Characterizing topological and dynamical properties of complex networks without border effects

The properties of complex networks are highly influenced by border effects frequently found as a consequence of the finite nature of real-world networks as well as network sampling. Therefore, it becomes critical to devise effective means for sound estimation of network topological and dynamical properties while avoiding these types of artifacts. In the current work, an algorithm for minimization of border effects is proposed and discussed, and its potential is illustrated with respect to two real-world networks, namely bone canals and air transportation.     

Reaction of 5-Allyl-5-Isobutylbarbituric Acid with Electrophilic Reagents

The reaction of 5-allyl-5-isobutylbarbituric acid with several electrophilic reagents gives products resulting from the addition of the electrophile to the double bond of the allyl group and/or bicyclic products.     

On abstract stochastic differential equation in hilbert spaces with dissipative drift

A multi–operative Markovian machine interference model with arbitrary inital number of breakdowns is studied by taking mean breakdown of each machine as λ^-1 and the mean repairtime of each machine as μ^-1. The transient state probabilities of number of breakdowns and initial busy period distributions of a given number of operatives have been obtained in closed form using Laplace transform and matrix theory. The efficacy of the method is tested by computing the state probabilities and measures of effectiveness such as machine availability function and operating efficiency function for various values of traffic intensity ρ=λ/μ.     

Dynamic force-penetration curves in rock by matching theoretical to experimental wave propagation response

A methodology to obtain the dynamic force-penetration curve of a rock specimen is presented. For this, a simple portable experimental setup is used. On one end, a hand-held hammer strikes a slender chisel. On the other end the chisel is in contact with the rock specimen into which the generated stress wave propagates. Strain gages installed at a selected section of the chisel are recorded throughout the impact duration. The theoretical signal at the same section is simulated using a numerical method based on the impulsemomentum principle previously developed by the author. Essentially the shape of the simulated theoretical response at the strain gage section depends on the impact velocity of the hammer and the slope of the assumed force-penetration curve. These two parameters are adjusted until the shape of the theoretical signal at the strain gage closely matches the experimental signal. Due to its simplicity, the proposed methodology has the potential of becoming a standard dynamic test for obtaining the force-penetration curvs in rocks.     

Dependence of the product on the P–P ligand in reactions of [RuCl3(NO)(P–P)] complexes (P–P = aromatic diphosphines) with 2-mercaptopyridine

This study presents the syntheses and characterization of 2-mercaptopyridine (pyS⁻) complexes containing ruthenium(II) with the following general formula [Ru(pyS)₂(P–P)], P–P = (c-dppen) = cis-1,2-bis(diphenylphosphino)ethylene) (1); (dppe) = 1,2-bis(diphenylphosphino)ethane (2); (dppp) = 1,3-bis(diphenylphosphino)propane (3) and (dppb) = 1,4-bis(diphenylphosphino)butane (4). The complexes were synthesized from the mer- or fac-[RuCl₃(NO)(P–P)] precursors in the presence of triethylamine in methanol solution with dependence of the product on the P–P ligand. The reaction of pyS⁻ with a ruthenium complex containing a bulky aromatic diphosphine dppb disclosed a major product with a dangling coordinated dppbO-P, the [Ru(pyS)₂(NO)(η¹-dppbO-P)]PF₆(5). In addition, this work also presents and discusses the spectroscopic and electrochemical behavior of 1–5, and report the X-ray structures for 1 and 5.     

Determination of trace elements in biological samples treated with formic acid by inductively coupled plasma mass spectrometry using a microconcentric nebulizer

A simple and fast method for the determination of As, Ba, Cd, Co, Cu, Fe, Ga, Mn, Mo, Ni, Pb, Rb, Se, Sr, Tl, U, V and Zn in biological samples by inductively coupled plasma mass spectrometry (ICP-MS), after sample solubilization with formic acid and introduction by a microconcentric nebulizer, is proposed. The sample is mixed with formic acid, kept at 90 °C for one hour and then diluted with nitric acid aqueous solution to a 50% v/v formic acid and 1% v/v nitric acid final concentrations. The final sample solution flow rate for introduction into the plasma was 30 μL min⁻¹. The optimized and adopted nebulizer gas flow rate was 0.7 L min⁻¹ and RF power was 800 W. These conditions are very different than those normally used when a conventional nebulizer is employed. Rodhium was used as internal standard. External calibration against aqueous standard solutions, without formic acid, could be used for quantification, except for As, Se and Zn. However, external calibration with 50% formic acid allows the determination of all analytes with high accuracy and it is recommended. The detection limits were between 0.0005 (Tl) and 0.22 mg kg⁻¹ (Fe) and the precision expressed by the relative standard deviations (RSD) were between 0.2% (Sr) and 3.5% (Ga). Accuracy was validated by the analysis of four certified reference biological materials of animal tissues, comparing the results by linear regressions and by the t-test at a 95% confidence level. The recommended procedure avoids plasma instability and carbon deposit on the cones.     

Comparative study of two extraction techniques to obtain representative aroma extracts for being analysed by gas chromatography-olfactometry: application to roasted pistachio aroma

This research paper presents a comparative study of two different extraction and concentration techniques to obtain representative pistachio aroma extracts: the traditional direct solvent extraction (DSE) followed by high-vacuum transfer (HVT) and the headspace solid-phase microextraction (HS-SPME). The results showed that, although both techniques provide accurate information about the aromatic composition that will be perceived by the consumer, the precision in terms of within-day repeatability and between-days repeatability (intermediate precision) of the chromatographic areas presented better values for HS-SPME than for DSE-HVT. Moreover the solvent-free HS-SPME allows the extraction of more odour-active regions, requires very little sample handling and shorter time for sampling.     

Synthesis and structural characterization of tris(2-seleno-1-mesitylimidazolyl) hydroborato complexes: a new type of strongly electron donating tripodal selenium ligand

A new tripodal ligand that features three selenium donors, namely the tris(2-seleno-1-mesitylimidazolyl)hydroborato ligand, [Tse(Mes)], has been constructed via the reaction of KBH(4) with 1-mesitylimidazole-2-selone; comparison of the IR spectroscopic data of [Tse(Mes)]Re(CO)(3) with those of a variety of related LRe(CO)(3) complexes demonstrates that the [Tse(Mes)] ligand is more strongly electron donating than Cp, Cp*, [Tp], [Tp(Me(2))] and [Tm(Mes)] ligands.     

Digital image-based titrations

The exploitation of digital images obtained from a CCD camera (WebCam) as a novel instrumental detection technique for titration is proposed for the first time. Named of digital image-based (DIB) titration, it also requires, as a traditional titration (for example, spectrophotometric, potentiometric, conductimetric), a discontinuity in titration curves where there is an end point, which is associated to the chemical equivalence condition. The monitored signal in the DIB titration is a RGB-based value that is calculated, for each digital image, by using a proposed procedure based on the red, green, and blue colour system. The DIB titration was applied to determine HCl and H₃PO₄ in aqueous solutions and total alkalinity in mineral and tap waters. Its results were compared to the spectrophotometric (SPEC) titration and, by applying the paired t-test, no statistic difference between the results of both methods was verified at the 95% confidence level. Identical standard deviations were obtained by both titrations in the determinations of HCl and H₃PO₄, with a slightly better precision for DIB titration in the determinations of total alkalinity. The DIB titration shows to be an efficient and promising tool for quantitative chemical analysis and, as it employs an inexpensive device (WebCam) as analytical detector, it offers an economically viable alternative to titrations that need instrumental detection.