Angular dependence of the thermal-lens effect on LiSrAlF6 and LiSrGaF6 single crystals

We apply thermal-lens (TL) spectrometry to measure the angular dependence of the TL effect on colquiriite single crystals. The experiments were performed with LiSrAlF(6) and LiSrGaF(6) using a two-beam mode-mismatched configuration. The results show that it is possible to minimize the TL effect by selecting the appropriate crystal orientation. Our data also show that the anisotropy of the linear thermal expansion coefficient drives the amplitude of the TL effect, including the inversion from focusing to defocusing as the crystal orientation angle tends to the c-axis direction. The results may be useful for those working to develop a high-power laser using LiSrAlF(6)(:Cr) and LiSrGaF(6)(:Cr) single crystals, allowing for optimization of the designed laser cavity.     

Faster than Lyapunov decays of the classical Loschmidt echo

We show that in the classical interaction picture the echo dynamics, namely, the composition of perturbed forward and unperturbed backward Hamiltonian evolution, can be treated as a time-dependent Hamiltonian system. For strongly chaotic (Anosov) systems we derive a cascade of exponential decays for the classical Loschmidt echo, starting with the leading Lyapunov exponent, followed by a sum of the two largest exponents, etc. In the loxodromic case a decay starts with the rate given as twice the largest Lyapunov exponent. For a class of perturbations of symplectic maps the echo dynamics exhibits a drift resulting in a superexponential decay of the Loschmidt echo.     

Noncovalent Substrate‐Directed Enantioselective Heck Reactions: Synthesis of S‐ and P‐Stereogenic Heterocycles

S‐ and P‐Stereogenic heterocycles were synthesized by a remarkably simple enantioselective Heck desymmetrization reaction based on the unprecedented noncovalent directing effect of S=O and P=O functionalities. Selected prochiral symmetric substrates were efficiently arylated using the recently disclosed chiral PyraBOx ligand under mild and open‐flask reaction conditions. Several five‐membered aryl‐ sulfones, sulfoxides, and phosphine oxides were synthesized in good to excellent yields, in good to high diastereoselectivity, and enantiomeric ratios up to 98:2. Theoretical calculations also support the noncovalent directing effect of the S=O and P=O functionalities during the arylation process.     

Spondias tuberosa (Anacardiaceae) leaves: profiling phenolic compounds by HPLC‐DAD and LC–MS/MS and in vivo anti‐inflammatory activity

Spondias tuberosa is a medicinal plant used by several local communities in northeast Brazil to treat infections, digestive disorders and inflammatory conditions. The study aimed to identify and quantify the major phenolic in hydroethanolic extract of leaves from S. tuberosa and to evaluate its anti‐inflammatory potential. The chemical profile of extract was analyzed by HPLC‐DAD and HPLC–MS. The in vivo anti‐inflammatory activity was investigated in carrageenan‐induced hind paw edema and peritonitis models in mice. Identified and quantified through HPLC‐DAD or HPLC‐MS analyses of S. tuberosa extract were the following compounds: chlorogenic acid, caffeic acid, rutin and isoquercitrin. The inflammatory response to carrageenan was significantly reduced in both models by S. tuberosa extract. In hind paw edema, the edematogenic response was reduced by up to 63.6% and the myeloperoxidase activity was completely inhibited. In the peritonitis model, the total cell migration into the peritoneal cavity was reduced by up to 65%. The results obtained give evidence of the anti‐inflammatory action of S. tuberosa and suggest the potential therapeutic benefit of this plant on inflammatory conditions. The chlorogenic acid, caffeic acid, rutin and isoquercitrin identified and quantified in S. tuberosa leaves enable us to suggest that these compounds could be used as chemical markers for quality control of derivative products from this species. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and characterization of a new adsorbent for capture of metal from aqueous solutions

A new material containing a potential ligand for transition metals was prepared through the reaction of 3-aminopropyltrimethoxysilane and thioglycolic acid. The new adsorbent was characterized by elemental analyses, infrared spectroscopy, solid-state ¹³C nuclear magnetic resonance, thermogravimetric analysis, transmission electron microscopy, and specific surface area calculations. The formulated material was used in the removal of cobalt, copper, and nickel cations from aqueous solutions. Calorimetric titration was applied to study the interaction of these cations with the new adsorbent; the latter displayed a chelating moiety with basic centers containing nitrogen, oxygen, and several sulfur atoms, capable of capturing cations from aqueous solutions. This process of extraction was carried out by a batch method to yield the following order of maximum retention capacity: Ni > Co > Cu. The process of cation interactions showed exothermic enthalpies. The calculated ΔG values are in agreement with the spontaneity of the proposed reactions and conformed to the values found by applying the Langmuir model to these systems. The positive entropy and negative enthalpy values indicated that the reactions are favorable.     

Peptide phage display as a tool for drug discovery: targeting membrane receptors

Ligands selected from phage-displayed random peptide libraries tend to be directed to biologically relevant sites on the surface of the target protein. Consequently, peptides derived from library screenings often modulate the target protein's activity in vitro and in vivo and can be used as lead compounds in drug design and as alternatives to antibodies for target validation in both genomics and drug discovery. This review discusses the use of phage display to identify membrane receptor modulators with agonistic or antagonistic activities. Because isolating or producing recombinant membrane proteins for use as target molecules in library screening is often impossible, innovative selection strategies such as panning against whole cells or tissues, recombinant receptor ectodomains, or neutralizing antibodies to endogenous binding partners were devised. Prominent examples from a two-decade history of peptide phage display will be presented, focusing on the design of affinity selection experiments, methods for improving the initial hits, and applications of the identified peptides.     

How visual representations participate in algebra classes’ mathematical activity

Our aim is to discuss how a visual display introduced in a classroom activity to represent a specific algebraic procedure is transformed, taking a central role and modifying the ongoing activity. To discuss how visualization comes about in this activity, we describe an illustrative example selected from observations carried out in a 9th grade classroom and analyze the class interaction from a cultural-historical perspective. Our analysis illuminates the tensions that emerge from a difference between the teacher’s way of signifying the algebraic procedure and the students’ overuse of a visual display they associate with it, and how these tensions impel changes in the activity. We further discuss some pros and cons of using visual displays in algebra classes, and we argue that it is very important for the teacher to be aware of them in order to realize the benefits of using such displays.     

Rapid Screening and Identification of Polar Constituents from Brazilian Arnica Lychnophora sp. by LC-UV/DAD-ESI-MS and LC-UV/DAD-ESI-MS/MS Analysis

This paper describes an analytical method for the rapid screening and identification of the phenolic constituents present in the polar extracts of different Lychnophora spp. using LC-UV/DAD-ESI-MS and LC-UV/DAD-ESI-MS/MS. Compounds were identified based on UV, retention time, MS experiments and MS/MS of precursor ion or standard. On-line phytochemical investigation of Lychnophora spp. allowed for the identification of flavonoids, chlorogenic acid derivatives and lactones. Some of the observed compounds were for the first time identified in Lychnophora species in a fast analytical procedure. The data obtained here may be helpful to the investigation of polar constituents from other Lychnophora species.