Antibacterial Activity and Amphidinol Profiling of the Marine Dinoflagellate Amphidinium carterae (Subclade III)

Microalgae have received growing interest for their capacity to produce bioactive metabolites. This study aimed at characterising the antimicrobial potential of the marine dinoflagellate Amphidinium carterae strain LACW11, isolated from the west of Ireland. Amphidinolides have been identified as cytotoxic polyoxygenated polyketides produced by several Amphidinium species. Phylogenetic inference assigned our strain to Amphidinium carterae subclade III, along with isolates interspersed in different geographic regions. A two-stage extraction and fractionation process of the biomass was carried out. Extracts obtained after stage-1 were tested for bioactivity against bacterial ATCC strains of Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa. The stage-2 solid phase extraction provided 16 fractions, which were tested against S. aureus and E. faecalis. Fractions I, J and K yielded minimum inhibitory concentrations between 16 μg/mL and 256 μg/mL for both Gram-positive. A targeted metabolomic approach using UHPLC-HRMS/MS analysis applied on fractions G to J evidenced the presence of amphidinol type compounds AM-A, AM-B, AM-22 and a new derivative dehydroAM-A, with characteristic masses of m/z 1361, 1463, 1667 and 1343, respectively. Combining the results of the biological assays with the targeted metabolomic approach, we could conclude that AM-A and the new derivative dehydroAM-A are responsible for the detected antimicrobial bioactivity.     

LIN28 Family in Testis: Control of Cell Renewal,Maturation, Fertility and Aging

Male reproductive development starts early in the embryogenesis with somatic and germ cell differentiation in the testis. The LIN28 family of RNA-binding proteins promoting pluripotency has two members—LIN28A and LIN28B. Their function in the testis has been investigated but many questions about their exact role based on the expression patterns remain unclear. LIN28 expression is detected in the gonocytes and the migrating, mitotically active germ cells of the fetal testis. Postnatal expression of LIN28 A and B showed differential expression, with LIN28A expressed in the undifferentiated spermatogonia and LIN28B in the elongating spermatids and Leydig cells. LIN28 interferes with many signaling pathways, leading to cell proliferation, and it is involved in important testicular physiological processes, such as cell renewal, maturation, fertility, and aging. In addition, aberrant LIN28 expression is associated with testicular cancer and testicular disorders, such as hypogonadotropic hypogonadism and Klinefelter’s syndrome. This comprehensive review encompasses current knowledge of the function of LIN28 paralogs in testis and other tissues and cells because many studies suggest LIN28AB as a promising target for developing novel therapeutic agents.     

Dynamic model of one‐cycle control for converters operating in continuous and discontinuous conduction modes

In this paper a new dynamic model of one‐cycle‐controlled converters operating either in continuous or in discontinuous conduction mode (DCM) is introduced. The static and dynamic behaviour is analysed by using sampled‐data modelling combined with the small‐signal linearization of the average model of the converter's power stage. The proposed model is valid for frequencies up to half the switching frequency and, while the other dynamic models presented in the literature cover continuous conduction mode only, it also gives an accurate prediction of the system's dynamic behaviour in the DCM. The model allows to determine the closed‐form expression of the reference‐to‐output transfer function G of the system, which is a fundamental prerequisite for the design of a conventional output feedback control circuit aimed at improving the dynamic behaviour of the system in response to load variations. In this paper it is also shown that one‐cycle control does not work properly in switching converters operating in deep DCM if some specific design constraints are not fulfilled. The theoretical predictions are confirmed by the results of suitable numerical simulations and laboratory experiments on a one‐cycle‐controlled buck‐switching converter. Copyright © 2008 John Wiley & Sons, Ltd.     

Enrichment of activated sludge for enhanced hydrogen production from crude glycerol

Enriched activated sludge that can effectively convert crude glycerol into bio-hydrogen was selected by an eco-biotechnological approach, in very strict conditions, using biodiesel-derived glycerol as the only carbon source. The thus obtained functional consortium was characterized by the genera Klebsiella, Escherichia/Shigella and Cupriavidus. During enrichment, the dominant metabolic end-product shifted from a 1,3 propanediol to ethanol, with a concomitant increase of the hydrogen yield from 0.18 ± 0.003 to 0.66 ± 0.06 mol/mol and an almost five-fold increase of the hydrogen production. Glycerol degradation efficiency showed an increase of around 50%. In optimized and upscaled conditions it was possible to obtain a hydrogen production rate of 2960 mL H₂/L/day ± 185 at a near stoichiometric yield (of 0.90 mol/mol ± 0.01), with a carbon recovery of almost 90%, both in sterile and non-sterile conditions. Glycerol was almost totally degraded (degradation efficiency of 97.42% ± 0.98), independently of the glycerol type used.     

From natural to mixed convection in horizontal and differentially heated annular ducts: Linear stability analysis

Linear stability analysis of a fully developed mixed convection flow of air in an annular horizontal duct is numerically investigated for the radius ratio R = 1.2, a Péclet and a Rayleigh number less than 200 and 6000, respectively. An iterative method is developed to enable the convergence of the dimensionless parameters to their marginal values at the transition. New mixed convection flows are highlighted that are highly correlated with those obtained in natural convection problems under the assumption of two dimensionality. The synthesis of our results on the transitions permits us to build the map of stability for the steady and established mixed convection flows and clearly shows the occurrence of multiplicity of solutions for some couples of Rayleigh and Péclet numbers.     

Electric and magnetic properties of ferromagnetic/piezoelectric bilayered composite

One of the most promising ways for the realization of multi-functional materials is the integration of oxides with different properties in artificial heterostructures. In this paper, a novel piezoelectric–ferromagnetic heterostructure consisting of 0.92Na_0.5Bi_0.5TiO₃–0.08BaTiO₃ (abbreviated as BNT–BT_0.08) and CoFe₂O₄ layers is fabricated on Si–Pt substrate, by sol–gel method coupled with spin-coating technique. The composite thin film shows only perovskite Bi_0.5Na_0.5TiO₃-like rhombohedral phase and CoFe₂O₄ cubic phase. The thickness of CoFe₂O₄ and BNT–BT_0.08 layers is ~?280 and?~?400 nm, respectively. BNT–BT_0.08/CoFe₂O₄ heterostructure thin film shows a saturation magnetization of 0.11 emu/g at 5 K and 0.07 emu/g at 295 K, dielectric constant of 235 at 1 kHz and tunability of 70% at 1 kHz and an electric field E?=?110 kV/cm. The results reveal that the investigated hybrid piezoelectric/ferromagnetic structure shows piezoelectric behavior, good ferroelectric and ferromagnetic properties. This bilayer composite can be used in miniature low-frequency magnetic sensor and piezoelectric sensor for biomedical domain.     

Antipseudomonal and Immunomodulatory Properties of Esc Peptides: Promising Features for Treatment of Chronic Infectious Diseases and Inflammation

Persistent infections, such as those provoked by the Gram-negative bacterium Pseudomonas aeruginosa in the lungs of cystic fibrosis (CF) patients, can induce inflammation with lung tissue damage and progressive alteration of respiratory function. Therefore, compounds having both antimicrobial and immunomodulatory activities are certainly of great advantage in fighting infectious diseases and chronic inflammation. We recently demonstrated the potent antipseudomonal efficacy of the antimicrobial peptide (AMP) Esc(1-21) and its diastereomer Esc(1-21)-1c, namely Esc peptides. Here, we confirmed this antimicrobial activity by reporting on the peptides’ ability to kill P. aeruginosa once internalized into alveolar epithelial cells. Furthermore, by means of enzyme-linked immunosorbent assay and Western blot analyses, we investigated the peptides’ ability to detoxify the bacterial lipopolysaccharide (LPS) by studying their effects on the secretion of the pro-inflammatory cytokine IL-6 as well as on the expression of cyclooxygenase-2 from macrophages activated by P. aeruginosa LPS. In addition, by a modified scratch assay we showed that both AMPs are able to stimulate the closure of a gap produced in alveolar epithelial cells when cell migration is inhibited by concentrations of Pseudomonas LPS that mimic lung infection conditions, suggesting a peptide-induced airway wound repair. Overall, these results have highlighted the two Esc peptides as valuable candidates for the development of new multifunctional therapeutics for treatment of chronic infectious disease and inflammation, as found in CF patients.     

Synthesis of CuGa2O4 nanoparticles by precursor and self-propagating combustion methods

Copper gallate spinels, CuGa₂O₄, have been synthesized by two wet chemical routes: precursor method and self-propagating combustion involving a glycine-nitrate system. All complex precursors have been characterized by chemical analysis, infrared spectroscopy (IR), ultraviolet visible spectroscopy (UV–vis), electron paramagnetic resonance spectroscopy (EPR), thermal analysis and scanning electron microscopy (SEM). The copper gallate spinel oxides have been further investigated by X-ray diffraction (XRD), SEM, IR, UV–vis, magnetic measurements and EPR. The crystallite size of the copper gallate was found about 280 Å.     

Synthesis and molecular modeling studies of derivatives of a highly potent peptidomimetic vinyl ester as falcipain-2 inhibitors

Herein we report the synthesis of a set of constrained peptidomimetics endowed with an electrophilic vinyl ester warhead and structurally related to a previously identified lead compound, a potent and irreversible inhibitor of falcipain‐2 (FP‐2). FP‐2 is the main hemoglobinase of the malaria parasite P. falciparum. The new compounds were evaluated for their inhibition against FP‐2, and the results were rationalized on the basis of docking experiments. These studies underscore the pivotal role of both the ester function at the P1′ site and the trifluoromethyl group of the P3 side chain in determining the correct orientation of the Michael acceptor warhead in the catalytic site, and as a consequence, the potency of the inhibitors as well as their reversible or irreversible mode of inhibition.     

Research opportunities for argumentation in social networks

Nowadays, many websites allow social networking between their users in an explicit or implicit way. In this work, we show how argumentation schemes theory can provide a valuable help to formalize and structure on-line discussions and user opinions in decision support and business oriented websites that held social networks between their users. Two real case studies are studied and analysed. Then, guidelines to enhance social decision support and recommendations with argumentation are provided.