Rate limitation within a single enzyme is directly related to enzyme intermediate levels.

AbstractThe extents to which different rate constants limit the steady-state rate of an isolated enzyme can be quantified as the control coefficients of those constants and elemental steps. We have found that the sum of the control coefficients of rate constants characterising unidirectional rates depleting a particular enzyme intermediate is equal to the concentration of that enzyme intermediate as a fraction of the total enzyme concentration. Together with simple measurements this powerful relation may be used (i) to estimate certain enzyme intermediate levels, in particular the free enzyme concentration, and (ii) to estimate the control coefficients of rate constants and steps

Toward high-precision values of the self energy of non-S states in hydrogen and hydrogen-like ions

The method and status of a study to provide numerical, high-precision values of the self-energy level shift in hydrogen and hydrogen-like ions is described. Graphs of the self energy in hydrogen-like ions with nuclear charge number between 20 and 110 are given for a large number of states. The self-energy is the largest contribution of Quantum Electrodynamics (QED) to the energy levels of these atomic systems. These results greatly expand the number of levels for which the self energy is known with a controlled and high precision. Applications include the adjustment of the Rydberg constant and atomic calculations that take into account QED effects.Comment: Minor changes since previous versio

Bowhead whales, and not right whales, were the primary target of 16th- to 17th-century Basque Whalers in the Western North Atlantic

During the 16th and 17th centuries, Basque whalers travelled annually to the Strait of Belle Isle and Gulf of St. Lawrence to hunt whales. The hunting that occurred during this period is of primary significance for the North Atlantic right whale, Eubalaena glacialis (Müller, 1776), because it has been interpreted as the largest human-induced reduction of the western North Atlantic population, with ~12250–21 000 whales killed. It has been frequently reported that the Basques targeted two species in this region: the North Atlantic right whale and the bowhead whale, Balaena mysticetus L., 1758. To evaluate this hypothesis and the relative impact of this period of whaling on both species, we collected samples from 364 whale bones during a comprehensive search of Basque whaling ports from the 16th to the 17th century in the Strait of Belle Isle and Gulf of St. Lawrence. Bones were found and sampled at 10 of the 20 sites investigated. DNA was extracted from a subset (n = 218) of these samples. Analysis of the mitochondrial cytochrome b region identified five whale species. The identification of only a single right whale bone and 203 bowhead whale bones from at least 72 individuals indicates that the bowhead whale was likely the principal target of the hunt. These results imply that this whaling had a much greater impact (in terms of numbers of whales removed) on the bowhead whale population than on the western North Atlantic right whale population.Aux XVIe et XVIIe siècles, les baleiniers basques se rendaient tous les ans au détroit de Belle Isle et au golfe du Saint- Laurent pour faire la chasse aux baleines. La chasse qui s’est effectuée pendant cette période revêt une grande importance pour la baleine franche ou baleine noire de l’Atlantique Nord, Eubalaena glacialis (Müller, 1776), car cette activité serait interprétée comme la plus grande réduction de la population de baleines franches de l’Atlantique Nord causée par l’être humain, au rythme d’environ 12 250 à 21 000 baleines tuées. On a souvent signalé que les Basques visaient deux espèces dans cette région, soit la baleine franche de l’Atlantique Nord et la baleine boréale, Balaena mysticetus L., 1758. Pour évaluer cette hypothèse et l’incidence relative de cette période de pêche aux baleines sur ces deux espèces, nous avons recueilli des échantillons provenant de 364 ossements de baleines dans le cadre d’une recherche approfondie de ports basques de chasse à la baleine remontant aux XVIe et XVIIe siècles dans le détroit de Belle Isle et le golfe du Saint-Laurent. Des ossements ont été trouvés et échantillonnés à 10 des 20 sites ayant fait l’objet de notre recherche. De l’ADN a été extrait d’un sous-ensemble (n = 218) de ces échantillons. L’analyse mitochondriale cytochrome b de la région a permis d’identifier cinq espèces de baleines. L’identification d’un seul os de baleine franche et de 203 os de baleines boréales provenant d’au moins 72 individus laisse croire que la baleine boréale était probablement la cible principale des chasseurs. Ces résultats impliquent que la chasse à la baleine a eu des incidences beaucoup plus grandes (en termes de nombres de baleines éliminées) sur la population de baleines boréales que sur la population de baleines franches de l’ouest de l’Atlantique Nord

Observations of quasi-periodic solar X-ray emission as a result of MHD oscillations in a system of multiple flare loops

We investigate the solar flare of 20 October 2002. The flare was accompanied by quasi-periodic pulsations (QPP) of both thermal and nonthermal hard X-ray emissions (HXR) observed by RHESSI in the 3-50 keV energy range. Analysis of the HXR time profiles in different energy channels made with the Lomb periodogram indicates two statistically significant time periods of about 16 and 36 seconds. The 36-second QPP were observed only in the nonthermal HXR emission in the impulsive phase of the flare. The 16-second QPP were more pronounced in the thermal HXR emission and were observed both in the impulsive and in the decay phases of the flare. Imaging analysis of the flare region, the determined time periods of the QPP and the estimated physical parameters of magnetic loops in the flare region allow us to interpret the observations as follows. 1) In the impulsive phase energy was released and electrons were accelerated by successive acts with the average time period of about 36 seconds in different parts of two spatially separated, but interacting loop systems of the flare region. 2) The 36-second periodicity of energy release could be caused by the action of fast MHD oscillations in the loops connecting these flaring sites. 3) During the first explosive acts of energy release the MHD oscillations (most probably the sausage mode) with time period of 16 seconds were excited in one system of the flare loops. 4) These oscillations were maintained by the subsequent explosive acts of energy release in the impulsive phase and were completely damped in the decay phase of the flare.Comment: 14 pages, 4 figure

Environmental evaluations for deepening of Richmond Harbor and Santa Fe Channels

Richland, California is an important commercial port in San Francisco Bay. The San Francisco District of the US Army Corps of Engineers (USACE) plans to increase the depth of Richmond Harbor and Santa Fe Channels to -38 feet Mean Lower Low Water (MLLW) to accommodate deep-draft commercial vessels. The total volume of dredged material is expected to be approximately 1.4 million cubic yards. The options for disposal of the dredged material are aquatic disposal and upland disposal. The purpose of this study was to develop a database on chemical compounds in the dredged material to assist with determination of disposal methods and the need for additional testing. This purpose was accomplished through an extensive field sampling program followed by chemical analysis of samples. Field sampling involved collection of core samples from Sante Fe and Richmond Harbor Channels. Cores were shipped to Battelle/Marine Sciences Laboratory, where they were subsampled for chemical analysis and/or archived by freezing. All sediment and water samples were analyzed for priority pollutants, including metals, organotins, base/neutral semivolatile organic compounds, chlorinated pesticides and PCBs, herbicide acids, and acidic phenols. Sediment samples were also analyzed for oil and grease and total organic carbon. Organophosphorus pesticides and dioxins and furans were measured in selected sediment samples from Richland Harbor Channel and from both sediment and water samples from Santa Fe Channel. 21 refs., 10 figs., 60 tabs

Magnetic Reversal on Vicinal Surfaces

We present a theoretical study of in-plane magnetization reversal for vicinal ultrathin films using a one-dimensional micromagnetic model with nearest-neighbor exchange, four-fold anisotropy at all sites, and two-fold anisotropy at step edges. A detailed "phase diagram" is presented that catalogs the possible shapes of hysteresis loops and reversal mechanisms as a function of step anisotropy strength and vicinal terrace length. The steps generically nucleate magnetization reversal and pin the motion of domain walls. No sharp transition separates the cases of reversal by coherent rotation and reversal by depinning of a ninety degree domain wall from the steps. Comparison to experiment is made when appropriate.Comment: 12 pages, 8 figure

Transient Magnetic and Doppler Features Related to the White-light Flares in NOAA 10486

Rapidly moving transient features have been detected in magnetic and Doppler images of super-active region NOAA 10486 during the X17/4B flare of 28 October 2003 and the X10/2B flare of 29 October 2003. Both these flares were extremely energetic white-light events. The transient features appeared during impulsive phases of the flares and moved with speeds ranging from 30 to 50 km s$^{-1}$. These features were located near the previously reported compact acoustic \cite{Donea05} and seismic sources \cite{Zharkova07}. We examine the origin of these features and their relationship with various aspects of the flares, {\it viz.}, hard X-ray emission sources and flare kernels observed at different layers - (i) photosphere (white-light continuum), (ii) chromosphere (H$\alpha$ 6563\AA), (iii) temperature minimum region (UV 1600\AA), and (iv) transition region (UV 284\AA).Comment: 26 pages, 13 figures, 2 tables, accepted for publication in Solar Physic

Structure and Dynamics of Liquid Iron under Earth's Core Conditions

First-principles molecular dynamics simulations based on density-functional theory and the projector augmented wave (PAW) technique have been used to study the structural and dynamical properties of liquid iron under Earth's core conditions. As evidence for the accuracy of the techniques, we present PAW results for a range of solid-state properties of low- and high-pressure iron, and compare them with experimental values and the results of other first-principles calculations. In the liquid-state simulations, we address particular effort to the study of finite-size effects, Brillouin-zone sampling and other sources of technical error. Results for the radial distribution function, the diffusion coefficient and the shear viscosity are presented for a wide range of thermodynamic states relevant to the Earth's core. Throughout this range, liquid iron is a close-packed simple liquid with a diffusion coefficient and viscosity similar to those of typical simple liquids under ambient conditions.Comment: 13 pages, 8 figure