New ΔR for the southwest Pacific Ocean

ΔR results of known-age shells from the Solomon and Coral Seas and the northwest coast of New Ireland are presented. The results are too few to be conclusive but indicate that ΔR in this region is variable. An average ΔR value of 370 ± 25 yr is recorded for a range of shell species from Kavieng Harbor, New Ireland, and is primarily attributed to weak equatorial upwelling of depleted 14C due to seasonal current reversals. In contrast, values from the Solomon and Coral Seas are lower (average ΔR = 45 ± 19 yr). Higher ΔR values for some shellfish from these 2 seas is attributed to ingestion of 14Cdepleted sediment by deposit-feeding species

Color Breaking Baryogenesis

We propose a scenario that generates the observed baryon asymmetry of the Universe through a multi--step phase transition in which SU(3) color symmetry is first broken and then restored. A spontaneous violation of $B-L$ conservation leads to a contribution to the baryon asymmetry that becomes negligible in the final phase. The baryon asymmetry is therefore produced exclusively through the electroweak mechanism in the intermediate phase. We illustrate this scenario with a simple model that reproduces the observed baryon asymmetry. We discuss how future electric dipole moment and collider searches may probe this scenario, though future EDM searches would require an improved sensitivity of several orders of magnitude.Comment: Updated to comply with referees suggestions and mirror published versio

Studies of the Structure and Catalytic Mechanism of Chorismate Synthase

1. The established methods for the purification of the N. crassa chorismate synthase have been modified to overcome proteolytic damage and to obtain electrophoretically homogeneous enzyme free from substrates. 2. The purified N. crassa chorsmate synthase is a homotetramer with a subunit Mr of 50 000. The enzyme is bifunctional, showing both chorismate synthase and flavin reductase activity. 3. A simple anaerobic assay procedure has been developed which enables chorismate synthase activity to be monitored under strict anaerobic conditions. This procedure was used to detect and purify chorismate synthase from an overproducing strain of E. coli. 4. The purified E. coli chorismate synthase is a homotetramer with a subunit Mr of 38 000. The enzyme is active only in the presence of exogeneously supplied reduced flavin and appears to lack the ability to reduce this cofactor intrinsically. 5. The N-terminal sequence of the E. coli chorismate synthase has been determined for the first thirty residues and matches exactly that predicted from the nucleotide sequence. The complete amino acid sequence of the aroC structural gene is confirmed. The E. coli chorismate synthase snows primary structure homology with internal sequences derived from peptides isolated from the N. crassa enzyme. 6. Gross overexpression of the E. coli cnonsmate synthase using an IPTG induced overproducing strain resulted in the concomitant overproduction of a yellow chromophore. Spectroscopic and enzymatic analyses indicate that this chromophore is FMN. The E. coli enzyme contains limited amounts of residually bound flavin, as determined by fluorescence spectroscopy. Both the N. crassa and E. coIi chorismate synthase have a preference for FMN over FAD as the flavin cofactor. A putative FMN-phosphate binding region is identified from the E. coli chorismate synthase amino acid sequence. 7. Analysis of aromatic and flavin fluorescence spectra indicate that in vivo tne E. coli chorismate synthase subunit is the binding site for FMN. The N. crassa enzyme is nighly sensitive to thiol directed agents and insensitive to metal activation or metal chelation. 8. All of the structural and kinetic analyses presented suggest that the N. crassa enzyme is a fusion protein; a chorismate synthase domain coupled to a flavin reductase activity. 9. Preliminary evidence suggests that neither a thiol nor a metal is involved at the chorismate synthase active site, but that flavin itself could adequately assume the role of a nucleophile in a two-step reaction mechanism

Alien Registration- White, Peter J. (Orono, Penobscot County)

https://digitalmaine.com/alien_docs/5789/thumbnail.jp

INVESTIGATION OF PARAMETERS AFFECTING THE OPERATING CHARACTERISTICS OF TOGGLE-SWITCHES WITH SILVER-CADMIUM-OXIDE CONTACTS

Experimental and theoretical studies are made of small snap-action switches designed for use in thermostatic controls operating on a.c. at 240 volts r.m.s., 50Hz. The performance of the silver cadmium oxide contacts (Ag. CdO, 85/15%) is evaluated over a range of currents from 1 to 10 amps, for make and break operations. The arc at break is found to be the predominant factor contributing to the erosion of the contacts for the range of currents used. Tests using a high speed camera show that the energy dissipated in the arc between the contacts can be evaluated from equations describing the arc in terms of its voltage, current and length as functions of time. Subsequently work is carried out to develop the relation between arc energy and contact erosion, with specific regard to the distribution of energy between the two contact surfaces and the arc column. This is related to the power dissipation in the two electrode fall regions, and the resulting direction of net material transfer is thought to be influenced by the length achieved by the arc before extinction. Erosion is generally in the form of anodic loss and cathodic gain and the reasons for the directional bias in this type of switch are suggested. Ways of reducing the amount of erosion per operation by changing the switch opening characteristic are discussed and supported with experimental results.PETER J

Multi-epoch Sub-arcsecond [Fe II] Spectroimaging of the DG Tau Outflows with NIFS. II. On the Nature of the Bipolar Outflow Asymmetry

The origin of bipolar outflow asymmetry in young stellar objects (YSOs) remains poorly understood. It may be due to an intrinsically asymmetric outflow launch mechanism, or it may be caused by the effects of the ambient medium surrounding the YSO. Answering this question is an important step in understanding outflow launching. We have investigated the bipolar outflows driven by the T Tauri star DG Tauri on scales of hundreds of AU, using the Near-infrared Integral Field Spectrograph (NIFS) on Gemini North. The approaching outflow consists of a well-collimated jet, nested within a lower-velocity disc wind. The receding outflow is composed of a single-component bubble-like structure. We analyse the kinemat- ics of the receding outflow using kinetic models, and determine that it is a quasi-stationary bubble with an expanding internal velocity field. We propose that this bubble forms because the receding counterjet from DG Tau is obstructed by a clumpy ambient medium above the circumstellar disc surface, based on similarities between this structure and those found in the modeling of active galactic nuclei outflows. We find evidence of interaction between the obscured counterjet and clumpy ambient material, which we attribute to the large molecular envelope around the DG Tau system. An analytical model of a momentum-driven bubble is shown to be consistent with our interpretation. We conclude that the bipolar outflow from DG Tau is intrinsically symmetric, and the observed asymmetries are due to environmental effects. This mechanism can potentially be used to explain the observed bipolar asymmetries in other YSO outflows.Comment: 16 pages, 10 figures, accepted for publication in MNRA

Turbulent mixing layers in supersonic protostellar outflows, with application to DG Tauri

Turbulent entrainment processes may play an important role in the outflows from young stellar objects at all stages of their evolution. In particular, lateral entrainment of ambient material by high-velocity, well-collimated protostellar jets may be the cause of the multiple emission-line velocity components observed in the microjet-scale outflows driven by classical T Tauri stars. Intermediate-velocity outflow components may be emitted by a turbulent, shock- excited mixing layer along the boundaries of the jet. We present a formalism for describing such a mixing layer based on Reynolds decomposition of quantities measuring fundamental properties of the gas. In this model, the molecular wind from large disc radii provides a continual supply of material for entrainment. We calculate the total stress profile in the mixing layer, which allows us to estimate the dissipation of turbulent energy, and hence the luminosity of the layer. We utilize MAPPINGS IV shock models to determine the fraction of total emission that occurs in [Fe II] 1.644 {\mu}m line emission in order to facilitate comparison to previous observations of the young stellar object DG Tauri. Our model accurately estimates the luminosity and changes in mass outflow rate of the intermediate-velocity component of the DG Tau approaching outflow. Therefore, we propose that this component represents a turbulent mixing layer surrounding the well-collimated jet in this object. Finally, we compare and contrast our model to previous work in the field.Comment: 18 pages, 13 figures, accepted for publication in MNRA

Sub-millimetre molecular lines in the circumstellar envelope IRC+10216

The study reports observations of the circumstellar envelope IRC+10216 obtained with the 15-m James Clerk Maxwell Telescope. Maps with the 15" FWHM beam were made in the CO J = 3-2, CS J = 7-6, and HCN J = 4-3 transitions. The HCN J = 4-3 intensity is significantly greater than that of CO J = 3-2, but drops off almost twice as rapidly with distance from the source center. This rapid fall-off of the HCN intensity is indicative of the dominance of radiative excitation, which contrasts with the mainly collisional mechanism driving CO excitation. Single spectra at or near the source center are also presented for the isotopes 13CO, H13CN, C34S, for the J = 3-2 line of HCN and its isotope H13CN and for CO J = 4-3. Simple modeling results in estimates of relative abundances and excitation temperatures of CO, HCN, and CS, and an upper limit to the neutral carbon abundance