Set-based corral control in stochastic dynamical systems: making almost invariant sets more invariant

We consider the problem of stochastic prediction and control in a time-dependent stochastic environment, such as the ocean, where escape from an almost invariant region occurs due to random fluctuations. We determine high-probability control-actuation sets by computing regions of uncertainty, almost invariant sets, and Lagrangian coherent structures. The combination of geometric and probabilistic methods allows us to design regions of control, which provide an increase in loitering time while minimizing the amount of control actuation. We show how the loitering time in almost invariant sets scales exponentially with respect to the control actuation, causing an exponential increase in loitering times with only small changes in actuation force. The result is that the control actuation makes almost invariant sets more invariant.     

Field induced phase transitions on NdRhIn5 and Nd2RhIn8 antiferromagnetic compounds

In this work, we have investigated the low temperature magnetic phase diagram of the tetragonal NdRhIn₅ and Nd₂RhIn₈ single crystals by means of temperature and field dependent heat capacity and magnetic susceptibility measurements. These compounds order antiferromagnetically with a Néel temperature (T_N) of 11 and 10.7 K for NdRhIn₅ and Nd₂RhIn₈, respectively. The constructed magnetic phase of both compounds are anisotropic and show, as expected, a decrease of T_N as a function of the magnetic field for c crystallographic direction. However when the magnetic field is applied along of the c-axis, which is the magnetic easy axis, first-order-like field induced transitions are observed within the antiferromagnetic state. We compare the phase diagrams obtained for NdRhIn₅ and Nd₂RhIn₈ with those for their cubic relative NdIn₃.     

Accurate Mass Fragment Library for Rapid Analysis of Pesticides on Produce Using Ambient Pressure Desorption Ionization with High-Resolution Mass Spectrometry

U.S. food imports have been increasing steadily for decades, intensifying the need for a rapid and sensitive screening technique. A method has been developed that uses foam disks to sample the surface of incoming produce. This work provides complimentary information to the extensive amount of published pesticide fragmentation data collected using LCMS systems (Sack et al. Journal of Agricultural and Food Chemistry, 59, 6383–6411, 2011; Mol et al. Analytical and Bioanalytical Chemistry, 403, 2891–2908, 2012). The disks are directly analyzed using transmission-mode direct analysis in real time (DART) ambient pressure desorption ionization coupled to a high resolution accurate mass-mass spectrometer (HRAM-MS). In order to provide more certainty in the identification of the pesticides detected, a library of accurate mass fragments and isotopes of the protonated parent molecular ion (the [M+H]⁺) has been developed. The HRAM-MS is equipped with a quadrupole mass filter, providing the capability of “data-dependent” fragmentation, as opposed to “all -ion” fragmentation (where all of the ions enter a collision chamber and are fragmented at once). A temperature gradient for the DART helium stream and multiple collision energies were employed to detect and fragment 164 pesticides of varying chemical classes, sizes, and polarities. The accurate mass information of precursor ([M+H]⁺ ion) and fragment ions is essential in correctly identifying chemical contaminants on the surface of imported produce. Additionally, the inclusion of isotopes of the [M+H]⁺ in the database adds another metric to the confirmation process. The fragmentation data were collected using a Q-Exactive mass spectrometer and were added to a database used to process data collected with an Exactive mass spectrometer, an instrument that is more readily available for this screening application. The commodities investigated range from smooth-skinned produce such as apples to rougher surfaces like broccoli. The minimal sample preparation and absence of chromatography has shortened the analysis time to about 15 min per sample, and the simplicity and robustness of the technique make it ideal for rapid screening.

[PbAsSiiPr3]6 — the First Structurally Characterized Compound with Chemical Bonds between Lead and Arsenic

The compound [PbAsSiiPr₃]₆ ( 1 ) could be obtained by the reaction of PbCl₂ with iPr₃SiAs(SiMe₃)₂ in THF at 0 °C. Central structural motif is a hexagonal prism built by six lead and six arsenic atoms. The average Pb—As bond length is 281 pm. The cluster crystallizes in the monoclinic space group C2/c, the lattice constants are: a = 4460.8(9) b = 2296.6(5), c = 2734.4(6) pm, β = 117.57(3)°. The thermogravimetric analysis in vacuum shows the tendecy of 1 to decompose under formation of elementary lead and volatile arsenic compounds.     

High-sensitivity material with reversible photo-induced anisotropy

A new high-sensitivity material with reversible photo-induced anisotropy, suitable for real-time recording, is investigated. The material (methyl-red dye introduced in a polymer layer) requires low recording intensities (tens of mW cm^-2) and possesses excellent reusability.     

Photochromism and dynamic holographic recording in a rigid solution of fluorescein

An investigation was made of the spectra, the kinetics of induction and thermal decay and the dichroism of the photoinduced triplet absorption band in a rigid solution of fluorescein in orthoboric acid. Dynamic holographic recording was possible on this material. An experimental study was conducted into the polarizing properties of the volume transmission holograms. The experiments on four-wave mixing with continous laser light revealed a very high resolution for this rigid solution when used as a medium for optical recording. As a result of the investigations, some possible applications of the rigid solution of fluorescein are pointed out.     

A new generation of cyanide ion-selective membranes for flow injection application: part II. Comparative study of cyanide flow-injection detectors based on thin electroplated silver chalcogenide membranes

Using induced cathodic electrodeposition a number of silver chalcogenide thin layer membranes of non-trivial composition have been synthesized and their performance as ion-selective flow-injection potentiometric detectors (FIPDs) for free cyanide has been critically estimated in the context of the stringent requirements for toxic cyanide environmental monitoring. AgSCN/Ag₂S, Ag₂S, Ag_2+δSe, Ag_2+δSe_1−xTe_x (0 < δ < 0.25 and x ≈ 0.13), Ag₂Se and Ag₂Se_1−xTe_x electroplated membranes were selected for the present performance-based comparative study in order to obtain a feedback information about the effect of membrane composition. Both silver selenide and Te-doped silver selenide membranes, irrespective of their stoichiometry with respect to silver, exhibit the lowest detection limit for CN⁻ (52 ppb) with linear double-Nernstian response down to 130 ppb. The type of chalcogene anion in the membrane composition proves to exert dominant effect on the general performance characteristics of the newly developed FIPDs. The silver stoichiometry (intrinsic defects factor) and the inclusion of Te-dopant (extrinsic defects factor) have more pronounced effect on the profile of the output signal and exert moderate control on the detectors selectivity and baseline stability. This new generation of CN⁻—ion-selective membranes for FIPDs exhibits high selectivity against the common interferents present in cyanide effluents such as SCN⁻, S₂O₃²⁻, Cl⁻ and do not get poisoned in the presence of S²⁻. Moreover, their long-term stability and signal reproducibility, which make redundant the regular day-to-day calibration, coupled with the cost-effective technology for membranes preparation and easy re-generation make them attractive candidates for incorporation into automated in-field devices for in situ cyanide toxic species monitoring.     

Direct Red 28 Adsorption on Amosil and <Emphasis Type="Italic">Avena sativa </Emphasis> L.: Mass Transfer and Kinetics Modelling on the Solid/Solution Interface

Adsorption kinetics is a key issue for successful sorbent selection and the proper design of batch and fixed-bed adsorption systems. The aim of the present study was to determine the kinetics, mass transfer and diffusion coefficients and to establish the rate-controlling mechanism/s during Direct Red 28 adsorption on Amosil and Avena sativa L. biomass. Five kinetic models (pseudo-second order, Blanchard, Avrami, Ritchie and power function) and and four mass transfer (external diffusion, film diffusion, particle diffusion, intraparticle diffusion) mathematical models were applied to the experimental data. To confirm the best-fitting model(s), error analyses were conducted. The integrative comparative analyses of the values of the predicted model parameters, coefficients and error functions established that the intraparticle diffusion model best represented the experimental results of the dye sorption on dried A. sativa L. biomass, while for the Direct Red 28/Amosil system, the kinetic behavior is the best described by either the pseudo-second or Blanchard’s model. Boyd’s effective intraparticle diffusion coefficient (D _i ), characterizing the dye sorption on Amosil, is significantly lower than that for the system Direct Red 28/A. sativa L. biomass. The low values of the Bi number (Bi < 0.5) suggests that the mass transfer resistance, for both systems, is concentrated at the fluid/solid phase surface.     

Microwave assisted synthesis and X-ray structure of a novel anthracene-derived aminophosphonate. Enantioseparation of two α-aminophosphonates and genotoxicity in vivo

A novel anthracene-derived α-aminophosphonate has been synthesized through a classical addition reaction of dimethyl phosphite to a Schiff base and via a microwave assisted Kabachnik–Fields reaction. The compound has been characterized by elemental analysis, TLC, IR, NMR, and fluorescent spectra. The X-ray analysis showed that the compound crystallizes in the orthorhombic space group Pbca (N° 61) with one molecule per asymmetric unit. The enantioseparation of two racemic aminophosphonates (5 and 6) into enantiomers (5a, 5b and 6a, 6b, respectively) has been performed. Data about genotoxicity and antiproliferative activity in vivo of the racemic compounds and their enantiomeric forms is also presented. The studied racemic α-aminophosphonates 5 and 6 and their enantiomers have weak genotoxic effect. Both pairs of enantiomers did not show a significant inhibition of cell dividing processes in the bone marrow cells compared to 5 and 6. The hematopoietic function of the bone marrow will not be discontinued after exposure of the tested compounds.