Detecting periodicity in experimental data using linear modeling techniques

Fourier spectral estimates and, to a lesser extent, the autocorrelation function are the primary tools to detect periodicities in experimental data in the physical and biological sciences. We propose a new method which is more reliable than traditional techniques, and is able to make clear identification of periodic behavior when traditional techniques do not. This technique is based on an information theoretic reduction of linear (autoregressive) models so that only the essential features of an autoregressive model are retained. These models we call reduced autoregressive models (RARM). The essential features of reduced autoregressive models include any periodicity present in the data. We provide theoretical and numerical evidence from both experimental and artificial data, to demonstrate that this technique will reliably detect periodicities if and only if they are present in the data. There are strong information theoretic arguments to support the statement that RARM detects periodicities if they are present. Surrogate data techniques are used to ensure the converse. Furthermore, our calculations demonstrate that RARM is more robust, more accurate, and more sensitive, than traditional spectral techniques.Comment: 10 pages (revtex) and 6 figures. To appear in Phys Rev E. Modified styl

A \u3cem\u3eMycobacterium ulcerans\u3c/em\u3e Toxin, Mycolactone, Causes Apoptosis in Guinea Pig Ulcers and Tissue Culture Cells

Mycobacterium ulcerans is the causative agent of Buruli ulcer, a tropical ulcerative skin disease. One of the most intriguing aspects of this disease is the presence of extensive tissue damage in the absence of an acute inflammatory response. We recently purified and characterized a macrolide toxin, mycolactone, from M. ulcerans. Injection of this molecule into guinea pig skin reproduced cell death and lack of acute inflammatory response similar to that seen following the injection of viable bacteria. We also showed that mycolactone causes a cytopathic effect on mouse fibroblast L929 cells that is characterized by cytoskeletal rearrangements and growth arrest within 48 h. However, these results could not account for the extensive cell death which occurs in Buruli ulcer. The results presented here demonstrate that L929 and J774 mouse macrophage cells die via apoptosis after 3 to 5 days of exposure to mycolactone. Treatment of cells with a pan-caspase inhibitor can inhibit mycolactone-induced apoptosis. We demonstrate that injection of mycolactone into guinea pig skin results in cell death via apoptosis and that the extent of apoptosis increases as the lesion progresses. These results may help to explain why tissue damage in Buruli ulcer is not accompanied by an acute inflammatory response

Host Restriction Phenotypes of \u3cem\u3eSalmonella typhi\u3c/em\u3e and \u3cem\u3eSalmonella gallinarum\u3c/em\u3e

Salmonella typhi and Salmonella gallinarum phenotypes correlated with mouse host restriction have been identified by using in vitro and in vivo systems. S. typhi is capable of entering the murine intestinal epithelium via M cells, as is Salmonella typhimurium, which causes systemic infection in the mouse. But, unlike S. typhimurium, S. typhi does not destroy the epithelium and is cleared from the Peyer’s patches soon after M-cell entry. S. gallinarum appears to be incapable of entering the murine Peyer’s patch epithelium. Our in vitro evidence suggests that S. gallinarum is taken up in murine phagocytic cells by a mechanism different from that of S. typhimurium. S. typhimurium is taken up at a higher frequency and is maintained at higher viable counts throughout a 24-h time course in a murine macrophage-like cell line than are S. gallinarum and S. typhi

Maternal and child health nurse screening and care for mothers experiencing domestic violence (MOVE): A cluster randomised trial

BACKGROUND: Mothers are at risk of domestic violence (DV) and its harmful consequences postpartum. There is no evidence to date for sustainability of DV screening in primary care settings. We aimed to test whether a theory-informed, maternal and child health (MCH) nurse-designed model increased and sustained DV screening, disclosure, safety planning and referrals compared with usual care. METHODS: Cluster randomised controlled trial of 12 month MCH DV screening and care intervention with 24 month follow-up. The study was set in community-based MCH nurse teams (91 centres, 163 nurses) in north-west Melbourne, Australia. Eight eligible teams were recruited. Team randomisation occurred at a public meeting using opaque envelopes. Teams were unable to be blinded. The intervention was informed by Normalisation Process Theory, the nurse-designed good practice model incorporated nurse mentors, strengthened relationships with DV services, nurse safety, a self-completion maternal health screening checklist at three or four month consultations and DV clinical guidelines. Usual care involved government mandated face-to-face DV screening at four weeks postpartum and follow-up as required. Primary outcomes were MCH team screening, disclosure, safety planning and referral rates from routine government data and a postal survey sent to 10,472 women with babies ≤ 12 months in study areas. Secondary outcomes included DV prevalence (Composite Abuse Scale, CAS) and harm measures (postal survey). RESULTS: No significant differences were found in routine screening at four months (IG 2,330/6,381 consultations (36.5 %) versus CG 1,792/7,638 consultations (23.5 %), RR = 1.56 CI 0.96-2.52) but data from maternal health checklists (n = 2,771) at three month IG consultations showed average screening rates of 63.1 %. Two years post-intervention, IG safety planning rates had increased from three (RR 2.95, CI 1.11-7.82) to four times those of CG (RR 4.22 CI 1.64-10.9). Referrals remained low in both intervention groups (IGs) and comparison groups (CGs) (<1 %). 2,621/10,472 mothers (25 %) returned surveys. No difference was found between arms in preference or comfort with being asked about DV or feelings about self. CONCLUSION: A nurse-designed screening and care model did not increase routine screening or referrals, but achieved significantly increased safety planning over 36 months among postpartum women. Self-completion DV screening was welcomed by nurses and women and contributed to sustainability. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry, ACTRN12609000424202, 10/03/2009

Overcoming the risk of inaction from emissions uncertainty in smallholder agriculture

The potential for improving productivity and increasing the resilience of smallholder agriculture, while also contributing to climate change mitigation, has recently received considerable political attention (Beddington et al 2012). Financial support for improving smallholder agriculture could come from performance-based funding including sale of carbon credits or certified commodities, payments for ecosystem services, and nationally appropriate mitigation action (NAMA) budgets, as well as more traditional sources of development and environment finance. Monitoring the greenhouse gas fluxes associated with changes to agricultural practice is needed for performance-based mitigation funding, and efforts are underway to develop tools to quantify mitigation achieved and assess trade-offs and synergies between mitigation and other livelihood and environmental priorities (Olander 2012)

Optimal control strategies for tuberculosis treatment: a case study in Angola

We apply optimal control theory to a tuberculosis model given by a system of ordinary differential equations. Optimal control strategies are proposed to minimize the cost of interventions. Numerical simulations are given using data from Angola.Comment: This is a preprint of a paper whose final and definite form will appear in the international journal Numerical Algebra, Control and Optimization (NACO). Paper accepted for publication 15-March-201

A Faraday Rotation Search for Magnetic Fields in Large Scale Structure

Faraday rotation of radio source polarization provides a measure of the integrated magnetic field along the observational lines of sight. We compare a new, large sample of Faraday rotation measures (RMs) of polarized extragalactic sources with galaxy counts in Hercules and Perseus-Pisces, two nearby superclusters. We find that the average of RMs in these two supercluster areas are larger than in control areas in the same galactic latitude range. This is the first RM detection of magnetic fields that pervade a supercluster volume, in which case the fields are at least partially coherent over several megaparsecs. Even the most conservative interpretation of our observations, according to which Milky Way RM variations mimic the background supercluster galaxy overdensities, puts constraints on the IGM magneto-ionic ``strength'' in these two superclusters. We obtain an approximate typical upper limit on the field strength of about 0.3 microGauss l/(500 kpc), when we combine our RM data with fiducial estimates of electron density from the environments of giant radio galaxies, and of the warm-hot intergalactic medium (WHIM).Comment: 8 pages, 3 figures, 1 table, to appear in the Astrophysical Journa

The faint end of the QSO luminosity function at z=3

We present the first measurement of the faint end of the QSO luminosity function at z=3. The QSOs, which range from M_1450 = -21 to M_1450 = -27, were discovered in 17 fields totaling 0.43 deg^2 using multicolor selection criteria (the Lyman break technique) and spectroscopic followup. We find that the faint-end slope of the luminosity function is beta_l=1.24 +/- 0.07, flatter than the value of beta_l=1.64 +/- 0.18 measured at lower redshift. The integrated rest 1450 A UV luminosity of z=3 QSOs is only 50% of most previous estimates, and is only ~8% of that produced by Lyman break galaxies at the same redshifts. Assuming that ionizing photons from faint QSOs are as successful in escaping their host galaxies as bright QSOs, we estimate the total contribution of QSOs to the ionizing flux J_912 at z=3, J_912=2.4*10^-22 ergs/s/cm^2/Hz. This estimate, which we regard as an upper limit, remains consistent with rough estimates of J_912 based on the Lyman-alpha forest "proximity effect."Comment: 14 pages, 3 figures, accepted for publication in the Astrophysical Journa

Identifying the Achilles heel of multi-host pathogens : the concept of keystone 'host' species illustrated by Mycobacterium ulcerans transmission

Pathogens that use multiple host species are an increasing public health issue due to their complex transmission, which makes them difficult to mitigate. Here, we explore the possibility of using networks of ecological interactions among potential host species to identify the particular disease-source species to target to break down transmission of such pathogens. We fit a mathematical model on prevalence data of Mycobacterium ulcerans in western Africa and we show that removing the most abundant taxa for this category of pathogen is not an optimal strategy to decrease the transmission of the mycobacterium within aquatic ecosystems. On the contrary, we reveal that the removal of some taxa, especially Oligochaeta worms, can clearly reduce rates of pathogen transmission, and these should be considered as keystone organisms for its transmission because they lead to a substantial reduction in pathogen prevalence regardless of the network topology. Besides their potential application for the understanding of M. ulcerans ecology, we discuss how networks of species interactions can modulate transmission of multi-host pathogens