Symmetric differentiation on time scales

We define a symmetric derivative on an arbitrary nonempty closed subset of the real numbers and derive some of its properties. It is shown that real-valued functions defined on time scales that are neither delta nor nabla differentiable can be symmetric differentiable.     

Polarization‐angle dependence of photoluminescence intensity of ordered GaInP2 layers: observation of polarization memory

We compare measured and calculated polarization‐angle dependencies of the intensity of the photoluminescence emission from MOVPE‐grown GaInP₂ layers with different ordering parameters. We measured the polarization‐angle dependencies of the emission propagating along the [001], [110] and [1 0] directions at room temperature. Symmetry considerations were used to calculate the dependence of the relative intensity of the PL emission which was linearly polarized along different directions and to estimate the value of the valence‐band splitting by fitting the measured dependencies with calculated curves. An intriguing influence of the polarization of the exciting beam on the relative amount of the polarized PL emission was observed in the emission from the (110) plane. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Quenching of the Singlet and Triplet Excited States of Pterin by Amino Acids

Unconjugated oxidized pterins accumulate in the skin of patients suffering from vitiligo and, under UVA irradiation, photosensitize the oxidation of amino acids. In this work, we study the interaction of the singlet and triplet excited states of pterin (Ptr), the parent compound of oxidized pterins, with four oxidizable amino acids: tryptophan (Trp), tyrosine (Tyr), histidine (His) and methionine (Met). Steady‐state and time‐resolved fluorescence measurements and laser flash photolysis experiments were performed to investigate the quenching of the Ptr excited states by the amino acids in aqueous solution. The singlet excited states of Ptr are quenched by Met mainly via a dynamic process and by Trp via a combination of dynamic and static processes. His does not quench singlet excited states of Ptr, and quenching by Tyr could not be investigated due to the low solubility of this amino acid. The triplet excited states of Ptr are quenched by the four studied amino acids, and the corresponding bimolecular quenching rate constants are in the range of diffusion controlled limit. The assessment of the results in the context of the Ptr‐photosensitization of amino acids suggests that triplet excited state of Ptr is the species that initiates the photochemical processes.     

Enantioselective Iridium‐Catalyzed Allylation of Acetylenic Ketones via 2‐Propanol‐Mediated Reductive Coupling of Allyl Acetate: C14‐C23 of Pladienolide D

Highly enantioselective catalytic reductive coupling of allyl acetate with acetylenic ketones occurs in a chemoselective manner in the presence of aliphatic or aromatic ketones. This method was used to construct C14‐C23 of pladienolide D in half the steps previously required.     

Exposure risk assessment of uranium intake of the milk products from the region of Pernambuco,Brazil

Journal of Radioanalytical and Nuclear Chemistry - Haloperidol (HP) is a dopamine blocking agent. HP was radiolabeled with 125I using direct electrophilic substitution. Different HP formulations...     

Electroanalysis of Bisphenols A,F, and Z Using Graphene Based Stochastic Microsensors

Two stochastic microsensors based on immobilization of the complex between protoporphyrin IX and cobalt on nanographene paste and on the reduced graphene oxide paste were proposed for the simultaneous identification and quantification of bisphenols A (BPA), F (BPF) and Z (BPZ) from water samples. The signatures obtained for the BPA, BPF, and BFZ when both stochastic microsensors were used shown that the microsensors can be used for the discrimination between the three bisphenols in water samples. Very low limits of determination were obtained for the three bisphenols: 1fmol/L for BPA and BPF when the microsensor based on the immobilization of the complex between protoporphyrin IX and cobalt on nanographene paste was used, and 10fmol/L for BPZ when the microsensor based on the immobilization of the complex between protoporphyrin IX and cobalt on reduced graphene oxide paste was used. The linear concentration ranges covered by the proposed stochastic microsensors were: between 10^?15 and 10^?5 mol/L for BPA, between 10^?15 and 10^?7 mol/L for BPF, and between 10^?13 and 10^?10 mol/L for BPZ. The recoveries of the bisphenols in water samples were higher than 99.50 %, with RSD values lower than 1.00 %.     

Thermal,spectral and biological characterisation of copper(II) complexes with isoniazid-based hydrazones

Journal of Thermal Analysis and Calorimetry - A series of complexes [Cu(L)(CH3COO)2]·nH2O (L: isonicotinic acid 2-(2-hydroxy-8-substituted-tricyclo[7.3.1.02.7]tridec-13-ylidene)-hydrazones)...     

Brown HT

Journal of Thermal Analysis and Calorimetry - Thermal behavior of Brown HT food dye was studied in correlation with the physical and biological antioxidant properties. Brown HT’s structure...     

Novel 4-azaandrostenes as prostate cancer cell growth inhibitors: Synthesis,antiproliferative effects,and molecular docking studies

In this study, synthesis, structural characterization, molecular docking studies, and antiproliferative effects in four different cell lines of several novel 16-arylidene-4-azaandrost-5-ene compounds are reported. These compounds were prepared by oxidative cleavage of the enone system of androstenedione followed by an azacyclization reaction and an aldol condensation with various aldehydes at C16. In the androgen-dependent LNCaP cells, the most relevant antiproliferative effects were observed with the 16-phenyl, 16-p-tolyl, and 16-p-nitrophenyl derivatives. Compound 16E-[(4-methylphenyl)methylidene]-4-azaandrost-5-ene-3,17-dione was the most potent in these cells (IC₅₀ = 28.28 μM), having lower antiproliferative effects in the androgen-independent PC-3 cells (IC₅₀ = 45.31 μM). In addition, an interesting selectivity toward cancer cell lines was found for all compounds because a generally low cytotoxicity was detected in healthy human fibroblasts. Furthermore, the 16-p-tolylazaandrostene steroid induced a reduction of viability in LNCaP cells similar to that observed with finasteride, a clinically used 5α-reductase inhibitor. Moreover, molecular docking studies predicted that these 4-azaandrostene derivatives can interact with 5β-reductase, which has a high level of similarity to 5α-reductase enzyme, and with other common targets of steroidal drugs, particularly the enzyme 17α-hydroxylase/17,20-lyase.     

Physical,Thermal and Biological Properties of Yellow Dyes with Two Azodiphenylether Groups of Anthracene

Two yellow bis-azo dyes containing anthracene and two azodiphenylether groups (BPA and BTA) were prepared, and an extensive investigation of their physical, thermal and biological properties was carried out. The chemical structure was confirmed by the FTIR spectra, while from the UV–Vis spectra, the quantum efficiency of the laser fluorescence at the 476.5 nm was determined to be 0.33 (BPA) and 0.50 (BTA). The possible transitions between the energy levels of the electrons of the chemical elements were established, identifying the energies and the electronic configurations of the levels of transition. Both crystals are anisotropic, the optical phenomenon of double refraction of polarized light (birefringence) taking place. Images of maximum illumination and extinction were recorded when the crystals of the bis-azo compounds rotated by 90° each, which confirms their birefringence. A morphologic study of the thin films deposited onto glass surfaces was performed, proving the good adhesion of both dyes. By thermal analysis and calorimetry, the melting temperatures were determined (~224–225 °C for both of them), as well as their decomposition pathways and thermal effects (enthalpy variations during undergoing processes); thus, good thermal stability was exhibited. The interaction of the two compounds with collagen in the suede was studied, as well as their antioxidant activity, advocating for good chemical stability and potential to be safely used as coloring agents in the food industry.