Argon, uranium, thorium and lead composition and ages of ODP Leg 180 sites

During Ocean Drilling Program (ODP) Leg 180, 11 sites were drilled in the vicinity of the Moresby Seamount to study processes associated with the transition from continental rifting to seafloor spreading in the Woodlark Basin. This paper presents thermochronologic (40Ar/39Ar, 238U/206Pb, and fission track) results from igneous rocks recovered during ODP Leg 180 that help constrain the latest Cretaceous to present-day tectonic development of the Woodlark Basin. Igneous rocks recovered (primarily from Sites 1109, 1114, 1117, and 1118) consist of predominantly diabase and metadiabase, with minor basalt and gabbro. Zircon ion microprobe analyses gave a 238U/206Pb age of 66.4 ± 1.5 Ma, interpreted to date crystallization of the diabase. 40Ar/39Ar plagioclase apparent ages vary considerably according to the degree to which the diabase was altered subsequent to crystallization. The least altered sample (from Site 1109) yielded a plagioclase isochron age of 58.9 ± 5.8 Ma, interpreted to represent cooling following intrusion. The most altered sample (from Site 1117) yielded an isochron age of 31.0 ± 0.9 Ma, interpreted to represent a maximum age for the timing of subsequent hydrothermal alteration. The diabase has not been thermally affected by Miocene-Pliocene rift-related events, supporting our inference that these rocks have remained at shallow and cool levels in the crust (i.e., upper plate) since they were partially reset as a result of middle Oligocene hydrothermal alteration. These results suggest that crustal extension in the vicinity of the Moresby Seamount, immediately west of the active seafloor spreading tip, is being accommodated by normal faulting within latest Cretaceous to early Paleocene oceanic crust. Felsic clasts provide additional evidence for middle Miocene and Pliocene magmatic events in the region. Two rhyolitic clasts (from Sites 1110 and 1111) gave zircon 238U/206Pb ages of 15.7 ± 0.4 Ma and provide evidence for Miocene volcanism in the region. 40Ar/39Ar total fusion ages on single grains of K-feldspar from these clasts yielded younger apparent ages of 12.5 ± 0.2 and 14.4 ± 0.6 Ma due to variable sericitization of K-feldspar phenocrysts. 238U/206Pb zircon, 40Ar/39Ar K-feldspar and biotite total fusion, and apatite fission track analysis of a microgranite clast (from Site 1108) provide evidence for the existence of a rapidly cooled 3.0 to 1.8 Ma granitic protolith. The clast may have been transported longitudinally from the west (e.g., from the D'Entrecasteaux Islands). Alternatively, it may have been derived from a more proximal, but presently unknown, source in the vicinity of the Moresby Seamount.

Mixing of 0(+) and 0(-) observed in the hyperfine and Zeeman structure of ultracold Rb-2 molecules

We study the combination of the hyperfine and Zeeman structure in the spin-orbit coupled A(1)Sigma(+)(u) = b(3)Pi(u) complex of Rb-87(2). For this purpose, absorption spectroscopy at a magnetic field around B = 1000 G is carried out. We drive optical dipole transitions from the lowest rotational state of an ultracold Feshbach molecule to various vibrational levels with 0(+) symmetry of the A - b complex. In contrast to previous measurements with rotationally excited alkali-dimers, we do not observe equal spacings of the hyperfine levels. In addition, the spectra vary substantially for different vibrational quantum numbers, and exhibit large splittings of up to 160 MHz, unexpected for 0(+) states. The level structure is explained to be a result of the repulsion between the states 0(+) and 0(-) of b(3)Pi(u), coupled via hyperfine and Zeeman interactions. In general, 0(-) and 0(+) have a spin-orbit induced energy spacing Delta, that is different for the individual vibrational states. From each measured spectrum we are able to extract Delta, which otherwise is not easily accessible in conventional spectroscopy schemes. We obtain values of Delta in the range of +/- 100 GHz which can be described by coupled channel calculations if a spin-orbit coupling is introduced that is different for 0(-) and 0(+) of b(3)Pi(u).

Reduced local energy calculations on X¹Sigmaâ ½gHâ and 1¹S He /|nGerald F. Thomas. -- 260 St. Catharines [Ont.] : Dept. of Chemistry, Brock University,

The one-electron reduced local energy function, t ~ , is introduced and has the property < tL)=(~>. It is suggested that the accuracy of SL reflects the local accuracy of an approximate wavefunction. We establish that <~~>~ <~2,> and present a bound formula, E~ , which is such that where Ew is Weinstein's lower bound formula to the ground state. The nature of the bound is not guaranteed but for sufficiently accurate wavefunctions it will yield a lower bound. ,-+ 1'S I I Applications to X LW Hz. and ne are presented.

Étude de la protéine sigma 1 de réovirus par génétique inverse.

Réovirus, connu sous le nom REOLYSIN®, est présentement à l'étude à titre d'agent oncolytique. Or, la spécificité du virus pour les cellules cancéreuses pourrait être optimisée par une modification au niveau de la protéine d'attachement σ1. La présente étude vise à démontrer qu'une telle amélioration est possible par l'utilisation de la méthode nouvellement décrite de génétique inverse. Par cette technique, il est possible d'ajouter un polypeptide d'une longueur de quarante acides aminés à l'extrémité C-terminale de σ1. Il est aussi possible d'engendrer des virus mutés en leur site d'activité mucinolytique. Les virus nouvellement créés démontrent une efficacité de réplication diminuée, mais demeurent infectieux. Contrairement aux méthodes traditionnellement utilisées avec réovirus, la méthode de génétique inverse permet de conserver les mutations engendrées, par substitution ou addition, au cours des cycles de réplication. Une telle étude démontre qu'il serait possible de modifier le tropisme de réovirus.

Measurement of the ratio of inclusive cross sections sigma(p(p)over-bar -> Z plus b jet)/sigma(p(p)over-bar -> Z plus jet) at root s=1.96 TeV

Using the data collected with the D0 detector at root s=1.96 TeV, for integrated luminosities of about 180 pb(-1), we have measured the ratio of inclusive cross sections for p(p) over bar -> Z+b jet to p(p) over bar -> Z+jet production. The inclusive Z+b-jet reaction is an important background to searches for the Higgs boson in associated ZH production at the Fermilab Tevatron collider. Our measurement is the first of its kind, and relies on the Z -> e(+)e(-) and Z ->mu(+)mu(-) modes. The combined measurement of the ratio yields 0.021 +/- 0.005 for hadronic jets with transverse momenta p(T)> 20 GeV/c and pseudorapidities vertical bar eta vertical bar < 2.5, consistent with next-to-leading-order predictions of the standard model.

Measurement of sigma(p(p)over-bar -> Z)center dot Br(Z ->tau tau) at root s=1.96 TeV

We present a measurement of the cross section for Z production times the branching fraction to tau leptons, sigma.Br(Z ->tau(+)tau(-)), in p (p) over bar collisions at root s=1.96 TeV in the channel in which one tau decays into mu nu(mu)nu(tau), and the other into hadrons+nu(tau) or e nu(e)nu(tau). The data sample corresponds to an integrated luminosity of 226 pb(-1) collected with the D0 detector at the Fermilab Tevatron collider. The final sample contains 2008 candidate events with an estimated background of 55%. From this we obtain sigma.Br(Z ->tau(+)tau(-)) = 237 +/- 15(stat)+/- 18(sys)+/- 15(lum)pb, in agreement with the standard model prediction.

Measurement of sigma(p(p)over-bar -> Z plus X)Br(Z -> tau(+)tau(-)) at root s=1.96 TeV

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Measurement of three-jet differential cross sections d sigma(3jet)/dM(3jet) in p(p)over-bar collisions at root s=1.96 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurement of the ratio of inclusive cross sections sigma(p(p)over-bar -> Z plus b-quark jet)/sigma(p(p)over-bar -> Z plus jet) at root s=1.96 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurement of the differential cross section d sigma/dt in elastic p(p)over-bar scattering at root s=1.96 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Molecular analysis of Sigma-1 receptor modulation of the dopamine transporter

Sigma (σ) receptors are well established as a non-opioid, non-phencyclidine, and haloperidol-sensitive receptor family with its own binding profile and a characteristic distribution in the central nervous system (CNS) as well as in endocrine, immune, and some peripheral tissues. Two σ receptors subtypes, termed σ1 and σ2, have been pharmacologically characterized, but, to date, only the σ1 has also been cloned. Activation of σ1 receptors alter several neurotransmitter systems and dopamine (DA) neurotrasmission has been often shown to constitute an important target of σ receptors in different experimental models; however the exact role of σ1 receptor in dopaminergic neurotransmission remains unclear. The DA transporter (DAT) modulates the spatial and temporal aspects of dopaminergic synaptic transmission and interprer the primary mechanism by wich dopaminergic neurons terminate the signal transmission. For this reason present studies have been focused in understanding whether, in cell models, the human subtype of σ1 (hσ1) receptor is able to directly modulate the human DA transporter (hDAT). In the first part of this thesis, HEK-293 and SH-SY5Y cells were permanently transfected with the hσ1 receptor. Subsequently, they were transfected with another plasmid for transiently expressing the hDAT. The hDAT activity was estimated using the described [3H]DA uptake assay and the effects of σ ligands were evaluated by measuring the uptaken [3H]DA after treating the cells with known σ agonists and antagonists. Results illustrated in this thesis demonstrate that activation of overexpressed hσ1 receptors by (+)-pentazocine, the σ1 agonist prototype, determines an increase of 40% of the extracellular [3H]DA uptake, in comparison to non-treated controls and the σ1 antagonists BD-1047 and NE-100 prevent the positive effect of (+)-pentazocine on DA reuptake DA is likely to be considered a neurotoxic molecule. In fact, when levels of intracellular DA abnormally invrease, vescicles can’t sequester the DA which is metabolized by MAO (A and B) and COMT with consequent overproduction of oxygen reactive species and toxic catabolites. Stress induced by these molecules leads cells to death. Thus, for the second part of this thesis, experiments have been performed in order to investigate functional alterations caused by the (+)-pentazocine-mediated increase of DA uptake; particularly it has been investigated if the increase of intracellular [DA] could affect cells viability. Results obtained from this study demonstrate that (+)-pentazocine alone increases DA cell toxicity in a concentration-dependent manner only in cells co-expressing hσ1 and hDAT and σ1 antagonists are able to revert the (+)-pentazocine-induced increase of cell susceptibility to DA toxicity. In the last part of this thesis, the functional cross-talking between hσ1 receptor and hDAT has been further investigated using confocal microscopy. From the acquired data it could be suggested that, following exposure to (+)-pentazocine, the hσ1 receptors massively translocate towards the plasma membrane and colocalize with the hDATs. However, any physical interaction between the two proteins remains to be proved. In conclusion, the presented study shows for the first time that, in cell models, hσ1 receptors directly modulate the hDAT activity. Facilitation of DA uptake induced by (+)-pentazocine is reflected on the increased cell susceptibility to DA toxicity; these effects are prevented by σ1 selective antagonists. Since numerous compounds, including several drugs of abuse, bind to σ1 receptors and activating them could facilitate the damage of dopaminergic neurons, the reported protective effect showed by σ1 antagonists would represent the pharmacological basis to test these compounds in experimental models of dopaminergic neurodegenerative diseases (i.e. Parkinson’s Disease).

Messung der Zerfallsasymmetrien der radiativen Hyperonzerfälle Xi 0 Lambda gamma und Xi 0 Sigma 0 gamma mit dem NA48/1-Experiment

Der radiative Zerfall eines Hyperons in ein leichteres Hyperon und ein Photon erlaubt eine Untersuchung der Struktur der elektroschwachen Wechselwirkung von Hadronen. Dazu wird die Zerfallsasymmetrie $alpha$ betrachtet. Sie beschreibt die Verteilung des Tochterhyperons bezüglich der Polarisation $vec{P}$ des Mutterhyperons mit $dN / d cos(Theta) propto 1 + alpha |vec{P}| cos(Theta)$, wobei $Theta$ der Winkel zwischen $vec{P}$ und dem Impuls des Tochterhyperons ist. Von besonderem Interesse ist der radiative Zerfall $Xi^0 to Lambda gamma$, für den alle Rechnungen auf Quarkniveau eine positive Asymmetrie vorhersagen, wohingegen bisher eine negative Asymmetrie von $alpha_{Lambda gamma} = -0,73 +- 0,17$ gemessen wurde. Ziel dieser Arbeit war es, die bisherigen Messungen zu überprüfen und die Asymmetrie mit einer deutlich höheren Präzision zu bestimmen. Ferner wurden die Zerfallsasymmetrie des radiativen Zerfalls $Xi^0 to Sigma^0 gamma$ ermittelt und zum Test der angewandten Analysemethode der gut bekannte Zerfall $Xi^0 to Lambda pi^0$ herangezogen. Während der Datennahme im Jahr 2002 zeichnete das NA48/1-Experiment am CERN gezielt seltene $K_S$- und Hyperonzerfälle auf. Damit konnte der weltweit größte Datensatz an $Xi^0$-Zerfällen gewonnen werden, aus dem etwa 52.000 $Xi^0 to Lambda gamma$-Zerfälle, 15.000 $Xi^0 to Sigma^0 gamma$-Zerfälle und 4 Mill. $Xi^0 to Lambda pi^0$-Zerfälle mit nur geringem Untergrund extrahiert wurden. Ebenso wurden die entsprechenden $antiXi$-Zerfälle mit etwa einem Zehntel der obigen Ereigniszahlen registriert. Die Bestimmung der Zerfallsasymmetrien erfolgte durch den Vergleich der gemessene Daten mit einer detaillierten Detektorsimulation und führte zu den folgenden Resultaten dieser Arbeit: $alpha_{Lambda gamma} = -0,701 +- 0,019_{stat} +- 0,064_{sys}$, $alpha_{Sigma^0 gamma} = -0,683 +- 0,032_{stat} +- 0,077_{sys}$, $alpha_{Lambda pi^0} = -0,439 +- 0,002_{stat} +- 0,056_{sys}$, $alpha_{antiLambda gamma} = 0,772 +- 0,064_{stat} +- 0,066_{sys}$, $alpha_{antiSigma^0 gamma} = 0,811 +- 0,103_{stat} +- 0,135_{sys}$, $alpha_{antiLambda pi^0} = 0,451 +- 0,005_{stat} +- 0,057_{sys}$. Somit konnte die Unsicherheit der $Xi^0 to Lambda gamma$-Zerfallsasymmetrie auf etwa ein Drittel reduziert werden. Ihr negatives Vorzeichen und damit der Widerspruch zu den Vorhersagen der Quarkmodellrechnungen ist so zweifelsfrei bestätigt. Mit den zum ersten Mal gemessenen $antiXi$-Asymmetrien konnten zusätzlich Grenzen auf eine mögliche CP-Verletzung in den $Xi^0$-Zerfällen, die $alpha_{Xi^0} neq -alpha_{antiXi}$ zur Folge hätte, bestimmt werden.

The role of conserved region 1 of Escherichia coli sigma-70 in transcription initiation

The sigma (σ) subunit of eubacterial RNA polymerase is essential for initiation of transcription at promoter sites. σ factor directs the RNA polymerase core subunits ( a2bb′ ) to the promoter consensus elements and thereby confers selectivity for transcription initiation. The N-terminal domain (region 1.1) of Escherichia coli σ70 has been shown to inhibit DNA binding by the C-terminal DNA recognition domains when σ is separated from the core subunits. Since DNA recognition by RNA polymerase is the first step in transcription, it seemed plausible that region 1 might also influence initiation processes subsesquent to DNA binding. This study explores the functional roles of regions 1.1 and 1.2 of σ70 in transcription initiation. Analysis in vitro of the transcriptional properties of a series of N-terminally truncated σ70 derivates revealed a critical role for region 1.1 at several key stages of initiation. Deletion of the first 75 to 100 amino acids of σ70 (region 1.1) resulted in both a slow rate of transition from a closed promoter complex to a DNA-strand-separated open complex, as well as a reduced efficiency of transition from the open complex to a transcriptionally active open complex. These effects were partially reversed by addition of a polypeptide containing region 1.1 in trans. Therefore, region 1.1 not only modulates DNA binding but is important for efficient transcription initiation, once a closed complex has formed. A deletion of the first 133 amino acids which removes both regions 1.1 and 1.2 resulted in arrest of initiation at the earliest closed complex, suggesting that region 1.2 is required for open complex formation. Mutagenesis of region 1.1 uncovered a mechanistically important role for isoleucine at position 53 (I53). Substitution of I53 with alanine created a σ factor that associated with the core subunits to form holoenzyme, but the holoenzyme was severely deficient for promoter binding. The I53A phenotype was suppressed in vivo by truncation of five amino acids from the C-terminus of σ 70. These observations are consistent with a model in which σ 70I53A fails to undergo a critical conformational change upon association with the core subunits, which is needed to expose the DNA-binding domains and confer promoter recognition capability upon holoenzyme. To understand the basis of the autoinhibitory properties of the σ70 N-terminal domain, in the absence of core RNA polymerase, a preliminary physical assessment of the interdomain interactions within the σ70 subunit was launched. Results support a model in which N-terminal amino acids are in close proximity to residues in the C-terminus of the σ 70 polypeptide. ^

An analysis of the function of region 1.2 of the primary sigma factor, sigma 70, from Escherichia coli

The sigma (σ) subunit of eubacterial RNA polymerase is required for recognition of and transcription initiation from promoter DNA sequences. One family of sigma factors includes those related to the primary sigma factor from E. coli, σ70. Members of the σ70 family have four highly conserved domains, of which regions 2 through 4 are present in all members. Region 1 can be subdivided into regions 1.1 and 1.2. Region 1.1 affects DNA binding by σ 70 alone, as well as transcription initiation by holoenzyme. Region 1.2, present and highly conserved in most sigma factors, has not yet been assigned a putative function, although previous work demonstrated that it is not required for either association with the core subunits of RNA polymerase or promoter specific binding by holoenzyme. This study primarily investigates the functional role of region 1.2 during transcription initiation. In vivo and in vitro characterization of thirty-two single amino acid substitutions targeted to region 1.2 of E. coli σ70 as well as a deletion of region 1.2, revealed that mutations in region 1.2 can affect promoter binding, open complex formation, initiated complex formation, and the transition from abortive transcription to elongation. The relative degree of solvent exposure of several positions in region 1.2 has been determined, with positions 116 and 122 likely to be located near the surface of σ70. ^ During the course of this study, the existence of two “wild type” variants of E. coli σ70 was discovered. The identity of amino acid 149 has been reported variably as either arginine or aspartic acid in published articles and in online databases. In vivo and in vitro characterization of the two reported variations of E. coli σ70 (N149 and D149) has determined that the two variants are functionally equivalent. However, in vivo and in vitro characterization of single amino acid substitutions and a region 1.2 deletion in the context of each variant background revealed that the behavior of some mutations are greatly affected by the identity of amino acid 149. ^

The LAR/PTP delta/PTP sigma subfamily of transmembrane protein-tyrosine-phosphatases: multiple human LAR, PTP delta, and PTP sigma isoforms are expressed in a tissue-specific manner and associate with the LAR-interacting protein LIP.1.

The transmembrane protein-tyrosine-phosphatases (PTPases) LAR, PTP delta, and PTP sigma each contain two intracellular PTPase domains and an extracellular region consisting of Ig-like and fibronectin type III-like domains. We describe the cloning and characterization of human PTP sigma (HPTP sigma) and compare the structure, alternative splicing, tissue distribution, and PTPase activity of LAR, HPTP delta, and HPTP sigma, as well their ability to associate with the intracellular coiled-coil LAR-interacting protein LIP.1. Overall, these three PTPases are structurally very similar, sharing 64% amino acid identity. Multiple isoforms of LAR, HPTP delta, and HPTP sigma appear to be generated by tissue-specific alternative splicing of up to four mini-exon segments that encode peptides of 4-16 aa located in both the extracellular and intracellular regions. Alternative usage of these peptides varies depending on the tissue mRNA analyzed. Short isoforms of both HPTP sigma and HPTP delta were also detected that contain only four of the eight fibronectin type III-like domains. Northern blot analysis indicates that LAR and HPTP sigma are broadly distributed whereas HPTP delta expression is largely restricted to brain, as is the short HPTP sigma isoform containing only four fibronectin type III-like domains. LAR, HPTP delta, and HPTP sigma exhibit similar in vitro PTPase activities and all three interact with LIP.1, which has been postulated to recruit LAR to focal adhesions. Thus, these closely related PTPases may perform similar functions in various tissues.