Anomalous centrality evolution of two-particle angular correlations from Au-Au collisions at root s(NN)=62 and 200 GeV

We present two-dimensional (2D) two-particle angular correlations measured with the STAR detector on relative pseudorapidity eta and azimuth phi for charged particles from Au-Au collisions at root s(NN) = 62 and 200 GeV with transverse momentum p(t) >= 0.15 GeV/c, vertical bar eta vertical bar <= 1, and 2 pi in azimuth. Observed correlations include a same-side (relative azimuth <pi/2) 2D peak, a closely related away-side azimuth dipole, and an azimuth quadrupole conventionally associated with elliptic flow. The same-side 2D peak and away-side dipole are explained by semihard parton scattering and fragmentation (minijets) in proton-proton and peripheral nucleus-nucleus collisions. Those structures follow N-N binary-collision scaling in Au-Au collisions until midcentrality, where a transition to a qualitatively different centrality trend occurs within one 10% centrality bin. Above the transition point the number of same-side and away-side correlated pairs increases rapidly relative to binary-collision scaling, the eta width of the same-side 2D peak also increases rapidly (eta elongation), and the phi width actually decreases significantly. Those centrality trends are in marked contrast with conventional expectations for jet quenching in a dense medium. The observed centrality trends are compared to perturbative QCD predictions computed in HIJING, which serve as a theoretical baseline, and to the expected trends for semihard parton scattering and fragmentation in a thermalized opaque medium predicted by theoretical calculations and phenomenological models. We are unable to reconcile a semihard parton scattering and fragmentation origin for the observed correlation structure and centrality trends with heavy-ion collision scenarios that invoke rapid parton thermalization. If the collision system turns out to be effectively opaque to few-GeV partons the present observations would be inconsistent with the minijet picture discussed here. DOI: 10.1103/PhysRevC.86.064902

Detection of glucose and triglycerides using information visualization methods to process impedance spectroscopy data

In this paper we discuss the detection of glucose and triglycerides using information visualization methods to process impedance spectroscopy data. The sensing units contained either lipase or glucose oxidase immobilized in layer-by-layer (LbL) films deposited onto interdigitated electrodes. The optimization consisted in identifying which part of the electrical response and combination of sensing units yielded the best distinguishing ability. It is shown that complete separation can be obtained for a range of concentrations of glucose and triglyceride when the interactive document map (IDMAP) technique is used to project the data into a two-dimensional plot. Most importantly, the optimization procedure can be extended to other types of biosensors, thus increasing the versatility of analysis provided by tailored molecular architectures exploited with various detection principles. (C) 2012 Elsevier B.V. All rights reserved.

Structural and Interaction Studies of Bacterial Polysaccharides by NMR Spectroscopy

An introduction to bacterial polysaccharides and the methods for structural determination are described in the first two parts of the thesis. In a structural elucidation of bacterial polysaccharides NMR experiments are important as is component analysis. A short description of immunochemical methods such as enzyme immunoassays is included. Two NMR techniques used for interaction studies, trNOE and STD NMR, are also discussed. The third part of the thesis discusses and summarizes the results from the included papers. The structures of the exopolysaccharides produced by two lactic acid bacteria are determined by one- and two dimensional NMR experiments. One is a heteropolysaccharide produced by Streptococcus thermophilus and the other a homopolysaccharide produced by Propionibacterium freudenreichii. The structure of an acidic polysaccharide from a marine bacterium with two serine residues in the repeating unit is also investigated. The structural and immunological relationship between two O-antigenic polysaccharides from Escherichia coli strain 180/C3 and O5 is discussed and investigated. Finally, interaction studies of an octasaccharide derived from the Salmonella enteritidis O-antigen and a bacteriophage are described which were performed with NMR experiments.

Heteronuclear recoupling methods in solid-state NMR

This thesis is focused on the development of heteronuclear correlation methods in solid-state NMR spectroscopy, where the spatial dependence of the dipolar coupling is exploited to obtain structural and dynamical information in solids. Quantitative results on dipolar coupling constants are extracted by means of spinning sideband analysis in the indirect dimension of the two-dimensional experiments. The principles of sideband analysis were established and are currently widely used in the group of Prof. Spiess for the special case of homonuclear 1H double-quantum spectroscopy. The generalization of these principles to the heteronuclear case is presented, with special emphasis on naturally abundant 13C-1H systems. For proton spectroscopy in the solid state, line-narrowing is of particular importance, and is here achieved by very-fast sample rotation at the magic angle (MAS), with frequencies up to 35 kHz. Therefore, the heteronuclear dipolar couplings are suppressed and have to be recoupled in order to achieve an efficient excitation of the observed multiple-quantum modes. Heteronuclear recoupling is most straightforwardly accomplished by performing the known REDOR experiment, where pi-pulses are applied every half rotor period. This experiment was modified by the insertion of an additional spectroscopic dimension, such that heteronuclear multiple-quantum experiments can be carried out, which, as shown experimentally and theoretically, closely resemble homonuclear double-quantum experiments. Variants are presented which are well-suited for the recording of high-resolution 13C-1H shift correlation and spinning-sideband spectra, by means of which spatial proximities and quantitative dipolar coupling constants, respectively, of heteronuclear spin pairs can be determined. Spectral editing of 13C spectra is shown to be feasible with these techniques. Moreover, order phenomena and dynamics in columnar mesophases with 13C in natural abundance were investigated. Two further modifications of the REDOR concept allow the correlation of 13C with quadrupolar nuclei, such as 2H. The spectroscopic handling of these nuclei is challenging in that they cover large frequency ranges, and with the new experiments it is shown how the excitation problem can be tackled or circumvented altogether, respectively. As an example, one of the techniques is used for the identification of a yet unknown motional process of the H-bonded protons in the crystalline parts of poly(vinyl alcohol).

Untersuchung magnetischer Nanostrukturen mittels Rastertunnelspektroskopie und Kerr-Magnetometrie am Beispiel von Fe, Co, Co-Fe und Fe-Mn Nanostrukturen

Nach einer kurzen Einführung in die Entwicklung der magnetischen Anwendungen, werden in Kapitel 2 und 3 die physikalischen Grundlagen der Messmethoden, insbesondere die Rastertunnelspektroskopie und Kerr-Magnetometrie, sowie der experimentelle Aufbau erläutert. Kapitel 4 beschäftigt sich mit den magnetischen Eigenschaften von quasi ein-dimensionalen ferromagnetischen Nanostreifen und Monolagen, die durch Selbstorganisation auf einem Wolfram(110)-Einkristall mit vizinaler und glatter Oberfläche präpariert werden. Hierbei wird die Temperaturabhängigkeit der magnetischen Größen, wie Remanenz, Sättigungsmagnetisierung und Suszeptibilität, sowie die Auswirkung einer Abdeckung des Systems auf die Domänenwandenergie und Anisotropie untersucht. Zusätzlich wird die Kopplung von parallelen Nanostreifen in Abhängigkeit des Streifenabstandes betrachtet. In Kapitel 5 werden das Wachstum und die Morphologie von Co-Monolagen auf W(110) untersucht. Der Übergang von pseudomorphem zu dicht gepacktem Wachstum in der Monolage wird mit Hilfe der Rastertunnelspektroskopie sichtbar gemacht, ebenso wie unterschiedliche Stapelfolgen in Tripellagen Co-Systemen. Atomar aufgelöste Rastertunnelmikroskopie erlaubt die genauen Atompositionen der Oberfläche zu bestimmen und mit theoretischen Wachstumsmodellen zu vergleichen. Auf die Untersuchung zwei-dimensionaler binärer Co-Fe und Fe-Mn Legierungen auf W(110) wird in Kapitel 6 eingegangen. Mit einer Präparationstemperatur von T=520 K ist es möglich, atomar geordnete Co-Fe Legierungsmonolagen wachsen zu lassen. Ein direkter Zusammenhang zwischen der Magnetisierung und der lokalen Zustandsdichte in Abhängigkeit der Legierungszusammensetzung wird gezeigt.

Surface plasmon fluorescence spectroscopy and microscopy studies for biomolecular interaction studies

ABSTARCT Biotechnology has enabled the modification of agricultural materials in a very precise way. Crops have been modified through the insertion of new traits or the inhibition of existing gene functions, named Genetically Modified Organism (GMO), and resulted in improved tolerance of herbicide and/or increased resistance against pests, viruses and fungi. Commercial cultivation of GMO started in 1996 and increased rapidly in 2003 according to a recently released report by the International Service for the Acquisition of Agri-Biotech Applications (ISAAA), depicted continuing consumer resistance in Europe and other part of the world. Upon these developments, the European Union regulations mandated labeling of GMOs containing food and as a consequence, the labeling of GMO containing product in the case of exceeding the1% threshold of alien DNA is required. The aim of the study is to be able to detect and quantify the GMO from the mixture of natural food components. The surface plasmon resonance (SPR) technique combined with fluorescence was used for this purpose. During the presented studies, two key issues are addressed and tried to solve; what is the best strategy to design and built an interfacial architecture of a probe oligonucletide layer either on a two dimensional surface or on an array platform; and what is the best detection method allowing for a sensitive monitoring of the hybridisation events. The study includes two parts: first part includes characterization of different PNAs on a 2D planar surface by defining affinity constants using the very well established optical method “Surface Plasmon Fluorescence Spectroscopy”(SPFS) and on the array platform by “Surface Plasmon Fluorescence Microscopy” (SPFM), and at the end comparison of the sensitivity of these two techniques. The second part is composed of detection of alien DNA in food components by using DNA and PNA catcher probes on the array platform in real-time by SPFM.

Nanoporous alumina based hypersonic phononic hybrid structures studied by brillouin spectroscopy

Phononische Kristalle sind strukturierte Materialien mit sich periodisch ändernden elastischen Moduln auf der Wellenlängenskala. Die Interaktion zwischen Schallwellen und periodischer Struktur erzeugt interessante Interferenzphänomene, und phononische Kristalle erschließen neue Funktionalitäten, die in unstrukturierter Materie unzugänglich sind. Hypersonische phononische Kristalle im Speziellen, die bei GHz Frequenzen arbeiten, haben Periodizitäten in der Größenordnung der Wellenlänge sichtbaren Lichts und zeigen daher die Wege auf, gleichzeitig Licht- und Schallausbreitung und -lokalisation zu kontrollieren, und dadurch die Realisierung neuartiger akusto-optischer Anordnungen. Bisher bekannte hypersonische phononische Kristalle basieren auf thermoplastischen Polymeren oder Epoxiden und haben nur eingeschränkte thermische und mechanische Stabilität und mechanischen Kontrast. Phononische Kristalle, die aus mit Flüssigkeit gefüllten zylindrischen Kanälen in harter Matrix bestehen, zeigen einen sehr hohen elastischen Kontrast und sind bislang noch unerforscht. In dieser Dissertation wird die experimentelle Untersuchung zweidimensionaler hypersonischer phononischer Kristalle mit hexagonaler Anordnung zylindrischer Nanoporen basierend auf der Selbstorganisation anodischen Aluminiumoxids (AAO) beschrieben. Dazu wird die Technik der hochauflösenden inelastischen Brillouin Lichtstreuung (BLS) verwendet. AAO ist ein vielsetiges Modellsystem für die Untersuchung reicher phononischer Phänomene im GHz-Bereich, die eng mit den sich in den Nanoporen befindlichen Flüssigkeiten und deren Interaktion mit der Porenwand verknüpft sind. Gerichteter Fluss elastischer Energie parallel und orthogonal zu der Kanalachse, Lokalisierung von Phononen und Beeinflussung der phononischen Bandstruktur bei gleichzeitig präziser Kontrolle des Volumenbruchs der Kanäle (Porosität) werden erörtert. Außerdem ermöglicht die thermische Stabilität von AAO ein temperaturabhängiges Schalten phononischer Eigenschaften infolge temperaturinduzierter Phasenübergänge in den Nanoporen. In monokristallinen zweidimensionalen phononischen AAO Kristallen unterscheiden sich die Dispersionsrelationen empfindlich entlang zweier hoch symmetrischer Richtungen in der Brillouinzone, abhängig davon, ob die Poren leer oder gefüllt sind. Alle experimentellen Dispersionsrelationen werden unter Zuhilfenahme theoretische Ergebnisse durch finite Elemente Analyse (FDTD) gedeutet. Die Zuordnung der Verschiebungsfelder der elastischen Wellen erklärt die Natur aller phononischen Moden.

Fluctuation spectroscopy of single plasmonic nanostructures

Plasmonic nanoparticles are great candidates for sensing applications with optical read-out. Plasmon sensing is based on the interaction of the nanoparticle with electromagnetic waves where the particle scatters light at its resonance wavelength. This wavelength depends on several intrinsic factors like material, shape and size of the nanoparticle as well as extrinsic factors like the refractive index of the surrounding medium. The latter allows the nanoparticle to be used as a sensor; changes in the proximate environment can be directly monitored by the wavelength of the emitted light. Due to their minuscule size and high sensitivity this allows individual nanoparticles to report on changes in particle coverage.rnrnTo use this single particle plasmon sensor for future sensing applications it has to meet the demand for detection of incidents on the single molecule level, such as single molecule sensing or even the detection of conformational changes of a single molecule. Therefore, time resolution and sensitivity have to be enhanced as today’s measurement methods for signal read-out are too slow and not sensitive enough to resolve these processes. This thesis presents a new experimental setup, the 'Plasmon Fluctuation Setup', that leads to tremendous improvements in time resolution and sensitivity. This is achieved by implementation of a stronger light source and a more sensitive detector. The new setup has a time resolution in the microsecond regime, an advancement of 4-6 orders of magnitude to previous setups. Its resonance wavelength stability of 0.03 nm, measured with an exposure time of 10 ms, is an improvement of a factor of 20 even though the exposure time is 3000 times shorter than in previous reports. Thus, previously unresolvable wavelength changes of the plasmon sensor induced by minor local environmental alteration can be monitored with extremely high temporal resolution.rnrnUsing the 'Plasmon Fluctuation Setup', I can resolve adsorption events of single unlabeled proteins on an individual nanorod. Additionally, I monitored the dynamic evolution of a single protein binding event on a millisecond time scale. This feasibility is of high interest as the role of certain domains in the protein can be probed by a study of modified analytes without the need for labels possibly introducing conformational or characteristic changes to the target. The technique also resolves equilibrium fluctuations in the coverage, opening a window into observing Brownian dynamics of unlabeled macromolecules. rnrnA further topic addressed in this thesis is the usability of the nanoruler, two nanospheres connected with a spacer molecule, as a stiffness sensor for the interparticle linker under strong illumination. Here, I discover a light induced collapse of the nanoruler. Furthermore, I exploit the sensing volume of a fixed nanorod to study unlabeled analytes diffusing around the nanorod at concentrations that are too high for fluorescence correlation spectroscopy but realistic for biological systems. Additionally, local pH sensing with nanoparticles is achieved.

High-resolution three-dimensional 3 T magnetic resonance angiography for the evaluation of experimental aneurysm in the rabbit

OBJECTIVE: The standard technique of two-dimensional intra-arterial digital subtraction angiography (2D-DSA) for the imaging of experimental rabbit aneurysms is invasive and has considerable surgical risks. Therefore, minimally invasive techniques ideally providing three-dimensional imaging for intervention planning and follow-up are needed. This study evaluates the feasibility and quality of three-dimensional 3-T magnetic resonance angiography (3D-3T-MRA) and compares 3D-3T-MRA with 2D-DSA in experimental aneurysms in the rabbit. METHOD: Three microsurgically created aneurysms in three rabbits were evaluated using 2D-DSA and 3D-3T-MRA. Imaging of the aneurysms was performed 2 weeks after creation using 2D-DSA and contrast-enhanced (CE) MRA. Measurements included aneurysm dome (length and width) and aneurysm neck. Aneurysm volumes were determined using CE-MRA. RESULTS: The measurements of the aneurysms' dimensions and the evaluation of vicinity vessels with both techniques showed a good correlation. The mean aneurysm length, aneurysm width and neck width measured with DSA (6.9, 4.1 and 2.8 mm, respectively) correlated with the measurements performed in 3D-3T-MRA (6.9, 4 and 2.5 mm, respectively). The mean aneurysm volumes measured with CE-MRA was 46.7 mm(3). CONCLUSION: 3D-3T CE-MRA is feasible and less invasive and is a safer imaging alternative to DSA for experimental aneurysm. Additionally, aneurysm technique this precise offers the possibility of repetitive 3D aneurysm volumetry for long-term follow-up studies after endovascular aneurysm occlusion.

On the use of Cramér-Rao minimum variance bounds for the design of magnetic resonance spectroscopy experiments

Localized Magnetic Resonance Spectroscopy (MRS) is in widespread use for clinical brain research. Standard acquisition sequences to obtain one-dimensional spectra suffer from substantial overlap of spectral contributions from many metabolites. Therefore, specially tuned editing sequences or two-dimensional acquisition schemes are applied to extend the information content. Tuning specific acquisition parameters allows to make the sequences more efficient or more specific for certain target metabolites. Cramér-Rao bounds have been used in other fields for optimization of experiments and are now shown to be very useful as design criteria for localized MRS sequence optimization. The principle is illustrated for one- and two-dimensional MRS, in particular the 2D separation experiment, where the usual restriction to equidistant echo time spacings and equal acquisition times per echo time can be abolished. Particular emphasis is placed on optimizing experiments for quantification of GABA and glutamate. The basic principles are verified by Monte Carlo simulations and in vivo for repeated acquisitions of generalized two-dimensional separation brain spectra obtained from healthy subjects and expanded by bootstrapping for better definition of the quantification uncertainties.

Oxygen isotopes from two snow trenches from Kohnen Station, Dronning Maud Land, Antarctica from the 2012/13 field season

In low-accumulation regions, the reliability of d18O-derived temperature signals from ice cores within the Holocene is unclear, primarily due to the small climate changes relative to the intrinsic noise of the isotopic signal. In order to learn about the representativity of single ice cores and to optimise future ice-core-based climate reconstructions, we studied the stable-water isotope composition of firn at Kohnen station, Dronning Maud Land, Antarctica. Analysing d18O in two 50 m long snow trenches allowed us to create an unprecedented, two-dimensional image characterising the isotopic variations from the centimetre to the hundred-metre scale. This data set includes the complete trench oxygen isotope record together with the meta data used in the study.

Comparative study about the use of two and three-dimensional methods in surface finishing characterization

The increasing number of works related to the surface texture characterization based on 3D information, makes convenient rethinking traditional methods based on two-dimensional measurements from profiles. This work compares results between measurements obtained using two and three-dimensional methods. It uses three kinds of data sources: reference surfaces, randomly generated surfaces and measured. Preliminary results are presented. These results must be completed trying to cover a wider number of possibilities according to the manufacturing process and the measurement instrumentation since results can vary quite significantly between them.

Attenuated T2 relaxation by mutual cancellation of dipole–dipole coupling and chemical shift anisotropy indicates an avenue to NMR structures of very large biological macromolecules in solution

Fast transverse relaxation of 1H, 15N, and 13C by dipole-dipole coupling (DD) and chemical shift anisotropy (CSA) modulated by rotational molecular motions has a dominant impact on the size limit for biomacromolecular structures that can be studied by NMR spectroscopy in solution. Transverse relaxation-optimized spectroscopy (TROSY) is an approach for suppression of transverse relaxation in multidimensional NMR experiments, which is based on constructive use of interference between DD coupling and CSA. For example, a TROSY-type two-dimensional 1H,15N-correlation experiment with a uniformly 15N-labeled protein in a DNA complex of molecular mass 17 kDa at a 1H frequency of 750 MHz showed that 15N relaxation during 15N chemical shift evolution and 1HN relaxation during signal acquisition both are significantly reduced by mutual compensation of the DD and CSA interactions. The reduction of the linewidths when compared with a conventional two-dimensional 1H,15N-correlation experiment was 60% and 40%, respectively, and the residual linewidths were 5 Hz for 15N and 15 Hz for 1HN at 4°C. Because the ratio of the DD and CSA relaxation rates is nearly independent of the molecular size, a similar percentagewise reduction of the overall transverse relaxation rates is expected for larger proteins. For a 15N-labeled protein of 150 kDa at 750 MHz and 20°C one predicts residual linewidths of 10 Hz for 15N and 45 Hz for 1HN, and for the corresponding uniformly 15N,2H-labeled protein the residual linewidths are predicted to be smaller than 5 Hz and 15 Hz, respectively. The TROSY principle should benefit a variety of multidimensional solution NMR experiments, especially with future use of yet somewhat higher polarizing magnetic fields than are presently available, and thus largely eliminate one of the key factors that limit work with larger molecules.

Detection of a Yb3+ binding site in regenerated bacteriorhodopsin that is coordinated with the protein and phospholipid head groups

Near infrared Yb3+ vibronic sideband spectroscopy was used to characterize specific lanthanide binding sites in bacteriorhodopsin (bR) and retinal free bacteriorhodopsin (bO). The VSB spectra for deionized bO regenerated with a ratio of 1:1 and 2:1 ion to bO are identical. Application of a two-dimensional anti-correlation technique suggests that only a single Yb3+ site is observed. The Yb3+ binding site in bO is observed to consist of PO2− groups and carboxylic acid groups, both of which are bound in a bidentate manner. An additional contribution most likely arising from a phenolic group is also observed. This implies that the ligands for the observed single binding site are the lipid head groups and amino acid residues. The vibronic sidebands of Yb3+ in deionized bR regenerated at a ratio of 2:1 ion to bR are essentially identical to those in bO. The other high-affinity binding site is thus either not evident or its fluorescence is quenched. A discussion is given on the difference in binding of Ca2+ (or Mg2+) and lanthanides in phospholipid membrane proteins.

Simultaneous two-photon excitation of distinct labels for dual-color fluorescence crosscorrelation analysis

Confocal fluorescence correlation spectroscopy as a time-averaging fluctuation analysis combining maximum sensitivity with high statistical confidence has proved to be a very versatile and powerful tool for detection and temporal investigation of biomolecules at ultralow concentrations on surfaces, in solutions, and in living cells. To probe the interaction of different molecular species for a detailed understanding of biologically relevant mechanisms, crosscorrelation studies on dual or multiple fluorophore assays with spectrally distinct excitation and emission are particularly promising. Despite the considerable improvement of detection specificity provided by fluorescence crosscorrelation analysis, few applications have so far been reported, presumably because of the practical challenges of properly aligning and controlling the stability of the experimental setup. In this work, we demonstrate that two-photon excitation combined with dual-color fluorescence correlation spectroscopy can be the key to simplifying simultaneous investigations of multiple fluorescent species significantly on a single-molecule scale. Two-photon excitation allows accession of common fluorophores of largely distinct emission by the same excitation wavelength, because differences in selection rules and vibronic coupling can induce considerable shifts between the one-photon and two-photon excitation spectra. The concept of dual-color two-photon fluorescence crosscorrelation analysis is introduced and experimentally demonstrated with an established assay probing the selective cleavage of dual-labeled DNA substrates by restriction endonuclease EcoRI.