Rates of organic matter processing are key parameters for studies of stream ecosystem function and stream community ecology. Most studies of organic matter processing in streams use leaves in ...leafpacks or litterbags, which are immobilized and partly shielded from contact with stones in transport and in the stream bottom. As a result, these studies may underestimate the contribution of mechanical abrasion to overall processing rate (of coarse organic detritus to fine particles). We compared leaf processing rates in litter bags with and without stones (5 cm crushed limestone ballast) in Big Mill Creek, eastern Iowa. In two of three experiments, processing was significantly more advanced in bags with stones than in bags without stones: the fraction of leaf mass reduced to small fragments (1.4-9.5 mm) was 45% and 93% higher in bags with stones. In a fourth experiment, we compared the effects of stones and shredders (Gammarus pseudolimnaeus, at near-natural densities) on fragmentation of leaves in litterbags. This experiment indicated that mechanical and biological agents of processing are roughly equally important in Big Mill Creek. Our results indicate that mechanical abrasion can be an important contributor to organic matter processing in streams. If so, it may be an important source of the finer particles used by collectors. Litterbag and leafpack experiments may underestimate total processing rates and overestimate the relative importance of processing by microbes and invertebrates.PUBLICATION ABSTRACT
Using the South Pole Acoustic Test Setup (SPATS) and a retrievable transmitter deployed in holes drilled for the IceCube experiment, we have measured the attenuation of acoustic signals by South Pole ...ice at depths between 190 m and 500 m. Three data sets, using different acoustic sources, have been analyzed and give consistent results. The method with the smallest systematic uncertainties yields an amplitude attenuation coefficient α = 3.20 ± 0.57 km-1 between 10 and 30 kHz, considerably larger than previous theoretical estimates. Expressed as an attenuation length, the analyses give a consistent result for λ ≡ 1/α of ˜300 m with 20% uncertainty. No significant depth or frequency dependence has been found.
We report on the search for electromagnetic and hadronic showers ("cascades") produced by a diffuse flux of extraterrestrial neutrinos in the AMANDA neutrino telescope. Data for this analysis were ...recorded during 1001 days of detector livetime in the years 2000-2004. The observed event rates are consistent with the background expectation from atmospheric neutrinos and muons. An upper limit is derived for the diffuse flux of neutrinos of all flavors assuming a flavor ratio of νe:νμ:ντ = 1:1:1 at the detection site. The all-flavor flux of neutrinos with an energy spectrum Φ ∝ E-2 is less than 5.0 × 10-7 GeV s-1 sr-1 cm-2 at a 90% C.L. Here, 90% of the simulated signal would fall within the energy range 40 TeV to 9 PeV. We discuss flux limits in the context of several specific models of extraterrestrial and prompt atmospheric neutrino production.
The muon and anti-muon neutrino energy spectrum is determined from 2000-2003 AMANDA telescope data using regularised unfolding. This is the first measurement of atmospheric neutrinos in the energy ...range 2-200 TeV. The result is compared to different atmospheric neutrino models and it is compatible with the atmospheric neutrinos from pion and kaon decays. No significant contribution from charm hadron decays or extraterrestrial neutrinos is detected. The capabilities to improve the measurement of the neutrino spectrum with the successor experiment IceCube are discussed.
Structure of neutron-rich even-even 124, 126Cd Kautzsch, T.; Wöhr, A.; Walters, W. B. ...
The European physical journal. A, Hadrons and nuclei,
9/2005, Letnik:
25, Številka:
S1
Journal Article
Organisational performance, and how this performance can be influenced, continue to be primary concerns for managers. Although many motivational and performance related theories are presented by ...literature, the role and importance of responsibility and accountability as concepts within the organisation and in performance theory have been neglected, to the point that authors clearly highlight the need for further research in this regard (Mero, Guidice, & Werner, 2014; Greenwood & Miller, 2010).;
This research developed a speculative model which integrates organisational design theory with responsibility and accountability theory. The aim of the speculative model is to enhance managers understanding of how responsibility and accountability fit into the organisation and how an organisation can be designed to strengthen these concepts to the extent that performance can be positively influenced. The study also presented guiding principles as examples of the practical implication inferred from the results of the study and the speculative model developed.;
The qualitative research was conducted at an engineering firm in South Africa. Fifteen in-depth interviews were conducted with employees in positions at different levels (organisational level, group level and individual level) of the organisation. These interviews enabled the researcher to explore mechanisms related to responsibility and accountability and inductively develop the speculative model.;
It was found that the various links that determine how strong responsibility and accountability are present in a specific context could successfully be linked to different design components within the organisation, highlighting a specific area of focus within the organisation when a specific link of responsibility or accountability needs to be addressed.
Mini Dissertation (MBA)--University of Pretoria, 2015.
ms2016
Gordon Institute of Business Science (GIBS)
MBA
Unrestricted
New levels are reported for 124,126Cd populated in the decay of 124,126Ag isomers, respectively. In addition, new data from direct population of levels in 124Cd from alpha-induced fission of 238U are ...reported, along with new shell-model calculations for 126Cd.
The exosome regulates the processing, degradation, and surveillance of a plethora of RNA species. However, little is known about how the exosome recognizes and is recruited to its diverse substrates. ...We report the identification of adaptor proteins that recruit the exosome-associated helicase, Mtr4, to unique RNA substrates. Nop53, the yeast homolog of the tumor suppressor PICT1, targets Mtr4 to pre-ribosomal particles for exosome-mediated processing, while a second adaptor Utp18 recruits Mtr4 to cleaved rRNA fragments destined for degradation by the exosome. Both Nop53 and Utp18 contain the same consensus motif, through which they dock to the “arch” domain of Mtr4 and target it to specific substrates. These findings show that the exosome employs a general mechanism of recruitment to defined substrates and that this process is regulated through adaptor proteins.
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•Exosome co-factor Mtr4 is recruited to distinct pre-ribosomes via adaptor proteins•Adaptors Nop53 and Utp18 harbor an arch interaction motif that recruits Mtr4•Mtr4-AIM interaction is required for exosome-mediated rRNA processing and turnover
The identification of factors that, channel pre-ribosomal particles and rRNA fragments to the exosome provides a rationale of how the exosome recognizes its diverse RNA substrates.
Because of its relevance for the global climate the Atlantic meridional overturning circulation (AMOC) has been a major research focus for many years. Yet the question of which physical mechanisms ...ultimately drive the AMOC, in the sense of providing its energy supply, remains a matter of controversy. Here we review both observational data and model results concerning the two main candidates: vertical mixing processes in the ocean's interior and wind‐induced Ekman upwelling in the Southern Ocean. In distinction to the energy source we also discuss the role of surface heat and freshwater fluxes, which influence the volume transport of the meridional overturning circulation and shape its spatial circulation pattern without actually supplying energy to the overturning itself in steady state. We conclude that both wind‐driven upwelling and vertical mixing are likely contributing to driving the observed circulation. To quantify their respective contributions, future research needs to address some open questions, which we outline.
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