Remarks on torsionfreeness and its applications

In this article, we shall characterize torsionfreeness of modules with respect to a semidualizing module in terms of the Serre’s condition (S_n). As its applications, we give a characterization of Cohen-Macaulay rings R such that R_𝔭 is Gorenstein for all prime ideals 𝔭 of height less than n, and we will give a partial answer of Tachikawa conjecture and Auslander-Reiten conjecture.     

Mutually disjoint designs and new 5‐designs derived from groups and codes

The article gives constructions of disjoint 5‐designs obtained from permutation groups and extremal self‐dual codes. Several new simple 5‐designs are found with parameters that were left open in the table of 5‐designs given in (G. B. Khosrovshahi and R. Laue, t‐Designs with t⩾3, in “Handbook of Combinatorial Designs”, 2nd edn, C. J. Colbourn and J. H. Dinitz (Editors), Chapman & Hall/CRC, Boca Raton, FL, 2007, pp. 79–101), namely, 5−(v, k, λ) designs with (v, k, λ)=(18, 8, 2m) (m=6, 9), (19, 9, 7m) (m=6, 9), (24, 9, 6m) (m=3, 4, 5), (25, 9, 30), (25, 10, 24m) (m=4, 5), (26, 10, 126), (30, 12, 440), (32, 6, 3m) (m=2, 3, 4), (33, 7, 84), and (36, 12, 45n) for 2⩽n⩽17. These results imply that a simple 5−(v, k, λ) design with (v, k)=(24, 9), (25, 9), (26, 10), (32, 6), or (33, 7) exists for all admissible values of λ. © 2010 Wiley Periodicals, Inc. J Combin Designs 18: 305–317, 2010     

Macrocystis pyrifera Extract Residual as Nutrient Source for the Production of Sophorolipids Compounds by Marine Yeast Rhodotorula rubra

Seaweed processing generates liquid fraction residual that could be used as a low-cost nutrient source for microbial production of metabolites. The Rhodotorula strain is able to produce antimicrobial compounds known as sophorolipids. Our aim was to evaluate sophorolipid production, with antibacterial activity, by marine Rhodotorula rubra using liquid fraction residual (LFR) from the brown seaweed Macrocystis pyrifera as the nutrient source. LFR having a composition of 32% w/w carbohydrate, 1% w/w lipids, 15% w/w protein and 52% w/w ash. The best culture condition for sophorolipid production was LFR 40% v/v, without yeast extract, artificial seawater 80% v/v at 15 °C by 3 growth days, with the antibacterial activity of 24.4 ± 3.1 % on Escherichia coli and 21.1 ± 3.8 % on Staphylococcus aureus. It was possible to identify mono-acetylated acidic and methyl ester acidic sophorolipid. These compounds possess potential as pathogen controllers for application in the food industry.     

Distance-Regular Graphs with c i = b d-i and Antipodal Double Covers

Let be a distance-regular graph of diameter d and valency k > 2. Suppose there exists an integer s with d 2s such that c _i = b _d-i for all 1 i s. Then is an antipodal double cover.     

Impact of electrodialytic parameters on cation migration kinetics and fouling nature of ion-exchange membranes during treatment of solutions with different magnesium/calcium ratios

During electrodialysis (ED) treatment of solutions with different Mg/Ca ratios (R = 0, 1/20, 1/10, 1/5 and 2/5) and in different pH conditions (acid, neutral and basic), foulings on ion-exchange membranes were previously characterized and identified, by the way of X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. A mineral fouling was observed in neutral and basic conditions (for R = 1/5 and 2/5) on the anion-exchange membrane (AEM) concentrate side and in basic conditions on the cation-exchange membrane (CEM) concentrate side as well as on the diluate side for R = 1/5 and 2/5. The objectives of this present work were to link the morphological characterization and identification of membrane fouling to electrodialytic parameters and cation migration kinetics. It appeared that the CEM permselectivity was severely affected in basic conditions for R ≥ 1/5. The consequence of this alteration was the migration of OH⁻ through the CEM, a pH increase in the diluate compartment and different treatment durations. The calcite observed on AEM concentrate side for Mg/Ca ≥ 1/5 would be due first to the particular operating conditions such as the recirculation of the concentrate solution, and also to the supersaturated conditions reached or not at the AEM interface and favourable pH conditions.     

Understanding the stereo‐ and regioselectivities of the polar Diels–Alder reactions between 2‐acetyl‐1,4‐benzoquinone and methyl substituted 1,3‐butadienes: a DFT study

The polar Diels–Alder (DA) reactions of 2‐acetyl‐1,4‐benzoquinone (acBQ) with methyl substituted 1,3‐butadienes have been studied using DFT methods at the B3LYP/6‐31G(d) level of theory. These reactions are characterized by a nucleophilic attack of the unsubstituted ends of the 1,3‐dienes to the β conjugated position of the acBQ followed by ring‐closure. The reactions present a total regioselectivity and large endo selectivity. The analysis based on the global electrophilicity of the reagents at the ground state, and the natural bond orbital (NBO) population analysis at the transition states correctly explain the polar nature of these cycloadditions. The large electrophilic character of acBQ is responsible for the acceleration observed in these polar DA reactions. Copyright © 2008 John Wiley & Sons, Ltd.     

Comparison between computational fluid dynamics,fluid–structure interaction and computational structural dynamics predictions of flow-induced wall mechanics in an anatomically realistic cerebral aneurysm model

Haemodynamically induced stress plays an important role in the progression and rupture of cerebral aneurysms. The current work describes computational fluid dynamics (CFD), fluid–structure interaction (FSI) and computational structural dynamics (CSD) simulations in an anatomically realistic model of a carotid artery with two saccular cerebral aneurysms in the ophthalmic region. The model was obtained from three-dimensional (3D) rotational angiographic imaging data. CFD and FSI were studied under a physiologically representative waveform of inflow. The arterial wall was assumed elastic or hyperelastic, as a 3D solid or as a shell depending on the type of modelling used. The flow was assumed to be laminar, non-Newtonian and incompressible. The CFD, FSI and CSD models were solved with the finite elements package ADINA. Predictions of velocity field and wall shear stress (WSS) on the aneurysms made using CFD and FSI were compared. The CSD model of the aneurysms using complete geometry was compared with isolated aneurysm models. Additionally, the effects of hypertensive pressure on CSD aneurysm models are also reported. The vortex structure, WSS, effective stress, strain and displacement of the aneurysm walls showed differences, depending on the type of modelling used.     

Analytical performance of Compton/Rayleigh signal ratio by total reflection X-ray fluorescence (TXRF): A potential methodological tool for sample differentiation

The high sensitivity Compton and Rayleigh X-ray scattering signals can be used to gain valuable information on the chemical composition of various matrices, by exploiting the ratio of those signals as a function of the effective atomic number (Z_eff). Neither total reflection X-ray fluorescence (TXRF) nor the effect of the experimental setup, including sample preparation, X-ray excitation source selection, and band deconvolution procedure, has been assessed in this kind of approach. Here, a Compton/Rayleigh ratio and Z_eff-based TXRF method was set up and tested as an analytical tool for milk samples differentiation. The method was developed using a 90° scattering angle and assessed using different X-ray excitation sources: a molybdenum tube (Mo Kα 17.5 KeV) and a tungsten tube (W Lα 8.5 KeV and W-Brems 35 KeV). The evaluation of independent Compton and Rayleigh signals was performed by non-Gaussian and Gaussian curve resolution methods, and both height and area-based calculations were evaluated. Different sample preparation conditions were assessed. By using 11 standard materials, a calibration curve for Compton/Rayleigh ratio versus Z_eff was established. The method was tested to determine the Z_eff of milk samples, which enabled its use as a parameter to differentiate them. Good precisions were obtained with the Mo excitation source and the area-based calculations, which allowed to differentiate undiluted milk samples by species, treatment, and fat content according to their Compton/Rayleigh ratio. This simple and rapid method has the potential to be used for the differentiation of various types of samples, including liquids, solids, and aerosols.     

Uncertainty estimation of anions and cations measured by ion chromatography in fine urban ambient particles (PM2.5)

The present work presents a measurement uncertainty evaluation according to Guide to the Expression of Uncertainty in Measurement (GUM) of the concentration of the cations K⁺ and Li⁺ and anions NO₃⁻² and SO₄⁻² in fine airborne particulate matter, refers to particles less than 2.5 μm in diameter (PM_2.5), as measured by ion chromatography (US-EPA 300 method). The GUM method is not typically used to report uncertainty. In general, the analytical results only report the measurement’s standard deviation under repetition as an uncertainty; thus, not all sources of uncertainty are considered. In this work, the major sources of uncertainty regarding the measurements were identified as contributions to linear least square regression lines, repeatability, precision, and trueness. The expanded uncertainty was approximately 20% for anions and cations. The largest contribution to uncertainty was found to be repeatability.     

On a hierarchical error estimator combined with a stabilized method for the Navier–Stokes equations

This work combines two complementary strategies for solving the steady incompressible Navier–Stokes model with a zeroth‐order term, namely, a stabilized finite element method and a mesh–refinement approach based on an error estimator. First, equal order interpolation spaces are adopted to approximate both the velocity and the pressure while stability is recovered within the stabilization approach. Also designed to handle advection dominated flows under zeroth‐order term influence, the stabilized method incorporates a new parameter with a threefold asymptotic behavior. Mesh adaptivity driven by a new hierarchical error estimator and built on the stabilized method is the second ingredient. The estimator construction process circumvents the saturation assumption by using an enhancing space strategy which is shown to be equivalent to the error. Several numerical tests validate the methodology. © 2011 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2011