Infinite groups with Sylow permutable subgroups

If a subgroup H of a periodic group G satisfies HP = PH for all Sylow subgroups P of G, then we call H a Sylow-permutable, or S-permutable, subgroup of G. It is well known that S-permutability is not a transitive relation. In this paper, we study infinite periodic groups in which the relation to be S -permutable is transitive (PST-groups) and infinite periodic groups whose ascendant subgroups are S-permutable (ASP-groups).     

Performance comparison of power fading mitigation techniques in multiband OFDM-UWB signals transmission along LR-PONs

The single sideband （SSB） modulation is assessed as a means to mitigate the dispersion-induced power fading on the distribution of ortogonal frequency division multiplexing （OFDM） ultra wideband （UWB） radio signals along long-reach passive optical networks （LR-PONs）. Particularly, two different SSB ar- chitectures, namely, Sieben＇s architecture and four phase modulator （FPM） architecture are optimized to provide maximum sideband suppression. The minimum optical signal-to-noise ratio （OSNR） required to simultaneously distribute all the 14 OFDM-UWB sub-bands along the LR-PON distances ranging between 80 and 100 km is also evaluated through numerical simulation. FPM architecture is preferable over Sieben＇s architecture because the latter SSB architecture generates carriers-carriers beat term at the photodetector output with high power, thereby causing significant degradation in the OFDM-UWB sub-bands with lower central frequencies. The simultaneous distribution of the 14 SSB OFDM-UWB sub-bands in the LR-PON using the FPM architecture shows a minimum OSNR penalty of 3 dB compared with the centralized dis- persion compensation technique.     

Projected explicit lawson methods for the integration of Schrödinger equation

In this article, it is proved that explicit Lawson methods, when projected onto one of the invariants of nonlinear Schrödinger equation (norm) are also automatically projected onto another invariant (momentum) for many solutions. As this procedure is very cheap and geometric because two invariants are conserved, it offers an efficient tool to integrate some solutions of this equation till long times. On the other hand, we show a detailed study on the numerical performance of these methods against splitting ones, with fixed and variable stepsize implementation. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq31: 78–104, 2015     

Characterization and Antineoplasic Effect of Extracts Obtained from <Emphasis Type="Italic">Pleurotus sajor</Emphasis>-<Emphasis Type="Italic">caju</Emphasis> Fruiting Bodies

Fungi of the Pleurotus genus present a great industrial interest due to their possibility of producing pharmacological compounds, pigments, aromas, organic acids, polysaccharides, enzymes, vitamins, amino acids, etc. Among the therapeutic products, we can highlight those with antineoplasic activity, attributed to the fungi cell wall components. Based on this, the objective of this work was to study the antineoplasic capacity of the polysaccharidic fractions obtained from Pleurotus sajor-caju fruiting bodies. Female Swiss mice were inoculated with the Ehrlich ascitic tumor (5 × 10⁶ cells/animal) in ascitic form. The polysaccharidic fractions were administered intraperitoneally, during a 6-day period. Fractions FI and FII presented a lower volume of ascitic liquid (3.1 and 1.8 mL, respectively) and a higher reduction in the number of neoplasic cells present in the ascitic liquid (86.2% and 85%, respectively), when compared to the positive control (group inoculated with the tumor but without treatment). These fractions were characterized in terms of monosaccharide composition. Glucose was the major component detected, followed by galactose and mannose. The anomeric carbon configuration of the β-glucan was confirmed by the ¹³C NMR (δ 103.7). Substituted and free C3 and C6 were also detected. Protein bands were confirmed through infrared analysis.     

Ultrasound-assisted pressurized solvent extraction for aliphatic and polycyclic aromatic hydrocarbons from soils

In the present work the efficiency of extraction of aliphatic diesel range organics (DROs) and polycyclic aromatic hydrocarbons (PAHs) from soil was assessed by using dynamic modes of pressurized solvent extraction (PSE), and ultrasound-assisted pressurized solvent extraction (US-PSE). Optimization studies were carried out using a blank soil (Non-Polluted Soil#1, CLN-1, RTC) and a real soil which was previously spiked with the analyte mixture and aged for 90 days. A laboratory-made manifold with controlled temperature and pressure was used to carry out the leaching processes. The extraction cell was inserted into an oven for PSE and into an ultrasound bath for US-PSE. The following variables were studied in each case, keeping the pressure at about 1800 psi: extraction temperature, time of static and dynamic extraction and solvent flow rate. In addition, the time of ultrasound application was also studied in US-PSE. For PSE with dichloromethane (DCM) the recoveries were about 90-95% for both the families of analytes, using extraction times of 20 min. Analyte extraction was quantitative by using US-PSE with DCM for 10 min. In all cases, after the extraction process, the analytes were determined by GC-MS. Application of the method to a natural contaminated sample suggests that either the extraction time used in US-PSE should be increased to 20 min or the solvent (DCM) should be replaced by a mixture of DCM:acetone (1:1), to reach comparability with Soxhlet extraction.     

On squares in polynomial products

Let ${f(X) \in \mathbb {Z}[X]}$ be an irreducible polynomial of degree D ≥ 2 and let N be a sufficiently large positive integer. We estimate the number of positive integers n ≤ N such that the product $$F(n) = \prod\limits_{k =1}^n f(k)$$ is a perfect square. We also consider more general questions and give a lower bound on the number of distinct quadratic fields of the form ${\mathbb {Q}(\sqrt{F(n)})}$ , n  = M + 1, ... , M + N.     

A preliminary information about continuous fermentation using cell recycling for improving microbial xylitol production rates

Xylitolis a sugar-alcohol with important technological properties, such as anticariogenicity, low caloric value, and negative dissolution heat. It can be used successfully in food for mulations and pharmaceutical industries. Its production is therefore in great demand. Biotechnological xylitol production has several economic advantages in comparison with the conventional process based on the chemical reduction of xylose. The efficiency and the productivity of this fermentation chiefly depends on the microorganism and the process conditions employed. In this article a simple continuous culture with cell recycling was evaluated to enhance the capability of Candida guilliermondii FTI 20037 to produce xylitol. The fermentation was initiated batchwise by directly inoculating the grown seed culturein a 2-L bench-scale fermentor. Continuous feeding was begun at a dilution rate (D) of 0.060/h after the xylose concentration had completely consumed and the cell concentration was a bout 4.0 g/L. At a dilution rate of 0.060/h the xylitol concentration was about 15g/L and in creased by about 35%, whereas the dilution rate decreased by about 58%. Furthermore, the volumetric productivity, Q_p, markedly depended on the dilution rate, diminishing by about 37% as D was changed from 0.060 to 0.025/h. These preliminary results show us that the continous fermentation with cell recycling is a good way to study the xylitol production by xylose-fermenting yeasts.     

Synthesis of Polysantol and related sandalwood-type odorants using magnesium α-bromoketone enolates

The syntheses of the commercial sandalwood-type odorant Polysantol^® and several structurally related compounds are described. The methodology followed is based on a selective and efficient magnesium-mediated aldol reaction of the starting material, α-campholenic aldehyde and different α-bromoketones. Dehydration of the resulting secondary alcohol and reduction of the carbonyl group allowed the completion of the syntheses of the target molecules in 30-56% overall yields.     

Variational calculation of vibrational energies of triatomic molecules using SCF optimized modes

A self-consistent field optimization of the vibrational coordinates for nonlinear triatomic molecules is presented. The optimal coordinates are obtained by making a three-dimensional rotational transformation of the normal modes and determining the rotation angles as those for which the SCF energy is stationary. The utility of the optimized coordinates in full variational calculations of vibrational energies is studied for the molecules of H₂O, O₃, H₂D⁺, H₂T⁺, and D₂T⁺. For H₂O and O₃, the optimization procedure leads to the local mode representation. It is shown that the use of the optimal coordinates in variational calculations allows a large reduction of the dimension of the Hamiltonian matrix to be diagonalized in order to reach convergence.