Comparison of Walleye: Stizostedion Vitreum Vitreum (Mitchell), Ecology and Biology From Three Discrete Areas of Lake Sakakawea, North Dakota

Various aspects of the ecology and biology of the walleye were examined from three discrete areas of Lake Sakakawea during the summer of 1982. Spatial distribution, predator-prey relationships and species association data were procured by simultaneously placing experimental and 0.5 in mesh gill nets at three depth ranges: 0-10 ft, 11-20 ft and 21-40 ft. Temporal distribution data were collected by lifting and resetting the gill nets approximately every six hours. Four time periods were used: 0600-1200 h, 1200-1800 h, 1800-2400 h and 2400-0600 h. Walleye age, growth and food habit data were also collected from the fish caught. The Van Hook Area produced the largest numbers of walleye and rainbow smelt, 03merus mordax (Mitchill). The 0-10 ft range produced the largest catches of walleyes for all areas. The total rainbow smelt catch was the largest in the 21-40 ft range. The Williston Area had the largest rainbow smelt catch in the 0-10 ft range. The total catch of walleye and rainbow smelt was significantly correlated for the 12 sampling periods. Walleyes and rainbow smelt numbers were also significantly correlated in the 11-20 ft range. More saugers, otizostedion canadense (Smith), were caught in the Wiiliston Area than walleyes. The differences in the total walleye and rainbow smelt catch among time periods were s/nall. The 2400-0600 h period produced the largest number of walleyes of the four time periods, while the 1800-2400 h period was the most productive for rainbow smelt. The largest catches of walleye and rainbow smelt came during the 1200-1800 h period in the Williston Area. There was a positive relationship between walleye and rainbow smelt during the 1800-2*100 h and 0600-1200 h periods. Ten age classes were found for the total walleye catch. Age classes III and VII were the largest for the total walleye catch. There were few age I and II walleye caught. The weight-length relationship for all of the walleye was explained by the equation: log W = - 5.793 +■ 3.299 log L. The mean coefficient of condition for the total walleye catch was 1.0*4. The walleyes caught in the Van Hook Area had significantly higher condition factors than did the other two areas. Rainbow smelt was the only forage species that was identified in the walleye stomachs. The stomachs of walleyes caught in the 11-20 ft range contained the greatest number and volume of rainbow smelt per stomach. Area morphometry, water temperature, light penetration and prey density are factors which may explain the larger numbers and faster growth rates of walleye caught in the Van Hook Area. The large catch of walleyes in the 0-10 ft range appear to be related to water temperature. Year class strength of walleyes is apparently closely related to water levels during spawning. Walleyes probably feed heavily on rainbow smelt because they are abundant, soft-rayed and easily caught

Comparison of Walleye: Stizostedion Vitreum Vitreum (Mitchell), Ecology and Biology From Three Discrete Areas of Lake Sakakawea, North Dakota

Various aspects of the ecology and biology of the walleye were examined from three discrete areas of Lake Sakakawea during the summer of 1982. Spatial distribution, predator-prey relationships and species association data were procured by simultaneously placing experimental and 0.5 in mesh gill nets at three depth ranges: 0-10 ft, 11-20 ft and 21-40 ft. Temporal distribution data were collected by lifting and resetting the gill nets approximately every six hours. Four time periods were used: 0600-1200 h, 1200-1800 h, 1800-2400 h and 2400-0600 h. Walleye age, growth and food habit data were also collected from the fish caught. The Van Hook Area produced the largest numbers of walleye and rainbow smelt, 03merus mordax (Mitchill). The 0-10 ft range produced the largest catches of walleyes for all areas. The total rainbow smelt catch was the largest in the 21-40 ft range. The Williston Area had the largest rainbow smelt catch in the 0-10 ft range. The total catch of walleye and rainbow smelt was significantly correlated for the 12 sampling periods. Walleyes and rainbow smelt numbers were also significantly correlated in the 11-20 ft range. More saugers, otizostedion canadense (Smith), were caught in the Wiiliston Area than walleyes. The differences in the total walleye and rainbow smelt catch among time periods were s/nall. The 2400-0600 h period produced the largest number of walleyes of the four time periods, while the 1800-2400 h period was the most productive for rainbow smelt. The largest catches of walleye and rainbow smelt came during the 1200-1800 h period in the Williston Area. There was a positive relationship between walleye and rainbow smelt during the 1800-2*100 h and 0600-1200 h periods. Ten age classes were found for the total walleye catch. Age classes III and VII were the largest for the total walleye catch. There were few age I and II walleye caught. The weight-length relationship for all of the walleye was explained by the equation: log W = - 5.793 +■ 3.299 log L. The mean coefficient of condition for the total walleye catch was 1.0*4. The walleyes caught in the Van Hook Area had significantly higher condition factors than did the other two areas. Rainbow smelt was the only forage species that was identified in the walleye stomachs. The stomachs of walleyes caught in the 11-20 ft range contained the greatest number and volume of rainbow smelt per stomach. Area morphometry, water temperature, light penetration and prey density are factors which may explain the larger numbers and faster growth rates of walleye caught in the Van Hook Area. The large catch of walleyes in the 0-10 ft range appear to be related to water temperature. Year class strength of walleyes is apparently closely related to water levels during spawning. Walleyes probably feed heavily on rainbow smelt because they are abundant, soft-rayed and easily caught

Physical parameters of the Cen X-3 system

Photographic spectra of Cen X-3 show that the primary star has a spectral type near 06.5 with weak, variable emission at wavelength 4640 and 4686. No orbital motion of the emission or absorption lines is detected; for the latter the upper limit is approximately + or - 50 km/s. Analysis of the available data indicates that the primary is a factor of 2-3 less massive than expected from normal evolutionary models while the X-ray source has a solar mass near 1.5

The 125th anniversary of the first postulation of the soil origin of endophytic bacteria – a tribute to M.L.V. Galippe

In both managed and natural ecosystems, a wide range of various non-nodulating bacteria can thrive as endophytes in the plant interior, and some can be beneficial to their hosts (Hallmann and Berg 2007; Reinhold-Hurek and Hurek 2011). Colonizationmechanisms, the ecology and functioning of these endophytic bacteria as well as their interactions with plants have been investigated (Hardoim et al. 2008; Compant et al. 2010). Although the source of colonization can also be the spermosphere, anthosphere, caulosphere, and the phyllosphere,most endophytic bacteria are derived from the soil environment (Hallmann and Berg 2007; Compant et al. 2010)

Polarization Effects in Reflecting Coronagraphs for White Light Applications in Astronomy

The properties of metal thin films have been largely overlooked in discussions of the technical limitations and problems that arise in the field of direct detection of exoplanets. Here, polarization properties and anisotropy properties of highly reflecting thin metal films are examined within the context of the requirements for the ultra-low scattered-light system performance of coronagraphs applied to space and ground-based high-contrast, white-light astronomy. Wavelength-dependent optical constants for highly reflecting thin metal films, taken from the literature are used to calculate the polarization-dependent transmissivity of a typical coronagraph. The effects of degraded performance on the astronomical science are examined. Suggestions are made for future work.Comment: 14 Pages, 7 Figures, Accepted to Astrophysical Journa

Age Estimations of M31 Globular Clusters from Their Spectral Energy Distributions

This paper presents accurate spectral energy distributions (SEDs) of 16 M31 globular clusters (GCs) confirmed by spectroscopy and/or high spatial-resolution imaging, as well as 30 M31 globular cluster candidates detected by Mochejska et al. Most of these candidates have m_V > 18, deeper than previous searches, and these candidates have not yet been confirmed to be globular clusters. The SEDs of these clusters and candidates are obtained as part of the BATC Multicolor Survey of the Sky, in which the spectrophotometrically-calibrated CCD images of M31 in 13 intermediate-band filters from 4000 to 10000 A were observed. These filters are specifically designed to exclude most of the bright and variable night-sky emission lines including the OH forest. In comparison to the SEDs of true GCs, we find that some of the candidate objects are not GCs in M31. SED fits show that theoretical simple stellar population (SSP) models can fit the true GCs very well. We estimate the ages of these GCs by comparing with SSP models. We find that, the M31 clusters range in age from a few ten Myr to a few Gyr old, as well as old GCs, confirming the conclusion that has been found by Barmby et a, Williams & Hodge, Beasley et al., Burstein et al. and Puzia et al. in their investigations of the SEDs of M31 globular clusters.Comment: Accepted for Publication in A&Ap, 13 pages, 6 figure

Polarization due to rotational distortion in the bright star Regulus

This is the full published article (retrieved from the 6 months post-publication posting on arXiv) including the Methods and Supplementary Information sections: 33 pages, 10 figures, 8 tablesPolarization in stars was first predicted by Chandrasekhar [1] who calculated a substantial linear polarization at the stellar limb for a pure electron-scattering atmosphere. This polarization will average to zero when integrated over a spherical star but could be detected if the symmetry is broken, for example by the eclipse of a binary companion. Nearly 50 years ago, Harrington and Collins [2] modeled another way of breaking the symmetry and producing net polarization - the distortion of a rapidly rotating hot star. Here we report the first detection of this effect. Observations of the linear polarization of Regulus, with two different high-precision polarimeters, range from +42 parts-per-million (ppm) at a wavelength of 741 nm to -22 ppm at 395 nm. The reversal from red to blue is a distinctive feature of rotation-induced polarization. Using a new set of models for the polarization of rapidly rotating stars we find that Regulus is rotating at 96.5(+0.6/-0.8)% of its critical angular velocity for breakup, and has an inclination greater than 76.5 degrees. The rotation axis of the star is at a position angle of 79.5+/-0.7 degrees. The conclusions are independent of, but in good agreement with, the results of previously published interferometric observations of Regulus [3]. The accurate measurement of rotation in early-type stars is important for understanding their stellar environments [4], and course of their evolution [5].Peer reviewedFinal Accepted Versio

The holistic rhizosphere: integrating zones, processes, and semantics in the soil influenced by roots

Despite often being conceptualized as a thin layer of soil around roots, the rhizosphere is actually a dynamic system of interacting processes. Hiltner originally defined the rhizosphere as the soil influenced by plant roots. However, soil physicists, chemists, microbiologists, and plant physiologists have studied the rhizosphere independently, and therefore conceptualized the rhizosphere in different ways and using contrasting terminology. Rather than research-specific conceptions of the rhizosphere, the authors propose a holistic rhizosphere encapsulating the following components: microbial community gradients, macroorganisms, mucigel, volumes of soil structure modification, and depletion or accumulation zones of nutrients, water, root exudates, volatiles, and gases. These rhizosphere components are the result of dynamic processes and understanding the integration of these processes will be necessary for future contributions to rhizosphere science based upon interdisciplinary collaborations. In this review, current knowledge of the rhizosphere is synthesized using this holistic perspective with a focus on integrating traditionally separated rhizosphere studies. The temporal dynamics of rhizosphere activities will also be considered, from annual fine root turnover to diurnal fluctuations of water and nutrient uptake. The latest empirical and computational methods are discussed in the context of rhizosphere integration. Clarification of rhizosphere semantics, a holistic model of the rhizosphere, examples of integration of rhizosphere studies across disciplines, and review of the latest rhizosphere methods will empower rhizosphere scientists from different disciplines to engage in the interdisciplinary collaborations needed to break new ground in truly understanding the rhizosphere and to apply this knowledge for practical guidance

Polarization in young open cluster NGC 6823

We present multiwavelength linear polarimetric observations of 104 stars towards the region of young open cluster NGC 6823. The polarization towards NGC 6823 is dominated by foreground dust grains and we found the evidence for the presence of several layers of dust towards the line of sight. The first layer of dust is located approximately within 200 pc towards the cluster, which is much closer to the Sun than the cluster (~ 2.1 kpc). The radial distribution of the position angles for the member stars are found to show a systematic change while the polarization found to reduce towards the outer parts of the cluster and the average position angle of coronal region of the cluster is very close to the inclination of the Galactic parallel (~ 32 degree). The size distribution of the grains within NGC 6823 is similar to those in general interstellar medium. The patchy distribution of foreground dust grains are suggested to be mainly responsible for the both differential reddening and polarization towards NGC 6823. The majority of the observed stars do not show the evidence of intrinsic polarization in their light.Comment: 16 pages, 6 tables, 11 figures, Accepted for publication in MNRA

Results of X-ray and optical monitoring of SCO X-1

Sco X-1 was monitored at optical and X-ray wavelengths from 1970 April 26 to 1970 May 21. The optical observations were made at six observatories around the world and the X-ray observations were made by the Vela satellites. There was a tendency for the object to show greater variability in X-ray when the object is optically bright. A discussion of the intensity histograms is presented for both the optical and X-ray observations. No evidence for optical or X-ray periodicity was detected