408 research outputs found
Stochastic Semigroups and Coagulation Equations
A general class of bilinear systems of discrete or continuous coagulation equations is considered. It is shown that their solutions can be approximated by the solutions of appropriate stochastic systems describing the coagulation process in terms of stochastic semigroups.Розглянуто загальний клас білінійних систем дискретних або неперервних рівнянь коагуляції. Показано, що їх розв'язки можуть бути наближені розв'язками стохастичних систем, які описують процес коагуляції через стохастичні напівгрупи
The model constraints from the observed trends for the quasi-periodic oscillation in RE J1034+396
We analyze the time variability of the X-ray emission of RE J1034+396 -- an
active galactic nucleus with the first firm detection of a quasi-periodic
oscillations (QPO). Based on the results of a wavelet analysis, we find a drift
in the QPO central frequency. The change in the QPO frequency correlates with
the change in the X-ray flux with a short time delay. The data specifically
suggest a linear dependence between the QPO period and the flux, and this gives
important constraints on the QPO models. In particular, it excludes explanation
in terms of the orbiting hot spot model close to a black hole. Linear
structures such as shocks, spiral waves, or very distant flares are favored.Comment: Astronomy & Astrophysics, in pres
QPO in RE J1034+396: model constraints from observed trends
We analyze the time variability of the X-ray emission of RE J1034+396, an
active galactic nucleus with the first firm detection of a quasi-periodic
oscillations (QPO). Based on the results of a wavelet analysis, we find a drift
in the QPO central frequency. The change inthe QPO frequency correlates with
the change in the X-ray flux with a short time delay. Linear structures such as
shocks, spiral waves, orvery distant flares seem to be a favored explanation
for this particular QPO event.Comment: to appear in the proceedings to "The Central Kiloparsec in Galactic
Nuclei (AHAR2011)", Journal of Physics: Conference Series (JPCS), IOP
Publishin
Unusual PLS application for Pd(ii) sensing in extremely acidic solutions
An economic and extremely selective device for Pd(ii) determination in very acidic solutions, TazoC-Mar@ is presented. The sensor was prepared via an ion exchange technique of an azoic ligand, (2-(tetrazolylazo)-1,8 dihydroxy naphthalene-3,6,-disulphonic acid), named TazoC, on a Macroporous Strong Anion Exchange Resin, namely Marathon® (Dow Chemical-USA). The TazoC-Mar@ rapidly forms complexes with palladium(ii) ions, which give an intense blue colour to the solid phase, even at low pH. The reaction is highly selective and no other metal ions react with the device at this pH. Moreover, the quantification of Pd(ii) is reliable when applying partial least squares regression (PLS) to relate the signal to the metal ion concentration. The regression model gives a good fit and correct predictions of Pd(ii) concentrations in unknown samples. The method presented here is highly sensitive with an LOD and LOQ equal to 0.2 nM and 0.5 nM, respectively
Effects of natural plant tenderizers on proteolysis and texture of dry sausages produced with wild boar meat addition
This study was conducted to develop a method for improving tenderness and overall qualities of tough wild boar meat used to dry sausage production with direct addition of raw pineapple (Ananas comosus), mango (Mangifera indica), kiwifruit - fuzzy kiwi (Actinidia deliciosa), or ginger (Zingiber officinale roscoe - ginger rhizome) juices contained a plant proteolytic enzyme. Dry-sausages were subjected to various chemical, mechanical and sensory evaluations. An increase in proteolysis was observed in all enzyme-treated samples compared to the control and as a consequence an improvement in juiciness, tenderness and overall acceptability scores were observed. Ginger or kiwifruit juice-treated sausages received better scores for texture, flavor, and overall acceptability. From these results, it is shown that those enzymes as a raw plant juices could be used as tenderizers in dry sausage production.Keywords: Dry sausages, wild boar meat, plant enzymes, proteolysis, texture, sensory properties.African Journal of Biotechnology Vol. 12(38), pp. 5670-567
Cell starvation increases uptake of extracellular Thymosin β4 and its complexes with calcium
Cell metastasis is the main cause of cancer mortality. Inhibiting early events during cell metastasis and invasion could significantly improve cancer prognosis, but the initial mechanisms of cell transition and migration are barely known. Calcium regulates cell migration, whilst Thymosin β4 is a G-actin and iron binding peptide associated with tumor metastasis and ferroptosis. Under normal cell growth conditions, intracellular free calcium ions and Thymosin β4 concentrations are strictly regulated, and are not influenced by extracellular supplementation. However, cell starvation decreases intracellular Thymosin β4 and increases extracellular peptide uptake above the normal range. Unexpectedly, cell starvation significantly increases internalization of extracellular Ca2+/Thymosin β4 complexes. Elucidating the role of Ca2+/Thymosin β4 in the early events of metastasis will likely be important in the future to develop therapies targeting metastasis
The interaction of aluminum with catecholamine-based neurotransmitters: Can the formation of these species be considered a potential risk factor for neurodegenerative diseases?
The potential neurotoxic role of Al(iii) and its proposed link with the insurgence of Alzheimer's Disease (AD) have attracted increasing interest towards the determination of the nature of bioligands that are propitious to interact with aluminum. Among them, catecholamine-based neurotransmitters have been proposed to be sensitive to the presence of this non-essential metal ion in the brain. In the present work, we characterize several aluminum-catecholamine complexes in various stoichiometries, determining their structure and thermodynamics of formation. For this purpose, we apply a recently validated computational protocol with results that show a remarkably good agreement with the available experimental data. In particular, we employ Density Functional Theory (DFT) in conjunction with continuum solvation models to calculate complexation energies of aluminum for a set of four important catecholamines: l-DOPA, dopamine, noradrenaline and adrenaline. In addition, by means of the Quantum Theory of Atoms in Molecules (QTAIM) and Energy Decomposition Analysis (EDA) we assessed the nature of the Al-ligand interactions, finding mainly ionic bonds with an important degree of covalent character. Our results point at the possibility of the formation of aluminum-catecholamine complexes with favorable formation energies, even when proton/aluminum competition is taken into account. Indeed, we found that these catecholamines are better aluminum binders than catechol at physiological pH, because of the electron withdrawing effect of the positively-charged amine that decreases their deprotonation penalty with respect to catechol. However, overall, our results show that, in an open biological environment, the formation of Al-catecholamine complexes is not thermodynamically competitive when compared with the formation of other aluminum species in solution such as Al-hydroxide, or when considering other endogenous/exogenous Al(iii) ligands such as citrate, deferiprone and EDTA. In summary, we rule out the possibility, suggested by some authors, that the formation of Al-catecholamine complexes in solution might be behind some of the toxic roles attributed to aluminum in the brain. An up-to-date view of the catecholamine biosynthesis pathway with sites of aluminum interference (according to the current literature) is presented. Alternative mechanisms that might explain the deleterious effects of this metal on the catecholamine route are thoroughly discussed, and new hypotheses that should be investigated in future are proposed
Binuclear Rhodium(II) Complexes With Selective Antibacterial Activity
Binuclear rhodium(II) complexes [Rh2Cl2(μ-OOCR)2(N-N)2] {R = H, Me; N-N = 2,2'-bipyridine (bpy), 1,10-phenanthroline (phen)} and [Rh2(μ-OOCR)2(N-N)2(H2O)2](RCOO)2 (R = Me, Et;) have been synthesized and their structure and properties have been studied by electronic, IR and 1H NMR spectroscopy. Antibacterial activity of these complexes against Escherichia coli and Staphylococcus aureus has been investigated. The most active antibacterial agents against E. coli were [Rh2Cl2(μ-OOCR)2(N-N)2] and [Rh2(μ-OOCR)2(N-N)2(H2O)2](RCOO)2 {R = H and Me} which were considerably more active than the appropriate nitrogen ligands. The complexes show low activity against S. aureus. The activity of the complexes [Rh2(OOCR)2(N-N)2(H2O)2](OOCR)2 against E. coli decreases in the series: R=H≅CH3>C2H5>C3H7≅C4H9. The reverse order was found in the case of S. aureus
Salicylamide derivatives for iron and aluminium sequestration. From synthesis to complexation studies
This paper presents an easy, fast and economic synthesis of chelating agents for medical, environmental and analytical applications, and the evaluation of the stability of their complexes with Fe3+ and Al3+. Complex formation equilibria with Cu2+ and Zn2+ metal ions were also studied to evaluate if the chelating agents can perturb the homeostatic equilibria of these essential metal ions. Effective chelating agents for metal ions, in addition to their well-known medical uses, find an increasing number of applications in environmental remediation, agricultural applications (supplying essential elements in an easily available form), and in analytical chemistry as colorimetric reagents. Besides the stability of the complexes, the lack of toxicity and the low cost are the basic requisites of metal chelating agents. With these aims in mind, we utilized ethyl salicylate, a cheap molecule without toxic effects, and adopted a simple synthetic strategy to join two salicylate units through linear diamines of variable length. Actually, the mutual position of the metal binding oxygen groups, as well as the linker length, affected protonation and complex formation equilibria. A thorough study of the ligands is presented. In particular, the complex formation equilibria of the three ligands toward Fe3+, Al3+, Zn2+ and Cu2+ ions were investigated by combined potentiometric and spectrophotometric techniques. The results are encouraging: all the three ligands form stable complexes with all the investigated metal ions, involving the oxygen donor atoms from the 2-hydroxybenzamido unit, and nitrogen atoms in copper and zinc coordination
A pilot study of occupational exposure to ultrafine particles during 3D printing in research laboratories
Introduction3D printing is increasingly present in research environments, and could pose health risks to users due to air pollution and particulate emissions. We evaluated the nanoparticulate emissions of two different 3D printers, utilizing either fused filament fabrication with polylactic acid, or stereolithography (SLA) with light curing resin. MethodsNanoparticulate emissions were evaluated in two different research environments, both by environmental measurements in the laboratory and by personal sampling. ResultsThe SLA printer had higher nanoparticulate emissions, with an average concentration of 4,091 parts/cm(3), versus 2,203 particles/cm(3) for the fused filament fabrication printer. The collected particulate matter had variable morphology and elemental composition with a preponderance of carbon, sulfur and oxygen, the main byproducts. DiscussionOur study implies that when considering the health risks of particulate emissions from 3D printing in research laboratories, attention should be given to the materials used and the type of 3D printer
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