71 research outputs found

    A process algebra for wireless mesh networks used for modelling, verifying and analysing AODV

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    We propose AWN (Algebra for Wireless Networks), a process algebra tailored to the modelling of Mobile Ad hoc Network (MANET) and Wireless Mesh Network (WMN) protocols. It combines novel treatments of local broadcast, conditional unicast and data structures. In this framework we present a rigorous analysis of the Ad hoc On-Demand Distance Vector (AODV) protocol, a popular routing protocol designed for MANETs and WMNs, and one of the four protocols currently standardised by the IETF MANET working group. We give a complete and unambiguous specification of this protocol, thereby formalising the RFC of AODV, the de facto standard specification, given in English prose. In doing so, we had to make non-evident assumptions to resolve ambiguities occurring in that specification. Our formalisation models the exact details of the core functionality of AODV, such as route maintenance and error handling, and only omits timing aspects. The process algebra allows us to formalise and (dis)prove crucial properties of mesh network routing protocols such as loop freedom and packet delivery. We are the first to provide a detailed proof of loop freedom of AODV. In contrast to evaluations using simulation or model checking, our proof is generic and holds for any possible network scenario in terms of network topology, node mobility, etc. Due to ambiguities and contradictions the RFC specification allows several interpretations; we show for more than 5000 of them whether they are loop free or not, thereby demonstrating how the reasoning and proofs can relatively easily be adapted to protocol variants. Using our formal and unambiguous specification, we find shortcomings of AODV that affect performance, e.g. the establishment of non-optimal routes, and some routes not being found at all. We formalise improvements in the same process algebra; carrying over the proofs is again easy

    Classification comparison.

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    <p>Prevalence by standard deviation cutoffs for weight-for-height and arm circumference-for-age z-scores for single and means of repeated measures among children 0–4.9 years of age.</p

    Mean z-score, standard deviation, and test of equal variance between age groups for height-for-age (HAZ), weight-for-height (WHZ), weight-for-age (WAZ), arm circumference-for-age (ACZ), and head circumference-for-age (HCZ) from manual measurements (n = 474), BINA 2017.

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    <p>Mean z-score, standard deviation, and test of equal variance between age groups for height-for-age (HAZ), weight-for-height (WHZ), weight-for-age (WAZ), arm circumference-for-age (ACZ), and head circumference-for-age (HCZ) from manual measurements (n = 474), BINA 2017.</p

    Terminal digit preference expressed as percentage of anthropometrists’ first measurement for height, head circumference and arm circumference ending in .0 to .9 compared to the expected 10% among children 0–4.9 years (n = 948 observations from 474 children), BINA 2017.

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    <p>Terminal digit preference expressed as percentage of anthropometrists’ first measurement for height, head circumference and arm circumference ending in .0 to .9 compared to the expected 10% among children 0–4.9 years (n = 948 observations from 474 children), BINA 2017.</p

    Measurement reliability.

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    <p>Closest two manual measures from single observer (intra-observer) and measurement reliability in average of closest two manual measures between two observers (inter-observer) for stature, head circumference (HC) and arm circumference (MUAC) among children 0–4.9 years of age (intra-observer n = 948, inter-observer n = 474).</p

    Agronomic, breeding, and biotechnological approaches to parasitic plant management through manipulation of germination stimulant levels in agricultural soils

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    A number of plant species have adapted to parasitize other plants, and some parasitic species pose severe constraints to major crops. The role of strigolactones and other metabolites present in host root exudates as germination stimulants for weedy root parasitic weed seeds has been known for the last 40 years. Recently, the ecological and developmental roles of strigolactones have been clarified by the discovery that they are a new class of plant hormone that controls shoot branching and serve as host recognition signals for mycorrhizal fungi. Parasitic plants also recognize these chemicals and use them to coordinate their life cycle with that of their host. Here we review agronomic practices that use parasitic germination stimulant production as a target for manipulation to control parasitic weeds.This work was supported by projects P07-AGR-02883 and AGL2008-01239/AGR cofinanced by European fund for regional development (FEDER) funds to D. Rubiales and a National Science Foundation Plant Genome award (DBI-0701748 US Department of Agriculture (Hatch project No. 135798)) to J.H. Westwood. M. Fernández-Aparicio is supported by an International Outgoing European Marie Curie postdoctoral fellowship (PIOF-GA-2009-252538).Peer Reviewe

    Individual-level factors of study population by prevalence of iron and folic acid receipt and consumption.

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    <p><sup>a</sup> It should be noted that all women in the study population received at least one ANC visit. Those who did not attend ANC were not asked about IFA receipt or consumption;</p><p><sup>b</sup> Early enrollment: 1<sup>st</sup> trimester, Late enrollment: 2<sup>nd</sup>-3<sup>rd</sup> trimester; ANC: Antenatal care; IFA: Iron and Folic Acid</p><p>Individual-level factors of study population by prevalence of iron and folic acid receipt and consumption.</p

    Flowchart of Health Sub-Center exclusions and final sample.

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    <p>Flowchart of exclusions and final sample of health sub-centers surveyed in Bihar through DLHS-3. HSC: Health Sub-Center; DLHS: District Level Household Survey; PSU: Primary Sampling Unit; IFA: iron and folic acid tablets or syrup.</p
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