1,665 research outputs found
Contextualizing Senior Executive Advice Seeking: The Role of Decision Process Comprehensiveness and Empowerment Climate
Maximizing realized yield by breeding for disease tolerance: A case study for Septoria tritici blotch
Disease-tolerant cultivars maintain yield in the presence of disease. When disease intensity is high, they can improve a grower's net return compared to less tolerant cultivars. Many authors report a trade-off, whereby higher fully protected yields are correlated with a lower disease tolerance. We analyse the question for breeders: to what extent should they breed for tolerance when it compromises maximizing fully protected yield? Field trials with 147 progeny from five parental crosses of wheat were used to measure yield and tolerance under a range of disease intensities from Septoria tritici blotch (STB; causal organism Zymoseptoria tritici) at a range of sites and seasons. The data define the variation for these traits from which breeders can select. A simple data-driven descriptive model was used to calculate the combination of tolerance and fully protected yield that maximizes actual yield for any given level of disease—quantified by loss of healthy canopy area duration (HAD-loss). This model was combined with data on the year-to-year variability of HAD-loss in the UK to calculate the tolerance and fully protected yield that maximizes the mean actual yield. We found that even when an effective fungicide treatment programme is applied, breeding for tolerance increases the mean actual yield. Some commercially available cultivars were found to have a level of tolerance that leads to yields close to the maximum yield in the presence of disease, others had a lower tolerance leading to suboptimal yields
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Evolutionary bi-stability in pathogen transmission mode
Many pathogens transmit to new hosts by both infection (horizontal transmission) and transfer to the
infected host's offspring (vertical transmission). These two transmission modes require speci®c adap-
tations of the pathogen that can be mutually exclusive, resulting in a trade-off between horizontal and
vertical transmission. We show that in mathematical models such trade-offs can lead to the simultaneous
existence of two evolutionary stable states (evolutionary bi-stability) of allocation of resources to the two
modes of transmission. We also show that jumping between evolutionary stable states can be induced by
gradual environmental changes. Using quantitative PCR-based estimates of abundance in seed and vege-
tative parts, we show that the pathogen of wheat, Phaeosphaeria nodorum, has jumped between two
distinct states of transmission mode twice in the past 160 years, which, based on published evidence,
we interpret as adaptation to environmental change. The ®nding of evolutionary bi-stability has impli-
cations for human, animal and other plant diseases. An ill-judged change in a disease control
programme could cause the pathogen to evolve a new, and possibly more damaging, combination of
transmission modes. Similarly, environmental changes can shift the balance between transmission
modes, with adverse effects on human, animal and plant health
Evidence for a massive BH in the S0 galaxy NGC 4342
We present axisymmetric dynamical models of the edge-on S0 galaxy NGC 4342. A
combination of observations from the ground and with the Hubble Space Telescope
(HST) has shown that NGC 4342 rotates rapidly and has a strong central increase
in velocity dispersion. We construct simple two-integral Jeans models as well
as fully general, three-integral models. The latter are built using a modified
version of Schwarzschild's orbit-superposition technique. The two-integral
Jeans models suggest a black hole (BH) mass between 3 and 6x10^8 Msun,
depending on the data set used to constrain the model, but they fail to fit the
details of the observed kinematics. The three-integral models can fit all
ground-based and HST data simultaneously, but only when a central BH is
included. Models without BH are ruled out to a confidence level better than
99.73 per cent. We determine a BH mass of 3x10^8 Msun. This corresponds to 2.6
per cent of the total mass of the bulge, making NGC 4342 one of the galaxies
with the highest BH mass to bulge mass ratio currently known. The models that
best fit the data do not have a two-integral phase-space distribution function.
They have rather complex dynamical structures: the velocity anisotropies are
strong functions of radius reflecting the multi-component structure of this
galaxy. The best fit model without BH tries to fit the high central velocity
dispersion by placing stars on radial orbits. The measured rotation velocities,
however, restrict the amount of radial anisotropy such that the central
velocity dispersion measured with the HST can only be fit when a massive BH is
included in the models.Comment: 47 pages, 14 figures (postscript). Submitted to Ap
An Over-Massive Black Hole in a Typical Star-Forming Galaxy, 2 Billion Years After the Big Bang
Supermassive black holes (SMBHs) and their host galaxies are generally
thought to coevolve, so that the SMBH achieves up to about 0.2 to 0.5% of the
host galaxy mass in the present day. The radiation emitted from the growing
SMBH is expected to affect star formation throughout the host galaxy. The
relevance of this scenario at early cosmic epochs is not yet established. We
present spectroscopic observations of a galaxy at redshift z = 3.328, which
hosts an actively accreting, extremely massive BH, in its final stages of
growth. The SMBH mass is roughly one-tenth the mass of the entire host galaxy,
suggesting that it has grown much more efficiently than the host, contrary to
models of synchronized coevolution. The host galaxy is forming stars at an
intense rate, despite the presence of a SMBH-driven gas outflow.Comment: Author's version, including the main paper and the Supplementary
Materials (16+21 pages, 3+3 figures
Semi-Analytical Models for the Formation of Disk Galaxies II. Dark Matter versus Modified Newtonian Dynamics
We present detailed semi-analytical models for the formation of disk galaxies
both in a Universe dominated by dark matter (DM), and in one for which the
force law is given by modified Newtonian dynamics (MOND). We tune the models to
fit the observed near-infrared Tully-Fisher (TF) relation, and compare numerous
predictions of the resulting models with observations. The DM and MOND models
are almost indistinguishable. They both yield gas mass fractions and dynamical
mass-to-light ratios which are in good agreement with observations. Both models
reproduce the narrow relation between global mass-to-light ratio and central
surface brightness, and reveal a characteristic acceleration, contrary to
claims that these relations are not predicted by DM models. Both models require
SN feedback in order to reproduce the lack of high surface brightness dwarf
galaxies. However, the introduction of feedback to the MOND models steepens the
TF relation and increases the scatter, making MOND only marginally consistent
with observations. The most serious problem for the DM models is their
prediction of steep central rotation curves. However, the DM rotation curves
are only slightly steeper than those of MOND, and are only marginally
inconsistent with the poor resolution data on LSB galaxies.Comment: 26 pages, 11 figures. Accepted for publication in Ap
Moderate-to-deep sedation technique, using propofol and ketamine, allowing synchronised breathing for magnetic resonance high-intensity focused ultrasound (MR-HIFU) treatment for uterine fibroids: a pilot study
BACKGROUND: Magnetic resonance high-intensity focused ultrasound (MR-HIFU) treatment for uterine fibroids is rapidly gaining popularity as a treatment modality. This procedure is generally uncomfortable, painful, and requires minimal or absence of movement and an MR-HIFU synchronised breathing pattern of the patient. Procedural sedation and analgesia protocols have become the standard practice in interventional radiology departments worldwide. The aim of this study was to explore if a sedation regimen with low-dose propofol and ketamine performed by trained non-medical sedation practitioners could result in relief of discomfort for the patient and in adequate working conditions for MR-HIFU treatment for uterine fibroids. METHODS: In this study, conducted from August 2013 until November 2014, 20 patients were subjected to MR-HIFU treatment of uterine fibroids. Patients were deeply sedated using intravenous propofol and esketamine according to a standardised hospital protocol to allow synchronisation of the breathing pattern to the MR-HIFU. The quality of sedation for MR-HIFU and complications were recorded and analysed. The side effects of the sedation technique, the propofol and esketamine consumption rate, the duration of recovery, and patient satisfaction after 24 h were examined. RESULTS: A total of 20 female patients (mean age 42.4 [range 32-53] years) were enrolled. Mean propofol/esketamine dose was 1309 mg/39.5 mg (range 692-1970 mg/ 23.6-87.9 mg). Mean procedure time was 269 min (range 140-295 min). Application of the sedation protocol resulted in a regular breathing pattern, which could be synchronised with the MR-HIFU procedures without delay. The required treatment was completed in all cases. There were no major adverse events. Hypoxemia (oxygen desaturation <92%) and hallucinations were not observed. CONCLUSIONS: The use of a specific combination of IV propofol and esketamine for procedural sedation and analgesia reduced the discomfort and pain during MR-guided HIFU treatments of uterine fibroids. The resulting regular breathing pattern allowed for easy synchronisation of the MR-HIFU procedure. Based on our results, esketamine and propofol sedation performed by trained non-medical sedation practitioners is feasible and safe, has a low risk of major adverse events, and has a short recovery time, avoiding a session of general anaesthesia
Scaling Relations of Spiral Galaxies
We construct a large data set of global structural parameters for 1300 field
and cluster spiral galaxies and explore the joint distribution of luminosity L,
optical rotation velocity V, and disk size R at I- and 2MASS K-bands. The I-
and K-band velocity-luminosity (VL) relations have log-slopes of 0.29 and 0.27,
respectively with sigma_ln(VL)~0.13, and show a small dependence on color and
morphological type in the sense that redder, early-type disk galaxies rotate
faster than bluer, later-type disk galaxies for most luminosities. The VL
relation at I- and K-bands is independent of surface brightness, size and light
concentration. The log-slope of the I- and K-band RL relations is a strong
function of morphology and varies from 0.25 to 0.5. The average dispersion
sigma_ln(RL) decreases from 0.33 at I-band to 0.29 at K, likely due to the
2MASS selection bias against lower surface brightness galaxies. Measurement
uncertainties are sigma_ln(V)~0.09, sigma_ln(L)~0.14 and somewhat larger and
harder to estimate for ln(R). The color dependence of the VL relation is
consistent with expectations from stellar population synthesis models. The VL
and RL residuals are largely uncorrelated with each other; the RV-RL residuals
show only a weak positive correlation. These correlations suggest that scatter
in luminosity is not a significant source of the scatter in the VL and RL
relations. The observed scaling relations can be understood in the context of a
model of disk galaxies embedded in dark matter halos that invokes low mean spin
parameters and dark halo expansion, as we describe in our companion paper
(Dutton et al. 2007). We discuss in two appendices various pitfalls of standard
analytical derivations of galaxy scaling relations, including the Tully-Fisher
relation with different slopes. (Abridged).Comment: Accepted for publication at ApJ. The full document, with
high-resolution B&W and colour figures, is available at
http://www.astro.queensu.ca/~courteau/papers/VRL2007ApJ.pdf . Our data base
for 1303 spiral galaxies is also available at
http://www.astro.queensu.ca/~courteau/data/VRL2007.da
Taming our wild data: On intercoder reliability in discourse research
Many research questions in the field of applied linguistics are answered by manually analyzing data collections or corpora: collections of spoken, written and/or visual communicative messages. In this kind of quantitative content analysis, the coding of subjective language data often leads to disagreement among raters. In this paper, we discuss causes of and solutions to disagreement problems in the analysis of discourse. We discuss crucial factors determining the quality and outcome of corpus analyses, and focus on the sometimes tense relation between reliability and validity. We evaluate formal assessments of intercoder reliability. We suggest a number of ways to improve the intercoder reliability, such as the precise specification of the variables and their coding categories and carving up the coding process into smaller substeps. The paper ends with a reflection on challenges for future work in discourse analysis, with special attention to big data and multimodal discourse
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