4,547 research outputs found
Challenging otherness : a reassessment of early Greek attitudes toward the divine
Includes bibliographical references
Eutrophication
Eutrophication is a syndrome of [../152248/index.html ecosystem]] responses to human activities that fertilize water bodies with nitrogen (N) and phosphorus (P), often leading to changes in animal and plant populations and degradation of water and habitat quality. Nitrogen and phosphorus are essential components of structural proteins, enzymes, cell membranes, nucleic acids, and molecules that capture and utilize light and chemical energy to support life. The biologically available forms of N and P are present at low concentrations in pristine lakes, rivers, estuaries, and in vast regions of the upper ocean.https://inspire.redlands.edu/oh_chapters/1160/thumbnail.jp
Seeking the Ultraviolet Ionizing Background at z~3 with the Keck Telescope
We describe the initial results of a deep long-slit emission line search for
redshifted (2.7<z<4.1) Lyman-alpha. These observations are used to constrain
the fluorescent Ly-alpha emission from the population of clouds whose
absorption produces the higher-column-density component of the Ly-alpha forest
in quasar spectra. We use the results to set an upper limit on the ultraviolet
ionizing background. Our spectroscopic data obtained with the Keck II telescope
at lambda/(Delta lambda FWHM)~2000 reveals no candidate Ly-alpha emission over
the wavelength range of 4500-6200 Ang along a 3 arcmin slit in a 5400 s
integration. Our 3 sigma upper bound on the mean intensity of the ionizing
background at the Lyman limit is J(nu 0) < 2E-21 erg/s/cm**2/Hz/sr for
2.7<z<3.1 (where we are most sensitive), assuming Lyman limit systems have
typical radii of 70 kpc (q_0=0.5, H_0=50 km/s/Mpc). This constraint is more
than an order of magnitude more stringent than any previously published direct
limit. However, it is still a factor of three above the ultraviolet background
level expected due to the integrated light of known quasars at z~3. This pilot
study confirms the conclusion of Gould \& Weinberg (1996) that integrations of
several hours on a 10-m class telescope should be capable of measuring J(nu 0)
at high redshift.Comment: 22 pages, 2 postscipt figures. Latex requires aaspp4.sty and epsf.sty
(included). Accepted for publication in the Astronomical Journal (Nov 1998
Zeolite Degradation: An Investigation of CO2 Capacity Loss of 13x Sorbent
System testing of the Carbon Dioxide Removal and Compression System (CRCS) has revealed that sufficient CO2 removal capability was not achieved with the designed system. Subsystem component analysis of the zeolite bed revealed that the sorbent material suffered significant degradation and CO2 loading capacity loss. In an effort to find the root cause of this degradation, various factors were investigated to try to reproduce the observed performance loss. These factors included contamination by vacuum pump oil, o-ring vacuum grease, loading/unloading procedures, and operations. This paper details the experiments that were performed and their results
The significance of motivation in student-centred learning : a reflective case study
The theoretical underpinnings of student-centred learning suggest motivation to be an integral component. However, lack of clarification of what is involved in motivation in education often results in unchallenged assumptions that fail to recognise that what motivates some students may alienate others. This case study, using socio-cognitive motivational theory to analyse previously collected data, derives three fuzzy propositions which, collectively, suggest that motivation interacts with the whole cycle of episodes in the teachinglearning process. It argues that the development of the higherlevel cognitive competencies that are implied by the term, student-centred learning, must integrate motivational constructs such as goal orientation, volition, interest and attributions into pedagogical practices
5-Hydroxyethyl-3-tetradecanoyltetramic acid represents a novel treatment for intravascular catheter infections due to Staphylococcus aureus
Objectives: Biofilm infections of intravascular catheters caused by Staphylococcus aureus may be treated with catheter lock solutions (CLSs). Here we investigated the antibacterial activity, cytotoxicity and CLS potential of 5-hydroxyethyl-3-tetradecanoyltetramic acid (5HE-C14-TMA) compared with the related compounds 3-tetradecanoyltetronic (C14-TOA) and 3-tetradecanoylthiotetronic (C14-TTA), which are variants of quorum sensing signalling molecules produced by Pseudomonas aeruginosa.
Methods: Antibacterial activity and mechanism of action of 5HE-C14-TMA, C14-TOA and C14-TTA were determined via MIC, bacterial killing, membrane potential and permeability assays. Susceptibility of S. aureus biofilms formed in the presence of plasma in vitro was investigated, MTT cytotoxicity testing was undertaken and cytokine release in human blood upon exposure to 5HE-C14-TMA and/or S. aureus biofilms was quantified. The effectiveness of 5HE-C14-TMA as CLS therapy in vivo was assessed using a rat intravascular catheter biofilm infection model.
Results: MICs of 5HE-C14-TMA, C14-TOA and C14-TTA ranged from 2 to 4 mg/L. 5HE-C14-TMA and C14-TTA were bactericidal; all three compounds perturbed the staphylococcal membrane by increasing membrane permeability, depolarized the transmembrane potential and caused ATP leakage. Cytotoxicity and haemolytic activity were compound and target cell type-dependent. 5HE-C14-TMA reduced S. aureus biofilm viability in a dose-dependent manner in vitro and in vivo and did not trigger release of cytokines in human blood, but inhibited the high levels of IL-8 and TNF-α induced by S. aureus biofilms.
Conclusions: 5HE-C14-TMA, C14-TOA and C14-TTA are membrane-active agents. 5HE-C14-TMA was the most potent, eradicating S. aureus biofilms at 512–1024 mg/L both in vitro and in vivo as a CLS
Foundations of character: methodological aspects of a study of character development in three- to six-year-old children with a focus on sharing behaviours
This article focuses on methodological issues arising in a study of character development, using illustrations of ‘sharing behaviours.’ Based primarily in six early years settings in southeast England the research records naturalistic observations of peer interactions for 55 children aged three to six years. Applying grounded theory to the processes of observing, analysing and interpreting evidence required a cautious and collectively reflective approach. The methodology sought to moderate the influence of the researchers' prior knowledge of ‘grand theories’ of moral development and assumptions about relevance to the observation records. The study's originality lay in the exploration of moral development without reference to any particular grand theory as an explanatory framework; and in the reluctance to be drawn to potentially simplistic rationalisations of the children's intentions on the basis of their observed behaviours. Exploring young children's subjective experiences, this research provides insights into the intricacy of this process, steering away from ‘neat’ findings and attempting to reflect the sophistication of the children's skilful and sometimes surprising negotiations of moral dilemmas. Implications for practice relate to the complexities involved in attempts to unravel the developing moral characters of young children and the practice through which this may be nurtured
Tests of the Accelerating Universe with Near-Infrared Observations of a High-Redshift Type Ia Supernova
We have measured the rest-frame B,V, and I-band light curves of a
high-redshift type Ia supernova (SN Ia), SN 1999Q (z=0.46), using HST and
ground-based near-infrared detectors.
A goal of this study is the measurement of the color excess, E_{B-I}, which
is a sensitive indicator of interstellar or intergalactic dust which could
affect recent cosmological measurements from high-redshift SNe Ia. Our
observations disfavor a 30% opacity of SN Ia visual light by dust as an
alternative to an accelerating Universe. This statement applies to both
Galactic-type dust
(rejected at the 3.4 sigma confidence level) and greyer dust (grain size >
0.1 microns; rejected at the 2.3 to 2.6 sigma confidence level) as proposed by
Aguirre (1999). The rest-frame -band light cur ve shows the secondary
maximum a month after B maximum typical of nearby SNe Ia of normal luminosi ty,
providing no indication of evolution as a function of redshift out to z~0.5. A
n expanded set of similar observations could improve the constraints on any
contribution of extragalactic dust to the dimming of high-redshift SNe Ia.Comment: Accepted to the Astrophysical Journal, 12 pages, 2 figure
Recommended from our members
Evaluating the structure and magnitude of the ash plume during the initial phase of the 2010 Eyjafjallajökull eruption using lidar observations and NAME simulations
The Eyjafjallajökull volcano in Iceland erupted explosively on 14 April 2010, emitting a plume of ash into the atmosphere. The ash was transported from Iceland toward Europe where mostly cloud-free skies allowed ground-based lidars at Chilbolton in England and Leipzig in Germany to estimate the mass concentration in the ash cloud as it passed overhead. The UK Met Office's Numerical Atmospheric-dispersion Modeling Environment (NAME) has been used to simulate the evolution of the ash cloud from the Eyjafjallajökull volcano during the initial phase of the ash emissions, 14–16 April 2010. NAME captures the timing and sloped structure of the ash layer observed over Leipzig, close to the central axis of the ash cloud. Relatively small errors in the ash cloud position, probably caused by the cumulative effect of errors in the driving meteorology en route, result in a timing error at distances far from the central axis of the ash cloud. Taking the timing error into account, NAME is able to capture the sloped ash layer over the UK. Comparison of the lidar observations and NAME simulations has allowed an estimation of the plume height time series to be made. It is necessary to include in the model input the large variations in plume height in order to accurately predict the ash cloud structure at long range. Quantitative comparison with the mass concentrations at Leipzig and Chilbolton suggest that around 3% of the total emitted mass is transported as far as these sites by small (<100 μm diameter) ash particles
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