1,155 research outputs found
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 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 cases remain to be
explored, and as a first step we discuss two illustrative cases,
an alternating-layer structure and a geometry with a continuously varying
viscosity
Can loss of agency and oppositional perturbation associated with antidepressant monotherapy and low-fidelity psychological treatment dilute the benefits of guideline-consistent depression treatment at the population level?
Contains fulltext :
226202.pdf (publisher's version ) (Open Access
An algorithm to obtain global solutions of the double confluent Heun equation
A procedure is proposed to construct solutions of the double confluent Heun
equation with a determinate behaviour at the singular points. The connection
factors are expressed as quotients of Wronskians of the involved solutions.
Asymptotic expansions are used in the computation of those Wronskians. The
feasibility of the method is shown in an example, namely, the Schroedinger
equation with a quasi-exactly-solvable potential
The effect of surveillance and appreciative inquiry on puerperal infections : a longitudinal cohort study in India
Peer reviewedPublisher PD
The role of TcdB and TccC subunits in secretion of the photorhabdus Tcd toxin complex
The Toxin Complex (TC) is a large multi-subunit toxin encoded by a range of bacterial pathogens. The best-characterized examples are from the insect pathogens Photorhabdus, Xenorhabdus and Yersinia. They consist of three large protein subunits, designated A, B and C that assemble in a 5:1:1 stoichiometry. Oral toxicity to a range of insects means that some have the potential to be developed as pest control technology. The three subunit proteins do not encode any recognisable export sequences and as such little progress has been made in understanding their secretion. We have developed heterologous TC production and secretion models in E. coli and used them to ascribe functions to different domains of the crucial B+C sub-complex. We have determined that the B and C subunits use a secretion mechanism that is either encoded by the proteins themselves or employ an as yet undefined system common to laboratory strains of E. coli. We demonstrate that both the N-terminal domains of the B and C subunits are required for secretion of the whole complex. We propose a model whereby the N-terminus of the C-subunit toxin exports the B+C sub-complex across the inner membrane while that of the B-subunit allows passage across the outer membrane. We also demonstrate that even in the absence of the B-subunit, that the C-subunit can also facilitate secretion of the larger A-subunit. The recognition of this novel export system is likely to be of importance to future protein secretion studies. Finally, the identification of homologues of B and C subunits in diverse bacterial pathogens, including Burkholderia and Pseudomonas, suggests that these toxins are likely to be important in a range of different hosts, including man
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