5,568 research outputs found
Functional Analysis of the Role of Toxin-Antitoxin (TA) Loci in Bacterial Persistence.
Bacterial Persistence: Methods and ProtocolsThe final publication is available at Springer via http://dx.doi.org/10.1007/978-1-4939-2854-5_11We have developed a method to analyze the functionality of putative TA loci by expressing them in Escherichia coli. Here, we describe the procedure for cloning recombinant TA genes into inducible plasmids and expressing these in E. coli. Following expression, toxicity, resuscitation of growth, and changes in persister cell formation are assayed. This can confirm whether predicted TA loci are active in E. coli and whether expression can affect persister cell formation
Jet-Induced Nucleosynthesis in Misaligned Microquasars
The jet axes and the orbital planes of microquasar systems are usually
assumed to be approximately perpendicular, eventhough this is not currently an
observational requirement. On the contrary, in one of the few systems where the
relative orientations are well-constrained, V4641Sgr, the jet axis is known to
lie not more than ~36 degrees from the binary plane. Such a jet, lying close to
the binary plane, and traveling at a significant fraction of the speed of light
may periodically impact the secondary star initiating nuclear reactions on its
surface. The integrated yield of such nuclear reactions over the age of the
binary system (less the radiative mass loss) will detectably alter the
elemental abundances of the companion star. This scenario may explain the
anomalously high Li enhancements (roughly ~20-200 times the sun's photospheric
value; or, equivalently, 0.1-1 times the average solar system value) seen in
the companions of some black-hole X-ray binary systems. (Such enhancements are
puzzling since Li nuclei are exceedingly fragile - being easily destroyed in
the interiors of stars - and Li would be expected to be depleted rather than
enhanced there.) Gamma-ray line signatures of the proposed process could
include the 2.22 MeV neutron capture line as well as the 0.478 MeV 7Li*
de-excitation line, both of which may be discernable with the INTEGRAL
satellite if produced in an optically thin region during a large outburst. For
very energetic jets, a relatively narrow neutral pion gamma-decay signature at
67.5 MeV could also be measurable with the GLAST satellite. We argue that about
10-20% of all microquasar systems ought to be sufficiently misaligned as to be
undergoing the proposed jet-secondary impacts.Comment: ApJ, accepted. Includes referee's suggestions and some minor
clarifications over previous versio
A practical approach to anaesthesia for paediatric liver transplantation
Anaesthesia for paediatric liver transplantation requires meticulous attention to detail, an understanding of the disease process leading up to the need for transplantation, and an awareness of the haematological, biochemical, and multi-organ consequences of this operation. In the past 20 years, significant advances in surgical techniques, organ procurement and preservation, immunosuppression, anaesthetic management and monitoring, and postoperative care in the intensive care unit have contributed to improved outcomes of both the graft and the patient. In more recent years, the use of reduced size and living related organs has increased the donor pool for infants and children. Paediatric liver transplantation in South Africa, up until the present time, has been centered at the Red Cross Children's Hospital in Cape Town, and survival rates here are comparable with international figures. This paper highlights the preoperative problems which face the anaesthetist, emphasises the importance of good planning and preparation for the intraoperative procedure, simplifies the surgical technique of the operation, and stresses the value of a multidisciplinary approach to the child requiring liver transplantation.Southern African Journal of Anaesthesia and Analgesia Vol. 12(1) 2006: 11-1
Characteristics and health burden of the undiagnosed population at risk of chronic obstructive pulmonary disease in China
BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality in China. However, identifying patients has proved challenging, resulting in widespread under-diagnosis of the condition. We examined the prevalence of COPD diagnosis and COPD risk among adults in urban mainland China, the factors associated with having a COPD diagnosis or COPD risk, and the healthcare resource use and health outcomes of these groups compared with controls. METHODS: Respondents to the 2017 National Health and Wellness Survey in China (n = 19,994) were classified into three groups: 'COPD Diagnosed', 'COPD Risk (undiagnosed)', and Control (unaffected), based on their self-reported diagnosis and Lung Function Questionnaire (LFQ) score. The groups were characterised by sociodemographic, health-related quality of life (HRQoL), productivity impairment, and healthcare resource use. Pairwise comparisons (t tests and chi-squared tests) and multivariable regression analyses were used to investigate factors associated with being at risk of, or diagnosed with, COPD. RESULTS: 3320 (16.6%) respondents had a suspected risk of COPD but did not report receiving a diagnosis. This was projected to 105.3 million people, or 16.9% of adult urban Chinese. Of these respondents with an identified risk, only 554 (16.7%) were aware of COPD by name. Relative to those without COPD, those with a risk of COPD (undiagnosed) had significantly greater healthcare resource use, lower productivity and lower HRQoL not only compared to those without COPD, but also compared to people with a COPD diagnosis. Factors associated with increased odds of being at risk of COPD were older age, smoking, alcohol consumption, overweight BMI, occasional exercise, higher comorbidities, asthma diagnosis, being female, lower education, not being employed, and living in a high pollution province (p < 0.05). CONCLUSIONS: There is a substantial group of individuals, undiagnosed, but living with a risk of COPD, who have impaired HRQoL, lower productivity and elevated healthcare resource use patterns. Case-detection tools such as the LFQ may prove a quick and cost-effective approach for identifying these at-risk individuals for further definitive testing and appropriate treatment in China
The Highest Energy Neutrinos
Measurements of the arrival directions of cosmic rays have not revealed their
sources. High energy neutrino telescopes attempt to resolve the problem by
detecting neutrinos whose directions are not scrambled by magnetic fields. The
key issue is whether the neutrino flux produced in cosmic ray accelerators is
detectable. It is believed that the answer is affirmative, both for the
galactic and extragalactic sources, provided the detector has kilometer-scale
dimensions. We revisit the case for kilometer-scale neutrino detectors in a
model-independent way by focussing on the energetics of the sources. The real
breakthrough though has not been on the theory but on the technology front: the
considerable technical hurdles to build such detectors have been overcome.
Where extragalactic cosmic rays are concerned an alternative method to probe
the accelerators consists in studying the arrival directions of neutrinos
produced in interactions with the microwave background near the source, i.e.
within a GZK radius. Their flux is calculable within large ambiguities but, in
any case, low. It is therefore likely that detectors that are larger yet by
several orders of magnitudes are required. These exploit novel techniques, such
as detecting the secondary radiation at radio wavelengths emitted by neutrino
induced showers.Comment: 16 pages, pdflatex, 7 jpg figures, ICRC style files included.
Highlight talk presented at the 30th International Cosmic Ray Conference,
Merida, Mexico, 200
Global and regional trends in particulate air pollution and attributable health burden over the past 50 years
Long-term exposure to ambient particulate matter (PM2.5, mass of particles with an aerodynamic dry diameter of < 2.5 μm) is a major risk factor to the global burden of disease. Previous studies have focussed on present day or future health burdens attributed to ambient PM2.5. Few studies have estimated changes in PM2.5 and attributable health burdens over the last few decades, a period where air quality has changed rapidly. Here we used the HadGEM3-UKCA coupled chemistry-climate model, integrated exposure-response relationships, demographic and background disease data to provide the first estimate of the changes in global and regional ambient PM2.5 concentrations and attributable health burdens over the period 1960 to 2009. Over this period, global mean population-weighted PM2.5 concentrations increased by 38%, dominated by increases in China and India. Global attributable deaths increased by 89% to 124% over the period 1960 to 2009, dominated by large increases in China and India. Population growth and ageing contributed mostly to the increases in attributable deaths in China and India, highlighting the importance of demographic trends. In contrast, decreasing PM2.5 concentrations and background disease dominated the reduction in attributable health burden in Europe and the United States. Our results shed light on how future projected trends in demographics and uncertainty in the exposure–response relationship may provide challenges for future air quality policy in Asia
Cosmic Physics: The High Energy Frontier
Cosmic rays have been observed up to energies times larger than those
of the best particle accelerators. Studies of astrophysical particles (hadrons,
neutrinos and photons) at their highest observed energies have implications for
fundamental physics as well as astrophysics. Thus, the cosmic high energy
frontier is the nexus to new particle physics. This overview discusses recent
advances being made in the physics and astrophysics of cosmic rays and cosmic
gamma-rays at the highest observed energies as well as the related physics and
astrophysics of very high energy cosmic neutrinos. These topics touch on
questions of grand unification, violation of Lorentz invariance, as well as
Planck scale physics and quantum gravity.Comment: Topical Review Paper to be published in the Journal of Physics G, 50
page
Multiwavelength Observations of LS I +61 303 with VERITAS, Swift and RXTE
We present results from a long-term monitoring campaign on the TeV binary LSI
+61 303 with VERITAS at energies above 500 GeV, and in the 2-10 keV hard X-ray
bands with RXTE and Swift, sampling nine 26.5 day orbital cycles between
September 2006 and February 2008. The binary was observed by VERITAS to be
variable, with all integrated observations resulting in a detection at the 8.8
sigma (2006/2007) and 7.3 sigma (2007/2008) significance level for emission
above 500 GeV. The source was detected during active periods with flux values
ranging from 5 to 20% of the Crab Nebula, varying over the course of a single
orbital cycle. Additionally, the observations conducted in the 2007-2008
observing season show marginal evidence (at the 3.6 sigma significance level)
for TeV emission outside of the apastron passage of the compact object around
the Be star. Contemporaneous hard X-ray observations with RXTE and Swift show
large variability with flux values typically varying between 0.5 and 3.0*10^-11
ergs cm^-2 s^-1 over a single orbital cycle. The contemporaneous X-ray and TeV
data are examined and it is shown that the TeV sampling is not dense enough to
detect a correlation between the two bands.Comment: 30 pages, 5 figures, 2 table, Accepted for publication in The
Astrophysical Journa
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