On the Distribution of Signal Phase in Body Area Networks

In this letter, we investigate the distribution of the phase component of the complex received signal observed in practical experiments using body area networks. Two phase distributions, the recently proposed kappa-mu and eta-mu probability densities, which together encompass the most widely used fading models, namely Semi-Gaussian, Rayleigh, Hoyt, Rice, and Nakagami-m, have been compared with measurement data. The kappa-mu distribution has been found to provide the best fit over a range of on-body links, while the user was mobile. The experiments were carried out in two dissimilar indoor environments at opposite ends of the multipath spectrum. It has also been found that the uniform phase distribution has not arisen in anyone of the experiments.

Adsorption and photocatalysed destruction of cationic and anionic dyes on mesoporous titania films: Reactions at the air-solid interface

Cationic dyes, such as methylene blue (MB), Thionine (TH) and Basic Fuschin (BF), but not anionic dyes, such as Acid Orange 7 (AO7), Acid Blue 9 (AB9) and Acid Fuschin (AF), are readily adsorbed onto mesoporous titania films at high pH (pH 11), i.e. well above the pzc of titania (pH 6.5), due to electrostatic forces of attraction and repulsion, respectively. The same anionic dyes, but not the cationic dyes, are readily adsorbed on the same titania films at low pH (pH 3), i.e. well below titania's pzc. MB appears to adsorb on mesoporous titania films at pH 11 as the trimer (lambda(max) = 570 nm) but, upon drying, although the trimer still dominates, there is an absorption peak at 665 nm, especially notable at low [MB], which may be due to the monomer, but more likely MB J-aggregates. In contrast, the absorption spectrum of AO7 adsorbed onto the mesoporous titania film at low pH is very similar to the dye monomer. For both MB and AO7 the kinetics of adsorption are first order and yield high rate constants (3.71 and 1.481 g(-1) min(-1)), indicative of a strong adsorption process. Indeed, both MB and AO7 stained films retained much of their colour when left overnight in dye-free pH 11 and 3 solutions, respectively, indicating the strong nature of the adsorption. The kinetics of the photocatalytic bleaching of the MB-titania films at high pH are complex and not well-described by the Julson-Ollis kinetic model [A.J. Julson, D.F. Ollis, Appl. Catal. B. 65 (2006) 315]. Instead, there appears to be an initial fast but not simple demethylation step, followed by a zero-order bleaching and further demethylation steps. In contrast, the kinetics of photocatalytic bleaching of the AO7-titania film give a good fit to the Julson-Ollis kinetic model, yielding values for the various fitting parameters not too dissimilar to those reported for AO7 adsorbed on P25 titania powder. (C) 2008 Elsevier B.V. All rights reserved.

A preliminary structural design procedure for laser beam welded airframe stiffened panels

Initial sizing procedures for aircraft stiffened panels that include the influence of welding fabrication residual process effects are missing. Herein, experimental and Finite Element analyses are coupled to generate knowledge to formulate an accurate and computationally efficient sizing procedure which will enable designers to routinely consider panel fabrication, via welding, accounting for the complex distortions and stresses induced by this manufacturing process. Validating experimental results demonstrate the need to consider welding induced material property degradation, residual stresses and distortions, as these can reduce static strength performance. However, results from fuselage and wing trade-studies, using the validated sizing procedure, establish that these potential reductions in strength performance may be overcome through local geometric tailoring during initial sizing, negating any weight penalty for the majority of design scenarios.

Functional and biochemical characterisation of the Escherichia coli major facilitator superfamily multidrug transporter MdtM

Multidrug resistance (MDR) occurs when bacteria simultaneously acquire resistance to a broad spectrum of structurally dissimilar compounds to which they have not previously been exposed. MDR is principally a consequence of the active transport of drugs out of the cell by proteins that are integral membrane transporters. We characterised and purified the putative Escherichia coli MDR transporter, MdtM, a 410 amino acid residue protein that belongs to the large and ubiquitous major facilitator superfamily. Functional characterisation of MdtM using growth inhibition and whole cell transport assays revealed its role in intrinsic resistance of E. coli cells to the antimicrobials ethidium bromide and chloramphenicol. Site-directed mutagenesis studies implied that the MdtM aspartate 22 residue and the highly conserved arginine at position 108 play a role in proton recognition. MdtM was homologously overexpressed and purified to homogeneity in dodecyl maltopyranoside detergent solution and the oligomeric state and stability of the protein in a variety of detergent solutions was investigated using size-exclusion HPLC. Purified MdtM is monomeric and stable in dodecyl maltopyranoside solution and binds chloramphenicol with nanomolar affinity in the same detergent. This work provides a firm foundation for structural studies on this class of multidrug transporter protein.

COMPARISON OF THE GROWTH INHIBITORY AND BACTERIOCIDAL EFFECTS OF TAUROLIDINE AND TAURULTAM ON A CLINICAL ISOLATE OF ESCHERICHIA-COLI

To investigate the mode of action of Taurolin, an antimicrobial preparation, the growth inhibitory and bacteriocidal effects of taurolidine and taurultam solutions on Escherichia coli isolated from a diagnosed urinary tract infection were examined at 37-degrees-C. The inhibitory effects of taurolidine solutions were observed to be greater than those of taurultam solutions at comparative concentrations; however, the presence of sublethal concentrations of formaldehyde (methylene glycol) associated with taurolidine was sufficient to account for this. The bacteriocidal activity of taurolidine (2.0% w/v) was greater than that of taurultam (4.5% w/v). Both compounds produced biphasic death rates with dissimilar initial slopes, suggested to be due to the presence of formaldehyde in taurolidine solutions. These observations indicate that the growth inhibitory and bacteriocidal effects of Taurolin solutions are primarily due to taurultam, however, the presence of sublethal concentrations of formaldehyde is significant in the expression of this activity.

Buckling/post-buckling strength of friction stir welded aircraft stiffened panels

Assembling aircraft stiffened panels using friction stir welding offers potential to reduce fabrication time in comparison to current mechanical fastener assembly, making it economically feasible to select structurally desirable stiffener pitching and novel panel configurations. With such a departure from the traditional fabrication process, much research has been conducted on producing strong reliable welds, with less examination of the impact of welding process residual effects on panel structural behaviour and the development of appropriate design methods. This article significantly expands the available panel level compressive strength knowledge, demonstrating the strength potential of a welded aircraft panel with multiple lateral and longitudinal stiffener bays. An accompanying computational study has determined the most significant process residual effects that influence panel strength and the potential extent of panel degradation. The experimental results have also been used to validate a previously published design method, suggesting accurate predictions can be made if the conventional aerospace design methods are modified to acknowledge the welding altered panel properties.

The pmrF polymyxin-resistance operon of Yersinia pseudotuberculosis is upregulated by the PhoP-PhoQ two-component system but not by PmrA-PmrB, and is not required for virulence

The Yersinia pseudotuberculosis chromosome contains a seven-gene polycistronic unit (the pmrF operon) whose products share extensive homologies with their pmrF counterparts in Salmonella enterica serovar Typhimurium (S. typhimurium), another Gram-negative bacterial enteropathogen. This gene cluster is essential for addition of 4-aminoarabinose to the lipid moiety of LPS, as demonstrated by MALDI-TOF mass spectrometry of lipid A from both wild-type and pmrF-mutated strains. As in S. typhimurium, 4-aminoarabinose substitution of lipid A contributes to in vitro resistance of Y. pseudotuberculosis to the antimicrobial peptide polymyxin B. Whereas pmrF expression in S. typhimurium is mediated by both the PhoP-PhoQ and PmrA-PmrB two-component regulatory systems, it appears to be PmrA-PmrB-independent in Y. pseudotuberculosis, with the response regulator PhoP interacting directly with the pmrF operon promoter region. This result reveals that the ubiquitous PmrA-PmrB regulatory system controls different regulons in distinct bacterial species. In addition, pmrF inactivation in Y. pseudotuberculosis has no effect on bacterial virulence in the mouse, again in contrast to the situation in S. typhimurium. The marked differences in pmrF operon regulation in these two phylogenetically close bacterial species may be related to their dissimilar lifestyles.

Protecting group and switchable pore-discriminating adsorption properties of a hydrophilic-hydrophobic metal-organic framework

Formed by linking metals or metal clusters through organic linkers, metal-organic frameworks are a class of solids with structural and chemical properties that mark them out as candidates for many emerging gas storage, separation, catalysis and biomedical applications. Important features of these materials include their high porosity and their flexibility in response to chemical or physical stimuli. Here, a copper-based metal-organic framework has been prepared in which the starting linker (benzene-1,3,5-tricarboxylic acid) undergoes selective monoesterification during synthesis to produce a solid with two different channel systems, lined by hydrophilic and hydrophobic surfaces, respectively. The material reacts differently to gases or vapours of dissimilar chemistry, some stimulating subtle framework flexibility or showing kinetic adsorption effects. Adsorption can be switched between the two channels by judicious choice of the conditions. The monoesterified linker is recoverable in quantitative yield, demonstrating possible uses of metal-organic frameworks in molecular synthetic chemistry as 'protecting groups' to accomplish selective transformations that are difficult using standard chemistry techniques.

Compositional Divergence and Convergence in Local Communities and Spatially Structured Landscapes

Community structure depends on both deterministic and stochastic processes. However, patterns of community dissimilarity (e.g. difference in species composition) are difficult to interpret in terms of the relative roles of these processes. Local communities can be more dissimilar (divergence) than, less dissimilar (convergence) than, or as dissimilar as a hypothetical control based on either null or neutral models. However, several mechanisms may result in the same pattern, or act concurrently to generate a pattern, and much research has recently been focusing on unravelling these mechanisms and their relative contributions. Using a simulation approach, we addressed the effect of a complex but realistic spatial structure in the distribution of the niche axis and we analysed patterns of species co-occurrence and beta diversity as measured by dissimilarity indices (e.g. Jaccard index) using either expectations under a null model or neutral dynamics (i.e., based on switching off the niche effect). The strength of niche processes, dispersal, and environmental noise strongly interacted so that niche-driven dynamics may result in local communities that either diverge or converge depending on the combination of these factors. Thus, a fundamental result is that, in real systems, interacting processes of community assembly can be disentangled only by measuring traits such as niche breadth and dispersal. The ability to detect the signal of the niche was also dependent on the spatial resolution of the sampling strategy, which must account for the multiple scale spatial patterns in the niche axis. Notably, some of the patterns we observed correspond to patterns of community dissimilarities previously observed in the field and suggest mechanistic explanations for them or the data required to solve them. Our framework offers a synthesis of the patterns of community dissimilarity produced by the interaction of deterministic and stochastic determinants of community assembly in a spatially explicit and complex context.

Aspasing Out Metacaspases and Caspases: Proteases of Many Trades

Execution of programmed cell death (PCD) in nonmetazoan organisms is morphologically different from apoptotic PCD in animals and lacks a number of key molecular components of apoptotic machinery, including caspases. Yet protozoan, fungal, and plant cells exhibit caspase-like proteolytic activities, which increase in a PCD-dependent manner. This poses a question whether nonmetazoan organisms contain structurally dissimilar proteases that functionally substitute for caspases. Putative ancestors of caspases, metacaspases, are candidates for this role; however, their distinct substrate specificity raises doubts. The identification of a common biological target of caspases and metacaspases and previously unknown functions unrelated to cell death of metacaspases provide new food for thought.

'Translated Verse': Milton's Latin Poetry in the Long Eighteenth Century

This chapter assesses ways in which the emergence in the long eighteenth century of a cluster of verse translations of Milton’s Poemata engendered an intellectual discourse and debate on translation itself, not dissimilar to the magazine warfare of the day. It argues that poetical renderings of Milton’s Latin verse, and the biographical and literary contexts in which they appeared, facilitated the interrogation of key issues that are still being debated by modern translation theorists: the nature and function of translation; the viability of rendering a source text in a target language that is also in this instance a poetic language; the potential ‘fetters’ which, in Drydenesque terms, might constrain ‘the verbal copier’; or by contrast the quasi-liberating fluency, the ‘fluent strategy’, attendant upon recourse to verse as translational medium; canonicity, amplification and omission; the much-debated issue of authorial equivalence, evinced here, it is suggested, by the editorial showcasing of the translator; and not least, the perennial question of translation as reading and critical interpretation. In short, verse renderings of Milton’s Latin poetry and the debates that they engendered assume a not inconsequential place in the history of translation theory, which, as Venuti notes, is forever concerned with ‘the changing relationships between the relative autonomy of the translated text and two other categories: equivalence and function.’

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In vitro mesenchymal stem cell responses on laser-welded NiTi alloy

The biocompatibility of NiTi after laser welding was studied by examining the in vitro (mesenchymal stem cell) MSC responses at different sets of time varying from early (4 to 12 h) to intermediate phases (1 and 4 days) of cell culture. The effects of physical (surface roughness and topography) and chemical (surface Ti/Ni ratio) changes as a consequence of laser welding in different regions (WZ, HAZ, and BM) on the cell morphology and cell coverage were studied. The results in this research indicated that the morphology of MSCs was affected primarily by the topographical factors in the WZ: the well-defined and directional dendritic pattern and the presence of deeper grooves. The morphology of MSCs was not significantly modulated by surface roughness. Despite the possible initial Ni release in the medium during the cell culture, no toxic effect seemed to cause to MSCs as evidenced by the success of adhesion and spreading of the cells onto different regions in the laser weldment. The good biocompatibility of the NiTi laser weldment has been firstly reported in this study.

Fatigue behavior of laser-welded NiTi wires in small-strain cyclic bending

NiTi wires and their weldments are commonly used in micro-electro-mechanical systems (MEMS), and in such applications, cyclic loading are commonly encountered. In this paper, the bending-rotation fatigue (BRF) test was used to study the bending fatigue behavior of NiTi wire laser weldment in the small-strain regime. The fracture mechanism, which includes crack initiation, crack growth and propagation of the weldment in the BRF test, was investigated with the aid of SEM fractography and discussed in terms of the microstructure. It was found that crack initiation was primarily surface-condition dependent. The cracks were found to initiate at the surface defects at the weld zone (WZ) surface, and the crack propagation was assisted by the gas inclusions in the WZ. The weldment was finally fractured in a ductile manner. The fatigue life was found to decrease with increasing surface strain and also with increasing bending frequency (controlled by the rotational speed in the BRF test). In comparison, the fatigue life of the unwelded NiTi wires was higher than their welded counterparts at all strain levels and bending frequencies. The decrease in fatigue resistance of the weldment could be attributed to the surface and microstructural defects introduced during laser welding.

Constitutive model for localized Lüders-like stress-induced martensitic transformation and super-elastic behaviors of laser-welded NiTi wires

The application of the shape memory alloy NiTi in micro-electro-mechanical-systems (MEMSs) is extensive nowadays. In MEMS, complex while precise motion control is always vital. This makes the degradation of the functional properties of NiTi during cycling loading such as the appearance of residual strain become a serious problem to study, in particular for laser micro-welded NiTi in real applications. Although many experimental efforts have been put to study the mechanical properties of laser welded NiTi, surprisingly, up to the best of our understanding, there has not been attempts to quantitatively model the laser-welded NiTi under mechanical cycling in spite of the accurate prediction required in applications and the large number of constitutive models to quantify the thermo-mechanical behavior of shape memory alloys. As the first attempt to fill the gap, we employ a recent constitutive model, which describes the localized SIMT in NiTi under cyclic deformation; with suitable modifications to model the mechanical behavior of the laser welded NiTi under cyclic tension. The simulation of the model on a range of tensile cyclic deformation is consistent with the results of a series of experiments. From this, we conclude that the plastic deformation localized in the welded regions (WZ and HAZs) of the NiTi weldment can explain most of the extra amount of residual strain appearing in welded NiTi compared to the bare one. Meanwhile, contrary to common belief, we find that the ability of the weldment to memorize its transformation history, sometimes known as ‘return point memory’, still remains unchanged basically though the effective working limit of this ability reduces to within 6% deformation.

Susceptibility to environmentally induced cracking of laser-welded NiTi wires in Hanks’ solution at open-circuit potential

In the present study the tensile and super-elastic behaviours of laser-welded NiTi wires in Hanks’ solution at open-circuit potential (OCP) were investigated using tensile and cyclic slow-strain-rate tests (SSRT). In comparison with NiTi weldment tested in oil (non-corrosive environment), the weldment in Hanks’ solution suffered from obvious degradation in the tensile properties as evidenced by lower tensile strength, reduced maximum elongation, and a brittle fracture mode. Moreover, a larger residual strain was observed in the weldment after stress–strain cycles in Hanks’ solution. In addition to the microstructural defects resulting from the welding process, the inferior tensile and super-elastic behaviours of the NiTi weldment in Hanks’ solution could be attributed to the trapping of a large amount of hydrogen in the weld zone and heat-affected zone.