiaoxia; Gao, Lei; Chen, Jie; Song, Xianmin; Zhang, Weiping; Wang, Jianmin; Yang, Jianmin

2016-01-01

Primary gastric B-cell lymphoma is the second most common malignancy of the stomach. There are many controversial issues about its diagnosis, treatment and clinical management. "Double-hit" and "double-protein" involving gene rearrangement and protein expression of c-Myc and bcl2/bcl6 are the most used terms to describe DLBCL poor prognostic factors in recent years. However, very little is known about the role of these prognostic factors in primary gastric B-cell lymphomas. This study aims to obtain a molecular pathology prognostic model of gastric B-cell lymphoma for clinical stratified management by evaluating how the "double-hit" and "double-protein" in tumor cells as well as microenvironmental reaction of tumor stromal tissue affect clinical outcome in primary gastric B-cell lymphomas. Data and tissues of 188 cases diagnosed with gastric B-cell lymphomas were used in this study. Tumor tissue microarray (TMA) of formalin fixed and paraffin embedded (FFPE) tissues was constructed for fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) analysis with a serial of biomarkers containing MYC, BCL2, BCL6, CD31, SPARC, CD10, MUM1 and Ki-67. Modeled period analysis was used to estimate 3-year and 5-year overall survival (OS) and disease-free survival (DFS) distributions. There was no definite "double-hit" case though the gene rearrangement of c-Myc (5.9%), bcl2 (0.1%) and bcl6 (7.4%) was found in gastric B-cell lymphomas. The gene amplification or copy gains of c-Myc (10.1%), bcl-2 (17.0%) and bcl-6 (0.9%) were present in these lymphomas. There were 12 cases of the lymphomas with the "double-protein" expression of MYC and BCL2/BCL6. All patients with "double-protein" gastric B-cell lymphomas had poor outcome compared with those without. More importantly, "MYC-BCL2-BCL6" negative group of gastric B-cell lymphoma patients had favorable clinical outcome regardless clinical stage, pathological types and therapeutic modalities. And the similar better

Polarization Selectivity of Artificial Anisotropic Structures Based on DNA-Like Helices

International Nuclear Information System (INIS)

Semchenko, I. V.; Khakhomov, S. A.; Balmakov, A. P.

2010-01-01

Currently, 2D and 3D structures of different symmetries can be formed from DNA molecules. The electromagnetic properties of this new natural chiral material can be changed by metalizing DNA. Spatial structures of this type can be used in nanotechnology to prepare metamaterials for the far-UV region. It is shown by the example of an octahedron and a cube composed of DNA-like helices that these structures may exhibit polarization selectivity to electromagnetic radiation. In addition, it is suggested that the effect of the polarization selectivity of DNA-like artificial structures may also occur in the soft X-ray region for all living organisms in nature due to the universal DNA form.

ICRF heating on helical devices

International Nuclear Information System (INIS)

Rasmussen, D.A.; Lyon, J.F.; Hoffman, D.J.; Murakami, M.; England, A.C.; Wilgen, J.B.; Jaeger, E.F.; Wang, C.; Batchelor, D.B.

1995-01-01

Ion cyclotron range of frequency (ICRF) heating is currently in use on CHS and W7-AS and is a major element of the heating planned for steady state helical devices. In helical devices, the lack of a toroidal current eliminates both disruptions and the need for ICRF current drive, simplifying the design of antenna structures as compared to tokamak applications. However the survivability of plasma facing components and steady state cooling issues are directly applicable to tokamak devices. Results from LHD steady state experiments should be available on a time scale to strongly influence the next generation of steady state tokamak experiments. The helical plasma geometry provides challenges not faced with tokamak ICRF heating, including the potential for enhanced fast ion losses, impurity accumulation, limited access for antenna structures, and open magnetic field lines in the plasma edge. The present results and near term plans provide the basis for steady state ICRF heating of larger helical devices. An approach which includes direct electron, mode conversion, ion minority and ion Bernstein wave heating addresses these issues

ICRF heating on helical devices

International Nuclear Information System (INIS)

Rasmussen, D.A.; Lyon, J.F.; Hoffman, D.J.

1995-01-01

Ion cyclotron range of frequency (ICRF) heating is currently in use on CHS and W7AS and is a major element of the heating planned for steady state helical devices. In helical devices, the lack of a toroidal current eliminates both disruptions and the need for ICRF current drive, simplifying the design of antenna structures as compared to tokamak applications. However the survivability of plasma facing components and steady state cooling issues are directly applicable to tokamak devices. Results from LHD steady state experiments should be available on a time scale to strongly influence the next generation of steady state tokamak experiments. The helical plasma geometry provides challenges not faced with tokamak ICRF heating, including the potential for enhanced fast ion losses, impurity accumulation, limited access for antenna structures, and open magnetic field lines in the plasma edge. The present results and near term plans provide the basis for steady state ICRF heating of larger helical devices. An approach which includes direct electron, mode conversion, ion minority and ion Bernstein wave heating addresses these issues

The final inclusive and semi-inclusive longitudinal double-spin asymmetries at HERMES. Extraction of quark helicity distributions of the nucleon from deep-inelastic scattering

Energy Technology Data Exchange (ETDEWEB)

Kravchenko, Polina

2010-10-15

The thesis focuses on two aspects of the HERMES data analysis: the measurement of the semi-inclusive double spin asymmetries and the extraction of quark helicity distributions and quark polarizations of the nucleon from deep-inelastic scattering, as a possible interpretation of the HERMES data. The asymmetries are presented using all possible and accessible information about the HERMES data, including the latest systematic studies provided during the last years by HERMES collaboration. (orig.)

Stimuli-Directed Helical Chirality Inversion and Bio-Applications

Directory of Open Access Journals (Sweden)

Ziyu Lv

2016-08-01

Full Text Available Helical structure is a sophisticated ubiquitous motif found in nature, in artificial polymers, and in supramolecular assemblies from microscopic to macroscopic points of view. Significant progress has been made in the synthesis and structural elucidation of helical polymers, nevertheless, a new direction for helical polymeric materials, is how to design smart systems with controllable helical chirality, and further use them to develop chiral functional materials and promote their applications in biology, biochemistry, medicine, and nanotechnology fields. This review summarizes the recent progress in the development of high-performance systems with tunable helical chirality on receiving external stimuli and discusses advances in their applications as drug delivery vesicles, sensors, molecular switches, and liquid crystals. Challenges and opportunities in this emerging area are also presented in the conclusion.

Helical Antimicrobial Sulfono- {gamma} -AApeptides

Energy Technology Data Exchange (ETDEWEB)

Li, Yaqiong; Wu, Haifan; Teng, Peng; Bai, Ge; Lin, Xiaoyang; Zuo, Xiaobing; Cao, Chuanhai; Cai, Jianfeng

2015-06-11

Host-defense peptides (HDPs) such as magainin 2 have emerged as potential therapeutic agents combating antibiotic resistance. Inspired by their structures and mechanism of action, herein we report the fi rst example of antimicrobial helical sulfono- γ - AApeptide foldamers. The lead molecule displays broad-spectrum and potent antimicrobial activity against multi-drug-resistant Gram- positive and Gram-negative bacterial pathogens. Time-kill studies and fl uorescence microscopy suggest that sulfono- γ -AApeptides eradicate bacteria by taking a mode of action analogous to that of HDPs. Clear structure - function relationships exist in the studied sequences. Longer sequences, presumably adopting more-de fi ned helical structures, are more potent than shorter ones. Interestingly, the sequence with less helical propensity in solution could be more selective than the stronger helix-forming sequences. Moreover, this class of antimicrobial agents are resistant to proteolytic degradation. These results may lead to the development of a new class of antimicrobial foldamers combating emerging antibiotic-resistant pathogens.

Helical Confinement Concepts

Energy Technology Data Exchange (ETDEWEB)

Beidler, C; Brakel, R; Burhenn, R; Dinklage, A; Erckmann, V; Feng, Y; Geiger, J; Hartmann, D; Hirsch, M; Jaenicke, R; Koenig, R; Laqua, H P; Maassberg, H; Wagner, F; Weller, A; Wobig, H [Max-Planck Institut fuer Plasmaphysik, EURATOM Association, Greifswald (Germany)

2012-09-15

Stellarators, conceived 1951 by Lyman Spitzer in Princeton, are toroidal devices that confine a plasma in a magnetic field which originates from currents in coils outside the plasma. A plasma current driven by external means, for example by an ohmic transformer, is not required for confinement. Supplying the desired poloidal field component by external coils leads to a helically structured plasma topology. Thus stellarators - or helical confinement devices - are fully three-dimensional in contrast to the toroidal (rotational) symmetry of tokamaks. As stellarators can be free of an inductive current, whose radial distribution depends on the plasma parameters, their equilibrium must not be established via the evolving plasma itself, but to a first order already given by the vacuum magnetic field. They do not need an active control (like positional feedback) and therefore cannot suffer from its failure. The outstanding conceptual advantage of stellarators is the potential of steady state plasma operation without current drive. As there is no need for current drive, the recirculating power is expected to be smaller than in equivalent tokamaks. The lack of a net current avoids current driven instabilities; specifically, no disruptions, no resistive wall modes and no conventional or neoclassical tearing modes appear. Second order pressure-driven currents (Pfirsch-Schlueter, bootstrap) exist but they can be modified and even minimized by the magnetic design. The magnetic configuration of helical devices naturally possesses a separatrix, which allows the implementation of a helically structured divertor for exhaust and impurity control. (author)

Integrated Structural Biology for α-Helical Membrane Protein Structure Determination.

Science.gov (United States)

Xia, Yan; Fischer, Axel W; Teixeira, Pedro; Weiner, Brian; Meiler, Jens

2018-04-03

While great progress has been made, only 10% of the nearly 1,000 integral, α-helical, multi-span membrane protein families are represented by at least one experimentally determined structure in the PDB. Previously, we developed the algorithm BCL::MP-Fold, which samples the large conformational space of membrane proteins de novo by assembling predicted secondary structure elements guided by knowledge-based potentials. Here, we present a case study of rhodopsin fold determination by integrating sparse and/or low-resolution restraints from multiple experimental techniques including electron microscopy, electron paramagnetic resonance spectroscopy, and nuclear magnetic resonance spectroscopy. Simultaneous incorporation of orthogonal experimental restraints not only significantly improved the sampling accuracy but also allowed identification of the correct fold, which is demonstrated by a protein size-normalized transmembrane root-mean-square deviation as low as 1.2 Å. The protocol developed in this case study can be used for the determination of unknown membrane protein folds when limited experimental restraints are available. Copyright © 2018 Elsevier Ltd. All rights reserved.

Phase diagram of structure of radial electric field in helical plasmas

International Nuclear Information System (INIS)

Toda, S.; Itoh, K.

2002-01-01

A set of transport equations in toroidal helical plasmas is analyzed, including the bifurcation of the radial electric field. Multiple solutions of E r for the ambipolar condition induces domains of different electric polarities. A structure of the domain interface is analyzed and a phase diagram is obtained in the space of the external control parameters. The region of the reduction of the anomalous transport is identified. (author)

Helicity and Filament Channels? The Straight Twist!

Science.gov (United States)

Antiochos, Spiro K.

2010-01-01

One of the most important and most puzzling features of the coronal magnetic field is that it appears to have smooth magnetic structure with little evidence for non-potentiality except at special locations, photospheric polarity inversions lines where the non-potentiality is observed as a filament channel. This characteristic feature of the closed-field corona is highly unexpected given that photospheric motions continuously tangle its magnetic field. Although reconnection can eliminate some of the injected structure, it cannot destroy the helicity, which should build up to produce observable complexity. We propose that an inverse cascade process transports the injected helicity from the interior of closed flux regions to their boundaries, polarity inversion lines, creating filament channels. We describe how the helicity is injected and transported and calculate the relevant rates. We argue that one process, helicity transport, can explain both the observed lack and presence of structure in the coronal magnetic field.

The helical tomotherapy thread effect

International Nuclear Information System (INIS)

Kissick, M.W.; Fenwick, J.; James, J.A.; Jeraj, R.; Kapatoes, J.M.; Keller, H.; Mackie, T.R.; Olivera, G.; Soisson, E.T.

2005-01-01

Inherent to helical tomotherapy is a dose variation pattern that manifests as a 'ripple' (peak-to-trough relative to the average). This ripple is the result of helical beam junctioning, completely unique to helical tomotherapy. Pitch is defined as in helical CT, the couch travel distance for a complete gantry rotation relative to the axial beam width at the axis of rotation. Without scattering or beam divergence, an analytical posing of the problem as a simple integral predicts minima near a pitch of 1/n where n is an integer. A convolution-superposition dose calculator (TomoTherapy, Inc.) included all the physics needed to explore the ripple magnitude versus pitch and beam width. The results of the dose calculator and some benchmark measurements demonstrate that the ripple has sharp minima near p=0.86(1/n). The 0.86 factor is empirical and caused by a beam junctioning of the off-axis dose profiles which differ from the axial profiles as well as a long scatter tail of the profiles at depth. For very strong intensity modulation, the 0.86 factor may vary. The authors propose choosing particular minima pitches or using a second delivery that starts 180 deg off-phase from the first to reduce these ripples: 'Double threading'. For current typical pitches and beam widths, however, this effect is small and not clinically important for most situations. Certain extremely large field or high pitch cases, however, may benefit from mitigation of this effect

Stable single helical C- and I-chains inside single-walled carbon nanotubes

International Nuclear Information System (INIS)

Yao Z; Li Y; Jing X D; Meng F S; Zhao X; Li J H; Qiu Z Y; Yuan Q; Wang W X; Bi L; Liu H; Zhang Y P; Liu C J; Zheng S P; Liu B B

2016-01-01

The helicity of stable single helical carbon chains and iodine chains inside single-walled carbon nanotubes (SWCNTs) is studied by calculating the systematic van der Waals interaction energy. The results show that the optimal helical radius increases linearly with increasing tube radius, which produces a constant separation between the chain structure and the tube wall. The helical angle exhibits a ladder-like decrease with increasing tube radius, indicating that a large tube can produce a small helicity in the helical structures. (paper)

Contribution of double scattering to structural coloration in quasiordered nanostructures of bird feathers

Science.gov (United States)

Noh, Heeso; Liew, Seng Fatt; Saranathan, Vinodkumar; Prum, Richard O.; Mochrie, Simon G. J.; Dufresne, Eric R.; Cao, Hui

2010-05-01

We measured the polarization- and angle-resolved optical scattering and reflection spectra of the quasiordered nanostructures in the bird feather barbs. In addition to the primary peak that originates from single scattering, we observed a secondary peak which exhibits depolarization and distinct angular dispersion. We explained the secondary peak in terms of double scattering, i.e., light is scattered successively twice by the structure. The two sequential single-scattering events are considered uncorrelated. Using the Fourier power spectra of the nanostructures obtained from the small-angle x-ray scattering experiment, we calculated the double scattering of light in various directions. The double-scattering spectrum is broader than the single-scattering spectrum, and it splits into two subpeaks at larger scattering angle. The good agreement between the simulation results and the experimental data confirms that double scattering of light makes a significant contribution to the structural color.

Contribution of double scattering to structural coloration in quasiordered nanostructures of bird feathers

Energy Technology Data Exchange (ETDEWEB)

Noh, Heeso; Liew, Seng Fatt; Saranathan, Vinodkumar; Prum, Richard O.; Mochrie, Simon G.J.; Dufresne, Eric R.; Cao, Hui (Yale)

2010-07-28

We measured the polarization- and angle-resolved optical scattering and reflection spectra of the quasiordered nanostructures in the bird feather barbs. In addition to the primary peak that originates from single scattering, we observed a secondary peak which exhibits depolarization and distinct angular dispersion. We explained the secondary peak in terms of double scattering, i.e., light is scattered successively twice by the structure. The two sequential single-scattering events are considered uncorrelated. Using the Fourier power spectra of the nanostructures obtained from the small-angle x-ray scattering experiment, we calculated the double scattering of light in various directions. The double-scattering spectrum is broader than the single-scattering spectrum, and it splits into two subpeaks at larger scattering angle. The good agreement between the simulation results and the experimental data confirms that double scattering of light makes a significant contribution to the structural color.

Observation of Fermi Arc Surface States Induced by Organic Memristive/Memcapacitive Devices with a Double-Helical Polarized Single-Wall Nanotube Membrane for Direct Chelating with Matrix Matelloproteinase-2

Directory of Open Access Journals (Sweden)

E. T. CHEN

2017-07-01

Full Text Available Matrix Matelloproteinase-2 (MMP-2 plays a key role in many diseases. A new type of dual-functioning device was developed for fast, direct ultrasensitive detection of MMP-2. We report a memristive/memcapacitive device with vertex double-helical polarized biomimetic protein nanotubules forming double membranes with potential gradient mimicking mitochondria’s inner double membrane has developed. We also report Fermi arcs with nodes on the surface of the nanostructured membrane was observed at the first time by using a 3D real-time - energy-current dynamic mapping method based on data obtained from the Cyclic Voltammetry (CV method. The memristive/memcapacitive device comprises a cross- linked organic polymer having single-wall cross-bar polarized nanotube self-assembling membrane (SAM on a gold chip, under an applied potential, a pair of vertex double- helical circular current flow induced the Fermi arcs states occurrence and these Fermi arcs promoted a direct chelating with zinc ions of the MMP-2 to become possible without any antibody, tracer, or reagent used at room temperature was accomplished. We observed the pair of Dirac Cones became alignment and strengthened with each other in the presence of MMP-2 compared without MMP-2. The MMP-2 can be detected with ag/mL level sensitivity and the value of Detection of Limits (DOL reached orders of magnitude lower than published reports with simplified procedures by a Chronoamperometry (CA method and a Double Step Chronopotentiometry (DSCPO method using NIST SRM 965A standard human serum, respectively. The results show a feasible application for developing the commercial fast and real-time MMP monitoring devices for various diseases.

Preliminary evaluation of helical CT colonography in detection of colonic diseases compared with double contrast barium enema

International Nuclear Information System (INIS)

Zhai Xiaoli; Zhang Lei; Zhai Renyou; Li Jie; Wang Yajie; Ding Yi

2000-01-01

Objective: To evaluate helical CT colonography in regard to technology principles, limitations, and clinical applications. Methods: Fifty-six patients underwent volume scanning using helical CT. The diseases included adenocarcinoma 39, adenomatous polyp 3, multiple diverticular 7, mucocele of appendix 1, and normal colon 6. All cases had been compared with double contrast barium enema (DCBE), proved by histology except the 6 normal colon and the 7 multiple diverticular. All CTC images were reconstructed using shaded surface display (SSD) on workstation. Then, perspective images such as the ones from DCBE were generated via ray sum. The images could clearly demonstrate the extent and detail of the disorder by using 'CUT' software, 'revolve' function, and zoom. Results: CTC correctly demonstrated 3-5 mm diverticulum, 3 mm ulcer, and 6 mm polyps. Not only show colon straitness clearly, CTC is also very sensitive to demonstrate the stenotic end of masses. In these cases, discovery rate of CTC is 100.0%, the rate of DCBE is 88.6%; CTC is more sensitive than DCBE in cases of tumor nodules. Ray sum can show the boundary of colonic mass extending to both proximal and distal ends, its discovery rate is 62.6%. Accuracy of localization for CTC is 100.0%. Conclusion: CTC is a novel technique for detecting colonic diseases. It is a safe, accurate, and non-invasive means for detection of lesions and is an efficient complement for DCBE. Further development in CTC technique is expected in the future

Structural analysis of compression helical spring used in suspension system

Science.gov (United States)

Jain, Akshat; Misra, Sheelam; Jindal, Arun; Lakhian, Prateek

2017-07-01

The main aim of this work has to develop a helical spring for shock absorber used in suspension system which is designed to reduce shock impulse and liberate kinetic energy. In a vehicle, it increases comfort by decreasing amplitude of disturbances and it improves ride quality by absorbing and dissipating energy. When a vehicle is in motion on a road and strikes a bump, spring comes into action quickly. After compression, spring will attempt to come to its equilibrium state which is on level road. Helical springs can be made lighter with more strength by reducing number of coils and increasing the area. In this research work, a helical spring is modeled and analyzed to substitute the existing steel spring which is used in suspension. By using different materials, stress and deflection of helical spring can be varied. Comparability between existing spring and newly replaced spring is used to verify the results. For finding detailed stress distribution, finite element analysis is used to find stresses and deflection in both the helical springs. Finite element analysis is a method which is used to find proximate solutions of a physical problem defined in a finite domain. In this research work, modeling of spring is accomplished using Solid Works and analysis on Ansys.

Synthesis, structure, and magnetic properties of two 1-D helical coordination polymeric Cu(II) complexes

Science.gov (United States)

Bian, He-Dong; Yang, Xiao-E.; Yu, Qing; Chen, Zi-Lu; Liang, Hong; Yan, Shi-Ping; Liao, Dai-Zheng

2008-01-01

Two helical coordination polymeric copper(II) complexes bearing amino acid Schiff bases HL or HL', which are condensed from 2-hydroxy-1-naphthaldehyde with 2-aminobenzoic acid or L-valine, respectively, have been prepared and characterised by X-ray crystallography. In [CuL] n ( 1) the copper(II) atoms are bridged by syn- anti carboxylate groups giving infinite 1-D right-handed helical chains which are further connected by weak C-H⋯Cu interactions to build a 2-D network. While in [CuL'] n ( 2) the carboxylate group acts as a rare monatomic bridge to connect the adjacent copper(II) atoms leading to the formation of a left-handed helical chain. Magnetic susceptibility measurements indicate that 1 exhibits weak ferromagnetic interactions whereas an antiferromagnetic coupling is established for 2. The magnetic behavior can be satisfactorily explained on the basis of the structural data.

Simulation of plasma double-layer structures

International Nuclear Information System (INIS)

Borovsky, J.E.; Joyce, G.

1982-01-01

Electrostatic plasma double layers are numerically simulated by means of a magnetized 2 1/2-dimensional particle-in-cell method. The investigation of planar double layers indicates that these one-dimensional potential structures are susceptible to periodic disruption by instabilities in the low-potential plasmas. Only a slight increase in the double-layer thickness with an increase in its obliqueness to the magnetic field is observed. Weak magnetization results in the double-layer electric-field alignment of accelerated particles and strong magnetization results in their magnetic-field alignment. The numerial simulations of spatially periodic two-dimensional double layers also exhibit cyclical instability. A morphological invariance in two-dimensional double layers with respect to the degree of magnetization implies that the potential structures scale with Debye lengths rather than with gyroradii. Electron-beam excited electrostatic electron-cyclotron waves and (ion-beam driven) solitary waves are present in the plasmas adjacent to the double layers

Helical filaments

Energy Technology Data Exchange (ETDEWEB)

Barbieri, Nicholas; Lim, Khan; Durand, Magali; Baudelet, Matthieu; Richardson, Martin [Townes Laser Institute, CREOL—The College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816 (United States); Hosseinimakarem, Zahra; Johnson, Eric [Micro-Photonics Laboratory – Center for Optical Material Science, Clemson, Anderson, South Carolina 29634 (United States)

2014-06-30

The shaping of laser-induced filamenting plasma channels into helical structures by guiding the process with a non-diffracting beam is demonstrated. This was achieved using a Bessel beam superposition to control the phase of an ultrafast laser beam possessing intensities sufficient to induce Kerr effect driven non-linear self-focusing. Several experimental methods were used to characterize the resulting beams and confirm the observed structures are laser air filaments.

Three-dimensional structure of a schistosome serpin revealing an unusual configuration of the helical subdomain

Energy Technology Data Exchange (ETDEWEB)

Granzin, Joachim [Institute of Complex Systems, ICS-6: Structural Biochemistry, Forschungszentrum Jülich, 52425 Jülich (Germany); Huang, Ying; Topbas, Celalettin [Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195 (United States); Huang, Wenying [Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195 (United States); Wu, Zhiping [Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195 (United States); Misra, Saurav [Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195 (United States); Hazen, Stanley L. [Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195 (United States); Blanton, Ronald E. [Department of Infectious Diseases, Case Western Reserve University, Cleveland, OH 44190 (United States); Lee, Xavier [Department of Cell Biology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195 (United States); Weiergräber, Oliver H., E-mail: o.h.weiergraeber@fz-juelich.de [Institute of Complex Systems, ICS-6: Structural Biochemistry, Forschungszentrum Jülich, 52425 Jülich (Germany)

2012-06-01

The crystal structure of ShSPI, a serpin from the blood fluke S. haematobium, reveals some peculiar features of the helical subdomain which have not been observed previously in the serpin superfamily. Parasitic organisms are constantly challenged by the defence mechanisms of their respective hosts, which often depend on serine protease activities. Consequently, protease inhibitors such as those belonging to the serpin superfamily have emerged as protective elements that support the survival of the parasites. This report describes the crystal structure of ShSPI, a serpin from the trematode Schistosoma haematobium. The protein is exposed on the surface of invading cercaria as well as of adult worms, suggesting its involvement in the parasite–host interaction. While generally conforming to the well established serpin fold, the structure reveals several distinctive features, mostly concerning the helical subdomain of the protein. It is proposed that these peculiarities are related to the unique biological properties of a small serpin subfamily which is conserved among pathogenic schistosomes.

Analysis of stacking overlap in nucleic acid structures: algorithm and application.

Science.gov (United States)

Pingali, Pavan Kumar; Halder, Sukanya; Mukherjee, Debasish; Basu, Sankar; Banerjee, Rahul; Choudhury, Devapriya; Bhattacharyya, Dhananjay

2014-08-01

RNA contains different secondary structural motifs like pseudo-helices, hairpin loops, internal loops, etc. in addition to anti-parallel double helices and random coils. The secondary structures are mainly stabilized by base-pairing and stacking interactions between the planar aromatic bases. The hydrogen bonding strength and geometries of base pairs are characterized by six intra-base pair parameters. Similarly, stacking can be represented by six local doublet parameters. These dinucleotide step parameters can describe the quality of stacking between Watson-Crick base pairs very effectively. However, it is quite difficult to understand the stacking pattern for dinucleotides consisting of non canonical base pairs from these parameters. Stacking interaction is a manifestation of the interaction between two aromatic bases or base pairs and thus can be estimated best by the overlap area between the planar aromatic moieties. We have calculated base pair overlap between two consecutive base pairs as the buried van der Waals surface between them. In general, overlap values show normal distribution for the Watson-Crick base pairs in most double helices within a range from 45 to 50 Å(2) irrespective of base sequence. The dinucleotide steps with non-canonical base pairs also are seen to have high overlap value, although their twist and few other parameters are rather unusual. We have analyzed hairpin loops of different length, bulges within double helical structures and pseudo-continuous helices using our algorithm. The overlap area analyses indicate good stacking between few looped out bases especially in GNRA tetraloop, which was difficult to quantitatively characterise from analysis of the base pair or dinucleotide step parameters. This parameter is also seen to be capable to distinguish pseudo-continuous helices from kinked helix junctions.

Overview of results from the Large Helical Device

International Nuclear Information System (INIS)

Yamada, H.

2010-11-01

The physical understanding of net-current free helical plasmas has progressed in the Large Helical Device (LHD) since the last Fusion Energy Conference in Geneva, 2008. The experimental results from LHD have promoted detailed physical documentation of features specific to net-current-free 3-D helical plasmas as well as complementary to the tokamak approach. The primary heating source is NBI with a heating power of 23 MW, and ECH with 3.7 MW plays an important role in local heating and power modulation in transport studies. The maximum central density has reached 1.2 x 10 21 m -3 due to the formation of an Internal Diffusion Barrier (IDB) at the magnetic field of 2.5 T. The IDB has been maintained for 3 s by refueling with repetitive pellet injection. The plasma with a central ion temperature reaching 5.6 keV exhibits the formation of an Internal Transport Barrier (ITB). The ion thermal diffusivity decreases to the level predicted by neoclassical transport. This ITB is accompanied by spontaneous toroidal rotation and an Impurity Hole which generates an impurity-free core. Impurity Hole is due to a large outward convection of impurities in spite of the negative radial electric field. The magnitude of the Impurity Hole is enhanced in the magnetic configuration with larger helical ripple and for higher Z impurities. Another mechanism to suppress impurity contamination has been identified at the plasma edge with a stochastic magnetic field. A helical system shares common physics issues with tokamaks such as 3-D equilibria, transport in a stochastic magnetic field, plasma response to a Resonant Magnetic Perturbation (RMP), divertor physics, and the role of radial electric field and meso-scale structure. (author)

Two unique ligand-binding clamps of Rhizopus oryzae starch binding domain for helical structure disruption of amylose.

Directory of Open Access Journals (Sweden)

Ting-Ying Jiang

Full Text Available The N-terminal starch binding domain of Rhizopus oryzae glucoamylase (RoSBD has a high binding affinity for raw starch. RoSBD has two ligand-binding sites, each containing a ligand-binding clamp: a polyN clamp residing near binding site I is unique in that it is expressed in only three members of carbohydrate binding module family 21 (CBM21 members, and a Y32/F58 clamp located at binding site II is conserved in several CBMs. Here we characterized different roles of these sites in the binding of insoluble and soluble starches using an amylose-iodine complex assay, atomic force microscopy, isothermal titration calorimetry, site-directed mutagenesis, and structural bioinformatics. RoSBD induced the release of iodine from the amylose helical cavity and disrupted the helical structure of amylose type III, thereby significantly diminishing the thickness and length of the amylose type III fibrils. A point mutation in the critical ligand-binding residues of sites I and II, however, reduced both the binding affinity and amylose helix disruption. This is the first molecular model for structure disruption of the amylose helix by a non-hydrolytic CBM21 member. RoSBD apparently twists the helical amylose strands apart to expose more ligand surface for further SBD binding. Repeating the process triggers the relaxation and unwinding of amylose helices to generate thinner and shorter amylose fibrils, which are more susceptible to hydrolysis by glucoamylase. This model aids in understanding the natural roles of CBMs in protein-glycan interactions and contributes to potential molecular engineering of CBMs.

In situ structure solution of helical sulphur at 3 GPa and 400 C

International Nuclear Information System (INIS)

Crichton, W.A.; Vaughan, G.B.M.; Mezouar, M.

2001-01-01

The structure of a 2-chain helical form of sulphur with 9 atoms per unit-cell has been determined from powder synchrotron X-ray diffraction data obtained at 3 GPa and 400 C, using a combination of global optimization, simulated annealing and Rietveld refinement techniques. Final refinement of the structure in trigonal space group P3 2 21 (no. 154) results in a = 7.0897(2) A, c = 4.30238(9) A and V = 187.282(10) A 3 . There are two unique S sites per unit cell, the general S1 6c position with x = 0.7727(9), y = 0.3067(11) and z = 0.6105(12) and the S2 3b with x = 0.8755(8) A. Bond length and angle analysis shows S1-S1 = 2.070(4) A and S2-S2 = 2.096(7) A with an helical S1-S1-S1 divalent angle of 102.7(2) and 101.7(3) for S2-S2-S2. The 2 helices formed, contrary to other polymeric sulphur phases (principally, ψ-S), are non-chiral and evidently have repeats along the (001) translation; that is one turn includes each of the 3 equivalent atoms about the 3 2 -screw axis (S1 helix) and vertex (S2) of the cell. This phase, although temperature quenchable, is observed to back transform to a 4.04 A phase at pressures less than 0.5 GPa. It is likely that this phase represents the true form of the phase XII of Vezzoli and Walsh. (orig.)

Kinetic assembly of block copolymers in solution helical cylindrical micelles and patchy nanoparticles

Science.gov (United States)

Zhong, Sheng

There is always an interest to understand how molecules behave under different conditions. One application of this knowledge is to self-assemble molecules into increasingly complex structures in a simple fashion. Self-assembly of amphiphilic block copolymer in solution has produced a large variety of nanostructures through the manipulation in polymer chemistry, assembly environment, and additives. Moreover, some reports suggest the formation of many polymeric assemblies is driven by kinetic process. The goal of this dissertation is to study the influence of kinetics on the assembly of block copolymer. The study shows kinetic control can be a very effective way to make novel polymeric nanostructures. Two examples discussed here are helical cylindrical micelles and patchy nanoparticles. Helical cylindrical micelles are made from the co-assembly of amphiphilic triblock copolymer poly(acrylic acid)-block-poly(methyl acrylate)- block-polystyrene and organoamine molecules in a mixture of tetrahydrofuran (THF) and water (H2O). This system has already shown promise of achieving many assembled structures. The unique aspects about this system are the use of amine molecules to complex with acid groups and the existence of cosolvent system. Application of amine molecules offers a convenient control over assembled morphology and the introduction of PMA-PS selective solvent, THF, promotes the mobility of the polymer chains. In this study, multivalent organoamine molecules, such as diethylenetriamine and triethylenetetramine, are used to interact with block copolymer in THF/water mixture. As expected, the assembled morphologies are dependent on the polymer architecture, selection and quantity of the organoamine molecules, and solution composition. Under the right conditions, unprecedented, multimicrometer-long, supramolecular helical cylindrical micelles are formed. Both single-stranded and double-stranded helices are found in the same system. These helical structures share

Helicity content and tokamak applications of helicity

International Nuclear Information System (INIS)

Boozer, A.H.

1986-05-01

Magnetic helicity is approximately conserved by the turbulence associated with resistive instabilities of plasmas. To generalize the application of the concept of helicity, the helicity content of an arbitrary bounded region of space will be defined. The definition has the virtues that both the helicity content and its time derivative have simple expressions in terms of the poloidal and toroidal magnetic fluxes, the average toroidal loop voltage and the electric potential on the bounding surface, and the volume integral of E-B. The application of the helicity concept to tokamak plasmas is illustrated by a discussion of so-called MHD current drive, an example of a stable tokamak q profile with q less than one in the center, and a discussion of the possibility of a natural steady-state tokamak due to the bootstrap current coupling to tearing instabilities

Signs of helicity in solar prominences and related features

Science.gov (United States)

Martin, S.

This review illustrates several ways to identify the chirality (handedness) of solar prominences (filaments) from their structure and the structure of their surrounding magnetic fields in the chromosphere and corona. For prominences, these structural elements include the axial magnetic field direction, orientation of barbs, and direction of the prominence fine structure. The surrounding structures include the pattern of fibrils beneath the prominences and the pattern of coronal loops above the prominences. These ways of identifying chirality are then interpreted in terms of the formal definitions of helicity to yield a consistent set of one-to-one helicity relationships for all features. The helicity of some prominences can also be independently determined during their eruption by their fine structure, apparent crossings in the line-of-sight of different parts of the same prominence, and by large- scale twist of the prominence structure. Unlike observations of prominences (filaments) observed prior to eruption, in some cases evidence of both signs of helicity are found within the same erupting prominence. This indicates the continued application of forces on the prominences during the eruption process or the possible introduction of force(s) not present during earlier stages of their evolution.

Efficacy of double arterial phase dynamic magnetic resonance imaging with the sensitivity encoding technique versus dynamic multidetector-row helical computed tomography for detecting hypervascular hepatocellular carcinoma

International Nuclear Information System (INIS)

Kumano, Seishi; Okada, Masahiro; Murakami, Takamichi; Uemura, Masahiko; Haraikawa, Toyoaki; Hirata, Masaaki; Kikuchi, Keiichi; Mochizuki, Teruhito; Kim, Tonsok

2009-01-01

The aim of this study was to evaluate the efficacy of double arterial phase dynamic magnetic resonance imaging (MRI) with the sensitivity encoding technique (SENSE dynamic MRI) for detection of hypervascular hepatocellular carcinoma (HCC) in comparison with double arterial phase dynamic multidetector-row helical computed tomography (dynamic MDCT). A total of 28 patients with 66 hypervascular HCCs underwent both double arterial SENSE dynamic MRI and dynamic MDCT. The diagnosis of HCC was based on surgical resection (n=7), biopsy (n=10), or a combination of CT during arterial portography (CTAP), CT during hepatic arteriography (CTA), and/or the 6-month follow-up CT (n=49). Based on alternative-free response receiving operating characteristic (ROC) analysis, the diagnostic performance for detecting HCC was compared between double arterial phase SENSE dynamic MRI and double arterial phase dynamic MDCT. The mean sensitivity, positive predictive value, and mean A Z values for hypervascular HCCs were 72%, 80%, and 0.79, respectively, for SENSE dynamic MRI and 66%, 92%, and 0.78, respectively, for dynamic MDCT. The mean sensitivity for double arterial phase SENSE dynamic MRI was higher than that for double arterial phase dynamic MDCT, but the difference was not statistically significant. Double arterial phase SENSE dynamic MRI is as valuable as double arterial phase dynamic MDCT for detecting hypervascular HCCs. (author)

Syntheses, structures and luminescence properties of lanthanide coordination polymers with helical character

International Nuclear Information System (INIS)

Zhou Ruisha; Cui Xiaobing; Song Jiangfeng; Xu Xiaoyu; Xu Jiqing; Wang Tiegang

2008-01-01

A series of lanthanide coordination polymers, (Him) n [Ln(ip) 2 (H 2 O)] n [Ln=La(1), Pr(2), Nd(3) and Dy(4), H 2 ip=isophthalic acid, im=imidazole] and [Y 2 (ip) 3 (H 2 O) 2 ] n .nH 2 O (5), have been synthesized and characterized by elemental analyses, infrared (IR), ultraviolet-visible-near infrared (UV-Vis-NIR) and single-crystal X-ray diffraction analyses. The isostructural compounds 1-4 possess 3-D structures with three different kinds of channels. Compound 5 features a 2-D network making of two different kinds of quadruple-helical chains. Compounds 2 and 3 present the characteristic emissions of Pr(III) and Nd(III) ions in NIR region, respectively. Compound 4 shows sensitized luminescence of Dy(III) ions in visible region. - Graphical abstract: A series of lanthanide coodination polymers, (Him) n [Ln(ip) 2 (H 2 O)] n [Ln=La(1), Pr(2), Nd(3) and Dy(4)] and [Y 2 (ip) 3 (H 2 O) 2 ] n .nH 2 O (5), have been reported. The isostructural compounds 1-4 possess 3-D structures with three different kinds of channels. Compound 5 displays a 2-D network making of two kinds of quadruple-helical chains. Display Omitted

Primary structure and conformational analysis of peptide methionine-tyrosine, a peptide related to neuropeptide Y and peptide YY isolated from lamprey intestine

DEFF Research Database (Denmark)

Conlon, J M; Bjørnholm, B; Jørgensen, Flemming Steen

1991-01-01

A peptide belonging to the pancreatic-polypeptide-fold family of regulatory peptides has been isolated from the intestine of an Agnathan, the sea lamprey (Petromyzon marinus). The primary structure of the peptide (termed peptide methionine-tyrosine) was established as Met-Pro-Pro-Lys-Pro-Asp-Asn-...... in a preferred structure in which the conformation of the beta-turn between the two helical domains (residues 9-14) is appreciably different....

In situ structure solution of helical sulphur at 3 GPa and 400 C

Energy Technology Data Exchange (ETDEWEB)

Crichton, W.A.; Vaughan, G.B.M.; Mezouar, M. [European Synchrotron Radiation Facility (ESRF), 38 - Grenoble (France)

2001-07-01

The structure of a 2-chain helical form of sulphur with 9 atoms per unit-cell has been determined from powder synchrotron X-ray diffraction data obtained at 3 GPa and 400 C, using a combination of global optimization, simulated annealing and Rietveld refinement techniques. Final refinement of the structure in trigonal space group P3{sub 2}21 (no. 154) results in a = 7.0897(2) A, c = 4.30238(9) A and V = 187.282(10) A{sup 3}. There are two unique S sites per unit cell, the general S1 6c position with x = 0.7727(9), y = 0.3067(11) and z = 0.6105(12) and the S2 3b with x = 0.8755(8) A. Bond length and angle analysis shows S1-S1 = 2.070(4) A and S2-S2 = 2.096(7) A with an helical S1-S1-S1 divalent angle of 102.7(2) and 101.7(3) for S2-S2-S2. The 2 helices formed, contrary to other polymeric sulphur phases (principally, {psi}-S), are non-chiral and evidently have repeats along the (001) translation; that is one turn includes each of the 3 equivalent atoms about the 3{sub 2}-screw axis (S1 helix) and vertex (S2) of the cell. This phase, although temperature quenchable, is observed to back transform to a 4.04 A phase at pressures less than 0.5 GPa. It is likely that this phase represents the true form of the phase XII of Vezzoli and Walsh. (orig.)

Oral S-adenosylmethionine in primary fibromyalgia. Double-blind clinical evaluation

DEFF Research Database (Denmark)

Jacobsen, Søren; Danneskiold-Samsøe, B; Andersen, R B

1991-01-01

S-adenosylmethionine is a relatively new anti-inflammatory drug with analgesic and anti-depressant effects. Efficacy of 800 mg orally administered s-adenosylmethionine daily versus placebo for six weeks was investigated in 44 patients with primary fibromyalgia in double-blind settings. Tender poi...... effects on primary fibromyalgia and could be an important option in the treatment hereof.......S-adenosylmethionine is a relatively new anti-inflammatory drug with analgesic and anti-depressant effects. Efficacy of 800 mg orally administered s-adenosylmethionine daily versus placebo for six weeks was investigated in 44 patients with primary fibromyalgia in double-blind settings. Tender point...... = 0.03) and mood evaluated by Face Scale (P = 0.006) in the actively treated group compared to placebo. The tender point score, isokinetic muscle strength, mood evaluated by Beck Depression Inventory and side effects did not differ in the two treatment groups. S-adenosylmethionine has some beneficial...

Structure-activity relationship study of Aib-containing amphipathic helical peptide-cyclic RGD conjugates as carriers for siRNA delivery.

Science.gov (United States)

Wada, Shun-Ichi; Takesada, Anna; Nagamura, Yurie; Sogabe, Eri; Ohki, Rieko; Hayashi, Junsuke; Urata, Hidehito

2017-12-15

The conjugation of Aib-containing amphipathic helical peptide with cyclo(-Arg-Gly-Asp-d-Phe-Cys-) (cRGDfC) at the C-terminus of the helix peptide (PI) has been reported to be useful for constructing a carrier for targeted siRNA delivery into cells. In order to explore structure-activity relationships for the development of potential carriers for siRNA delivery, we synthesized conjugates of Aib-containing amphipathic helical peptide with cRGDfC at the N-terminus (PII) and both the N- and C-termini (PIII) of the helical peptide. Furthermore, to examine the influence of PI helical chain length on siRNA delivery, truncated peptides containing 16 (PIV), 12 (PV), and 8 (PVI) amino acid residues at the N-terminus of the helical chain were synthesized. PII and PIII, as well as PI, could deliver anti-luciferase siRNA into cells to induce the knockdown of luciferase stably expressed in cells. In contrast, all of the truncated peptides were unlikely to transport siRNA into cells. Copyright © 2017 Elsevier Ltd. All rights reserved.

Kinematical vortices in double photoionization of helium by attosecond pulses

Science.gov (United States)

Djiokap, J. M. Ngoko; Meremianin, A. V.; Manakov, N. L.; Hu, S. X.; Madsen, L. B.; Starace, Anthony F.

2017-07-01

Two-armed helical vortex structures are predicted in the two-electron momentum distributions produced in double photoionization (DPI) of the He atom by a pair of time-delayed elliptically polarized attosecond pulses with opposite helicities. These predictions are based upon both a first-order perturbation theory analysis and numerical solutions of the two-electron, time-dependent Schrödinger equation in six spatial dimensions. The helical vortex structures originate from Ramsey interference of a pair of ionized two-electron wave packets, each having a total angular momentum of unity, and appear in the sixfold differential DPI probability distribution for any energy partitioning between the two electrons. The vortex structures are exquisitely sensitive to the time delay between the two pulses, their relative phase, their ellipticity, and their handedness; moreover, they occur in a variety of electron detection geometries. However, the vortex structures only occur when the angular separation β =cos-1(p̂1.p̂2) between the electron momenta p1 and p2 is held fixed. The vortex structures can also be observed in the fourfold differential DPI probability distribution obtained by averaging the sixfold differential probability over the emission angles of one electron. Such kinematical vortices are a general phenomenon that may occur in any ionization process, initiated by two time-delayed short pulses with opposite ellipticities, for particular detection geometries.

Multispectroscopic and Theoretical Exploration of the Comparative Binding Aspects of Bioflavonoid Fisetin with Triple- and Double-Helical Forms of RNA.

Science.gov (United States)

Bhuiya, Sutanwi; Haque, Lucy; Goswami, Rapti; Das, Suman

2017-12-14

The interactions of RNA triplex (U.A*U) and duplex (A.U) with naturally occurring flavonoid fisetin (FTN) have been examined at pH 7.0 using various spectroscopic, viscometric, and theoretical studies. Experimental observations showed that the ligand binds with both double- and triple-helical forms of RNA, although the binding affinity is greater for the triplex structure (5.94 × 10 6 M -1 ) compared to that for the duplex counterpart (1.0 × 10 5 M -1 ). Thermal melting experiments revealed that the Hoogsteen base-paired third strand of triplex was stabilized to a greater extent (∼14 °C) compared with the Watson-Crick base-paired second strand (∼4 °C) in the presence of FTN. From fluorimetric study, we observed that U.A*U and A.U primarily bind to the photoproduced tautomer of FTN in the excited state. Steady-state and time-resolved anisotropy measurements illustrate considerable modulations of the spectroscopic properties of the tautomeric FTN within the RNA environment. Viscometric, fluorescence quenching, and thermal melting studies all together support the mode of binding to be intercalation. Theoretical study explains the experimental absorption and emission (dual fluorescence) behavior of FTN along with the excited-state intramolecular proton transfer process.

TRANSAT-- method for detecting the conserved helices of functional RNA structures, including transient, pseudo-knotted and alternative structures.

Science.gov (United States)

Wiebe, Nicholas J P; Meyer, Irmtraud M

2010-06-24

The prediction of functional RNA structures has attracted increased interest, as it allows us to study the potential functional roles of many genes. RNA structure prediction methods, however, assume that there is a unique functional RNA structure and also do not predict functional features required for in vivo folding. In order to understand how functional RNA structures form in vivo, we require sophisticated experiments or reliable prediction methods. So far, there exist only a few, experimentally validated transient RNA structures. On the computational side, there exist several computer programs which aim to predict the co-transcriptional folding pathway in vivo, but these make a range of simplifying assumptions and do not capture all features known to influence RNA folding in vivo. We want to investigate if evolutionarily related RNA genes fold in a similar way in vivo. To this end, we have developed a new computational method, Transat, which detects conserved helices of high statistical significance. We introduce the method, present a comprehensive performance evaluation and show that Transat is able to predict the structural features of known reference structures including pseudo-knotted ones as well as those of known alternative structural configurations. Transat can also identify unstructured sub-sequences bound by other molecules and provides evidence for new helices which may define folding pathways, supporting the notion that homologous RNA sequence not only assume a similar reference RNA structure, but also fold similarly. Finally, we show that the structural features predicted by Transat differ from those assuming thermodynamic equilibrium. Unlike the existing methods for predicting folding pathways, our method works in a comparative way. This has the disadvantage of not being able to predict features as function of time, but has the considerable advantage of highlighting conserved features and of not requiring a detailed knowledge of the cellular

Helicity conservation under quantum reconnection of vortex rings.

Science.gov (United States)

Zuccher, Simone; Ricca, Renzo L

2015-12-01

Here we show that under quantum reconnection, simulated by using the three-dimensional Gross-Pitaevskii equation, self-helicity of a system of two interacting vortex rings remains conserved. By resolving the fine structure of the vortex cores, we demonstrate that the total length of the vortex system reaches a maximum at the reconnection time, while both writhe helicity and twist helicity remain separately unchanged throughout the process. Self-helicity is computed by two independent methods, and topological information is based on the extraction and analysis of geometric quantities such as writhe, total torsion, and intrinsic twist of the reconnecting vortex rings.

Continuous liquid level detection based on two parallel plastic optical fibers in a helical structure

Science.gov (United States)

Zhang, Yingzi; Hou, Yulong; Zhang, Yanjun; Hu, Yanjun; Zhang, Liang; Gao, Xiaolong; Zhang, Huixin; Liu, Wenyi

2018-02-01

A simple and low-cost continuous liquid-level sensor based on two parallel plastic optical fibers (POFs) in a helical structure is presented. The change in the liquid level is determined by measuring the side-coupling power in the passive fiber. The side-coupling ratio is increased by just filling the gap between the two POFs with ultraviolet-curable optical cement, making the proposed sensor competitive. The experimental results show that the side-coupling power declines as the liquid level rises. The sensitivity and the measurement range are flexible and affected by the geometric parameters of the helical structure. A higher sensitivity of 0.0208 μW/mm is acquired for a smaller curvature radius of 5 mm, and the measurement range can be expanded to 120 mm by enlarging the screw pitch to 40 mm. In addition, the reversibility and temperature dependence are studied. The proposed sensor is a cost-effective solution offering the advantages of a simple fabrication process, good reversibility, and compensable temperature dependence.

Godbillon Vey Helicity and Magnetic Helicity in Magnetohydrodynamics

Science.gov (United States)

Webb, G. M.; Hu, Q.; Anco, S.; Zank, G. P.

2017-12-01

The Godbillon-Vey invariant arises in homology theory, and algebraic topology, where conditions for a layered family of 2D surfaces forms a 3D manifold were elucidated. The magnetic Godbillon-Vey helicity invariant in magnetohydrodynamics (MHD) is a helicity invariant that occurs for flows, in which the magnetic helicity density hm= A\\cdotB=0 where A is the magnetic vector potential and B is the magnetic induction. Our purpose is to elucidate the evolution of the magnetic Godbillon-Vey field η =A×B/|A|2 and the Godbillon-Vey helicity hgv}= η \\cdot∇ × η in general MHD flows in which the magnetic helicity hm≠q 0. It is shown that hm acts as a source term in the Godbillon-Vey helicity transport equation, in which hm is coupled to hgv via the shear tensor of the background flow. The transport equation for hgv depends on the electric field potential ψ , which is related to the gauge for A, which takes its simplest form for the advected A gauge in which ψ =A\\cdot u where u is the fluid velocity.

Bifurcation structure of successive torus doubling

International Nuclear Information System (INIS)

Sekikawa, Munehisa; Inaba, Naohiko; Yoshinaga, Tetsuya; Tsubouchi, Takashi

2006-01-01

The authors discuss the 'embryology' of successive torus doubling via the bifurcation theory, and assert that the coupled map of a logistic map and a circle map has a structure capable of generating infinite number of torus doublings

Complete primary structure of rainbow trout type I collagen consisting of alpha1(I)alpha2(I)alpha3(I) heterotrimers.

Science.gov (United States)

Saito, M; Takenouchi, Y; Kunisaki, N; Kimura, S

2001-05-01

The subunit compositions of skin and muscle type I collagens from rainbow trout were found to be alpha1(I)alpha2(I)alpha3(I) and [alpha1(I)](2)alpha2(I), respectively. The occurrence of alpha3(I) has been observed only for bonyfish. The skin collagen exhibited more susceptibility to both heat denaturation and MMP-13 digestion than the muscle counterpart; the former had a lower denaturation temperature by about 0.5 degrees C than the latter. The lower stability of skin collagen, however, is not due to the low levels of imino acids because the contents of Pro and Hyp were almost constant in both collagens. On the other hand, some cDNAs coding for the N-terminal and/or a part of triple-helical domains of proalpha(I) chains were cloned from the cDNA library of rainbow trout fibroblasts. These cDNAs together with the previously cloned collagen cDNAs gave information about the complete primary structure of type I procollagen. The main triple-helical domain of each proalpha(I) chain had 338 uninterrupted Gly-X-Y triplets consisting of 1014 amino acids and was unique in its high content of Gly-Gly doublets. In particular, the bonyfish-specific alpha(I) chain, proalpha3(I) was characterized by the small number of Gly-Pro-Pro triplets, 19, and the large number of Gly-Gly doublets, 38, in the triple-helical domain, compared to 23 and 22, respectively, for proalpha1(I). The small number of Gly-Pro-Pro and the large number of Gly-Gly in proalpha3(I) was assumed to partially loosen the triple-helical structure of skin collagen, leading to the lower stability of skin collagen mentioned above. Finally, phylogenetic analyses revealed that proalpha3(I) had diverged from proalpha1(I). This study is the first report of the complete primary structure of fish type I procollagen.

Selective synthesis of double helices of carbon nanotube bundles grown on treated metallic substrates

Energy Technology Data Exchange (ETDEWEB)

Cervantes-Sodi, Felipe; Iniguez-Rabago, Agustin; Rosas-Melendez, Samuel; Ballesteros-Villarreal, Monica [Departamento de Fisica y Matematicas, Universidad Iberoamericana, Prolongacion Paseo de la Reforma 880, Lomas de Santa Fe (Mexico); Vilatela, Juan J. [IMDEA Materials Institute, E.T.S. de Ingenieros de Caminos, Madrid (Spain); Reyes-Gutierrez, Lucio G.; Jimenez-Rodriguez, Jose A. [Ingenieria Industrial, Grupo JUMEX, Ecatepec de Morelos, Estado de Mexico (Mexico); Palacios, Eduardo [Lab. de Microscopia Electronica de Ultra Alta Resolucion, Instituto Mexicano del Petroleo, San Bartolo Atepehuacan (Mexico); Terrones, Mauricio [Department of Physics, Department of Materials Science and Engineering and Materials Research Institute, Pennsylvania State University, University Park, PA (United States); Research Center for Exotic Nanocarbons (JST), Shinshu University, Nagano (Japan)

2012-12-15

Double-helix microstructures consisting of two parallel strands of hundreds of multi-walled carbon nanotubes (MWCNTs) have been synthesized by chemical vapour deposition of ferrocene/toluene vapours on metal substrates. Growth of coiled carbon nanostructures with site selectivity is achieved by varying the duration of thermochemical pretreatment to deposit a layer of SiO{sub x} on the metallic substrate. Production of multibranched structures of MWCNTs converging in SiO{sub x} microstructure is also reported. In the abstract figure, panel (a) shows a coloured micrograph of a typical double-helix coiled microstructure of MWCNTs grown on SiO{sub x} covered steel substrate. Green and blue show each of the two individual strands of MWCNTs. Panel (b) is an amplification of a SiO{sub x} microparticle (white) on the tip of the double-stranded coil (green and blue). The microparticle guides the collective growth of hundreds of MWCNTs to form the coiled structure. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Pressure effect on the amide I frequency of the solvated α-helical structure in water

International Nuclear Information System (INIS)

Takekiyo, T; Yoshimura, Y; Shimizu, A; Koizumi, T; Kato, M; Taniguchi, Y

2007-01-01

As a model system of the pressure dependence of the amide I mode of the solvated α-helical structure in a helical peptide, we have calculated the frequency shifts of the amide I modes as a function of the distance between trans-N-methylacetamide (t-NMA) dimer and a water molecule (d C=O···H-O ) by the density-functional theory (DFT) method at the B3LYP/6-31G++(d,p) level. Two amide I frequencies at 1652 and 1700 cm -1 were observed under this calculation. The former is ascribed to the amide I mode forming the intermolecular hydrogen bond (H-bond) between t-NMA and H 2 O in addition to the intermolecular H-bond in the t-NMA dimer. The latter is due to the amide I mode forming only the intermolecular H-bond in the t-NMA dimer. We have found that the amide I frequency at 1652 cm -1 shifts to a lower frequency with decreasing d C=O···H-O ) (i.e., increasing pressure), whereas that at 1700 cm -1 shifts to a higher frequency. The amide I frequency shift of 1652 cm -1 is larger than that of 1700 cm -1 by the intermolecular H-bond. Thus, our results clearly indicate that the pressure-induced amide I frequency shift of the solvated α-helical structure correlates with the change in d C=O···H-O )

Probing conserved helical modules of portal complexes by mass spectrometry-based hydrogen/deuterium exchange.

Science.gov (United States)

Kang, Sebyung; Poliakov, Anton; Sexton, Jennifer; Renfrow, Matthew B; Prevelige, Peter E

2008-09-05

The Double-stranded DNA bacteriophage P22 has a ring-shaped dodecameric complex composed of the 84 kDa portal protein subunit that forms the central channel of the phage DNA packaging motor. The overall morphology of the P22 portal complex is similar to that of the portal complexes of Phi29, SPP1, T3, T7 phages and herpes simplex virus. Secondary structure prediction of P22 portal protein and its threading onto the crystal structure of the Phi29 portal complexes suggested that the P22 portal protein complex shares conserved helical modules that were found in the dodecameric interfaces of the Phi29 portal complex. To identify the amino acids involved in intersubunit contacts in the P22 portal ring complexes and validate the threading model, we performed comparative hydrogen/deuterium exchange analysis of monomeric and in vitro assembled portal proteins of P22 and the dodecameric Phi29 portal. Hydrogen/deuterium exchange experiments provided evidence of intersubunit interactions in the P22 portal complex similar to those in the Phi29 portal that map to the regions predicted to be conserved helical modules.

Buckwheat trypsin inhibitor with helical hairpin structure belongs to a new family of plant defence peptides.

Science.gov (United States)

Oparin, Peter B; Mineev, Konstantin S; Dunaevsky, Yakov E; Arseniev, Alexander S; Belozersky, Mikhail A; Grishin, Eugene V; Egorov, Tsezi A; Vassilevski, Alexander A

2012-08-15

A new peptide trypsin inhibitor named BWI-2c was obtained from buckwheat (Fagopyrum esculentum) seeds by sequential affinity, ion exchange and reversed-phase chromatography. The peptide was sequenced and found to contain 41 amino acid residues, with four cysteine residues involved in two intramolecular disulfide bonds. Recombinant BWI-2c identical to the natural peptide was produced in Escherichia coli in a form of a cleavable fusion with thioredoxin. The 3D (three-dimensional) structure of the peptide in solution was determined by NMR spectroscopy, revealing two antiparallel α-helices stapled by disulfide bonds. Together with VhTI, a trypsin inhibitor from veronica (Veronica hederifolia), BWI-2c represents a new family of protease inhibitors with an unusual α-helical hairpin fold. The linker sequence between the helices represents the so-called trypsin inhibitory loop responsible for direct binding to the active site of the enzyme that cleaves BWI-2c at the functionally important residue Arg(19). The inhibition constant was determined for BWI-2c against trypsin (1.7×10(-1)0 M), and the peptide was tested on other enzymes, including those from various insect digestive systems, revealing high selectivity to trypsin-like proteases. Structural similarity shared by BWI-2c, VhTI and several other plant defence peptides leads to the acknowledgement of a new widespread family of plant peptides termed α-hairpinins.

Polymorphic transformation of helical flagella of bacteria

Science.gov (United States)

Lim, Sookkyung; Howard Berg Collaboration; William Ko Collaboration; Yongsam Kim Collaboration; Wanho Lee Collaboration; Charles Peskin Collaboration

2016-11-01

Bacteria such as E. coli swim in an aqueous environment by utilizing the rotation of flagellar motors and alternate two modes of motility, runs and tumbles. Runs are steady forward swimming driven by bundles of flagellar filaments whose motors are turning CCW; tumbles involve a reorientation of the direction of swimming triggered by motor reversals. During tumbling, the helical flagellum undergoes polymorphic transformations, which is a local change in helical pitch, helical radius, and handedness. In this work, we investigate the underlying mechanism of structural conformation and how this polymorphic transition plays a role in bacterial swimming. National Science Foundation.

Time allocated to mathematics in post-primary schools in Ireland: are we in double trouble?

Science.gov (United States)

O'Meara, Niamh; Prendergast, Mark

2018-05-01

Mathematics educators and legislators worldwide have begun placing a greater emphasis on teaching mathematics for understanding and through the use of real-life applications. Revised curricula have led to the time allocated to mathematics in effected countries being scrutinised. This has resulted in policy-makers and educationalists worldwide calling for the inclusion of double class periods on the mathematics timetable. Research from the United States suggests that the introduction of double or block periods allow for the objectives of revised curricula to be realized. The aim of this study, which is set in the school context, is first to ascertain if schools in Ireland are scheduling double periods for mathematics at both lower post-primary level (Junior Cycle) and upper post-primary level (Senior Cycle). It also seeks to determine if there is a link between teachers' levels of satisfaction with the time allocated to mathematics and the provision of double periods and to get insights from teachers in relation to their opinions on what can be achieved through the introduction of such classes. Questionnaires were sent to 400 post-primary schools (approximately 1600 teachers) which were selected using stratified sampling techniques. It was found that 8.7% of mathematics teachers reported the provision of double periods at Junior Cycle while 55% reported that double periods were included on their timetable at Senior Cycle. The study also identified a link between teachers' levels of satisfaction with the time allocated to mathematics and the provision of double periods. Finally, teachers felt that double periods allowed for new teaching methodologies, which were promoted by the revised curricula, to be implemented and teaching for understanding was also more feasible. In essence, it was found that double periods have an influence on the mathematical experience of post-primary students as well as the teaching approaches employed.

Influence of 63Ser phosphorylation and dephosphorylation on the structure of the stathmin helical nucleation sequence: a molecular dynamics study.

Science.gov (United States)

Missimer, John H; Steinmetz, Michel O; van Gunsteren, Wilfred F; Dolenc, Jožica

2012-10-23

Phosphorylation is an important mechanism regulating protein-protein interactions involving intrinsically disordered protein regions. Stathmin, an archetypical example of an intrinsically disordered protein, is a key regulator of microtubule dynamics in which phosphorylation of 63Ser within the helical nucleation sequence strongly down-regulates the tubulin binding and microtubule destabilizing activities of the protein. Experimental studies on a peptide encompassing the 19-residue helical nucleation sequence of stathmin (residues 55-73) indicate that phosphorylation of 63Ser destabilizes the peptide's secondary structure by disrupting the salt bridges supporting its helical conformation. In order to investigate this hypothesis at atomic resolution, we performed molecular dynamics simulations of nonphosphorylated and phosphorylated stathmin-[55-73] at room temperature and pressure, neutral pH, and explicit solvation using the recently released GROMOS force field 54A7. In the simulations of nonphosphorylated stathmin-[55-73] emerged salt bridges associated with helical configurations. In the simulations of 63Ser phosphorylated stathmin-[55-73] these configurations dispersed and were replaced by a proliferation of salt bridges yielding disordered configurations. The transformation of the salt bridges was accompanied by emergence of numerous interactions between main and side chains, involving notably the oxygen atoms of the phosphorylated 63Ser. The loss of helical structure induced by phosphorylation is reversible, however, as a final simulation showed. The results extend the hypothesis of salt bridge derangement suggested by experimental observations of the stathmin nucleation sequence, providing new insights into regulation of intrinsically disordered protein systems mediated by phosphorylation.

High-n helicity-induced shear Alfven eigenmodes

International Nuclear Information System (INIS)

Nakajima, N.; Cheng, C.Z.; Okamoto, M.

1992-05-01

The high-n Helicity-induced shear Alfven Eigenmodes (HAE) are considered both analytically and numerically for the straight helical magnetic system, where n is the toroidal mode number. The eigenmode equation for the high-n HAE modes is derived along the field line and with the aid of the averaging method is shown to reduce to the Mathieu equation asymptotically. The discrete HAE modes are shown to exist inside the continuum spectrum gaps. The continuous spectrum gaps appear around ω 2 = ω A 2 [N(lι-m)/2] 2 for N = 1,2,.., where ω A is the toroidal Alfven transit frequency, and l, m, and ι are the polarity of helical coils, the toroidal pitch number of helical coils, and the rotational transform, respectively. For the same ω A and ι, the frequency of the helical continuum gap is larger than that of the continuum gap in tokamak plasmas by |l-ι -1 m|. The polarity of helical coils l plays a crucial role in determining the spectrum gaps and the properties of the high-n HAE modes. The spectrum gaps near the magnetic axis are created by the helical ripple with circular flux surfaces for l = 1, and ≥ 3 helicals. For l = 2 helical systems, the spectrum gaps are created by the ellipticity of the flux surfaces. These analytical results for the continuum gaps and the existence of the high-n HAE modes in the continuum gaps are confirmed numerically for the l = 2 case, and we find that the HAE modes exist for mode structures with the even and the odd parities. (author)

A Lennard-Jones-like perspective on first order transitions in biological helices

DEFF Research Database (Denmark)

Oskolkov, Nikolay N.; Bohr, Jakob

2013-01-01

Helical structures with Lennard-Jones self-interactions are studied for optimal conformations. For this purpose, their self-energy is analyzed for extrema with respect to the geometric parameters of the helices. It is found that Lennard-Jones helices exhibit a first order phase transition from...

CHSalign: A Web Server That Builds upon Junction-Explorer and RNAJAG for Pairwise Alignment of RNA Secondary Structures with Coaxial Helical Stacking.

Directory of Open Access Journals (Sweden)

Lei Hua

Full Text Available RNA junctions are important structural elements of RNA molecules. They are formed when three or more helices come together in three-dimensional space. Recent studies have focused on the annotation and prediction of coaxial helical stacking (CHS motifs within junctions. Here we exploit such predictions to develop an efficient alignment tool to handle RNA secondary structures with CHS motifs. Specifically, we build upon our Junction-Explorer software for predicting coaxial stacking and RNAJAG for modelling junction topologies as tree graphs to incorporate constrained tree matching and dynamic programming algorithms into a new method, called CHSalign, for aligning the secondary structures of RNA molecules containing CHS motifs. Thus, CHSalign is intended to be an efficient alignment tool for RNAs containing similar junctions. Experimental results based on thousands of alignments demonstrate that CHSalign can align two RNA secondary structures containing CHS motifs more accurately than other RNA secondary structure alignment tools. CHSalign yields a high score when aligning two RNA secondary structures with similar CHS motifs or helical arrangement patterns, and a low score otherwise. This new method has been implemented in a web server, and the program is also made freely available, at http://bioinformatics.njit.edu/CHSalign/.

On Rational Design of Double Hull Tanker Structures against Collision

DEFF Research Database (Denmark)

Paik, Jeom Kee; Chung, Jang Young; Choe, Ich Hung

1999-01-01

This paper is a summary of recent research and development in areas related to the design technology for double hull tanker structures against low energy collision, jointly undertaken by the Hyundai Heavy Industries, the American Bureau of Shipping, the Technical University of Denmark and the Pusan...... in the present study were (i) developing a framework for the collision design procedure for double hull tanker structures, (ii) experimental investigation of the structural crashworthiness of the collided vessels in collision or stranding, using double skinned structural models, (iii) validation of the special...... investigation of the energy absorption capability characteristics of a collided double hull VLCC side structure in collision, and (vi) development of a new modified Minorsky method for double hull tanker side structures. The tools developed and the results and insights obtained by the present study should...

Design study of a normal conducting helical snake for AGS

CERN Document Server

Takano, Junpei; Okamura, Masahiro; Roser, Thomas; MacKay, William W; Luccio, Alfredo U; Takano, Koji

2004-01-01

A new normal conducting snake magnet is being fabricated for the Alternate Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL). In the Relativistic Heavy Ion Collider (RHIC) project, a superconducting type helical dipole magnets had been developed and it performed successfully in high-energy polarized proton acceleration. The new AGS helical snake has the same basic magnetic structure but is more complicated. To achieve no beam shift and no beam deflection in one magnetic device, helical pitches and rotating angles were carefully calculated. Compared to a superconducting magnet, a normal warm magnet must have a large cross- sectional area of conductors which make it difficult to design a magnet with large helical pitch. We developed a modified window frame structure to accommodate the large number of conductors. Its three dimensional magnetic field was simulated by using OPERA3D/TOSCA. 3 Refs.

Brickworx builds recurrent RNA and DNA structural motifs into medium- and low-resolution electron-density maps

Energy Technology Data Exchange (ETDEWEB)

Chojnowski, Grzegorz, E-mail: gchojnowski@genesilico.pl [International Institute of Molecular and Cell Biology, Trojdena 4, 02-109 Warsaw (Poland); Waleń, Tomasz [International Institute of Molecular and Cell Biology, Trojdena 4, 02-109 Warsaw (Poland); University of Warsaw, Banacha 2, 02-097 Warsaw (Poland); Piątkowski, Paweł; Potrzebowski, Wojciech [International Institute of Molecular and Cell Biology, Trojdena 4, 02-109 Warsaw (Poland); Bujnicki, Janusz M. [International Institute of Molecular and Cell Biology, Trojdena 4, 02-109 Warsaw (Poland); Adam Mickiewicz University, Umultowska 89, 61-614 Poznan (Poland)

2015-03-01

A computer program that builds crystal structure models of nucleic acid molecules is presented. Brickworx is a computer program that builds crystal structure models of nucleic acid molecules using recurrent motifs including double-stranded helices. In a first step, the program searches for electron-density peaks that may correspond to phosphate groups; it may also take into account phosphate-group positions provided by the user. Subsequently, comparing the three-dimensional patterns of the P atoms with a database of nucleic acid fragments, it finds the matching positions of the double-stranded helical motifs (A-RNA or B-DNA) in the unit cell. If the target structure is RNA, the helical fragments are further extended with recurrent RNA motifs from a fragment library that contains single-stranded segments. Finally, the matched motifs are merged and refined in real space to find the most likely conformations, including a fit of the sequence to the electron-density map. The Brickworx program is available for download and as a web server at http://iimcb.genesilico.pl/brickworx.

Brickworx builds recurrent RNA and DNA structural motifs into medium- and low-resolution electron-density maps

International Nuclear Information System (INIS)

Chojnowski, Grzegorz; Waleń, Tomasz; Piątkowski, Paweł; Potrzebowski, Wojciech; Bujnicki, Janusz M.

2015-01-01

A computer program that builds crystal structure models of nucleic acid molecules is presented. Brickworx is a computer program that builds crystal structure models of nucleic acid molecules using recurrent motifs including double-stranded helices. In a first step, the program searches for electron-density peaks that may correspond to phosphate groups; it may also take into account phosphate-group positions provided by the user. Subsequently, comparing the three-dimensional patterns of the P atoms with a database of nucleic acid fragments, it finds the matching positions of the double-stranded helical motifs (A-RNA or B-DNA) in the unit cell. If the target structure is RNA, the helical fragments are further extended with recurrent RNA motifs from a fragment library that contains single-stranded segments. Finally, the matched motifs are merged and refined in real space to find the most likely conformations, including a fit of the sequence to the electron-density map. The Brickworx program is available for download and as a web server at http://iimcb.genesilico.pl/brickworx

Helicity, Reconnection, and Dynamo Effects

International Nuclear Information System (INIS)

Ji, Hantao

1998-01-01

The inter-relationships between magnetic helicity, magnetic reconnection, and dynamo effects are discussed. In laboratory experiments, where two plasmas are driven to merge, the helicity content of each plasma strongly affects the reconnection rate, as well as the shape of the diffusion region. Conversely, magnetic reconnection events also strongly affect the global helicity, resulting in efficient helicity cancellation (but not dissipation) during counter-helicity reconnection and a finite helicity increase or decrease (but less efficiently than dissipation of magnetic energy) during co-helicity reconnection. Close relationships also exist between magnetic helicity and dynamo effects. The turbulent electromotive force along the mean magnetic field (alpha-effect), due to either electrostatic turbulence or the electron diamagnetic effect, transports mean-field helicity across space without dissipation. This has been supported by direct measurements of helicity flux in a laboratory plasma. When the dynamo effect is driven by electromagnetic turbulence, helicity in the turbulent field is converted to mean-field helicity. In all cases, however, dynamo processes conserve total helicity except for a small battery effect, consistent with the observation that the helicity is approximately conserved during magnetic relaxation

Probing alpha-helical and beta-sheet structures of peptides at solid/liquid interfaces with SFG.

Science.gov (United States)

Chen, Xiaoyun; Wang, Jie; Sniadecki, Jason J; Even, Mark A; Chen, Zhan

2005-03-29

We demonstrated that sum frequency generation (SFG) vibrational spectroscopy can distinguish different secondary structures of proteins or peptides adsorbed at solid/liquid interfaces. The SFG spectrum for tachyplesin I at the polystyrene (PS)/solution interface has a fingerprint peak corresponding to the B1/B3 mode of the antiparallel beta-sheet. This peak disappeared upon the addition of dithiothreitol, which can disrupt the beta-sheet structure. The SFG spectrum indicative of the MSI594 alpha-helical structure was observed at the PS/MSI594 solution interface. This research validates SFG as a powerful technique for revealing detailed secondary structures of interfacial proteins and peptides.

A double-sided linear primary permanent magnet vernier machine.

Science.gov (United States)

Du, Yi; Zou, Chunhua; Liu, Xianxing

2015-01-01

The purpose of this paper is to present a new double-sided linear primary permanent magnet (PM) vernier (DSLPPMV) machine, which can offer high thrust force, low detent force, and improved power factor. Both PMs and windings of the proposed machine are on the short translator, while the long stator is designed as a double-sided simple iron core with salient teeth so that it is very robust to transmit high thrust force. The key of this new machine is the introduction of double stator and the elimination of translator yoke, so that the inductance and the volume of the machine can be reduced. Hence, the proposed machine offers improved power factor and thrust force density. The electromagnetic performances of the proposed machine are analyzed including flux, no-load EMF, thrust force density, and inductance. Based on using the finite element analysis, the characteristics and performances of the proposed machine are assessed.

Endoscopic placement of double-J ureteric stents in children as a treatment for primary obstructive megaureter

Directory of Open Access Journals (Sweden)

Carroll Daniel

2010-01-01

Full Text Available Aim: To determine the efficacy and potential complications of double-J ureteric stents in the treatment of persistent or progressive primary obstructive megaureter in pediatric patients within our institution. Materials and Methods: A retrospective case-note review of all patients with double-J ureteric stents, between 1997 and 2004, was performed. In all, 38 stents were inserted in 31 patients aged between 2 months and 15 years of age. Complications and results of follow-up investigations and the need for follow-up investigations were recorded. Patients were followed up clinically and radiologically for a minimum of 2 years following stent insertion. Results: Endoscopic placement of double-J ureteric stents in childhood is straightforward and complications are uncommon (8/38 insertions. In non-resolving or progressive primary non-refluxing megaureter, double-J ureteric stenting alone is effective with resolution of primary non-refluxing megaureter in 66% of cases (25/38 insertions. Conclusions: Ureteric stenting provides an alternative to early surgery in patients with primary non-refluxing megaureter. The youngest patient in our series was 2 months old at the time of endoscopic ureteric double-J stent insertion. Endoscopic placement of ureteric double-J stents should be considered as a first-line treatment in the management of persistent or progressive non-refluxing megaureter leading to progressive hydronephrosis or pyonephrosis.

Exploring biological effects of MoS2 nanosheets on native structures of α-helical peptides

International Nuclear Information System (INIS)

Gu, Zonglin; Li, Weifeng; Hong, Linbi; Zhou, Ruhong

2016-01-01

Recent reports of mono- and few-layer molybdenum disulfide (MoS 2 ), a representative transition metal dichacogenide (TMD), as antibacterial and anticancer agents have shed light on their potential in biomedical applications. To better facilitate these promising applications, one needs to understand the biological effects of these TMDs as well, such as their potential adverse effects on protein structure and function. Here, we sought to understand the interaction of MoS 2 nanosheets with peptides using molecular dynamics simulations and a simple model polyalanine with various lengths (PA n , n = 10, 20, 30, and 40; mainly α − helices). Our results demonstrated that MoS 2 monolayer has an exceptional capability to bind all peptides in a fast and strong manner. The strong attraction from the MoS 2 nanosheet is more than enough to compensate the energy needed to unfold the peptide, regardless of the length, which induces drastic disruptions to the intra-peptide hydrogen bonds and subsequent secondary structures of α − helices. This universal phenomenon may point to the potential nanotoxicity of MoS 2 when used in biological systems. Moreover, these results aligned well with previous findings on the potential cytotoxicity of TMD nanomaterials.

Helical modes generate antimagnetic rotational spectra in nuclei

Science.gov (United States)

Malik, Sham S.

2018-03-01

A systematic analysis of the antimagnetic rotation band using r -helicity formalism is carried out for the first time. The observed octupole correlation in a nucleus is likely to play a role in establishing the antimagnetic spectrum. Such octupole correlations are explained within the helical orbits. In a rotating field, two identical fermions (generally protons) with paired spins generate these helical orbits in such a way that its positive (i.e., up) spin along the axis of quantization refers to one helicity (right-handedness) while negative (down) spin along the same quantization-axis decides another helicity (left-handedness). Since the helicity remains invariant under rotation, therefore, the quantum state of a fermion is represented by definite angular momentum and helicity. These helicity represented states support a pear-shaped structure of a rotating system having z axis as the symmetry axis. A combined operation of parity, time-reversal, and signature symmetries ensures an absence of one of the signature partner band from the observed antimagnetic spectrum. This formalism has also been tested for the recently observed negative parity Δ I =2 antimagnetic spectrum in odd-A 101Pd nucleus and explains nicely its energy spectrum as well as the B (E 2 ) values. Further, this formalism is found to be fully consistent with twin-shears mechanism popularly known for such type of rotational bands. It also provides significant clue for extending these experiments in various mass regions spread over the nuclear chart.

Increasing the magnetic helicity content of a plasma by pulsing a magnetized source.

Science.gov (United States)

Woodruff, S; Stallard, B W; McLean, H S; Hooper, E B; Bulmer, R; Cohen, B I; Hill, D N; Holcomb, C T; Moller, J; Wood, R D

2004-11-12

By operating a magnetized coaxial gun in a pulsed mode it is possible to produce large voltage pulses of duration approximately 500 mus while reaching a few kV, giving a discrete input of helicity into a spheromak. In the sustained spheromak physics experiment (SSPX), it is observed that pulsing serves to nearly double the stored magnetic energy and double the temperature. We discuss these results by comparison with 3D MHD simulations of the same phenomenon.

Helical magnetized wiggler for synchrotron radiation laser

International Nuclear Information System (INIS)

Wang Mei; Park, S.Y.; Hirshfield, J.L.

1999-01-01

A helical magnetized iron wiggler has been built for a novel infrared synchrotron radiation laser (SRL) experiment. The wiggler consists of four periods of helical iron structure immersed in a solenoid field. This wiggler is to impart transverse velocity to a prebunched 6 MeV electron beam, and thus to obtain a desired high orbit pitch ratio for the SRL. Field tapering at beam entrance is considered and tested on a similar wiggler. Analytic and simulated characteristics of wigglers of this type are discussed and the performance of the fabricated wigglers is demonstrated experimentally. A 4.7 kG peak field was measured for a 6.4 mm air gap and a 5.4 cm wiggler period at a 20 kG solenoid field. The measured helical fields compare favorably with the analytical solution. This type of helical iron wigglers has the potential to be scaled to small periods with strong field amplitude

Helical magnetized wiggler for synchrotron radiation laser

CERN Document Server

Wang Mei; Hirshfield, J L

1999-01-01

A helical magnetized iron wiggler has been built for a novel infrared synchrotron radiation laser (SRL) experiment. The wiggler consists of four periods of helical iron structure immersed in a solenoid field. This wiggler is to impart transverse velocity to a prebunched 6 MeV electron beam, and thus to obtain a desired high orbit pitch ratio for the SRL. Field tapering at beam entrance is considered and tested on a similar wiggler. Analytic and simulated characteristics of wigglers of this type are discussed and the performance of the fabricated wigglers is demonstrated experimentally. A 4.7 kG peak field was measured for a 6.4 mm air gap and a 5.4 cm wiggler period at a 20 kG solenoid field. The measured helical fields compare favorably with the analytical solution. This type of helical iron wigglers has the potential to be scaled to small periods with strong field amplitude.

Examining the Conservation of Kinks in Alpha Helices.

Directory of Open Access Journals (Sweden)

Eleanor C Law

Full Text Available Kinks are a structural feature of alpha-helices and many are known to have functional roles. Kinks have previously tended to be defined in a binary fashion. In this paper we have deliberately moved towards defining them on a continuum, which given the unimodal distribution of kink angles is a better description. From this perspective, we examine the conservation of kinks in proteins. We find that kink angles are not generally a conserved property of homologs, pointing either to their not being functionally critical or to their function being related to conformational flexibility. In the latter case, the different structures of homologs are providing snapshots of different conformations. Sequence identity between homologous helices is informative in terms of kink conservation, but almost equally so is the sequence identity of residues in spatial proximity to the kink. In the specific case of proline, which is known to be prevalent in kinked helices, loss of a proline from a kinked helix often also results in the loss of a kink or reduction in its kink angle. We carried out a study of the seven transmembrane helices in the GPCR family and found that changes in kinks could be related both to subfamilies of GPCRs and also, in a particular subfamily, to the binding of agonists or antagonists. These results suggest conformational change upon receptor activation within the GPCR family. We also found correlation between kink angles in different helices, and the possibility of concerted motion could be investigated further by applying our method to molecular dynamics simulations. These observations reinforce the belief that helix kinks are key, functional, flexible points in structures.

Ruby-Helix: an implementation of helical image processing based on object-oriented scripting language.

Science.gov (United States)

Metlagel, Zoltan; Kikkawa, Yayoi S; Kikkawa, Masahide

2007-01-01

Helical image analysis in combination with electron microscopy has been used to study three-dimensional structures of various biological filaments or tubes, such as microtubules, actin filaments, and bacterial flagella. A number of packages have been developed to carry out helical image analysis. Some biological specimens, however, have a symmetry break (seam) in their three-dimensional structure, even though their subunits are mostly arranged in a helical manner. We refer to these objects as "asymmetric helices". All the existing packages are designed for helically symmetric specimens, and do not allow analysis of asymmetric helical objects, such as microtubules with seams. Here, we describe Ruby-Helix, a new set of programs for the analysis of "helical" objects with or without a seam. Ruby-Helix is built on top of the Ruby programming language and is the first implementation of asymmetric helical reconstruction for practical image analysis. It also allows easier and semi-automated analysis, performing iterative unbending and accurate determination of the repeat length. As a result, Ruby-Helix enables us to analyze motor-microtubule complexes with higher throughput to higher resolution.

Generation of uniform magnetic field using a spheroidal helical coil structure

International Nuclear Information System (INIS)

Öztürk, Yavuz; Aktaş, Bekir

2016-01-01

Uniformity of magnetic fields are of great importance especially in magnetic resonance studies, namely in magnetic resonance spectroscopy applications (NMR, FMR, ESR, EPR etc.) and magnetic resonance imaging applications (MRI, FMRI). Field uniformity is also required in some other applications such as eddy current probes, magnetometers, magnetic traps, particle counters etc. Here we proposed a coil winding regime, which follows the surface of a spheroid (an ellipsoid of rotation); in light of previous theoretical studies suggesting perfect uniformity for a constant ampere per turn in the axial direction thereof. We demonstrated our theoretical results from finite element calculations suggesting 0.15% of field uniformity for the proposed structure, which we called a Spheroidal Helical Coil. (paper)

Pion double charge exchange and nuclear structure

International Nuclear Information System (INIS)

Ginocchio, J.N.

1987-01-01

Pion double charge exchange to both the double-analog state and the ground state is studied for medium weight nuclei. The relative cross section of these two transitions and the importance of nuclear structure as a function of pion kinetic energy is examined. 16 figs., 5 tabs

Double smectic self-assembly in block copolypeptide complexes

KAUST Repository

Haataja, Johannes S.

2012-11-12

We show double smectic-like self-assemblies in the solid state involving alternating layers of different polypeptide α-helices. We employed rod-coil poly(γ-benzyl l-glutamate)-block-poly(l-lysine) (PBLG-b-PLL) as the polymeric scaffold, where the PLL amino residues were ionically complexed to di-n-butyl phosphate (diC4P), di(2-ethylhexyl) phosphate (diC2/6P), di(2-octyldodecyl) phosphate (diC8/12P), or di-n-dodecyl phosphate (diC12P), forming PBLG-b-PLL(diC4P), PBLG-b-PLL(diC2/6P), PBLG-b-PLL(diC8/12P), and PBLG-b-PLL(diC12P) complexes, respectively. The complexes contain PBLG α-helices of fixed diameter and PLL-surfactant complexes adopting either α-helices of tunable diameters or β-sheets. For PBLG-b-PLL(diC4P), that is, using a surfactant with short n-butyl tails, both blocks were α-helical, of roughly equal diameter and thus with minor packing frustrations, leading to alternating PBLG and PLL(diC4P) smectic layers of approximately perpendicular alignment of both types of α-helices. Surfactants with longer and branched alkyl tails lead to an increased diameter of the PLL-surfactant α-helices. Smectic alternating PBLG and PLL(diC2/6P) layers involve larger packing frustration, which leads to poor overall order and suggests an arrangement of tilted PBLG α-helices. In PBLG-b-PLL(diC8/12P), the PLL(diC8/12P) α-helices are even larger and the overall structure is poor. Using a surfactant with two linear n-dodecyl tails leads to well-ordered β-sheet domains of PLL(diC12P), consisting of alternating PLL and alkyl chain layers. This dominates the whole assembly, and at the block copolypeptide length scale, the PBLG α-helices do not show internal order and have poor organization. Packing frustration becomes an important aspect to design block copolypeptide assemblies, even if frustration could be relieved by conformational imperfections. The results suggest pathways to control hierarchical liquid-crystalline assemblies by competing interactions and by

Double smectic self-assembly in block copolypeptide complexes

KAUST Repository

Haataja, Johannes S.; Houbenov, Nikolay; Iatrou, Hermis; Hadjichristidis, Nikolaos; Karatzas, A.; Faul, Charl F. J.; Rannou, Patrice; Ikkala, Olli T.

2012-01-01

We show double smectic-like self-assemblies in the solid state involving alternating layers of different polypeptide α-helices. We employed rod-coil poly(γ-benzyl l-glutamate)-block-poly(l-lysine) (PBLG-b-PLL) as the polymeric scaffold, where the PLL amino residues were ionically complexed to di-n-butyl phosphate (diC4P), di(2-ethylhexyl) phosphate (diC2/6P), di(2-octyldodecyl) phosphate (diC8/12P), or di-n-dodecyl phosphate (diC12P), forming PBLG-b-PLL(diC4P), PBLG-b-PLL(diC2/6P), PBLG-b-PLL(diC8/12P), and PBLG-b-PLL(diC12P) complexes, respectively. The complexes contain PBLG α-helices of fixed diameter and PLL-surfactant complexes adopting either α-helices of tunable diameters or β-sheets. For PBLG-b-PLL(diC4P), that is, using a surfactant with short n-butyl tails, both blocks were α-helical, of roughly equal diameter and thus with minor packing frustrations, leading to alternating PBLG and PLL(diC4P) smectic layers of approximately perpendicular alignment of both types of α-helices. Surfactants with longer and branched alkyl tails lead to an increased diameter of the PLL-surfactant α-helices. Smectic alternating PBLG and PLL(diC2/6P) layers involve larger packing frustration, which leads to poor overall order and suggests an arrangement of tilted PBLG α-helices. In PBLG-b-PLL(diC8/12P), the PLL(diC8/12P) α-helices are even larger and the overall structure is poor. Using a surfactant with two linear n-dodecyl tails leads to well-ordered β-sheet domains of PLL(diC12P), consisting of alternating PLL and alkyl chain layers. This dominates the whole assembly, and at the block copolypeptide length scale, the PBLG α-helices do not show internal order and have poor organization. Packing frustration becomes an important aspect to design block copolypeptide assemblies, even if frustration could be relieved by conformational imperfections. The results suggest pathways to control hierarchical liquid-crystalline assemblies by competing interactions and by

Seismic analysis of a helical coil type heat exchanger

International Nuclear Information System (INIS)

Nishiguchi, I.; Baba, O.; Yatabe, H.

1984-01-01

The intermediate heat exchanger (IHX) which forms the reactor coolant pressure boundary is one of the most important components of the Multi-purpose Experimental Very High Temperature Gas-cooled Reactor (ex. VHTR) under development at Japan Atomic Energy Research Institute. This paper presents the results of the finite element modeling, eigenvalue analysis and dynamic response analysis of the IHX. For the modeling, the structure of the IHX was separated into a helical tube bundle, inner and outer vessels, and a center pipe. The eigenvalue analysis was made for each structure with a detailed three-dimensional finite element model. Then the simplified model of the whole structure of the IHX was constructed using the result of the eigenvalue analysis. A dynamic response analysis was made for the simplified model with and without stoppers of the helical tube bundle supports and the center pipe. The effect of stoppers on the behavior of the center pipe, the helical tube, and the connecting tube is discussed. (author)

Right-Handed Helical Foldamers Consisting of De Novo d -AApeptides

Energy Technology Data Exchange (ETDEWEB)

Teng, Peng; Ma, Ning; Cerrato, Darrell Cole; She, Fengyu; Odom, Timothy; Wang, Xiang; Ming, Li-June; van der Vaart, Arjan; Wojtas, Lukasz; Xu, Hai; Cai, Jianfeng

2017-05-16

New types of foldamer scaffolds are formidably challenging to design and synthesize, yet highly desirable as structural mimics of peptides/proteins with a wide repertoire of functions. In particular, the development of peptidomimetic helical foldamers holds promise for new biomaterials, catalysts, and drug molecules. Unnatural l-sulfono-γ-AApeptides were recently developed and shown to have potential applications in both biomedical and material sciences. However, d-sulfono-γ-AApeptides, the enantiomers of l-sulfono-γ-AApeptides, have never been studied due to the lack of high-resolution three-dimensional structures to guide structure-based design. Herein, we report the first synthesis and X-ray crystal structures of a series of 2:1 l-amino acid/d-sulfono-γ-AApeptide hybrid foldamers, and elucidate their folded conformation at the atomic level. Single-crystal X-ray crystallography indicates that this class of oligomers folds into well-defined right-handed helices with unique helical parameters. The helical structures were consistent with data obtained from solution 2D NMR, CD studies, and molecular dynamics simulations. Our findings are expected to inspire the structure-based design of this type of unique folding biopolymers for biomaterials and biomedical applications.

Helical type vacuum container

International Nuclear Information System (INIS)

Owada, Kimio.

1989-01-01

Helical type vacuum containers in the prior art lack in considerations for thermal expansion stresses to helical coils, and there is a possibility of coil ruptures. The object of the present invention is to avoid the rupture of helical coils wound around the outer surface of a vacuum container against heat expansion if any. That is, bellows or heat expansion absorbing means are disposed to a cross section of a helical type vacuum container. With such a constitution, thermal expansion of helical coils per se due to temperature elevation of the coils during electric supply can be absorbed by expansion of the bellows or absorption of the heat expansion absorbing means. Further, this can be attained by arranging shear pins in the direction perpendicular to the bellows axis so that the bellows are not distorted when the helical coils are wound around the helical type vacuum container. (I.S.)

HANFORD DOUBLE SHELL TANK (DST) THERMAL & SEISMIC PROJECT BUCKLING EVALUATION METHODS & RESULTS FOR THE PRIMARY TANKS

Energy Technology Data Exchange (ETDEWEB)

MACKEY TC; JOHNSON KI; DEIBLER JE; PILLI SP; RINKER MW; KARRI NK

2007-02-14

This report documents a detailed buckling evaluation of the primary tanks in the Hanford double-shell waste tanks (DSTs), which is part of a comprehensive structural review for the Double-Shell Tank Integrity Project. This work also provides information on tank integrity that specifically responds to concerns raised by the Office of Environment, Safety, and Health (ES&H) Oversight (EH-22) during a review of work performed on the double-shell tank farms and the operation of the aging waste facility (AWF) primary tank ventilation system. The current buckling review focuses on the following tasks: (1) Evaluate the potential for progressive I-bolt failure and the appropriateness of the safety factors that were used for evaluating local and global buckling. The analysis will specifically answer the following questions: (a) Can the EH-22 scenario develop if the vacuum is limited to -6.6-inch water gage (w.g.) by a relief valve? (b) What is the appropriate factor of safety required to protect against buckling if the EH-22 scenario can develop? (c) What is the appropriate factor of safety required to protect against buckling if the EH-22 scenario cannot develop? (2) Develop influence functions to estimate the axial stresses in the primary tanks for all reasonable combinations of tank loads, based on detailed finite element analysis. The analysis must account for the variation in design details and operating conditions between the different DSTs. The analysis must also address the imperfection sensitivity of the primary tank to buckling. (3) Perform a detailed buckling analysis to determine the maximum allowable differential pressure for each of the DST primary tanks at the current specified limits on waste temperature, height, and specific gravity. Based on the I-bolt loads analysis and the small deformations that are predicted at the unfactored limits on vacuum and axial loads, it is very unlikely that the EH-22 scenario (i.e., progressive I-bolt failure leading to global

Escherichia coli DnaA forms helical structures along the longitudinal cell axis distinct from MreB filaments.

Science.gov (United States)

Boeneman, Kelly; Fossum, Solveig; Yang, Yanhua; Fingland, Nicholas; Skarstad, Kirsten; Crooke, Elliott

2009-05-01

DnaA initiates chromosomal replication in Escherichia coli at a well-regulated time in the cell cycle. To determine how the spatial distribution of DnaA is related to the location of chromosomal replication and other cell cycle events, the localization of DnaA in living cells was visualized by confocal fluorescence microscopy. The gfp gene was randomly inserted into a dnaA-bearing plasmid via in vitro transposition to create a library that included internally GFP-tagged DnaA proteins. The library was screened for the ability to rescue dnaA(ts) mutants, and a candidate gfp-dnaA was used to replace the dnaA gene of wild-type cells. The resulting cells produce close to physiological levels of GFP-DnaA from the endogenous promoter as their only source of DnaA and somewhat under-initiate replication with moderate asynchrony. Visualization of GFP-tagged DnaA in living cells revealed that DnaA adopts a helical pattern that spirals along the long axis of the cell, a pattern also seen in wild-type cells by immunofluorescence with affinity purified anti-DnaA antibody. Although the DnaA helices closely resemble the helices of the actin analogue MreB, co-visualization of GFP-tagged DnaA and RFP-tagged MreB demonstrates that DnaA and MreB adopt discrete helical structures along the length of the longitudinal cell axis.

Improved particle confinement in transition from multiple-helicity to quasi-single-helicity regimes of a reversed-field pinch.

Science.gov (United States)

Frassinetti, L; Predebon, I; Koguchi, H; Yagi, Y; Hirano, Y; Sakakita, H; Spizzo, G; White, R B

2006-10-27

The quasi-single-helicity (QSH) state of a reversed-field pinch (RFP) plasma is a regime in which the RFP configuration can be sustained by a dynamo produced mainly by a single tearing mode and in which a helical structure with well-defined magnetic flux surfaces arises. In this Letter, we show that spontaneous transitions to the QSH regime enhance the particle confinement. This improvement is originated by the simultaneous and cooperative action of the increase of the magnetic island and the reduction of the magnetic stochasticity.

Solution structure of CEH-37 homeodomain of the nematode Caenorhabditis elegans

International Nuclear Information System (INIS)

Moon, Sunjin; Lee, Yong Woo; Kim, Woo Taek; Lee, Weontae

2014-01-01

Highlights: •We have determined solution structures of CEH-37 homedomain. •CEH-37 HD has a compact α-helical structure with HTH DNA binding motif. •Solution structure of CEH-37 HD shares its molecular topology with that of the homeodomain proteins. •Residues in the N-terminal region and HTH motif are important in binding to Caenorhabditis elegans telomeric DNA. •CEH-37 could play an important role in telomere function via DNA binding. -- Abstract: The nematode Caenorhabditis elegans protein CEH-37 belongs to the paired OTD/OTX family of homeobox-containing homeodomain proteins. CEH-37 shares sequence similarity with homeodomain proteins, although it specifically binds to double-stranded C. elegans telomeric DNA, which is unusual to homeodomain proteins. Here, we report the solution structure of CEH-37 homeodomain and molecular interaction with double-stranded C. elegans telomeric DNA using nuclear magnetic resonance (NMR) spectroscopy. NMR structure shows that CEH-37 homeodomain is composed of a flexible N-terminal region and three α-helices with a helix-turn-helix (HTH) DNA binding motif. Data from size-exclusion chromatography and fluorescence spectroscopy reveal that CEH-37 homeodomain interacts strongly with double-stranded C. elegans telomeric DNA. NMR titration experiments identified residues responsible for specific binding to nematode double-stranded telomeric DNA. These results suggest that C. elegans homeodomain protein, CEH-37 could play an important role in telomere function via DNA binding

Solution structure of CEH-37 homeodomain of the nematode Caenorhabditis elegans

Energy Technology Data Exchange (ETDEWEB)

Moon, Sunjin [Structural Biochemistry and Molecular Biophysics Lab, Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749 (Korea, Republic of); Lee, Yong Woo; Kim, Woo Taek [Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749 (Korea, Republic of); Lee, Weontae, E-mail: wlee@spin.yonsei.ac.kr [Structural Biochemistry and Molecular Biophysics Lab, Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University, Seoul 120-749 (Korea, Republic of)

2014-01-10

Highlights: •We have determined solution structures of CEH-37 homedomain. •CEH-37 HD has a compact α-helical structure with HTH DNA binding motif. •Solution structure of CEH-37 HD shares its molecular topology with that of the homeodomain proteins. •Residues in the N-terminal region and HTH motif are important in binding to Caenorhabditis elegans telomeric DNA. •CEH-37 could play an important role in telomere function via DNA binding. -- Abstract: The nematode Caenorhabditis elegans protein CEH-37 belongs to the paired OTD/OTX family of homeobox-containing homeodomain proteins. CEH-37 shares sequence similarity with homeodomain proteins, although it specifically binds to double-stranded C. elegans telomeric DNA, which is unusual to homeodomain proteins. Here, we report the solution structure of CEH-37 homeodomain and molecular interaction with double-stranded C. elegans telomeric DNA using nuclear magnetic resonance (NMR) spectroscopy. NMR structure shows that CEH-37 homeodomain is composed of a flexible N-terminal region and three α-helices with a helix-turn-helix (HTH) DNA binding motif. Data from size-exclusion chromatography and fluorescence spectroscopy reveal that CEH-37 homeodomain interacts strongly with double-stranded C. elegans telomeric DNA. NMR titration experiments identified residues responsible for specific binding to nematode double-stranded telomeric DNA. These results suggest that C. elegans homeodomain protein, CEH-37 could play an important role in telomere function via DNA binding.

Flavour separation of helicity distributions from deep inelastic muon-deuteron scattering

Czech Academy of Sciences Publication Activity Database

Alekseev, M.; Alexakhin, V. Yu.; Alexandrov, Yu.; Alexeev, G. D.; Amoroso, A.; Austregisilio, A.; Badelek, B.; Balestra, F.; Ball, J.; Barth, J.; Baum, G.; Bedfer, Y.; Bernhard, J.; Bertini, R.; Bettinelli, M.; Birsa, R.; Bisplinghoff, J.; Bordalo, P.; Bradamante, F.; Bravar, A.; Bressan, A.; Brona, G.; Burtin, E.; Bussa, M.; Chapiro, A.; Chiosso, M.; Chung, S.U.; Cicuttin, A.; Colantoni, M.; Crespo, M.; Dalla Torre, S.; Dafni, T.; Das, S.; Dasgupta, S. S.; Denisov, O.; Dhara, L.; Diaz, V.; Dinkelbach, A.; Donskov, S.; Doshita, N.; Duic, V.; Dünnweber, W.; Efremov, A.V.; El Alaoui, A.; Eversheim, P.; Eyrich, W.; Faessler, M.; Ferrero, A.; Finger, M.; Finger jr., M.; Fischer, H.; Franco, C.; Friedrich, J.; Garfagnini, R.; Gautheron, F.; Gavrichtchouk, O.; Gazda, R.; Gerassimov, S.; Geyer, R.; Giorgi, M.; Gobbo, B.; Goertz, S.; Grabmüller, S.; Grajek, O.; Grasso, A.; Grube, B.; Gushterski, R.; Guskov, A.; Haas, F.; Hagemann, R.; von Harrach, D.; Hasegawa, T.; Heckmann, J.; Heinsius, F.; Hermann, R.; Herrmann, F.; Hess, C.; Hinterberger, F.; Horikawa, N.; Höppner, Ch.; d'Hose, N.; Ilgner, C.; Ishimoto, S.; Ivanov, O.; Ivanshin, Yu.; Iwata, T.; Jahn, R.; Jasinski, P.; Jegou, G.; Joosten, R.; Kabuss, E.; Käfer, W.; Kang, D.; Ketzer, B.; Khaustov, G.; Khokhlov, Y.; Kiefer, J.; Kisselev, Y.; Klein, F.; Klimaszewski, K.; Koblitz, S.; Koivuniemi, J.; Kolosov, V.; Komissarov, E.; Kondo, K.; Königsmann, K.; Konopka, R.; Konorov, I.; Konstantinov, V.; Korzenev, A.; Kotzinian, A.; Kouznetsov, O.; Kowalik, K.; Krämer, M.; Kral, A.; Kroumchtein, Z.; Kuhn, R.; Kunne, F.; Kurek, K.; Le Goff, J.; Lednev, A.; Lehmann, A.; Levorato, S.; Lichtenstadt, J.; Liska, T.; Maggiora, A.; Maggiora, M.; Magnon, A.; Mallot, G.; Mann, A.; Marchand, C.; Marroncle, J.; Martin, A.; Marzec, J.; Massmann, F.; Matsuda, T.; Maximov, A.; Meyer, W.; Michigami, T.; Mikhailov, Y.; Moinester, M.; Mutter, A.; Nagaytsev, A.; Nagel, T.; Nassalski, J.; Negrini, S.; Nerling, F.; Neubert, S.; Neyret, D.; Nikolaenko, V.; Olshevsky, A.; Ostrick, M.; Padee, A.; Panknin, R.; Panzieri, D.; Parsamyan, B.; Paul, S.; Pawlukiewicz-Kaminska, B.; Perevalova, E.; Pesaro, G.; Peshekhonov, D.; Piragino, G.; Platchkov, S.; Pochodzalla, J.; Polak, J.; Polyakov, V.; Pontecorvo, G.; Pretz, J.; Quintans, C.; Rajotte, J.; Ramos, S.; Rapatsky, V.; Reicherz, G.; Reggiani, D.; Richter, A.; Robinet, F.; Rocco, E.; Rondio, E.; Ryabchikov, D.; Samoylenko, V.; Sandacz, A.; Santos, H.; Sapozhnikov, M.; Sarkar, S.; Savin, I.; Sbrizzai, G.; Schiavon, P.; Schill, C.; Schmitt, L.; Schröder, W.; Shevchenko, O.; Siebert, H.; Silva, L.; Sinha, L.; Sissakian, A.; Slunecka, M.; Smirnov, G.; Sosio, S.; Sozzi, F.; Srnka, Aleš; Stolarski, M.; Sulc, M.; Sulej, R.; Takekawa, S.; Tessaro, S.; Tessarotto, F.; Teufel, A.; Tkatchev, L.; Venugopal, G.; Virius, M.; Vlassov, N.; Vossen, A.; Weitzel, Q.; Wenzl, K.; Windmolders, R.; Wislicki, W.; Wollny, H.; Zaremba, K.; Zavertyaev, M.; Zemlyanichkina, E.; Ziembicki, M.; Zhao, J.; Zhuravlev, N.; Zvyagin, A.

2009-01-01

Roč. 680, č. 5 (2009), s. 217-224 ISSN 0370-2693 R&D Projects: GA MŠk ME 492 Institutional research plan: CEZ:AV0Z20650511 Keywords : COMPASS * double-spin asymmetry * helicity density * Parton distribution function * flavour separation analysis * polarised DIS and SIDIS reactions * charged kaon asymmetry Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 5.083, year: 2009

Conformal avoidance helical tomotherapy for dogs with nasopharyngeal tumors

International Nuclear Information System (INIS)

Welsh, J.S.; Turek, M.; Mackie, T.R.; Miller, P.; Mehta, M.P.; Forrest, L.J.

2003-01-01

Helical tomotherapy provides a unique means of delivering intensity-modulated radiation therapy (IMRT) using a novel treatment unit, which merges features of a linear accelerator with a helical CT scanner. Thanks to the CT imaging capacity, targeted regions can be visualized prior to, during, or immediately after each treatment. Such image-guidance through megavoltage CT will allow the realization and refinement of the concept of adaptive radiotherapy - the reconstruction of the actually delivered daily dose (as opposed to planned dose) accompanied by prescription adjustments when appropriate. In addition to this unique feature, helical tomotherapy promises further improvements in the specific avoidance of critical normal structures, i.e. conformal avoidance, the counterpart of conformal therapy. The first definitive treatment protocol using helical tomotherapy is presently underway for dogs with nasopharyngeal tumors. In general, such tumors can be treated with conventional external beam radiation therapy but at the cost of severe ocular toxicity due to the anatomy of the canine head. These are readily measurable toxicities and are almost universal in incidence; therefore, the canine nasopharyngeal tumor presents an ideal model to assess the ability to conformally avoid critical structures. It is hoped that conformal avoidance helical tomotherapy will improve tumor control via dose-escalation while reducing ocular toxicity in these veterinary patients. A total of 10 fractions are scheduled for these patients; the first 3 dogs have all received at least 7 fractions delivered via helical tomotherapy. Although preliminary, the first 3 dogs treated have not shown any evidence of ocular toxicity in this ongoing study

Designing self-standing silicon-copper composite helices as anodes for lithium ion batteries

International Nuclear Information System (INIS)

Polat, B.D.; Keles, O.

2016-01-01

In this study, we have fabricated helical thin films to be used as an anode material in lithium ion batteries (LIB). The thin films having various Cu−Si atomic ratios (30–70%, 20–80%, and 10–90%) are prepared by using ion-assisted glancing angle co-deposition. Cu plays a crucial role in holding the electrode together, minimizing overall capacity loss and enabling faster electron transfer thus, improving the electrochemical performances of the electrodes. Increasing the Cu/Si atomic ratio affects the structure of the helices and their alignment. Implementing ion assisted deposition at the beginning of the film deposition helps to improve film adhesion. The Si-20 at.% Cu anode delivers 1885 mAh g"−"1 initially with 98% coulombic efficiency and retains 77% of the capacity after 100 cycles at 100 mA g"−"1. - Highlights: • Highly adherent SiCu helices are deposited by ion assisted glancing angle deposition. • Cu content in the SiCu helices affects the helice' morphology and structure. • SiCu helices with different Cu contents have been used as anodes for LIB. • Helices being like microsprings, improve the mechanical resistance of the anode.

Structure determination of a peptide model of the repeated helical domain in Samia cynthia ricini silk fibroin before spinning by a combination of advanced solid-state NMR methods.

Science.gov (United States)

Nakazawa, Yasumoto; Asakura, Tetsuo

2003-06-18

Fibrous proteins unlike globular proteins, contain repetitive amino acid sequences, giving rise to very regular secondary protein structures. Silk fibroin from a wild silkworm, Samia cynthia ricini, consists of about 100 repeats of alternating polyalanine (poly-Ala) regions of 12-13 residues in length and Gly-rich regions. In this paper, the precise structure of the model peptide, GGAGGGYGGDGG(A)(12)GGAGDGYGAG, which is a typical repeated sequence of the silk fibroin, was determined using a combination of three kinds of solid-state NMR studies; a quantitative use of (13)C CP/MAS NMR chemical shift with conformation-dependent (13)C chemical shift contour plots, 2D spin diffusion (13)C solid-state NMR under off magic angle spinning and rotational echo double resonance. The structure of the model peptide corresponding to the silk fibroin structure before spinning was determined. The torsion angles of the central Ala residue, Ala(19), in the poly-Ala region were determined to be (phi, psi) = (-59 degrees, -48 degrees ) which are values typically associated with alpha-helical structures. However, the torsion angles of the Gly(25) residue adjacent to the C-terminal side of the poly-Ala chain were determined to be (phi, psi) = (-66 degrees, -22 degrees ) and those of Gly(12) and Ala(13) residues at the N-terminal of the poly-Ala chain to be (phi, psi) = (-70 degrees, -30 degrees ). In addition, REDOR experiments indicate that the torsion angles of the two C-terminal Ala residues, Ala(23) and Ala(24), are (phi, psi) = (-66 degrees, -22 degrees ) and those of N-terminal two Ala residues, Ala(13) and Ala(14) are (phi, psi) = (-70 degrees, -30 degrees ). Thus, the local structure of N-terminal and C-terminal residues, and also the neighboring residues of alpha-helical poly-Ala chain in the model peptide is a more strongly wound structure than found in typical alpha-helix structures.

Inorganic-organic hybrid polyoxometalate containing supramolecular helical chains: Preparation, characterization and application in chemically bulk-modified electrode

International Nuclear Information System (INIS)

Han Zhangang; Zhao Yulong; Peng Jun; Liu Qun; Wang Enbo

2005-01-01

An inorganic-organic hybrid polyoxometalate (POM) (Hbpy) 4 [SiMo 12 O 40 ] (1) (bpy = 2,4-bipyridine), has been prepared and characterized. X-ray diffraction study reveals that compound 1 contains interesting organic double helical chains. The hybrid nanoparticles was used as a solid bulkmodifier to fabricate a three-dimensional chemically modified carbon paste electrode (1-CPE) by direct mixing. The electrochemical behavior and electrocatalysis of 1-CPE has been studied in detail. The results indicate that 1-CPE has a good electrocatalytic activity toward the reduction of nitrite in 1 M H 2 SO 4 aqueous solution. 1-CPE shows remarkable stability that can be ascribed to the interactions existed between POM anions and organic double helical bpy chains, which are very important for practical applications in electrode modification

Manipulation of wavefront using helical metamaterials.

Science.gov (United States)

Yang, Zhenyu; Wang, Zhaokun; Tao, Huan; Zhao, Ming

2016-08-08

Helical metamaterials, a kind of 3-dimensional structure, has relatively strong coupling effect among the helical nano-wires. Therefore, it is expected to be a good candidate for generating phase shift and controlling wavefront with high efficiency. In this paper, using the finite-difference time-domain (FDTD) method, we studied the phase shift properties in the helical metamaterials. It is found that the phase shift occurs for both transmitted and reflected light waves. And the maximum of reflection coefficients can reach over 60%. In addition, the phase shift (φ) is dispersionless in the range of 600 nm to 860 nm, that is, it is only dominated by the initial angle (θ) of the helix. The relationship between them is φ = ± 2θ. Using Jones calculus we give a further explanation for these properties. Finally, by arranging the helixes in an array with a constant phase gradient, the phenomenon of anomalous refraction was also observed in a broad wavelength range.

Biot-Savart helicity versus physical helicity: A topological description of ideal flows

Science.gov (United States)

Sahihi, Taliya; Eshraghi, Homayoon

2014-08-01

For an isentropic (thus compressible) flow, fluid trajectories are considered as orbits of a family of one parameter, smooth, orientation-preserving, and nonsingular diffeomorphisms on a compact and smooth-boundary domain in the Euclidian 3-space which necessarily preserve a finite measure, later interpreted as the fluid mass. Under such diffeomorphisms the Biot-Savart helicity of the pushforward of a divergence-free and tangent to the boundary vector field is proved to be conserved and since these circumstances present an isentropic flow, the conservation of the "Biot-Savart helicity" is established for such flows. On the other hand, the well known helicity conservation in ideal flows which here we call it "physical helicity" is found to be an independent constant with respect to the Biot-Savart helicity. The difference between these two helicities reflects some topological features of the domain as well as the velocity and vorticity fields which is discussed and is shown for simply connected domains the two helicities coincide. The energy variation of the vorticity field is shown to be formally the same as for the incompressible flow obtained before. For fluid domains consisting of several disjoint solid tori, at each time, the harmonic knot subspace of smooth vector fields on the fluid domain is found to have two independent base sets with a special type of orthogonality between these two bases by which a topological description of the vortex and velocity fields depending on the helicity difference is achieved since this difference is shown to depend only on the harmonic knot parts of velocity, vorticity, and its Biot-Savart vector field. For an ideal magnetohydrodynamics (MHD) flow three independent constant helicities are reviewed while the helicity of magnetic potential is generalized for non-simply connected domains by inserting a special harmonic knot field in the dynamics of the magnetic potential. It is proved that the harmonic knot part of the vorticity

HANFORD DOUBLE SHELL TANK THERMAL AND SEISMIC PROJECT BUCKLING EVALUATION METHODS AND RESULTS FOR THE PRIMARY TANKS

Energy Technology Data Exchange (ETDEWEB)

MACKEY TC; JOHNSON KI; DEIBLER JE; PILLI SP; RINKER MW; KARRI NK

2009-01-14

This report documents a detailed buckling evaluation of the primary tanks in the Hanford double-shell waste tanks (DSTs), which is part of a comprehensive structural review for the Double-Shell Tank Integrity Project. This work also provides information on tank integrity that specifically responds to concerns raised by the Office of Environment, Safety, and Health (ES&H) Oversight (EH-22) during a review of work performed on the double-shell tank farms and the operation of the aging waste facility (AWF) primary tank ventilation system. The current buckling review focuses on the following tasks: (1) Evaluate the potential for progressive anchor bolt failure and the appropriateness of the safety factors that were used for evaluating local and global buckling. The analysis will specifically answer the following questions: (a) Can the EH-22 scenario develop if the vacuum is limited to -6.6-inch water gage (w.g.) by a relief valve? (b) What is the appropriate factor of safety required to protect against buckling if the EH-22 scenario can develop? (c) What is the appropriate factor of safety required to protect against buckling if the EH-22 scenario cannot develop? (2) Develop influence functions to estimate the axial stresses in the primary tanks for all reasonable combinations of tank loads based on detailed finite element analysis. The analysis must account for the variation in design details and operating conditions between the different DSTs. The analysis must also address the imperfection sensitivity of the primary tank to buckling. (3) Perform a detailed buckling analysis to determine the maximum allowable differential pressure for each of the DST primary tanks at the current specified limits on waste temperature, height, and specific gravity. Based on the concrete anchor bolt loads analysis and the small deformations that are predicted at the unfactored limits on vacuum and axial loads, it is very unlikely that the EH-22 scenario (i.e., progressive anchor bolt

HANFORD DOUBLE-SHELL TANK THERMAL AND SEISMIC PROJECT-BUCKLING EVALUATION METHODS AND RESULTS FOR THE PRIMARY TANKS

International Nuclear Information System (INIS)

Mackey, T.C.; Johnson, K.I.; Deibler, J.E.; Pilli, S.P.; Rinker, M.W.; Karri, N.K.

2009-01-01

This report documents a detailed buckling evaluation of the primary tanks in the Hanford double-shell waste tanks (DSTs), which is part of a comprehensive structural review for the Double-Shell Tank Integrity Project. This work also provides information on tank integrity that specifically responds to concerns raised by the Office of Environment, Safety, and Health (ES and H) Oversight (EH-22) during a review of work performed on the double-shell tank farms and the operation of the aging waste facility (AWF) primary tank ventilation system. The current buckling review focuses on the following tasks: (1) Evaluate the potential for progressive anchor bolt failure and the appropriateness of the safety factors that were used for evaluating local and global buckling. The analysis will specifically answer the following questions: (a) Can the EH-22 scenario develop if the vacuum is limited to -6.6-inch water gage (w.g.) by a relief valve? (b) What is the appropriate factor of safety required to protect against buckling if the EH-22 scenario can develop? (c) What is the appropriate factor of safety required to protect against buckling if the EH-22 scenario cannot develop? (2) Develop influence functions to estimate the axial stresses in the primary tanks for all reasonable combinations of tank loads based on detailed finite element analysis. The analysis must account for the variation in design details and operating conditions between the different DSTs. The analysis must also address the imperfection sensitivity of the primary tank to buckling. (3) Perform a detailed buckling analysis to determine the maximum allowable differential pressure for each of the DST primary tanks at the current specified limits on waste temperature, height, and specific gravity. Based on the concrete anchor bolt loads analysis and the small deformations that are predicted at the unfactored limits on vacuum and axial loads, it is very unlikely that the EH-22 scenario (i.e., progressive anchor

EVOLUTION OF MAGNETIC HELICITY AND ENERGY SPECTRA OF SOLAR ACTIVE REGIONS

International Nuclear Information System (INIS)

Zhang, Hongqi; Brandenburg, Axel; Sokoloff, D. D.

2016-01-01

We adopt an isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field to estimate the magnetic energy and helicity spectra as well as current helicity spectra of two individual active regions (NOAA 11158 and NOAA 11515) and the change of the spectral indices during their development as well as during the solar cycle. The departure of the spectral indices of magnetic energy and current helicity from 5/3 are analyzed, and it is found that it is lower than the spectral index of the magnetic energy spectrum. Furthermore, the fractional magnetic helicity tends to increase when the scale of the energy-carrying magnetic structures increases. The magnetic helicity of NOAA 11515 violates the expected hemispheric sign rule, which is interpreted as an effect of enhanced field strengths at scales larger than 30–60 Mm with opposite signs of helicity. This is consistent with the general cycle dependence, which shows that around the solar maximum the magnetic energy and helicity spectra are steeper, emphasizing the large-scale field

EVOLUTION OF MAGNETIC HELICITY AND ENERGY SPECTRA OF SOLAR ACTIVE REGIONS

Energy Technology Data Exchange (ETDEWEB)

Zhang, Hongqi [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Brandenburg, Axel [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden); Sokoloff, D. D., E-mail: hzhang@bao.ac.cn [Department of Physics, Moscow University, 119992 Moscow (Russian Federation)

2016-03-10

We adopt an isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field to estimate the magnetic energy and helicity spectra as well as current helicity spectra of two individual active regions (NOAA 11158 and NOAA 11515) and the change of the spectral indices during their development as well as during the solar cycle. The departure of the spectral indices of magnetic energy and current helicity from 5/3 are analyzed, and it is found that it is lower than the spectral index of the magnetic energy spectrum. Furthermore, the fractional magnetic helicity tends to increase when the scale of the energy-carrying magnetic structures increases. The magnetic helicity of NOAA 11515 violates the expected hemispheric sign rule, which is interpreted as an effect of enhanced field strengths at scales larger than 30–60 Mm with opposite signs of helicity. This is consistent with the general cycle dependence, which shows that around the solar maximum the magnetic energy and helicity spectra are steeper, emphasizing the large-scale field.

Double-helix stellarator

International Nuclear Information System (INIS)

Moroz, P.E.

1997-09-01

A new stellarator configuration, the Double-Helix Stellarator (DHS), is introduced. This novel configuration features a double-helix center post as the only helical element of the stellarator coil system. The DHS configuration has many unique characteristics. One of them is the extreme low plasma aspect ratio, A ∼ 1--1.2. Other advantages include a high enclosed volume, appreciable rotational transform, and a possibility of extreme-high-β MHD equilibria. Moreover, the DHS features improved transport characteristics caused by the absence of the magnetic field ripple on the outboard of the torus. Compactness, simplicity and modularity of the coil system add to the DHS advantages for fusion applications

Turbulent Helicity in the Atmospheric Boundary Layer

Science.gov (United States)

Chkhetiani, Otto G.; Kurgansky, Michael V.; Vazaeva, Natalia V.

2018-05-01

We consider the assumption postulated by Deusebio and Lindborg (J Fluid Mech 755:654-671, 2014) that the helicity injected into the Ekman boundary layer undergoes a cascade, with preservation of its sign (right- or alternatively left-handedness), which is a signature of the system rotation, from large to small scales, down to the Kolmogorov microscale of turbulence. At the same time, recent direct field measurements of turbulent helicity in the steppe region of southern Russia near Tsimlyansk Reservoir show the opposite sign of helicity from that expected. A possible explanation for this phenomenon may be the joint action of different scales of atmospheric flows within the boundary layer, including the sea-breeze circulation over the test site. In this regard, we consider a superposition of the classic Ekman spiral solution and Prandtl's jet-like slope-wind profile to describe the planetary boundary-layer wind structure. The latter solution mimics a hydrostatic shallow breeze circulation over a non-uniformly heated surface. A 180°-wide sector on the hodograph plane exists, within which the relative orientation of the Ekman and Prandtl velocity profiles favours the left rotation with height of the resulting wind velocity vector in the lowermost part of the boundary layer. This explains the negative (left-handed) helicity cascade toward small-scale turbulent motions, which agrees with the direct field measurements of turbulent helicity in Tsimlyansk. A simple turbulent relaxation model is proposed that explains the measured positive values of the relatively minor contribution to turbulent helicity from the vertical components of velocity and vorticity.

Experimental measurement of fluid force coefficients for helical tube arrays in air cross flow

International Nuclear Information System (INIS)

Shen Shifang; Liu Reilan

1993-01-01

A helical coil steam generator is extensively used in the High Temperature Gas Cooled Reactor (HTGCR) and Sodium Cooled Reactor (SCR) nuclear power stations because of its compact structure, good heat-exchange, and small volume. The experimental model is established by the structure parameter of 200MW HTGCR. The fluid elastic instability of helical tube arrays in air cross flow is studied in this experiment, and the fluid force coefficients of helical tube arrays having the same notational direction of two adjacent layers in air cross flow are obtained. As compared to the fluid force coefficients of cylinder tube arrays, the fluid force coefficients of helical tube arrays are smaller in the low velocity area, and greater in the high velocity area. The experimental results help the study of the dynamic characteristics of helical tube arrays in air cross flow

Effect of Anisotropy Structure on Plume Entropy and Reactive Mixing in Helical Flows

DEFF Research Database (Denmark)

Ye, Yu; Chiogna, Gabriele; Lu, Chunhui

2018-01-01

Plume dilution and reactive mixing can be considerably enhanced by helical flows occurring in three-dimensional anisotropic porous media. In this study, we perform conservative and reactive transport simulations considering different anisotropy structures of a single inclusion with the objective...... of exploring the effect of the inclusion’s geometry and orientation on the patterns of twisted streamlines and on the overall dilution and reaction of solute plumes. We analyzed 100 different scenarios by varying key parameters such as the angle of the anisotropic structures with respect to the average flow...... velocity, the spacing between alternated heterogeneous zones of coarse and fine materials, the permeability contrast between such matrices, and the magnitude of the seepage velocity. Entropy conservation equations and entropy-based metrics for both conservative and reactive species were adopted to quantify...

Helical CT in acute lower gastrointestinal bleeding

International Nuclear Information System (INIS)

Ernst, Olivier; Leroy, Christophe; Sergent, Geraldine; Bulois, Philippe; Saint-Drenant, Sophie; Paris, Jean-Claude

2003-01-01

The purpose of this study was to assess the usefulness of helical CT in depicting the location of acute lower gastrointestinal bleeding. A three-phase helical CT of the abdomen was performed in 24 patients referred for acute lower gastrointestinal bleeding. The diagnosis of the bleeding site was established by CT when there was at least one of the following criteria: spontaneous hyperdensity of the peribowel fat; contrast enhancement of the bowel wall; vascular extravasation of the contrast medium; thickening of the bowel wall; polyp or tumor; or vascular dilation. Diverticula alone were not enough to locate the bleeding site. The results of CT were compared with the diagnosis obtained by colonoscopy, enteroscopy, or surgery. A definite diagnosis was made in 19 patients. The bleeding site was located in the small bowel in 5 patients and the colon in 14 patients. The CT correctly located 4 small bowel hemorrhages and 11 colonic hemorrhages. Diagnosis of the primary lesion responsible for the bleeding was made in 10 patients. Our results suggest that helical CT could be a good diagnostic tool in acute lower gastrointestinal bleeding to help the physician to diagnose the bleeding site. (orig.)

A cosmic double helix in the archetypical quasar 3C273.

Science.gov (United States)

Lobanov, A P; Zensus, J A

2001-10-05

Finding direct evidence for plasma instability in extragalactic jets is crucial for understanding the nature of relativistic outflows from active galactic nuclei. Our radio interferometric observations of the quasar 3C273 made with the orbiting radio telescope, HALCA, and an array of ground telescopes have yielded an image in which the emission across the jet is resolved, revealing two threadlike patterns that form a double helix inside the jet. This double helical structure is consistent with a Kelvin-Helmholtz instability, and at least five different instability modes can be identified and modeled by a light jet with a Lorentz factor of 2 and Mach number of 3.5. The model reproduces in detail the internal structure of the jet on scales of up to 30 milli-arc seconds ( approximately 300 parsecs) and is consistent with the general morphology of the jet on scales of up to 1 kiloparsec.

Neutronics investigation of advanced self-cooled liquid blanket systems in helical reactor

International Nuclear Information System (INIS)

Tanaka, T.; Sagara, A.; Muroga, T.; Youssef, M.Z.

2006-10-01

Neutronics performances of advanced self-cooled liquid blanket systems have been investigated in design activity of the helical-type reactor FFHR2. In the present study, a new three-dimensional (3-D) neutronics calculation system has been developed for the helical-type reactor to enhance quick feedback between neutronics evaluation and design modification. Using this new calculation system, advanced Flibe-cooled and Li-cooled liquid blanket systems proposed for FFHR2 have been evaluated to make clear design issues to enhance neutronics performance. Based on calculated results, modification of the blanket dimensions and configuration have been attempted to achieve the adequate tritium breeding ability and neutron shielding performance in the helical reactor. The total tritium breeding ratios (TBRs) obtained after modifying the blanket dimensions indicated that all the advanced blanket systems proposed for FFHR2 would achieve adequate tritium self-sufficiency by dimension adjustment and optimization of structures in the breeder layers. Issues in neutron shielding performance have been investigated quantitatively using 3-D geometry of the helical blanket system, support structures, poloidal coils etc. Shielding performance of the helical coils against direct neutrons from core plasma would achieve design target by further optimization of shielding materials. However, suppression of the neutron streaming and reflection through the divertor pumping areas in the original design is important issue to protect the poloidal coils and helical coils, respectively. Investigation of the neutron wall loading indicated that the peaking factor of the neutron wall load distribution would be moderated by the toroidal and helical effect of the plasma distribution in the helical reactor. (author)

Design windows and cost analysis on helical reactors

International Nuclear Information System (INIS)

Kozaki, Y.; Imagawa, S.; Sagara, A.

2007-01-01

The LHD type helical reactors are characterized by a large major radius but slender helical coil, which give us different approaches for power plants from tokamak reactors. For searching design windows of helical reactors and discussing their potential as power plants, we have developed a mass-cost estimating model linked with system design code (HeliCos), thorough studying the relationships between major plasma parameters and reactor parameters, and weight of major components. In regard to cost data we have much experience through preparing ITER construction. To compare the weight and cost of magnet systems between tokamak and helical reactors, we broke down magnet systems and cost factors, such as weights of super conducting strands, conduits, support structures, and winding unit costs, through estimating ITER cost data basis. Based on FFHR2m1 deign we considered a typical 3 GWth helical plant (LHD type) with the same magnet size, coil major radius Rc 14 m, magnetic energy 120 GJ, but increasing plasma densities. We evaluated the weight and cost of magnet systems of 3 GWth helical plant, the total magnet weights of 16,000ton and costs of 210 BYen, which are similar values of tokamak reactors (10,200 ton, 110 BYen in ITER 2002 report, and 21,900 ton, 275 BYen in ITER FDR1999). The costs of strands and winding occupy 70% of total magnet costs, and influence entire power plants economics. The design windows analysis and comparative economics studies to optimize the main reactor parameters have been carried out. Economics studies show that it is misunderstanding to consider helical coils are too large and too expensive to achieve power plants. But we should notice that the helical reactor design windows and economics are very sensitive to allowable blanket space (depend on ergodic layer conditions) and diverter configuration for decreasing heat loads. (orig.)

Bearing capacity of helical pile foundation in peat soil from different, diameter and spacing of helical plates

Science.gov (United States)

Fatnanta, F.; Satibi, S.; Muhardi

2018-03-01

In an area dominated by thick peat soil layers, driven piles foundation is often used. These piles are generally skin friction piles where the pile tips do not reach hard stratum. Since the bearing capacity of the piles rely on the resistance of their smooth skin, the bearing capacity of the piles are generally low. One way to increase the bearing capacity of the piles is by installing helical plates around the pile tips. Many research has been performed on helical pile foundation. However, literature on the use of helical pile foundation on peat soil is still hardly found. This research focus on the study of axial bearing capacity of helical pile foundation in peat soil, especially in Riau Province. These full-scale tests on helical pile foundation were performed in a rectangular box partially embedded into the ground. The box is filled with peat soil, which was taken from Rimbo Panjang area in the district of Kampar, Riau Province. Several helical piles with different number, diameter and spacing of the helical plates have been tested and analysed. The tests result show that helical pile with three helical plates of uniform diameter has better bearing capacity compared to other helical piles with varying diameter and different number of helical plates. The bearing capacity of helical pile foundation is affected by the spacing between helical plates. It is found that the effective helical plates spacing for helical pile foundation with diameter of 15cm to 35cm is between 20cm to 30cm. This behaviour may be considered to apply to other type of helical pile foundations in peat soil.

Plasmodium vivax antigen discovery based on alpha-helical coiled coil protein motif

DEFF Research Database (Denmark)

Céspedes, Nora; Habel, Catherine; Lopez-Perez, Mary

2014-01-01

Protein α-helical coiled coil structures that elicit antibody responses, which block critical functions of medically important microorganisms, represent a means for vaccine development. By using bioinformatics algorithms, a total of 50 antigens with α-helical coiled coil motifs orthologous to Pla...

Energy and helicity of magnetic torus knots and braids

Science.gov (United States)

Oberti, Chiara; Ricca, Renzo L.

2018-02-01

By considering steady magnetic fields in the shape of torus knots and unknots in ideal magnetohydrodynamics, we compute some fundamental geometric and physical properties to provide estimates for magnetic energy and helicity. By making use of an appropriate parametrization, we show that knots with dominant toroidal coils that are a good model for solar coronal loops have negligible total torsion contribution to magnetic helicity while writhing number provides a good proxy. Hence, by the algebraic definition of writhe based on crossing numbers, we show that the estimated values of writhe based on image analysis provide reliable information for the exact values of helicity. We also show that magnetic energy is linearly related to helicity, and the effect of the confinement of magnetic field can be expressed in terms of geometric information. These results can find useful application in solar and plasma physics, where braided structures are often present.

Endoscopic placement of double-J ureteric stents in children as a treatment for primary hydronephrosis.

Science.gov (United States)

Pogorelić, Zenon; Brković, Tomislava; Budimir, Dražen; Todorić, Jakov; Košuljandić, Đurđica; Jerončić, Ana; Biočić, Mihovil; Saraga, Marijan

2017-06-01

The aim of this study was to determine the efficacy and potential complications of double-J ureteric stents in the treatment of primary hydronephrosis in pediatric patients. A retrospective case-records review of 133 patients (45 girls and 88 boys) treated because of primary hydronephrosis with double-J ureteric stents, in Department of Pediatric Surgery, Split University Hospital, between December 1997 and December 2014, was performed. Success of treatment, results of follow up investigations and complications were recorded. Patients were followed up clinically and radiologically for a minimum of 2 years following stent insertion. In all, 133 endoscopic double-J ureteric stents insertions were performed. Of the total number of patients, left-sided hydronephrosis was found in 82 patients, right-sided in 38, and bilateral in 13 patients. The median age of children was 2 years (range 0-17 years). Mean hospital stay was 2 days (range 1-10 days). In primary hydronephrosis, double-J ureteric stenting alone was effective with resolution of hydronephrosis in 73% of cases (97/133 insertions). Regarding the age of the patients the highest success of 83.5% was achieved in age group 0-4 years. Success in groups 5-9 years; 10-14 years and 15-17 years were 47%; 33.5% and 0%, respectively. Several complications have been recorded: symptomatic infections, migration in the renal pelvis and bladder, progression of hydronephrosis, spontaneously prolapse of prosthesis, bleeding and perforation of the renal pelvis. A significant, decreasing trend in success rates by age of participants was observed (p hydronephrosis. Endoscopic placement of ureteric double-J stents should be considered as a first-line treatment in the management of primary hydronephrosis especially in children till 4 years of age, with success rate of 83.5% and without the need for conventional surgery. In a case of failure we are time-consuming to definitive surgery.

Exploring biological effects of MoS{sub 2} nanosheets on native structures of α-helical peptides

Energy Technology Data Exchange (ETDEWEB)

Gu, Zonglin; Li, Weifeng, E-mail: wfli@suda.edu.cn, E-mail: ruhong@us.ibm.com [School for Radiological and Interdisciplinary Sciences (RAD-X) and Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123 (China); Hong, Linbi [Computational Biological Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Zhou, Ruhong, E-mail: wfli@suda.edu.cn, E-mail: ruhong@us.ibm.com [School for Radiological and Interdisciplinary Sciences (RAD-X) and Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Soochow University, Suzhou 215123 (China); Computational Biological Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Department of Chemistry, Columbia University, New York, New York 10027 (United States)

2016-05-07

Recent reports of mono- and few-layer molybdenum disulfide (MoS{sub 2}), a representative transition metal dichacogenide (TMD), as antibacterial and anticancer agents have shed light on their potential in biomedical applications. To better facilitate these promising applications, one needs to understand the biological effects of these TMDs as well, such as their potential adverse effects on protein structure and function. Here, we sought to understand the interaction of MoS{sub 2} nanosheets with peptides using molecular dynamics simulations and a simple model polyalanine with various lengths (PA{sub n}, n = 10, 20, 30, and 40; mainly α − helices). Our results demonstrated that MoS{sub 2} monolayer has an exceptional capability to bind all peptides in a fast and strong manner. The strong attraction from the MoS{sub 2} nanosheet is more than enough to compensate the energy needed to unfold the peptide, regardless of the length, which induces drastic disruptions to the intra-peptide hydrogen bonds and subsequent secondary structures of α − helices. This universal phenomenon may point to the potential nanotoxicity of MoS{sub 2} when used in biological systems. Moreover, these results aligned well with previous findings on the potential cytotoxicity of TMD nanomaterials.

Topological characteristics of helical repeat proteins

NARCIS (Netherlands)

Groves, M R; Barford, D

The recent elucidation of protein structures based upon repeating amino acid motifs, including the armadillo motif, the HEAT motif and tetratricopeptide repeats, reveals that they belong to the class of helical repeat proteins. These proteins share the common property of being assembled from tandem

Helical CT defecography

International Nuclear Information System (INIS)

Ferrando, R.; Fiorini, G.; Beghello, A.; Cicio, G.R.; Derchi, L.E.; Consigliere, M.; Resasco, M.; Tornago, S.

1999-01-01

The purpose of this work is to investigate the possible role of Helical CT defecography in pelvic floor disorders by comparing the results of the investigations with those of conventional defecography. The series analyzed consisted of 90 patients, namely 62 women and 28 men, ranging in age 24-82 years. They were all submitted to conventional defecography, and 18 questionable cases were also studied with Helical CT defecography. The conventional examination was performed during the 4 standard phases of resting, squeezing, Valsalva and straining; it is used a remote-control unit. The parameters for Helical CT defecography were: 5 mm beam collimation, pitch 2, 120 KV, 250 m As and 18-20 degrees gantry inclination to acquire coronal images of the pelvic floor. The rectal ampulla was distended with a bolus of 300 mL nonionic iodinated contrast agent (dilution: 3g/cc). The patient wore a napkin and was seated on the table, except for those who could not hold the position and were thus examined supine. Twenty-second helical scans were performed at rest and during evacuation; multiplanar reconstructions were obtained especially on the sagittal plane for comparison with conventional defecographic images. Coronal Helical CT defecography images permitted to map the perineal floor muscles, while sagittal reconstructions provided information on the ampulla and the levator ani. To conclude, Helical CT defecography performed well in study of pelvic floor disorders and can follow conventional defecography especially in questionable cases [it

HELICAL MOTIONS OF FINE-STRUCTURE PROMINENCE THREADS OBSERVED BY HINODE AND IRIS

Energy Technology Data Exchange (ETDEWEB)

Okamoto, Takenori J. [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Liu, Wei [Bay Area Environmental Research Institute, 625 2nd Street, Suite 209, Petaluma, CA 94952 (United States); Tsuneta, Saku, E-mail: joten.okamoto@nao.ac.jp [ISAS/JAXA, Sagamihara, Kanagawa 252-5210 (Japan)

2016-11-10

Fine-structure dynamics in solar prominences holds critical clues to understanding their physical nature of significant space-weather implications. We report evidence of rotational motions of horizontal helical threads in two active-region prominences observed by the Hinode and/or Interface Region Imaging Spectrograph satellites at high resolution. In the first event, we found transverse motions of brightening threads at speeds up to 55 km s{sup -1} seen in the plane of the sky. Such motions appeared as sinusoidal space–time trajectories with a typical period of ∼390 s, which is consistent with plane-of-sky projections of rotational motions. Phase delays at different locations suggest the propagation of twists along the threads at phase speeds of 90–270 km s{sup -1}. At least 15 episodes of such motions occurred in two days, none associated with an eruption. For these episodes, the plane-of-sky speed is linearly correlated with the vertical travel distance, suggestive of a constant angular speed. In the second event, we found Doppler velocities of 30–40 km s{sup -1} in opposite directions in the top and bottom portions of the prominence, comparable to the plane-of-sky speed. The moving threads have about twice broader line widths than stationary threads. These observations, when taken together, provide strong evidence for rotations of helical prominence threads, which were likely driven by unwinding twists triggered by magnetic reconnection between twisted prominence magnetic fields and ambient coronal fields.

Silica biomineralization via the self-assembly of helical biomolecules.

Science.gov (United States)

Liu, Ben; Cao, Yuanyuan; Huang, Zhehao; Duan, Yingying; Che, Shunai

2015-01-21

The biomimetic synthesis of relevant silica materials using biological macromolecules as templates via silica biomineralization processes attract rapidly rising attention toward natural and artificial materials. Biomimetic synthesis studies are useful for improving the understanding of the formation mechanism of the hierarchical structures found in living organisms (such as diatoms and sponges) and for promoting significant developments in the biotechnology, nanotechnology and materials chemistry fields. Chirality is a ubiquitous phenomenon in nature and is an inherent feature of biomolecular components in organisms. Helical biomolecules, one of the most important types of chiral macromolecules, can self-assemble into multiple liquid-crystal structures and be used as biotemplates for silica biomineralization, which renders them particularly useful for fabricating complex silica materials under ambient conditions. Over the past two decades, many new silica materials with hierarchical structures and complex morphologies have been created using helical biomolecules. In this review, the developments in this field are described and the recent progress in silica biomineralization templating using several classes of helical biomolecules, including DNA, polypeptides, cellulose and rod-like viruses is summarized. Particular focus is placed on the formation mechanism of biomolecule-silica materials (BSMs) with hierarchical structures. Finally, current research challenges and future developments are discussed in the conclusion. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Concept and development of measurement method of time sensitivity profile (TSP) in X-ray CT. Comparison of non-helical, single-slice helical, and multi-slice helical scans

International Nuclear Information System (INIS)

Tsujioka, Katsumi; Ida, Yoshihiro; Ohtsubo, Hironori; Takahashi, Yasukata; Niwa, Masayoshi

2000-01-01

We focused on the time element contained in a single CT image, and devised the concept of a time-sensitivity profile (TSP) describing how the time element is translated into an image. We calculated the data collection time range when the helical pitch is changed in non helical scans, single slice helical scans, and multi slice helical scans. We then calculated the time sensitivity profile (TSP) from the weighting applied when the data collection time range is translated into an image. TSP was also measured for each scanning method using our self-made moving phantom. TSPs obtained from the calculation and the experiments were very close. TSP showed interesting characteristics with each scanning method, especially in the case of multi slice helical scanning, in which TSP became shorter as helical pitch increased. We referred to the TSP's FWHM as the effective scanning time. When we conducted multi slice helical scanning at helical pitch 3, the effective scanning time increased to about 24% longer than that of a non helical scan. When we conducted multi slice helical scanning at helical pitch 5 or 6, the effective scanning time was about half that of a non helical scan. The time sensitivity profile (TSP) is a totally new concept that we consider an important element in discussing the time resolution of a CT scanner. The results of this review will provide significant data in determining the scanning parameters when scanning a moving object. (author)

A Theoretical-Experimental Comparison of an Improved Ammonia-Water Bubble Absorber by Means of a Helical Static Mixer

Directory of Open Access Journals (Sweden)

Jesús Cerezo

2017-12-01

Full Text Available The heat transfer in double pipe heat exchangers is very poor. This complicates its application in absorption cooling systems, however, the implementation of simple passive techniques should help to increase the heat and mass transfer mainly in the absorber. This paper carried out a simulation and its experimental comparison of a NH3-H2O bubble absorption process using a double tube heat exchanger with a helical screw static mixer in both central and annular sides. The experimental results showed that the absorption heat load per area is 31.61% higher with the helical screw mixer than the smooth tube. The theoretical and experimental comparison showed that the absorption heat load difference values were 28.0 and 21.9% for smooth tube and the helical mixer, respectively. These difference values were caused by the calculation of the log mean temperature difference in equilibrium conditions to avoid the overlap of solution temperatures. Therefore, the theoretical and experimental results should be improved when the absorption heat is included in the heat transfer equation or avoiding the operation condition when output is lower than input solution temperature.

Secondary structure of prokaryotic 5S ribosomal ribonucleic acids: a study with ribonucleases

DEFF Research Database (Denmark)

Douthwaite, S; Garrett, R A

1981-01-01

The structures of 5S ribosomal RNAs from Escherichia coli and Bacillus stearothermophilus were examined by using ribonucleases A, T1, and T2 and a double helix specific cobra venom ribonuclease. By using both 5' and 3'-32P-end labeling methods and selecting for digested but intact 5S RNA molecules...... evidence for three of the helical regions of the Fox and Woese model of 5S RNA [Fox, G. E., & Woese, C. (1975) Nature (London) 256, 505] and support other important structural features which include a nucleotide looped out from a helical region which has been proposed as a recognition site for protein L18....

HANFORD DOUBLE-SHELL TANK (DST) THERMAL and SEISMIC PROJECT-BUCKLING EVALUATION METHODS and RESULTS FOR THE PRIMARY TANKS

International Nuclear Information System (INIS)

Mackey, T.C.; Johnson, K.I.; Deibler, J.E.; Pilli, S.P.; Rinker, M.W.; Karri, N.K.

2007-01-01

This report documents a detailed buckling evaluation of the primary tanks in the Hanford double-shell waste tanks (DSTs), which is part of a comprehensive structural review for the Double-Shell Tank Integrity Project. This work also provides information on tank integrity that specifically responds to concerns raised by the Office of Environment, Safety, and Health (ES and H) Oversight (EH-22) during a review of work performed on the double-shell tank farms and the operation of the aging waste facility (AWF) primary tank ventilation system. The current buckling review focuses on the following tasks: (1) Evaluate the potential for progressive I-bolt failure and the appropriateness of the safety factors that were used for evaluating local and global buckling. The analysis will specifically answer the following questions: (a) Can the EH-22 scenario develop if the vacuum is limited to -6.6-inch water gage (w.g.) by a relief valve? (b) What is the appropriate factor of safety required to protect against buckling if the EH-22 scenario can develop? (c) What is the appropriate factor of safety required to protect against buckling if the EH-22 scenario cannot develop? (2) Develop influence functions to estimate the axial stresses in the primary tanks for all reasonable combinations of tank loads, based on detailed finite element analysis. The analysis must account for the variation in design details and operating conditions between the different DSTs. The analysis must also address the imperfection sensitivity of the primary tank to buckling. (3) Perform a detailed buckling analysis to determine the maximum allowable differential pressure for each of the DST primary tanks at the current specified limits on waste temperature, height, and specific gravity. Based on the I-bolt loads analysis and the small deformations that are predicted at the unfactored limits on vacuum and axial loads, it is very unlikely that the EH-22 scenario (i.e., progressive I-bolt failure leading to

Hexagonally Ordered Arrays of α-Helical Bundles Formed from Peptide-Dendron Hybrids

Energy Technology Data Exchange (ETDEWEB)

Barkley, Deborah A. [Department; Rokhlenko, Yekaterina [Department; Marine, Jeannette E. [Department; David, Rachelle [Department; Sahoo, Dipankar [Department; Watson, Matthew D. [Department; Koga, Tadanori [Department; Department; Osuji, Chinedum O. [Department; Rudick, Jonathan G. [Department

2017-10-24

Combining monodisperse building blocks that have distinct folding properties serves as a modular strategy for controlling structural complexity in hierarchically organized materials. We combine an α-helical bundle-forming peptide with self-assembling dendrons to better control the arrangement of functional groups within cylindrical nanostructures. Site-specific grafting of dendrons to amino acid residues on the exterior of the α-helical bundle yields monodisperse macromolecules with programmable folding and self-assembly properties. The resulting hybrid biomaterials form thermotropic columnar hexagonal mesophases in which the peptides adopt an α-helical conformation. Bundling of the α-helical peptides accompanies self-assembly of the peptide-dendron hybrids into cylindrical nanostructures. The bundle stoichiometry in the mesophase agrees well with the size found in solution for α-helical bundles of peptides with a similar amino acid sequence.

Helical polyurethane-attapulgite nanocomposite: Preparation, characterization and study of optical activity

International Nuclear Information System (INIS)

Wang Zhiqiang; Zhou Yuming; Sun Yanqing; Fan Kai; Guo Xingxing; Jiang Xiaolei

2009-01-01

Helical polyurethane-attapulgite (BM-ATT) based on R-1,1'-binaphthyl-2',2-diol (R-BINOL) composite was prepared after the surface modification of attapulgite (ATT). BM-ATT was characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HTEM) and vibrational circular dichroism (VCD) spectroscopy. FT-IR and XRD analyses indicate that the helical polyurethane has been successfully grafted onto the surfaces of the modified ATT without destroying the original crystalline structure of ATT. BM-ATT exhibits the rod-like structure by SEM, TEM, and HTEM photographs. BM-ATT displays obvious Cotton effect for some absorbance in VCD spectrum, and its optical activity results from the singlehanded conformation of helical polyurethane. - Graphical Abstract: Helical polyurethane-attapulgite (BM-ATT) based on R-1,1'-binaphthyl-2',2-diol (R-BINOL) nanocomposite was prepared after surface modification of attapulgite (ATT). This rod-like composite is coated by the optically active polyurethane shell on the surfaces.

Temperature-dependent structural changes in intrinsically disordered proteins: formation of alpha-helices or loss of polyproline II?

DEFF Research Database (Denmark)

Kjærgaard, Magnus; Nørholm, Ann-Beth; Hendus-Altenburger, Ruth

2010-01-01

temperature, which most likely reflects formation of transient alpha-helices or loss of polyproline II (PPII) content. Using three IDPs, ACTR, NHE1, and Spd1, we show that the temperature-induced structural change is common among IDPs and is accompanied by a contraction of the conformational ensemble...... with increasing temperature, and accordingly these were not responsible for the change in the CD spectra. In contrast, the nonhelical regions exhibited a general temperature-dependent structural change that was independent of long-range interactions. The temperature-dependent CD spectroscopic signature of IDPs...

Quark helicity distributions from longitudinal spin asymmetries in muon-proton and muon-deuteron scattering

CERN Document Server

Alekseev, M G; Alexandrov, Yu; Alexeev, G D; Amoroso, A; Austregesilo, A; Badelek, B; Balestra, F; Barth, J; Baum, G; Bedfer, Y; Bernhard, J; Bertini, R; Bettinelli, M; Birsa, R; Bisplinghoff, J; Bordalo, P; Bradamante, F; Bravar, A; Bressan, A; Brona, G; Burtin, E; Bussa, M P; Chaberny, D; Chiosso, M; Chung, S U; Cicuttin, A; Colantoni, M; Crespo, M L; Dalla Torre, S; Das, S; Dasgupta, S S; Denisov, O Yu; Dhara, L; Diaz, V; Donskov, S V; Doshita, N; Duic, V; Dunnweber, W; Efremov, A; El Alaoui, A; Eversheim, P D; Eyrich, W; Faessler, M; Ferrero, A; Filin, A; Finger, M; Finger, M., Jr; Fischer, H; Franco, C; Friedrich, J M; Garfagnini, R; Gautheron, F; Gavrichtchouk, O P; Gazda, R; Gerassimov, S; Geyer, R; Giorgi, M; Gnesi, I; Gobbo, B; Goertz, S; Grabmuller, S; Grasso, A; Grube, B; Gushterski, R; Guskov, A; Haas, F; von Harrach, D; Hasegawa, T; Heinsius, F H; Herrmann, F; Hess, C; Hinterberger, F; Horikawa, N; Hoppner, Ch; d'Hose, N; Ilgner, C; Ishimoto, S; Ivanov, O; Ivanshin, Yu; Iwata, T; Jahn, R; Jasinski, P; Jegou, G; Joosten, R; Kabuss, E; Kang, D; Ketzer, B; Khaustov, G V; Khokhlov, Yu.A; Kisselev, Yu; Klein, F; Klimaszewski, K; Koblitz, S; Koivuniemi, J H; Kolosov, V N; Kondo, K; Konigsmann, K; Konopka, R; Konorov, I; Konstantinov, V F; Korzenev, A; Kotzinian, A M; Kouznetsov, O; Kowalik, K; Kramer, M; Kral, A; Kroumchtein, Z V; Kuhn, R; Kunne, F; Kurek, K; Lauser, L; Le Goff, J M; Lednev, A A; Lehmann, A; Levorato, S; Lichtenstadt, J; Liska, T; Maggiora, A; Maggiora, M; Magnon, A; Makke, N; Mallot, G K; Mann, A; Marchand, C; Martin, A; Marzec, J; Massmann, F; Matsuda, T; Meyer, W; Michigami, T; Mikhailov, Yu.V; Moinester, M A; Mutter, A; Nagaytsev, A; Nagel, T; Nassalski, J; Negrini, T; Nerling, F; Neubert, S; Neyret, D; Nikolaenko, V I; Nunes, A S; Olshevsky, A G; Ostrick, M; Padee, A; Panknin, R; Panzieri, D; Parsamyan, B; Paul, S; Pawlukiewicz-Kaminska, B; Perevalova, E; Pesaro, G; Peshekhonov, D V; Piragino, G; Platchkov, S; Pochodzalla, J; Polak, J; Polyakov, V A; Pontecorvo, G; Pretz, J; Quintans, C; Rajotte, J F; Ramos, S; Rapatsky, V; Reicherz, G; Richter, A; Robinet, F; Rocco, E; Rondio, E; Ryabchikov, D I; Samoylenko, V D; Sandacz, A; Santos, H; Sapozhnikov, M G; Sarkar, S; Savin, I A; Sbrizzai, G; Schiavon, P; Schill, C; Schluter, T; Schmitt, L; Schopferer, S; Schroder, W; Shevchenko, O Yu; Siebert, H W; Silva, L; Sinha, L; Sissakian, A N; Slunecka, M; Smirnov, G I; Sosio, S; Sozzi, F; Srnka, A; Stolarski, M; Sulc, M; Sulej, R; Takekawa, S; Tessaro, S; Tessarotto, F; Teufel, A; Tkatchev, L G; Uhl, S; Uman, I; Virius, M; Vlassov, N V; Vossen, A; Weitzel, Q; Windmolders, R; Wislicki, W; Wollny, H; Zaremba, K; Zavertyaev, M; Zemlyanichkina, E; Ziembicki, M; Zhao, J; Zhuravlev, N; Zvyagin, A

2010-01-01

Double-spin asymmetries for production of charged pions and kaons in semi-inclusive deep-inelastic muon scattering have been measured by the COMPASS experiment at CERN. The data, obtained by scattering a 160 GeV muon beam off a longitudinally polarised NH_3 target, cover a range of the Bjorken variable x between 0.004 and 0.7. A leading order evaluation of the helicity distributions for the three lightest quarks and antiquark flavours derived from these asymmetries and from our previous deuteron data is presented. The resulting values of the sea quark distributions are small and do not show any sizable dependence on x in the range of the measurements. No significant difference is observed between the strange and antistrange helicity distributions, both compatible with zero. The integrated value of the flavour asymmetry of the helicity distribution of the light-quark sea, \\Delta u-bar - \\Delta d-bar, is found to be slightly positive, about 1.5 standard deviations away from zero.

Unique microporous NbO-type Co{sup II}/Zn{sup II} MOFs from double helical chains: Sorption and luminescent properties

Energy Technology Data Exchange (ETDEWEB)

Dong, Wen-Wen; Xia, Liang; Peng, Zhen; Zhao, Jun; Wu, Ya-Pan [College of Materials and Chemical Engineering, Hubei Provincial Collaborative Innovation Center for New Energy Microgrid, Key laboratory of inorganic nonmetallic crystalline and energy conversion materials, China Three Gorges University, Yichang 443002 (China); Zhang, Jian [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fujian, Fuzhou 350002 (China); Li, Dong-Sheng, E-mail: lidongsheng1@126.com [College of Materials and Chemical Engineering, Hubei Provincial Collaborative Innovation Center for New Energy Microgrid, Key laboratory of inorganic nonmetallic crystalline and energy conversion materials, China Three Gorges University, Yichang 443002 (China)

2016-06-15

Under solvothermal conditions, the reactions of Co{sup II}/Zn{sup II} ions with bent ligand 3-(pyridin-4-yl)-5-(pyrazin-2-yl)-1H-1,2,4-triazole (4-Hpzpt) afford two compounds {[M(4-pzpt)_2] guest}{sub n} (guest=H{sub 2}O, M=Co{sup II} (1), Zn{sup II} (2)). Both compounds are the thermally and hydrolytically robust 4-connected 3D NbO framework, which formed by double helical chains to give rise to 1D hollow nanochannel with uncoordinated nitrogens completely exposed on the pore surface. Compound 1 exhibits improved N{sub 2}, CO{sub 2} and H{sub 2} uptake capacities, while compound 2 displays the strong luminescent emission with obvious red shift. - Graphical abstract: Two 2-fold interpenetrated NbO-type MOFs with 1D nanochannel were synthesized. Compound 1 exhibits improved N{sub 2}, CO{sub 2} and H{sub 2} uptake capacities, while compound 2 displays the strong fluorescent emission with obvious red shift. Display Omitted.

Pulling Helices inside Bacteria: Imperfect Helices and Rings

Science.gov (United States)

Allard, Jun F.; Rutenberg, Andrew D.

2009-04-01

We study steady-state configurations of intrinsically-straight elastic filaments constrained within rod-shaped bacteria that have applied forces distributed along their length. Perfect steady-state helices result from axial or azimuthal forces applied at filament ends, however azimuthal forces are required for the small pitches observed for MreB filaments within bacteria. Helix-like configurations can result from distributed forces, including coexistence between rings and imperfect helices. Levels of expression and/or bundling of the polymeric protein could mediate this coexistence.

Double-hit or dual expression of MYC and BCL2 in primary cutaneous large B-cell lymphomas.

Science.gov (United States)

Menguy, Sarah; Frison, Eric; Prochazkova-Carlotti, Martina; Dalle, Stephane; Dereure, Olivier; Boulinguez, Serge; Dalac, Sophie; Machet, Laurent; Ram-Wolff, Caroline; Verneuil, Laurence; Gros, Audrey; Vergier, Béatrice; Beylot-Barry, Marie; Merlio, Jean-Philippe; Pham-Ledard, Anne

2018-03-26

In nodal diffuse large B-cell lymphoma, the search for double-hit with MYC and BCL2 and/or BCL6 rearrangements or for dual expression of BCL2 and MYC defines subgroups of patients with altered prognosis that has not been evaluated in primary cutaneous large B-cell lymphoma. Our objectives were to assess the double-hit and dual expressor status in a cohort of 44 patients with primary cutaneous large B-cell lymphoma according to the histological subtype and to evaluate their prognosis relevance. The 44 cases defined by the presence of more than 80% of large B-cells in the dermis corresponded to 21 primary cutaneous follicle centre lymphoma with large cell morphology and 23 primary cutaneous diffuse large B-cell lymphoma, leg type. Thirty-one cases (70%) expressed BCL2 and 29 (66%) expressed MYC. Dual expressor profile was observed in 25 cases (57%) of either subtypes (n = 6 or n = 19, respectively). Only one primary cutaneous follicle centre lymphoma, large-cell case had a double-hit status (2%). Specific survival was significantly worse in primary cutaneous diffuse large B-cell lymphoma, leg type than in primary cutaneous follicle centre lymphoma, large cell (p = 0.021) and for the dual expressor primary cutaneous large B-cell lymphoma group (p = 0.030). Both overall survival and specific survival were worse for patients belonging to the dual expressor primary cutaneous diffuse large B-cell lymphoma, leg type subgroup (p = 0.001 and p = 0.046, respectively). Expression of either MYC and/or BCL2 negatively impacted overall survival (p = 0.017 and p = 0.018 respectively). As the differential diagnosis between primary cutaneous follicle centre lymphoma, large cell and primary cutaneous diffuse large B-cell lymphoma, leg type has a major impact on prognosis, dual-expression of BCL2 and MYC may represent a new diagnostic criterion for primary cutaneous diffuse large B-cell lymphoma, leg type subtype and further identifies patients with

DNA Structure and Supercoiling: Ribbons and a Yo-Yo Model

Science.gov (United States)

Van Horn, J. David

2011-01-01

The double-helical structure of DNA is a pop cultural icon. Images of the DNA molecule appear in newspapers, popular journals, and advertisements. In addition to scientific instrument sales, the aura surrounding the central molecule of life has been used to sell everything from perfume to beverages and is the inspiration of items ranging from…

Sequence and conformational preferences at termini of α-helices in membrane proteins: role of the helix environment.

Science.gov (United States)

Shelar, Ashish; Bansal, Manju

2014-12-01

α-Helices are amongst the most common secondary structural elements seen in membrane proteins and are packed in the form of helix bundles. These α-helices encounter varying external environments (hydrophobic, hydrophilic) that may influence the sequence preferences at their N and C-termini. The role of the external environment in stabilization of the helix termini in membrane proteins is still unknown. Here we analyze α-helices in a high-resolution dataset of integral α-helical membrane proteins and establish that their sequence and conformational preferences differ from those in globular proteins. We specifically examine these preferences at the N and C-termini in helices initiating/terminating inside the membrane core as well as in linkers connecting these transmembrane helices. We find that the sequence preferences and structural motifs at capping (Ncap and Ccap) and near-helical (N' and C') positions are influenced by a combination of features including the membrane environment and the innate helix initiation and termination property of residues forming structural motifs. We also find that a large number of helix termini which do not form any particular capping motif are stabilized by formation of hydrogen bonds and hydrophobic interactions contributed from the neighboring helices in the membrane protein. We further validate the sequence preferences obtained from our analysis with data from an ultradeep sequencing study that identifies evolutionarily conserved amino acids in the rat neurotensin receptor. The results from our analysis provide insights for the secondary structure prediction, modeling and design of membrane proteins. © 2014 Wiley Periodicals, Inc.

Experimental study on the double barrier structure at room temperature

Energy Technology Data Exchange (ETDEWEB)

Sheng, H Y; Chua, S J [Centre for Optoelectronics, Dept. of Electrical Engineering, National Univ. of Singapore (Singapore)

1994-06-15

An experimental study of AlAs / GaAs / AlAs double barrier structure is carried out. The double barrier and quantum well structure are grown by MBE. The peak-to-valley ratio 2.6 : 1 with peak current density of 1.6 kA/cm/sup 2 at room temperature have been achieved. (authors)

Helically symmetric experiment, (HSX) goals, design and status

International Nuclear Information System (INIS)

Anderson, F.S.B.; Almagri, A.F.; Anderson, D.T.; Matthews, P.G.; Talmadge, J.N.; Shohet, J.L.

1995-01-01

HSX is a quasi-helically symmetric (QHS) stellarator currently under construction at the Torsatron-Stellarator Laboratory of the University of Wisconsin-Madison. This device is unique in its magnetic design in that the magnetic field spectrum possesses only a single dominant (helical) component. This design avoids the large direct orbit losses and the low-collisionality neoclassical losses associated with conventional stellarators. The restoration of symmetry to the confining magnetic field makes the neoclassical confinement in this device analogous to an axisymmetric q=1/3 tokamak. The HSX device has been designed with a clear set of primary physics goals: demonstrate the feasibility of construction of a QHS device, examine single particle confinement of injected ions with regard to magnetic field symmetry breaking, compare density and temperature profiles in this helically symmetric system to those for axisymmetric tokamaks and conventional stellarators, examine electric fields and plasma rotation with edge biasing in relation to L-H transitions in symmetric versus non-symmetric stellarator systems, investigate QHS effects on 1/v regime electron confinement, and examine how greatly-reduced neoclassical electron thermal conductivity compares to the experimental χ e profile. 3 refs., 4 figs., 1 tab

Helical chirality: a link between local interactions and global topology in DNA.

Directory of Open Access Journals (Sweden)

Youri Timsit

Full Text Available DNA supercoiling plays a major role in many cellular functions. The global DNA conformation is however intimately linked to local DNA-DNA interactions influencing both the physical properties and the biological functions of the supercoiled molecule. Juxtaposition of DNA double helices in ubiquitous crossover arrangements participates in multiple functions such as recombination, gene regulation and DNA packaging. However, little is currently known about how the structure and stability of direct DNA-DNA interactions influence the topological state of DNA. Here, a crystallographic analysis shows that due to the intrinsic helical chirality of DNA, crossovers of opposite handedness exhibit markedly different geometries. While right-handed crossovers are self-fitted by sequence-specific groove-backbone interaction and bridging Mg(2+ sites, left-handed crossovers are juxtaposed by groove-groove interaction. Our previous calculations have shown that the different geometries result in differential stabilisation in solution, in the presence of divalent cations. The present study reveals that the various topological states of the cell are associated with different inter-segmental interactions. While the unstable left-handed crossovers are exclusively formed in negatively supercoiled DNA, stable right-handed crossovers constitute the local signature of an unusual topological state in the cell, such as the positively supercoiled or relaxed DNA. These findings not only provide a simple mechanism for locally sensing the DNA topology but also lead to the prediction that, due to their different tertiary intra-molecular interactions, supercoiled molecules of opposite signs must display markedly different physical properties. Sticky inter-segmental interactions in positively supercoiled or relaxed DNA are expected to greatly slow down the slithering dynamics of DNA. We therefore suggest that the intrinsic helical chirality of DNA may have oriented the early

Self-assembly of hard helices: a rich and unconventional polymorphism.

Science.gov (United States)

Kolli, Hima Bindu; Frezza, Elisa; Cinacchi, Giorgio; Ferrarini, Alberta; Giacometti, Achille; Hudson, Toby S; De Michele, Cristiano; Sciortino, Francesco

2014-11-07

Hard helices can be regarded as a paradigmatic elementary model for a number of natural and synthetic soft matter systems, all featuring the helix as their basic structural unit, from natural polynucleotides and polypeptides to synthetic helical polymers, and from bacterial flagella to colloidal helices. Here we present an extensive investigation of the phase diagram of hard helices using a variety of methods. Isobaric Monte Carlo numerical simulations are used to trace the phase diagram; on going from the low-density isotropic to the high-density compact phases a rich polymorphism is observed, exhibiting a special chiral screw-like nematic phase and a number of chiral and/or polar smectic phases. We present full characterization of the latter, showing that they have unconventional features, ascribable to the helical shape of the constituent particles. Equal area construction is used to locate the isotropic-to-nematic phase transition, and the results are compared with those stemming from an Onsager-like theory. Density functional theory is also used to study the nematic-to-screw-nematic phase transition; within the simplifying assumption of perfectly parallel helices, we compare different levels of approximation, that is second- and third-virial expansions and a Parsons-Lee correction.

cgHeliParm : analysis of dsDNA helical parameters for coarse-grained MARTINI molecular dynamics simulations

NARCIS (Netherlands)

Faustino, Ignacio; Marrink, S. J.

2017-01-01

Summary: We introduce cgHeliParm, a python program that provides the conformational analysis of Martini-based coarse-grained double strand DNA molecules. The software calculates the helical parameters such as base, base pair and base pair step parameters. cgHeliParm can be used for the analysis of

Passive base isolation with superelastic nitinol SMA helical springs

International Nuclear Information System (INIS)

Huang, Bin; Zhang, Haiyang; Wang, Han; Song, Gangbing

2014-01-01

Seismic isolation of structures such as multi-story buildings, nuclear reactors, bridges, and liquid storage tanks should be designed to preserve structural integrity. By implementing seismic isolation technology, the deformation of superstructures can be dramatically reduced, consequently helping to protect their safety as well. In this paper, an innovative type of passive base isolation system, which is mainly composed of superelastic nitinol SMA helical springs, is developed. In order to verify the effectiveness of the proposed system, a two-story experimental steel frame model is constructed, and two superelastic SMA helical springs are thermo-mechanically built in the laboratory. To describe the nonlinear mechanical properties of the superelastic SMA helical springs under reciprocating load, a phenomenological model is presented in terms of a series of tensile tests. Afterwards, a numerical model of the two-story frame with the suggested isolation system is set up to simulate the response of the isolated frame subjected to an earthquake. Both the experimental and the numerical simulation results indicate that the proposed base isolation system can remarkably suppress structural vibrations and has improved isolation effects when compared with a steel spring isolation system. Due to the capabilities of energy dissipation as well as fully re-centering, it is very applicable to utilize the suggested isolation system in base isolated structures to resist earthquakes. (paper)

Helical system. History and current state of helical research

International Nuclear Information System (INIS)

Yokoyama, Masayuki

2017-01-01

This paper described the following: (1) history of nuclear fusion research of Japan's original heliotron method, (2) worldwide development of nuclear fusion research based on helical system such as stellarator, and (3) worldwide meaning of large helical device (LHD) aiming to demonstrate the steady-state performance of heliotron type in the parameter area extrapolable to the core plasma, and research results of LHD. LHD demonstrated that the helical system is excellent in steady operation performance at the world's most advanced level. In an experiment using deuterium gas in 2017, LHD achieved to reach 120 million degrees of ion temperature, which is one index of nuclear fusion condition, demonstrated the realization of high-performance plasma capable of extrapolating to future nuclear fusion reactors, and established the foundation for full-scale research toward the realization of nuclear fusion reactor. Besides experimental research, this paper also described the helical-type stationary nuclear fusion prototype reactor, FFHR-d1, which was based on progress of large-scale simulation at the world's most advanced level. A large-scale superconducting stellarator experimental device, W7-X, with the same scale as LHD, started experiment in December 2015, whose current state is also touched on here. (A.O.)

Self/anti-self charge conjugate states in the helicity basis

International Nuclear Information System (INIS)

Dvoeglazov, Valeriy V.

2013-01-01

We construct self/anti-self charge conjugate (Majorana-like) states for the (1/2,0)⊕(0,1/2) representation of the Lorentz group, and their analogs for higher spins within the quantum field theory. The problem of the basis rotations and that of the selection of phases in the Dirac-like and Majorana-like field operators are considered. The discrete symmetries properties (P, C, T) are studied. Particular attention has been paid to the question of (anti)commutation of the Charge conjugation operator and the Parity in the helicity basis. Dynamical equations have also been presented. In the (1/2,0)⊕(0,1/2) representation they obey the Dirac-like equation with eight components, which has been first introduced by Markov. Thus, the Fock space for corresponding quantum fields is doubled (as shown by Ziino). The chirality and the helicity (two concepts which are frequently confused in the literature) for Dirac and Majorana states have been discussed

Void fraction correlations analysis and their influence on heat transfer of helical double-pipe vertical evaporator

International Nuclear Information System (INIS)

Parrales, Arianna; Colorado, Dario; Huicochea, Armando; Díaz, Juan; Alfredo Hernández, J.

2014-01-01

Highlights: • 50 void fraction correlations were evaluated on heat transfer in vertical evaporators. • Two-phase flow model based on control volume formulation was used. • The drift flux parameter is common in all correlations with satisfactory results. - Abstract: An analysis of 50 void fraction correlations available in the literature was performed to describe two-phase flow mechanism inside two helical double-pipe vertical evaporators. The evaporators considered water as working fluid connected in countercurrent so the change of phase was carried out into the internal tube. The discretized equations of continuity, momentum and energy in each flow were coupled using an implicit step by step method. The selection of the void fraction correlations for the mathematical model was based on inclusion of some theoretical limits. The results of this analysis were compared with the experimental data in steady state for two different evaporators, obtaining good agreement in the evaporation process for only 7 void fraction correlations. The Armand and Massena correlation had a mean percentage error (MPE) of 3.08%, followed by Rouhanni and Axelsson I adquired MPE=3.16%, Chisholm and Armand obtained MPE=3.18%, Steiner as well as Rouhanni and Axelsson II with MPE=3.19%, Bestion reached MPE=3.20% and Flanigan presented MPE=3.21%. Furthermore, the experimental and simulated heat flux were acceptable (R 2 =0.939). Finally, the results showed that the drift flux parameter was important to evaluate the void fraction

Review of the helicity formalism

International Nuclear Information System (INIS)

Barreiro, F.; Cerrada, M.; Fernandez, E.

1972-01-01

Our purpose in these notes has been to present a brief and general review of the helicity formalism. We begin by discussing Lorentz invariance, spin and helicity ideas, in section 1 . In section 2 we deal with the construction of relativistic states and scattering amplitudes in the helicity basis and we study their transformation properties under discrete symmetries. Finally we present some more sophisticated topics like kinematical singularities of helicity amplitudes, kinematical constraints and crossing relations 3, 4, 5 respectively. (Author) 8 refs

Women with double primary cancers of the colorectum and endometrium: do they have Lynch syndrome?

Science.gov (United States)

Song, Taejong; Kim, Min Kyu; Lee, Yoo-Young; Choi, Chel Hun; Kim, Tae-Joong; Lee, Jeong-Won; Bae, Duk-Soo; Kim, Byoung-Gie

2016-04-01

The aim of this study was to determine the clinical characteristics of women with double primary cancers of the colorectum and endometrium and assess the probability of Lynch syndrome. We identified 15 women with paraffin-embedded blocks available who were diagnosed, treated and followed for double primary colorectal and endometrial cancers at in a single institution between 1994 and 2014. If there was a family history that met the revised Amsterdam criteria for Lynch syndrome, the woman was considered to have 'clinically defined Lynch syndrome'. If immunohistochemical (IHC) loss of expression of mismatch repair genes (MLH1, MSH2, MSH6, or PMS2) or high microsatellite instability (MSI) was demonstrated in molecular testing, the case was considered 'suspected Lynch syndrome'. The incidence of clinically defined Lynch syndrome according to the revised Amsterdam criteria was 66% (8 of 15). All 8 of the women clinically diagnosed with Lynch syndrome had either abnormal IHC loss or MSI-high, indicating a suspected Lynch syndrome. Furthermore, 27% (4 of 15) experienced second primary colorectal cancer or other Lynch syndrome-related cancers. Overall, 66% (10 of 15) met the criteria for clinically defined Lynch syndrome or suspected Lynch syndrome. Based on our findings, a large percentage (66%) of women with double primary cancers of the colorectum and endometrium are likely to be diagnosed with Lynch syndrome. Copyright © 2015. Published by Elsevier Ireland Ltd.

Electron image reconstruction of helical protein assemblies

International Nuclear Information System (INIS)

Cremers, A.F.M.

1980-01-01

The analysis of projections of large ordered biological systems obtained by electron microscopy of negatively stained specimens is described. The biological structures amenable to this approach are constructed from a large number of identical protein molecules, which are arranged according to helical symmetry. Electron images of these structures generally contain sufficient information in order to calculate a three-dimensional density map. (Auth.)

Volume doubling time and growth rate of renal cell carcinoma determined by helical CT: a single-institution experience

International Nuclear Information System (INIS)

Lee, Ji Young; Kim, Chan Kyo; Choi, Dongil; Park, Byung Kwan

2008-01-01

The purpose of this study was to retrospectively evaluate the volume doubling time (VDT) and growth rate of renal cell carcinomas (RCC) on a serial computed tomography (CT) scan. Thirty pathologically proven RCCs were reviewed with helical CT. Each tumor underwent at least two CT scans. Tumor volume was determined using an area measuring tool and the summation-of-areas technique. Growth rate was evaluated in terms of diameter and volume changes. VDT and volume growth rate were compared in relation to several factors (initial diameter, initial volume, diameter growth rate, volume growth rate, tumor grade, tumor subtype, sex or age). Mean VDT of RCCs was 505 days. Mean diameter and volume growth rate were 0.59 cm/year and 19.1 cm 3 /year, respectively. For volume and diameter growth rate, tumors ≤4 cm showed lower rates than those >4 cm (P 0.05). Volume growth rate was moderately to strongly positively correlated with initial diameter, initial volume and diameter growth rate (P < 0.05). In conclusion, small RCCs grew at a slow rate both diametrically and volumetrically. More accurate assessment of tumor growth rate and VDT may be helpful to understand the natural history of RCC. (orig.)

Alpha-Helical Fragaceatoxin C Nanopore Engineered for Double-Stranded and Single-Stranded Nucleic Acid Analysis

NARCIS (Netherlands)

Wloka, Carsten; Mutter, Natalie Lisa; Soskine, Misha; Maglia, Giovanni

2016-01-01

Nanopores are used in single-molecule DNA analysis and sequencing. Herein, we show that Fragaceatoxin C (FraC), an α-helical pore-forming toxin from an actinoporin protein family, can be reconstituted in sphingomyelin-free standard planar lipid bilayers. We engineered FraC for DNA analysis and show

Hamiltonian theory of vacuum helical torus lines of magnetic force

International Nuclear Information System (INIS)

Gnudi, Giovanni; Hatori, Tadatsugu

1994-01-01

For making plasma into equilibrium state, the lines of magnetic force must have magnetic surfaces. However in a helical system, space is divided into the region having magnetic surface structure and the region that does not have it. Accordingly, it is an important basic research for the plasma confinement in a helical system to examine where is the boundary of both regions and how is the large area structure of the lines of magnetic force in the boundary region. The lines of magnetic force can be treated as a Hamilton mechanics system, and it has been proved that the Hamiltonian for the lines of magnetic force can be expressed by a set of canonical variables and the function of time. In this research, the Hamiltonian that describes the lines of magnetic force of helical system torus coordination in vacuum was successfully determined concretely. Next, the development of new linear symplectic integration method was carried out. The important supports for the theory of determining Hamiltonian are Lie transformation and paraxial expansion. The procedure is explained. In Appendix, Lie transformation, Hamiltonian for the lines of magnetic force, magnetic potential, Taylor expansion of the potential, cylindrical limit approximation, helical toroidal potential and integrable model are described. (K.I.)

Effects of dielectric inhomogeneity on electrostatic twist rigidity of a helical biomolecule in Debye-Hückel regime

Science.gov (United States)

Rezaie-Dereshgi, Amir; Mohammad-Rafiee, Farshid

2018-04-01

The electrostatic interactions play a crucial role in biological systems. Here we consider an impermeable dielectric molecule in the solvent with a different dielectric constant. The electrostatic free energy in the problem is studied in the Debye-Hückel regime using the analytical Green function that is calculated in the paper. Using this electrostatic free energy, we study the electrostatic contribution to the twist rigidity of a double stranded helical molecule such as a DNA and an actin filament. The dependence of the electrostatic twist rigidity of the molecule to the dielectric inhomogeneity, structural parameters, and the salt concentration is studied. It is shown that, depending on the parameters, the electrostatic twist rigidity could be positive or negative.

A note on helicity

International Nuclear Information System (INIS)

Bialynicki-Birula, I.; Newmann, E.T.; Porter, J.; Winicour, J.; Lukacs, B.; Perjes, Z.; Sebestyen, A.

1981-03-01

The authors give a formal definition of the helicity operator for integral spin fields, which does not involve their momentum-space decomposition. The discussion is based upon a representation of the Pauli-Lubanski operator in terms of the action on tensor fields by the Killing vectors associated with the generators of the Poincare group. This leads to an identification of the helicity operator with the duality operator defined by the space-time alternating tensor. Helicity eigenstates then correspond to self-dual or anti-self-dual fields, in agreement with usage implicit in the literature. In addiition, the relationship between helicity eigenstates which are intrinsically non-classical, and states of right or left circular polarization in classical electrodynamics are discussed. (author)

l=1 helical axis heliotron device in Kyoto university

International Nuclear Information System (INIS)

Nagasaki, K.; Sano, F.; Mizuuchi, T.; Hanatani, K.; Okada, H.; Obiki, T.

1999-01-01

Helical systems are an attractive candidate for magnetic fusion reactor. Recently, there has been great progress in theoretical research of three dimensional magnetic field structures, resulting in several kinds of confinement optimization being proposed for toroidal magnetic confinement system. For example, some sophisticated ideas have appeared on stage such as quasi-helical symmetry and quasi-isodynamic system. To find experimentally which way is the best Optimisation, a new helical axis heliotron device, so called 'Heliotron J', is under construction in the Institute of Advanced Energy, Kyoto University, Japan. In this conference, the basic concept and the present status will be presented. In the conventional plane axis helical system, it was difficult to have both good particle confinement and good MHD stability simultaneously. The goal of Heliotron J project is to clarify their compatibility in the spatial axis toroidal device. The best way for Optimising the helical magnetic field configuration will be explored by investigating the plasma response to the change in the field components. The main subjects for plasma experiment are: demonstration of the existence of good magnetic flux surfaces, reduction of neoclassical transport in collisionless regime, MHD Stabilisation in high β plasma, controllability of bootstrap current, good confinement of high energy particles

TIME EVOLUTION OF CORONAL MAGNETIC HELICITY IN THE FLARING ACTIVE REGION NOAA 10930

International Nuclear Information System (INIS)

Park, Sung-Hong; Jing, Ju; Wang Haimin; Chae, Jongchul; Tan, Changyi

2010-01-01

To study the three-dimensional (3D) magnetic field topology and its long-term evolution associated with the X3.4 flare of 2006 December 13, we investigate the coronal relative magnetic helicity in the flaring active region (AR) NOAA 10930 during the time period of December 8-14. The coronal helicity is calculated based on the 3D nonlinear force-free magnetic fields reconstructed by the weighted optimization method of Wiegelmann, and is compared with the amount of helicity injected through the photospheric surface of the AR. The helicity injection is determined from the magnetic helicity flux density proposed by Pariat et al. using Solar and Heliospheric Observatory/Michelson Doppler Imager magnetograms. The major findings of this study are the following. (1) The time profile of the coronal helicity shows a good correlation with that of the helicity accumulation by injection through the surface. (2) The coronal helicity of the AR is estimated to be -4.3 x 10 43 Mx 2 just before the X3.4 flare. (3) This flare is preceded not only by a large increase of negative helicity, -3.2 x 10 43 Mx 2 , in the corona over ∼1.5 days but also by noticeable injections of positive helicity through the photospheric surface around the flaring magnetic polarity inversion line during the time period of the channel structure development. We conjecture that the occurrence of the X3.4 flare is involved with the positive helicity injection into an existing system of negative helicity.

Primary intestinal lymphangiectasia diagnosed by double-balloon enteroscopy and treated by medium-chain triglycerides: a case report.

Science.gov (United States)

Lai, Yu; Yu, Tao; Qiao, Xiao-Yu; Zhao, Li-Na; Chen, Qi-Kui

2013-01-14

Primary intestinal lymphangiectasia is a disorder characterized by exudative enteropathy resulting from morphologic abnormalities of the intestinal lymphatics. Intestinal lymphangiectasia can be primary or secondary, so the diagnosis of primary intestinal lymphangiectasia must first exclude the possibility of secondary intestinal lymphangiectasia. A double-balloon enteroscopy and biopsy, as well as the pathology can be used to confirm the diagnosis of intestinal lymphangiectasia. A polymeric diet containing medium-chain triglycerides and total parenteral nutrition may be a useful therapy. A 17-year-old girl of Mongoloid ethnicity was admitted to our hospital with a history of diarrhea and edema. She was diagnosed with protein-losing enteropathy caused by intestinal lymphangiectasia. This was confirmed by a double-balloon enteroscopy and multi-dot biopsy. After treatment with total parenteral nutrition in hospital, which was followed by a low-fat and medium-chain triglyceride diet at home, she was totally relieved of her symptoms. Intestinal lymphangiectasia can be diagnosed with a double-balloon enteroscopy and multi-dot biopsy, as well as the pathology of small intestinal tissue showing edema of the submucosa and lymphangiectasia. Because intestinal lymphangiectasia can be primary or secondary, the diagnosis of primary intestinal lymphangiectasia must first exclude the possibility of secondary intestinal lymphangiectasia. A positive clinical response to the special diet therapy, namely a low-fat and medium-chain triglyceride diet, can further confirm the diagnosis of primary intestinal lymphangiectasia.

Three-dimensional printing of freeform helical microstructures: a review.

Science.gov (United States)

Farahani, R D; Chizari, K; Therriault, D

2014-09-21

Three-dimensional (3D) printing is a fabrication method that enables creation of structures from digital models. Among the different structures fabricated by 3D printing methods, helical microstructures attracted the attention of the researchers due to their potential in different fields such as MEMS, lab-on-a-chip systems, microelectronics and telecommunications. Here we review different types of 3D printing methods capable of fabricating 3D freeform helical microstructures. The techniques including two more common microfabrication methods (i.e., focused ion beam chemical vapour deposition and microstereolithography) and also five methods based on computer-controlled robotic direct deposition of ink filament (i.e., fused deposition modeling, meniscus-confined electrodeposition, conformal printing on a rotating mandrel, UV-assisted and solvent-cast 3D printings) and their advantages and disadvantages regarding their utilization for the fabrication of helical microstructures are discussed. Focused ion beam chemical vapour deposition and microstereolithography techniques enable the fabrication of very precise shapes with a resolution down to ∼100 nm. However, these techniques may have material constraints (e.g., low viscosity) and/or may need special process conditions (e.g., vacuum chamber) and expensive equipment. The five other techniques based on robotic extrusion of materials through a nozzle are relatively cost-effective, however show lower resolution and less precise features. The popular fused deposition modeling method offers a wide variety of printable materials but the helical microstructures manufactured featured a less precise geometry compared to the other printing methods discussed in this review. The UV-assisted and the solvent-cast 3D printing methods both demonstrated high performance for the printing of 3D freeform structures such as the helix shape. However, the compatible materials used in these methods were limited to UV-curable polymers and

LHD helical divertor

International Nuclear Information System (INIS)

Ohyabu, N.; Watanabe, T.; Ji Hantao

1993-07-01

The Large Helical Device (LHD) now under construction is a heliotron/torsatron device with a closed divertor system. The edge LHD magnetic structure has been studied in detail. A peculiar feature of the configuration is existence of edge surface layers, a complicated three dimensional magnetic structure which does not, however, seem to hamper the expected divertor functions. Two divertor operational modes are being considered for the LHD experiment, high density, cold radiative divertor operation as a safe heat removal scheme and high temperature divertor plasma operation. In the latter operation, a divertor plasma with temperature of a few kev, generated by efficient pumping, expects to lead to significant improvement in core plasma confinement. Conceptual designs of the LHD divertor components are under way. (author)

Generalized helicity and its time derivative

International Nuclear Information System (INIS)

Jarboe, T.R.; Marklin, G.J.

1985-01-01

Spheromaks can be sustained against resistive decay by helicity injection because they tend to obey the minimum energy principle. This principle states that a plasma-laden magnetic configuration will relax to a state of minimum energy subject to the constraint that the magnetic helicity is conserved. Use of helicity as a constraint on the minimization of energy was first proposed by Woltjer in connection with astrophysical phenomena. Helicity does decay on the resistive diffusion time. However, if helicity is created and made to flow continuoiusly into a confinement geometry, these additional linked fluxes can relax and sustain the configuration indefinitely against the resistive decay. In this paper we will present an extension of the definition of helicity to include systems where B vector can penetrate the boundary and the penetration can be varying in time. We then discuss the sustainment of RFPs and spheromaks in terms of helicity injection

Synthesis, model and stability of helically coiled carbon nanotubes

DEFF Research Database (Denmark)

Fejes, Dora; Raffai, Manuella; Hernadi, Klara

2013-01-01

. Our experiments focused on the production and development of catalysts for the synthesis of helically coiled CNTs (carbon nanotubes). The catalysts were tested in the decomposition of acetylene by CCVD (Catalytic Chemical Vapor Deposition) method. The carbon deposit was imaged by TEM (Transmission......Structural model of helically coiled carbon nanotubes is proposed. It is constructed by means of topological coordinate method. Relaxation and cohesive energy calculation are performed by molecular mechanics, using second-generation bond order potential for hydrocarbons introduced by D. W. Brenner...

Strategies for revision surgery after primary double-bundle anterior cruciate ligament (ACL) reconstruction

NARCIS (Netherlands)

Hofbauer, Marcus; Muller, Bart; Murawski, Christopher D.; Baraga, Michael; van Eck, Carola Franziska; Fu, Freddie H.

2013-01-01

The purpose of this article was to discuss pre- and intra-operative considerations as well as surgical strategies for different femoral and tibial tunnel scenarios in revision surgery following primary double-bundle anterior cruciate ligament (ACL) reconstruction. Based on the current literature of

Structural fragment clustering reveals novel structural and functional motifs in α-helical transmembrane proteins

Directory of Open Access Journals (Sweden)

Vassilev Boris

2010-04-01

Full Text Available Abstract Background A large proportion of an organism's genome encodes for membrane proteins. Membrane proteins are important for many cellular processes, and several diseases can be linked to mutations in them. With the tremendous growth of sequence data, there is an increasing need to reliably identify membrane proteins from sequence, to functionally annotate them, and to correctly predict their topology. Results We introduce a technique called structural fragment clustering, which learns sequential motifs from 3D structural fragments. From over 500,000 fragments, we obtain 213 statistically significant, non-redundant, and novel motifs that are highly specific to α-helical transmembrane proteins. From these 213 motifs, 58 of them were assigned to function and checked in the scientific literature for a biological assessment. Seventy percent of the motifs are found in co-factor, ligand, and ion binding sites, 30% at protein interaction interfaces, and 12% bind specific lipids such as glycerol or cardiolipins. The vast majority of motifs (94% appear across evolutionarily unrelated families, highlighting the modularity of functional design in membrane proteins. We describe three novel motifs in detail: (1 a dimer interface motif found in voltage-gated chloride channels, (2 a proton transfer motif found in heme-copper oxidases, and (3 a convergently evolved interface helix motif found in an aspartate symporter, a serine protease, and cytochrome b. Conclusions Our findings suggest that functional modules exist in membrane proteins, and that they occur in completely different evolutionary contexts and cover different binding sites. Structural fragment clustering allows us to link sequence motifs to function through clusters of structural fragments. The sequence motifs can be applied to identify and characterize membrane proteins in novel genomes.

Meso-Helical Ag(I) Coordination Polymer Based on a Pyridylimidazole Ligand

International Nuclear Information System (INIS)

Kang, Youngjin; Kim, Jinho; Lee, Eunji; Park, Ki-Min; Moon, Suk-Hee

2016-01-01

In the fields of material science and metallosupramolecular chemistry, coordination polymers with various helical types have been extensively explored because of their charming structures, and their potential applications in material chemistry. Among them, meso-helical coordination polymers consisting of achiral 1D strands, which are generally constructed by a crystallographic inversion symmetry, are relatively rare. The coordination polymer 1 exhibits a rare one-dimensional meso-helical chain topology constructed by its internal inversion symmetry. The skeleton of this meso-helical chain is preserved up to 300°C. The complexation of silver(I) ion to the free pyim ligand give rise to the enhanced photoluminescence intensity and slightly blue-shifted emission maximum, originated from intraligand (IL) π[BOND]π* transition and rigidochromic effect. Further exploration of complexation of this ligand with other transition metal ions is currently in progress

MH2c: Characterization of major histocompatibility α-helices - an information criterion approach.

Science.gov (United States)

Hischenhuber, B; Frommlet, F; Schreiner, W; Knapp, B

2012-07-01

Major histocompatibility proteins share a common overall structure or peptide binding groove. Two binding groove domains, on the same chain for major histocompatibility class I or on two different chains for major histocompatibility class II, contribute to that structure that consists of two α -helices ("wall") and a sheet of eight anti-parallel beta strands ("floor"). Apart from the peptide presented in the groove, the major histocompatibility α -helices play a central role for the interaction with the T cell receptor. This study presents a generalized mathematical approach for the characterization of these helices. We employed polynomials of degree 1 to 7 and splines with 1 to 2 nodes based on polynomials of degree 1 to 7 on the α -helices projected on their principal components. We evaluated all models with a corrected Akaike Information Criterion to determine which model represents the α -helices in the best way without overfitting the data. This method is applicable for both the stationary and the dynamic characterization of α -helices. By deriving differential geometric parameters from these models one obtains a reliable method to characterize and compare α -helices for a broad range of applications. Program title: MH 2 c (MH helix curves) Catalogue identifier: AELX_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AELX_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 327 565 No. of bytes in distributed program, including test data, etc.: 17 433 656 Distribution format: tar.gz Programming language: Matlab Computer: Personal computer architectures Operating system: Windows, Linux, Mac (all systems on which Matlab can be installed) RAM: Depends on the trajectory size, min. 1 GB (Matlab) Classification: 2.1, 4.9, 4.14 External routines: Curve

Plasmodium vivax antigen discovery based on alpha-helical coiled coil protein motif.

Directory of Open Access Journals (Sweden)

Nora Céspedes

Full Text Available Protein α-helical coiled coil structures that elicit antibody responses, which block critical functions of medically important microorganisms, represent a means for vaccine development. By using bioinformatics algorithms, a total of 50 antigens with α-helical coiled coil motifs orthologous to Plasmodium falciparum were identified in the P. vivax genome. The peptides identified in silico were chemically synthesized; circular dichroism studies indicated partial or high α-helical content. Antigenicity was evaluated using human sera samples from malaria-endemic areas of Colombia and Papua New Guinea. Eight of these fragments were selected and used to assess immunogenicity in BALB/c mice. ELISA assays indicated strong reactivity of serum samples from individuals residing in malaria-endemic regions and sera of immunized mice, with the α-helical coiled coil structures. In addition, ex vivo production of IFN-γ by murine mononuclear cells confirmed the immunogenicity of these structures and the presence of T-cell epitopes in the peptide sequences. Moreover, sera of mice immunized with four of the eight antigens recognized native proteins on blood-stage P. vivax parasites, and antigenic cross-reactivity with three of the peptides was observed when reacted with both the P. falciparum orthologous fragments and whole parasites. Results here point to the α-helical coiled coil peptides as possible P. vivax malaria vaccine candidates as were observed for P. falciparum. Fragments selected here warrant further study in humans and non-human primate models to assess their protective efficacy as single components or assembled as hybrid linear epitopes.

Long time scale plasma dynamics driven by the double tearing mode in reversed shear plasmas

International Nuclear Information System (INIS)

Ishii, Y.; Azumi, M.; Kishimoto, Y.; Leboeuf, J.N.

2003-01-01

The new nonlinear destabilization process is found in the nonlinear phase of the double tearing mode (DTM) by using the reduced MHD equations in a helical symmetry. The nonlinear destabilization causes the abrupt growth of DTM and subsequent collapse after long time scale evolution in the Rutherford-type regime. The nonlinear growth of the DTM is suddenly triggered, when the triangular deformation of magnetic islands with sharp current point at the x-point around the outer rational surface exceeds a certain value. Such structure deformation is accelerated during the nonlinear growth phase. Decreasing the resistivity increases the sharpness of the triangularity and the spontaneous growth rate in the abrupt growth phase is almost independent on the resistivity. Current point formation is also confirmed in the multi-helicity simulation, where the magnetic fields become stochastic between two rational surfaces. (author)

Long time scale plasma dynamics driven by the double tearing mode in reversed shear plasmas

International Nuclear Information System (INIS)

Ishii, Yasutomo; Azumi, M.; Kishimoto, Y.

2003-01-01

The new nonlinear destabilization process is found in the nonlinear phase of the double tearing mode(DTM) by using the reduced MHD equations in a helical symmetry. The nonlinear destabilization causes the abrupt growth of DTM and subsequent collapse after long time scale evolution in the Rutherford-type regime. The nonlinear growth of the DTM is suddenly triggered, when the triangular deformation of magnetic islands with sharp current point at the x-point around the outer rational surface exceeds a certain value. Such structure deformation is accelerated during the nonlinear growth phase. Decreasing the resistivity increases the sharpness of the triangularity and the spontaneous growth rate in the abrupt growth phase is almost independent on the resistivity. Current point formation is also confirmed in the multi-helicity simulation, where the magnetic fields become stochastic between two rational surfaces. (author)

Markov analysis of alpha-helical, beta-sheet and random coil regions of proteins

International Nuclear Information System (INIS)

Macchiato, M.; Tramontano, A.

1983-01-01

The rules up to now used to predict the spatial configuration of proteins from their primary structure are mostly based on the recurrence analysis of some doublets, triplets and so on of contiguous amino acids, but they do not take into account the correlation characteristics of the whole amino acid sequence. A statistical analysis of amino acid sequences for the alpha-helical, beta-sheet and random coil regions of about twenty proteins with known secondary structure by considering correlations effects has been carried out. The obtained results demonstrate that these sequences are at least a second-order Markov chain, i.e. they appear as if they were generated by a source that remembers at least the two aminoacids before the one being generated and that these two previous symbols influence the present choice

Numerical simulation of helical-vortex effects in Rayleigh-Bénard convection

Directory of Open Access Journals (Sweden)

G. V. Levina

2006-01-01

Full Text Available A numerical approach is substantiated for searching for the large-scale alpha-like instability in thermoconvective turbulence. The main idea of the search strategy is the application of a forcing function which can have a physical interpretation. The forcing simulates the influence of small-scale helical turbulence generated in a rotating fluid with internal heat sources and is applied to naturally induced fully developed convective flows. The strategy is tested using the Rayleigh-Bénard convection in an extended horizontal layer of incompressible fluid heated from below. The most important finding is an enlargement of the typical horizontal scale of the forming helical convective structures accompanied by a cells merging, an essential increase in the kinetic energy of flows and intensification of heat transfer. The results of modeling allow explaining how the helical feedback can work providing the non-zero mean helicity generation and the mutual intensification of horizontal and vertical circulation, and demonstrate how the energy of the additional helical source can be effectively converted into the energy of intensive large-scale vortex flow.

The management of helical rim keloids with excision, split thickness skin graft and intralesional triamcinolone acetonide

Directory of Open Access Journals (Sweden)

Ibrahim Abdul Rasheed

2014-01-01

Full Text Available Keloids of the helical rim are disfiguring. A cosmetically acceptable reconstruction is difficult especially in moderate to large sized lesions because the helical rim is a 3-dimensional structure with curved and thin cartilage. We report our experience in the management of moderate (4-10 cm and large (>10 cm helical rim keloids in five patients. Six helical rim keloids were reconstructed. There were four moderate (4-10 cm and two large (>10 cm helical rim keloids. Four were on the right helix and two on the left helix. One patient had bilateral helical rim keloids. The follow-up period ranged from 6 months to 4 years. No secondary surgical revision was required to improve the contour of the reconstructed helical rim. The aesthetic results were satisfactory in all the patients.

Magnetic helicity and active filament configuration

Science.gov (United States)

Romano, P.; Zuccarello, F.; Poedts, S.; Soenen, A.; Zuccarello, F. P.

2009-11-01

Context: The role of magnetic helicity in active filament formation and destabilization is still under debate. Aims: Although active filaments usually show a sigmoid shape and a twisted configuration before and during their eruption, it is unclear which mechanism leads to these topologies. In order to provide an observational contribution to clarify these issues, we describe a filament evolution whose characteristics seem to be directly linked to the magnetic helicity transport in corona. Methods: We applied different methods to determine the helicity sign and the chirality of the filament magnetic field. We also computed the magnetic helicity transport rate at the filament footpoints. Results: All the observational signatures provided information on the positive helicity and sinistral chirality of the flux rope containing the filament material: its forward S shape, the orientation of its barbs, the bright and dark threads at 195 Å. Moreover, the magnetic helicity transport rate at the filament footpoints showed a clear accumulation of positive helicity. Conclusions: The study of this event showed a correspondence between several signatures of the sinistral chirality of the filament and several evidences of the positive magnetic helicity of the filament magnetic field. We also found that the magnetic helicity transported along the filament footpoints showed an increase just before the change of the filament shape observed in Hα images. We argued that the photospheric regions where the filament was rooted might be the preferential ways where the magnetic helicity was injected along the filament itself and where the conditions to trigger the eruption were yielded.

Pulsed electron beam generation with fast repetitive double pulse system

Energy Technology Data Exchange (ETDEWEB)

Sharma, Surender Kumar; Deb, Pankaj; Shyam, Anurag, E-mail: surender80@gmail.com [Energetics and Electromagnetics Division, Bhabha Atomic Research Centre, Visakhapatnam (India); Sharma, Archana [Accelerator and Pulse Power Division, Bhabha Atomic Research Centre, Mumbai (India)

2014-07-01

Longer duration high voltage pulse (∼ 100 kV, 260 ns) is generated and reported using helical pulse forming line in compact geometry. The transmission line characteristics of the helical pulse forming line are also used to develop fast repetition double pulse system with very short inter pulse interval. It overcomes the limitations caused due to circuit parameters, power supplies and load characteristics for fast repetitive high voltage pulse generation. The high voltage double pulse of 100 kV, 100 ns with an inter pulse repetition interval of 30 ns is applied across the vacuum field emission diode for pulsed electron beam generation. The electron beam is generated from cathode material by application of negative high voltage (> 100 kV) across the diode by explosive electron emission process. The vacuum field emission diode is made of 40 mm diameter graphite cathode and SS mesh anode. The anode cathode gap was 6 mm and the drift tube diameter was 10 cm. The initial experimental results of pulsed electron beam generation with fast repetitive double pulse system are reported and discussed. (author)

Experimental investigation on enhanced heat transfer of vertical condensers with trisection helical baffles

International Nuclear Information System (INIS)

Wu, Jiafeng; Zhou, Jiahao; Chen, Yaping; Wang, Mingchao; Dong, Cong; Guo, Ya

2016-01-01

Highlights: • Trisection helical baffles are introduced for vertical condenser enhancement. • Condensation in short-section and intermediate drainage is applied in new schemes. • Helical baffles with liquid dam and drainage gaps can promote condenser performance. • Dual-thread baffle scheme is superior to that of single-thread one by about 19%. • Condensation enhancement ratio of helical schemes is 1.5–2.5 over segment one. - Abstract: The vertical condensers have advantages of small occupation area, convenient in assemble or dismantle tube bundle and simple structure etc. However, the low heat transfer performance limits their applications. To enhance the heat transfer, a novel type of vertical condensers was designed by introducing trisection helical baffles with liquid dams and gaps for facilitating condensate drainage. Four configurations of vertical condensers with trisection helical baffle are experimentally studied and compared to a traditional segment baffle condenser. The enhancement ratio of trisection helical baffle schemes is about 1.5–2.5 and the heat transfer coefficient of the dual-thread trisection helical baffle scheme is superior to that of the single-thread one by about 19%. Assistant by the theoretical study, the experimental data is simulated and the condensation enhancement mechanisms by applying trisection helical baffle in vertical condenser are summarized as condensate drainage, short tube construct and reduce steam dead zone functions of the helical baffles.

Structures and related properties of helical, disulfide-stabilized peptides

Energy Technology Data Exchange (ETDEWEB)

Pagel, Mark D. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

1993-11-01

The three dimensional structure of several peptides were determined by NMR spectroscopy and distance geometry calculations. Each peptide formed a predictable, rigid structure, consisting of an α-helix, a "scaffold" region which packed along one face of the helix, and two disulfide bridges which covalently connect the helix and scaffold regions. The peptide Apa-M5 was designed to constrain the M5 peptide from MLCK in a helical geometry using the apamin disulfide scaffold. This scaffold constrains the N- terminal end of the helix with two disulfide bridges and a reverse turn. Like the M5 peptide, Apa-M5 was found to bind calmodulin in a Ca²⁺-dependent 1:1 stoichiometry. However, the dissociation constant of the (Apa-M5)-calmodulin complex, 107 nM, was 100-fold higher than the dissociation constant of the M5-calmodulin complex. This difference was due to a putative steric overlap between the Apa-M5 scaffold and calmodulin. The peptide Apa-Cro was designed to replace the large structural protein matrix of λ Cro with the apamin disulfide scaffold. However, Apa-Cro did not bind the consensus DNA operator half-site of λ Cro, probably due to a steric overlap between the Apa-Cro disulfide framework and the DNA. The amino acid sequence of the scaffold-disulfide bridge arrangement of the peptide Max was derived from the core sequence of scyllatoxin, which contains an α-helix constrained at the C-terminal end by two disulfide bridges and a two-stranded βsheet scaffold. Max was shown to fold with >84% yield to form a predictable, stable structure that is similar to scyllatoxin. The folding and stability properties of Max make this scaffold and disulfide bridge arrangement an ideal candidate for the development of hybrid sequence peptides. The dynamics of a fraying C-terminal end of the helix of the peptide Apa-AlaN was determined by analysis of ¹⁵N NMR relaxation properties.

Esthetic double-structure fixed partial dentures.

Science.gov (United States)

Ravasini, G; Ugolini, G; Ravasini, F

1996-04-01

A new technical procedure for fixed partial dentures and single inlays allows the use of a metal supporting structure with independent ceramic coverage. The advantages of the technique are the bonding of metal to beveled dentinal margins with conventional cement and the acid-etched resin composite cementation of the ceramic, which permits more conservative preparation of the teeth. The complexity of the structure, the laboratory costs, and the doubling of the cementation procedures are the main disadvantages of the technique.

Nonlocal Poisson-Fermi double-layer models: Effects of nonuniform ion sizes on double-layer structure

Science.gov (United States)

Xie, Dexuan; Jiang, Yi

2018-05-01

This paper reports a nonuniform ionic size nonlocal Poisson-Fermi double-layer model (nuNPF) and a uniform ionic size nonlocal Poisson-Fermi double-layer model (uNPF) for an electrolyte mixture of multiple ionic species, variable voltages on electrodes, and variable induced charges on boundary segments. The finite element solvers of nuNPF and uNPF are developed and applied to typical double-layer tests defined on a rectangular box, a hollow sphere, and a hollow rectangle with a charged post. Numerical results show that nuNPF can significantly improve the quality of the ionic concentrations and electric fields generated from uNPF, implying that the effect of nonuniform ion sizes is a key consideration in modeling the double-layer structure.

A finite element model for independent wire rope core with double ...

Indian Academy of Sciences (India)

1Istanbul Technical University, Institute of Informatics, Computational Science and ... a little work has been done using the double helical geometry and real ... Finite element approach has been embedded in wire rope analysis since 1999.

Primary intestinal lymphangiectasia diagnosed by double-balloon enteroscopy and treated by medium-chain triglycerides: a case report

Directory of Open Access Journals (Sweden)

Lai Yu

2013-01-01

Full Text Available Abstract Introduction Primary intestinal lymphangiectasia is a disorder characterized by exudative enteropathy resulting from morphologic abnormalities of the intestinal lymphatics. Intestinal lymphangiectasia can be primary or secondary, so the diagnosis of primary intestinal lymphangiectasia must first exclude the possibility of secondary intestinal lymphangiectasia. A double-balloon enteroscopy and biopsy, as well as the pathology can be used to confirm the diagnosis of intestinal lymphangiectasia. A polymeric diet containing medium-chain triglycerides and total parenteral nutrition may be a useful therapy. Case presentation A 17-year-old girl of Mongoloid ethnicity was admitted to our hospital with a history of diarrhea and edema. She was diagnosed with protein-losing enteropathy caused by intestinal lymphangiectasia. This was confirmed by a double-balloon enteroscopy and multi-dot biopsy. After treatment with total parenteral nutrition in hospital, which was followed by a low-fat and medium-chain triglyceride diet at home, she was totally relieved of her symptoms. Conclusion Intestinal lymphangiectasia can be diagnosed with a double-balloon enteroscopy and multi-dot biopsy, as well as the pathology of small intestinal tissue showing edema of the submucosa and lymphangiectasia. Because intestinal lymphangiectasia can be primary or secondary, the diagnosis of primary intestinal lymphangiectasia must first exclude the possibility of secondary intestinal lymphangiectasia. A positive clinical response to the special diet therapy, namely a low-fat and medium-chain triglyceride diet, can further confirm the diagnosis of primary intestinal lymphangiectasia.

Helical Phase Inflation and Monodromy in Supergravity Theory

Directory of Open Access Journals (Sweden)

Tianjun Li

2015-01-01

Full Text Available We study helical phase inflation which realizes “monodromy inflation” in supergravity theory. In the model, inflation is driven by the phase component of a complex field whose potential possesses helicoid structure. We construct phase monodromy based on explicitly breaking global U(1 symmetry in the superpotential. By integrating out heavy fields, the phase monodromy from single complex scalar field is realized and the model fulfills natural inflation. The phase-axion alignment is achieved from explicitly symmetry breaking and gives super-Planckian phase decay constant. The F-term scalar potential provides strong field stabilization for all the scalars except inflaton, which is protected by the approximate global U(1 symmetry. Besides, we show that helical phase inflation can be naturally realized in no-scale supergravity with SU(2,1/SU(2×U(1 symmetry since the supergravity setup needed for phase monodromy is automatically provided in the no-scale Kähler potential. We also demonstrate that helical phase inflation can be reduced to another well-known supergravity inflation model with shift symmetry. Helical phase inflation is free from the UV-sensitivity problem although there is super-Planckian field excursion, and it suggests that inflation can be effectively studied based on supersymmetric field theory while a UV-completed framework is not prerequisite.

Numerical simulation of an excited round jet under helical disturbances by three-dimensional discrete vortex method; Helical kakuran ni yoru reiki enkei funryu no uzuho simulation

Energy Technology Data Exchange (ETDEWEB)

Izawa, S.; Kiya, M.; Mochizuki, O. [Hokkaido University, Sapporo (Japan)

1998-09-25

The evolution of vortical structure in an impulsively started round jet has been studied numerically by means of a three-dimensional vortex blob method. The viscous diffusion of vorticity is approximated by a core spreading model originally proposed by Leonard (1980). The jet is forced by axisymmetric, helical and multiple disturbances. The multiple disturbances are combinations of two helical disturbances of the same mode rotating in the opposite directions. The multiple disturbances are found to enhance both the generation of small-scale structures and the growth rate of the jet. The small-scale structures have highly organized spatial distributions. The core spreading method is effective in aquiring the core overlapping in regions of high extensional rate of strain. 21 refs., 12 figs.

Hydrogen bonds and heat diffusion in α-helices: a computational study.

Science.gov (United States)

Miño, German; Barriga, Raul; Gutierrez, Gonzalo

2014-08-28

Recent evidence has shown a correlation between the heat diffusion pathways and the known allosteric communication pathways in proteins. Allosteric communication in proteins is a central, yet unsolved, problem in biochemistry, and the study and characterization of the structural determinants that mediate energy transfer among different parts of proteins is of major importance. In this work, we characterized the role of hydrogen bonds in diffusivity of thermal energy for two sets of α-helices with different abilities to form hydrogen bonds. These hydrogen bonds can be a constitutive part of the α-helices or can arise from the lateral chains. In our in vacuo simulations, it was observed that α-helices with a higher possibility of forming hydrogen bonds also had higher rates of thermalization. Our simulations also revealed that heat readily flowed through atoms involved in hydrogen bonds. As a general conclusion, according to our simulations, hydrogen bonds fulfilled an important role in heat diffusion in structural patters of proteins.

Comparison of AMI-25 enhanced MRI and helical dynamic CT in the detection of hepatic lesions

International Nuclear Information System (INIS)

Saitou, Kazuhiro; Matsuda, Hiromichi; Fukushima, Hiroaki; Kanzaki, Hiroshi; Hirose, Takashi; Karizaki, Dai; Abe, Kimihiko; Amino, Saburou

1994-01-01

We performed AMI-25 enhanced MRI and helical dynamic CT in 12 cases of hepatic lesions. Nine of these were hepatocellular carcinomas. Two cases were metastatic liver tumors (the primary lesion was gastric in one and the other was gallbladder cancer). One case was suspected to be adenomatous hyperplasia. Thirty-two lesions were detected in T2-weighted SE images before AMI-25 administration, while 46 lesions were detected in AMI-25 enhanced MRI images. In particular, AMI-25 enhanced MRI was superior to plain MRI in lesions less than 10 mm in size. A total of 48 lesions were detected in helical dynamic CT. Although AMI-25 enhanced MRI almost equaled helical dynamic CT in the detection of liver tumors, helical dynamic CT was slightly superior to AMI-25 enhanced MRI in the detection of subphrenic lesions. It was possible to know the hemodynamics in each hepatic lesion by helical dynamic CT. AMI-25 enhanced MRI was useful to know the inclusion of reticuloendothelial system, and that yielded different diagnoses in adenomatous hyperplasia and well differentiated hepatocellular carcinoma. Helical dynamic CT was useful for qualitative diagnosis. Both AMI-25 enhanced MRI and helical dynamic CT contributed to the detection of liver tumor and qualitative diagnosis. (author)

Helical waves in easy-plane antiferromagnets

Science.gov (United States)

Semenov, Yuriy G.; Li, Xi-Lai; Xu, Xinyi; Kim, Ki Wook

2017-12-01

Effective spin torques can generate the Néel vector oscillations in antiferromagnets (AFMs). Here, it is theoretically shown that these torques applied at one end of a normal AFM strip can excite a helical type of spin wave in the strip whose properties are drastically different from characteristic spin waves. An analysis based on both a Néel vector dynamical equation and the micromagnetic simulation identifies the direction of magnetic anisotropy and the damping factor as the two key parameters determining the dynamics. Helical wave propagation requires the hard axis of the easy-plane AFM to be aligned with the traveling direction, while the damping limits its spatial extent. If the damping is neglected, the calculation leads to a uniform periodic domain wall structure. On the other hand, finite damping decelerates the helical wave rotation around the hard axis, ultimately causing stoppage of its propagation along the strip. With the group velocity staying close to spin-wave velocity at the wave front, the wavelength becomes correspondingly longer away from the excitation point. In a sufficiently short strip, a steady-state oscillation can be established whose frequency is controlled by the waveguide length as well as the excitation energy or torque.

Evaluation of CFD Methods for Simulation of Two-Phase Boiling Flow Phenomena in a Helical Coil Steam Generator

Energy Technology Data Exchange (ETDEWEB)

Pointer, William David [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Shaver, Dillon [Argonne National Lab. (ANL), Argonne, IL (United States); Liu, Yang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Vegendla, Prasad [Argonne National Lab. (ANL), Argonne, IL (United States); Tentner, Adrian [Argonne National Lab. (ANL), Argonne, IL (United States)

2016-09-30

The U.S. Department of Energy, Office of Nuclear Energy charges participants in the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program with the development of advanced modeling and simulation capabilities that can be used to address design, performance and safety challenges in the development and deployment of advanced reactor technology. The NEAMS has established a high impact problem (HIP) team to demonstrate the applicability of these tools to identification and mitigation of sources of steam generator flow induced vibration (SGFIV). The SGFIV HIP team is working to evaluate vibration sources in an advanced helical coil steam generator using computational fluid dynamics (CFD) simulations of the turbulent primary coolant flow over the outside of the tubes and CFD simulations of the turbulent multiphase boiling secondary coolant flow inside the tubes integrated with high resolution finite element method assessments of the tubes and their associated structural supports. This report summarizes the demonstration of a methodology for the multiphase boiling flow analysis inside the helical coil steam generator tube. A helical coil steam generator configuration has been defined based on the experiments completed by Polytecnico di Milano in the SIET helical coil steam generator tube facility. Simulations of the defined problem have been completed using the Eulerian-Eulerian multi-fluid modeling capabilities of the commercial CFD code STAR-CCM+. Simulations suggest that the two phases will quickly stratify in the slightly inclined pipe of the helical coil steam generator. These results have been successfully benchmarked against both empirical correlations for pressure drop and simulations using an alternate CFD methodology, the dispersed phase mixture modeling capabilities of the open source CFD code Nek5000.

Study on reinforced concrete beams with helical transverse reinforcement

Science.gov (United States)

Kaarthik Krishna, N.; Sandeep, S.; Mini, K. M.

2018-02-01

In a Reinforced Concrete (R.C) structure, major reinforcement is used for taking up tensile stresses acting on the structure due to applied loading. The present paper reports the behavior of reinforced concrete beams with helical reinforcement (transverse reinforcement) subjected to monotonous loading by 3-point flexure test. The results were compared with identically similar reinforced concrete beams with rectangular stirrups. During the test crack evolution, load carrying capacity and deflection of the beams were monitored, analyzed and compared. Test results indicate that the use of helical reinforcement provides enhanced load carrying capacity and a lower deflection proving to be more ductile, clearly indicating the advantage in carrying horizontal loads. An analysis was also carried out using ANSYS software in order to compare the test results of both the beams.

Comparison of various decentralised structural and cavity feedback control strategies for transmitted noise reduction through a double panel structure

NARCIS (Netherlands)

Ho, J.; Berkhoff, Arthur P.

This paper compares various decentralised control strategies, including structural and acoustic actuator–sensor configuration designs, to reduce noise transmission through a double panel structure. The comparison is based on identical control stability indexes. The double panel structure consists of

Comparison of various decentralised structural and cavity feedback control strategies for transmitted noise reduction through a double panel structure

NARCIS (Netherlands)

Ho, J.H.; Berkhoff, A.P.

2014-01-01

This paper compares various decentralised control strategies, including structural and acoustic actuator-sensor configuration designs, to reduce noise transmission through a double panel structure. The comparison is based on identical control stability indexes. The double panel structure consists of

Pyrolysis of Helical Coordination Polymers for Metal-Sulfide-Based Helices with Broadband Chiroptical Activity.

Science.gov (United States)

Hirai, Kenji; Yeom, Bongjun; Sada, Kazuki

2017-06-27

Fabrication of chiroptical materials with broadband response in the visible light region is vital to fully realize their potential applications. One way to achieve broadband chiroptical activity is to fabricate chiral nanostructures from materials that exhibit broadband absorption in the visible light region. However, the compounds used for chiroptical materials have predominantly been limited to materials with narrowband spectral response. Here, we synthesize Ag 2 S-based nanohelices derived from helical coordination polymers. The right- and left-handed coordination helices used as precursors are prepared from l- and d-glutathione with Ag + and a small amount of Cu 2+ . The pyrolysis of the coordination helices yields right- and left-handed helices of Cu 0.12 Ag 1.94 S/C, which exhibit chiroptical activity spanning the entire visible light region. Finite element method simulations substantiate that the broadband chiroptical activity is attributed to synergistic broadband light absorption and light scattering. Furthermore, another series of Cu 0.10 Ag 1.90 S/C nanohelices are synthesized by choosing the l- or d-Glu-Cys as starting materials. The pitch length of nanohelicies is controlled by changing the peptides, which alters their chiroptical properties. The pyrolysis of coordination helices enables one to fabricate helical Ag 2 S-based materials that enable broadband chiroptical activity but have not been explored owing to the lack of synthetic routes.

Comparison of various decentralised structural and cavity feedback control strategies for transmitted noise reduction through a double panel structure

Science.gov (United States)

Ho, Jen-Hsuan; Berkhoff, Arthur

2014-03-01

This paper compares various decentralised control strategies, including structural and acoustic actuator-sensor configuration designs, to reduce noise transmission through a double panel structure. The comparison is based on identical control stability indexes. The double panel structure consists of two panels with air in between and offers the advantages of low sound transmission at high frequencies, low heat transmission, and low weight. The double panel structure is widely used, such as in the aerospace and automotive industries. Nevertheless, the resonance of the cavity and the poor sound transmission loss at low frequencies limit the double panel's noise control performance. Applying active structural acoustic control to the panels or active noise control to the cavity has been discussed in many papers. In this paper, the resonances of the panels and the cavity are considered simultaneously to further reduce the transmitted noise through an existing double panel structure. A structural-acoustic coupled model is developed to investigate and compare various structural control and cavity control methods. Numerical analysis and real-time control results show that structural control should be applied to both panels. Three types of cavity control sources are presented and compared. The results indicate that the largest noise reduction is obtained with cavity control by loudspeakers modified to operate as incident pressure sources.

Measurements of the Canonical Helicity Evolution of a Gyrating Kinked Flux Rope

Science.gov (United States)

von der Linden, J.; Sears, J.; Intrator, T.; You, S.

2017-12-01

Magnetic structures in the solar corona and planetary magnetospheres are often modelled as magnetic flux ropes governed by magnetohydrodynamics (MHD); however, inside these structures, as exhibited in reconnection, conversions between magnetic and kinetic energies occur over a wide range of scales. Flux ropes based on the flux of canonical momentum circulation extend the flux rope concept to include effects of finite particle momentum and present the distinct advantage of reconciling all plasma regimes - e.g. kinetic, two-fluid, and MHD - with the topological concept of helicity: twists, writhes, and linkages. This presentation shows the first visualization and analysis of the 3D dynamics of canonical flux ropes and their relative helicity evolution from laboratory measurements. Ion and electron canonical flux ropes are visualized from a dataset of Mach, triple, and Ḃ probe measurements at over 10,000 spatial locations of a gyrating kinked flux rope. The flux ropes co-gyrate with the peak density and electron temperature in and out of a measurement volume. The electron and ion canonical flux ropes twist with opposite handedness and the ion flux ropes writhe around the electron flux ropes. The relative cross helicity between the magnetic and ion flow vorticity flux ropes dominates the relative ion canonical helicity and is anti-correlated with the relative magnetic helicity. The 3D nature of the kink and a reverse eddy current affect the helicity evolution. This work is supported by DOE Grant DE-SC0010340 and the DOE Office of Science Graduate Student Research Program and prepared in part by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-735426

Swimming Characteristics of Bioinspired Helical Microswimmers Based on Soft Lotus-Root Fibers

Directory of Open Access Journals (Sweden)

Jia Liu

2017-11-01

Full Text Available Various kinds of helical swimmers inspired by E. coli bacteria have been developed continually in many types of researches, but most of them are proposed by the rigid bodies. For the targeted drug delivery, the rigid body may hurt soft tissues of the working region with organs. Due to this problem, the biomedical applications of helical swimmers may be restricted. However, the helical microswimmers with the soft and deformable body are appropriate and highly adaptive in a confined environment. Thus, this paper presents a lotus-root-based helical microswimmer, which is fabricated by the fibers of lotus-root coated with magnetic nanoparticles to active under the magnetic fields. The helical microstructures are derived from the intrinsic biological structures of the fibers of the lotus-root. This paper aims to study the swimming characteristic of lotus-root-based microswimmers with deformable helical bodies. In the initial step under the uniform magnetic actuation, the helical microswimmers are bent lightly due to the heterogeneous distribution of the internal stress, and then they undergo a swimming motion which is a spindle-like rotation locomotion. Our experiments report that the microswimmers with soft bodies can locomote faster than those with rigid bodies. Moreover, we also find that the curvature of the shape decreases as a function of actuating field frequency which is related to the deformability of lotus-root fibers.

Employing helicity amplitudes for resummation

International Nuclear Information System (INIS)

Moult, Ian; Stewart, Iain W.; Tackmann, Frank J.; Waalewijn, Wouter J.; Amsterdam Univ.

2015-08-01

Many state-of-the-art QCD calculations for multileg processes use helicity amplitudes as their fundamental ingredients. We construct a simple and easy-to-use helicity operator basis in soft-collinear effective theory (SCET), for which the hard Wilson coefficients from matching QCD onto SCET are directly given in terms of color-ordered helicity amplitudes. Using this basis allows one to seamlessly combine fixed-order helicity amplitudes at any order they are known with a resummation of higher-order logarithmic corrections. In particular, the virtual loop amplitudes can be employed in factorization theorems to make predictions for exclusive jet cross sections without the use of numerical subtraction schemes to handle real-virtual infrared cancellations. We also discuss matching onto SCET in renormalization schemes with helicities in 4- and d-dimensions. To demonstrate that our helicity operator basis is easy to use, we provide an explicit construction of the operator basis, as well as results for the hard matching coefficients, for pp → H+0,1,2 jets, pp → W/Z/γ+0,1,2 jets, and pp → 2,3 jets. These operator bases are completely crossing symmetric, so the results can easily be applied to processes with e + e - and e - p collisions.

Behavior of magnetic islands in 3D MHD equilibria of helical devices

International Nuclear Information System (INIS)

Hayashi, T.; Sato, T.; Nakajima, N.

1994-09-01

Magnetic island formation in three-dimensional finite-β equilibria in the H-1 Heliac is studied by using the HINT code. It is found that the size of a dangerous island should increase with β but that a destruction of the equilibrium at low β is avoided because the rotational transform evolves to exclude the rational surface concerned. At higher β there is evidence of near-resonant flux surface deformations which may lead to an equilibrium limit. A reconnected equilibrium at still higher β exhibits a double island structure which is similar to homoclinic phase portraits which have been observed after separatrix reconnection in Hamiltonian systems. Physical mechanism of the island formation in finite-β helical equilibria is investigated to confirm there are cases where the global effect of the Pfirsch-Schlueter currents is important. The earlier theory is extended to elucidate the occurence of the complete self-healing of island when the resistive interchange criterion satisfied. (author)

Amino acid pair- and triplet-wise groupings in the interior of α-helical segments in proteins.

Science.gov (United States)

de Sousa, Miguel M; Munteanu, Cristian R; Pazos, Alejandro; Fonseca, Nuno A; Camacho, Rui; Magalhães, A L

2011-02-21

A statistical approach has been applied to analyse primary structure patterns at inner positions of α-helices in proteins. A systematic survey was carried out in a recent sample of non-redundant proteins selected from the Protein Data Bank, which were used to analyse α-helix structures for amino acid pairing patterns. Only residues more than three positions apart from both termini of the α-helix were considered as inner. Amino acid pairings i, i+k (k=1, 2, 3, 4, 5), were analysed and the corresponding 20×20 matrices of relative global propensities were constructed. An analysis of (i, i+4, i+8) and (i, i+3, i+4) triplet patterns was also performed. These analysis yielded information on a series of amino acid patterns (pairings and triplets) showing either high or low preference for α-helical motifs and suggested a novel approach to protein alphabet reduction. In addition, it has been shown that the individual amino acid propensities are not enough to define the statistical distribution of these patterns. Global pair propensities also depend on the type of pattern, its composition and orientation in the protein sequence. The data presented should prove useful to obtain and refine useful predictive rules which can further the development and fine-tuning of protein structure prediction algorithms and tools. Copyright © 2010 Elsevier Ltd. All rights reserved.

Helical bifurcation and tearing mode in a plasma—a description based on Casimir foliation

International Nuclear Information System (INIS)

Yoshida, Z; Dewar, R L

2012-01-01

The relation between the helical bifurcation of a Taylor relaxed state (a Beltrami equilibrium) and a tearing mode is analyzed in a Hamiltonian framework. Invoking an Eulerian representation of the Hamiltonian, the symplectic operator (defining a Poisson bracket) becomes non-canonical, i.e. the symplectic operator has a nontrivial cokernel (dual to its nullspace), foliating the phase space into level sets of Casimir invariants. A Taylor relaxed state is an equilibrium point on a Casimir (helicity) leaf. Changing the helicity, equilibrium points may bifurcate to produce helical relaxed states; a necessary and sufficient condition for bifurcation is derived. Tearing yields a helical perturbation on an unstable equilibrium, producing a helical structure approximately similar to a helical relaxed state. A slight discrepancy found between the helically bifurcated relaxed state and the linear tearing mode viewed as a perturbed, singular equilibrium state is attributed to a Casimir element (named ‘helical flux’) pertinent to a ‘resonance singularity’ of the non-canonical symplectic operator. While the helical bifurcation can occur at discrete eigenvalues of the Beltrami parameter, the tearing mode, being a singular eigenfunction, exists for an arbitrary Beltrami parameter. Bifurcated Beltrami equilibria appearing on the same helicity leaf are isolated by the helical-flux Casimir foliation. The obstacle preventing the tearing mode to develop in the ideal limit turns out to be the shielding current sheet on the resonant surface, preventing the release of the ‘potential energy’. When this current is dissipated by resistivity, reconnection is allowed and tearing instability occurs. The Δ′ criterion for linear tearing instability of Beltrami equilibria is shown to be directly related to the spectrum of the curl operator. (paper)

Water-stable helical structure of tertiary amides of bicyclic β-amino acid bearing 7-azabicyclo[2.2.1]heptane. Full control of amide cis-trans equilibrium by bridgehead substitution.

Science.gov (United States)

Hosoya, Masahiro; Otani, Yuko; Kawahata, Masatoshi; Yamaguchi, Kentaro; Ohwada, Tomohiko

2010-10-27

Helical structures of oligomers of non-natural β-amino acids are significantly stabilized by intramolecular hydrogen bonding between main-chain amide moieties in many cases, but the structures are generally susceptible to the environment; that is, helices may unfold in protic solvents such as water. For the generation of non-hydrogen-bonded ordered structures of amides (tertiary amides in most cases), control of cis-trans isomerization is crucial, even though there is only a small sterical difference with respect to cis and trans orientations. We have established methods for synthesis of conformationally constrained β-proline mimics, that is, bridgehead-substituted 7-azabicyclo[2.2.1]heptane-2-endo-carboxylic acids. Our crystallographic, 1D- and 2D-NMR, and CD spectroscopic studies in solution revealed that a bridgehead methoxymethyl substituent completely biased the cis-trans equilibrium to the cis-amide structure along the main chain, and helical structures based on the cis-amide linkage were generated independently of the number of residues, from the minimalist dimer through the tetramer, hexamer, and up to the octamer, and irrespective of the solvent (e.g., water, alcohol, halogenated solvents, and cyclohexane). Generality of the control of the amide equilibrium by bridgehead substitution was also examined.

Higher order structure in the 3'-minor domain of small subunit ribosomal RNAs from a gram negative bacterium, a gram positive bacterium and a eukaryote

DEFF Research Database (Denmark)

Douthwaite, S; Christensen, A; Garrett, R A

1983-01-01

of additional higher order structure in the renatured free RNA. It can be concluded that a high level of conservation of higher order structure has occurred during the evolution of the gram negative and gram positive eubacteria and the eukaryote in both the double helical regions and the "unstructured" regions...

Portrait of a discovery. Watson, Crick, and the double helix.

Science.gov (United States)

de Chadarevian, Soraya

2003-03-01

This essay examines an iconic image of twentieth-century science: Antony Barrington Brown's photograph of James Watson, Francis Crick, and the double-helical model of DNA. The detailed reconstruction of the production, reception, and uses of the photograph reveals the central role of the image in making the discovery it portrays. Taken in May 1953, two full months after the scientists built the model, to accompany a report on the structure in Time magazine, the photograph (like the report) was never published. It came into circulation only fifteen years later, as an illustration in Watson's best-selling book The Double Helix. While the image served as a historical document and advertisement for the book, only the book provided the description that made the image as well as the people and the model it represented famous. The history of the image provides insights into the retrospective construction of the discovery, which has since been celebrated as the origin of a new science of life.

Helical CT in the primary trauma evaluation of the cervical spine: an evidence-based approach

Energy Technology Data Exchange (ETDEWEB)

Blackmore, C.C. [Washington Univ., Seattle, WA (United States). Dept. of Radiology; Center for Cost and Outcomes Research, Univ. of Washington, Seattle (United States); Dept. of Radiology, Harborview Medical Center, Seattle, WA (United States); Mann, F.A. [Washington Univ., Seattle, WA (United States). Dept. of Radiology; Harborview Injury Prevention and Research Center, University of Washington, Seattle (United States); Wilson, A.J. [Washington Univ., Seattle, WA (United States). Dept. of Radiology

2000-11-01

This review provides a summary of the cost-effectiveness, clinical utility, performance, and interpretation of screening helical cervical spine CT for trauma patients. Recent evidence supports the use of helical CT as a cost-effective method for screening the cervical spine in high-risk trauma patients. Screening cervical spine CT can be performed at the time of head CT to lower the cost of the evaluation, and when all short- and long-term costs are considered, CT may actually save money when compared with traditional radiographic screening. In addition to having higher sensitivity and specificity for cervical spine injury, CT screening also allows more rapid radiological clearance of the cervical spine than radiography. Patients who are involved in high-energy trauma, who sustain head injury, or who have neurological deficits are candidates for CT screening. Screening with CT may enhance detection of other potentially important injuries of the cervical region. (orig.)

RosettaTMH: a method for membrane protein structure elucidation combining EPR distance restraints with assembly of transmembrane helices

Directory of Open Access Journals (Sweden)

Andrew Leaver-Fay

2015-12-01

Full Text Available Membrane proteins make up approximately one third of all proteins, and they play key roles in a plethora of physiological processes. However, membrane proteins make up less than 2% of experimentally determined structures, despite significant advances in structure determination methods, such as X-ray crystallography, nuclear magnetic resonance spectroscopy, and cryo-electron microscopy. One potential alternative means of structure elucidation is to combine computational methods with experimental EPR data. In 2011, Hirst and others introduced RosettaEPR and demonstrated that this approach could be successfully applied to fold soluble proteins. Furthermore, few computational methods for de novo folding of integral membrane proteins have been presented. In this work, we present RosettaTMH, a novel algorithm for structure prediction of helical membrane proteins. A benchmark set of 34 proteins, in which the proteins ranged in size from 91 to 565 residues, was used to compare RosettaTMH to Rosetta’s two existing membrane protein folding protocols: the published RosettaMembrane folding protocol (“MembraneAbinitio” and folding from an extended chain (“ExtendedChain”. When EPR distance restraints are used, RosettaTMH+EPR outperforms ExtendedChain+EPR for 11 proteins, including the largest six proteins tested. RosettaTMH+EPR is capable of achieving native-like folds for 30 of 34 proteins tested, including receptors and transporters. For example, the average RMSD100SSE relative to the crystal structure for rhodopsin was 6.1 ± 0.4 Å and 6.5 ± 0.6 Å for the 449-residue nitric oxide reductase subunit B, where the standard deviation reflects variance in RMSD100SSE values across ten different EPR distance restraint sets. The addition of RosettaTMH and RosettaTMH+EPR to the Rosetta family of de novo folding methods broadens the scope of helical membrane proteins that can be accurately modeled with this software suite.

Structural Pre-sizing of a Coaxial Double-tube Type Hot Gas Duct

Energy Technology Data Exchange (ETDEWEB)

Song, Kee Nam; Kim, Y-W [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2008-10-15

The nuclear hydrogen system being researched at KAERI is planning to produce hydrogen in the order of 950 .deg. C by using nuclear energy and a thermo-chemical process, and helium gas is tentatively considered as the choice for the coolant. A hot gas duct (HGD) is a key component connecting the reactor pressure vessel and the intermediate heat exchanger (IHX) for the nuclear hydrogen system. The HGD is a unique component exclusively found in an HTR-module concept where a nuclear core and IHX are placed separately into two pressure vessels, which require a connecting duct between them. A coaxial double-tube type cross vessel is considered for the HGD structure of the nuclear hydrogen system because of its successive extensive experience. In this study, a structural pre-sizing for the primary HGD was carried out. These activities include a predecision on the geometric dimensions, a pre-evaluation on the strength, and a pre-selection on the material of the coaxial double-tube type cross vessel components. A predecision on the geometric dimensions was undertaken based on various engineering concepts, such as a constant flow velocity (CFV) model, a constant flow rate (CFR) model, a constant hydraulic head (CHH) model, and finally a heat balanced (HB) model. For the CFV model, CFR model, and CHH model, the HGD structure might be insensitive to a flow induced vibration (FIV) in the case where there are no pressure differences between the hot and cold helium regions. Also we compared the geometric dimensions from the various models.

The efficacy of low-dose helical CT screening as an option for health examination

International Nuclear Information System (INIS)

Kishi, Kazuma; Hara, Shigeko; Kurosaki, Atsuko; Fujii, Takeshi; Yoshimura, Kunihiko

2007-01-01

We retrospectively evaluated the results of low-dose helical CT screening as an option for health examinations. From November 2002 to October 2005, CT screening was performed in 2,306 individuals (men 1,766, women 540, mean age 56.1 years). Among them, 71 individuals (3.1%) were diagnosed as having active thoracic diseases consisting of 14 neoplasms and 57 non-neoplastic diseases. Of 14 patients with neoplastic lesions, 13 had lung cancer, 1 of whom had double primary lung cancer, and 1 had atypical adenomatous hyperplasia. The mean diameter of the 14 lung cancers was 14.4 mm. The histology of these lesions was adenocarcinoma in 13 and squamous cell carcinoma in 1. The pathological stage was IA in 12 patients and IIA in 1. All patients underwent surgical resection. On the other hand, emphysema was diagnosed in 40 asymptomatic individuals based on CT and spirometry, and smoking cessation was strongly implemented for those who were current smokers. CT screening is useful for detecting not only early lung cancer but also non-neoplastic lung diseases. (author)

Double thermal transitions of type I collagen in acidic solution.

Science.gov (United States)

Liu, Yan; Liu, Lingrong; Chen, Mingmao; Zhang, Qiqing

2013-01-01

Contributed equally to this work. To further understand the origin of the double thermal transitions of collagen in acidic solution induced by heating, the denaturation of acidic soluble collagen was investigated by micro-differential scanning calorimeter (micro-DSC), circular dichroism (CD), dynamic laser light scattering (DLLS), transmission electron microscopy (TEM), and two-dimensional (2D) synchronous fluorescence spectrum. Micro-DSC experiments revealed that the collagen exhibited double thermal transitions, which were located within 31-37 °C (minor thermal transition, T(s) ∼ 33 °C) and 37-55 °C (major thermal transition, T(m) ∼ 40 °C), respectively. The CD spectra suggested that the thermal denaturation of collagen resulted in transition from polyproline II type structure to unordered structure. The DLLS results showed that there were mainly two kinds of collagen fibrillar aggregates with different sizes in acidic solution and the larger fibrillar aggregates (T(p2) = 40 °C) had better heat resistance than the smaller one (T(p1) = 33 °C). TEM revealed that the depolymerization of collagen fibrils occurred and the periodic cross-striations of collagen gradually disappeared with increasing temperature. The 2D fluorescence correlation spectra were also applied to investigate the thermal responses of tyrosine and phenylalanine residues at the molecular level. Finally, we could draw the conclusion that (1) the minor thermal transition was mainly due to the defibrillation of the smaller collagen fibrillar aggregates and the unfolding of a little part of triple helices; (2) the major thermal transition primarily arose from the defibrillation of the larger collagen fibrillar aggregates and the complete denaturation of the majority part of triple helices.

Circularly polarized luminescence of helically assembled pyrene π-stacks on RNA and DNA duplexes.

Science.gov (United States)

Nakamura, Mitsunobu; Ota, Fuyuki; Takada, Tadao; Akagi, Kazuo; Yamana, Kazushige

2018-05-01

In this report, we describe the circularly polarized luminescence (CPL) of the RNA duplexes having one to four 2'-O-pyrene modified uridines (Upy) and the DNA duplexes having two, four, and six pyrene modified non-nucleosidic linkers (Py). Both the pyrene π-stack arrays formed on the RNA and DNA double helical structures exhibited pyrene excimer fluorescence. In the pyrene-modified RNA systems, the RNA duplex having four Upys gives CPL emission with g lum value of <0.01 at 480 nm. The structure of pyrene stacks on the RNA duplex may be rigidly regulated with increase in the Upy domains, which resulted in the CPL emission. In the DNA systems, the pyrene-modified duplexes containing two and four Pys exhibited CPL emission with g lum values of <0.001 at 505 nm. The pyrene π-stack arrays presented here show CPL emission. However, the g lum values are relatively small when compared with our previous system consisting of the pyrene-zipper arrays on RNA. © 2018 Wiley Periodicals, Inc.

Metastatic tumor of the pancreas: helical CT findings

International Nuclear Information System (INIS)

Lee, Soon Jin; Lee, Won Jae; Lim, Hyo Keun; Kim, Seung Hoon; Kim, Kyeong Ah; Choi, Sang Hee; Jang, Hyun Jung; Lee, Ji Yeon

2000-01-01

To analyze the helical computed tomographic (CT) findings of distant metastatic tumors to the pancreas and to determine the differential points between these and primary pamcreatic carcinomas. We sruveyed 22 patients with metastatic tumor of the pancreas, proven on the basis of clinical and pathological findings. Seventeen patients were men, and five were women, and their ages ranged between 36 and 83 years. Their primary conditions were lung cancer (n=3D15), rectal cancer (n=3D2), melanoma of the foot, chondrosarcoma of the sacrum, cervical cancer, leiomyosarcoma of the uterus, and extragonadal choriocarcinoma of the mediastinum. We retrospectively reviewed the abdominal helical CT findings, analysing the number, location, size and attenuation of masses, as well as secondary change, which included dilatation of the pancreatic and biliary ducts and invasion of peripancreatic tissue or vessels. We also evaluated the differential findings of primary pancreatic cancer. Sixteen patients had a solitary focal mass, while in five, two masses were present. Among the 22 patients, low-density nodular masses were present in 21; in the other, in whom multiple metastasis from chondrosarcoma had occurred, there was dense calcification. The size of metastatic masses varied, ranging from 0.6 to 6 cm in diameter. The pancreatic duct proximal to the mass was dilated in ten cases, while the bile duct was dilated in six. The metastatic masses masses demonstrated no peripancreatic or vascular invasion, though they showed a discrete margin and contour bulging. Single metastasis to the pancreas was most common, and metastatic masses had a discrete margin, with contour bulging. There was no peripancreatic or vascular invasion. If the metastasis involved a single low-attenuated mass, however, with pancreatic or biliary dilatation, it was difficult to differentiate this from primary pancreatic cancer. (author)

Action detection by double hierarchical multi-structure space-time statistical matching model

Science.gov (United States)

Han, Jing; Zhu, Junwei; Cui, Yiyin; Bai, Lianfa; Yue, Jiang

2018-03-01

Aimed at the complex information in videos and low detection efficiency, an actions detection model based on neighboring Gaussian structure and 3D LARK features is put forward. We exploit a double hierarchical multi-structure space-time statistical matching model (DMSM) in temporal action localization. First, a neighboring Gaussian structure is presented to describe the multi-scale structural relationship. Then, a space-time statistical matching method is proposed to achieve two similarity matrices on both large and small scales, which combines double hierarchical structural constraints in model by both the neighboring Gaussian structure and the 3D LARK local structure. Finally, the double hierarchical similarity is fused and analyzed to detect actions. Besides, the multi-scale composite template extends the model application into multi-view. Experimental results of DMSM on the complex visual tracker benchmark data sets and THUMOS 2014 data sets show the promising performance. Compared with other state-of-the-art algorithm, DMSM achieves superior performances.

Transmission loss of orthogonally rib-stiffened double-panel structures with cavity absorption.

Science.gov (United States)

Xin, F X; Lu, T J

2011-04-01

The transmission loss of sound through infinite orthogonally rib-stiffened double-panel structures having cavity-filling fibrous sound absorptive materials is theoretically investigated. The propagation of sound across the fibrous material is characterized using an equivalent fluid model, and the motions of the rib-stiffeners are described by including all possible vibrations, i.e., flexural displacements, bending, and torsional rotations. The effects of fluid-structure coupling are account for by enforcing velocity continuity conditions at fluid-panel interfaces. By taking full advantage of the periodic nature of the double-panel, the space-harmonic approach and virtual work principle are applied to solve the sets of resultant governing equations, which are eventually truncated as a finite system of simultaneous algebraic equations and numerically solved insofar as the solution converges. To validate the proposed model, a comparison between the present model predictions and existing numerical and experimental results for a simplified version of the double-panel structure is carried out, with overall agreement achieved. The model is subsequently employed to explore the influence of the fluid-structure coupling between fluid in the cavity and the two panels on sound transmission across the orthogonally rib-stiffened double-panel structure. Obtained results demonstrate that this fluid-structure coupling affects significantly sound transmission loss (STL) at low frequencies and cannot be ignored when the rib-stiffeners are sparsely distributed. As a highlight of this research, an integrated optimal algorithm toward lightweight, high-stiffness and superior sound insulation capability is proposed, based on which a preliminary optimal design of the double-panel structure is performed.

Optimization of the Magnetic Field Structure for Sustained Plasma Gun Helicity Injection for Magnetic Turbulence Studies at the Bryn Mawr Plasma Laboratory

Science.gov (United States)

Cartagena-Sanchez, C. A.; Schaffner, D. A.; Johnson, H. K.; Fahim, L. E.

2017-10-01

A long-pulsed magnetic coaxial plasma gun is being implemented and characterized at the Bryn Mawr Plasma Laboratory (BMPL). A cold cathode discharged between the cylindrical electrodes generates and launches plasma into a 24cm diameter, 2m long chamber. Three separately pulsed magnetic coils are carefully positioned to generate radial magnetic field between the electrodes at the gun edge in order to provide stuffing field. Magnetic helicity is continuously injected into the flux-conserving vacuum chamber in a process akin to sustained slow-formation of spheromaks. The aim of this source, however, is to supply long pulses of turbulent magnetized plasma for measurement rather than for sustained spheromak production. The work shown here details the optimization of the magnetic field structure for this sustained helicity injection.

Is gadolinium a helical antiferromagnet or a collinear ferromagnet?

Indian Academy of Sciences (India)

that a helical spin structure similar to that prevalent in other heavy rare-earth .... magnetocrystalline anisotropy factor, HK is the uniaxial anisotropy field and MS is .... lends firm support to the observation that the asymptotic critical behaviour of ...

Chirality induction and protonation-induced molecular motions in helical molecular strands.

Science.gov (United States)

Kolomiets, Elena; Berl, Volker; Lehn, Jean-Marie

2007-01-01

The long oligopyridinedicarboxamide strand 9, containing 15 heterocyclic rings has been synthesized and its helical structure determined by X-ray crystallography. It was shown that the shorter analogue 6 displays induced circular dichroism and amplification of induced chirality upon dissolution in an optically active solvent, diethyl-L-tartrate. A novel class of helical foldamers was prepared, strands 14-16, based on two oligopyridine carboxamide segments linked through a L-tartaric acid derived spacer. These tartro strands display internal chirality induction as well as chirality amplification. NMR spectroscopy (on 8 and 9) and circular dichroism (on 16) studies show that the oligopyridine carboxamide strands undergo reversible unfolding/folding upon protonation. The protonation-induced unfolding has been confirmed by X-ray crystallographic determination of the molecular structure of the extended protonated heptameric form 8(+). The molecular-scale mechano-chemical motions of the protonation-induced structural switching consist of a change of the length of the molecule, from 6 angstroms (6, coiled form) to 29 angstroms (8(+), uncoiled form) for the heptamer and from 12.5 angstroms (9, coiled form, X-ray structure) to 57 angstroms (9(+), uncoiled form, from modeling) for the pentadecamer. Similar unfolding/folding motional processes take place in the L-tartro strands 15 and 16 upon protonation/deprotonation, with loss of helicity-induced circular dichroism on unfolding as shown for the protonated form 16(+).

Active structural acoustic control of noise transmission through double panel systems

Science.gov (United States)

Carneal, James P.; Fuller, Chris R.

1995-04-01

A preliminary parametric study of active control of sound transmission through double panel systems has been experimentally performed. The technique used is the active structural acoustic control (ASAC) approach where control inputs, in the form of piezoelectric actuators, were applied to the structure while the radiated pressure field was minimized. Results indicate the application of control inputs to the radiating panel resulted in greater transmission loss due to its direct effect on the nature of the structural-acoustic coupling between the radiating panel and the receiving chamber. Increased control performance was seen in a double panel system consisting of a stiffer radiating panel with a lower modal density. As expected, more effective control of a radiating panel excited on-resonance is achieved over one excited off-resonance. In general, the results validate the ASAC approach for double panel systems and demonstrate that it is possible to take advantage of double panel behavior to enhance control performance, although it is clear that further research must be done to understand the physics involved.

Double quick, double click reversible peptide "stapling".

Science.gov (United States)

Grison, Claire M; Burslem, George M; Miles, Jennifer A; Pilsl, Ludwig K A; Yeo, David J; Imani, Zeynab; Warriner, Stuart L; Webb, Michael E; Wilson, Andrew J

2017-07-01

The development of constrained peptides for inhibition of protein-protein interactions is an emerging strategy in chemical biology and drug discovery. This manuscript introduces a versatile, rapid and reversible approach to constrain peptides in a bioactive helical conformation using BID and RNase S peptides as models. Dibromomaleimide is used to constrain BID and RNase S peptide sequence variants bearing cysteine (Cys) or homocysteine ( h Cys) amino acids spaced at i and i + 4 positions by double substitution. The constraint can be readily removed by displacement of the maleimide using excess thiol. This new constraining methodology results in enhanced α-helical conformation (BID and RNase S peptide) as demonstrated by circular dichroism and molecular dynamics simulations, resistance to proteolysis (BID) as demonstrated by trypsin proteolysis experiments and retained or enhanced potency of inhibition for Bcl-2 family protein-protein interactions (BID), or greater capability to restore the hydrolytic activity of the RNAse S protein (RNase S peptide). Finally, use of a dibromomaleimide functionalized with an alkyne permits further divergent functionalization through alkyne-azide cycloaddition chemistry on the constrained peptide with fluorescein, oligoethylene glycol or biotin groups to facilitate biophysical and cellular analyses. Hence this methodology may extend the scope and accessibility of peptide stapling.

Magnetic helicity balance in the Sustained Spheromak Plasma Experiment

International Nuclear Information System (INIS)

Stallard, B.W.; Hooper, E.B.; Woodruff, S.; Bulmer, R.H.; Hill, D.N.; McLean, H.S.; Wood, R.D.

2003-01-01

The magnetic helicity balance between the helicity input injected by a magnetized coaxial gun, the rate-of-change in plasma helicity content, and helicity dissipation in electrode sheaths and Ohmic losses have been examined in the Sustained Spheromak Plasma Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, and R. H. Bulmer, Nucl. Fusion 39, 863 (1999)]. Helicity is treated as a flux function in the mean-field approximation, allowing separation of helicity drive and losses between closed and open field volumes. For nearly sustained spheromak plasmas with low fluctuations, helicity balance analysis implies a decreasing transport of helicity from the gun input into the spheromak core at higher spheromak electron temperature. Long pulse discharges with continuously increasing helicity and larger fluctuations show higher helicity coupling from the edge to the spheromak core. The magnitude of the sheath voltage drop, inferred from cathode heating and a current threshold dependence of the gun voltage, shows that sheath losses are important and reduce the helicity injection efficiency in SSPX

Primary intestinal lymphangiectasia diagnosed by double-balloon enteroscopy and treated by medium-chain triglycerides: a case report

OpenAIRE

Lai, Yu; Yu, Tao; Qiao, Xiao-yu; Zhao, Li-na; Chen, Qi-kui

2013-01-01

Abstract Introduction Primary intestinal lymphangiectasia is a disorder characterized by exudative enteropathy resulting from morphologic abnormalities of the intestinal lymphatics. Intestinal lymphangiectasia can be primary or secondary, so the diagnosis of primary intestinal lymphangiectasia must first exclude the possibility of secondary intestinal lymphangiectasia. A double-balloon enteroscopy and biopsy, as well as the pathology can be used to confirm the diagnosis of intestinal lymphang...

On the inverse transfer of (non-)helical magnetic energy in a decaying magnetohydrodynamic turbulence

Science.gov (United States)

Park, Kiwan

2017-12-01

In our conventional understanding, large-scale magnetic fields are thought to originate from an inverse cascade in the presence of magnetic helicity, differential rotation or a magneto-rotational instability. However, as recent simulations have given strong indications that an inverse cascade (transfer) may occur even in the absence of magnetic helicity, the physical origin of this inverse cascade is still not fully understood. We here present two simulations of freely decaying helical and non-helical magnetohydrodynamic (MHD) turbulence. We verified the inverse transfer of helical and non-helical magnetic fields in both cases, but we found the underlying physical principles to be fundamentally different. In the former case, the helical magnetic component leads to an inverse cascade of magnetic energy. We derived a semi-analytic formula for the evolution of large-scale magnetic field using α coefficient and compared it with the simulation data. But in the latter case, the α effect, including other conventional dynamo theories, is not suitable to describe the inverse transfer of non-helical magnetic energy. To obtain a better understanding of the physics at work here, we introduced a 'field structure model' based on the magnetic induction equation in the presence of inhomogeneities. This model illustrates how the curl of the electromotive force leads to the build up of a large-scale magnetic field without the requirement of magnetic helicity. And we applied a quasi-normal approximation to the inverse transfer of magnetic energy.

The α-Helical Structure of Prodomains Promotes Translocation of Intrinsically Disordered Neuropeptide Hormones into the Endoplasmic Reticulum*

Science.gov (United States)

Dirndorfer, Daniela; Seidel, Ralf P.; Nimrod, Guy; Miesbauer, Margit; Ben-Tal, Nir; Engelhard, Martin; Zimmermann, Richard; Winklhofer, Konstanze F.; Tatzelt, Jörg

2013-01-01

Different neuropeptide hormones, which are either too small to adopt a stable conformation or are predicted to be intrinsically disordered, are synthesized as larger precursors containing a prodomain in addition to an N-terminal signal peptide. We analyzed the biogenesis of three unstructured neuropeptide hormones and observed that translocation of these precursors into the lumen of the endoplasmic reticulum (ER) is critically dependent on the presence of the prodomain. The hormone domains could be deleted from the precursors without interfering with ER import and secretion, whereas constructs lacking the prodomain remained in the cytosol. Domain-swapping experiments revealed that the activity of the prodomains to promote productive ER import resides in their ability to adopt an α-helical structure. Removal of the prodomain from the precursor did not interfere with co-translational targeting of the nascent chain to the Sec61 translocon but with its subsequent productive translocation into the ER lumen. Our study reveals a novel function of prodomains to enable import of small or intrinsically disordered secretory proteins into the ER based on their ability to adopt an α-helical conformation. PMID:23532840

Photoproduction of η mesons from the neutron: Cross sections and double polarization observable E

Energy Technology Data Exchange (ETDEWEB)

Witthauer, L.; Dieterle, M.; Challand, T.; Kaeser, A.; Keshelashvili, I.; Krusche, B.; Rostomyan, T.; Walford, N.K.; Werthmueller, D. [University of Basel, Department of Physics, Basel (Switzerland); Afzal, F.; Beck, R.; Boese, S.; Funke, C.; Gottschall, M.; Gruener, M.; Hammann, C.; Hartmann, J.; Hoffmeister, P.; Honisch, C.; Kaiser, D.; Kalinowsky, H.; Kalischewski, F.; Klassen, P.; Koop, K.; Lang, M.; Mahlberg, P.; Mueller, J.; Muellers, J.; Piontek, D.; Schmidt, C.; Seifen, T.; Sokhoyan, V.; Spieker, K.; Thiel, A.; Thoma, U.; Urban, M.; Pee, H. van; Walther, D.; Wendel, C.; Winnebeck, A. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn, Bonn (Germany); Anisovich, A.V.; Bayadilov, D.; Nikonov, V.; Sarantsev, A. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn, Bonn (Germany); Petersburg Nuclear Physics Institute, National Research Centre ' ' Kurchatov Institute' ' , Gatchina (Russian Federation); Bantes, B.; Dutz, H.; Eberhardt, H.; Elsner, D.; Ewald, R.; Fornet-Ponse, K.; Frommberger, F.; Goertz, S.; Hammann, D.; Hannappel, J.; Hillert, W.; Jude, T.; Kammer, S.; Kleber, V.; Klein, F.; Schmieden, H. [Universitaet Bonn, Physikalisches Institut, Bonn (Germany); Bichow, M.; Meyer, W.; Reicherz, G. [Ruhr-Universitaet Bochum, Institut fuer Experimentalphysik I, Bochum (Germany); Brinkmann, K.T.; Gutz, E. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn, Bonn (Germany); Universitaet Giessen, II. Physikalisches Institut, Giessen (Germany); Crede, V. [Florida State University, Department of Physics, Tallahassee, FL (United States); Friedrich, S.; Makonyi, K.; Metag, V.; Nanova, M. [Universitaet Giessen, II. Physikalisches Institut, Giessen (Germany); Gridnev, A.; Lopatin, I. [Petersburg Nuclear Physics Institute, National Research Centre ' ' Kurchatov Institute' ' , Gatchina (Russian Federation); Wilson, A. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn, Bonn (Germany); Florida State University, Department of Physics, Tallahassee, FL (United States); Collaboration: The CBELSA/TAPS Collaboration

2017-03-15

Results from measurements of the photoproduction of η mesons from quasifree protons and neutrons are summarized. The experiments were performed with the CBELSA/TAPS detector at the electron accelerator ELSA in Bonn using the η → 3π{sup 0} → 6γ decay. A liquid deuterium target was used for the measurement of total cross sections and angular distributions. The results confirm earlier measurements from Bonn and the MAMI facility in Mainz about the existence of a narrow structure in the excitation function of γn → nη. The current angular distributions show a forward-backward asymmetry, which was previously not seen, but was predicted by model calculations including an additional narrow P{sub 11} state. Furthermore, data obtained with a longitudinally polarized, deuterated butanol target and a circularly polarized photon beam were analyzed to determine the double polarization observable E. Both data sets together were also used to extract the helicity-dependent cross sections σ{sub 1/2} and σ{sub 3/2}. The narrow structure in the excitation function of γn → nη appears associated with the helicity-1/2 component of the reaction. (orig.)

Diffusion in a tokamak with helical magnetic cells

International Nuclear Information System (INIS)

Wakatani, Masahiro

1975-05-01

In a tokamak with helical magnetic cells produced by a resonant helical magnetic field, diffusion in the collisional regime is studied. The diffusion coefficient is greatly enhanced near the resonant surface even for a weak helical magnetic field. A theoretical model for disruptive instabilities based on the enhanced transport due to helical magnetic cells is discussed. This may explain experiments of the tokamak with resonant helical fields qualitatively. (author)

Nano-structure and optical properties (plasmonic) of graded helical square tower-like (terraced) Mn sculptured thin films

Energy Technology Data Exchange (ETDEWEB)

Savaloni, Hadi, E-mail: savaloni@khayam.ut.ac.ir [Department of Physics, University of Tehran, North-Kargar Street, Tehran (Iran, Islamic Republic of); Fakharpour, Mahsa [Department of Physics, Islamic Azad University, Science and Research Branch, Tehran (Iran, Islamic Republic of); Siabi-Garjan, Araz [Department of Advanced Technologies, University of Mohaghegh Ardabili, Namin, Ardabil (Iran, Islamic Republic of); Department of Materials Engineering and Nanotechnology, Sabalan University of Advanced Technologies (SUAT), Namin (Iran, Islamic Republic of); Placido, Frank [SUPA and Institute of Thin Films, Sensors and Imaging, University of The West of Scotland, High Street, Paisley (United Kingdom); Babaei, Ferydon [Department of Physics, University of Qom, Qom (Iran, Islamic Republic of)

2017-01-30

Highlights: • Graded helical square tower-like terraced sculptured Mn thin films are produced with different number of arms. • XRD, AFM, FESEM and optical analyses as well as theoretical calculations are carried out. • Intensity of Plasmon peaks depend on the polarization, the incident angle, and the distance from the shadowing block. • The presence of defects in these sculptured structures can be predicted by theoretical investigation. • Experimental and theoretical investigations show consistent results. - Abstract: Graded helical square tower-like terraced sculptured Mn thin films (GHSTTS) are produced in three stages with different number of arms using oblique angle deposition together with rotation of substrate holder about its surface normal, plus a shadowing block fixed at the centre of the substrate holder. The structural characterization of the produced samples was obtained using field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). Results showed a structural gradient with distance from the edge of the shadowing block, which in turn is responsible for the decrease in the volume of void fraction and increase of grain size. Plasmon absorption peaks observed in the optical analysis of these nano-structures showed that their wavelength region and intensity depend on the polarization and the incident angle of light, as well as the distance from the edge of the shadowing block. According to our model and discrete dipole approximation (DDA) calculations, when the number of parallel nano-rods of different lengths and radii are increased the peak in the spectrum shifts to shorter wavelengths (blue shift). Also when the diameters of the nano-rods increases (a situation that occurs with increasing film thickness) the results is again a blue shift in the spectrum. The presence of defects in these sculptured structures caused by the shadowing effect is predicted by the theoretical DDA investigation of their optical spectra

How reverse turns may mediate the formation of helical segments in proteins: an x-ray model.

OpenAIRE

Perczel, A; Foxman, B M; Fasman, G D

1992-01-01

The three-dimensional structure of a protein is the assembly of different secondary structural elements, such as alpha-helices, beta-pleated sheets, and beta-turns. Although the conformation of hundreds of proteins has been elaborated in the solid state, only a vague understanding of the mechanism of their conformational folding is known. One facet of this topic is the conformational interconversion of one or more beta-turns to a helical structure (and vice versa), which may also be related t...

Modeling of Heat Transfer in the Helical-Coil Heat Exchanger for the Reactor Facility "UNITERM"

Directory of Open Access Journals (Sweden)

V. I. Solonin

2014-01-01

Full Text Available Circuit heat sink plays an important role in the reactor system. Therefore it imposes high requirements for quality of determining thermal-hydraulic parameters. This article is aimed at modeling of heat exchange process of the helical-coil heat exchanger, which is part of the heat sink circuit of the reactor facility "UNITERM."The simulation was performed using hydro-gas-dynamic software package ANSYS CFX. Computational fluid dynamics of this package allows us to perform calculations in a threedimensional setting, giving an idea of the fluid flow nature. The purpose of the simulation was to determine the parameters of the helical-coil heat exchanger (temperature, velocity at the outlet of the pipe and inter-tubular space, pressure drop, and the nature of the fluid flow of primary and intermediate coolants. Geometric parameters of the model were determined using the preliminary calculations performed by the criterion equations. In calculations Turbulence models k-ε RNG, Shear Stress Transport (SST are used. The article describes selected turbulence models, and considers relationship with wall function.The calculation results allow us to give the values obtained for thermal-hydraulic parameters, to compare selected turbulence models, as well as to show distribution patterns of the coolant temperature, pressure, and velocity at the outlet of the intermediate cooler.Calculations have shown that:- maximum values of primary coolant temperature at the outlet of the heat exchanger surface are encountered in the space between the helical-coil tubes;- higher temperatures of intermediate coolant at the outlet of the coils (in space of helicalcoil tubes are observed for the peripheral row;- primary coolant movement in the inter-tubular space of helical-coil surface is formed as a spiral flow, rather than as a in-line tube bank cross flow.

Gear Design Effects on the Performance of High Speed Helical Gear Trains as Used in Aerospace Drive Systems

Science.gov (United States)

Handschuh, R.; Kilmain, C.; Ehinger, R.; Sinusas, E.

2013-01-01

The performance of high-speed helical gear trains is of particular importance for tiltrotor aircraft drive systems. These drive systems are used to provide speed reduction / torque multiplication from the gas turbine output shaft and provide the necessary offset between these parallel shafts in the aircraft. Four different design configurations have been tested in the NASA Glenn Research Center, High Speed Helical Gear Train Test Facility. The design configurations included the current aircraft design, current design with isotropic superfinished gear surfaces, double helical design (inward and outward pumping), increased pitch (finer teeth), and an increased helix angle. All designs were tested at multiple input shaft speeds (up to 15,000 rpm) and applied power (up to 5,000 hp). Also two lubrication, system-related, variables were tested: oil inlet temperature (160 to 250 degF) and lubricating jet pressure (60 to 80 psig). Experimental data recorded from these tests included power loss of the helical system under study, the temperature increase of the lubricant from inlet to outlet of the drive system and fling off temperatures (radially and axially). Also, all gear systems were tested with and without shrouds around the gears. The empirical data resulting from this study will be useful to the design of future helical gear train systems anticipated for next generation rotorcraft drive systems.

Dynamics of zonal flows in helical systems.

Science.gov (United States)

Sugama, H; Watanabe, T-H

2005-03-25

A theory for describing collisionless long-time behavior of zonal flows in helical systems is presented and its validity is verified by gyrokinetic-Vlasov simulation. It is shown that, under the influence of particles trapped in helical ripples, the response of zonal flows to a given source becomes weaker for lower radial wave numbers and deeper helical ripples while a high-level zonal-flow response, which is not affected by helical-ripple-trapped particles, can be maintained for a longer time by reducing their bounce-averaged radial drift velocity. This implies a possibility that helical configurations optimized for reducing neoclassical ripple transport can simultaneously enhance zonal flows which lower anomalous transport.

Antiviral activity of α-helical stapled peptides designed from the HIV-1 capsid dimerization domain

Directory of Open Access Journals (Sweden)

Cowburn David

2011-05-01

Full Text Available Abstract Background The C-terminal domain (CTD of HIV-1 capsid (CA, like full-length CA, forms dimers in solution and CTD dimerization is a major driving force in Gag assembly and maturation. Mutations of the residues at the CTD dimer interface impair virus assembly and render the virus non-infectious. Therefore, the CTD represents a potential target for designing anti-HIV-1 drugs. Results Due to the pivotal role of the dimer interface, we reasoned that peptides from the α-helical region of the dimer interface might be effective as decoys to prevent CTD dimer formation. However, these small peptides do not have any structure in solution and they do not penetrate cells. Therefore, we used the hydrocarbon stapling technique to stabilize the α-helical structure and confirmed by confocal microscopy that this modification also made these peptides cell-penetrating. We also confirmed by using isothermal titration calorimetry (ITC, sedimentation equilibrium and NMR that these peptides indeed disrupt dimer formation. In in vitro assembly assays, the peptides inhibited mature-like virus particle formation and specifically inhibited HIV-1 production in cell-based assays. These peptides also showed potent antiviral activity against a large panel of laboratory-adapted and primary isolates, including viral strains resistant to inhibitors of reverse transcriptase and protease. Conclusions These preliminary data serve as the foundation for designing small, stable, α-helical peptides and small-molecule inhibitors targeted against the CTD dimer interface. The observation that relatively weak CA binders, such as NYAD-201 and NYAD-202, showed specificity and are able to disrupt the CTD dimer is encouraging for further exploration of a much broader class of antiviral compounds targeting CA. We cannot exclude the possibility that the CA-based peptides described here could elicit additional effects on virus replication not directly linked to their ability to bind

Evaluation of mechanical integrity for helical coil hold-down spring of PLUS7TM fuel

International Nuclear Information System (INIS)

Choi, Ki Sung; Kim, Yong Hwan; Kwon, Jung Tack; Kim, Kyu Tae

2004-01-01

Nuclear fuel assembly is subject to hydraulic forces generated by primary coolant flow during reactor operation. These forces may be sufficient to overcome the fuel assembly weight thereby allowing the fuel assembly to lift off of its support. To provide a positive hold-down margin against the upward coolant flow forces, helical coil springs or leaf springs are installed in the fuel assemblies. An advanced fuel for Korean Standard Nuclear Power Plants (KSNP), PLUS7 fuel has developed to get the thermal margin increase, failure free and high seismic resistance, etc. And the new designed helical coil hold-down spring was introduced into PLUS7 fuel assembly. The purpose of this paper is to evaluate the mechanical integrity for the helical coil hold-down spring of PLUS7 fuel assembly

Parameterization and measurements of helical magnetic fields

International Nuclear Information System (INIS)

Fischer, W.; Okamura, M.

1997-01-01

Magnetic fields with helical symmetry can be parameterized using multipole coefficients (a n , b n ). We present a parameterization that gives the familiar multipole coefficients (a n , b n ) for straight magnets when the helical wavelength tends to infinity. To measure helical fields all methods used for straight magnets can be employed. We show how to convert the results of those measurements to obtain the desired helical multipole coefficients (a n , b n )

Synthesis of Norbornene Derived Helical Copolymer by Simple Molecular Marriage Approach to Produce Smart Nanocarrier.

Science.gov (United States)

Mane, Shivshankar R; Sathyan, Ashlin; Shunmugam, Raja

2017-03-22

A novel library of norbornene derived helical copolymer has been synthesized through the coupling of two homopolymers via Molecular Marriage Approach. The helicity is governed by the non-covalent interactions like hydrogen bonding, π-π stacking and the influence of hydrophobic and hydrophilic motifs. The detailed characterization of the copolymer (Copoly 1) has been provided and the super structures are confirmed through dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The observed size of the aggregates was about 200 nm. The density functional theory (DFT) is favorably supported for the formation of proposed structure of Copoly 1. Circular dichroism (CD) measurement has confirmed the one handed helical structure of the copolymer. Reservoir capability of this pH responsive polymer (Copoly 1) to encapsulate anti-cancer drug doxorubicin (DOX) warrants its potential applications in the field of bio-medical sciences.

Conceptual design of the superconducting magnet system for the helical fusion reactor

International Nuclear Information System (INIS)

Yanagi, Nagato; Hamaguchi, Shinji; Takahata, Kazuya; Natsume, Kyohei

2013-01-01

Current status of conceptual design of superconducting magnet system and low temperature system for the helical fusion reactor are introduced. There are three kinds of candidates of superconducting magnets such as Cable-in-conduit (CIC), Low-Temperature Superconductor (LTS) and High-Temperature Superconductor (HTS). Their characteristic properties, coil designs and cooling systems are stated. The freezer and low temperature distribution system, bus line and current lead, and excitation power source for superconducting coil are reported. The various elements of superconducting magnet system of FFHR-d1, partial cross section of FFHR helical coil using CIC, conceptual diagram of helical coil winding method of FFHR using CIC, relation among mass flow of supercritical helium supplied into CIC conductor and temperature increasing and pressure loss, cross section structure of LTS indirect-cooling conductor at 100 kA, cross section of 100-kA HTS conductor, connection method of helical coil segment and YBCO conductor are illustrated. (S.Y.)

Supramolecular Architectures and Mimics of Complex Natural Folds Derived from Rationally Designed alpha-Helical Protein Structures

Science.gov (United States)

Tavenor, Nathan Albert

Protein-based supramolecular polymers (SMPs) are a class of biomaterials which draw inspiration from and expand upon the many examples of complex protein quaternary structures observed in nature: collagen, microtubules, viral capsids, etc. Designing synthetic supramolecular protein scaffolds both increases our understanding of natural superstructures and allows for the creation of novel materials. Similar to small-molecule SMPs, protein-based SMPs form due to self-assembly driven by intermolecular interactions between monomers, and monomer structure determines the properties of the overall material. Using protein-based monomers takes advantage of the self-assembly and highly specific molecular recognition properties encodable in polypeptide sequences to rationally design SMP architectures. The central hypothesis underlying our work is that alpha-helical coiled coils, a well-studied protein quaternary folding motif, are well-suited to SMP design through the addition of synthetic linkers at solvent-exposed sites. Through small changes in the structures of the cross-links and/or peptide sequence, we have been able to control both the nanoscale organization and the macroscopic properties of the SMPs. Changes to the linker and hydrophobic core of the peptide can be used to control polymer rigidity, stability, and dimensionality. The gaps in knowledge that this thesis sought to fill on this project were 1) the relationship between the molecular structure of the cross-linked polypeptides and the macroscopic properties of the SMPs and 2) a means of creating materials exhibiting multi-dimensional net or framework topologies. Separate from the above efforts on supramolecular architectures was work on improving backbone modification strategies for an alpha-helix in the context of a complex protein tertiary fold. Earlier work in our lab had successfully incorporated unnatural building blocks into every major secondary structure (beta-sheet, alpha-helix, loops and beta

Double-layer structure in polar mesospheric clouds observed from SOFIE/AIM

Directory of Open Access Journals (Sweden)

H. Gao

2017-02-01

Full Text Available Double-layer structures in polar mesospheric clouds (PMCs are observed by using Solar Occultation for Ice Experiment (SOFIE data between 2007 and 2014. We find 816 and 301 events of double-layer structure with percentages of 10.32 and 7.25 % compared to total PMC events, and the mean distances between two peaks are 3.06 and 2.73 km for the Northern Hemisphere (NH and Southern Hemisphere (SH respectively. Double-layer PMCs almost always have less mean ice water content (IWC than daily IWC during the core of the season, but they are close to each other at the beginning and the end. The result by averaging over all events shows that the particle concentration has obvious double peaks, while the particle radius exhibits an unexpected monotonic increase with decreasing altitude. By further analysis of the background temperature and water vapour residual profiles, we conclude that the lower layer is a reproduced one formed at the bottom of the upper layer. 56.00 and 47.51 % of all double-layer events for the NH and SH respectively have temperature enhancements larger than 2 K locating between their double peaks. The longitudinal anti-correlation between the gravity waves' (GWs' potential energies and occurrence frequencies of double-layer PMCs suggests that the double-layer PMCs tend to form in an environment where the GWs have weaker intensities.

Lasing thresholds of helical photonic structures with different positions of a single light-amplifying helix turn

Energy Technology Data Exchange (ETDEWEB)

Blinov, L M; Palto, S P [A.V. Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, Russian Federaion (Russian Federation)

2013-09-30

Numerical simulation is used to assess the lasing threshold of helical structures of cholesteric liquid crystals (CLCs) in which only one turn amplifies light. This turn is located either in the centre of symmetric structures of various sizes or in an arbitrary place in asymmetric structures of preset size. In all cases, we find singularities in light amplification by a one-dimensional CLC structure for the most important band-edge modes (m1, m2 and m3) and plot the threshold gain coefficient k{sub th} against the position of the amplifying turn. For the symmetric structures, the lasing threshold of the m1 mode is shown to vary linearly with the inverse of the square of the cavity length. Moreover, modes with a lower density of photonic states (DOS) in the cavity may have a lower lasing threshold. This can be accounted for by the dependence of the density of photonic states on the position of the amplifying turn and, accordingly, by the nonuniform electromagnetic field intensity distribution along the cavity for different modes. In the asymmetric structures, the same field energy distribution is responsible for a correlation between k{sub th} and DOS curves. (lasers)

Studies on positive conveying in helically channeled single screw extruders

Directory of Open Access Journals (Sweden)

L. Pan

2012-07-01

Full Text Available A solids conveying theory called double-flight driving theory was proposed for helically channeled single screw extruders. In the extruder, screw channel rotates against static barrel channel, which behaves as cooperative embedded twin-screws for the positive conveying. They turn as two parallel arc plates, between which an arc-plate solid-plug was assumed. By analyzing the forces on the solid-plug in the barrel channel and screw channel, the boundary conditions when the solid-plug is waived of being cut off on barrel wall, were found to have the capacity of the positive conveying. Experimental data were obtained using a specially designed extruder with a helically channeled barrel in the feeding zone and a pressure-adjustable die. The effects of the barrel channel geometry and friction coefficients on the conveying mechanism were presented and compared with the experimental results. The simulations showed that the positive conveying could be achieved after optimizing extruder designs. Compared with the traditional design with the friction-drag conveying, the throughput is higher while screw torque and energy consumption are decreased. Besides, the design criteria of the barrel channel were also discussed.

Evidence for Mixed Helicity in Erupting Filaments

Science.gov (United States)

Muglach, K.; Wang, Y.-M.; Kliem, B.

2009-09-01

Erupting filaments are sometimes observed to undergo a rotation about the vertical direction as they rise. This rotation of the filament axis is generally interpreted as a conversion of twist into writhe in a kink-unstable magnetic flux rope. Consistent with this interpretation, the rotation is usually found to be clockwise (as viewed from above) if the post-eruption arcade has right-handed helicity, but counterclockwise if it has left-handed helicity. Here, we describe two non-active-region filament events recorded with the Extreme-Ultraviolet Imaging Telescope on the Solar and Heliospheric Observatory in which the sense of rotation appears to be opposite to that expected from the helicity of the post-event arcade. Based on these observations, we suggest that the rotation of the filament axis is, in general, determined by the net helicity of the erupting system, and that the axially aligned core of the filament can have the opposite helicity sign to the surrounding field. In most cases, the surrounding field provides the main contribution to the net helicity. In the events reported here, however, the helicity associated with the filament "barbs" is opposite in sign to and dominates that of the overlying arcade.

Helicity and potential vorticity in the surface boundary layer turbulence

Science.gov (United States)

Chkhetiani, Otto; Kurgansky, Michael; Koprov, Boris; Koprov, Victor

2016-04-01

An experimental measurement of all three components of the velocity and vorticity vectors, as well as the temperature and its gradient, and potential vorticity, has been developed using four acoustic anemometers. Anemometers were placed at vertices of a tetrahedron, the horizontal base of which was a rectangular triangle with equal legs, and the upper point was exactly above the top of the right angle. The distance from the surface to the tetrahedron its base was 5.5 m, and the lengths of legs and a vertical edge were 5 m. The measurements were carried out of total duration near 100 hours both in stable and unstable stratification conditions (at the Tsimlyansk Scientific Station in a uniform area of virgin steppe 700 x 650 m, August 2012). A covariance-correlation matrix for turbulent variations in all measured values has been calculated. In the daytime horizontal and vertical components of the helicity are of the order of -0.03 and +0.01 m s-2, respectively. The nighttime signs remain unchanged, but the absolute values are several times smaller. It is confirmed also by statistics of a relative helicity. The cospectra and spectral correlation coefficients have been calculated for all helicity components. The time variations in the components of "instantaneous" relative helicity and potential vorticity are considered. Connections of helicity with Monin-Obukhov length and the wind vertical profile structure are discussed. This work was supported by the Russian Science Foundation (Project No 14-27-00134).

Applications of 2D helical vortex dynamics

DEFF Research Database (Denmark)

Okulov, Valery; Sørensen, Jens Nørkær

2010-01-01

In the paper, we show how the assumption of helical symmetry in the context of 2D helical vortices can be exploited to analyse and to model various cases of rotating flows. From theory, examples of three basic applications of 2D dynamics of helical vortices embedded in flows with helical symmetry...... of the vorticity field are addressed. These included some of the problems related to vortex breakdown, instability of far wakes behind rotors and vortex theory of ideal rotors....

Theoretical aspects of magnetic helicity

International Nuclear Information System (INIS)

Hammer, J.H.

1985-01-01

The magnetic helicity, usually defined as K=integralA.Bdv, where A is the vector potential and B the magnetic field, measures the topological linkage of magnetic fluxes. Helicity manifests itself in the twistedness and knottedness of flux tubes. Its significance is that it is an ideal MHD invariant. While the helicity formalism has proven very useful in understanding reversed field pinch and spheromak behavior, some problems exist in applying the method consistently for complex (e.g., toroidal) conductor geometries or in situations where magnetic flux penetrates conducting walls. Recent work has attempted to generalize K to allow for all possible geometries

Influence of crystallite size and temperature on the antiferromagnetic helices of terbium and holmium metal

Energy Technology Data Exchange (ETDEWEB)

Bick, Jens-Peter; Michels, Andreas [Universitaet des Saarlandes, D-66041 Saarbruecken (Germany); University of Luxembourg, L-1511 Luxembourg (Luxembourg); Ferdinand, Adrian; Birringer, Rainer [Universitaet des Saarlandes, D-66041 Saarbruecken (Germany); Baller, Joerg; Sanctuary, Roland [University of Luxembourg, L-1511 Luxembourg (Luxembourg); Philippi, Stefan [Leibniz Institute for Solid State and Materials Research, D-01069 Dresden (Germany); Lott, Dieter [GKSS Research Center, D-21502 Geesthacht (Germany); Balog, Sandor [Paul Scherrer Institute, CH-5232 Villigen (Switzerland); Rotenberg, Eli [Lawrence Berkeley National Laboratory, California 94720 (United States); Kaindl, Guenter [Freie Universitaet Berlin, D-14195 Berlin-Dahlem (Germany); Doebrich, Kristian M. [Freie Universitaet Berlin, D-14195 Berlin-Dahlem (Germany); Max-Born-Institut, D-12489 Berlin (Germany)

2011-07-01

We report on the results of grain-size and temperature-dependent magnetization, specific-heat, neutron-scattering, and angle-resolved photoelectron spectroscopy (ARPES) experiments on the heavy rare-earth metals terbium and holmium, with particular emphasis on the temperature regions where the helical antiferromagnetic phases exist. In contrast to Ho, we find that the helical structure in Tb is relative strongly affected by microstructural disorder, specifically, it can no longer be detected for the smallest studied grain size of D=18 nm. Moreover, in coarse-grained Tb a helical structure persists even in the ferromagnetic regime, down to about T=215 K, in agreement with the ARPES data, which reveal a nesting feature of the Fermi surface at the L point of the Brillouin zone at T=210 K.

Effects of Magnetic and Kinetic Helicities on the Growth of Magnetic Fields in Laminar and Turbulent Flows by Helical Fourier Decomposition

Energy Technology Data Exchange (ETDEWEB)

Linkmann, Moritz; Sahoo, Ganapati; Biferale, Luca [Department of Physics and INFN, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Rome (Italy); McKay, Mairi; Berera, Arjun [School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, EH9 3FD, Edinburgh (United Kingdom)

2017-02-10

We present a numerical and analytical study of incompressible homogeneous conducting fluids using a helical Fourier representation. We analytically study both small- and large-scale dynamo properties, as well as the inverse cascade of magnetic helicity, in the most general minimal subset of interacting velocity and magnetic fields on a closed Fourier triad. We mainly focus on the dependency of magnetic field growth as a function of the distribution of kinetic and magnetic helicities among the three interacting wavenumbers. By combining direct numerical simulations of the full magnetohydrodynamics equations with the helical Fourier decomposition, we numerically confirm that in the kinematic dynamo regime the system develops a large-scale magnetic helicity with opposite sign compared to the small-scale kinetic helicity, a sort of triad-by-triad α -effect in Fourier space. Concerning the small-scale perturbations, we predict theoretically and confirm numerically that the largest instability is achived for the magnetic component with the same helicity of the flow, in agreement with the Stretch–Twist–Fold mechanism. Vice versa, in the presence of Lorentz feedback on the velocity, we find that the inverse cascade of magnetic helicity is mostly local if magnetic and kinetic helicities have opposite signs, while it is more nonlocal and more intense if they have the same sign, as predicted by the analytical approach. Our analytical and numerical results further demonstrate the potential of the helical Fourier decomposition to elucidate the entangled dynamics of magnetic and kinetic helicities both in fully developed turbulence and in laminar flows.

The helical ventricular myocardial band of Torrent-Guasp.

Science.gov (United States)

Kocica, Mladen J; Corno, Antonio F; Lackovic, Vesna; Kanjuh, Vladimir I

2007-01-01

We live in an era of substantial progress in understanding myocardial structure and function at genetic, molecular, and microscopic levels. Yet, ventricular myocardium has proven remarkably resistant to macroscopic analyses of functional anatomy. Pronounced and practically indefinite global and local structural anisotropy of its fibers and other ventricular wall constituents produces electrical and mechanical properties that are nonlinear, anisotropic, time varying, and spatially inhomogeneous. The helical ventricular myocardial band of Torrent-Guasp is a revolutionary new concept in understanding global, 3-dimensional, functional architecture of the ventricular myocardium. This concept defines the principal, cumulative vectors, integrating the tissue architecture (ie, form) and net forces developed (ie, function) within the ventricular mass. The primary purpose of this review is to emphasize the importance of this concept, in the light of collaborative efforts to establish an integrative approach, defining ventricular form and function by linking across multiple scales of biological organization, as explained in the ongoing Physiome project. Because one of the most important scientific missions in this century is integration of basic research with clinical medicine, we believe that this knowledge is not of merely academic importance, but is also the essential prerequisite in clinical evaluation and treatment of different heart diseases.

Electronic transport in single-helical protein molecules: Effects of multiple charge conduction pathways and helical symmetry

Energy Technology Data Exchange (ETDEWEB)

Kundu, Sourav, E-mail: sourav.kunduphy@gmail.com; Karmakar, S.N.

2016-07-15

We propose a tight-binding model to investigate electronic transport properties of single helical protein molecules incorporating both the helical symmetry and the possibility of multiple charge transfer pathways. Our study reveals that due to existence of both the multiple charge transfer pathways and helical symmetry, the transport properties are quite rigid under influence of environmental fluctuations which indicates that these biomolecules can serve as better alternatives in nanoelectronic devices than its other biological counterparts e.g., single-stranded DNA.

Structural similarities between prokaryotic and eukaryotic 5S ribosomal RNAs

International Nuclear Information System (INIS)

Welfle, H.; Boehm, S.; Damaschun, G.; Fabian, H.; Gast, K.; Misselwitz, R.; Mueller, J.J.; Zirwer, D.; Filimonov, V.V.; Venyaminov, S.Yu.; Zalkova, T.N.

1986-01-01

5S RNAs from rat liver and E. coli have been studied by diffuse X-ray and dynamic light scattering and by infrared and Raman spectroscopy. Identical structures at a resolution of 1 nm can be deduced from the comparison of the experimental X-ray scattering curves and electron distance distribution functions and from the agreement of the shape parameters. A flat shape model with a compact central region and two protruding arms was derived. Double helical stems are eleven-fold helices with a mean base pair distance of 0.28 nm. The number of base pairs (26 GC, 9 AU for E. coli; 27 GC, 9 AU for rat liver) and the degree of base stacking are the same within the experimental error. A very high regularity in the ribophosphate backbone is indicated for both 5S RNAs. The observed structural similarity and the consensus secondary structure pattern derived from comparative sequence analyses suggest the conclusion that prokaryotic and eukaryotic 5S RNAs are in general very similar with respect to their fundamental structural features. (author)

Electrotransfection of Polyamine Folded DNA Origami Structures.

Science.gov (United States)

Chopra, Aradhana; Krishnan, Swati; Simmel, Friedrich C

2016-10-12

DNA origami structures are artificial molecular nanostructures in which DNA double helices are forced into a closely packed configuration by a multitude of DNA strand crossovers. We show that three different types of origami structures (a flat sheet, a hollow tube, and a compact origami block) can be formed in magnesium-free buffer solutions containing low (origami folding is proportional to the DNA concentration. At excessive amounts, the structures aggregate and precipitate. In contrast to origami structures formed in conventional buffers, the resulting structures are stable in the presence of high electric field pulses, such as those commonly used for electrotransfection experiments. We demonstrate that spermidine-stabilized structures are stable in cell lysate and can be delivered into mammalian cells via electroporation.

Total scalp irradiation using helical tomotherapy

International Nuclear Information System (INIS)

Orton, Nigel; Jaradat, Hazim; Welsh, James; Tome, Wolfgang

2005-01-01

Homogeneous irradiation of the scalp poses technical and dosimetric challenges due to the extensive, superficial, curved treatment volume. Conventional treatments on a linear accelerator use multiple matched electron fields or a combination of electron and photon fields. Problems with these techniques include dose heterogeneity in the target due to varying source-to-skin distance (SSD) and angle of beam incidence, significant dose to the brain, and the potential for overdose or underdose at match lines between the fields. Linac-based intensity-modulated radiation therapy (IMRT) plans have similar problems. This work presents treatment plans for total scalp irradiation on a helical tomotherapy machine. Helical tomotherapy is well-suited for scalp irradiation because it has the ability to deliver beamlets that are tangential to the scalp at all points. Helical tomotherapy also avoids problems associated with field matching and use of more than one modality. Tomotherapy treatment plans were generated and are compared to plans for treatment of the same patient on a linac. The resulting tomotherapy plans show more homogeneous target dose and improved critical structure dose when compared to state-of-the-art linac techniques. Target equivalent uniform dose (EUD) for the best tomotherapy plan was slightly higher than for the linac plan, while the volume of brain tissue receiving over 30 Gy was reduced by two thirds. Furthermore, the tomotherapy plan can be more reliably delivered than linac treatments, because the patient is aligned prior to each treatment based on megavoltage computed tomography (MVCT)

Employing Helicity Amplitudes for Resummation

NARCIS (Netherlands)

Moult, I.; Stewart, I.W.; Tackmann, F.J.; Waalewijn, W.J.

2015-01-01

Many state-of-the-art QCD calculations for multileg processes use helicity amplitudes as their fundamental ingredients. We construct a simple and easy-to-use helicity operator basis in soft-collinear effective theory (SCET), for which the hard Wilson coefficients from matching QCD onto SCET are

Helicity multiplexed broadband metasurface holograms.

Science.gov (United States)

Wen, Dandan; Yue, Fuyong; Li, Guixin; Zheng, Guoxing; Chan, Kinlong; Chen, Shumei; Chen, Ming; Li, King Fai; Wong, Polis Wing Han; Cheah, Kok Wai; Pun, Edwin Yue Bun; Zhang, Shuang; Chen, Xianzhong

2015-09-10

Metasurfaces are engineered interfaces that contain a thin layer of plasmonic or dielectric nanostructures capable of manipulating light in a desirable manner. Advances in metasurfaces have led to various practical applications ranging from lensing to holography. Metasurface holograms that can be switched by the polarization state of incident light have been demonstrated for achieving polarization multiplexed functionalities. However, practical application of these devices has been limited by their capability for achieving high efficiency and high image quality. Here we experimentally demonstrate a helicity multiplexed metasurface hologram with high efficiency and good image fidelity over a broad range of frequencies. The metasurface hologram features the combination of two sets of hologram patterns operating with opposite incident helicities. Two symmetrically distributed off-axis images are interchangeable by controlling the helicity of the input light. The demonstrated helicity multiplexed metasurface hologram with its high performance opens avenues for future applications with functionality switchable optical devices.

Collagenolytic Matrix Metalloproteinase Activities toward Peptomeric Triple-Helical Substrates.

Science.gov (United States)

Stawikowski, Maciej J; Stawikowska, Roma; Fields, Gregg B

2015-05-19

Although collagenolytic matrix metalloproteinases (MMPs) possess common domain organizations, there are subtle differences in their processing of collagenous triple-helical substrates. In this study, we have incorporated peptoid residues into collagen model triple-helical peptides and examined MMP activities toward these peptomeric chimeras. Several different peptoid residues were incorporated into triple-helical substrates at subsites P3, P1, P1', and P10' individually or in combination, and the effects of the peptoid residues were evaluated on the activities of full-length MMP-1, MMP-8, MMP-13, and MMP-14/MT1-MMP. Most peptomers showed little discrimination between MMPs. However, a peptomer containing N-methyl Gly (sarcosine) in the P1' subsite and N-isobutyl Gly (NLeu) in the P10' subsite was hydrolyzed efficiently only by MMP-13 [nomenclature relative to the α1(I)772-786 sequence]. Cleavage site analysis showed hydrolysis at the Gly-Gln bond, indicating a shifted binding of the triple helix compared to the parent sequence. Favorable hydrolysis by MMP-13 was not due to sequence specificity or instability of the substrate triple helix but rather was based on the specific interactions of the P7' peptoid residue with the MMP-13 hemopexin-like domain. A fluorescence resonance energy transfer triple-helical peptomer was constructed and found to be readily processed by MMP-13, not cleaved by MMP-1 and MMP-8, and weakly hydrolyzed by MT1-MMP. The influence of the triple-helical structure containing peptoid residues on the interaction between MMP subsites and individual substrate residues may provide additional information about the mechanism of collagenolysis, the understanding of collagen specificity, and the design of selective MMP probes.

Vorticity field, helicity integral and persistence of entanglement in reaction-diffusion systems

International Nuclear Information System (INIS)

Trueba, J L; Arrayas, M

2009-01-01

We show that a global description of the stability of entangled structures in reaction-diffusion systems can be made by means of a helicity integral. A vorticity vector field is defined for these systems, as in electromagnetism or fluid dynamics. We have found under which conditions the helicity is conserved or lost through the boundaries of the medium, so the entanglement of structures observed is preserved or disappears during time evolution. We illustrate the theory with an example of knotted entanglement in a FitzHugh-Nagumo model. For this model, we introduce new non-trivial initial conditions using the Hopf fibration and follow the time evolution of the entanglement. (fast track communication)

Vorticity field, helicity integral and persistence of entanglement in reaction-diffusion systems

Energy Technology Data Exchange (ETDEWEB)

Trueba, J L; Arrayas, M [Area de Electromagnetismo, Universidad Rey Juan Carlos, Camino del Molino s/n, 28943 Fuenlabrada, Madrid (Spain)

2009-07-17

We show that a global description of the stability of entangled structures in reaction-diffusion systems can be made by means of a helicity integral. A vorticity vector field is defined for these systems, as in electromagnetism or fluid dynamics. We have found under which conditions the helicity is conserved or lost through the boundaries of the medium, so the entanglement of structures observed is preserved or disappears during time evolution. We illustrate the theory with an example of knotted entanglement in a FitzHugh-Nagumo model. For this model, we introduce new non-trivial initial conditions using the Hopf fibration and follow the time evolution of the entanglement. (fast track communication)

Geometrical principles of homomeric β-barrels and β-helices: Application to modeling amyloid protofilaments.

Science.gov (United States)

Hayward, Steven; Milner-White, E James

2017-10-01

Examples of homomeric β-helices and β-barrels have recently emerged. Here we generalize the theory for the shear number in β-barrels to encompass β-helices and homomeric structures. We introduce the concept of the "β-strip," the set of parallel or antiparallel neighboring strands, from which the whole helix can be generated giving it n-fold rotational symmetry. In this context, the shear number is interpreted as the sum around the helix of the fixed register shift between neighboring identical β-strips. Using this approach, we have derived relationships between helical width, pitch, angle between strand direction and helical axis, mass per length, register shift, and number of strands. The validity and unifying power of the method is demonstrated with known structures including α-hemolysin, T4 phage spike, cylindrin, and the HET-s(218-289) prion. From reported dimensions measured by X-ray fiber diffraction on amyloid fibrils, the relationships can be used to predict the register shift and the number of strands within amyloid protofilaments. This was used to construct models of transthyretin and Alzheimer β(40) amyloid protofilaments that comprise a single strip of in-register β-strands folded into a "β-strip helix." Results suggest both stabilization of an individual β-strip helix and growth by addition of further β-strip helices can involve the same pair of sequence segments associating with β-sheet hydrogen bonding at the same register shift. This process would be aided by a repeat sequence. Hence, understanding how the register shift (as the distance between repeat sequences) relates to helical dimensions will be useful for nanotube design. © 2017 Wiley Periodicals, Inc.

Building of RNA and DNA double helices into electron density

Czech Academy of Sciences Publication Activity Database

Pavelčík, F.; Schneider, Bohdan

2008-01-01

Roč. 64, č. 6 (2008), s. 620-626 ISSN 0907-4449 R&D Projects: GA MŠk LC512 Grant - others:VEGA(SK) 1/2333/05; NSF(US) DBI0110076 Institutional research plan: CEZ:AV0Z40550506 Keywords : RNA * double helix * x-ray crystallography Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.943, year: 2008

Small-x Asymptotics of the Quark Helicity Distribution.

Science.gov (United States)

Kovchegov, Yuri V; Pitonyak, Daniel; Sievert, Matthew D

2017-02-03

We construct a numerical solution of the small-x evolution equations derived in our recent work [J. High Energy Phys. 01 (2016) 072.JHEPFG1029-847910.1007/JHEP01(2016)072] for the (anti)quark transverse momentum dependent helicity TMDs and parton distribution functions (PDFs) as well as the g_{1} structure function. We focus on the case of large N_{c}, where one finds a closed set of equations. Employing the extracted intercept, we are able to predict directly from theory the behavior of the quark helicity PDFs at small x, which should have important phenomenological consequences. We also give an estimate of how much of the proton's spin carried by the quarks may be at small x and what impact this has on the spin puzzle.

Single-superfield helical-phase inflation

Energy Technology Data Exchange (ETDEWEB)

Ketov, Sergei V., E-mail: ketov@tmu.ac.jp [Department of Physics, Tokyo Metropolitan University, Minami-ohsawa 1-1, Hachioji-shi, Tokyo 192-0397 (Japan); Kavli Institute for the Physics and Mathematics of the Universe (IPMU), The University of Tokyo, Chiba 277-8568 (Japan); Institute of Physics and Technology, Tomsk Polytechnic University, 30 Lenin Ave., Tomsk 634050 (Russian Federation); Terada, Takahiro, E-mail: takahiro@hep-th.phys.s.u-tokyo.ac.jp [Department of Physics, The University of Tokyo, Tokyo 113-0033 (Japan); Deutsches Elektronen-Synchrotron (DESY), 22607 Hamburg (Germany)

2016-01-10

Large-field inflation in supergravity requires the approximate global symmetry needed to protect flatness of the scalar potential. In helical-phase inflation, the U(1) symmetry of the Kähler potential is assumed, the phase part of the complex scalar of a chiral superfield plays the role of inflaton, and the radial part is strongly stabilized. The original model of helical phase inflation, proposed by Li, Li and Nanopoulos (LLN), employs an extra (stabilizer) superfield. We propose a more economical new class of the helical phase inflationary models without a stabilizer superfield. As the specific examples, the quadratic, the natural, and the Starobinsky-type inflationary models are studied in our approach.

A real-scale helical coil winding trial of the Large Helical Device

International Nuclear Information System (INIS)

Senba, T.; Yamamoto, T.; Tamaki, T.; Asano, K.; Suzuki, S.; Yamauchi, T.; Uchida, K.; Nakanishi, K.; Yamagiwa, T.; Suzuki, S.; Miyoshi, R.; Sasa, H.; Watanabe, S.; Tatemura, M.; Hatada, N.; Yamaguchi, S.; Imagawa, S.; Yanagi, N.; Satow, T.; Yamamoto, J.; Motojima, O.

1995-01-01

A real-scale helical coil winding trial of the Large Helical Device (LHD) has been conducted for a study of coil winding configuration and winding methods and for exhibiting the state of the art. It includes construction and test run of a specifically designed winding machine and development of various manufacturing methods for accurate coil winding. It has been carried out in Hitachi Works before in situ winding, and has provided much needed engineering data for construction of the LHD. (orig.)

Evidence for α-helices in the gas phase: a case study using Melittin from honey bee venom.

Science.gov (United States)

Florance, Hannah V; Stopford, Andrew P; Kalapothakis, Jason M; McCullough, Bryan J; Bretherick, Andrew; Barran, Perdita E

2011-09-07

Gas phase methodologies are increasingly used to study the structure of proteins and peptides. A challenge to the mass spectrometrist is to preserve the structure of the system of interest intact and unaltered from solution into the gas phase. Small peptides are very flexible and can present a number of conformations in solution. In this work we examine Melittin a 26 amino acid peptide that forms the active component of honey bee venom. Melittin is haemolytic and has been shown to form an α-helical tetrameric structure by X-ray crystallography [M. Gribskov et al., The RCSB Protein Data Bank, 1990] and to be helical in high concentrations of methanol. Here we use ion mobility mass spectrometry, molecular dynamics and gas-phase HDX to probe its structure in the gas phase and specifically interrogate whether the helical form can be preserved. All low energy calculated structures possess some helicity. In our experiments we examine the peptide following nano-ESI from solutions with varying methanol content. Ion mobility gives collision cross sections (CCS) that compare well with values found from molecular modelling and from other reported structures, but with inconclusive results regarding the effect of solvent. There is only a slight increase in CCS with charge, showing minimal coloumbically driven unfolding. HDX supports preservation of some helical content into the gas phase and again shows little difference in the exchange rates of species sprayed from different solvents. The [M + 3H](3+) species has two exchanging populations both of which exhibit faster exchange rates than observed for the [M + 2H](2+) species. One interpretation for these results is that the time spent being analysed is sufficient for this peptide to form a helix in the 'ultimate' hydrophobic environment of a vacuum.

Solid-state nuclear magnetic resonance measurements of HIV fusion peptide 13CO to lipid 31P proximities support similar partially inserted membrane locations of the α helical and β sheet peptide structures.

Science.gov (United States)

Gabrys, Charles M; Qiang, Wei; Sun, Yan; Xie, Li; Schmick, Scott D; Weliky, David P

2013-10-03

Fusion of the human immunodeficiency virus (HIV) membrane and the host cell membrane is an initial step of infection of the host cell. Fusion is catalyzed by gp41, which is an integral membrane protein of HIV. The fusion peptide (FP) is the ∼25 N-terminal residues of gp41 and is a domain of gp41 that plays a key role in fusion catalysis likely through interaction with the host cell membrane. Much of our understanding of the FP domain has been accomplished with studies of "HFP", i.e., a ∼25-residue peptide composed of the FP sequence but lacking the rest of gp41. HFP catalyzes fusion between membrane vesicles and serves as a model system to understand fusion catalysis. HFP binds to membranes and the membrane location of HFP is likely a significant determinant of fusion catalysis perhaps because the consequent membrane perturbation reduces the fusion activation energy. In the present study, many HFPs were synthesized and differed in the residue position that was (13)CO backbone labeled. Samples were then prepared that each contained a singly (13)CO labeled HFP incorporated into membranes that lacked cholesterol. HFP had distinct molecular populations with either α helical or oligomeric β sheet structure. Proximity between the HFP (13)CO nuclei and (31)P nuclei in the membrane headgroups was probed by solid-state NMR (SSNMR) rotational-echo double-resonance (REDOR) measurements. For many samples, there were distinct (13)CO shifts for the α helical and β sheet structures so that the proximities to (31)P nuclei could be determined for each structure. Data from several differently labeled HFPs were then incorporated into a membrane location model for the particular structure. In addition to the (13)CO labeled residue position, the HFPs also differed in sequence and/or chemical structure. "HFPmn" was a linear peptide that contained the 23 N-terminal residues of gp41. "HFPmn_V2E" contained the V2E mutation that for HIV leads to greatly reduced extent of fusion and

On the helicity of open magnetic fields

International Nuclear Information System (INIS)

Prior, C.; Yeates, A. R.

2014-01-01

We reconsider the topological interpretation of magnetic helicity for magnetic fields in open domains, and relate this to the relative helicity. Specifically, our domains stretch between two parallel planes, and each of these ends may be magnetically open. It is demonstrated that, while the magnetic helicity is gauge-dependent, its value in any gauge may be physically interpreted as the average winding number among all pairs of field lines with respect to some orthonormal frame field. In fact, the choice of gauge is equivalent to the choice of reference field in the relative helicity, meaning that the magnetic helicity is no less physically meaningful. We prove that a particular gauge always measures the winding with respect to a fixed frame, and propose that this is normally the best choice. For periodic fields, this choice is equivalent to measuring relative helicity with respect to a potential reference field. However, for aperiodic fields, we show that the potential field can be twisted. We prove by construction that there always exists a possible untwisted reference field.

Hydrogen recycling and transport in the helical divertor of TEXTOR

Energy Technology Data Exchange (ETDEWEB)

Clever, Meike

2010-07-01

The aim of this thesis was to investigate the hydrogen recycling at the target plates of the helical divertor in TEXTOR and by this the capability of this divertor configuration to access such favourable operational regimes. In order to study the different divertor density regimes in TEXTOR, discharges were performed in which the total plasma density was increased continuously up to the density limit. The recycling was investigated in a fixed helical divertor structure where four helical strike points with a poloidal width of about 8-10 cm are created at the divertor target plates. The experimental investigation of the hydrogen recycling was carried out using mainly spectroscopic methods supplemented by Langmuir probe, interferometric and atomic beam measurements. In the framework of this thesis a spectroscopic multi camera system has been built that facilitates the simultaneous observation of four different spectral lines, recording images of the divertor target plates and the plasma volume close to the target. The system facilitates the simultaneous measurement of the poloidal and toroidal pattern of the recycling flux at the divertor target without the need for sweeping the plasma structure. The simultaneous observation of different spectral lines reduces the uncertainty in the analysis based on several lines, as the contribution from uncertainties in the reproducibility of plasma parameters in different discharges are eliminated and only the uncertainty of the measurement method limits the accuracy. The spatial resolution of the system in poloidal and toroidal direction (0.8 mm{+-}0.01 mm) is small compared to the separation of the helical strike points, the capability of the measurement method to resolve these structures is therefore limited by the line-of-sight integration and the penetration depth of the light emitting species. The measurements showed that the recycling flux increases linearly with increasing plasma density, a high recycling regime is not

Hydrogen recycling and transport in the helical divertor of TEXTOR

International Nuclear Information System (INIS)

Clever, Meike

2010-01-01

The aim of this thesis was to investigate the hydrogen recycling at the target plates of the helical divertor in TEXTOR and by this the capability of this divertor configuration to access such favourable operational regimes. In order to study the different divertor density regimes in TEXTOR, discharges were performed in which the total plasma density was increased continuously up to the density limit. The recycling was investigated in a fixed helical divertor structure where four helical strike points with a poloidal width of about 8-10 cm are created at the divertor target plates. The experimental investigation of the hydrogen recycling was carried out using mainly spectroscopic methods supplemented by Langmuir probe, interferometric and atomic beam measurements. In the framework of this thesis a spectroscopic multi camera system has been built that facilitates the simultaneous observation of four different spectral lines, recording images of the divertor target plates and the plasma volume close to the target. The system facilitates the simultaneous measurement of the poloidal and toroidal pattern of the recycling flux at the divertor target without the need for sweeping the plasma structure. The simultaneous observation of different spectral lines reduces the uncertainty in the analysis based on several lines, as the contribution from uncertainties in the reproducibility of plasma parameters in different discharges are eliminated and only the uncertainty of the measurement method limits the accuracy. The spatial resolution of the system in poloidal and toroidal direction (0.8 mm±0.01 mm) is small compared to the separation of the helical strike points, the capability of the measurement method to resolve these structures is therefore limited by the line-of-sight integration and the penetration depth of the light emitting species. The measurements showed that the recycling flux increases linearly with increasing plasma density, a high recycling regime is not

NO and SCN -intercalated layered double hydroxides: structure and ...

Indian Academy of Sciences (India)

2018-02-05

Feb 5, 2018 ... Keywords. Nitrite ion; thiocyanate ion; layered double hydroxide; structure refinement. 1. Introduction .... applications of LDHs is sorption/uptake of toxic anions ... by ion chromatography using a Metrohm Model 861 Advanced.

Splitting of α-Helical Structure as Molecular Basis for Abolishing an Amyloid Formation by Multiple Glycosylation: A Molecular Dynamics Simulation Study

Energy Technology Data Exchange (ETDEWEB)

Choi, Youngjin [Hoseo University, Asan (Korea, Republic of); Cho, Eunae; Jung, Seunho [Konkuk University, Seoul (Korea, Republic of)

2016-07-15

Molecular details played by glycosylation are complicated by the subtle nature of variations in the glycan structure, and this complexity is one of the research barriers to establish structure-function relationship on the protein modification. This is particularly true for understanding the exact structural consequence of the glycosylation of the biological proteins. The present MD simulation revealed molecular-level mechanism of the glycosylation effect on the peptide to understand the experimentally observed phenomenon for inhibiting amyloid formation in the model peptide. The galactose residue on the Ser17 undermined the helical integrity of main protein region by enhancing sugar–amino acid interaction and perturbing natural interactions between amino acid residues.

Sound transmission through stiffened double-panel structures lined with elastic porous materials

Science.gov (United States)

Mathur, Gopal P.; Tran, Boi N.; Bolton, J. S.; Shiau, Nae-Ming

This paper presents transmission loss prediction models for a periodically stiffened panel and stiffened double-panel structures using the periodic structure theory. The inter-panel cavity in the double-panels structures can be modeled as being separated by an airspace or filled with an elastic porous layer in various configurations. The acoustic behavior of elastic porous layer is described by a theory capable of accounting fully for multi-dimensional wave propagation in such materials. The predicted transmission loss of a single stiffened panel is compared with the measured data.

Impact of helical boundary conditions on nonlinear 3D magnetohydrodynamic simulations of reversed-field pinch

International Nuclear Information System (INIS)

Veranda, M; Bonfiglio, D; Cappello, S; Chacón, L; Escande, D F

2013-01-01

Helical self-organized reversed-field pinch (RFP) regimes emerge both numerically—in 3D visco-resistive magnetohydrodynamic (MHD) simulations—and experimentally, as in the RFX-mod device at high current (I P above 1 MA). These states, called quasi-single helicity (QSH) states, are characterized by the action of a MHD mode that impresses a quasi-helical symmetry to the system, thus allowing a high degree of magnetic chaos healing. This is in contrast with the multiple helicity (MH) states, where magnetic fluctuations create a chaotic magnetic field degrading the confinement properties of the RFP. This paper reports an extensive numerical study performed in the frame of 3D visco-resistive MHD which considers the effect of helical magnetic boundary conditions, i.e. of a finite value of the radial magnetic field at the edge (magnetic perturbation, MP). We show that the system can be driven to a selected QSH state starting from both spontaneous QSH and MH regimes. In particular, a high enough MP can force a QSH helical self-organization with a helicity different from the spontaneous one. Moreover, MH states can be turned into QSH states with a selected helicity. A threshold in the amplitude of MP is observed above which is able to influence the system. Analysis of the magnetic topology of these simulations indicates that the dominant helical mode is able to temporarily sustain conserved magnetic structures in the core of the plasma. The region occupied by conserved magnetic surfaces increases reducing secondary modes' amplitude to experimental-like values. (paper)

Longitudinal Double Spin Asymmetry in Inclusive π0 Production at Forward Rapidities in √s=62.4 GeV Polarized p+p Collisions at RHIC

International Nuclear Information System (INIS)

Kazantsev, Andrey

2007-01-01

The gluons' Gluons spin contribution to proton spin is an important the key aspect for understanding the proton spin structure. It can be probed by the double helicity asymmetry of π0 production in polarized p+p collisions. During the longitudinally polarized proton run in 2006 PHENIX collected substantial data at √s=62.4 GeV and √s=200 GeV. In 2006 PHENIX commissioned a new electromagnetic calorimeter, the Muon Piston Calorimeter (MPC), located in the forward rapidity rapidities region. This calorimeter allows to significantly improves the PHENIX acceptance. In this report the MPC feasibility of the MPC for longitudinal double spin asymmetry studies is discussed

Whole brain radiotherapy with adjuvant or concomitant boost in brain metastasis: dosimetric comparison between helical and volumetric IMRT technique.

Science.gov (United States)

Borghetti, Paolo; Pedretti, Sara; Spiazzi, Luigi; Avitabile, Rossella; Urpis, Mauro; Foscarini, Federica; Tesini, Giulia; Trevisan, Francesca; Ghirardelli, Paolo; Pandini, Sara Angela; Triggiani, Luca; Magrini, Stefano Maria; Buglione, Michela

2016-04-19

To compare and evaluate the possible advantages related to the use of VMAT and helical IMRT and two different modalities of boost delivering, adjuvant stereotactic boost (SRS) or simultaneous integrated boost (SIB), in the treatment of brain metastasis (BM) in RPA classes I-II patients. Ten patients were treated with helical IMRT, 5 of them with SRS after whole brain radiotherapy (WBRT) and 5 with SIB. MRI co-registration with planning CT was mandatory and prescribed doses were 30 Gy in 10 fractions (fr) for WBRT and 15Gy/1fr or 45Gy/10fr in SRS or SIB, respectively. For each patient, 4 "treatment plans" (VMAT SRS and SIB, helical IMRT SRS and SIB) were calculated and accepted if PTV boost was included in 95 % isodose and dose constraints of the main organs at risk were respected without major deviations. Homogeneity Index (HI), Conformal Index (CI) and Conformal Number (CN) were considered to compare the different plans. Moreover, time of treatment delivery was calculated and considered in the analysis. Volume of brain metastasis ranged between 1.43 and 51.01 cc (mean 12.89 ± 6.37 ml) and 3 patients had double lesions. V95% resulted over 95 % in the average for each kind of technique, but the "target coverage" was inadequate for VMAT planning with two sites. The HI resulted close to the ideal value of zero in all cases; VMAT-SIB, VMAT-SRS, Helical IMRT-SIB and Helical IMRT-SRS showed mean CI of 2.15, 2.10, 2.44 and 1.66, respectively (optimal range: 1.5-2.0). Helical IMRT-SRS was related to the best and reliable finding of CN (0.66). The mean of treatment time was 210 s, 467 s, 440 s, 1598 s, respectively, for VMAT-SIB, VMAT-SRS, Helical IMRT-SIB and Helical IMRT-SRS. This dosimetric comparison show that helical IMRT obtain better target coverage and respect of CI and CN; VMAT could be acceptable in solitary metastasis. SIB modality can be considered as a good choice for clinical and logistic compliance; literature's preliminary data are confirming also a

HEMISPHERIC HELICITY TREND FOR SOLAR CYCLE 24

International Nuclear Information System (INIS)

Hao Juan; Zhang Mei

2011-01-01

Using vector magnetograms obtained with the Spectro-polarimeter (SP) on board Hinode satellite, we studied two helicity parameters (local twist and current helicity) of 64 active regions that occurred in the descending phase of solar cycle 23 and the ascending phase of solar cycle 24. Our analysis gives the following results. (1) The 34 active regions of the solar cycle 24 follow the so-called hemispheric helicity rule, whereas the 30 active regions of the solar cycle 23 do not. (2) When combining all 64 active regions as one sample, they follow the hemispheric helicity sign rule as in most other observations. (3) Despite the so-far most accurate measurement of vector magnetic field given by SP/Hinode, the rule is still weak with large scatters. (4) The data show evidence of different helicity signs between strong and weak fields, confirming previous result from a large sample of ground-based observations. (5) With two example sunspots we show that the helicity parameters change sign from the inner umbra to the outer penumbra, where the sign of penumbra agrees with the sign of the active region as a whole. From these results, we speculate that both the Σ-effect (turbulent convection) and the dynamo have contributed in the generation of helicity, whereas in both cases turbulence in the convection zone has played a significant role.

Raytracing, chopper, and guideline for double-headed Dragon monochromators (invited)

International Nuclear Information System (INIS)

Chen, C.T.

1992-01-01

The raytracing of the double-headed Dragon, a recently proposed monochromator for producing two simultaneous left and right circularly polarized soft x-ray beams, is presented. The energy resolution and wavelength of these two beams are confirmed to be identical, and the high performance of the original Dragon is found to be preserved in the double-headed configuration. A compact ultra-high vacuum compatible chopper for rapid alternation between left and right helicities is presented, and a guideline for collecting circularly polarized light from bending magnet sources is given

Ion temperature gradient modes in toroidal helical systems

Energy Technology Data Exchange (ETDEWEB)

Kuroda, T. [Graduate University for Advanced Studies, Toki, Gifu (Japan); Sugama, H.; Kanno, R.; Okamoto, M.

2000-04-01

Linear properties of ion temperature gradient (ITG) modes in helical systems are studied. The real frequency, growth rate, and eigenfunction are obtained for both stable and unstable cases by solving a kinetic integral equation with proper analytic continuation performed in the complex frequency plane. Based on the model magnetic configuration for toroidal helical systems like the Large Helical Device (LHD), dependences of the ITG mode properties on various plasma equilibrium parameters are investigated. Particularly, relative effects of {nabla}B-curvature drifts driven by the toroidicity and by the helical ripples are examined in order to compare the ITG modes in helical systems with those in tokamaks. (author)

Ion temperature gradient modes in toroidal helical systems

International Nuclear Information System (INIS)

Kuroda, T.; Sugama, H.; Kanno, R.; Okamoto, M.

2000-04-01

Linear properties of ion temperature gradient (ITG) modes in helical systems are studied. The real frequency, growth rate, and eigenfunction are obtained for both stable and unstable cases by solving a kinetic integral equation with proper analytic continuation performed in the complex frequency plane. Based on the model magnetic configuration for toroidal helical systems like the Large Helical Device (LHD), dependences of the ITG mode properties on various plasma equilibrium parameters are investigated. Particularly, relative effects of ∇B-curvature drifts driven by the toroidicity and by the helical ripples are examined in order to compare the ITG modes in helical systems with those in tokamaks. (author)

Generalized helicity and Beltrami fields

International Nuclear Information System (INIS)

Buniy, Roman V.; Kephart, Thomas W.

2014-01-01

We propose covariant and non-abelian generalizations of the magnetic helicity and Beltrami equation. The gauge invariance, variational principle, conserved current, energy–momentum tensor and choice of boundary conditions elucidate the subject. In particular, we prove that any extremal of the Yang–Mills action functional 1/4 ∫ Ω trF μν F μν d 4 x subject to the local constraint ε μναβ trF μν F αβ =0 satisfies the covariant non-abelian Beltrami equation. -- Highlights: •We introduce the covariant non-abelian helicity and Beltrami equation. •The Yang–Mills action and instanton term constraint lead to the Beltrami equation. •Solutions of the Beltrami equation conserve helicity

Molecular Dynamics with Helical Periodic Boundary Conditions

Czech Academy of Sciences Publication Activity Database

Kessler, Jiří; Bouř, Petr

2014-01-01

Roč. 35, č. 21 (2014), s. 1552-1559 ISSN 0192-8651 R&D Projects: GA ČR GAP208/11/0105; GA MŠk(CZ) LH11033 Grant - others:GA AV ČR(CZ) M200551205; GA MŠk(CZ) LM2010005 Institutional support: RVO:61388963 Keywords : periodic boundary conditions * helical symmetry * molecular dynamics * protein structure * amyloid fibrils Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.589, year: 2014

A vacuum with double structure

International Nuclear Information System (INIS)

Yamamoto, Hiroshi; Kudo, Kiyoshi

1975-01-01

For the purpose of proving the conservation of norm in the field theory of complex mass proposed by one of the present authors, a new space is introduced where the state vectors have a double structure and the norms are complex numbers in general. The new space contains the Hilbert space as a subspace where the norms are real and positive. It is shown that the S-matrix transforms a vector of the Hilbert space into a vector of the same space. Other states in the new space may appear as intermediate virtual states. In this way the field theory of complex mass is formally proved to be physically interpretable. (auth.)

Primary and secondary structural analyses of glutathione S-transferase pi from human placenta.

Science.gov (United States)

Ahmad, H; Wilson, D E; Fritz, R R; Singh, S V; Medh, R D; Nagle, G T; Awasthi, Y C; Kurosky, A

1990-05-01

The primary structure of glutathione S-transferase (GST) pi from a single human placenta was determined. The structure was established by chemical characterization of tryptic and cyanogen bromide peptides as well as automated sequence analysis of the intact enzyme. The structural analysis indicated that the protein is comprised of 209 amino acid residues and gave no evidence of post-translational modifications. The amino acid sequence differed from that of the deduced amino acid sequence determined by nucleotide sequence analysis of a cDNA clone (Kano, T., Sakai, M., and Muramatsu, M., 1987, Cancer Res. 47, 5626-5630) at position 104 which contained both valine and isoleucine whereas the deduced sequence from nucleotide sequence analysis identified only isoleucine at this position. These results demonstrated that in the one individual placenta studied at least two GST pi genes are coexpressed, probably as a result of allelomorphism. Computer assisted consensus sequence evaluation identified a hydrophobic region in GST pi (residues 155-181) that was predicted to be either a buried transmembrane helical region or a signal sequence region. The significance of this hydrophobic region was interpreted in relation to the mode of action of the enzyme especially in regard to the potential involvement of a histidine in the active site mechanism. A comparison of the chemical similarity of five known human GST complete enzyme structures, one of pi, one of mu, two of alpha, and one microsomal, gave evidence that all five enzymes have evolved by a divergent evolutionary process after gene duplication, with the microsomal enzyme representing the most divergent form.

Helical-D pinch

International Nuclear Information System (INIS)

Schaffer, M.J.

1997-08-01

A stabilized pinch configuration is described, consisting of a D-shaped plasma cross section wrapped tightly around a guiding axis. The open-quotes helical-Dclose quotes geometry produces a very large axial (toroidal) transform of magnetic line direction that reverses the pitch of the magnetic lines without the need of azimuthal (poloidal) plasma current. Thus, there is no need of a open-quotes dynamoclose quotes process and its associated fluctuations. The resulting configuration has the high magnetic shear and pitch reversal of the reversed field pinch (RFP). (Pitch = P = qR, where R = major radius). A helical-D pinch might demonstrate good confinement at q << 1

Structure and dynamics of double helical DNA in torsion angle hyperspace: a molecular mechanics approach.

Science.gov (United States)

Borkar, Aditi; Ghosh, Indira; Bhattacharyya, Dhananjay

2010-04-01

Analysis of the conformational space populated by the torsion angles and the correlation between the conformational energy and the sequence of DNA are important for fully understanding DNA structure and function. Presence of seven variable torsion angles about single covalent bonds in DNA main chain puts a big challenge for such analysis. We have carried out restrained energy minimization studies for four representative dinucleosides, namely d(ApA):d(TpT), d(CpG):d(CpG), d(GpC):d(GpC) and d(CpA):d(TpG) to determine the energy hyperspace of DNA in context to the values of the torsion angles and the structural properties of the DNA conformations populating the favorable regions of this energy hyperspace. The torsion angles were manipulated by constraining their values at the reference points and then performing energy minimization. The energy minima obtained on the potential energy contour plots mostly correspond to the conformations populated in crystal structures of DNA. Some novel favorable conformations that are not present in crystal structure data are also found. The plots also suggest few low energy routes for conformational transitions or the associated energy barrier heights. Analyses of base pairing and stacking possibility reveal structural changes accompanying these transitions as well as the flexibility of different base steps towards variations in different torsion angles.

Cavity Control and Panel Control Strategies in Double-Panel Structures for Transmitted Noise Reduction

NARCIS (Netherlands)

Ho, J.; Kalverboer, J.; Berkhoff, Arthur P.

2012-01-01

Investigation and comparisons of the cavity control and the panel control in a double-panel structure are presented in this paper. The double-panel structure, which comprises two panels with air in the gap, provides the advantages of low sound-transmission at high frequency, low heat-transmission

Inclusive cross section and double-helicity asymmetry for π0 production at midrapidity in p +p collisions at √{s }=510 GeV

Science.gov (United States)

Adare, A.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Akimoto, R.; Alexander, J.; Alfred, M.; Aoki, K.; Apadula, N.; Aramaki, Y.; Asano, H.; Atomssa, E. T.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Bai, X.; Bandara, N. S.; Bannier, B.; Barish, K. N.; Bathe, S.; Baublis, V.; Baumann, C.; Baumgart, S.; Bazilevsky, A.; Beaumier, M.; Beckman, S.; Belmont, R.; Berdnikov, A.; Berdnikov, Y.; Black, D.; Blau, D. S.; Bok, J. S.; Boyle, K.; Brooks, M. L.; Bryslawskyj, J.; Buesching, H.; Bumazhnov, V.; Butsyk, S.; Campbell, S.; Chen, C.-H.; Chi, C. Y.; Chiu, M.; Choi, I. J.; Choi, J. B.; Choi, S.; Christiansen, P.; Chujo, T.; Cianciolo, V.; Citron, Z.; Cole, B. A.; Cronin, N.; Crossette, N.; Csanád, M.; Csörgő, T.; Danley, T. W.; Datta, A.; Daugherity, M. S.; David, G.; Deblasio, K.; Dehmelt, K.; Denisov, A.; Deshpande, A.; Desmond, E. J.; Ding, L.; Dion, A.; Diss, P. B.; Do, J. H.; D'Orazio, L.; Drapier, O.; Drees, A.; Drees, K. A.; Durham, J. M.; Durum, A.; Engelmore, T.; Enokizono, A.; En'yo, H.; Esumi, S.; Eyser, K. O.; Fadem, B.; Feege, N.; Fields, D. E.; Finger, M.; Finger, M.; Fleuret, F.; Fokin, S. L.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Fukao, Y.; Fusayasu, T.; Gainey, K.; Gal, C.; Gallus, P.; Garg, P.; Garishvili, A.; Garishvili, I.; Ge, H.; Giordano, F.; Glenn, A.; Gong, X.; Gonin, M.; Goto, Y.; Granier de Cassagnac, R.; Grau, N.; Greene, S. V.; Grosse Perdekamp, M.; Gu, Y.; Gunji, T.; Guragain, H.; Hachiya, T.; Haggerty, J. S.; Hahn, K. I.; Hamagaki, H.; Hamilton, H. F.; Han, S. Y.; Hanks, J.; Hasegawa, S.; Haseler, T. O. S.; Hashimoto, K.; Hayano, R.; He, X.; Hemmick, T. K.; Hester, T.; Hill, J. C.; Hollis, R. S.; Homma, K.; Hong, B.; Hoshino, T.; Hotvedt, N.; Huang, J.; Huang, S.; Ichihara, T.; Ikeda, Y.; Imai, K.; Imazu, Y.; Inaba, M.; Iordanova, A.; Isenhower, D.; Isinhue, A.; Ivanishchev, D.; Jacak, B. V.; Jeon, S. J.; Jezghani, M.; Jia, J.; Jiang, X.; Johnson, B. M.; Joo, E.; Joo, K. S.; Jouan, D.; Jumper, D. S.; Kamin, J.; Kanda, S.; Kang, B. H.; Kang, J. H.; Kang, J. S.; Kapustinsky, J.; Kawall, D.; Kazantsev, A. V.; Key, J. A.; Khachatryan, V.; Khandai, P. K.; Khanzadeev, A.; Kihara, K.; Kijima, K. M.; Kim, C.; Kim, D. H.; Kim, D. J.; Kim, E.-J.; Kim, G. W.; Kim, H.-J.; Kim, M.; Kim, Y.-J.; Kim, Y. K.; Kimelman, B.; Kistenev, E.; Kitamura, R.; Klatsky, J.; Kleinjan, D.; Kline, P.; Koblesky, T.; Kofarago, M.; Komkov, B.; Koster, J.; Kotchetkov, D.; Kotov, D.; Krizek, F.; Kurita, K.; Kurosawa, M.; Kwon, Y.; Lacey, R.; Lai, Y. S.; Lajoie, J. G.; Lebedev, A.; Lee, D. M.; Lee, G. H.; Lee, J.; Lee, K. B.; Lee, K. S.; Lee, S.; Lee, S. H.; Leitch, M. J.; Leitgab, M.; Lewis, B.; Li, X.; Lim, S. H.; Liu, M. X.; Lynch, D.; Maguire, C. F.; Makdisi, Y. I.; Makek, M.; Manion, A.; Manko, V. I.; Mannel, E.; Maruyama, T.; McCumber, M.; McGaughey, P. L.; McGlinchey, D.; McKinney, C.; Meles, A.; Mendoza, M.; Meredith, B.; Miake, Y.; Mibe, T.; Mignerey, A. C.; Miller, A. J.; Milov, A.; Mishra, D. K.; Mitchell, J. T.; Miyasaka, S.; Mizuno, S.; Mohanty, A. K.; Mohapatra, S.; Montuenga, P.; Moon, T.; Morrison, D. P.; Moskowitz, M.; Moukhanova, T. V.; Murakami, T.; Murata, J.; Mwai, A.; Nagae, T.; Nagamiya, S.; Nagashima, K.; Nagle, J. L.; Nagy, M. I.; Nakagawa, I.; Nakagomi, H.; Nakamiya, Y.; Nakamura, K. R.; Nakamura, T.; Nakano, K.; Nattrass, C.; Netrakanti, P. K.; Nihashi, M.; Niida, T.; Nishimura, S.; Nouicer, R.; Novák, T.; Novitzky, N.; Nyanin, A. S.; O'Brien, E.; Ogilvie, C. A.; Oide, H.; Okada, K.; Orjuela Koop, J. D.; Osborn, J. D.; Oskarsson, A.; Ozaki, H.; Ozawa, K.; Pak, R.; Pantuev, V.; Papavassiliou, V.; Park, I. H.; Park, J. S.; Park, S.; Park, S. K.; Pate, S. F.; Patel, L.; Patel, M.; Peng, J.-C.; Perepelitsa, D. V.; Perera, G. D. N.; Peressounko, D. Yu.; Perry, J.; Petti, R.; Pinkenburg, C.; Pinson, R.; Pisani, R. P.; Purschke, M. L.; Qu, H.; Rak, J.; Ramson, B. J.; Ravinovich, I.; Read, K. F.; Reynolds, D.; Riabov, V.; Riabov, Y.; Richardson, E.; Rinn, T.; Riveli, N.; Roach, D.; Rolnick, S. D.; Rosati, M.; Rowan, Z.; Rubin, J. G.; Ryu, M. S.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Sako, H.; Samsonov, V.; Sarsour, M.; Sato, S.; Sawada, S.; Schaefer, B.; Schmoll, B. K.; Sedgwick, K.; Seele, J.; Seidl, R.; Sekiguchi, Y.; Sen, A.; Seto, R.; Sett, P.; Sexton, A.; Sharma, D.; Shaver, A.; Shein, I.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shoji, K.; Shukla, P.; Sickles, A.; Silva, C. L.; Silvermyr, D.; Singh, B. K.; Singh, C. P.; Singh, V.; Skolnik, M.; Slunečka, M.; Snowball, M.; Solano, S.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Sourikova, I. V.; Stankus, P. W.; Steinberg, P.; Stenlund, E.; Stepanov, M.; Ster, A.; Stoll, S. P.; Stone, M. R.; Sugitate, T.; Sukhanov, A.; Sumita, T.; Sun, J.; Sziklai, J.; Takahara, A.; Taketani, A.; Tanaka, Y.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tennant, E.; Tieulent, R.; Timilsina, A.; Todoroki, T.; Tomášek, M.; Torii, H.; Towell, C. L.; Towell, M.; Towell, R.; Towell, R. S.; Tserruya, I.; van Hecke, H. W.; Vargyas, M.; Vazquez-Zambrano, E.; Veicht, A.; Velkovska, J.; Vértesi, R.; Virius, M.; Vrba, V.; Vznuzdaev, E.; Wang, X. R.; Watanabe, D.; Watanabe, K.; Watanabe, Y.; Watanabe, Y. S.; Wei, F.; Whitaker, S.; White, A. S.; Wolin, S.; Woody, C. L.; Wysocki, M.; Xia, B.; Xue, L.; Yalcin, S.; Yamaguchi, Y. L.; Yanovich, A.; Yokkaichi, S.; Yoo, J. H.; Yoon, I.; You, Z.; Younus, I.; Yu, H.; Yushmanov, I. E.; Zajc, W. A.; Zelenski, A.; Zhou, S.; Zou, L.; Phenix Collaboration

2016-01-01

PHENIX measurements are presented for the cross section and double-helicity asymmetry (AL L ) in inclusive π0 production at midrapidity from p +p collisions at √{s }=510 GeV from data taken in 2012 and 2013 at the Relativistic Heavy Ion Collider. The next-to-leading-order perturbative-quantum-chromodynamics theory calculation is in excellent agreement with the presented cross section results. The calculation utilized parton-to-pion fragmentation functions from the recent DSS14 global analysis, which prefer a smaller gluon-to-pion fragmentation function. The π0AL L results follow an increasingly positive asymmetry trend with pT and √{s } with respect to the predictions and are in excellent agreement with the latest global analysis results. This analysis incorporated earlier results on π0 and jet AL L and suggested a positive contribution of gluon polarization to the spin of the proton Δ G for the gluon momentum fraction range x >0.05 . The data presented here extend to a currently unexplored region, down to x ˜0.01 , and thus provide additional constraints on the value of Δ G .

Employing helicity amplitudes for resummation in SCET

International Nuclear Information System (INIS)

Moult, Ian; Stewart, Iain W.; Tackmann, Frank J.; Waalewijn, Wouter J.; Nikhef, Amsterdam

2016-05-01

Helicity amplitudes are the fundamental ingredients of many QCD calculations for multi-leg processes. We describe how these can seamlessly be combined with resummation in Soft-Collinear Effective Theory (SCET), by constructing a helicity operator basis for which the Wilson coefficients are directly given in terms of color-ordered helicity amplitudes. This basis is crossing symmetric and has simple transformation properties under discrete symmetries.

MHD stability analysis of helical system plasmas

International Nuclear Information System (INIS)

Nakamura, Yuji

2000-01-01

Several topics of the MHD stability studies in helical system plasmas are reviewed with respect to the linear and ideal modes mainly. Difference of the method of the MHD stability analysis in helical system plasmas from that in tokamak plasmas is emphasized. Lack of the cyclic (symmetric) coordinate makes an analysis more difficult. Recent topic about TAE modes in a helical system is also described briefly. (author)

SU-E-T-197: Helical Cranial-Spinal Treatments with a Linear Accelerator

Energy Technology Data Exchange (ETDEWEB)

Anderson, J; Bernard, D; Liao, Y; Templeton, A; Turian, J; Chu, J [Rush University Medical Center, Chicago, IL (United States)

2014-06-01

Purpose: Craniospinal irradiation (CSI) of systemic disease requires a high level of beam intensity modulation to reduce dose to bone marrow and other critical structures. Current helical delivery machines can take 30 minutes or more of beam-on time to complete these treatments. This pilot study aims to test the feasibility of performing helical treatments with a conventional linear accelerator using longitudinal couch travel during multiple gantry revolutions. Methods: The VMAT optimization package of the Eclipse 10.0 treatment planning system was used to optimize pseudo-helical CSI plans of 5 clinical patient scans. Each gantry revolution was divided into three 120° arcs with each isocenter shifted longitudinally. Treatments requiring more than the maximum 10 arcs used multiple plans with each plan after the first being optimized including the dose of the others (Figure 1). The beam pitch was varied between 0.2 and 0.9 (couch speed 5- 20cm/revolution and field width of 22cm) and dose-volume histograms of critical organs were compared to tomotherapy plans. Results: Viable pseudo-helical plans were achieved using Eclipse. Decreasing the pitch from 0.9 to 0.2 lowered the maximum lens dose by 40%, the mean bone marrow dose by 2.1% and the maximum esophagus dose by 17.5%. (Figure 2). Linac-based helical plans showed dose results comparable to tomotherapy delivery for both target coverage and critical organ sparing, with the D50 of bone marrow and esophagus respectively 12% and 31% lower in the helical linear accelerator plan (Figure 3). Total mean beam-on time for the linear accelerator plan was 8.3 minutes, 54% faster than the tomotherapy average for the same plans. Conclusions: This pilot study has demonstrated the feasibility of planning pseudo-helical treatments for CSI targets using a conventional linac and dynamic couch movement, and supports the ongoing development of true helical optimization and delivery.

Detergent-associated solution conformations of helical and beta-barrel membrane proteins.

Science.gov (United States)

Mo, Yiming; Lee, Byung-Kwon; Ankner, John F; Becker, Jeffrey M; Heller, William T

2008-10-23

Membrane proteins present major challenges for structural biology. In particular, the production of suitable crystals for high-resolution structural determination continues to be a significant roadblock for developing an atomic-level understanding of these vital cellular systems. The use of detergents for extracting membrane proteins from the native membrane for either crystallization or reconstitution into model lipid membranes for further study is assumed to leave the protein with the proper fold with a belt of detergent encompassing the membrane-spanning segments of the structure. Small-angle X-ray scattering was used to probe the detergent-associated solution conformations of three membrane proteins, namely bacteriorhodopsin (BR), the Ste2p G-protein coupled receptor from Saccharomyces cerevisiae, and the Escherichia coli porin OmpF. The results demonstrate that, contrary to the traditional model of a detergent-associated membrane protein, the helical proteins BR and Ste2p are not in the expected, compact conformation and associated with detergent micelles, while the beta-barrel OmpF is indeed embedded in a disk-like micelle in a properly folded state. The comparison provided by the BR and Ste2p, both members of the 7TM family of helical membrane proteins, further suggests that the interhelical interactions between the transmembrane helices of the two proteins differ, such that BR, like other rhodopsins, can properly refold to crystallize, while Ste2p continues to prove resistant to crystallization from an initially detergent-associated state.

Panel Resonance Control and Cavity Control in Double-Panel Structures for Active Noise Reduction

NARCIS (Netherlands)

Ho, J.; Berkhoff, Arthur P.

2011-01-01

An analytical and experimental investigation of panel resonance control and cavity control in a double-panel structure is presented in this paper. The double-panel structure, which consists of two panels with air in the gap, is widely adopted in many applications such as aerospace due to its low

Helical CT scan for emergent patients with cerebrovascular diseases

International Nuclear Information System (INIS)

Matsumoto, Masato; Sato, Naoki; Nakano, Masayuki; Watanabe, Youichi; Kodama, Namio

1995-01-01

We studied 44 emergent patients with cerebrovascular diseases (18 cases of subarachnoid hemorrhage, 15 of occlusive lesions, 7 of intracerebral hematoma and 4 of suspected subarachnoid hemorrhage) using helical CT scan. The helical CT scan was performed with contrast medium at a rate of 3 ml/sec with a delay of 20 sec, and was carried out before conventional angiography. The reconstruction time of 3D-CTA was within 10 min. We were able to obtain findings for the lesion on 3D-CTA before those on conventional angiography. The 3D-CTA yielded excellent images of the vascular structures and anatomical relationships of the aneurysm, its neck and parent artery, and surrounding arteries. However, it proved difficult to visualize vessels of less than 1 mm in diameter, especially the perforating arteries. In occlusive diseases, the degree of stenosis depended on the changes in CT number threshold: at present, evaluations of the lesions should be made by conventional angiography. 3D-CTA using helical CT scan can thus be applied for emergent patients with cerebrovascular diseases. Surgical simulation images of 3D-CTA were especially useful at the time of operation. (author)

Helical CT scan for emergent patients with cerebrovascular diseases

Energy Technology Data Exchange (ETDEWEB)

Matsumoto, Masato; Sato, Naoki; Nakano, Masayuki; Watanabe, Youichi; Kodama, Namio [Fukushima Medical Coll. (Japan)

1995-08-01

We studied 44 emergent patients with cerebrovascular diseases (18 cases of subarachnoid hemorrhage, 15 of occlusive lesions, 7 of intracerebral hematoma and 4 of suspected subarachnoid hemorrhage) using helical CT scan. The helical CT scan was performed with contrast medium at a rate of 3 ml/sec with a delay of 20 sec, and was carried out before conventional angiography. The reconstruction time of 3D-CTA was within 10 min. We were able to obtain findings for the lesion on 3D-CTA before those on conventional angiography. The 3D-CTA yielded excellent images of the vascular structures and anatomical relationships of the aneurysm, its neck and parent artery, and surrounding arteries. However, it proved difficult to visualize vessels of less than 1 mm in diameter, especially the perforating arteries. In occlusive diseases, the degree of stenosis depended on the changes in CT number threshold: at present, evaluations of the lesions should be made by conventional angiography. 3D-CTA using helical CT scan can thus be applied for emergent patients with cerebrovascular diseases. Surgical simulation images of 3D-CTA were especially useful at the time of operation. (author).

Double acting stirling engine phase control

Science.gov (United States)

Berchowitz, David M.

1983-01-01

A mechanical device for effecting a phase change between the expansion and compression volumes of a double-acting Stirling engine uses helical elements which produce opposite rotation of a pair of crankpins when a control rod is moved, so the phase between two pairs of pistons is changed by +.psi. and the phase between the other two pairs of pistons is changed by -.psi.. The phase can change beyond .psi.=90.degree. at which regenerative braking and then reversal of engine rotation occurs.

Effect of double-tailed surfactant architecture on the conformation, self-assembly, and processing in polypeptide-surfactant complexes.

Science.gov (United States)

Junnila, Susanna; Hanski, Sirkku; Oakley, Richard J; Nummelin, Sami; Ruokolainen, Janne; Faul, Charl F J; Ikkala, Olli

2009-10-12

This work describes the solid-state conformational and structural properties of self-assembled polypeptide-surfactant complexes with double-tailed surfactants. Poly(L-lysine) was complexed with three dialkyl esters of phosphoric acid (i.e., phosphodiester surfactants), where the surfactant tail branching and length was varied to tune the supramolecular architecture in a facile way. After complexation with the branched surfactant bis(2-ethylhexyl) phosphate in an aqueous solution, the polypeptide chains adopted an alpha-helical conformation. These rod-like helices self-assembled into cylindrical phases with the amorphous alkyl tails pointing outward. In complexes with dioctyl phosphate and didodecyl phosphate, which have two linear n-octyl or n-dodecyl tails, respectively, the polypeptide formed antiparallel beta-sheets separated by alkyl layers, resulting in well-ordered lamellar self-assemblies. By heating, it was possible to trigger a partial opening of the beta-sheets and disruption of the lamellar phase. After repeated heating/cooling, all of these complexes also showed a glass transition between 37 and 50 degrees C. Organic solvent treatment and plasticization by overstoichiometric amount of surfactant led to structure modification in poly(L-lysine)-dioctyl phosphate complexes, PLL(diC8)(x) (x = 1.0-3.0). Here, the alpha-helical PLL is surrounded by the surfactants and these bottle-brush-like chains self-assemble in a hexagonal cylindrical morphology. As x is increased, the materials are clearly plasticized and the degree of ordering is improved: The stiff alpha-helical backbones in a softened surfactant matrix give rise to thermotropic liquid-crystalline phases. The complexes were examined by Fourier transform infrared spectroscopy, small- and wide-angle X-ray scattering, transmission electron microscopy, differential scanning calorimetry, polarized optical microscopy, and circular dichroism.

Generalized helicity and Beltrami fields

Energy Technology Data Exchange (ETDEWEB)

Buniy, Roman V., E-mail: roman.buniy@gmail.com [Schmid College of Science, Chapman University, Orange, CA 92866 (United States); Isaac Newton Institute, University of Cambridge, Cambridge, CB3 0EH (United Kingdom); Kephart, Thomas W., E-mail: tom.kephart@gmail.com [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Isaac Newton Institute, University of Cambridge, Cambridge, CB3 0EH (United Kingdom)

2014-05-15

We propose covariant and non-abelian generalizations of the magnetic helicity and Beltrami equation. The gauge invariance, variational principle, conserved current, energy–momentum tensor and choice of boundary conditions elucidate the subject. In particular, we prove that any extremal of the Yang–Mills action functional 1/4 ∫{sub Ω}trF{sub μν}F{sup μν}d{sup 4}x subject to the local constraint ε{sup μναβ}trF{sub μν}F{sub αβ}=0 satisfies the covariant non-abelian Beltrami equation. -- Highlights: •We introduce the covariant non-abelian helicity and Beltrami equation. •The Yang–Mills action and instanton term constraint lead to the Beltrami equation. •Solutions of the Beltrami equation conserve helicity.

CURRENT AND KINETIC HELICITY OF LONG-LIVED ACTIVITY COMPLEXES

International Nuclear Information System (INIS)

Komm, Rudolf; Gosain, Sanjay

2015-01-01

We study long-lived activity complexes and their current helicity at the solar surface and their kinetic helicity below the surface. The current helicity has been determined from synoptic vector magnetograms from the NSO/SOLIS facility, and the kinetic helicity of subsurface flows has been determined with ring-diagram analysis applied to full-disk Dopplergrams from NSO/GONG and SDO/HMI. Current and kinetic helicity of activity complexes follow the hemispheric helicity rule with mainly positive values (78%; 78%, respectively, with a 95% confidence level of 31%) in the southern hemisphere and negative ones (80%; 93%, respectively, with a 95% confidence level of 22% and 14%, respectively) in the northern hemisphere. The locations with the dominant sign of kinetic helicity derived from Global Oscillation Network Group (GONG) and SDO/HMI data are more organized than those of the secondary sign even if they are not part of an activity complex, while locations with the secondary sign are more fragmented. This is the case for both hemispheres even for the northern one where it is not as obvious visually due to the large amount of magnetic activity present as compared to the southern hemisphere. The current helicity shows a similar behavior. The dominant sign of current helicity is the same as that of kinetic helicity for the majority of the activity complexes (83% with a 95% confidence level of 15%). During the 24 Carrington rotations analyzed here, there is at least one longitude in each hemisphere where activity complexes occur repeatedly throughout the epoch. These ''active'' longitudes are identifiable as locations of strong current and kinetic helicity of the same sign

Simplification of the helical TEN2 laser

Science.gov (United States)

Krahn, K.-H.

1980-04-01

The observation that the helical TEN2 laser can effectively be simplified by giving up the use of decoupling elements as well as by abolishing the segmentation of the electrode structure is examined. Although, as a consequence of this simplification, the operating pressure range was slightly decreased, the output power could be improved by roughly 30%, a result which is attributed to the new electrode geometry exhibiting lower inductance and lower damping losses.

Primary double contrast study of the colon with citrate-sorbitol-barium suspension in the diagnosis of chronic colitis

International Nuclear Information System (INIS)

Sidorov, V.S.

1991-01-01

X-ray investigation of the colon was conducted in 292 patients with clinically diagnosed chronic colitis: standard 3-phase irrigoscopy-in 189 patients and a primary double contrast study of the colon with citrate-sorbitol-barium suspenzion - in 103. Basing on X-ray and morphological findings, the diagnosis was confirmed in 128 patients of the 1st group (68.2 %) and in 89 patients of the 2nd group (86 %). The primary double contrast study of the colon was found more effective as it permitted the detection of elements of the mucosal microcontours: transversal strips, not coinciding with haustration, focal granularity, diffuse granularity, small barium suspension depots or niches, nodular granularity. It permitted the recommendation of the method for a wide clinical use

Structural transitions and guest/host complexing of liquid crystal helical nanofilaments induced by nanoconfinement.

Science.gov (United States)

Kim, Hanim; Ryu, Seong Ho; Tuchband, Michael; Shin, Tae Joo; Korblova, Eva; Walba, David M; Clark, Noel A; Yoon, Dong Ki

2017-02-01

A lamellar liquid crystal (LC) phase of certain bent-core mesogenic molecules can be grown in a manner that generates a single chiral helical nanofilament in each of the cylindrical nanopores of an anodic aluminum oxide (AAO) membrane. By introducing guest molecules into the resulting composite chiral nanochannels, we explore the structures and functionality of the ordered guest/host LC complex, verifying the smectic-like positional order of the fluidic nematic LC phase, which is obtained by the combination of the LC organization and the nanoporous AAO superstructure. The guest nematic LC 4'- n -pentyl-4-cyanobiphenyl is found to form a distinctive fluid layered ordered LC complex at the nanofilament/guest interface with the host 1,3-phenylene bis[4-(4-nonyloxyphenyliminomethyl)benzoate], where this interface contacts the AAO cylinder wall. Filament growth form is strongly influenced by mixture parameters and pore dimensions.

Helical Root Buckling: A Transient Mechanism for Stiff Interface Penetration

Science.gov (United States)

Silverberg, Jesse; Noar, Roslyn; Packer, Michael; Harrison, Maria; Cohen, Itai; Henley, Chris; Gerbode, Sharon

2011-03-01

Tilling in agriculture is commonly used to loosen the topmost layer of soil and promote healthy plant growth. As roots navigate this mechanically heterogeneous environment, they encounter interfaces between the compliant soil and the underlying compacted soil. Inspired by this problem, we used 3D time-lapse imaging of Medicago Truncatula plants to study root growth in two-layered transparent hydrogels. The layers are mechanically distinct; the top layer is more compliant than the bottom. We observe that the roots form a transient helical structure as they attempt to penetrate the bi-layer interface. Interpreting this phenotype as a form of buckling due to root elongation, we measured the helix size as a function of the surrounding gel modulus. Our measurements show that by twisting the root tip during growth, the helical structure recruits the surrounding medium for an enhanced penetration force allowing the plants access to the lower layer of gel.

Adjustable threshold-voltage in all-inkjet-printed organic thin film transistor using double-layer dielectric structures

International Nuclear Information System (INIS)

Wu, Wen-Jong; Lee, Chang-Hung; Hsu, Chun-Hao; Yang, Shih-Hsien; Lin, Chih-Ting

2013-01-01

An all-inkjet-printed organic thin film transistor (OTFT) with a double-layer dielectric structure is proposed and implemented in this study. By using the double-layer structure with different dielectric materials (i.e., polyvinylphenol with poly(vinylidene fluoride-co-hexafluoropropylene)), the threshold-voltage of OTFT can be adjusted. The threshold-voltage shift can be controlled by changing the composition of dielectric layers. That is, an enhancement-mode OTFT can be converted to a depletion-mode OTFT by selectively printing additional dielectric layers to form a high-k/low-k double-layer structure. The printed OTFT has a carrier mobility of 5.0 × 10 −3 cm 2 /V-s. The threshold-voltages of the OTFTs ranged between − 13 V and 10 V. This study demonstrates an additional design parameter for organic electronics manufactured using inkjet printing technology. - Highlights: • A double-layer dielectric organic thin film transistor, OTFT, is implemented. • The threshold voltage of OTFT can be configured by the double dielectric structure. • The composition of the dielectric determines the threshold voltage shift. • The characteristics of OTFTs can be adjusted by double dielectric structures

Effect of Ovality on Maximum External Pressure of Helically Coiled Steam Generator Tubes with a Rectangular Wear

Energy Technology Data Exchange (ETDEWEB)

Shin, Dong In; Lim, Eun Mo; Huh, Nam Su [Seoul National Univ. of Science and Technology, Seoul (Korea, Republic of); Choi, Shin Beom; Yu, Je Yong; Kim, Ji Ho; Choi, Suhn [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2013-10-15

A structural integrity of steam generator tubes of nuclear power plants is one of crucial parameters for safe operation of nuclear power plants. Thus, many studies have been made to provide engineering methods to assess integrity of defective tubes of commercial nuclear power plants considering its operating environments and defect characteristics. As described above, the geometric and operating conditions of steam generator tubes in integral reactor are significantly different from those of commercial reactor. Therefore, the structural integrity assessment of defective tubes of integral reactor taking into account its own operating conditions and geometric characteristics, i. e., external pressure and helically coiled shape, should be made to demonstrate compliance with the current design criteria. Also, ovality is very specific characteristics of the helically coiled tube because it is occurred during the coiling processes. The wear, occurring from FIV (Flow Induced Vibration) and so on, is main degradation of steam generator tube. In the present study, maximum external pressure of helically coiled steam generator tube with wear is predicted based on the detailed 3-dimensional finite element analysis. As for shape of wear defect, the rectangular shape is considered. In particular, the effect of ovality on the maximum external pressure of helically coiled tubes with rectangular shaped wear is investigated. In the present work, the maximum external pressure of helically coiled steam generator tube with rectangular shaped wear is investigated via detailed 3-D FE analyses. In order to cover a practical range of geometries for defective tube, the variables affecting the maximum external pressure were systematically varied. In particular, the effect of tube ovality on the maximum external pressure is evaluated. It is expected that the present results can be used as a technical backgrounds for establishing a practical structural integrity assessment guideline of

Modelling simple helically delivered dose distributions

International Nuclear Information System (INIS)

Fenwick, John D; Tome, Wolfgang A; Kissick, Michael W; Mackie, T Rock

2005-01-01

In a previous paper, we described quality assurance procedures for Hi-Art helical tomotherapy machines. Here, we develop further some ideas discussed briefly in that paper. Simple helically generated dose distributions are modelled, and relationships between these dose distributions and underlying characteristics of Hi-Art treatment systems are elucidated. In particular, we describe the dependence of dose levels along the central axis of a cylinder aligned coaxially with a Hi-Art machine on fan beam width, couch velocity and helical delivery lengths. The impact on these dose levels of angular variations in gantry speed or output per linear accelerator pulse is also explored

Evolution and breakdown of helical vortex wakes behind a wind turbine

International Nuclear Information System (INIS)

Nemes, A; Jacono, D Lo; Sheridan, J; Blackburn, H M; Sherry, M

2014-01-01

The wake behind a three-bladed Glauert model rotor in a water channel was investigated. Planar particle image velocimetry was used to measure the velocity fields on the wake centre-line, with snapshots phase-locked to blade position of the rotor. Phase- locked averages of the velocity and vorticity fields are shown, with tip vortex interaction and entanglement of the helical filaments elucidated. Proper orthogonal decomposition and topology-based vortex identification are used to filter the PIV images for coherent structures and locate vortex cores. Application of these methods to the instantaneous data reveals unsteady behaviour of the helical filaments that is statistically quantifiable

MAGNETIC HELICITY FLUX IN THE PRESENCE OF SHEAR

International Nuclear Information System (INIS)

Hubbard, Alexander; Brandenburg, Axel

2011-01-01

Magnetic helicity has risen to be a major player in dynamo theory, with the helicity of the small-scale field being linked to the dynamo saturation process for the large-scale field. It is a nearly conserved quantity, which allows its evolution equation to be written in terms of production and flux terms. The flux term can be decomposed in a variety of fashions. One particular contribution that has been expected to play a significant role in dynamos in the presence of mean shear was isolated by Vishniac and Cho. Magnetic helicity fluxes are explicitly gauge dependent however, and the correlations that have come to be called the Vishniac-Cho flux were determined in the Coulomb gauge, which turns out to be fraught with complications in shearing systems. While the fluxes of small-scale helicity are explicitly gauge dependent, their divergences can be gauge independent. We use this property to investigate magnetic helicity fluxes of the small-scale field through direct numerical simulations in a shearing-box system and find that in a numerically usable gauge the divergence of the small-scale helicity flux vanishes, while the divergence of the Vishniac-Cho flux remains finite. We attribute this seeming contradiction to the existence of horizontal fluxes of small-scale magnetic helicity with finite divergences.

Magnetic Helicity Flux in the Presence of Shear

Science.gov (United States)

Hubbard, Alexander; Brandenburg, Axel

2011-01-01

Magnetic helicity has risen to be a major player in dynamo theory, with the helicity of the small-scale field being linked to the dynamo saturation process for the large-scale field. It is a nearly conserved quantity, which allows its evolution equation to be written in terms of production and flux terms. The flux term can be decomposed in a variety of fashions. One particular contribution that has been expected to play a significant role in dynamos in the presence of mean shear was isolated by Vishniac & Cho. Magnetic helicity fluxes are explicitly gauge dependent however, and the correlations that have come to be called the Vishniac-Cho flux were determined in the Coulomb gauge, which turns out to be fraught with complications in shearing systems. While the fluxes of small-scale helicity are explicitly gauge dependent, their divergences can be gauge independent. We use this property to investigate magnetic helicity fluxes of the small-scale field through direct numerical simulations in a shearing-box system and find that in a numerically usable gauge the divergence of the small-scale helicity flux vanishes, while the divergence of the Vishniac-Cho flux remains finite. We attribute this seeming contradiction to the existence of horizontal fluxes of small-scale magnetic helicity with finite divergences.

Transport barrier in Helical system

International Nuclear Information System (INIS)

Ida, Katsumi

1998-01-01

Experiments on the transport barrier in Helical plasmas are reviewed. There are two mechanisms of transport improvement, that results in the formation of the transport barrier. One is the improvement of neoclassical transport by reducing the ripple loss with radial electric field, which exist only in helical plasma. The other is the improvement of anomalous transport due to the suppression of fluctuations associated with a radial electric field shear both in tokamak and helical plasma. The formation of the transport barrier can be triggered by the radial electric field shear associated with the transition of the radial electric field (L/H transition or ion-electron root transition) or the peaked density or the optimization of magnetic field shear. The mechanisms of transport barrier formation are also discussed. (author). 60 refs

Toroidal helical quartz forming machine

International Nuclear Information System (INIS)

Hanks, K.W.; Cole, T.R.

1977-01-01

The Scyllac fusion experimental machine used 10 cm diameter smooth bore discharge tubes formed into a simple toroidal shape prior to 1974. At about that time, it was discovered that a discharge tube was required to follow the convoluted shape of the load coil. A machine was designed and built to form a fused quartz tube with a toroidal shape. The machine will accommodate quartz tubes from 5 cm to 20 cm diameter forming it into a 4 m toroidal radius with a 1 to 5 cm helical displacement. The machine will also generate a helical shape on a linear tube. Two sets of tubes with different helical radii and wavelengths have been successfully fabricated. The problems encountered with the design and fabrication of this machine are discussed

Simulation of injector dynamics during steady inductive helicity injection current drive in the HIT-SI experiment

Energy Technology Data Exchange (ETDEWEB)

Hansen, C., E-mail: hansec@uw.edu [PSI-Center, University of Washington, Seattle, Washington 98195 (United States); Columbia University, New York, New York 10027 (United States); Marklin, G. [PSI-Center, University of Washington, Seattle, Washington 98195 (United States); Victor, B. [HIT-SI Group, University of Washington, Seattle, Washington 98195 (United States); Akcay, C. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Jarboe, T. [HIT-SI Group, University of Washington, Seattle, Washington 98195 (United States); PSI-Center, University of Washington, Seattle, Washington 98195 (United States)

2015-04-15

We present simulations of inductive helicity injection in the Helicity Injected Torus with Steady Inductive helicity injection (HIT-SI) device that treats the entire plasma volume in a single dynamic MHD model. A new fully 3D numerical tool, the PSI-center TETrahedral mesh code, was developed that provides the geometric flexibility required for this investigation. Implementation of a zero-β Hall MHD model using PSI-TET will be presented including formulation of a new self-consistent magnetic boundary condition for the wall of the HIT-SI device. Results from simulations of HIT-SI are presented focusing on injector dynamics that are investigated numerically for the first time. Asymmetries in the plasma loading between the two helicity injectors and progression of field reversal in each injector are observed. Analysis indicates cross-coupling between injectors through confinement volume structures. Injector impedance is found to scale with toroidal current at fixed density, consistent with experimental observation. Comparison to experimental data with an injector drive frequency of 14.5 kHz shows good agreement with magnetic diagnostics. Global mode structures from Bi-Orthogonal decomposition agree well with experimental data for the first four modes.

Chiral charge erasure via thermal fluctuations of magnetic helicity

International Nuclear Information System (INIS)

Long, Andrew J.; Sabancilar, Eray

2016-01-01

We consider a relativistic plasma of fermions coupled to an Abelian gauge field and carrying a chiral charge asymmetry, which might arise in the early Universe through baryogenesis. It is known that on large length scales, λ≳1/(αμ_5), the chiral anomaly opens an instability toward the erasure of chiral charge and growth of magnetic helicity. Here the chemical potential μ_5 parametrizes the chiral asymmetry and α is the fine-structure constant. We study the process of chiral charge erasure through the thermal fluctuations of magnetic helicity and contrast with the well-studied phenomenon of Chern-Simons number diffusion. Through the fluctuation-dissipation theorem we estimate the amplitude and time scale of helicity fluctuations on the length scale λ, finding δ H∼λT and τ∼αλ"3T"2 for a relativistic plasma at temperature T. We argue that the presence of a chiral asymmetry allows the helicity to grow diffusively for a time t∼T"3/(α"5μ_5"4) until it reaches an equilibrium value H∼μ_5T"2/α, and the chiral asymmetry is partially erased. If the chiral asymmetry is small, μ_5< T/α, this avenue for chiral charge erasure is found to be slower than the chiral magnetic effect for which t∼T/(α"3μ_5"2). This mechanism for chiral charge erasure can be important for the hypercharge sector of the Standard Model as well as extensions including U(1) gauge interactions, such as asymmetric dark matter models.

Endodontic treatment and esthetic management of a primary double tooth with direct composite using silicone buildup guide

Directory of Open Access Journals (Sweden)

Vinaya Kumar Kulkarni

2012-01-01

Full Text Available Gemination and fusion are morphological dental anomalies, characterized by the formation of a clinically wide tooth. Gemination occurs when one tooth bud tries to divide, while fusion occurs if two buds unite. The terms double teeth, double formation, conjoined teeth, geminifusion, vicinifusion and dental twinning are often used to describe fusion and gemination. Double teeth are associated with clinical problems such as poor esthetics, spacing problems and caries susceptibility. Management of such cases requires a comprehensive knowledge of the clinical entity as well as the problems associated with it. This report presents a case of primary double tooth in a 6-year-old boy involving maxillary left central incisor. The anomalous tooth was carious and pulpally involved. This was treated conservatively by endodontic treatment and esthetic rehabilitation was done with direct composite restoration using a silicone buildup guide. The treated tooth was followed up until exfoliation.

A novel sandwich differential capacitive accelerometer with symmetrical double-sided serpentine beam-mass structure

International Nuclear Information System (INIS)

Xiao, D B; Li, Q S; Hou, Z Q; Wang, X H; Chen, Z H; Xia, D W; Wu, X Z

2016-01-01

This paper presents a novel differential capacitive silicon micro-accelerometer with symmetrical double-sided serpentine beam-mass sensing structure and glass–silicon–glass sandwich structure. The symmetrical double-sided serpentine beam-mass sensing structure is fabricated with a novel pre-buried mask fabrication technology, which is convenient for manufacturing multi-layer sensors. The glass–silicon–glass sandwich structure is realized by a double anodic bonding process. To solve the problem of the difficulty of leading out signals from the top and bottom layer simultaneously in the sandwich sensors, a silicon pillar structure is designed that is inherently simple and low-cost. The prototype is fabricated and tested. It has low noise performance (the peak to peak value is 40 μg) and μg-level Allan deviation of bias (2.2 μg in 1 h), experimentally demonstrating the effectiveness of the design and the novel fabrication technology. (paper)

Whole brain radiotherapy with adjuvant or concomitant boost in brain metastasis: dosimetric comparison between helical and volumetric IMRT technique

International Nuclear Information System (INIS)

Borghetti, Paolo; Pedretti, Sara; Spiazzi, Luigi; Avitabile, Rossella; Urpis, Mauro; Foscarini, Federica; Tesini, Giulia; Trevisan, Francesca; Ghirardelli, Paolo; Pandini, Sara Angela; Triggiani, Luca; Magrini, Stefano Maria; Buglione, Michela

2016-01-01

To compare and evaluate the possible advantages related to the use of VMAT and helical IMRT and two different modalities of boost delivering, adjuvant stereotactic boost (SRS) or simultaneous integrated boost (SIB), in the treatment of brain metastasis (BM) in RPA classes I-II patients. Ten patients were treated with helical IMRT, 5 of them with SRS after whole brain radiotherapy (WBRT) and 5 with SIB. MRI co-registration with planning CT was mandatory and prescribed doses were 30 Gy in 10 fractions (fr) for WBRT and 15Gy/1fr or 45Gy/10fr in SRS or SIB, respectively. For each patient, 4 “treatment plans” (VMAT SRS and SIB, helical IMRT SRS and SIB) were calculated and accepted if PTV boost was included in 95 % isodose and dose constraints of the main organs at risk were respected without major deviations. Homogeneity Index (HI), Conformal Index (CI) and Conformal Number (CN) were considered to compare the different plans. Moreover, time of treatment delivery was calculated and considered in the analysis. Volume of brain metastasis ranged between 1.43 and 51.01 cc (mean 12.89 ± 6.37 ml) and 3 patients had double lesions. V95% resulted over 95 % in the average for each kind of technique, but the “target coverage” was inadequate for VMAT planning with two sites. The HI resulted close to the ideal value of zero in all cases; VMAT-SIB, VMAT-SRS, Helical IMRT-SIB and Helical IMRT-SRS showed mean CI of 2.15, 2.10, 2.44 and 1.66, respectively (optimal range: 1.5–2.0). Helical IMRT-SRS was related to the best and reliable finding of CN (0.66). The mean of treatment time was 210 s, 467 s, 440 s, 1598 s, respectively, for VMAT-SIB, VMAT-SRS, Helical IMRT-SIB and Helical IMRT-SRS. This dosimetric comparison show that helical IMRT obtain better target coverage and respect of CI and CN; VMAT could be acceptable in solitary metastasis. SIB modality can be considered as a good choice for clinical and logistic compliance; literature’s preliminary data are confirming

Magnetic Helicity Estimations in Models and Observations of the Solar Magnetic Field. III. Twist Number Method

Energy Technology Data Exchange (ETDEWEB)

Guo, Y. [School of Astronomy and Space Science and Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University, Nanjing 210023 (China); Pariat, E.; Moraitis, K. [LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, F-92190 Meudon (France); Valori, G. [University College London, Mullard Space Science Laboratory, Holmbury St. Mary, Dorking, Surrey, RH5 6NT (United Kingdom); Anfinogentov, S. [Institute of Solar-Terrestrial Physics SB RAS 664033, Irkutsk, P.O. box 291, Lermontov Street, 126a (Russian Federation); Chen, F. [Max-Plank-Institut für Sonnensystemforschung, D-37077 Göttingen (Germany); Georgoulis, M. K. [Research Center for Astronomy and Applied Mathematics of the Academy of Athens, 4 Soranou Efesiou Street, 11527 Athens (Greece); Liu, Y. [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States); Thalmann, J. K. [Institute of Physics, Univeristy of Graz, Universitätsplatz 5/II, A-8010 Graz (Austria); Yang, S., E-mail: guoyang@nju.edu.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2017-05-01

We study the writhe, twist, and magnetic helicity of different magnetic flux ropes, based on models of the solar coronal magnetic field structure. These include an analytical force-free Titov–Démoulin equilibrium solution, non-force-free magnetohydrodynamic simulations, and nonlinear force-free magnetic field models. The geometrical boundary of the magnetic flux rope is determined by the quasi-separatrix layer and the bottom surface, and the axis curve of the flux rope is determined by its overall orientation. The twist is computed by the Berger–Prior formula, which is suitable for arbitrary geometry and both force-free and non-force-free models. The magnetic helicity is estimated by the twist multiplied by the square of the axial magnetic flux. We compare the obtained values with those derived by a finite volume helicity estimation method. We find that the magnetic helicity obtained with the twist method agrees with the helicity carried by the purely current-carrying part of the field within uncertainties for most test cases. It is also found that the current-carrying part of the model field is relatively significant at the very location of the magnetic flux rope. This qualitatively explains the agreement between the magnetic helicity computed by the twist method and the helicity contributed purely by the current-carrying magnetic field.

Localization of functional receptor epitopes on the structure of ciliary neurotrophic factor indicates a conserved, function-related epitope topography among helical cytokines.

Science.gov (United States)

Panayotatos, N; Radziejewska, E; Acheson, A; Somogyi, R; Thadani, A; Hendrickson, W A; McDonald, N Q

1995-06-09

By rational mutagenesis, receptor-specific functional analysis, and visualization of complex formation in solution, we identified individual amino acid side chains involved specifically in the interaction of ciliary neurotrophic factor (CNTF) with CNTFR alpha and not with the beta-components, gp130 and LIFR. In the crystal structure, the side chains of these residues, which are located in helix A, the AB loop, helix B, and helix D, are surface accessible and are clustered in space, thus constituting an epitope for CNTFR alpha. By the same analysis, a partial epitope for gp130 was also identified on the surface of helix A that faces away from the alpha-epitope. Superposition of the CNTF and growth hormone structures showed that the location of these epitopes on CNTF is analogous to the location of the first and second receptor epitopes on the surface of growth hormone. Further comparison with proposed binding sites for alpha- and beta-receptors on interleukin-6 and leukemia inhibitory factor indicated that this epitope topology is conserved among helical cytokines. In each case, epitope I is utilized by the specificity-conferring component, whereas epitopes II and III are used by accessory components. Thus, in addition to a common fold, helical cytokines share a conserved order of receptor epitopes that is function related.

System assessment of helical reactors in comparison with tokamaks

International Nuclear Information System (INIS)

Yamazaki, K.; Imagawa, S.; Muroga, T.; Sagara, A.; Okamura, S.

2002-10-01

A comparative assessment of tokamak and helical reactors has been performed using equivalent physics/engineering model and common costing model. Higher-temperature plasma operation is required in tokamak reactors to increase bootstrap current fraction and to reduce current-drive (CD) power. In helical systems, lower-temperature operation is feasible and desirable to reduce helical ripple transport. The capital cost of helical reactor is rather high, however, the cost of electricity (COE) is almost same as that of tokamak reactor because of smaller re-circulation power (no CD power) and less-frequent blanket replacement (lower neutron wall loading). The standard LHD-type helical reactor with 5% beta value is economically equivalent to the standard tokamak with 3% beta. The COE of lower-aspect ratio helical reactor is on the same level of high-β N tokamak reactors. (author)

Using Magnetic Helicity Diagnostics to Determine the Nature of Solar Active-Region Formation

Science.gov (United States)

Georgoulis, Manolis K.

Employing a novel nonlinear force-free (NLFF) method that self-consistently infers instantaneous free magnetic-energy and relative magnetic-helicity budgets from single photospheric vector magnetograms, we recently constructed the magnetic energy-helicity (EH) diagram of solar active regions. The EH diagram implies dominant relative helicities of left-handed or right-handed chiralities for the great majority of active regions. The amplitude (budget) of these helicities scales monotonically with the free magnetic energy. This constructive, strongly preferential accumulation of a certain sense of magnetic helicity seems to disqualify recently proposed mechanisms relying on a largely random near-surface convection for the formation of the great majority of active regions. The existing qualitative formation mechanism for these regions remains the conventional Omega-loop emergence following a buoyant ascension from the bottom of the convection zone. However, exceptions to this rule include even eruptive active regions: NOAA AR 11283 is an obvious outlier to the EH diagram, involving significant free magnetic energy with a small relative magnetic helicity. Relying on a timeseries of vector magnetograms of this region, our methodology shows nearly canceling amounts of both senses of helicity and an overall course from a weakly left-handed to a weakly right-handed structure, in the course of which a major eruption occurs. For this and similarly behaving active regions the latest near-surface formation scenario might conceivably be employed successfully. Research partially supported by the EU Seventh Framework Programme under grant agreement No. PIRG07-GA-2010-268245 and by the European Union Social Fund (ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program: Thales. Investing in knowledge society through the European Social Fund.

THE EFFECTS OF SPATIAL SMOOTHING ON SOLAR MAGNETIC HELICITY PARAMETERS AND THE HEMISPHERIC HELICITY SIGN RULE

Energy Technology Data Exchange (ETDEWEB)

Ocker, Stella Koch [Department of Physics, Oberlin College, Oberlin, OH 44074 (United States); Petrie, Gordon, E-mail: socker@oberlin.edu, E-mail: gpetrie@nso.edu [National Solar Observatory, Boulder, CO 80303 (United States)

2016-12-01

The hemispheric preference for negative/positive helicity to occur in the northern/southern solar hemisphere provides clues to the causes of twisted, flaring magnetic fields. Previous studies on the hemisphere rule may have been affected by seeing from atmospheric turbulence. Using Hinode /SOT-SP data spanning 2006–2013, we studied the effects of two spatial smoothing tests that imitate atmospheric seeing: noise reduction by ignoring pixel values weaker than the estimated noise threshold, and Gaussian spatial smoothing. We studied in detail the effects of atmospheric seeing on the helicity distributions across various field strengths for active regions (ARs) NOAA 11158 and NOAA 11243, in addition to studying the average helicities of 179 ARs with and without smoothing. We found that, rather than changing trends in the helicity distributions, spatial smoothing modified existing trends by reducing random noise and by regressing outliers toward the mean, or removing them altogether. Furthermore, the average helicity parameter values of the 179 ARs did not conform to the hemisphere rule: independent of smoothing, the weak-vertical-field values tended to be negative in both hemispheres, and the strong-vertical-field values tended to be positive, especially in the south. We conclude that spatial smoothing does not significantly affect the overall statistics for space-based data, and thus seeing from atmospheric turbulence seems not to have significantly affected previous studies’ ground-based results on the hemisphere rule.

Helical magnetic axis configuration combined with l = 1 and weak l = -1 torsatron fields

International Nuclear Information System (INIS)

Kikuchi, Hitoshi; Saito, Katsunori; Gesso, Hirokazu; Shiina, Shoichi

1989-01-01

The superposition of a relatively weak l = -1 torsatron field on a main l = 1 torsatron field leads to the improvement of the confinement properties due to the formation of a local magnetic well, which results from the local curvature of the helical magnetic axis with a larger excursion in the major radius direction. This l±1 helical magnetic axis system has a comparatively simple, compact coil structure. Here the vacuum configuration properties of l = ±1 system are described. (author)

Double soft theorems in gauge and string theories

Energy Technology Data Exchange (ETDEWEB)

Volovich, Anastasia [Brown University Department of Physics,182 Hope St, Providence, RI, 02912 (United States); Wen, Congkao [I.N.F.N. Sezione di Roma “Tor Vergata”,Via della Ricerca Scientifica, 00133 Roma (Italy); Zlotnikov, Michael [Brown University Department of Physics,182 Hope St, Providence, RI, 02912 (United States)

2015-07-20

We investigate the tree-level S-matrix in gauge theories and open superstring theory with several soft particles. We show that scattering amplitudes with two or three soft gluons of non-identical helicities behave universally in the limit, with multi-soft factors which are not the product of individual soft gluon factors. The results are obtained from the BCFW recursion relations in four dimensions, and further extended to arbitrary dimensions using the CHY formula. We also find new soft theorems for double soft limits of scalars and fermions in N=4 and pure N=2 SYM. Finally, we show that the double-soft-scalar theorems can be extended to open superstring theory without receiving any α{sup ′} corrections.

A constraint logic programming approach to associate 1D and 3D structural components for large protein complexes.

Science.gov (United States)

Dal Palù, Alessandro; Pontelli, Enrico; He, Jing; Lu, Yonggang

2007-01-01

The paper describes a novel framework, constructed using Constraint Logic Programming (CLP) and parallelism, to determine the association between parts of the primary sequence of a protein and alpha-helices extracted from 3D low-resolution descriptions of large protein complexes. The association is determined by extracting constraints from the 3D information, regarding length, relative position and connectivity of helices, and solving these constraints with the guidance of a secondary structure prediction algorithm. Parallelism is employed to enhance performance on large proteins. The framework provides a fast, inexpensive alternative to determine the exact tertiary structure of unknown proteins.

Spin versus helicity in processes involving transversity

CERN Document Server

Mekhfi, Mustapha

2011-01-01

We construct the spin formalism in order to deal in a direct and natural way with processes involving transversity which are now of increasing popularity. The helicity formalism which is more appropriate for collision processes of definite helicity has been so far used also to manage processes with transversity, but at the price of computing numerous helicity amplitudes generally involving unnecessary kinematical variables.In a second step we work out the correspondence between both formalisms and retrieve in another way all results of the helicity formalism but in simpler forms.We then compute certain processes for comparison.A special process:the quark dipole magnetic moment is shown to be exclusively treated within the spin formalism as it is directly related to the transverse spin of the quark inside the baryon.

Hierarchically Structured Electrospun Fibers

Directory of Open Access Journals (Sweden)

Nicole E. Zander

2013-01-01

Full Text Available Traditional electrospun nanofibers have a myriad of applications ranging from scaffolds for tissue engineering to components of biosensors and energy harvesting devices. The generally smooth one-dimensional structure of the fibers has stood as a limitation to several interesting novel applications. Control of fiber diameter, porosity and collector geometry will be briefly discussed, as will more traditional methods for controlling fiber morphology and fiber mat architecture. The remainder of the review will focus on new techniques to prepare hierarchically structured fibers. Fibers with hierarchical primary structures—including helical, buckled, and beads-on-a-string fibers, as well as fibers with secondary structures, such as nanopores, nanopillars, nanorods, and internally structured fibers and their applications—will be discussed. These new materials with helical/buckled morphology are expected to possess unique optical and mechanical properties with possible applications for negative refractive index materials, highly stretchable/high-tensile-strength materials, and components in microelectromechanical devices. Core-shell type fibers enable a much wider variety of materials to be electrospun and are expected to be widely applied in the sensing, drug delivery/controlled release fields, and in the encapsulation of live cells for biological applications. Materials with a hierarchical secondary structure are expected to provide new superhydrophobic and self-cleaning materials.

Evaporation-based method for preparing gelatin foams with aligned tubular pore structures

Energy Technology Data Exchange (ETDEWEB)

Frazier, Shane D.; Srubar, Wil V., E-mail: wsrubar@colorado.edu

2016-05-01

Gelatin-based foams with aligned tubular pore structures were prepared via liquid-to-gas vaporization of tightly bound water in dehydrated gelatin hydrogels. This study elucidates the mechanism of the foaming process by investigating the secondary (i.e., helical) structure, molecular interactions, and water content of gelatin films before and after foaming using X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry and thermogravimetric analysis (TGA), respectively. Experimental data from gelatin samples prepared at various gelatin-to-water concentrations (5–30 wt.%) substantiate that resulting foam structures are similar in pore diameter (approximately 350 μm), shape, and density (0.05–0.22 g/cm{sup 3}) to those fabricated using conventional methods (e.g., freeze-drying). Helical structures were identified in the films but were not evident in the foamed samples after vaporization (~ 150 °C), suggesting that the primary foaming mechanism is governed by the vaporization of water that is tightly bound in secondary structures (i.e., helices, β-turns, β-sheets) that are present in dehydrated gelatin films. FTIR and TGA data show that the foaming process leads to more disorder and reduced hydrogen bonding to hydroxyl groups in gelatin and that no thermal degradation of gelatin occurs before or after foaming. - Highlights: • A new method is presented for fabricating gelatin foams with aligned, tubular pores. • Gelatin hydrogels were dehydrated then heated to 150 °C to induce foaming. • Vaporization of tightly (vs. loosely) bound water is the primary foaming mechanism • Foaming induced no thermal degradation but caused disorder in secondary structures • Foam microstructures are similar to those prepared using conventional methods.

Evaporation-based method for preparing gelatin foams with aligned tubular pore structures

International Nuclear Information System (INIS)

Frazier, Shane D.; Srubar, Wil V.

2016-01-01

Gelatin-based foams with aligned tubular pore structures were prepared via liquid-to-gas vaporization of tightly bound water in dehydrated gelatin hydrogels. This study elucidates the mechanism of the foaming process by investigating the secondary (i.e., helical) structure, molecular interactions, and water content of gelatin films before and after foaming using X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry and thermogravimetric analysis (TGA), respectively. Experimental data from gelatin samples prepared at various gelatin-to-water concentrations (5–30 wt.%) substantiate that resulting foam structures are similar in pore diameter (approximately 350 μm), shape, and density (0.05–0.22 g/cm"3) to those fabricated using conventional methods (e.g., freeze-drying). Helical structures were identified in the films but were not evident in the foamed samples after vaporization (~ 150 °C), suggesting that the primary foaming mechanism is governed by the vaporization of water that is tightly bound in secondary structures (i.e., helices, β-turns, β-sheets) that are present in dehydrated gelatin films. FTIR and TGA data show that the foaming process leads to more disorder and reduced hydrogen bonding to hydroxyl groups in gelatin and that no thermal degradation of gelatin occurs before or after foaming. - Highlights: • A new method is presented for fabricating gelatin foams with aligned, tubular pores. • Gelatin hydrogels were dehydrated then heated to 150 °C to induce foaming. • Vaporization of tightly (vs. loosely) bound water is the primary foaming mechanism • Foaming induced no thermal degradation but caused disorder in secondary structures • Foam microstructures are similar to those prepared using conventional methods.

Time resolved observations of helical disruptions in a gas embedded Z-pinch

International Nuclear Information System (INIS)

Favre, M.; Chuaqui, H.; Bruzzone, H.; Soto, L.; Wyndham, E.

1990-01-01

Multiframe holographic interferometry has been applied to a gas embedded Z-pinch driven by a 1.5 ω, 100 kV coaxial line generator. The Z-pinch is triggered by a 1.06 μm, 10 ns laser pulse, at the onset of the applied voltage. A hydrogen background pressure of 0.33 atmospheres, with a 3 cm interelectrode separation is used. The laser output is also doubled and it is passed through an optical system giving two or more pulses separated by up to 10 ns for the optical diagnostics. The complete evolution of the helical instability is observed and the main features are discussed. (Author)

New formulae for magnetic relative helicity and field line helicity

Science.gov (United States)

Aly, Jean-Jacques

2018-01-01

We consider a magnetic field {B} occupying the simply connected domain D and having all its field lines tied to the boundary S of D. We assume here that {B} has a simple topology, i.e., the mapping {M} from positive to negative polarity areas of S associating to each other the two footpoints of any magnetic line, is continuous. We first present new formulae for the helicity H of {B} relative to a reference field {{B}}r having the same normal component {B}n on S, and for its field line helicity h relative to a reference vector potential {{C}}r of {{B}}r. These formulae make immediately apparent the well known invariance of these quantities under all the ideal MHD deformations that preserve the positions of the footpoints on S. They express indeed h and H either in terms of {M} and {B}n, or in terms of the values on S of a pair of Euler potentials of {B}. We next show that, for a specific choice of {{C}}r, the field line helicity h of {B} fully characterizes the magnetic mapping {M} and then the topology of the lines. Finally, we give a formula that describes the rate of change of h in a situation where the plasma moves on the perfectly conducting boundary S without changing {B}n and/or non-ideal processes, described by an unspecified term {N} in Ohm’s law, are at work in some parts of D.

A supramolecular ''Double-cable'' structure with a 129{sub 44} helix in a columnar porphyrin-C{sub 60} dyad and its application in polymer solar cells

Energy Technology Data Exchange (ETDEWEB)

Wang, Chien-Lung [College of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH (United States); Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan (China); Zhang, Wen-Bin; Sun, Hao-Jan; Van Horn, Ryan M.; Kulkarni, Rahul R.; Tsai, Chi-Chun; Gong, Xiong; Cheng, Stephen Z.D. [College of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH (United States); Hsu, Chain-Shu [Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan (China); Lotz, Bernard [Institut Charles Sadron, Strasbourg (France)

2012-11-15

A novel porphyrin-C{sub 60} dyad (PCD1) is designed and synthesized to investigate and manipulate the supramolecular structure where geometrically isotropic [such as [60]fullerene (C{sub 60})] and anisotropic [such as porphyrin (Por)] units coexist. It is observed that PCD1 possesses an enantiomeric phase behavior. The melting temperature of the stable PCD1 thermotropic phase is 160 C with a latent heat ({Delta}H) of 18.5 kJ mol{sup -1}. The phase formation is majorly driven by the cooperative intermolecular Por-Por and C{sub 60}-C{sub 60} interactions. Structural analysis reveals that this stable phase possesses a supramolecular ''double-cable'' structure with one p-type Por core columnar channel and three helical n-type C{sub 60} peripheral channels. These ''double-cable'' columns further pack into a hexagonal lattice with a = b = 4.65 nm, c = 41.3 nm, {alpha} = {beta} = 90 , and {gamma} = 120 . The column repeat unit is determined to possess a 129{sub 44} helix. With both donor (D; Pro) and acceptor (A; C{sub 60}) units having their own connecting channels as well as the large D/A interface within the supramolecular ''double-cable'' structure, PCD1 has photogenerated carriers with longer lifetimes compared to the conventional electron acceptor [6,6]-phenyl-C{sub 61}-butyric acid methyl ester. A phase-separated columnar morphology is observed in a bulk-heterojunction (BHJ) material made by the physical blend of a low band-gap conjugated polymer, poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothia-diazole)] (PCPDTBT), and PCD1. With a specific phase structure in the solid state and in the blend, PCD1 is shown to be a promising candidate as a new electron acceptor in high performance BHJ polymer solar cells. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

First Principles Study of Electronic and Magnetic Structures in Double Perovskites

Science.gov (United States)

Ball, Molly

At present, electronic devices are reaching their storage and processing limit causing a major push to find materials that can be used in the next generation of devices. Double perovskites with A2BB'O 6 stoichiometry form one of the leading classes of materials currently being studied as a potential candidate because of their extremely wide range and tunability of functional properties, along with economic and highly scalable synthesis routes. Having a thorough understanding of their electronic and magnetic structure and their dependence on composition and local structure is the basis for targeted development of novel and optimized double perovskites. While the body of knowledge and rules within the field of materials chemistry has enabled many previous discoveries, recent developments within density functional theory (DFT) allow by now a rather realistic description of the electronic and magnetic properties of materials and especially identification of their origin from geometry and orbital structure. This thesis details computational work based on DFT within several collaborative studies to better understand the electronic and magnetic properties of double perovskites and related materials that show promise for future use in multifunctional devices. First, we will begin with a general introduction to the double perovskite structure, their properties, and the computational methods used to study them. In the next section, we will look at the case of the antiferromagnetic, insulating double perovskite Sr2CoOsO6, where measurements showed that the transition metal ions in the two sublattices undergo magnetic ordering independently of each other, indicating weak magnetic short-range coupling and a dominance of longer-range interactions, which has previously not been observed. Here, we performed DFT calculations to extract the exchange strengths between the ions and explain this unique dominance of the long-range interactions. Then, we will look at studies done on thin

ADDITIVE SELF-HELICITY AS A KINK MODE THRESHOLD

International Nuclear Information System (INIS)

Malanushenko, A.; Longcope, D. W.; Fan, Y.; Gibson, S. E.

2009-01-01

In this paper, we propose that additive self-helicity, introduced by Longcope and Malanushenko, plays a role in the kink instability for complex equilibria, similar to twist helicity for thin flux tubes. We support this hypothesis by a calculation of additive self-helicity of a twisted flux tube from the simulation of Fan and Gibson. As more twist gets introduced, the additive self-helicity increases, and the kink instability of the tube coincides with the drop of additive self-helicity, after the latter reaches the value of H A /Φ 2 ∼ 1.5 (where Φ is the flux of the tube and H A is the additive self-helicity). We compare the additive self-helicity to twist for a thin subportion of the tube to illustrate that H A /Φ 2 is equal to the twist number, studied by Berger and Field, when the thin flux tube approximation is applicable. We suggest that the quantity H A /Φ 2 could be treated as a generalization of a twist number, when the thin flux tube approximation is not applicable. A threshold on a generalized twist number might prove extremely useful studying complex equilibria, just as the twist number itself has proven useful studying idealized thin flux tubes. We explicitly describe a numerical method for calculating additive self-helicity, which includes an algorithm for identifying a domain occupied by a flux bundle and a method of calculating potential magnetic field confined to this domain. We also describe a numerical method to calculate twist of a thin flux tube, using a frame parallelly transported along the axis of the tube.

Counting and tensorial properties of twist-two helicity-flip nucleon form factors

International Nuclear Information System (INIS)

Chen Zhang; Ji Xiangdong

2005-01-01

We perform a systematic analysis on the off-forward matrix elements of the twist-two quark and gluon helicity-flip operators. By matching the allowed quantum numbers and their crossing channel counterparts (a method developed by Ji and Lebed), we systematically count the number of independent nucleon form factors in off-forward scattering of matrix elements of these quark and gluon spin-flip operators. In particular, we find that the numbers of independent nucleon form factors of twist-two, helicity-flip quark (gluon) operators are 2n-1 (2n-5) if n is odd, and 2n-2 (2n-6) if n is even, with n≥2 (n≥4). We also analyze and write down the tensorial/Lorentz structure and kinematic factors of the expansion of these operators' matrix elements in terms of the independent form factors. These generalized form factors define the off-forward quark and gluon helicity-flip distributions in the literature

Helicity and other conservation laws in perfect fluid motion

Science.gov (United States)

Serre, Denis

2018-03-01

In this review paper, we discuss helicity from a geometrical point of view and see how it applies to the motion of a perfect fluid. We discuss its relation with the Hamiltonian structure, and then its extension to arbitrary space dimensions. We also comment about the existence of additional conservation laws for the Euler equation, and its unlikely integrability in Liouville's sense.

Helicity non-conserving form factor of the proton

Energy Technology Data Exchange (ETDEWEB)

Voutier, E.; Furget, C.; Knox, S. [Universite Joseph Fourier, Grenoble (France)] [and others

1994-04-01

The study of the hadron structure in the high Q{sup 2} range contributes to the understanding of the mechanisms responsible for the confinement of quarks and gluons. Among the numerous experimental candidates sensitive to these mechanisms, the helicity non-conserving form factor of the proton is a privileged observable since it is controlled by non-perturbative effects. The authors investigate here the feasibility of high Q{sup 2} measurements of this form factor by means of the recoil polarization method in the context of the CEBAF 8 GeV facility. For that purpose, they discuss the development of a high energy proton polarimeter, based on the H({rvec p},pp) elastic scattering, to be placed at the focal plane of a new hadron spectrometer. It is shown that this experimental method significantly improves the knowledge of the helicity non-conserving form factor of the proton up to 10 GeV{sup 2}/c{sup 2}.

NIMROD simulations and physics assessment of possible designs for a next generation Steady Inductive Helicity Injection HIT device

Science.gov (United States)

Penna, James; Morgan, Kyle; Grubb, Isaac; Jarboe, Thomas

2017-10-01

The Helicity Injected Torus - Steady Inductive 3 (HIT-SI3) experiment forms and maintains spheromaks via Steady Inductive Helicity Injection (SIHI) using discrete injectors that inject magnetic helicity via a non-axisymmetric perturbation and drive toroidally symmetric current. Newer designs for larger SIHI-driven spheromaks incorporate a set of injectors connected to a single external manifold to allow more freedom for the toroidal structure of the applied perturbation. Simulations have been carried out using the NIMROD code to assess the effectiveness of various imposed mode structures and injector schema in driving current via Imposed Dynamo Current Drive (IDCD). The results are presented here for varying flux conserver shapes on a device approximately 1.5 times larger than the current HIT-SI3 experiment. The imposed mode structures and spectra of simulated spheromaks are analyzed in order to examine magnetic structure and stability and determine an optimal regime for IDCD sustainment in a large device. The development of scaling laws for manifold operation is also presented, and simulation results are analyzed and assessed as part of the development path for the large scale device.

Control source development for reduction of noise transmitted through a double panel structure

OpenAIRE

Ho, J.

2014-01-01

A double panel structure, which consists of two panels with air in between, is widely adopted in many applications such as aerospace, automotive industries, and buildings due to its low sound transmission at high frequencies, low heat transmission, and low weight. Nevertheless, the resonance of the cavity and the poor sound transmission loss at low frequencies limit the double panel’s noise control performance. Applying active structural acoustic control to the panels or active noise control ...

Distributed temperature sensors development using an stepped-helical ultrasonic waveguide

Science.gov (United States)

Periyannan, Suresh; Rajagopal, Prabhu; Balasubramaniam, Krishnan

2018-04-01

This paper presents the design and development of the distributed ultrasonic waveguide temperature sensors using some stepped-helical structures. Distributed sensing has several applications in various industries (oil, glass, steel) for measurement of physical parameters such as level, temperature, viscosity, etc. This waveguide incorporates a special notch or bend for obtaining ultrasonic wave reflections from the desired locations (Gage-lengths) where local measurements are desired. In this paper, a multi-location measurement wave-guide, with a measurement capability of 18 locations in a single wire, has been fabricated. The distribution of these sensors is both in the axial as well as radial directions using a stepped-helical spring configuration. Also, different high temperature materials have been chosen for the wave-guide. Both lower order axi-symmetric guided ultrasonic modes (L(0,1) and T(0,1)) were employed. These wave modes were generated/received (pulse-echo approach) using conventional longitudinal and shear transducers, respectively. Also, both the wave modes were simultaneously generated/received and compared using shear transducer for developing the distributed helical wave-guide sensors. The effect of dispersion of the wave modes due to curvature effects will also be discussed.

Clinical application of helical CT colonography

International Nuclear Information System (INIS)

Zeng Huiliang; Zhu Xinjin; Liang Rujian; Liang Jianhao; Ou Weiqian; Wen Haomao

2009-01-01

Objective: To investigate the clinical value of 16-slice helical CT colonography in the diagnosis of colon tumor and polypus. Methods: 16-slice helical CT volumetric scanning was performed in 18 patients with colonic disease, including colonic tumor (n=16) and colonic polypus (n=2). 3D images, virtual endoscopy and multiplanar reformation were obtained in the AW4.1 workstation. CT appearances were compared with operation and fiberoptic colonoscopy. Results: Satisfied results were achieved from 18 patients, no difference found in results between CT colonography and operation in 16 patients with colonic tumor. Conclusion: 16-slice helical CT colonography is of great value in preoperative staging of colonic tumor and have a high value in clinical application. (authors)

Neutrino's helicity in a gravitational field

International Nuclear Information System (INIS)

Pansart, J.P.

1996-01-01

By using approximated solutions of Dirac's equation, we show that there is no helicity reversal for light neutrinos in the Schwarzschild metric nor in an expanding universe. The actual coupling between a particle spin and the angular momentum of a heavy rotating body induces a possible helicity reversal but with an unobservable probability proportional to m 2 p / E 2 , where m p is the particle mass and E its energy. In these calculations, the helicity is defined through the spin orientation with respect to the current and not with respect to the linear momentum. This definition gives simple expressions and is equal to the usual definition in the case of a flat space. (N.T.)

Functional and structural outcomes of single-row versus double-row versus combined double-row and suture-bridge repair for rotator cuff tears.

Science.gov (United States)

Mihata, Teruhisa; Watanabe, Chisato; Fukunishi, Kunimoto; Ohue, Mutsumi; Tsujimura, Tomoyuki; Fujiwara, Kenta; Kinoshita, Mitsuo

2011-10-01

Although previous biomechanical research has demonstrated the superiority of the suture-bridge rotator cuff repair over double-row repair from a mechanical point of view, no articles have described the structural and functional outcomes of this type of procedure. The structural and functional outcomes after arthroscopic rotator cuff repair may be different between the single-row, double-row, and combined double-row and suture-bridge (compression double-row) techniques. Cohort study; Level of evidence, 3. There were 206 shoulders in 201 patients with full-thickness rotator cuff tears that underwent arthroscopic rotator cuff repair. Eleven patients were lost to follow-up. Sixty-five shoulders were repaired using the single-row, 23 shoulders using the double-row, and 107 shoulders using the compression double-row techniques. Clinical outcomes were evaluated at an average of 38.5 months (range, 24-74 months) after rotator cuff repair. Postoperative cuff integrity was determined using Sugaya's classification of magnetic resonance imaging (MRI). The retear rates after arthroscopic rotator cuff repair were 10.8%, 26.1%, and 4.7%, respectively, for the single-row, double-row, and compression double-row techniques. In the subcategory of large and massive rotator cuff tears, the retear rate in the compression double-row group (3 of 40 shoulders, 7.5%) was significantly less than those in the single-row group (5 of 8 shoulders, 62.5%, P row group (5 of 12 shoulders, 41.7%, P row and suture-bridge techniques, which had the lowest rate of postoperative retear, is an effective option for arthroscopic repair of the rotator cuff tendons because the postoperative functional outcome in patients with a retear is inferior to that without retear.

Introduction to the m = 1 helicity source

International Nuclear Information System (INIS)

Platts, D.A.; Jarboe, T.R.; Wright, B.L.

1985-01-01

The m = 1 Helicity Source, formerly called the Kinked Z-pinch, was developed as part of the Electrode Studies program at Los Alamos. The Electrode Studies program was initiated to study the control of electrode erosion in long discharge duration spheromak sources. Erosion control is necessary to reduce plasma impurities and to obtain adequate electrode lifetimes. The first task of the Electrode Studies program is to determine, from among a variety of configurations including the coaxial one, a helicity source geometry with good prospects for erosion control. The more efficient the helicity source the easier it will be to control erosion, but the source most also be easy to diagnose and modify if it is to be a useful test bed. The various erosion control techniques which have been proposed will require extensive experimentation to evaluate and optimize. Proposed techniques include, using refractory metals, profiling of the electrodes and magnetic fields, and various gas injection schemes including porous electrodes. It is considered necessary to do these experiments on an optimized helicity source so that the electrode geometries and plasma properties will be relevant. Therefore the present Electrode Studies program is aimed at developing an improved helicity source design

Magnetic Helicities and Dynamo Action in Magneto-rotational Turbulence

Energy Technology Data Exchange (ETDEWEB)

Bodo, G.; Rossi, P. [INAF/Osservatorio Astrofisico di Torino, Strada Osservatorio 20, I-10025 Pino Torinese (Italy); Cattaneo, F. [Department of Astronomy and Astrophysics, The University of Chicago, 5640 S. Ellis Avenue, Chicago IL 60637 (United States); Mignone, A., E-mail: bodo@oato.inaf.it [Dipartimento di Fisica, Università degli Studi di Torino, Via Pietro Giuria 1, 10125 Torino (Italy)

2017-07-10

We examine the relationship between magnetic flux generation, taken as an indicator of large-scale dynamo action, and magnetic helicity, computed as an integral over the dynamo volume, in a simple dynamo. We consider dynamo action driven by magneto-rotational turbulence (MRT) within the shearing-box approximation. We consider magnetically open boundary conditions that allow a flux of helicity in or out of the computational domain. We circumvent the problem of the lack of gauge invariance in open domains by choosing a particular gauge—the winding gauge—that provides a natural interpretation in terms of the average winding number of pairwise field lines. We use this gauge precisely to define and measure the helicity and the helicity flux for several realizations of dynamo action. We find in these cases that the system as a whole does not break reflectional symmetry and that the total helicity remains small even in cases when substantial magnetic flux is generated. We find no particular connection between the generation of magnetic flux and the helicity or the helicity flux through the boundaries. We suggest that this result may be due to the essentially nonlinear nature of the dynamo processes in MRT.

Role of α-Helical Structure in Organic Solvent-Activated Homodimer of Elastase Strain K

Directory of Open Access Journals (Sweden)

Chee Fah Wong

2011-09-01

Full Text Available Recombinant elastase strain K overexpressed from E. coli KRX/pCon2(3 was purified to homogeneity by a combination of hydrophobic interaction chromatography and ion exchange chromatography, with a final yield of 48% and a 25-fold increase in specific activity. The purified protein had exhibited a first ever reported homodimer size of 65 kDa by SDS-PAGE and MALDI-TOF, a size which is totally distinct from that of typically reported 33 kDa monomer from P. aeruginosa. The organic solvent stability experiment had demonstrated a stability pattern which completely opposed the rules laid out in previous reports in which activity stability and enhancement were observed in hydrophilic organic solvents such as DMSO, methanol, ethanol and 1-propanol. The high stability and enhancement of the enzyme in hydrophilic solvents were explained from the view of alteration in secondary structures. Elastinolytic activation and stability were observed in 25 and 50% of methanol, respectively, despite slight reduction in α-helical structure caused upon the addition of the solvent. Further characterization experiments had postulated great stability and enhancement of elastase strain K in broad range of temperatures, pHs, metal ions, surfactants, denaturing agents and substrate specificity, indicating its potential application in detergent formulation.

Helicity amplitudes for matter-coupled gravity

International Nuclear Information System (INIS)

Aldrovandi, R.; Novaes, S.F.; Spehler, D.

1992-07-01

The Weyl-van der Waerden spinor formalism is applied to the evaluation of helicity invariant amplitudes in the framework of linearized gravitation. The graviton couplings to spin-0, 1 - 2 , 1, and 3 - 2 particles are given, and, to exhibit the reach of this method, the helicity amplitudes for the process electron + positron → photon + graviton are obtained. (author)

Alloy Dependence of Electron-Phonon Interactions in Double Barrier Structures

National Research Council Canada - National Science Library

Wallis, Corinne

1996-01-01

...)As double barrier structures as a function of the alloy concentration in the barrier. We have measured current-voltage and conductance-voltage curves associated with phonon-assisted tunneling with magnetic fields from 0 to 6.8 Tesla...

Assembly of Huntingtin headpiece into α-helical bundles.

Science.gov (United States)

Ozgur, Beytullah; Sayar, Mehmet

2017-05-24

Protein aggregation is a hallmark of neurodegenerative disorders. In this group of brain-related disorders, a disease-specific "host" protein or fragment misfolds and adopts a metastatic, aggregate-prone conformation. Often, this misfolded conformation is structurally and thermodynamically different from its native state. Intermolecular contacts, which arise in this non-native state, promote aggregation. In this regard, understanding the molecular principles and mechanisms that lead to the formation of such a non-native state and further promote the formation of the critical nucleus for fiber growth is essential. In this study, the authors analyze the aggregation propensity of Huntingtin headpiece (htt NT ), which is known to facilitate the polyQ aggregation, in relation to the helix mediated aggregation mechanism proposed by the Wetzel group. The authors demonstrate that even though htt NT displays a degenerate conformational spectrum on its own, interfaces of macroscopic or molecular origin can promote the α-helix conformation, eliminating all other alternatives in the conformational phase space. Our findings indicate that htt NT molecules do not have a strong orientational preference for parallel or antiparallel orientation of the helices within the aggregate. However, a parallel packed bundle of helices would support the idea of increased polyglutamine concentration, to pave the way for cross-β structures.

Progressive and resonant wave helices application to electron paramagnetic resonance; Helices a ondes progressives et resonnantes application a la resonance paramagnetique electronique

Energy Technology Data Exchange (ETDEWEB)

Volino, F [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1969-07-01

We show that helices can be used as resonant systems. Their properties are theoretically and experimentally studied. We describe resonant helices for electron paramagnetic resonance in X-band and develop a comparison between their sensitivity and the sensitivity of a normal resonant cavity. For cylindrical samples less than 3 mm diameter, the helix is more sensitive and can produce more intense microwave magnetic fields. (author) [French] Il est montre que les helices peuvent etre utilisees comme systeme resonnant. Leurs proprietes sont discutees theoriquement et experimentalement. Des helices resonnantes en bande X pour la resonance paramagnetique electronique sont decrites et leur sensibilite est comparee a celle des cavites resonnantes. Pour des echantillons cylindriques de moins de 3 mm de diametre, l'helice est plus sensible et peut produire des champs magnetiques hyper fins plus intenses. (auteur)

Highlights from the assembly of the helical field coils for the Advanced Toroidal Facility

International Nuclear Information System (INIS)

Benson, R.D.

1985-01-01

The helical field (HF) coils in the Advanced Toroidal Facility (ATF) device consist of a set of 24 identical segments connected to form a continuous pair of helical coils wrapped around a toroidal vacuum vessel. Each segment weighs approximately 1364 kg (3000 lb) and is composed of 14 water-cooled copper plate conductors bolted to a cast stainless steel structural support member with a T-shape cross section (known as the structural tee). The segment components are electrically insulated with Kapton adhesive tape, G-10, Tefzel, and rubber to withstand 2.5 kV. As a final insulator and structural support, the entire segment is vacuum impregnated with epoxy. This paper offers a brief overview of the processes used to assemble the component parts into a completed segment, including identification of items that required special attention. 4 figs

Comparisons between various cavity and panel noise reduction control in double-panel structures

NARCIS (Netherlands)

Ho, J.H.; Kalverboer, J.; Berkhoff, A.P.

2012-01-01

This paper presents comparisons between various panel and cavity resonance control methods to reduce the transmitted sound in a double-panel structure. The double-panel, which consists of two panels with air in the gap, has the advantages of low weight and effective transmission-loss at high

Nuclear fuel assembly incorporating primary and secondary structural support members

International Nuclear Information System (INIS)

Carlson, W.R.; Gjertsen, R.K.; Miller, J.V.

1987-01-01

A nuclear fuel assembly, comprising: (a) an upper end structure; (b) a lower end structure; (c) elongated primary structural members extending longitudinally between and rigidly interconnecting the upper and lower end structures, the upper and lower end structures and primary structural members together forming a rigid structural skeleton of the fuel assembly; (d) transverse grids supported on the primary structural members at axially spaced locations therealong between the upper and lower end structures; (e) fuel rods extending through and supported by the grids between the upper and lower end structures so as to extend in generally side-by-side spaced relation to one another and to the primary structural members; and (f) elongated secondary structural members extending longitudinally between but unconnected with the upper and lower end structures, the secondary structural members extending through and rigidly interconnected with the grids to extend in generally side-by-side spaced relation to one another, to the fuel rods and to the primary structural members so as to bolster the stiffness of the structural skeleton of the fuel assembly

Magnetic properties of the Ce2Fe17-x Mn x helical magnets up to high magnetic fields

International Nuclear Information System (INIS)

Kuchin, A.G.; Mushnikov, N.V.; Bartashevich, M.I.; Prokhnenko, O.; Khrabrov, V.I.; Lapina, T.P.

2007-01-01

Magnetic properties of the Ce 2 Fe 17- x Mn x , x=0-2, alloys in magnetic fields up to 40 T are reported. The compounds with x=0.5-1 are helical antiferromagnets and those with 1 B that couple antiparallelly to the Fe moments. Easy-plane magnetic anisotropy in the Ce 2 Fe 17- x Mn x compounds weakens upon substitution of Mn for Fe. The absolute value of the first anisotropy constant in the Ce 2 Fe 17- x Mn x helical ferromagnets decreases slower with increasing temperature than that calculated from the third power of the spontaneous magnetization. Noticeable magnetic hysteresis in the Ce 2 Fe 17- x Mn x , x=0.5-2, helical magnets over the whole range of magnetic fields reflects mainly irreversible deformation of the helical magnetic structure during the magnetization of the compounds. A contribution from short-range order (SRO) magnetic clusters to the magnetic hysteresis of the helical magnets has been also estimated

Particle orbit analysis for LHD helical axis configurations

International Nuclear Information System (INIS)

Guasp, J.; Yamazaki, K.; Motojima, O.

1993-04-01

Fast ion orbits for helical magnetic axis configurations in LHD (Large Helical Device) are analyzed and compared with the standard circular axis case. Boundaries between passing and helically trapped particle regions show clear differences: in the non-planar axis case the helically trapped region spreads, near the magnetic axis, over a much wider band across the 90deg pitch angle value and shows a very marked asymmetry. The locally trapped particle region is also wider than in the standard case. The differences in the loss cone boundaries of the two cases are rather small, however, the effects of re-entering criteria are very important in both cases. On the contrary, effects of finite coil size are not significant. (author)

Helically linked mirror arrangement

International Nuclear Information System (INIS)

Ranjan, P.

1986-08-01

A scheme is described for helical linking of mirror sections, which endeavors to combine the better features of toroidal and mirror devices by eliminating the longitudinal loss of mirror machines, having moderately high average β and steady state operation. This scheme is aimed at a device, with closed magnetic surfaces having rotational transform for equilibrium, one or more axisymmetric straight sections for reduced radial loss, a simple geometrical axis for the links and an overall positive magnetic well depth for stability. We start by describing several other attempts at linking of mirror sections, made both in the past and the present. Then a description of our helically linked mirror scheme is given. This example has three identical straight sections connected by three sections having helical geometric axes. A theoretical analysis of the magnetic field and single-particle orbits in them leads to the conclusion that most of the passing particles would be confined in the device and they would have orbits independent of pitch angle under certain conditions. Numerical results are presented, which agree well with the theoretical results as far as passing particle orbits are concerned

Helicity and evanescent waves. [Energy transport velocity, helicity, Lorentz transformation

Energy Technology Data Exchange (ETDEWEB)

Agudin, J L; Platzeck, A M [La Plata Univ. Nacional (Argentina); Albano, J R [Instituto de Astronomia y Fisica del Espacio, Buenos Aires, Argentina

1978-02-20

It is shown that the projection of the angular momentum of a circularly polarized electromagnetic evanescent wave along the mean velocity of energy transport (=helicity) can be reverted by a Lorentz transformation, in spite of the fact that this velocity is c.

Magnetic islands created by resonant helical windings

International Nuclear Information System (INIS)

Fernandes, A.S.; Heller, M.V.; Caldas, I.L.

1986-01-01

The triggering of disruptive instabilities by resonant helical windings in large aspect-ratio tokamaks is associated to destruction of magnetic surfaces. The Chirikov condition is applied to estimate analytically the helical winding current thresholds for ergodization of the magnetic field lines. (Autor) [pt

Structure of the acidianus filamentous virus 3 and comparative genomics of related archaeal lipothrixviruses

DEFF Research Database (Denmark)

Vestergaard, Gisle Alberg; Aramayo, Ricardo; Basta, Tamara

2008-01-01

Four novel filamentous viruses with double-stranded DNA genomes, namely, Acidianus filamentous virus 3 (AFV3), AFV6, AFV7, and AFV8, have been characterized from the hyperthermophilic archaeal genus Acidianus, and they are assigned to the Betalipothrixvirus genus of the family Lipothrixviridae....... The structures of the approximately 2-mum-long virions are similar, and one of them, AFV3, was studied in detail. It consists of a cylindrical envelope containing globular subunits arranged in a helical formation that is unique for any known double-stranded DNA virus. The envelope is 3.1 nm thick and encases...... structural proteins; (iii) multiple overlapping open reading frames, which may be indicative of gene recoding; (iv) putative 12-bp genetic elements; and (v) partial gene sequences corresponding closely to spacer sequences of chromosomal repeat clusters....

Progressive and resonant wave helices application to electron paramagnetic resonance; Helices a ondes progressives et resonnantes application a la resonance paramagnetique electronique

Energy Technology Data Exchange (ETDEWEB)

Volino, F. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1969-07-01

We show that helices can be used as resonant systems. Their properties are theoretically and experimentally studied. We describe resonant helices for electron paramagnetic resonance in X-band and develop a comparison between their sensitivity and the sensitivity of a normal resonant cavity. For cylindrical samples less than 3 mm diameter, the helix is more sensitive and can produce more intense microwave magnetic fields. (author) [French] Il est montre que les helices peuvent etre utilisees comme systeme resonnant. Leurs proprietes sont discutees theoriquement et experimentalement. Des helices resonnantes en bande X pour la resonance paramagnetique electronique sont decrites et leur sensibilite est comparee a celle des cavites resonnantes. Pour des echantillons cylindriques de moins de 3 mm de diametre, l'helice est plus sensible et peut produire des champs magnetiques hyper fins plus intenses. (auteur)

Superposition of helical beams by using a Michelson interferometer.

Science.gov (United States)