Linear stability analysis of capillary instabilities for concentric cylindrical shells

Motivated by complex multi-fluid geometries currently being explored in fibre-device manufacturing, we study capillary instabilities in concentric cylindrical flows of $N$ fluids with arbitrary viscosities, thicknesses, densities, and surface tensions in both the Stokes regime and for the full Navier--Stokes problem. Generalizing previous work by Tomotika (N=2), Stone & Brenner (N=3, equal viscosities) and others, we present a full linear stability analysis of the growth modes and rates, reducing the system to a linear generalized eigenproblem in the Stokes case. Furthermore, we demonstrate by Plateau-style geometrical arguments that only axisymmetric instabilities need be considered. We show that the N=3 case is already sufficient to obtain several interesting phenomena: limiting cases of thin shells or low shell viscosity that reduce to N=2 problems, and a system with competing breakup processes at very different length scales. The latter is demonstrated with full 3-dimensional Stokes-flow simulations. Many $N > 3$ cases remain to be explored, and as a first step we discuss two illustrative $N \to \infty$ cases, an alternating-layer structure and a geometry with a continuously varying viscosity

Seroprevalence of Toxoplasmosis and associated risk factors in pregnant women at the Protestant Hospital, Mbouo-Bandjoun, Cameroon

Background: Toxoplasmosis is a common worldwide infection caused by the protozoan Toxoplasma gondii. In Cameroon, several recent studies have reported high seroprevalence of this parasitosis in various hospitals (Douala, Limbe, Njinikom and Yaoundé). The aim of this study was to determine whether this high prevalence of toxoplasmosis might occur in other regions of the country.Methodology: Serological tests by the indirect Enzyme Linked Immunosorbent Assay (ELISA) for IgG and IgM were carried out on 200 pregnant women (36 HIV-positive and 164 HIV-negative) at the Protestant Hospital of Mbouo-Bandjoun in western Cameroon to determine the presence of Toxoplasma gondii infection and to identify the risk factors associated with seropositivity of the subjects.Results: The overall seroprevalence of anti-Toxoplasma antibodies was 45.5%. The prevalence rate was 80.5% in the HIV-positive group (47.2% IgG, 22.2% IgM and 11.1% IgG + IgM) and 37.8% in the HIV-negative group (25.6%, 9.7% and 2.4% respectively). Using a multivariate logistic regression analysis, the secondary level of educational, presence of HIV infection, and frequency of close contacts with cats were significantly associated with the prevalence of IgG and/or IgM antibodies.Conclusion: Compared with previous reports of human toxoplasmosis in Cameroon, the prevalence in our study showed a decrease in the disease occurrence. Further studies are needed to determine whether this decrease is localised to our study or a general phenomenon currently affecting the country.Keywords: Cameroon, IgG, IgM, pregnant women, seroprevalence, Toxoplasma gondi

Efficiency-based design of bending-active tied arches

[EN] Active bending is recently attracting considerable attention as a new paradigm to build lightweight structures both in research and practice. While there are many references dealing with form-finding methods for bending-active structures, the literature on their performance in relation to their shape and member proportioning is still scarce. This paper addresses the relationship between configuration finding and structural performance in bending-active tied arches: planar arches composed of a bent (active) rod, lower spanning cables and secondary struts that are joined to the rod and act as cable deviators. This simple bending-active arrangement allows to state key relationships between shape, proportion and performance. Starting from the fact that rod segments between struts behave as elastica segments, and selecting the mechanical slenderness of the rod as key parameter, scale-independent relationships between rise-to-span ratio, rod slenderness and stresses after activation have been established for a three-strut tied arch. The limitations posed by keeping stresses in cables after the activation within an acceptable range have been also addressed. Span-deflection ratios corresponding to Eurocode loads for the serviceability limit state have been obtained for a set of three-strut configurations using a non-linear structural model. Results have been represented in terms of rod slenderness, cable slenderness and rise-to-span ratio. The same procedure has been used to determine and represent proper utilization ratios for rod cross-sections in ultimate limit state. All the results have been combined to show the design space corresponding to the given constraints and to exemplify how to extract from it a suitable structural configuration. Finally, we explain how to extend the proposed method to design bending-active tied arches with an arbitrary number and proportion of deviators.The authors gratefully acknowledge the financial support from the Spanish Ministry of Economy and Competitiveness through grant BIA2015-69330-P (MINECO) and the support from CALTER Ingenieria and SOFiSTiK AG for providing a software license.Bessini, J.; Lazaro, C.; Casanova Colón, J.; Monleón Cremades, S. (2019). Efficiency-based design of bending-active tied arches. Engineering Structures. 200:1-11. https://doi.org/10.1016/j.engstruct.2019.109681S11120

Irish in Britain Representation Group (IBRG)

An information leaflet on the Irish in Britain Representation Group IBRG - Cumann Ionadaíochta na n-Éireannach sa Bhreatai

Bacillus thuringiensis Cry5B Protein Is Highly Efficacious as a Single-Dose Therapy against an Intestinal Roundworm Infection in Mice

Intestinal parasitic nematode diseases infect over one billion people and cause significant disease burden in children (growth and cognitive stunting, malnutrition), in pregnant women, and via their dampening of the immune system in infected individuals. In over thirty years, no new classes of anti-roundworm drugs (anthelmintics) for treating humans have been developed. Because of limitations of the current drugs and the threat of parasite resistance, new anthelmintics are needed. The soil bacterium Bacillus thuringiensis (Bt) produces crystal (Cry) proteins that specifically target and kill insects and nematodes and is used around the world as a safe insecticide. Here we test the effects of the Bt Cry protein Cry5B on a chronic, natural intestinal roundworm infection in mice, namely the helminth parasite Heligmosomoides bakeri. We find that a single dose of Cry5B can eliminate 70% of the parasites and can almost completely block the ability of the parasites to produce progeny. Comparisons of Cry5B's efficacy with known anthelmintics suggest its activity is as good as or perhaps even better than those currently used. Furthermore, this protein is rapidly digested by simulated stomach juices, suggesting that protecting it from these juices would reveal a superior anthelmintic

BCR-signalling synergizes with TLR-signalling for induction of AID and immunoglobulin class-switching through the non-canonical NF-κB pathway

By diversifying antibody biological effector functions, class switch DNA recombination has a central role in the maturation of the antibody response. Here we show that BCR-signalling synergizes with Toll-like receptor (TLR) signalling to induce class switch DNA recombination. BCR-signalling activates the non-canonical NF-κB pathway and enhances the TLR-dependent canonical NF-κB pathway, thereby inducing activation-induced cytidine deaminase (AID), which is critical for class switch DNA recombination. Escherichia coli lipopolysaccharide (LPS) triggers dual TLR4/BCR-signalling and induces hallmarks of BCR-signalling, including CD79a phosphorylation and Ca2+ mobilization, and activates both the NF-κB pathways to induce AID and class switch DNA recombination in a PI(3)K p85α-dependent fashion. CD40-signalling activates the two NF-κB pathways to induce AID and class switch DNA recombination independent of BCR-signalling. Finally, dual BCR/TLR-engaging NP–lipopolysaccharide effectively elicits class-switched NP-specific IgG3 and IgG2b in mice. Thus, by integrating signals of the non-canonical and canonical NF-κB pathways, BCR and TLRs synergize to induce AID and T-cell-independent class switch DNA recombination