Neimark–Sacker bifurcation analysis in an intraguild predation model with general functional responses

We analyse the dynamics of a discrete system coming from an intraguild food web model by using the average method. The intraguild predation model is formed by three populations corresponding to prey (P), mesopredator (MP) and superpredator (SP), where these last two populations are specialist. We give sufficient condition to guarantee the existence of a coexistence point at which the intraguild predation discrete model undergoes a Neimark–Sacker bifurcation independently of the functional responses that govern the interactions. We show numerical applications that consist in to assume that P has logistic growth and that the relation of MP–P is through a Holling type II functional response. Besides, we will consider that the interaction of MP–P is such that population MP has defense. The interaction of SP–P will be through a Holling functional response type III or IV. In particular, we give sufficient conditions to guarantee that the three species coexist. The techniques used to obtain the results can be applied to other models with different functional responses.     

Synthesis and spectral properties of starch capped CdS nanoparticles in aqueous solution

Synthesis of cadmium sulphide nanoparticles has been carried out in aqueous solution precipitation. Starch added during the synthesis of the nanoparticles resulted in cadmium-rich nanoparticles forming a stable complex with starch. The morphology and crystalline structure of such structures were measured by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD), respectively. The grain size of the nanoparticles determined by these techniques was of the order of 5 nm, which correlates well with measurements performed by Raman scattering and photoacoustic spectroscopy.     

Chemometric-assisted MIP-optosensing system for the simultaneous determination of monoamine naphthalenes in drinking waters

In the present work a chemometric-assisted molecularly imprinted polymer (MIP)-fluorescence optosensing system has been developed for determining monoamines naphthalene compounds in drinking waters. The use of chemometrics for processing flow injection analysis with MIP fluorescence optosensor data allowed the simultaneous determination of the principal monoamine naphthalene compounds 1-naphthylamine (1-NA) and 2-naphthylamine (2-NA) even in presence of potential interferent 1-naphthalenemethylamine (1-NMA). Classical chemometrics tools such as partial least-squares (PLS-1), as well as second-order algorithms like multiway PLS (N-PLS) and unfolded PLS (U-PLS), were successfully applied, assisting fluorescence emission spectra at a fixed excitation wavelength or excitation-emission fluorescence matrices (EEM), respectively, when interferents are considered in the calibration set. The combinations of both N-PLS and U-PLS with residual bilinearization (RBL), achieving the second-order advantage, were satisfactory applied for the simultaneous determination of the main monoamine naphthalene compounds in drinking water, in the presence of a potential interferent without sample pretreatment, even when the later is not modeled in calibration set. Predictive ability, accuracy, figures of merit, as well as advantages and disadvantages of the different strategies were discussed.     

Special issue on “Innovations on model based clustering and classification”

Advances in Data Analysis and Classification -     

Intermolecular C—H...π interactions in 1,5‐diphenyl‐3‐(2‐pyridyl)‐2‐pyrazoline

The title compound, C₂₀H₁₇N₃, is a derivative of 1,3,5‐triaryl‐2‐pyrazoline and can act as an N,N′‐bidentate ligand. This molecule features strong fluorescence that can be explained by an extended pyridyl–C=N—N–phenyl system. The three‐dimensional structure is formed by means of an extended network of weak C—H...π hydrogen bonds supported by π–π interactions.     

Grade Transition Dynamic Optimization of the Living Nitroxide‐Mediated Radical Polymerization of Styrene in a Tubular Reactor

In this work, the dynamic optimization of tubular reactors where nitroxide‐mediated radical polymerization (NMRP) of styrene takes place is performed. The effect of potential manipulated variables is addressed. The system is governed by partial differential equations (PDEs). The PDEs are discretized spatially giving rise to a differential‐algebraic equation (DAE) system. The DAE optimization problem is then solved using a simultaneous approach wherein the differential and the algebraic variables are fully discretized leading to a large‐scale nonlinear programming (NLP) problem. The resulting optimization problem is solved using an interior point algorithm capable of handling large‐scale NLPs.

     

Molecular weight changes induced in an anionic polydimethylsiloxane by gamma irradiation in vacuum

An anionic almost monodisperse linear polydimethylsiloxane (PDMS) was subjected to gamma irradiation under vacuum at room temperature. The molecular weight changes induced by the radiation process have been investigated using size exclusion chromatography (SEC) with refraction index (RI) and multi angle laser light scattering (MALLS) detectors, to obtain the number and weight average molecular weights of the irradiated samples.The analysis of the data indicates that crosslinking reactions predominated over scission reactions. The results obtained by an SEC-RI have confirmed the presence of small, but measurable amounts of scission.A previously developed mathematical model of the irradiation process that accounts for simultaneous scission and crosslinking and allows for both H- and Y-crosslinks, fitted well the measured molecular weight data. This prediction is in accordance with the experimental data obtained by ²⁹Si-Nuclear Magnetic Resonance spectroscopy (NMR) and previously reported data for commercial linear PDMS (Satti et al., 2008).     

Variability of the Chemical Composition and Bioactivity between the Essential Oils Isolated from Male and Female Specimens of Hedyosmum racemosum (Ruiz & Pav.) G. Don

Hedyosmum racemosum (Ruiz & Pav.) G. is a native species of Ecuador used in traditional medicine for treatment of rheumatism, bronchitis, cold, cough, asthma, bone pain, and stomach pain. In this study, fresh H. racemosum leaves of male and female specimens were collected and subjected to hydrodistillation for the extraction of the essential oil. The chemical composition of male and female essential oil was determined by gas chromatography–gas chromatography equipped with a flame ionization detector and coupled to a mass spectrometer using a non-polar and a polar chromatographic column. The antibacterial activity was assayed against five Gram-positive and two Gram-negative bacteria, and two dermatophytes fungi. The scavenging radical properties of the essential oil were evaluated by DPPH and ABTS assays. The chemical analysis allowed us to identify forty-three compounds that represent more than 98% of the total composition. In the non-polar and polar column, α-phellandrene was the principal constituent in male (28.24 and 25.90%) and female (26.47 and 23.90%) essential oil. Other main compounds were methyl chavicol, germacrene D, methyl eugenol, and α-pinene. Female essential oil presented a strong activity against Klebsiella pneumoniae (ATCC 9997) with an minimum inhibitory concentration (MIC) of 500 μg/mL and a scavenging capacity SC₅₀ of 800 µg/mL.     

New dendrimers containing a single cobaltocenium unit covalently attached to the apical position of Newkome dendrons: electrochemistry and guest binding interactions with cucurbit[7]uril

Two new dendrimer series were prepared and characterized. These dendrimers contain a single bis(cyclopentadienyl)cobalt(III) (cobaltocenium, Cob+) unit covalently attached to the apical (focal) position of Newkome-type dendrons, ranging in size from first to third generation. The dendrimers in the first series (1ECob+-3ECob+) are hydrophobic and have 3, 9, and 27 tert-butyl esters on their peripheries, whereas the dendrimers in the second series (1Cob+-3Cob+) are hydrophilic with 3, 9, and 27 carboxylic acid groups on their surfaces, respectively. In voltammetric experiments, all dendrimers showed the expected one-electron reversible reduction of the cobaltocenium center, and the heterogeneous rate of electron transfer decreased with generation in both dendrimer series. The host-guest binding interactions between water-soluble dendrimers 1Cob+-3Cob+ and the cucurbit[7]uril (CB7) host were investigated using 1H NMR spectroscopy, MALDI-TOF mass spectrometry, and electrochemical techniques. The association equilibrium constants (K) for all dendrimer guests were significantly lower than that measured for the inclusion complex between underivatized Cob+ and CB7 (K = 5.7 x 10(9) M(-1)). Nonetheless, among the three dendrimers surveyed, the second-generation dendrimer, 2Cob+, afforded optimum stabilization for the CB7 inclusion complex.