Mercury concentrations in muscle tissue from sportfish in Lake Mead, Nevada

Lake Mead is the largest reservoir by volume in the United States and provides fishing opportunities for numerous anglers. Considerable attention has been given to the bioaccumulation of methylmercury in fish tissues, however, no formal study utilizing approved USEPA methodology has been conducted to quantify the amount of mercury present in fish tissue from Lake Mead. The purpose of this study is to determine the concentrations of mercury present in the most commonly consumed fish from Lake Mead and to identify if any of the 4 major basins contain fish with elevated concentrations of mercury. Largemouth bass (n=49), striped bass (n=94), and channel catfish (n=78) were collected from selected sites in Boulder Basin, Overton Arm, Virgin Basin, and Gregg Basin of Lake Mead by gill netting or electrofishing. Muscle tissue was homogenized, digested, and analyzed for mercury in accordance with USEPA Method 245.6 which must be used to construct human health based fish consumption advisories. Mean mercury concentrations were (x ±SD) 0.089±0.065 ppm, 0.154±0.127 ppm, and 0.098±0.080 ppm in largemouth bass, striped bass, and channel catfish, respectively. An analysis of covariance (ANCOVA) indicated a significant difference between mercury concentrations among the three species (F 2,208 = 22.448, p\u3c 0.001). Contrasts revealed that each species differed significantly from each other (p\u3c0.050). There was a significant overall difference in mean mercury concentration between fish from the four major basins of Lake Mead (F3,208 = 20.541, p\u3c0.001). The mean mercury concentration in Boulder Basin was significantly lower than that of Gregg Basin (p\u3c0.001), Virgin Basin (p\u3c0.001), and Overton Arm (p\u3c0.001). Out of 221 samples analyzed, 2 samples (both striped bass) were found to have mean mercury concentrations above the Environmental Protection Agency\u27s action level of 0.5 ppm. There were no samples found containing concentrations above the Food and Drug Administration\u27s maximum allowable mercury concentration in fish and food products (1.0 ppm)

Toward An Empirical Theory of Pulsar Emission. VII. On the Spectral Behavior of Conal Beam Radii and Emission Heights

In this paper we return to the old problem of conal component-pair widths and profile dimensions. Observationally, we consider a set of 10 pulsars with prominent conal component pairs, for which well measured profiles exist over the largest frequency range now possible. Apart from some tendency to narrow at high frequency, the conal components exhibit almost constant widths. We use all three profile measures, the component separation as well as the outside half-power and 10% widths, to determine conal beam radii, which are the focus of our subsequent analysis. These radii at different frequencies are well fitted by a relationship introduced by Thorsett (1991), but the resulting parameters are highly correlated. Three different types of behavior are found: one group of stars exhibits a continuous variation of beam radius which can be extrapolated down to the stellar surface along the ``last open field lines''; a second group exhibits beam radii which asymptotically approach a minimum high frequency value that is 3--5 times larger; and a third set shows almost no spectral change in beam radius at all. The first two behaviors are associated with outer-cone component pairs; whereas the constant separation appears to reflect inner-cone emission.Comment: 21 pages, 11 figures, accepted for publication in Astrophysical Journal, uses aaste

On the long and short nulls, modes and interpulse emission of radio pulsar B1944+17

We present a single pulse study of pulsar B1944+17, whose non-random nulls dominate nearly 70% of its pulses and usually occur at mode boundaries. When not in the null state, this pulsar displays four bright modes of emission, three of which exhibit drifting subpulses. B1944+17 displays a weak interpulse whose position relative to the main pulse we find to be frequency independent. Its emission is nearly 100% polarized, its polarization-angle traverse is very shallow and opposite in direction to that of the main pulse, and it nulls approximately two-thirds of the time. Geometric modeling indicates that this pulsar is a nearly aligned rotator whose alpha value is hardly 2 degrees--i.e., its magnetic axis is so closely aligned with its rotation axis that its sightline orbit remains within its conal beam. The star's nulls appear to be of two distinct types: those with lengths less than about 8 rotation periods appear to be pseudonulls--that is, produced by "empty" sightline traverses through the conal beam system; whereas the longer nulls appear to represent actual cessations of the pulsar's emission engine

Toward an Empirical Theory of Pulsar Emission. IX. On the Peculiar Properties and Geometric Regularity of Lyne & Manchester's "Partial Cone" Pulsars

Lyne & Manchester (1988) identified a group of some 50 pulsars they called "partial cones" which they found difficult to classify and interpret. They were notable for their asymmetric average profiles and asymmetric polarization position-angle (PPA) traverses, wherein the steepest gradient (SG) point fell toward one edge of the total intensity profile. Over the last two decades, this population of pulsars has raised cautions regarding the core/cone model of the radio pulsar-emission beam which implies a high degree of order, symmetry and geometric regularity. In this paper we reinvestigate this population "partial cone" pulsars on the basis of new single pulse polarimetric observations of 39 of them, observed with the Giant Meterwave Radio Telescope in India and the Arecibo Observatory in Puerto Rico. These highly sensitive observations help us to establish that most of these "partial cones" exhibit a core/cone structure just as did the "normal" pulsars studied in the earlier papers of this series. In short, we find that many of these "partial cones" are partial in the sense that the emission above different areas of their polar caps can be (highly) asymmetric. However, when studied closely we find that their emission geometries are overall identical to core/double cone structure encountered earlier-that is, with specific conal dimensions scaling as the polar cap size.Comment: Accepted for publication in ApJ, 42 pages with 45 figures, notes to table 2 and 3 are in the beginning of the appendix sectio

A model for double notches and bifurcated components in radio profiles of pulsars and magnetars - Evidence for the parallel acceleration maser in pulsar magnetosphere

Averaged pulse profiles of three nearby pulsars: B1929+10, J0437-4715 and B0950+08 exhibit unusual `double notches'. These W-like looking features consist of two adjacent V-shaped dips that approach each other at increasing observation frequency nuobs roughly at a rate sep \propto nuobs^{-1/2}, where sep is the separation between the notches' minima. We show that basic properties of the notches, namely their W-like look and the rate of their converging can be understood within a narrow class of models of coherent radio emission from pulsars: the free electron maser models based on coherent inverse Compton scattering of parallel oscillations of ambient electric field. The observed properties of the pulsars imply that the Fourier spectrum of the wiggler-like oscillations is narrow and that the broad-band character of the radio emission reflects the width of the electron energy distribution. Such a model provides a natural explanation for the frequency-independent separation between the main pulse and interpulse of B0950+08 as well as for the lack of radius to frequency mapping in the conal-like emission of J0437-4715. The frequency behaviour of the main pulse in the profile of the first radio magnetar XTE J1810-197 can also be explained within this model.Comment: 15 pages, 10 figures, accepted by A&A after minor change

Oculomotor function in frontotemporal lobar degeneration, related disorders and Alzheimer's disease

Frontotemporal lobar degeneration (FTLD) often overlaps clinically with corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP), both of which have prominent eye movement abnormalities. To investigate the ability of oculomotor performance to differentiate between FTLD, Alzheimer's disease, CBS and PSP, saccades and smooth pursuit were measured in three FTLD subtypes, including 24 individuals with frontotemporal dementia (FTD), 19 with semantic dementia (SD) and six with progressive non-fluent aphasia (PA), as compared to 28 individuals with Alzheimer's disease, 15 with CBS, 10 with PSP and 27 control subjects. Different combinations of oculomotor abnormalities were identified in all clinical syndromes except for SD, which had oculomotor performance that was indistinguishable from age-matched controls. Only PSP patients displayed abnormalities in saccade velocity, whereas abnormalities in saccade gain were observed in PSP > CBS > Alzheimer's disease subjects. All patient groups except those with SD were impaired on the anti-saccade task, however only the FTLD subjects and not Alzheimer's disease, CBS or PSP groups, were able to spontaneously self-correct anti-saccade errors as well as controls. Receiver operating characteristic statistics demonstrated that oculomotor findings were superior to neuropsychological tests in differentiating PSP from other disorders, and comparable to neuropsychological tests in differentiating the other patient groups. These data suggest that oculomotor assessment may aid in the diagnosis of FTLD and related disorders

Estimation of efficiency of the use of financial resources on enterprises

Стаття присвячена дослідженню теоретичних та практичних питань аналітичного забезпечення управління використанням фінансових ресурсів підприємств. Запропоновані комплексні показники оцінки даного процесуThe article is devoted to research of theoretical and practical questions of the analytical providing of management the use of financial resources of enterprises. The complex indexes of estimation of this process are offere

Науково-інформаційні ресурси порталу бібліотеки: формування, використання

Визначено шляхи вдосконалення процесів формування та використання електронних ресурсів порталу національної бібліотеки як базової компоненти єдиного науково-інформаційного простору держави.Определены пути усовершенствования процессов формирования и использования электронных ресурсов портала национальной библиотеки как базовой компоненты единого научно-информационного пространства государства.The ways of improvement of formation and usage processes of the electronic resources of the national library portal as a base component of unified scientific information space of the state are determined

Evolutionary changes in the Leishmania eIF4F complex involve variations in the eIF4E–eIF4G interactions

Translation initiation in eukaryotes is mediated by assembly of the eIF4F complex over the m7GTP cap structure at the 5′-end of mRNAs. This requires an interaction between eIF4E and eIF4G, two eIF4F subunits. The Leishmania orthologs of eIF4E are structurally diverged from their higher eukaryote counterparts, since they have evolved to bind the unique trypanosomatid cap-4 structure. Here, we characterize a key eIF4G candidate from Leishmania parasites (LeishIF4G-3) that contains a conserved MIF4G domain. LeishIF4G-3 was found to coelute with the parasite eIF4F subunits from an m7GTP-Sepharose column and to bind directly to LeishIF4E. In higher eukaryotes the eIF4E-eIF4G interaction is based on a conserved peptide signature [Y(X4)Lϕ], where X is any amino acid and Φ is a hydrophobic residue. A parallel eIF4E-binding peptide was identified in LeishIF4G-3 (20-YPGFSLDE-27). However, the binding motif varies extensively: in addition to Y20 and L25, binding strictly requires the presence of F23, whereas the hydrophobic amino acid (Φ) is dispensable. The LeishIF4E–LeishIF4G-3 interaction was also confirmed by nuclear magnetic resonance (NMR) studies. In view of these diversities, the characterization of the parasite eIF4E–eIF4G interaction may not only serve as a novel target for inhibiting Leishmaniasis but also provide important insight for future drug discovery