3,631 research outputs found
Building a flagellum in biological outer space.
Flagella, the rotary propellers on the surface of bacteria, present a paradigm for how cells build and operate complex molecular 'nanomachines'. Flagella grow at a constant rate to extend several times the length of the cell, and this is achieved by thousands of secreted structural subunits transiting through a central channel in the lengthening flagellum to incorporate into the nascent structure at the distant extending tip. A great mystery has been how flagella can assemble far outside the cell where there is no conventional energy supply to fuel their growth. Recent work published by Evans et al. [Nature (2013) 504: 287-290], has gone some way towards solving this puzzle, presenting a simple and elegant transit mechanism in which growth is powered by the subunits them selves as they link head-to-tail in a chain that is pulled through the length of the growing structure to the tip. This new mechanism answers an old question and may have resonance in other assembly processes.This is the published version of the manuscript. It was published in the journal Microbial Cell by Shared Science Publishers OG and can be found here: http://microbialcell.com/wordpress/wp-content/uploads/2014/01/2014A-Evans-Microbial-Cell.pd
Building a flagellum outside the bacterial cell.
Flagella, the helical propellers that extend from the bacterial surface, are a paradigm for how complex molecular machines can be built outside the living cell. Their assembly requires ordered export of thousands of structural subunits across the cell membrane and this is achieved by a type III export machinery located at the flagellum base, after which subunits transit through a narrow channel at the core of the flagellum to reach the assembly site at the tip of the nascent structure, up to 20ÎĽm from the cell surface. Here we review recent findings that provide new insights into flagellar export and assembly, and a new and unanticipated mechanism for constant rate flagellum growth.This is the final published version. It is published by Elsevier and can be found online here: http://www.sciencedirect.com/science/article/pii/S0966842X14001188
From Molecular Cores to Planet-forming Disks with SIRTF
The SIRTF mission and the Legacy programs will provide coherent data bases
for extra-galactic and Galactic science that will rapidly become available to
researchers through a public archive. The capabilities of SIRTF and the six
legacy programs are described briefly. Then the cores to disks (c2d) program is
described in more detail. The c2d program will use all three SIRTF instruments
(IRAC, MIPS, and IRS) to observe sources from molecular cores to protoplanetary
disks, with a wide range of cloud masses, stellar masses, and star-forming
environments. The SIRTF data will stimulate many follow-up studies, both with
SIRTF and with other instruments.Comment: 6 pages, from Fourth Cologne-Bonn-Zermatt-Symposium, The Dense
Interstellar Matter in Galaxie
Qualitative Environmental Health Research: An Analysis of the Literature, 1991-2008
BACKGROUND. Recent articles have advocated for the use of qualitative methods in environmental health research. Qualitative research uses nonnumeric data to understand people's opinions, motives, understanding, and beliefs about events or phenomena. OBJECTIVE. In this analysis of the literature, I report the use of qualitative methods and data in the study of the relationship between environmental exposures and human health. DATA SOURCES. A primary search on ISI Web of Knowledge/Web of Science for peer-reviewed journal articles dated from 1991 through 2008 included the following three terms: qualitative, environ*, and health. Inclusion and exclusion criteria are described. DATA EXTRACTION. Searches resulted in 3,155 records. Data were extracted and findings of articles analyzed to determine where and by whom qualitative environmental health research is conducted and published, the types of methods and analyses used in qualitative studies of environmental health, and the types of information qualitative data contribute to environmental health. DATA SYNTHESIS. Ninety-one articles met inclusion criteria. These articles were published in 58 different journals, with a maximum of eight for a single journal. The results highlight a diversity of disciplines and techniques among researchers who used qualitative methods to study environmental health, with most studies relying on one-on-one interviews. Details of the analyses were absent from a large number of studies. Nearly all of the studies identified increased scientific understanding of lay perceptions of environmental health exposures. DISCUSSION AND CONCLUSIONS. Qualitative data are published in traditionally quantitative environmental health studies to a limited extent. However, this analysis demonstrates the potential of qualitative data to improve understanding of complex exposure pathways, including the influence of social factors on environmental health, and health outcomes.National Institute of Environmental Health Sciences (R25 ES012084, P42ES007381
Molecular Gas in Quasar Hosts
The study of molecular gas in quasar host galaxies addresses a number of interesting questions pertaining to the hosts' ISM, to unified schemes relating quasars and IR galaxies, and to the processes fueling nuclear activity. In this contribution I review observations of molecular gas in quasar hosts from z=0.06 to z=4.7. The Cloverleaf quasar at z=2.5 is featured as a case where there are now enough detected transitions (four in CO, and one each in CI and HCN) to allow detailed modeling of physical conditions in the molecular ISM. We find that the CO-emitting gas is warmer, denser, and less optically thick than that found in typical Galactic molecular clouds. These differences are probably due to the presence of the luminous quasar in the nucleus of the Cloverleaf's host galaxy
Pancreatic adenocarcinoma in a patient with Situs Inversus: a case report of this rare coincidence
<p>Abstract</p> <p>Background</p> <p><it>Situs inversus </it>(SI) is a relatively rare occurrence in patients with pancreatic adenocarcinoma. Pancreatic resection in these patients has rarely been described. CT scan imaging is a principle modality for detecting pancreatic cancer and its use in SI patients is seldom reported.</p> <p>Case Presentation</p> <p>We report a 48 year old woman with SI who, despite normal CT scan 8 months earlier, presented with obstructive jaundice and a pancreatic head mass requiring a pancreaticoduodenectomy. The surgical pathology report demonstrated pancreatic adenocarcinoma.</p> <p>Conclusion</p> <p>SI is a rare condition with concurrent pancreatic cancer being even rarer. Despite the rarity, pancreaticoduodenectomy in these patients for resectable lesions is safe as long as special consideration to the anatomy is taken. Additionally, radiographic imaging has significantly improved detection of early pancreatic cancer; however, there continues to be a need for improved detection of small neoplasms.</p
Long range correlations generated by phase separation. Exact results from field theory
We consider near-critical planar systems with boundary conditions inducing phase separation. While order parameter correlations decay exponentially in pure phases, we show by direct field theoretical derivation how phase separation generates long range correlations in the direction parallel to the interface, and determine their exact analytic form. The latter leads to specific contributions to the structure factor of the interface
World health system performance revisited: the impact of varying the relative importance of health system goals
BACKGROUND: In 2002, the World Health Organization published a health system performance ranking for 191 member countries. The ranking was based on five indicators, with fixed weights common to all countries. METHODS: We investigate the feasibility and desirability of using mathematical programming techniques that allow weights to vary across countries to reflect their varying circumstances and objectives. RESULTS: By global distributional measures, scores and ranks are found to be not very sensitive to changes in weights, although differences can be large for individual countries. CONCLUSIONS: Building the flexibility of variable weights into calculation of the performance index is a useful way to respond to the debates and criticisms appearing since publication of the ranking
The foot posture index, ankle lunge test, Beighton scale and the lower limb assessment score in healthy children: a reliability study
<p>Abstract</p> <p>Background</p> <p>Outcome measures are important when evaluating treatments and physiological progress in paediatric populations. Reliable, relevant measures of foot posture are important for such assessments to be accurate over time. The aim of the study was to assess the intra- and inter-rater reliability of common outcome measures for paediatric foot conditions.</p> <p>Methods</p> <p>A repeated measures, same-subject design assessed the intra- and inter-rater reliability of measures of foot posture, joint hypermobility and ankle range: the Foot Posture Index (FPI-6), the ankle lunge test, the Beighton scale and the lower limb assessment scale (LLAS), used by two examiners in 30 healthy children (aged 7 to 15 years). The Oxford Ankle Foot Questionnaire (OxAFQ-C) was completed by participants and a parent, to assess the extent of foot and ankle problems.</p> <p>Results</p> <p>The OxAFQ-C demonstrated a mean (SD) score of 6 (6) in adults and 7(5) for children, showing good agreement between parents and children, and which indicates mid-range (transient) disability. Intra-rater reliability was good for the FPI-6 (ICC = 0.93 - 0.94), ankle lunge test (ICC = 0.85-0.95), Beighton scale (ICC = 0.96-0.98) and LLAS (ICC = 0.90-0.98). Inter-rater reliability was largely good for each of the: FPI-6 (ICC = 0.79), ankle lunge test (ICC = 0.83), Beighton scale (ICC = 0.73) and LLAS (ICC = 0.78).</p> <p>Conclusion</p> <p>The four measures investigated demonstrated adequate intra-rater and inter-rater reliability in this paediatric sample, which further justifies their use in clinical practice.</p
Flavor in Minimal Conformal Technicolor
We construct a complete, realistic, and natural UV completion of minimal
conformal technicolor that explains the origin of quark and lepton masses and
mixing angles. As in "bosonic technicolor", we embed conformal technicolor in a
supersymmetric theory, with supersymmetry broken at a high scale. The exchange
of heavy scalar doublets generates higher-dimension interactions between
technifermions and quarks and leptons that give rise to quark and lepton masses
at the TeV scale. Obtaining a sufficiently large top quark mass requires strong
dynamics at the supersymmetry breaking scale in both the top and technicolor
sectors. This is natural if the theory above the supersymmetry breaking also
has strong conformal dynamics. We present two models in which the strong top
dynamics is realized in different ways. In both models, constraints from
flavor-changing effects can be easily satisfied. The effective theory below the
supersymmetry breaking scale is minimal conformal technicolor with an
additional light technicolor gaugino. We argue that this light gaugino is a
general consequence of conformal technicolor embedded into a supersymmetric
theory. If the gaugino has mass below the TeV scale it will give rise to an
additional pseudo Nambu-Goldstone boson that is observable at the LHC.Comment: 37 pages; references adde
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