A parameter-free dynamic diffusion method for advection–diffusion–reaction problems

In this paper, we present a two-scale finite element formulation, named Dynamic Diffusion (DD), for advection–diffusion–reaction problems. By decomposing the velocity field in coarse and subgrid scales, the latter is used to determine the smallest amount of artificial diffusion to minimize the coarse-scale kinetic energy. This is done locally and dynamically, by imposing some constraints on the resolved scale solution, yielding a parameter-free consistent method. The subgrid scale space is defined by using bubble functions, whose degrees of freedom are locally eliminated in favor of the degrees of freedom that live on the resolved scales. Convergence tests on a two-dimensional example are reported, yielding optimal rates. In addition, numerical experiments show that DD method is robust for a wide scope of application problems.     

Stabilization and reference tracking for constrained switching systems: A predictive control approach

In this paper, the problem of designing a compensator capable of ensuring constraint satisfaction and tracking performance for a plant switching among a finite family of constrained linear time‐invariant configurations is investigated. We assume that switching occurrences are governed by a logical rule, which prescribes that any information pertaining to time or state dependence of the system mode transitions is unavailable to the controller side. The novelty of the proposed approach, based on the exploitation of command governor ideas in connection with the receding horizon control philosophy, relies on the capability to online manage unpredictable mode switching by jointly preserving uniformly ultimate boundedness and constraint fulfillment despite any admissible disturbance effect.     

Spaces of resilience,ingenuity, and entrepreneurship in informal work in Ghana

Despite playing an important role in the economies of low-income countries, there is a perception that informal markets are haphazard and disorganized. Using in-depth interviews conducted in Accra, Ghana, this study examines the strategic choices that market women pursue to gain access to and thrive in informal working spaces and ensure long-term survival. The findings reveal that entry into the informal working spaces is contingent on women’s ability to forge and nourish ties with acquaintances, kinsmen and middlemen. Further, the study found that in contrast to the notion of unregulated competition typically associated with street vending, market relations among women traders in informal market spaces are marked by alliances between rival sellers that transcended religious, ethnic, linguistic, and generational divides. As well, a strict code of conduct governs market behaviour, underpinned by an ethos of cooperation and mutual assistance among rival sellers. Furthermore, market women in Accra articulate the rationale behind informal entrepreneurship in ways that align with local and national development agenda. In so doing, the market women lend legitimacy to their trade, demand accountability from local authorities, and oppose repressive practices by the state. We highlight the implications of our findings for city planning and development.     

Fatigue and healing properties of bituminous mastics reinforced with nano-sized additives

The research work described in the paper focused on fatigue and healing properties of bituminous mastics reinforced with nano-sized additives.Commercially available multiwall carbon nanotubes (CNTs) and montmorillonite nanoclay (NC) were combined with a single base bitumen and a standard mineral filler to produce bituminous mastics. These blends were prepared in the laboratory by making use of a technique consisting in simple shear mixing followed by sonication.Fatigue behaviour of mastics under repeated loading was investigated by means of time sweeps performed in the strain-controlled mode at various amplitudes. Healing potential was assessed by adopting a testing protocol specifically conceived to discriminate between recovery of damage induced by fatigue loading and other artefact phenomena which may affect material response. All rheological measurements were carried out with a dynamic shear rheometer in the parallel plates geometry.Outcomes of the experimental investigation were found to be highly dependent on the nature of additive type, as a result of the key role played by interaction mechanisms that nano-particles can establish within the bituminous mastic.     

Marine Antimicrobial Peptides: Nature Provides Templates for the Design of Novel Compounds against Pathogenic Bacteria

The discovery of antibiotics for the treatment of bacterial infections brought the idea that bacteria would no longer endanger human health. However, bacterial diseases still represent a worldwide treat. The ability of microorganisms to develop resistance, together with the indiscriminate use of antibiotics, is mainly responsible for this situation; thus, resistance has compelled the scientific community to search for novel therapeutics. In this scenario, antimicrobial peptides (AMPs) provide a promising strategy against a wide array of pathogenic microorganisms, being able to act directly as antimicrobial agents but also being important regulators of the innate immune system. This review is an attempt to explore marine AMPs as a rich source of molecules with antimicrobial activity. In fact, the sea is poorly explored in terms of AMPs, but it represents a resource with plentiful antibacterial agents performing their role in a harsh environment. For the application of AMPs in the medical field limitations correlated to their peptide nature, their inactivation by environmental pH, presence of salts, proteases, or other components have to be solved. Thus, these peptides may act as templates for the design of more potent and less toxic compounds.     

Innovative films with tunable permeability for fresh vegetable packaging applications

Blends of a commercial polypropylene (PP), typically used as food contact material, with increasing amounts of poly(4‐methyl‐1‐pentene) (PMP) are prepared in a twin‐screw extruder to obtain thin films with improved gas permeation for fresh vegetable packaging. Permeability, haze, and transparency of monolayer films produced by casting are investigated under conditions mimicking the industrial ones. O₂ and CO₂ permeability can be tuned by increasing PMP content in the blends from 5 to 20 wt %. Transparency and haze are practically unchanged in the presence of low content of PMP. Moreover, tensile and rheological tests show that PMP does not significantly affect the related properties of blends compared to the neat PP matrix, thus allowing for the industrial applicability of these new formulations. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39503.     

Influence of longitudinal stiffeners on elastic stability of girder webs

In this paper, linear buckling analyses of plates with longitudinal stiffeners having various shapes and positions and subjected to axial force, in-plane bending and shear are developed. The aim is to give some new practical insights about the shape and optimum position of longitudinal stiffener in webs when axial force, bending moment and shear act. By means of a comprehensive numerical investigation, some practical issues for buckling phenomena in stiffened plates, taking into account (a) dimensions and shape (square and rectangular) of the plate, (b) dimensions and shape of the stiffener (with open and closed cross-sections), (c) location of the stiffener, and (d) load configuration (uniform compression, pure bending, combinations of axial compression and bending, and shear) are developed.     

Endophytic Microbiome Responses to Sulfur Availability in Beta vulgaris (L.)

Sulfur is an essential plant macronutrient, and its adequate supply allows an efficient root storage and sugar extractability in sugar beets (Beta vulgaris L.). In this study, we investigated the effect of changes in sulfur availability on the endophytic community structure of sugar beets. Plants were hydroponically grown in a complete nutrient solution (S-supplied), a nutrient solution without MgSO₄ (S-deprived), and a nutrient solution without MgSO₄ for six days and resupplied with 100 μM MgSO₄ for 48 h (S-resupplied). The sulfur status was monitored by inductively coupled plasma ICP–OES, and combustion analysis together with the evaluation of microRNA395 as a biomarker for sulfate status. Metabarcoding of the bacterial 16S rRNA gene was carried out in order to determine leaf endophytic community structure. The Shannon diversity index significantly differed (p < 0.05) between sulfate-supplied and sulfate-deprived seedlings. Validation by Real-Time PCR showed a significant increase (p < 0.05) of Burkholderia spp. in sulfate-deprived plants as compared to sulfate-supplied ones. The study sheds new light on the effects of nutrient deficiency on the microbiome of sugar beet plants.     

Identification of Nrl1 Domains Responsible for Interactions with RNA-Processing Factors and Regulation of Nrl1 Function by Phosphorylation

Pre-mRNA splicing is a key process in the regulation of gene expression. In the fission yeast Schizosaccharomyces pombe, Nrl1 regulates splicing and expression of several genes and non-coding RNAs, and also suppresses the accumulation of R-loops. Here, we report analysis of interactions between Nrl1 and selected RNA-processing proteins and regulation of Nrl1 function by phosphorylation. Bacterial two-hybrid system (BACTH) assays revealed that the N-terminal region of Nrl1 is important for the interaction with ATP-dependent RNA helicase Mtl1 while the C-terminal region of Nrl1 is important for interactions with spliceosome components Ctr1, Ntr2, and Syf3. Consistent with this result, tandem affinity purification showed that Mtl1, but not Ctr1, Ntr2, or Syf3, co-purifies with the N-terminal region of Nrl1. Interestingly, mass-spectrometry analysis revealed that in addition to previously identified phosphorylation sites, Nrl1 is also phosphorylated on serines 86 and 112, and that Nrl1-TAP co-purifies with Cka1, the catalytic subunit of casein kinase 2. In vitro assay showed that Cka1 can phosphorylate bacterially expressed Nrl1 fragments. An analysis of non-phosphorylatable nrl1 mutants revealed defects in gene expression and splicing consistent with the notion that phosphorylation is an important regulator of Nrl1 function. Taken together, our results provide insights into two mechanisms that are involved in the regulation of the spliceosome-associated factor Nrl1, namely domain-specific interactions between Nrl1 and RNA-processing proteins and post-translational modification of Nrl1 by phosphorylation.     

Hydrophobation of silica surface by silylation with new organo‐silanes bearing a polybutadiene oligomer tail

To enhance dispersion of silica into styrene‐butadiene emulsion copolymer (e‐SBR), used in tyres production, two new modifiers, characterized by 3‐mercaptopropyltrimethoxysilane grafted onto polybutadiene oligomers of <Mn> = 900 (sb1) and 5000 (sb3), were used. Silica was modified with several degrees of the two new silanes. Thermodynamic surface properties of the modified silicas were estimated by inverse gas chromatography as a function of the grafting degree of sb1 and sb3. e‐SBR/silica compounds, with silica pre‐modified and in situ modified during the mixing, were prepared and characterized using vulcanization tests, dynamic‐mechanical analysis, and morphological observations by TEM. At degree of silylation lower than 10 wt%, the method of pre‐modification allows a better dispersion of the silica within the elastomeric matrix and the best results were obtained using sb3. In particular, the lowest Payne effect, similar to that of a sample containing silica modified with bis‐triethoxysilylpropyltetrasulfide, usually used in tyre production, was found for the sample containing silica grafted with about 10 wt% of sb3. POLYM. COMPOS., 35:1603–1613, 2014. © 2013 Society of Plastics Engineers