639 research outputs found
Reliable time multiplexing by replacement
Electromechanical, magnetic switching circuit for redundant time division multiplex transmission - behavior and failure analysi
Changes in calcification of coccoliths under stable atmospheric CO2
The response of coccolithophore calcification to ocean acidification has been studied in culture experiments as well as in present and past oceans. The response, however, is different between species and strains, and for the relatively small carbonate chemistry changes observed in natural environments, a uniform response of the entire coccolithophore community has not been documented so far. Moreover, previous palaeo-studies basically focus on changes in coccolith weight due to increasing CO2 and the resulting changes in the carbonate system, and only few studies focus on the influence of other environmental factors. In order to untangle changes in coccolithophore calcification due to environmental factors such as temperature and/or productivity from changes caused by increasing pCO2 and decreasing carbonate ion concentration, we here present a study on coccolith calcification from the Holocene North Atlantic Ocean. The pre-industrial Holocene, with its predominantly stable atmospheric CO2, provides the conditions for such a comprehensive analysis. For an analysis on changes in major components of Holocene coccolithophores under natural conditions, the family Noelaerhabdaceae was selected, which constitutes the main part of the assemblage in the North Atlantic.
Records of average coccolith weights from three Holocene sediment cores along a north–south transect in the North Atlantic were analysed. During the Holocene, mean weight (and therefore calcification) of Noelaerhabdaceae (Emiliania huxleyi and Gephyrocapsa) coccoliths decreased at the Azores (Geofar KF 16) from around 7 to 6 pg, but increased at the Rockall Plateau (ODP site 980) from around 6 to 8 pg, and at the Vøring Plateau (MD08-3192) from 7 to 10 pg. The amplitude of average weight variability is within the range of glacial–interglacial changes that were interpreted to be an effect of decreasing carbonate ion concentration. By comparison with SEM assemblage counts, we show that weight changes are not only partly due to variations in the coccolithophore assemblage but also an effect of a change in calcification and/or morphotype variability within single species. Our results indicate that there is no single key factor responsible for the observed changes in coccolith weight. A major increase in coccolith weight occurs during a slight decrease in carbonate ion concentration in the late Holocene at the Rockall Plateau and Vøring Plateau. Here, more favourable productivity conditions apparently lead to an increase in coccolith weight, either due to the capability of coccolithophore species, especially E. huxleyi, to adapt to decreasing carbonate ion concentration or due to a shift towards heavier calcifying morphotypes
More Than the Sum of Its Parts: Unlocking the Power of Network Structure for Understanding Organization and Function in Microbiomes
Plant and soil microbiomes are integral to the health and productivity of plants and ecosystems, yet researchers struggle to identify microbiome characteristics important for providing beneficial outcomes. Network analysis offers a shift in analytical framework beyond who is present to the organization or patterns of coexistence between microbes within the microbiome. Because microbial phenotypes are often significantly impacted by coexisting populations, patterns of coexistence within microbiomes are likely to be especially important in predicting functional outcomes. Here, we provide an overview of the how and why of network analysis in microbiome research, highlighting the ways in which network analyses have provided novel insights into microbiome organization and functional capacities, the diverse network roles of different microbial populations, and the eco-evolutionary dynamics of plant and soil microbiomes
The Oxygen Abundance of Nearby Galaxies from Sloan Digital Sky Survey Spectra
We have derived the oxygen abundance for a sample of nearby galaxies in the
Data Release 5 of the Sloan Digital Sky Survey (SDSS) which possess at least
two independent spectra of one or several HII regions with a detected
[OIII]4363 auroral line. Since, for nearby galaxies, the [OII]3727 nebular line
is out of the observed wavelength range, we propose a method to derive (O/H)_ff
abundances using the classic Te method coupled with the ff relation. (O/H)_7325
abundances have also been determined, based on the [OII]7320,7330 line
intensities, and using a small modification of the standard Te method. The
(O/H)_ff and (O/H)_7325 abundances have been derived with both the one- and
two-dimensional t_2 - t_3 relations. It was found that the (O/H)_ff abundances
derived with the parametric two-dimensional t_2 - t_3 relation are most
reliable. Oxygen abundances have been determined in 29 nearby galaxies, based
on 84 individual abundance determinations in HII regions. Because of our
selection methods, the metallicity of our galaxies lies in the narrow range 8.2
< 12 + log (O/H) < 8.4. The radial distribution of oxygen abundances in the
disk of the spiral galaxy NGC 4490 is determined for the first time.Comment: 39 pages, 10 figures, 4 tables, accepted for publication in the
Astrophysical Journa
Staging of endometrial cancer with MRI: Guidelines of the European Society of Urogenital Imaging
The purpose of this study was to define guidelines for endometrial cancer staging with MRI. The technique included critical review and expert consensus of MRI protocols by the female imaging subcommittee of the European Society of Urogenital Radiology, from ten European institutions, and published literature between 1999 and 2008. The results indicated that high field MRI should include at least two T2-weighted sequences in sagittal, axial oblique or coronal oblique orientation (short and long axis of the uterine body) of the pelvic content. High-resolution post-contrast images acquired at 2min ± 30 s after intravenous contrast injection are suggested to be optimal for the diagnosis of myometrial invasion. If cervical invasion is suspected, additional slice orientation perpendicular to the axis of the endocervical channel is recommended. Due to the limited sensitivity of MRI to detect lymph node metastasis without lymph node-specific contrast agents, retroperitoneal lymph node screening with pre-contrast sequences up to the level of the kidneys is optional. The likelihood of lymph node invasion and the need for staging lymphadenectomy are also indicated by high-grade histology at endometrial tissue sampling and by deep myometrial or cervical invasion detected by MRI. In conclusion, expert consensus and literature review lead to an optimized MRI protocol to stage endometrial cance
The impact of the National HIV Health Care Worker Hotline on patient care in South Africa
<p>Abstract</p> <p>Background</p> <p>South Africa has a huge burden of illness due to HIV infection. Many health care workers managing HIV infected patients, particularly those in rural areas and primary care health facilities, have minimal access to information resources and to advice and support from experienced clinicians. The Medicines Information Centre, based in the Division of Clinical Pharmacology at the University of Cape Town, has been running the National HIV Health Care Worker (HCW) Hotline since 2008, providing free information for HIV treatment-related queries via telephone, fax and e-mail.</p> <p>Results</p> <p>A questionnaire-based study showed that 224 (44%) of the 511 calls that were received by the hotline during the 2-month study period were patient-specific. Ninety-four completed questionnaires were included in the analysis. Of these, 72 (77%) were from doctors, 13 (14%) from pharmacists and 9 (10%) from nurses. 96% of the callers surveyed took an action based on the advice received from the National HIV HCW Hotline. The majority of actions concerned the start, dose adaption, change, or discontinuation of medicines. Less frequent actions taken were adherence and lifestyle counselling, further investigations, referring or admission of patients.</p> <p>Conclusions</p> <p>The information provided by the National HIV HCW Hotline on patient-specific requests has a direct impact on the management of patients.</p
The Composition Gradient in M101 Revisited. II. Electron Temperatures and Implications for the Nebular Abundance Scale
(Abridged) We use high S/N spectra of 20 HII regions in the giant spiral
galaxy M101 to derive electron temperatures for the HII regions and robust
metal abundances over radii R = 0.19-1.25 Ro (6-41 kpc). We compare the
consistency of electron temperatures measured from the [O III]4363, [N II]5755,
[S III]6312, and [O II]7325 auroral lines. Temperatures from [O III], [S III],
and [N II] are correlated with relative offsets that are consistent with
expectations from nebular photoionization models. However, the temperatures
derived from the [O II]7325 line show a large scatter and are nearly
uncorrelated with temperatures derived from other ions. Our derived oxygen
abundances O/H are well fitted by an exponential distribution over six disk
scale lengths, from approximately 1.3 solar in the center to 1/15 solar in the
outermost region studied (for solar 12 + log (O/H)=8.7). We measure significant
radial gradients in N/O and He/H abundance ratios, but relatively constant S/O
and Ar/O. Our abundances are systematically lower by 0.2-0.5 dex than those
derived from the most widely used strong-line "empirical" abundance indicators.
We suspect that most of the disagreement with the strong-line abundances arises
from uncertainties in the nebular models that are used to calibrate the
"empirical" scale, and that strong-line abundances derived for HII regions and
emission-line galaxies are as much as a factor of two higher than the actual
oxygen abundances. However other explanations, such as the effects of
temperature fluctuations on the auroral line based abundances cannot be
completely ruled out. These results point to the need for direct abundance
determinations of a larger sample of extragalactic HII regions, especially for
objects more metal-rich than solar.Comment: 50 pages, 14 figures, 8 tables. Accepted by Ap
Staging of endometrial cancer with MRI: guidelines of the european society of urogenital imaging
The purpose of this study
was to define guidelines for endometrial
cancer staging with MRI. The
technique included critical review and
expert consensus of MRI protocols by the female imaging subcommittee of
the European Society of Urogenital
Radiology, from ten European institutions,
and published literature between
1999 and 2008. The results
indicated that high field MRI should
include at least two T2-weighted
sequences in sagittal, axial oblique or
coronal oblique orientation (short and
long axis of the uterine body) of the
pelvic content. High-resolution postcontrast
images acquired at 2 min ± 30 s
after intravenous contrast injection
are suggested to be optimal for the
diagnosis of myometrial invasion. If
cervical invasion is suspected, additional
slice orientation perpendicular
to the axis of the endocervical channel
is recommended. Due to the limited
sensitivity of MRI to detect lymph
node metastasis without lymph nodespecific
contrast agents, retroperitoneal
lymph node screening with
pre-contrast sequences up to the level
of the kidneys is optional. The likelihood
of lymph node invasion and
the need for staging lymphadenectomy
are also indicated by high-grade histology
at endometrial tissue sampling
and by deep myometrial or cervical
invasion detected by MRI. In conclusion,
expert consensus and literature
review lead to an optimized MRI
protocol to stage endometrial cancer
Evidence of distributed subpial T2* signal changes at 7T in multiple sclerosis : an histogram based approach
Subpial lesions are the most frequent type of cortical lesion in multiple sclerosis (MS), and are thought to be closely associated with poor clinical outcome. Neuropathological studies report that subpial lesions may come in two major types: they may appear as circumscribed, focal lesions, or extend across multiple adjacent gyri leading to a phenomenon termed “general subpial demyelination” [1]. The in vivo evaluation of diffuse subpial disease is challenging – signal changes may be subtle, and extend across large regions where signal inhomogeneities due to B1 and RF receive coil non-uniformities become more pronounced. Here, we investigate whether a histogram-based analysis of T2* signal intensity in the cortex, at 7T MRI, can show evidence of distributed subpial cortical changes in patients with MS, as described histopathologically. We hypothesized that this phenomenon would be associated with significantly increased T2* signal intensity in patients compared to age-matched controls.Center Algoritm
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