662 research outputs found
Design of crystal-like aperiodic solids with selective disorder--phonon coupling
Functional materials design normally focuses on structurally-ordered systems
because disorder is considered detrimental to many important physical
properties. Here we challenge this paradigm by showing that particular types of
strongly-correlated disorder can give rise to useful characteristics that are
inaccessible to ordered states. A judicious combination of low-symmetry
building unit and high-symmetry topological template leads to aperiodic
"procrystalline" solids that harbour this type of topological disorder. We
identify key classes of procrystalline states together with their
characteristic diffraction behaviour, and establish a variety of mappings onto
known and target materials. Crucially, the strongly-correlated disorder we
consider is associated with specific sets of modulation periodicities
distributed throughout the Brillouin zone. Lattice dynamical calculations
reveal selective disorder-phonon coupling to lattice vibrations characterised
by these same periodicities. The principal effect on the phonon spectrum is to
bring about dispersion in energy rather than wave-vector, as in the
poorly-understood "waterfall" effect observed in relaxor ferroelectrics. This
property of procrystalline solids suggests a mechanism by which
strongly-correlated topological disorder might allow new and useful
functionalities, including independently-optimised thermal and electronic
transport behaviour as required for high-performance thermoelectrics.Comment: 4 figure
Mode of action and choice of antimalarial drugs for intermittent preventive treatment in infants.
Intermittent preventive treatment in infants (IPTi) is an effective and safe malaria control strategy. However, it remains unclear what antimalarials should be used to replace sulfadoxine-pyrimethamine (SP) when and where SP is no longer an effective drug for IPTi. Work recently conducted in Tanzania, combined with the findings of previous studies, indicates that IPTi is essentially intermittent chemoprophylaxis; consequently, long-acting antimalarials that provide a long period of post-treatment prophylaxis will be the most effective alternative to SP. However, because of concerns about development of drug resistance, new combinations of long-acting drugs are urgently needed
Screening and treatment of malaria in pregnancy in West Africa
The efficacy of intermittent preventive treatment for malaria with sulfadoxine-pyrimethamine (IPTp-SP) in pregnancy is threatened in parts of Africa by the emergence and spread of resistance to SP. Intermittent screening with a rapid diagnostic test (RDT) and treatment of positive women (ISTp) is an alternative approach. The study conducted an open, individually randomized, non-inferiority trial of IPTp-SP versus ISTp in 5,354 primi- or secundigravidae in The Gambia, Mali, Burkina Faso and Ghana
Composite endpoints for malaria case-management: not simplifying the picture?
Rapid diagnostic tests (RDTs) for infection with Plasmodium spp. offer two main potential advantages related to malaria treatment: 1) ensuring that individuals with malaria are promptly treated with an effective artemisinin-based combination therapy, and 2) ensuring that individuals without malaria do not receive an anti-malarial they do not need (and instead receive a more appropriate treatment). Some studies of the impact of RDTs on malaria case management have combined these two different successes into a binary outcome describing 'correct management'. However combining correct management of positives and negatives into a single summary measure can be misleading. The problems, which are analogous to those encountered in the evaluation of diagnostic tests, can largely be avoided if data for patients with and without malaria are presented and analysed separately. Where a combined metric is necessary, then one of the established approaches to summarise the performance of diagnostic tests could be considered, although these are not without their limitations. Two graphical approaches to help understand case management performance are illustrated
Getting antimalarials on target: impact of national roll-out of malaria rapid diagnostic tests on health facility treatment in three regions of Tanzania.
OBJECTIVES: Parasitological confirmation of malaria prior to treatment is recommended for patients of all ages, with malaria rapid diagnostic tests (mRDTs) an important tool to target artemisinin-based combination therapies (ACTs) to patients with malaria. To evaluate the impact on case management practices of routine government implementation of mRDTs, we conducted large-scale health facility surveys in three regions of Tanzania before and after mRDT roll-out. METHODS: Febrile patients at randomly selected health facilities were interviewed about care received at the facility, and blood samples were collected for reference blood smears. Health facility staff were interviewed about their qualifications and availability of malaria diagnostics and drugs. RESULTS: The percentage of febrile patients tested for malaria at the facility increased from 15.8% in 2010 to 54.9% in 2012. ACTs were obtained by 65.8% of patients positive by reference blood smear in 2010 and by 50.2% in 2012 (PÂ =Â 0.0675); no antimalarial was obtained by 57.8% of malaria-negative patients in 2010 and by 82.3% in 2012 (PÂ <Â 0.0001). Overall, ACT use decreased (39.9-21.3%, PÂ <Â 0.0001) and antibiotic use increased (31.2-48.5%, PÂ <Â 0.0001). CONCLUSION: Roll-out of mRDTs in Tanzania dramatically improved diagnostic testing for malaria and reduced overuse of ACTs for patients without parasitemia. However, post-roll-out almost 50% of febrile patients did not receive a diagnostic test, and almost 50% of patients testing positive did not receive ACTs. Stock-outs of ACTs and mRDTs were important problems. Further investigation is needed to determine reasons for not providing ACTs to patients with malaria and potential for inappropriate antibiotic use
Laboratory evidence for stochastic plasma-wave growth
The first laboratory confirmation of stochastic growth theory is reported. Floating potential fluctuations are measured in a vacuum arc centrifuge using a Langmuir probe. Statistical analysis of the energy density reveals a lognormal distribution over roughly 2 orders of magnitude, with a high-field nonlinear cutoff whose spatial dependence is consistent with the predicted eigenmode profile. These results are consistent with stochastic growth and nonlinear saturation of a spatially extended eigenmode, the first evidence for stochastic growth of an extended structure
Aseptic meningitis in a patient taking etanercept for rheumatoid arthritis: a case report
Background \ud
We report a case of a 53 year old lady recently commenced on etanercept, an anti-TNF (tumour necrosis factor) therapy for rheumatoid arthritis presenting with \ud
confusion, pyrexia and an erythematous rash. \ud
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Case presentation \ud
A lumbar puncture was highly suggestive of bacterial meningitis, but CSF cultures produced no growth, and polymerase chain reactions (PCR) for all previously reported bacterial, fungal and viral causes of meningitis were negative. \ud
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Conclusions \ud
This case report describes aseptic meningitis as a previously unreported complication of etanercept therapy, and serves as a reminder of the rare but potentially lifethreatening risk of serious infections in patients taking anti-TNF therapy for a variety of conditions
Seasonal malaria chemoprevention in an area of extended seasonal transmission in Ashanti, Ghana: an individually randomised clinical trial.
OBJECTIVE: To investigate the effectiveness of seasonal malaria chemoprevention (SMC) and community case management with long-acting artemisinin-based combination therapies (ACTs) for the control of malaria in areas of extended seasonal malaria transmission. METHOD: Individually randomised, placebo-controlled trial in the Ashanti Region of Ghana. A total of 2400 children aged 3-59 months received either: (i) a short-acting ACT for case management of malaria (artemether-lumefantrine, AL) plus placebo SMC, or (ii) a long-acting ACT (dihydroartemisinin-piperaquine, DP) for case management plus placebo SMC or (iii) AL for case management plus active SMC with sulphadoxine-pyrimethamine and amodiaquine. SMC or placebo was delivered on five occasions during the rainy season. Malaria cases were managed by community health workers, who used rapid diagnostic tests to confirm infection prior to treatment. RESULTS: The incidence of malaria was lower in children given SMC during the rainy season. Compared to those given placebo SMC and AL for case management, the adjusted hazard ratio (aHR) was 0.62 (95% CI: 0.41, 0.93), P = 0.020 by intention to treat and 0.53 (95% CI: 0.29, 0.95), P = 0.033 among children given five SMC courses. There were no major differences between groups given different ACTs for case management (aHR DP vs. AL 1.18 (95% CI 0.83, 1.67), P = 0.356). CONCLUSION: SMC may have an important public health impact in areas with a longer transmission season, but further optimisation of SMC schedules is needed to maximise its impact in such settings
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