North Atlantic multidecadal to centennial variability in a model and a marine proxy dataset

Variability on decadal and longer timescales is of great interest in climate research due to it’s socio-economic impacts, potential for predictability and masking of anthroprogenic global warming. Observational evidence of multidecadal variability in the North Atlantic exists in the sea surface temperature (SST), often referred to as the Atlantic Multidecadal Variability (AMV), and also in the atmosphere, for example seen in sea level pressure variations associated with the North Atlantic Os- cillation (NAO). Observational oceanic data on these timescales is mainly restricted to the surface, does not extend past the last 145 years and becomes quite sparsely sampled in the higher latitudes in the earlier years. Hence, to increase our understanding of climate variability on these timescales it is essential to turn to both proxy and model data. The first part of this thesis focuses on an annually-resolved proxy record (1818- 1967) of Mg/Ca variations from a North Pacific/ Bering Sea coralline alga. Not only does the algal Mg/Ca have a very strong connection to the local winter SST and a lagged relation to the Aleutian Low it also it has a correlation of -0.87 with the winter NAO and 0.60 with the AMV index on decadal timescales. The link can explain the coherence of decadal North Pacific and AMV, as suggested by earlier studies using climate models and in the limited observational data. The second part of the thesis focuses on the ocean general circulation model, NEMO to better understand AMV. For this purpose the model was forced only with the atmospheric patterns associated with the NAO, both from the observed NAO index and from a 2000 year long white NAO index. Focusing on key ocean circulation patterns, we show that the Atlantic Meridional Overturning Circula- tion (AMOC) and sub-polar gyre (SPG) strength have a red noise response but no dominant timescale, providing no evidence for a oscillatory ocean-only mode of variability. The time derivative of both the AMOC at 30◦N and SPG strength show a strong, almost linear relation to the NAO for timescales longer than 86 and 15 years, respectively. The different response characteristics are confirmed by constructing simple statistical models that show AMOC and SPG variability can be reconstructed by integrating the NAO index by the previous 53 and 10 winters, respectively. Alternatively, the AMOC and the SPG strength can be reconstructed with auto-regressive (AR) models of order seven and five, respectively. A closer look at the ocean model response of the 2000 year long ocean model integration shows three distinct timescales of variability. The first, an interannual timescale with variability shorter than 15 years, can be mainly related to Ekman dynamics. Secondly, the multidecadal timescale, 15-65 years, is mainly concentrated in the SPG and is controlled by temperature variability. Finally, the centennial timescales, with variability longer than 65 years, can be attributed to the ocean being in a series of quasi-equilibrium with the forcing. The statistical models presented in this thesis to reconstruct the AMOC and SPG strength on multidecadal and longer timescales can be useful for prediction and model inter-comparision

Electroproduction of K* mesons at CLAS

The electroproduction of K$^{*0}$ mesons using the CLAS detector is described. Data for two electron beam energies, 4.056 and 4.247 GeV, were measured and the normalized yields are compared.Comment: 4 pages, 3 figures, HYP2003 Proceeding

Les particularités lexicales de l'œuvre spondienne (Meditations sur les Pseaumes, 1588)

Le vocabulaire de Jean de Sponde est quasiment inconnu et nous avons choisi les Méditations sur les Pseaumes de 1588 comme corpus à exploiter. Nous partons du principe que le vocabulaire spondien demeure quasiment inconnu sur le plan lexico-historique : il est absent des dictionnaires de Littré , de Huguet , de Godefroy et de Lacurne , et nous n'en trouvons aucune trace dans l'immense corpus informatisé que représente le TLFi . Fort de ce constat, notre étude se propose de présenter une première vue d'ensemble des particularités lexicales du corpus exploité par nos soins pour l'élaboration de laquelle nous nous sommes servi du Französisches Etymologisches Wörterbuch (FEW) de Walter von Wartburg , le fameux thesaurus galloromanicus, dont l'utilisation, pour des raisons historiques et méthodologiques, n'est certes pas aisée pour le néophyte

Умная лампа

Cationic palladium allyl complexes [η3-C3H5)Pd(k2P^O)]+SbF6- (2[SbF6],P^O= Ph2P(CH2)2C-(=O)OEt; 3[SbF6], o-Ph2PC6H4C(=O)OEt; 4[SbF6], Ph2P(CH2)2P(=O)Ph2) have been prepared. In all complexes the oxygen donor can be displaced by other ligands such as carbon monoxide and ethylene. Displacement of an ester donor occurs much more readily than displacement of the phosphine oxide function. Above 0°C, the resulting ethylene complexes [η3-C3H5)Pd(C2H4)(k1P~O)]+ react to give (1,2,5-η3)-pent-1-en-5-yl complexes [(H2C=CH(CH2)3Pd(k2P^O)]+. A rate constant of e.g. k(17°C) = (2.27 ± 0.11) × 10-4 s-1 was determined for P,O ≡ Ph2P(CH2)2C(O)OEt by 1H NMR spectroscopy. Using 2-4 as catalyst precursors for ethylene dimerization, the allyl moiety is ultimately cleaved from the metal center as 1,4-pentadiene

Precise Determination of the Neutron Magnetic Form Factor to Higher Q2Q^2

The neutron elastic magnetic form factor $G_M^n$ has been extracted from quasielastic scattering from deuterium in the CEBAF Large Acceptance Spectrometer, CLAS. The kinematic coverage of the measurement is continuous over a broad range, extending from below 1 $GeV^2$ to nearly 5 $GeV^2$ in four-momentum transfer squared. High precision is achieved by employing a ratio technique in which most uncertainties cancel, and by a simultaneous in-situ calibration of the neutron detection efficiency, the largest correction to the data. Preliminary results are shown with statistical errors only.Comment: Contribution to the proceedings of the Tenth International Conference on Baryons (2004), to be published in Nuclear Physics, Section

Photoproduction of the doubly-strange Xi Hyperons

We report on the first measurement of exclusive Xi- and Xi0 photoproduction. The Xi- states are produced in the reaction gamma p --> K+ K+ Xi-, and the Xi0 states in gamma p --> K+ K+ pi- Xi0. Identification is made by the unique mass measured as the missing mass of the K+ K+ (or K+ K+ pi-) system using the CLAS detector at the Thomas Jefferson National Accelerator Facility. A systematic study of the excited Xi spectrum improves our understanding of the N* and Delta* states, since the Xi* states are related to them by SU(3) flavor symmetry. At the highest energies available at Jefferson Lab, we begin to find evidence for known excited Xi- states in the photoproduction process, and possibly new states at 1770 and 1860 MeV, although we do not have enough statistics to draw a strong conclusion. A search for the Xi5--(1862) pentaquark state seen by NA49 is made using the process gamma p -> K+ K+ pi+ X, but the result is inconclusive for lack of statistics.Comment: 7 pages, 9 figures; invited talk given at the 8th International Conference on Hypernuclear and Strange Particle Physics, Jefferson Lab, Newport News, VA, 14-18 October 200

Национальная детализация товарной номенклатуры внешнеэкономической деятельности: исторический опыт, правовые основы, методология

Cationic palladium catalysts have been used to cooligomerize ethylene and carbon monoxide. At high ethylene/CO ratios (m /m = 10:1) in methylene chloride as a solvent, unsaturated alternating cooligomers of the general structure R[C(O)CH2CH2]mH ( m ≥ 1 ; R ≡CH2=CH-, CH2=CHCH2CH2- and CH3CH = CHCH2-) were obtained for the first time. Single component catalyst precursors [(allyl)Pd(P^X )]+Y- (P^X = Ph2P(CH2)nC(= O )OR, Ph2P(CH2)2P(=O)Ph2, Ph2P(CH2)n Ph2P(CH2)2S (=O )Ph, n = 1 - 3 , R = Me, Et; Y- = BF4 -, SbF6 - ) with bidentate P,O- and P,S-ligands as well as in situ catalysts with unfunctionalized phosphine ligands were used. With P"Bu3 as a ligand, selectivities for ethylvinylketone of 40% based on the CO converted were obtained. The hemilabile phosphino-ester and phosphinothiophene ligands behave like monodentate phosphines under catalytic conditions.</jats:p

Resonances in Ferromagnetic Gratings Detected by Microwave Photoconductivity

We investigate the impact of microwave excited spin excitations on the DC charge transport in a ferromagnetic (FM) grating. We observe both resonant and nonresonant microwave photoresistance. Resonant features are identified as the ferromagnetic resonance (FMR) and ferromagnetic antiresonance (FMAR). A macroscopic model based on Maxwell and Landau-Lifschitz equations reveals the macroscopic nature of the FMAR. The experimental approach and results provide new insight in the interplay between photonic, spintronic, and charge effects in FM microstructures.Comment: 4 pages, 4 figure

Energy Calibration of the JLab Bremsstrahlung Tagging System

In this report, we present the energy calibration of the Hall B bremsstrahlung tagging system at the Thomas Jefferson National Accelerator Facility. The calibration was performed using a magnetic pair spectrometer. The tagged photon energy spectrum was measured in coincidence with $e^+e^-$ pairs as a function of the pair spectrometer magnetic field. Taking advantage of the internal linearity of the pair spectrometer, the energy of the tagging system was calibrated at the level of $\pm 0.1$. The absolute energy scale was determined using the $e^+e^-$ rate measurements close to the end-point of the photon spectrum. The energy variations across the full tagging range were found to be $<3$ MeV.Comment: 15 pages, 12 figure